Re: rack and pinion advice

I would guess you need to reduce at least 10:1, to get the required
torgue to move the axis. Reduction will be required to get good
resolution as well, as a 200 step stepper will move .015" per step
if you use a 1" dia. gear.

What sort of drive, steppers etc, will you be using?

Eric

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Troy"
<superscooby3000@y...> wrote:

> I am designing a 4'x8'gantry router with rack and pinion on the x
> and y. Does anyone have any advice on wether I should gear down
> nema 34 stepper motors with timing belts and pullys?
>
> I am thinking without gearing down I would get the fastest rapids
> and at cutting speed, and I think I would get the most torque
> because the motor wouldn't have to run as fast to move the gantry
> (I was under the impression that the faster you ran a stepper

motor

> the less torque you get.) Am I correct in this thinking or am I
> missing something?
>
> I was planning on using pullys and timing belts anyways figuring

it

> would be easier to upgrade to servos if I wanted to in the

future.

> I just cannot decide if I need a 1:1 ratio or something else. If

I

> did need a different ratio does anyone have advice on what that
> should be? I was figuring on using the smallest spur gear I could
> get, or do I need something with more teeth engaged.
>
>
> Another question: I was planning on using 14deg 20pitch gears and
> rack because that seems to be the cheapest route at Mcmaster, and

it

> seems mcmaster doesn't carry long lenghts of 20deg rack.
> Does 20deg make much of a difference on smoothness and is it worth
> the extra expense? (and does someone have a better source for

20deg

> rack?) How about gears and rack with helical teeth, I saw
> somewhere on the net but can no longer find the site, is that

worth

> while?
>
> any other advice you rack and pinioners and give would be greatly
> appreciated.
>
> Troy