Plastic Injection Molding Project

Ever wondered how your old toys from McDonalds were made? Last quarter I took a Mechanical Engineering project class on plastic injection molding. Basically, the majority of plastic items (including  McDonalds toys) are made through a process called Plastic Injection Molding.

 In this class we split into about 15 teams of four and each team had to make a plastic injected part. It sounds so simple it but it is a very complex, stressful, and involved process. This project was also a competition so the best three teams got a prize.

 Brainstorming- What kind of carousel we wanted to make. The pic on the left is a 3D render of a carousel I made for a CAD class last year.

After much thought and Ad's stroke of brilliance (she thought of doubling the bottom and top), we designed and drew out the separate parts. Initially we were having a lot of trouble simplifying the carousel into something we can make- but in the end we came up with an intelligent design that could be made with repeats of three distinct parts.

Then we had to make 3D computer models of our parts.

Plastic Injection is essentially pushing melted plastic into a mold. For this class we had to make our own molds. Each mold has two halves which come apart after the plastic is injected. Here are the mold designs- we had a constraint of 2 molds (4 mold halves). We put the horses on one set and the base and column on the other. Our mold design was efficient, economic, and intelligent since we designed the molds so that plastic would flow evenly into it..

In order to make our molds, we need to get block of Aluminum and cut it down to the exact shape and size of our computer modeled molds. A CNC machine can cut everything automatically. We can tell the CNC machine how to cut it by making the programs in UG NX, generating the code, and then uploading it into the machine via floppy disk (i know- so old school). Here is a snap shot of a program. The light blue lines represent the path of the cutting tool but they are so close together it is hard to tell.

Here is a CNC machine that is similar to the one we used.

Pic of tool cutting a metal block to make one of our molds.

So after so plastic injection moldig all we had to do was assemble them to get a cute carousel. Did i mention that it spins around too?

My SolidWorks render of our carousel.

So we won second place in the competition!!! The judges granted us second cause they were impressed by our part and mold design. I was surprised cause we were the only newb team that won anything. I really enjoyed the project and my team.

 Anyway, here are a few of the other group projects.

This won first place. Although it looks very simple- inside of the fish it is quite complicated. They won because the engineering behind their project was perfect.