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Surface area calculations of irregular shaped objects
I have some parts that I need to figure the surface area on. The first is circular with several irregular shaped holes to keep the weight down, and the second is sort of an oval piece with even more holes of various shapes and it also has little nodes sticking up off it and a dual layer over some of it. Is there an easy way to figure out the surface area of this with out the actual blue print.
Jeff Garrettanodizing shop employee - Elgin, Oregon
May 26, 2009
May 25, 2009
Hi, Jeff. Divide the weight of the item by the density of the alloy and you'll have the volume of the component. If it's a stamping or extrusion of consistent thickness, divide by the thickness and you'll have the area. Multiply by 2 sides for the approximate surface area.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
If the reason for surface area is to do hard coat anodizing, then you could use the parallel circuit method shown in Harold Weisner's paper published in the 1958 AES Proceedings and plaguerized in my book.
Or you may use Alcoa's 1957 table of voltage for alloy for up to
0.0008 at 70F 165.3 gm/L. Spend 7 minutes ramping up the voltage to the volts indicated per alloy (16 for 6061, 21 for 2024) which will be at 12 ASF (for 70F 165.4 gm/L). Now observe the amperage, then spend the next 8 minutes to double the first read amperage and you will be at 24 ASF. LOck and hold for time cycle to thickness.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
May 27, 2009
May 28, 2009
Another option (and the most accurate, I've found), if you don't mind going back to your customer, is if the drawing was done on Solid Works they can easily figure out the surface area with a built in feature on that program.
We do that with all the parts we design, and manufacture/anodize in my shop...I've found it to be extremely helpful.
Marc Green
anodizer - Boise, Idaho
June 4, 2009
Hi,
I recently started machining and anodising on a small scale and had this exact same problem, and seemingly the area calcs have to be pretty close or it throws out the entire process. I found that drawing the part first using Google Sketchup 3D will provide you with an accurate area calculation. Sketchup is a free download and tons of video tutorials are available. I'm no draughtsman, but I find it easy and great to use for this purpose.
Regards,
- Lancashire, UK
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