Re: Re: bridgeport series 1 retrofit

Hi Bob (comments mixed in)

> From: "Bob Japundza" <bjapundza@...>
>
> Thanks for the help guys. I really like the idea of booting off the
> morphix cd. Right now I'm going to stick with the Morphix-based
> BDI. I was just thinking that more recent versions of Redhat might
> be more stable/reliable. But it just doesn't get any easier than
> booting from cd and not having to do any setup. That's pretty cool.

I built a custom CD here a while back for my Sherline. It worked.

> Last evening I was studying how the bridgeportio piece works. The
> way I understand it there is a PLC piece to EMC that handles the
> coolant, spindle, oiler, variable speed, etc. So now that has
> brought up a bunch of questions in my mind.

The file bridgeportio is a c language program that watches a parport for
some input signals and watches the EMC for some output signals like those
you list. It is a logic controller but programming it is not easy. The
specific pins and polarities can be changed in the INI file but that and
how long to wait for spindle brake is about all that you can do.

> When I bought my bridgeport two years ago the machine was
> cannabalized, no steppers or air motors, enclosure, etc. So I
> assume that the plc code was designed to operate plc's which
> controlled air motors, solenoids and relays. Since my machine came
> without these parts, I was thinking that instead of the air motors
> that were used to control the variable speed and brake mechanisms, I
> would use a small stepper and a solenoid instead, driven by a PIC18F
> and an allegro stepper driver and some relay drivers. So, my
> question is (before I scope it to see what is happening), what type
> of output on the bridgeportio pins am I going to expect? I assume
> for spindle speed control (for example) that I would get some sort
> of pulse train to increase, and a different one to decrease; logic-
> level outputs for coolant on/off, etc. Is this correct?

The file was written for exactly that kind of bridgeport control. It uses
the same kind of logic as for coolant -- pin 1 on for up and pin 14 on
for down. I don't know of anyone using these pins so I can't say that
they work but they should.

> Also, I will be using a vfd to control the motor (no three-phase
> where I live); I'm wondering if this may be the better route to
> controlling the spindle from emc than it would be to control it
> mechanically. I could put a crank on the variable speed and leave
> it somewhere in the middle, and use the vfd to do braking, rapid
> reverse for tapping, increase/decrease spindle speed etc. What do
> you guys think? VFD or go the manual route?

If you run this as open loop (no spindle speed feedback) we would have to
figure out a way to get the signal to the vfd. If the vfd had speed
increase and decrease inputs that would work. The ones that I've seen
had +-10 or 0->10 volt and direction. I've also seen ones with a couple
of fixed speeds that could be triggered by external contact closures.

The direction and 0->10 volt might be interesting. There was an analog
pin that worked a long time ago. I believe that it was pin 3 on a
standard setup. If we could get the code to spit out a pwm signal there
you could integrate that and use it along with the forward and reverse
pins.

Hard tapping would require that you also feed spindle speed into the EMC.
This would require an encoder reader card like Jon Elson's servo setup.
It would also require a bit of code work to enable electronic gearing
during the tapping move.

Hope this helps

Ray