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Answered Print dimensions off.

Discussion in 'Troubleshooting' started by joea, Nov 20, 2019.

  1. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Well, that is usually a thermistor issue (shorted since MAX temp is a short and MINTEMP is an open circuit).
    Wiggle the wires and trace them back to make sure you didn't have anything obvious shorted or crossed. Also look at the temperatures in MC (or whatever host program you use) and see if one of them is reading wrong (bed or hotend).
     
  2. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    IIRC the shafts have a flat spot on them and you want the setscrew to press into that flat spot.

    However, this may be usesless information given how hit-or-miss consistency of construction was with the Robos. Even in the same series, there could be two machines that were different so ... if you do not have flats on the shafts, I would be unsurprised (but this application really calls for shafts with flats).


    edit: At least on of my betas DOES have the flats. Can't check the others ATM, but agian I would not be shocked if some were different.
     
  3. joea

    joea Member

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    There are two set screws, no flats that I noticed. I did expect at least one.

    I'll take a break now. Time to go walkabout when you make something "right" and have it end up worse. .
     
  4. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Yea, again -- not shocking.
    I actually ground a flat onto the shaft of the extruder stepper when I replaced one and the new one had no flat.

    However if you have two set screws and no flat, just make sure they are nice and tight (and I would absolutely use loctite).
    It would be a pain to have to pull the stepper and grind a flat on the shaft :(
     
  5. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Probably not a bad themistor, just a loose wire I would imagine
     
  6. joea

    joea Member

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    I have a "penetrating grade" version for stuff already assembled. That should suffice I think.
     
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  7. joea

    joea Member

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    Unable to get calibration circle to print properly. While I have gone through the printer, mechanically, and adjusted this and that, this problem actually started after I had removed the Y stepper driver, to look it over for any obvious issues.

    That was probably a mistake. And, of course, Amazon has chosen my stepper driver order to "teach me the value of Prime". Usually, they ship my stuff out in day or two anyway. But, I guess after I gave their Vet discount a miss, they became exasperated. (just kidding Mr. Bezos . . . whew! that was a close one!)

    Below is a picture of what is happening. Regarding the prints.
    20191126_142226 (Small).jpg
     
  8. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    That is (sadly) probably not a mechanical failure.
    While circles are hard on X/Y printers -- and easy on a delta :) -- they are not THAT hard.
     
  9. joea

    joea Member

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    Yeah . . . they used to be pretty nice.

    So, what is it likely to be? Just stepper drivers?
     
  10. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Well, if you want a complete list that includes all of the electrical/electronic, but I would start with the stepper driver because they are cheapest. Don't forget you can swap stepper drivers between steppers to experiment if you need.

    (the Z drivers are not much stressed and on many printers share a single driver, try swapping for one of them)
     
    #30 mark tomlinson, Nov 26, 2019
    Last edited: Nov 26, 2019
  11. joea

    joea Member

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    I think I will first search for, or build, a square print, not a cube, just a square, as a calibration/troubleshooting aid. Maybe with a grid pattern or an X from corner to corner.

    That might make it easier to isolate to an axis. Or not.

    There must be one already made.
     
  12. joea

    joea Member

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    Seek and Ye shall find.

    https://www.thingiverse.com/thing:2563185
     
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  13. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Sure, at a guess it is probably the Y axis misbehaving (that one has more mass to move around) but that is just pulling a rabbit out of the hat. Testing will tell the tale.
     
  14. joea

    joea Member

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    Replaced the y stepper. seemed quieter, but could be same.

    Did not solve problem.

    After a few more prints it became apparent filament was not adhering to bed, nor laying down nicely.

    Eventually reduce z offset by about half of what worked well prior to my mechanical fiddling.

    One thing I had not mentioned is that one of the bed magnets was broken free.from the bed and needed regluing. perhaps that allowed the bed to rise up a bit.

    Anyway prints are reasonably equal now, but short in x and y by about .014 inches.
     
  15. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Across what area? The entire bed? That is not bad... If you really wanted to you could tweak the steps for those axis to get it perfect, but I usually say don't bother. Steps are a mechanical thing and should be what they are.... it is a way to calibrate it if you really want it perfect.
     
  16. joea

    joea Member

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    Across 4 inches. The square says 4.09 in if I read the print correctly, but measures 3.95
     
  17. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    The movements of the print head/extruder are all mechanical so if everything works as designed it won't be far from what is calculated. If you are noticing variances then they are most likely mechanical inconsistencies. If that is the case it will just as likely be under-sized as over and not specific to a fixed axis either.

    The commodity level parts used int he printer will limit your absolute tolerances, but not by a lot. You can still get pretty repetitive numbers and accuracy to 0.1-0.3% normally. If everything is working correctly.
     
  18. Titaniumboy

    Titaniumboy New Member

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    That seems to me to be 0.140”, not 0.014”.

    14 thou would be an awesome accuracy. 140 thou (which is more than 1/8”) would bug me also.
     
  19. mark tomlinson

    mark tomlinson ༼ つ ◕_ ◕ ༽つ
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    Don't guess. resize the print in the slicer/host program to be a specific size and then print and measure

    Make it exactly 4 inches (most use metric so 101.5 mm is pretty much 4 inches) -- also most STLs are in metric if you did not create it yourself. Sadly that format does NOT embed the units so if you get one that looks to be about 25.4x too small -- it is metric :)
     

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