plating, anodizing, & finishing Q&As since 1989

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# Measure Surface Area of 3D parts?

Q. I have been retained by a local plating company to develop a procedure for measuring the surface area of complex 3D metal stampings. We do not have access to the drawing of the original flat part, so can not use a planimeter. The parts are up to 10" x 4". I am considering measuring volume by immersion in water and dividing by thickness to get surface area. Is there a better way? Any equipment or software out there?

Thank you,

- Freeport, Illinois

2003

A. I think you are on the best and simplest track if the article is of constant thickness.

Ted Mooney, P.E.

Striving to live Aloha

finishing.com - Pine Beach, New Jersey

2003

A. You could determine surface area by plating your sample together with a flat sheet with a known surface in an electroless nickel bath. You should weigh sample and sheet before and after plating and calculate the unknown surface by the simple relations.

Daniel Livshitz- Tel Aviv, Israel

2003

! Thank you for this idea, Mr. Livshitz, it's a great one!

Ted Mooney, P.E.

Striving to live Aloha

finishing.com - Pine Beach, New Jersey

2003

Q. Could you find the surface area with metal thickness and weight. Is there a conversion chart.

Tom Scherr- Cleveland, Ohio

2004

A. Certainly, Tom. Just divide the weight of the article by the density of the metal in question, and you have its volume. Divide the volume by the thickness and you have the area.

Ted Mooney, P.E.

Striving to live Aloha

finishing.com - Pine Beach, New Jersey

2004

Q. We are in a similar situation at the company which I am working for. We also have 3-d objects in which we are trying to plate, but some parts are fabricated before they come to us. We are in need of a way to find the surface area of our parts for plating. Right now we are using the standard form of surface area measurement.

Darla RobertsDarla Roberts - Ohio

2004

Q. Hi, I noticed all your questions and answers on this subject were quite old and wondered if you had found a simpler/better way to work out the surface area

many thanks,

kt

designer - england

2007

A. Three pretty good ways were proposed, KT -- I especially liked the one about plating the part with electroless nickel. A better way would be a camera and software that could inspect the part and calculate its surface area. It doesn't sound hopelessly difficult but I haven't seen such a thing marketed yet. Good luck.

Ted Mooney, P.E.

Striving to live Aloha

finishing.com - Pine Beach, New Jersey

2007

Q. How to calculate Dm2 of extremely irregular jewelry?

We manufacture filigree and filigree is completely hand made made from silver fine wire; pieces can be very large, e.g., 10 cm diameter but weigh 22 grams as the piece is full of holes between the wire.

Which is the best way to accurately calculate the Dm2 of each piece?

manufacture - BANGKOK, THAILAND

June 26, 2012

A. Measure the surface of a given length of wire and then weigh that piece of wire to get surface area per gram.

Neil BellRed Sky Plating

Albuquerque, New Mexico

June 29, 2012

A. The surface area of a steel stamping can be determined fairly readily mathematically. The surface area of the faces (in square feet per pound) is given by 0.04903 divided by the thickness in inches. To this can be added the edge area, determined by estimating (or calculating) the edge area as a percent of the face area. I won't go through the arithmetic, but it is quite straightforward. It is important to recognize that the stamping can be bent, shaped, twisted, or deformed in many ways without changing the surface area. So all you need to do is weigh the part and apply the formula. For other metals, you can adjust this formula by comparing the density of steel with the density of the metal from which the article was fabricated. For example, an article fabricated from 12 gage steel (thickness of 0.1046 inches) will have 0.4687 square feet per pound on the faces of the article. This is the easiest way to determine the surface area of the part, and this approach has many other derivative benefits, including the gravimetric determination of coating weight.

Tom Rochester

CTO - Jackson, Michigan, USA

Plating Systems & Technologies, Inc.

July 3, 2012

Q. Re. your previous reply, it's quite complicated to do as mentioned as one piece of jewelry can be made of several types of wire thicknesses and produced on a large volume scale. What we were doing is, but we don't know if correct, we suspend one sample piece to be plated in D.I. water and check its weight, then we suspend in the same water 1cm x 1cm flat silver piece and take its weight as follows...

So 1 cm x 1 cm flat silver pieces = 1cm2 =0.01 dm2 ...... it's volume weight in water = .10/ gram

One jewelry piece its volume weight in water is .60/ gram so according to our calculation its dm2 is 0.06dm2

Is this correct?

- BANGKOK THAILAND

July 4, 2012

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A. Silvio, I do not think your approach is viable. For example, consider two pieces of wire of the same weight. One has half the diameter of the other. Therefore it will have twice the surface area. Yet they will displace the same amount of water. The only thing your test will tell you is the density of the material tested, and, unless your technique is exceptionally good, it is unlikely that it will be as accurate as the densities you can look up in the Handbook of Chemistry and Physics or Machinery's Handbook or the like.

You might remember the story of Archimedes of Syracuse shouting 'Eureka!' when he discovered this approach while immersing himself in a bathtub. (This is a little different from Archimedes Principle.)

In my humble opinion, the best way to determine the surface area of an article fabricated from wire is to use this formula (which applies to steel): the surface area in square feet is given by 0.09805 divided by the diameter in inches. This assumes that the article is long enough to ignore the ends of the wire. I won't go through the arithmetic, but is is quite straightforward. So all you need to do is weigh the article and apply the formula. For example, an article fabricated from 24 gage steel (U.S. Steel Wire Gage; there are other gaging systems; check Machinery's Handbook for details) which has a diameter of 0.0230 inches, will have 4.263 square feet per pound. If the article were fabricated from copper (density 8.92 g/cc) instead of steel (approximately 7.75 g/cc) it would have 13.12% less surface area or 3.704 square feet per pound. You can make other adjustments for other metals or alloys. I believe that this approach is a lot easier and more accurate than plate-weigh-strip-weigh measurements.

This approach and formula has many other derivative benefits, including the gravimetric determination of coating weight.

Tom Rochester

CTO - Jackson, Michigan, USA

Plating Systems & Technologies, Inc.

July 10, 2012

A. Draw it, if possible, on Rhino and then calculate area.

Daniel Hernandez- Bucaramanga, Santander, Colombia

July 7, 2012

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