Duet3 not changing Z height on second layer

[rjenkinsgb]

You file has the correct Z moves, from what I can see.

Try doing a basic test:
Reference (home) the printer, move up in Z a few mm then down until the nozzle is just noticeably gripping a sheet of paper.

Then move away just 0.1mm in a single move and see if the paper is loose?

If not, the problem is mechanical; either something is sticking or there is backlash in the Z mechanics.

The moves to get a light grip on the paper must be one way only for the test to be valid, no back & forth; if you overdo it, move eg. 5mm clear and start again, as the whole point is to test a single reversal of Z direction.

Likewise when moving away from it the 0.1mm; no further, or start over.

[eduard]

@rjenkinsgb Thank you for your reply.
The nozzle distance from bed was set with a precision 0.2mm metal gauge. The movement of the bed was calibrated with a 0,001mm precison indicator (+-0.015mm)
Mechanical failure is completely ruled out.
All already layers except the second are executed and perfect. When I use raft, the print is perfect and in all directions.

[eduard]

@eduard
This is what the table leveling process I follow looks like:
The duet is set above 3 points on the bed:
M558 P0; No Z probe
G30 P0 X90 Y0 Z-99999; probe near an adjusting screw
G30 P1 X150 Y185 Z-99999; probe near an adjusting screw
G30 P2 X30 Y185 Z-99999; probe near an adjusting screw and report adjustments needed

At each point, I adjust the duet to Z0 and adjust the head bed distance to 0.2mm with the bed adjustment screw. Then OK and restart the process to check back.
The thickness of the first layer in the slider is set to 0.25mm.

[rjenkinsgb]

@eduard said in Duet3 not changing Z height on second layer:

All already layers except the second are executed and perfect.

That does not rule out backlash - all layers have Z moving in the same direction except the first, which follows a move in to the 0.2mm clearance; ie. that first layer change is the reversal point, where motion would be lost.

Do a test with the dial gauge, as you have one:

Step 0.1mm several times towards the head & note the needle movement - then do a single 0.1mm step the opposite direction and see if you get the same movement??

If that is correct, then it clears the mechanics.

[Nothing personal, but having worked on machine tools for decades, it's a familiar problem].

[eduard]

@rjenkinsgb Sure, I don't take personal
If there was a backlash, the motor shaft would move, but the bed would not. However, the motor shaft does not move at the second layer.
I measured the backlash and about 0.01mm (the bed moves on a ball screw)

[rjenkinsgb]

@eduard
That could still be mechanical stiffness, giving the same effect.

The same test would prove or disprove that.

[rjenkinsgb]

Have you posted your config.g file yet?

[eduard]

@rjenkinsgb When I built it, I measured the backlash using the method you wrote. I have measured it several times since then and get the same value. This is unlikely to be where the problem comes from. Mainly because the bed goes higher (endstop) to the first layer and then comes lower, 0.2mm.

[eduard]

@rjenkinsgb Yes, but you can find here again:

config (1).g
homez (1).g
homeall (1).g
bed.g

[rjenkinsgb]

@eduard
If you reference it, get the bed & extruder up to temperature and then command Z to 0.2mm, can you still get the 0.2mm gauge in the gap without excess force?
Just to rule out any thermal effects.

I'm guessing the 0.6mm Z offset in the tool definition is the difference between the Z home height and the tool nozzle height?

You also try adding M669 K0 at the top of the config, before any drive or motor stuff. It should not make any difference as the default is cartesian mode, but you never know!

Other than mine being corexy and having two z motors, your general setup is quite similar, which is why it's so puzzling..
I'm also having problems with Z, but only relating to probing accuracy and not layer movements.

[deckingman]

@eduard In addition to the other advice you have been given, there is one other thing you can do which is to observe the commanded Z position in the web interface when you run your print. Looking through your gcode, after homing the printer using G28, there is a G1 Z move to +15 prior to priming the extruder. Does DWC show the Z position as being +15 at this point? After that, there is a G0..... Z move to 0.2. Is DWC showing the Z position to be 0.2 at this point in the file? The next Z move that I can see is on line 448 which is another G0 .......Z 0.4. Does DWC show Z0.4 at this point? If it does then the hardware and firmware would appear to be working as intended and if the Z axis doesn't move, then it must be for mechanical reasons or some issue which prevents the Z motor from moving as commanded. If DWC still shows the Z position to be 0.2 after the G0.....Z0.4 command, then there is a firmware issue which might be related to using G0 rather than the more normal G1.

[eduard]

@deckingman Thanks, I'll try and give feedback.

[eduard]

@deckingman It is possible to print out the G code while printing like on CNC?

[eduard]

Thank you all for your quick and efficient help.
I found the error, it was here:
G10 P0 X0 Y0 Z0 ; set tool 0 axis offsets
It was Z0.6, after an earlier setup and I skipped over it several times. In my case, zero is a good solution.

Hi,
Eduard