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Author Topic: Text out of Line - Picture included!  (Read 2059 times)

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Text out of Line - Picture included!
« on: December 14, 2013, 09:03:15 AM »
Hi,

I have an ebay 3040 cnc  machine - in general it works fine, however been experiencing wonky lettering. The machine seems to be pushing itself out of line when cutting.

The output display looks fine - its not wonky, and I have re-made the gcode in VCarve and still the same issue. I ran this SUPER slow took 4+ hours to get this far and it's still wonky.

What could be causing it to go out of line like this? Would backlash comp help?

Picture included!

Offline ger21

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Re: Text out of Line - Picture included!
« Reply #1 on: December 14, 2013, 09:51:32 AM »
Your machine is losing position during rapid moves. Reduce the acceleration and velocity in motor tuning by 25%-50%.

It's imperative that the machine is perfectly aligned and well lubricated, and not binding anywhere. These machines are notorious for having very poor electronics, which greatly limit performance. If everything is in good working order mechanically, then it's likely that you'll need to upgrade the electronics to get better performance from it.
Gerry

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Re: Text out of Line - Picture included!
« Reply #2 on: December 14, 2013, 10:18:35 AM »
Your machine is losing position during rapid moves. Reduce the acceleration and velocity in motor tuning by 25%-50%.

It's imperative that the machine is perfectly aligned and well lubricated, and not binding anywhere. These machines are notorious for having very poor electronics, which greatly limit performance. If everything is in good working order mechanically, then it's likely that you'll need to upgrade the electronics to get better performance from it.

Hi Thanks for your answer! I did slow the cut right down and its still slipping which is not encouraging! It seems to work fine on wood but come to metal its alll over the shop.

I'm pretty sure everything is mechanically okay, no visual issues from it which just leaves upgrading the machine?
Re: Text out of Line - Picture included!
« Reply #3 on: December 21, 2013, 07:31:33 AM »
If it works in wood but not metal your cutting forces may be too great for the machine, things you could try in no particular order are -

Reducing your feed per flute.
Clearing the chips with air.
A light cutting lube intermittently sprayed on the work, WD-40 or a 20/80 mix of engine oil/paraffin.
Doing the job in multiple passes, getting just a little deeper each time rather than a single full depth cut.

Regards,
Nick
Re: Text out of Line - Picture included!
« Reply #4 on: December 21, 2013, 09:31:04 AM »
As the letters seem to be OK, the feed rate is OK while cutting so I don't think the cutting loads are the issue. As Ger21 said, it is losing position in the rapids.

<I did slow the cut right down> Implies that you reduced the feed rate but not the velocity and acceleration.

If so, you need to do as Ger21 suggested and that is go into Mach's motor tuning and reduce the velocity and acceleration.

You can test the results without cutting by exercising the machine with a bunch of G0 's and verify that it always returns to the correct position.
--------------------
Graham
Re: Text out of Line - Picture included!
« Reply #5 on: December 21, 2013, 11:05:19 AM »
Looks maybe more like a mechanical issue to me.  If it was losing position (lost steps) wouldn't the letters be messed up?

Check for a loose coupling.
John Champlain