Re: Auto tool changers

Hi Bill,

I can see two ways to implement control of the tool changer. A
standalone unit driven by a PIC, or by a "canned routine" that is part
of the controller. I could quite easily add a canned routine to my
code, which wouldn't need the "handshake" that an external PIC
controller would require. An offshoot of this effort could be a small
program that would run on a "spare PC". It could a PC with only a
floppy (or solid state disk), no monitor or keyboard. As small as
possible. This is kind of a "black box" approach (good way to try some
of that out). If a keyboard and monitor were supplied, a parameter
screen could allow "tuning" the way the tool changer worked (positions,
travel past stops, stepper parameters, etc).

The PIC version is what I think you are interested in from previous
conversations. The PIC controller would only need a pb or so, and
perhaps a few LED's. The code can be written in C, however there would
probably not be parameters that could be modified. A small LCD screen
would indeed be possible, but would add to the complexity.

What stepper driver are you planning on using? You could cobble up a
unipolar drive. Four TIP120's, a 10 ohm power resistor, a 7400 gate,
and a 5V regulator would be about all you'd need.

Do you have a stepper bolted up to the tool changer? If you do, you can
try moving it with a controller program. This would determine worm
screw ratio, gear ratio, etc. What we're interested in is the number of
stepper counts for a full revolution of the tool changer head, and how
far past the positions we must travel.

Alan KM6VV


wanliker@... wrote:

>
> In a message dated 2/23/2002 11:17:44 AM Mountain Standard Time,
> KM6VV@... writes:
>
> > I am doubtful that the ratchet/paw mechanism on
> > the tool changer would allow reverse rotation for anything other then
> > "falling back" against the paw, and thus "shortest path", while
> > interesting, may not be allowed.
> >
>
> this is a correct assumption rotation is advance to position, reverst to lock
> into indexed/cutting position
>
> > From index, rotate 140 degrees,
> > then fall back 20 degrees. How about videotape? Or a movie file?
> >
> >
> With six tool positions it would be 60 degrees plus that required for the
> ratcher bar to fall. Then back that amount of overtravel plus maybe one or
> two degrees to insure stepper stall.
>
>
> > The controller can wait for the
> > M6 line "tool change" before the part program is allowed to continue.
>
> Don't forget to move the cross slide back to a tool setting position, away
> from any work in the unit incase you don't have all tools exactly set right.
> EMCO used a microscope to set all the tools to the same positions aimed at
> the tool points using cross hairs.
> I will look up the site and send it later.
>
> Hope all of this helps.
> bill