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Auto Bed Level: Marlin retracts servo before clearing bed

Posted by ultralame 
Auto Bed Level: Marlin retracts servo before clearing bed
June 15, 2015 03:45PM
I implemented the ABL, and it ALMOST works perfectly.

G29 first homes X and Y, moves to the first location,then extends the servo and uses that to find the the first zero point.

However, the servo is retracted BEFORE the Z up motion, and it collides with the bed. The Z-up occurs directly after the servo motion.

It actually slid past on the first 3 points, but then dislodged on the 4th causing the tip to smash into the bed on the final point.

Note: My servo is a Tower Pro SG90, which appears to be reversed when using Marlin with ABL. So my servo angles were 27 for extended and 115 for retracted (counter to the examples I have seen online where they are ~100/0).

(This is a Makerfarm Prusa iv3 variant, but I just pulled the latest production marlin, 1.0.2)

Any ideas? Is this something to do with the reversed servo angles? Thanks.

Edited 1 time(s). Last edit at 06/15/2015 03:46PM by ultralame.
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