DRO linear encoder scales

I recently had the displeasure of parting out an HP 2000C printer. ( it died and I wasn't just going to throw it away! ). When I got the top cover off I noticed a strange looking plastic strip running parallel to the print head path. Turns out HP uses a plastic encoder strip with a standard Heds sensor for the X axis positioning on this printer.

Which brought up the idea. Has anyone ever tried making their own encoder scales?
Are these things even called scales? Do I have the correct term?

It seems to me that it would be fairly easy to laser etch the correct kind of plastic and then wipe on some ink to fill the resulting stripes.

Or create them photographically. I know I used to print PC board layouts at 2x or 4x and have a print shop reduce them to a 1:1 negative with fantastic results. Why couldn't you do this with the encoder scales? It appears US Digital does this with the rotary encoders. Inside is just a plastic disc with stripes.

To me this seems like an elegent and cheap solution to the home shop DRO. HP mounted the strip at one end rigidly and the other end with a spring.

The first problem I see is variations due to temperature. But surely there is some stable plastic out there we could use for this?

Will it or will it not work?

later,
Larry E.



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