On 2007-11-28, Jon Elson wrote:
DoN. Nichols wrote:
Jon Elson wrote :

Just as it is the one advantage of a drum plotter which I have.
Resolution is 0.010", almost direct drive of stepper motors from the
computer, something like a 15 V input signal, even though it was low
current. It required a special wire-wrapped interface from my SWTP
6809.

I still have a Calcomp 1076C plotter,

Yep! Calcomp was the brand.

takes up to size E paper,
has servos that give 3 G accel and 50+ IPS motion. Mostly it
just tears paper and wrecks $30 ceramic pen nibs (probably
because I don't know how to set it up right.) I haven't turned
it on in 5+ years, but being high-quality gear it most likely
would fire right up if I did.

Hmm ... a much faster one than what I have. The pitch of the
steppers is in the mid-low audio region -- 100 Hz, IIRC.

I did just get a color laser printer off the loading dock at
work, where people set cast-offs that somebody may want. It
almost worked, and with a little web searching, I found there's
a little damper pad that works out of position and fouls up the
pull-in time of a solenoid. Difficult to get to, but insanely
easy to fix once you have it apart. Prints incredibly good
color output.

Nice! I've got an HP LaserJet 5C which has died as a result of
a series of power glitches when a tree was blowing into the big
three-phase wiring at the head of the block -- which I can't get as
three phase in the house here. :-(

It appears to have blown a fuse -- but I can't find a fuse
anywhere accessible from the outside, I guess that I'll have to rip it
apart, which is going to need some help moving it to where I can work on
it. Too little access from any side but the front where it is.

Or -- get a more recent laser printer -- though the LaserJet 4+
still works beautifully.

The advantage of that roll paper feed was that I could directly
plot the fret positions for a stringed instrument.

A friend of mine did exactly the same on an ancient Calcomp at
the Wash Univ. data center some 30+ years ago.

Probably the same model of Calcomp. It was a three digit
starting with 8 (the paper roll width in inches, IIRC). There was also
a three-foot wide one at work.

[ ... ]

My hardware runs on an IEEE-1284
capable parallel port. Is the real time compatible with rtai?


RTAI? What is that?
Rtai is the current real time "extension" for Linux. It
actually runs above the Linux kernel, and makes Linux the lowest
priority task. The RT programs run as loadable kernel modules,
and run with kernel privileges, and also kernel restrictions.

Hmm -- I don't know, to be honest. I seem to remember that the
EMC project has gone through about three real-time mods to Linux over
time, and what you are describing sounds like the first.

The later Suns (including my SB-1000s)
have a fully programmable parallel port, once you find the right termio
signals to send to the driver.

The advantage of the IEEE-1284 (EPP) mode of the PC parallel
port is it does all the handshaking between the PC CPU and the
device(s) on the parallel port in hardware, so you can read or
write a register on the device with a single CPU instruction,
and do single-byte transfers at the rate of every 800 ns or so.

O.K. I've not tried low-level driving the parallel port on
these -- I've pretty much ignored it.

What I would like would be a small box which would hang on the
ethernet and translate packets to what is needed for the controller
hardware.

Do you know that the X-axis ballscrew does not turn?

Yes, and I've actually got a screw made like that from some
other machine, but it is obviously not a Bridgeport BOSS part.
It actually would work pretty well, and I may use it, but I will
have to machine all the attachment hardware to use it. I'm
still deciding whether that screw should go on the mill or the
lathe.

O.K.

And do you have the Series-I head for the CNC version? The ball
screw for that is hollow -- surrounding the quill, with the ball nut
rotating around that, so the thrust is truly on axis.

No, I do not have this. I have a usable 1J head that I have
added a ballscrew assembly to the front of the housing, as close
to the quill as I can get it. It has a little flex in the
linkage, but the backlash is barely over .001",

That sounds like the conversion which Anilam hung on a Taiwanese
clone of the Bridgeport which we had at work. The main worry was that
the off-center thrust would accelerate wear of the quill in the head
casting -- especially with the number of cycles possible with CNC.

so I am mostly
satisfied with it. You can see my insane hack job of a retrofit
http://jelinux.pico-systems.com/CNCconv.html

O.K. That looks reasonably workable.

You know that the EMC project has moved outside of NIST now, and
is under the URL of www.linuxcnc.org IIRC.

Interestingly enough, this has drifted back *on* topic -- still
without the "Subject: " header changing, however. :-)

Enjoy,
DoN.

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