On Tuesday 30 July 2019 23:52:23 TJoseph Powderly wrote: > > So it appears I will have to dig the keyways by EDM.
> you ask for long lasting > that would be tungsten carbide > but > i suggest using easy to manufacture, easy to find, low cost > because it will wear anyway > > so copper, with little lead ( often copper sold will be 'machineable' > which means lead which means higher wear ) > > for a key way you should be able to mill machine the electrodes > and use the largest face ( dont cut with small end of rectangular > prism , cut with side ) > ( do the hokey pokey - put your big foot out i used to teach the > operators ) > use LOTS of pecking, just get a sizzle and jump away > > you dont have real edm equipment, just a hack so you gotta play safe > Power supply is homemade, average voltage OC is around 40, 10 uf paper cap, hundred ohm 100 watt current limiter. Noisy is an understatement. probably does one bang per half cycle of line voltage when its cutting good. > and set it up vertical and submerged if possible so the jump opens up > to a flood of the submerged fluid pee down the cut from above and to the side, you want to see the black > puff out each jump With a wobbling, rotating 12 or 14 ga copper wire to stir the water, getting brushed on a file during the gcode motion to keep the end sharp, and moving lengthwise down one side of the slot. offsetting to the other side of the slot for the trip back. Won't be very fast, but my back could use some rest before I tackle the re-assembly anyway. > > Negative polarity ( tool neg, work pos ) If you use an r/c pulse > generator then always negative tool. > Short ontimes and hi freq ( say 10to50uS on and 200 or more off , 2000 > is good for lash-up ) > > The exaggerated offtimes aid in letting the dielectric recuperate to > non conductive state. > The short cut times ( jump cycle ) aid in poor gap control, you > actually cut while ' in the zome' > but your system cant maintain the zone > So you get efficiency by 'drive by edm', you go thru the zone each > jump pass and get a little work done. > You jump away right away and reduce the heat build up ( because you > likely crashed into the work and shorted ) > > you're a scope kinda guy, try this... > reduce the gap using a resistor divider giving max 5v and watch the > process when you get more 'chairs' then you are cutting more > when you flat line, you're crashing > when its open voltage all the time you're missing > ( old elox guys look for 'grass' like on a lawn , > there was a scope on all old elox generators, > the 'grass' was due to slow scope ) Chuckle, I haven't had a "slow" scope since '77. That gives me an idea of how to use an offset module to jiggle the Z, but the response time of that big nema 34 motor raises an ugly limit as it can't follow an individual discharge. But with the electrode wobbling as its spinning its pretty self quenching anyway. I've used a 3" thin (0.03125") brass disk at 100 to 300 revs to cut a taperlock into leaves, usually 6, to give it room to get crushed by the taper, and I can plow right along, making a cut 7/8" deep in around 15 minutes with my jury rigged supply. Thats where I found distilled water worked better than k2 for a dielectic fluid. K2 gets dirty faster and has to be changed more often. I'm wondering if it would do any better than just doing the keys back profile at a decent feed rate. That, combined with the rotation and wobble ought to bring in fresh dielectric > hth > tomp Makes me think about the "what if's", as usual, tomp and thats good, thanks. 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
