On 2/22/2012 9:35 PM, gene heskett wrote: > On Wednesday, February 22, 2012 09:14:52 PM R.L. Wurdack did opine: > >> Whatever you use, beware of reflections from the sides of the slots >> themselves. > Precisely my concern. The front& rear faces of the disk are basically a > never mind. Its the walls of the slots I am concerned with. > >> i.e. The surface of the disk may not be the only reflection >> problem. Will lampblack with a coat of clear flat Krylon work, or just >> flat black Krylon.? > Lampblack would be fine IF one could find a binder as effective as the > krylon that wasn't glossy at low incident angles. A case where thin is > good, but I expect trying to mill the outside 1/3" of it down to the point > where knife edge diffraction was the major effect, would be pretty > frustrating. Hence the search for something that would leave a truly non- > glossy surface. I, after thinking about it, may just clean it up with > Tarnex to dull& degrease the surface, and after much rinsing, try the > vinegar dip and ammonia fumes route. After adjusting a few more params in > the gcode, just made another, considerably neater cut one I am quite a bit > happier with, if I can get it suitable blackened inside the slots. Low res > .jpg attached > > Actually Dick, this is a case where a roughing bit might have been an > advantage. :-) But I don't know as I've ever seen a 1/16" diameter > rougher. That doesn't mean they don't exist, just that I never thought of > it till a couple minutes ago. > > Hindsight, always 20/05 or better you know. :) > Gene:
Back when Jimmy Carter was President, I was engaged in some high-end optical physics work that included measuring the specular and diffuse reflectance of a large number of materials as a function of wavelength and of angle of incidence. I could tell you what it was for but then I'd have to...well, you know the saying. I never found anything better than lampblack smoked right onto the test coupon. It became our reference material. Of course, it lasted only as long as we didn't touch it. One technique that can help mitigate the reflectance from the sides of the slots is to collimate the light source and use baffles before and after. Simple pencil-and-paper raytracings of prospective geometries can reveal a lot. So can a test rig with a scope. Good luck. Regards, Kent ------------------------------------------------------------------------------ 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
