Re: [CAD_CAM_EDM_DRO] RE:hand jive

> most but not all of the machines I've worked with have both
> the jog buttons can be used in combination with the feed override
> for large moves where acuracy is not as important while the
> the handweels are both graduated and have magnetic or spring
> detents and work with the jog increment settings to give a feel
> of the work (most of the feel is actualy in your eyes and ears)
> and let you do exact moves without having to look at the display
> for example set jog to .0001 to touch off an edge finder then to .1 to
> move to the real part edge with one click of the handweel
> they also let you adjust the cutting speed without having to stop
> ,when you hear the tool start to complain just crank it slower
>
> the comercial ones ARE expensive but its not all that hard to make
> one yourself (hint:all the parts for one are in a 360k floppy drive)
> the jog handweel may seem like a luxury item at first but once you
> start using it you will have a hard time working without one
>
> interfacing the encoder is where it gets tricky
> the hardware interface can be just two pins on the lpt port like
> you have already done
> ?was it wired in as phase A&B or step&direction?
> the software needs to poll the bits once each time thru the
> jog loop and command a move only on a change of state
> if it only polls while in jog mode it shouldnt cause much of a
> slowdown ,it should be less of a drain than the mouse is anyway
>
> if you just stuff pulses into a fifo buffer like a keyboard does you
> can have an axis run away from you if you spin the weel to fast ie,
> if the jog increment is set at .1 then one casual spin of the knob can
> cause big trouble (krunch!)
> commercial machines dont let this happen ,they stop when the handweel
> stops no matter how many pulses came in
>
> Brian
>
> On Sat, 04 Nov 2000, you wrote:
> > Brian and the list,
> >
> > The Pulse generators look interesting (but expensive)! Would there be
> > an advantage to having a shaft encoder to spin rather then a pair of jog
> > buttons? Would the shaft encoder just provide pulses, or would it be
> > "calibrated" like a real hand wheel? What do the big machines with this
> > (electronic handwheels) do?
> >
> > I interfaced a shaft encoder through a spare pair of bits in a parallel
> > interface to my RDF (Radio Direction Finder) hardware (Stepper spins
> > antenna, A/D sync'd with antenna direction takes signal strength data).
> > I didn't have all that smooth a motion, probably due to overhead of
> > reading the encoder. I want to try it again with something like US
> > Digital encoder interfaces (like DRO). I guess one could interface the
> > encoder and simulate keyboard codes? Or if you're writing your own
> > program... Any thoughts writers?
> >
> > Alan
>
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