The cost and payback of contact tips in robotic welding

Robotic welding systems are designed to yield measurable advantage to companies, including increased productivity, and improved accuracy and quality compared to semi-automatic welding. These benefits, however, do not happen by chance. They require careful planning, oversight and execution on a regular basis.

Maintaining a vigilant watch over the expenses in the operation is also important. It can help companies not only become more profitable, but also more competitive. When it comes to providing appealing bids, companies that have learned to manage costs effectively can often pass those savings onto their customers, gaining more business and greater loyalty in the long term.

For an accurate assessment, it is important to look at the amount of labor needed to oversee the robotic system, as well as capital investments for the equipment, the purchase price for materials, and also replaceable items like robotic welding guns and consumables.

While only a very small part of a robotic welding operation, consumables — nozzles, contact tips and gas diffusers (or retaining heads) — represent an ongoing cost since they must be changed over frequently, in some cases multiple times in a shift. If these products are not durable enough for the job, companies could be spending much less upfront but significantly more over a period of time. Careful selection is imperative, particularly when it comes to contact tips. These consumables encounter significant heat from the welding arc and require changeover more frequently than a nozzle, for example. As a general rule, they contribute more to overall consumable costs, too. On average, companies spend approximately $1,000 to $2,000 on consumables per robot annually. Of that, around half can be contributed to the cost for contact tips.

Types of contact tips

There are a variety of different types of contact tips, each of which offer specific results for an application. Many standard contact tips are made of copper, which provides good electrical and thermal conductivity; however, this material has lower wear resistance. For higher amperage applications where the chance is greater that the contact tip will wear due to heat, some companies prefer to use heavy-duty copper contact tips or choose those made of chrome zirconium. Extra-heavy-duty consumables are also available and are good choices for high-amperage applications requiring larger-diameter welding wires — 0.052 inch and greater. There are also contact tips that are specifically designed to provide extended life in specific applications. These products are made from a copper alloy with an insert made of a harder material that can resist wear and extend the contact tip life.

For any type of contact tip, it is imperative to use those that are well-machined and have smooth surfaces. These higher-quality contact tips are less prone to collecting spatter and tend to last longer.

The impact of contact tip failure

Contact tip failure occurs as the result of one of two factors: burnback or wear (keyholing). Burnbacks result from a weld forming within the contact tip and are often the result of too slow of wire feed speeds and/or incorrect contact-tip-to-work distance (CTWD) — the distance between the end of the contact tip and the base material. Too short of a CTWD, in particular, can cause a burnback. Poor wire quality and incorrect welding parameters or wire feed speed can also cause this issue. Welding operators will often be alerted to issues with burnback if they start experiencing poor arc starts or stability or the wire stops feeding completely. This form of contact tip failure causes costly, unplanned downtime.

Contact tip wear results from both mechanical and electrical means. The friction of the wire feeding through the contact tip can wear away at the material, resulting in issues with tool center point (TCP) and leading to rework for offset welds.

Regardless of whether a contact tip fails by burnback or wear, there are cost considerations — and consequences — to each occurrence. The accrued costs can take many forms:

• Downtime for troubleshooting weld quality issues
• Loss of productivity during unscheduled contact tip changeover
• Increased labor and material costs for rework of weld defects
• Increased costs for purchasing and maintaining a high level of inventory

Simply stated, if the robot isn’t producing parts, it is costing the company money. These costs, however, will vary according to customer and industry. An automotive customer, for example, stands to generate greater cost for contact tip failure and replacement due to the high production levels — shutting down the welding operation has a larger impact on the bottom line. Conversely, in an industry like heavy equipment manufacturing, where larger parts are being welded, the cost impact may not be as detrimental.

Minimizing the costs

In addition to selecting the most appropriate type of contact tip for the robotic welding application — for example, heavy-duty or chrome zirconium for high-amperage jobs — it is also important to track usage of these consumables. Understand how long a contact tip lasts and schedule changeover during periods of time when welding isn’t taking place, such as during the fixturing of parts. By knowing how long a contact tip lasts, welding operators can replace old ones before the component fails, thereby minimizing costs for downtime, quality issues and rework, and lost productivity. A carefully planned preventive maintenance (PM) program is recommended.

It is equally important that welding operators do not change contact tips too frequently, as it can also increase costs dramatically. Contact tip changeover can become a matter of habit, resulting in excessive usage. As stated before, changeovers should take place before a failure, but it is best that they occur at a scheduled time according to careful tracking and assessment.

To ensure the appropriate contact tip is in place for the given robotic welding application, consult with a trusted distributor or consumable manufacturer.

Andrew Marchand is product manager at Tregaskiss.