Re: [CAD_CAM_EDM_DRO] How to establish repeatable home position w/steppers?

In a message dated 27-Aug-00 12:01:49 Central Daylight Time,
dougrasmussen@... writes:

<< On an open loop stepper system how do you establish a repeatable home
position? I'm thinking of a home position that will repeat to within
the resolution of the machine. >>

Doug: I have been running a home-brew CNC lathe (and a little plotter and a
CNC PCB drill, all home-brew) since '78, and am building two new ones right
now. You simply have to "keep track" of how many steps you make in your
machining-moves, and simply "go back" that many steps, when done, being sure
you make this rapid-traverse "through air" and not finished parts!.

If the machine can "keep track" well enough to machine useful parts, it can
surely "keep track" accurately enough to "go home", once done!

I did a GIANT machine I sent to England in '85/'86, and put micro-switches on
it which would "tell" the puter when the carriage was at "0,0" again. In my
initial testing (this was the first time such a machine had been built for
the particlar application, anywhere in the world: PIPE-ORGANBUILDING!), the
computer never once finished going "home", to find it had not "made contact"
on both X- and Y- microswitches! (The resolution was NOT 0.0001", mind you,
but 0.005", I think it was.)

SO glad I'm retired, now! Whew! Too much like work! Jan Rowland, Troll