How to use mass as an input and density as an output

[caelan_babenko]

I want to input the mass of a part and the density to be automatically calculated (fusion 360). The only way I've been able to find online to get your part to be the exact mass of your part in real life is to manually calculate your density or have every your part be modeled exactly how it is in real life.
How can I do this?
And why is it so hard to find how to do this?

[Drewpan]

Hi,

Fusion uses materials with the physical properties defined by the user or pre-defined. Normally you would create

your part and since the default material is steel, fusion would work out the volume of the part and return the mass.

This is the opposite to what you want. Unless you started programming with the API, I don't think you can get fusion

to work out a density from an input mass because the density is one of the defined parameters.

Why would you not know the density of the material you are using? Fusion has many materials in the library and all of

them can be customised by the user. Fusion automagically works out the volume from the part and gives you the mass

calculated from the material density. Fusion will not adjust the size of the part to fit a mass as this would change the

part. It also would not remove material from the part to hit a targeted mass as it doesn't have a way to select what to

remove. It may be possible to do this with generative design in fusion but again I think you would need to program

the API to get what you want.

Surely you are not designing a part and calculating a density to take to a manufacturer to "cook up" some exotic

material of a very specific density for your application? The cost of such an exercise would be immense. Engineers

are paid big bucks to redesign parts to hit mass targets and it is hard to do. There is only so much material you can

get rid of before strength and other properties degrade the safety factor below acceptable. The Airbus A380 was

way over initial calculated weight when they were designing it and it still ended up heavy on the final product. Airbus

would be using the best people and huge computing power to get what they want and they still missed target.

Cheers

Andrew

[jeff_strater]

Isn't is as simple as finding out the volume, then dividing your desired mass by that volume to get the density?  Create a new physical material, and assign it that density.

[g-andresen]

Hi,

A density is defined for every substance.
A mass is calculated from this density and the volume, but not vice versa.

günther

[caelan_babenko]

The idea was so you don’t have to manually calculate the density, it calculates itself when you put in the mass

think of an online calculator for something where you put in a few values (in this case 1 value; mass) and it spits out the number by itself calculating everything itself instead of you having to calculate it via a calculator or spreadsheet. The output of the calculator would be the density of your part.

do you see what I’m trying to say?

[Drewpan]

Hi,

I think you have missed the whole point here. As a student you might do theoretical calculations about density,

but as an engineer or designer we create things for the real world. We use existing materials with existing properties

we don't design something and get a manufacturer to hit a specific density for a material. What you are asking for

would never be used in the real world.

Fusion has materials that can be fully customisable. If you want a specific material with a specific density then copy

and edit a material and set this to be the material for your model. What you are asking for is a tool that would never

be used. Except maybe students to do their homework.

Not even NASA who are totally dependent upon strengths of materials and densities would go to a manufacturer and

say "hey develop us this material with this specific density and mass characteristics". If it were possible in this world

then I am sure they would do it but instead they give researchers millions of dollars to find new materials and then

use them.

Cheers

Andrew

[caelan_babenko · Accepted solution]

Hi Andrew, I'm just used to using solidworks where I use the density of the material (before manufacturing), but after a part is manufactured I just overwrite the mass value, and solidworks dose the rest. (I think its a rule to not compare other software to fusion) but I was just used to the method solidworks used, but I guess I'll have to learn to get accustom to calculating the density's myself in fusion.

Thanks,
Caelan

[Drewpan]

Hi,

I am wondering then exactly what you are trying to do. Solidworks would do the same thing - have set properties

for each material. The density should not change before and after manufacture as you are removing mass AND

volume. The density numbers should be identical unless you are trying to work out the density of an imaginary box

around the part and use the mass of the part before and after. This does not make sense either.

In fusion you can make a cube of material and fusion will work out the mass and volume for you. If you then drill a

hole in that cube, fusion will recalculate the mass and volume. The density of the material does not change but the

mass and volume will. I don't use Solidworks but I cannot think of how and why it would work the way you suggest

for the reasons I have given - density is a property of the material.

Can you please attach your model so we can see what you are trying to do as your last post has muddied the water

not clarified your issue.

Cheers

Andrew