Re: Alternative Stepper Motor mountings, etc.

regarding the gearing portion of your question,

I had looked at gearing a stepper for a machine I'm building.

I am doing the prototype with 1/2-13 threaded rod, 10 feet long.
with plans to use 1/2-10 ACME on the final unit. (still looking
for 10 ft ACME rod)

Using a 10 TPI for discussion, my stepper does 200 steps per
revolution, and with 10 rotations per inch, each rotation is 0.1"
travel. each step therefore is 1/200 of 0.1" or 0.005" per step.
Simple math.

I looked at using a smaller stepper (I'm cheap) and gearing
up to get better torque. a 6:1 gear arrangement would allow
me to use tiny motors, but travel time would be too long.

My gear train design would use about $45.00 in
spur gears, require lubrication, and put is gear slop.
and then there is the cost of manufacture, a few hours at least.

For the money, and speed, and time savings, I am going with
a larger motor and direct connection.

I am looking for an overall accuracy of 0.005" in the final
unit, so all I really need to concentrate on is one connection
that being the ACME rod to the nut. In my application, I am
more interested in repeating a location, than overall accuracy
from end to end. If I neeed metter accuracy, I'd go with ballscrews.

Hope this helps.

Dave

--- In CAD_CAM_EDM_DRO@y..., Alan Marconett KM6VV <KM6VV@a...> wrote:
> Rab,
>
> I haven't studied the Tang lathe, but if you can mount a little
square
> plate behind the handwheel (on the lathe bed), you should be able
to get
> by with four spacers out to the #23 motors. Then you need
a "slitted"
> (sp) coupler from the handwheel shaft (.25"?) to the motor shaft
> (.25"). IMO, this is easier then trying to rig timing belts, as you
> don't need additional gearing. We have 20 TPI threads on the
Sherline,
> I'm assuming Tang has something similar. Seems the timing belts and
> pulleys are required when ball screws are used, they only get 8 tpi
or
> so there, and a 3:1 ratio helps torque and resolution (as I
understand).
>
> Check out the way Dennis at SuperCam, Dan Mauch at CamTronics, or
Otto
> at MaxNC do it with Sherline mills for Ideas. I personally use the
> Sherline CNC mounting kit on my Sherline/Sears mill. Flashcut and
> Microkinetics also are possible sources of information.
>
> Hope this gets you going in CNC!
>
> Alan KM6VV
>
> rab@r... wrote:
> >
> > I'm looking for good cheap / low tech alternatives of mounting
size
> > 23 steppers, coupling them to some leadscrews and fit some
bearings (
> > this being on a Taig lathe retrofit ), as the off the shelf
> > components seem quite pricy by the time you buy a full set.
> > Also, what's the pros and cons of direct couplings versus timing
belt
> > connections ?
> > I should mention that I'm not looking for total accuracy just now,
> > but trying to put together a quick and cheap system to test some
> > ideas on.
> >
> > Thanks,
> >
> > Rab