Introduction and Background (Group 15, 2023)

For this project, we were tasked with creating a mechanism with a specific purpose that would showcase various concepts that were learned over the course of the class and our previous builds. The design we had settled on was a reusable plastic bag opener which would use a single motor to both grip onto both sides of the reusable plastic bag as well as tear it apart.

In particular, the design was heavily inspired by Mechanical Movement #166 from Henry T. Brown’s Five Hundred and Seven Mechanical Movements, pictured below:

Figure #1.1: Mechanical Movement #166 from Five Hundred and Seven Mechanical Movements

The crank pictured in Figure #1’s main appeal is being able to create a back and forth movement that comes to rest at the peak of each stroke in both directions. This is accomplished by the crank pin on the side of the disk and the unique loop built into the rod on its crank-side end. Additionally, the design was inspired by various simple tools that are capable of closing and opening, such as pliers and nail clippers.

Figure #1.2: A variety of pliers on display, which served as the inspiration for the design project, image from Primer Magazine

The original design of the mechanism was to be similar to that of using two different pairs of pliers on two sides of a reusable plastic bag, but automatic using a single crank with a pin, a rod with a slot, and a motor.