Evolution of our design
Left: The left most design in the picture above is our first design based on a melt flow index machine. We would use a 3″ pipe as the cylinder and push the plastic through using a piston. We decided to use a pineapple during this design to help melt and mix the plastic. The initial pineapple was made from a huge threaded steel rod. It was hard to find any 3″ steel around and that was our only option. We also had a valve in the design to turn on and off the flow of plastic. But we scrapped this later because the nozzle was not heating up.
Center: Our next design was still a piston cylinder design but with some adjustments. We actually broke the cnc mill we machined our first prototype on. We over extended the X axis and got it stuck. So this design our goal was to make the biggest piece fit within the area of the mill we would be machining everything on. The original height of the side pieces was 32″ (which is the limit we could machine), so we shortened it up by dropping the spool down and making the height of the pot lower. This brought the height down to 28″, which was much safe for us to machine. The original had two smaller fans mounted to the side next to the nozzle. We went with one large fan located in the back. another big improvement was adding tabs to all the wooden pieces. This will help with the strength of the structure and simplicity of assembly. The first prototype is held together with wood glue and finish nails. Now we just need wood glue.
Right: This is our current design and what our second prototype is based on. This has the same height as the last revision but the extruder assembly is lower. This allows for the top section to be used as a hopper for plastic. The width of the side panels is an inch thinner due to the limits of the mill. The extruder assembly consist of a double threaded 1″ pipe, 2 caps, a 1″ wood auger, 12V dc motor,AL pineapple, and a nozzle. The design allows for the extruder assembly to be removes easily. This will allow the extruder Assembly to be designated to types of plastics or colors and changed out when switching plastics. A box was added to the side to house the electronics.
I am making a video to show the evolution of our design and point out the features that changed.