I have a Mazak Nexus 410A running on EIA codes most of the time.

Over the last few months I have had 4 z-axis crashes, the crash always happen after a tool change the z-axis rapids down to my plane, and basically never stops when it should. The problem is very intermittent, it might work fine on the first 50 identical parts, no zero or program change, then destroys 51, but will then cut 52 to 100 fine. It likes to keep my on my toes. Has anyone else had a problem like this? if so what was the culprit?

- Thanks in advance for any input