XY offset for SCARA
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I'm working on a SCARA printer by using DuetWifi 2.02RC4. So far, my design homes both arms and remains align at angle 0. However, I don't fully understand how to obtain the X and Y offset for X0 Y0.
I tried with some basic offset from 0 to 20, just for trial and error. Minor offset changes result in the printhead in places where I cannot get the relation between the offset and the final position.
For testing, the command G0 S2 X0 Y0 return both arms to the home position.
How can I calculate those offsets?
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You can specify the offsets for X0 and Y0 in the M669 commands that defines the SCARA parameters. By default, X0 Y0 is the location of the proximal joint, which is probably not where you want it to be. So use the X and Y parameters to shift it to be within the printable area.
As an example, this is what I use on my Robotdigg SCARA printer:
M669 K4 P160 D159.5 A-130:22 B-27:157.5 C0:0:0 X165 Y-75 S100 ; set SCARA mode and parameters
M208 S1 X-100 Y-220 Z-1 ; Axis minima
M208 X100 Y230 Z150 ; Axis maximaThis puts (0, 0) close to the centre of the 200mm x 450mm build area.
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But how can I calculate those values?
The values of M208 for SCARA are in mm or degrees? -
They are in mm. Decide where you want X=0 Y=0 to be relative to the proximal joint, and put those offsets in the X and Y parameters of your M669 command. The +X direction is the direction that the proximal arm points towards when it is at zero degrees angle.
