RE: [CAD_CAM_EDM_DRO] Re: Electronic Gearing

It's not my system. It from a guy in Germany. I've misplaced the rest of
the documents and email corresponsance with him. (somewhere on my PC) And
hence I have forgotten his name for which I apologize since I can't give him
direct credit.

How it works is quite simple really. A geared lathe cuts threads by turning
the lead screw a given number of turns for every turn of the spindle. For
example, cutting an 8TPI thread on a lathe with an 8TPI lead screw means a
1:1 connection with the spindle. To cut 16TPI we want the carriage to move
half the distance for each revolution of the spindle so the ratio is 2:1
and so on.

Electronic gearing electronically puts a gear onto the spindle (the encoder)
and another gear onto the lead screw and a dc motor. It then uses the
pulses from each, after suitable processing to create a voltage level to
drive the lead screw motor.

The idea is that the pulses from the spindle can be divided electronically
as can the pulses from the lead screw. A number of thumbwheel switches (or
rotary) set up a divider; similar to the gears on a lathe. For example
your system could divide a 100 pulser per revolution spindle by 2 and a 100
pulse per revolution lead screw by 4 and the spindle would create 50 pulses
for every 25 from the lead screw; a 2:1 ratio.

The hardware phase lock loop part of the circuit takes care of determining
the correct lead screw voltage to make the lead screw track at a 2:1 ratio.
Chose different divisors on spindle and lead screw and you get different
speeds.

Why isn't it used more? I think with the advent of MACH2 and TURBOCNC etc.
there's so much more that can be done with a PC especially since cost wise,
I think a couple of stepper drivers for X and Z allow automated multi-pass.

John Dammeyer

>
> Can you give an explanation of how your system works ?
>
> Sounds like this general idea has been in circulation for a while. Can
> you explain why we don't see more of it ?
>
>
> ---John Dammeyer <johnd@a...> wrote:
> > A number of years ago I figured the digital gearing would be perfect
> > for the Gingery Lathe as I wouldn't have to go through the process
> > of making gears.
> > Got as far as transferring the original schematics to Protel 99SE
> > and even went one step further and created a number of GAL devices
> > that condensed the circuit.
> > But, like so many plans, it never went any further. However,
> > here's a link to the schematics.
> > http://www.autoartisans.com/cnc/digitalgear.htm
> > John Dammeyer
>
>
>
>