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Z-axis rail catching - improper prints performed  

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sharkminnow
(@sharkminnow)
New Member
Z-axis rail catching - improper prints performed

I finished assembling my Prusa i3 Mk3s yesterday and have been troubleshooting since then. I cannot finish a benchy print without the nozzle digging into it - and or skipping a layer. I'm currently performing XYZ calibrations and re-setting the PIDNA height. However, at the second calibration point - it seems to grab the paper.  I first believed that my failed prints were calibration issues, however, I noticed when toggling the Z - axis, the right rod catches. If you keep toggling up and down, the sudden change in direction can create this catch, thus the X-axis extruder rails are not balanced across the horizontal plane (it's visible). This is not seen in the left Z - axis rod. Here's what I've done since assembly. 

1. Initial XYZ calibration passed using booklet recommendation of a zip - tie to set the PIDNA height. 
2. First print failed due to the X - axis motor not grabbing on the gear (batman logo)- tightened it and solved the problem. I moved on to a benchy and it failed midway.
3. Whenever a Z - axis test is performed - the left locknut reaches the end of the stage first. Sometimes it will also stop 3/4 of the way and stop to transition to the 9 point calibration. It's both failed and proceeded to calibration. 
4. I released the locknut from the right Z-axis rod and it can move freely with no resistance - now is re-attached. 
5. Updated firmware to the lastest version as well.
6. Measured the distance of the X-axis rods - 12 and 1/16th of an inch. Close to 307 mm.

Essentially - I believe something in the right Z-axis arm is causing my prints to fail. When the extrusion head is stepping at consistent heights, print layers are fine. However, over time, when movements on the Y and X axis quicken, I'll notice it start to dig into the print and or miss a layer. 

Is this an assembly issue? Or is this a bearing / rod issue? What tests do I need to do in order to rule these out?

Much appreciated. 

This topic was modified 5 years ago 2 times by sharkminnow
Posted : 13/09/2019 4:03 am
Bunny Science
(@bunny-science)
Noble Member
RE: Z-axis rail catching - improper prints performed

Your x-axis has not been properly leveled physically.

1. Loosen bolts on both top z-axis mounts. Recheck that both top Z-axis brackets are fully seated down onto the vertical smooth rods. Retighten the mounting bolts.

2. Manually raise x-axis all the way up. (Long press to activate z-motion and rotate control knob). If you can't raise it all the way to the top, press reset to to get more motion range upward. 

3. Move x-axis up until both the left and right sides impact against the top. You hear the machine go brrrrrt as the physical limits are hit. Hitting the physical limit at the top levels the x-axis.

Now that the x-axis has been leveled, repeat xyz calibration. It should be more uniform left/right.

Posted : 13/09/2019 12:03 pm
sharkminnow
(@sharkminnow)
New Member
Topic starter answered:
RE: Z-axis rail catching - improper prints performed

Okay, I'll check the Z - axis mounts. I can't get to fixing it at the moment but will update. However, before each XYZ calibration, I ensure that the X-axis makes it to the top and makes the brrrrt sound.  

"Long press to activate z-motion and rotate control knob" Is this different than going into Settings - Movement - Z-axis? That's what I've been using to toggle the axis's. 

Thanks,

Posted : 13/09/2019 4:52 pm
Bunny Science
(@bunny-science)
Noble Member
RE: Z-axis rail catching - improper prints performed

Not different. Just a short cut way to adjust the z-axis position.

Posted : 13/09/2019 5:16 pm
sharkminnow
(@sharkminnow)
New Member
Topic starter answered:
RE: Z-axis rail catching - improper prints performed

I've done your suggestion(s).
1. checked the Z-axis mounts - all normal - the rod is seated in the mount.
2. Left and right hit the top with free toggle travel.
3. Erased all previous calibrations with Wizard : Re-calibrated the XYZ axis - passed. 
4. Set my Z-axis first layer. 
5. I went to print out the batman logo and it failed. (I have pictures).

I toggled the Z-axis travel after calibration from the bottom of the bed, to the top, to the bottom, and then returning to the top. Within those two cycles. The following have occurred :
1. The right Z-axis makes a "clunk" noise and is happens most often at 110 mm measuring from the bottom Z-axis motor.
2. When the X-axis reaches the top : There is a 5 mm difference between the left Z-axis rail and the right Z-axis rail when maximum Z-axis travel is reached. Here is a picture emphasizing this :

Any thoughts on what could be the culprit?

Much appreciated.

Posted : 14/09/2019 6:46 am
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