Probe Basic — 4-axis XYZB wrapped rotary backplot support

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15 Apr 2026 10:44 #345574 by dredivan
Hi,

Setting up Probe Basic 0.6.6 on a 4-axis gantry machine (MPCNC with a fixed rotary B axis mounted at the end of the Y travel).

Configuration:
- LinuxCNC 2.9.8
- Mesa 7I76E (Ethernet)
- trivkins coordinates=XXYYZB, 6 joints
- B axis is a rotary chuck, fixed position at Y=700mm

What works:
DRO displays all 4 axes correctly using DRO_DISPLAY = XYZAB (A axis is unused but present — there is no XYZB option available).

What does not work:
The backplot renders the toolpath as 3-axis only — B axis rotation is not applied when building the path. For wrapped rotary applications (tube machining) the toolpath preview is not meaningful.

Also, machine bounds are not displayed in the 4-axis config, while they display correctly in the 3-axis config on the same machine.

Are there any plans to support wrapped rotary backplot rendering in Probe Basic / qtpyvcp?

3 axis configuration - mpcnc_probebasic.ini
4 axis configuration - probebasic_4b.ini
Attachments:

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15 Apr 2026 20:07 #345579 by Lcvette
do you have the plot turned on for machine bounds in the ui? sidebar tab "PLOT"

for the dro display, you can use the user custom dro template and setup however you desire, just remove the rows for a and c and leave xyzb

for the wrapped rotary, this will be something coming down the line, we are currently working on multi axis plotting and simulation so if you have a model of your machine and would like to be a tester for the currently existing test branch you can give it a try if you like, the feedback would be good for us to have someone outputting multiaxis gcode for testing.

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16 Apr 2026 04:51 #345585 by dredivan
Regarding DRO — I already did exactly that, edited dros_user.ui removing the A and C rows. DRO now shows only XYZB. However the A+/A- jog buttons remain — they are controlled separately from the DRO file. Is there a way to remove the unused jog buttons without touching system files?

Regarding wrapped rotary — very interesting! I am ready to test. What do I need to get started with the test branch and what machine model is required?

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16 Apr 2026 10:19 - 16 Apr 2026 10:22 #345588 by dredivan
   
Update: DRO is now showing only XYZB.

Edited dros_user.ui and offset_dros_user.ui removing the A and C rows and fixed the ZERO ALL command.

Added to INI:
DRO_DISPLAY = USER
USER_DROS_PATH = user_dro_display/
OFFSET_COLUMNS = XYZB

Screenshot attached.

The A+/A- jog buttons are still present — is there a way to remove them without touching system files?

Regarding the wrapped rotary test branch — ready to test. My setup is a standard XYZ milling machine with a B axis mounted parallel to Y. Where can I get the test branch and how do I get started?
Attachments:
Last edit: 16 Apr 2026 10:22 by dredivan.

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