On Saturday 19 June 2021 02:08:02 John Dammeyer wrote: > So I settled for a 3D printed coupler. All mounted it definitely > vibrates less. Enough so I can get back to the Pi4 LinuxCNC and > spindle information. I'm finding the AXIS Spindle speed oscillates > about +/- 5 RPM. I thought that I was filtering it. The ramp > feature works so the motor speeds up slowly as desired.
Why should it? Because I can do rigid tapping, the only reason to slow a motors response to a speed/direction change is to profile itsa change rates so Z can keep up. No other slowdowns allowed. My PMDC spindle on my G0704 can do a full reverse at 3000 rpms in about 400 milliseconds. So can TLM. The 1hp on my sheldon lathe is rigged for rigid tapping and can reverse a 35 lb 4 jaw chuck controlled by a clone vfd, with .25 turns of overshoot at the turnaround point. The belts might yelp, but it gets it done. > Before I start posting HAL and INI fragments can I get some feedback > on others who report the encoder RPM on the display. Does it jitter > or is it rock solid? > I display rpms from the encoder if there is one, and only the tach on the sheldon has any wibbles, but they are created in the encoder due to uneven tooth wear on the bull gear, created by 50 some years of backgear way the hell and gone over engaged, causeing wear on the tooth profiles from banging the edges of the teeth against the bottoms of the backgear. This is the major cause of broken teeth on these gears in Sheldon lathes as the smaller tooth count is flexed by several ton of over engagement, breaking the tooth off from the flexing of the tooth at the base of the tooth. Because of this uneven wear on the gear profile being detected by the ats-667's I made the encoder from, the tach display has about a 5% jiggle. And I went public with that on the Sheldon list as it appears this was the normal setting at Sheldon by someone in final assembly who was never schooled in the finer points of proper gear engagements. If, with the backgear engaged, it rumbles, loosen the engagement by a couple thou. I don't use it that much with a vfd. Don't need it with the vfd. > Maybe what I'm seeing is normal. I'm used to seeing target RPM which > of course doesn't change. Thanks > John As has been reported here, I put a 1000 line encoder on the g0704's motor, but the index still comes from the spindle. The original install had an elastomer coupling that eventually broke due to a slight miss-alignment, so its now driven for the last 2 years by a piece of heat shrink. Works fine. And I run a Pgain in that PID well above 1000 now. > > -----Original Message----- > > From: John Dammeyer [mailto:jo...@autoartisans.com] > > Sent: June-18-21 3:51 PM > > To: 'Enhanced Machine Controller (EMC)' > > Subject: Re: [Emc-users] Machining question > > > > Andy's approach is what I had in mind. Additionally I also made > > sure that I turned the outside to be concentric with the inside. > > > > It's a very tight fit on the 14mm motor shaft. And a firm fit on > > the encoder shaft. And still it wobbles. > > > > So out comes the dial indicator with the encoder clamped in the mill > > vise. At the top of the shaft the encoder shaft wobbles by 0.0125" > > while just pushing on the shaft moves the indicator by 0.0005" > > > > Pushing my new coupler onto this measuring at the same shaft point > > but on the coupler shows 0.00125" wobble. Move and inch up into the > > area of the 14mm hole and that wobble is exaggerated to 0.025" > > > > Now I know why I was given that $800 encoder over 10 years ago. > > Obviously taken out of service because it had been damaged. > > > > So time to rethink if I want to install a flex coupling instead. > > This is after all just for testing. What I'm finding is the RPM > > indication on the servo drive will read 101RPM but the display on > > Axis is oscillating between 93 and 107RPM. I don't know how much of > > that is electrical noise from the AC Servo and how much is due to > > the wobble or if the motor really is bouncing around like that. > > > > Might be better to initially use the Servo Drive Encoder outputs. > > But then I have to wire up a 3 pair differential receiver. > > > > This will never end I think... > > > > John > > > > > -----Original Message----- > > > From: andy pugh [mailto:bodge...@gmail.com] > > > Sent: June-18-21 9:50 AM > > > To: Enhanced Machine Controller (EMC) > > > Subject: Re: [Emc-users] Machining question > > > > > > On Fri, 18 Jun 2021 at 16:52, John Dammeyer <jo...@autoartisans.com> wrote: > > > > I'm thinking the better approach would be to drill all the way > > > > through undersize 3/8" and then drill half way with 13mm. Then > > > > only > > > > > use the boring tool to bring the back half up to 3/8" and the > > > front up to 14mm. > > > > > > I would drill 8.5mm then bore all the way through to 3/8 for the > > > fit I wanted on the encoder shaft. > > > Then bore half way through to the 14mm testing the motor fit. > > > The point is that you can machine the 3/8 first on the accessible > > > side of the work, then machine half of it away. > > > > > > -- > > > atp > > > "A motorcycle is a bicycle with a pandemonium attachment and is > > > designed for the especial use of mechanical geniuses, daredevils > > > and lunatics." > > > ? George Fitch, Atlanta Constitution Newspaper, 1912 > > > > > > > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > _______________________________________________ > > Emc-users mailing list > > Emc-users@lists.sourceforge.net > > https://lists.sourceforge.net/lists/listinfo/emc-users 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
