Re: [CAD_CAM_EDM_DRO] Spindle RPM control

Jon,
You are so right. Oh well.
RichD


Jon Elson wrote:

>
> RichD wrote:
>
> > CNC Idea!
> > RPM control of a spindle motor (controller) with a frequency to voltage
> > converter by using a spare axis CNC control program step output.
> > The rate is set in any block with the F word as needed.
> > The direction bit can control on/off/disable if wanted.
> > The FVC output will substitute for the pot in a typical PWM full wave
> > rectifier controller such as used in the Sherline machines.
> > The KBE controllers can be used in this manner.
> > This idea sort of is a poor mans constant velocity control or speed change
> > for various reasons in special cases.
> >
> > Is this viable, plausible or practical?
>
> The problem is that most CNC programs do coordinated motion on all axes
> simultaneously, so the spindle would stop every time the other axes stopped,
> and would be ramping up and down with every feedrate change as the axes
> accelerated and slowed.
>
> > I have not identified a VFC chip as yet. Do they exist?
>
> Yes, but for this purpose, simple circuits might do just as good a job.
> A pulse stretcher, made from a one-shot, followed by an integrating
> op-amp to smooth out the pulses would do it.
>
> Jon
>