Re: [CAD_CAM_EDM_DRO] Re: EMC spindle speed control

Marty Escarcega wrote:

> Nice to know some people are on board that can do some of the
> programming with EMC to make it a really versatile piece of
> software. Indeed, it would be nice to have have those
> outputs(forward/reverse/brake) drive a 3 phase FWD/REVERSE
> contactor arrangement, that would easily take care of that options,
> just use 3 control relays, FWD, REVERSE, STOP

Oh, this is all there, and has been for 2 years or so. I have the forward
and reverse hooked up through the parallel port, an Opto-22 type
SSR board, and to my VFD. I don't use the brake signal, as my VFD
determines the braking cycle all by itself, and has no brake command.
It will apply AC, and then DC braking every time the run signal is turned
off. There is a separate output pin on the parallel port for forward, reverse
and brake. So, you can hook up SSRs in the manner you choose to command
power contactors. I'd wire some sort of interlock contacts so the forward
reverse and brake relays are mutually exclusive, as closing any two
at once could cause a dead short, and weld the relays.

>
> Now the spindle speed control, only think I can think of is to use
> the control input of a VFD. Once set, don't the VFD's remain pretty
> constant? Feedback would be another issue. Only think I could
> think of is a rotary encoder like the one Dan Mauch sells to provide
> feedback to EMC/Computer.

EMC definitely doesn't have any provisions for feedback on spindle speed
to close a spindle speed loop. If you have a spindle encoder, it can take a
reference off that to do threading operations on a lathe, making another
axis follow the spindle at some ratio, also known as "electronic gearing".

>
> So, am I way out in left field? :-) Or reasonably close to home
> plate?

The particular parallel port pins for spindle forward, reverse and brake
are specified in the .ini file, in the [EMCIO] section. IE. spindle_forward_index
is the bit number on the parallel port that commands the spindle to start running
forward. Spindle_forward_polarity sets what polarity of that bit is intended
to mean start the spindle.

Jon