Q1: What else is there when trying to get closed loop performance with a PC component that plays well with the steppers and such. Drivers for Mach 3/4 seem hot or miss. Amen for Jim and his work on some software!
Q2: from Jim's post on an attempt with Mach 3. It seemed he is noting that mach3 and the controller do no play nice unless you can get into velocity mode. Is that what we're trying to solve here w all the new gear?
Good questions. I will only address Mach3 here, I've had no experience with Mach4. Thank you for the kind words.
Using Mach3 with closed loop steppers might work OK, I have never had the opportunity to try it. IMHO that is still only a partial fix. The closed loop stepper motors will try their best to go where the program tells them to go, but the program still has no idea what the motors are actually doing. But still much better than an open loop (or more properly, no loop) Without error correcting feed back (servo loop, that is updated every few micro seconds) the system can not be accurate all the time.
I have found that real problems happen if you undersize the stepper motors or you are using the correct steppers and try to run at higher speed. If the motors lose pulses there is no way to compensate because the controller program has no idea what the motor is actually doing. I have not had this problem running at low speeds and low acceleration rates. There is one other factor and that is the Windows OS, if it decides to go do something else for a bit, Mach3 gets confused and loses its mind. The fact that ArtSoft can get their software to run on Windows at all is a testament to their creativity. In Mach3 have only used the standard parallel interface and the Galil plug-in. IMHO the gentleman who wrote the Galil plug-in made a tactical error in the architecture of the software. He tried to make a parallel port out of the Galil controller rather than letting it do the heavy lifting.
Mach3 won't work at all with steppers in velocity mode with out adding a motion controller of some kind and encoders because position feedback is required. There are a few motion controllers available that may be compatible with Mach3, at least their advertising indicates that they are, I have no personal experience with them.
In velocity mode, the stepper acts exactly like a servo motor under analog control, and the servo loop must be closed. Most stepper drives do not have the capability of operating in velocity mode. The analog input signal is converted to a bi-directional pulse train inside of the drive, normally in the 20,000 pulse per revolution range. The motion controller normally would not know it is running a stepper motor.
