When I was working on robotics at Matsu, I was told to go check a Motoman K100 robot that had recently been reprogrammed. The robot was sometimes doing cold welds, and sometimes blowing a hole through the part. The first thing I did was ask the operator to show me what was happening. He showed me the robot, but the problem didn't happen -- it was supposedly random.
The workcell had been set up so that the robot had two different tooling fixtures: one for a plain steel part, and another for a galvanized part. I watched the robot weld a few more parts and saw the error. The robot blew a hole after the first weld on the plain steel part. It happened while the robot was welding a galvanized part. Now I had an idea of what to look for.
I reviewed the robot program and noticed that the weld calls were explicit. Usually the weld calls are in a subroutine that is called when the robot is at the weld position. Then I noticed the weld schedule was commanded after the weld was commanded. So the weld was always done with the schedule of the previous weld.
I edited the robot programs to add weld subroutines, one for each weld schedule, with the schedule set before the weld command. Besides fixing the problem, this also made the program shorter and easier to read.
This entry was submitted by Glenn Aitchison and edited by Rob Spiegel.
Glenn Aitchison's first field service job was in 1987. Since then he has worked in robotics, automotive, as well as industrial automation and machinery. He received his Certificates of Qualification as an Industrial Electrician and as an Industrial Mechanic (Millwright).
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