Metal version of Thingiverse "Threadless Ballscrew" (Page 3 of 3)

Hey everybody

Don't think I have forgotten about you I've just been busy with my job and this is a
side project.

I still have two more ops to go but it's getting there.

Initially I'm creating 4 for testing. I will be sending out two of them,
one to Ian Johnson, 2n2r5 and I'll be keeping one for myself.

The fourth will be sent to the winner in the Christmas raffle

The part still has to be faced on the mill so it will be about a 1/16" of an inch smaller then the photo.

I haven't had the chance to use it on the printer since I figured I'd wait till I finish the metal version

I'm getting really impatient though and was amazed when I tested it down the 8mm rod.

I think I want one! My 5mm rod is bent causing some banding. I have some leftover 8mm rod from my carriage upgrade.... Do I want to take my machine apart right now though.....

On another note. Is there any left to be claimed? I am interested in one.

Sounds good. I'll keep an eye out.

This weekend I'll have a big teaser pic up

In a simple one word answer - "Gravity".

Upwards you have to overcome the additional weight of pushing the platform 'up' which requires more energy than it does to push down where the weight of the platform assists movement which causes additional friction to overcome against the rod.

Consequently, an upward motion actually causes the bearings to 'climb' less than a downward motion enables them to 'descend' .

they don't exhibit the same behavior in a horizontal plane, where they are more traditionally used within linear motion.... hence me dumbing it down to "gravity". pushing up, as the bearings roll against the face of the rod, they actually will microslip, causing less upward motion. Downwards they also microslip, but its in an advantageous direction.

I probably could have said 'friction coefficients' but that wasn't dumbing it down enough I thought (and I wasn't doing it for your benefit, more for making a simple explanation for greater and wider readership - so sorry if it seemed apparently condescending...)

But I am by no means an expert and could be full of it This is simply my understanding and extrapolated belief on the basis of their non-exhibition of the problem in a "parallel to earth" orientation...

its a constant in the respective directions, so is fine in that regard as it is factored in. But the constants are just different due to the different forces at play.

Is it gravity in respect to the angle of the bearings?  Supposedly putting two bearing assemblies back to back gives you the same steps/mm in both directions.  Or is the extra support of the second assembly preventing the slippage?

This I have tried. Although you effectively double the surface area on the shaft, you increase torsional resistance on the rod. The stepper needs to be much more powerful/driven slow to account for this and the distance traveled is still asymmetrical, although to a lesser extent.