[Fargo]

I have a sieg kx3. Recently while machining aluminum with a 3/8 two flute endmill, the spindle stalled during a plunge cut of only 0.1875". I immediately hit the ebrake and retracted the tool. Since then the z axis randomly loses steps. I have checked the ball screws and every thing appears tight. Everything is lubed up well and I wrote a short code that brought the head up and down from z0 to z3 repeatedly without it losing its zero. What am I missing here? Sometimes it machines perfectly with a 0.125 endmill, other times it loses a step, and drags the endmill into the material on a retract and breaks it.

[neilw20]

Is the Z axis coupling broken? Crack can hide nicely in those wire cut ones if that's what you have.
A coupling slipping on shaft is another thing, that no amount of tightening will fix. Pull it apart and examine closely.
A screw digging a hole in the shaft and moving back and forwards in the fretted groove it has made.
Couplings that clamp on the shaft are generally less of a problem.
A loose wire in a connector to the stepper is a likely electrical problem.

[Fargo]

I pulled the mill apart again and checked the coupling. No cracks, very tight and is of the clamp on type. Did notice that if I push on the stepper shaft, it moves in and out 0.125 inches or so with a lot of resistance, due to magnetism? Never noticed that on a stepper motor before, but never pushed on one either.

[Fargo]

Gas strut also has no spring to it

[neilw20]

That won't help. Original was too strong at 60KG. You only want 40KG.
Car strut supply people will do a custom one.
Make sure thin part of strut is down so the oil covers the seal and it never leaks.
Mount skinny end up, and it will fail in a short amount of time, as well as getting crud in the seal.

Look here...
http://www.cnczone.com/forums/showth...ighlight=strut

[Fargo]

Everything else looks fine. Ball screw is tight, couplers look good, no cracks. I have no clue what could be causing the lost steps.

[Fastest1]

Just for info, most steppers I have played with will move in and out a little bit. That being said the screw should be secured via a thrust bearing or AC of some type prior to any stepper connection so that movement will not be an issue.

[Fargo]

Thanks, I thought as much. I've decided to polish the gib, then reinstall mach 3.

[DonKes]

If you have a bent gib (I did), it can be tight and can still have play.

Don

[Fargo]

Do you know wha t caused it to bend?

[Fastest1]

Bent or not flat?

[Fargo]

Just pulled out the gib. It was flat, gave it a polish on a surface plate anyways.

[HawkJET]

if I push on the stepper shaft, it moves in and out 0.125 inches

Gas strut also has no spring to it

These are the problem. Re-installing MACH3 won't solve a thing.

[Fargo]

Thanks for the reply. I got ahold of a gas spring for an X3. It's 3.5 inches shorter than I need, but should work to see if it solves the problem. Just waiting for my garage it return to above freezing temperatures to test it out!

[R.M.S.]

It sounds like everything is mechanically sound from what your saying. My next step I would lower my motor timing and acceleration values in mach and see if that helps.

[Fargo]

Finally got back to the mill since the weather has warmed up. When moving the z axis up and down while looking at the Z stepper motor, I noticed that the stepper itself looks to be the cause of the problem as it randomly seems to stuter and get caught up. No idea what is causing this.

[Fargo]

I pulled off the side panel to watch the stepper driver lights while cutting air. I then noticed that the X and Y stepper driver overheating lights were slowly coming on. Touching the heat sinks showed that they were warming up, though the Z axis was not, probably because the program had fewer Z motions. Machine was run for about an hour and did not loose any steps in the Z axis. Could this possible be the culprit?

[Fastest1]

Absolutely. You must run heat sinks on many drivers. The overheating will cause errors. Try a fan blowing directly on your electronics.

[Fargo]

Thought I would relate my progress thus far. I removed the saddle nuts for the x and y axis and ran a program with only the stepper motors moving , not the table. This was to see if the gibs were over tight and causing excessive drag. To my surprise, the stepper drivers still began overheating. Currently looking for a fan that I can wire in to cool the drivers. I find it odd though that this is a problem. Is it just a poor layout of the drivers. There is one fan at the top of the compartment drawing air up, but apperently its not enough.