On Sunday 31 May 2020 22:58:31 Chris Albertson wrote: > 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.
First, its a 3NM motor. And I can easily envision a job where it may have to pass over both pulleys several hundred times using the BS-1 as a slow spindle. Belt length might be 240 teeth, 10 on the motor 25 to 40 on the idler. from the idler, 14 fine teeth in a herringbone pattern driving a bigger gear, whatever diameter & number of teeth fits with low backlash to drive the worm shaft. I found a similar parametric gear maker that I'll put a solid hub into and use the mill to make a double D-flat to turn the worm shaft. If I don't fall over first, these pla gears only have to live long enough to make their own metal replacements. Unless I find they find they really are tough enough to Just Work. Only time can answer that question. Second, my testing for motor heating may not have been close enough to stopped as I was just turning the speed down to about a tick a second from the generator which may not have been long enough to cause a current turndown. So I'll plug it in w/o any drive for a hour tomorrow to see if it still gets that hot. Maybe watch it with a kill-a-watt? > On Sun, May 31, 2020 at 4:32 PM Gene Heskett <ghesk...@shentel.net> 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 > > > <thadw...@gmail.com> > > > > 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-o > > > >pens cad-5838dcb65b39 > > > > > > > > Can’t argue with the price. > > > > > > > > > On May 31, 2020, at 12:50 PM, Chris Albertson > > > > > <albertson.ch...@gmail.com> > > > > > > > > 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 > > > > Emc-users@lists.sourceforge.net > > > > 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 > > Emc-users@lists.sourceforge.net > > 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 Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
