Low Cost Plastic Shredder

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Posted in Technology3D-Printing

Introduction: Low Cost Plastic Shredder

About: I am a Senior in college studying Mechanical Engineering. My interests include woodworking, 3D printing, electronics and building computers

I have been looking for a way to shred my waste 3D printed parts and support material so i would be able to turn it back into filament. Most of the commercially available ones on the market start at around $500 and having parts water jet to make a shredder can cost over $100 plus all of the bearings and hardware to make it functional. I wanted something inexpensive that would get the job done so i came up with the idea of using an electric hand planer. This is my first iteration of the design and will be updating it to make it work better as i go. The total cost for me was $31.50 but that was because I only had to buy the planer and electrical, with all the other materials the cost should be between $40-50

Step 1: Materials

What I Had to Buy

  • Electric Planer - $30 (Harbor Freight, Use 20% off coupon)
  • Light Switch , Box, Cover - $1.50 (Any hardware store)

What I Had on Hand

  • 2x4
  • Particle Board
  • Plexi Glass (Optional)
  • Silicone (You could use duct tape to cover the cracks if you wanted)
  • Various Length Screws
  • Wire Nut
  • 3D Printer (Optional)

Tools

  • Drill
  • Drill Bits
  • Jig Saw / Circular Saw ( You could use a table saw and chop saw or even a hand saw)
  • Clamps (Optional, just make things easier)

Step 2: Base

Depending on the planer you have/buy you might need to modify the base.

  1. Cut the two sides to the drawing specs
  2. Cut two ends to 6 inches
  3. Attach together using screws
  4. Zip tie trigger down
  5. Predrill holes in both side discharges so that the plastic does not crack when screws are placed in

Step 3: Feed Chute

I made the feed chute out of 3/4 particle board because that is what i had laying around. It could be made out of almost anything and dimensions would just need to be changed.

  1. Cut 2 sides to approximate dimensions shown in the plan
  2. Cut a 3.125 x 12.5in long piece of particle board and cut a 45 degree angle on each end as shown in the pictures
  3. Attach dies to center piece, predrill screw holes so the particle board doesn't break out
  4. Cut cleats to appropriate size that they can attach the chute to the base. I used particle board for these and they started to break apart when screwing in so a harder wood would work better.
  5. Attach Plexi glass to top of chute. If you don't want to be able to see the inside of the chute wood could just be used to cover the top.
  6. Use silicone to seal all cracks so plastic pieces cant work their way out. If you don't care about looks you could just use some tape.

Step 4: Wiring

This is optional, i wanted to be able to switch the shredder on and off from a switch instead of plugging and unplugging it.

  1. Cut cord to length of where you want the switch mounted
  2. Strip wires
  3. Mount Box
  4. Wire nut the white wires together
  5. Wire black wires to switch

Step 5: Push Stick

A feed stick of some sort will be needed to force the material down into the blades. I 3D printed an end that i attached to a length of particle board but a 2x4 could be ripped down to size and used instead. If you 3D print the end, some sanding might be needed to make a good fit.

Step 6: Finshed Prototype / Future Plans

When I first turned my shredder on I made sure to wear safety glasses just in case something might fly off and i would advise to do the same. I used the bag that came with the planer to catch the shredded plastic but would eventually like to make some sort of bin for the plastic to discharge into so that when different plastics are shredded they can be sorted.

I plan on making some changed to my design because the push stick doesn't work the best because it gets plastic ground into it and doesn't want to move very well. I am going to try using a piece of hard foam so it would have some flex but also seal off the chute and not allow plastic particles to come back up.

The video is a little loud so might want to check your volume before playing, this shows the push stick kind of sticking and not wanting to move very well.

Hope you enjoyed my Instructable and would like to hear any ideas you have on improving the shredder. As ive said this is a prototype / work in progress so it is far from finished.

Thank you

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    34 Comments

    I'm planning on building an extruder to make it into new filament

    ever build an Extruder?

    OVERENGINEERING WARNING!! :-) I wonder how well things would work if one combined a screen tumbler with this kind of device. The video really makes me want to run the output back into the input and see how fine things can be cut up to. Using a screen tumbler small pieces would fall through and larger pieces would have another chance to get ground up smaller. Occasionally the user would have to purge the tumbler of obstinate items but they may be rare. I don't know. :-) Another innovative use for inexpensive Harbour Freight tools. :-)

    This... is... Clever !

    As easy it have to be just for some plastics ! Thanks for the idea.

    I'm wondering how thin plastic little water bottle will move into that.

    Do you still use it ? Do you find how to re-use the shredded plastic ?

    Very nice! I wonder if it had a spiral cutter if it would cut finer pieces but still allow for a wide throat?

    Wonder if you could use the shredded plastic as growth medium in aquaponics...It's not water soluble right?

    3 replies

    plastic in NFT hydroponic systems dont do well, the plants actually try to avoid the plastic when used as a growing medium

    Hmmm...Didn't know that...Thanks

    However, I don't see that as a problem necessarily...as long as the plants are able to take in nutrients...

    I don't mind if they avoid the plastic, as long as that doesn't stop them from putting out enough root...

    Just noodling here, I'm certainly no aquaponics expert...and trying to think of another way to use recycled materials...

    The issue is that plastic is not hygroscopic, ie.... does not hold moisture therefore the roots cant pick up nutrients in the proper amounts, instead it sheds moisture immediately. As a medium for growing in hydroponics in does not work well, IMHO recycled plastic could be used to make custom grow containers or used as filter media for your grow system, kudos on the re-purposing of materials, bags can be melted in oil (see you tube), the clumps of bags are allowed to cool and then run thru the shredder

    I have looked at his and they still require water jet parts which is fine if you can find someone local to do it but having to order costs quite a bit

    If you can waterjet or lasercut something, you can bandsaw or jigsaw it. Might take a bit longer, but the end result is the same.

    Yes that is always an option to cut material. just not the ideal method. I had looked into 1/4 in thick precut metal disks and then would only have to cut teeth into them. Going this route would give perfect circle blades so they would mesh good but the cost of the steel and the time used to cut each would still be more then i wanted to spend. If i had the time i would like to go this route but at the moment it will probably not happen.

    I wonder if some cheap 7 1/4" circular saw blades would would. I know, you've already got the power planer and that seems to work well, but just some food for thought... ;)

    Or a grinder, that's what he used to cut out the parts for the hopper.

    I haven't checked now, but I think that he lasercut them. I'm pretty sure that it's what he said in one of his videos...