G29 Mesh Level: Pass / Fail Tolerance

CCS86

I think it would be very useful to add a parameter to the G29 command which allows a maximum threshold for either:

Maximum deviations
Mean error
RMS error

Once you have characterized your bed, you could add some threshold above these deviations that you are comfortable with / seem realistic. If the G29 returns values that exceed these defined values, it would return a failed result and stop the printer.

I just had an odd case where I got a few errant points that are way out of my expected flatness. This caused the nozzle to drag badly on the bed. A G29 threshold could have prevented this.

moth4017

@CCS86 i do the deviation check in the bed.g G32

;G32  Auto calibration routine for large bed
M561                    ; clear any bed transform

; If the printer hasn't been homed, home it
if !move.axes[0].homed || !move.axes[1].homed || !move.axes[2].homed
  G28
M98 P"/macros/ProbePickUp"	; probe pick up

; Probe the bed and do auto calibration
;G1 X149.5 Y179.5 Z30 F6000        ; go to just above the first probe point
;G30 P0 X152.5 Y152.5 S-2
G28 Z
;echo sensors.probes[0].lastStopHeight , "REF center probe"

while true
  if iterations = 5
    abort "Too many auto calibration attempts"
  G30 P0 X5 Y5 Z-99999               ; probe starboard bow 
  echo sensors.probes[0].lastStopHeight, "P0"
  if result != 0
    continue
  G30 P1 X305 Y5 Z-99999             ; probe port bow
  echo  sensors.probes[0].lastStopHeight, "P1"
  if result != 0
   continue
  ;G30 P2 X305 Y276 Z-99999          ; probe port stern
 ; echo  sensors.probes[0].lastStopHeight, "P2"
  ;if result != 0
  ; continue
  G30 P2 X152.5 Y276 Z-99999  s3           ; probe port bow
  echo  sensors.probes[0].lastStopHeight, "P3"
  if result != 0
   continue
  if move.calibration.initial.deviation <= 0.02
   break
  echo "Repeating calibration because deviation is too high (" ^ move.calibration.initial.deviation ^ "mm)"
; end loop
echo "Auto calibration successful, deviation", move.calibration.final.deviation ^ "mm"
M558 F200
;G1 F6000 X152.5 Y152.5				; probe to center bed 	
echo" center probe"
;G30 P0 X152.5 Y152.5 S-2								;single probe
;echo  sensors.probes[0].lastStopHeight 
G28 Z
M98 P"/macros/ProbeDropOff"	; probe drop off
M558 F600
G1 Z30 F10000                ; get the head out of the way

and just use the mesh.g file G29 for fine tuning

OwenD

@CCS86
I think that would be valid option, so +1 from me.
You can achieve it using the object model, after you load the mesh.
A macro like this should work.
You'd have to tune to suit what is correct for you, but you'd have to do that with a firmware option as well.

;macro to check bed mesh deviation
var abortNoMeshLoaded = true ; options true/false - choose whether to abort print if no mesh loaded, or just exit macro
var RMSdeviationLimit = 0.05 ; or whatever you want (use positive values)
var meanLimit = 0.003 ; or whatever you want (use positive values)

if var.RMSdeviationLimit < 0 || var.meanLimit < 0
   abort "RTFM - limits set must be positve numbers"

if move.compensation.file = null
   if var.abortNoMeshLoaded = true
      abort "No mesh loaded. Print cancelled"
   else
      echo "No mesh loaded.  Print will have no compensaton applied"
      M99

echo "checking validity of mesh: " ^ move.compensation.file
echo "Mean limit =", var.meanLimit, "RMS limit =", var.RMSdeviationLimit

var meshMean = move.compensation.meshDeviation.mean
var meshRMS = move.compensation.meshDeviation.deviation

echo "Mesh mean =", var.meshMean, "Mesh RMS =", var.meshRMS
 
if abs(var.meshRMS) > var.RMSdeviationLimit ; absolute value used to account for negative values in mesh
   abort "Mesh RMS deviation limit exceeded. Print aborted"
if abs(var.meshMean) > var.meanLimit ; absolute value used to account for negative values in mesh
   abort "Mesh mean deviation exceeded.  Print aborted"

echo "Mesh is within limits"

CCS86

Thank you, both of you guys, for sharing your work. Much appreciated!

@OwenD that is a very efficient macro that does exactly what I was looking for. I need to work on my object model knowledge.

o_lampe

@OwenD It would be cool, if this check would happen before the old heightmap was overwritten.
Or if bed.g would create a backup of the current heightmap before probing.

Forgive me if that is already happening, I don't know for sure what's the latest and greatest

OwenD

@o_lampe said in G29 Mesh Level: Pass / Fail Tolerance:

@OwenD It would be cool, if this check would happen before the old heightmap was overwritten.

That could only be done in the firmware

Or if bed.g would create a backup of the current heightmap before probing.

You could do this by using M374
More likely in mesh.g than bed.g

G29 S1 ; load heightmap
M374 P"heightmap.bak" ; create backup

;do rest of probing

CCS86

@o_lampe said in G29 Mesh Level: Pass / Fail Tolerance:

@OwenD It would be cool, if this check would happen before the old heightmap was overwritten.
Or if bed.g would create a backup of the current heightmap before probing.

Forgive me if that is already happening, I don't know for sure what's the latest and greatest

I think this is a good reason to implement in the firmware vs the macro approach.

Phaedrux

With flash space so tight on the older boards new features would have to be pretty unique. When something can be achieved with conditional gcode and a macro instead that's a pretty tough sell.

o_lampe

@Phaedrux The code to backup a file before editing is already implemented for config.g. It's probably not a big step to implement it for other files, too?
I've manually backup'd the heightmap a few times. Not a big deal either.

Phaedrux

@o_lampe I'll bring it up.