Posts: 18
Joined: Sat Dec 09, 2017 11:44 pm

G28 Home fail before G29 Auto Leveling?

Thu Dec 31, 2020 2:57 pm

I am experiencing an intermittent failure of auto leveling at the start of a print job. I will post this on both the Simplify3D site and the Robo3D site. I do not know if it is a software, firmware, or hardware failure.

Simplify3D version 4.1.2
Robo3D R1+ with Marlin V1 firmware connected via USB through a simple USB-C adapter
MacBook Pro running Catalina 10.15.7 (problem has occurred on earlier OS versions)

I usually start with motors disabled, the print head roughly centered in X and Y, and about 30 to 60 mm up from the bed.

Simplify3D starts by sending G90, M82, M106 S0, M140 S45, M190 S45 to set things up. Then:

G28 to move to the home (0,0) position.
G29 to initiate auto leveling. The head moves to about the middle of the bed, moves down slowly to probe Z, then moves to nine points to measure the height. The first point is near (0,0).

When the failure occurs, it seems that the G28 move to home fails. Then when the auto level starts, the head is in the middle of the bed for the first point. Moving in X for the second point causes the head to hit the right side X stop and then the motor or belt grinds. Because the first point was not near (0,0), the whole auto level sequence is off. At this point I hit the Emergency Stop.

I do not know what, if anything, triggers a failure vs. a success.
I have tried moving the head to (0,0)
I have tried Zero X and Zero Y in the software.
I have tried different starting Z heights.
I have turned the printer off and on (which does not shut down all power).
I have unplugged the printer from power and plugged back in.
I have started the print job before and after the print head is up to temperature.

I have captured the Communication log entries from S3D for a success and a failure. In both cases I see G28 and G29 being sent, so S3D is not failing to send the Home command. Annotated log snippets are attached.
Good start.png

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