Re: [CAD_CAM_EDM_DRO] Linear Encoders

Tim Barnard wrote:

>
>
> >-----Original Message-----
> >From: Eric Keller [mailto:eek105@...]
> >Sent: Thursday, April 06, 2000 3:01 PM
> >To: cad
> >Subject: [CAD_CAM_EDM_DRO] Linear Encoders
> >
> >
> >So, here i am answering my own post. Hp makes only 360 line heads
> according to the search i did on the agilent (argh! hate >that name)
> web
> site. So i mosey down to the machine shop where they just had a bp
> retrofitted with a new Accurite CNC for
> >10k$. Accurite came in and replaced the old scales with new ones, so
> i
> took one of the old ones apart. They have 4 tiny
> >leds on one side and 4 tiny leds on the other side

One side is, indeed, LEDs. The other side has photo diodes (detectors).

> and a piece of glass
> scale mounted on the head in between. The
> >interesting thing is that there is a spring to jam the head up
> against the
> glass scale.

Usually, there is a thin strip of Teflon on each side of the analyzer,
to keep it from
scraping on the scale. If these fall off or wear away, the analyzer and
scale rum, and
it destroys them.

> The glass scale appears to be 2
> >pieces of glass bonded together. I didn't have the guts to take
> apart the
> ones on the cnc:).
>
> The only difference between the old ones and the new ones is the old
> one is
> a square wave signal and the new ones are a sine wave signal.
>
> >Just to add to the SI (metric)/GOAU (good old american units) debate,
> all
> of the glass scales i have seen, including the 30 >year old accurite
> described above actually are laid out in microns and the DRO converts
> it to
> inches. I guess the mylar guys >are using inches because the like to
> be
> GOA's

Yes, Teledyne/Gurley changed over in the late 60's, I think. I got a
lot of historical info
while talking to one of their people about a very old scale I got from
another guy, who
got it from the scrap pile at a machine tool supplier.

Jon