Use a ball cage that snaps in. I designed an example that uses 12 steel BBs.
https://www.thingiverse.com/thing:1769802
Bearings are made with the parts sized so that when the inner race is shifted
as far to one side as it can, the gap on the opposite side is just wide enough
to insert the balls. When as many balls as can be are put in, the balls are
distributed around as the inner race is moved to the center. Then either a one
piece plastic cage is snapped in from one side or a two piece metal cage is
riveted or spot welded between the balls.
On Monday, March 29, 2021, 8:56:37 AM MDT, Gene Heskett
<[email protected]> wrote:
On Sunday 28 March 2021 22:51:17 Gene Heskett wrote:
> On Sunday 28 March 2021 21:00:56 Chris Albertson wrote:
> > Back to printing ball bearings. The best way is not to do it. Buy
> > sealed bearing units and press them into a printed recess. But
> > large diameter sealed bearings can be expensive. The next best
> > design is to buy metal balls and print the races and assemble them.
> > Printing the rollers never works well. If you want everything to
> > be made of plastic buy the plastic balls used by "airsoft" guns.
> > These make pretty good bearings, much better than you can print and
> > 2,000 balls, 6mm in diameter cost only $10.
> >
That is an enticing thought, but that will require and entrance notch in
one side if the races, possibly slightly smaller than the balls since
the plastic can be stretched a bit to insert the balls. But 6mm is about
the size of these rollers. and as I play with openscad, I think I just
found the problem with the rollers vs printing them. The rollers are
shorter than the races, so the first layer of the rollers is NOT on the
glass, but .5mm up in the air! Fixed that by reduceing that clearance
offset to zero. Looks a hell of a lot more printable now. And by the
time I fined up the rendering to make the straight line facets never
mind small, its takeing openscad around 5 minutes to render a change.
cura doesn't slice it that fast either. But cura uses all 6 cores of this
i5, where openscad is single threaded, jumping from core to core as is
spreads the heat around.
I also found that once wire frameing the view is enabled it can't be
turned off, but it also a good indicator of how many facets are in the
circles as rendered. And if print_view is 0 at the top of this design,
it only renders 3/4 of a circle so you can look into the end and see all
the clearances. Sorta like an xray view. Nice for fine tuning this
design.
And I may have found a bug in cura 4.8.0, or a setting that needs
changed, it is not rendering the rollers as a solid, but with a filler
hole down the center that renders the roller very weak in the center
area. Openscad hands it to cura as a solid, cura make a hole filled with
infill, and its the same diameter from end to end of the roller. So I
need to fix that if I can. What does cura do when walls are thick enough
to kill the infill?
I have some foot square sheets of that PEI Andy mentioned, and I have 2
hardened steel .4 nozzles for it coming from microswiss via amazon,
seems burning out the blockage of the brass dremel nozzle did something
to it, so since I now know how to change it w/o returning the machine to
dremel in WI. If the stuff coming doesn't make it print, then I'll do
just the races in openscad to use the airsoft bb's. I think I can do
those in openscad reasonably quick.
> > If you like a challenge, try printing a sealed ball bearing unit on
> > one "go". It can be done as a stint but does not make a good
> > bearing for use in a machine.
I think you meant "stunt". But I am counting on the stretch of the inner
race when installed over the outside of the moving spline to take up
some the clearance, and some compression of the outer race when
installed in an alu output shaft with a ring of alu about 1/4" thick
around it, both intended to take up some of the clearances rendered.
By making the rollers bigger, tis code is thinning the inner and outer
races, and I'm still tweeking that. Thinner, to a point, will be better
as long as the centering guide rings have sufficient support. I'll send
you a pix of the magnified end view when I'm actually getting a
printable output.
> > As for getting plastic to stick to glass try cleaning it very well
> > with "Bar Keepers Friend". The stuff is a powder like "Comet" but is
> > acidic and is much better for removing oils and such from
> > fingerprints. Hairspray usually works too.
My now departed Dee had some, leftovers from her school teaching years,
but I didn't find it effective at PETG temps. It was quite old but one
can of it still had some propellant left.
Thanks Chris.
Cheers, Gene Heskett
--
"There are four boxes to be used in defense of liberty:
soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
If we desire respect for the law, we must first make the law respectable.
- Louis D. Brandeis
Genes Web page <http://geneslinuxbox.net:6309/gene>
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