On Saturday, March 31, 2012 01:44:21 AM Jon Elson did opine: > Jan de Kruyf wrote: > > Do you get those errors with servos Gene? or with steppers! > > > > I am interested, since Jon was praising that board so much. > > > >> But I am encountering following errors after the motor has reached > >> speed and moved a good distance at that speed, but don't know what > >> to adjust that affects that. > > This is caused by requesting a greater pulse rate than the base thread > can put out. One possible cause is if the pulse width setting is > made too large. You want this set correctly for the motor drive, > but not any larger. Then, figure out at what feedrate the error shows > up. Say that is 50 IPM. And, for example, say it takes 30,000 > steps to move one inch. (50 IPM / 60) X 30,000 = 25000 steps/second. > Now, assuming you are using the best step generator scheme which > times the pulse width, if your base thread was greater than 40 us > (40,000 ns) then you can't go that fast. Or, if you set the step pulse > width to 20 us, then you can't go that fast. (50% hi, 50% low, of > 20us each adds up to 40 us. > > So, just do the calc, and see what time is 1/step pulse rate, and then > compare to your base thread time. Your base thread really needs to > be MUCH higher than the fastest step pulse rate, due to the granularity. > > If the machine were running at a speed where every other base thread > cycle produced a step pulse, then the next higher speed would require > a step pulse EVERY base thread cycle, which is a 100% speed jump. > LinuxCNC can certainly send pulses at that rate, but that is too > large a speed jump for the motor to follow. > > > Jon
ATM, I am waiting on connectors that will allow me to make much shorter parport cables so I can experiment with narrower pulses. A 6 foot, round cable has got to ring like the liberty bell so I hadn't tired shorter pulses. ATM pulse widths are set to 3 u-s, as is dir setup and dir hold. 20 u-s base thread on a D525MW board. I'm hitting the errors at 39-40 ipm. I am beginning to think I should tolerate the noise and go back to 8 microsteps to get the higher speed. I expect I'll have to make a damper for the z motor in that event. Thanks Jon. 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) My web page: <http://coyoteden.dyndns-free.com:85/gene> HEAD CRASH!! FILES LOST!! Details at 11. ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
