Re: Auto tool changers

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


ballendo wrote:

>
> Alan,
>
> The "model" is a homing routine. Of the type used by T-tech. No
> switches. Run the stepper "enough" to be "sure" you are TO/past the
> next tool position, and then reverse and STALL the stepper against
> the detent, as Bill described. K.I.S.S. Then stop the pulse train,
> and do not idle the motor. (see the P.s. for a "better" idea, IMO.)
>
> <SNIP>
> Hope this helps.
>
> Ballendo
>
> --- In CAD_CAM_EDM_DRO@y..., Alan Marconett KM6VV <KM6VV@a...> wrote:
> > Hi Drew,
> >
> > OK, I saw the slots, and I now see three holes on the
> circumference, Are
> > these the ones? Yes, three photo interrupters could give a direct
> > readout of the positions. the "edge" encoder I mentioned was to be
> used
> > as an index. The PIC can "find" the index on startup, and keep
> track
> > of the 6 positions. I understand that ENCO already has this type of
> > encoder setup on the spindle (I think I've got one coming!).
> >
> > Bill tells me that the turret "drops back" into the detent, so I'm
> > guessing that a "ratchet" effect is in play here, and one would only
> > have to insure enough steps to get a little past the next detent
> > position, and then allow the mechanism to drop back.
> >
> > I suspect that the original DC motor was just shut off, and the
> detent
> > took over, therefore, the stepper implementation should do the same.
> >
> > Instead of a PIC, a Cybernetic Microsystems CY545 stepper controller
> > could be "programmed" to the the job. A little more costly then a
> PIC,
> > 'tho. (I've just been talking to them again).
> >
> > Interesting project! I wish there was a (simple) way to "model" the
> > mechanism, so that the driver/code could be worked on. The worm
> gear
> > data would have to be known, and other details of the mechanism, or
> the
> > actual hardware.
> >
> > Alan KM6VV