Re: [CAD_CAM_EDM_DRO] First Post (and a question re using a plotter as a power feed)

Hi Bill (William),

Sure, this is a great list! Glad you got us out of the trash!

Bill Darby wrote:

> Thanks for the quick comeback Alan.
>
> First, I had no idea that all the posts would be circulated as
> part of a mailing list and was quite amazed to find these
> eight or so messages all in my trash. (I have a filter operating to
> dump everything without my name overboard) I will have to fix
> that.
>
> The steppers are 3.8 amp at 1.4 volt and have 53 oz in hold.
> I realize that they are quite light but to start with I
> think It would please me to see if I could just get something going.
> The steppers, flat out, are rotating at about 150 rpm and the
> lead screw on the lathe needs about 30 rpm to provide a reasonable
> feed, So,,, with a reduction of about (1/4) and the change gears
> removed I kind of think that there might be enough beef there to see
> how the whole thing would work.

For example, My little Sherline now as 70 oz/in (direct), and that's not
really enough! if you 4:1 reduce, you might just have it. At any rate,
it's a cheap way to try out some steppers! You can always buy bigger
ones later!

>
> I gather from your assessment as being analog that there is little hope
> of using these drivers as part of a computer driven system.

Well, don't give up yet. If you have a schematic, look for the state
logic (stuff like 7474 and 7486 IC's, where the four phases of stepper
motor drive are generated. You should be able to trace back from the
driver TIP's (transistors). I'm guessing you have unipolar motors,
maybe not. Doesn't really matter. Anyway, the inputs to this logic are
probably either step & direction, or CW & CCW. Disconnect (or put in a
switch) everything before these two signals per axis, and run in your
own signals. You can get them from a parallel port quite easily, but be
sure to buffer them! Then you have a simple computer drive. If you
have S&D, then you're lucky! There are inexpensive control programs out
there (see Bill's info list), and even if you have CW & CCW, it's just a
few gates to convert it to S&D.

But don't give up yet! You could also use a D/A board, even drive a D/A
chip from a parallel port, and feed the X & Y plotter inputs from these
signals. It could work. You'll find that if you have a controller
program generating S&D, that the manual input mode will allow you to
"command moves" just as easily as the joystick you lost. In my case,
the handwheels I removed from my Sherline!

Good luck! And we'd like to hear how it's going.

Alan

>
> OK then will have to look at a plan B no matter what though I do think
> that the joystick control would be quite desirable for
> manual turning.
>
> Bill Darby (TKS again)
>
> Alan Marconett KM6VV wrote:
>
> >
> > Hi William,
> >
> > You have a Houston Instrument Plotter, as I understand. Is it analog
> > input? I haven't seen one of them for probably 22 years. Or perhaps
> > does it have an RS-232 serial interface? That would probably be
> > better. Then computer control consists of sending a "plot file" (not
> > HPGL :>( ). I'd seriously doubt if the steppers had enough power
> > (torque) to run a Myford 7" (lathe?). What stepper motors do you see?
> >
> > Alan
> >
> > William Darby wrote:
> > >......cut
> > > I would like to lead off my first post with a question about this
> > > Houston plotter that I have just dismantled to see if I can power
> > > feed
> > > the X and Z axis of my little Myford Super Seven with the steppers.
> > >
> > > Right now it will operate on local and allow the use of the joystick
> > > to provide speed, direction and selection of axis plus a scaling
> > > switch which provides for the selection of four distinct speed
> > > ranges.
> > >
> > > If I can select a gearing range that will provide enough power to
> > > move
> > > the existing gear train at a reasonable speed I would be quite
> > > pleased
> > > (I think it is quite doable with what I have)
> > >
> > > What I would really like to do, however, is to be able to select
> > > remote and control the steppers from a computer. .
> > >
> > > I am currently trying to locate the proper plotter drivers and a
> > > round, 15 pin plotter cable connector to fit the plotter.
> > >
> > > Any and all assistance would be appreciated.
> > >
> > > Bill Darby