An ACM (Air Classifier Mill) is an integrated impact grinding and air classification system. It combines mechanical pulverization with dynamic air separation inside a single machine housing. Its main components can be grouped into grinding section, classification section, air handling system, feeding assembly, power drive unit, and powder collection system.
1. Grinding chamber & rotor assembly
This is the core comminution zone.
- Rotor shaft and hammer carrier: High-speed rotating assembly driven by the main motor. It holds the grinding hammers and spins at adjustable peripheral speed.
- Grinding hammers / impact bars: Replaceable wear parts mounted on the rotor. They strike incoming feed particles to create impact and shear fracture. Hammer shape and material directly influence particle morphology and grinding efficiency.
- Liner plates: Fixed wear-resistant liners fitted to the inner wall of the grinding chamber. Particles collide against these liners for secondary breakage. Ceramic or alloy liners are used for highly abrasive materials to maintain consistent grinding gap.
2. Dynamic air classifier assembly
Mounted on top or rear of the grinding chamber, this unit separates fine finished powder from coarse oversize particles.
- Classifier wheel (classifier rotor): A vane-type impeller rotating independently from the grinding rotor. It generates centrifugal force. Fine particles follow airflow through the wheel; coarse particles are rejected and fall back into the grinding zone for re-grinding.
- Classifier drive: Separate variable-frequency drive motor for independent speed regulation. Adjusting classifier wheel RPM changes the product cut size.
- Classifier housing: Sealed casing guiding air-particle mixture toward the classifier vanes.
3. Feeding system
Delivers controlled, uniform raw material into the grinding chamber.
- Feeder: Typically screw feeder or vibratory feeder with speed control. It maintains constant material loading inside the mill to avoid over-feeding or starvation.
- Feed inlet: Sealed material entry port, often with an air lock to prevent air leakage and stabilize internal airflow.
4. Air handling & blower system
Air acts as the conveying and classification medium in the ACM mill.
- Main blower: Creates the circulating air stream that transports particles from grinding zone to classifier, then to powder collectors.
- Air duct network: Connects mill outlet, cyclone separator and dust collector.
- Air regulating dampers: Adjust air volume and system pressure to match feed rate and target fineness.
5. Power transmission & support components
- Main drive motor: Powers the grinding rotor, usually equipped with VFD for rotor speed adjustment.
- Bearings and bearing housings: Support high-speed rotating shafts for both grinding rotor and classifier wheel. They require lubrication and thermal monitoring.
- Machine base and frame: Heavy rigid structure to minimize vibration and preserve precise assembly alignment during continuous operation.
6. Powder collection system
Captures finished fine powder and filters exhaust air.
- Cyclone separator: Primary collector; most qualified fine powder drops out here.
- Baghouse dust collector / pulse jet filter: Secondary collection unit to trap ultra-fine particles. Clean air is discharged after filtration.
- Airlock discharge valves: Rotary air locks at cyclone and filter hoppers. They discharge collected powder while maintaining negative pressure inside the closed air loop and preventing air infiltration.
7. Auxiliary control & safety components
- VFD control panel: Sets rotor speed, classifier speed and feed rate.
- Temperature and vibration sensors: For equipment protection.
- Seals and gaskets: Prevent powder leakage and maintain closed-loop air balance. Explosion-proof versions include pressure relief vents for combustible powders.
The ACM air classifying mill’s key modules are the hammer grinding rotor assembly, dynamic classifier wheel, controlled feeding unit, circulating air blower, powder collection system and independent drive controls. All components work together in a closed air circuit: raw material is impact-ground, fine particles are sorted by the rotating classifier, oversize recirculates for re-grinding, and finished powder is collected. The independent speed control of grinding rotor and classifier wheel gives flexible adjustment of particle size and powder quality.
