BigBox Z offset problems

Discussion in 'Calibration, Help, and Troubleshooting' started by John McDonald, Aug 22, 2016.

  1. John McDonald

    John McDonald Member

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    I am having tons of trouble with my BigBox. Ever since I got it several months ago, I haven't been able to print anything properly. I am having MAJOR z offset issues. I followed the directions under commissioning down to the letter. Print nozzle too close to bed. Everytime! Nothing I did seemed to fix the issue. Well, you say, why have you waited so many months? I was so frustrated I wanted to toss the BigBox. I put it away, and cleared my mind for several months and now have gotten back to work on it. I started printing at z offset at -.8 which the commissioning left me with. I talked to a friend who has been 3d printing for years helped me out. He told me to raise z offset. And I have slowly worked my way up. I am now at -.4 and the -.4 doesn't look any different than -.5 or -.6 IMG_20160822_152054.jpg IMG_20160822_153601.jpg
     

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  2. Stian Indal Haugseth

    Stian Indal Haugseth Well-Known Member

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    What firmware do you have? Are you using MBL mesh bed leveling?

    I would recommend RC6 with MBL. With the correct FW you can use babystepping to manually fix the z offset at print start whenever it's off.
     
  3. Jasons_BigBox

    Jasons_BigBox Well-Known Member

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    Morning,

    You may have already done this so excuse me if you know all of this.............

    A couple of things to double-check, is your z axis steps/mm correct? Different types of z-screws need different steps.
    Have you checked the calibration of your extruder for the filament? Could be over-extruding some too.
    Check the nozzle settings from your slicer software too.

    For the z offset, what I found worked for me was this:

    Heat the bed to the temperature I am going to use (normally 60degrees) then run 'Autohome'. That should reset your x,y and z axes. After that, the bed will probably move away from the nozzle a little.

    You can then use Prepare>Move axis>0.1mm>z-axis slowly turn the knob while checking the position of the nozzle relative to the bed. You can do this by eye but a piece of paper works well. I've seen a video that recommends using paper, a strip about 25mm wide by 200mm long (1"x8") works well. What you do is slide the sheet between the nozzle and the bed and push it away from you then pull it back towards you. Keep doing that while moving the bed in 0.1mm increments. As the bed nears the nozzle you will feel the paper begin drag as you pull it. When you push the paper if it slides nicely, move the bed another 0.1mm. The video recommended a position where you can still pull the paper towards you but when you try to push it, it curls up so you can't push it back through.

    When you hit that point, look at the z position on the LCD. If it's zero then the position should be OK. If it's greater than zero then you need to increase your z offset (so from -0.5 to, say -0.3). Don't forget to 'store memory' too. Re-run the 'Autohome' and try again with the paper. You may need to repeat this many times until you feel it's consistent. A few of us have found that the IR sensor seems to be unreliable depending upon the bed/room conditions. Bright sunlight or what you have on your bed (UHU glue for example) may alter the reading.

    Once you're happy that the homing is correct, try a print. If the nozzle is too close, you may find that nothing can come out for the first layer (mine does this sometimes on 0.1mm layer prints). If nothing is happening then stop the print, clean the bed and go back and
    increase the z-offset again. 0.1mm at a time is usually enough but persevere.

    Looking at your photos, it's not too clear what they look like in height. The later ones look like a first layer.

    Good luck!

    Jason
     
    Jean VISCONTE and mike01hu like this.

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