On Fri, Mar 25, 2022 at 2:02 PM Thaddeus Waldner <[email protected]> wrote:
> I would suggest that you calibrate the xy shrinkage, and z shrinkage in > your printer slicer, instead of compensating for it in your design. > Yes, then you can rotate the part 90 degress and it still prints accurately. I just ran into this here. I rotated the part and now the dimensions are different. I think belt tension does it, not shrinkage. The tight belt has a different tooth pitch. 0.5% over 200mm is 1mm. I might buy some kevlar belt. > > > > > > On Mar 25, 2022, at 3:29 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 > _______________________________________________ > 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
