Plastic Shredder Machine: heading towards zero waste 2019-03-21
RecyclingShredder
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What can be done with all of the waste plastic around the land? There are places that recycle plastic, but not all plastic gets recycled. Bottles and cups do. But what about the foil/plastic wrappers, etc? There doesn’t appear to be any recycling places around Bangkok that recycle these. When they do accept it, it still just ends up in a landfill.

How can we keep these plastics out of a landfill and hopefully do something useful with them? We stumbled across this article:
https://www.nbmcw.com/tech-articles/concrete/25795-plastic-mixed-reinforced-concrete-behaviour.html

Apparently, scrap plastic can be mixed with concrete to increase the force at which it cracks. We can always use more stepping stones around the land where we walk during the rainy season and it gets muddy. About 1kg of plastic can be mixed into each stepping stone, making the stone less likely to crack, and keeping 1kg of scrap plastic out of the landfills.

Now, anything we can’t find a way to recycle, we can still keep it out of the trash/landfills.

The catch is that you need to shred the plastic. We tried everything. Scissors (too much work), blenders (jammed and burned out), paper cutters (the scrap plastic isn’t usually flat).

Finally, we saw a unit of this opensource shredder machine at a Recycling Eco Exhibit at the Siam Paragon Mall (https://preciousplastic.com/en/videos/build/shredder.html). This machine is used for shredding scrap plastics into small flakes. We used the laser cut files and drawing from this website to order the pieces cut from stainless steel for the shredding part and assembled it.

We designed it to use a 48 V 1000 W BLDC motor to drive this shredder. The motor that we bought has a built in gearbox which reduces the speed to about 500 rpm. We added 2 stages of chain transmission (1:3) to increase the torque to 173 N.m. The force at the shredding tip is theoretically 352 kg.

For electrical part, We use 48 V 10A switching supply. Direction control switch and speed knob were attached in front of the control box. It’s time to test the machine.
Shredder can shred bottle to plastic flakes. The power was occasionally cut when the switching supply went over current. So we tested it by supplying power from the old batteries from our electric vehicle project (48V 40AH). The shredding result was awesome, with the 5 mm sieve making the plastic flakes small and uniform. We shredded 20 of the standard 600 ml plastic water bottles to 0.75 l of flakes. (We will be recycling these bottles, but we wanted a standard unit of plastic just for this test.)
We added the slope under the shredding unit for easily getting the plastic flakes into a bucket or bag. We also added a bar on the top to push the plastic into shredding unit safely.