Identifying the causes and fixes for robotic welding troubles

Five common issues and solutions to save time and money

04/15/2013


Robotic welding systems are built for speed, accuracy, and repeatability. Knowing how to troubleshoot problems quickly and effectively can help prevent issues with quality, productivity, and costs. Courtesy: TregaskissKnowing how to troubleshoot quickly and efficiently is critical in any welding operation. For robotic welding systems it is especially important, as there is a lot at stake when something goes wrong in the process. These systems are built specifically for speed, accuracy, and repeatability. Therefore, any downtime to address problems can adversely affect the quality and productivity improvements sought by investing in the equipment. It can also lead to increased costs.

When a problem occurs with a robotic welding system, it’s valuable to identify any variables that may have recently changed. Asking questions like the following may be beneficial:

  • Has a welding operator recently reprogrammed the robot?
  • Has the robot recently been restarted after a long shutdown?
  • Have there been any changes with the consumables or robotic MIG gun?

 

 

In many cases, it may be a simple fix to get the robotic welding system back up and running. To help in the process, consider these causes and remedies for robotic welding troubles to get back to welding sooner.

Trouble 1: Poor wire feeding

Causes:
There are two key causes to poor wire feeding in a robotic welding system: one, issues with the liner such as debris buildup; or two, an improperly functioning wire feeder, particularly the drive rolls. A third issue, wire cable kinking, can sometimes lead to poor wire feeding performance, too. Regardless of the cause, the result is typically the same: poor arc and weld quality. 

Remedies: To prevent and/or address issues with the liner, be certain to change out this component during routine maintenance. Doing so helps prevent debris from building up inside, either from the welding wires or the shop environment.

Using a robotic MIG gun with an “air blast” feature is also very helpful to eliminate debris. This feature blows air through the liner during scheduled downtime in the robotic welding cycle. That downtime may be during a reaming or cleaning cycle and/or during parts changeover. In the absence of an air blast feature, welding operators can also manually blow compressed air through the liner.

If a welding operator suspects that the drive rolls may be the culprits of poor wire feeding, there are two options to assess the situation. One, visually inspect the drive rolls for signs of wear. Over time, these components can become worn and may not guide the welding wire properly. The welding operator  can also conduct a “two-finger” test: Disengage the drive rolls, grasp the welding wire, and pull it through the gun. If the wire pulls through easily, it is likely that the drive rolls are the cause of the poor wire feeding. In both instances, replace the drive rolls as necessary.

Finally, look for kinks in the power cable, as these can also lead to wire feeding problems. Unwind and straighten the cable as necessary.

Trouble 2: Welds are inconsistent or off-location

Causes: Inconsistent or off-location welds are the antithesis of what companies desire from a robotic welding system. Often this problem is the result of an issue with the tool center point (TCP). TCP is the focal point of a tool; in the case of a robotic welding system, it is the location of the robotic MIG gun to the position of the welding wire in the joint (gun-to-work distance). Typically, TCP issues occur after a collision that causes the robotic MIG gun neck to bend.

Variations in part fit-up or fixturing can also cause inconsistent or off-location welds.

Remedies: To rectify issues with TCP (particularly after a collision), welding operators need to bend the neck back to the proper angle. A neck-checking fixture or neck alignment tool is the best tool for this task.  It is also important to check that the neck has been installed correctly. If the neck isn’t fully seated, it may extend too far and lead to TCP problems. Program a TCP check to verify the proper neck position to protect against future issues.

There are steps to take to differentiate between inconsistent welds caused by a TCP problem versus a part fit-up or fixture problem. First, remove the robotic MIG neck, implement a TCP check via the robotic program, and verify that everything is on-location. If everything checks out properly, the problem is likely a part or position variation.

Check that the fixturing and robot base are both securely in place—any movement in these components can cause inconsistency in the welds. Also, check for part variations and rectify these accordingly. 


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