Simulation is Child’s Play, Broken Toys Aren’t

This is my presentation from CAASE20: The Conference on Advanced Analysis & Simulation in Engineering. This is my favorite simulation conference because it’s solver agnostic. You can meet analysts outside of your particular software silo. Alas, this year it’s virtual, however, as a plus side I have the recording of my presentation. 7 programs in 18m 43s, lets get to it!

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This is a case study of multiple knit line failures on the popular fidget spinner toy. The toy’s geometry has been reverse engineered to create suitable geometry for a variety of simulations and redesigns. From an injection molding standpoint, the three lobed design, with 4 holes allow for a deceptively difficult molding problem. Knit lines are inevitable but where should the gates be located and where will the knit likes be located? Injection molding simulation is used to investigate a variety of gate locations and the use of multiple gates. Once the molding technique has been selected what can be done to maximize the strength of the part without deviating too far from the iconic design? Finite element analysis is performed to simulate the stresses induced through press fitting of the bearings. The simulation was carried out by having the bearings in place using contact with removing overclosures. This method is more computationally efficient than pressing the bearing in which would include sliding contact. The bearing insertion causes hoop stresses in each lobe. These stresses put the knit lines in tension which causes part failure. We will assume that the locations and sizes of the bearings are fixed and the outside diameter for ergonomic reasons. This sets the allowable design space for the redesign. Topology optimization was then used to evolve the design to maximize strength and stiffness while minimizing weight and cost, creating a design suitable for 3DPrinting.

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