14 May

10 Mistakes in Running a Welding Operation and How to Fix Them

With so many factors to monitor — equipment, weld procedures, filler metals and MIG gun consumables — it’s inevitable that mistakes will occur in most welding operations on any given day. Human error dictates that a welding operator can easily set a power source and wire feeder to the wrong parameters or trim and install a MIG gun liner improperly. But there are other mistakes that can occur in welding operations on a regular basis — ones that many companies may not even realize that they are making.

The reality is, however, that these mistakes can have a significant impact on quality, productivity and a company’s bottom line. Fortunately, they don’t have to happen. Consider these top 10 mistakes involved in running a welding operation, along with some recommendations for solving them.

Mistake No. 1: Improper Filler Metal Storage and Handling

Storing filler metals in an area where they are prone to accumulating moisture or exposed to other contaminants (e.g., dirt, oil or grease) can have an adverse effect on their welding performance. To prevent damage, companies should store filler metals in a dry, clean area with a relatively constant temperature until they are ready for use. Spools and coils of wire that are kept on the wire feeder for an extended period should be covered securely with a plastic bag or removed from the wire feeder and stored in the original packaging. An enclosed wire feeder can also protect against contaminants. Such precautions prevent damage that can lead to poor weld quality, and ultimately, rework.

Mistake No. 2: Repurposing Old Equipment

It is important for companies to use the best equipment for the job. Repurposing old or dilapidated power sources, welder/generators or wire feeders can cause quality issues, not to mention downtime and additional costs for troubleshooting problems that inevitably arise from using dated equipment and technology. Instead, companies should consider the newer technologies available in the marketplace, recognizing the advantages these can offer in terms of improving weld quality and productivity. In most cases, newer equipment can provide companies with a quick return on investment and greater long-term savings – in a relatively short payback period.

Newer technologies often offer benefits like improved power efficiency, better deposition rates, lower weld prep time and faster training, all of which ultimately add up to greater arc-on time and productivity. Performing a thorough cost-savings analysis before buying new equipment can help companies assess their potential return on investment, as well as justify the capital expenditure.

Mistake No. 3: Using the Wrong Size MIG Gun

Using a too-low or too-high amperage MIG gun can lead to unnecessary costs for purchasing and replacing this equipment. Welding operators rarely spend the entire day welding or welding continuously, as there is downtime for part preparation, movement and/or fixturing. For that reason, it may be possible to use a lower amperage MIG gun or one with a lesser duty cycle on some applications. For example, using a lighter and smaller 300-amp MIG gun instead of a 400-amp model can provide welding operators with greater maneuverability and reduce downtime for fatigue. Lower amperage MIG guns tend to cost less, as well.

Conversely, on higher amperage applications and/or those that require longer periods of welding, it is important to use a higher amperage gun. Skimping and purchasing a lower amperage MIG gun in this situation can lead to overheating, premature failure and greater long-term costs. Companies should consult with a trusted welding distributor for MIG gun recommendations for their application.

Mistake No. 4: Improper Preheat or Interpass Temperature Control

It is not uncommon for companies to preheat too little or skip this portion of the
weld procedure altogether. Yet preheating is one of the biggest deterrents against cracking, as it slows down the cooling rate after welding. The type and thickness of the material being welded will determine preheat and interpass temperature. These requirements can be found in the application’s welding procedure, welding codes or other fabrication documents. For the best results, welding operators need to preheat the material completely through and extend the heated area to approximately three inches on either side of the weld joint. Welding should commence while the material is at or above the preheat temperature. Allowing the weldment to cool below the required interpass temperature may also lead to cracking.

Mistake No. 5: Ignoring Preventive Maintenance

Preventive maintenance (PM) is a frequently overlooked part of the welding operation, but it is critical to preventing unscheduled downtime and keeping repair costs low. A well-performed PM program can also help increase productivity, extend equipment life and create a workplace philosophy that encourages shared responsibility for, and interest in, preserving the integrity of the welding equipment. Companies should develop a regular timetable to inspect their power sources, wire feeders and MIG gun or TIG torches during scheduled downtime in production. Between welding shifts is often enough time to perform routine inspections. Checking consumables regularly for spatter build-up — and replacing these components as needed — is also an important part of a viable PM program.

How to TIG Weld Stainless Steel Effectively: Preventing Carbide Precipitation

Whether companies have MIG processes or TIG processes in their welding operations, carefully selecting equipment, guns, torches, and filler metals can lead to significant savings and better productivity.

Mistake No. 6: Shielding Gas Inconsistencies

Using the correct type and/or mixture of shielding gas can help companies prevent weld defects, minimize excessive spatter and reduce costs for rework or post-weld cleanup. Shielding gases also determine arc characteristics and weld penetration on a given application. Straight CO2 provides good weld penetration, but it is prone to spatter and has a less stable arc than mixtures that include argon.

High argon mixtures (a minimum of 85 percent argon for solid wire or as low as 75 percent for metal-cored wires) are the best choice. These mixtures can be used in the spray transfer process to promote higher deposition rates and generate less spatter. For TIG welding, the appropriate argon/helium mixture can improve speed, quality and arc characteristics. For both MIG and TIG welding operations, companies should purchase their shielding gas from a reputable welding distributor and be certain that it meets the purity requirements for their application. All gas delivery systems should be free of contaminants that could enter the weld puddle and welding operators should use the correct shielding gas flow rate. Too little gas flow    won’t properly shield the molten weld pool, while too much flow can cause turbulence and aspirate air into the weld puddle. Protecting the weld puddle from drafts is also critical.

Mistake No. 7: Purchasing Filler Metals Based on Cost Only

Due to the initial up-front cost savings, the temptation may be great for companies to purchase less expensive filler metals. However, doing so can often lead to greater long-term costs and lower productivity levels. It is not uncommon, for example, to experience downtime associated with poor wire feeding, excessive spatter or, potentially, weld defects when using lower quality filler metals. Companies may also find themselves experiencing an excessive amount of time for non-value-added activities (those that do not directly contribute to their throughput), such as applying anti-spatter and post-weld grinding or rework. For that reason, it is important to look at the total cost of using particular filler metals, as opposed to the per-unit cost. If more expensive, higher quality filler metals can minimize labor costs for non-value-added activities and provide better weld quality and/or greater productivity, then the higher up-front cost makes good sense in the long run.

Mistake No. 8: Improper Weld Preparation

Skipping steps in weld preparation can lead to weld defects, rework or scrapped parts. Welding operators should always take care to clean the base material before welding to prevent contaminants like dirt, oil or grease from entering the weld puddle. Similarly, monitoring part fit-up is a critical part of the pre-weld process. Welding operators should carefully assess the weld joints to ensure there are no excessive gaps, as poor part fit-up can lead to issues like burn-through or distortion on all materials, but particularly when welding on materials like aluminum or stainless steel. Clamping or fixturing a part in the correct position is also a good practice to help protect materials like stainless steel against distortion or buckling.

mig gun consumables

Look for consumables where the diffuser locks and aligns the liner with the contact tip and power pin for flawless wire feeding.

Mistake No. 9: Disregarding MIG Gun Consumables

It is not uncommon for companies to overlook the importance of their MIG gun consumables. Unfortunately, that oversight can lead to a host of problems, including unscheduled downtime for changeover and/or rework of weld defects caused by a poorly performing contact tip, nozzle or liner. To help avoid problems, select consumables with a tapered design that locks conductive parts together to reduce heat buildup. Contact tips with coarse threads are a good way to speed up replacement and make sure installation is accurate. Look for consumables where the diffuser locks and aligns the liner with the contact tip and power pin for flawless wire feeding. These systems also offer error-proof liner installation with no measuring required; the liner is simply locked in and trimmed flush with the power pin at the back of the gun.

Mistake No. 10: Overlooking Training Opportunities

As with other parts of the welding operation, investing time and money in training can yield significant long-term benefits for companies. Not only do welding operators benefit individually from process and equipment training, but in many cases it can also help them optimize the welding operation for greater efficiency. Too, proper training can give companies a competitive edge over those who have less-skilled labor and it promotes greater teamwork among employees. Typically, training opportunities are available through equipment and filler metal manufacturers or through welding distributors. In some cases, working with a local technical college can lead to training for specific applications and markets, allowing companies to bring in welding operators who are already trained for a given application and better promote their position in a given industry.

Making mistakes is human nature, but with some careful consideration, it is easy to avoid some of the more common ones associated with running a welding operation. Measuring out long-term savings, versus cutting costs up front, is a particularly good way to avoid pitfalls that could lead to excessive downtime, quality issues or lost productivity. And it can have an excellent impact on a company’s bottom line.

 

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14 May

Troubleshooting Common Industrial MIG Welding Problems

Like any welding process, MIG welding has its complications. Even so, there is no reason to let common problems slow you down. With a bit of knowledge and some solid troubleshooting skills, you can easily find the right solution to get back to welding—sooner than later. Consider the following guidelines to help you along the way.

Keep Covered

Getting Started with Welding: A Welding Guide for Beginner’s

MIG welding defects can cause downtime and lost productivity due to rework. Use these tips to help you minimize these costs by quickly identifying and resolving MIG welding problems.

Porosity occurs when a gas pocket becomes caught in the weld metal. This discontinuity can appear at any specific point on the weld or along its full length, and/or on the surface or the inside of a weld. The result, regardless of the location, is always the same: a weaker weld.

Inadequate shielding gas coverage is one of the most common causes of porosity. To correct this problem, first check the regulator or flow meter for adequate gas flow, increasing it if necessary, and check the gas hoses and the gun for leaks. Whether welding inside or outside, shield the arc and weld puddle from drafts with a welding screen.

Next, confirm that the MIG gun nozzle is large enough for the application, as too small of a nozzle can prevent proper shielding gas flow. Keep the nozzle one-fourth to one-half inch away from the work piece, make certain it is free of spatter, and always use the correct contact tip recess. Slow your travel speed and hold the MIG gun near the bead at the end of the weld until the molten metal solidifies; pulling the gun away too soon can interrupt gas coverage and leave the setting weld vulnerable to the atmosphere.

Additional causes of porosity include: using the wrong gas (always use a welding-grade shielding gas appropriate for the base metal and filler metal), using too much or the wrong type of anti-spatter (use the correct amount and type for your application) and extending the welding wire too far out of the nozzle (extend no more than one-half inch beyond the nozzle).

Impurities in the base metal, such as sulfur and phosphorous in steel, or a dirty base metal can be further causes of porosity. If specifications allow, consider changing to a different composition of base metal, and always remove rust, grease, paint, coatings, oil, moisture and dirt prior to welding. Filler metals with added deoxidizers can help to “clean” the weld, but should never be solely relied upon to minimize porosity. Finally, replace any wet or contaminated shielding cylinders immediately.

Don’t Be Undercut

Undercutting occurs when a groove melts into the base metal next to the toe of the weld and the weld metal fails to fill that area. This discontinuity weakens the toe of the weld, increasing the chances of cracking. Correcting the problem is relatively simple: reduce the welding current, decrease the welding arc voltage and adjust your MIG gun angle toward the joint. Reduce your travel speed so the weld metal completely fills the melted-out areas of the base metal. When using a weaving technique, pause slightly at each side of the weld bead.

When the weld metal fails to completely fuse the weld metal with the base metal or with the preceding weld bead in multi-pass applications, incomplete fusion can occur. Some people refer to this problem as lack of fusion. Generally, an incorrect MIG gun angle is the cause and you should adjust it accordingly. Follow these steps:

  • Place the stringer bead near the proper point on the joint, adjusting the work angle or widening the groove as needed to access it fully.
  • Keep the arc on the leading edge of the welding puddle by maintaining an angle of zero to 15 degrees.
  • When using a weaving technique, momentarily hold the arc on the groove sidewall.

If correcting the MIG gun angle does not remedy incomplete fusion, look to see if the welding puddle is too far ahead of the wire. If so, increase your travel speed and/or the welding current to correct the problem. Conversely, if you suspect insufficient heat input has caused incomplete fusion, select a higher voltage range and/or adjust the wire feed speed as necessary. Finally, always clean the surface of the base metal prior to welding to remove contaminants that may prevent the metal from fusing together.

work angle large

Proper work angles are important for avoiding GMA welding pitfalls like incomplete fusion.

Another common MIG welding problem—spatter—occurs when the weld puddle expels molten metal and scatters it along the weld bead; this molten metal then cools and forms a solid mass on the workpiece. Excessive spatter not only creates a poor weld appearance, but it can also lead to incomplete fusion in multiple welding pass applications. Too fast of a wire feed speed, too high of a voltage setting, and too long of a welding wire extension, or stick-out, can cause spatter. Lowering the given settings and using a shorter stick-out can help.

Like porosity, insufficient shielding gas and/or dirty base materials can cause spatter. As necessary, increase the shielding gas flow at the regulator and minimize drafts near the welding arc, clean and dry the welding wire, and remove all grease, dirt and other contaminants from the base metal.

Other factors that can cause spatter are: the wrong size contact tip, a worn contact tip or the wrong tip to nozzle recess. Be certain you have the right contact tips, nozzles and recess parameters for the application.

Keep Track of the Heat

Excessive penetration occurs when the weld metal melts through the base metal and hangs underneath the weld. Excessive heat input is usually to blame for the problem. To correct this, select a lower voltage range, reduce the wire feed speed and increase your travel speed.

Conversely, insufficient heat input can cause lack of penetration, or the shallow fusion between the weld metal and the base metal. Selecting higher wire feed speed, a higher voltage range and/or reducing travel speed are all viable remedies. Preparing the joint correctly also helps prevent lack of penetration—the preparation and design should permit access to the bottom of the groove and allow you to maintain proper stick-out and arc characteristics.

diagram welding penetration

Lack of penetration and excessive penetration can be remedied by adjusting factors such as voltage, wire feed speed and travel speeds.

All About Wire

Wire feed stoppages and wire feed system malfunctions can adversely affect the welding arc and create irregularities that may weaken the weld bead. Birdnesting, a tangle of wire that halts the wire from being fed, is a common problem. You can resolve birdnesting by flipping up the drive roll and pulling the wire back out of the gun. Next, trim the affected wire and re-thread it through the feeder and back to the gun. If the welding specifications allow, decrease the drive roll tension, use a larger diameter wire and/or reduce the distance the wire feeds (use shorter cables) to minimize the chance of birdnesting.

contact tip

If the wire melts back and fuses with the contact tip, as shown, the tip should be replaced and the drive rolls checked for a birdnest before continuing to weld.

Burnback is also very common. It results when a weld forms in the contact tip, and usually occurs because of too slow of wire feed speeds and/or from holding the MIG gun too close to the base metal during welding. To correct burnback, increase the wire feed speed and lengthen the distance of the MIG gun from the workpiece (the nozzle should be no further than one-half inch from the metal). Replace burnback-damaged contact tips by removing the nozzle and the contact tip (which may be melted to the wire), snipping the wire, installing the new contact tip and replacing the nozzle with one that has the appropriate tip recess for the application.

Other causes of wire feeding problems include liner blockages, improperly trimmed liners (too short/burred/pinched) or the wrong size liner. To remedy these problems, replace any liner if you find a blockage, always trim the liner according to the manufacturer’s direction and be certain you are using the correct size liner for the welding wire diameter.

No Cure-All

Remember, quality MIG welds are the result of not only good welding technique, but also your ability to identify and solve problems quickly if they do occur. Continue arming yourself with some basic information and you’ll be able to tackle the most common problems associated with MIG welding without sacrificing time or quality.

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18 March

5 Tips for Keeping MIG Gun Consumables Cleaner and Lasting Longer

Every welder wants their consumables to last as long as possible, however operators are often changing over parts and consumables frequently. Below are some helpful tips we have put together that can help your consumables last longer. As a result, it can positively affect productivity, quality and the bottom line.

The Heat Factor

Heat produced in the welding process can impact on the cleanliness and longevity of GMAW consumables. Processes like pulsed GMAW and/or higher amperage applications expose consumables to higher levels of heat, along with applications in which there is a large amount of reflective heat.

The hotter the consumables becomes while welding, the softer the material (usually copper or brass) becomes, resulting spatter to accumulate and premature failure.

It’s important to choose the best consumables for each application. High-amperage applications (above 300 amps) are often best for heavy-duty consumables because they have greater mass and are capable of dissipating the heat more readily. However, if the welding procedure indicates that the contact tip must be changed frequently, a standard-duty contact tip may suffice.

Proper Storage and Handling

Always keep GMAW consumables in their original packaging until they are ready for use. Opening them and placing them in a bin can lead to scratches or dents that allow spatter to adhere and will ultimately shorten the products’ life. Removing contact tips or diffusers from their packaging and storing them in open or dirty containers can cause dirt and oil to accumulate in the threads, which can impede them from properly seating together. Finally, welding operators should always use clean gloves when handling or replacing contact tips, nozzles and diffusers to prevent dirt, oil or other contaminants from adhering to them.

Establish and Maintain Good Connections

Installing GMAW consumables correctly and checking the connections can minimise the chance of poor conductivity, spatter accumulation or premature failure. Operators should follow the manufacturer’s suggestions for contact tip and gas diffuser installation. Never use wire cutters or side cutters — too much pressure from these tools can damage the inside diameter of the contact tip, which leads to poor welding performance and a shortened lifespan. Also these tools tend to scratch the surface of the consumables leaving marks that attract spatter.

Suggested practice – tighten the contact tip until it’s fully seated into the diffuser, then grip the contact tip with an appropriate tool as close to the base as possible, tightening it 1/4 to 1/2 turn past finger tight. This helps ensure a good connection that minimizes electrical resistance, overheating and damage to the consumables, as well as excessive spatter accumulation. Bernard consumables require no tools and can simply be installed by hand tightening the nozzle.

Tip: Inspect consumable connections regularly to ensure that they are secure.

Trim Liners Correctly

An improperly trimmed and installed liner can cause wire-feeding problems that lead to downtime. It can also affect the performance of consumables, how clean they stay and their longevity. Cutting a liner too short can cause the liner to be misaligned with or in the gas diffuser. The result is a welding wire that feeds off-center, leading to premature contact tip failure. Liners that are too short can lead to the build-up of debris between the liner and retaining head, which causes wire feeding issues and poor weld quality. A liner that’s too long can cause kinking that again leads to wire-feeding issues that shorten the life of the contact tip. Always make sure that to remove any burrs or sharp edges after cutting a liner to ensure smooth and consistent feeding of the welding wire.

Welding operators should always consult with the liner manufacturer’s recommendation for proper trimming and installation instructions. It’s also important to protect the liner from contaminants and handle it with clean hands or gloves, don’t let it drag on the ground.

Contact Tip Position and Nozzle Size

The position of the contact tip (extended or recessed) affects how long consumables last, along with how clean they stay. The farther the contact tip extends from the nozzle, the closer it is to the arc and the more prone it is to reflective heat. This can cause spatter accumulation and burnbacks. Using a recessed contact-tip-to-nozzle relationship when possible can minimise these problems and provide better shielding gas coverage at the same time.

For applications that require access into restricted areas, it is important to select a nozzle that provides that access, but isn’t tapered so much that it minimizes the space around the contact tip. If there isn’t enough space for shielding gas to flow out of the nozzle, it can cause the shielding gas to hit the work piece and begin jetting back and/or swirling. The result an increase in spatter. Also the smaller the bore size on the nozzle, the more prone it is to absorbing heat and having spatter adhere to it.

Other Considerations

As a general rule, companies should select the largest consumable that will work for the application and provide the necessary joint access. Larger consumables are able to resist heat and spatter build-up, and they often last longer as a result.

Selecting consumables with the right material for the application is important, too. For example, brass nozzles tend to resist spatter well and are good for lower-amperage applications (100 to 300 amps), whereas copper nozzles are better for high-amperage applications (above 300 amps) or for those with longer arc-on time.

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