Originally Posted by pgruendema  You mentioned 2000 line encoders which are the same as 8000 count per revolution. This allows extremely fine position control, finer than is needed for milling but might be ok for a cnc jig grinder. And your PC controller can output perhaps 30,000- 50,000 steps / second so you might be stuck with a machine that positions very precisely but has a top speed of ten inches/ minute.
Generally the USB port is by design not a real-time device. The parallel port is. To get real time pulses out of the USB port the pulses are generally stored in an external box which then parses them out on a real time basis. Extra complexity but it can do so faster than the parallel port.
Pete |
Mach3 can output 100,000 steps per second through the parallel port, and up to 4,000,000 with the soon to be released SmoothStepper which uses USB.
www.warp9td.com Projected price is just over $150
You can also use a Gecko G100 with Mach3 to get up to 4,000,000 steps per second via ethernet.