The Cactus dryer is mounted directly on the feed throat of the molding machine. A hopper or loader mounted on the top of the dryer provides a continuous supply of resin to the dryer. The pellets are supplied directly from the bag, barrel, or Gaylord and do not require pre-drying.
The plastic resin feeds continuously from the hopper (1) into the throat (2) and down through the body (3) of the dryer. The material is heated using conduction and radiated heat using electric heater bands mounted on the body (4) to generate the heat. A closed-loop P.I.D precisely controls heat temperature controller (5). Simultaneously a partial vacuum is generated inside the dryer’s body by a compressed air-powered venturi creating the vacuum.
The fast heating causes moisture trapped within the plastic pellet to the pellet surface. The moisture is carried away by the airflow created by the venturi. Ambient air enters through an inlet (7) in the lower flange (8), passes over the heater bands, through slots in the body (9) across the plastic resin, picking up the moisture, then exits via the filter basket (10) and though the venturi to the atmosphere.
When the resin reaches the molding machine’s screw, most moisture is removed. Should any moisture remain, the action of the screw will cause it to vaporize in the rear zone. These vapors are extracted by the extension tube (11) and out through the venturi. As a result, all moisture is removed before plasticization, and dry resin is injected into the mold.
The residence time of the resin in the Cactus dryer usually is about 30 minutes.
The critical elements of the system are; Precise temperature control, accurate airflow by the venturi, injection settings, and throughput lbs. (kg) per hour. If these elements are considered and adjusted for each setup, the Cactus will provide reliable and economical drying of most thermoplastic resins.