Re: Futaba Pulscale "CMC" Manual Needed

Are you sure the servos are AC motors? It was common with this
vintage of equipment (1970's) to use DC motors (have brushes) driven
by phase angle controlled SCRs powered from 3 phase AC input. If this
is the case you will need real 3 phase power input. These systems had
really low servo bandwidth (100 Hz typical) and are prime candidates
for retrofit. Keep the motors, add rotary encoders to the motor, and
use a PWM servo amplifier that uses a DC power supply that can be
built to operate from single phase. The encoders on the motor are
recommended because wider bandwidth servos can difficult to tune if
there is any backlash between the motor and the encoder. Put a VFD on
the spindle if it is really an AC motor (check, many were DC in the
1970's).

Regards,
Steve Stallings
www.PMDX.com


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "m_gershowitz"
<mgershowitz@s...> wrote:

> Hi Folks:
>
> I'm hoping someone can help me out with some information on an

older

> CNC controller that was used on a Bridgport retrofit that I just
> acquired (but have yet to take delivery on) for home/hobby use.
>
> The unit is a Futaba PulscaleCMC model PCM001 with AC servo motors.
>
> I know that Futaba made DROs - this isn't one, it's a CNC
> controller. It does use glass scales, I'm presuming to 'close the
> loop', but it happens that the scales on the mill

are "Heidenhain".

> The controller panel, servos and servo drivers are all clearly
> Futuba labeled (although the servos are Shinko Electric, re-labled
> by Futaba).
>
> From the way it the drivers are wired it appears that 3-phase is
> used by the servo motors.
>
> I'm hoping someone is familar with this setup, and maybe even has
> some manuals on it. I'd gladly pay the cost of repro for the
> documentation. I haven't been able to find anything on the web.
>
> My understanding is that Futaba was in the CNC business in the '70s
> but got out of the business shortly after entering.
>
> I've got plenty of photos I could post if that would help ID the
> unit. It's in great shape, and I'm told it works fine (still need
> to get the machine powered before I'll take delivery). My biggest
> concern is if I'll need true 3-phase supply (ie; rotary converter)
> to operate the system, or if I can get by with single phase and a
> VFD for the motor.
>
> Thanks for any insights you can provide.
>
> Mike G.