If you don't want a multiplier that you can add or subtract is the "Walls/Horizontal Expansion" and "Wall/Hole Expansion"
But every part likely needs a different expansion setting. On Fri, Mar 25, 2022 at 10:09 PM gene heskett <[email protected]> wrote: > On Saturday, 26 March 2022 00:08:26 EDT Thaddeus Waldner wrote: > > Z direction does not shrink so much because each layer is placed at an > > absolute position rather than relative to the previous layer. So the > > only shrinkage you should see in the z direction is the amount of > > thermal expansion from your build enclosure to ambiant. > > > XY shrinkage is a common issue with 3d printing. In the Stratasys > > software that I use, it’s something you set on each print—if you > > bother changing it, that is. > > > It would be difficult (for me, at least) to come up with a mathematical > > formula for calculating xy shrinkage. All the recommendation I have > > seen are to print, measure it, compensate using the scaling controls, > > and print again. > > Scaling, IMO, is the wrong place to correct this error. > > What should be done in the slicer is, when approaching air, is to stop > half the nozzle diameter away from the air, regardless of the direction, > remmebering that a .4mm nozzle actaully prints .2mm from the center of > the nozzle, making up that .2mm short stop. I think cura has such a > setting and that I just haven't translated it into old Iowa Farm boy > english. In the meantime I have 4 of the 3% modified bearings building on > the plate now. And some experimental button pushing on a TI-36X Pro > seems to indicate 3% is not enough. Someplace around 4.5% seems to get it > about right. We'll see how much effect in actual use. > > > If you find that you use a consistent amount of scaling from one print > > to the next, you could change the X and Y stepper scale in firmware. > > Or maybe add a scale factor to your g-code preamble in Cura. But keep > > in mind that this would change your extrusion rate slightly. > > > > > [Image.jpeg] > > > > Thaddeus Waldner > > ________________________________ > > From: gene heskett <[email protected]> > > Sent: Friday, March 25, 2022 9:15:23 PM > > To: Enhanced Machine Controller (EMC) > > <[email protected]> > Subject: Re: [Emc-users] Using bb's > > for ball bearing balls while 3d printing. > > On Friday, 25 March 2022 16:59:37 EDT Thaddeus Waldner 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. > > > > Cura doesn't make that obvious as how to do that, and AFAICT there is > > no > shrinkage or growth in Z. Its finest z layer is .12mm all the way > > up, or dynamic depending on the layer but its not plain what might > > trigger the thicker layer. If I tell it to make a part to fit inside a > > 24mm internal housing with .125mm movement clearance on each side for > > two parts totalling 23.85mm tall, it will measure 23.81" high for the > > stack when done. That's about the right room for some synthetic > > plastic grease... > > My reticence to messing with cura is that this is an end to end fix, > > and > that fix also adds that red layer of thickness to the actual > > plastic laid when making the bearing races, making it stronger yet. > > Perhaps in newer code I might fix cura if I knew precisely how to fix > > it instead. > > This is all part of my $10 material cost for a miniature harmonic > > drive > to add to the 4th axis of a 6040 gantry mill. And I am probably > > going to wear it out making a wooden (hard maple) vise screw for a > > woodworking vise, I've already made the buttress thread nut, a 12mm > > pitch, 2 start affair on the 3d printer. Now I have to make the screw > > that fits it. And then design and print the thrust bearings. > > > > If you are familiar with how to make cura do that, plz advise as it > > would > be nice to spec a ball 4.35mm in diameter like a bb measures, > > to cut a ball track, instead of the 4.56mm I'm currently using for > > such. Any less and its too tight a fit, won't roll well and will > > split either track at the center, thin place before it rolls very far. > > > > Thank you Thaddeus. > > > > Take care and stay well. > > > > > > > > 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 > > > > > > > > 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 > > > 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
