Help with 3 independant Z motor leveling

PaulHew

So I have gone back to basics.
Calculated my probe offset 7mm left of the nozzle, 35mm behind the nozzle.
Changed G31 to suit.

G31 X-7 Y35 Z1.324 P25                            ; Customize your offsets appropriately - do a paper test, and put the probed value in the Z value here

My 3screw.g contains

G30 P0 X10 Y35 Z-99999
G30 P1 X10 Y275 Z-99999
G30 P2 X280 Y150 Z-99999 S3

When I probe it probes @ X17 for points 0 and 1

Have I configured the G31 wrong?

I use M208 to define my 0,0 so it will print on the bed and not off it.

Regards,

Paul.

Veti

@PaulHew said in Help with 3 independant Z motor leveling:

When I probe it probes @ X17 for points 0 and 1

10-7 = 17. sound correct

PaulHew

No, 10-7=3

Veti

when probing at position 10 the nozzle has to be at x=17

so 17 -7 = 10

that way

fcwilt

@PaulHew said in Help with 3 independant Z motor leveling:

Please post your homeZ.g file.

Thanks.

Frederick

PaulHew

Homez.g as requested

; New 2/5/2020
; homez.g
; called to home the Z axis
;
; generated by RepRapFirmware Configuration Tool v2.1.8 on Sat May 02 2020 07:42:48 GMT+0100 (British Summer Time)
G91              ; relative positioning
G1 H2 Z5 F6000   ; lift Z relative to current position
G90              ; absolute positioning
G1 X150 Y150 F6000 ; go to first probe point
G30              ; home Z by probing the bed

; Uncomment the following lines to lift Z after probing
G91             ; relative positioning
G1 Z5 F100      ; lift Z relative to current position
G90             ; absolute positioning

fcwilt

@PaulHew said in Help with 3 independant Z motor leveling:

Homez.g as requested

G1 X150 Y150 F6000 ; go to first probe point

Thanks.

It doesn't appear you are taking into account the Z probe X and Y offsets in the G1 above - assuming you are tying to probe the center of the bed.

Frederick

PaulHew

No, I can probe the centre of the bed with no issues.
I was struggling with what looked like the Z offsets were not being taken into account and have had 2 gantry crashes.
Also on the lhs it was trying to probe off of the bed, even though I had defined my offsets.

I use M208 to define where my bed is but it seems like RRF does not take any of this into consideration when bed tramming.

My main issue is that I cannot print on the right hand side of my bed, hence why I went back to basics to try and alleviate the issue.
Nozzle is too far from the bed on the RHS.

fcwilt

@PaulHew said in Help with 3 independant Z motor leveling:

I use M208 to define where my bed is but it seems like RRF does not take any of this into consideration when bed tramming.

My main issue is that I cannot print on the right hand side of my bed, hence why I went back to basics to try and alleviate the issue.
Nozzle is too far from the bed on the RHS.

Here is your M208 X-10:310 Y-8:293 Z-0:550. The values for X and Y I gather are based on the locations of the end stop sensors. Correct?

I use a different approach.

My M208 specifies just the printable area - in my case M208 X-150:150 Y-150:150 - which puts 0,0 in the middle of the bed - which is where I like it.

The X end stop sensor triggers very close to -150 but the Y sensor triggers at +160.

After homing the firmware thinks X is at -150 and Y is at +150 because the axis min or max value is used with the end stop sensor triggers during a G1 H1 move - even though the actual Y position is +160.

So after homing X and Y I do this:

G90			; absolute moves
G1 X0 Y-10 F6000	; move as needed to place nozzle at bed center (adjusting for actual endstop location)
G92 X0 Y0		; set this position as X = 0 and Y = 0

When probing the bed the limits are ignored since the probe is offset from the nozzle.

When using G30 P0 Xaaa Ybbb as an example the firmware takes into account the probe offsets and puts the probe at the specified location.

When setting the Z=0 datum with a "plain" G30 you have to use a G1 move to position the probe taking into account the probe offsets yourself.

Frederick

Phaedrux

Using M208 to set 0,0 or G92 in a homing file are both valid ways of doing it. The important thing is that the lead screw positions in M671 are relative to the 0,0 point.

The points used for probing should get the probe as close to the lead screws as possible.