Re: [CAD_CAM_EDM_DRO] DRO Encoders

> It is not as easy as you think. If you add up all the time it takes
> research, manufacturer and install the brackets for the encoders it's

about

> the same cost as linear scales.

For a hobbiest, time isn't a factor. Cash usually is. I really doubt it'll
take anyone that
could use a mill and DRO very long to mount three encoders to it. I mean
gee, I designed,
posted and CNC machined two mounting brackets for encoders yesterday,
mounted them on
the machine ( and they fit first time ) in less than 1 hour start to finish.
It wasn't a mill or lathe though.

> Then you have the issues of inaccuracy due
> to the measuring device being so far away for the work area, repeatability
> due to backlash in the machine, the screws might be english pitch while

the

> encoders are metric so the count per revolution are not correct and other
> matters.

If you are measuring the actual movement of the slide, NOT the rotation of
the
lead screw, then you are measuring the actual movment of the work piece as
accurately as possible since the encoder wheel is rotating against the
actual slide the
workpiece is mounted on. I don't see how backlash is an issue unless you are
trying to
measure the rotation of the screw. Backlash is the difference between
commanded movement
of the screw versus actual movement of the slide isn't it? It comes from
slop in the lead screw / nut
union or slop in the fit of the ways and gibs.

The issue of metric versus English doesn't matter as the movement of the
slide is what is
being measured, not the rotation of the screw.

> A set of calipers that are 20" x 9" are still expensive and not a as
> accurate as a standard dro system

True, if your machine is that big, calipers won't be practical.

later,
Larry E.