Economics of cutting processes
& Cutting tools
Made by :
Ziad Ayman Abdelaziz Hendy (200073)
Abdallah Amr Abdel Gawad Farag (200104)
Amr Asaad Mohamed Mowafy (200115)
Ibrahim Wael Ibrahim ElTayeb (200003)
Hossam Mohamed Abuelsoud (200054)
Mohamed Ahmed Ali Mohamed (200124)
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introduction
we all know that machining process is important in manufacturing but
it has many disadvantages such as the waste of materials and time
consuming, so we work hard to solve these problems to achieve the
highest benefit from machining
machining time must be shortened.
today the golden goal of industries is to manufacture the product at a
faster rate but at minimal cost and that too without sacrificing product
quality because of course you know the quality of the finished product
is so important for the consumer. As long as conventional machining is
utilized, in order to achieve the first requirement (faster production
rate), the cutting speed and feed rate must be increased. However, this
may lead to reduced cutting tool life due to faster wear rate and higher
heat generation.
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Overall machining time and cost
In today’s competitive market, time is so important as
money. Basically, overall or total machining time (Tm) is the
summation of three different time elements closely
associated with the machining. These three elements
include—actual cutting time (Tc), total tool changing time (Tct)
and other handling or idle time (Ti). Beside these three-time
elements, cost of cutting tool is also needed to incorporate for
any optimization. All these time or cost elements, except
handling time, are affected by the variation of cutting speed
and feed rate as explained below. Mathematically, total time
for machining (Tm) can be expressed as:
T =T +T +T
m
c
ct
i
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What is actual cutting time (Tc)?
cutting time is the time taken during actual material removal
process, i.e., from the beginning of chip production to the end
for uninterrupted machining. In case of any planned or
unplanned stoppage in cutting, the pause period will not
come under this time element. so, increase in cutting speed
and feed rate will result in reduction of actual cutting time as
material removal rate (MRR) will increase. Hence, cost related
to cutting time will decrease if speed or feed is increased. The
adjacent diagram depicts how cost associated with the actual
cutting time varies with speed or feed employed during
machining.
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Tooling cost – cost of the cutting tool
Although it is not directly related to cutting speed, tool cost
also helps in overall machining economy. If higher speed or
feed is employed, the result will be faster tool wear and
reduced tool life, which will generally multiply the funds as
more tools are needed for cutting same length. The adjacent
diagram shows how tool cost varies with the speed or feed
employed during machining time.
Tooling cost can be calculated by multiplying the price of
single cutting tool (K2) with the amount of tool required.
amount of tool needed can again be determined by dividing
actual machining time by tool life. Mathematically, tooling
cost can be determined by the formula:
Tooling cost = (TcTL)×K2
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perfect Cutting Speed for Maximum
Efficiency:
The perfect speed to achieve the maximum efficiency, i.e., the
maximum gain rate, can be also found out without much difficulty.
Of course, for doing this, a closed form expression for vopt will not
be possible, and the numerical or graphical ways have to be
employed. If S is the amount received per piece, then the
expression for the gain rate is –
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OPTIMIZATION OF CUTTING
PARAMETERS IN TURNING PROCESS
the main cutting force during turning is of great importance as it helps
in setting the suitable cutting parameters before machining starts,
optimization of cutting parameters is one of the most important
elements in any process planning of metal parts as economy of
machining operation plays a main role in gaining emulative advantage.
This report presents an experimental study of main cutting force in
turning of AISI 1040 steel and developing a model of the main cutting
force during turning using Response surface Methodology (RSM) as well
as optimization of machining parameters using Genetic Algorithm (GA).
The second order empirical model of the main cutting force in
conditions of machining parameters are developed based on
experimental results. The experimentation is carried out considering
three machining parameters: cutting speed, feed rate and depth of cut
as independent variables and the main cutting force as the response
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variable. The former model is validated against new set of experimental
values using Mean Absolute Percent Error (MAPE) method. The Genetic
Algorithm approach is also used to optimize the cutting parameters to
keep the main cutting force to a minimum.
Cutting tools
Cutting Tool Materials provides an in-depth discussion of various
cutting tool materials and their properties. Effective cutting tools
combine a handful of valuable properties: hardness, toughness, and
wear resistance. Cutting material selection is based primarily on the
workpiece material, machine tool, and cutting operation, and involves
an appropriate balance of properties. Available cutting tool materials
have expanded and improved over the years, ranging from the very
tough and inexpensive to the very hard and expensive. Other tool
modifications, such as heat treatment and tool coatings, can also
improve cutting tools.
Selecting the proper cutting tool material is essential for a successful
machining operation. The tool material dictates the material removal
rate, surface finish and part quality.
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Metal-cutting tools are classified as single
point or multiple point:
A single point cutting tool can be used for increasing the size of holes,
or boring. Turning and boring are performed on lathes and boring mills.
Multiple point cutting tools have two or more cutting edges and include
milling cutters, drills, and broaches.
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Properties of cutting tool material:
1.
Hardness: The cutting tool can withstand high temperature
during the machining without any losses in cutting edges.
2.
Wear resistance: It is the tool ability of resist the wearing.
The friction due to contact between tools and work materials
during the machining operation. In this reason wear in the tool. If
tool not having the sufficient amount of wear resistance, so it will
be failing quickly. That give poor surface finish of work material.
So, the additional of Cobalt material added in the tool combination
to increase the wear resistance property.
Types of cutting tools materials:
•
•
Carbon tool Steel
High speed Steel
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•
Cemented carbide
•
Diamonds
Finding out economic condition and Gilbert’s Model
Undoubtedly the final thing is to find out the optimum
condition for either maximizing profit or minimizing time
requirement. For paper-based optimization, only cutting
velocity or speed is considered in order to keep the analytical
process less complicated. Moreover, cutting velocity is the
main parameter that affects machining performance. A
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number of constraints can be handled effectively using
computer programming-based optimization techniques.
Now there exist several objectives for optimization, among
which Gilbert’s Model (1952) for Maximum Production Rate
and Minimum Production Time are more prominent. These
models are based on the Taylor’s Tool Life equation, which
consider only cutting velocity to determine tool life.
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Reference
. Book: Metal Cutting: Theory And Practice by
A. Bhattacharya (New Central Book Agency).
. Book: Machining and Machine Tools by A. B.
Chattopadhyay (Wiley)
. journal of engineering production
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