On Tuesday 28 July 2020 15:38:19 Chris Albertson wrote: > I'm looking at this imported step file. I see many details I'd > change. For example the "bearing cap" has some M4 screws thread into > holes with no threads and the blocks with the unthreaded holes look > like they would break. I'd fill that area with plastic or use some > big fillets. Lots of detailed design changes are needed. Some are > just personal preferences (like brass inserts vs nut pockets) and > others are fixing shortcuts the designer took.
Your thoughts are correct, I just checked the hole size against a 4mm reamer, and its bigger, enough the screw will make its own threads. I don't care for that either unless the screw is installed hot. But all I'll do is ream the hole in the top plate below the head of the screw for sample #1.. > > Also, it would be better if the unit was designed around 608 skate > bearings just because those are so cheap and easy to get but I'm not > going to de-dimension the entire unit for this. 608's would be bigger, which would expand it all. And these aren't that much pricier. > > But I bet this would work as-is. The idea is that you build one, > see what needs changing then build a second version. Precisely. > After perfecting > it then I assume everyone reading this owns a CNC machine, you make > some parts in metal from your perfected CAD files. Certainly, the > housings and output plates could be made on a hobby-grade CNC machine. > That is the best use of printing from CAD files, the same files can > drive CNC or 3D prints so you prototype in plastic before cutting an > expensive block of metal. Not to mention the body alone is over 39 hours to print. Maybe even 40 hrs. :( > I bet I'd never find the exact motor the designer had and I'd have to > adapt the design to whatever I wanted to use. I'm salvaging old 5.25" drives, figure on spinning off some of the tape pulley, and double flatting it once I am inside the SQ nuts. And JBWeld it once it runs by itself. That 5mm shaft is a huge weak point, nowhere near enough materiel in back of the nuts. JBWelding the top to the nut risers will also help considerably. I've not yet found if the drivers I have can be turned down enough to keep the motor cool enough to be bolted to the PLA. Thats another consideration... > If the goal is to drive a machine tool axis this would work as it > can't be back driven like a belt of spur gear reductio can. Ditto a well balanced Meade DS-10 scope, which may have a half pound eyepiece in the holder, or a 2+lb 35mm SLR film camera. Suitable balancing counterweights will be needed. > On Tue, Jul 28, 2020 at 11:41 AM Gene Heskett <[email protected]> wrote: > > On Tuesday 28 July 2020 12:52:09 Chris Albertson wrote: > > > Don't scale the entire part unless caliper show you the entire > > > part is scaled too small. (this is very unlikely) Better to > > > simply adjust the one hole you need to be larger. Or if it is > > > less than about 0.1mm put the part on a lather and bore it out to > > > size. I did this to all my timing belt rings to make them fit > > > perfectly to the 24mm hubs. If you go slow so as not to melt the > > > PLA the carbide boring bar works and just took off "fuzz" > > > > holes aren't bothering me, other than hard toremove support crap. > > What is bothering me is the incomplete mesh I saw in the movies, and > > that easily fixed by changing the printer x and y scales. > > > > I think its obvious now that whats published is not 100% optimized. > > > > > The hole seems small but usually, it is because the plastic was > > > not laid down perfectly and there are bumps and ridges and lines > > > inside the hole. Make the hole perfect rather then making another > > > larger not-perfect hole. Also it is MUCH quicker to bore the hole > > > then re-print the part. > > > > > > The other trick I do is to make "temporary" bearings with either > > > aluminum or even PLA while waiting for the real bearing to arrive. > > > You could make them on a manual lathe in a few minutes and then > > > you could verify the parts work and there is not OTHER problem > > > before doing another 16 hour print > > > > > > I'd be surprised if you did not need to clean up the fine pitch > > > gears with a nail file. > > > > They are amazingly clean after removal of the brim. 10 minute job to > > clean them up. > > > > > Most 3D prints require some post-processing with a > > > tiny file and maybe #600 wet and dry paper. A boring bar makes > > > the inside of holes smooth as glass. > > > > > > A read a translation of the designer's blog page and it seems he > > > wants to make a 6 axis arm with these. He will probably need to > > > make some of the parts near the base of the arm in metal > > > > I wouldn't be surprised. These are, if built as published, going to > > have enough backlash to wreck a 6 joint arm. What I'm getting off > > the printer, does not always match his pix. Properly fine tuned it > > definitely has commercial prospects to be exploited, and I can do a > > bit of that fine tuning. > > > > Thanks Chris > > > > [...] > > > > > > 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 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
