Wheels Loosening Under Acceleration

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Wheels Loosening Under Acceleration

Postby mikegrundvig » Sun Aug 26, 2012 8:42 pm

Hi all; I've spoken with someone who has created a MakerSlide-based 3d printer (NOT an ORD bot but not far off) and he expressed frustration at the wheels working loose under the high acceleration used in 3d printing. He said they all work loose a fair bit but the eccentric wheel worked loose the most frequently and it was a real problem. I just wanted to know if anyone has experienced this with the ORD bots or laser cutters? Or if there is a good way to head this off before it even raises it's head. Thanks!

-Mike
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Re: Wheels Loosening Under Acceleration

Postby orcinus » Sun Aug 26, 2012 9:44 pm

Haven't experienced anything like it.
If i do, i'll just add a drop of loctite.

FWIW, though, i've tweaked the jerk values for my Hadron, because i hate having it bounce and vibrate all over the table.
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Re: Wheels Loosening Under Acceleration

Postby mikegrundvig » Sun Aug 26, 2012 9:47 pm

Thanks - according to him, Loctite wasn't enough to keep it from happening with the eccentric wheel - it would slowly rotate in place. What velocities are you using?
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Re: Wheels Loosening Under Acceleration

Postby macona » Mon Aug 27, 2012 12:49 am

What kind of Loctite? Does he know how to apply it?
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Re: Wheels Loosening Under Acceleration

Postby mikegrundvig » Mon Aug 27, 2012 3:25 am

He was not specific, but I suspect he knew what he was using as he had other 3d printers and built this one from scratch.
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Re: Wheels Loosening Under Acceleration

Postby orcinus » Mon Aug 27, 2012 1:13 pm

Sorry, don't have any numbers here, i'm away from home.

I print at fairly low speeds (up to 60 mm/s), but have done stress tests up to speeds high enough that they're not attainable with the Hadron footprint and default accelerarion in Marlin. Anyway, it's not the speed that causes loosening and stress, it's the jerk.

I did a few stress tests with high-frequency prints (patches of very small range, repetitive, fast movements) and saw no loosening.

Frankly, i don't see a way things could loosen in the first place. The friction of wheels over makerslide is orders of magnitude lower than friction of the bolts, nuts or even the eccentric spacers against the plate or bearing.

Regarding "knowing what people are doing", i've recently come to realise that people in the 3d printing (and reprap in particular) communities often do blunders that you'd never expect them to do, considering the prints they output or experience and effort they've invested in 3d printing. For example, i've read a post from someone the other day outlining how their Nth 3D printer developed a "sudden" fault and outlining at length how strange it is that lateral forces made their off-center mounted screw terminal on a build platform develop a solder fault after a few 100 hours of printing. Musing how they should probably devise a strain relief next time... SERIOUSLY?! Yathink? After xx printers and xxxx hours of printing, that only occurred to you just now?!
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