FA info icon.svgAngle down icon.svgDevice data
Manufacturing files
Hardware license CERN-OHL-S
Certifications Start OSHWA certification
FA info icon.svgAngle down icon.svgProject data
Authors Jeremy Bell
Weston Butler
Michael James
Completed 2018
Made Yes
Replicated No
Cost USD 70
OKH Manifest Download

There is a very large need for an affordable and strong plastic grinder. With current models on the market that are made from steel and require numerous parts and fittings costing upwards of $400, cheaper versions could be appealing to customers. We have created a mostly 3D printed grinder using a combination of PLA and Polycarbonate parts and a few other pieces of hardware. This design utilizes two hex shafts with 5 teeth per shaft, encased in a solid 3D printed box. The shaft is driven using a windshield wiper motor which is powered by an old computer power supply. This shredder design takes a lot of the guess work of tolerances and proper fits out of the equation.

There are some plastic grinders that are 3D printable currently, but they are not as robust as this design, nor are they automated.

Bill of Materials[edit | edit source]


  1. DeltaBot Athena II Printer
  2. PLA Filament - 1 roll (any of the common 3d print filaments will work)
  3. Polycarbonate Filament - 1 roll (Polycarbonate is needed here for high strength teeth)
  4. Windshield wiper motor
  5. 12 Volt computer power supply
  6. 1- 6mm Wingnut

The following link is to all openSCAD and STL files related to this project:

Tools needed[edit | edit source]

  1. MOST Delta RepRap or similar RepRap 3-D printer
  2. Wire Strippers
  3. Adjustable Wrench
  4. Drill
  5. Drill Bit
  6. 6 Screws

Skills and knowledge needed[edit | edit source]

  1. Ability to run Cura or another Slicing program
  2. Operate Deltabot Athena II
  3. Ability to splice together positive and negative wires from motor to power supply

Technical Specifications and Assembly Instructions[edit | edit source]

Box Cura Settings

  1. 45% Infill
  2. Tri-hexagonal Infill
  3. 150 mm/s print speed
  4. 200 C print temp

Motor Mount Cura Settings

  1. 25% Infill
  2. Tri-hexagonal Infill
  3. 150 mm/s print speed
  4. 200 C print temp

Shaft Cura Settings (Polycarbonate print)

  1. 95% Infill
  2. Tri-hexagonal Infill
  3. 60 mm/s
  4. 255 C print temp
  5. 90 C bed temp

Teeth Cura Settings (Polycarbonate print)

  1. 95% Infill
  2. Tri-hexagonal Infill
  3. 60 mm/s
  4. 255 C print temp
  5. 90 C bed temp

Wing nut coupler Cura Settings (Polycarbonate print)

  1. 95% Infill
  2. Tri-hexagonal Infill
  3. 60 mm/s
  4. 255 C print temp
  5. 90 C bed temp

Bearing Cura Settings

  1. 100% Infill
  2. 150 mm/s print speed
  3. 200 C print temp

Clamp Cura Settings

  1. 45 % Infill
  2. Tri-hexagonal Infill
  3. 150 mm/s print speed
  4. 200 C print temp

Print times

All prints done at 150 mm/s

  1. Box = 5.5 hours
  2. Motor Mount = 5.5 hours
  3. 2 Shafts = 5 hours total
  4. 10 teeth = 5 hours total
  5. Wing nut coupler = 1 hour
  6. 2 Bearings = 16 minutes total
  7. 2 Clamps = 6 hours total

Total Time = 28.25 hours

Assembly Instructions

  1. After printing of all parts, test fit all teeth on shafts to make sure of proper fit.
  2. Slide a bearing onto the shorter of the 2 shafts all the way toward the gear.
  3. Insert one of the teeth into the opposite side of the box that you plan to insert the shaft through. This will make things easier when fitting the shaft through. This tooth will act as a bearing on the non gear side.
  4. Insert another tooth into the side of the box that you are going to insert the first shaft through, but in the hole that shaft #2 will be in. This tooth will act as a bearing on the gear side.
  5. Begin inserting the remaining 4 teeth for this shaft into the box from the top while feeding the first shaft through each individual tooth.
  6. After the first shaft is in place, insert the second shaft into the other hole and begin inserting it through teeth just as with the other shaft.
  7. Place the wing nut coupler on the drive shaft (shaft #2).
  8. Insert the Windsheild Wiper motor into its circular housing with the screw outlet lined up within the slot provided.
  9. Screw the wingnut onto the drive shaft of the motor.
  10. Drill holes in the tabs on the motor mount with the size screw you are using. Do the same for the tabs on the grinder box clamp.
  11. Fix both the box and the motor housing to the desired work area or work bench using screws.
  12. Connect the motor to the computer power supply.

Assembly time

  • 30 Mins

Common Problems and Solutions[edit | edit source]

  1. Overextrusion of polycarbonate pieces. With slight over extrusion, the parts are too big in some cases.
  2. Tolerancing of parts based on a different sized nozzle. With different sized nozzles, some parts may need to be scaled in order to make them fit.
  3. It may take a bit of elbow grease to insert the teeth that also act as a bearing into the box.
  4. It also takes a bit of pounding and pushing to get the motor into its housing.

Cost savings[edit | edit source]

The high cost part for this machine is currently the windshield wiper motor. Due to time constraints for this project, the motor was purchased on amazon for $45 but the cost of the overall machine can be decreased drastically if this part is found in a scrap yard.

Cost List

  1. PLA Filament = $20/ 1 kg roll (should need 1 roll)
  2. Polycarbonate = $40/1 kg roll (need less than a roll)
  3. Windshield wiper motor = $45
  4. Computer power supply = donation (most models $20-$40 for cheap ones)
  5. Wingnut = $1.50
  6. Cost Total = approximately $60-$70 (could be $80 if you don't have a power source)
  7. Cost of similar model = $400
  8. Cost Savings = $340

Benefited Internet Communities[edit | edit source]

  • Name and add links to at least 5 using single brackets around [url name]
  1. Most Delta Users [1]
  2. Africa Recycling [2]
  3. Michigan Tech 3d Printing [3]
  4. Joshua Pearce Printing [4]
  5. Lulzbot Users [5]

References[edit | edit source]

  • The sources of information (e.g. engineering handbooks, journal articles, government documents, webpages, books, magazine articles etc.). References should use the and <references />tags and can be in any format but should include all the information necessary for someone else to find the same information you did. For example:[1]
  1. web page: Department of Energy (DOE) Landscaping and Energy Efficiency, DOE/GO-10095 (1995) Available:

Based on the developmental needs addressed (e.g. food, heat, electricity, clean water, health care, etc.) be sure to label your device in the proper categories e.g. use. Be sure to categorize your device so that it will be easy to find – for example "Low voltage connection basics" is categorized in .

FA info icon.svgAngle down icon.svgPage data
Keywords 3d printing, plastic grinder, recycle, plastic
SDG SDG13 Climate action, SDG15 Life on land
Authors Jeremy Bell
License CC-BY-SA-3.0
Organizations MTU, Michigan_Tech's_Open_Sustainability_Technology_Lab, MY4777
Language English (en)
Related 0 subpages, 3 pages link here
Aliases Automated Plastic Grinder/Recycler
Impact 607 page views
Created December 6, 2018 by Jeremy Bell
Modified January 29, 2024 by Felipe Schenone
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