RX 90 joint 6 turns

[afelix]

I have a slight problem with RX 90 robot controller and CS7.
 when I teach some locations and then move it several times to those locations it does it well.

 But after a day or two without turning off the controller I try to move it to that same locations and I notice that the joint 6 has move a little. I have to re-teach to correct it.
 this happens in all locations and without turnig off the controller.

do you know what could be happening?
thanks

[Jim C]

a simple check is to move joint 6 to 0 degrees and check the witness mark on the joint. Ideally at 0 degrees the marks should be perfectly aligned. In practice there is often a slight different. To account for this there is usually a "MARK" file with a "#mark" joint location which has the correct joint angle to make the witness marks line up.

By check to see if the witness marks have moved, you can determine it the issue with the robot or with the end of arm tooling shifting.

If the witness mark is moving, about the only cause I can think of is that the coupling between the joint 6 motor shaft and the wrist was not tightened down.

Less common is a calibration error on start up which shifts the joint position by a full motor turn, 6 degrees or sometimes much more. This was seen some times on the original RX90 / CS7 (today call an 'A' system). Later RX90 / CS7 had a software correction (called Delta calibration). It was never an issue on the RX90B / CS7B which has a different calibration system.

The most common cause I used to see was the end of arm tooling not being properly fixed to the flange (for example no alignment pin) and flexing as the arm moves.

[afelix]

hi,

I have a new problem with the robot Rx90,
when I try to teach a new location me the controller displays an error
*motor amplifier fault *   Mtr3

to see the error message returned by the bts10 card, corresponds to electronic fuse.
that is activated when the current supplied to the motor exceeds the nominal value.
it can due to heavy motor load, but this is only 3 kg.

when checking the engine, I discovered that the button for the release break does not work for the motor 3.
Could this be the reason you show me the error?

thanks

[Jim C]

Most likely the brake in the motor has failed. You are seeing the fault because the brake is dragging putting an additional load on the motor. This will also wear down the brake disk causing the brake to fail, when you turn off or lose power the arm will drop crashing into whatever is under it. The motor will have to be replaced.