On Monday 26 April 2021 08:02:34 andy pugh wrote: > On Mon, 26 Apr 2021 at 11:19, andrew beck <andrewbeck0...@gmail.com> wrote: > > Still need to automate changing ramp > > If you wanted to do it based on commanded spindle speed, then > "lincurve" would probably work. > > Alternatively, you could consider basing it on spindle.0.revs, noting > that a threading pass is unlikely to get higher than 100 full turns > between index resets. > > Or, maybe even just base it on the spindle running in reverse. I think > that rigid tapping does a reverse without a stop?
It does indeed do that Andy, zero smarts about that. And I can't think of a better way to blow a vfd and/or a 30 amp 240 volt breaker abuseing a horse or more motor by slamming it into reverse while spinning at its normal rpms. Thats why /all/ of my machines have extra hal code and modules loaded to control that. I tried to describe the sequence of events that I use to control that yesterday. It works, and does /not/ trip 15 amp breakers doing it. My 11" Sheldon lathe, with a vfd but no PID's in the config, has this hal code in it, and additional hal code to report the overtravel both in terms of spindle travel in turns, and If the gcode makes use of it, travel distance of the overtavel provided you tell it what the tpi of the tap loaded is. With a nearly 40 pound 8" 4 jaw chuck mounted, my overtravel is at 100 rpms, .25 turns, and I can and have done it at 5 second intervals for half an hour at a time without tripping anything off, and I'm doing it with a cheap clone vfd that has no breaking resistor hookups, controlling the vfd thru a pwmgen and a spinx-1. Similar hal code is used in the go704 and in tlm but tlm's idea was to preserve drive parts as none of a 7x12's was ever designed for a motor that size with millisecond response times. The slowdown in the go704 was actually designed to stop the z following errors at the bottom of a stroke, it can reverse faster than z can keep up, so the overshoot is still substantial at 1000 rpms. So I tap at 2 or 3 hundred rpms in low gear. But it also means that if my gcode accidently outputs an m4 while its turning 3 grand, its back to 3 grand in reverse in less than 400 milliseconds. Thats a bit hard on the filter caps, but no great surge from the powerline thanks to Jon's pwm-servo being a full 4 quadrant control, so it sucks energy out of the spinning motor as it stops it, running the filters up to around 170 volts, 40 volts above their rating. but once the motor is stopped, it then uses that stored energy to re-accelerate the motor in the other direction, so the overvoltage only exists for less that 50 milliseconds. I usually hear the iron in the motor chirp from the servo amps programmed 17 amp limit, which is about 190% of those motors nameplate full load amps of 9.7, as both motors are 90 volt rated motors getting about 125 to 130 volts if the going gets tough. So it can be done and I'm disappointed that no one is asking me how to do it. 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
