Quick & Dirty stepper mounting
Posted by
Chris Stratton
on 2001-05-28 18:02:23 UTC
Got a completely unmarked, covered in grime, 8-wire NEMA 34 object at
a hamfest for $5. Turns out to be a stepper of respectable torque.
Wanted to try it on the 9" lathe carriage feed to see if it might do
the job.
The 9" south bend (model C) has a gear bracket that can rotate on the
leadscrew bearing bracket. Took it off and put it on rotated around
so the gear-stud grooves are in front of the leadscrew rather than
behind. Ran a 1/4-20 tap through two diagonally opposite mounting
lugs on the stepper. Put fender washers on 1/4" bolts, stuck them
through the stud-gear-grooves, and bolted the stepper to the bracket
so that it can be slid to various position. Can't get the stepper
shaft close enough to the leadscrew, so I used a 72 or so tooth gear
as an idler in between. Machined up a sleeve to fit over the NEMA34
shaft and hold the bore of a 16-tooth change gear. Put an 80-tooth on
the leadscrew for 5:1 reduction driving the 8-pitch screw.
That's 16,000 steps/inch in half-step mode. Produces a usefull amount
of torque at a low speeds, but poor high speed performance may be due
to having to wire the coils in series for the 4amp, 25volt driver I
had on hand.
Changed over to 3:1 (*8) or 9600 steps/inch. Rapids perhaps a little
better and will take a 1/8" deep cut on 1/2" brass stock with a slow
feed. In other words, it will do real work!
Actually, really low speeds are horrible, as the stepper resonates the
gear train. This is obviously not a practical setup, but it does
indicate that it would be worth machining out some timing belt pulleys
to mount this motor on this machine in a more usefull manner.
I've already got a mount for a NEMA-23 that clamps around the
crossfeed screw boss, just behind the small graduated collar and holds
the motor in position for a timing belt drive to a pulley fit in place
of the crank handle - total time to switch both axis between manual
and CNC is probably about 10-15 minutes
Chris
--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
22 Adrian Street, Somerville, MA 02143
http://www.mdc.net/~stratton
NEW PHONE NUMBER: (617) 628-1062 home, 253-2606 MIT
a hamfest for $5. Turns out to be a stepper of respectable torque.
Wanted to try it on the 9" lathe carriage feed to see if it might do
the job.
The 9" south bend (model C) has a gear bracket that can rotate on the
leadscrew bearing bracket. Took it off and put it on rotated around
so the gear-stud grooves are in front of the leadscrew rather than
behind. Ran a 1/4-20 tap through two diagonally opposite mounting
lugs on the stepper. Put fender washers on 1/4" bolts, stuck them
through the stud-gear-grooves, and bolted the stepper to the bracket
so that it can be slid to various position. Can't get the stepper
shaft close enough to the leadscrew, so I used a 72 or so tooth gear
as an idler in between. Machined up a sleeve to fit over the NEMA34
shaft and hold the bore of a 16-tooth change gear. Put an 80-tooth on
the leadscrew for 5:1 reduction driving the 8-pitch screw.
That's 16,000 steps/inch in half-step mode. Produces a usefull amount
of torque at a low speeds, but poor high speed performance may be due
to having to wire the coils in series for the 4amp, 25volt driver I
had on hand.
Changed over to 3:1 (*8) or 9600 steps/inch. Rapids perhaps a little
better and will take a 1/8" deep cut on 1/2" brass stock with a slow
feed. In other words, it will do real work!
Actually, really low speeds are horrible, as the stepper resonates the
gear train. This is obviously not a practical setup, but it does
indicate that it would be worth machining out some timing belt pulleys
to mount this motor on this machine in a more usefull manner.
I've already got a mount for a NEMA-23 that clamps around the
crossfeed screw boss, just behind the small graduated collar and holds
the motor in position for a timing belt drive to a pulley fit in place
of the crank handle - total time to switch both axis between manual
and CNC is probably about 10-15 minutes
Chris
--
Christopher C. Stratton, stratton@...
Instrument Maker, Horn Player & Engineer
22 Adrian Street, Somerville, MA 02143
http://www.mdc.net/~stratton
NEW PHONE NUMBER: (617) 628-1062 home, 253-2606 MIT