Re: Auto tool changers (more)

--- In CAD_CAM_EDM_DRO@y..., Alan Marconett KM6VV <KM6VV@a...> wrote:
> Hi Ballendo,
>
> Good thoughts. Since I'm not thinking of designing a tool changer
(I'd
> just like to come up with something Bill and others could use), This
> effort will rely on the ENCO hardware Bill has. I have digitized
some
> angle data from the escapement pix
>
> http://www.grifftek.com/c5cnc/c5cnc.html
>
> And I can see that only a few degrees past the 20 degree width of
the
> ratchet's tip is necessary. I am thinking I might mill out a
ratchet
> for test on the Sherline rotary table. This would be an ideal way
to
> "simulate" the mechanism. I'm guessing that the ratchet part is
about
> 1.5" OD.
>
> It would appear that some "reverse force" would be needed to secure
the
> ratchet.
>
> Just using a delay sounds risky. I think we need a tool # command,
and
> the use of M06 "complete" (?) line to signal that the selected tool
is
> in position.
>
> I've already mentioned in a previous post that a "canned cycle"
could be
> implemented in the controller software to implement this quite
easily,
> but that option is not open (as far as I know) to the majority of
> controllers. Perhaps we can put it into TurboCNC, or Master5
(guys?),
> even CNCpro, but I'd like to be able to add it to anything.
>
> I suppose a primitive implementation could just run the existing DC
> motor! And putting in a tool change command, and the user pushing a
> button until the proper tool (t2, t3, etc) is in position, and then
> pressing the "tool change continue" sw on the controller would also
be
> fine for a start. Bill?
>
> Tripping a microswitch at the "tool change stall" IS a clever way to
> start the automated sequence. We just need 3 bits...
>
> And yes, as I suggested, the use of a 4th axis to rotate the tool
> changer would also work (OK, put it in a subroutine).
>
> Bill, any place we can mount an encoder disk? Something like the
one
> on the spindle (I'm told)?
>
> Anyone else interested in this (ENCO5 list?)?
>
> Alan KM6VV
>
>
> ballendo wrote:
> >
> > Alan,
> >
> > You're right.
> >
> > For shortest path, use a geneva. Or the worm wheel and a
brake/lock.
> > Or lever acting tapered shot pin, as used in turret lathe
tailstocks.
> >
> > <SNIP>
> >
> > Alan, you don't need anything like 20 degrees "fallback"! Plan for
> > MUCH less. Yes, the sherline rotary table would make an
> > excellent "model". You could pretty easily set up the pawl
> > arrangement on its face a la a "sacrificial" plate. The "shortest
> > path" is only needed for larger numbers of tools, IMO.
> >
> > The simplest, though not fastest way to implement somethinng like
> > this for a control that doesn't know it exists is to use G04
(delay)
> > with the M06 (toolchange). Set the delay for "worst case" rotation
> > time. Even this assumes the M06 will at least have a "start
process"
> > bit. If this is unavailable, use an AUX I/O output bit (which most
> > programs have) in the same block. Personally, I'd set it up for
one
> > position index and repeat the I/O bit command as necessary to get
the
> > tool I want.
> >
> > Another way, that doesn't use ANY output bits is to program a
motion
> > to a switch (use a subroutine; or cut and paste), such that the
> > motion trips the switch, causing the index. In this case, a PIC
could
> > set a specific number of steps, and issue the needed motion
profile,
> > answering back to ITSELF. Then, if the PIC is not satisfied
that "all
> > is well", IT could trip a home or limit switch! Or be wired into
an
> > opstop, or feedhold, or... you get the idea.
> >
> > A similar, and even "lower tech", is to use a "canned routine"
> > (subroutine) motion which causes the index manually!
> >
> > Sometimes we can look at how things were solved in the "mechanical
> > only" days, and use some updated version to accomplish what we
need...
> > Not EVERYTHING needs to be computer controlled to be automatic!
> >
> > Hope this helps.
> >
> > Ballendo
> >
> > <SNIP>
> >
> > --- In CAD_CAM_EDM_DRO@y..., Alan Marconett KM6VV <KM6VV@a...>
wrote:
> > > Hi Bill, Ballendo,
> > >
> > > I've got the "two sensor" indexing scheme down from previous
> > projects
> > > (see previous posts). 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.
> > >
> > > It sounds like there are only three positions; slots take three
> > tools,
> > > and holes take another three tools (boreing). Three positions
are
> > thus
> > > needed, and Bill has suggested "tool loading" positions, which
can
> > also
> > > be accomodated.
> > >
> > > Given the ammount of "over travel" needed, and the worm gear
ratio,
> > I
> > > believe I can use a rotary table to simulate the action. So
what
> > I'm
> > > looking for is a detailed plan, such as: From index, rotate 140
> > degrees,
> > > then fall back 20 degrees. How about videotape? Or a movie
file?
> > >
> > > What driver will be used on the stepper motor? How many steps
on
> > the
> > > motor? I have an Idea to send a DOS program, with the "canned"
code
> > > needed to implement the actions. This would have a simple LPT
port
> > > interface, which would later be used by the PIC based unit.
> > >
> > > How to interface to the controller program? Two bits out can
code
> > three
> > > tool bit positions. The three "tool loading" positions would be
> > > selected from a pb on the electronics. The controller can wait
for
> > the
> > > M6 line "tool change" before the part program is allowed to
> > continue. I
> > > KNOW how to get the needed three bits out of a program, but we
need
> > to
> > > get them out of a controller program Bill (and others?) are
going to
> > > USE. What controller program are you going to use Bill?
> > >
> > > Alan KM6VV
> > >