On 2026-07-08 02:46, Tim wrote:
On Tue, 2026-07-07 at 11:09 -0400, Frank Bures wrote:
In early 70-ties I worked as an electronics engineer in the design of a CNC
system. A prototype was being tested at a machine tool factory on a 6-axis
large milling center. As we made the system work for the first time,
feeling great about ourselves, a guy from the factory appeared and started
to madly press random keys. Suddenly the system moved, broke off a 25mm
milling bit that went flying, fortunately not hitting anyone, until it
stopped at the end point switch. "HA!", said the guy, "now explain why the
system moved when it should not".
Try to troubleshoot that, friends.
Yes, that's a hard case to work on. Software should check its inputted
data for sanity before carrying on. If more software did that, we'd
have far less exploits (work on acceptable data, completely and safely
discard anything else). But some random things could potentially be
acceptable inputs. Though that particular case of commanding the mill
to move past it's possible travel limits should have produced a "don't
do anything until corrected" error response, beforehand.
It reminds me of a story of how many people got burnt by an X-ray
machine that had been operated incorrectly in an unexpected way.
Absolutely.
However, bear in mind that this happened in early 70's in Eastern European
socialist country. CNC systems then were nothing more than interpreters,
reading G-language (something like a relatively primitive assembler) from a
punch tape (or keyboard in case of manual step-by-step operation). There
was no memory to speak of, no logs, nothing that we take for granted today.
What's more, we were under embargo (very effective, not like the current
sanctions against Russia) so almost no western parts were available. We
actually became sort of a legend when we created an Intel 8008 emulator
from discreet components on two Euro-sized cards, that actually ran the
system. The only info we had was a stolen Intel programming and
application manual. When the 8008 actually became available through some
Middle-Eastern country, they could simply scrap the two cards and wire the
8008 in. I was somewhere else by then.
Cheers
Frank
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