For plastic granules (resins), a Column Depalletizing & Emptying System is a specialized automation cell designed to take pallets of 25kg (or 50lb) bags and convert them into a continuous stream of raw material for extruders, injection molding machines, or silos.
Unlike bottle depalletizers that move layers, this system focuses on destructive unpacking: picking a bag, slicing it open, and ensuring every last granule is fed into your production line.
The Automated Workflow
Phase 1: Picking (The Column/Robot)
The Column Mast: The system uses a vertical column to manage the height of the pallet. A robotic arm or a specialized lifting carriage moves up and down the column.
Needle Gripper: Since granule bags are often woven or plastic, the “hand” uses a matrix of stainless steel needles that pierce the bag to provide a secure grip without letting granules leak prematurely.
Phase 2: Unpacking (Cutting & Emptying)
Rotary Blades: The bag is moved over a set of high-speed serrated blades.
The Sifter/Shaker: Once cut, the bag is held over a hopper and subjected to high-frequency vibration. For expensive granules (like medical-grade PEEK or specialized additives), this ensures a 99.9% emptying rate.
Dust Containment: Plastic granules often produce “fines” (dust). The entire unpacking zone is enclosed in a negative pressure cabinet with an integrated dust collector to keep the factory floor clean and safe.
Phase 3: Feeding (Conveying)
Pneumatic Conveying: From the hopper, the granules are usually sucked into a pipe (vacuum) or blown (pressure) directly to your processing machines.
Screw Conveyor: For shorter distances or glass-filled/abrasive granules, a mechanical screw might be used to prevent pipe wear.
System Components
Pallet Infeed: Automatically positions the full pallet of resin.
3D Vision: Scans the bag stack to detect shifted bags or uneven layers.
Bag Compactor: Squeezes the empty, cut bags into a tight bundle to reduce waste volume.
Fine Mesh Screen: Catches any pieces of the bag (plastic or paper) before they reach your extruder.
Why Automate Granule Unpacking?
Manual cutting often creates small shards of the bag (plastic or paper) that fall into the granules. These “contaminants” can clog extruder screens or cause defects in the final molded part. An automated system uses a precision “U-cut” that keeps the bag skin intact.
In a manual operation, it is common to leave 50g–100g of resin in every “empty” bag. If you process 500 bags a day, that is 25kg–50kg of wasted material daily. The automated shaker mechanism recovers this lost profit.
A column depalletizer can maintain a steady rhythm (e.g., 400 bags per hour) 24/7, ensuring your extruders never “run dry” due to a worker being on a break or being tired.
