G29 vs G32 with regards to G31 and M557

So on one of my CoreXY machines, I've been playing with the Duet 0.8.5 RepRapFirmware-1.17-RC3 firmware and the new G29. I've also been comparing it to the old G32 and I've noticed something that I wasn't sure was intended or could be a bug.

Before the new G29 command, I used the M557 to specify 4 points
M557 P0 X43 Y10 ; Four...
M557 P1 X43 Y180 ; ...probe points...
M557 P2 X180 Y180 ; ...for bed...
M557 P3 X180 Y10 ; ...levelling

These 4 points, seemed to utilize or offset themselves based on the values I had in my G31 command (G31 P500 X33.0 Y0.0 Z1.31).

Now with the new firmware I'm using a different M557 command (M557 X10:190 Y10:180 S20), but while watching it probe around the bed it doesn't appear to be utilizing my offsets in G31. I noticed this when it physically went to X200 which actually put my sensor off the bed platform (this was while trying out M557 X0:200 Y0:200 S20). I adjusted the M557 command to the smaller area above, but it had me wondering if it was using the offsets in G31 for anything anymore.

Was this an intentional change? A bug or oversight? Working as intended? It's not that big of a deal, but it does present some issues if its not using G31 offset values as the probe isn't in the same location as the nozzle.

Hi PDBeal,

My intention is:

- The Z probe (not the nozzle) is placed at the locations defined by the grid, taking account of the Z probe offset;

- The bed dimensions (defined by the M208 parameters for a Cartesian/CoreXY printer, or the B parameter in the M665 command for a delta printer) limit the nozzle positions that will be used, and any grid points that would place the nozzle outside that area are not probed.

If you think this intention is not being fulfilled, please provide details..

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Quote

- The Z probe (not the nozzle) is placed at the locations defined by the grid, taking account of the Z probe offset;

Does that mean, we have to inverse the offset definition or does the firmware know?

The offset is that of the Z probe relative to the print head reference point, which on a single-nozzle head will be the nozzle position. The firmware subtracts the offset from the desired probing coordinates when positioning the head for probing.

---

Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].