Re: To tool change, or not tool change

Doug,

This was what Roland and I discussed...

There are a few ways to orient the spindle: A shot-pin tied to rpm;
i.e.,doesn't shoot-out until rpm is nearly zero. Adding a slow-speed
motor and sensor used like a car starter motor (stays out of the way
until a spindle orient is needed, at which point it "takes over" til
the sensor is read). sensor could be anything from a magnet/hall-
effect to a "real" encoder index pulse. And the one Roland
mentioned, "turn the HOLDER!, rather than the spindle".

Those who have used these "ratchet wrench" draw bars either love 'em
or hate 'em, IME. Screwed up threads on holders and drawbar; did it
or didn't it "take" seem to be the main reasons I've heard).

This becomes more of a problem in something expected to run
unattended; i.e., fully automatic.

Hope this helps.

Ballendo

--- In CAD_CAM_EDM_DRO@y..., "doug98105" <dougrasmussen@c...> wrote:
> Rab,
>
> There's a fairly easy way to implement an automated tool change on
> small mills. That is, provided the mill has some sort of draw bar
> pulling the toolholder/collet up into the spindle.
>
> Fit the mill with a Kurt type pneumatic draw bar assembly. These
are
> not much more than an inexpensive air rachet wrench. Chances are
> you'd have to fabricate this yourself, I doubt Kurt & others make
> these for the small mills. You'd need a spare M-code to activate
the
> pneumatics.
>
> Fabricate a rack, mount on the back or end of your mill table to
hold
> a few toolholders (note, this rack will use up some of your
machine's
> travel). To retrieve a tool move into position so the empty
spindle
> is over the tool, bring the spindle down over the tool and activate
> the power draw bar. The tool will be pulled up into the spindle
and
> locked.
>
> To change that tool, position back over the empty tool rack
position
> and drop the tool out by activating the power draw bar in reverse.
> Then move over to the next tool and repeat the above change
procedure.
>
> If your mill has a key (like R8) or locating tabs (like 40 taper)
in
> the spindle those would have to be removed since you have no way to
> orient the spindle to align with toolholder.
>
> This isn't the most elegant tool changer, but it's far less
> complicated than those used on high production machines.
>
> Doug
>