Re: Bridgeport retrofit servo questions

This is not directly related, but I thought the application was
pretty cool, so I'll throw it out here:

I saw a photo (I forget where) of a guy who wanted to reduce the
shaft size of one of his motors. He clamped the motor to the table
of his Bridgeport (shaft up). He then put a boring bar in a
Brigeport tool holder and ran the motor. He used the boring bar as a
lathe tool against the turning motor shaft. I suspect getting it
right the first time is REAL important <G>

Jeff



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

>
> No...for a few reasons...and take with grain of salt because I am

no

> expert ~ learning here too!
>
> 1. the shaft size of the motors I mentioned is .625". The hole in
> that encoder is only .25".
>
> 2. the shaft of the motor is 1" long. You need an encoder with a

thru

> hole option for the shaft to poke thru. You may also need an amp

for

> the encoder (as mentioned on US Digital) if the leads are longer

than

> 2 meters (doubt it) when using an open encoder.
>
> 3. That encoder only gives you 200 lines per rev. If used on a BP
> with 1:1 gearing, there may not be enough lines on the encoder to

get

> tight tolerance. If you increase the number of lines, the servo can
> be more precisely governed. Now...just for an anaolgy, if you

changed

> the belt ratio to let's say 4:1, then the motor would have to turn

4

> times for each turn of the screw (actually 20X/1" if using .2"
> pitch)...therfore one turn of the pulley @ 1:1 might move the
> axis .2" where a 4:1 would move it only .05". You can imagine how
> much movement the motor would have between encoder lines if run
> 1:1...this is why Les suggested running a higher line encoder so

that

> the distance between the 2 lines is smaller ~ resulting in less

slop.

>
> Does that make any kind of sense? Again...don't take this as
> gospel...I'm in the same class as you! (the one in the back

throwing

> paper airplanes)
>
> -Brady
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Luke1027 <luke1027@p...>
> wrote:
> > Brady,
> >
> > What about the encoders off this motor?
> > Buy the motor, pull the encoder, and discard the motor....
> > would it work?
> > http://www.surpluscenter.com/item.asp?
> UID=2005011818310844&catname=&qty=1&item=10-1834
> > I am very limited on electronics ... but trying to learn fast to
> convert
> > my BP to servos.
> >
> > Luke
> >
> > braidmeister wrote:
> >
> > >.... and it has a
> > >long enough rear shaft to mount a number of encoders. Looks like
> one
> > >of the US Digital ones will work nicely. ...
> > >
> > >-Brady
> > >
> > >
> > >