Re: [CAD_CAM_EDM_DRO] Re: Auto tool changers (more)

When I first asked this question I was thinking more along the lines of
something to just swap the tools over while I'm out at school erm....
'learign'. Sounds more like it's going to solve world peace at the moment.
And using the shortest possible root at that too! I'm only kidding.

John H.

> 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.
> Could be solenoid activated. As long as a solenoid is being
> considered, it could "release" the pawl for "backwards" operation.
>
> I'd use failsafe logic, as used in mill tool changers and lathe
> spindle collets; i.e., the tool is held in position mechanically, and
> the release force works against the mechanical device(s) holding the
> tool in position to create the RELEASE (also like semi truck brakes).
> This way, if the solenoid (or whatever) fails, the tool position will
> be maintained. You just won't be able to index/remove it! (until you
> correct the defective part)
>
> 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
>
> P.S. With one input bit, or an output bit and a pic, we can
> accomodate any number of tool positions on a turret; it just may not
> be particularly fast, or efficient. But it MAY still beat "hand"
> change-overs, and allow unattended (tho' watched<G>) operation
>
> P.P.S. To allow for "loading" positions, just use a different number
> of steps in another sub. (putting the setscrews in a favourable
> position)
>
> Does anybody besides me see a few "marketable products" here?!?!
>
>
> --- 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
> >
>
>
>
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