Re: [CAD_CAM_EDM_DRO] Turning directions....... CNC Without a PC for Amish

wanliker@... wrote:

>In a message dated 12/23/2005 10:52:10 AM Mountain Standard Time,
>elson@... writes:
>
>We're going to get yelled at by the moderator any second, now, but ....
>
>
>
>
>Yup, please return to the original problem, how to do CNC without a PC, but
>keeping to the hobby side of the group, not the commercial usage.
>
>

OK, if electronics are OK, just not a computer, then you can use a
GE Century 100 control, or any of the other tape NC controls of that
same vintage, about 1965 or so. These had electronic digital servo controls
that did not use a stored-program computer, but instead had dedicated
circuitry to perform the calculations for servo loop and interpolations.
They usually used EIA character codes, but some could probably handle
ASCII by flipping a switch somewhere.

I don't really recommend such an outdated control, with several thousand
germanium transistors on paper-phenolic circuit boards. But, they would
fill
the bill for an NC control without a computer.

There is the Moog Hydrapoint, that used an entirely pneumatic NC control,
but it used a very bizarre tape format that would require a computer to
generate. The block of data that the tape reader detects all at once
literally matches the pattern of holes in coded plates that form the linear
position encoders on the machine. Fluidic logic determined how far to
deflect
the spool in the proportional servo valve to move the axis' hydraulic
cylinder.
If you know how to keep these running, it might actually be possible to run
one of these. But, you'd really have to have a special need, like running a
machine tool with no electrons being disturbed anywhere. I suppose if
somebody
had a need to run a milling machine in an explosive atmosphere this might be
pretty attractive.

As for the spindle, there have got to be many ways to do that.
Something like
a line shaft rig could be run to the belt on a Bridgeport-type head.
Hydraulic
or air motors could be adapted in place of the electric motor.

One could also set up an emulation of the old tape-NC control schemes
that could send step and direction signals to a Gecko-type drive. Normally,
one would use a CPU to do this, but you could do it in an FPGA without
the use of stored programs, if that is the objection somebody has to using
a computer.

Jon