SCHOOL OF ENGINEERING AND TECHNOLOGY
DEPARTMENT OF INDUSTRIAL AND MANUFACTURING ENGINEERING
HIT300 DESIGN PROJECT
CNC ACETYLENE GAS PROFILE CUTTER FOR SMEs
BY
MICCURRIE DANIEL HUDUBE
(H180029P)
SUPERVISOR:
Eng. G. NYAKUJARA
Eng. T. MUNETSIWA
A HIT 300 DESIGN AND INNOVATION PROJECT SUBMITTED IN PARTIAL
FULLFILMENT OF THE REQUIREMENTS OF A BACHELOR OF TECHNOLOGY
(HONOURS) DEGREE IN INDUSTRIAL AND MANUFACTURING ENGINEERING
2020
Copyright
All rights reserved. No part of this design and innovation project may be reproduced, stored in any
retrieval system, or transmitted in any form or by any means, electronic, mechanical,
photocopying, recording or otherwise for scholarly purpose, without the prior written permission
of the author or of Harare Institute of Technology on behalf of the author.
ii
Declaration
I MicCurrie D. Hudube, bearing registration number H180029P do hereby declare that this
research project is my original work except where sources have been acknowledged, under the
esteem guidance of my supervisor Engineer G. Nyakujara and Engineer T. Munetsiwa of Harare
Institute of Technology. The work has never been submitted, nor will it ever be, to another
University in the awarding of a degree.
Harare institute of Technology
Department of Industrial and Manufacturing Engineering
P.O. Box Be277
Belvedere
Harare
Zimbabwe
STUDENT ………………………………………………... DATE………………………….
SUPERVISOR SIGNATURE ……………………………...DATE………………………….
SUPERVISOR SIGNATURE ……………………………...DATE………………………….
iii
Dedication
I dedicate this project to all the scholars and engineers interested in plate metal engineering and
quality assurance as well as To God Almighty the Giver of life and capacity
.
iv
Acknowledgements
Special mention goes to my Supervisors who made the work a success through their unwavering
support throughout the course of the project, along with entire personnel from the Industrial and
Manufacturing Engineering department.
I appreciate the support and love shown by friends with specialties in different areas that made the
project a success. I dedicate the work also to my Parents acknowledging their financial and
emotional support that played a huge role in seeing to the fruition of the project.
Above all I thank the Almighty for good health and the power to keep pushing through tough times
till the eventual success of the project.
v
Abstract
The purpose of the project is to Design a CNC Plate Metal Profile cutter for Low-cost investors
and SMEs in Zimbabwe. Currently the Profile cutting equipment available on the market is very
expensive and cannot be afforded by SMEs in Zimbabwe who do Plate metal working. At the
moment plate metal cutting is done manually as a whole which puts quality directly in the hands
of the person doing the cutting and his/her skill. This has problems of poor quality of cuts which
results in poor products as well as impossibility of identical cutting as errors are a part of human
nature. Which skilled Gas Cutters, repeatability of operations is still a problem as it is affected by
fatigue and boredom. A prototype was designed using Wiper motors for mechanical power as well
as illustration of controllability of the designed setup. The project is recommended for Small to
Medium enterprises whose operations are limited to standard plate sizes (1200 x 2400mm).
vi
Table of Contents
Copyright ........................................................................................................................................ ii
Declaration ..................................................................................................................................... iii
Dedication ...................................................................................................................................... iv
Acknowledgements ......................................................................................................................... v
Abstract .......................................................................................................................................... vi
CHAPTER ONE: INTRODUCTION ............................................................................................. 1
1.1
Introduction ...................................................................................................................... 1
1.2
Problem Background ........................................................................................................ 1
1.3
Problem statement ............................................................................................................ 2
1.4
Aim ................................................................................................................................... 2
1.5
Objectives ......................................................................................................................... 2
1.6
Justification ...................................................................................................................... 3
1.7
Scope of the Project.......................................................................................................... 3
1.8
Research Questions .......................................................................................................... 3
1.9
Conclusion........................................................................................................................ 3
CHAPTER TWO: LITERATURE REVIEW ................................................................................. 4
2.1
Oxy-Fuel gas cutting ........................................................................................................ 4
2.1.1
Process Fundamentals ............................................................................................... 4
2.1.2
Basic Requirements for gas cutting. ......................................................................... 4
2.2
Fuel used in Oxy-Fuel gas Cutting................................................................................... 5
2.2.1
Acetylene .................................................................................................................. 5
2.2.2
Propane ..................................................................................................................... 5
2.2.3
MAPP........................................................................................................................ 6
2.2.4
Propylene .................................................................................................................. 6
vii
2.2.5
2.3
Natural Gas ............................................................................................................... 6
Gas Cutting Components. ................................................................................................ 7
2.3.1
Nozzle ....................................................................................................................... 7
2.3.2
Oxy-Fuel Gas piping. ................................................................................................ 9
2.4
CNC Mechanical set up.................................................................................................. 10
2.4.1
Traversal Basics. ..................................................................................................... 10
2.4.2
X_Y_Z Traversal systems....................................................................................... 11
2.4.3
Railing Setup (Sliding Mechanisms) ...................................................................... 15
2.5
Powering Equipment. ..................................................................................................... 16
2.5.1
Stepper Motors ........................................................................................................ 16
2.5.2
Servo motors ........................................................................................................... 18
2.6
Motor Control Systems. ................................................................................................. 18
2.6.1
PLC Controller ........................................................................................................ 18
2.6.2
PIC Controller ......................................................................................................... 19
2.6.3
Arduino controller ................................................................................................... 20
2.7
Gas Cutting Operations. ................................................................................................. 22
2.7.1
Straight line cutting ................................................................................................. 22
2.7.2
Bevel Cutting .......................................................................................................... 23
2.7.3
Circular Cutting ...................................................................................................... 24
2.7.4
Pipe/Radial Cutting ................................................................................................. 25
2.8
Gas Cutting Equipment already in place. ....................................................................... 26
2.8.1
Multi-Station Gantry fitted Cutter .......................................................................... 26
2.8.2
CG2-Tracing cutter. ................................................................................................ 27
2.8.3
Straight line Cutter. ................................................................................................. 27
2.9
Conclusion...................................................................................................................... 27
viii
CHAPTER THREE: RESEARCH METHODOLOGY. .............................................................. 28
3
.................................................................................. Ошибка! Закладка не определена.
3.1
Introduction .................................................................................................................... 28
3.2
Feasibility and cost analysis. .......................................................................................... 28
3.2.1
Data Collection ....................................................................................................... 29
3.3
Engineering Tools. ......................................................................................................... 29
3.4
Experiments and Testing. ............................................................................................... 29
3.5
Analysis of Results. ........................................................................................................ 30
3.6
Development of Design Solutions.................................................................................. 30
3.7
Conclusion...................................................................................................................... 30
CHAPTER FOUR: DESIGN ........................................................................................................ 31
4.1
Introduction .................................................................................................................... 31
4.2
Conceptual design .......................................................................................................... 31
4.3
Concept Generation ........................................................................................................ 32
4.3.1
Concept generation table......................................................................................... 32
4.4
Concept screening .......................................................................................................... 40
4.5
Concept Scoring ............................................................................................................. 41
4.6
Hardware Process layout. ............................................................................................... 44
4.7
Final Hardware Design................................................................................................... 45
4.8
Software Design ............................................................................................................. 46
4.8.1
4.9
Machine Display. .................................................................................................... 46
Circuit Components........................................................................................................ 53
4.10 Calculations. ................................................................................................................... 54
4.10.1
Electronic (key components) Calculations ............................................................. 54
4.10.2
Worm Properties Calculations ................................................................................ 54
ix
CHAPTER FIVE: ECONOMIC ANALYSIS .............................................................................. 56
5.1
Bill of Electronic Units. ................................................................................................. 56
5.2
Inclusive Bill of Quantities ............................................................................................ 56
5.3
Bill of labor .................................................................................................................... 57
5.4
Break Even Analysis ...................................................................................................... 58
5.5
Initial Capital Investment. .............................................................................................. 59
5.6
Return on Investment (ROI) ........................................................................................... 59
5.7
Payback Period ............................................................................................................... 59
5.8
Conclusion...................................................................................................................... 59
CHAPTER 6: CONCLUSION AND RECOMMENDATION. ................................................... 60
6.1
Physical structure. .......................................................................................................... 60
6.2
Internal calculations. ...................................................................................................... 61
6.2.1
Profile Calculations ................................................................................................. 61
6.2.2
Pre-Heating. ............................................................................................................ 62
6.3
State of machine Interface. ............................................................................................. 63
6.4
Circuiting and Control. ................................................................................................... 64
6.4.1
6.5
Intelligent zero positioning. .................................................................................... 65
Recommendations. ......................................................................................................... 66
6.5.1
Mechanical setup. ................................................................................................... 66
6.5.2
Monitoring, Control, Program and Circuit. ............................................................ 66
6.6
Conclusion...................................................................................................................... 66
BIBLIOGRAPHY ......................................................................................................................... 67
Appendix ....................................................................................................................................... 70
x
Table of figures
Fig 1 Gas Cutting Fundamentals..................................................................................................... 4
Fig 2 Standard nozzle with central bore for oxygen jet and pre-heating gas mixture ports. .......... 8
Fig 3 Standard nozzle with central bore for oxygen jet and ring of ports for pre-heating gas
mixture. ........................................................................................................................................... 9
Fig 4 SIEMENS SINUMERIK 840D Control (performed traversal) ........................................... 11
Fig 5 Conventional Lathe machine Cross slide Showing worm and nut ...................................... 12
Fig 6 Rack and Pinion set up ........................................................................................................ 12
Fig 7 Roller pinion and rack set up ............................................................................................... 13
Fig 8 Ball bearing.......................................................................................................................... 15
Fig 9 Roller Gate wheel ................................................................................................................ 16
Fig 10 Stepper Motor .................................................................................................................... 16
Fig 11 Servo motor ....................................................................................................................... 18
Fig 12 PLC Controller .................................................................................................................. 18
Fig 13 PIC Controller.................................................................................................................... 19
Fig 14 Arduino Controller ............................................................................................................ 20
Fig 15 Use of roller guides (a) ...................................................................................................... 22
Fig 16 Use of Angle Section ......................................................................................................... 22
Fig 17 Beveling set ups ................................................................................................................. 23
Fig 18 Use of radius rod................................................................................................................ 24
Fig 19 Use of radius plate ............................................................................................................. 24
Fig 20 Use of radius bar ................................................................................................................ 24
Fig 21 Tube on Rollers ................................................................................................................. 25
Fig 22 Magnetic Pipe Cutter ......................................................................................................... 25
Fig 23 Multi-Station gantry fitted cutter ....................................................................................... 26
Fig 24 Tracing Gas cutter. ............................................................................................................ 27
Fig 25 Straight line Gas cutter. ..................................................................................................... 27
Fig 26 Research methodology Representation ............................................................................. 28
Fig 27 Concept 1 ........................................................................................................................... 33
Fig 28 Concept 2 ........................................................................................................................... 35
Fig 29 Concept 3 ........................................................................................................................... 37
xi
Fig 30 Concept 4 ........................................................................................................................... 39
Fig 31 Hardware Process Layout. ................................................................................................. 44
Fig 32 Final CNC Profile cutter. ................................................................................................... 45
Fig 33 InteliCUT Login window. ................................................................................................. 46
Fig 34 InteliCUT HOME window ................................................................................................ 47
Fig 35 Properties window. ............................................................................................................ 48
Fig 36 SQUARE window ............................................................................................................. 49
Fig 37 CIRCLE window ............................................................................................................... 50
Fig 38 SPECIAL window. ............................................................................................................ 51
Fig 39 CUTTING Interface. ......................................................................................................... 52
Fig 40 Final Mechanical Design ................................................................................................... 60
Fig 41 Code for Circle Cut. (With test result) .............................................................................. 61
Fig 42 G Code For Ambo-Bag Holder ......................................................................................... 62
Fig 43 Properties Window. ........................................................................................................... 63
Fig 44 Properties window-Code snippet. (Back) .......................................................................... 63
Fig 45 Simplified circuit layout. ................................................................................................... 64
Fig 46 G-Code for Ambo-Bag Holder. ......................................................................................... 65
List of tables
Table 1 Fuel and Oxygen Volumes and Heat Distribution ............................................................. 7
Table 2 Color coding for gas piping ............................................................................................. 10
Table 3 Concept generation .......................................................................................................... 32
Table 4 Concept Screening ........................................................................................................... 41
Table 5 Concept Scoring Performance vs rating .......................................................................... 42
Table 6 Concept Screening. .......................................................................................................... 43
Table 7 Login buttons ................................................................................................................... 46
Table 8 Home window buttons. .................................................................................................... 47
Table 9 Properties Buttons ............................................................................................................ 48
Table 10 SQUARE buttons. .......................................................................................................... 49
Table 11 CIRCLE Buttons ............................................................................................................ 50
Table 12 SPECIAL Buttons. ......................................................................................................... 51
xii
Table 13 CUTTING window buttons. .......................................................................................... 52
Table 14 Electronic components list. ............................................................................................ 53
Table 15 Worm Calculation Symbols. .......................................................................................... 54
Table 16 Bill of Electronic Components ...................................................................................... 56
Table 17 Bill of Materials ............................................................................................................. 56
Table 18 Bill of Labor................................................................................................................... 57
xiii
CHAPTER ONE: INTRODUCTION
1.1
Introduction
Plate metalwork is a key aspect in the metalwork industry. Plate metal is used in the mining
Industry as chutes, chute liners, transport and transfer buckets for heavy vehicles. In the general
transport industry plate metal is used for chassis reinforcements and brackets. Owing to the nature
of products from plate metal there is great need for the proper processing of the plate metal itself.
Generally, plate metalwork features Cutting/Profiling, fabrication, welding and other pertinent
processes owing to the intended use of the final product i.e., Coating or hardening. Of the three
main processes the one that affects quality the most is the Cutting/Profiling. The Cutting/Profiling
is normally done using acetylene gas owing to the costs associated with the more complex cutting
methods like water jet technologies and Laser cutting
1.2
Problem Background
Gas cutting is a key aspect of industrial fabrication and welding. A common gas cutting set features
2 gas tanks, Cutting/Soldering Torch and Connecting hose with connectors. This set up requires
one to possess skills like hand stability and control as to produce a good finish.
Owing to dependance on human skill, the conventional gas cutting is limited to straight and less
complex cuts, with more complex and elegant profiles are a big problem. Adherence to dimensions
is also a big problem with manual gas cutting and to get the required dimensions requires the
Furthermore, as the whole process is centered on human skill, repeatability is impossible as one
cut can never be exact to the previous one, which compromises quality with supposedly identical
products.(OSHA.Gov, 2018). Application of additional processing like surface grinding and in
worse cases there may be need for milling operations which makes processing cost and time
inevitably high, and in most cases too high to be encompassed in the Value of the product there
of.(Collewet et al., 2019)
In a bid to evade high processing costs local manufacturers of plate metal products like Grinding
mills and different types of crushers have resorted to changes in materials used (Thickness and
quality) which has seen compromised products, with some sticking to the right materials but using
manual cutting which has seen supposedly identical products being unidentical and quality being
1
a serious problem. In November 2020 it was observed at Maneuver Manufacturing produced 4
grinding mills that had side plates that were dimensionally different, yet supposed to be identical
and equal. According to B. Hudube| (Assistant Workshop Manger) the gas profiled side plates
were cut by hand and a as a result the compromise in quality and increase in cost as there was need
to grind and pack in to try and produce functional equipment. It was collected that this is not the
first time that this problem has been seen and it has led to loss of customers as some of the
implications of poor cut quality is visible even to some with little to no engineering acumen.
Generally, With the conventional cutting method, the range of plate metal products is narrow. This
has seen the nation at large depending on quality products imported from neighboring countries.
Products like pressure tank brackets and clamps are imported from South Africa, and Vehicle
chassis reinforcement brackets and engine mountings are also imported from the neighboring
nations and other further away nations. The project will serve to improve cut quality and integrity
thereby minimizing the need to import gas profiled components.
In addition, the other issue is that with the profile cutters currently available on the market, there
is high cost of acquisition and also maintenance is a serious problem owing to unavailability of
relative spares on the local front.
1.3
Problem statement
Quality of Plate metal products is low owing to high dependance of the process on human skill,
and range of products is limited owing to inability to cut/profile complex shapes.
1.4
Aim
To Develop a low-cost CNC Oxy-Fuel Profiler that operates with minimized dependance on
human cutting expertise, for small to medium enterprises.
1.5
Objectives

To design a gas (acetylene) profile cutter, that is cheap and easy to use.

To Make Profile cutting machine that reduces need for manning during operation. .

To incorporate Computer control and Arithmetic and Logic unit to improve ease of
operation and better cut quality.

To incorporate human interface for feedback and ease of Human-Machine communication
2
1.6
Justification
The project will improve the quality of cuts and increase the range of plate metal products as
complex profiles can be cut at lower costs than machines already in the field. Furthermore, there
is going to be an improvement on time taken in profiling operations. Repeatability will also be
possible with identical and elegant products.
1.7
Scope of the Project
Focus is strictly on acetylene gas cutting technology and incorporating it on a traversal setup and
computer control and calculation for intelligent profiling.
1.8
1.9
Research Questions

What mechanical systems can be used in profiling systems.

What material can be used with gas cutting.

What are the best nozzles for high-speed cutting?

What is the best low cost yet effective nozzle?

What is the best circuit set up and layout for profiling machine?

What safety measures are necessary with gas cutting operations.

What are the alternatives to gas cutting?

What innovations are there currently with gas cutting technology?

What are the rooms for improvement in the current equipment?
Conclusion
With registers success the proposed solution will serve to improve quality, integrity of cuts thereby
reducing scrapped material and also reduce time in profiling operations.
3
CHAPTER TWO: LITERATURE REVIEW
2.1 Oxy-Fuel gas cutting
2.1.1 Process Fundamentals
The cutting process is illustrated in Fig. 1. Basically, a mixture of oxygen and the fuel gas is used
to preheat the metal to its 'ignition' temperature which, for steel, is 700°C - 900°C (bright red heat)
but well below its melting point. A jet of pure oxygen is then directed into the preheated area
instigating a vigorous exothermic chemical reaction between the oxygen and the metal to form
iron oxide or slag. The oxygen jet blows away the slag enabling the jet to pierce through the
material and continue to cut through the material.(Equipment, n.d.)
Fig 1 Gas Cutting Fundamentals.
2.1.2 Basic Requirements for gas cutting.
The ignition temperature of the material must be lower than its melting point. The chief reason
why this is necessary is to ensure material does not melt and start flowing before cutting is possible.
The oxide melting point must be lower than that of the surrounding material. If the surrounding
material has a lower melting point than the oxide formed, then the jet of oxygen meant to blow
away the slag formed will not be able to do so, or the quality of cut is greatly compromised.(Victor,
2011)
4
The oxidation reaction between the oxygen jet and the metal must be sufficient to maintain the
ignition temperature. This aids with the quality of cut produced.
A minimum of gaseous reaction products should be produced so as not to dilute the cutting oxygen.
Purity of oxygen affects quality of cut and speed of cutting, and when diluted the effects are
undesirable i.e., the purity of oxygen should be at least 99.5%. A decrease in purity of 1% will
typically reduce the cutting speed by 25% and increase the gas consumption by 25%. (twi-global,
2020)
2.2 Fuel used in Oxy-Fuel gas Cutting
According TWI Ltd.’s published newsletter (twi-global, 2020) Oxy-fuel cutting is a thermal
cutting process that uses oxygen and fuel gas (such as acetylene, propane, MAPP, propylene and
natural gas) to cut through materials. (Resource, n.d.)
2.2.1 Acetylene
Acetylene produces the highest flame temperature of all the fuel gases. The maximum flame
temperature for acetylene (in oxygen) is approximately 3,160°C compared with a maximum
temperature of 2,828°C with propane. The hotter flame produces more rapid piercing of the
materials with the pierce time being typically one third that produced with propane.
The higher flame speed (7.4m/s compared with 3.3m/s for propane) and the higher calorific value
of the primary flame (inner cone) (18,890kJ/m3 compared with 10,433 kJ/m3 for propane) produce
a more intense flame at the surface of the metal reducing the width of the Heat Affected Zone
(HAZ) and the degree of distortion. This has the advantage that material properties (chemical) are
not affected greatly thereby reducing hardening of the material itself.
Acetylene gas is best used with machine setups as it makes high speed operations to be possible.
The high Flame temperature means the time taken to heat material to cutting point is less which is
best for machine cutting.
2.2.2 Propane
Propane produces a lower flame temperature than acetylene (the maximum flame temperature in
oxygen is 2,828°C compared with 3,160°C for acetylene). It has a greater total heat of combustion
5
than acetylene but the heat is generated mostly in the outer cone (see Table1). The characteristic
appearance of the flames for acetylene and propane are shown in Figs.2 and 3 where the propane
flame appears to be less focused. Consequently, piercing is much slower but as the burning and
slag formation are affected by the oxygen jet, cutting speeds are about the same as for acetylene.
Propane has a greater stoichiometric oxygen requirement than acetylene; for the maximum flame
temperature in oxygen, the ratio of the volume of oxygen to fuel gas are 1.2 to 1 for acetylene and
4.3 to 1 for propane.
2.2.3 MAPP
MAPP gas is a mixture of various hydrocarbons, principally, methylacetylene and propidine. It
produces a relatively hot flame (2,976°C) with a high heat release in the primary flame (inner cone)
(15,445kJ/m3), less than for acetylene (18,890kJm3) but much higher than for propane
(10,433kJm3). The secondary flame (outer cone) also gives off a high heat release, similar to
propane and natural gas. The combination of a lower flame temperature, more distributed heat
source and larger gas flows compared with acetylene results in a substantially slower pierce time.
As MAPP gas can be used at a higher pressure than acetylene, it can be used for underwater cutting
in deep water as it is less likely to dissociate into its components of carbon and hydrogen which
are explosive.
2.2.4 Propylene
Propylene is a liquid petroleum gas (LPG) product and has a similar flame temperature to MAPP
(2896°C compared to 2,976°C for MAPP); it is hotter than propane, but not as hot as acetylene. It
gives off a high heat release in the outer cone (72,000kJ/m3) but, like propane, it has the
disadvantage of having a high stoichiometric fuel gas requirement (oxygen to fuel gas ratio of
approximately 3.7 to 1 by volume).
2.2.5 Natural Gas
Natural gas has the lowest flame temperature similar to propane and the lowest total heat value of
the commonly used fuel gases, e.g., for the inner flame 1,490kJ/m3 compared with 18,890kJ/m3
for acetylene. Consequently, natural gas is the slowest for piercing.
6
Table 1 Fuel and Oxygen Volumes and Heat Distribution
Fuel Gas
Maximum
Oxygen to fuel Heat
Flame
gas Ratio (Vol) Distribution
Temperature 0C
(kJ/m3)
Primary
Secondary
ACETYLENE
2160
1.2:1
18890
35882
PROPANE
2828
4.3:1
10433
85325
MAPP
2976
3.3:1
15445
56431
PROPYLENE
2896
3.7:1
16000
72000
HYDROGEN
2856
0.42:1
-
-
NATURAL GAS
2770
1.8:1
1490
35770
Acetylene gas is best used as fuel because of its low stoichiometric oxygen demand, making the
process relatively cheap as less oxygen is needed. Hydrogen as fuel gas requires special handling
as it is highly active with possibilities of explosion being very high because of its chemical nature.
In addition, Heat distribution for acetylene fuel is high (18890 Kj/m3) which makes it possible to
produce good quality cuts with thick materials.
2.3 Gas Cutting Components.
2.3.1 Nozzle
The primary functions of the nozzle are to provide:

A method of preheating the metal to its ignition temperature

A jet of oxygen to react with the material to be cut and at a flow rate sufficient to blow
away the slag
Each torch should be fitted with the appropriate nozzle for the type of fuel gas. Nozzles can be of
a one- or two-piece design. The nozzle type will depend on:

Fuel gas

Manual or machine operation

Manufacturer's preference
7
Acetylene nozzles are usually one-piece but two-piece nozzles similar to those for other fuel gases
are produced for machine cutting. (Butbro & Butbro, 2014)
The diameter of the cutting oxygen hole is selected according to the material thickness. There are
two types of nozzle; standard and high speed. The standard nozzle usually has a parallel sided,
central bore for the oxygen jet, which is surrounded by an annulus or a ring of smaller diameter
ports for the pre-heating gas mixture, Figs. 2 and 3. There are many designs and arrangements of
the preheating ports that focus the flame for heating and to protect the oxygen jet from air
entrainment.(Nozzles Cutting Nozzles Cutting Nozzles, n.d.)
Fig 2 Standard nozzle with central bore for oxygen jet and pre-heating gas mixture ports.
8
Fig 3 Standard nozzle with central bore for oxygen jet and ring of ports for pre-heating gas
mixture.
High-speed nozzles are capable of being used with higher oxygen pressures, up to 10 bar. The
essential difference is that the cutting oxygen is forced through a convergent / divergent orifice
which speeds up the gas flow rate to near supersonic levels. High-speed nozzles are primarily used
in automated equipment to exploit the higher speeds for cutting long lengths.(Executive, n.d.)
Oxy-Fuel Gas cutting is evidently affected by various factors. Of greatest concern is the purity of
oxygen used as it will affect cutting speed as well the finish on the cut edge, and the fuel being
used as this determines the amount of heat produced in a period of time thus affecting cutting
speed, additionally the type of fuel used will affect the amount of oxygen used and the fuel itself
owing to the ratios in which the fuel is mixed with the oxygen. (TorchandNozzle.Pdf, n.d.)
Nozzles used with gas cutting also have a bearing on the process itself as cutting nozzles are
classified according to the possibility of using them on mechanized systems or with manual cutting
mainly because of the speeds associated in the cutting process.
2.3.2 Oxy-Fuel Gas piping.
2.3.2.1 Structure and properties
Gas piping is meant to be corrosion resistant as well as operate at high temperatures. Flexible
piping is most relevant for machine systems as it makes it possible to move
components.(Hardened, n.d.)
9
The most common flexible pipe used with oxy-fuel gas systems is Flexible high gloss nylon which
is color coded according to the gas piped through it.
(Engineering Toolbox, (2008). Gas Pipes - Approved Materials. [online] Available at:
https://www.engineeringtoolbox.com/approved-gas-pipes-d_1112.html [Accessed 11 28. 2020])
2.3.2.2 Color coding for gas piping
Table 2 Color coding for gas piping
Gas
Color
Propylene
Natural gas
Brown/White
Acetylene
Yellow/Black
Propane
Brown/White
Hydrogen
Yellow/Black
MAPP
(The Engineering Toolbox, 2010)
2.4 CNC Mechanical set up.
2.4.1 Traversal Basics.
There are basically two types of mechanical traversal system methods, which are worm and nut
system and the rack and pinion set up. These two set ups are gear systems with their various
benefits and demerits but can both be used in Traversal systems.(FUN Da MENTALS of Design,
2008)
A conventional CNC Traversal set up has 3 degrees of freedom, Movement possible in the X, Y
and Z directions. This three-direction movement is very key as it affects a machine’s ability to
adhere to measurements (as calibrated) which is why electronic control is necessary.(Eucheuma,
2004)
10
2.4.2 X_Y_Z Traversal systems
2.4.2.1 Worm and Nut on Carriage Set up.
Worm And nut systems are
widely
used
with
CNC
Machines. (Manual, 2005)
Worm gears are the most
compact type of system and
provide
high-ratio
speed
reduction. They are often the
preferred type of gearing system
when space is limited and large
gear reductions are needed.
Worm gears can be used to
Fig 4 SIEMENS SINUMERIK 840D Control (performed traversal)
either greatly increase torque or
greatly reduce speed. They are
also the smoothest and quietest of the gear systems, as long as they are properly mounted and
lubricated. Another advantage of worm gear is that they have good meshing effectiveness. To be
most effective, it is important that they are manufactured with high quality standards to ensure all
gear requirements are precisely met. (https://gearmotions.com/advantages-of-worm-gears/)
Due to commendable meshing quality of worm gears with nuts, it is made possible to have high
accuracy with calibrated systems hence the preferred use with conventional lathe traversal
systems.(Aktan et al., 2016)
11
Conventional lathe machine Cross slide system use worm and
nut system to carry the tool post across lathe axis. The worm
and nut are not directly loaded as the tool post mounting
Nuta rail/Guides leaving the worm and nut system for
slides on
the driving of the tool post across the carriage way(FUN Da
Worm
MENTALS of Design, 2008)
Lathe Bed
Cross Slide Rail
Fig 5 Conventional Lathe machine Cross slide
Showing worm and nut
2.4.2.2 Rack and Pinion Drive.
Rack-and-pinion drives are used in
machine
tools,
pick-and-place
mechanisms, and so forth to provide
linear motion of slides, gantries, etc.
Sometimes a lead- or ball-screw is
preferred,
especially
for
shorter
motions, but racks and pinions provide
Fig 6 Rack and Pinion set up
an economical way of achieving long
runs. One drawback is accuracy, as the
pinion and rack need a certain amount of clearance to mesh properly, resulting in backlash.
Depending on the diametral pitch of the gear, the recommended backlash can range from as little
as 0.002 in. to as much as 0.025 in. For something as crude as a CNC plasma cutter, backlash
would play no role in the quality of the cut product but would certainly be a factor in the work
12
produced on precision equipment. (Machines et al., n.d.)Rack-and-pinion manufacturers do offer
zero-backlash designs for these purposes which use technologies such as dual- or split-pinions. In
addition, fairly new roller-pinion systems are making inroads into some of these markets.
(https://www.thomasnet.com/articles/machinery-tools-supplies/rack-and-pinion-gears/)
2.4.2.3 Roller pinion Drives.
This is a fairly new technology that is aimed at improving the conventional rack and pinion set up.
Fig 7 Roller pinion and rack set up
A rack and roller pinion system are a variation of a standard rack-and-pinion. It takes the traditional
rack and pinion concept and advances it by replacing spur gear teeth with bearing supported rollers
that engage a unique rack tooth profile. Rollers ride the rack-tooth surfaces with repeatability to
about 2.5 μm from one direction (or better than 5.8 μm from both). The bearing supported rollers
replace the sliding friction of a traditional rack and pinion with smooth rolling friction that gives
up to a 99% efficient rotary to linear motion conversion.
The benefits of rack-and-pinion, including roller pinion, sets are that they can operate without
enclosures or protective covers. They’re also efficient to 98% or better, and many exhibit
backlashes of 1 arc-min or less. Another strength is that they’re often less expensive than
13
comparable linear motors when stroke lengths are long, so that a rack-and-pinion set can cost half
of what a linear motor costs, especially for many-meter strokes. Rack-and-pinion sets sometimes
perform better than ball screw actuators because they’re not affected by adjacent bearings,
couplings or bores. They’re also immune to stiffness degradation, even over long lengths.
Roller pinion systems are capable of speeds up to 11 m/sec making them the fastest mechanical
linear drive system second only to linear motors. Even at these speeds, the extremely low-friction
design creates minimal heat and wear on components.
Due to the smooth way the rollers engage the rack teeth, roller pinion systems generate low noise
and vibration. They don’t suffer from the noise caused by tooth slap or recirculating balls that other
linear drive systems have. Eliminating sliding friction allows roller pinions to operate substantially
quieter than a standard rack and pinion sets. (November 10, 2017 By Miles Budimir;
https://www.motioncontroltips.com/rack-roller-pinion/)
Rack/Roller pinion systems are designed to reduce the hassles with conventional rack and pinion
setups which are mainly noises and damage due to friction. This implies that with rack/roller pinion
systems there is higher performance for traversal Systems.
According to Atlanta Drive Systems in an article on their website, the issue of backlash that is
addresses with roller pinion set ups, can also be addressed with a modified conventional pinion.
ATLANTA Zero-Backlash Rack & Pinion Drive Systems utilize a split-pinion, which consists of
two pinion halves and an axial spring pack, to remove the system backlash. The pinions halves
mesh with opposite tooth flanks on the same rack, eliminating the backlash. One pinion half drives
the axis while the second pinion half is "preloaded" to remove the backlash.
(https://www.atlantadrives.com/RPS.htm)
There are possible ways to improve traversal systems so that they can be used with various
machines but some aspects to traversal systems cannot be changed without affecting the operation
of these up itself or the physical size.
Conclusively Rack and pinion systems can be used where long linear traversal is needed with not
much attention to accuracy of movement step, whereas worm and nut systems will offer high
14
accuracy in stepping though length can be a huge drawback. With small machinery (Traversed
length), with high need for accuracy the best traversal set up would be a Worm and nut Set up.
2.4.3 Railing Setup (Sliding Mechanisms)
Traversal mechanism need to have minimum friction in the moving components thus the need for
sliding mechanism on the components being moved i.e., carriages and tool posts.
2.4.3.1 Ball Bearings
A ball bearing is a type of rolling-element bearing that uses balls to
maintain the separation between the bearing races.
The purpose of a ball bearing is to reduce rotational friction and
support radial and axial loads. It achieves this by using at least two
races to contain the balls and transmit the loads through the balls. In
most applications, one race is stationary and the other is attached to
Fig 8 Ball bearing
the rotating assembly (e.g., a hub or shaft). As one of the bearing
races rotates it causes the balls to rotate as well. Because the balls
are rolling, they have a much lower coefficient of friction than if two flat surfaces were sliding
against each other.
Ball bearings tend to have lower load capacity for their size than other kinds of rolling-element
bearings due to the smaller contact area between the balls and races. However, they can tolerate
some misalignment of the inner and outer races. (Bearing Self Study Guide, n.d.)
15
2.4.3.2 Sliding Gate wheels
Widely used with relatively high axial loads. Owing to the
mounting system that comes with gate wheels, they
become bulky and notably affect the height of the structure
being traversed.
Fig 9 Roller Gate wheel
2.5 Powering Equipment.
2.5.1 Stepper Motors
A stepper motor is an electromechanical device it converts
electrical power into mechanical power. Also, it is a brushless,
synchronous electric motor that can divide a full rotation into an
expansive number of steps. The motor’s position can be
controlled accurately without any feedback mechanism, as long
as the motor is carefully sized to the application. Stepper motors
Fig 10 Stepper Motor
are
similar
to
switched
reluctance
motors.
(https://www.elprocus.com/stepper-motor-types-advantagesapplications/)
2.5.1.1 Types of stepper motors
Permanent Magnet Stepper Motor.
Permanent magnet motors use a permanent magnet (PM) in the rotor and operate on the attraction
or repulsion between the rotor PM and the stator electromagnets.
16
Variable Reluctance Stepper Motor.
Variable reluctance (VR) motors have a plain iron rotor and operate based on the principle that
minimum reluctance occurs with minimum gap, hence the rotor points are attracted toward the
stator magnet poles.
Hybrid Synchronous Stepper Motor.
Hybrid stepper motors are named because they use a combination of permanent magnet (PM) and
variable reluctance (VR) techniques to achieve maximum power in small package size.
(Stepper Motor, n.d.)
2.5.1.2 Benefits of using Stepper motors.
Stepper motors give a rotation angle proportional to the input pulse which makes electronic
control easy. In addition, Stepper motors have full torque at standstill. Stepper motors have
excellent response to starting, stopping, and reversing because of the use of current for control
and function. Furthermore, the motor’s response to digital input pulses provides open-loop
control, making the motor simpler and less costly to control.
The structure of stepper motors makes them reliable since there are no contact brushes in the
motor
2.5.1.3 Primary uses of stepper motors.

Industrial Machines – Stepper motors are used in automotive gauges and machine tooling
automated production equipment.

Security – new surveillance products for the security industry.

Medical – Stepper motors are used inside medical scanners, samplers, and also found inside
digital dental photography, fluid pumps, respirators, and blood analysis machinery.

Consumer Electronics – Stepper motors in cameras for automatic digital camera focus and
zoom functions.
(Plotter et al., 2015)
17
2.5.2 Servo motors
A servo motor is a type of motor that can rotate with great
precision. Normally this type of motor consists of a
control circuit that provides feedback on the current
position of the motor shaft, this feedback allows the servo
motors to rotate with great precision.(Supply et al., 2004)
If you want to rotate an object at some specific angles or
distance, then you use a servo motor. It is just made up of
a simple motor which runs through a servo mechanism. If
motor is powered by a DC power supply then it is called
Fig 11 Servo motor
DC servo motor, and if it is AC-powered motor then it is
called AC servo motor. For this tutorial, we will be discussing only about the DC servo motor
working. Apart from these major classifications, there are many other types of servo motors based
on the type of gear arrangement and operating characteristics. A servo motor usually comes with
a gear arrangement that allows us to get a very high torque servo motor in small and lightweight
packages. Due to these features, they are being used in many applications like toy car, RC
helicopters and planes, Robotics, etc. (https://circuitdigest.com/article/servo-motor-working-andbasics)
2.6 Motor Control Systems.
2.6.1 PLC Controller
A PROGRAMMABLE LOGIC CONTROLLER (PLC) is an
industrial computer control system that continuously
monitors the state of input devices and makes decisions based
upon a custom program to control the state of output devices.
Almost any production line, machine function, or process can
be greatly enhanced using this type of control system.
However, the biggest benefit in using a PLC is the ability to
Fig 12 PLC Controller
change and replicate the operation or process while collecting
and communicating vital information.
18
Another advantage of a PLC system is that it is modular. That is, you can mix and match the types
of Input and Output devices to best suit your application.( et al., 2017)
How Does A PLC Operate?
There are four basic steps in the operation of all PLCs; Input Scan, Program Scan, Output Scan,
and Housekeeping. These steps continually take place in a repeating loop.
Four Steps in The PLC Operations

Input Scan: Detects the state of all input devices that are connected to the PLC

Program Scan: Executes the user created program logic

Output Scan: Energizes or de-energize all output devices that are connected to the PLC.

Housekeeping: This step includes communications with programming terminals, internal
diagnostics, etc...
(amci, 2020)
2.6.2 PIC Controller
PIC microcontrollers (Programmable Interface
Controllers), are electronic circuits that can be
programmed to carry out a vast range of tasks.
They can be programmed to be timers or to
control a production line and much more. They
are found in most electronic devices such as
alarm systems, computer control systems,
phones, in fact almost any electronic device.
Fig 13 PIC Controller
Many types of PIC microcontrollers exist,
although the best is probably found in the
GENIE range of programmable microcontrollers. These are programmed and simulated by Circuit
Wizard software.
19
PIC Microcontrollers are relatively cheap and can be bought as pre-built circuits or as kits that can
be assembled by the user. (Matic, 2003)
2.6.2.1 Advantages of PIC Microcontroller:

They are reliable and malfunctioning of PIC percentage is very less. And performance of
the PIC is very fast because of using RISC architecture.

Power conception is also very less when compared to other micro controllers. When we
see in the programmer point of view interfacing is very easy, also we can connect analog
devices directly without any extra circuitry and use them. Programming is also very easy
when compared to other microcontrollers.
2.6.2.2 Disadvantages of PIC Microcontroller:

The length of the program will be big because of using RISC (35 instructions).

Program memory is not accessible and only one single accumulator is present.
(https://www.electronicshub.org/pic-microcontroller-architecture/)
2.6.3 Arduino controller
Arduino is an open-source electronics platform based on
easy-to-use hardware and software. Arduino boards are
able to read inputs - light on a sensor, a finger on a button,
or a Twitter message - and turn it into an output - activating
a motor, turning on an LED, publishing something online.
You can tell your board what to do by sending a set of
Fig 14 Arduino Controller
instructions to the microcontroller on the board. To do so
you use the Arduino programming language (based on
Wiring), and the Arduino Software (IDE), based on Processing.(Arduino, 2018)
20
2.6.3.1 Benefits of using Arduino as ALU/CU include:

Inexpensive - Arduino boards are relatively inexpensive compared to other microcontroller
platforms. The least expensive version of the Arduino module can be assembled by hand,
and even the pre-assembled Arduino modules cost less than $50.

Cross-platform - The Arduino Software (IDE) runs on Windows, Macintosh OSX, and
Linux operating systems. Most microcontroller systems are limited to Windows.

Simple, clear programming environment - The Arduino Software (IDE) is easy-to-use for
beginners, yet flexible enough for advanced users to take advantage of as well. For
teachers, it's conveniently based on the Processing programming environment, so students
learning to program in that environment will be familiar with how the Arduino IDE works.

Open source and extensible software - The Arduino software is published as open-source
tools, available for extension by experienced programmers. The language can be expanded
through C++ libraries, and people wanting to understand the technical details can make the
leap from Arduino to the AVR C programming language on which it's based. Similarly,
you can add AVR-C code directly into your Arduino programs if you want to.

Open source and extensible hardware - The plans of the Arduino boards are published
under a Creative Commons license, so experienced circuit designers can make their own
version of the module, extending it and improving it. Even relatively inexperienced users
can build the breadboard version of the module in order to understand how it works and
save money.
21
2.7 Gas Cutting Operations.
2.7.1 Straight line cutting
2.7.1.1 Use of roller guides
Fig 15 Use of roller guides (a)
With the use of roller guides the key achievement is a close straight line because of the presence
of a rail for the rollers. Rollers mounted on the cutting torch maintain the height of the Cutting
torch above the plate being cut. Cutting speed is entirely dependent on the person doing the
operation, which implies that quality and finish of cut can be compromised.(Resource, n.d.)
2.7.1.2
Use of heavy section Angle iron
This method of straight cutting is highly dependent
on personal skill and experience. Height of cutting
torch above the material being cut is not controlled
as well as the cutting speed. This set up gives high
Fig 16 Use of Angle Section
chance of straight cutting with a manual set up.
22
2.7.2 Bevel Cutting
Fig 17 Beveling set ups
Machine beveling produces a consistently high-quality finish. Bevels produced by hand cutting
can also be of a similar standard where machines cannot be used conveniently or economically.
Bevel cuts a necessary with brackets and angle plates where welding is necessary at certain angles.
23
2.7.3 Circular Cutting
2.7.3.1 Using Radius Rod
Circle cutting using radius bars is very demanding as it
requires steady hands for properly straight cut edges.
Challenges with the use of radius rods is unintentional
beveling as a result of unsteady handling of the cutting torch
during the cutting process. The wheel shown fitted is
Fig 18 Use of radius rod
optional as it may hinder the operator in small work but can
be a steadying influence with slightly larger radii.
2.7.3.2 Radius Plate
Radius plate has a larger range than the radius rod and
can be used for both small and medium sized radii.
The design of the fixing device must be made to suit
the particular model of cutting blowpipe used.
Convenience relative to the use of radius plates is the
possibility of cutting larger radii, of course subject to
Fig 19 Use of radius plate
the size of the blow pipe in use.
2.7.3.3 Radius Bar
Fig 20 Use of radius bar
24
Radius bar is used in conjunction with roller guides and is suitable for medium to large circle
cutting.
2.7.4 Pipe/Radial Cutting
Tube on Rollers
The roller system can be motorized or manual.
With the manual system the rollers are free to roll
and the cutting torch can be fixed at a cutting
point with the pipe being turned manually as the
cut is made.
With the semi powered set up the roller system
Fig 21 Tube on Rollers
receives power from a motor with variable speeds
for the various materials and thicknesses of the
material to be cut. The cutting torch is kept in cutting position and the pipe rotates as cut is made.
With more intelligent set ups the cutting machine is mounted to the pipe and goes around the pipe
through a chain drive.(To, n.d.)
Fig 22 Magnetic Pipe Cutter
25
2.8 Gas Cutting Equipment already in place.
2.8.1 Multi-Station Gantry fitted Cutter
Fig 23 Multi-Station gantry fitted cutter
the set up features a gantry system as the supporting structure and traversal system. Conventionally
this system has 2 degrees of freedom, the x and y traversal.
The gantry mounted cutting system is mainly applicable with production of many identical
products.
The system encompasses a Computer processing unit that is an interface between CAD/CAM
software
and
the
machine
itself
enabling
the
system
to
produce
profiles
from
drawings.(Equipment, n.d.)
26
2.8.2 CG2-Tracing cutter.
The CG2 Profiler Series is a tracing machine that
uses gas to reproduce a pre-cut profile. The setup
is dependent on other operations being done first
on other machinery i.e., the creation of the trace
profile.
The equipment encompasses center seeking
technology that is made possible through the use of
a magnetic probe.
Conventionally the system is mounted on a vertical
Fig 24 Tracing Gas cutter.
column with a height adjusted base for levelling.
2.8.3 Straight line Cutter.
The straight cutter encompasses a rail that enables straight line
cutting. The system can be modified for circular cutting but is
limited to a range of radii, thus the need for various sizes for
the same operation with different radii sizes.
Fig 25 Straight line Gas cutter.
2.9 Conclusion
The main reason for this literature review was to show a comparison of the existing technologies
that can be used in the build-up of a CNC Oxy-Fuel Gas Cutting Machine. The Chapter made it
possible to understand the components relative to gas cutting as a process.
27
CHAPTER THREE: RESEARCH METHODOLOGY.
3.1 Introduction
The main aim of this chapter is to outline and explain the types of research methods used in
carrying out the research for this project. Pointed out in this chapter is how the data was collected
as well as the limitations therein the research, so as to give comprehensive information about the
project. The Success, validity and reliability of a project is are largely subject to research methods
implemented.(Sam, 2012)
The research methodology used is best represented as the diagram below.
Problem
Identification
Data gathering
and exploration
Reflect on
Solution
Design and
Develop
Test and
Evaluate
Fig 26 Research methodology Representation
3.2 Feasibility and cost analysis.
The key reasons for doing a feasibility Study relative to this project are to understand thoroughly
all aspects of a project, concept, or plan, to become aware of any potential problems that could
occur while implementing the project and to determine if, after considering all significant factors,
the project is viable—that is, worth undertaking. With Cost analysis the key factors were Cost of
production of the machine itself and the affordability of the machine to the SMEs who do plate
metal work.
Overall, the feasibility and cost analysis were done to ensure the final product satisfies the relevant
customers in function and investment. (Mukherjee & Roy, 2017)
28
3.2.1 Data Collection
To collect data the researcher used mainly three methods: Observations, and Consultations,
Interviews as well as Internet Journals.
3.2.1.1 Observations and Field Consultations.
Observations and Field consultations are particularly helpful with getting information on manual
oxy-fuel gas cutting methods and bringing to the light areas of concern and the real problem.
Additionally, Field consultations will help with expertise pertinent to the operations done in oxyfuel gas cutting.
3.2.1.2 Interviews.
Face to face sessions can be designed for Gas Cutters and Personnel who come in between the gas
cutting process and the end product. i.e., Machinists, Fabricators and Welders. The key benefit is
that information can be gathered on the implications of the gas cutting processes on other processes
therein the overall production line.
3.2.1.3 Internet Journals.
Published internet journals and manufacturers’ newsletters were used with the aim of collecting
the relevant information for the project. The researcher used the internet to gather information on
designing and modelling principles as can be applied with CNC Equipment.
3.3 Engineering Tools.
The Concepts were developed using Engineering Design Software which are AutoCAD and Solid
works.
AutoCAD was used to model components and create rendered images for near realistic
representation of the components.
Solid works was used to Develop CAD Drawings of the CNC Oxy-Fuel cutter, as well as to do
motion studies to ensure the mechanical functionality of the machine.
3.4 Experiments and Testing.
After modelling a prototype of the CNC Oxy-fuel gas cutter, experiments and Tests will be
conducted to test whether the machine conforms to the expectations of the end user as well as the
29
Engineer. At this level it will be possible to determine the operational safety of the machine. The
results are documented.
3.5 Analysis of Results.
The collected data will be noted and analyzed using Microsoft Excel and SPSS. The results will
be documented for statistical analysis.
3.6 Development of Design Solutions.
The first stage would be to develop various concepts, so as to come up with the best solution to
the problem at hand. The designer will design each concept separately with the core focus being
the CNC Profiling system which should be common with every concept. Relevant Calculations
(Torque, load and Distances per Revolution), will be done prior to final design. The eventuality is
that the right motor and power source will be determined.
3.7 Conclusion.
With the necessary steps being performed there is possible success in determining whether a
project should go on or not. Various methods are used from finding the actual problem, caring out
a market analysis, finding what is on the market as well as producing the final product that answers
the problem found in the first stage. However, all the methods chosen are not all perfect and have
disadvantage.
30
CHAPTER FOUR: DESIGN
4.1 Introduction
In this chapter, the various concepts that can be used to answer the problem are highlighted and
scrutinized, that is concepts that can be used in reducing quality of oxy-fuel gas cutting and
profiling dependance on a person skill through the use Computer Numeric Control system along
with designed mechanical structure to incorporate the many cutting operations. The chapter goes
on through to the weighing of the different concepts in choosing a concept which addresses the
problem at hand.
4.2 Conceptual design
Idea generation (Concept Design), is a critical step in the engineering design process. In this
chapter the chief focus is to highlight the components of a CNC Set up; Powering System,
Mechanical set up and Control unit. In comparing and highlighting differences in the concepts
various criterions were employed till the settlement on the best concept that is effective, efficient
and economically answering the problem at hand. The concepts brought forward are different in
the components, methodology and the structures that will be used in the design. Below are the
design criterions that the designer focused on:
a. Robustness
It is the ability of a system or setup to work in various physical and weather conditions.
b. Control Accuracy
Refers to the ability of a system to adhere to dimensions as well be able to repeat the same operation
or set of operations with no errors.
c. Structural Complexity
It refers to the physical set up particularly the mechanical system that affects reliability,
maintainability and space in volume occupied.
d. Cost Effectiveness
This is the extent to which invested time and money is incorporated in the cost of the finished
product which will affect market penetration.
31
4.3 Concept Generation
In this section the designer focuses on coming up with different ways that possibly address the
problem, then eventually comes up with the best solution.
4.3.1 Concept generation table
Mechanical Set up
Power Source
Controller
Table Top Rails
Electricity
PIC
SHAFT_RAILS
Electricity
PLC
Pillar Bottom Rail
Electricity
Arduino
4D Roller mount
Electricity
PIC
Table 3 Concept generation
32
4.3.1.1 Concept 1
Fig 27 Concept 1
4.3.1.1.1 Operating Principle.
The system works in three distinct Stages:

G-Code loading
The system allows for plugging in a computer with the Generated G-Code of the profile to be
produced.

Home Seeking.
This is when the system automatically locates its calibrated zero position.

Profiling
This stage has the Code being executed on the computer and the Controller sending the relevant
signals to the stepper motors there in place.
33
The setup has stepper motors fitted with pinion gears, that are meshed to racks for the x and y
Traversal directions. The powered motors are the ones that produce the required movement of the
crab and in turn the cutting torch.
Fuel used is acetylene
4.3.1.1.2 Safety.
Safety wise the concept has no risk of endangering operator as the operator does not man the
machine during operation. Risk of explosion is minimized as the machine uses standard
connections in adherence to requirements for oxy-fuel gas cutting and welding.
4.3.1.1.3 Accuracy.
Rack and pinion systems are not the best when it comes to fine movements. Doe to the weight
relative to the crab being traversed, the system cannot stop when meshing tooth are not in resting
position which introduces unwanted movements of the system.
4.3.1.1.4 Service and maintainability.
Racks are easy to machine and can be easily seen as to have been damaged or not as they are of a
clear profile. Pinions can be replaced with much ease hence the maintainability of the system.
Cost Analysis.
The cost related to the concept are tied to the stepper motors and the rack and pinion set up.
Advantages.

Rack and pinion setups can used for long traversal distances.

Cheap

Easy to assemble

Portable
Disadvantages.

Accuracy of mechanical set is a huge problem.

Physical structure is bulky.
34
4.3.1.2 Concept 2
Fig 28 Concept 2
4.3.1.2.1 Operating Principle.
The system works in three distinct Stages:

G-Code loading
The machine is interfaced to a Computer which runs a software that then helps with the cutting
process. G-Code is generated from the software and the commands are sent to the machine via the
PIC Unit which then makes it possible to produce the profile.

Intelligent zero positioning.
The system for control overrides so as to determine the initial cutting position and setting the
position as zero position.

Profiling
35
This stage has the Code being executed on the computer and the Controller sending the relevant
signals to the stepper motors there in place.
The setup has stepper motors coupled to worm gears, that are meshed to nuts fitted onto the moving
mounts for the x and y Traversal directions. The powered motors are the ones that produce the
required movement of the crab and in turn the cutting torch.
Fuel used is acetylene
4.3.1.2.2 Safety.
Safety wise the concept has no risk of endangering operator as the operator does not man the
machine during operation. Risk of explosion is minimized as the machine uses standard
connections in adherence to requirements for oxy-fuel gas cutting and welding as well as
incorporated alarm and feedback system that gives warning and machine well-being.
4.3.1.2.3 Accuracy.
Worm and wheel the best when it comes to fine movements. Because the ultimate traversal in the
system depends on the rotation of the worms/(screws) in the set up the crab and other moving
components can move and stop exactly when needed.
4.3.1.2.4 Service and maintainability.
Screws are not as easy to machine and cannot be easily seen as to have been damaged. Worms
however are not directly loaded hence do not wear as to cause a service and maintenance headache.
Nuts used in the setup can be replaced with much ease hence the maintainability of the system.
Cost Analysis.
The cost related to the concept are tied to the stepper motors which can be imported at affordable
prices, and the screw and nut setup, which are cheap to machine.
Advantages.
 Mobile

Easy to fabricate.

Cheap.

Easy to assemble

Portable
36
Disadvantages.
 Worms cannot be used for long traversal distances as they will need support.
4.3.1.3 Concept 3
Fig 29 Concept 3
4.3.1.3.1 Operating Principle.
The system works in four distinct Stages:

G-Code loading
The system allows for plugging in a T-Flash with the Generated G-Code of the profile to be
produced.

Home Seeking.
This is when the system automatically locates its pre-calibrated zero position.
37

Intelligent zero positioning.
The system for control overrides so as to determine the initial cutting position and setting the
position as zero position.

Profiling
This stage has the Code being executed on the computer and the Controller sending the relevant
signals to the stepper motors there in place.
The setup has stepper motors coupled to worm gears, that are meshed to nuts fitted onto the moving
mounts for the x and y Traversal directions. The powered motors are the ones that produce the
required movement of the crab and in turn the cutting torch.
Fuel used is acetylene
4.3.1.3.2 Safety.
Safety wise the concept has no risk of endangering operator as the operator does not man the
machine during operation. Risk of explosion is minimized as the machine uses standard
connections in adherence to requirements for oxy-fuel gas cutting and welding as well as
incorporated alarm and feedback system that gives warning and machine well-being.
4.3.1.3.3 Accuracy.
Worm and wheel the best when it comes to fine movements. Because the ultimate traversal in the
system depends on the rotation of the worms/(screws) in the set up the crab and other moving
components can move and stop exactly when needed.
4.3.1.3.4 Service and maintainability.
Screws are not as easy to machine and cannot be easily seen as to have been damaged. Worms
however are not directly loaded hence do not wear as to cause a service and maintenance headache.
Nuts used in the setup can be replaced with much ease hence the maintainability of the system.
Cost Analysis.
The cost related to the concept are tied to the stepper motors which can be imported at affordable
prices, and the screw and nut setup, which are cheap to machine.
Advantages.
 High accuracy and productivity.
38
Disadvantages.
 Worms cannot be used for long traversal distances as they will need support.

High manufacturing cost.
4.3.1.4 Concept 4
Fig 30 Concept 4
4.3.1.4.1 Operating Principle.
The setup has stepper motors coupled to worm gears, that are meshed to nuts fitted onto the moving
mounts for the x and y Traversal directions. The powered motors are the ones that produce the
required movement of the crab and in turn the cutting torch.
Fuel used is acetylene
4.3.1.4.2 Safety.
Safety wise the concept has no risk of endangering operator as the operator does not man the
machine during operation. Risk of explosion is minimized as the machine uses standard
39
connections in adherence to requirements for oxy-fuel gas cutting and welding as well as
incorporated feedback system that gives warning and machine well-being.
4.3.1.4.3 Accuracy.
Worm and wheel the best when it comes to fine movements. Because the ultimate traversal in the
system depends on the rotation of the worms/(screws) in the set up the crab and other moving
components can move and stop exactly when needed.
4.3.1.4.4 Service and maintainability.
Screws are not as easy to machine and cannot be easily seen as to have been damaged. Worms
however are not directly loaded hence do not wear as to cause a service and maintenance headache.
Nuts used in the setup can be replaced with much ease hence the maintainability of the system.
Cost Analysis.
The cost related to the concept are tied to the stepper motors which can be imported at affordable
prices, and the screw and nut setup, which are cheap to machine.
Advantages.
 Cheap.

Easy to assemble
Disadvantages.
 Worms cannot be used for long traversal distances as they will need support.

System is fixed.
4.4 Concept screening
There are four different concepts proposed by the designer and these concepts are rated and
screened basing on the chosen design criteria as so that at the end the designer has best solution
for the problem relative to the problem. The rating scale applied is entirely based on the designer’s
knowledge from research and critical thinking. In the ratings; positive (+) represents “better than”,
negative (-) representing “worse” and zero (0) representing “same as”. The least rated concept will
be rejected and the remaining concepts will be put together to give an ultimate solution.
40
Table 4 Concept Screening
Selection Criteria
Concepts
1
2
3
4
(Reference)
rating
rating
Rating
rating
Stability
+
+
0
-
Ease of manufacture
0
+
0
-
Maintenance
+
+
0
0
sustainability
0
+
0
-
Structural Complexity
-
-
0
-
Cost
-
+
0
+
Feasibility of design
-
+
0
-
Robustness
+
0
0
+
Accuracy
+
+
0
+
Sum +’s
4
7
0
3
Sum 0‘s
2
1
8
1
Sum – ‘s
3
1
0
5
Net score
1
6
0
-2
Continue?
YES
YES
-
NO
Concepts 1 and 2 have the highest ratings and can be combined to come up with a final machine
that addresses the problem at hand.
4.5 Concept Scoring
This stage the designer weighs the importance of the selected criteria and focuses on more
prominent comparisons based on each selected criterion. A level, hierarchical breakdown of each
41
criterion will be used in order to evaluate the concept with the required features comparing to other
concepts.
To critically evaluate the concepts a scale rating ranging from 1 – 5 is used, the translation of each
scale component is explained in table 5
Table 5 Concept Scoring Performance vs rating
Relative Performance
Rating
Much worse than
1
Worse than
2
Same as
3
Better than
4
Much better than
5
The designer will select the best concept based on the highest ranked score which will be calculated
using the following mathematical formulae
𝑛
𝑆𝑗 ∑ 𝑟𝑖𝑗 𝑤𝑖
𝑖=1
Were
𝑤𝑖 = 𝑤𝑒𝑖𝑔ℎ𝑡𝑖𝑛𝑔 𝑓𝑜𝑟 𝑡ℎ𝑒 𝑐𝑒𝑟𝑡𝑎𝑖𝑛 𝑐𝑟𝑖𝑡𝑒𝑟𝑖𝑎
𝑟𝑖𝑗 = 𝑟𝑎𝑡𝑖𝑛𝑔 𝑜𝑓 𝑐𝑜𝑛𝑐𝑒𝑝𝑡
𝑆𝑗 = 𝑡𝑜𝑡𝑎𝑙 𝑠𝑐𝑜𝑟𝑒 𝑓𝑜𝑟 𝑡ℎ𝑒 𝑐𝑜𝑛𝑐𝑒𝑝𝑡
42
Table 6 Concept Screening.
Concepts
Concept 3
Concept 2
Concept 1
Weighted
Rating
Weighted
Rating
Weighted
20
3
0.60
4
0.80
4
0.80
Ease of manufacture
10
3
0.30
5
0.50
5
0.50
Sustainability
25
3
0.75
3
075
4
1.00
Structural Complexity
15
3
0.45
4
0.60
3
0.45
Cost
10
3
0.30
5
0.50
4
0.40
Robustness
20
3
0.60
4
0.80
3
0.60
score
Rating
Stability
Criteria
Score
Weight (%)
Selection
Total Weighted Score
3
3.95
3.75
Rank
3
1
2
Decision
Reject
Accept
Reject
score
(reference)
43
4.6 Hardware Process layout.
This section explores the machine’s physical layout and the flow of instructions and feedback in
the machine.
Fig 31 Hardware Process Layout.
During operation, the machine receives and processes values of pressure levels from the two
pressure sensors so that the machine either sounds an alarm or stops the operation altogether. The
two limit switches are a second safety layer measure that ensures the machine does not traverse
outside the designed lengths.
DRIVES 1 and 2 are connected to the controller so that they receive the signals as per the CODE
Generated from the entered values or from the drawing. The drives then control the respective
motors which result in traversal of the cutting torch to give the required profile.
The controller consistently updates the database that helps keep track of the jobs done.
The USER INTERFACE makes it possible to initiate cutting operations as well as to keep track
of cutting operations.
44
4.7 Final Hardware Design.
Fig 32 Final CNC Profile cutter.
The final Design is such that the Bottom (X-traversal) ha sone Stepper motor powering one screw,
and the powered screw transfers power to the second screw via a chain and sprockets drive system.
The whole structure is not to be fixed but rather mobile because of the wheels that have been put
in place to help with the movement. Material seats are also put in place but do not move with the
whole machine rather they are moved to be positioned where they are needed.
Moving components have been covered up to avoid injuries as well as damage of the components.
The final Design has been made to have a maximum plate capacity of 1250 x 2500mm (Standard
plate size) with a maximum traversal area of 1000 x 2000mm.
The interface box is fixed on the bottom frame and has the USB Ports for interfacing with computer
units as well as Flash plug-in.
45
4.8 Software Design
The software encompasses the user interface in place for the operation of the machine and the
Control unit therein the machine designed to do calculations and comparisons as well as decision
making.
4.8.1 Machine Display.
The machine is operated from a Computer, where the user makes selections for the various
operations possible, machine diagnostics and load G-Code for the machine to operate.
4.8.1.1 User Interface(s)
Fig 33 InteliCUT Login window.
This is the point of entry for the operator of the machine. The machine allows for the use of various
operator accounts which can be added or removed.
Table 7 Login buttons
Button
Function
LOGIN
Checks if entered details are correct then allows/Blocks access.
HELP
Opens list of help details for machine operation.
EXIT
Closes the InteliCUT Interface.
46
Fig 34 InteliCUT HOME window
The HOME window is the first operations windows that allows for the operator to quickly choose
the relevant operations as per the requirements of a job.
Table 8 Home window buttons.
Button
Function
SPECIAL
Opens the windows for special operations
SQUARE
Opens the window for square cut operations.
CIRCLE
Opens the window for circular profile cutting operations.
PROPERTIES
Opens the properties window.
HELP
Opens a message box with explanations relative to the window.
EXIT
Closes the InteliCUT Application.
47
Fig 35 Properties window.
The properties window displays the state of the machine and alarm options. It displays the
Pressures for the fuel used in the cutting process, and the pressure for gas to keep operator informed
as to whether or not a refill is necessary.
The alarm trigger switch can be either ON(Green) or OFF (Red). When of the machine does not
sound an alarm in the case of low pressure.
The emergency tripping switch can either be ON(Green) or off (Red). When on the system will
cut off upon sudden drop in pressure which is designed to mean leakage of either the fuel or the
oxygen.
Table 9 Properties Buttons
Button
Function
DONE
Closes the properties window and opens the HOME window.
HELP
Open a message box that explains the window.
BACK
Closes the window and goes back to the login window.
48
Fig 36 SQUARE window
The SQUARE Cut window allows the operator to enter the dimensions of the square profile to be
cut. It has 2 active textboxes that accept the entering of only integer values that are less than
1000mm. (Effective Traversal Area 1m2)
Table 10 SQUARE buttons.
Button
Function
CUT
Initiates the cutting process and opens the ‘CUTTING’ window.
HELP
Open a message box that explains the window.
BACK
Closes the window and goes back to the ‘HOME’ window.
49
Fig 37 CIRCLE window
The CIRCLE Cut window allows the operator to enter the radius of the square profile to be cut. It
has 1 active textbox that accepts the entering of only integer values that are less than 500mm.
(Effective Traversal Area 1m2)
Table 11 CIRCLE Buttons
Button
Function
CUT
Initiates the cutting process and opens the ‘CUTTING’ window.
HELP
Open a message box that explains the window.
BACK
Closes the window and goes back to the ‘HOME’ window.
INPUT CENTER
Opens a window that allows operator to input center coordinates.
MANUAL CENTER
Checks the position of the cutting torch against the radius then picks the
position of the torch as the center or requests a new center upon conflict.
50
Fig 38 SPECIAL window.
The SPECIAL Cut window allows the operator to load generated G-Code from Drawing software.
The operator can also enter dimensions manual for profiles that are of straight line yet have got
non-90° Angles.
Table 12 SPECIAL Buttons.
Button
Function
LOAD CODE
Opens a load Code interface that allows for user to select a G-Code
Equivalent of the profile to be cut.
ENTER
Opens a Dimensions entering Interface that allows for user to enter details
DIMENSIONS
of the profile to be cut like number of sides and angles for polygons.
DRAW
Opens the Microsoft Paint software then generates the code from the
drawing made therein.
CUT
Initiates the cutting process and opens the ‘CUTTING’ window.
HELP
Open a message box that explains the window.
BACK
Closes the window and goes back to the ‘HOME’ window.
51
Fig 39 CUTTING Interface.
The CUTTING window displays graphically the progress of the cutting process. The operator has
options to stop the cutting process, permanently of temporarily and even select for the machine to
operate without human interference.
Table 13 CUTTING window buttons.
Button
Function
PAUSE/PLAY
Stops/starts the cutting operation on the case of the need to make
adjustments on the material clamping/sitting.
RESET
Initializes the machine to its zero positions and stops all operations.
ALARM OFF
Turns of the alarm after the correction of the trigger situation.
NO MAN
Activates the mode where the machine operates without human
intervention.
COMPLETE
Confirms that a job is done.
SETTINGS
Open the display options window.
52
4.9 Circuit Components
Table 14 Electronic components list.
Component
Description
Microcontroller (PIC18F46K22)
Full 5.5V operation (PIC18F2XK22/4XK22),
Low voltage option available for 1.8V-3.6V
operation
(PIC18LF2XK22/4XK22).
reprogrammable
under
software
Self-
control,
Power-on Reset (POR), Power-up Timer
(PWRT) and Oscillator Start-up Timer (OST)
Limit switch (Normally Closed)
Limit switches are used to restrict the
movement of a component by physical contact.
Normally closed switches will conduct current
in their optimal/zero/resting position without
being activated. One activated they won’t
allow current to pass through thus removing
power from all devices connected thereafter.
Pressure sensor
The Pressure sensors will give the pressure
from the Oxygen and fuel tanks, which is then
used to calculate the amount of gas present.
Transformer
Used to provide the right amount of voltage for
the respective electronic components.
Relay
A relay is an electrically operated switch. It
consists of a set of input terminals for a single
or multiple control signals, and a set of
operating contact terminals.
Rectifier
A rectifier will convert AC to DC Power.
Buzzer
A buzzer is a small yet efficient component
to
add sound when triggered by the
microcontroller. It has a compact 2-pin
configuration hence can be easily used on
PCBs.
53
4.10
Calculations.
4.10.1 Electronic (key components) Calculations
𝑃𝑜𝑤𝑒𝑟 = 𝐼𝑉
Where 𝐼 = 𝐶𝑢𝑟𝑟𝑒𝑛𝑡
𝑉 = 𝑉𝑜𝑙𝑡𝑎𝑔𝑒

Relay
𝑃𝑜𝑤𝑒𝑟 = 100𝑚𝐴 × 5𝑉
= 0.1 × 5
= 0.5𝑊

PIC18F46K22
𝑃𝑜𝑤𝑒𝑟 = 25𝑚𝐴 × 5𝑉
= 0.025 × 5
= 0.125𝑊
4.10.2 Worm Properties Calculations
All calculations done in this section are based on the Lewis formula for Worm gearing.
Table 15 Worm Calculation Symbols.
SYMBOL
REPRESENTATION
P
Linear pitch.
L
Lead of worm.
n
Number of threads in worm.
S
Addendum (height of worm tooth above pitch line).
d
Pitch diameter of worm.
o
Outside Diameter of worm
54
A smaller pitch worm gear reduces noise during operation and more accuracy with smaller
rotations as there is little-.
A triangular tooth worm gear is better to use than a square tooth gear because it is cheaper to
manufacture, which reduces the cost of manufacturing of the machine itself as well as helps with
maintenance.
A chosen pitch of 1.5mm is to be used to allow for an effective traversal of 1500mm on both axes.
The crab is designed to be 200mm along the X-Rail, and the uprights are to be 300mm along the
Y-Rail.
Number of threads
𝑃=
𝐿
𝑁
𝑁=
𝐿
𝑃
𝑃 = 1.5
𝐿 = 1500 + 300 = 1800
𝑁=
1800
= 1200 𝑇ℎ𝑟𝑒𝑎𝑑𝑠
1.5
Addendum of worm tooth.
𝑆 = 0.3183𝑃
𝑆 = 0.3183𝑃 = 0.3183 ∗ 1.5
𝑆 = 0.5𝑚𝑚
55
CHAPTER FIVE: ECONOMIC ANALYSIS
This chapter deals with the economic feasibility of the project. It is in this section that the designer
had to check on the monetary value of the project thereby dictating whether the project is of any
benefit relative to value and cost. In this stage there is a consideration of all the costs incurred
during the design process. Overall, the aim is to determine if the implementation of the CNC OxyAcetylene gas cutter for small to medium plate metal fabricators makes economic sense.
5.1 Bill of Electronic Units.
Table 16 Bill of Electronic Components
Component
CODE
UNIT
Qty
Total
$300
2
$600
COST
Geared
Stepper CH-4008 Basel
motor (INDUR)
Integrated circuit
PIC16F877A
$5
1
$5
Transformer
-
$12
1
$12
GREEN, $1
3
$3
(24V)
Diode
LED-RED,
YELLOW
BUZZER
-
$2
1
$2
Miscellaneous
-
$24
1
$24
Pressure Sensor
-
$3
2
$6
DRIVE
ULN2003
$150
2
$300
Limit switch
-
$10
2
$20
Total
$972
Unit Price
Total
power
circuit
components
5.2 Inclusive Bill of Quantities
Table 17 Bill of Materials
Components
Qty
56
Electronic Components
1
$972
$972
4mm sheeting
1
$50
$50
50*25*1.6mm Rectangular tube
4
$7
$28
40*40*1.6mm Square tube
1
$8
$8
30*30*1.6mm Square tube
1
$4.50
$4.50
10mm Round bar.
1
$2
$2
40*40*5mm angle iron
1
$6
$6
Fasteners
1
$15
$15
Cutting torch
1
$48
$48
20mm Round bar
1
$5
$5
Electrodes
1
$10
$10
Cutting and Grinding Disk
1
$9
$9
Paint and thinners.
1
$12
$12
Heavy duty cabling
1
$13
$13
2mm Sheeting
1
$38
$38
TOTAL
$1220.50
5.3 Bill of labor
Table 18 Bill of Labor.
Task
Personnel Rate
for Working
Total cost
work ($/hr.)
Time(hr.)
($)
Mechanical system Setup
2
5
16
160
Software and Circuiting
2
3
20
120
Calibration
1
3
5
15
Total
295
Cost of production for 1 unit.
𝐶𝑜𝑠𝑡 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 = 𝐶𝑜𝑠𝑡 𝑜𝑓 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙𝑠 + 𝐶𝑜𝑠𝑡 𝑜𝑓 𝑙𝑎𝑏𝑜𝑢𝑟
𝐶𝑜𝑠𝑡 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 = 1220.50 + 295 = $1515.5
57
Production per year is estimated to be 50 units per year.
𝐶𝑜𝑠𝑡 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 𝑝𝑒𝑟 𝑦𝑒𝑎𝑟 = 1515.50 ∗ 50 = $75775
Under mass production the cost is expected to go down by 30%
𝐶𝑜𝑠𝑡 𝑜𝑓 𝑚𝑎𝑠𝑠 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛(𝑦𝑒𝑎𝑟𝑙𝑦) = 75775 ∗ 0.7 = $53.042.50
Cost of production for 1 unit under mass production.
53042.50
𝐶𝑜𝑠𝑡 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛(1 𝑢𝑛𝑖𝑡) =
= $1060.85
50
Annual material cost
𝐴𝑛𝑛𝑢𝑎𝑙 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 𝑐𝑜𝑠𝑡 = 𝐶𝑜𝑠𝑡 𝑜𝑓 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙𝑠 ∗ 50
𝐴𝑛𝑛𝑢𝑎𝑙 𝑚𝑎𝑡𝑒𝑟𝑖𝑎𝑙 𝑐𝑜𝑠𝑡 = 1220.50 ∗ 0.7 ∗ 50 = $42717.50
Annual labor cost
𝐴𝑛𝑛𝑢𝑎𝑙 𝑙𝑎𝑏𝑜𝑟 𝑐𝑜𝑠𝑡 = 𝐶𝑜𝑠𝑡 𝑜𝑓 𝑙𝑎𝑏𝑜𝑢𝑟 ∗ 50
𝐴𝑛𝑛𝑢𝑎𝑙 𝑙𝑎𝑏𝑜𝑟 𝑐𝑜𝑠𝑡 = 295 ∗ 0.7 ∗ 50 = $10325
Total Capital investment for the year.
(with 15% inclusion labor overhead expenses)
𝑇𝐶 = (10325 ∗ 1.15) + 42717.50 = $54591.25
(Cost of investment is 40%)
𝐹𝑖𝑥𝑒𝑑 𝐶𝑜𝑠𝑡 = 0.4 ∗ 54591.25 = $28960.75
5.4 Break Even Analysis
𝐵𝑟𝑒𝑎𝑘 𝑒𝑣𝑒𝑛 =
𝑓𝑖𝑥𝑒𝑑 𝑐𝑜𝑠𝑡
𝐶𝑜𝑛𝑡𝑟𝑖𝑏𝑢𝑡𝑖𝑜𝑛 𝑚𝑎𝑟𝑔𝑖𝑛
𝐵𝑟𝑒𝑎𝑘 𝑒𝑣𝑒𝑛 =
28960.75
= 20.51
1412
58
5.5 Initial Capital Investment.
𝑇𝑜𝑡𝑎𝑙 𝐶𝑜𝑠𝑡 𝑜𝑓 𝐼𝑛𝑣𝑒𝑠𝑡𝑚𝑒𝑛𝑡 = 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 + 𝑓𝑖𝑥𝑒𝑑 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 𝑐𝑜𝑠𝑡𝑠
= 𝑣𝑎𝑟𝑖𝑎𝑏𝑙𝑒 𝑐𝑜𝑠𝑡 + 𝑜𝑣𝑒𝑟ℎ𝑒𝑎𝑑 + 𝑓𝑖𝑥𝑒𝑑 𝑐𝑜𝑠𝑡 @40%
= 54591.25 + 28960.75 = $83552
5.6 Return on Investment (ROI)
𝑅𝑂𝐼 =
𝐴𝑛𝑛𝑢𝑎𝑙 𝑃𝑟𝑜𝑓𝑖𝑡
× 100%
𝐼𝑛𝑖𝑡𝑖𝑎𝑙 𝑖𝑛𝑣𝑒𝑠𝑡𝑚𝑒𝑛𝑡
𝑅𝑂𝐼 = 0.87%
5.7 Payback Period
𝑃𝑎𝑦𝑏𝑎𝑐𝑘 𝑃𝑒𝑟𝑖𝑜𝑑 =
𝑖𝑛𝑖𝑡𝑖𝑎𝑙 𝑐𝑎𝑝𝑖𝑡𝑎𝑙 𝑟𝑒𝑞𝑢𝑖𝑟𝑒𝑑
𝑛𝑜. 𝑜𝑓 𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑠 𝑠𝑜𝑙𝑑 ∗ 𝑟𝑒𝑣𝑒𝑛𝑢𝑒 𝑝𝑒𝑟 𝑦𝑒𝑎𝑟
𝑃𝑎𝑦𝑏𝑎𝑐𝑘 𝑃𝑒𝑟𝑖𝑜𝑑 = 0.483 ∗ 12
𝑃𝑎𝑦𝑏𝑎𝑐𝑘 𝑃𝑒𝑟𝑖𝑜𝑑 = 5.796𝑚𝑜𝑛𝑡ℎ𝑠
5.8 Conclusion
This chapter has brought to the light the details of the cost and economic sense of implementing
the project, which therefore makes to possible to draw a qualitative and quantitative justification.
59
CHAPTER 6: CONCLUSION AND RECOMMENDATION.
This chapter gives the outcomes, conclusions and recommendation relative to the Development of a
CNC Profile cutter for Small to Medium Enterprises in Zimbabwe. In this chapter there is a clear outline
of the designer’s final product as well as a highlight of the areas for further development of the concept.
6.1 Physical structure.
The physical structure proved to work well after being made in the exact proposed size on the
prototype. The mechanical setup can have better railing set up to reduce noise in traversal though with
a bearing on the cost of the machine overall. Shown below is the prototype made to represent the
actual machine up 70%. The third degree of freedom which allows for the adjustment of the vertical
distance from the surface of the plate material to the cutting torch nozzle is done manually on the
prototype but the design has this done through the use of a stepper motor, coupled to a screw which
drives a nut. By simulation in solidworks using motion study the mechanical setup for the nozzle clamp
proves to work.
Fig 40 Final Mechanical Design
60
6.2 Internal calculations.
6.2.1 Profile Calculations
The software that was developed by the project developer was continuously revised and upgraded
during the course of the project development particularly the formulae used for the relevant cutting
calculations.
Profiles to be produced were tested on MATLAB, and the G-Code for the x and y plane is extracted from
the points created. Below is a snippet of the code used to draw a circle.
Fig 41 Code for Circle Cut. (With test result)
61
6.2.2 Pre-Heating.
The calculations for preheating time were finalized to be done by comparison of material being cut to
the relevant material-Heating time table material.
Upon entering the material being cut the system is designed to look for the equivalent material then
determine the heating time relevant for the material. Due to minimized access to plate metal,
experiments were only done with the common plate metal (8mm, 10mm,16mm and 20mm), and the
information collected was tabulated and the other missing values for material thickness and pre-heat
time were extracted from plotted a plotted graph. More experiments need to be done to improve on
the accuracy in determining the preheating times for various materials.
The code was developed and tested in MATLAB and it proved to work. Below is the code used to cut a
Custom Profile of ambu-bag holder. The G-Code below was generated using
The highlighted piece of Code denotes (Z-.200) a pre-heating time of 200 seconds and (Z1.20) is the code
to initiate the cutting process.
Fig 42 G Code for Ambo-Bag Holder
62
6.3 State of machine Interface.
The state of the machine is only limited to the gas pressures and no mechanical components are
designed to be monitored in any way. The designer settled on the interface shown below because it is
easy to understand as well as interact with.
Fig 43 Properties Window.
Fig 44 Properties Window-Code snippet. (Back)
63
6.4 Circuiting and Control.
The incorporation of limit switches as a safety measured proved to be important as tested on the
prototype as it proved to safeguard the mechanical components from damage by continued drive after
collision of components. The circuit shown below was developed in Tinker cad.
Fig 45 Simplified circuit layout.
The three motors are for the x, y and z traversal. The z is an up and down adjustment of the cutting
torch to accommodate different sizes of plates to be cut.
6 limit switches are used as; 4 for the x and y plane, and 2 for the z adjustment. This safety measure is
supported by an Emergency stop button that allows for instantaneous stop of the whole machine when
pressed.
For electrical safety the whole electronic system is grounded via the ground block.
64
6.4.1 Intelligent zero positioning.
Intelligent zero positioning was incorporated in the design but it’s overrides which is supposed to have
first preference when activated has not been successfully made to take precedence.
Fig 46 G-Code for Ambo-Bag Holder.
The last three lines of code represent Gas supply cut off, x, y plane zeroing and beep alarming
respectively.
65
6.5 Recommendations.
6.5.1 Mechanical setup.
There is possibility to improve on the design of the physical structure to increase/maintain robustness
while keeping cost of manufacturing low hence the price of the machine. The railing system put in place
needs further design to decrease noise during operation.
Further research can be done on the torch clamping system and z-Adjustment system in order to ensure
ease of adjustment as well as the ability to maintain set position.
There is a possibility of further development on the worm bearing sits to allow for adjustment and
alignments.
6.5.2 Monitoring, Control, Program and Circuit.
The designer recommends the use of shorter modules of code to replace the long codes which are
complex to run and require powerful Control, Arithmetic and Logic units.
The circuit developed was made to come close to Profiling equipment already in the market which
leaves possibility for further development using even better components at the same time incorporating
new components as may be relevant.
Furthermore, the designer suggests research on smoke detection technologies and the smoke levels
acceptable in Oxy-Acetylene gas cutting so as to incorporate the use of smoke detection so as to make
sure the machine is safe to use as well as to maintain cut integrity.
6.6 Conclusion.
The project proved to be a success as it was done in the stipulated time and the prototype was
developed to come as close to the intended design (60%). The project incorporated electronics and
mechanical systems which is in line with industry 4.0. Conclusively there is a clear improvement in plate
metal cutting through the use of the developed Profile Cutter.
66
BIBLIOGRAPHY
Aktan, M. E., Akkuş, N., Yılmaz, A., & Akdoğan, E. (2016). Design and Implementation of 3 Axis
CNC Router for Computer Aided Manufacturing Courses Design and Implementation of 3
Axis
CNC
Router
for
Computer
Aided
Manufacturing
Courses.
March.
https://doi.org/10.1051/matecconf/20164505002
Arduino. (2018). Arduino For Beginners What Is Arduino ? Www.Arduino.Cc, 4(2), 457–463.
Makerspaces.com%0Awww.arduino.cc
Bearing self study guide. (n.d.).
Butbro, G. C. E., & Butbro, G. C. E. (2014). HEATING NOZZLES.
Collewet, M., Sauermann, J., & Policy, E. (2019). Working hours and productivity Marion
Collewet. May. https://doi.org/10.1016/j.labeco.2017.03.006
Equipment, O. C. (n.d.). Gas cutting.
Eucheuma, A. K. (2004). No Title血清及尿液特定蛋白检测在糖尿病肾病早期诊断中的意义.
August.
Executive, S. (n.d.). Safety in gas welding , cutting and similar processes. 1–11.
FUN da MENTALS of Design. (2008).
Hardened, H. (n.d.). 2. Rust and acid-resistant fasteners 2.1. 1758–1765.
Hudedmani, M. G., Umayal, R. M., Kabberalli, S. K., & Hittalamani, R. (2017). Programmable
Logic Controller (PLC) in Automation. Advanced Journal of Graduate Research, 2(1), 37–
45. https://doi.org/10.21467/ajgr.2.1.37-45
Machines, C. N. C., Elements, M., Hydraulic, C. N. C. M., Machines, C. N. C., Systems, C. N. C.,
Feed, D., Controllers, P. L., Machines, C. N. C., Tests, A., & Machines, C. N. C. (n.d.). CNC
MAINTENANCE. I.
Manual, M. (2005). SIEMENS SINUMERIK 840D CONTROL MAINTENANCE MANUAL.
October.
Matic, N. (2003). BASIC for PIC microcontrollers.
67
Mukherjee, M., & Roy, S. (2017). Feasibility Studies and Important Aspect of Project
Management. International Journal of Advanced Engineering and Management, 2(4), 98.
https://doi.org/10.24999/ijoaem/02040025
Nozzles Cutting Nozzles Cutting Nozzles. (n.d.). 15–17.
OSHA.Gov. (2018). Identifying and Addressing Ergonomic Hazards Workbook. 3, 28.
https://www.osha.gov/sites/default/files/2018-12/fy15_sh-27643sh5_ErgonomicsWorkbook.pdf
Plotter, C. D. I. Y., Motors, S., Plotter, D. I. Y., Motors, S., Basics, T., Motors, S., Motor, S.,
Angle, C. S., Downloads, F., Peculiarity, S., & Instructables, R. (2015). workshop living food
outside DIY Plotter with Stepper Motors.
Resource, L. (n.d.). Basic gas welding and cutting.
Sam, G. (2012). Chapter 3 – Research Methodology and Research Method. Research Methodology
and Research Method, May.
Stepper Motor. (n.d.).
Supply, L., Supply, M., Sensors, H., Decoder, Q., & Feedback, E. (2004). Servo and Motor
Controller Description : The servo motor controller drives three R / C servomotors and one
brushless DC motor . All four motors are controlled by PWM signals sent from a PIC 18F252
micro- controller . The PWM signal to the brushless motor .
To, A. N. I. (n.d.). AN INTRODUCTION TO OXY / ACETYLENE WELDING AND CUTTNG.
TorchandNozzle.pdf. (n.d.).
Victor, A. (2011). Kinetics of Oxyfuel Gas Cutting of Steels. XXXIII(2), 183–188.
(https://www.twi-global.com/technical-knowledge/job-knowledge/oxyfuel-cutting-process-andfuel-gases-049)
(https://www.engineeringtoolbox.com/identifying-colors-materials-transported-piping-systemsd_1596.html)
(https://www.thomasnet.com/articles/machinery-tools-supplies/rack-and-pinion-gears/)
68
(M Budimir, 2017)
(https://www.atlantadrives.com/RPS.htm)
(https://www.elprocus.com/stepper-motor-types-advantages-applications/)
(https://circuitdigest.com/article/servo-motor-working-and-basics)
(https://www.amci.com/industrial-automation-resources/plc-automation-tutorials/what-plc/)
(https://www.elprocus.com/stepper-motor-types-advantages-applications/)
69
Appendix
Appendix A: Bottom rail traversal.
Appendix B: Material seat.
70
Appendix C: Interface Box
Appendix D: Cutting torch clamp setup.
71
Appendix E: Gantt Chart
PROJECT GANTT CHART
Topic Development
12
1
Literature Review
85
21
Material Research
15
20
Results Analysis
Design Testing
9
15
2
1
Final Presenation
72