The right tip
- Created: 2018-08-06
Choosing the right contact tip can make all the difference for pulsed MIG applications in the automotive world
by Andrew Marchand, product manager – automotive segment, Tregaskiss
Optimizing the robotic weld cell helps improve productivity, allowing a manufacturing facility to save time and money. It can be especially beneficial in applications that use pulsed MIG, a process that results in rapid wear to the welding gun’s front-end consumables.
While the choice of a contact tip for a MIG gun may seem like a small factor in the entire welding operation, consider how much time it takes for an operator to enter the weld cell and change the contact tip – and how many times per day the tip is changed in most robotic welding operations. For example, copper contact tips are changed on average four times per shift. In a three-shift operation averaging 10 min. per tip change, that equates to spending 2 hours per day changing contact tips.
This type of time drain can be a major issue for any manufacturer, including automakers and their Tier suppliers. Fortunately, contact tip innovations are available that help significantly reduce the downtime spent on changeover – time that can be spent on other tasks in the operation, such as increasing production uptime.
In addition, when the operator spends less time in the weld cell, it reduces the potential of health and safety incidents and the possibility of weld quality issues through altering weld settings and parameters such as tool center point.
For these reasons, it’s important to consider the total cost of ownership when selecting the right contact tip for a robotic welding operation.
As more manufacturers – including automakers – are using thinner, lighter and more corrosion-resistant materials to meet industry demands, this increases the use of pulsed MIG processes, which offer benefits for welding thin-gauge materials. Pulsed waveform technology continues to develop, offering faster travel speeds, reduced spatter levels and high weld quality in many robotic applications.
However, pulsed processes typically require a higher frequency of contact tip changeover due to the energy of the process. Faster contact tip deterioration is caused by peaks in pulse waveforms where the energy/heat is five times greater than in traditional constant voltage (CV) MIG.
Because of this, arc erosion is a common failure for contact tips in pulsed MIG. A new contact tip design has resulted in tips with improved resistance to arc erosion that last much longer in pulsed MIG.
Contact tip advances
Contact tips made from copper or chrome zirconium are commonly used in many welding applications. However, adoption of a pulsed MIG process can double contact tip replacement frequency and related downtime when using copper or chrome zirconium tips.
A new innovative technology can significantly extend the time between contact tip changeover thanks to a combination of proprietary materials and tip design. Tough Lock HDP contact tips from Tregaskiss last more than 10 times longer than copper or chrome zirconium tips, allowing operations to go from changing contact tips two to four times each shift to only changing the tips once every third shift or less.
HDP contact tips are engineered to resist wear, providing increased resistance to arc erosion in pulsed MIG, as well as spray transfer and CV MIG. The precise fit between the tip and the wire also results in good arc stability to help produce high-quality welds, and because the degradation of welding current from the power source to the contact tip is reduced, it provides a truer representation of the pulsed waveform program.
The tips currently come in 0.035 in., 0.040 in. and 0.045 in. sizes and can be used with standard nozzles and Tough Lock gas diffusers as well as with air-cooled guns or water-cooled guns. The contact tips can be used with Tregaskiss guns as well as welding guns from other manufacturers.
Because the tip bore is sized so tightly to the welding wire, it’s best to use the HDP contact tip with good quality welding wire that has a large cast. A high-quality wire typically has a consistent wire diameter, which promotes better feeding and optimized performance.
Typically, operations conduct contact tip changeovers on a preventative maintenance schedule to avoid unplanned downtime in the manufacturing process. The necessary frequency of contact tip changeover varies based on many factors including application, wire type and quality, waveform and base material.
Many robotic welding operations have 100 welding arcs or more and run three shifts per day. In robotic welding operations, copper tips are changed on average four times per shift – or 12 times per day. Chrome zirconium tips are changed about half as often, or six times per day. A scheduled contact tip change typically takes 10 to 15 min. to complete.
Compare this to real-world results from several manufacturing operations using HDP contact tips.
One manufacturing operation converted to HDP contact tips in a solid wire pulsed MIG application. The operation produces 600 parts per shift, and the previous chrome zirconium contact tip required changeover every 60 to 80 parts – or about 10 times per shift. In the company’s trial, one HDP contact tip was still running after 2,500 parts under the same parameters.
Another manufacturing operation running a standard MIG process tried HDP contact tips on a line of 18 robots. Where previous contact tip usage for the operation was 216 per day – or about 1,500 tips per week – one HDP contact tip lasted an entire week on each cell, totaling 18 tips per week.
Reduced frequency in contact tip changeover not only increases throughput while saving time and money, it also reduces the risk of safety incidents since every time an operator enters the weld cell it increases the risk of injury.
Also, each time someone touches the welding gun, there is the risk putting it out of alignment. The less frequently an operator must enter the cell, the less chance there is for human error that can disrupt tool center point that reduces part quality.
Frequently changing the contact tip can cover up other issues that may be occurring within the weld cell. When the contact tip is changed less often, other issues such as wire feeding problems, wire routing or a loose ground can come to the forefront.
With standard contact tips, changing the tip out is often the first go-to fix when there is a problem in the weld cell – even if something else is the root cause. With a longer-lasting contact tip that is changed less frequently, other issues that may not have been noticed before can now be fixed to improve the overall efficiency of the weld cell.
Return on investment
It’s important to consider total cost of ownership when evaluating contact tips and other consumables. The cost of a contact tip is just one factor in total overall costs. A longer lasting contact tip may be more expensive upfront, but it can provide significant payback in time and labor savings and reduced downtime. Be sure to look at the big picture in terms of productivity and efficiency improvements for the entire operation.
In considering a consumables switch, any operation should make sure there is time to conduct a trial, which should always be part of changing the type of consumable or contact tip. The numbers will often speak for themselves when vetting the option and analyzing return on investment.
An operation may think the welding process is optimized, but that may not be the case if operators must frequently enter the weld cell to change the contact tip. As manufacturing operations look for ways to improve production efficiency and throughput in automated welding, choosing the right contact tip can make all the difference.