On Monday 30 June 2014 02:32:52 Marius Liebenberg did opine And Gene did reply: > On 2014-06-29 23:14, andy pugh wrote: > > On 29 June 2014 13:47, John Thornton <[email protected]> wrote: > >> CSS requires Spindle Feedback and an index pulse once per rev. > >> Rigid tapping in addition requires a way to reverse the spindle. > > > > I don't think CSS needs an index, but as threading really does, a > > lathe needs an index. > > rigid tapping needs the second quadrature channel to spot spindle > > reversal. > > So fitting a quadrature encoder is the best option then?
Yes, the only one really. I made mine, both the pcb for the photocells, and the disk too. And now that I have ball screws in the mill, I might make another disk, more accurately than the previous version. The older acme screws were difficult to keep the nuts adjusted for less than about 3 thou of backlash and it shows in the encoders velocity output. There are a pair of files on my web page (see sig) under Genes-os9-stf/spindle- encoder.ngc, which is the code I found on the net and started with but it makes a much larger disk than I could use inside the headstock cover of the 7x12, so in Genes-os9-stf/LCNC/genes-encoder.ngc is the code that I used. It can be studied, and scaled to suit with your fav text editor. I made the index slot inward from the slot circle as that allowed the photo- interrupters to be mounted in a row, with the center one becoming the Z, index. I mounted them on a eagle generated board, a hair high so they could be pushed around a bit for better quadrature timing. I have since added a very small strip with 3 mini pots on one end of the board so I could trim the brightness of the leds, getting an improved match in the timing from that. I think the big central hole (it mounts between the bearing preload nut and the locknut) might be made about a thou bigger, as its thin enough it sinks into the gap between the threads, also contributing to a very small eccentricity. Mine is from .03125" thick brass door kickplate. The 6 hole mount pattern holes are non-functional on mine. I used a carbide pcb mill, available in almost any size in the .020" to .125" range, a .03125" IIRC, not pushed enough to bend it I hope. Feel free to snarf it and adjust to suit. With better math than I have, one can adjust the number of slots to fit the photo-interrupter spacing on the pcb they are mounted on since eagle makes it difficult to change the default .1" spacing increments when laying down the footprints. Given a little more diameter room than I had gives more freedom. The run time says 224 minutes for genes-encoder.ngc. I wasn't pushing a tiny mill. :) > > On my mill I have it set up so I can choose a gear suitable for the > > cutter/job, and a bit of HAL trickery auto-detects the gear and > > adjusts the VFD frequency request to suit. > > I would have the same on my lathe, except the lathe has no gears. > > (which I often wish were not the case) > > http://linuxcnc.org/dapper/emc2/emc2/index.php/italian/forum/47-hal-e > > xamples/27071-automatic-spindle-gear-detection#39583 > > > > You may not need a braking resistor, I don't have one and have > > noticed no real problems. (If I was to reverse too quickly I would > > worry about the chuck screwing off anyway) Not a problem on my 7x12, its bolted to the spindle flange. 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 ------------------------------------------------------------------------------ Open source business process management suite built on Java and Eclipse Turn processes into business applications with Bonita BPM Community Edition Quickly connect people, data, and systems into organized workflows Winner of BOSSIE, CODIE, OW2 and Gartner awards http://p.sf.net/sfu/Bonitasoft _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
