Injection Molding the Body: Round 1

Noa & Jordan

4/1/14

Injection Molding the Body: Mold Version 1

Today we ran our first trial of injection molded bodies. As seen in Figure 1, we did multiple trials to fine tune the injection mold parameters. A picture of our parameter sheet is seen in Figure 2.

Figure 1: This shows the progression of runs varying the injection parameters

Figure 2: Our parameter sheet showing the evolution of parameters with our final parameters used.

We learned a few interesting things while running our first run of injection molded Yoyo bodies. First, we noticed that the shrinkage of the part during cooling was more than we expected. The layers that are supposed to fit within the body do not: the inner diameter of our body was 2.05 in and it should have been ~2.13 in. This means that we will have to scale up our molds and re-machine them. We will be going into lab tomorrow to measure the final diameters after the plastic has had time to cool and cure.

Figure 3: These are five injection molds of our final set of injection parameters

We also noticed that at the weld line, there is a small air bubble (Figure 3). This is problematic, as it means that we need to drill a small hole as a vent to 4llow the air to escape. Once we have our new mold, we will increase the speed and pressure of the injection mold to create a burn mark at the air bubble. This will show us exactly where to drill the vent hole.

Figure 4: An injection molded body showing a trapped air bubble.