Steve Blackmore wrote: > On Wed, 16 Sep 2009 12:16:02 -0500, you wrote: > > >> >> This whole thread is about using the SOFTWARE enocder counter (a HAL >> component) for the >> spindle position. >> > > Is it? I started the thread :) Well, I thought that was the original problem, that the software encoder counter couldn't keep up with a moderately high resolution encoder on the spindle. > All I'm personally interested in is > threading accurately. As I understand it, it waits for an index pulse > before starting a threading pass - I know that to be true, as > disconnecting the index pulse - it waits forever on a G33. > > Then information becomes woolly - I guess it uses the quadrature count > to get an accurate speed and adjusts the Z feed accordingly?? > > My 3 phase VFD driven spindle isn't capable of behaving like a servo, so > spindle positioning is unnecessary for me. > > Yes, but EMC2 by default expects a 3-channel encoder on the spindle to accurately slice up the rotation and synchronize the Z feed. Without the quadrature counts, it can only extimate velocity once per revolution, and the velocity estimate may take a long time to settle after and disturbance. Also, without the quadrature signals, it is impossible to tell spindle direction, so rigid tapping is impossible. > > > 125 count (500 quadrature counts/rev) works fine here via parallel port. > > Depending on the BASE_THREAD interval and the maximum spindle RPM, you can get by. At 3000 RPM, you'd have 50 * 500 = 25,000 counts/second. If your BASE_THREAD was 40,000 (40 us) you'd be right on the edge. If your spindle never goes that fast, or your BASE_THREAD is faster, then you are OK. I just prefer to have LOTS of headroom on the encoder counter.
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