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13.10.16 08:55
Henk1969 
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GRBL setting for 9i
QUick question here,
My shapeoko 2 seems to be working fine, but at a closer look it's a about .2 of a millimeter of when I cnc a 50 x 50 mm square in 3mm plywood.
Since its both off in x and y direction I suspect the Grbl settings to be faulty. I used the settings I found via this forum: http://www.cramernetz.de/fraese/GRBL-Params.pdf
Can someone shed some light on my problem or give me a push in the right direction?
Much obliged :-) and dearest regards,
Hnk
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13.10.16 09:48
crixnicht registriert
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Re: GRBL setting for 9i
Hi Hnk,
is it .2 mm too big or .2mm too small?
The Parameters $100 and $101 are responsible for translation of Motor Steps into distance traveled in X and Y direction.
However they are determined by the stepper motor pully and belt. 33.33 steps/mm should be correct.
You could try to adjust them until your rectangle is correkt, but this will most likely be only ok for this exact dimension and another rectangle will be off again.
If the square is too small, you may have lossed steps due to too high friction on the axis. Check if everything runs smooth.
Here's a thread about acuracy that may contain some hints: http://www.shapeoko.com/forum/viewtopic.php?f=7&t=1279
Zuletzt bearbeitet am 13.10.16 10:02
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13.10.16 10:08
crixnicht registriert
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Re: GRBL setting for 9i
There's also some more Info on Calibration in the ShapeOko Wiki:
http://www.shapeoko.com/wiki/index.php/C...ing_the_Machine
Be aware that the parameters are not identical between ShapeOko and the modified Versions you can buy from here.
The original ShapeOko uses GT2 Belts and possibly different stepper motors.
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15.10.16 15:03
Henk1969
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Re: GRBL setting for 9i
Thnx Crix,
Its always smaller, but the links seem useful I'll check them out and post my findings.
Regards Hnk
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17.10.16 10:51
crixnicht registriert
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Re: GRBL setting for 9i
You could try to test accuracy without load using a calliber. If you fix the caliber on one side to the wastboard and displace it's other end with the mill, you can easily check what's happening. This way you can also check how much tolerance on direction change occurs.
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04.11.16 09:37
freelncr77
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Re: GRBL setting for 9i
You need to adjust your Motor steps. 33.3333 like in the document - is to be seen as a startup value.
The formula is the following:
new motor steps = (actual steps * actual measure mm or inch ) / desired measure in inch or mm
Zuletzt bearbeitet am 04.11.16 09:37
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04.11.16 10:38
crixnicht registriert
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Re: GRBL setting for 9i
@freelncr77: That statement is not correct. 33.33 is not a starting value but follows from the tooth count and dimensions of the belt.
tooth count has no tolerances, so there's no need to calibrate this value.
An adjustment of this value will only fix accuracy for one specific position and dimension of a part as the inaccuracies result from other sources.
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