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Welding Automation - Robotic welding
General remarks
Prepared by: DSc Dževad Hadžihafizović (DEng)
Sarajevo 202
3
Through Arm TA3 Gun
Panasonic
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Guide to Welding Automation
From proper robotic weld cell design to choosing the right gun, many factors play a role in
optimizing a robotic welding system.
Robotic welding tips
A robotic welding system can offer companies a competitive advantage over those that have
not made the shift to welding automation.
There are several steps manufacturers can take — from choosing the right system to proper
weld cell design and operator training — to optimize results and help ensure maximum ROI
from the investment.
In this guide to welding automation, learn more about:
1. Benefits of robotic welding
2. Types of welding robots
3. Choosing a robotic gun and nozzle
4. Robotic weld cell design
5. Operator training
6. Best practices for welding automation
7. Benefits of robotic welding
Automated welding is especially well-suited for operations that produce highly repeatable
parts and have low variability in what they are making. The change can help companies
increase productivity, more aggressively and accurately bid work, and identify inefficiencies
elsewhere in the manufacturing process.
Before automating your welding operation, read this article to learn about four common
challenges to address.
Key benefits manufacturers see with welding automation:
Eliminate variation: The main goal of automated welding is eliminating variation. This
allows operations to reduce costs and produce a higher-quality product. Adding an
automated welding system doesn’t just help increase welding throughput, it also
helps identify variation elsewhere in the production line. Think of the robot as a
constant — it will always perform the same work repeatedly. If there are problems
with the way the pieces are brought together, it can help operations identify
inefficiencies upstream. Advanced features like touch sensing, vision systems and
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through-arc-seam tracking can help overcome some part variation but can also add
complexity, cycle time and cost to the system and operation.
Address a labor shortage: Many manufacturing operations struggle to find skilled
welders. A move to automation can help ease this labor crunch and allow operators
to produce more in the same amount of time.
Reduce waste and rework: Automated systems create noticeably less spatter than a
manual welder, and the process can be continuously refined to the point where
spatter is almost eliminated altogether. Anyone who is spending time to manually
grind a part after the weld to remove spatter is performing rework. That’s an
expensive factor that can be greatly reduced with automated welding. It’s also a cost
that many operations overlook.
Increase productivity: A general ratio to use for automated welding compared to
manual welding is three to one: If an operator can make 100 parts per shift with
manual welding, that same operator overseeing a robot can make 300 parts per shift.
Efficiency helps create growth in the operation, allowing companies to do more work,
bid more work and get more work.
Types of welding robots
Robotic welding options are available in pre-engineered cells and custom-designed systems.
Once a company decides to invest in automation, determining the right option hinges on
several factors, including the space available, throughput goals, part repeatability and cost.
Pre-engineered robotic welding systems can be dropped into existing workflows and put into
operation with training and much of the basic tooling that manual welders are already using.
These cells are designed for welding specific parts in a certain size range. Among their
benefits are easy and fast installation and a much lower first cost. However, pre-engineered
robotic welding cells do have limitations regarding the type and size of parts that can be
welded. Part size is often the key determining factor when choosing between the two
systems.
If there isn’t a pre-engineered weld cell available to fit the parts — perhaps there is a reach
or weight capacity issue — then a custom robotic weld cell is the better option. Custom cells
have a higher initial cost and typically a longer lead time for design and installation, but the
upside is that they can be customized to meet specific needs.
When installing either type of robotic weld cell, the system integrator should be involved in
planning and testing to ensure cell layout is optimized for the application.
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Choosing a robotic gun and nozzle
The right welding gun is a critical factor that can help reduce or eliminate the sources of
common problems in the weld cell. Gun choice should not be an afterthought; welding guns
must have proper access and be able to maneuver around fixturing in the cell.
Robotic welding systems are available in two styles: through-arm or conventional. Through-
arm systems are gaining popularity, and most through-arm robots allow for mounting either
type of gun — providing more options and flexibility depending upon the needs of the
application.
As the name suggests, the power cable assembly of a through-arm MIG gun runs through
the arm of the robot as opposed to over the top of it like in a conventional gun. Because of
this design, the through-arm gun style is often more durable since the power cable is
protected. However, because conventional guns can be used on either type of system — a
through-arm or a conventional robot — they can sometimes offer greater flexibility and can
be used with more robot makes and models. Consider which type of gun provides the best
access to the welds when making the selection.
With conventional robotic welding systems especially, proper cable management is
important. Once the hardware is installed and the system is set up — but before full
production begins — be sure to do a test run or two through the welding sequence to
determine how the gun cable moves and if it gets caught on tooling.
Another choice in selecting a gun is air-cooled versus water-cooled. This essentially comes
down to the required duty cycle. The base material thickness, weld length and wire size all
help determine the necessary duty cycle. Water-cooled guns are typically used in
manufacturing heavy equipment and in the case of long cycle times and large wire
diameters.
Once the system type and gun are chosen, it’s all about proper fit and function of the gun.
It’s critical to ensure the robot arm can access all the welds — ideally in one position with
one neck if possible. If not, different neck sizes, lengths and angles — and even custom
necks — as well as different consumables or mounting arms can be used to improve weld
access.
The choice of nozzle is another important consideration since it can greatly hinder or
improve access to the weld in a robotic cell. If a standard nozzle is not providing the
necessary access, consider making a change. Nozzles are available in varying diameters,
lengths and tapers to improve joint access. While many companies like to choose a nozzle
with the smallest outside diameter available, it may be necessary to size the nozzle up to
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avoid spatter buildup and loss of shielding gas coverage. A nozzle with a 5/8-inch bore or
larger is recommended because it allows the most access.
Robotic weld cell design
Think of weld cell layout as the footprint for the entire process. Poor cell layout can create a
bottleneck or result in parts not being properly welded. These problems cost time and money
in the long term.
When considering proper layout for a robotic weld cell, gun and consumable selection, robot
reach, parts flow in and out of the cell, and weld sequencing are all important.
Key considerations for proper weld cell layout:
Robot reach: It’s critical to match the size of the part being welded with the reach of
the robot. A small robot welding on a very large part won’t work well, and a large
robot shouldn’t be welding on a very small part. The robot must have the capability
and position to reach all the areas on the part that require welding. If there is a weld
on the edge of the reach envelope, for example, it might force a company to sacrifice
optimal gun angle or work angle to reach that weld. This can impact weld quality,
resulting in potential rework and added costs. It can also lead to premature gun or
cable failure, if the robot is constantly trying to access a weld that isn’t accessible in
the configuration. Many robotic welding cells mount the robot on a riser for better
access to the part. Pay attention to proper riser height to optimize the access of the
arm to the welds. Also keep in mind that weld gun type (if it’s thru-arm vs.
conventional) and neck angle can affect overall robot reach.
Size and weight capacity: To ensure proper operation, the size and weight capacity
of the positioners in the robotic weld cell must factor in not only the weight of the part,
but also the weight of the tooling. Undersizing the positioner or weight capacity of the
cell is a common mistake. To address this, design the cell for the heaviest part to be
welded. Consider the project scope to ensure the welding system always has the
capacity to handle the heaviest part in the operation.
Material flow: The flow of material in and out of the weld cell, in addition to the
sequencing of the welding process, are key in determining the right layout and
positioning. Understand the material flow to the robot, how the material will be
presented to the robot, and then how that welded component will be removed from
the cell and moved to the next step in the operation. The weld sequence should be
planned in advance to ensure the robot can reach all the welds with the gun
configuration being used.
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Test it with modeling: Software programs that allow virtual modeling or simulation of
the weld cell provide the ability to test the many factors involved in proper robotic
weld cell layout — from gun and nozzle choice to material flow. Take the time to
simulate the weld cell layout and welding process during development. This helps
determine which product and positions are needed — and helps avoid issues that
could arise later once the weld cell is installed and running. In modeling, consider the
components, gun, positioner, tooling, arm movements and the part itself. All these
pieces must fit together and work properly to ensure the desired results. The beauty
of offline programming and 3D modeling is that these components and factors can be
tested virtually, without wasting materials or consumables. It’s better to prepare and
prevent problems — rather than face repairs later.
Best practices for welding automation
Gaining the desired results from welding automation doesn’t happen by chance. It is
important to follow best practices throughout the process to gain the best efficiencies and a
desirable return on the investment. Consider these five robotic welding best practices to
optimize results:
Manage workflow
The most efficiently programmed robotic welding system means nothing if the parts it needs
to weld don’t reach or leave the cell in a consistent manner. Bottlenecks upstream or
downstream can negate the benefits of automation. Companies should always look carefully
at the steps involved with bringing the parts to the robotic welding cell and determine the
best course of action for handling them after the robot finishes welding. In some cases, it
may be necessary to reconfigure an existing operation or change the way parts are
fabricated upstream and completed downstream (e.g., finishing, painting, etc.). Companies
may also need to assess the way employees supply parts to the robot to ensure they can
match its cycle time. The goal when establishing a good workflow is to eliminate any non-
value-added activities including unnecessary transporting, lifting or handling of parts.
Omitting these activities can be as simple as changing the way an employee removes the
parts from the tooling or minimizing the distance they walk to place them on the pallet.
Pay attention to part design and fit-up
Designing parts up front is critical, as is ensuring proper part fit-up. Complex parts or those
with large gaps or fit-up or access challenges do not lend themselves well to robotic welding.
These parts are best left to an operator who can weld manually. Make certain that parts
intended for the robotic system are simple and repeatable. If there is a mature part that was
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originally welded manually, look for ways to change the part design to make it easier and
faster to weld with a robotic welding system while still preserving its function. For parts that
are new to automation, look for ways to build efficiencies into the design from the ground up.
A careful assessment of a part’s blueprint or electronic CAD drawing is a good start. In
addition to ensuring proper part fit-up when first implementing automation, it’s also critical to
assess it in the days, weeks and months following. Normal wear that occurs on a die, for
example, can lead to slight variations in the parts that it produces and affect the way the
parts fit together. Ultimately, if a company doesn’t take the time to address poor part fit-up, it
can lead to poor weld quality and/or overwelding — sources of unnecessary costs.
Use appropriate welding cell tooling
Using weld cell tooling suited to the volume and variation of the parts being produced is
essential to ensuring good quality and high productivity. In addition to securing the parts so
the robotic system can execute consistent welds, the proper tooling can also have a
measurable impact on the comfort and efficiency of operators overseeing the loading and
unloading of parts. Job shops and small manufacturers tend to have a low volume and high
mixture of parts, which typically means that tooling with basic manual clamps will be
adequate. For companies that weld a higher volume, lower variety of parts, more
sophisticated tooling with automatic clamping capabilities can bring significant benefits.
Automatic clamping can minimize downtime for manually clamping what could be thousands
of parts over a relatively short period of time, and it minimizes fatigue and ergonomic
problems for operators that can result in potential mistakes.
Implement weld management program
Weld management programs are an excellent way to get results from a robotic welding
system. These programs allow companies to track the parameters of individual welds,
determine the cause of weld defects and identify general inefficiencies in order to rectify
those problems and optimize the process for quality and productivity. Most often — and
producing the most effective results — weld management programs are integrated into the
power source. In some cases, companies can utilize this software by way of third-party
integration. The basic goal of any weld management program is to provide actionable data
— information that can help the company predict and rectify potential problems that could
cause downtime and added costs. Additionally, weld data management can track
consumable usage so companies can implement changeovers during routine pauses in
production and help companies address overwelding, which adds costs.
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Don’t neglect maintenance
Implementing a preventive maintenance program is among the easiest and most important
best practices to protect the investment in welding automation. These programs should
cover the robot and the robotic MIG gun, consumables, cables and peripherals. Scheduling
time to check connections, clean fixturing (to prevent debris that may affect part fit-up) and
confirm tool center point, for instance, helps ensure that the system continues to operate
within its proper parameters. Usually, it’s possible to schedule maintenance during routine
pauses in production.
Optimize results with welding automation
Implementing welding automation can be a daunting task, especially for first-time
purchasers. From justifying the expenditure to determining space requirements for the
robotic welding cell and ensuring parts are suitable for the operation, every detail is critical.
When done properly, these steps can lead to drastic improvements in productivity, quality
and cost savings compared to manual welding. Following some key best practices can go far
in establishing high weld quality and productivity, as well as a solid return on the investment
in welding automation.
K-zell Metals Diversifies with Pre-Engineered Robotic Welding Cells; Achieves Faster
Part Start-up, Increased Throughput, Production Efficiencies
At a time when manufacturers are looking for new ways to diversify and compete against
global competition, K-zell Metals, Inc. of Phoenix has been proactive in anticipating changes
in the market through process improvement. The specialty fabrication and contract
manufacturing business was started in 1986 by Don Kammerzell, a metallurgical engineer
with more than 40 years experience in steel fabrication.
“About ten years ago, we started getting involved in military work, and rapidly noticed that
our business model was changing from being the traditional job shop into a contract
manufacturing facility,” says Kammerzel. “As we looked at the work that was out there, we
saw that there was a need for more precise assemblies in the work that we were doing. We
found that if we combined a laser, CNC press brakes and a robotic welding cell, we could be
much more competitive in the marketplace. The combined precision of the laser and CNC
press brakes allowed us to fixture our parts properly, so robotic welding made a lot of
sense.”
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Through the addition of two Miller PerformArc™ pre-engineered robotic weld cells, K-zell
was able to substantially increase productivity (by more than 20 percent), reduce set-up time
and find new efficiencies in its welding processes — even on relatively short production runs.
A modular design allowed each system to be quickly dropped into the flow of the shop floor,
and features such as offline programming have helped the company quickly take on new
work with minimal start-up time.
Implementing a Robotic Welding Solution
As Kammerzell puts it, “I’m really not afraid of too many metals.” K-zell’s global customer
base requires the company to be well versed in everything from mild steels and HSLAs to
stainless and aluminum — the company also does a sizable amount of work with silicon
bronze. Much of the work put through its robotic cells is parts for military and commercial
products, ranging from basic mild carbon steel to 4130 chrome-moly. Run sizes range as
high as 4,000 to 5,000 parts. Precision is critical as many of the parts K-zell fabricates are
sub-assemblies that must fit perfectly into larger structures. In selecting a robotic welding
solution, K-zell needed a system suitable for varying run sizes that could be programmed
quickly and efficiently, and could also handle varying thicknesses and types of alloys. The
two PerformArc cells currently at work in the company’s plant are the PA 1100 FW and PA
550 HW with advanced 350-amp TAWERS™ robotic welding systems from Panasonic.
(Miller and Panasonic Welding Systems Co., Ltd., entered into a strategic partnership in
2010 to form a new business unit within Miller — Miller Welding Automation — designed to
deliver these products to market as a complete automated welding system).
“What we really found was that there was a cost advantage to selecting a pre-engineered
system because it was already done,” says Kammerzell. “We didn’t need someone to go out
and find all of the components and put it all together. And no matter what we looked at, this
was the fastest way to get us in the business.”
Pre-engineered weld cells can be dropped into existing workflows and put into operation with
much of the basic tooling your manual welders are already using. With three mechanical
engineers on staff, K-zell builds all of its own quick-change tooling and fixtures, a feature that
helps the company adjust to product runs of all sizes and quantities. Each cell features a
fully welded frame and comes pre-wired and pre-assembled (the PA 1100 FW comes in
three sections that can be joined with quick assembly and connection capabilities). The cell
is completely integrated and can be easily relocated by disconnecting the utilities and
moving it to a new location.
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Automated welding best practices
An automated welding system is a significant investment, and one component that can
substantially impact weld quality and productivity in automated welding applications is the
layout and performance of the secondary circuit.
The weld cables and circuit in a robotic weld cell are exposed to spatter, corrosion and heat
over time, causing them to wear. This can affect the welding parameters in the cell —
ultimately impacting weld quality and productivity.
Choosing a welding power source with secondary compensation technology can help
operations avoid the issues that stem from wear to the weld cables and circuit — and keep
robotic weld cells performing as they should.
How does the secondary circuit wear?
The secondary circuit refers to the welding circuit — the part of the system that carries the
welding current from the power source to the weld joint. To reach the weld joint, the current
must travel through the weld cable and the work clamp attaching the cable to the tooling or
workpiece. If there is any fixturing holding the workpiece in place, the weld circuit travels
through this as well. All of these components make up the secondary circuit.
With normal use over time, these components can wear and degrade. For example, weld
spatter buildup reduces the contact area, which affects weld current flow. The heat of the
welding process can also cause weld cables to break down over time, lessening the
connection in the circuit.
These wear factors contribute to increased resistance in the secondary circuit, which
significantly impacts weld quality. As resistance increases, it reduces the voltage being
delivered to the weld — and voltage is a critical parameter in welding. If resistance increases
enough, it can cause the cell to fall outside of its programmed parameters. Any changes that
occur in the secondary circuit affect the weld, and the more factors that change, the greater
the impact.
Resistance in the secondary circuit is less critical in semi-automated welding applications
since the operator is controlling the weld and can easily watch the puddle and make
adjustments. It’s a more important factor in robotic MIG welding applications that use
advanced arcs, which require the welding power source to constantly monitor what’s
happening in the weld and adjust parameters as necessary.
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The more resistance that’s built up in the weld circuit, the more difficult it is for the power
source to accurately monitor what’s happening during the weld. Without good feedback on
what’s happening, the power source can’t make proper adjustments to maintain a good arc.
Start with proper weld cell design
The design and layout of the secondary circuit within the robotic weld cell is a key factor that
impacts performance and weld quality.
As pulsed MIG welding processes have advanced, another welding innovation developed:
the voltage sensing lead. This lead monitors weld voltage at the arc outside of the weld
cables. Previously, the power source would only monitor the weld voltage output at the
welder — before the weld current traveled through the secondary circuit. The voltage
sensing lead allows the system to measure the voltage closer to the arc, so the power
source can make better adjustments to maintain weld quality.
Proper weld cell layout and design helps ensure the best positioning of the voltage sensing
lead. Because of its important role in the cell, the lead should be placed as close to the
welding arc as possible without being in the return current path. The lead can often be bolted
to the welding fixture. If the lead is placed improperly in the return current path, interaction
between the welding circuits will affect voltage drop in the workpiece. Voltage feedback to
the power source won’t be correct, resulting in poor arc starts and arc quality.
Cables also must be sized and routed properly to ensure quality performance. Weld cables
should be sized for peak amperage rating when pulsed MIG welding, and cables should be
kept as short as possible with no extra coils or loops to minimize inductance and resistance.
In addition, minimizing the welding circuit loop helps prevent extreme voltage drops that
produce poor welding characteristics.
Utilize a secondary compensation circuit
While proper cell layout is important, the secondary circuit will deteriorate with use no matter
how well-designed the weld cell is. This is where secondary compensation circuit technology
can help.
The secondary compensation circuit, a technology available in advanced MIG welding power
sources from Miller, measures the resistance of the entire secondary circuit and the voltage
drop that is occurring.
Lets operators see the health of the secondary circuit, a measurement they can use to
determine if anything in the cell needs to be changed or fixed.
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Automatically compensates to offset voltage drops in the weld circuit, to ensure the cell isn’t
welding outside of specified parameters.
In high-volume manufacturing facilities with dozens or even hundreds of robotic welding
arcs, secondary compensation circuit technology can save significant time and money in
improper welds and rework.
Regular maintenance is critical
Performing regular inspection and maintenance of the welding circuit and its various
components plays an important role in the continued optimization of the weld cell. Be sure to
have a preventive maintenance program in place to inspect components frequently and
repair them as needed.
While this can require building some planned downtime into the welding operation,
neglecting or skipping regular inspection and maintenance can cost much more in time and
money in the long run.
Consider installing a reamer, a peripheral that can automate part of weld cell maintenance to
help maximize performance. A reamer is a nozzle cleaning station that can be integrated into
a robotic weld cell and programmed to work during pauses in the welding cycle. Reamers
remove the spatter from inside the MIG gun’s front-end consumables that accumulates
during welding. Keeping consumables free of spatter helps extend consumable life and
reduces downtime for maintenance. Using a reamer also helps prevent loss of shielding gas
coverage, an issue that can lead to costly rework.
For the best results, place the reamer close to the robot so it’s easily accessible, and
program the system to use it in between cycles, such as during part loading or tool transfer.
Investing in a reamer can make the robotic welding process more efficient and productive.
Improve robotic welding performance
Following key best practices for weld cell design, including placement of the voltage sensing
lead and layout of the secondary circuit, promotes arc quality and performance in robotic
welding applications. In addition, choosing a power source with secondary compensation
technology helps welding operations reduce or eliminate costly issues related to wear in the
secondary circuit — so they can maintain parameters and keep the weld cell optimized.
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Robotic welding system