Re: [CAD_CAM_EDM_DRO] Re: Auto tool changers

on 2002-02-23 14:24:16 UTC

Mines going to be a stand alone unit driven by hard wiring. I don't think
the unit needs to be programmable. All you need is a signal to the device
telling the unit which tool you need.

Smoke.

> 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

> > 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

> > the tool points using cross hairs.
> > I will look up the site and send it later.
> >
> > Hope all of this helps.
> > bill
>
>
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