A “Jack of all trades” shredder is a master of downtime. While it is tempting to buy one machine to process “everything” (Purging, Film, Pipe, Pallets), the physics of material reduction dictate that you will lose 30-40% efficiency on every ton. This guide explains why specialization is the only path to profitability.
Related equipment: PE/PP film shredder, rigid plastic shredder.
1. The RPM Mismatch
- Film/Fiber (Soft): Requires High Torque + High Speed (80-100 RPM). You need momentum to shear the material before it stretches.
- Hard Plastic (Lumps): Requires High Torque + Low Speed (40-60 RPM). High speed causes the rotor to bounce off the block, creating shock loads.
- The “Universal” Compromise: A machine running at 70 RPM is too fast for lumps (shock) and too slow for film (jamming).
2. Rotor Geometry: Spline vs. Smooth
- Film/Fiber: Often uses an Anti-Winding Spline Rotor. The raised surfaces prevent the material from lying flat and wrapping.
- Rigid Plastic: Uses a Smooth Rotor. Splines would create stress concentration points that could crack when hitting a solid block of PP.
- Result: Running film on a smooth rotor often leads to wrapping. Running dense lumps on a spline rotor can increase stress concentrations and risk mechanical damage, depending on rotor design and control settings.
3. Ram Logic (Hydraulics)
- Film: Light and fluffy. Requires a Turbo Ram (fast approach, low pressure) to constantly force material into the blades.
- Pipe/Purging: Dense and solid. Requires a Load Sensing Ram (slow approach, high pressure) that “nibbles” the material to prevent stalling.
- Conflict: A universal ram logic will either overfeed the lumps (stall) or underfeed the film (throughput drop).
4. Screen Design
- Film: 40mm screen with 50% Open Area.
- Rigid: 40mm screen with 35% Open Area (stronger web thickness).
- Failure: Running lumps on a film screen will bend or break the screen due to lack of structural rigidity.
Conclusion
Buying two specialized machines (one for film, one for rigid) often has a lower Total Cost of Ownership (TCO) than buying one “Universal” machine that runs at 60% efficiency and requires constant maintenance.
References
[1] “Efficiency in Plastic Recycling,” Waste Management World. Efficiency in Plastic Recycling
[2] “Design Principles of Industrial Shredders,” Journal of Engineering. Design Principles of Industrial Shredders
