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Author Topic: Z axis losing steps.  (Read 1147 times)

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Z axis losing steps.
« on: January 06, 2017, 09:15:00 PM »
Im a 28 yr old veteran very mechanically inclined volunteering at a church that cuts cross designs out of 9/16in plywood. They have ran the machine for years without any issues but I know nothing of cnc. I am familiar with computers and brushless step motors.

The photos here show how the machine decided to start jumping around randomly after being restarted 2x. It was also losing the z depth and dragging the bit when it should have hovered on to the next cross. Quick googling means its losing steps which they say it has never done. The gear tracks, pulleys and gears appear to be clean and clear of obstructions but i plan to do a meticulous cleaning tomorrow. Hoping to get some quick guidance to what may be going on before i stick my head into these forums and try to learn as much of the trade as I can. Thanks - Nick
Re: Z axis losing steps.
« Reply #1 on: January 07, 2017, 01:45:06 AM »
Hi,

This issue has been mentioned in other forums and posts by users who found it was one of the following

- loose spindle motor mounting
- loose grubscrews on a flexible coupling which is often found between the Z stepper motor shaft and the Z ballscrew, especially on Chinese CNC routers
- mismatch or looseness on the shank of the cutter in the collet. I found this with what proved to be a 6 mm shank in a 1/4" ER11 collet. Due to the cutting angles, the cutting forces can push or pull a given cutter in or out.
- collapsed thrust bearing on the spindle motor shaft (that would be rare)

Good luck

Re: Z axis losing steps.
« Reply #2 on: January 09, 2017, 02:05:31 AM »
I want to thank you for the fast reply. That next morning i went out to the shop was 0'ing the router out and noticed the router bit hitting the ply way sooner than our last 0. The bit came loose and pulled itself out a half inch and it just slipped our sloppy diagnoses. Weve started to screw the middle of the sgeet so it doesnt bind up anymore. However tho as tight as we put the bits on im amazed the collet would give slack before the bit broke