Understanding MIG Liners – Types, Installing, Optimization

MIG Welder Liner
Source: https://daddyspick.com

MIG Gun consumables and the liner play a significant role in gun performance and weld quality. MIG Gun Liners. This might be a new term for those who have just started out with welding or haven’t gathered enough information about your MIG welding gun.

Well, we are here to get you all the required knowledge about these MIG liners. Being very simple to install and execute, this is one of the most influential components of a MIG gun.

A MIG gun liner is either a tube or helically wound wire which acts as a conduit to guide the welding through the MIG gun to the contact tip. The sole role that it plays is to feed the welding wire from the wire feeder to the contact tip via the gun cable.

This significantly affects your gun performance and weld quality. Proactive maintenance is required to optimize the weld performance and reduce operator downtime and rework too.

General feeding problems are known by erratic wire feeding, wire burn-back, and bird-nesting too. Most of the causes of these issues are incorrect drive rolls, clogged liners, improper installation of wire liner, and other liner issues.

Types of MIG gun liners for a welding job

MIG welding liners are divided into several types based on the semi-automatic and robotic applications in the welding industry. Based on personal preference and maintenance possibilities, one can choose the type of liners. The basic three types of liners are – conventional liners, front-loading liners, and spring-loaded front-loading liners.

Conventional Liners

These gun liners are installed through the back of the gun. They are used in MIG welding units which have only industrial uses. The changeover is a lengthy and tedious process. The cable keeps growing and shrinking with more and more twisting.

Front-loading liners:

These MIG gun liners are installed in the front of the gun. It reduces downtime and helps provide more time-saving advantages. Here the wire does not grow or shrink as the cable begins twisting.

Front-loading liners with a spring-loaded module:

Allows more than 1 inch of the motion of the cable twists and more. If you can trim the liner properly, it can be more forgiving than being incorrect.

Plastic MIG gun liners

There are a bunch of plastic MIG gun liners which are quite inexpensive and more popular among welders than steel or other metallic gun liners. Each type of plastic used makes the liner durable and a better fit for certain types of filler metal. They are as follows:

MIG Liners
Source: ABICOR BINZEL

Polyamide(PA):

This is a carbon-filled nylon liner that can be used only in low temperatures and for low-duty air-cooled with a large amount of versatility. It can be used for push-pull operations of smaller gauge aluminum, stainless steel, and silicon-bronze welding wires.

Combi-PA:

It has a bronze spiral-wound liner attached to the front-end which enables us to use the MIG gun at very high temperatures. The brass jumper also allows a better flow of current and low-melting-point liners to be used in high amperage duty cycles.

Polyethylene (PE):

These MIG gun liners are made for being used with soft wires and those having poor column strength like aluminum, bronze, and 4000 series aluminum. These liners have smooth interiors and provide stable wire feeding. Polyethylene has a low melting point.

Teflon (PTFE):

Teflon has a higher melting point than Polyethylene and is ideal to be used in high-temperature applications that have a water-cooled torch and have brass neck liners. Teflon is abrasion-resistant and is can be used for a variety of wires.

Teflon liner MIG
Source: Tokentools Welding Supplies

Carbon Teflon (CTFE):

These MIG gun liners are suitable for stainless steel applications (ER308, ER309, ER409cb) and so on. It has good temperature and abrasion resistance when compared to other plastic liners.

High-Density Teflon (HD-PTFE):

These liners have a similar melting point as that of carbon Teflon liners providing long lifetime service and efficiency. These liners are compatible with wires ranging from soft to stiff wires.

What are ‘Neck-liners’?

MIG Neck Liner
Source: Lincoln Electric

Neck liners are some specially designed tools that extend the life of our wire liners. They are also known as ‘Jump-liners’ and have a small collet that sits in the welding torch itself and is very easy to be replaced if so needed.

The most common issue comes with the failure at the gun’s neck and this can be the best way to save your time. Moreover, using a neck-liner is ecological-friendly and hence is cost-efficient. It is important to match the neck liner size to the wire we use because the neck liner material should be a good fit for the wire.

Installing a MIG gun liner

Step 1:

  • Make sure the power supply is turned ‘OFF’ and the gun is removed from the feeder.
  • First remove the nozzle, contact tip, and gas diffuser.
  • If the power pins your MIG gun has a liner set screw, loosen the set screw using a 5/64 inch Allen wrench.
  • But if your power pin has a thread-in liner type screw, use a 10-mm wrench to turn the collet in such a way that the liner is free from the power pin.
  • Grip the conduit liner with some cutting-pliers once the gun is straightened and then remove it.

Step 2:

  • Now you may feed the liner either a new one or the replacement one using short strokes to avoid any sort of kink. Twist the liner clockwise as much as needed.
  • Once again, here if your power pin uses a liner set screw, tighten the liner set screw properly by seating it with the o-ring to place it into the bore of the power-pin.
  • Whereas if the power-pin is of a thread-type, then use a 10mm wrench to turn the thread-in liner collet in a clockwise direction and make sure you tighten it.

Step 3:

  • Push the liner back into the gun and then hold it in place.
  • Remove any obstructions or debris that inhibits proper wire feed, mainly using a flat wire type of conduit liner.
  • Re-place the nozzle, contact tip, and the gas diffuser back into the neck.

Replacing the MIG gun liner: (Miller)

  • Disconnect the gun first. Pull all of the spools of wire out of the machine as much as possible.
  • Remove the 4-pin control cable out from the front panel and start losing the power pin slowly.
  • The power-pin will start coming out of the driver compartment of the MIG gun. Place it in a straight line before servicing your product.
  • This will help you cut your new liner to the perfect dimensions and shape and also reduces stress while working on the product.
  • Remove the front-end consumables of the gun including the diffuser. Blow the inside of your liner using compressed air to remove dirt and debris that causes obstruction in the liner feed and overall performance.
  • Loosen the nut on the power-pin end and remove the liner. Now insert the new liner feed into the gun in such a way that the excess wire feed is at the end of the gun.
  • The extra liner is cut off of the exact liner length required for our gun. Use the wrench to tighten the liner at the power pin. Always make sure the MIG gun liner is placed in a straight line. Until the liner is perfectly placed inside the MIG gun.
  • Using a side-cutter or welfare cutter, remove the mono coil of around ¾ inches from the head tube.
  • Now you have successfully installed/replaced the old liner with a new one. So, here is the time to install all the new front-end consumables. The sequential order is to place the diffuser, then the contact tip, and finally the nozzle all using the wrench.
  • Once done, install the MIG gun back into the machine. Insert the core pin completely into the drive casting and then the 4-pin control cable into the front panel socket. Cut and tread the welding wire back into the gun feeder.
Replacing the MIG Liner
Source: MIG-Welding

Cut, Fit, and Install a New Liner:

  • The MIG gun is arranged in a straight line and must be free of twists and turns whenever you are installing or even removing any sort of wire liner.
  • Remove the MIG gun’s nozzle and contact tip to remove the old liner. Pull out the old liner from the casing assembly from the feeder adapter plug end. If the feeder adapter that you use has an inlet, then it must also be removed.
  • If the old liner that use had used was of the perfect length and did give you good overall weld performance, then place the old liner along the new liner to cut the new liner to the perfect length.
  • The length cutoff must be accurate and should not have any part of it sticking out. Once you have the new liner cutout, insert it into the casing/conduit by inserting it via the feeder adapter first.
  • Once again, make sure the MIG Gun cable is kept in a straight line free from twists and turns. Using two people to do these tasks easy and efficiently done.
  • Once the new liner comes out of the torch, use the copper gas nozzle end to cut off the extra liner.
  • Carefully cut the liners’ edge now to remove the length of the contact tip. Once you have cut the tip and the tip setback (1/8” or 3/8”), you may back up the new liner into the tip chamfer.
  • Always check the condition of the insulation tube in-front of the torch. Replace the spatter disc, diffuser, contact tip, and nozzle after all the above processes are completed.
  • Tighten the flat screw head in the inner body of the liner and the Allen set screw on the docking of the casing to prevent any unnecessary backward movements.

Tips to Optimize MIG liner installation:

  • Always remember to keep the MIG gun in a straight line and make sure the cable is flattened before you remove any consumables.
  • Trim the wire only at the front end of the gun to remove all of the beads of molten wire.
  • For installing a conventional liner, first, remove the power-pin from the feeder adapter from the back of the gun and then cut the excess wire off. This enables us to easily remove the wire and the conventional liner from the gun.
  • After inserting the conventional liner, reinsert the power pin back into place and feed a few inches of the wire back into the power pin.
  • Conventional and front-loading liners, come with a plastic gauge that has ¾-inch of the wire sticking out.
  • Hit the trigger once you pull the wire up and hence will purge the gun with shielding has at the same time.

How does a MIG welding liner become dirty?

Being ignorant and unaware of how your MIG liner is working and getting affected over time will cause a lot of damage to your liner affecting your weld performance and damage to your entire career. Being proactive and considerate at all times can save you a lot of maintenance and repair costs and also save you some useful time.

Liners must be maintained in such a way that they are flexible and rigid at the same time. Bending the cable too much can lead to problems like poor wire feeds, bird-nesting, and dirty liners. Tight bends between the wires increase the friction between the edges and increase the tension to bring the liner out of the gun.

This in turn causes the accumulation of metal fragments in your liner and causes some unintentional and hazardous wear and tear. This happens regularly can cause large debris to be formed in the wire feed causing blockage and poor performance rate.

Make sure your cable/wire after cutting is formed in a straight line. Because if it is found to be curved and twisted, it may cause a shortage of liner causing the liner to have more spaces and unwanted gaps making it viable to a lot of dirt and debris.

How do you clean a MIG welding liner?

  • Loosen the flat head screw and remove the front consumables like the nozzle, diffuser, and weld tip.
  • Remove the wire from the liner and remove the liner from the weld gun. Blow compressed air through the casing into the liner to remove all the debris present on the liner.
  • Make sure the liner is free from and damage and bends. If necessary, you can replace this liner with a new one.
  • Now install the clean liner back in place.