plastic part weight to square inches

This question is meaningless as it stands.

DEAR SIR ,i do mean square inches of surface area

It depends on the thickness of the plastic!

The question is still pretty vauge....

You need to explain exactly what you mean...

With any injection molding the weight of the part plus any sprue will give you some idea of the amount of plastic per part....

But Area ??? area is meaningless unless you are making sheet of uniform thickness.

You need to realise that you may know what you are talking about , but we have no idea unless you tell us!

part thickness is aprox. one eighth of an inch thick

mass and area as you have stated. It is an openended question.

It is like saying how big (area) a pan do I need for a liter of liquid (volume).

Does that make sense?

just for the record. There was no z value given when I made previous response.

Oh, the ego. The most delicate of man's senses: sense of self.

Density = Mass / Volume

Volume = x*y*z

Area = x*y, so Volume = Area * z

Density = Mass / (Area * z)

So Area = Mass / (Density * z)

You could look up the density of the given material. You gave z as 1/8 inch.

Remember that mass and weight are not the same, and the English unit for mass is the slug, which is not used very often. I recommend you convert everything into metric before plugging into the formula, then convert back to inches. To convert pounds to grams, multiply by 453.59.

Find the volume of the part in either of two ways:

1) If you know the density of the plastic used to make the part, weigh the part on a precision scale (particularly if the part is small) and divide the part weight by the density to get the part volume.

2) If you don't know the density, completely submerge the part in water (use a precision graduated cylinder or something similar) to measure the displacement. Ensure no air bubbles remain trapped in or on the part, as these will increase the apparent volume. The displacement will be the part volume.

Note: Precision laboratory scales, graduated cylinders, etc., tend to use metric units: grams, kilograms, cubic centimetres, etc., so you will need to convert your results into imperial units (sigh).

Having converted to imperial units, calculate the volume of a one-square-inch sheet of the desired thickness (say, 1/8 inch thick): 1" x 1" x 1/8" = 1/8 cubic inch. This will be the volume "constant" of your sheet which, in this example, is 1/8 in³ per square inch of sheet area. Now divide the volume of your part by this constant. Let's say your part's volume is exactly 3 in³. Dividing the volume by 1/8 in³ (per in² of sheet area) will result in the area of a 3 in³ sheet in square inches, ie, 24 in². Naturally, this sheet will weigh the same as the original part.

If you know the type of plastic ,propylene polycarbonate styrene and if it is filled. EG. glass,mineral ,talk and the percent of the fill you should be able to look on most material manufactures web site and get the density of their material or another manufactures material in the same family should be very close.

try GE plastics,Bayer,ect.

Are you looking for the square inches to determine the clamping pressure required to know how big of a machine is required to run the part? If so, it has nothing to do with the weight of the part. If it is a simple round or rectangular part then the calculations are simple. If it is an odd shapped part, just measure beyond the part in 2 directions and multiply times each other to get square inches. Multiply the square inches times the estimated molding pressure (obtained from plastic manufacturer, 1000psi is a good place to start for things like ABS or Polycarbonate). This will give you a rough idea of the clamping pressure required to keep the mold closed during injection. Molding machines are rated in clamping tons and injection capacity usually in grams. You need enough clamping pressure to keep the mold closed plus extra for saftey and enough injection cpacity to fill the cavity, runners, and sprue.

Not my line of work, but fascinating nonetheless. Thanks!

Just use total surface area of the part.

How much area will you cover if someone lay you out flat? Say 1 atom thick.

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