Prusa X Motor End Issue

Pawl

Prusa X Motor End Issue
March 25, 2012 02:47AM

Registered: 14 years ago
Posts: 17

I think the X Motor End needs to be modified to allow the pulley to be more in line with the idler's 608 bearing. Even if the pulley was backwards and flush against the motor, only 3mm of belt would be able to fit on the 608 bearing. Here's a picture of what I'm talking about:

7NIff.jpg

Here's my temporary fix (I added some washers between the motor and x end):

ze3hC.jpg

Edited 1 time(s). Last edit at 03/25/2012 02:50AM by Pawl.

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brnrd

Re: Prusa X Motor End Issue
March 25, 2012 08:29AM

Registered: 15 years ago
Posts: 1,780

Yes. I see this too in the Prusa iteration 2 that I'm currently building. But it looks like it's the x idler end that needs to be changed since the x carriage lines up with the x motor end. I printed my parts a few months ago (end of Nov or beginning of Dec) so it's possible that some parts have changed since then.

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Pawl

Re: Prusa X Motor End Issue
March 25, 2012 06:57PM

Registered: 14 years ago
Posts: 17

Hs5Fv.jpg

Here's a picture of how it lines up with the x-carriage. The wall that the bolt sits against on the x-idler could move toward the rod ~7mm before the belt would be on top of the x-carriage's bolt hole. However, the motor can only move away from the rods ~4mm before the same thing happens (that's how much spacing you need with your washers - 4mm, 8 m3 washers, or 5 m4 washers).

If we're going to change the .scad files, moving the motor out and idler wall in would give us the most room.

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ttsalo

Re: Prusa X Motor End Issue
March 26, 2012 08:06AM

Registered: 14 years ago
Posts: 313

Pawl Wrote:
-------------------------------------------------------
> Here's my temporary fix (I added some washers
> between the motor and x end):

I had the same problem, but fixed it by adding just one washer in the bolt closest to the X carriage. That tilted the motor a tiny bit and made the belt run correctly without rubbing against anything. It's still a hack, though. Would be nicer to have everything line up correctly.

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brnrd

Re: Prusa X Motor End Issue
March 26, 2012 05:28PM

Registered: 15 years ago
Posts: 1,780

I think using the printable bearing guide that comes with Prusa Iteration 2 helps since you'll only need one washer instead of 2. But instead of printing that one, use the one that I modified and posted in thingiverse.

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droftarts

Re: Prusa X Motor End Issue
March 28, 2012 06:22AM

Registered: 15 years ago
Posts: 1,612

I had this issue too. I hacked the x-end-motor mount to create a 4mm spacer that is the same shape as the motor bracket. The belt is nicely aligned now. Another way to fix this is to use the x-rod adjusters in the motor end to 'turn' the whole motor mount a little, so the belt doesn't rub on the face of the motor.

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Pawl

Re: Prusa X Motor End Issue
March 29, 2012 01:11AM

Registered: 14 years ago
Posts: 17

I think I fixed it. I'm going to use this on my new build and see if it fixes the problem: http://www.thingiverse.com/thing:20241

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droftarts

Re: Prusa X Motor End Issue
March 29, 2012 09:39AM

Registered: 15 years ago
Posts: 1,612

That will undoubtedly help, Pawl, but I think the X-carriage is pushing the belt out too. This will be more difficult to fix, as there isn't much space to move the clamps inwards.

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NewPerfection

Re: Prusa X Motor End Issue
March 29, 2012 04:31PM

Admin
Registered: 17 years ago
Posts: 1,472

Use two bearings on the x-idler, one washer between the bearings and the idler mount, and one washer on the other side. No fender washers necessary. Having two bearings make them stay perfectly straight, and you don't have to worry about the belt wandering off or rubbing on either side. That will also give you more room on the idler side, equivalent to moving the idler mount in a couple mm.

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L4nce0

Re: Prusa X Motor End Issue
March 29, 2012 07:36PM

Registered: 16 years ago
Posts: 68

I think you have the exact same issue I have. The main problem for me is my rods arn't cut 99.99% correct. They are different by a few mm. So When you tighten that belt, combined with the super minimalistic design, the one side gets pulled in and the belts get out of alignment. I've not really found a solution except I added a second bearing on the x idler

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brnrd

Re: Prusa X Motor End Issue
April 12, 2012 09:13AM

Registered: 15 years ago
Posts: 1,780

I fixed the alignment issue and improved z clearance by moving the idler bearing inside the x end. This arrangement allows me to go up to a z of at least 120 mm without having the belt hit the angled frame rods.

Photo

Edited 3 time(s). Last edit at 04/12/2012 09:21AM by brnrd.

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