Re: How to get a signal to controll spindle speed?

["Peter Cook" <kf2qd-at-terraworld.net>]

Using a standard servo axis should work - a spindle is basically an axis
jogging at a fixed feedrate indefinately. Shouldn't be a real problem for a
card like the Servo-to-go board. Other options would be to look into the
brushless drives built by several manufacturers - most allow parameters to
be set through a serial connection with +- jogs through hardware pins.
Also - a spindle may need more torque than a axis. Still would not allow
thread followinf, but would allow a stable spindle. But what about constant
surface speed - on a lathe?

Much of this conversation seems to be thinking only steppers - While they
may be inexpensive there is still a great deal of trying to design around
the limitations of steppers speed and torque both hit the wall rather early
as compared to servos - servos do have a higher cost but they have much
higher performance - speed and torque as well as position feedback which
makes for much more opportunity for precision and repeatability.

I had thought that EMC was intended as project with a view towards
developing a viable CNC for real machines in an industrial environment.

Has anyone looked at Sercos - a PCI card with 2 fiber connections and you
can daisy-chai a number of axis from it. I ave seen a machine running this
way at my former job. Amp and motor are a bit expensive but no encoders are
required - feedback comes through sercos.

Pete
>
> the PC speaker can be reprogrammed to generate a PWM signal
> using the spindle enable pin on the paraport to gate the output from the
> speaker to the spindle
>
> or using serial DACs
> paraport version (bit banging a crude serial port on the lpt port)
> long URL
> [
>
http://www.e-insite.net/ednmag/index.asp?layout=article&stt=000&articleid=CA
170222&pubdate=10/11/2001
> ]
> serial port (RS232) version
> [
> http://archives.e-insite.net/archives/ednmag/reg/1997/030397/05DI_03.htm
> ]
>
> for the feedback signal a PIC to read the spindle encoder and
> send position or velocity updates back on the serial port
> if the PIC has enough pins it could also be used to offload the
> analog/PWM function from the PC
>
> there are some multifunction 'smart' servo amps that have all this built
in
> a good example would be this one (cause its the one I have :-)
> http://www.compumotor.com/manuals/BL/BLHX.pdf
> the drive can be programmed to work in several modes for
> positioning,velocity and pulse folowing with an electronic gear ratio
> for threading/tapping
> it communicates over the serial port with simple mnemonic commands and
> includes some extra user I/O pins
>
> Brian
>
>
>
>