Strange layer offset on coreXY

[DVD479]

thanks for the tip, i tried right now but it seems the change is minimal.

thanks anyway

[Spanners]

Seems to me that your currents to the stepper moters is too low which maybe causing missed steps ....
your settings--> M906 X300 Y300 Z300 E300 I30

I have a coreXY and my currents are set to 700 ma (duet 2 wifi with NEMA 17 17HS4401 steppers)

my settings --> M906 X700 Y700 Z700 E700 I30

[JoergS5]

@dvd479 your offsets are so regular, I would suspect that either microstepping is wrong or pulley teeth. Microstepping of external stepper needs DM542 to be set e.g. (please check table printed on the DM542) on-on-off-on of the switches SW5 to 8 (arrow shows where is on), and please check that you're using 20 teeth pulley, not other number (to get 200*16/40 = 80 M92 setting).

[DVD479]

I tried to check your suggestions but unfortunately I didn't get any particular changes.

for the pulleys I have checked now and they are 20 teeth so they shouldn't be the cause of the problem, and the drivers are also set to the correct sequence

thanks anyway

[JoergS5]

@dvd479 strange.

An additional idea is that the pulleys are sliding on the stepper shafts. You can check by marking with a felt tip pen over pulley and shaft.

And to be sure, you're using GT2, not HTD or other belts?

[DVD479]

I used 20 tooth gt2 pulleys, I checked the pulleys on the motors and I did not see any oscillations

thanks for the tips

[Stephen6309]

@dvd479 I use M906 X800 Y800 Z800 E800 I30 for the stepper currents on my CoreXY. I believe the 300 your using is not enough.

[rjenkinsgb]

@stephen6309 said in Strange layer offset on coreXY:

I use M906 X800 Y800 Z800 E800 I30 for the stepper currents on my CoreXY. I believe the 300 your using is not enough.

He says early on that he is using external stepper drivers.

Back to the question - another thing to try; reduce the maximum speed from 18000 down to eg. 10000 to be sure the drivers are not missing steps?

[whosrdaddy]

This is a mechanical problem, not an electronics problem.
Can we see pictures of your belt setup. I guess one or more belts paths are not perpendicular to X or Y motion...

[JoergS5]

@whosrdaddy that's a good point, and the best description I know about it is in https://drmrehorst.blogspot.com/2018/08/corexy-mechanism-layout-and-belt.html

[rjenkinsgb]

@whosrdaddy said in Strange layer offset on coreXY:

This is a mechanical problem, not an electronics problem.

The "cube" appears to be slanted, not just deformed scale-wise - or is it just the photo angle?

Any mechanical setup or steps per mm error would give x-y distortion, but not drift, surely?
A given X-Y point should always be the same, no matter how far off true position it is??

If there is no slant or layer drift, and only shape distortion, then scaling and mechanics are the likely cause.

[mrehorstdmd]

I would try modifying the step/dir/en timing parameters in the M569 statements. You may be operating right at the limits of the external hardware. Try increasing the values until they are well above the minimum specs in the driver manual. In my sand table with servomotors I use

M569 P5 S1 R0 T4.0:5.0:6.0:12.0 ; drive 5 reverse, lo enable, timing parameters for servomotors
M569 P6 S1 R0 T4.0:5.0:6.0:12.0 ; drive 6 reverse, lo enable, timing parameters for servomotors

These values allow the motors to hit their back-emf speed limit of 3k rpm.

Some photos of the printer might be useful...

[DVD479]

thanks everyone for the advice. at the moment I can't send the photo of the corexy logic used but I think the problem is not due to the positioning of the belts since I used a scheme similar to the voron 2.4. I had also tried to increase the delay times of the motors and also reduced the microsteps to reduce the data flow. I am attaching some photos to show the problem that I have honestly never encountered. I fear it is a software problem and not a mechanical one because as you can see from the photos keeping the same mechanical configuration, generating the gcode with CURA and slic3r I got a different result. do you think it could be a problem of the slicer with the corexy logic?

[JoergS5]

@dvd479 said in Strange layer offset on coreXY:

generating the gcode with CURA and slic3r I got a different result.

you can analyze the two g-codes for differences, they are simple text files. Probably at the beginning is something different. To help you look into it, please publish it.

The corexy logic cannot be the reason, because g-code files contain cartesian coordinates and the firmware translates it into the specific kinematics like corexy.

[DVD479]

slic3rCube.gcode CuraCube.gcode

[DVD479]

these are the two files, however, I don't know if the engine of the two slicers behave in an equivalent way, giving similar Cartesian coordinates as values.

I wanted to hear your opinion regarding a doubt, in your opinion it is possible that in a Gcode file a certain coordinate with the information for XYE is repeated for each layer or it is not probable as a repetition

[JoergS5]

This post is deleted!

[JoergS5]

@dvd479 I am wondering why your printout is so height, when it should be a cube. Either XY print much shorter than calculated or your Z layer heights are heigher than 20 mm. Can you please tell me the dimensions of the printouts?

Do you have any gears at X, Y or Z steppers or Nema steppers with 400 instead of 200 steps?

[JoergS5]

@dvd479 Something is wrong with your config.g:

M669 K1 ; switch to CoreXY mode
M569 P5 T2.5:2.5:5:5 S0 ; physical drive 0 goes backwards
M569 P6 T2.5:2.5:5:5 S1 ; physical drive 1 goes backwards
M569 P2 S0 ; physical drive 2 goes backwards
M569 P3 S1 ; physical drive 3 goes forwards
M584 X6 Y5 Z7 E8 ; set drive mapping

Z7 and E8 have no mapping to steppers, there are no M569 definitions.

M350 Z2 with M92 Z80 is also a strange combination, what do you use for Z?

[mrehorstdmd]

Photos of the printer...?