On Sunday 23 May 2021 02:17:28 Roland Jollivet wrote: > On Sun, 23 May 2021 at 03:31, Jon Elson <el...@pico-systems.com> wrote: > > On 05/22/2021 07:12 PM, dave engvall wrote: > > >> Has anyone tried homing off the reference channel on a > > >> glass scale? There is information on the web indicating > > >> that at least some of the chinese glass > > >> scales mask and compare the 4 lines each side of the > > >> reference mark in addition to the reference. This might > > >> imply that the usual homing routine would work. > > >> I haven't tried this only because I have nothing running > > >> at the moment capable of doing this. > > > > If the "reference channel" produces one pulse at a specific > > spot on the scale with no other pulses within a few tenths > > of an inch, you should be able to use it for precise > > homing. You'd have a limit switch that would begin the > > search for index sequence of the homing routine. Then, it > > would advance until it saw the pulse from the scale. Just > > like the Z mark on a rotary encoder. > > > > Jon > > I often feel like that I live in a world where cars have three wheels, > and no-one wants to believe that 4 wheels are better.. > > So.... I don't understand why the reference strip in an encoder isn't > half black, half clear, along the full length. Now; > - there is only a single transition that marks the reference point > - it's always obvious which way to go to find that transition; 0:go > left 1:go right > - you don't have to worry (as much) about missing that obscure 'pulse' > - it will remove the homing dilemma plaguing machinists all over the > world > > What am I missing here? > > Roland
Nothing Roland. I do exactly that but with a switch thats closed from its hit point clear to the chuck and beyond on my Sheldom lathe for Z homing. It's 10" or so from the chuck. Cheap mini micro switches. $5 for a bag of 10. An error from either of the 2 stepper servos unhomes the machine as the reset on those requires a driver powerdown achieved with an f2 disable that shuts down a pair of 40 amp SSR's killing both sides of the 250 volt line. And I have .hal configured to do that. So after an error, I pull the tool holder, hit f2 to re-enable and rehome the machine which goes not destroy the previously set touch-offs. The rehome is within .0002" with those cheap switches, then re-install the tool and comtinue where it was interrupted. Whats not to like? Take care and stay well. 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
