@chrishamm - finally figured this out. I was using 5V from the 6HC mainboard to power my display. During power off with M81, the 5V line voltage to the display would vary a lot (enough to cause the problems seen). Connecting the display to a separate (dedicated) 5V power source has eliminated the problem reliably. Probably should have used an O-Scope to quantify the variation; however, the cleaner power clears up the display.

Here is a photo of what I'm using.

• Raspberry Pi 7" Touch Screen Display
  https://www.amazon.com/Raspberry-Pi-7-Touchscreen-Display/dp/B0153R2A9I
• Smart Pi case (to hold) https://smarticase.com/
• A 24" ribbon to reach my Pi (not able to mount in the Smart Pi case as the ribbon cable to the Duet 3 board isn't long enough
  https://www.amazon.com/gp/product/B00M4DAQH8
• Touch screen works, but I rather use the wireless mouse seen in the photo (I also have a wireless keyboard for when I need to key in G or M Codes)
  7" isn't too bad if you have a good mounting plan and cable plan
  

Once you have your steps/mm feed rate working, you will want to know what your hot end is capable extruding by volume. Need to know so your X-Y moves/speeds set in your slicer program are not so fast that the hot end cannot extrude filament to match. CNC Kitchen has a good article w/ video here:
https://www.cnckitchen.com/blog/flow-rate-benchmarking-of-a-hotend

@oozeBot - thanks for the picture - literally worth a 1000 words....
PS: I have a very similar setup too!

Have you tried using a Cricut cutting mat ?
My wife uses a Cricut and the mats last a long time and have a low tack adhesive to hold your cutting material (paper, vinyl, gasket material) while the knife passes around the path.

@BryanH Thanks for the details. Suggest changing your main board jumpers and power the Pi independently (separate power source like an AC adapter) to see if that helps resolve.

@oozeBot - thanks for the picture - literally worth a 1000 words....
PS: I have a very similar setup too!

Ahh, thank you - yes this is a good question..

So, the big question is where else can we connect 5 VDC input to the Duet 3 if "EXT 5V" is consumed for PSON (power supply on)? In my case, applying 5 VDC here would power the solid state relay and defeat the PSON feature.

Currently, I power the Duet 3 via the micro USB connector (5 VDC) - is this they only work around? I'm not keen on soldering stuff to the expensive Duet 3 board.

@oozeBot - Thank you for the help. I'm using that currently to control a solid state relay to power on/off 120VAC input to my main power supply. So explains my confusion...

@CaLviNx - which connector are you using for "external 5v in socket" ?
I'm having trouble locating this connection in the diagram here, https://duet3d.dozuki.com/Wiki/Duet_3_Mainboard_6HC_Wiring_Diagram#main

@dc42 - thank you for the note, the F parameter is indeed in the M563 notes but is buried in the text, probably why I missed that. Can the gcode note be updated in the Wiki to make this more noticeable? That note / coding isn't formatted like other examples in the text. Something like this?

M563 P0 D0 H1 F0:1     
; tool 0 uses extruder drive 0 and heater 1. Fan 0 and Fan 1 are mapped to tool 0

@OwenD - Looking at your "G10 S" code, it should be "G10 P0 S" where "P0" is the tool/extruder being used, this could be harder for folks with multiple extruders, so if you are using more than one extruder, the Python script will need additional edits to seek and correct for each tool.

Also, while looking at & trying your Python code, I found these changes to get the gcode edited, probably the way Python handles variables.

f = open(sys.argv[1],"r")
filedata = f.read()
f.close()
 
newdata = filedata.replace("M104 S","G10 P0 S")
newdata1 = newdata.replace("M204 S","M204 P")
newdata2 = newdata1.replace("M106 S","M106 P0 S")
newdata3 = newdata2.replace("M107","M106 P0 S0")
 
f = open(sys.argv[1],"w")
f.write(newdata3)
f.close()

@OwenD - Thanks!

I've also found that Prusa Slicer doesn't handle layer cooling fans in RRF, missing the tool number, in my case "P0" but depending on your setup these may change to something different.

So depending on what tool # you have for your cooling fan you may want to add something like this after line 12 in your Python script.

newdata = filedata.replace("M106 S","M106 P0 S")
newdata = filedata.replace("M107","M106 P0 S0")

@BryanH Thanks for the details. Suggest changing your main board jumpers and power the Pi independently (separate power source like an AC adapter) to see if that helps resolve.

Have you tried using a Cricut cutting mat ?
My wife uses a Cricut and the mats last a long time and have a low tack adhesive to hold your cutting material (paper, vinyl, gasket material) while the knife passes around the path.

How are you powering the SBC (Raspberry Pi)?

I saw similar happenings powering the Pi from the 6HC Main board. Changing the main board jumpers to not power the Pi and using a wall wart to power the Pi separately resolved my issues.