On Wed, 8 Oct 2003, Stefan Trethan wrote:
stuff. I didn't have any tapping fluid, and needed to tap about 30 holes
in some 1/4" steel plate (5-6mm). Turns out moly grease makes a great
tapping compound. It's just messy messy messy.
driver, all the better. Regarding microstepping drivers: Unless the
driver has been tuned for the particular motor you're using, don't expect
the microstepping to give you more positional accuracy. It will, however,
make for smoother motion.
though. Mount the motor to your workbench (clamp, screws, whatever), and
mount an arm on the shaft of the motor. Hang weights at a fixed distance
out on the shaft while the motor is energized. When you can get it to
slip, you know the holding torque of the motor. Measuring the torque of a
moving motor is a little trickier, but for a first-pass measurement the
holding torque works well.
machine, but it means you need to build the machine first: Stick an arm
on the leadscrew and start hanging weights. When you can just get the
leadscrew to rotate, you know the minimum torque necessary to move the
thing. If possible, get a motor with at least four times the holding
torque, preferably larger.
toothed belt should not slip, but it does happen for a variety of reasons.
Unfortunately this has happened on a machine at work. Luckily nothing was
hurt. If you go this route, you can always rig up motor kill switches
that engage if the bridge skews.
Tom
> I see..Absolutely.
> all say: most important: KEEP IT SIMPLE.
> It just hapens i have some of this Molybdenum grease (in a spray can)Give it a try. For what it's worth, moly grease is good for lots of
> here. So i will use it.
stuff. I didn't have any tapping fluid, and needed to tap about 30 holes
in some 1/4" steel plate (5-6mm). Turns out moly grease makes a great
tapping compound. It's just messy messy messy.
> The motors, again...200 steps per rev should be fine. If you wind up with a microstepping
>
> I wonder wich power the steppers should have.
> 200 steps is ok?
driver, all the better. Regarding microstepping drivers: Unless the
driver has been tuned for the particular motor you're using, don't expect
the microstepping to give you more positional accuracy. It will, however,
make for smoother motion.
> Most motors are rated in volt / ampere.... I know it would be better toThat's a shame they're not rated by torque. You can always measure this,
> compare them by N/m but the ones i have are not labeled in torqe...
though. Mount the motor to your workbench (clamp, screws, whatever), and
mount an arm on the shaft of the motor. Hang weights at a fixed distance
out on the shaft while the motor is energized. When you can get it to
slip, you know the holding torque of the motor. Measuring the torque of a
moving motor is a little trickier, but for a first-pass measurement the
holding torque works well.
> I have some, but they are too small i think... So please anybody havingYou can use the same trick to find out how big a motor to mount on your
> firsthand experience please tell me what is needed.
machine, but it means you need to build the machine first: Stick an arm
on the leadscrew and start hanging weights. When you can just get the
leadscrew to rotate, you know the minimum torque necessary to move the
thing. If possible, get a motor with at least four times the holding
torque, preferably larger.
> I also wonder if the main axis should be driven by one or two motors. IfYes there is. There is also the problem of skew if the belt slips. A
> there is only one motor the screw is centered. or two screws are coupled
> by tooth belt... isn't there the problem of carriage skew if the
> spindle is centered and the load applied on one side only?
toothed belt should not slip, but it does happen for a variety of reasons.
Unfortunately this has happened on a machine at work. Luckily nothing was
hurt. If you go this route, you can always rig up motor kill switches
that engage if the bridge skews.
Tom