Specialist Diploma in Robotic and Automation
Assignment
Project: Design, Build & Commission Automated
Manufacturing Equipment
Project Title - Robotic Welding for
Railing Frames
Date: 11 June 2022
This project is created solely for fulfilling the training requirements of the Specialist
Diploma in Robotic and Automation
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Specialist Diploma in Robotic and Automation
Project Information
Module
ECMF 205 : Manufacturing Equipment and Troubleshooting
Project Facilitator:
Derrick Boey
Project team:
1. Lee Meng Kong
Project Start Date:
Project End Date:
11 June 2022
Project Summary Page
Expecting increasing demand, Marcus Advance welding Pte Ltd is looking for automation
solution for fabricating a range of guard railing frames. Among the series of the fabrication
processes, from beam members preparation, cutting, grounding, fitting, welding, and
inspection, welding is identified as the “hot-spot” for automation.
We are building a feasibility study to build a robotic system that can increase our production
by 300% and improve weld quality with 0.5% rejection rate and ability to bid for high
specifications projects.
Project objectives:
1. The objective of this project is to develop a robotic welding system that will increase
the production of the handrail frames by at least 300% by the end of September 2023.
2. Reduce the cost of the product by 20% by benefiting from process
3. Reduce reliance on manual welders in tight labour supply situations by 80 % using
robotic automation.
4. Increase the quality and consistency of the final deliverable product with rejection rate
from 5% to 0.5% so as to be able to tender for higher precision, high-specification,
and higher margin projects.
5. Our Proposed system must be able to fulfill
1. High mixed, low volume
2. Product identification & tracking
3. Machine to machine communication
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1. Introduction
1.1 Background
Expecting increasing demand, a local metal structure fabrication company is looking
for automation solution for fabricating a range of guard railing frames. Among the series
of the fabrication processes, from beam members preparation, cutting, grounding,
fitting, welding, and inspection, welding is identified as the “hot-spot” for automation.
The objective is to increase the productivity by eliminating the manual welding process
(Figure 1.1) while improving welding quality.
Figure 1.1
The railing frames that the company wants to fabricate are the handrails and fences
(Figure 1.2, 1.3 & 1.4) for protecting workers and pedestrians in industrial sites and
roadsides. The volume is high, and the configuration variety is also high. In other
words, it is a high volume and high mix type of manufacturing.
Figure 1.2
Figure 1.3
Figure 1.4
1.2 Existing Problems and Challenges
The welding for connection joints of railings is considered as most time consuming task
in the whole process. Firstly, the welding path of these 3-dimensional geometric joints
are very complicated and various for different diameter of pipe combinations and angle
of the components of the joints (Figure 1.5, 1.6 & 1.7). Secondly, it demands the highest
skill of welders for these joints comparing with the typical flat, horizontal or vertical weld
joints. Under the current pandemic situations, the shortage of skillful welders poses
the challenge for the company to fulfil the production schedules.
Figure 1.5
Figure 1.6
Figure 1.7
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Hence, the objective of this project is to develop a robotic welding system to increase
the productivity of the welding process by at least 10 times as well as to improve the
quality and consistency of the weld joints by significantly reduction of reject / rework
rate.
1.3 Current Fabrication Processes
The brief fabrication steps are as follows:
a. Measure and cut beam / bar members
b. Machine and grind the joints to required geometric dimension and tolerance
c. Position be frame in a template or fixtures
d. Tack weld or fasten the beam members to hold the member in the required
positions
e. Weld the joints in full length – Targeted process for this project
f. Remove the finished frame from the welding station
1.4 Desired Specifications for the Product / Process by Robotic Welding System
a. Overall dimensions range of guard railing frames: Length 1 m to 3 m; Height:
500 mm to 1500 mm
b. Joint type: T, K or Y configurations
c. Tolerance requirement of finished frame: +/- 1 mm
d. Members diameters: 25 mm to 65 mm
e. Materials: Mild Steel, Stainless Steel, Aluminum
f. Welding processes: Arc Welding
g. Number of passes: one
h. Eliminate the tack weld work during assembly process
i. Still use manpower to load, assembly and unload of railings
j. Production volume: Over 1,000 pieces frames per month
k. Batch size: 10 to 200 pieces per batch
1.5 Key Components for the Robotic Welding System
The major components of the required robotic welding system are listed as follows:
1.
2.
3.
4.
Arc Welding System
Fixture for the Railing Frames Assembly
Robotic System
Robot Teaching and Sensing Parts
The individual key components are described in detail in subsequent sessions.
2. Arc Welding System
2.1. Available Options in Existing Market
Metal Inert Gas (MIG) or Gas Metal Arc Welding (GMAW), is a common high deposition
rate process that involves feeding a solid wire continuously toward the heated weld
joint with shielded gas to protect the molten weld pool from oxidation.
Gas Shielded Flux Cored Arc Welding (FCAW GS) is a semi-automatic arc welding
process that is similar to Metal Inert Gas (MIG) welding. FCAW GS uses a continuous
tubular cored wire (electrode) filled with flux, a constant-voltage welding power source,
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and similar equipment to MIG welding. It usually uses an external shielding gas similar
to that used by MIG welding. It is also termed as "dual shield" welding and slag is
formed after the molten pool solidifies. As such removal of the slag is required. Both
MIG and FCAW are considered as semi-automatic welding process.
Based on the above characteristics, MIG is selected as the welding process in our
robotic system because it does not produce fume and slag due to absence of flux
during welding process. MIG is one of the most popular form of welding in industrial
applications and is an easy process to integrate to a robot system. MIG welding
provides a faster process than others forms of welding, especially when roots are
incorporated. MIG are capable of:
 all -position
 adding flexibility to the welding system
 safety from dangerous fumes
 higher quality welds
 more efficient process
 In pulse mood provide lower heat input
2.2. Power Source - Rectifier or Inverter Type



350 or 400 amps DC at 100 Duty Cycle
Constant Current (CC) or Constant Voltage (CV) Type
Multi process capability
2.3. Wire Feeder

Arc voltage-controlled wire feed unit
2.4. Miscellaneous Components







Welding Torch : Robotic Torch Necks e.g..Tregaskiss G1 Style Robotic Neck
Gas : Argon or Argon CO2,
Electrode : Stainless Steel, Mild Steel, Aluminium Filler Wire
Delivery Equipment : Drum Hood, Wire Guide, Dispensing System, Wire
Straightener,
Nozzle Cleaning Station : Torch Wizard Robotic Nozzle Cleaning Station
Control Cable : Power source to Wire Feeder cable, Power Source to Work
cable
Gas Hose : Gas Delivery of Shielding Gas
Finally, total weight of welding components to be mounted on the robotic system is
estimated about 25 to 30 kg. This will be one of the factors for selection of robot
mechanism.
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3. Fixture for the Railing Frames Assembly
3.1. Available Options in Existing Market
Jigs & Fixtures are created for a purpose and that does not mean that all jigs are the
same. Progressive improvements in design always occur ahead of the traditional tools
& welding tables that many welders & toolmakers still use today. Traditionally, welders
often used jigs & fixture together with welding tables to support the workpiece and
today welding tables & fixtures also have become increasingly sophisticated.
When a fixture is used, the tool & workpiece move together & fixtures have a much
wider scope of application. So modern fixtures are suitable for all types of welding from
manual to robotic, designed that fulfil the traditional jig function as well as the function
for the whole welding process. There are 3 options of fixture / robot combination as
shown in Figure 3.1 (1 Manual Fixture + 1 Robot), 3.2 (1 Semi-Automated Fixture + 1
Robot) & 3.3 (2 Semi-Automated Fixtures + 1 Robot) below.
Figure 3.1
Figure 3.2
Figure 3.3
The best welding jigs or fixtures on the market today reduce welding time, simplify
welding jobs, streamline manufacturing processes and ultimately minimize production
costs. Modern equipment also is ergonomic & designed to minimized effort. Bottom
line when looking for an ideal welding jig or fixture platforms for welding frames or
railings is that the tool should make the job easier, quicker, as accurate as possible,
more comfortable for the person who operates the whole process & ultimately more
cost efficient.
Whether you are creating individual, custom-made products or multiple items produced
on an assembly line, fixtures & jigs are vital to their success. It does not matter which
industry is involved, what type of metal is welded or how the welding job is to be carried
out, whether welding process is manual, automated, mechanized or even Robotic, jigs
& fixture platforms are all important tools for the trade.
In the welding industries, jigs & platform fixtures are used to precisely and firmly
position parts while they are welded. Welding jigs are typically custom made, per
application. With such customization in industrial settings, jigs often come with the
followings :




It can be Manually operated, semi-automated or fully automated.
They can cost in a range of several $10's or $100's of thousands of dollars.
There will also be minimal prone to errors because the Parts are usually fed to
the jig or fix platform by a human operator. In some cases, the product are
made from tens or hundreds of different parts, yet similar parts.
They require low value added work of filling them with parts.
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In reducing labor costs and increasing quality through expertly designed tooling and
fixtures. Precision built tooling is essential to successful manufacturing. We need to
achieve the following goals:







Manpower Savings
Time Savings
Speed of Production
High Quality product
Maintaining standards & consistency
Customer satisfaction
Lucrative profit in the long run
3.2. Selection of Fixtures for Rail Welding Fixture
Therefore with all these considerations & findings, we decided to make a selection to
have 2 fixtures (Figure 3.3) for the railings with a semi-automated operations rotating
at 180 deg with precise & firmly position onto fixtures with proper manual clampings
(Figure 3.4).
Figure 3.4
Manual positioning of the precut CNC railing members of the frames or pipes onto
the fixture with preset positioning & manual clamping. The various steel members for
railings ideally should be placed on the fixture according to how wide they are. Frame
welding fixtures are available in various sizes to suit different sized frames. It should
be possible to manual clamp the horizontal members of the railing, including the
railings so that they can be positioned perfectly in the X & Y axis. Once everything is
clamped into place, the fixture can be tilted & swung into the optimum welding
position to make the procedure as quick & easy as possible.
The robot will then weld all joints on 1 side of the railings on the first fixture and once
completed, the fixture will automatically rotate 180° deg to weld on the other side of
the railings. Robot will then move to second jig fixture to weld onto the railing joints
on both sides. Simultaneously the completed welded railings on the first fixture will be
manually removed & newly installed members of the railing frames will be placed in
position to repeat the process.
Our new railing welding fixtures can reduce the welding time for railing production up
to 50% by streamlining the welding task to make the project as simple and seamless
as possible. With the new railing welding jigs & fixtures, producing railings on
stainless steel, aluminum or carbon steel has never been so fast and easy.
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In today’s welding, fixtures are suitable for all types of welding, including Robotics &
enable operators to produce top quality work more easily & more efficiently than ever
before. Good railing & frame welding fixtures are versatile, adaptable & comply with
precision requirements during production. They are also easy to maintain & safe to
use.
And finally, of course, the final programming that brings all this together. From our
point of view, this is a very promising way to simplify jigs in order to add flexibility,
reduce scrap and improve through.
4. Robotic System
4.1. Robotic System Selection Process
Among the various robotic options available (Figure 4.1), it was clear given specific
demands of welding complex joints, our needs were best served by a robot that
promised the highest degree of movement and flexibility. For this reason, we opted for
a serial articulated robot – more commonly known as a robotic arm.
Figure 4.1
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There are numerous companies that produce and sell serial articulated robots. Some
of the major players include ABB, Kuka, Fanuc, Kawasaki, Panasonic, Yaskawa.
One added advantage with these companies is that they do not simply offer a robotic
arm, they offer an entire welding package. This would be an ideal option for our
purposes as it would mean a robotic system readily configured for welding.
Kuka, for example, has a pre-configured arc welding system called KUKA ready2-arc.
This system comes as a package that includes a six-axis robot, a welding machine,
along with wire feeder and associated torch, cables and necessary adapters. Such a
package would be an ideal starting point on which to build a system tailored to our
requirements.
This is because an automated welding system is application-specific and depends on
many variables including the size and complexity of the work piece, nature of joints,
type of fixture, and so on. Additionally, a company such as Kuka produce many robots
of yarying speed, payload, size and reach. Each component within the robotic welding
system needs to be thoughtfully selected, if the system is to function as intended.
4.2. Robot Performance Parameters
Given the specific demands of the task, it was clear that the robotic arm selected
needed to meet a number of key welding parameters. In the interest of keeping things
as simple as possible, the team opted to run a solitary robotic arm. This unit
nevertheless still needed to have six degrees of freedom (DOF), at the very minimum,
in order to be up to the job of welding complex shapes.
Robot payload was deemed non-critical as the arm only needed to support the weight
of portions of welding components, which weighs 25 to 30kg. Additionally, it needed to
have an operating precision of +/- 1 mm, based on the tolerance requirements for the
finished product – a figure that is well within the operating range of a good 6-axis robot.
Given the work piece dimension of 3 x 1.5 meter, the robotic arm would require a
dexterous workspace radius of at least 2.2 m. Although the operating environment will
be sheltered, it may be subject to high levels of humidity, heat and dust typical of a
non-airconditioned metalworking and manufacturing environment in Singapore. A
suitable level of weather resistance - tolerance to dust and water-splashes – is also
required.
In terms of user-friendliness, a robotic system that was easy, or rather, easier to
program was preferable. This would reduce setup time and training needs.
Additionally, robotic arms need to be serviced so a system that offered longer
maintenance intervals would also mean reduced downtime.
4.3. Proposed Equipment Kuka KR 50 IONTEC
Based on our specific requirements, we decided on the Kuka KR 50 Iontec.
Measuring 603 mm x 480 mm x 1865 mm, and weighing 559 kg, it is not a small robot
by any means. Its 50-kg payload is sufficient in our application since the welding
equipment components needed to be carried is in the range of 25 to 30kg.
However, the team realized that, although the railing system did not make large
demands on payload, it had a huge ask in terms of reach. Many of the smaller robots
in Kuka’s lineup are perfectly up the task of welding. Many boast higher speed and
precision that would be useful in welding application. The problem with these smaller
robots is, as you guessed, reduced reach. Most top out at 1.8m. Between 1.8m and
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Specialist Diploma in Robotic and Automation
2.4m, there really are not a lot of options. In fact, we could not find one. The next best
suitable robot was the one we selected, due to it wide 2.5m reach.
Apart from offering the required dexterous workspace, the KR 50 Iontec is a six-DOF
robot that can be outfitted with a foundry option that allows it to operate in hot
environments of up to 55͑° C. The robot also features waterproof and dustproof in-line
wrist and protected motors.
Another reason for going with Kuka was its advanced suite of welding-specific software
that promised greater weld accuracy and more intuitive and simpler robot teaching.
For example, the list of options included:
KUKA Arc Tech welding module
KUKA SeamTech - uses triangulation of laser sensors to detect and track weld seam.
KUKA TouchSense - uses torch or wire tip to detect and compensate for deviations
in workpiece from master contour.
KUKA ArcSense - uses laser to sense for distortion and variances in tolerance and
compensates in real time.
KUKA ready2_pilot – uses a 6D mouse attached to effector to allow robot teaching
by manually moving the robot along desired path instead of programming.
5. Robot Teaching and Sensing Parts
5.1. Software and Sensors selection
Online v.s. Offline: Based on the background setting provided, the Teach & Play
method is not applicable as it is a high mix, high vol product type.
Our robot requirements are to locate T, K, Y joint (Figure 5.1) based on the CAD data
and then use appropriate sensors to counter the effects of variation in the seam caused
by distortion, uneven heat transfer, variability of gap size, staggered edges, etc.
Figure 5.1
Computer vision is required to quickly match the fence type and numbers to joints type
within the fence. Thus, Seam Tracking is recommended as it can perform automatic
vertical and horizontal correction of the path and have a lower programming time.
We will use adaptive control as the welding robot should have the capabilities to
address two main aspects. The first aspect is the control of the end effector’s path and
orientation so that the robot is able to track the joint to be welded with high precision.
The second one is the control of welding process variables in real time, for example,
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Specialist Diploma in Robotic and Automation
the control of the amount of metal deposition into the joint as per the dimensions. Our
design solution should also be able to table CAD/CAM drawing and start training.
5.2. Setup of sensors and system
Figure 5.2
The schematic in Figure 5.2 from Kuka serves the basic configuration of the design
installation. The robot arm is connected to the robot controller CS4. Its sensors, in our
case laser vision SeamTech and 3D camera sensor will connect to EtherCat / Switcher
that is connected back to the PC / laptop.
For the system to work, system software Kuka System Work 8.2, EtherCat software
and Kuka visual work 4 will be installed in the PC. To further meet our requirement
active compliance tool and software such as Kuka SeamTech will be installed.
To auto identify product type and joint type, 3D depth camera Intel RealSense (stereo)
custom written python code to identify image and shapes will be integrated with
RobotMaster that serve as the operator software.
5.3. System Operation
Basic Operator knowledge includes:
 CAD/CAM drawing reading and modification
 Welding processes
 RobotMaster training
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Software process is shown in Figure 5.3 below:
Figure 5.3
Operation process
1. 3D camera will be mounted on the ceiling with workpiece identification by image
and joint type by segmentation.
2. The 3D image will match CAD / CAM drawing joint type.
3. Operator will mark weld points over the CAD drawing in robot software.
4. Robot program will optimize welding path in simulation.
5. Operator will hold robot weld gun to calibrate the exact laser guide distance over
the workpiece.
6. Robot is calibrated and repetitive workpiece will enjoy auto compensation in
mounting distortion.
6. Overall Robotic Welding System Design
After finalization of 4 key components of robotic welding system, the next step is to
streamline the overall working process of the system. Basically, it can be divided into 3
categories:
1. Robot programming process
2. Railing material preparation process
3. Welding process
The above processes can be consolidated into the flow chart as follows:
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Project approach/methodology
We will adopt the waterfall model, which is a linear project management approach, where
stakeholder and customer requirements are gathered at the beginning of the project, and then
a sequential project plan is created to accommodate those requirements. The waterfall model
is so named because each phase of the project cascades into the next, following steadily down
like a waterfall.
List of milestones
Milestones
Description
Planned Date
1
Project approval
1 Mar 2021
2
Completion of overall design
14 Jun 2021
3
Arrival of all key components
9 Aug 2021
4
Completion of testing and commissioning
20 Sep 2021
5
Robot start production
27 Sep 2021
Deliverables and requirements
1. Robotic welding system of the following specification:
a.
Overall dimensions range of guard railing frames: Length 1 m to 3 m; Height: 500 mm
to 1500 mm
b.
Joint type: T, K or Y configurations
c.
Tolerance requirement of finished frame: +/- 1 mm
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Specialist Diploma in Robotic and Automation
d.
Members diameters: 25 mm to 65 mm
e.
Materials: Mild Steel, Stainless Steel, Aluminum
f.
Welding processes: Arc Welding
g.
Number of passes: one
h.
Production volume: Over 300 pieces frames per month (3 times of current)
i.
Batch size: 10 to 200 pieces per batch
2. Operation manual
3. Maintenance manual
4. Annual preventive maintenance program
Acceptance test and criteria
Automation dept. will be signing off the acceptance test and the new robot system is able to
run in parallel with the existing manual process and collected data shows the new system
achieving 300% productivity improvement defined in the project goals.
Work breakdown structure
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WBS Dictionary
ID
Activity
Resources
Total Cost
6.1
Overall Design of robotic system
Design Engineer
$20k
6.3
Installation of robotic system
Project Engineer
$40k
6.4
Testing and commissioning
Testing Engineer
$10k
Activity list
1. Upload CAD file of railing into robotic system
2. Install and clamp rail tubes into jig
3. Robot teaching - scan and collect ACTUAL coordinates of rail and weld points
4. Synchronise the scanned data with CAD data - adjust/compensate for discrepancies
between CAD coordinates and actual coordinates
5. Dry run (and if no issues, perform welding)
6. Welding
( For duration of activities , please refer to Gantt Chart)
Project schedule
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7. Discussion
After this robotic welding system is implemented, we expect the following immediate
benefits and advantages:
1.
2.
3.
4.
The skilled welder shortage problem can be solved.
The quality of weld joints can be significantly improved and kept consistent.
The production duration can be easily extended from current daytime only to 24 hours.
Once the program and welding parameters have been established for particular type
of railings, they can be easily stored and kept for future similar production process so
that additional operation cost can be reduced.
Of course, there are also some limitation or concerns of our robotic welding system in this
stage:
1. It is still necessary to rely on labour for assembly, loading and unloading the steel
material at fixture. If the time of this operation is greater than the duration of robot
welding of one set of railing, it will cause the bottle neck of the whole process and
hinder the productivity of the whole robotic system.
2. There will be potential obstruction of fixture frame to trajectory of robot welding path
after it rotates 180 degree.
3. As the robot arm is selected based on 1.5m x 3m railing components, it will be
limitation for us to extend for larger size structure.
4. The system can only deal with the single pass welding of weld joint. If our tubular
section of thicker wall is needed in future so that more than 1 pass of weld is required,
the system may not be easy to enhance.
5. The robotic system will create new risk in the working environment of which we would
not face in majority of manual working process. Hence, a thorough study of risk
assessment must be carried out in order to ensure all workers will be working in safe
environment. For examples, some safety sensors to ensure that the robot will not
move to the area where workers are carrying out the railing assembly work at fixture.
Suitable shielding partition to block the welding radiation but not obstruct the
movement of robot, etc.
For further development in future, we should explore more options of fixture available in
the market and then further develop the full automation of loading, assembly and
unloading railing components.
We will also keep an eye on the trend of machine learning technology (or AI) together with
the sensor and camera technology. Once they become mature and cost affordable, we
can apply these elements so that the robotic system can identify the location and
geometry of each weld joint by itself. If successful, we can even reduce the time and cost
in the programing and CAD process.
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8. Conclusion
Our robotic welding system in this stage shall be capable to meet the objective and
specification of this project since the structural requirement of weld joint of railing is not
as stringent as the structural steelwork. But it is still expected that further fine tune or
modification of our system will be necessary when some minor hidden problems are
exposed during the production process.
References:
1. Arc Welding System
https://www.robots.com/applications/mig-welding
2. Fixture for the Railing Frames Assembly
https://youtu.be/dIZpdjlsGiI
https://youtu.be/5Rj0aQBBtZ0
https://www.forsteramerica.com/products/
3. Robotic System
KUKA robots for arc welding | KUKA AG
https://www.kuka.com/en-us/industries/metal-industry/kuka-robots-for-arc-welding
KR IONTEC | KUKA AG
https://www.kuka.com/en-us/products/robotics-systems/industrial-robots/kr-iontec
4. Robot Teaching and Sensing Parts
https://issuu.com/kopel/docs/robotmaster_v6_-_tutorials
Depth camera
https://www.intel.com/content/dam/support/us/en/documents/emergingtechnologies/intel-realsense-technology/Intel-RealSense-D400-Series-Datasheet.pdf
Seamtech Tracking
http://supportwop.com/IntegrationRobot/content/5Applicatifs_metiers_KST/SeamTech/KST_SeamTech_Tracking_20_en.pdf
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