Re: Re: DON'T CUT THOSE WIRES !! and My CNC Mill retrofit project
Posted by
Jon Elson
on 1999-10-13 22:15:36 UTC
Andrew Werby wrote:
up a circuit to simulate the function of the paper tape with a program
that ran under DOS. I could download the executive software that
made the machine into a CNC, and then 'drip-feed' the part program
as the CNC needed it. It would even pretend to back up the tape if
you wanted to re-execute a block or two, and allow you to search
the 'tape' for specific block numbers, etc. It was also at least 4 times
faster than the physical paper tape reader. I had to limit it to about
1000 chars/sec or it could overload the CNC cpu.
Well, it worked, and it got my CNC system making parts, but it had
a lot of problems, mostly loose connections, but also a blown high-voltage
diode in the CRT sweep circuits, and a blown static RAM in the
video generator. Bad connections in the battery back-up power supply
caused it to lose its program memory every once in a while. It became
obvious that it was not going to get any more reliable, at least without
a lot of work. Every time a problem developed, and you pulled a
card out, connectors all over the thing went flakey, and front panel
buttons or lights failed to work, etc.
Fortunately, EMC was getting usable at about that time, and when I was
able to make the switch, I never went back!
Jon
> You can feed G-codes from any program and computer. These oftenI did this with an Allen-Bradley 7320, a 1978 vintage control. I built
> used paper hole tapes, and don't always have a high baud rate, but
> - it is so much faster than the movement of the axis anyway.
>
> [I thought of trying this, but the machine's controller seems to be in such
> a fragile state of health that I figured it would be best put out of its
> misery. Doing this, I can easily see getting into a situation where I
> wouldn't know what was screwing things up- the patched-in drip-feed, the
> old computer, or the associated maze of circuitry.]
up a circuit to simulate the function of the paper tape with a program
that ran under DOS. I could download the executive software that
made the machine into a CNC, and then 'drip-feed' the part program
as the CNC needed it. It would even pretend to back up the tape if
you wanted to re-execute a block or two, and allow you to search
the 'tape' for specific block numbers, etc. It was also at least 4 times
faster than the physical paper tape reader. I had to limit it to about
1000 chars/sec or it could overload the CNC cpu.
Well, it worked, and it got my CNC system making parts, but it had
a lot of problems, mostly loose connections, but also a blown high-voltage
diode in the CRT sweep circuits, and a blown static RAM in the
video generator. Bad connections in the battery back-up power supply
caused it to lose its program memory every once in a while. It became
obvious that it was not going to get any more reliable, at least without
a lot of work. Every time a problem developed, and you pulled a
card out, connectors all over the thing went flakey, and front panel
buttons or lights failed to work, etc.
Fortunately, EMC was getting usable at about that time, and when I was
able to make the switch, I never went back!
Jon