Injection Molded Patrick
Mechanical Engineering Classwork
Designed and produced a custom injection-molded component, managing material selection and mold design to achieve repeatable, high-quality part geometry at volume.
Skills: SolidWorks CAD, Siemens NX CAM, CNC Milling, Injection Molding, Injection Molding Design
Overview and Design
As part of my Mechanical Engineering curriculum, I participated in an injection molding class. I worked as part of a team of 4 to develop a polypropylene Patrick figurine. We were required to design a part with two unique halves as well as assembly features to connect both pieces.
Our team utilized Siemens NX to design both pieces. We designed two thin-walled shells with in-part pin and socket features. We took special to ensure proper design for injection molding, such as draft angles, no overhangs or side pockets, runner placement, and press fit tolerances. We then used the pieces to design a core and a cavity for each half. I designed the core of the back half.
CAM & CNC
Using Siemens NX, we each wrote a CAM program for the mold part we design. My goals were to minimize machine time and tool usage. Feeds and speeds were given to us as to limit the risk to the class’s tools. The CAM programs were reviewed by the TA’s and professor, but each were written entirely by the team.
CNC-ing was done on a 3-axis Haas Super Mini Mill. The parts were machine out of a 6061 billet that had been prepared by the TA’s.
My mold was machined without issue, though the surface finish was rougher than expected, which we cleaned up using sandpaper and Scotch-Brite.
After CNC-ing, I press fit steel dowel pins in three places to create the injection molding socket assembly features.
Injection Molding & Metrology
Finally, we injection molded the parts. Polypropylene was used due to its favorable injection parameters, and its overall durability for assembly features. The injection parameters were chosen by the team as we iterated through parts until we found ones that worked.
Using 20 of our molded parts, we performed a metrology study to compared the final part to the CAD model.
Griffin Braunreiter 