If you can hear it, it isn't smooth. I'd recommend using the finest micro stepping setting your driver offers, but simply not counting on more than 1/4 of a full step in your resolution accuracy. But just because the motor and drive may not be able to physically achieve positioning accuracy much better than 1/4 step, doesn't mean that having the finer micro step resolution won't significantly contribute to smoother quieter motion.
Todd Zuercher P. Graham Dunn Inc. 630 Henry Street Dalton, Ohio 44618 Phone: (330)828-2105ext. 2031 -----Original Message----- From: R C <cjv...@gmail.com> Sent: Tuesday, July 14, 2020 9:39 AM To: emc-users@lists.sourceforge.net Subject: Re: [Emc-users] off topic: pwm with a stepper driver/motor [EXTERNAL EMAIL] Be sure links are safe. Hi Chris, for the go to part I am not "too worried"about that possibly not being too smooth, of course it is the goal to do that, but the point there is to get there. The equatorial tracking indeed needs to be as smooth as possible. With the hearing I have I think I can run the stepper motors smooth without having to do any micro stepping. thanks, Ron On 7/14/20 3:49 AM, Chris Albertson wrote: > Gene is correct when he wrote the precision might be off when > micro-stepping. > > Motors are mechanically built for 1.8 degree steps so that is likely > to be accurate but half steps depend on the driver. > > But what I wanted to add is that when you read the speed vs. torque > curve it is for FULL steps. The amount of holding torque is reduced with > microsteps. It makes sense too, full steps use full current that is > switched between coils just 100% on or 100% off. With microsteps one > coild gets perhaps 3/8 of full current and the other gets something > like 5/8. So the current is overall reduced. > > In any case, run the motors at a step rate that causes them to run > smoothly without actually stepping. You want to see continuous motion. > > BTW I'm using a DM542, the same driver you have on this vertical axis test > (link below). It has enough power even when doing 1/2 steps to move a 35 > pound chunk of steel up and up at a decent rate of speed. machine is > obviously not balanced like a telescope The DM542 is set for only 2.0 amps > so it is not running at full power. SO you will be fine even with the > reduced torque. > > > This is the first time this axis ran. Just some jogs up and down. But > listen to the motor, you can't start and stop these stepper motors > instantly the velocity ramps up and down. In fact this rate of change > is as fast as I can go with this setup and the DM542's 2.0 amp current limit. > If you do a fast slew to a target, you need to ramp up the speed > then slow down and hit the mark and then pick up the star tracking > rate. That second loop controls the speed and the rate of change of that > speed. > Software was to plan the motion in advance so that it start to slow > soon enough not to over shoot https://youtu.be/tlMTksuOuZQ > > On Mon, Jul 13, 2020 at 11:51 PM Gene Heskett <ghesk...@shentel.net> wrote: > >>> The driver tech-sheet basically says it can do pretty all it's >>> available micro stepping with a 1.8 degree stepper motor, I wonder >>> if that is really true. >>> >> In theory yes, in practice, no. There is resistor tolerances and all >> sorts of errors that can creep into a motor being held by the >> relative balance of the currents thru 2 sets of coils. > _______________________________________________ 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
