RE: [CAD_CAM_EDM_DRO] Tool changing

Hi Alan -

I have a design that uses this approach, for a .75" shank tool
holder. I modeled it after the Defiance VTX(?) headstock, and
with help from Marcus on this list who had good things to say
about it. There should still be 3D CAD images in the files
section. This is not a common approach for most commercial VMCs,
which use CAT-40 type tapered toolholders with pull knobs, but I
have seen it used on several types of smaller machines. My design
is for a ground-up headstock, but I don't see why you couldn't
adapt it to a mill-drill. In fact, you might be able to replace
the unclamping air cylinder with an upward action of the quill. I
think I've seen this done with a different kind of quick-change
toolholder. Whoops, if you want this to be automatic, you'll need
the air cylinder, but then you'll have to lock the quill very
tightly. You'll need a stack of disk springs under the drawbar,
which is what pulls the collet closed, and it needs to provide a
lot of force. One of the bearings will see this load during
unclamping, so it needs to be sized appropriately, or else you'll
get brinneling and early bearing failure.

Regards,

Carlos Guillermo
VERVE Engineering & Design

-----Original Message-----
From: Alan Matheson [mailto:hokianga@...]
Sent: Wednesday, October 16, 2002 4:33 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Tool changing

I'm interested in the possibilty of fitting an automatic tool
change
mechanisim to my R8 CNC converted drill mill. My thoughts were to
use a
pneumatically activated 20 mm R8 collet that picked up tools
(mainly drills
and small slot mills ) each mounted in 20 mm diameter holders.
These would
be in a dispenser at one end of the mill table. The holders
would have a
flange of some sort at the collet end to fix the position when the
collet
was closed. Means I could only use tools up to a shank diameter
of say 16
mm but that would be enough for many jobs. All activated by a
modified
TurboCNC.

Has anyone done this sort of thing. Ive looked around the web
quite a bit
but so far haven't found too much detail on how automatic tool
changing on
commercial CNC machines is accomplished. Any leads would be
appreciated.

I don't really have to have this feature BUT what a nice toy!

Alan Matheson



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