Last Friday my group finally got to mold our cars with the injection molding machine. Unfortunately, our molding process didn’t go as smooth as we had expected. There were several issues with our mold design that caused some headaches and improvisation to get our mold to work. Pictured above were three of the many rejects we made while we tuned the machine and fixed our mold.
At first, the major problem we experienced was that our top half of the plane was sticking to the stationary mold plate after the plates separated. This was a very annoying problem because it required us to remove the plate from the machine and pry it out pliers. Our vertical stabilizer on the tail of our plane was the culprit to this problem. To fix it, we replaced the ejector pins for the part with shorter ones. This meant that the extra space filled with plastic and allowed the part to stay on the proper plate when they separated. Another problem we had was that our bottom half of our plane wasn’t filling. The CNC machine didn’t remove enough material from the extrusion, so the whole cavity was blocked off. We used a Dremel tool to remove a small amount of material so the plastic could fill the cavity. After a bunch more tries we finally dialed the machine in properly and molded a big set of cars, probably around 30. From there we had to post-process them because of the impromptu changes we made to our mold. This involved shaving down excess plastic and removing flash.
Next, we had to prep our planes for our partners at Broughal Middle School. They are in charge of painting the cars and specifying which one we will race. But before they can paint them, we had to glue parts together and coat them in primer. Once that was done we wrote up some simple instructions for painting and shipped them off. We’ll get back our race cars next week and are eagerly awaiting their arrival. In the meantime, we are tasked with going out and acquiring axles and wheels to attach to our painted cars to prep them for the race. More updates to come!