Initial tuning for corexy with 3 z independent z screws



  • I am homing Z with the Z probe and yes I have a G28 on my Kisslicer start:

    ; [mm] mode
    G21
    ; Absolute position mode
    G90
    ; Absolute Extruder mode
    M82
    ; Start heating the Bed
    M140 S0
    ; Starting heating the Extruder
    M104 S210
    ; Home the axes
    G28
    ; Wait till stuff is heated
    M190 S0
    M109 S210
    ;
    ; *** Main G-code ***
    
    


  • After you've homed the Z axis, if you then do G1 Z0, is the nozzle just touching the bed (within 0.1mm)? If not, then the probe offset is incorrect.



  • @deckingman:

    After you've homed the Z axis, if you then do G1 Z0, is the nozzle just touching the bed (within 0.1mm)? If not, then the probe offset is incorrect.

    After homed and G1 Z0'ed, I can fit a 0.063 feeler between nozzle and bed confortably. The 0.076 one is a little tight and the 0.102 only goes in with some pushing, so I will guess it's around 0.07, at 0,0,0. At the middle of the bed (100,125,0) I can get the 0.102 to fit snuggly and the 0.152 can't go in. Finally at max (200,250,0) the first gauge that will fit snuggly is the 0.680.

    There's definitely a slant there, but I am pretty sure one of the things (bed screw level or mesh) should be taking care of this, unless I am terribly mistaken.

    WHen I setup the independent motor thing, the doc mentions that I have to use the coordiates for the screws. I am assuming lead screws on this case, and tht the coordiates will be outside the printable area because, well, the screws are out of the printable area. I did my best on measuring the distance between head and screws to find out the values, but I may be doing something stupid, would not be the first time.



  • That should be fine I'd have thought. I was just concerned that in one of your posts, you said that you had to use 2mm of baby stepping but using those figures, that would put the nozzle about 1.9mm below the build surface.

    If those figures are correct, then I would conclude that the reason for the first layer not sticking is not due to layer height but something else. I note that you aren't heating the bed (M140 and M190 both have S0 in you slicer start gcode) and I also note that Lokbuild recommend an unheated bed for PLA but that is unusual. I also notice that in one of your pictures, you were using Kapton tape. If it were me, I'd try the Kapton tape again but heat the bed to around 50 deg C or so (assuming you are using PLA). Clean it well with Acetone or similar first. If that works, then I'd try heating the Lokbuild, despite what the manufacturer recommends.



  • @deckingman:

    That should be fine I'd have thought. I was just concerned that in one of your posts, you said that you had to use 2mm of baby stepping but using those figures, that would put the nozzle about 1.9mm below the build surface.

    If those figures are correct, then I would conclude that the reason for the first layer not sticking is not due to layer height but something else. I note that you aren't heating the bed (M140 and M190 both have S0 in you slicer start gcode) and I also note that Lokbuild recommend an unheated bed for PLA but that is unusual. I also notice that in one of your pictures, you were using Kapton tape. If it were me, I'd try the Kapton tape again but heat the bed to around 50 deg C or so (assuming you are using PLA). Clean it well with Acetone or similar first. If that works, then I'd try heating the Lokbuild, despite what the manufacturer recommends.

    So my first few tests where LokBuild with heated bed at 87 C and PETG (that I use on my delta over PEI and works fine). It didn't stick at all. The Kapton and no temperature where already parts of the I will randomly try things to see if something works phase.

    I removed the Lokbuild (it didn't seem to work heated or cold with PETG or PLA) and ordered a PEI sheet that should be here later this week, and was trying the tape to see if worked, but until now, no success.

    I find it weird that the nozzle distance seems ok but when printing it looks like it's not even close to those values.

    I will try tape at 50c and PLA to see what goes.



  • @coredump:

    …....................................
    I find it weird that the nozzle distance seems ok but when printing it looks like it's not even close to those values.
    .....................

    Yes, that's not right. When printing, the nozzle height above the bed should be at whatever you've set the first layer height to. Maybe that's the problem? Check your slicer settings. If you had to use 2mm of baby stepping then it would indicate that the first layer height is set to around 2mm - maybe 2.0 instead of 0.2?



  • I was using the variable layer height on KISS, from 0.1 to 0.3, I am trying with 0.3 fixed now, but I am pretty sure it wasn't 2mm 🙂



  • So I tried with 50C bed and tape. First try I got this

    Then I started a new one and while the priming loop detached, I used babystepping to -0.4 and got this

    It's at 60% now and seems to be holding and working, I just don't udnerstand why I am havign so much problem with the first layer. I only have used PEI on my printers and never had issues, I am hoping that helps, but I also want to make sure that the Duet bed things are being used to make my life easier.



  • TBH, if that's aluminium tooling plate (which it looks like it is) then all you need do is level it manually. No need to apply compensation to something that is already flat. It's just another added layer of (unnecessary) complication. I don't bother with any of that because my bed is flat and level - just home and print. That doesn't answer why you are having first layer problems but if you are having to set -0.4mm baby stepping for a first layer that ought to be 0.3mm then either Z=0 isn't true (but you've measure it and it is more or less) or there is something amiss with the slicer which is "telling" duet to go to Z=0.7 instead of Z=0.3. Have you had a look at the gcode file to see what the first G1 Z value is?



  • Yeah it's tooling plate, so it is supposed to be super flat, but still have to level the actual gantry/bed

    G1 X99.4 Y138.5 Z0.35 E0 F6000
    G1 X99.4 Y138.5 Z0.3 E0 F1800
    
    

    Those are the first Z changes for the prime pillar, the first layer starts with 0.35 too.



  • I guess what you could try is starting a print then aborting it while it's doing the first layer. Make sure that any pause.g file doesn't have a Z lift in it. Then with your feeler gauges, measure the nozzle height which should be whatever you've set the first layer to be (0.35). If it is (within 0.05mm or so), then you can pretty much discount anything to do with bed level or flatness compensation.

    The other thing to check is your steps per mm for the Z axis. I see you have that set to 400 which would be correct for those God awful 4 start 8mm lead screws that people will insist on using - sorry but its a pet hate of mine. Anyway, assuming you have 1.8 degree motors, 1 revolution is 200 steps. If the lead of the screw is 8mm that means 25 full steps per mm and at 16X micro stepping that's 400 which is what you have it set to. But if the lead is different, then you'd need to change the steps per mm accordingly.

    By the way, you should avoid using a layer height that is an odd number. The reason is that with 25 full steps per mm, 0.1 mm will be 2.5 full steps - i.e half way between 2 and 3 full steps so you'd be relying on micro stepping for positional accuracy which is not so good. So 0.2mm layer height would be 5 full steps which is OK, 0.3mm is 7.5 full steps which is not good. 0.35 is even worse as it's 8.75 full steps. 0.4 is 10 full steps so that's OK.

    I'm not saying that is the cause of your first layer problems but it won't help.



  • I think that I am indeed using the awful lead screws that you mention 😛

    I let the babystepping there to be able to test other stuff, and I am getting stuff like this

    I tried to make my xy belts as tight as they can, and I don't think that kind of ringing is related to that but who knows.



  • 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 🙂



  • @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 😐


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