Shreder and injection machine – Low cost – Brazil

Hi guys
Just came to share what we’ve been doing in Brasília- Brazil.

So basically I work for a school but we didn’t have lots of money to put in the construction of the machines so we develop a low cost (lower cost) version of the machines.

We’ve just built the shredder and the injection machine and made the very first run this weekend.


Basically the cutting unit was developed using hand cut standard steel plates in order to save money with the laser cutting procedure which is very (very) expensive here (especially with  stainless steel).

The power unit was made using 2 sets of bike gears which provided us with a 7 times torque increase. We were doing something similar to what this guys did (LINK), but we developed a casing for the bearings and just ignored the flywheel which we felt was really not necessary.

There is some space to put another 2 sets of gears and latter attach an electric motor (2hp – 3600 rpm from a grass cutter) to the unit. Latter when we attach the motor the total rotation reduction  will to around 73 rpm and then we will install the safety covers.

The power system using a closed gear box is around 220~250$ here. And we used second hand bike gears which were from the scrap yard.

With this unit we were able to shred around 15  pet bottle per hour with some hard work. But the machine worked fine.


The injection machine we kept to the precious plastic original project but we changed the control unit.

Instead of using 4 small resistances we used 2 big one 100 mm long and 350 W each.

The temperature control is what really makes it different (but less precise).  We used two  0-300°C (220V-10A) thermostats (5 USD  each) instead of the PID controller and the K temperature sensor.

It worked pretty well on the first run. We’ve tried it with PET bottles and managed to make a small hex tile.


The students will be running the project (from now on) and we’re looking forward to share what we accomplish here.

(If you guys interested I can do and share the drawings of the shredder in a CAD file when I get some spare time).

If there is some here one from Brasília here we are looking for people to come and join us.