Dimensions of a reflector

Is there anyone out there who knows how, or has the ability & tools, to accurately measure a reflector?

Illuminated - I need enough dimensions to give someone so they can reproduce it if they wanted, which I assume would mean the profile. I'm not worried about the finish getting scratched while measuring it. My brother, Eric, suggested I chuck a 2" dial indicator in a mill and plot the incremental measurements in ACAD. I could then use the spine tool to join the points. If anyone can provide a more accurate means of measuring it for me, I'll offer some incentive for doing it....???

Chris

Chris,

No additional incentive necessary - only more time. I can't promise anything, but I'll talk to some co-workers about possible measurement methods/instruments.

Exactly what level of accuracy is required here? Can you give some relative idea what is needed?

John

John - I'm not sure about the accuracy. How much does it take to actually change the beam? Since one of the reflectors I'm measuring is spun, I would assume the accuracy of it in its production form is not as consistent and a mold, press, or hydroform....??? My thought is that it doesn't need to be extremely accurate, but fairly accurate. Vague enough?

Chris

Chris,

OK - that gives me some idea - I would guess that the machine marks would be at least +/- .001", maybe more.

We should consider what texturing does to a beam, and maybe just create a small "imperfection" in a reflector, such as a very small dent or punch mark, and see to what extent it affects the reflected light.

I'm also thinking that "where" a surface variation appears on a reflector might have a greater or lesser affect (or produce a different type of effect), depending on whether it is close to the filament vs farther out near the rim, etc.

I wish I had more junk reflectors to play with. I'm a "try it and see" kind of guy when I have the need to quickly establish a starting point based on cause/effect relationship experiments. I call this my "shotgun" method of doing debug on custom automated machinery. It works very well for me, and has taught me a great many things.

Later - John

Chris,

Are you looking for something like a profile of the parabola, sectioned exactly down the middle?

I can think of ways to do that, but using a dial indicator might leave visible marks on a mirrored surface...

I'm not sure if I have access to laser gaging equipment, but I'll try to find out.

John

Chris,

I checked with a guy at work today, and our CMM does not have the setup or software capability to do the measurements you want. There are some machines that can do this handily, but ours doesn't.

I was initially thinking that you'd want measurements perpendicular from the plane of the reflector rim (used as the datum line) to the reflector surface. A series of measurements at very small fixed increments all the way across the width of the reflector's diameter would represent the entire cross-sectional profile.

I'll keep thinking about this if you're still interested and see what I can come up with.

John

can you saw it in half?

that way a machinist/whoever could see the angle and dupicate it right?

John,
Thanks for trying. I am going to try the dial indicator/milling table technique. I cut a reflector in half to do it more accurately. Once I get the profile, I can measure the openings at both ends and construct the drawing in ACAD.

Thanks!!
Chris