Zugnoni's Zen Piano Palace (Z2P2)
- Course ID: DSGN 106-2
- Course Title: Design Thinking and Communication II
- Date: March 2022 - June 2022
- URL: Final_Project_Report.pdf
- Skills: CNC Mill, CAD/CAM, Injection Molding, Team Management
Project: Develop a product that involves an assembly of two or more molded plastic parts.
My team was tasked with creating an assembly of injection-molded parts. Through CAD modeling, mold design, and CNC programming, we produced Egguardo (she/her), a penguin sitting in an eggshell. This product required two mold designs composed of three separate parts, which assembled the two penguin halves and the eggshell.
Initial Product Ideation
We began with initial ideation sketches and decided to make a penguin using one mold. Since we were required to use 2 molds, we designed an egg for the penguin to sit in. Initially, the penguin had an ambitious design with many small details and 3 pin holes on the bottom to connect it to the egg. The egg was initially designed to be half the height of the penguin with a zig-zag top pattern to emulate the “cracked” egg. The penguin was to be assembled in 2 parts, with its parting line on the vertical front plane. This design allowed for the penguin halves to fit in one mold, with the egg fitting in the center of our second mold.
Part & Mold Design
The CAD part and mold designs underwent the most iterations throughout this project. Design for manufacturability (DFM) concepts were learned and applied through design changes. Because, in this case, the pins had to be perpendicular to the mold surface, one large hole was created on the bottom of the penguin for alignment to the egg using a shuttoff feature. The front and back halves of the penguins were connected by 4 pins with interference fits around the penguins's perimeter. The "cracked" egg feature was removed as there was no safe way to manufacture the ridges with the tools available. The egg mold did not require a runner, only a gate, due to the minimal distance from the sprue. The penguin mold required one runner between both halves of the egg with one gate per half, ensuring that both halves would fill and cool evenly.
Manufacturing the Molds
We scheduled machining times using NX Siemen CNC Programming to create Egguardo and her egg-saucer home. The CAM process went smoothly overall. The main challenge was the limited tool heights for the 1/16” and 1/8” tools, which caused issues with our original egg design. We addressed this by measuring tool lengths and offsets carefully for future programs. During the machining of the eggshell core, an oversight caused the x and y planes to offset by 0.2” in opposite directions, misaligning the molds. We fixed this by re-running the program with the correct offset. Drilling pin holes was also challenging due to the intricate geometry. Initial attempts required interrupting the roughing operation to make space for the drills without risking collisions. Minor issues like excess material around the core edges were resolved with light sanding and filing to improve the surface finish.
Injection Molding the Final Product
We used the manufactured molds to create 20 functional injection-molded assemblies. Since some parts were short-shot, heat-deformed, or otherwise defective, we injected 32 penguin molds and 22 egg molds to produce 20 acceptable assemblies. We then conducted a metrology analysis to assess the variations in our molds, examining factors like gate size, part shrinkage, heat fluctuation, and the heating, injection, and cooling times.
Takeaways: Understand the applications, advantages, and disadvantages of injection-molded manufacturing.
The most time-intensive aspect was iterating on the part design to ensure the molds were machinable. Considering tool sizing, machining time, and tolerancing allowed for the penguin halves to fit well. Working in a team of four presented challenges in delegating work and scheduling machining times while meeting deadlines and outside responsibilities. Setting standard expectations, maintaining consistent communication, and our dedication to the design of Egguardo kept us focused throughout the quarter.