Re: [CAD_CAM_EDM_DRO] Re: Bridgeport retrofit servo questions 1:1 ratio

braidmeister <braidmeister@...> wrote:


Ron,
I get what you are saying about 4th gear. I will try them 1:1 1st,
and if need be, I will reduce to a 2:1 or better ratio. No sense in
spending the $ for pulleys and belts if it is not necessary.

In all actuality, yes it is a 3100 RPM servo @ 130 vdc. Since I am
planning on running them @ 75v max, then I will have a max RPM of
only about 1700. That brings the rapids down quite a bit. I doubt
that I will need the full 2HP of the motor since I can easily move
the axes by hand turning the pulley.

/// We discussed the power input at the screw just recently. A handcrank has about a 6" diameter path of travel, 3" radius. A crank revolved 1 rev constitutes about 18.84 " of circular travel. This circular distance produces .200" inches of linear table travel (5 tpi). Or 94.2:1 ratio. Each pound of force presented to the handle of the crank equals 94.2 lbs of linear force. 10 lbs , roughly 1/2 ton. So, servo torque is really not that big of an issue. The little Ameteks will work for X and Y. Except in the case of Z driving the knee. Different situation altogether. About 800lbs going up, coming down is no problem. And then add a large bit hogging out material...Z is the biggest headache by far. Put the biggest motor you can power on it. I only get 50 ipm out of Z with a 40 in-lb motor. ///

bounce things back and forth on...to me it is 100% American ~ Better,
cheaper, faster

/// As I told an engineer recently about those attributes, pick two, ya can't have all three.///Ron

& elimination of the middleman for those of us who
know how to turn a wrench.

-Brady

--- In CAD_CAM_EDM_DRO@yahoogroups.com, R Rogers
wrote:

>
>
> braidmeister

wrote:

>
>
> No I was the one throwing planes!!
>
> Yes, that's the motor in question. It seems to me that it would be

an

> ideal fit for the BP. I am hoping that I can get away with 1:1 and

a

> decent encoder.
>
> /// Trying to run a 3100 rpm servo 1:1 to a 5 tpi ballscrew will

produce rapids of 620 ipm. One needs from 2:1 to 3:1 reduction on all
3 axies using servos (driving the knee, its half the increment of X
and Y per rev.). Simply increasing encoder count to attain resolution
is not practical. An E5S-200 encoder, Gecko 320's and Mach2 work
perfectly together using the above ratios. 1:1 ratio is like driving
a car around in 4th gear. Servos operate best at 80% of their rated
RPM. I just ordered a set of pullies from mcmaster carr three L (.375
pitch)series 30 tooth (3.5" dia) and three L series 12 tooth ( 1.4"
dia) for a 2.5:1 setup/// Ron

>
>
>
> [Non-text portions of this message have been removed]

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