Initial tuning for corexy with 3 z independent z screws



  • OK so that's some sort of progress. It looks to me like the Z height is very inconsistent and now that we've established what you your lead screws are, it could well be that your acceleration and instantaneous speed settings are too high for that course lead and my best guess is that you are skipping steps. I see that you have acceleration set to 450mm/sec^2 which is way too high IMO. Try something like 10 or 20 (M201 Z20) and do the same for instantaneous speed change i.e set M566 Z10 or 20 (mm/sec). Set maximum speed for Z to around 300 (M203). While you are at it, the Y axis acceleration is way too low at 20 - set that to around 1,000 (I use 1000 and my moving mass in Y is 4Kg !).

    Edit, here is why those multi start screws are my pet hate https://somei3deas.wordpress.com/2017/01/31/z-axis-lead-screws/



  • Ok, I did the Z change, but it didn't stick again. The Y is really faster and the Z seems more controlled.

    I am going to change belts and re-tighten and re-check the build to see if I messed up somewhere, and will report back with, probably, more questions on Friday πŸ™‚



  • @deckingman:

    Edit, here is why those multi start screws are my pet hate https://somei3deas.wordpress.com/2017/01/31/z-axis-lead-screws/

    Also I read this and now want to find a way to adapt a 1:2 gear on my current screws. Or change them to a 1 start or threaded rod.



  • You can also try using a wider first layer which sometimes helps - up to 200% of the nozzle width.



  • So I changed the belts, added a 300mm PEI cover to the bed, and that seems to have helped on some of the shift issues

    The first layer problems still here tho. I am printing a big box for my duet now, and for the first layer to stick I had to print it with like 10 mm/s, on a Pei bed at 70 degrees. Still I get this:

    In this the skirt is raising up on the border because when the nozzle goes throug there, it forces it up.

    This is a photo of the first layer, as you can see the bottom part is very squished to the bed while the top part totally isn' t.

    I tought that with a MIC6 plate, independent screw correction and mesh maps, I would not have to worry about it getting a correct first layer ever again, but it seems that I may be better manually changing bed screws since I can't reliably believe this printer.



  • What I first would look at is that your piezo probe is working correctly and is consistent.
    I find it weird that you have to use the H parameter for G30 in bed.g.
    Try to do G31's on the different bed.g locations and repeat like 5 times, you should get values within 10 microns, if not you will need to tune the probe.
    If G31 is working as it should then do the same multiple G32's and see if the compensation values vary wildly or not.



  • From those pics it looks fairly clear that the bed isn't level so I agree with whosrdaddy that you ought to check that teh probe is functioning as it should. If it's inconsistent then that would explain things.



  • Got some good prints the last few days. I had to use the bed compensation AND mesh leveling. I guess somehow I got a 6mm aluminum plate bent 😐



  • After generating my own RRF config. g file I was having bed adhesion problems like you. What seemed to be the issue was that I messed up with the thermistor values. When the hotend was set to 235ΒΊc it was actually 215ΒΊc.

    Try this value:

    M305 P1 T100000 B4725 R4700 C7.06e-8 H0 L0
    ```Β 
    
    BTW, I'm also using OEM TitanAero with the stock thermistor cartridge.


  • I have the same values, but not the H0 and L0. What those do?

    I got those values from the official E3D docs.



  • @coredump:

    …............................ but not the H0 and L0. What those do?

    See here. https://duet3d.com/wiki/G-code#M305:_Set_temperature_sensor_parameters

    BTW, the duet g-code wiki is a great resource if ever you have similar questions.


  • administrators

    The H and L parameters are not generally needed for the Duet WiFi/Ethernet. They are sometimes needed on the older Duets.



  • @coredump:

    ….................... I guess somehow I got a 6mm aluminum plate bent 😐

    Not necessarily. It is possible that the X Y rails are not truly parallel (tram) with the bed or that they are not truly straight. Either way, mesh compensation would work though.



  • @deckingman:

    @coredump:

    …............................ but not the H0 and L0. What those do?

    See here. https://duet3d.com/wiki/G-code#M305:_Set_temperature_sensor_parameters

    BTW, the duet g-code wiki is a great resource if ever you have similar questions.

    Sorry, I read the wiki and I understood what the parameters do, was just asking why those values exactly πŸ™‚



  • Lol this is probably a dead one, but this sounds almost EXACTLY the same issue I had been having with my printer when I finally bought a Duet WiFi and tried to get my bed probe working. When It would home/level, and I did the paper trick, everything looked perfectly fine. But when I would start a print, the nozzle would be anywhere between 0.3 to 3mm above the bed and sometimes below... scratched a freshly installed aluminum plate that day...

    Anyway, I posted on here about it, and everyone suggested that it was because I didn't actually have the bed leveling action dictating the final Z height. As in, after it homed Z using the probe, it didn't actually 'save' the detected height. And so when it went to level the bed, it didn't have the proper height saved to begin with, and thus all the leveling showed my bed was 1-3mm below/above the expected Z0. Thus when it started a print, it'd float up in the air/dig into the bed...

    I forget what the actual code is, and I'm not near the printer atm to be able to look at my configs, but I know there was some GCODE I had to implement after homing and after probing, that dc42 had told me to add if I remember correctly. It basically forced the Z Position to set based on whatever the sensor detected. Since then I've had nothing but amazing first layers print after print. Only issues I've had is when the extruder borks up and I gotta clear the ptfe tube...


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