The Injection Molder
By Matthew Bell
The injection molder is the first machine to be made by ARC that will create a finished product. Plastic pellets are fed into the hopper, which leads into the melting chamber. The melting chamber is brought to the appropriate melting temperature of the plastic that is being used. After the plastic has been melted, it is then pressed down the melting chamber using a lever and piston. The plastic exits the melting chamber into the desired mold, which is in the shape of the finished product. After the plastic cools and solidifies, the mold is removed, leaving the finished product.
There are many different ways to reform plastic into new products, but we chose to make an injection molder as our first recycling machine for a number of reasons. First, it seemed to be the cheapest option, with Precious Plastics estimating it cost them around $185. Also, we discovered we could make the machine without the need for intense machining or welding, therefore satisfying our goal of accessibility and ease of manufacture. This way, others can easily follow our initiative and expand the impact of this mission. Secondly, the injection molder offers a lot of creativity when it comes to products it can make. The parts are virtually only restricted by the mold design. In addition, once a mold is made, many replicas of the same part can be made quickly and easily, with just the pull of a lever. This would allow us to jump-start our operation, offering a very short lead time and large available quantity to our stakeholders right out of the gate.
Our design (represented in the CAD model below) takes inspiration from the Precious Plastics design, online research, and advice from Cornell professors. The main structure is built from 80/20Ⓡ, easily-assembled aluminum railed akin to an Erector SetⓇ. The lever and mounting pieces are made from aluminum bars, and the only necessary machining is drilling a few holes. The melting chamber is made from standard ¾ NPT tubing, allowing it to interface with standard nozzles, so the plastic won’t leak out. An adapter and nozzle attach to the end of the tube, which feeds the melted plastic into the mold. An aluminum cylinder is used for the piston to push the plastic through the melting chamber. The plastic is heated using band heaters that wrap around the tube and are controlled to the correct temperature by a temperature controller (not shown in the CAD model, shown separately). It is important to get the correct temperature, as going too high can create hazardous fumes. In all, the system easily fits on a desk and stands at about 3 feet tall.
A little bit more research and more testing need to be done to ensure that this design will work. However, we are very hopeful because similar designs have been successful in the past. After the completion of the injection molder, the next step is to make the molds for the products that we will be creating.