Auto Z offset calibration

Proschi3D

@T3P3Tony I plan to do it with a piezo.
The question is what the macro should look like in order to measure the nozzle on the piezo and then use the ir sensor to measure the height of the sample and then save it automatically.

T3P3Tony

@Proschi78 there are some examples in the CNC forum as people use this for setting tool offsets. for example:
https://forum.duet3d.com/topic/29771/fusion-360-cnc-and-laser-post-processors-with-tool-workflow/2?=1679327030257
https://forum.duet3d.com/topic/19698/rrf3-2-request-to-enable-g43-g44-tool-height-offset/10?=1679400956475

Proschi3D

@T3P3Tony thank you very much, I'll take a look around

Proschi3D

How do I connect a z offset plate to a duet mini as a limit switch

Proschi3D

Phaedrux

If it's a simple microswitch with positive and negative wires you should be able to connect it as such to an endstop input.

Proschi3D

@Phaedrux OK thanks. So red at signal input and black gnd?

Phaedrux

Typically. And if it's a simple switch it shouldn't really matter.

Phaedrux

Do you have any info on it?

Proschi3D

@Phaedrux No it came without any information. then just test it thank you

Proschi3D

it works fine now.
here is the gcode if anyone is interested

var errorfix = 0.000  		; constant offset
G31 Z0						; set Z-offset to Z=0
echo >"0:/sys/config_probe.g" "G31 Z0"

M291 S3 R"Heating up nozzle" P"Wait for the nozzle to reach printing temperatures"
M568 P0 S210				; set tool 0 (primary hotend) temperature to 210c
T0							; select tool 0 (primary hotend)
M116 P0 H5					; wait for temperature to reach within 5c of set temperature

M300 S666 P666 				; beep
M291 S3 R"Automatic Z Offset Calibration" P"Press OK to continue, or CANCEL to abort"
M291 S3 R"Homing axes" P"Remove the puck. The printer will home the X, Y, and Z axises without the puck"

M98 P"config_probe.g"												; Load BLTouch probe settings
M280 P0 S60 I1														; clear any probe errors
G29 S2                      										; cancel mesh bed compensation
G91                    												; relative positioning
M913 X50 															; X axis 50% power
G1 H2 Z5 F200          												; lift Z relative to current position
G28 X0 U0 Y0  		; Home X,U and Y axis      												; go back a few mm 		
M913 X100 															; X axis 100% power
G90                    												; absolute positioning
G1 X{move.axes[0].min+175} Y{move.axes[1].min+110} F6000 				; move to center
G1 F600																; reduce speed
G30                    												; home Z by probing the bed

G31 Z0						; set Z-offset to Z=0
M564 H1 S0             		; Negative movements are allowed
G29 S2						; cancel mesh bed compensation
G90 						; absolute positioning
G1 Z35						; raise Z to 35mm
M83							; relative extruder moves
G1 E-5 F300 				; retract 5mm of filament
G4 P0						; wait for the moves to finish       
M291 S3 R"Clean the nozzle" P"The nozzle has been pre-heated. Clean it from any plastic debris"
G1 X100 Y200 F6000			; go to X100, Y200
G4 P0						; wait for movements to have stopped


M300 S666 P666				; beep
M291 S3 P"Place the offset tool below the nozzle and press OK to perform the macro, or CANCEL to abort"

G4 P200 					; wait 200ms
G91							; relative moves
G1 H1 Z-19 F50				; move 19mm down, stop when hitting the offset tool (but don't risk crashing the bed)
G92 Z0 						; set current position as Z=0
G4 P200 					; wait 200ms
G1 Z11 F200					; move up 11mm

G91							; relative moves
G1 X{sensors.probes[0].offsets[0] * -1} Y{sensors.probes[0].offsets[1] * -1} F1500 ; move nozzle so that BLTouch is in it's position 
G90							; absolute moves

G30 S-3 					; probes Z and adjusts the probe trigger height to match the actual stop height.
G4 P200 					; wait 200ms
G91							; relative movement
M568 P0 S0					; set tool 0 temperatures to 0

var Z_auto_offset = {sensors.probes[0].triggerHeight+var.errorfix} ; math to calculate the BLTouch offset

	if var.Z_auto_offset < 0.01
		M291 S2 R"The nozzle has not touched the puck." P"Please check the guide for troubleshooting"
		echo "The nozzle has not touched the puck. Please check the guide for troubleshooting"
		echo >"0:/sys/config_probe.g" "G31 Z-3"
	elif var.Z_auto_offset >= 0.01 & var.Z_auto_offset < 3.5
		echo >"0:/sys/config_probe.g" "G31 Z"^{var.Z_auto_offset}
		M291 S2 R"Z-offset has been stored" P"the Z-offset has been stored in the config_probe.g file. Verify the value stored with the value displayed in the console" 
		echo "the Z-offset has been stored in the config_probe.g file. The Z-offset is", var.Z_auto_offset, "mm. Remove the offset tool and place it back in the box"
	elif var.Z_auto_offset >= 3.5
		M291 S2 R"Z-Offset is too high" P"Please verify the probe height using the probe-calibration"
		echo "Z-Offset is too high. Please verify the probe height using the probe-calibration"
		echo >"0:/sys/config_probe.g" "G31 Z-3"

M564 S1 H1      			; Negative movements are forbidden
M300 S666 P666 				; beep

G91							; relative moves
G1 Z5						; lift nozzle up 5mm
G90							; absolute moves

T-1							; deselect all tools
M18							; release steppers

stuartofmt

@Proschi78

Very interesting - I will likely try something similar. Do you have a sense at the accuracy / effectiveness?

Specifically, it seems that there likely would be some mechanical hysteresis in the switch (i.e. measured zero will be a bit lower than the nominal top of the puck). Then the BLT comes along and triggers, perhaps moving the top of the puck, perhaps not.

In other words, it seems there would be some offset between the two trigger points and that could vary from puck-to-puck or in similar solutions that use a microswitch.

What I'm thinking is (maybe) set up the nozzle itself as one side of the "switch" (gnd) and using a puck with a fixed plate as the other side(+ve). That would eliminate the variation that could occur due to a microswitch.

Of course, it may be prudent to have a little "give" in the puck to guard against over zealous probing by the nozzle but stiff enough to (effectively) not move during the probes.

Thoughts?

Proschi3D

@stuartofmt This puck works with gnd and + on the nozzle. Of course there is a small - value, but this is very consistent and can be compensated with var errorfix = 0.000.

stuartofmt

@Proschi78 said in Auto Z offset calibration:

@stuartofmt This puck works with gnd and + on the nozzle. Of course there is a small - value, but this is very consistent and can be compensated with var errorfix = 0.000.

Many thanks for the input and also the gcodes. I'll print up a puck and give it a whirl. Never did like the sliding paper thing

Proschi3D

I would like to automatically measure the z offset of the left and right extruder.

How can I retrieve the current z height with a meta code and then display it?
would like to go to the puk with the left extruder and save the z height as a variable.
then go to the puk with the right extruder and subtract the variable from this position and display it

stuartofmt

@Proschi78
Use global variables to capture the results ? Then use M291 or M117 to display ?

Proschi3D

@stuartofmt

I tried that, but something is still wrong

; Idex Auto Nozzle Offset Tool 1
M291 S3 R"Automatic Idex Offset Calibration" P"Press OK to continue, or CANCEL to abort"
M291 S3 R"Homing axes" P"Remove the puck. The printer will home the X, Y, and Z axes without the puck"
G28
T0
G90 ; absolute positioning
G1 X175 Y110 Z5 F3000
M291 S3 R"Heating up nozzle" P"Wait for the nozzle to reach printing temperatures"
M568 P0 S200 ;T0 200c
M568 P1 S200 ;T1 200c
M116 P0 H5 ;Wait for Temp +-5c
G1 Z50 F800
M291 S3 R"Clean the nozzle" P"The nozzle has been pre-heated. Clean it from any plastic debris"
G1 Z25 F800
G4 P0
M300 S666 P666 ; beep
M291 S3 P"Place the offset tool below the nozzle and press OK to perform the macro, or CANCEL to abort"
G29 S2
G4 P200 ; wait 200ms
G1 H1 Z-19 F50 ; move 19mm down, stop when hitting the offset tool (but don't risk crashing the bed)
{global.tool0 = move.axes[2].machinePosition} ; Store the current Z position in tool0
G1 Z25 F3000
G28 X0
T1
G1 U175 Y110 Z25 F3000
G1 H1 Z-20 F50 ; Move Z-axis down 20 mm
{global.tool1 = move.axes[2].machinePosition - global.tool0} ; Calculate the difference between current Z position and tool0 and store in tool1
{echo "The difference between the two nozzle heights is: " + str(round(global.tool1, 3)) + " mm."} ; Output the difference to the console
G4 S15
G1 Z25 F500
G28 U0

stuartofmt

@Proschi78

Have you declared the global variables ?

https://forum.duet3d.com/topic/24795/a-couple-of-questions-regarding-global-variables?_=1681490684446

OwenD

@Proschi78 said in Auto Z offset calibration:

{global.tool0 = move.axes[2].machinePosition}

Should be
set global.tool0 = move.axes[2].machinePosition
however it will always be zero (or whatever your axis minima is set to with M208)
Also no need for curly brackets here.

Likewise the second calculation is going to return zero (axis minima) because you use H1
I feel you should be using H4 on the second test at least and that creating the firt global is largely redundant.

I can't test, but maybe

G1 Z50 F800
M291 S3 R"Clean the nozzle" P"The nozzle has been pre-heated. Clean it from any plastic debris"
G1 Z25 F800
G4 P0
M300 S666 P666 ; beep
M291 S3 P"Place the offset tool below the nozzle and press OK to perform the macro, or CANCEL to abort"
G29 S2
G4 P200 ; wait 200ms
G1 H1 Z-19 F50 ; move 19mm down, stop when hitting the offset tool (but don't risk crashing the bed)
M400
set global.tool0 = move.axes[2].machinePosition ; Store the current Z position in tool0
G1 Z25 F3000
G28 X0
T1
G1 U175 Y110 Z25 F3000
G1 H4 Z-20 F50 ; Move Z-axis down 20 mm
M400
set global.tool1 = move.axes[2].machinePosition - global.tool0 ; Calculate the difference between current Z position and tool0 and store in tool1
echo "The difference between the two nozzle heights is: " ^ global.tool1 ^ " mm." ; Output the difference to the console
G4 S15
G1 Z25 F500
G28 U0