Cannot keep bed level

[Gramsey]

Hi there.

I have A20M printer and using glass super plate.

I’m having significant & unusual issues keeping the bed level - even between consecutive prints.

This was a cumbersome issue when using manual levelling, and has continued after installing 3DTouch.
With 3DTouch I’m constantly having to adjust the z-offset to ensure reasonable first layers.

I have disassembled and re-assembled the printer today without much improvement.

Few points on the reassembly:
- The X axis bar allows for movement and appears to sag on one side - when held upward it sits level with the bed, however I can’t seem to keep it in this position due to the screw placement?
- The hex nut for the rear Y axis wheel has been drilled notably off-center.
- Some wheels for Y axis spin freely - I’ve managed to resolve this for all but 1 on the motor side.

Any advise you can offer to resolve this levelling issue would be appreciated.

Thanks!

[3DAngel]

Are you aware of the eccentric spacer?
If you have deassembled all wheels, there must put back in the same order.
The eccentric one, should be stand alone.
It main purpose is to tighten the carriage to allow all three wheels to be engaging evenly ...

And when you adjust the z offset, did you save it in eeeprom? Cause you likely lost your adjustment once power cycled your printer.
Hope this helps

[Gramsey]

Thanks for the replies & assistance.

@3DAngel
Yes the spacer is placed well has allowed the wheels I reassembled to now fit & no longer spin freely. Also the Z-offset has been saved to EEPROM.
Only 1 wheel remains "loose", which is on the side I did not re-assemble, sat between the motors. The other 2 wheels on this side appear fine.

@vert
I've run the M48 test and calibrated - achieving the following results:

Code: Select all

Mean: 0.011100 Min: 0.006 Max: 0.016 Range: 0.011
Standard Deviation: 0.003611

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Mean: 0.009450 Min: -0.005 Max: 0.015 Range: 0.019
Standard Deviation: 0.005241

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Mean: -0.020500 Min: -0.080 Max: 0.012 Range: 0.093
Standard Deviation: 0.031478

My concern is this adjustment on the z-offset needs to be anything from 0.15mm all the way up to 0.5mm
Roughly fluctuating between -0.75mm to -1.2mm.

Importantly I do not understand why the bed level is so sporadic? I could appreciate this if it had been sat for a day, or was wildly fluctuating in temps.
However I can simply print a levelled object, remove from the bed upon completion and immediately start again - only to find the bed (or some other axis) has shifted.

Regards.

[3DAngel]

then we should look at someting mechanical..eg the springs and the knob under the bed.
mine is tighten quite a bit, so the bed is well loaded with the spring s' tension on them.
this seems to be little things, but, I have seen them to come off during the print sue to the harmonic vibrations on the belt that transmit to the bed...
ask me how I learned... lol

[Gramsey]

Hi 3DAngel.

I’ve replaced the springs tonight.
I’m now using much thicker (yellow) springs.

I was calibrating my Z-offset again afterwards and really noticed this shift.

Had it dialled down (using 0.02mm changes) to around 1.10mm
Suddenly something shifted.. simply during auto-home...
I was then down to 0.90mm to achieve a similar friction.

Any advice for a next test?

Thanks for you ongoing help!

[Gramsey]

Anyone have any suggestions?

[Gramsey]

The issue exists regardless of BLTouch, 3D Touch or manual levelling.

Something is shifting structurally.

I will attempt another rebuild, if that doesn’t resolve the issue I’ll return the printer.

[3DAngel]

hope by now you got it sorted out, or returned the printer.
I've been busy with my work and only now New Year holiday breaks...
if not sorted out and not returned your printer, the other thing it might be is the lead screw.
you might want to flip it and see if that helps.