Drying Cooling System for Injection Machine

Drying Cooling System for Injection Machine

Most thermoplastics (e.g., PA, PET, PC, PBT) are hygroscopic (absorb moisture from the air). Moisture in raw materials causes defects like bubbles, silver streaks, or cracks in finished products, and may even degrade the plastic.

Cooling dried materials or system components: Prevents overheating of raw materials (which can cause 结块 or degradation) and ensures stable operation of the drying system itself.

Before plastic pellets enter the injection machine’s barrel, the drying cooling system must achieve two goals:

Moisture removal: Reduce the moisture content of raw materials to a safe range (typically 0.02%–0.1%, depending on the plastic type; e.g., PA6 requires <0.1%, PET requires <0.02%).

Temperature control: Cool dried materials (which are often heated to 80–180°C during drying) to 40–60°C (close to room temperature) before feeding them into the injection machine, avoiding premature melting in the feed throat and ensuring uniform feeding.

Dry coolers operate on the air-to-fluid heat exchange principle, with no water involved. The core process is simple and reliable:

Heat Absorption: Hot fluid (e.g., hydraulic oil, heat transfer fluid from the drying unit) is pumped into the dry cooler’s finned heat exchanger coils.

Air Contact: A built-in fan (axial or centrifugal) blows ambient air over the finned coils. The fins increase the surface area of the coils, maximizing contact between hot fluid and cool air.

Heat Dissipation: Heat from the fluid transfers to the ambient air through the coils/fins. The cooled fluid is then pumped back to the target system (e.g., hydraulic tank, drying unit) to absorb heat again.

Temperature Regulation: A thermostat or PLC (connected to the injection machine’s control system) monitors the fluid temperature. If the temperature exceeds the set threshold, the fan speeds up; if it drops too low, the fan slows or stops—saving energy.