During the welding production process, there are many reasons why a welding robot might burn the contact tip.
Observable symptoms indicating frequent replacement of the contact tip include: wear at the tip’s exit causing the wire to deviate, which in turn offsets the actual welding trajectory and the TCP point location. This could lead to welding defects such as offset or missed welds.
Analysis of Issues Arising from Welding Robot’s Burnout of Contact Tips
1. Causes of Contact Tip Failure
The wear of the welding robot’s contact tip can be traced back to the friction caused by continuous wire feeding under the increasing temperature of the contact tip. This wear, which occurs at the contact tip’s outlet, often leads to calibration errors that diminish production efficiency during the robot’s welding operation.
Efforts should be made to lower the temperature of the contact tip, including considerations in the composition and structural processing of the contact tip.
The materials for the contact tip include brass, copper, and the best among these is chromium-zirconium copper. Even the inclusion of ceramic components in the contact tip can enhance its abrasiveness.
Furthermore, the precision of the contact tip’s processing is often compromised due to the precision of the processing equipment or other issues, resulting in less than desirable smoothness and concentricity of the contact tip’s inner hole.
2. Arc Instability Leading to Arc Blowback
Causes of this issue include poor arc initiation, unstable arc, hindered wire feeding, and the cleanliness of the workpiece surface. However, these factors do not necessarily affect the performance of the contact tip itself.
Welding malfunctions at this point are generally related to the characteristics of the welding power source, the quality of the welding wire, the effectiveness of wire feeding, the wire hose, and the structural design of the contact tip.
When the welding wire’s conductive point within the contact tip frequently changes, its lifespan becomes only half of what it is when the conductive point is stable.
3. Factors such as straightness and surface cleaniness of welding wire
The welding wire used by welding robots is often packed in drums or reels, and may have burrs or grooves. These imperfections can potentially interfere with the contact between the wire and the contact tip.
During robotic welding, the contact tip should provide minimal friction while maintaining stable conductivity. The lifespan of a contact tip used with dirty welding wire might be only one-third that of a tip used with clean wire.
To judge the quality of the wire, we consider the degree to which annealing stress has been relieved, which is manifested in the wire’s straightness. Test feedback shows how the wire automatically bends 50mm in front of the welding torch tip: if it bends forward, the wire is too soft; if it bends backward, it’s too hard.
Hard wire is more damaging to the contact tip. Furthermore, whether the wire feed hose from the wire feeder to the welding gun is bent can also cause the wire to bend.
4. Wire feed speed or deposition rate
Generally, the smaller the diameter of the contact tip, the shorter its lifespan. For a current of 300A, both 1.2 and 1.6 welding wires have roughly the same fill (melting) volume per unit of time.
The length of the 1.2 wire is twice that of the 1.6 wire, which means that for the same current and time, the wear on the 1.2 contact tip is almost double that of the 1.6 tip.
Assuming both the 1.6 and 1.2 contact tips have worn by 0.2mm, this 0.2mm represents 12.5% of the 1.6 tip and 16.7% of the 1.2 tip, so the 1.2 wire has a larger range of deviation.
5. Open grounding devices or wires can cause high temperatures, leading to slag adhesion
How to Prevent Welding Robots from Burning the Contact Tip and Strategies for Improvement
1. Purchase contact tips made of chromium-zirconium copper from reputable brands that guarantee precision.
2. Ensure the straightness of the welding wire.
3. The contact tip must be tightened with pliers, it’s inadequate to just hand-tighten it. This could lead to an unstable arc and greater wear on the contact tip.
4. Maintain a normal cleaning gun station and apply anti-spatter silicone oil.
5. It’s recommended to use a lower voltage, selecting an approximate formula of 14+0.04 current. Higher voltage leads to greater loss.
6. Regularly clean the wire feed pathway.
7. The quality of the welding wire is also a decisive factor.
8. Keep the workpiece surface as clean as possible, minimizing oil contamination.