On Sunday, April 03, 2011 10:06:18 AM Andrew did opine: > Hi, > I'm new to EMC2, so please help me correctly understand stepper setup. I > have DMM tech servos
Googling for DMM tech, I was unable to find any readily posted info that would be helpful. Perhaps buried in the PDF's from their site? > in step mode, 2000 steps per rev, Step Time is 2000 > ns, Step Space is 1000 ns, Dir Hold and Setup 10000 ns, Latency is 6500 > ns. Stepconf gives Min base period 15500 ns and Max Step rate 64516 Hz. > But calculating > http://wiki.linuxcnc.org/uploads/StepTimingCalculator.odsgives > absolutely other values: > Recommended BASE_PERIOD 9500 ns, and let's say Actual BASE_PERIOD is > 12000 ns, then Maximum step rate is 41667 steps/s. > Manual > http://www.linuxcnc.org/docview/html/motion_tweaking_steppers.html says > "two periods to make a step", but it seems that Stepconf calculates it > different way, or I just do not understand something? > Also, in Stepconf I set Driver microstepping to 1, is it correct? Probably not. If these were real steppers, and the setting was for 2000 steps/rev, then the micro-stepping would probably be set to 10 since the raw step size of a normal stepper motor means 200 steps/rev, and finer positioning is achieved by tweaking the individual coil currents to set the motor in smaller steps. emc needs the steps setup in the measurement units you are using, and this is dependent of the TPI of your driving screws times any gear reduction times the microstepping setting in use. Assuming your machine is running in inches, and the screw is a 10 tpi screw, direct drive, then that axis will be set for 2000*10 or 20,000 steps per inch. If you have any reduction drives between the motor and the screw, this number gets multiplied by the ratio of the reduction. Emc happily munches these numbers in floating point format, my z axis setting is running with 5 digits either side of the decimal point. Working in the millimeter world, the approach is identical in that the number emc expects will be the steps it takes to move that axis by 1mm. Its all just numbers to emc. However, it has not been 2 base periods/step in emc for quite a while as emc now resets the step it issued at the start of a base period at the end of that period, so that emc can now issue a full step per base period. That wiki page may be in need of some TLC. ;-) Those timing figures above indicate DMM Tech has considerable noise filtering in their interfaces, and meeting those specs will probably slow the maximum base period somewhat. My own, much smaller stepper driven setup is speed limited by the motor power supply (28 volts) to about 25 IPM, and the computer, an XP1400 athlon running at 1600, and while I can run at a 30 u-secs base period, the machine is just as happy, and the computer much more responsive at 40 to 50 u-secs. I would DL and read the PDF files available from their site as there may be more precisely stated info in them that would be helpful. What sort of a machine are you driving? Links to pix, or a you-tube video would be nice. :) -- Cheers, Gene "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) <http://tinyurl.com/ddg5bz> <http://www.cantrip.org/gatto.html> Function reject. ------------------------------------------------------------------------------ Create and publish websites with WebMatrix Use the most popular FREE web apps or write code yourself; WebMatrix provides all the features you need to develop and publish your website. http://p.sf.net/sfu/ms-webmatrix-sf _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
