What Materials Can ACM Mill Grind

ACM (Air Classifier Mill) combines high-speed impact grinding and built-in dynamic air classification. It is best suited for brittle, dry, free-flowing materials with low to medium Mohs hardness. Elastic, sticky, fibrous or highly ductile materials are generally not suitable, as they deform rather than fracture under hammer impact. The mill can produce powder from 120 mesh up to 800 mesh, matching the PSD range we covered earlier. Material selection must also consider wear risk, heat sensitivity, dust explosion and toxic hazards.

Main Categories of Processable Materials

1. Non-metallic minerals (most common application)

• Carbonate: calcium carbonate, dolomite
• Silicate minerals: diatomaceous earth, talc, kaolin, wollastonite, mica
• Oxides: quartz, alumina, iron oxide pigments, titanium dioxide
• Sulfates: barium sulfate (barite), gypsum
• Other minerals: limestone, feldspar, marble

Notes: Diatomaceous earth is typical; ACM performs gentle deagglomeration to preserve frustule structure. Hard crystalline silica needs ceramic/tungsten carbide wear protection to reduce metal contamination and liner wear.

2. Battery & advanced inorganic functional powders

• LFP (lithium iron phosphate), NCM, LCO cathode materials
• Graphite (natural / artificial graphite, limited to medium fineness)
• Aluminum hydroxide (ATH), magnesium hydroxide flame retardant
• Silica, precipitated silica

Notes: Many battery materials are combustible; closed nitrogen inerting and static grounding are required. Hard abrasive grades require wear-resistant liners.

3. Metal & precious metal powders

• Ruthenium powder, tungsten, molybdenum and other brittle metal powders
• Metal oxides

Notes: High density and abrasion accelerate hammer and liner wear; full containment and dust hazard control are mandatory.

4. Powder coating & organic resins

• Extruded polyester, epoxy, hybrid powder coating chips
• Solid organic pigments, some wax-free resin systems

Notes: Heat-sensitive. ACM must be equipped with water cooling jacket to avoid melting, sticking and premature curing. Cannot process soft, low-melting sticky resins.

5. Food, agro and pharmaceutical dry brittle materials

• Food additives: calcium phosphate, food-grade calcium carbonate
• Agricultural materials: diatomaceous earth insecticide carrier, mineral soil amendments
• Herbal brittle roots, shells, plant mineral extracts (only dry, non-fibrous varieties)

Notes: Food/pharma grade requires polished stainless steel construction, easy clean-in-place design, and strict cross-contamination control. High oil/fat plant materials are not suitable.

6. Chemical fillers & pigments

• Inorganic color pigments, extender fillers, ceramic raw materials

Materials NOT suitable for ACM mill

1. Ductile / malleable materials: pure soft aluminum, copper, plastic pellets that deform instead of breaking. They will flatten, stick to hammers instead of fracturing.
2. Fibrous materials: wood fiber, cotton, hemp, long fiber plant material. Fibers wrap around rotor and classifier wheel, causing blockage and vibration.
3. Sticky, high oil, high moisture feed: wet clay, high-fat plant powder, sticky resin. Causes wall buildup, blinding of classifier wheel and filter bags. Feed moisture is generally required below 3–4%.
4. Highly elastic rubber / elastomer: absorbs impact energy and will not grind into fine powder.

Key selection rules tied to ACM operation

1. Mohs hardness guideline: Best for Mohs 1–5. Harder materials (Mohs >5) can be ground but wear parts consumption rises sharply, requiring tungsten carbide or ceramic liners.
2. Brittleness requirement: Material must fracture under impact. If it bends, ACM cannot grind efficiently.
3. Heat sensitivity: Organic materials need water cooling; high hammer count increases heat generation and must be limited.
4. Safety constraints: Combustible, toxic or oxidizable powders (LFP, ruthenium, organic dust) require inert gas, explosion venting and anti-static full containment.

ACM mill grinds dry brittle materials including most non-metallic minerals, battery inorganic powders, brittle precious metal powders, powder coating resin chips, dry agro-mineral fillers and inorganic pigments. It is not recommended for ductile metals, long fibrous materials, sticky or high-oil substances. Hammer count, rotor tip speed and wear protection are adjusted according to material hardness and brittleness to hit target particle size.