| | |
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
Kenneth Lerman
55 Main Street
Newtown, CT 06470
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.
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
Kenneth Lerman
55 Main Street
Newtown, CT 06470
Did you see the previous forum post on using a PC for a dro? http://www.lindsayengraving.com/othe...rests/dro.html
Al
CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
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.
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.Originally Posted by lerman
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
CNC, Mechatronics Integration and Custom Machine Design (Skype Avail).
“Logic will get you from A to B. Imagination will take you everywhere.”
Albert E.
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
Kenneth Lerman
55 Main Street
Newtown, CT 06470
Posting Permissions
| | |
LinkBack URL
About LinkBacks
