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« on: May 23, 2013, 12:48:18 PM »
Hi guys,
Just joined the forums after finding this thread, after several years of good operation the exact same problem as described by Lewis has popped up with my Sherline mill and lathe, both setup using the Sherline box. All attempts at changing Mach software settings were fruitless, so I got out the oscilloscope and starting probing around. The Mach output signals from the parallel port seems good, with ~40usec separation between the direction and step pulses and nice sharp transitions, but the direction signal at the microcontroller pin inside the Sherline box gets smoothed out on the downward edge only, making it likely that the step pulse immediately after this change in direction is counted for the opposing direction. The net result is that one direction change is OK but the reverse direction change misses a step. Accounting for this step error in how the Gcode is written does fix the problem, but of course the coordinates shown in Mach3 no longer represent reality.
I have two of the Sherline boxes and will probe all x-y-z-a channels to see if this problem occurs on all of them. In the meantime, is it possible in Mach3 to adjust the separation time between a change in direction pulse and the next step pulse? Otherwise I need to try to sharpen up the direction pulse in hardware somehow.
Really appreciate this thread and everyone's contribution to it!
Freddy