On Thursday 18 July 2019 05:57:28 andy pugh wrote: > On Thu, 18 Jul 2019 at 03:01, Gene Heskett <[email protected]> > wrote: > > I have a G0704 John, and have not managed to damage those plastic > gears > > > yet, but I found a 67 slot wheel replacing the original drilled tach > > wheel, with slot interruptors had way too much quantization noise to > > be used as spindle speed feedback. > > The requirements for rigid tapping are less stringent than for PID > spindle speed control. My 50-tooth one was entirely adequate for > gear-hobbing. > > Another option would be to use a single index from the spindle and use > the motor encoder for the A and B phases.
Perhaps I glossed over that but that is what I did. osed the z from the old optical lashup, then a cobbled up a pair of counters in hal stuff and started it at three, let it count A pulses till the counter was at 103. Then divided the A count by 100 to get a scale for each gear. Got the ratio, set the scale to the low gear number, and ran it thru a scale by that ratio to get the high gear scale. Seems to be plenty accurate for the job. > Though you will need a hardware counter for that many PPR. You can > change the scale on-the-fly in HAL when you change gear. The 5i25 can handle up to about a 10 mhz A/B so thats not a problem. But I was about out of i/o so the firmware got changed to slave a 7i76, did the same for the 6040. So now I have i/o to spare. I took one of the bobs out to TLM, mounted in a plastic clamshell glued to the side of the motor power and driver box and cabled it up to the computer, but haven't gone any farther as I'm doing all the housework and careing for my bride of 30 years this December and who is now in the final stages of copd. Basicly wanting independent home switches which it doesn't have now. And I am still shopping for a solidly built CBN coated wheel to sharpen lathe tools with, 2 to 2.5" in diameter, maybe up to 1/4" thick. I figure on writing some gcode to do that on the 6040, turning the wheel only 1500 revs or so. About as slow as the vfd can drive it. I have a 4.5" CBN cup but the arbor has some runout or the hole in the cup isn't centered. But thats way to big to swing in the 6040. Works passably well in the G0704 though. I need to make a jig thats keyed to that A table somehow because its 3 jaw isn't precisely centered. I need to work on that but thats a $100 table and its main feature is variable backlash. I think its bull gear is off center, by about 50 thou. I've even put chalk in the grease, trying to wear it in. Isn't helping. Maybe someday I'll throw money at it. One immutable rule John, you get what you pay for. And purchase mistakes like that are the experience from which we learn. :) But you need to get up around an 8" table to get a good one. And it it says Made in India, it IS going to be duff someplace. But with my back, I can't handle an 8"ers weight and thats too big for a G0704 anyway. I've been plotting how to rig a hoist to handle the Sheldon's chucks too, that 8" 4 jaw is around 40 lbs, and over my comfort limit. I've made a sled that holds it the right height or I couldn't change it. I've a 3 jaw and an ER42 kit for it. Had to make quite a bit of that due to the bent spindle, which I had to grind about 5 thou to make the MT5 run true again. And reface the backplates to take that same wobble out of them. All running pretty true these days. 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
