Final Design

Machine Overview: 

Our project aims to improve the usability of the Precious Plastic Injection Machine. We focused on four main components of the machine: 

• Pull-Down Lever

• Nozzle & Barrel

• Mold & Cage

• PID & Sensors 

Figure 1: Precious Plastic Injection Machine

Figure 2: Plastic Shreds 

Plastic waste is collected to be sorted and shredded into smaller pieces as shown in Figure 2. The plastic shreds are put into the hopper of the injection machine, where they are melted in the heated barrel. 

Figure 3: Products Made From Recycled Plastic 

The melted plastic is injected into a mold attached to the nozzle at the base of the barrel. The machine can be used with a variety of molds to create useful products such as planters, phone cases, and trinkets to sell. 

Problem Areas:

The original injection machine was difficult to operate and had a slow production time. The lack of temperature control also resulted in unsuccessful prints when the mold was cooled improperly or not filled entirely. These are the four main components that are modified to address the problems: 

• Pull-Down Lever - The lever is difficult to pull down, requiring up to 200 lbf from the machine user. 

• Nozzle & Barrel - The barrel takes around 10 minutes to heat up to the final temperature, slowing down the time to print. 

• Mold & Cage - The mold is threaded to the nozzle and it takes time to remove the final product between prints. 

• PID & Sensors - There is no indication of when the plastic is at the optimal temperature to be injected. 

Design Solutions: 

Figure 4: Pull-Down Lever 

The initial lever design required up to 200lbf from the user for each injection. To reduce the force required, an actuator is added between the ram and the lever to assist with injecting the melted plastic. The lever is clamped in place while the actuator is turned on. Alternatively, the lever can be held down using a ratchet wheel mechanism or hook and chain. 

Figure 5: Mold & Cage

The mold is threaded to the nozzle and it originally had to be unthreaded between prints to remove the plastic product. To reduce the time for each print, a mold cage was designed to quickly release the bottom mold part without having to separate the mold from the nozzle. 3D printed molds were also researched to find a variety of different filaments that can be used to create reusable molds that fit in the mold cage. This reduces the cost of creating a mold and increases accessibility of different mold designs. 

Figure 6: Experimental Setup  

Heating up the steel barrel with heating bands previously slowed down the injection process. To improve the efficiency of the injection machine and reduce the time to heat, experiments were done to test different barrel materials and the effect of insulation. A 6063-T2 Aluminum barrel was found to have a 24% reduction in heat up time and is available for a comparable price to the original steel barrel.