Fantastic idea, I really like it.

 

Looking at only the DOW stuff, that comes out to a density of 0.0193 Oz / Cu inch.
Compare that to what http://www.wolframalpha.com says about "EPS Density" and you get 0.013 Oz / Cu inch. I'd say you are right on, given the film covering.

To obtain the weight for your pure sytro part, you multiply the density by the volume.
Unfortunately SketchUP is a surface modelling program and obtaining an accurate volume can be tricky. Lucky for us we are printing PHLAT!

The equation can be simplified by saying that per sq inch it holds so much weight...
Therefore you get about 0.005 Oz / Sq Inch...
So all you need now is the area of your part to multiply by that constant and you have an estimated weight.

OZ . . . . . . Sq Inches
----------- x -------------- = OZ
Sq Inches

 

Hey no problem 7up.
This should be an easy operation to add to the script as SU already computes the area of each part you layout! To get an area (of any face), just right click and go to entity info, the number it gives you in sq inches, multiply by the 0.005, and you will have a good estimated weight for that part in OZ!

 

Here is how you crunch this out for the metric folks (who design in mm). First, we need a density of the material. Density is mass / volume, but we are working with a flat surface with a constant height so the depth can be omitted in this example, doing that leaves area.
To get the area of the 2x4' sheet of foam that's:
609.6mm x 1219.2mm = 743224.32mm(squared), 7up provides the mass at: 158grams
158g divided by 743224.32mm squared equals:
.00021258723073001701558958673472903 grams per square mm of foam.
Pretty light stuff, we are dealing with very small units, and those are hard to use.

It might make better sense to use milligrams to do the computation.
so that be, 158 000mg / 743224.32 square mm...
meaning 0.21 mg / square mm, given that the stuff is a constant 6mm thick
(Still very small units, but easier to work with now).

And that is your given (metric) density for the DOW III stuff.

Kinda neat, so if you right click to find out you have 5000 square mm in a given area, all you have to do is run the math... but don't lose track of your units!!

0.21 mg . . . 5000 Sq mm
----------- x -------------- = 1050 mg (top units cancels the same units on bottom)
Sq mm . . . . . . .1

For the metric heads out there getting grams from mg is easy, I still get confused though because it seems to easy... to go from mg to grams divide by 1000.
So for the example given face, you'd have about a 1.05 gram for the given part.
Btw, this can be double checked with a simple 70mmx70mm part. I'd do it now, but I don't have a scale or foam on hand... :mrgreen:

 

Why not just give area and not weight? Then it will work for any material?