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Selftest Fails for the X-Axis  

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rudye.m
(@rudye-m)
Active Member
Selftest Fails for the X-Axis

Hi Everyone,

I just finished my MK3 build. The organization of the kit and the instructions are a thing of beauty. However, I can't get my printer past the Selftest. It fails at the X-axis check with the message to check the axis length.

It doesn't seem to be exercising the X-axis correctly at all. When it starts the test, it actually moves the Z-axis. It moves the extruder up a bit, then seems to jog the x-axis. Then, the LCD displays the Selftest fail.

I've tried moving the x-axis manually also, and that doesn't seem to work either. When I go to the manual move menu item, it shows the X-axis at 0.000. Then, I can move it towards positive, but not negative. It'll move in the positive direction for just a short distance. Then, it suddenly stops on the X-axis, moves the Y-axis (the bed) to the back, jogs the Z-axis, and resets the X-axis display to 0.000 again. Manually moving the Z-axis or the Y-axis work as expected.

I've updated the firmware to the latest (B143), and checked that it isn't in "Stealth" mode. I saw that suggestion in another X-axis Selftest fail post.

I'd appreciate any ideas for debugging this issue. Thanks!

Posted : 31/12/2017 9:33 pm
josefprusa
(@josefprusa)
Admin
Re: Selftest Fails for the X-Axis

Check if something isn't blocking g the X axis to go all the way to the sides. For example a ziptie head of loose cable.
B143 switched to normal mode automatically.

Founder and owner / Majitel a zakladatel...
Posted : 31/12/2017 10:19 pm
rudye.m
(@rudye-m)
Active Member
Topic starter answered:
Re: Selftest Fails for the X-Axis

Thanks for your response. I don't think there is anything blocking it from traveling.

It isn't close to either side of the X-axis travel. The extruder assembly is towards the middle. When the X-axis self test begins, the assembly moves up instead of over.

Posted : 31/12/2017 11:18 pm
stoofer
(@stoofer)
Estimable Member
Re: Selftest Fails for the X-Axis

Moving up vertically along the Z axis?

Sounds like your motors are not connected to the correct headers on the board.

Posted : 01/01/2018 1:07 am
Hansen
(@hansen)
Eminent Member
Re: Selftest Fails for the X-Axis


I've tried moving the x-axis manually also, and that doesn't seem to work either. When I go to the manual move menu item, it shows the X-axis at 0.000. Then, I can move it towards positive, but not negative. It'll move in the positive direction for just a short distance. Then, it suddenly stops on the X-axis, moves the Y-axis (the bed) to the back, jogs the Z-axis, and resets the X-axis display to 0.000 again. Manually moving the Z-axis or the Y-axis work as expected.

I get the same, when the X axis belt is too tight.

Best regards
Hansen > Greetings from Denmark <...
Posted : 01/01/2018 2:59 am
rudye.m
(@rudye-m)
Active Member
Topic starter answered:
Re: Selftest Fails for the X-Axis

Hi stuart.b4,

Yeah, I thought a wrong connection might be the problem at first too. But I've doubled checked the connections, and they are correct. Plus, both the Y-axis and the Z-axis work correctly when moved manually from the control panel.

Hi jrh,

I think you are on to something. I just tried releasing the set screws on the X-axis motor pulley. Running free like that, it seemed to run just fine. Of course, Selftest still didn't pass, but when moving the X-axis from the control panel, it seemed to spin as expected.

I guess I'll try loosening some of the tension in the belt and see if that helps.

Posted : 01/01/2018 3:34 am
rudye.m
(@rudye-m)
Active Member
Topic starter answered:
Re: Selftest Fails for the X-Axis

Hi Everyone,

Here's the latest. I took the back of the extruder apart and loosened the belt tension some. Now, X-axis moves more during the self test, but it still fails. Here's what it looks like when I go through the self test: [youtube] [/youtube]

If I take the motor off and run the self test, it spins as expected.

I've also moved the extruder all the way to one side and moved it via the manual move in the firmware. In that case, I can move the extruder the whole length, but at the side it does the weird thing where it jumps up, moves the platform to the back, and puts the firmware in a state requiring reset.

Again, any ideas are appreciated. Does the X-axis belt tension have a very narrow "Goldilocks" zone?

Posted : 02/01/2018 2:16 pm
stahlfabrik
(@stahlfabrik)
Honorable Member
Re: Selftest Fails for the X-Axis

I have the same issue and noticed scratches from the linear bearing on the rod.

So when the extruder moves to the very left the test stopped and failed. If I push the extruder just a little when it hits the extrem left position to the right, the self test proceeds and does not fail.

But what also helped (and now does not help anymore): Loose the 5 screws on extruder back a little (to much pressure sadly pushes the bearings it seems), maybe consider rewrapping the cables - a too stiff cable bundle is also potentially the quantum of too much force that lets the test fail.

I wished the self test was more robust - or would not say there was something wrong with the length when in reality there is something wrong with resistance.

Posted : 02/01/2018 2:34 pm
rudye.m
(@rudye-m)
Active Member
Topic starter answered:
Re: Selftest Fails for the X-Axis

Woohoo! Thanks stahlfabrik! Loosening the bolts on the back of the extruder did the trick. The self test completed without any issue as soon as I did that.

I had switched out the linear ball bearings for DryLin bearings. They work nicely, but are relatively easily deformed. The extruder back cover probably puts enough force on them to deform them in one direction.

Posted : 02/01/2018 3:50 pm
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