Losing Z steps

I ran the code that you (John) suggested- and the tool ends up exactly at .5 above the table- I lower it to zero, and it was perfect.

From your experience, does this mean that the acceleration is set to an acceptable level? I understand I could do better if I went to a higher voltage drive, but as I understand it, it isn't the root of my problem.

I don't have any binding in the Z axis. I'm using the spring arm that came with the mill as the counterbalance- I understand that it doesn't provide near 100%, but it is something.

When you ran the test was your spindle on? The spindle motor might be causing a problem with the stepper drive boards... bad ground or something like that...

John

When I first tried, the spindle was off, but I tried it with the spindle on (at about 75% of max speed, the speed I was running when trying to engrave) and the results were the same- after the test, the tool was exactly 0.5" above the table. I think I will try this while only moving a very small amount and see if this reproduces losing the z steps.

I'm quite open to other experiments/suggestions.

FYI: I have not adjusted the trim on the geckodrive- it is as it came from the factory.

You could try running the test again but with moving the x and y axis at the same time, perhaps three axis moving at once is pulling the power supply amps down.
Are you sure you are not trying to lower the z axis into the work too fast when running your program? Try lowering the z axis speed even lower.

Rick G

If the steppers don't growl in the mid range no need to adjust the trim.

Does the back plot show the tool Z level changing higher and higher?

Can you apply some side loads to your column to simulate cutting loads while testing the Z?

John

The plot does show the Z tool level changing- I did some experimenting and I found that it is only losing steps in a slow (G1) move, I had set the tool speed very low (F0.1 in the G-code) and the stepper was not moving at all, while I could see the back-plot changing. I sped *up* the feed rate during cutting to F2.5, and it was able to do the entire engraving cycle without losing any Z.

And then... I broke the last tiny end-mill I had, so I ended up doing the engraving with some cheap Harbor Freight "diamond" grinding tools (meant for a dremel tool, I believe).

I have never lost steps (I am aware of/have evidence of) in X or Y- the only real difference is the thread pitch on the feed- 32,000 microsteps per inch on X and Y, 20,000 microsteps per inch on Z.