MIG Welding contact tips

Typical Size Range & Tolerances

Welding Contact Tip Alloy Comparison

There are 2 main reasons a welding tip wears

1. Common physical wear or abrasion, if you were to place a tip on the wire before the feeder with NO electrical contact, that tip would eventually wear completely through.

2. Electrical erosion is similar to the brushes on an electrical motor or the spark jumping across the gap on a spark plug. As the wire is traveling through the Contact tip at say 300 IPM the electricity has to jump across from the copper tip to the Mig wire. (Hence the name “Contact Tip”) The inside bore of the tip / wire is in constant electrical arcing as this process is happening. Electrical erosion is melting of the welding tip ID.

If you are attempting to get a “sure start” you need to choose the best alloy whether for electrical or physical wear. The next reason a tip wears is to do with heat. As the tip heats from the welding process the properties of the alloys start to break down.

The ability of the tip to dissipate the heat (thermal conductivity) will aid in keeping the tip cooler. The (electrical resistance) of the alloy is also in direct inverse proportion to the electrical conductivity.

As we need a “sure start” and are attempting to jump the gap from the contact tip to wire these two factors play a critical role, if the tip has higher conductivity of electricity it will transfer the current easier (or with less resistance) which will also cause the tip to run cooler.

Resistance equals heat. The additional benefit to higher conductivity is that the arc transfer from the tip to the wire is easier.

Easier arc transfer means a superior “sure start” and less arc failure or wire BURN BACK, sputtering and spatter.

Understanding contact tip recess

Correct contact tip recess can reduce the opportunity for excessive spatter, porosity and burnthrough or warping on thinner materials. It can also help minimize radiant heat that could cause premature contact tip failure. 

Contact tip recess directly impacts wire stickout, also called electrode extension. The greater the recess, the longer the stickout is and the higher the voltage, which can make the arc slightly less stable. For that reason, the best wire stickout is generally the shortest one allowable for the application; it provides a more stable arc and better low-voltage penetration. Typical contact tip positions are 1/4-inch recess, 1/8-inch recess, flush and 1/8-inch extension.

Extending contact tip life
Contact tip failure can result from a number of influences, including burnbacks, mechanical and electrical wear, poor welding operator technique and reflective heat from the base material, which is common in tighter access weld joints or confined areas. 

The quality of the wire being used can also affect contact tip life. Poor quality wire often has an undesirable cast or helix that can cause it to feed erratically. To extend contact tip life, consider the following:

• Keep the contact tip free of spatter. 
• Use the proper drive rolls to ensure smooth wire feeding. 
• Select contact tips with a smooth surface to prevent wire snagging.
• Trim the MIG gun liner to the correct length so that the wire feeds through properly. 
• Lower operating temperatures, if possible, to reduce electrical wear. 

In some instances, it may be desirable to convert to a water-cooled MIG gun to help keep the front-end consumables, including the contact tip, cooler and running for longer.