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Y Axis Length Fail on Bear MK3S+ build  

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Blippio
(@blippio)
New Member
Y Axis Length Fail on Bear MK3S+ build

Hi- I hope you can help with my first build... I purchased the MK3S+ but jumped straight into building it onto a Bear frame with Bondtech extruder and Mosquito hotend. I'm currently trying to run the selftest but always fail at the Y Axis check. I've tried a lot of things but I bet I'm overlooking something really silly--hopefully you can help!

SOME BACKGROUND:

- MK3S+

- Bear 2.1 frame

- Einsy 10a

- Using stock smooth idler for Y Axis

- Y Belt tension at 260

- Running Bear Firmware for initial self-test

 

THINGS I'VE TRIED:

- Running Bondtech/Bear-specific firmware

- Adjusting and attempting Y belt tension from 240 to 285

- Initially tried with heatbed on and still failed (removed HB to take one variable out and get better visibility into anything going on)

- Double-checked and adjusted rod alignment, center belt alignment

- Confirmed there were no teeth damaged on Gates belt (new and ok)

- Ensured adequate lube on rods and bearings (using NSK lithium soap based as per Misumi)

- Double checked and adjusted all three bearings

- Swapped out three bearings for different set

- Flipped Y carriage over and reinstalled bearings

- Tried using original (new design) Prusa bearing clips AND Bear printed bearing holders

- Confirmed belt path is running center/aligned on idler and Y motor gear

- Swapped out Y motor for Prusa extruder motor (had this left over as I had the Bondtech setup; pretty sure extruder motor is spec'd the same as Y motor)

 

Ughh! Any ideas? Thanks in advance!!!

 

The video shows what I consistently see, no matter what changes to hardware/tweaking I make. Look for (and hear) a small stutter at around 00:14 seconds, where the arrows meet:

Posted : 18/10/2021 4:11 pm
BogdanH
(@bogdanh)
Honorable Member

It seems you've done pretty much everything that comes to mind.
What I would do now is, I would install Prusa firmware. Of course you can't print with it -is only for testing and trying to eliminate the suspects related to your current "Y axis" problem. If issue still happens, then there must be some mechanical problem.

[Mini+] [MK3S+BEAR]...
Posted : 18/10/2021 7:00 pm
Blippio
(@blippio)
New Member
Topic starter answered:

Thanks Bogdan- It was worth a try but no luck. Same Y Axis length error.

I still get that slight stutter "at the arrows" like before, as shown in the video... I can't help but think that is a clue to the problem? Is it normal to see that stutter, at the same place, when no physical obstructions are around?

Posted : 18/10/2021 10:04 pm
BogdanH
(@bogdanh)
Honorable Member

To be honest, I can't see stutter on video, but I believe you that there is. If you detach belt and slowly move bed forth and back, can you notice some resistance at that point?
I don't know what actually is checked (measured) during Y-axis test. I mean, if there (at arrows) would be very small resistance, stepper motor has power enough to overcome that -at least I think so.
I assume Y-axis test is measuring the length of bed travel, which should be 21cm I think. I have no idea within what tolerances that should be kept, though. Maybe there's error shown, if length just slightly shorter than it should be... just thinking aloud here.

[Mini+] [MK3S+BEAR]...
Posted : 19/10/2021 7:42 am
Blippio
(@blippio)
New Member
Topic starter answered:

You're right, it's hard to see the stutter at the arrows (but you definitely HEAR it if you take a close listen--it goes silent at the arrows for a split second)... Again, wonder if that is a clue for anything?

I don't notice any resistance without the belt and actually changed it for a new one. Still the same stutter and Y Axis failure. Ugh! (appreciate your help though 🙂

Posted : 20/10/2021 7:24 pm
BogdanH
(@bogdanh)
Honorable Member

I cranked up the volume and yes, I can hear noise gap at arrows point (but only when bed moves forward). And as you said, hard to say if that means something.
But there's another thing.. is it just my impression, that bed frame hits the back wall when traveling fully back?

[Mini+] [MK3S+BEAR]...
Posted : 20/10/2021 8:25 pm
Blippio
(@blippio)
New Member
Topic starter answered:

Thanks for checking. It actually does *not* hit the backwall (checked, adjusted many times)... Im using an Ikea cab and its a battle of millimeters but it DOES fit without hitting anything, lol

Posted : 20/10/2021 8:57 pm
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