the first diffraction gratings were made of a warp of very fine wire. --- On Sat, 2/25/12, Jon Elson <el...@pico-systems.com> wrote:
From: Jon Elson <el...@pico-systems.com> Subject: Re: [Emc-users] Film Emulsion for Encoder Wheels? To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> Date: Saturday, February 25, 2012, 12:22 PM Kirk Wallace wrote: > I wonder if one could make an encoder wheel with a thin glass disk, coat > it with a film emulsion, expose it to an image of an encoder wheel, and > develop it like regular film? > Well, of course, that's how the major makers of glass disk encoders make them. The last step is that film is actially an etch resist, and they etch away a nichrome or pure chrome layer. But, there were plastic-backed film encoders made some time ago. I saw some of them in VERY old disk drives. > Or, use a thin sheet metal disk with photoresist and etch the slots? > Lower-cost US Digital, Avago, HEDSS, Renco etc. etc. encoders are made EXACTLY this way. > I know these techniques are use commercially, I'm just wondering if one > of us shed based folks might be able to pull it off. > I have a technology to make solder stencils out of .003" brass shim stock. I make two photo masters in mirror image format on my laser photoplotter (also home made) and then laminate the dry film photoresist to the shim stock. align the mirror image film to each other and glue together. Slip the laminated shim stock between, expose to UV from both sides, develop and etch in ferric chloride. With fresh etchant at 45 C, it takes just about a minute to etch through the brass. One trick is to make the UV exposure JUST enough to harden the resist, so it doesn't bounce under the black squares on the master and partially harden the stuff that is supposed to become clear of resist. This process is not a pretty as the stuff used commercially, I get rough edges and have a big problem with the etchant undercutting the windows in the resist. Getting it to etch in the shortest time possible and then rinsing vigorously immediately is important or the apertures just keep growing. I've never tried making an encoder, but I know I could do it. But, with encoder discs being so cheap, I really don't see the point. However, if you wanted a high-resolution encoder disc for wrapping around a spindle bore, I could see how this would make something you can't buy off the shelf. I machined a 60-tooth encoder disc about 6" diameter for my lathe, but that would only be 240 counts as an encoder. I use it right now for tach only service. Jon ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users ------------------------------------------------------------------------------ Virtualization & Cloud Management Using Capacity Planning Cloud computing makes use of virtualization - but cloud computing also focuses on allowing computing to be delivered as a service. http://www.accelacomm.com/jaw/sfnl/114/51521223/ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
