[lerman]

US Digital (www.usdigital.com) sells linear encoders which are based on mylar strips. I'm interested in applying this technology to add a DRO to my existing Bridgeport style milling machine.

Does anyone out there have any suggestions on how to mount the mylar strips?

Obvious requirements are:

1 -- should mount them in a straight and ridgid fashion
2 -- should have immunity to chips, coolant, dirt, ...

My thought at this point is to clamp the edge between two pieces of metal (probably aluminum). Mount one end with a pin in a round hole and the other end with a pin in a slotted hole (to allow for changes in length as the temperature changes). Put a channel with the opening facing down over the whole thing.

These encoders are downright cheap. Does anyone out there know the claimed accuracy?

Thanks,

Ken

[ViperTX]

US Digital should be able to provide accuracy info. Do the also provide the mylar tape...if this is similar to what you see on some of the tape measuring units (homeowner / builder stuff) then the tape should be coiled and spring loaded so the encoder is somewhat protected from contaminants.

[lerman]

They just provide a scale -- that is, a strip of mylar, and a head -- an electronic device with an LED, a lense, and some photo transistors (I'd guess).

I've sent them email asking for more info. I've ordered a 7 inch scale and head. $62.00 doesn't seem bad for a 500 cycles per inch device. I also bought an electronic up/down counter kit with four digit display for $16.50. I'll swap out the process and reprogram it to interface with the encoder.

I still have to design and build a mounting for it.

Ken

[Al_The_Man]

Did you see the previous forum post on using a PC for a dro? http://www.lindsayengraving.com/othe...rests/dro.html
Al

[ViperTX]

Lerman,

The mylar strip is designed to have one end pinned to the table's base. As the table moves the rolled up mylar passes over / between the encoder....the mylar is not designed to be rigidly mounted just the end and the rolled up coil....take a trip to your local home improvement center and look at the new tape measure units that use the mylar...they'll have an LCD or LED readout.

I believe that StraitLine is one of the brand names...they also have a laser measuring unit.

[Al_The_Man]

US Digital (www.usdigital.com)
Does anyone out there have any suggestions on how to mount the mylar strips?
1 -- should mount them in a straight and ridgid fashion
2 -- should have immunity to chips, coolant, dirt, ...
Thanks,
Ken

I think if you do a search of the google groups you should find some users that were coming up with mounting designs such as mounting to glass, no expansion.
There was one post I remember of someone designing a square tubular housing similar to a linear scale. There was alot of activity in the metalworking ng a few years back on this item.
Al

[lerman]

Did you see the previous forum post on using a PC for a dro? http://www.lindsayengraving.com/othe...rests/dro.html
Al

Yes, I saw it, but I had forgotten about it. I would like to avoid putting a PC in the shop. But it might work out well until I write the code for the micro.

Ken