On Friday, 6 May 2022 07:16:38 EDT andy pugh wrote: > On Fri, 6 May 2022 at 11:42, gene heskett <ghesk...@shentel.net> wrote: > > The other thing that surprises me is the low frequencies they use, > > I'd > > have to assume search speeds would be limited if a direct approach, > > as > > opposed to a slide-by, for no other reason than to have room to > > overshoot w/o a damaging crash. > > I doubt that the excitation frequency is the limiting factor here. > It's more limited by how fast your machine can stop so that it doesn't > use up all the 4mm. > > On my machines I have the sensor looking at a hole in the way that it > slides past, then use the encoder index for the actual home position. > Then the sensor response time is not an issue.
stepgens don't have an index. I don'tknow for sure but I don't think these new 3 phase stepper/servos have one either. So I'm stuck with backing away and re-approaching at about 10% of the search speed, which with cheap microswitches, has been amazingly repeatable. But its a "dry" circuit and the switch eventually develops a high resistance contact. They are now about 3 years old and I've had to replace two of them since starting this project a week ago. > Here is the target on the bed of my lathe. > https://photos.app.goo.gl/HHbUobLPZbkUTcth9 Looks good. Where did you find that bolt cover? It looks as if it collapses better than the rubberized fabric I used on the sheldon. It gets pretty tightly compressed on the Sheldon when its right at the chuck. Errant tools don't damage it? Thats 6 of one anf half a dozen of the other, as hot swarf could burn a hole in my fabric, but hasn't yet in 5 years. I think the hot stuff misses it, falling outside of the bed ways, and the screw is closer to the bed than the OEM acme was. Better shielded from falling stuff. > It's a hole drilled in the bed, then filled with a delrin plug. Delrin being more consistent than a hole full of swarf. ;o) The homing logic reverses the search if the switch is closed, so my home switch is about 10" downbed. IOW, no chance of starting a home on the wrong side of the switch. I home x all the way out first, so its more habitual than required to remove the tool from the post while homing. > Thanks Andy. 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, 1940) If we desire respect for the law, we must first make the law respectable. - Louis D. Brandeis _______________________________________________ Emc-developers mailing list Emc-developers@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-developers
