Re: To tool change, or not tool change

Doug--The idea of a turret type tool changer on a little benchtop
mill might have some merit. It was discussed briefly on the Maxnc
forum a couple months back. The Burgmaster concept makes for a very
quick tool change. For those of you not familiar with it, the
spindles are arranged as Doug describes below except are driven from
one power source and only when the spindle is in the working (down)
position. I do like the thought of air driven spindles as this would
eliminate the need for a drive coupling mechanism plus the air
turbines would be fairly light, a big issue on a 50 lb. machine. Will
attach here a copy of the message I posted on Maxnc several months
back:
Hello all--I can see the need for a toolchanger when running the
various jobs on the Maxnc. The special "screw-on" endmill adapters
(collets) that are discussed in this forum are a step in the right
direction but do have the disadvantage of longer cutter overhang.
I'm wondering about taking it a step further and making an indexing
turret head with at least four, possibly six, spindles ala Burgmaster
etc.
In order to be cost effective the indexing would probably have to
be done manually with the spindle stopped. I find that most of my
work is done with 1/16", 1/8" and 1/4" endmills which could be left
in their respective spindles. Remaining spindles could be used for
the various other size and shape cutters.
This may all be a pipedream but would sure like to hear some input
from all of you. I am aware of the router toolchangers that stage
the tools in a row at the end of the table.
Nelson Palen

--- In CAD_CAM_EDM_DRO@y..., "doug98105" <dougrasmussen@c...> wrote:
> Ballendo,
>
> SCMI CNC routers have a neat way to get around the need for spindle
> orientation. The holders and the spindle nose both have face gears
> that loosely mesh as the toolholder is pulled up into the spindle.
> The gear teeth are pointed so they'll mesh no matter how they're
> oriented. This method would be easy to retrofit onto almost any
> machine.
>
> As to having machines that'll automatically "switch" tools, I've
seen
> a couple of clever ideas. The easiset to implement on a home-built
> was a design on a gantry type wood router. They used multiple Z-
axis
> slides, each having it's own spindle motor with a different tool in
> each spindle. Simply activate a different Z-axis slide when
changing
> to another tool.
>
> Another idea on a wood router was to mount a number of air tools on
a
> six-position rotary table which was mounted in the normal spindle
> location. The air tools were fixtured such that they pointed
> radially out from the rotary table. The rotary table was attached
to
> the Z slide so the current tool was aimed vertically downward. At
> tool change command, the rotary table indexed, bringing the next
tool
> into position. Very much like old Burgmaster drilling machines.
>
> I agree about the ratcheting type automatic drawbars. Hate 'em!!
>
>
> FWIW, even on high dollar production CNC's the toolchanger is one
of
> the biggest headaches. Have you seen any successfully operating
home
> built changers?
>
> thanks,
>
> Doug
>
>
>
>
> --- In CAD_CAM_EDM_DRO@y..., "ballendo" <ballendo@y...> wrote:
> > 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
> > >