Thanks for those ideas. I really would like black buttons with white lettering, but the only way to get translucent buttons is in white. I guess I could consider reversing it, and infilling the engraving.
My initial experiments didn't work well doing infilling, so I did one using a black auto primer and engraved the button, which worked well. Really the right way to do this would be to get a silicon keypad made, but for a one off project that is unworkable. On Fri, Dec 7, 2012 at 11:20 PM, dave <dengv...@charter.net> wrote: > On Fri, 2012-12-07 at 22:44 -0500, Bruce Layne wrote: > > I reverse laser engrave legend plates, device labels, operator panels > > and sometimes prototype membrane switches. I've also done front surface > > engraving. I assume that's what you're doing on these switches. The > > big problem with that is that fingers activating the switches will erode > > the paint from a front engraving. > > > > If you're stuck with front surface engraving, then I'd engrave deeply > > and use a lot of paint, or several layers of paint and several layers of > > clear coat on top. Another trick that can work well is to use a liquid > > paint instead of a rattle can of spray paint, fill the deeply engraved > > letters with it rather than using several coats of spray paint, and use > > a solvent to remove the excess paint from the top surface of the key > > cap. Make sure the solvent is compatible with the key cap plastic. Or, > > let the paint dry thoroughly and mechanically remove it from the top of > > the key cap so it only remains in the engraved letters. Fine sandpaper > > or ScotchBrite works well for this. If you want a glossy surface > > instead of the brushed finish you'd get with unidirectional sanding or > > the matte finish you'd get from random sanding, you can finish with 600 > > grit paper and then Micromesh or Abralon (1200-1500 grit foam backed > > ultra-fine sandpaper). > > > > I have an EFD-1500 electronic fluid dispenser that I've used with a very > > fine gauge needle on the syringe to dispense paint into engraving. It > > helps to use a lighted magnifier, have a steady rest for your hand, and > > go easy on the caffeine for this delicate operation, but the paint wicks > > well and fills the engraved letters with no mess on the unengraved top. > > Model paint from a hobby shop might work well for this. Fingernail > > polish might work too. > > > > For engraving jobs with large and simple fonts, there are paint sticks > > that look somewhat like felt tip markers. They dispense paint instead > > of ink, so they fill the engraving well and the paint is fairly opaque. > > > > You might have some luck putting tape over the top surface, engraving > > it, spray painting it, allow the paint to dry and then remove the tape > > which served as a spray shield. This would probably work a lot better > > for laser engraving rather than rotary engraving with a small cutting > bit. > > > > There is typically better coverage with a good brand of paint like the > > Krylon that you're using because there is apparently more pigment in the > > paint, and the solvent in the better brands of paint seems less likely > > to orange peel when applied to plastic than the 99 cent el-cheapo > > paint. I used some black spray paint recently from a major > > manufacturer, probably purchased at Lowe's, that advertised twice the > > coverage. It was marketed as something like "ultra coverage" or "ultra > > coat". That might help your translucency problem. > > > > I hope you bought extra buttons for a little trial and error. This > > one-off prototype stuff usually involves some waste. > > > > I recently got in a hurry and accidentally had the laser cut about half > > an inch off the edge of the $32 ultra scratch resistant polycarbonate > > sheet that I was reverse engraving for the top of the tool rack for my > > soon-to-be-CNC milling machine. Then I decided to try to front surface > > engrave the HDPE substrate even though I knew that was unlikely. Sure > > enough, the material didn't engrave well and required five passes to get > > the engraving depth I wanted. Then the paint wouldn't stick to the waxy > > surface, chipped and flaked out, and looked awful. I bought another $32 > > sheet of polycarbonate and laser engraved it the night before last, > > painted it yesterday, and I'm going to epoxy it to the HDPE substrate. > > Hopefully the two square feet of surface area will provide a strong > > enough epoxy bond, even on the HDPE. If not, I'll use countersunk flat > > head screws... or I'll use PVC for the 3/4" thick substrate. I'll test > > the bond strength with the botched piece of polycarbonate and a scrap of > > HDPE first. I don't want to buy a third sheet of $32 plastic! Oh, the > > joys of prototypes and one-off custom work. > > > > Good luck! > > Just a random thought ... front engrave decently deep and then fill with > colored epoxy and polish flush. This implies that you have clear buttons > tho. > > May the force be with you. > > Dave > > > > > > > > On 12/07/2012 08:25 PM, Erik Friesen wrote: > > > I painted some of these > > > http://www.digikey.com/product-detail/en/1WD16/679-2144-ND/2034700buttons > > > today, and engraved them, but find that the paint is not curing like I > > > would like (not very durable), and the paint is soft enough that they > did > > > not engrave very nice. Not only that, these are backlit buttons, and > the > > > paint I used(flat black krylon from wal-mart) is a little translucent. > Any > > > suggestions about a better type of paint? > > > > ------------------------------------------------------------------------------ > > > LogMeIn Rescue: Anywhere, Anytime Remote support for IT. Free Trial > > > Remotely access PCs and mobile devices and provide instant support > > > Improve your efficiency, and focus on delivering more value-add > services > > > Discover what IT Professionals Know. Rescue delivers > > > http://p.sf.net/sfu/logmein_12329d2d > > > _______________________________________________ > > > Emc-users mailing list > > > Emc-users@lists.sourceforge.net > > > https://lists.sourceforge.net/lists/listinfo/emc-users > > > > > > > > > > > > > ------------------------------------------------------------------------------ > > LogMeIn Rescue: Anywhere, Anytime Remote support for IT. 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