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Author Topic: Problem with cutting quality when turning  (Read 14341 times)

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Re: Problem with cutting quality when turning
« Reply #10 on: April 13, 2009, 02:38:36 PM »
Same result.  Maybe a little less pronounced.  Any other ideas?  I've gone as far as to move the job around within the travel area to see if it was a blem in one of the screws.  Nothing seems to change it.  One IPM or 40 IPM; same thing.


Here it is with the step and dir pulse set to 5 on both axis.


Offline Hood

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Re: Problem with cutting quality when turning
« Reply #11 on: April 13, 2009, 02:43:48 PM »
Try setting the active states to high on each axis, it probably wont help but is worth a shot.
 How tight/rigid is the machine/tooling?
 What kind of motors and drives?
Hood
Re: Problem with cutting quality when turning
« Reply #12 on: April 13, 2009, 02:50:49 PM »
How do you get it to travel in the right direction after doing that?

The machine is a harbor freight retrofit using some 90v NEMA 34s and a camtronics control box.  The Z screw is a known-good four-start screw with a very tight polymer anti-backlash nut.  The X-screw is the factory screw held tight with the coupler to the motor.  I suspected the X screw right away, but anything it's doing that would cause this would also show up in a diagonal/taper cut, right?

Offline Hood

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Re: Problem with cutting quality when turning
« Reply #13 on: April 13, 2009, 02:55:25 PM »
Homing and Limits, reverse axis.

Your pics show an interrupted cut, is that the shape of the stock you are turning? Was the diagonal on a round or similar to that (if it is as shown in pic :) )

Not familiar with Camtronics stuff, will have a search around in a while.
Hood
Re: Problem with cutting quality when turning
« Reply #14 on: April 13, 2009, 02:56:27 PM »
Here are a couple of pics of the setup.

Offline Hood

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Re: Problem with cutting quality when turning
« Reply #15 on: April 13, 2009, 03:46:58 PM »
If you can try a piece that will have the full 360 degrees getting turned.
Hood
Re: Problem with cutting quality when turning
« Reply #16 on: April 13, 2009, 03:58:12 PM »
I have done that in the past with the same result.  I don't mind trying again, but I'm not really able to do it now because all the material for this batch has already been through the milling operations that give you what you see in the pics.  I may have to wait until the weekend to troubleshoot this further because we have a deadline for those parts.  We'll just run them this way and sand them for now, but if anyone has another idea that I could try when I'm able, I'm all ears.

Can't thank you enough for your help.

John
Re: Problem with cutting quality when turning
« Reply #17 on: April 13, 2009, 05:47:43 PM »
Hello John

Your setup is very prone to vibration, part is far away from the chuck,tailstock could be shortened.
is the tool at the right height
are the tailstock and the shaft that holds the part center .

Just a tought

Marcel

Offline Graham Waterworth

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Re: Problem with cutting quality when turning
« Reply #18 on: April 13, 2009, 06:14:18 PM »
Check that the encoder is not loose on the shaft, you could also try swapping the x & z motor encoders over.

Graham
Without engineers the world stops

Offline RICH

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Re: Problem with cutting quality when turning
« Reply #19 on: April 16, 2009, 10:00:36 AM »
Hi John,
May be all wet but here are a few things you may want to try.
I echo what Marcel posted.
Try leaving a little more stock to be left in the rough cuts and do more than one finishing cut.
You may also try a different tool tip, one that shears / peals off the wood instead of scraping. Similar to doing the turning manualy on a wood lathe. High clearance and rake, razor sharp, depends on the wood. Also can try doing two at a time by glueing two halfs together with a piece of paper between and splitting them thus you get continuity of the cut around the profile.
Like i said, may be all wet, just some thoughts, been a long time since i did wood turning.
RICH
« Last Edit: April 16, 2009, 10:02:32 AM by RICH »