Re: [CAD_CAM_EDM_DRO] Re: Rotary to linear translation - an interesting idea.

>
> If we can back-track a little.
> The orginal idea was for a twag tight foil anchored at both ends.
> If you then deflect the foil by any means the effective lenth
> becomes greater, you can't get something for nothing.
> Even if the stretch returns with metal memory the lenth
> must alter for any deflection to take place.
> If the tape is longer the count of the code wheel must alter.
> Quite which way I don't know, I haven't thought it through yet.
>

You, by the way are one of those guys that need to get line-feeds in your
messages.

All I get in one huge line.


The bottom line is if you are traversing 12 inches of table movement,
you will be moving over 12 inches of tape.

Even if that tape is stretched to 12.5" long. You will simply have
unusable area at each end of the tape.

UNLESS you have vertical movement.
In this case that will mean releasing the tension on the tape.
That would not be smart, there would be no reason to do it.

That is the key The only way to see that extra length is to crawl
back up it at each end. Something with such a "Stretch factor"
will also show a non-liner relative movement as one side or the
other shows more or less stretching as you reach the extremes of
movement.

A system like I mentioned before with 2 rollers the tape passes
under before going over the top of the sensor pulley will not
show such effects if the bottom rollers are in line with each
other and the connection points at each end.

Althought the tape for such a system will be longer to go
over the pulleys, at a given position you will not see any more
movement than the table or tool the system is connected to.

In other words, Top dead center of the pulley will see 12 inches
if tape go by if you move 12 inches, period.
presuming you are looking at the neutral plane of the tape.

If you needed to add 4 inches of tape to go over the pulleys,
you will simply have 4 inches of additional tape the sensor
will never "See".


This is one of those time a good diagram and even more so a
demonstration would make all the difference.


Marc