(EGG)STRUDED DESKTOP SCULPTURE

Tools and Skills: CAD in Fusion 360, Shape Optimization, Static Simulation, Generative Design, Latticing & Parametric Modeling in nTop, FFF 3D Printing

Project Brief

Create a physical project that synthesizes your knowledge of material properties, design for additive manufacturing, and 3D modeling tools. The design should take advantage of the capabilities of additive manufacturing, and applications may include either the design of fixtures/tooling or algorithmic modeling

Challenges

The main challenge I faced in this project was scoping down my concept idea. Challenges I faced after pivoting were learning how to use nTop, an implicit modeling software for additive manufacturing, and manipulating obstacle geometries in using Fusion 360’s generative design feature in order to “force” a final product.

Results

The end goal of this project was to create an unconventional desktop art display that appears delicate but in reality is very durable so that it can be easily transported and stored. Both structures are more robust than expected thanks to their material properties, but if I had more time on this project, I would have liked to put more work into the aesthetic and mechanical design.

INITIAL CONCEPT IDEATION

Upon learning about algorithmic modeling and latticing in lecture and homeworks, I wanted to use these techniques to create something performance-optimized and geometrically complex for this project.

When looking for inspiration for this project, I came across these intricate eggs on Pinterest. As an egg-lover myself, I was intrigued and wanted to:

  1. Learn how to use nTop to create my own set of eye-catching, structurally complex eggs with latticing

  2. And create a shape optimized or generative designed, durable, transparent/translucent vessel in which to store and showcase them.

Initially, I wanted the display/storage vessel to be a shape optimized egg carton, which would have snap joints and a living hinge similar to a real egg carton. However, in performing shape optimization simulations, I learned that achieving this structure and functionality would be challenging and beyond the scope of this project.

(UNSUCCESSFUL) EGG CARTON SIMULATIONS

These simulations were meant to generate and test my initial idea egg carton idea. The intended material was polypropylene, which is great for living hinges for its high durability and fatigue resistance and is translucent.

Shape Optimization Set Up: Fusion 360 is able shape optimize a model given constraints and load cases that simulate potential use cases (ex. putting the eggs in the carton) and misuse cases (ex. accidentally squashing the carton by applying a large force).

Ultimately, these simulations were unsuccessful due to challenges with set up and accurately simulating the load cases given Fusion 360’s capabilities. What these results did tell me, however, was that it was time to go back to the drawing board.

Shape Optimization Results: were unsuccessful because the end product didn’t indicate essential geometries and removed material in areas where there material had to be (ex. missing materials where the eggs were going to be).

Static Simulation Set Up: This simulation was meant to test the viability of a living hinge. In order to see whether the hinge is flexible enough for the faces to meet each other, I applied a downward force to the outer face of the carton to simulate closing it.

Static Simulation Results: were unclear and inaccurate because this type of simulation only accounts for linear loads, when in reality the force and displacement of closing the egg carton would be nonlinear.

PIVOTING

The unreliable results from my egg carton simulations, worries about scoping, and what I ultimately wanted from this project (cool-looking eggs) led me to pivot away from the egg carton idea. 

With some guidance, I scoped down my project from 6 eggs to one, and from the egg carton to a pedestal/egg cup. I still planned to learn nTop in order to create the egg, but rather than use shape optimization to create the vessel, I decided to use generative design.

GENERATIVE DESIGN IN FUSION 360

Fusion 360’s generative design feature literally generates candidate end products given the following information:

  • Preserve geometry: features that must be included in the final model

  • Obstacle geometries: indicate areas where material cannot be generated

  • Starting shape (optional): influences the shape that the final model will take

  • Load cases: simulate use and misuse cases

  • Material(s): of which the final design is intended to be manufactured

  • And manufacturing methods: how the design is meant to be physically produced.

With this information and many hours, Fusion generates optimized and robust designs for each combination of materials and manufacturing methods.

First Pass: Initially, I only included preserve geometries (green) and obstacle geometries (red) that I thought would produce an interesting final shape. The resulting designs were Dixie Cup-like, and a bit underwhelming. I was envisioning something with more curvature and volume.

Final Iteration: In order to “force” a more bulbous, goblet shape, I kept the same preserve geometries and implemented a starting shape (yellow) surrounded by obstacle geometries (red and the egg). Since no material could be generated in the red areas, the design would be forced to follow the path established by the starting shape.

LATTICING & PARAMETRIC MODELING IN NTOP

As mentioned, nTop (formerly nTopology), an implicit modeling software for additive manufacturing, was introduced to us as an ideal tool for creating lattice structures, which are repeated patterns that give strength to otherwise lightweight materials.

First Pass: I wanted the egg to achieve an “impossible” look — one that makes the viewer wonder “how is that even possible?”. I thought that a surface lattice would be perfect for producing this appearance while maintaining strength, but this look was missing the dynamism and aesthetic that I was going for.

Final Iteration: In continuing to learn about nTop, I came across parametric modeling. In this case, the appearance of the egg’s surface was driven by fields, or “gradients of geometry,” that were constrained by parameters. The final design was a patterned intersection between gyroid and lidinoid fields.

SLICED DESIGNS

Because these models both had features with overhangs, or shapes that protrude from the main body, at angles greater than 45 degrees, they required removable supports in order to print properly (indicated by the area highlighted in aqua). Even though these prints were not large, they had long print times (6 hrs for the stand, 10 hrs for the egg) due to the fact that they have gaps in their shapes. Gaps prevent the printer from being able to print layers continuously, and the time it takes for the printer to repeatedly retract material and re-extrude it increases printing time significantly.

FINAL PRODUCT

Overall, this project was really fun and fulfilling for me. I got to learn how to use nTop, and I became much more familiar with Fusion’s simulation and algorithmic modeling features. I will say that if I were to do this project again, I would definitely put more time into thinking about the aesthetic and mechanical cohesion of the display. I was so focused on creating two geometrically interesting objects that I didn’t think about how they would interact with each other, and it would have been nice to incorporate way to secure the egg to the stand. Otherwise, both the stand and the egg are extremely robust, and they come together to create something interesting and unique!