Re: My new mill

> Message: 5
> Date: Fri, 28 May 1999 16:21:14 -0500
> From: Jon Elson <jmelson@...>
> Subject: Re: My new mill
>
> Andrew Werby wrote:
>
> > From: Andrew Werby <drewid@...>
> >
> > [I just got my new (old) mill delivered yesterday, and it's really a beast!

[]

> the worst part is that the DOS environment is not secure!
> Any haywire program could overwrite the motion control
> code or data areas, and cause a hazardous crash! I sure wouldn't
> use such a system!

just remember, that no matter what software you use, ALWAYS have an
emergency stop button that kills the power supply/s directly, with no
software inbetween. sure, the software can detect it too, and stop
whatever it's doing, but the first priority is to power down those
motors.

(place I worked for was doing a machine with an embedded 68hc
controller which had the emergency stop into the board/software. one
day it went mad and coudl not be stopped, so we had 2.5 tons of
machine bouncing around the floor. it was under development and so
had not been bolted down (erroneously, bolt everything down), and
since it had out of balance moving parts, it bounced under high speed
input. normal operation called for controlled slowish speed
rotation, so balance was not an issue.

I know someone will ask what the thing did....
it was a shock absorber tester, loadcell on the end of the shock, and
an adjustable throw crank with 11kw 3phase motor and gearbox to swing
it at various rates to test the pressure differentials.
eventually the 68hc board was discarded as not fast enough and we
fitted a 486 and I rewrote the software in Qbasic 4. this had the
advantage of being able to display the load graphs directly, though I
had a nice runaround to get the code fast enough (try a 500 line
subroutine, any 'gosubs' to do menial tasks slowed it down too
much,and this was when compiled)
(yes, I wanted to do it in C, which would have worked first time, but
the boss decided Qb was quicker to program for the graphics and the
thing was already over time and over budget)


steam and wind

--
David Forsyth DaForce A-T Iwr.Ru.Ac.Za
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