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Author Topic:   How do you calculate volume of gram weight?
alex
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posted 05-01-2003 10:05 AM              Reply w/Quote

I am designing a HDPE bottle. It's liquid volume plus headspace is 220mL (13.45 cu/in). I also have the estimated gram weight of the plastic at 20-22g. How do I translate the gram weight of the plastic into cu/in? I need to get an accurate TOTAL volume analysis on my 3D model.

Thanks.

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d guy
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posted 05-01-2003 05:33 PM              Reply w/Quote
how did you get gram weight?

you need to know the volume of plastic... if you are using cad it should be straight forward (in solidworks- select the menu command, Tools: mass properties)

the next thing you need is the "specific gravity" of the resin you intend to use... look it up in modern plastics encyclopedia (there are online resources as weel)
HDPE can be >.941-.965<

Multiply your volume in CC's by the specific gravity and you have your part weight...

you can convert to cubic inches if you want, but any molder I know will work with gram weight or volume to quote.

Just looking at your weight estimate, you should be looking at more than 22cc's or 1.34 cu/in

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alex
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posted 05-01-2003 10:56 PM              Reply w/Quote

thanks alot. that is some great info that i will certainly be passing along. just to fill you in, the gram weight was provided by the client -- for each "size" of bottle (there are 10 sizes in the family) there was an estimated gram weight.

thanks again.

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d guy
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posted 05-05-2003 09:24 AM              Reply w/Quote
good luck with the project Alex!
btw- here is a cool little conversion program to convert measurments...
http://www.joshmadison.com/software/

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