Re: Plasma table gear reduction

>
> Start with a top speed of 200 to 300 IPM for plasma. Depending on
> the servo motor and your max drive voltage take about 80% of the

max

> RPM of your motors. The Ke constant will give you your rpm per

volt.

> Usually a 3:1 to 4:1 reduction ratio will work for most
> applications. You don't have to spin the motors at full rpm all

the

> time. Most of you cutting on a plasma will be at 50 to 100 IPM

with

> some thin stuff up at 160 to 180 or faster. As long as most of

your

> cutting is being done in the middle range of the motor you will get
> good results. Servo motors are much more linear in their torque VS
> RPM than steppers. One of the problems with rack and pinion and
> servos is you can get speeds that are way to fast without gear
> reductions. I'm not sure a jackshaft and two levels of reduction

are

> needed.

Yestarday, this seemed to be getting simpler.....

OK, so with a Servo, the best performance is at/near top speed.

Motors are not too expensive, so you can buy one that is 5 times your
need in power, and run it at 1/5th speed. (not that you would want
to, but this is just for discussion) That way, you get the power you
need in the speed range you want. The alternative is to spend more
time with belt ratios and such.

McMaster lists XL pulleys with 72 teeth as the largest and 10 as the
smallest. (SDP lists 60 at the largest) using a 16 tooth, one gets a
4.5:1 ratio. Not excessive although one will only have about 4-6
teeth fully engaged on the small pulley without belt guide pulleys.

But, with servos, since you are spinning the motors fast, you get a
much higher power output due to the gear reduction. (multiplied
torque)

Plasma drive systems are often open belt or rack and pinion.
Ball screws cost too much for the long runs.
Endless belt is too long for easily available belts.
Roller Chain or cable is an alternative.


Out of the drive methods I see, there are screw type with high
rotations per inch, and rack type with inches per rotation.

At this point, it seems servo's and screws are made for each other as
are steppers and racks.

Still learning.

As for motors...... my head is about to explode.....

3,300 max rpm, 750mA no-load, but 960 at 5 amps... amps per oz-in...
seems motors don't have a very simple rating.

No wonder the list archive was not as helpful as it is with so many
other things.

Dave