Real sealed bearings units are not expensive, even large ones with 60mm or larger boreholes. Look on Amazon the like.
Here is a random example, two for $15 They would not drop into your existing design, but you design around them or something like them amazon.com/uxcell-6812ZZ-Groove-Bearings... <https://www.amazon.com/uxcell-6812ZZ-Groove-Bearings-Shielded/dp/B082PQ1NCY/ref=sr_1_7?crid=12OY4CUYLTJ6X&keywords=sealed%2Bball%2Bbearings%2B60mm&qid=1648252254&s=industrial&sprefix=sealed%2Bball%2Bbearings%2B60%2Bmm%2Cindustrial%2C130&sr=1-7&th=1> What I do is first find the cost-effective bearing then design the 3D printed part around the bearing. You can press-fit the bearing to the plastic. Sometimes the pocket in the plastic is not round enough, so I place the plastic part in the lathe and bore just a tiny bit out to true the hole. I tried printing bearing races, they never work well But pressed-in bearings do. I've got a dozen of them here Im installing on a robot quadruped. On Fri, Mar 25, 2022 at 1:29 PM gene heskett <[email protected]> wrote: > Greetings all; > > It has come to my attention that one of the potential failures in my > harmonic drive with a loose belt experimentation, which seems to be > caused by the unequal shrinkage in the xy direction as opposed to the z > direction is at least partially caused by the nozzle diameter. If I > attempt to achieve a zero clearance bearing simply by shrinking the dummy > ball from about .5mm bigger than the bearing, as it shrinks, the wider > edges of the bearing groove come into zero or a slight preload condition, > leading eventually to a race fatigue split at the center of the races > width. Working in openscad, a scale command would fix this by shrinking > the bb shape used for clearing that groove, only in the x direction. > > Th question is how much would it take to transfer the majority of the > stresses on the race from being on the outer edges of the race, to be > more concentrated on the center of the race, with an eye toward reducing > the splitting force on the bearing race. > > 1% x shrink, 2%, 3%, what would be the ideal amount of shrink to > compensate for the printers .4mm nozzle, being used to only lay .12mm per > layer? > > Seems to me there ought to be a way to mathematically predict how much > that shrinkage diff there is. Attached, an extra 2 lines to draw that > away from the bearing itself, showing how little the difference is for a > .97 x shrink. > > Comments plz? > > 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, 1940) > If we desire respect for the law, we must first make the law respectable. > - Louis D. Brandeis > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
