While I worked for ABB Flexible Automation, I provided support for ABB robots at the General Motors Oshawa Truck Plant, GMT 800 project. Part of the preventive maintenance at the plant was using a thermal imager to look for hot spots. A hot spot could include a loose electrical connection. During an inspection, they found one of the robots had hot servo motors. I was tasked to find out what was wrong with the robot and fix it.
During my investigation I found that the resistance welding gun the robot was carrying exceeded the rated payload. The perch position was programmed so that the minor axes -- the wrist axes, 4, 5, 6 -- were holding the weld gun at an awkward angle, causing each axis to carry a load against gravity. These three axes had the high temperatures. The servo-on time was set to maximum, effectively years. The robot would wait with the servos on, for years, before timing out, enabling the brakes, and turning off the servo power.
I presented these finding to the engineer in charge of that work cell. The options to get the servo motors to run cooler included:
Reduce the weight of the weld gun to within the payload specification of the robot.
Replace the robot with a higher-payload unit to match the weight of the weld gun.
Change the perch position so that the wrist axes were not carrying a load. This could be done by removing the servo-on signal, causing the servo motors to power off, and the brakes to engage. Then release the brakes of the wrist axes, allowing the weld gun to hang in an orientation that would not load the wrist servo motors, and re-teach the perch position.
Change the servo time out to minutes, allowing the servo motors to turn off and the brakes to engage. This would cost a few milliseconds of cycle time each time the servo system was enabled and the brakes released.
Each of these options was rejected. When I was asked again about the hot servo motors, my response was that if they were not willing to accept any of the options, they would continue to have hot motors.
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You're right GTOlover, once a procedure is approved in an ISO company, it's really hard to get the procedure to change. If this is a component part that is shipped to another company they may need to go through the qualification process all over again.
Rob, I have to agree to a point. When large coprporations set up quality systems of processes and procedures, changes become rigid and inflexible to the point that many people do not want to do the work to make any change (even when it is benefical). I have worked at a large manufacturing facility that it was nearly impossible to upgrade a simple proximity sensor. Then I worked at a small shop that I could completely re-engineer a robot cell with little resistance!
However, it would seem that this change should of been a worth while if it prolongs the servo motors life.
We're seen this type of management problem a couple times in recent Made by Monkeys postings. It's quite surprising that management would shrug off -- or refuse to accept -- solutiuons presented by engineers. This seems to be more than just a communications problem.
For industrial control applications, or even a simple assembly line, that machine can go almost 24/7 without a break. But what happens when the task is a little more complex? That’s where the “smart” machine would come in. The smart machine is one that has some simple (or complex in some cases) processing capability to be able to adapt to changing conditions. Such machines are suited for a host of applications, including automotive, aerospace, defense, medical, computers and electronics, telecommunications, consumer goods, and so on. This discussion will examine what’s possible with smart machines, and what tradeoffs need to be made to implement such a solution.