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X axis length error - tried everything  

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Ryan
 Ryan
(@ryan-8)
Active Member
X axis length error - tried everything

After asssembling my mk3s, I get "Axis length X" error when I run the selftest.  When the test runs the x axis moves completely to both sides, the side of the extruder back cover hits the orange brackets, which appears to be the farthest it can go.  I can also move it by hand easily.   If I use the manual move command, it will move easily from 0 to 241mm it hits the end.  I don't know if that is significant.

Support had me send a bunch of photos and they couldn't see anything wrong.  I am waiting for another message from them.

 

Things I've tried/checked:

Extruder cable bundle - Tightened wrap, made sure zip ties are not hitting, I even removed the zip ties and used tape to make sure that wasn't the issue.  Support looked at photos of this and said it looked really good.

x-axis bearings - Loosened extruder cover twice to make sure bearings aren't being deformed.  Lubricated bearings.

Extruder wiring - Removed the extruder cover and made sure wires were in the correct channels and tight.  Removed extruder fan and made sure wires was deeply in the correct channel and tightened screws.  Moved x axis all the way to the left to confirm the fan screws don't collide with the trapezoidal rod.

X axis rods - Confirmed they were seated all the way into the brackets, visually and by disassembling and trying.  Measured the rods to confirm I used the correct ones.

Flashed the latest firmware and did a full reset.

Calibrated z axis to makes sure uneven z height wasn't causing binding.

Looked for absolutely anything that could be hitting, it seems like it's going all the way it possibly could on both sides.

 

Thanks in advance for your help.

Posted : 22/07/2021 4:30 pm
JMH714
(@jmh714)
Estimable Member
Enter title here

Have you tried tighten the belt? The fail may because the belt is too loose and skipping the GT2-16 pulley teeth. 

I had same issue with my Mini+ (through I never had issue with two of my MKs), I found the belt too loose and I tighten it to reasonable and it passed the test. 

Posted : 23/07/2021 2:58 am
Dan
 Dan
(@dan-4)
Active Member
centered cog?

I had a similar problem with the Y axis and noticed that the problem was because I did not have the screw for the belt cog screwed in on the key of the motor shaft.  This made the cog off-center and that would cause the error.

Dan

Posted : 23/07/2021 3:52 am
Dan Rogers
(@dan-rogers)
Noble Member
One more oddball X thing

Since it is a new assembly - here's one that is rare but more likely on a new build.  Remember the nylon filament - the black plastic thing that lives inside of the extruder cable bundle?  It has a hole that it has to be seated in inside of the extruder head, and it is a pain in the butt to get it to firmly seat in that hole.  If that is not seated well, the nylon filament can exert intermittent forces on the print head - which can throw off prints and calibration.

Posted : 23/07/2021 8:07 am
Ryan
 Ryan
(@ryan-8)
Active Member
Topic starter answered:
Title

I had the belt very tight initially, I am positive it is not slipping.  The gear shaft isn't moving either.  I used a marker on the shaft and belt so I could see if it was slipping. I loosened it twice because chat support suggested it, but that made no difference.

If I move the extruder all the way to the left(with the printer off), then use the manual move command to move it right, it hits the end at +241 every time, even if I go back and forth a bunch before it gets there.  If the gear shaft or belt were slipping it would show a different number each time, right?

 

I'm beginning to think there is something wrong with my stepper motor or the board.  It seems like the motor is moving farther than the printer thinks it is moving.  If I run the XYZ calibration(or autohome) it find the first point every time, but when it goes to find the 2nd point, it goes about 10mm past the point and never finds it. 

 

Thanks for the suggestions.

Posted : 23/07/2021 9:00 am
Ryan
 Ryan
(@ryan-8)
Active Member
Topic starter answered:
Title

I also checked the idler pulley thinking it was the only thing that could make the axis move farther than the system thinks it is moving.  It was already spinning free, but I loosened it a little more just in case.  No change. 

Posted : 23/07/2021 9:03 am
Ryan
 Ryan
(@ryan-8)
Active Member
Topic starter answered:
Title

I thought the tightness of the cable bundle might be causing tension on the extruder as well, but I've rearranged the bundle 3 times now, and the nylon filament looks right to me.  I also tried to press on it to relieve the tension during the x axis movement, I'm pretty positive that isn't the issue. 

Posted : 23/07/2021 9:06 am
JoanTabb
(@joantabb)
Moderator
RE: at the Movies!

Hi Ryan. how many teeth are there on the motor pully?

I believe it should be 16
20 teeth would give you excess movement

regards Joan

 

I try to make safe suggestions,You should understand the context and ensure you are happy that they are safe before attempting to apply my suggestions, what you do, is YOUR responsibility. Location Halifax UK...
Posted : 23/07/2021 10:22 am
Ryan
 Ryan
(@ryan-8)
Active Member
Topic starter answered:
Title

Thank you!  That was it!  I counted the teeth 3 times and got 17 each time.  I removed the y axis gear to make sure I wasn't counting wrong.  The gear I was using on my x axis is 9.49mm and the y axis one is 10.10mm.

I can't even imagine how that mixup happened.

I'm contacting prusa right now.

 

Thanks again,

Ryan

Posted : 23/07/2021 11:36 am
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