While I can see the need (sometimes) for a durable metal encoder disc, and I have cut some out of .016" copper (was on hand, and never got tested), I wonder how useful, or how durable laser printed transparency film would be for many applications. Two of them glued back to back with the printing on the inside might be reasonably durable. all but the fingers could be clamped between an aluminum mounting piece giving some physical stability. The resolvers on our Shizuoka are located in sealed coffee can shaped bins, so reasonably protected from swarf. One could take a .JPG to Staples and have them print out a few with whatever resolution you choose (make THEM keep the stock of laser transparency film).
The original encoder code was borrowed by a guy doing robotic encoders for some surplus Pittman gearmotors for robotics, though he used reflective sensors with less than 30 segments. I borrowed the code from him and made changes to make it easier to center a large encoder wheel. I have printed out samples (though I haven't used any yet) and get reasonable looking prints with 512 segments or more. I haven't added the index wedge yet, but I will insert the code that I do have here. %! Postscript utility for printing an encoder wheel % /inch {72 mul} def % #points/inch (don't change me) /size 3.9 inch def % radius of encoder wheel /segments 1024 def % number of segments (black and white) /angle 360 segments div def /wedge { /radius exch def /angle_s exch def /angle_e exch def newpath 0 0 moveto 0 0 radius angle_s angle_e arc closepath } def % ADD IN THE ENCODER WHEEL AT THE SPECIFIED DIAMETER gsave %THIS LINE SPECIFIES WHERE TO PUT THE CENTER 4.0 inch 4.0 inch translate 0 1 segments { 360 segments div rotate angle 0 size wedge 2 mod 0 eq {1} {0} ifelse setgray fill } for grestore %THIS ROUTINE FILLS THE CENTER WITH WHITE, AND SOMEHOW PUTS A SOLID CIRCLE % INSIDE THE GROUP OF WEDGES %THIS LINE SPECIFIES WHERE TO PUT THE CENTER 4.0 inch 4.0 inch 3.0 inch 0 360 arc gsave stroke grestore 9 setgray fill %THIS ROUTINE PUTS A TINY DOT IN THE CENTER TO AID IN MOUNTING THE DISC %THIS LINE SPECIFIES WHERE TO PUT THE CENTER 4.0 inch 4.0 inch .01 inch 0 360 arc gsave stroke grestore 0 setgray fill showpage I open the .eps file in Gimp. Most Linuxes come with ghostscript installed, and that's what Gimp uses to write it out to a .JPG. To get good resolution, you need to print out a lot of dots, and that requires a lot of RAM, or a long time swapping to/from available RAM. I think I remember using 8000 by 8000 for the final file size. If Staples has a printer that handles postscript directly, you should be able to size and position the disc in the .eps code, and print it directly from .eps with much better resolution. With some care you should be able to get multiple encoders per sheet, depending on how big you want them. Hopefully this will be useful for someone. It sure is quicker than cutting that ultra thin aluminum, and the segments /should/ be equal in size (for 50% duty cycle). For test purposes, if you have clear spray paint on hand (Krylon works well here) printing on paper will give you the black. Several very light coats of Krylon on the print side will stabilize the print, then a heavier coat from the back will soak into the paper and make it more transparent. All the paint should make the disc stiffer, and seal it against some moisture. You could mount the disc in between cardboards with a hole cut in the middle to keep it flat while the paint dries. Does anyone think that this needs to go in the knowledgebase? I searched for encoder and didn't find any references that appeared to have this information. ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users