Re: Stepper spindle drive

Dave,

Thanks, I would like to look at the schematic. I believe mach3 does
just what you have described with user set accel, decel ramp using
step and dir pulses. If I can't get it to work, your idea may become
necessary.

Keith

--- In CAD_CAM_EDM_DRO@yahoogroups.com, David Speck <Dave@D...> wrote:
>
> Keith,
> I'm building a big CNC wood lathe (12" x 120"), and intend to use a
> salvaged 1.5 HP AC servo motor to turn the spindle. (The X axis
will be
> moved by a 4 HP AC servo salvaged from the same IC parts placer machine
> over an 80" travel.) By feeding a DC voltage to the input line of the
> servo amp, I can make it turn at a constant rate in either direction.
>
> I see no reason why you shouldn't be able to build a hardware pulse
> generator to produce a series of step pulses to the axis motor. When
> you are doing simple round turning, use a DPDT switch to switch the
step
> and direction inputs of your stepper driver board to a simple SPDT
> switch for your choice of directions on the direction line, and the
step
> line to your step pulse generator. When you want to do spiral turning,
> switch the driver input lines to the output lines of your computer.
>
> One of the list members sent me a schematic for an
> acceleration/deceleration circuit that produces a pulse train which
> gradually increases in frequency up to a preset limit when started, and
> then winds down gradually when shut off. If you have a big workpiece,
> this is much safer, and will produce much more reliable results than
> trying to accelerate a heavy workpiece instantaneously from a dead stop
> to full speed. I can dig up the PDF of the circuit and send you off a
> copy if you are interested.
>
> HTH,
> Dave
>