kawasaki robot joint 4 motor replacement

FIRST THING IS THERE IS NO NEED TO SHOUT...…….The majority of us can also understand lowercase....(Just my sense of humour).

Yes, Kawasaki have:

ZX

ZB

ZD

ZT

1. So which variant you're using would help.

2. Have you got the manual for your robot - and have you read it.

3. Why do you believe you have a bad motor - error code or description of problem.

Lol.....No worries......I have some bad habits, but I can't publicise them here......

Joints 4,5,6 are the same models, so you could exchange them over and re-zero to test whether it is the motor at fault.(gearing will need swapping too).

Useful if you haven't got a new motor to hand.

What do you mean 'out of tolerance at a certain spot in motion'.

- Does it produce an error if so what it is.

- Or is this just visually in a different location.

Sorry for the questions, I don't recall that type of fault.

- Can you be specific and include an error code - most Joint related faults also display the JTx including a description.

- Does it occur if you switch to Teach and manually check through the program to that position.

- Has the before, target or after positions been changed recently.

That error is sometimes attributed with the robots physical posture is close to singularity where a linear move is being executed applicable to a transformation (cartesian) location - ie JT4 is trying to change direction, when it shouldn't - You may visually see this and a burst of acceleration prior to the error.

Sorry for the questions, I just don't want you wasting time changing a motor when it could be something else.

- Has this just started to occur in normal production after successfully previously been operating.

- Or is a newly commissioned robot.

- Any chance you could post any code relating to it and the location values - specific area of the program where it errors out.

- Any chance you could re-teach the target position again, by checking back to the previous position and jogging to the new position.

Ah right, so it's been working fine for a period up until this point.

But any changes that have recently taken place regarding position teaching, zeroing, maintenance that could have attributed to it - anything minor......

It doesn't take long to swap motors around, and how you described the process is spot on, so you could swap it out to eliminate it.

Be interested to know what the final outcome is though.

In my experience Error 1118, command value of joint 4 has suddenly changed could still be motion related even if it suddenly started happening after the robot has been in and running for a few years.

Usually you'll find it happens on motion near the zero degrees of the joint in question where say for instance jt4 was meant to be 0 degrees or positive. but when the robot physically gets there jt4 has over shot the mark and now JT4 is slightly in the negative due to wear in the gearbox or other external factors.

So when the motion planner wants to issue the next motion it's expecting jt4 to be positive but now it's suddenly negative and this in turns generates the fault E1118 saying the command value suddenly changed.

I've had this happen on 1 of 13 RD80's robots on jt5 that all use the same code and only came up after 2 years of running. I changed my motion code of a calculated position so that jt5 didn't stop near it's zero as a test and it fixed the problem temporarily to keep production up and running until we could investigate further. I believe we ended up changing the belt on jt5 since those robots use belt and pulley for jt4 and 5.

I've also had this happen on an MX300 on jt7 since the robot was on a rail, a few years after installation we got E1118 on jt7 when the robot was doing motion near it's Zero when sometimes it overshot the mark. I can't remember what the outcome was but i think we replaced the gearbox on jt7 during the next maintenance shutdown. I vaguely remember changing the motion so that jt7 didn't stop near the zero mark by around 5mm as a temporary fix and also to try and prove my suspicion about the cause of E1118.

I'm not sure about your application or if it's feasible to change motion code for you but if you save the Error log and post the info on E1118 it could shed some light on what the robot pose was and if it was indeed the commanded value for JT4 did suddenly change or not. Generally you still want to find the root cause of the problem and not just work around it with a motion code fix.

ShAdOwDrAgOnS some very useful information indeed, thanks for sharing...……