by rungemach » Wed Feb 07, 2018 2:33 pm
Hello Joe,
It looks like you have already tried to check out some of the "usual suspects".
You can get a z drop by inadvertently hitting the upper z limit when the router retracts. Judging from the pictures it seems that is probably not the case. You can check that by running the tool path in air with no workpiece and see if it gets close to the high limit. That type of problem should be repeatable, and is easier to find.
The intermittent "takes off and plunges" problem seems to happen to a good number of folks, and I have not seen a definitive answer. Intermittent problems are very hard to track down.
The problem can be in the controller, or in everything downstream of the controller (wiring to the motor, axis sticking, etc.)
On the controller side, you may want to check and see if it is getting warm. If this is happening after it has been running for a while, and not when cold, you may have a heat related issue with the controller. The controller does not have any forced air cooling, and blowing a fan across it may help.
On the "everything downstream" side, check your wiring to the motor to be sure it does not look overheated or kinked. You have already checked the axis for binding, etc. Do you have any extra weight on the z axis that would make it harder to retract?
If the z is powering down into the work, and you bits are not slipping down in the collets, and you are not hitting the up limit of the axis, I would start to suspect the controler.
Hope this helps
Bob