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Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing 1989-2024
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Mirror Finishes for vision system
Q. I am currently designing a jig for a vision system. Because of the nature of the product and space constraints, I had to make my mirrors from machined parts rather than using commercial available ones. I had specified a mirror finish on some surfaces of my parts. Unfortunately, the local vendors have not been able to meet my specifications of an optical grade reflective surface.
Just like to know the following:
1) Are there any recommendations for the type of material I can used to machine my parts to increase the reflectivity?
2) What are the recommended finishing that can give me the desired results? Will electro polishing + Chrome Plating do it? Thanks a lot
- Penang, Malaysia
2000
A. Kevin, What type of machined parts are these? We do CMP mirror polished stainless steel sheets and sanitary fittings. Ra is below 1 microinch on sheet products while Ra is between 5-7 microinch on sanitary fittings. Substrate is stainless steel without coatings. Reflectivity # I'm told would be better with coatings. Cheers Mike
Michael Liu Taylor
specialty stainless steel distributor - Dallas, Texas
2000
A. Kevin:
A great deal depends on the size, shape and metallurgy of the parts you are working on. Very low Ra finishes can be developed on a variety of metals utilizing successively finer abrasive materials in sequence.
If your parts are random or non-flat in shape using a loose abrasive method such as centrifugal barrel polishing can produce low single digit Ra microinch surfaces with high reflectivity and image fidelity. These kinds of process may not be appropriate if the surfaces you are trying to work have larger broad flat areas. If this is the case you might want to consider precision lapping.
- Bartlett
2000
A. I don't think chrome is much used as an optical surface because of its high absorptivity. Although chrome is specular, it's dark. Silver plating (or ideally rhodium plating) would be better, or aluminum sputtering; or you might make the mirror from chemically polished or electropolished aluminum. Good luck.
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2000
Q. There are lots of site that I have visited that give step by step instruction on how to... br
Don't we all feel that in this community we should have a similar page where all the contributors input their expertise. Finishing companies usually require large and repetitive orders leaving the small batch finishers in the quandary. Any suggestions.
Thanks,
Insi - Singapore
2001
A. We have more than 12 thousand finishing topics on line here [ed. note: as of 2001, 60 thousand topics currently], Haider, and we'll be happy to take any of those threads as deep as you wish.
But my own experience is that, no matter how great the willingness to share, public forums are not a substitute for books, because a topic can't be presented in orderly tutorial fashion without the months or years of planning that writing involves -- it's not just a matter of serving up facts (this forum tries very hard to do that), it's a matter of serving them up in an order in which they can be digested. Cogently writing a book is a far far bigger job than just accumulating the information. Ask a specific question and we'll all try to help, but asking a public forum to give you a rounded education on a subject, and too many cooks will spoil the broth :-)
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2001
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