De Kunststof granulator is the precision tool of the recycling floor. While crushers handle bulk reduction, granulators are responsible for refining plastic scrap into high-quality regrind (typically 6mm–12mm) suitable for immediate re-introduction into the manufacturing process. For injection molders and extruders, the quality of this granulate directly impacts the mechanical properties of the final product.
Engineering Principles of Granulation
Unlike general-purpose shredders, a granulator cuts using a high-speed open rotor (typically 400-800 RPM) equipped with angled knives. This “scissor-cutting” action shears the plastic against stationary bed knives, producing a clean cut with minimal dust.
- Rotor Configuration:
- Open roter: Allows for high airflow, keeping the material cool. Ideal for heat-sensitive plastics like HDPE and PP.
- Solid Rotor: Provides high inertia for cutting thick, dense parts like solid purgings or extruder heads.
- Screen Sizing: The screen mounted below the rotor determines the final particle size. Rumtoo granulators use reversible screens to maximize wear life.
Critical Applications
1. In-Line Thermoforming Recycling
Edge trim from sheet lines is continuously fed into a granulator. The regrind is then pneumatically conveyed back to the extruder hopper, creating a closed-loop system with zero waste.
2. Injection Molding Runners
Sprues and runners are granulated beside the press. This “beside-the-press” granulation ensures that the material type remains segregated, preventing cross-contamination.
3. Kunststof Fles Recycling
In washing lines, wet granulators are used to simultaneously cut and pre-wash dirt from PET bottles. The water friction removes abrasive sand, extending blade life significantly.
De juiste machine selecteren
To specify the correct Kunststof granulator for your plant, Rumtoo engineers evaluate three variables:
- Feedstock Profile: Is it thin film (requires a V-cut rotor) or thick lumps (requires a claw rotor)?
- Doorvoer: Measured in kg/h. An undersized granulator will overheat the material, degrading its molecular structure.
- Maintenance Access: Our “tool-free” screen access design reduces cleaning downtime from hours to minutes, vital for plants running multiple colors.
Maximizing Blade Life
The operational cost of a granulator is driven by blade replacement.
* Materiaalkeuze: Use D2 steel for standard plastics. For abrasive engineering plastics (glass-filled nylon), Tungsten Carbide tips are mandatory.
* Gap Setting: Maintain a blade gap of 0.2mm–0.3mm for efficient cutting. A wider gap tears the plastic rather than cutting it, generating excessive dust and heat.
By viewing the granulator not just as waste machinery but as a material recovery asset, processors can significantly reduce raw material costs and improve profit margins.
