Bad circles plasma

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25 Sep 2021 17:34 - 25 Sep 2021 17:38 #221564 by paulsao
Bad circles plasma was created by paulsao
Hi guys, can someone help me in this problem that occurred. I realized that my plasma cuts were a bit strange so I decided to test the code with a circle it is observed that it has some flat parts and it is not a perfect circle, could someone help me with this? 
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Last edit: 25 Sep 2021 17:38 by paulsao.

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25 Sep 2021 18:19 #221568 by tommylight
Replied by tommylight on topic Bad circles plasma
Mechanical backlash from the looks of it.
Check for something loose, pulleys, gears, pinion to rack, belts...
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25 Sep 2021 20:17 #221573 by paulsao
Replied by paulsao on topic Bad circles plasma
Check everything and everything is safe, now that I think I have 2 dm556 drivers for the y axis and 1 tb6600 for the x axis, can there be a problem in that?

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25 Sep 2021 21:47 #221579 by chris@cnc
Replied by chris@cnc on topic Bad circles plasma
I think yes.  It looks like one axis accelerates faster than the other.  Compare the parameters.  It is good if all have same stepscale, acceleration and velocity.  Mark the transition. 
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26 Sep 2021 01:45 #221595 by paulsao
Replied by paulsao on topic Bad circles plasma
Someone has another idea, change the drivers to use the same I put the same bands and sprockets with the same number of teeth the same scale, check and everything is safe, the speeds of the x and y joints are the same I don't know what else to do 

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26 Sep 2021 03:09 #221597 by PCW
Replied by PCW on topic Bad circles plasma
It really looks like mechanical backlash or a
combination of spring and stiction to me.

I would try jogging back and forth in the axis with
the worst error and checking for lost motion with
a indicator

Its mainly along the axis which is a line between
the two arrows of the plot.
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26 Sep 2021 08:01 #221614 by tommylight
Replied by tommylight on topic Bad circles plasma
What is the step scale and what microstepping ?

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26 Sep 2021 14:18 #221632 by paulsao
Replied by paulsao on topic Bad circles plasma
Microsteps 1/32 64000 pulses
Scale 118.52 belt 3mm pitch pulley 18 teath. When I checked the linear rair I saw that some screws were not well fastened, I did another test and it is much better, but I think it could be improved, but not mechanically anymore. 
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26 Sep 2021 15:00 #221640 by chris@cnc
Replied by chris@cnc on topic Bad circles plasma
Looks better.  But circle is not quite round yet.  The xy axis is not square.  You can adjust y gantry little.  Attach a pencil and draw a square on paper.  Turn it same place around and draw again.  Now you see error and adjust the half in homing offset.
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26 Sep 2021 16:26 #221643 by tommylight
Replied by tommylight on topic Bad circles plasma
Can you set microstepping to 1/4 or 1/8 and scale accordingly and test again?
Direct drive with big pulley = no good.
Now that might be due to microstepping and the inability of motors to keep position when at any other angle than 1.8 degree due to forces/momentum/inertia/etc.
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