Thermoform Optimization

The parameters for our thermoform part went through a lot of alterations. It was important to us to get good definition in the plastic from our mold so that the ring parts could fit around the basketball. To achieve this, we drilled extra vacuum holes in the mold around the basketball shape.

The finished thermoform mold, machined on the CNC mill. Notice the vacuum holes around the basketball.

Through testing the mold on the thermoform machine, we found that a high heat time also helped give the final thermoform part good definition. However, too much heat time left the plastic looking warped. We settled on a twenty second heat time.

The final parameters for our thermoform design.

The thermoformed plastic parts came out of the machine like this : 

Early thermoform part.

We then decided on a die size to use to cut out the part that would go into the yo-yo. We settled on a diameter of 2.072 inches.

Thermoformed part cut out using a die.

However, we weren't happy with the bubbles that would form on the face of the basketball. Dave theorized that dust on the unformed plastic sheets might be causing static electricity that lead to the bubbles. He also suggested we wipe the face of the mold as the plastic was being heated in the oven, in case the clamping process upset any dust on the machine and caused it to go onto the plastic.

During the final production run, we paid special attention to the cleanliness of the plastic and the mold, blowing the unformed plastic sheets with compressed air before putting them in the machine and softly brushing the mold off by hand while the plastic heated. This greatly reduced the amount of bubbles on the final part!

Thermoform part number 100. Awwwwww yeah