Everyone is trying to save money these days. From implementing lean practices to repairing equipment instead of purchasing new, companies are seeking ways to reduce costs without sacrificing quality.
Selecting the right MIG gun consumables for your welding application can also help. Not only can the right consumables minimize unscheduled downtime for changeover, but they can also reduce the need to rework weld defects caused by a poorly performing contact tip, nozzle or liner.
The bottom line? You can spend more time welding, gain greater productivity and lower your costs.
Following are some suggestions for selecting the most appropriate MIG gun consumables for your application and ways you can best care for them.
Line Up for the Best Performance
Liners are responsible for guiding the welding wire from the wire feeder, through the gun cable and up to the contact tip. They are typically composed of steel coils, but can also be made of nylon or Teflon®, the latter of which is used for welding with aluminum wire.
|Selecting the right MIG gun consumable for your applications can help minimize downtime and reduce cost|
Selecting a liner is a relatively straightforward process: you need to match the liner’s inside diameter (within a specific range) to the diameter of wire you are using. For example, if you are welding with a .035-inch wire, you can use a liner that measures .035 to .045 inches in diameter. Making this match helps prevent wire-feeding problems that can lead to poor arc stability, bird-nesting (a tangle of wire that prevents the wire from feeding) and/or weld defects. Also, using premium quality liners is best, as these maintain a more consistent inside diameter than less expensive ones and provide better feeding performance.
To prevent shielding gas leaks that can increase costs and jeopardize gas coverage of your welding puddle, make certain that your liner has a good O-ring connection at the back of the liner and that you select liners with a durable coating. Replace your liner at a regularly scheduled time and always follow the manufacturer’s recommendation for trimming and installation. Poorly trimmed liners, liners that are worn excessively or ones that are kinked from use can easily cause wire feeding problems or an erratic arc that leads to poor weld quality. They can also cause excessive spatter that will require post-weld grinding, minimizing throughput and adding to your overall costs.
Some manufacturers offer partial liners that replace only the most commonly worn part of liner (along the length of the MIG gun) instead of the entire liner. These partial liners help reduce downtime for changeover as they usually take about half the amount of time to install compared to a full-length liner.
|The liner spans the length of the MIG gun (as shown in this cutaway) through the power pin and down the power cable to the front of the gun, and can often be the source of wire feeding problems. For that reason it is important to install the liner properly and replace it regularly.|
Tips for Making the Right Contact
While they may look like a small, and perhaps insignificant, part of the overall welding system, contact tips play a critical role in helping achieve good weld quality, reducing costs for downtime and minimizing rework. In addition to helping direct the welding wire to the weld puddle, contact tips are responsible for transmitting the current to that wire in order to initiate the arc.
The contact tip you select should correspond with the diameter of welding wire you are using. Typically, contact tips are available to accommodate wire diameters ranging from .023 to 1/8 inches.
Depending on the type of joint your application requires, you may need to select a tapered style contact tip. These contact tips are good for applications that have restricted joint access, but they tend to be a bit more delicate than non-tapered contact tips. They should be coupled with a tapered nozzle. If joint access is not a factor in your application, however, choosing a non-tapered contact tip is the best option as it has more mass and will last longer.
Different manufacturers offer either threaded or non-threaded styles of contact tips. Threaded contact tips are the most common and, as their name implies, they are held in place in the gas diffuser by threading or twisting them. Non-threaded contact tips, conversely, drop into the gas diffuser. This latter style of tips can be rotated when the contact tip starts to wear on one side (called keyholing) in order to create a new wear surface, extend the life of the contact tip and prevent arc instability that can in turn lead to spatter and rework. Non-threaded contact tips also tend to be easier to change out after a burnback, which is the formation of a weld in the contact tip. It most often occurs because of placing the contact tip too close to the workpiece or using too slow of a wire feed speed. Regardless of whether you choose a threaded or non-threaded style of contact tip, it is important that you install these according to the manufacturer’s recommendations. Doing so will help ensure a good electrical connection and, with it, reliable welding performance and quality.
Contact tips are generally available in sizes small or large and also in standard or heavy-duty varieties. If you are welding on higher temperature applications (generally, 300 amps and above) you should select a large contact tip, as these have greater mass and provide better cooling capacity than smaller contact tips. For higher amperage applications that also require prolonged welding, heavy-duty contact tips can provide greater conductivity, improve arc starts and they tend to provide longer lasting performance. Lighter amperage applications (generally, below 300 amps) are well-suited to using small, standard style contact tips.
To ensure the best welding performance, inspect the contact tip for spatter build-up on a regular basis and replace as needed. Waiting too long to replace a damaged contact tip can lead to arc irregularities and poor weld quality, not to mention unscheduled downtime for replacements, which can cut into your productivity and cost you money.
|The non-threaded style of contact tip (as shown in this cutaway) can be rotated to create a new wear surface and extend the life of the consumable.|
Know Your Nozzles
Depending on your application there are a variety of styles of nozzles from which to choose. Like contact tips, nozzles are an important part of gaining good weld quality and reducing costs. The main function of these components is to direct shielding gas to the weld. For that reason, you want to select a high-quality nozzle that is capable of providing smooth gas coverage and resisting damage (e.g., dents, scratches, etc.).
Usually, manufacturers offer either brass or copper nozzles. Brass nozzles provide good protection against spatter, while copper nozzles withstand heat better, particularly on heavy-duty applications.
There are two main styles of nozzles — threaded and non-threaded — as well as a variety of different shapes and sizes. Threaded nozzles tend to maintain a more secure connection than non-threaded styles, which protects against shielding gas leaks that can lead to weld defects like porosity. These nozzles also help keep the contact tip centered for greater accuracy. Non-threaded nozzles, however, are easier to change over.
Nozzles are available with small and large varieties and a range of inside diameter measurements, often from 3/8 to 5/8 inches. Ultimately, the best option for any application is to use the largest nozzle possible that still provides you access to the joint. Doing so provides greater gas coverage to protect against contaminants. For restricted joints, however, you will need to use a small, tapered nozzle that allows you to place the contact tip close to the weld puddle. Or if you have a high-amperage application that requires high gas flow rates, select a large diameter nozzle, as it provides the best shielding gas coverage.
Some MIG consumable manufacturers provide nozzles that keep the contact tip at a fixed position: flush, recessed or extended. Each provides distinct attributes. For example, if you are welding in a short-circuit transfer mode, a nozzle that keeps the contact tip flush to the end of the nozzle or slightly extended helps minimize the spatter that tends to be generated in this welding process. Similarly for spray arc transfer or pulsed spray mode when welding with solid wire, having a nozzle that keeps the contact tip slightly recessed can help the contact tip operate at cooler temperatures and provide greater shielding gas coverage.
For all styles and sizes of nozzles, regular inspection for spatter is crucial to achieving good gas coverage. Also, careful handling and storage of these consumables is important. Always wear gloves when changing out nozzles to prevent debris or oils from adhering to them and entering the weld puddle. To prevent damage, keep them in the original packaging until you are ready to use them.
Remember, whether you are selecting a nozzle, contact tip or liner, having the right MIG gun consumable for your application can go a long way in reducing uncessary downtime and lowering your overall costs.
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