Is the timing belt so long that it will never need to make one full revolution? If so you can buy a length of belt material, cut it to length and use a splice plate. Almost all 3D printers use this trick. A short length of belt material makes a nice splice plate if you turn the teeth around then zip-tie it in place. This actually works. Then later after it works replace with a real belt. My printer has been running well with a zip-tied belt for years. As long as the splice never runs over a pulley. Again you have a 1NM motor. It simply can never generate that much force on the belt.
On Sun, May 31, 2020 at 4:32 PM Gene Heskett <[email protected]> wrote: > On Sunday 31 May 2020 18:07:15 Chris Albertson wrote: > > > I was about to post the same thing. OpenSCAD s not a general purpose > > CAD system that you can use for machine design. > > > > How to check for clearance: On a normal CAD system you can have > > commands like "move this enough so it contacts this other object." I > > do that, then move it back by the required clearance distance. > > When working to 0.001" using eyeballs and scales don't work. > > > > If boring a bearing I'd say to make the hole "shaft diameter + twice > > the clearance" With gears yu now the pitch diameter so you place the > > gear shafts at "pitch diameter A + pitch diameter B + required > > clearance" Almost all CAD system allow dimension to be expressed as > > formulas > > > > A good CAD system is very much like working on a mill, you would touch > > the part then move from that reference. The only hard references I > > would use come from external requirements. Others are calculated. > > Never trust your eyes or hands. > > > > On Sun, May 31, 2020 at 1:06 PM Thaddeus Waldner <[email protected]> > wrote: > > > OpenSCAD doesn’t have a measure feature. All that you get is a model > > > preview overlaid on a 3D scale > > > > > > You can, of course, look at the code that created each feature and > > > read the dimensions there. > > > > > > I can’t imagine drawing up a complex machine with OpenSCAD, but > > > apparently some people do it. > > > > > > > > > https://medium.com/@urish/designing-3d-printable-mechanisms-in-opens > > >cad-5838dcb65b39 > > > > > > Can’t argue with the price. > > > > > > > On May 31, 2020, at 12:50 PM, Chris Albertson > > > > <[email protected]> > > > > > > wrote: > > > > Any CAD system should allow an exact measure, click on a circle, > > > > and see the diameter out to the full resolution you have set, > > > > typically 0.001mm. You should be reading out the numbers not > > > > visually comparing to an on-screen scale. An on-screen scale > > > > would be limited to the pixel resolution of the monitor > > > > > > > >> 1; Which is a measure of the OD of the rendered pulley, those > > > >> areas of the preview gfx are blank, although the scale marks are > > > >> there, they are drawn behind the sprocket image. so one could get > > > >> a very rough idea of the total radius of the finished gear in mm. > > > >> Am I missing a font, or is this a more serious concern that will > > > >> need me to make the gear before I can determine how it fits? > > > > In this case, I'd be far more confident once I get the motor in position, > so I can measure center to center distances. And since the motor mount > will block the back holddown cutaway in the base of the BS-1, it appears > I'll need to clear access to that nut via socket from the top. So the > xl belt is going to be quite long, as the pulley it will be driving has > to clear the worm shaft severely limiting its size, and therefore the > attainable gear ratio. But I need an anchor point at the center of the > tilt axis. So there are 2 measurements I can't make very precisely > until both of those operations are completed. See previous msgs. And > in order to get a straight bore in the side, I'll have to make a pair of > parallels to space the other side of this thing above the table and > level. But at least the mill itself is passably square for Z now. > > > _______________________________________________ > > > 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) > 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> > > > _______________________________________________ > 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
