Update from older software version

[LeChuck]

Unfortunately I'm having the worst time with this and still haven't been able to get back to production. I don't know if it's Acorn or the lathe itself, or both. I thought I had things dialed in today and maybe was about to make my first pen where everything fits together in one session, and a brand new problem happened that literally never happened before, it's been like this, one new thing after another. Right after one operation, it failed to return to 0:0 by about 2mm on Z, and then destroyed my part as it was now too close when I started the next program. Now when I home it, even after rebooting the whole system, it homes Z to about 2mm in front of where it used to, every time. I've done this many times over the past few weeks, and it's the first time it does that, and I have no idea why. I haven't changed any Acorn settings since last time I was here basically. I cut pen parts yesterday, I cut some this afternoon without this particular problem, returning to tool check over and over, and this latest one, bam, it's completely changed the Z home position. Since I've lost weeks of work, I'm contemplating returning to full manual work at this point.

[martyscncgarage]

Check the mechanics of the machine. Make sure nothing loosened. Also post a fresh report.

[LeChuck]

I'm having trouble imagining what this could be. Do you think a belt skipped? I'll post a report tomorrow although I can't see what that would do, it may not be Acorn at all at this point. If a belt skipped with the servo motor, could it cause this problem where it won't return to the old home position? If that's the case that's a bummer as I'm relying on that to cut repeat parts. I'll see what I can find tomorrow. Since last week, I've also started using coolant, and it's a big mess. I wonder if some of it found its way out to the mechanisms or pulleys. I wish I didn't have to because it's pretty horrible, but things get real hot without it.

[martyscncgarage]

Could be a loose pulley, coupling, thrust bearing retainer or it could be lost steps, we look at the error logs in your report. F7 Utility, F9 Logs, F1 Errors

[LeChuck]

Here's a report. Went out there early this morning because this is really worrying. There's nothing interesting in the error log.

But here's the thing: I started the computer again this morning, reset and homed, and it did it again like yesterday. I looked at whatever I could look at, tried to see if it looked like any coolant or debris got back there, shook things (nothing moving or loose), jogged the carriage back and forth. Oiled and greased everything, jogged some more. There's a regular rubbing sound from the Z pulley (and clunking from the X). The clunking has always been there but I don't remember about the rubbing. It's like a mole on your skin, when you notice it, you can't remember how long it's been there. After a while I went back out front and looked at the PID to see what the absolute positioning was. Found it strange that the zero on the Z axis was when the cursor is right on the mark, as opposed to where it actually homed (a few mm behind) so I homed it again, and this time it went to the usual spot! Moved it, did it again, and it went back to the correct spot, at least what looks to be correct by eye. The abs zero in PID being now at the homing point. WTF.

What could be causing it to switch machine zero all of a sudden (without homing, just G28), then home to this new new spot several times, then home again to the previous spot?

After I get ready I will go back out there and run an op on a part that's ready to go and see if it has the position right again.

[LeChuck]

It's doing it again, without changing anything. Just jogged a bit to check positioning, then did a tool check, and it went back to the "wrong" position. Homed it again, and it homes again to this position, and that shows zero in PID.

I'm also wondering if the "new" position is actually where it should be, and the other one happens when it misses finding the first pulse, then continues on to the next one, because that position is several mm from where it starts and further out than the homing position on X, which seems to be consistent. Inconsistency is the problem. But it does seem to be consistent for a while when it decides on a spot, so I don't think it's loose hardware. Is there a setting somewhere that I have wrong that makes it harder to find the pulse, like a frequency or something like that? This seems to happen only on Z though.

Also, it's worth noting that in the beta version of the software that was originally installed, the homing movement had to be incredibly slow in order to home. I had to take that macro and actually override the speed down to 7% or it would just pass by the pulse. In the new version, the standard homing macro has worked from the start without the speed override (with the old one it could take several minutes), but I'm wondering if it's still a tad too fast, even though it's pretty slow.

[LeChuck]

I don't think it's the homing speed actually, because it does lose it when using G28. It just seems that the machine zero position shifts and is sometimes detected in one spot, and sometimes in the next.

[martyscncgarage]

Are you homing to mechanical switches and then encoder index pulse, or just mechanical switches, or are you using the original sensors on the ball screw pulleys?

I would put an indicator at the home position and keep testing for repeatability. And then at a fixed point on the travel and write a little program that backs off a significant distance and returns to the fixed point and check for repeatability.

Have you tested for back lash? cncsnw.com has a neat program to properly test for back lash.

You also need to find the clunking and scraping noise. Check those pulley sensors. Etc

[LeChuck]

OK, I think there are 2 issues in one here. First I think it's got trouble finding the same homing pulse, That's a slow speed thing and it should be getting to the right spot each time.

But also, it seems to be losing steps. I've just done a series of G30 (a spot I defined near the chuck) and G28, and the G28 position is creeping closer each time on Z. It seems ok on X, but it's hard to tell exactly. I don't think it's been losing steps before. I've been doing a lot of tests including triple threading and have a few parts that work and fit properly.

[LeChuck]

It's not using mechanical switches at all. I only home by aligning to a mark then it looks for that servo pulse.