Re: Auto tool changers

Smoke & guys,

Something simple for indexing both lathe turrets and mill tool
carousels is to have the machine bump a switch somewhere near the
extreme of one of it's axis travels. This is especially easy on a
lathe, move the X axis to it's extreme where a limit switch is
tripped. Each trip causes one index of the turret. Of course, this
requires the CNC programmer to be a little more careful than if he's
working with an addressable turret.

We do something similiar with a large Cushman pneumatic indexer on my
biggest mill. Rather than go to the trouble of wiring this indexer
to actuate by Mcode, we use a plastic tipped switch mounted on the
mill table. To index, stop the spindle, move the tool tip over the
switch, depress switch with tool, rapid away and turn on spindle.

BTW, Smoke, automatically selecting the carousel to correct tool
seems easy on a mill in comparison to the issues involved in actual
tool change operation. What are your thoughts on achieving the tool
change?

Doug

--- In CAD_CAM_EDM_DRO@y..., "Smoke" <smoke@t...> wrote:
> There's also the possibility (for semiautomatic use) of selecting
the
> desired tool by using a selector switch. All you'd need then would
be an
> on/off signal. that sounds like something I could work up for my
Bridgeport
> to use temporarily until I get the CNC gear hooked up. Would have
to figure
> out a way of building the mechanicals first.
>
> Smoke
>
> ----- Original Message -----
> From: "ballendo" <ballendo@y...>
> To: <CAD_CAM_EDM_DRO@y...>
> Sent: Saturday, February 23, 2002 5:12 PM
> Subject: [CAD_CAM_EDM_DRO] Re: Auto tool changers
>
>
> > Smoke,
> >
> > Sounds like a good plan. With 2 output bits you could DIRECTLY
> > "select" 4 tools. With three bits, you could have 8 slots
directly
> > accesible.
> >
> > Hope this helps.
> >
> > Ballendo
> >
> > --- In CAD_CAM_EDM_DRO@y..., "Smoke" <smoke@t...> wrote:
> > > 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@a... wrote:
> > > > >
> > > > > In a message dated 2/23/2002 11:17:44 AM Mountain Standard
Time,
> > > > > KM6VV@a... 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
> > > >
> > > >
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