Re: [CAD_CAM_EDM_DRO] Re: low cost linear encoders

>> From: stratton@...
>>
>> > several people have asked for higher resolution encoder strips
>> > for similar purpose as the US Digital strips. I just got a magazine
>> > today with a blurb for Renishaw readheads for linear encoders.
>> > They have an RGH34 read head for their reflective RGS42
>> > "rolled Gold" scale made from a thin, flexible, gold-plated
>> > steel strip. I don't have prices for these items, yet, but I will
>> > check on them. I can guarantee they will be more than the
>> > US Digital unit, of course.
>>
>> I've worked with these a little and they are nice, although I'd be
>> concerned
>> about contaminating them in a machine environment unless fully
>> enclosed.
>
>I intended to make an enclosure, maybe with a slit in the bottom for the
>rod that drives the
>read head, or with the endless band design.
>
>>
>> I believe that they are substantially more expensive though - probably
>> enough to make commercial DRO's more attractive.
>
>Whew! You weren't kidding. The encoder strip is $360 / meter, and the
>RGH22-Z
>read head, which has a resolution of .5 uM (equal to ~ .00002") is
>$593. Ouch!
>
>Jon

You are quite right about the scales needing protection. They were
originally designed for use on Co-ordinate Measurement Machines (CMM's) and
similar very high accuracy linear devices. These tend to be used in
protected environments. The strips themselves are quite robust, certainly
more so than engraved glass scales, but using optical sensing they will not
tolerate high levels of debris and impact damage. Its a shame about the
price but they are designed for the professional market not the home
machinist. (and it helps pay my wages!) Also remember you still need the
DRO, Renishaw only make the encoder parts. If you want more info have a
search around on the web site at http://www.renishaw.com there is a lot of
information there about various methods of measuring.

Regards
Bill Philllips