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First layer calibration Z height changes every 2-3 prints  

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harrison.rhys
(@harrison-rhys)
New Member
First layer calibration Z height changes every 2-3 prints

I can't seem to find a recent issue that is similar. I have a MK3s that I put together on firmware 3.8.0-2684. The issue:

- Every 2 to 3 prints (around 8hrs or so total) I have to adjust the first layer Z two steps more negative to get a good pattern.

- This happens with prusa PLA, PETG, PLA + & glo in the dark PLA's.

- Happens during the same roll without changing the filament.

- Changed the tip to a hardened steel E3D, same issue.

- The PINDA probe seems tight (going to mark it next).

- Contacted support and they had no idea, said there's new firmware coming in the next few weeks.

- Tried drying the filaments with the same results (PLA 95F for 8 hrs).

I'm not sure what else to try except marking and thread locking the probe. Any help would greatly be appreciated.

Thanks!

 

Posted : 07/10/2019 10:01 pm
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(@)
Illustrious Member
RE: First layer calibration Z height changes every 2-3 prints

The mesh level is inordinately sensitive to the PINDA temperature.  Changes from 25c to 40c make huge differences in layer 1.

Most experienced users add M860 to our startup gcode to allow the PINDA to stabilize at a higher temp before doing the mesh level. Depending on environment, 35 to 40c works pretty well, adjust to keep print time reasonable - I just dropped to 37.5 from 40 because I'm now into heat mode rather than AC mode and my room temp has dropped a few c.

; soak PINDA then level
G0 X50 Y50 Z1 F3000; this is a good PINDA heating position
M860 S37.5 ; wait until PINDA reaches a good temp
G80 N7 R5; mesh bed leveling

 

Posted : 07/10/2019 10:55 pm
harrison.rhys
(@harrison-rhys)
New Member
Topic starter answered:
RE: First layer calibration Z height changes every 2-3 prints

@tim-m30

Fantastic thank you. I'll give that a try! (I'll also make sure i know what im doing first). 

Thanks again!

Posted : 07/10/2019 11:10 pm
KevinK
(@kevink)
Trusted Member
RE: First layer calibration Z height changes every 2-3 prints

Also, make sure that the PINDA probe is vertical.  One symptom of sagging of the PETG housing is that it begins to tilt off vertical.  The probe isn't moving in the clamp; the clamp itself is sagging.  I had this issue where the Z height needed to get more negative and that was the cause for me.  If you have been printing a lot of higher temperature stuff, particularly that is relatively large and flat so that the nozzle stays near the bed for a lot of the time this can happen.

Posted : 08/10/2019 1:02 am
harrison.rhys
(@harrison-rhys)
New Member
Topic starter answered:
RE: First layer calibration Z height changes every 2-3 prints

@kevin-k49

Great point thank you! Is there a solution that worked for you or some way i can remedy / check this? 

Cheers!

Posted : 08/10/2019 1:18 am
ManelTo
(@manelto)
Estimable Member
RE: First layer calibration Z height changes every 2-3 prints
Posted by: @tim-m30

The mesh level is inordinately sensitive to the PINDA temperature.  Changes from 25c to 40c make huge differences in layer 1.

Most experienced users add M860 to our startup gcode to allow the PINDA to stabilize at a higher temp before doing the mesh level. Depending on environment, 35 to 40c works pretty well, adjust to keep print time reasonable - I just dropped to 37.5 from 40 because I'm now into heat mode rather than AC mode and my room temp has dropped a few c.

; soak PINDA then level
G0 X50 Y50 Z1 F3000; this is a good PINDA heating position
M860 S37.5 ; wait until PINDA reaches a good temp
G80 N7 R5; mesh bed leveling

 

Where do you put this code? in printer configuration GCode?

Sorry for my poor English. I try to do my best.

Posted : 08/10/2019 8:46 am
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(@)
Illustrious Member
RE: First layer calibration Z height changes every 2-3 prints

re Melting MK3S parts, usually that happens after printing in an enclosure or after hours and hours at high printing temperatures for plastics like ABS and PolyCarb.   To check, you can simply look at the PINDA: melting parts tend to let it droop, and the droop is permanent and you can usually see the PINDA is crooked, and plastic near the heat sink fins are melting. 

Also, Prusa updated some of the extruder parts to reduce the tendency to melt.  You may or may not have the worst parts: it will depend on when you purchased the printer.  You can contact Prusa support via the store chat to ask.  The Rx version numbers are hidden when the extruder is assembled.  I think R5 is the latest.  These links can get you more info about the issue.

https://github.com/prusa3d/Original-Prusa-i3/tree/MK3S/Printed-Parts/STL

https://www.reddit.com/r/prusa3d/comments/bw4d01/has_anyone_else_had_this_part_melt_like_this/

https://www.reddit.com/r/prusa3d/comments/cycflf/if_you_have_a_mk3s_you_should_probably_install/

 

 

Posted : 08/10/2019 8:49 am
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(@)
Illustrious Member
RE: First layer calibration Z height changes every 2-3 prints

Brief how-to: 

My full start gcode ... and yes, I haven't upgraded to 3.8 yet ...

M115 U3.7.1 ; tell printer latest fw version
G90 ; use absolute coordinates
M83 ; extruder relative mode

; preheat things to a low temp, get nozzle plastic mushy before driving into the bed with G28
M140 S[first_layer_bed_temperature] ; set bed temp
M109 S175 ; wait for extruder temp
G28 W ; home all without mesh bed level
M190 S[first_layer_bed_temperature] ; set & wait for bed temp

; soak PINDA then level
G0 X50 Y50 Z1 F3000; this is a good PINDA heating position
M860 S37.5 ; wait until PINDA is >= 37.5C (I use 40C in summer)
G80 N7 R5; mesh bed leveling

; heat to extrude temp
G0 X0 Y-3.0 Z10 F3000; this is a good nozzle heating position
M109 S[first_layer_temperature] ; set & wait extruder temp

; purge
G1 Y-3.0 Z0.15 F1000.0 ; go outside print area
G92 E0.0
G1 X60.0 E9.0 F1000.0 ; intro line
G1 X100.0 E12.5 F1000.0 ; intro line
G92 E0.0
M221 S{if layer_height<0.075}100{else}95{endif}

; Some examples
;
; M104 S ; set extruder temp
; M140 S ; set bed temp

; M109 S ; wait for extruder temp
; M190 S ; wait for bed temp

; layer_height
' layer_z
This post was modified 4 years ago 2 times by --
Posted : 08/10/2019 8:57 am
ManelTo
(@manelto)
Estimable Member
RE: First layer calibration Z height changes every 2-3 prints

Thanks Tim!!!

Sorry for my poor English. I try to do my best.

Posted : 08/10/2019 6:42 pm
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