On Tuesday 15 July 2014 09:44:32 Marius Liebenberg did opine And Gene did reply: > On 2014-07-15 14:00, andy pugh wrote: > > On 15 July 2014 10:44, Marius Liebenberg <[email protected]> wrote: > >> What would the highest safe RPM be for a 2048 quadrature spindle > >> encoder on the 7i76. > >> I have to use some pulleys to mount the encoder on my spindle and I > >> would like to use what I have on the shelf if possible. > > > > 1:1 is the right ratio, if you want to use the index from the > > encoder. The encoder on the 7i76 can do 10Mhz according to the > > manual, so that should be OK to 292,000 rpm. > > OK so speed is not the problem. I will have to concoct another method > to mount the encoder if it is better to have it 1:1 > How do others do that on a lathe seeing that you cannot mount the > encoder on the back of the shaft. The shaft is hollow for material to > pass through.
I did put it there on mine, Marius, but made the encoder. The 7x12 doesn't have a lot of room for a disk so the diameter is limited to about 2.75", but I made a 50 slot disk on my tightened up, ball screws X,Y now, mill with the slot cuts as the outside circle, with one slot cut another .099 longer on the inside of the circle for an index pulse. It just clears the casting boss that the cover bolt screws into at the top/rear of the cover. I made in eagle, a pcb to mount 3 of the honeywell HOA2001 series opto interrupters that have active, schmidt triggered outputs, all in a row, mounted across the top of the disk so that the center opto, setting inline, actually sees only the long slot and the curvature of the slots lets the outside two optos see only the slots. The disk itself is held between the spindle bearing adjuster nut, and its locknut. I have made several of them, with the latest and best being made from .015" thick alu sheet that formerly lived in a dishwasher door to allow changing its color to match the other appliances. Used a 1/32" end mill. The sacrificial board under the sheet MUST be flat. Because its thinner than the nut threads, I put a dial on it and tapped it with the back nut only snug to remove radial eccentricity as best I could, then gave the locknut one last tap to tighten. I did have to file the back face of the adjuster nut to remove most of the disks axial wobble, those nuts have pretty trashy faces. The disk obviously has a large central opening to clear the OD of the rear of the spindle. The pcb did wind up having some tiny pots added so as to be able to adjust the brightness of the opto's led's as a method to fine tune the A/B duty cycles to 50%. I can round up the latest incarnation of the disk carving code, and either carve the pcb or make the eagle files available if you'd like. Getting a board house to do it and give you plated thru holes would be handier than bottled beer though. The pcb is double-sided, and without the plated thru holes and that makes soldering in the parts a bit difficult. With a bit more room it would be better with 3 individual mounts though, much more leeway to adjust for perfect quadrature timings that way. Gross adjustments in the timing could be done by changing the number of slots of course, I started with 39, but then found the next closest at 50 slots actually gave better timing. The Gcode for the disk can easily be massaged for a larger disk if you have room after the change gears are removed as you won't need those anymore. I started out with code that made about a 7" disk that I found on the net and modified it to suit. Its maybe 125 lines of gcode. 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) Genes Web page <http://geneslinuxbox.net:6309/gene> US V Castleman, SCOTUS, Mar 2014 is grounds for Impeaching SCOTUS ------------------------------------------------------------------------------ Want fast and easy access to all the code in your enterprise? Index and search up to 200,000 lines of code with a free copy of Black Duck Code Sight - the same software that powers the world's largest code search on Ohloh, the Black Duck Open Hub! Try it now. http://p.sf.net/sfu/bds _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
