Sustainable Mechanical Shredder Design for Costa Rican Coffee Farmers
Sophomore Project (Cabrillo College)
Successfully designed and executed a complete product solution for organic coffee farmers in Costa Rica. The farmers employed this shredder to decompose coffee husks, a key component of their compost piles. As a result of this innovation, they experienced an 80% increase in their compost production.
By shredding coffee husks into finer pieces, we can accelerate the composting process of organic materials. This approach not only boosts the production of compost but also substantially enhances the yield of our organic coffee plants for our farmers.
The complete system was conceived and developed at Cabrillo College, located in Aptos, California. The teeth of the shredder were meticulously crafted using the college's CNC machine. All other components were also cut and assembled on-site. Furthermore, we prioritized local resources by procuring raw steel sheets from a nearby shop.
The assembly of the shredder machine was carried out on-site at Providencia de Dota, Costa Rica. Our team traveled to the farm with the machined parts in tow, completing the design and assembly directly at the location where it would be put to use.
Shredder Machine Teeth Assembly Process
Final Product and Production Process
The image below shows the final initial prototype for the mechanical shredder. To further aid in the growth of organic coffee with compost I led the team in the development of compost bins with slidable overhead rabbit hutches. These rabbit hutches had mesh flooring which enabled rabbit manures to pass through and onto the compost bins, which benefits the compost potency.
Final Product of shredder machine and compost pits.
Shredder Assembly
Finalyzing Teeth The Teeth Layout on the shredder
Fabricating Shredder Teeth Key Holes
The images above show the final steps of the shredder assembly, specifically teeth fabrication and teeth spacing layout within the machine.
3D model of the shredder side view
3D model of the shredder mechanism top view
Final 3D Model
Picture of me enjoying the costa rican weather while building the shredder
Procut Design and Parts
| QTY | PART | DESCRIPTION | SUPPLIER | PART # |
| 1 | chain | ANS1 35 chain x 48" | McMaster | 6261k172 |
| 2 | Ball Bearing | 1/2" end mount bearing | McMaster | 6494k380 |
| 4 | Ball Bearing | 3/4" end mount bearing | McMaster | 6494K420 |
| 2 | keyed shaft | 3/4" x 24" fully keyed shaft | McMaster | 1497k610 |
| 1 | keyed shaft | 5/8" x 24" fully keyed shaft | McMaster | |
| 1 | shaft | 1/2" x 24" shaft | McMaster | |
| 4 | sleeve bearing | 1/2" flanged sleeve bearing | McMaster | 6338k423 |
| 8 | shaft collar | 1/2" one piece shaft collar | McMaster | 6435k140 |
| 4 | shaft collar | 3/4" one piece shaft collar | McMaster | 6435k160 |
| 4 | shaft collar | 5/8" one piece shaft collar | McMaster | 6435k150 |
| 1 | crank handle | aluminum crank handle | McMaster | 6473k780 |
| 1 | sprocket | ANSI 35 chain sprocket 5/8" bore | McMaster | 2500T321 |
| 2 | sprocket | ANSI 35 chain sprocket 3/4" bore | McMaster | 6280k373 |
| 1 | idler sprocket | ANSI 35 chain idler sprocket 1/2" bore | McMaster | 6663k120 |
| 2 | 8' x 4x4 Lumber | Lumber for legs | Home Depot | |
| 2 | 8' x 2x6 Lumber | Lumber for side supports | Home Depot | |
| 1 | 3/4" Plywood | Lumber for sheer supports and table top | Home Depot | |
| 8 | Cap Screw | 3/8'-16 x 2-1/4" grade 8 cap screw | McMaster | 91257A633 |
| 8 | Flat Washer | 3/8" Flat washer | McMaster | 98023A031 |
| 4 | Tee-Nut | 3/8"-16 Tee nut | McMaster | 91527A633 |
| 4 | Align Nut | 3/8"-16 align nut | McMaster | 90955A123 |
| 1 | Angle Steel | 1-3/4" x 1-3/4" x 1/4" x 24" angle steel | Pvfab | |
| 1 | Flat bar | 5-1/2" x 1/4" x 48" flat bar | Pvfab | |
| 1 | Angle Steel | 2" x 2" x 3/8" x 12" | Pvfab |
Product Design and Parts