MidAir

Discussion in 'Ask Team Openbeam' started by fengelman, Jul 3, 2016.

  1. fengelman

    fengelman New Member

    I'm hoping someone here can help me...I built a sintron delta kit and have been fiddling with it for months...I finally got my z-probe dialed in, my G29 running the entire area of the bed, and tried my first test print.....a simple 10 mm cube....
    It started printing where I hoped it would, except it was several mm in the air...so I got a pile of spaghetti, but low and behold, when that pile got tall enough..maybe 4 mm...my cube started to emerge...sides were straight, layer adhesion excellent, accuracy looked fabulous..I was proud of myself....except for that pile of spaghetti...can anyone suggest what's wrong...where to look ,etc?


    I swear my Zmax is within tenths of a mm, depending on temperatures...my z offsets are also that close...etc...

    Marlin firmware and arduino board...tight screw connections, and belts, etc etc etc


    someone, please?
  2. protoserge

    protoserge Member

    Is your first layer adhering to the bed or printing in mid-air?
  3. fengelman

    fengelman New Member

    it tries to start about 3.4 mm in the air, then piles up as spaghetti...when the pile gets tall enough, the rest of my test cube came out great....imagine a springy base to a 3/4 cube..lol
  4. protoserge

    protoserge Member

    Here is my printer setting. Sorry for the delay.

    Attached Files:

  5. protoserge

    protoserge Member

    Try manually running a G29, then command the printer to go to Z1 (G0 Z1). Do you have feeler gauges? You can measure the variation in the Z height per the commanded height and then input that offset in the Z-offset. Alternatively, get the printer to Z1 by the previous method, then use the software to incrementally decrease the height until the nozzle presses a piece of paper to the bed. Take the distance you manually moved the head and input that in as the Z-offset.
    Last edited: Jul 15, 2016
  6. fengelman

    fengelman New Member

    I did exactly this several times...when I did get my z height dialed in just right, where a piece of paper just dragged under the printer head ,and set that as my z height...then tried to print, the nozzle always hit the bed hard when it tried to move to the printing position...

    the manufacturers tech support guy says, for some unknown reason, that I MUST set the z height to more than the actual, measured height, of G29 won't run..which seems to be the case, because it skips (doesn't reach the bed) for as many as a third of it's probes

    this whole thing has me so confused and disgusted...
  7. protoserge

    protoserge Member

    I think I know what's going on. I'll have to get back to you. If you are able to, look at the printer height in Marlin. G29 creates an offset of G28.

    I vaguely remember having the same issue with my printer initially. Can you provide your leveling routine? Do you have a G28 called first?
  8. fengelman

    fengelman New Member

    yes, my printing routine requires that I manually trip the z-probe...then load the g-code of the item I'm trying to print...built into the G-code I get from my slicer is first, G28, then G29...after G29 runs....whether it actually touches the bed or not, it tries to retract the probe, but we haven't been able to get that retraction figured out yet, but I do that manually, and it waits...so long, that the stepper motors turn off, then it begins trying to print...up till now, unsuccessfully
  9. protoserge

    protoserge Member

    My best guess is you have a generic printer with a generic firmware that needs customization. Can you look at your Marlin image and look into the Configuration.h file?

    https://github.com/MarlinFirmware/Marlin/blob/RC/Marlin/Configuration.h

    Can you provide a link to your source code?

    If you can manually level your bed enough to print repeatably, you could also ditch G29 routine.
  10. fengelman

    fengelman New Member

    absolutely, I can look into the firm ware....it was supplied as "configured for this unit", by the kit seller.....if you think you can make heads or tails of it, I'll copy it off to you in it's entirety.

    I wish I could level the bed, but there's virtually no provision for doing that...I haven't yet figured a way to even attach it to the frame, other than several large binder clips
  11. protoserge

    protoserge Member

  12. fengelman

    fengelman New Member

    I do hope you can figure out if what's wrong is in here...the ONLY changes I have made are to the max Z height, and the x,y, and z endstop values...oops, also changed max build diameter to 170, from 140

    I can't figure a way to upload the files...I'm sorry....
  13. fengelman

    fengelman New Member

    OK, I'm an idiot....you either want me to upload them, to here, so you can go over them, or you want me to replace mine, with, these that you linked me to?
  14. protoserge

    protoserge Member

    Upload yours to here. Thanks. Do you have the upload a file option?
  15. fengelman

    fengelman New Member

    I do

    Attached Files:

  16. protoserge

    protoserge Member

    I did some looking in Configuration.h.

    https://github.com/jcrocholl/Marlin/blob/deltabot/Marlin/Configuration.h

    The printer is set by default to 250mm when the print is zeroed. Do you have a measurement of the height of the hot end over the table? For reference, I believe I set my OBKP to 250mm max height (it can go higher in small cylinders).

    Look at this set of code on lines 388-391 and see if it matches your printer dimensions for offsets.

    Code:
    // these are the offsets to the probe relative to the extruder tip (Hotend - Probe)
      #define X_PROBE_OFFSET_FROM_EXTRUDER 13.5
      #define Y_PROBE_OFFSET_FROM_EXTRUDER -5.0
      #define Z_PROBE_OFFSET_FROM_EXTRUDER -4.6  //changed sign to negative value 
    If these numbers aren't correct to your printer, when you run the G29, it will throw off the measurements each and every time, no matter how hard you try to zero it!!!

    Also note the -4.6mm. You may want to put a Z-offset such as - 2mm (instead of +correction) to see how it is affected before changing the Marlin code. This is more to guide the investigation.
  17. fengelman

    fengelman New Member

    all of these values were set by me...
    the "measured" Z height, is close to 242.3, but the maker said I needed to set it to 250 to take in any discrepancies in "flatness"

    the z probe offsets are also measured, and set by me...
  18. protoserge

    protoserge Member

    Is the Z-probe offset deployed or compressed? I'm thinking this number is so close to your measured air print that they are related.
  19. fengelman

    fengelman New Member

    that was my thought too...
    I was told, that the G29, somehow does some magic to the Gcode from the slicer, but I see no way that could work...not in any of the code I saw...anyway...

    at this point, there is so much "slop" in my extruder, that I don't know how this machine can printer accurately, anyway...I suspect the heat from my hot end has melted my printed fan mount so much, that it's useless...
  20. fengelman

    fengelman New Member

    sorry being slow to respond....I've managed to ignore the G29 commands, and print successfully...what a TRIP!!!
    after some minute inspections, I think I have a sensor issues, and a few loose screws (on the printer)....the really great news is I can actually print some of my own repair parts...


    YAY!@!!!
    protoserge likes this.

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