Design Problem

At the International School of Kenya we use 3D printers for numerous projects, using plastic filament to create models. The use of 3D printers allows for projects to have multiple iterations and changes since the 3D printers are fast and convenient. These iterations tend to build up and are never used; drafts, failed designs, rafts, and supports to hold the model, all of these extra prints build up and turn out as waste.

Design Process

First, there needed to be a grinder to crush up the plastic waste so that it could be melted. It’s impossible to melt all the pieces at once since they vary in size and material. The issue with creating a grinder was that it could melt the plastic as it crushed it up since this is what happened when we tried to put the plastic in the Plastiki Rafiki grinder. To design the grinder, I looked up different websites and companies that explored recycling plastic, and they mostly used shredders rather than grinders. Later on, I was able to find lots of videos looking at how to recycle 3D printing waste back into filament and was able to find a design that somebody had already made, which many others based their designs on.
All the parts were included, but this required me to cut aluminum, and this step would require a CNC Machine, which would have to be outsourced from somewhere else. Instead of making the grinder out of aluminum I thought it could be made from acrylic if the blades were thicker. In the unedited design there were multiple small blades because the tool that was used for melting and extruding the plastic was much smaller and the extruder we have could have bigger and less uniform pieces of plastic. Soon after customizing the design we found that the grinder in the middle school rotated at a much slower rate and it might be able to crush our PLA filament without melting, and it was able to do exactly that.

Since the grinder was then sorted the next step was to create a way to spool the filament onto a roll consistently. We already had a machine for spooling the filament, but it couldn’t keep the filament at a consistent diameter of 1.75mm. To do this, we had to find a way to measure the filament then adjust the spooling speed so when it speeds up it thins the plastic out, and slows down to make it thicker.

The first idea I had was to have two bearings on top of each other then feed the filament through but there was no way to measure the filament diameter accurately. To fix this, I found a youtube video that solves this exact issue within the same context.

This uses a caliper to measure the diameter of the filament, and reads out the values in mm or inches.

This is footage of the caliper measuring device working, it does this by connecting the ground, volt, data, and clock data pins to a caliper which reads the values then shares them to a searil monitor which will be replaced by an LCD Screen.

Link to Process Journal and Final Reflection Video