Re: Auto tool changers (more)

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
> >