Bed Leveling Failed on CoreONE upgrade  

RE: Bed Leveling Failed on CoreONE upgrade

See if the solutions/workarounds in this post/thread work for you in case you have the same issue as those. https://forum.prusa3d.com/forum/postid/750274/

RE: Bed Leveling Failed on CoreONE upgrade

Hi,
for a quick first test, try to disable the hotend heating for the MBL probing.
It's described here: https://forum.prusa3d.com/forum/prusa-core-one-assembly-and-first-prints-troubleshooting/z-axis-trouble-but-only-when-printing/paged/2/#post-750771

How to:
1. Enable Expert Mode: Top Right corner in the normal Slicer window.
2. Go to Settings -> Printers -> Custom G-code -> Start G-code
3. Select all in the Start G-code field, delete it and paste my G-code in that field

But here's my current Start G-code for 6.3.3:

;  04th June 25
M17 ; enable steppers
M862.1 P[nozzle_diameter] A{(filament_abrasive[0] ? 1 : 0)} F{(nozzle_high_flow[0] ? 1 : 0)} ; nozzle check
M862.3 P "COREONE" ; printer model check
M862.5 P2 ; g-code level check
M862.6 P"Input shaper" ; FW feature check
M115 U6.3.3+10442

M555 X{(min(print_bed_max[0], first_layer_print_min[0] + 32) - 32)} Y{(max(0, first_layer_print_min[1]) - 4)} W{((min(print_bed_max[0], max(first_layer_print_min[0] + 32, first_layer_print_max[0])))) - ((min(print_bed_max[0], first_layer_print_min[0] + 32) - 32))} H{((first_layer_print_max[1])) - ((max(0, first_layer_print_min[1]) - 4))}

G90 ; use absolute coordinates
M83 ; extruder relative mode

{if chamber_minimal_temperature[initial_tool]!=0}
M140 S115 ; set bed temp for chamber heating
{else}
M140 S[first_layer_bed_temperature] ; set bed temp
{endif}

M109 R{((filament_notes[0]=~/.*MBL160.*/) ? 160 : (filament_notes[0]=~/.*HT_MBL10.*/) ? (first_layer_temperature[0] - 10) : (filament_type[0] == "PC" or filament_type[0] == "PA") ? (first_layer_temperature[0] - 25) : (filament_type[0] == "FLEX") ? 210 : 170)} ; wait for temp

; custom G-code start						
M104 S0 ; turn off hotend heating for clean loadcell signals during homing
; custom G-code end

M84 E ; turn off E motor

G28 ; home all without mesh bed level

{if chamber_minimal_temperature[initial_tool]!=0}
; Min chamber temp section
M104 S{idle_temperature[initial_tool]} ; set idle temp
G1 Z10 F720 ; set bed position
G1 X242 Y-9 F4800 ; set print head position
M191 S{chamber_minimal_temperature[initial_tool]} ; wait for minimal chamber temp
M141 S{chamber_temperature[initial_tool]} ; set nominal chamber temp
M107 ; Fans off
M140 S[first_layer_bed_temperature] ; set bed temp
{else}
M141 S{chamber_temperature[initial_tool]} ; set nominal chamber temp
{endif}

{if first_layer_bed_temperature[initial_tool]<=60}M106 S70{endif}
G0 Z40 F10000
M104 T{initial_tool} S{if is_nil(idle_temperature[initial_tool])}100{else}{idle_temperature[initial_tool]}{endif}
M190 R[first_layer_bed_temperature] ; wait for bed temp
M107 ; Fans off

G29 G ; absorb heat

M109 R{((filament_notes[0]=~/.*MBL160.*/) ? 160 : (filament_notes[0]=~/.*HT_MBL10.*/) ? (first_layer_temperature[0] - 10) : (filament_type[0] == "PC" or filament_type[0] == "PA") ? (first_layer_temperature[0] - 25) : (filament_type[0] == "FLEX") ? 210 : 170)} ; wait for MBL temp

M302 S160 ; lower cold extrusion limit to 160C

{if filament_type[initial_tool]=="FLEX"}
G1 E-4 F2400 ; retraction
{else}
G1 E-2 F2400 ; retraction
{endif}

M84 E ; turn off E motor

; custom G-code start						
M104 S0 ; turn off hotend heating for clean loadcell signals nozzle cleaning
; custom G-code end

G29 P9 X208 Y-2.5 W32 H4 ; Nozzle Cleaning by probing a little rectangle

; custom G-code start
; Heat up again and then turn off for MBL
M109 R{((filament_notes[0]=~/.*MBL160.*/) ? 160 : (filament_notes[0]=~/.*HT_MBL10.*/) ? (first_layer_temperature[0] - 10) : (filament_type[0] == "PC" or filament_type[0] == "PA") ? (first_layer_temperature[0] - 25) : (filament_type[0] == "FLEX") ? 210 : 170)} ; wait for MBL temp
M104 S0 ; turn off hotend heating for Mesh Bed Levelling
; custom G-code end

;
; MBL
;
M84 E ; turn off E motor
G29 P1 ; invalidate mbl & probe print area
G29 P1 X150 Y0 W100 H20 C ; probe near purge place
G29 P3.2 ; interpolate mbl probes
G29 P3.13 ; extrapolate mbl outside probe area
G29 A ; activate mbl

; prepare for purge
M104 S{first_layer_temperature[0]}
G0 X249 Y-2.5 Z15 F4800 ; move away and ready for the purge
M109 S{first_layer_temperature[0]}

G92 E0
M569 S0 E ; set spreadcycle mode for extruder

;
; Extrude purge line
;
G92 E0 ; reset extruder position
G1 E{(filament_type[0] == "FLEX" ? 4 : 2)} F2400 ; deretraction after the initial one
G0 E5 X235 Z0.2 F500 ; purge
G0 X225 E4 F500 ; purge
G0 X215 E4 F650 ; purge
G0 X205 E4 F800 ; purge
G0 X202 Z0.05 F8000 ; wipe, move close to the bed
G0 X199 Z0.2 F8000 ; wipe, move quickly away from the bed

G92 E0

;Set flow rate
M221 S100 ; set flow to 100%

RE: Bed Leveling Failed on CoreONE upgrade

I'm having varied success.  I was able to start and complete a couple prints with this change.  I also changed from my MK3 textured build plate to a smooth  (thicker) build plate and that seemed to help.  I think the MK3 textured build plate may just be too thin to be compatible.  Below are the things I've tried.

• Textured Build plate (old MK3)- Generally unsuccessful
• Smooth Build Plate - semi successful
• Disabled Heater using above trick - allowed probing to complete on both build plates, but not consistently
• Rearranged the heater wire to give the load cell more consistent readings.
• 6.3.2 and 6.3.3 Firmware didn't have any effect

RE: Bed Leveling Failed on CoreONE upgrade

Maybe the extruder fan duct is hitting the print bed cable cover? 

If changing the print plate changes things, that sounds quite likely. 

Can you upload a photo of your rear left corner of the print bed (with the cable cover)? 

One screw should be visible with the cover on and it needs to be a flat screw head (kit assembly manual was adjusted right after I finished mine..).

RE:

Whilst the printer is idle, watch the Loadcell sensor value.  It should be fairly static - not continually moving in one direction - typically just wavering 5-10 around a mid point.

If it's just walking away in one direction, you have something applying a constant pressure - in my case it was the heater element wires.  I moved them well clear of everything and the loadcell value became level.

I still have bed probing issues though - but only ever at the back left and right corners.

** just read you already did the same 🙂 **

RE: Bed Leveling Failed on CoreONE upgrade

So after much experimentation, I've determined that the back right of my Core One upgrade is not usable if it has to be probed. The printer will not pass a probe sequence if it has to probe the back right corner. If I place a small print in the center where the back right doesn't have to be probed, the print will succeed. If for any reason the printer has to probe the back right, MBL fails and the print won't start.

RE: Bed Leveling Failed on CoreONE upgrade

Confirming, turning off heater during probing doesn't change anything on my printer.  It seems to be a physical or mechanical issue with the back right of the bed.

RE: Bed Leveling Failed on CoreONE upgrade

Posted by: @discojon

So after much experimentation, I've determined that the back right of my Core One upgrade is not usable if it has to be probed. The printer will not pass a probe sequence if it has to probe the back right corner. If I place a small print in the center where the back right doesn't have to be probed, the print will succeed. If for any reason the printer has to probe the back right, MBL fails and the print won't start.

Did your read the earlier post about the fan shroud hitting the heat bed cover?  Did you check this?

RE: Bed Leveling Failed on CoreONE upgrade

Posted by: @brian-12

 Posted by: @discojon

So after much experimentation, I've determined that the back right of my Core One upgrade is not usable if it has to be probed. [...]

Did your read the earlier post about the fan shroud hitting the heat bed cover?  Did you check this?

That cable cover (which can collide with the fan shroud) is in the back left though.

RE: Bed Leveling Failed on CoreONE upgrade

Yeah - I think the back left and right corners lack enough support for the loadcell to register them as well as the rest of the bed - the bed there gives too easily.
I've had no issues printing smaller centered items - just happened that my first prints were the community MMU spool holders that take up most of the bed....

Does anyone from Prusa frequent these forums ?

RE: Bed Leveling Failed on CoreONE upgrade

Posted by: @defsdoor

Yeah - I think the back left and right corners lack enough support for the loadcell to register them as well as the rest of the bed - the bed there gives too easily.
I've had no issues printing smaller centered items - just happened that my first prints were the community MMU spool holders that take up most of the bed....

Does anyone from Prusa frequent these forums ?

No.  All issues should be put on GitHub.  Please search to make sure someone else hasn't already started one on the same issue.

RE: Bed Leveling Failed on CoreONE upgrade

I did read the post.  There is no contact.  My current hypotheses is that that the bed isn't supported well enough leading to hysteresis in the load that the printer can't account for.  I am going to try stacking a couple build plates to see if that makes any difference.

RE: Bed Leveling Failed on CoreONE upgrade

New Development

Stacking two buildplates allowed the 49 point probing sequence to complete without error.  If i remove one of the build plates, the probing fails each and everytime int he back right corner.  Can we get some data from others on this?  Generate a print file that fails consistently, stack two build plates and run the file again and let us know if the probing completes.

RE:

Update: Lowering the nozzle ~1mm using the thumb screws also allows the probing sequence to complete without issue.

RE: Bed Leveling Failed on CoreONE upgrade

Mhhh, so it's either the bed hitting something, the extruder fan duct hitting something or the nozzle being able to go too far in. 

Can you upload a photo of your Nozzle, when it's "completely inserted" and with the 1 mm lowered? Make two photos:

Auto Home from the menu, then move Z to 0 and make a picture, so that we can see how far lower the nozzle is compared to the fan duct. And the other picture with the bed lowered so you can take a picture of the nozzle shaft going into the extruder. 

I'll try to do the same, but not at home right now. 

RE: Bed Leveling Failed on CoreONE upgrade

Nothing else is hitting anything else in my case.  I can watch it, the nozzle is the only thing touching the bed and I can see the bed deflect slightly....

RE: Bed Leveling Failed on CoreONE upgrade

Posted by: @defsdoor

Nothing else is hitting anything else in my case.  I can watch it, the nozzle is the only thing touching the bed and I can see the bed deflect slightly....

Mhh okay. I can't really imagine the actual bed deflecting, but maybe there's some play somewhere? 

Take off the print sheet and check the heatbed screws in the problematic corner. Is the heatbed deflecting or really the print bed frame, when watching from below the bed? 

Or is the whole bed tilting and something is loose on the rods/bearings/leadscrews? 

RE: Bed Leveling Failed on CoreONE upgrade

Posted by: @defsdoor

Nothing else is hitting anything else in my case.  I can watch it, the nozzle is the only thing touching the bed and I can see the bed deflect slightly....

Are you sure you are looking in the right place? The cable cover/fan shroud collision occurs behind the Nextruder, not that easy to see.

The fact that you see the bed actually deflecting downward suggests a significant force acting upon it -- certainly more than the slight nozzle touch. If the fan shroud were to make contact first, the Z drive it would have to push the heatbed upward until the fan shroud bends out of the way enough to let the nozzle male contact. That might mean enough force to also bend the heatbed down slightly. 

Alternatively -- any chance that there is a piece of debris between the heatbed and the print sheet, lifting the sheet up slightly in the back? In that case you might just see the print sheet bending downward, not the whole heatbed?

RE: Bed Leveling Failed on CoreONE upgrade

The cable cover is on the left.  It fails when the probing is on the rear right - where it probes first on my nearly full bed prints - and also on the left one the occasions that it succeeded on the right.
I also reported in my post ( https://forum.prusa3d.com/forum/prusa-core-one-assembly-and-first-prints-troubleshooting/bed-levelling-issues/)   that the loadcell offsets when probing the rear left and right are significantly lower (10-30) than anywhere else on the bed (100-200)

There are topics on GH where other users have the same issue - discussing the ability to tune the offset expectations.