Re: USB and ncPOD system

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Lester Caine <lsces@...>
wrote:

>
> Stephen Wille Padnos wrote:
> > Lester Caine wrote:
> >
> >> My thought had been - what happens when you turn the spindle by

hand.

> >> Impossible with a single pulse, but given a high res encoder you

would get the

> >> tool moving back and forth as you rock the chuck given the

ideal interface

> >> hardware :)
> >> Mach3 can't do that, and I doubt EMC2 could ( unless you can

leave it IN a

> >> screw cutting pass), but all the calculations say that it is

quite practical.

> >> So the next step is some of the fine detail.

The 2nd generation DeskCNC controller has a direct input from a
quadrature encoder with an index pulse. We have a threading kit that
fits on a Sherline. It has a 500 line encoder and electronically
gears the programmed axis motion to the spindle with a 2000 step per
rev resolution. You can stop the spindle, turn it by hand and
reverse it. The comanded axes will track the spindle rotation. A
Sherline spindle motor is only 1/3 hp, so it is very easy to stall it
out with what would be considered feeble threading cuts on an engine
lathe. With the encoder based threading, it is possible to thread
fairly coarse threads in steel, even if the machine is stalled during
the threading operation.

http://www.imsrv.com/sherlinemachines/#lathe

This was demonstrated at the last 2 CNC workshops.

What most users of fractional hp lathe spindles don't realize is that
steppers can't keep up with the needed feedrates to accomplish
effective metal cutting during threading. When our servos are
electronically geared to the spindle, more aggressive cutting is
posible. The quadrature encoder is also used in the lathe
configuration to display Spindle RPM. This is a little flaky as the
downstream machine operation priority is much higher than a display
of the spindle rpm.

The ncPOD has an spi serial interface, but no direct quadrature
encoder interface. Those that stopped by our booth at the 2006 NAMES
could see it running a 3D laser point scanner at about 10-20 times
the rates accomplished with a mechanical contact probe( 20-30,000
points per hour with DeskCNC). The SD card memory provided ample
capacity to store the copious data.

Fred Smith - IMService