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« on: April 26, 2009, 02:22:52 PM »
I see my previous post probably was an answer to a question nobody have asked......
Back to the continuous run question.
I don't know how fast an indexing board type axis can spin, probably not that fast due to the gear ratio. If so, not well suited to turning small diameter pieces.
But here is what I'm thinking on. Maybe a complicated system.....
Setup:
A turn spindle with a 3-phase motor and an encoder connected to a board receiving position signal from Mach3 and controlling the VFD with say a Hz signal. A Hz signal is probably the most accurate type of signal due to its precisely controlled frequency. Another encoder connected to Mach3 for visual control of the rotational position with high accuracy.
Control:
When requiring continuous rotation for turning, make a button in Mach3 sending a 5V signal via a BOB to the VFD. This VFD input is configured in the VFD to place it in "Continuous rotation mode" regulating the spindle speed from a spindle speed signal from Mach3. That should be easy to configure Mach3 to do.
Shifting back to "Rotational position control" is done by manually by hand or by manually driving the VFD to a position where the encoder in Mach3 is ending at 20, 40, 60 or 80.0000 degrees. A mark on the spindle indicates which of these rotational position is the original "zero" position. When this position is accurately achieved then zero the A position and switch off the button sending the "Continuous rotation mode" signal to the VFD. These two operations should be done by one single button with a VB script.
Edit:
It is also necessary to reset the encoder board controlling the VFD when shifting from Continous rotation to Rotational position control. Or possibly better remove the power from the board when shifting to Continous rotating mode and reconect the power when entering Rotational position mode.
In this way it is possible to run in "Rotational position control", shifting to "Continuous rotation mode" and back to "Rotational position control" without missing steps or position.
Say first milling some keyways, then do some turning and then do some more milling while retaining the exact same rotational position as when milling the first keyways.
The only thing is I don't know if it exists a board with an encoder input and a Hz or PWM output.