I've done this a few times. PVA is best used if the mold is new. You can spray in on the mold using an old spray bottle that used to hold kitchen and bath spray cleaner that is well rinsed out. But after the mold is used a few times mould release wax alone is OK. The PVA has some tiny film thickness and a slight irregular surface and can't be polished. Wax on the other hand can be buffed and made to shine. The part is only as nicely finished as the mould. Mould seem to get earlier to release with repeated use. PVA dissolves in water, so you can soak the mould and part to release it.
But it just might be that epoxy does not adhere to rubber and no release agent is needed. We never used a release agent on latex rubber moulds. Carbon fibre parts have this high-tech mystique around them but they can be made with very crude and low-cost methods using just paper cups, popsicle sticks and c-clamps. You can buy one yard of carbon cloth for about $10 and it is a lifetime supply. Then cut it on bias into 1/8th inch strips and stir the strip until they become 1/8th inch long unwoven fibers, (or for more money buy "chopped carbon fiber") mix with epoxy to make a fibrous paste and this mix is so strong when it sets you can not break it with a hammer and as lightweight as foam. Now that we have 3D printers we can print moulds and fill the mould with this DIY epoxy/carbon paste and in effect print strong-as-steel parts. I woud cast the ring gear directly inside the aluminum housing so the epoxy would bond to the aluminum. No need to use screws. The fit would be perfect On Wed, Mar 10, 2021 at 10:58 AM dave engvall <dengv...@charter.net> wrote: > PVA seems to be the release agent of choice for epoxy. However, IIUC it > has limited shelf life. Silicone oils will work but they tend to migrate > to places you > don't want them. > > Dave > > On 3/10/21 9:31 AM, Chris Albertson wrote: > > This is the best and most durable DIY drive I've seen. One > > improvement for the future is to make the internal tooth gears from > > something other than 3D printed plastic. Perhaps you can cast them in > > epoxy and fiber composite. If you used a timing belt as part of the > mold > > the cast teeth would be as perfect as the belt. > > > > I can imagine the mold is the square aluminum part with roughened up > > internal pocket. Then stretch a belt over a disk and place the disk in > the > > pocket leaving a ring then pour in the epoxy. With luck the epoxy bonds > > with the aluminum but not with the rubber belt. Perhaps the belt is > > coated in mould release wax. > > > > On Wed, Mar 10, 2021 at 7:58 AM Sam Sokolik <samco...@gmail.com> wrote: > > > >> another update - at 1/2 step - the discrete resolution should be about > >> 40,000 divisions per rotation. .009 deg. > >> > >> https://www.youtube.com/watch?v=IdfKre6zpEY > >> > >> On Thu, Feb 4, 2021 at 4:00 PM Sam Sokolik <samco...@gmail.com> wrote: > >> > >>> https://www.youtube.com/watch?v=ZVVffljc7kE > >>> > >>> On Tue, Feb 2, 2021 at 9:46 AM Gene Heskett <ghesk...@shentel.net> > >> wrote: > >>>> On Tuesday 02 February 2021 08:30:56 Sam Sokolik wrote: > >>>> > >>>>> I have looked at cycloidal drives and feel that they have too many > >>>>> parts :) > >>>>> > >>>>> Gene > >>>>> https://www.youtube.com/watch?v=Gx263nnTrqY > >>>>> > >>>>> Ran for over 6 hours like that - about 850rpm input. > >>>>> > >>>> I am highly impressed. > >>>> > >>>> Now finish the housing, and hang a load on it, like the worm of a BS-1 > >>>> while making another worm to replace the crappy worm in the Chinese > >>>> BS-1. That worm is doomed to a higher wear rate, a fact I'm becoming > >>>> aware of as I exercise this BS-1 servo for tuning. > >>>> > >>>> That is why I bought the ender3, but I was using O.P's code which was > >>>> crappy code IMO. Turns out the ender3 can make stuff a heck of a lot > >>>> better that the code I could DL from thingiverse. I now have the > >>>> extruder motor on the x carriage, moving a modified stock hot end, and > >>>> while its slower than some because the heating is only once the > filament > >>>> is in the nozzle, dozens of times more dependable than the stock > setup. > >>>> No clogging from cold filament because the hot stuff backs up into the > >>>> heat sink and freezes. > >>>> > >>>> I think this loose ring idea has the most promise of making a long > >>>> lasting drive, and shorter axially than any design so far. Please > >>>> continue. > >>>> > >>>> Thank you Sam S. > >>>> > >>>>> On Thu, Jan 28, 2021 at 3:13 AM andrew beck < > andrewbeck0...@gmail.com > >>>>> wrote: > >>>>>> Guys just to chime in here. > >>>>>> > >>>>>> Sam went don't you design a cycloidal drive instead. They are easy > >>>>>> to make on a normal 3 axis Cnc mill with a end mill and much more > >>>>>> rigid than a harmonic drive. As they are not so fragile. I'm > >>>>>> planning on making some on my VMC soon. I don't understand why > >>>>>> use a harmonic drive. (I actually have a big harmonic drive here > >>>>>> from a robot. ) > >>>>>> > >>>>>> On Thu, 28 Jan 2021, 18:53 Bari, <bari00...@gmail.com> wrote: > >>>>>>> On 1/27/21 10:55 AM, Sam Sokolik wrote: > >>>>>>>> Nice being able to make things while I sleep.. > >>>>>>>> > >>>>>>>> 2 outside side rings - one 202 teeth - one 200 teeth. > >>>>>>>> Inside flex ring - 200 teeth. Feels good - for what it is.. > >>>>>>>> > >>>>>>>> > >> http://electronicsam.com/images/greenmachine/IMG_20210127_104237 > >>>>>>>> .jpg > >>>>>>>> > >> http://electronicsam.com/images/greenmachine/IMG_20210127_104628 > >>>>>>>> .jpg > >>>>>>>> > >> http://electronicsam.com/images/greenmachine/IMG_20210127_104354 > >>>>>>>> .jpg > >>>>>>> Timing belts will take the flex > >>>>>>> > >>>>>>> https://www.youtube.com/watch?v=Y8ZELQdgBbU > >>>>>>> > >>>>>>> https://www.youtube.com/watch?v=2YC-0C8oPUo > >>>>>>> > >>>>>>> > >>>>>>> Cycloid prototype under microscope > >>>>>>> > >>>>>>> https://www.youtube.com/watch?v=um5GMOBgz6s > >>>>>>> > >>>>>>> > >>>>>>> Hybrid planetary/harmonic drive - check out how they made it flex > >>>>>>> > >>>>>>> https://www.youtube.com/watch?v=sdRGrTHq4hA > >>>>>>> > >>>>>>> > >>>>>>> > >>>>>>> _______________________________________________ > >>>>>>> Emc-users mailing list > >>>>>>> Emc-users@lists.sourceforge.net > >>>>>>> https://lists.sourceforge.net/lists/listinfo/emc-users > >>>>>> _______________________________________________ > >>>>>> Emc-users mailing list > >>>>>> Emc-users@lists.sourceforge.net > >>>>>> https://lists.sourceforge.net/lists/listinfo/emc-users > >>>>> _______________________________________________ > >>>>> 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 > >>>> > >> _______________________________________________ > >> Emc-users mailing list > >> Emc-users@lists.sourceforge.net > >> https://lists.sourceforge.net/lists/listinfo/emc-users > >> > > > > -- Chris Albertson Redondo Beach, California _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
