not able to get a good first layer using 3PL and bed mesh

gloomyandy

@moth4017 Do you see the same nozzle height of 0.3 all the way along the left side of the bed or does it change? TRy measuring the nozzle height at several points along the left edge front to back.

What point are you probing when you get a "front left" result of 0.141 and "front right" result of 0.166? Why are these readings different to the results you are getting from the front points in your 3PL probes? If you position the probe at the same point as used for your 3PL operation what readings do you get there?

moth4017

@gloomyandy
so the front of the bed is supported at each corner and the back is supported in the middle. (i have 3 z axis)

so the main error im concerned about is at the front as these 2 points should be the same height to keep the bed level.

im always probing and measuring at the same points (see drawing above) , so the left front point always seem to be around 0.3mm further away from the nozzle then the front right point after a 3PL.

i even took apart the x axis today just to make sure nothing was loose/broken/cracked etc at least i got to re-greese the x mgn.

did another test same error, so now i have re-trammed y rails rebuilt x axis , ive also removed the belts on the z axis to make sure there is no debris around the bottom pulley's . as you can see im clutching at straws , i know its going to be something simple at the end of this so lucking forward to kicking myself in the future

o_lampe

@moth4017
Did you mention, what type of z-probe sensor you're using? If it's an inductive or capacitive sensor, all sorts of issues can occur.

moth4017

@o_lampe I'm using a micro switch which is picked up and dropped off,

gloomyandy

@moth4017 said in not able to get a good first layer using 3PL and bed mesh:

M291 P"Probe will be tested 12 times and return mean and standard deviation. Ok or Cancel?" R"WARNING" S3 ; User must click OK or cancel.
M98 P"/macros/ProbePickUp"
G30 P0 X27 Y27 Z-9999
G30 P1 X283 Y27 Z-9999
G30 P2 X155 Y283 Z-9999
G30 P3 X27 Y27 Z-9999
G30 P4 X283 Y27 Z-9999
G30 P5 X155 Y283 Z-9999
G30 P6 X27 Y27 Z-9999
G30 P7 X283 Y27 Z-9999
G30 P8 X155 Y283 Z-9999
G30 P9 X27 Y27 Z-9999
G30 P10 X283 Y27 Z-9999
G30 P11 X155 Y283 Z-9999 S-1
M98 P"/macros/ProbeDropOff"
M402
result
G32 bed probe heights: 0.116 0.063 0.092 0.097 0.091 0.095 0.097 0.098 0.095 0.098 0.095 0.096, mean 0.095, deviation from mean 0.011

These results seem to indicate that there is something odd happening with the first 2 probes compared to the later ones at the same point. This may indicate some sort of backlash problem or perhaps there is still something pulling on the printhead and causing some (small movement) perhaps only when the head is moved in a certain way. The other possibility is that the probe is not fully in place after being picked up and is moving slightly during the probing process. What happens if after probing three points you return to the point you use for the probe pickup/dropoff and then repeat the three probes again? Do you get the same readings or do they change like they are doing above?

moth4017

@gloomyandy

OK so this time i did the 3PL and without dropping of the probe went straight into the corner repeatability test

M98 P"0:/macros/3 corner deveation"
G32 bed probe heights: 0.003 -0.003 0.006 0.003 -0.003 0.003 0.000 0.000 0.003 0.003 0.000 0.000, mean 0.001, deviation from mean 0.003
ProbeDropOff
12/20/2022, 9:10:04 AM Leadscrew adjustments made: -0.030 0.007 -0.006, points used 3, (mean, deviation) before (-0.009, 0.012) after (0.000, 0.000)
3PL finished

so as you pointed out the first 2 readings being different to the rest could have been probe not fully located.

moth4017

now with a drop off and pick up

M98 P"0:/macros/3 corner deveation"
G32 bed probe heights: 0.003 -0.003 0.006 0.003 -0.003 0.003 0.000 0.000 0.003 0.003 0.000 0.000, mean 0.001, deviation from mean 0.003
ProbeDropOff
12/20/2022, 9:10:04 AM Leadscrew adjustments made: -0.030 0.007 -0.006, points used 3, (mean, deviation) before (-0.009, 0.012) after (0.000, 0.000)
3PL finished

moth4017

im not sure if this is a valid test or not can someone let me know
also i have M561 to clear / disable bed mesh leveling.

i added these lines to my gcode at the begining and end of the print file
M569 P0.4
M569 P0.5
M569 P0.6
to check to see if the stepper motors were moving during the print

Finished printing file 0:/gcodes/300x300_0.25mm_PLA__3m.gcode, print time was 0h 6m
12/21/2022, 11:50:54 AM Drive 4 runs forwards, active low enable, timing fast, mode spreadCycle, ccr 0x00053, toff 3, tblank 0, hstart/hend/hdec 5/0/0, pos 680
Drive 5 runs in reverse, active low enable, timing fast, mode spreadCycle, ccr 0x00053, toff 3, tblank 0, hstart/hend/hdec 5/0/0, pos 264
Drive 6 runs forwards, active low enable, timing fast, mode spreadCycle, ccr 0x00053, toff 3, tblank 0, hstart/hend/hdec 5/0/0, pos 712
12/21/2022, 11:48:16 AM Drive 4 runs forwards, active low enable, timing fast, mode spreadCycle, ccr 0x00053, toff 3, tblank 0, hstart/hend/hdec 5/0/0, pos 104
Drive 5 runs in reverse, active low enable, timing fast, mode spreadCycle, ccr 0x00053, toff 3, tblank 0, hstart/hend/hdec 5/0/0, pos 828
Drive 6 runs forwards, active low enable, timing fast, mode spreadCycle, ccr 0x00053, toff 3, tblank 0, hstart/hend/hdec 5/0/0, pos 158

the POS numbers are different , does this mean the stepper motors have been moving even though it was only printing a single layer?

o_lampe

@moth4017
I don't know what the POS number means, but it's much too short for a position variable or step counter.

moth4017

Reprinting parts for new x axis going to put them on the surface table before reinstalling to check for twist .

moth4017

could not find a repeatable way to check the twist that i was happy with , so printed some more Y carrier parts as my others had cracks in them, reassembled did the 300 x 300 print test again, the same issue nozzle on the left-hand side of bed was further away then the right. look like about the same amount , not measured it yet

moth4017

OK i think i have solved the issue :-
Its to do with 3PL , i have always measured 3 points in the 3PL , but have discovered today if you do a 4 points it levels much better .

I now do this
;3PL
echo "3PL"
M561 ; cancels any bed-plane fitting as the result of probing
M564 S0 ; allow movement outside boundaries
G30 P0 X27 Y27 Z-99999 ; probe FR
G30 P1 X283 Y27 Z-99999 ; probe FL
G30 P2 X283 Y283 Z-99999 ; probe RL
G30 P3 X27 Y283 Z-99999 S3 ; probe RR S3 = 3 z axis
G90 ; Set to Absolute Positioning
echo "3PL finished" ;send Diagnose to console

dc42

@moth4017 thanks for updating us.

Exerqtor

Whats best practice regarding this btw @dc42 ? To tram with 3 or 4 probe points on a bed with three points of pivot/adjustment?

moth4017

@Exerqtor i used to probe 3 points but since going to 4 i can not get a good first layer doing a 300mm x 300mm print, my bed is supported on 3 points i would recommend it my bed is 320 x320 .

dc42

@Exerqtor said in not able to get a good first layer using 3PL and bed mesh:

Whats best practice regarding this btw @dc42 ? To tram with 3 or 4 probe points on a bed with three points of pivot/adjustment?

You can use between N points (where N = number of Z motors) and 32. RRF will minimise the RMS error over all the points. If the bed is flat and the gantry doesn't sag then 3 or 4 points should work well. If it isn't then a higher number may be better.

You may find it beneficial to run bed tramming more than once, if your mechanics don't match the model assumed by RRF. You can do this using a loop in the bed.g file.

moth4017

Good point DC42 makes about the loop, i spent time on this yesterday now only probes the amount of times required to get within your desired tolerance.

;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 X14 Y44 Z25 F20000        ; go to just above the first probe point
while true
  if iterations = 5
    abort "Too many auto calibration attempts"
  G30 P0 X17 Y17 Z-99999               ; probe starboard bow 
  if result != 0
    continue
  G30 P1 X293 Y17 Z-99999              ; probe port bow
  if result != 0
    continue
  G30 P2 X293 Y283 Z-99999             ; probe port stern 
  if result != 0
    continue
  G30 P3 X17 Y283  Z-99999 S3          ; probe starboard stern   S3 = 3 z axis 
  if result != 0
    continue
  if move.calibration.initial.deviation <= 0.04
    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"
G1 F6000 X155 Y185					; probe to center bed 	
G30 F2000							;Single Z-Probe
M98 P"/macros/ProbeDropOff"	; probe drop off
G10 Z30 F10000                ; get the head out of the way

instead of having to always do x rounds of G32 i usually can get away with 2 , results like this

1/15/2023, 9:20:14 AM	ProbeDropOff
1/15/2023, 9:20:06 AM	Leadscrew adjustments made: -0.041 -0.023 0.019, points used 4, (mean, deviation) before (-0.008, 0.023) after (0.000, 0.008)
Auto calibration successful, deviation 0.008mm
1/15/2023, 9:19:20 AM	Leadscrew adjustments made: 2.404 -0.150 -0.937, points used 4, (mean, deviation) before (0.137, 1.350) after (0.000, 0.002)
Repeating calibration because deviation is too high (1.350mm)
1/15/2023, 9:18:49 AM	Probe Pickup complete

dc42

@moth4017 it may be an artefact of inserting the file in your post, however it appears that the G28 command in line 6 may not be indented with respect to the if-command.

Exerqtor

@moth4017 said in not able to get a good first layer using 3PL and bed mesh:

@Exerqtor i used to probe 3 points but since going to 4 i can not get a good first layer doing a 300mm x 300mm print, my bed is supported on 3 points i would recommend it my bed is 320 x320 .

I got the feeling you went from 3-probes to 4-probes, not the other way around? 😅
And that going to 4 solved the issues, not the other way around? 🤔

@dc42 said in not able to get a good first layer using 3PL and bed mesh:

@Exerqtor said in not able to get a good first layer using 3PL and bed mesh:

Whats best practice regarding this btw @dc42 ? To tram with 3 or 4 probe points on a bed with three points of pivot/adjustment?

You can use between N points (where N = number of Z motors) and 32. RRF will minimise the RMS error over all the points. If the bed is flat and the gantry doesn't sag then 3 or 4 points should work well. If it isn't then a higher number may be better.

You may find it beneficial to run bed tramming more than once, if your mechanics don't match the model assumed by RRF. You can do this using a loop in the bed.g file.

Ok, gotcha. I thought the number of probe points had to be equal to the number of pivot points/steppers for some reason.

Allready running two passes with the first being a coarse'n quick pass just to get it trammed-ish then a second run inside a loop that breaks when the deviation goes bellow aset tolerance or if it does more than a set number of iterations.

Sorry for the edit, managed to press "post" rather than "minimize" earlier so i only got the first line lol.

moth4017

@Exerqtor i did go from 3 to 4 probes

my bed is on 3 points of support , (maxwell coupling )