A horizontal screen multi mill uses rotating impeller blades knife forward, knife reverse, or flat beater at 700–3,000 RPM sweeping material horizontally through a curved bottom screen (0.5–25 mm aperture). Processing 5–2,000 kg/h of wet or dry granules, slugs, and aggregates, it delivers D90 of 200–5,000 µm the most widely used GMP milling configuration for pharmaceutical wet-granule sizing after high-shear granulation, fluid bed processing, and roller compaction across lab-to-large-production scales.
Challenges
Wet Granule Screen Blinding at High Moisture (LOD >15%)
Moist granules pack into horizontal screen mesh wires progressive blinding reduces throughput.
Blade Wear from High-Density or Abrasive Granules
Dense sugar or mineral-doped granules abrade knife or beater blade edges PSD drift after 200–500 hours.
Inconsistent PSD at Feed Rate Variation
Over-feeding raises mill hold-up; under-feeding reduces impeller-material contact both widen PSD.
Heat Generation in Dry Milling Mode
High-speed dry milling raises granule bed temperature risk of API phase change above 40°C.
Containment for Potent Compound Granule Milling
Open top-entry feed hopper presents dust exposure risk in HPAPI granule milling operations.
Solutions
- Stainless Steel Rasping Screen (Raised Grater Profile): Raised surface prevents wet granule packing between wires extends continuous run 3–5× vs. woven wire.
- Hardened Replaceable Blade Inserts (D2 Tool Steel or Carbide-Tipped): Field-replaceable inserts restore blade edge without removing impeller 5-minute exchange under containment.
- Mass-Flow-Controlled Vibratory Feeder (±2% Rate Accuracy): Constant feed rate eliminates mill over/under-loading sustained PSD within ±10% of D90 setpoint.
- Jacketed Mill Housing with Chilled Water Circuit (15–25°C): Wall cooling limits milling chamber below 35°C throughout dry milling of thermolabile APIs.
- Contained Charging with RTP or SBV Interface at Feed Hopper: OEB 4–5 containment at feed hopper and discharge <1 µg/m³ operator exposure throughout.
Applications
- Pharmaceutical: Wet granule sizing after RMG or FBP, dry granule milling after roller compaction, blend conditioning.
- Nutraceuticals: Supplement granule sizing, vitamin tablet granule milling, herbal extract granule size reduction.
- Food & Beverage: Dried ingredient granule sizing, extrudate milling, sugar agglomerate reduction.
- Chemical: Catalyst granule sizing, specialty chemical compacted granule milling.
- Cosmetics: Pressed cosmetic granule reclaim milling, mineral pigment granule sizing.
Models & Capacities
| Model | Scale | Throughput [kg/h] | Impeller Speed [RPM] | Screen Aperture [mm] | Tip Speed [m/s] | D90 Output [µm] | Motor [kW] | L × W × H [mm] | Weight [kg] |
|---|---|---|---|---|---|---|---|---|---|
| MM-H-LAB | Lab | 5–30 | 700–3,000 VFD | 0.5–25 | 1–8 | 200–5,000 | 0.75–1.5 | 520×400×750 | 55 |
| MM-H-PIL | Pilot | 20–100 | 700–3,000 VFD | 0.5–25 | 2–9 | 200–5,000 | 1.5–3.0 | 720×520×950 | 110 |
| MM-H-300 | Production | 80–300 | 700–3,000 VFD | 0.5–25 | 2–10 | 250–5,000 | 3.0–7.5 | 960×680×1,200 | 230 |
| MM-H-700 | Production | 200–700 | 700–2,500 VFD | 0.5–25 | 3–10 | 300–5,000 | 7.5–15 | 1,250×880×1,500 | 420 |
| MM-H-1500 | Large Prod | 500–1,500 | 700–2,000 VFD | 0.5–25 | 3–9 | 350–5,000 | 15–30 | 1,600×1,100×1,800 | 720 |
| MM-H-2000 | Large Prod | 800–2,000 | 700–1,800 VFD | 0.5–25 | 3–8 | 400–5,000 | 22–45 | 2,000×1,400×2,100 | 1,200 |