MIG Welding Basics: Techniques and Tips for Success

It’s important for new welding operators to establish proper MIG techniques in order to achieve good weld quality and maximize productivity. Safety best practices are key, too. It’s just as important, however, for experienced welding operators to remember the fundamentals in order to avoid picking up habits that could negatively impact welding performance.

From employing safe ergonomics to using the proper MIG gun angle and welding travel speeds and more, good MIG welding techniques provide good results. Here are some tips.

Proper ergonomics

A comfortable welding operator is a safer one. Proper ergonomics should be among the first fundamentals to establish in the MIG welding process (along with proper personal protective equipment, of course). Ergonomics can be defined, simply, as the “study of how equipment can be arranged so that people can do work or other activities more efficiently and comfortably.”¹ The importance of ergonomics for a welding operator can have far reaching effects. A workplace environment or task that causes a welding operator to repetitively reach, move, grip or twist in an unnatural way, or even stay in a static posture for an extended period of time without rest, can lead to repetitive stress injuries with life-long impacts.

Proper ergonomics can protect welding operators from injury while also improving productivity and profitability of a welding operation by reducing employee absences.

Some ergonomic solutions that can improve safety and productivity include:

1. Using a MIG welding gun with a locking trigger to prevent “trigger finger,” which is caused by applying pressure to a trigger for an extended period of time.

2. Using a MIG gun with a rotatable neck to help the welding operator move more easily to reach a joint with less strain on the body.

3. Keeping hands at elbow height or slightly below while welding.

4. Positioning work between the welding operator’s waist and shoulders to ensure welding is being completed in as close of a neutral posture as possible.

5. Reducing the stress of repetitive motions by using MIG guns with rear swivels on the power cable.

6. Using different combinations of handle angles, neck angles and neck lengths to keep the welding operator’s wrist in a neutral position.

Proper work angle, travel angle and movement

The proper welding gun or work angle, travel angle and MIG welding technique depends on the thickness of the base metal and the welding position. Work angle is “the relationship between the axis of the electrode to the welders work piece.” Travel angle refers to employing either a push angle (pointing in the direction of travel) or a drag angle, when the electrode is pointed opposite of travel. (AWS Welding HandBook 9th Edition Vol 2 Page 184)².

Flat position
When welding a butt joint (a 180-degree joint), the welding operator should hold the MIG welding gun at a 90-degree work angle (in relation to the work piece). Depending on the thickness of the base material, push the gun at a torch angle between 5 and 15 degrees. If the joint requires multiple passes, a slight side-to-side motion, holding at the toes of the weld, can help fill the joint and minimize the risk of undercutting.

For T-joints, hold the gun at a work angle of 45 degrees and for lap joints a work angle around 60 degrees is appropriate (15 degrees up from 45 degrees).

Horizontal position
In the horizontal welding position, a work angle of 30 to 60 degrees works well, depending on the type and size of the joint. The goal is to prevent the filler metal from sagging or rolling over on the bottom side of the weld joint.

Vertical position
For a T-joint, the welding operator should use a work angle of slightly greater than 90 degrees to the joint. Note, when welding in the vertical position, there are two methods: weld in an uphill or a downhill direction.

The uphill direction is used for thicker material when greater penetration is needed. A good technique for a T-Joint is call the upside-down V. This technique assures the welding operator maintains consistency and penetration in the root of the weld, which is where the two pieces meet. This area is the most important part of the weld.The other technique is downhill welding. This is popular in the pipe industry for open root welding and when welding thin gauge materials.

Overhead position
The goal when MIG welding overhead is to keep the molten weld metal in the joint. That requires faster travel speeds and work angles will be dictated by the location of the joint. Maintain a 5 to 15 degree travel angle. Any weaving technique should be kept to a minimum to keep the bead small. To gain the most success, the welding operator should be in comfortable position in relation to both the work angle and the direction of travel.

Wire stickout and contact-tip-to-work distance
Wire stickout will change depending on the welding process. For short-circuit welding, it is good to maintain a 1/4- to 3/8-inch wire stickout to reduce spatter. Any longer of a stickout will increase electrical resistance, lowering the current and leading to spatter. When using a spray arc transfer, the stickout should be around 3/4 inch.

Proper contact-tip-to-work distance (CTWD) is also important to gaining good welding performance. The CTWD used depends on the welding process. For example, when using a spray transfer mode, if the CTWD is too short, it can cause burnbacks. If it’s too long, it could cause weld discontinuities due to lack of proper shielding gas coverage. For spray transfer welding, a 3/4-inch CTWD is appropriate, while 3/8 to 1/2 inch would work for short circuit welding.

Welding travel speed
Welding travel speed influences the shape and quality of a weld bead to a significant degree. Welding operators will need to determine the correct welding travel speed by judging the weld pool size in relation to the joint thickness.

With a welding travel speed that’s too fast, welding operators will end up with a narrow, convex bead with inadequate tie-in at the toes of the weld. Insufficient penetration, distortion and an inconsistent weld bead are caused by traveling too fast. Traveling too slow can introduce too much heat into the weld, resulting in an excessively wide weld bead. On thinner material, it may also cause burn through.

Final thoughts

When it comes to improving safety and productivity, it’s up to the experienced veteran welding operator as much as the new welding to establish and follow proper MIG technique right. Doing so helps avoid potential injury and unnecessary downtime for reworking poor quality welds. Keep in mind that it never hurts for welding operators to refresh their knowledge about MIG welding and it’s in their and the company’s best interest to continue following best practices.

1. Collins Dictionary, “ergonomics,” collinsdictionary.com/dictionary/english/ergonomics.
2. Welding Handbook, 9th ed., Vol. 2, Welding Processes, Part 1. American Welding Society: Miami, Fla., p. 184. 

Implementing Robotic Welding: What to Know to Be Successful

The potential advantages of robotic welding are well known — increased productivity, improved quality and greater cost savings compared to semi-automatic welding. But the question is: How do companies best implement this technology to gain these benefits? And how can they ensure a quick return on the investment (ROI)? Simply stated, planning.

More preparation upfront helps minimize the cost and time for correcting errors in the robotic welding system once it has gone into production. From the welding power source to the robot or weld process to the gun and consumables, each component should be thoroughly researched to make sure it is feasible to operate in the weld cell — not just on paper, but in reality.

Take advantage of turnkey integrators who run their own process and capability studies. They can provide useful double checks to a plan and often conduct reach studies that model the weld tooling and workpiece. These mock up how the robot would weld in the finished system to test the gun reach and the overall efficiency of the process.

Also remember, success in robotic welding is as much a matter of doing the right thing as it is avoiding pitfalls that could hinder the efficiency of the operation.

Budgeting and ROI

With planning comes budgeting. A robotic welding cell may be installed on time, produce good weld quality and meet cycle time, but if the implementation and use of the system is over budget it will be an uphill battle to gain a good ROI.

Consider the associated goals to help establish a feasible ROI. For example, a company with the goal of producing 1000 parts a day needs to determine how much it can make from those parts. From there, it would subtract the cost of utilities and labor, along with the cost to make the product and the cost of raw materials, to determine a budget on equipment costs that would make the company profitable. If this equipment will only be used for 5 years, the company may need a quicker ROI than if it’s planning to use the robotic welding system for 10 years or more.

Companies can make the most of their budget by considering equipment that could be reused. This can cut down on the investment in the long run. Robots can have an extensive life if maintained well, allowing them to be re-purposed from project to project. The same holds true with welding power sources and nozzle cleaning stations.

Ultimately, ROI depends on the company and what practices it follows for making profit. Some may be able to allow the equipment to take 18 months or more to pay for itself if the company plans on re-using or re-purposing the welding robots on multiple platforms over the next 10 years. Others may stand by the goal of a one-year ROI, which is common.

Effective training

Proper training is important for keeping a robotic welding system running successfully and profitably in the long term. Robot integrators and other equipment manufacturers often offer training as part of the implementation process. This training provides welding operators with a knowledge of robotic welding in general, as well as providing the information they need to operate the robot effectively for the application at hand. A well-trained operator will also be able to determine ways to maximize the efficiency of the robotic weld cell. They do this by troubleshooting and resolving issues quickly, keeping the robot online and supporting greater productivity and cost savings.

Likewise, train welding operators to implement PM for the robotic gas metal arc welding (GMAW) gun to gain longer life, reduce downtime and achieve more arc-on time. Regularly check that the gun connections, consumables and power pin are secure. Look for any signs of power cable wear and replace if necessary.Training geared toward the preventive maintenance (PM) of a robotic welding system and the weld cell is also key. For example, spatter build-up on the robotic welding gun can cause grounding issues and build-up on tooling may lead to dimensional movement of the steel from cycle to cycle. The latter can block the datum placements causing gun reach issues. In a worse-case scenario, spatter builds up on equipment over time, creating solid formations that are difficult to remove and prevent the re-use of the equipment. To avoid these problems, train operators to follow a regular cleaning schedule for the weld cell and the equipment.

Avoid common mistakes

There are several common mistakes that can negatively affect productivity and quality in a robotic welding system. Knowing how to avoid these can help companies make the most out of the equipment and gain greater success. Consider the following:

1. Implementing the wrong equipment in a robotic welding cell can lead to spending more money than is required. Be sure the power source, robotic GMAW gun and consumables are rated for the application. Doing so helps minimize the risk of premature equipment failures that can lead to unplanned downtime and costly equipment replacement. For example, if a company selects an air-cooled system, but actually requires a water-cooled system for the application, it could incur unnecessary costs to repair or upgrade a failed robotic GMAW gun system that cannot handle the heat.

2. Underutilizing the robotic welding system can prevent companies from realizing their full productivity potential. Robotic welding systems should be programmed to maximize the arc-on time during the weld process cycle. In some cases, it may be possible to have fewer robots that weld for slightly longer cycles. This helps drop the initial implementation costs.

Take this example. A company has four robots in cell welding at 30 inches per minute with a cycle time of 60 seconds. These robots are inefficient since they are only welding half of the cycle time. That could be due to the positioner rotating for weld access, too slow of robot air cut movements, poor welding angles or other limiting factors. In this scenario, the total length of completed welds for all four robots is 60 inches (30 in. / min. x 1 min. / 60 seconds x 30 seconds of welding per robot = 15 inches of weld per robot).

An alternative here is to keep the cycle time at 60 seconds and drop down to three robots by improving items like the weld angles, creating quicker air cuts between welds, utilizing gun reaming during positioner movements and more. Now with improvements, the robots could weld at an average of 35 inches per minute for 35 seconds each cycle. That provides an average of 20 inches of weld per cycle per robot, allowing for the same total of 60 inches of weld with one less robot.

3. Underutilizing available labor can also hinder productivity. While companies should take care not to overload operators, it’s important to balance manpower in robotic welding process so that employees are efficient and busy at the same time. If an operator is idle waiting for the weld cycle to complete, there could be room for process improvements by allocating labor to other activities near the weld cell.

4. Poor tooling design can impede quality. Thoroughly plan the tooling design and understand how the parts being welded will impact it. Different parts and materials react differently to heat and may draw, flex or bend during the welding process. Factor in how much heat a given weld sequence generates. The tooling will have to be designed with these in mind. If possible, design tooling to permit welding in the flat or horizontal position with appropriate robotic GMAW gun access. This allows for faster and more consistent results. Finally, remember, less expensive tooling may be attractive when looking at upfront costs, but it can be a pitfall later if it doesn’t meet the demands of the job.

5. Overlooking activities outside the robotic weld cell can be detrimental. Plan for part inspection and cosmetic rework, as well as the final stages of palletizing the product if that is part of the operation. Some of these processes can be automated or manual labor driven. These are key stages in a robotic welding operation that can quickly become bottlenecks that cause the entire process to slow down. These bottlenecks can also add unplanned manpower or equipment costs, which can become expensive.

Final thoughts

Remember that no plan for welding automation can be successful without a good schedule for its implementation. Being thorough is more important than being fast. Set realistic goals for completing the installation of the robotic weld cells and don’t rush or over-complicate the process. For first-time investors in robotic welding starting small can also help ensure greater success.

Once the robotic weld cell or cells begin operating, keep in mind that the startup may not be perfect. There may be adjustments required to optimize performance to gain the best productivity and quality.

Preventive Maintenance for Reamers, Accessories and Other Peripherals

From reamers or nozzle cleaning stations to wire cutters and anti-spatter sprayers, welding peripherals and accessories can contribute significantly to the success of a robotic welding operation. In addition to improving weld quality, they can also help companies maintain high levels of productivity.

Reamers, in particular, are most prevalent in automotive manufacturing, where uptime and quality are critical. This peripheral cleans the welding consumables — for example, welding nozzles and gas diffusers — free of spatter, and most automotive welding operations rely on the process after virtually every weld cycle. Other industries, such as heavy equipment manufacturing, also employ reamers and other peripherals in their robotic welding operations, as do some general manufacturers.

It’s not by chance that peripherals work the way they do. Like any equipment, caring for them with routine preventive maintenance (PM) is important to gaining optimal performance and longevity.

PM tips for reamers and accessories

A reamer requires regular attention since it operates frequently during the weld cycles. Its job is important though, as it performs essential welding nozzle cleaning that helps keep the robotic welding cell up and running and quality on par. With the PM for this equipment also comes PM for its associated accessories: the lubricator, cutter blades and anti-spatter sprayer. All require varying levels of PM activities — some daily, weekly, monthly or yearly.

In addition to inspecting the consumables for wear and replacing as needed, follow this PM routine on a daily basis:

1. Check that the consumables are aligned properly to the reamer. This helps ensure that the jaws of the reamer clamp the nozzle to the V-block correctly and that the consumables are lined up concentric and parallel to the cutter blade for optimal spatter cleaning.
    
2. Clean the spindle cover shroud free of spatter and also clean the clamp jaw and V-block surfaces to gain proper nozzle alignment. Use a brush or compressed air. Look for any signs of wear on these components.
    
3. Make sure the air lines connected to the reamer are free of frays, as leaks will prevent the reamer from receiving enough air to remove spatter properly. Look for any damage to the interface cable.
    
4. Check the oil level in the lubricator reserve — the reamer motor depends on a consistent supply of oil. Also check the level of anti-spatter liquid in the anti-spatter sprayer. Fill as needed. An option to simplify PM of the anti-spatter sprayer is to employ a multi-feed system that allows 5- or 55-gallon drums of anti-spatter liquid to be connected to a manifold system to feed multiple sprayers on multiple reamers. This eliminates the need for daily reservoir fills.

On a weekly basis, continue to examine the integrity of the consumables and follow these guidelines:

1. Inspect the cutter blades for dullness, clogging and possible breakage, replacing as necessary. Note the service life of cutter blades will vary based on the application.
    
2. Again, check that the lubricator is working properly with the right level of oil, and clean or replace the filter as needed.
    
3. Check the LEDs to ensure reamer and controller communication, and wipe the nozzle detect proximity sensors clean so they can function properly.
    
4. Look over the spray head on the anti-spatter sprayer to be sure it is delivering a normal amount of liquid spray. Clean the head and adjust as necessary.

Monthly PM for reamers and accessories requires less steps but is more intensive. It may require scheduling a time off cycle to complete.

1. Check that the belt tension lock screw and bolt are securely tightened.
    
2. Examine the spindle unit for wear, replacing if necessary, and inspect the solenoids, spooling them to prevent leaks and to make sure they are operating properly.

Lastly, on an annual basis:

1. Inspect the drive belt for signs of fraying and replace as necessary.
    
2. Replace the spindle cap seal and repair any visible damage.
    
3. Perform a complete cleanup of the reamer and anti-spatter sprayer.

While it may seem time-consuming to implement these PM measures, they can typically be completed during routine pauses in production. More intensive activities can be scheduled so as to prevent interruption to production. Ultimately, the PM is time well spent and can help protect the investment in the reamer and its accessories.

PM tips for wire cutters

Wire cutters are increasingly being used in automotive and other manufacturing operations. This equipment is integrated into a reamer configuration and used in conjunction with a wire brake on the robotic MIG gun. The wire brake prevents the welding wire from moving, while the wire cutter cuts it at a set distance. This allows for a consistent wire stickout so the robot can touch sense and track the joint before welding. The results are more accurate weld placement and smooth arc starting. 

PM for wire cutters is relatively simple.

1. On a daily basis, check the airlines and interface cable for leaks or frays. Be sure that the solenoid valve is providing air to the system.
    
2. Weekly, check that the cutter blades are sharp enough to cut the wire. Look for signs of dullness, looseness or breaks. Replace as needed. Also empty the wire catcher basket.
    
3. Quarterly, apply general purpose grease (NLGI Grade 1-1) through the grease fittings on the sides of the main body of the wire cutter. This helps lubricate the sliding surfaces of the equipment.

The value of peripherals

Peripherals like reamers with anti-spatter sprayers and wire cutters can help companies realize a greater return on their investment in a robotic welding system. They aid in high weld quality, minimize rework and help meet productivity goals. Train welding operators to follow recommended PM activities as a part of a routine care of the weld cell. The time and cost to care for them properly will be small in comparison to the improvements they can provide to the bottom line. 

Robotic Welding: Troubleshooting FAQs

Every operation wants to avoid downtime, as well as the cost for troubleshooting problems in the robotic welding cell. But sometimes issues happen, whether it’s due to equipment failure or human error.

Since most companies invest in welding automation to boost throughput and profitability, getting a robotic welding cell back online as quickly as possible is critical to production and the bottom line. The first things to consider are whether anything has changed in the welding process or with the equipment, or if the operator has recently reprogrammed the robot. In many cases, evaluating the most recently changed variable can help you pinpoint an issue’s cause.

After that, analyzing some of the most frequent sources of trouble in the robotic weld cell can help you get to the root of the problem sooner. Consider these five common issues and ways to fix them.

Q: What are causes of poor consumable performance?

A: The material being welded and the parameters being used affect welding consumables’ longevity. But if it seems that nozzles, contact tips, diffusers or liners aren’t lasting their typical life or are performing poorly, there could be several causes.

Check all connections between welding consumables and tighten them as needed. A loose connection increases electrical resistance and generates additional heat, which can shorten consumable life and cause poor performance. It’s especially important to ensure consumables are properly tightened when the application involves long welds or welds on thick materials, since any rework due to quality issues will cost more time and money in these cases.

Common contact tips issues, such as burnback, are often caused by a too-short liner. Always follow the manufacturer’s instructions for liner trimming and installation, and use a liner gauge to confirm length when possible. Over time, debris and spatter buildup inside the liner can contribute to shortened contact tip life. It’s important to create a schedule for changing liners, just as you would for other consumables.

If you’re frequently experiencing weld defects like porosity or lack of penetration, this can also stem from a consumables issue. Make sure the contact tip and nozzle are free of debris and replace them as needed.

Q: What causes poor wire feeding?

A: Erratic or poor wire feeding in robotic welding is a common issue that can ultimately result in poor weld quality. Poor wire feeding can have many causes.

Cutting a liner too short is particularly problematic when robotic welding with smaller diameter wires, which have less column strength.

Extreme articulation of the robotic MIG gun can also lead to poor wire feeding. Program the robotic MIG gun cable to stay as straight as possible. The robot may not weld quite as fast, but proper gun orientation helps minimize downtime for feeding problems.

Excessive conduit length and multiple bends or junctions can cause poor wire feeding as well. With the drive rolls open, you should be able to pull the wire through the contact tip by hand with minimal effort. If you need to pull with two hands or put your bodyweight into the process, that indicates interference with the wire path between the wire drum and the contact tip. Check for bends tighter than 90 degrees, multiple junctions between sections of conduit or worn conduit sections that can increase drag on the wire. Ideally, the conduit between the drum and the wire feeder should be less than 20 feet, with no junctions or tight bends.

Improper drive roll selection and tension setting can also lead to poor wire feeding. Consider the size and type of wire being used and match that to the drive rolls. Inspect drive rolls for signs of wear and replace them as necessary.

Q: Why is the cable prematurely failing?

A: Whether you have a through-arm robotic welding system, where the cable is routed through the robotic arm, or a standard over-the-arm robotic welding system, premature power cable failure can happen. A power cable that becomes kinked or worn can fail and short-out against the robot casting, leading to costly repairs.

To help prevent premature cable wear, consider the programmed path of the robot as well as the power cable’s length. If the robot’s movements cause the cable to bunch up or kink, it can cause the power cable to fail. If the power cable rubs against tooling or catches on components during the programmed cycle, this can also cause premature failure.
Proper cable length is also important. A cable that is too short or too long can be stretched beyond capacity or be prone to kinking.

Q: Why is there a problem with tool center point (TCP)?

A: In robotic welding, TCP refers to the location of the end of the welding wire with respect to the end of the robot arm. If you are experiencing inconsistent welds or welds that are off-location, this may stem from a problem with TCP.

If the robotic MIG gun neck is bent or damaged during a collision in the weld cell, this can result in TCP issues. Use a neck-checking fixture or neck alignment tool to help ensure proper angle of the neck bend. Also, be sure the neck and consumables are installed and torqued properly. Failure to do so may affect TCP. 

However, a problem with off-location welds isn’t always caused by TCP issues. Improper fixturing or part variations may also be the root cause. If a TCP check using the robotic program turns up with no issues, a part or position variation is the likely culprit.

Q: How do I fix poorly performing peripherals?

A: Companies often implement peripherals, such as reamers or nozzle cleaning stations, to optimize robotic welding performance and get more life out of consumables. But a problem with the reamer can cause spatter buildup on the consumables.

Reamers can perform poorly for three common reasons:

1. Improperly taught position of the robotic MIG gun nozzle in relation to the reamer. This position should be concentric to the cutting blade on the reamer at the proper insertion depth to ensure thorough cleaning of the nozzle.
   
2. Too much or too little anti-spatter spray in the wrong location. Anti-spatter spray should cover the inside of the nozzle and the outside should be covered within 3/4 of an inch from the bottom of the nozzle. Spray for only a half-second. In production, the anti-spatter should evaporate on contact with a hot nozzle — if your nozzle is dripping, you’re spraying too long.
   
3. Using the wrong cutting blade or improper insertion depth will not allow for proper removal of accumulated welding spatter.

Correcting common problems

Problems in the robotic welding cell can be as simple as a loose contact tip or more complex like incorrect TCP. Understanding the steps for proper troubleshooting helps narrow down potential causes and can prevent replacement of components that don’t need replacing — so the operation can save money and quickly get back to producing quality parts.

Learn more from the Tregaskiss Troubleshooting Guide.

7 Tips for Implementing a Robotic Welding Cell

Implementing robotic welding can significantly improve a manufacturing operation’s productivity and weld quality, but what are the robotic welding basics you should know to be successful? From choosing the right welding wire to establishing proper tool center point (TCP), many variables play a role in optimizing robotic welding cells to produce the best results.

Shaving even a few seconds from each weld cycle can save time and money. Minimizing the unplanned downtime for adjustments or repairs in the weld cell can also have a substantial impact on your bottom line.

Success with robotic welding requires a well-researched plan. The more planning done upfront, the less time and money you could spend later making fixes and process improvements.

Learning some basic tips for setting up a robotic weld cell can help to establish a repeatable and consistent process — so your operation can produce quality welds, reduce rework and maximize its investment.

Tip No. 1: Use proper weld settings

Proper weld settings for the application are based on factors including wire size and material thickness. Some welding power sources offer technology that allows welders to simply input the wire size and material thickness, and the machine will suggest recommended parameters for the application.

Without this technology, finding the correct parameters can involve a bit of trial and error. Sometimes the robot manufacturer, welding power source manufacturer or system integrator can assist in choosing and testing specific materials to provide a starting point for the proper welding parameters. Utilize the experience of these partners to help you arrive at the best starting point and be prepared for the future.

Tip No. 2: Choose the right wire

The choice of filler metal for a robotic welding system can significantly impact productivity, weld quality and the overall investment. Selecting the right wire for a robotic application is typically based on the material type and thickness, as well as the expected outcomes for the welded part. Welding equipment and filler metal manufacturers often offer charts to help you match a welding wire to your process needs.  

While solid wire has been the industry standard in robotic welding for many years, metal-cored wire is an alternative that can offer productivity and quality improvements in some applications, particularly in the manufacture of heavy equipment and automotive exhaust, chassis and wheels. However, be aware that each wire type offers pros and cons for certain applications, so it’s important to research the type that is best suited to your application.

Tip No. 3: Consider the gun and consumables

Robotic welding guns and consumables, including the nozzle, contact tip and gas diffuser, have a huge impact on performance in a robotic weld cell. The right combination can reduce unplanned downtime and improve overall efficiency of the cell.

Be sure the welding gun is rated with enough duty cycle and amperage for the application. To avoid excessive wear and premature failure, the gun should not rub against any part of the system or another robot in applications where multiple robots are being used on the same tooling.

Robotic welding systems typically operate at higher duty cycles than semi-automatic welding applications, and they may utilize transfer modes that are especially harsh on consumables. Consider using heavy-duty consumables that are more heat-resistant than standard-duty consumables. Chrome zirconium contact tips or tips specifically designed for pulsed welding processes are good options.

In addition, ensure all consumables are properly installed and tightened. Improper or loose connections produce more electrical resistance and heat that causes faster consumable wear with premature failures. Another common failure in robotic welding is improper liner installation. Always follow the manufacturer’s directions for liner installation and cut length. A liner that is cut too short can cause premature failures of other consumables in the system.

Tip No. 4: Reduce cable wear

Make sure there is good cable grounding in the weld cell to help prevent potential problems as the cell ages. There are two cables running from the welding power source; one is attached to the wire feeder and the other is grounded to the tooling. Often, these cables are long and run from the shop floor to an elevated platform or through wire trays. The section of cable running up the robot or running to a positioner will constantly move — causing greater wear over time.

Using a junction with high-flex ground cable at the base of the robot or the workpiece can save time and money in downtime and repair. With this solution, there is only a 6-foot section of cable to replace when it wears out, rather than replacing possibly 50 feet or more of ground cable that runs all the way back to the power source. However, keep in mind you should have as few breaks or junctions in the grounding cable as possible to maintain a better electrical connection.

When mounting a ground cable to the welding workpiece, it can be helpful to use copper anti-seize lubricant, sometimes referred to as copper slop. This supports the transfer of electrical current and helps prevent the mounting point from fusing together or deteriorating over time. The lubricant can be useful in all areas where there may be grounding current running through pins or any other semi-permanent contact points.

Proper cable management for the guns can also greatly extend cable life. The more any cable bends and flexes, the more wear and tear will occur — ultimately shortening cable life due to high heat and resistance. Work to minimize cable bending and flexing in your robotic process and tooling design.

Tip No. 5: Establish TCP

For repeatable and consistent weld quality, it’s critical to establish and maintain proper TCP. Welding operations can set their own standards for the acceptable amount of TCP drift, depending on the application and type of weld being made. When considering the tolerance of TCP variation, an acceptable starting point can be half the thickness of the wire diameter.

Many robotic systems today can use touch-sensing features to monitor TCP and determine how far it has moved from the original programmed settings. If a gun is determined to be out of the acceptable TCP range, the gun neck can be removed and recalibrated offline to factory specifications with a neck straightening fixture. Some systems also provide the capability to adjust TCP automatically with the robot. A third option is to leave the gun in place and adjust the robot teaching to accommodate the modified TCP. This is the most time-consuming solution and, therefore, often not acceptable for the manufacturing operation. It also requires the need to reprogram the robot if new factory specifications for TCP or a new neck are ever put into place — which is why this method is typically the last resort.

Set a schedule or standard for checking TCP, whether it’s every weld cycle, once a shift or even every time the torch goes through a reamer cycle. The length of time between checks is a matter of preference and weighing your priorities. It can be time-consuming to check every weld cycle, but this can save money in lost scrap and rework if a problem is found before welding occurs.

Tip No. 6: Program the robot path  

The initial programming of the robot’s welding path can also involve much trial and error. When programming the path, consider the application, material type, welding process being used and gap size that must be filled. The weld quality and amount of spatter created are also impacted by the travel angle and whether it’s a pull or push weld. It can take time to dial in the correct path to achieve the desired quality.

After setting the home positions in the robotic program, it’s recommended to have the robot move to perch points or ready-to-enter points that are safely away from any potential collision points, so the system can move quickly with air cut moves to and from these points.

When programming the robot to move to a weld, it’s common to set the approach point just above the weld start location. Have the robot approach the start location at a slower and safer speed with the arc on. This approach position provides a good lead-in and typically won’t require adjustment unless the weld is relocated. Some robotic welding systems include technology that aids in setting the initial robot path.  

The robot’s welding location can play a role in premature failure of the gun. If the robot is welding with a lot of flex in the gun at a tight angle, this can cause it to fail much faster. Minimizing robot axes five and six during welding can help extend gun life by reducing wear.

Tip No. 7: Ensure proper fit-up

Proper part fit-up in the upstream process is critical to consistent weld quality and robot path programming. Inconsistent fit-up or large gaps between the parts lead to weld quality issues such as burn-through, poor penetration, porosity and others — resulting in additional unplanned downtime to deal with these problems. Large gaps between the parts may also require double weld passes, adding to cycle times.

Closing

From wire and consumable selection to proper cable management and TCP, many variables play a role in weld quality and ultimately, the success of your robotic welding system. Careful planning at the start of the process and continued monitoring of these key factors helps optimize performance — so you can get the most from your robotic welding investment.

MIG Welding FAQs Answered

MIG welding, like any other process, takes practice to refine your skills. For those newer to it, building some basic knowledge can take your MIG welding operation to the next level. Or if you’ve been welding for a while, it never hurts to have a refresher. Consider these frequently asked questions, along with their answers, as welding tips to guide you.

1. What drive roll should I use, and how do I set the tension?

The welding wire size and type determines the drive roll to obtain smooth, consistent wire feeding. There are three common choices: V-knurled, U-groove and V-groove.

Pair gas- or self-shielded wires with V-knurled drive rolls. These welding wires are soft due to their tubular design; the teeth on the drive rolls grab the wire and pushes it through the feeder drive. Use U-groove drive rolls for feeding aluminum welding wire. The shape of these drive rolls prevents marring of this soft wire. V-groove drive rolls are the best choice for solid wire.

To set the drive roll tension, first release the drive rolls. Slowly increase the tension while feeding the wire into your gloved hand. Continue until the tension is one half-turn past wire slippage. During the process, keep the gun as straight as possible to avoid kinking the cable, which could lead to poor wire feeding.

2. How do I get the best results from my MIG welding wire?

MIG welding wires vary in their characteristics and welding parameters. Always check the wire’s spec or data sheet to determine what amperage, voltage and wire feed speed the filler metal manufacturer recommends. Spec sheets are typically shipped with the welding wire, or you can download them from the filler metal manufacturer’s website. These sheets also provide shielding gas requirements, as well as contact-to-work distance (CTWD) and welding wire extension or stickout recommendations.

Stickout is especially important to gaining optimal results. Too long of a stickout creates a colder weld, drops the amperage and reduces joint penetration. A shorter stickout usually provides a more stable arc and better low-voltage penetration. As a rule of thumb, the best stickout length is the shortest one allowed for the application.

Proper welding wire storage and handling is also critical to good MIG welding results. Keep the spool in a dry area, as moisture can damage the wire and potentially lead to hydrogen-induced cracking. Use gloves when handling the wire to protect it from moisture or dirt from your hands. If the wire is on the wire feeder, but not in use, cover the spool or remove it and place it in a clean plastic bag.

3. What contact recess should I use?

Contact tip recess, or the position of the contact tip within the MIG welding nozzle, depends on the welding mode, welding wire, application and shielding gas you are using. Generally, as the current increases, the contact tip recess should also increase. Here are some recommendations.

A 1/8- or 1/4-inch recess works well for welding at greater than 200 amps in spray or high-current pulse welding, when using a metal-cored wire and argon-rich shielding gases. You can use a wire stickout of 1/2 to 3/4 inches in these scenarios.

Keep your contact tip flush with the nozzle when welding less than 200 amps in short circuit or low-current pulse modes. A 1/4- to 1/2-inch wire stickout is recommended. At 1/4-inch stick out in short circuit, specifically, allows you to weld on thinner materials with less risk of burn-through or warping.

When welding hard-to-reach joints and at less than 200 amps, you can extend the contact tip 1/8 inch from the nozzle and use a 1/4-inch stickout. This configuration allows greater access to difficult-to-access joints, and works well for short circuit or low-current pulse modes.

Remember, proper recess is key to reducing the opportunity for porosity, insufficient penetration and burn-through and to minimizing spatter.

4. What shielding gas is best for my MIG welding wire?

The shielding gas you choose depends on the wire and the application. CO2 provides good penetration when welding thicker materials, and you can use it on thinner materials since it tends to run cooler, which decreases the risk of burn-through. For even more weld penetration and high productivity, use a 75 percent argon/25 percent CO2 gas mix. This combination also produces less spatter than CO2 so there is less post-weld cleanup.

Use 100 percent CO2 shielding gas or a 75 percent CO2/25 percent argon mix in combination with a carbon steel solid wire. Aluminum welding wire requires argon shielding gas, while stainless steel wire works best with a tri-mix of helium, argon and CO2. Always reference the wire’s spec sheet for recommendations.

5. What is the best way to control my weld puddle?

For all positions, it is best to keep the welding wire directed toward the leading edge of the weld puddle. If you are welding out of position (vertical, horizontal or overhead), keeping the weld puddle small provides the best control. Also use the smallest wire diameter that will still fill the weld joint sufficiently.

You can gauge heat input and travel speed by the weld bead produced and adjust accordingly to gain better control and better results. For example, if you produce a weld bead that is too tall and skinny, it indicates that the heat input is too low and/or your travel speed is too fast. A flat, wide bead suggests too high of heat input and/or too slow of travel speeds. Adjust your parameters and technique accordingly to achieve the ideal weld, which has a slight crown that just touches the metal around it.

These answers to frequently asked questions only touch on a few of the best practices for MIG welding. Always follow your welding procedures to gain optimal results. Also, many welding equipment and wire manufacturers have technical support numbers to contact with questions. They can serve as an excellent resource for you.

5 Common Failures in Robotic Welding and How to Prevent Them

Is your robotic welding operation costing time and money for problems like burnbacks, premature contact tip wear, loss of tool center point (TCP) or other issues? These common failures in robotic welding can be costly, resulting in downtime and unplanned part replacement.

Even issues that seem minor, such as the wire sticking to the contact tip and forcing tip replacement, can cost thousands of dollars per day when you consider lost consumables, cell downtime and labor costs for changeover. Beyond the time and money spent on minor issues, there’s also the risk of catastrophic failure that could short out the robot or damage system electronics — potentially costing tens of thousands of dollars.

Avoiding common failures is often a matter of proper weld cell setup and robot maintenance, in addition to following some best practices for consumable installation. Operator training is also critical in preventing common failures in robotic welding. 

Failure No. 1: Burnback and contact tip wear

One of the most common failures in a robotic weld cell is burnback and premature contact tip wear. The top cause of burnback is an improperly trimmed gun liner. When a liner is too short, it won’t seat in the retaining head properly, causing burnback.

To avoid this problem, follow the manufacturer’s recommendations for proper liner trimming. It’s also helpful to choose a high-quality liner designed for accurate liner trimming and installation.

Burnback is one cause of premature contact tip wear, but wear can also result from other factors. Using low-quality wire with a lot of cast can be another cause, as it quickly wears out the contact tip compared to using a better-quality, straighter wire. Drive rolls that are too tight can also cause wire cast issues that wear the contact tip faster.

Improper welding parameters — such as welding too hot or too cold — can also wear contact tips prematurely and force more frequent changeout. Adjust parameters accordingly to minimize this problem. 

Failure No. 2: Broken cutter blades in the reamer

The main cause of broken cutter blades in robotic welding is incorrect positioning or too much angle of the robotic MIG gun nozzle as it enters the reamer for cleaning. For example, if the depth of the Z axis is too deep, the torch will go in too far and may cause the reamer blades to break.

To prevent this, the nozzle should be concentric to the cutting blade. Use an angle finder app on your smartphone or tablet to ensure the positioning is straight up and down on the X and Y positions. Also, be sure the insertion depth on the nozzle goes past the gas holes on the diffuser. Drag marks on the diffuser or contact tip are signs of wear that mean the nozzle is not concentric to the reamer blade. Proper setup and positioning also helps ensure consistent coverage of anti-spatter spray on the nozzle.

Broken cutter blades can also result from excessive spatter in the nozzle, which can be caused by poor spraying setup, incorrect weld parameters or incorrect torch angle. Spatter sticks to spatter and as the buildup grows, it can break the cutter blade as it tries to enter the nozzle.

Keep in mind that you may need to ream and spray more frequently depending on the application and the material being welded to avoid some of these issues.

Problems with the contact tip, nozzle, reamer and excessive spatter can also result when there is poor grounding in the weld cell. Regularly inspect all cables for damage and be sure the ground cables are securely connected.

Failure No. 3: Loss of tool center point

When TCP is lost in a robotic weld cell, one common cause is improperly installed consumables. A cross-threaded consumable will angle the contact tip where it meets the retaining head, causing the tip to bend and disrupting TCP.

Be sure to tighten consumables to the manufacturer’s torque specifications. The general rule of thumb is one quarter turn past finger tight.

A worn clutch can also cause loss of TCP. The clutch system helps prevent damage to the robot or gooseneck during tooling collisions. After repeated incidents, the clutch may allow a few degrees of movement in either direction, which throws off TCP.

Consider using a neck inspection fixture, which tests and adjusts the tolerance of a robotic MIG gun’s neck to the TCP so you can readjust it after an impact or after bending due to routine maintenance. 

Failure No. 4: Broken discs

In a robotic weld cell, the disc functions as a buffer between the mount and the robot arm. It’s designed to be sacrificial; if the torch, mount or robot arm collide, the disc will absorb the bulk of the impact. However, the disc can be broken when it’s hit hard enough by the neck or torch mount, so replace it if damaged. Set the robot path correctly to avoid neck collisions.

Overtightening the screws can also break or crack the disc and cause it to fail. Discs have torque specifications from the manufacturer. Use those specifications to prevent overtightening and reduce the risk of cracking. The specification sheet also describes the order in which the screws on the disc should be tightened. 

Failure No. 5: Incorrect tool path

Robotic weld cell failures can also be caused by programming errors. If the robot’s path to the tooling is programmed incorrectly, the arm can come into contact with the tooling or the weld cell wall.

The torch rubbing on the cell wall can create holes in the cable. In addition, if the neck frequently hits the tooling, this can bend the neck or cause the disc to break.

To prevent these issues, program the robot so the arm is clear of the tooling and doesn’t encounter the tooling or the wall.

Maintenance is key

Preventive maintenance is key to keeping a robotic welding system and its components performing optimally — and extending consumable life. Regularly check all cables to make sure they are secure, free of damage and not rubbing anything.

Establish and follow a schedule for liner changeover. The required frequency of liner changeover depends on what type of filler metal is being used, what material is being welded and shop conditions. A shop that is very dusty means liners will clog faster, for example.

Consult the manufacturer’s maintenance recommendations and follow a preventive maintenance checklist to ensure all the system’s components and parts remain in good working order. Using high-quality robotic MIG guns and consumables also helps prevent problems that can arise in the weld cell.

Taking steps to avoid common failures in the robotic weld cell allows your operation to improve productivity, reduce consumable costs and ensure consistent part quality. 

Anti-Spatter Sprayer: How to See the Best Results

When using anti-spatter liquid in a robotic weld cell, there are steps you can take to optimize the application of the spray. The addition of an anti-spatter sprayer to a nozzle cleaning station helps ensure delivery of consistent amounts of anti-spatter liquid, leading to longer consumable life, better weld quality and higher productivity. You can also add an anti-spatter multi-feed system to help lower costs, minimize downtime and increase safety. These systems eliminate the need to refill spray reservoirs frequently by feeding up to 10 reamers from a single 5- or 55-gallon drum of anti-spatter liquid.

Follow these best practices for anti-spatter liquid usage

Position the robotic MIG Gun and front-end consumables correctly. Aligning these in the right location for the ream cycle and anti-spatter liquid application helps apply the liquid uniformly. Always follow the manufacturer’s instructions for proper setup based on the nozzle bore size. If the sprayer is too far away from the nozzle, it will not provide adequate coverage to prevent spatter buildup. If the nozzle and sprayer are too close, too much spray may saturate the nozzle insulator, which can lead to premature failure.

Spray for about a half-second. If you need to spray longer, it usually means the sprayer is too far away. Never spray the liquid for three or more seconds, as it can harm the consumables, cause residue buildup in the weld cell (and with it slippery surfaces) and may damage power sources by adversely affecting the electrical circuits.

Use a spray containment unit. This 3- to 4-inch unit fits over the spray head on the anti-spatter liquid sprayer to capture excess anti-spatter liquid. After the spatter has been cleared from the nozzle during the reaming cycle, the nozzle docks on the spray containment unit. An opening at the top of the cylinder allows the anti-spatter liquid to spray onto the nozzle while an O-ring seals the nozzle in place; only the outside edge and inside of the nozzle are sprayed.
The spray containment unit also collects anti-spatter liquid runoff so it can be easily drained into a container and disposed of in accordance with federal, state and local environmental control regulations. Anti-spatter liquid cannot be reused.

To care for a spray containment unit, routinely remove any spatter or debris from the bottom and clear the screen or filter inside the unit of contaminants using clean, compressed air.

Learn more about anti-spatter liquid and available accessories.
 
This article is the third in a three-part series focused on the use and benefits of anti-spatter liquid. Read article one, Spatter in Welding: Should You Consider Anti-Spatter Liquid? and article two, How to Select and Use Anti-Spatter Liquid.

How to Select and Use Anti-Spatter Liquid

Having the right products for your welding application impacts quality and productivity. Anti-spatter liquid is no exception. When selecting an anti-spatter liquid for a robotic welding application, be certain that it offers the following attributes: 

• Uniform coverage to protect the entire nozzle
• Easy cleanup and no residue
• Compatibility with the nozzle cleaning station or reamer being used

A water-soluble compound, like Tregaskiss® TOUGH GARD® anti-spatter liquid, is a popular option. This liquid is non-toxic and eco-friendly, helping companies to improve employee safety and provide a cleaner work environment. Oil-based anti-spatter liquid is also available in the marketplace, but is generally less desirable to use because it is more difficult to clean up if it settles on fixtures or other parts in the weld cell. Oil-based anti-spatter liquid is not always compatible with all nozzle cleaning stations, and it can clog this equipment.

Safety Tips

Even though the more popular water-based anti-spatter compound is non-toxic, you should always take care when handling and using it.
Consider these tips:

1. Avoid breathing in spray mists, and always wash your hands after encountering the compound. or example, when filling the sprayer or setting up an anti-spatter multi-feed system.
   
2. Use a NIOSH-certified (or equivalent) respirator during spraying.
   
3. Wear Nitrile or Butyl gloves and wear chemical safety goggles for the best protection.
   
4. Utilize local exhaust ventilation near the sprayer.
   
5. Store anti-spatter compound containers according to the temperatures recommended by the manufacturer.
   
6. Consult the SDS sheet for complete recommendations for proper anti-spatter liquid usage.

This article is the second in a three-part series focused on the use and benefits of anti-spatter liquid. Read article one, Spatter in Welding: Should You Consider Anti-Spatter Liquid? and article three, Anti-Spatter Sprayer: How to See the Best Results