On Saturday 25 July 2020 13:10:11 Chris Albertson wrote: > Common? Only once then people figure out to never again put support > in the nut packers or hole os com up with an even better solution than > using nuts. Like heated brass thread inserts or just model threads in > the plastic. > > There are many solutions for dealing with threads for screws and all > of them can be as strong as the screw. If you have enough depth for > about 8 screw diameters of thread engagement then printing threads in > a deep blind hole works (no support) Pushing in brass thread inserts > with a soldering iron works too. Nut pockets work too but as you > found out they don't need support inside. I use mostly either M3 or > M4 size screws. It surprised me the first time that my printer can > print usable M3 threads in PLA. > > Cura allows you to have different printer settings in different areas > of the same part. It is some work to do this But you can have support > under large overhangs and none in the nut pockets > > A good shortcut with holes that works in metal and plastic is to > always try to use through holes and not blind holes. They are easier > to tap in both metal and in plastic easier to clean out as pushing out > debris is easier than pulling it out. But if your design used nut > pockets then the holes must go clear through, try punching out the > support with a punch that is the minor thread diameter, then clean up > with a tap. > I wondered about that as it looks to me like a penetration point for sheet metal screws is left in a few of them that could be mounting points for the whole assembly. But I'm leary of doing that because when PLA fails it sugars like herculite glass. So I'm tempted to drill them out to about the sheet metal screw shank, and put the screw in with a hot screwdriver.
Another thing I noted, is that in the movie linked, the bearings don't press it all the way out, leaving a hair of backlash clearance. So I think I'll do one set of that arm, assemble it when the bearings arrive, measure the clearance, and add that percentage to the printer's xy scales as I'm making 3 more of that assembly. T'would have been nice to have made that center bearing of each triplet adjustable, but I don't see that in the assemblies freecad is showing me. Then I need to find a good grease for the spline, something that won't attack PLA over time. I have moly, both powder and grease, powder for coating bullets, and a very thick grease for coating barrels by pushing a patch thru them with some on the patch. But I've no clue from any of the propaganda for that stuff, what the grease carrier would do to the PLA, In the rifle barrel the grease burns up on the first shot, leaving the barrel with a coat of moly that never blows away once the fire is below the steel's melting point. 4 or 5 inches at the throat for the big magnums, and inch or less for the lower pressured stuff like a 30-30. What are you using for lube? Thanks Chris. > On Sat, Jul 25, 2020 at 3:22 AM Gene Heskett <ghesk...@shentel.net> wrote: > > Greetings all; > > > > I just pulled the first body off the plate, and was trying to clean > > out the nut pockets. I did well on the 6 that bolt the ring gear in, > > as the thru hole had been left empty but the other 6 thru holes have > > support in them and the pocket fillers can't be dug out. So I'll > > likely have to put it on the mill and cut them clear with a 1/16 > > mill. If I have one long enough Then change the setup and drill > > out the boltholes in the face too. Not impossible, but certainly a > > PITA. 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
