Shape Optimization

How to design parts that are stiff and light

Shape optimization is a powerful tool for finding a balance between two parameters.

 

Lets say you're designing a C-Clamp frame.

 

You want two main things:

  • Maximize stiffness of assembly

  • Minimize amount of material

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The less material you use, the cheaper is will be to make in mass production. 

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The question is, how do you get there?

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Fusion 360 offers a great tool for this! Best of all it takes like 30 seconds to set one of these up and then it's all solved in the cloud.

adding constraints in fusion 360 shape optimization

Step 1: Constrain some part of the model.

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This is the "fixed" part that cannot be moved. In the c-clamp case, it's the threads of the screw. This could also be the top clamping surface. It doesn't really make a huge difference. 

adding forces in fusion 360 shape optimization

Step 2: Apply a force to the model.

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This is where all the force will be applied. This is the top clamping surface for the c-clamp. As mentioned above, this and the constrained part of the model are interchangeable for this c-clamp frame.

adding symmetry in fusion 360 shape optimization

Step 3: Add keep-out zones and symmetry.

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Keep out zones make sure the simulation leaves material in certain areas. I've applied them to the top clamping surface and around the threads.

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I've also added a plane of symmetry down the middle of the part. This helps reduce the solution time. for the c-clamp, the result will be symmetric, so no point in taking longer to solve than necessary.

Results of shape optimization in Fusion 360 FEA

Step 4: Solution!

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Here is the solution for a mass target of 30% of the original.

Play with the Model

 

You can switch to the simulation view by hitting the button in the upper left corner:

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Controls:

  • Left click and hold to orbit

  • Right click and hold to pan

  • Scroll wheel to zoom

 

Download Model

Bike Frame
Results of FEA shape optimization on a bike frame in fusion 360
Chair
Results of FEA shape optimization on a chair in fusion 360
Bridge
Results of FEA shape optimization on a bridge in fusion 360
Cantilever Beam
Results of FEA shape optimization on a cantilever beam in fusion 360
Tips and Tricks

  1. Material doesn't matter for shape optimization. This is a linear optimization

  2. Unless you have multiple forces, magnitude of force doesn't matter either

  3. Given points 1 and 2, it's important to redraw the optimized shape, and run a classic static FEA on it to make sure the shape is strong enough

  4. Push the mesh density as high as you can. It makes a more accurate results. Low mesh densities will solve in the cloud in a few minutes, but are pretty rough. A maxed out mesh may take 4 hours to cloud solve, but the results are very good.

  5. Always specify planes of symmetry, and any keep-out zones