In a manufacturing methods course focused on injection molding, I worked on a team project where we were tasked with designing a part, designing the mold, machining the mold, and injection molding at least 10 "perfect" parts.
For this assignment, the only 2 constraints on our part design were that (1) it had to be based on drawings we received from students at a local elementary school and (2) it consisted of at least 2 components assembling to form the final part.
For design inspiration we were given a dinosaur, flying pencil, and flower.
Initially, we were drawn to the idea of a lotus flower with each petal being a separate part that fit into a lily pad base. Unfortunately, our professor deemed that the delicate and organic petal geometry of our flower would be a bit too difficult for designing and machining a mold within our time constraints.
Original lotus flower concept
Drawings received from local elementary school
Flowers aside, we switched our focus to a dinosaur! A cute miniature velociraptor with 2 symmetrical halves that assembled together via snap fit pins. This was the final model we landed on.
We designed both the CAD and CAM for the molds (core and cavity) in NX. For the cavity molds, we created 0.25” diameter wide runners from the sprew to the tail and foot of the dinosaur. We placed the runner edge 0.003” away from the cavity of the dinosaur to leave room for us to file in the gates after the mold was CNC machined. We made sure that the direction of the injection molded plastic would be towards a wall so that the plastic would pool and give an even consistency and spread throughout the mold effectively.
After checking repeatedly with our professors and TA's to ensure our CAM was accurate, safe, and efficient, we CNC machined our molds and were successful in creating perfect molds in our first attempt! This was pretty exciting for me as this class was my first experience with CNC machining.
The next step was injection molding the parts. This part took a bit of tuning temperates and troubleshooting a variety of surface defects, but eventually we got in the swing of things and made a bunch of colors! We were only assigned with making 10 "perfect" parts for grading, buuuut we all loved our little velociraptors so much we wanted to make enough for us all to take at least a few home 🙂 Here's a look at the finished parts!
Our first part off the mold came out pretty good with just a few defects around the pins.
