[Tech teacher]

Our school has an old EMCO F1 CNC mill that is now hiccuping quite a bit and losing its "memory". On several occasions, the machine hiccuped and randomly went to a new position and continued the tool paths at the new position. I heard the stepper motors click a few times, and I went in and cleaned, lubed and tightened the slides. Everything moves smoothly, but those hiccup's continue to happen less frequently. When moving on its own with no program loaded in, the table moves smoothly with no judder.
Lately the Z levels have been slowly drifting downward as the cuts cuts are taking place. I have never seen this before. What and where should I be looking at? Is it a potential software issue where something became corrupted, or is it something in the hardware/mechanical's. I have been using the same post processor that I been having success with in the past,( I use SOlidWorkjs with the HSMWorks add-in posting to a Mach 3 post processor) and the G-code works, but these issues are new.

[DSpeck]

Did you check the set screws on the axis pulleys? If they are loose, it could cause some of these problems - the "hiccupping" at least.

[Tech teacher]

Yes, I did check the set screws on the pulley axis. They were all fine. I ordered a "new" Z-axis drive and ball screw assembly. The current one felt loose and worn out when I tried to move it by hand, while other portions were binding. I hope the replacement
part fixes the issues.