Reduce Your Trash to Tiny Bits with This 3D-Printed Shredder
Brian Brocken's 3D-printable shredder is capable of crushing numerous items with its cutting discs and gearbox — just like a car crusher.
After an item is created, either through 3D printing, milling, or some other method, it gets thrown away after it is no longer useful. However, tossing it absentmindedly into a garbage container can consume valuable space, so having a way to reduce the volume of the object is desired. That's where this project by Brian Brocken is useful, as it can slowly crush down objects into tiny pieces for disposal.
How Shredders Work
Most people are probably familiar with paper shredders, and they work by using a set of moving blades to tear through the paper several times as it passes through the rollers. However, plastic items are far more resilient to being cut, and are often 3D as well, so merely cutting them apart isn't an option. In order to make this work, a different technique was required: using multiple rotating cutting heads. This is the same way car crushers operate, as they have large metal discs with teeth cut into them that slowly drag the car downwards and break it apart.
Design
Brocken began on his shredder design by planning where each disc would be located within the shredding area. He also used a previously created gearbox from another project to drive the discs. This is needed because a small DC motor on its own is good at spinning many times per second, but it lacks torque, which can cause the whole machine to jam when a tougher item is placed into it. By using reduction gears, a mechanical advantage can be created by converting the spins from the motor into extra torque for the cutting discs.
Fabrication
Nearly everything on this device is fabricated from PLA filament using a Creality Ender-3 printer, although for a more rigid build, ABS filament could have been substituted instead. After each part had been printed, it got smoothed down so it would fit properly. The gears inside of the gearbox are cut at two angles instead of being flat, and this helps to reduce loud, grinding noises whenever they spin. There are also two primary drive gears that rotate one another, with one of them coming off of the gearbox. From there, the two sets of five cutting discs are all slotted onto an aluminum extrusion, and this turns within a bearing.
Testing It Out
The gearbox itself is turned by a basic DC motor that is powered by a 3S 2200mAh battery. Brocken had attempted to use a 6S LiPo battery instead, but stated that the power from it resulted in the gears being destroyed almost immediately. From the included video, we can observe several materials being dropped into the machine, including a wooden board, a sheet of paper, and several 3D-printed plastic pieces. The cutting discs were able to grab onto each item eventually, even the plastic bottle.
However, it did struggle with parts that had more strength, such as the wood. Overall, this project is an excellent demonstration of how larger scale crushers work and how mechanical advantages are created by gearboxes.