John Thornton wrote: > I notice on stepper charts for speed vs torque that the bigger the motor > the lower the RPM at max. Looking at the Nema 23 STP-Mtr-23079 from > Automation Direct the Chart stops at 1350 RPM. > > http://web1.automationdirect.com/adc/Shopping/Catalog/Motion_Control/Stepper_Systems/Motors_-z-_Cables/STP-MTR-23079 > > Will the steppers go faster or is that about as fast as a 276 oz-in > holding torque, > 2.8 A/phase, 1.8 degrees / fullstep (200 steps/revolution), NEMA size 23 > motor will go? > > At 1350 RPM provided I can have low enough friction to go that fast and > a 10 to 1 pitch screw driven 1 to 1 from the stepper I can get 135 > inches per minute, right? > If you are not using hardware step generation, and especially with microstepping drives, this speed is not achievable. Consider 1350 RPM x 200 step/rev x 10x microstepping = 2.7 million steps/minute. Divide by 60 to get 45,000 (micro)steps/second. That is severely pushing even the fastest software step generator, requiring a transition every 11 us. Of course, the granularity at that speed and interrupt rate would be 33% (jump from a full cycle of the step pulse every 22us to every 33 us). No way can the motor follow that big a jump in speed.
I demoed a 150-Lb minimill at the NAMES shows in 2003 and 2004, I think, with the motors spinning at 1440 RPM, using Gecko 201A drives and my Universal Stepper Controller as the step pulse generator, driven by EMC1. This gave 90 IPM on that machine's 16 TPI leadscrews. The motors were very old, round, size 34 motors. > How cricitical is the acceleration of the motor to not loosing steps? > > In stepper_inch.ini the MAX_ACCELERATION = 20.0 > Is that number inches per minute? > Quite critical, and no, it is 20 inches/second squared, assuming your user units are inches. I'd go for a number between 3 and 5, then decide if you can increase it. > The intergrater manual says it is in user units per second per second. I > don't understand that, can anyone say that in common talk? > Your user units are defined in the [TRAJ] section of the ini file, and may look like this : [TRAJ] AXES = 3 # COORDINATES = X Y Z R P W COORDINATES = X Y Z HOME = 0 0 0 LINEAR_UNITS = 0.03937007874016 ANGULAR_UNITS = 1.0 In the newest version, you can have : LINEAR_UNITS = inch ANGULAR_UNITS = degree If you find the above confusing, 0.03937... is the definition of a mm in inches. The definition was obviously backwards, for strange NIST historical reasons. > My thought is to use the Xylotex board with the above motor for X and Y > and a much smaller motor for Z again this is a portable plasma table... I also have doubts you can get any torque out of many motors at this speed, due to the lower voltage limits on the Xylotex. Ask if anyone has ever run a size 23 motor at 1350 RPM on a Xylotex drive. Jon ------------------------------------------------------------------------- This SF.net email is sponsored by: Microsoft Defy all challenges. Microsoft(R) Visual Studio 2005. http://clk.atdmt.com/MRT/go/vse0120000070mrt/direct/01/ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
