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pillow bearings to reduce load on Prusa?

Posted by cfry999

cfry999

pillow bearings to reduce load on Prusa?
September 15, 2017 01:11PM

Registered: 10 years ago
Posts: 24

Question about these Z top pillow bearings that came with my new leadscrews. [www.amazon.com]

It seems like they're designed to grip the leadscrew at the top to take some of the load off of the compression coupler and stepper motor. Is this correct? Anyone have any experience with this? Does it also cause binding and friction during the z travel?

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obewan

Re: pillow bearings to reduce load on Prusa?
September 15, 2017 03:09PM

Registered: 7 years ago
Posts: 759

I think you will find they are a slide fit onto the 8mm leadscrews and just apply a lateral guide to the top of the leadscrew,

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cfry999

Re: pillow bearings to reduce load on Prusa?
September 15, 2017 03:44PM

Registered: 10 years ago
Posts: 24

Yeah, they have 2 allen screws in them, and I read somewhere that there's no point in using compression couplers to minimize vibrations if the couplers are already fully compressed by the weight of the X carriage. So I'm wondering if anyone has used those screws to take that weight off. Because I've also read that fixing the top of the leadscrews for alignment is a bad idea.

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o_lampe

Re: pillow bearings to reduce load on Prusa?
September 16, 2017 02:51AM

Registered: 8 years ago
Posts: 5,232

Top bearings were a bad idea with wobbling metric lead screws, but with machined lead screws it's no problem.

I've put a 4.5mm steelball between the stepper shaft and the leadscrew. Now the ( ever changing ) weight of the X-carriage rests on the stepper bearings and does not compress the coupler. Due to the ball, it can still bend.

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cfry999

Re: pillow bearings to reduce load on Prusa?
September 16, 2017 12:52PM

Registered: 10 years ago
Posts: 24

Interesting. But wouldn't the steel ball still allow vibrations to transfer up the leadscrew to the printhead? I thought the compression couplers were also intended to reduce vibrations?

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o_lampe

Re: pillow bearings to reduce load on Prusa?
September 17, 2017 02:39AM

Registered: 8 years ago
Posts: 5,232

If there are any vibrations I haven't noticed them yet. They'd occur only when the z-motors are running: at layer change and maybe during retractions with z-lift. So what?
I'd trade them in against varying compression of the couplers anytime.