Anyone care to guess what this is? Is it a computer even?

Rick Bensene rickb at
Sun Aug 14 14:02:50 CDT 2005

> Looks like a CNC controller to me.

Actually, it's most likely not a CNC controller. It's probably too early to
be a "Computized Numerical Control" device. There's probably no computer at
all in there.  It's likely an NC (Numerical Control) controller.  The
difference is that NC controllers are "hard-coded" logic,
purpousefully-designed for controlling a specific piece of Equipment.  Once
minicomputers got inexpensive enough (e.g., PDP 8/e and smaller PDP 11's),
they were a natural to become the controllers.  But, in the late '60's and
early '70's, it was more practical to build dedicated hardware to do the
work.  Later, microprocessors took over for the minicomputers, and nowadays,
the controls are generally just PC's with specialized interfaces in them to
drive the steppers, control spindle motor, and read absolute or incremental
position encoders.

This Houdaille controller looks VERY similar to a Houdaille control that was
connected up to a Burgmaster vertical mill at my Dad's machine shop in the
mid-70's.  He bought the machine used, and the control was dated from the
early '70's.  There was no computer was simply a dedicated
function state machine which read codes off of the paper tape
step-at-a-time, and directed the action of stepper motors connected to each
axis of the machine to carry out the operations.

The old hardwired control on the Burgmaster failed at one point, and it
wasn't worth it to repair it, so it was replaced with a later model
Houdaille control that utilized an Industrial 8/e as the brains for the
control.  This was the first "CNC" control in my Dad's shop.  Input was
still via paper tape, but the whole program was loaded into memory at once,
and executed out of memory, rather than the step-by-step reading of the
program on the earlier control.  It was also possible to edit the program in
memory to correct errors discovered once the program was run on the actual
hardware.  The Industrial 8/e had a ROM board in it that contained the
control software.  Software updates for the control were performed by
installing new ROMs.

The first NC machine in my Dad's shop was a Rambaudi vertical mill, with a
very early Superior Electric Slo-Syn NC Control.  The control was all IC's.  It was housed in a 6 ft. tall 19" rack, with many,
many small circuit boards plugged into a wire-wrapped backplane.  It wasn't
a very smart couldn't do absolute positioning...everything
was relative.  My dad let me write a program to do a complex part that had a
lot of drilled and tapped holes in a big plate of steel.  I got to punch it
up on the Flexowriter, and it ran perfect the first time.

Rick Bensene
The Old Calculator Web Museum
Beavercreek, Oregon

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