Generative- Minimize mass and Safety Factor

[admaiora]

Hi,

can you help me in this?

Often I see in generative studies an oversizing design.

If i choose as criteria to minimize the mass until I am satisfied to my minimum safety factor, I expect that.

Look at this:

It seems that in this design it can be removed material (mass 2724 Kg) as my minimum fos is 1238.

I can accept until 2 as fos, i would like  a lighter design

Can you help me to understand that?

Thanks!

[I_Forge_KC]

Are the results converging? Are they getting to a high number of iterations but giving the warning that they can't reach the objective?

Remember that the solver is exceptionally good at finding local minima. If you get a result that is only partially optimized, it may be struggling to get out of that specific local minima. Try throwing a starting ahape at it, especially one that is oddly shaped and maybe full of holes. This will move you to a different area on the design space and will likely lead to different results.

[admaiora]

Hi @I_Forge_KC !

Thank you as always!

"Are the results converging? "

Yes.

"Are they getting to a high number of iterations but giving the warning that they can't reach the objective?"

52 iterations. No warning. All smooth.

😕

So can this be considered a software limit?

I don't understand why, reading a fos so high, the algoritm doesn't go ahead to reduce weight,,,

[admaiora]

This with starting shape

Attached you will find the initial setup (with no starting shape)

Thanks!

[bmfrank · Accepted solution]

Thanks for posting this example.  A couple of things to consider here:

• When minimizing mass, the Factor of Safety value is a limit, not an optimization target.  That means that the system can stop synthesizing the form without "achieving" the FOS.  It looks to make sure it doesn't violate the FOS limit you have put in place.  So you can say you want a FOS of 2 as a limit, but higher FOS's can be achieved by the designs.  
• When minimizing mass, we do stop the synthesis when a certain ratio of mass removal has been achieved. This is a limit that we have put in place to prevent the system taking things too far. This typically works in your favor, but sometimes we can run into instances that this will create an issue. In your case, the design space is quite large, so the removal of this large volume of material is a contributing factor to the synthesis stopping, and additional mass may still be available to be removed to achieve a more reasonable design.  
• In order to overcome this limitation at this time, you can take one of two paths
  • Create some additional obstacle geometry that can help reduce the initial design space.  For instance in the inside of the "v" of this design you could create an obstacle that would eliminate the volume of material that will be removed.
  • Alternatively, you can download the outcome and use this shape as a "seed" geometry for another run.  This is a common technique when trying to drive very efficient structures.  

We will continue to collect feedback like this so we can further enhance our methods for synthesizing solutions for problems like this. hopefully the suggestions above can help you reach your design intent.

[admaiora]

Hi Frank thanks for the clarification an suggestions!!

This phrase just confunded me: "Minimizes the mass so that your design has the lowest possible mass"

[TrippyLighting]

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@bmfrank wrote:

• • Alternatively, you can download the outcome and use this shape as a "seed" geometry for another run.  This is a common technique when trying to drive very efficient structures.  

Wouldn't that get expensive pretty quickly ?