Understanding And Extending Contact Tip Life | R.S Electro Alloys

Premature contact tip failure is a common problem that can lead to unexpected downtime — and added costs — in a welding operation. This issue not only hinders productivity, it can also negatively affect weld quality and create rework.

Contact tips play a critical part in achieving high quality welds. Because of the constant friction from the wire and the exposure to the heat of the arc (and, in some cases, the reflective heat from the base material), contact tips take a tremendous amount of abuse during welding. This can easily turn into premature contact tip failure without the proper precautions.

Understanding the typical types of contact tip failures and their causes is the best approach to preventing them.

Types of contact tip failure

There are two main types of contact tip failure.

1. Failure that leads to a burnback and its associated problems

2. Failure that produces contact tip wear

Burnbacks occur when a weld forms within the contact tip and can occur at any point along the weld. They are not necessarily the result of poor contact tip performance, but rather burnbacks can result from too slow of wire feed speeds and/or incorrect contact-tip-to-work distance (also referred to as CTWD). The CTWD is the distance between the end of the contact tip and the base material; if the distance is too short (i.e. the contact tip is too close to the workpiece), a burnback can occur. The quality of the wire, incorrect parameter settings and micro-spatter buildup, as well as incorrect wire feeder and liner adjustments can all contribute to burnbacks. When they occur, burnbacks reveal themselves by way of poor arc starts, arc instability, inconsistent wire feeding and, ultimately, stoppages in wire feeding altogether.

Contact tip wear can be both mechanical and electrical. It occurs from the friction of the wire feeding through the bore of the contact tip and is especially prevalent in higher amperage semi-automatic and robotic applications. In the latter, contact tip wear can produce issues with tool center point (TCP), resulting in offset welds and potentially rework, especially in robotic welding systems that do not employ seam tracking. The design of the contact tip and the material it is composed of are two factors that affect a contact tip’s tendency toward wear. Typically, manufacturers use copper for contact tips because it is readily available and offers good electrical and thermal conductivity. Copper, however, has a relatively low resistance to wear, making it more prone to failures. For higher amperage applications, companies often turn to chrome zirconium contact tips due to their strength and their ability to resist wear by heat.

Rectifying contact tip failure

All contact tips, regardless of the material used to manufacture them, will eventually fail if used or abused for a long enough periods of time and/or at a high enough temperature. They are, after all, consumables with a finite lifespan. The goal, nonetheless, is to prolong the life of the consumables in order to avoid unnecessary downtime, as well as cost for additional inventory. A good step in achieving those goals is to understand the ways to help prevent contact tip failure.

Burnbacks: There is no one solution to minimize contact tip failure due to burnbacks; each situation is unique and may require a series of corrective actions. The goal is to address the associated errors or issues that are leading to the burnback in the first place.

Rectifying contact tip failure

All contact tips, regardless of the material used to manufacture them, will eventually fail if used or abused for a long enough periods of time and/or at a high enough temperature. They are, after all, consumables with a finite lifespan. The goal, nonetheless, is to prolong the life of the consumables in order to avoid unnecessary downtime, as well as cost for additional inventory. A good step in achieving those goals is to understand the ways to help prevent contact tip failure.

Burnbacks: There is no one solution to minimize contact tip failure due to burnbacks; each situation is unique and may require a series of corrective actions. The goal is to address the associated errors or issues that are leading to the burnback in the first place.

Matching a welding wire with the appropriate cast for the contact tip bore tolerance can also reduce the risk for burnbacks, as it helps improve electrical contact and reduce CTWD variability. The wire’s cast is affected by three main factors: the supply reel (spool or drum); drive roll tension; and MIG gun neck angle. A tight wire cast may allow for a looser bore tolerances and still be able to make the appropriate electrical contact with the contact tip to create a stable arc. A straighter cast may require a contact tip with a tighter bore to exert pressure on the wire and create consistent conductivity. It is important to note that with a smaller contact tip bore, there is a risk of the spatter build up, so cleanliness is key.

Selecting contact tips with a smooth surface and bore can also help prevent the wire from snagging on the consumable and causing a burnback. Using a contact tip/gas diffuser design that maximizes the surface area between these consumables is another option to reduce the potential for this problem — the tight connection creates less heat and can reduce micro-spatter that could hinder the wire from feeding and becoming blocked in the contact tip bore.

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