The mystery of the Lost Z
So I was minding my business and all of the sudden the Z decides to go nuts and overshoot it’s target.
Well as a reader you probably go yea, I would proceed to change my shorts 
, after cursing 
at the sky for 5 minutes and to be honest you wouldn’t be wrong 
.
My reaction however was different, I was quite staring at my part 
wondering what in the world I just witnessed. Needless to say it was on the chamfer tool operation where I first witnessed this and my chamfer tool turned into a drill bit…yea go ahead and laugh 
thinking back at the stunned look on my face I’m sure I looked pretty funny.
Cause of the issue
I will spare you all the non-issues and jump right to it the Servo drives are so AWESOME that the older design of coupling couldn’t handle the torque of the new drive. In my experiments I found that the Z only had an issue when traveling in the negative Z not when returning to a G30 and only when going full rapid. My hypothesis which was later confirmed by the support guru’s at Tormach HQ is that the coupling would slip just a little and the motor would try to catch up before finally erroring out. If the velocity was at 50% the issue would go away so basically if the machine was running at stepper speeds no issue.
Solution
So after trying to tighten the screws on the coupling and then a second time with LocTite I found that the issue came down to a worn coupling. I proceeded to replace the coupling and while I was at it coated the inside of the mating surfaces with a light coat of BLUE Loctite which is considered removable and should you need to replace the coupling in the future you will thank me.
Video of the process
To document it I decided to record all the experience via video and upload to Rumble.
Please note the purpose of the video wasn’t to make a massive presentation but rather simply to document the process so it is a little crude but shows all the steps taken to troubleshoot and resolve the issue.
#Mill #770M #770MX