Printer ignoring ABL?

Filament 3D Printer Technical Help
21

Thanks, Loosenut.
There’s nothing worse than overlooking the basics…
Here’s my bed levelling process. It starts with manual, then the ABL.

Tighten the bed level screws fully, then back off 1 full turn.
With the machine powered on, bed at 60C, hot end 215C,
-Home the nozzle.
-Bring the nozzle down in the home position (On my printer X204 Y167) until either it just touches the bed, or Z height reads 0.
(Yesterday, the bed touched at 0, .1mm was a good fit on a piece of paper.)

  • Use Octoprint to move the nozzle to each corner of the bed.
    First time, just to check which is the highest corner.
    Go back to each corner and adjust so that there is a similar drag on paper under each corner.
    -Run ABL to check level (G28 then G29)
    Yesterday, I stopped there. This was the ABL matrix:
    Recv: 0 1 2 3 4
    Recv: 0 +0.255 +0.205 +0.080 -0.065 -0.243
    Recv: 1 +0.262 +0.165 +0.040 -0.093 -0.290
    Recv: 2 +0.262 +0.175 +0.045 -0.088 -0.290
    Recv: 3 +0.212 +0.105 -0.013 -0.140 -0.325
    Recv: 4 +0.197 +0.102 -0.010 -0.115 -0.278
    Not ideal, but good for a first go.

Usually, I will adjust the corners with the springs and repeat home, ABL until the corners are as close as I can get them. But no matter how many times, or how close I’ve gotten the corners, I still have the uneven first layer across the bed, and in the same places.

I’ll try to tweak the level next time I get a chance to work on it.

22

I have had that also, don’t know why but so far it hasn’t interfered with a print. It is usually only noticeable on the brim. Next time it has gone away. Possibly a spring shifts, who knows.

23

From the numbers you posted earlier, it looks like something is mechanically loose like the bed is on a bad wheel or the right side gantry has some play in it. Numbers are a bit wild, when high on the left and low on the right, Don’t think it’s bad BLtouch, trigger seems ok.

24

Thanks, Jason, everyone.
I replaced the BLTouch, no difference.
I’ve tweaked the bed level, using the output from the BLTouch. Much closer to level in the corners, but still the same symptoms.
I’m waiting for a borosilicate glass plate, I’ll update once that arrives. Could be a week or so.

1 Like
25

I received my new, 5mm borosilicate glass bed.
I’ve tweaked the level manually, and have run the bed levelling multiple times.
I’ve printed bed levelling squares multiple times as I tweak the Z offset.

Results: much the same, except that I have a fairly smooth transition from the rear left, which is now too far away from the bed, to the right front, which is so close to the bed that the extruder grinds when printing.

While I can at least print now, I’m intrigued by the challenge.

What I don’t understand is: The printer KNOWS where the bed is, because it has measured it immediately prior to printing (G28 then G29 in the pre-print gcode)
Why, when it goes back over it, does it think it is somewhere else?

So, a question:
Can I turn ABL off, and use the BLTouch only for homing? Just to see what happens?
Does anyone know the gcode to do this? Or is it simply a matter of leaving out the G29 command?

26

Just remove the G29 and it will not run the levelling routine each time you print.

1 Like
27

Hmmm. Still working on this, as time allows.

I found that if you just comment out the G29, ABL is still on, and it is still moving the Z axis.
Where it gets its information is anybody’s guess.

I found out that I have to turn ABL off in the printer’s menu as well, then I can adjust the bed manually.
I’ve been able to get a near-perfect first layer with a manual bed level.

I’m wondering if the issue is somewhere in my Marlin setup for ABL.
It is as if the printer is using a stored, outdated ABL matrix instead of the one that was just completed?

I’ll continue to plug away at it!

28

HI @era99

Are you using bilinear mesh or UBL?

I think UBL is handled differently than bilinear.

29

It’s a bilinear mesh.

30

I would try the G29 S0 will disable it outright. Can you post up a copy of your start Gcode just so I can see anything else in there?

31

It’s pretty basic.

; Ender start code modified for Micro-Swiss extruder

; Modified for BLTouch, Feb 3,2022, Gerald McKeown

; Thanks to 3D Print Beast for start code suggestions!

; Ender 3 Custom Start G-code

; Preheat the bed

M140 S{material_bed_temperature_layer)0}; Start heating the bed

M190 S{material_bed_temperature_layer_0}; Wait until bed reaches temperature

M104 S{material_print_temp}; Heat nozzle to print temperature

G28 ; Home all axes - Homes in middle of bed for BLTouch

G29 ; Do bed levelling

G92 E0 ; Reset Extruder

G0 Z4 F3000 ; Keep the nozzle away from the clips.

G0 X0 Y0 F5000; Go to home (0, 0)

G92 Y-10.0; This sets the offsets for the Micro-Swiss direct drive extruder.

M109 S{material_print_temperture_layer_0}; Wait for the extruder to come to temperature

G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed

G1 X0.1 Y20 Z0.3 F5000.0 ; Move to start position

G1 X0.1 Y200.0 Z0.3 F1500.0 E15 ; Draw the first line

G1 X0.4 Y200.0 Z0.3 F5000.0 ; Move to side a little

G1 X0.4 Y20 Z0.3 F1500.0 E30 ; Draw the second line

G92 E0 ; Reset Extruder

G1 Z2.0 F3000 ; Move Z Axis up little to prevent scratching of Heat Bed

G1 X5 Y20 Z0.3 F5000.0 ; Move over to prevent blob squish

32

I have a question:
In Marlin’s configuration.h, there is a choice to either restore or enable levelling after G28, as follows:
#define RESTORE_LEVELING_AFTER_G28
//#define ENABLE_LEVELING_AFTER_G28

Does anyone know what this really means? I was wondering if this could be causing my problem?
(Only way to know is to try it…)

33

Just a note:
G29 S0 causes the printer to abort the print. (Disable ABL)
An error message about receiving a “Start” while printing
I’ve gone back to just taking out the G29