Hi Jim On Friday 03 March 2006 15:50, Jim Fong wrote:
I'm currently running BDI 4.38 on a Pentium2-400Mhz PC. I recently installed a new 276oz-in stepper motor on my X-axis and trying to tune EMC for higher rapid speed. The fastest reliable speed I can get is 25IPM (500RPM, 20TPI leadscrew, 13333 pulse/second) with my 8microstep driver. Anymore than 30IPM, you can hear the stepper motor getting rough sounding (jitter??) and motor stops spinning. The period is set at 0.000007. I have tested it set at 0.000005 (any lower PC locks up and resets) but I still can't get any faster or more reliable pulse out of the parallel port. I played around with the P setting but just makes it worse if set over 1000.
I currently set the MAX_VELOCITY = .41 (25IPM) since that seems to be the most reliable speed I can get for now.
Anyone out there running a similiar speed PC and what is your fastest pulse output? 13,000 steps/sec seems rather slow to me.
Dug out my little Sherline and ran a few tests this morning. The computer is a Celeron 433 with a 440BX chipset, and a C&T 69000 graphics controller (2MB memory running at 800x600), currently with 256M of memory installed. Probably close enough in specifications to do a reasonable comparison of EMC's performance.. The stepper motors on the Sherline are fairly wimpy little NEMA23 rated at 134oz-in running from a unipolar driver - Not the best combination for maximum performance.. About the best I can achieve is 25ipm with a 7.5uSec base period before the motors start squawking and I loose steps (some 6.7KHz). Reducing period to 15uSec, and the maximum speed increases to 30ipm. [Sherline uses 16000 steps per inch when using their driver box]. Hooking up a scope, I see a pulse train right up to 240ipm or 64KHz with a 7.5uSec period. There is a fair bit of jitter which could explain the lower max speed. At 15uSec, the pulse train is much smoother with little noticable jitter, but maximum frequency is limited to 33.3KHz. I would suggest hooking up a scope if you can get your hands on one, quantifying the jitter and selecting a period to suit - I can run at 7.5uSec, but jitter is a problem, the same at 10uSec. 15uSec produces the better results when using quickstep, but your milage may vary. Regards, Paul. -- From the Klingon book of C: Klingon function calls do not have 'parameters' - they have 'arguments' - and they ALWAYS WIN THEM.