Delta Tower Angle Adjustment

Cheddy

I am trying to calibrate my delta printer using the instructions and calibration wheel object found at https://www.thingiverse.com/thing:745523. This script is focusing on Marlin firmware, but I am using the calibration object to measure tower angles and arm length, etc. and attempting to adjust the Repetier firmware parameters accordingly. I have measured the tower angles and made adjustments in the firmware (Alpha-A, Alpha-B and Alpha-C), but it doesn't seem to have any effect on the calibration object, in fact the more I adjust the angles the worse it gets.

Is there something I'm missing? 

Unfortunately, the firmware parameters in Marlin are quite a bit different from Repetier, so I am a bit of a loss to know how to adjust for sizing and squareness errors, etc. I am guessing that the Delta Radius parameters are intended for correcting these issues, but I don't know what the values should be or how to calculate them, and the form doesn't specify what the units are. Millimetres, I presume.

Also, are there a similar detailed calibration instructions anywhere intended for Repetier firmware driving a delta printer?

Repetier

In comments I had already the description. Copy here:

Adaption to Repetier-Firmware

If you have eeprom enabled you can do all the calibration without recompiling or changing the code.

For the angles just change the Alpha A/B/C values like you would change the angle in Marlin formula.

For the diagonal rod length correction change the Corr. diagonal A/B/C values in EEPROM. Here you do not enter a factor like the instuctions computes but the difference between the target diagonal length and the one you have set. Just think that the value you enter gets added to the nominal diagonal length.

If all changes are in one direction, reduce them by the mean value and add that to the nominal value.

Cheddy

Thank you. That makes sense, and seems so much easier than the Marlin adjustment.

Cheddy

Update: tip for anyone using the small calibration wheel from the instructable above, the arm length should be measured from the raised end of the arm (should be 60mm), not from the V point in the wheel opposite the arm end. There is 1+ mm difference in the arm length which can mess up your calibration if measured incorrectly.