Particle size control is fundamental to pharmaceutical manufacturing. Whether the goal is de-agglomerating a granulated blend ahead of tablet compression, milling an API to increase bioavailability, or sizing excipients for consistent capsule fill weight, the milling step must deliver a defined, repeatable particle size distribution — without contaminating the product, generating excessive heat, or requiring lengthy equipment changeovers.
The Hanningfield Uni-Mill conical mill (or cone mill) is designed to meet each of these requirements in a single, validated platform. Advanced Packaging Systems (APS) is the exclusive New Zealand distributor for Hanningfield Process Systems.
What Is the Hanningfield Uni-Mill?
The Uni-Mill is a conical screen mill — also referred to as a cone mill or conical mill — that reduces particle size by forcing material through a precisely sized conical screen using a rotating impeller. The machine is available in two drive configurations:
Under-driven (UD): The impeller rotates beneath the screen cone, making it suitable for coarser milling and gentle de-agglomeration of friable granules.
Over-driven (OD): The impeller rotates above the screen cone, applying greater force for finer milling of compacted materials or hard granulates.
By selecting the appropriate screen aperture and impeller type from a modular range of interchangeable components, a single Uni-Mill unit covers the full particle size range from approximately 150 µm to 2 mm — without requiring a separate machine or significant engineering intervention.
Hanningfield Milling Machine
The Challenge of Pharmaceutical Particle Size Reduction
In GMP pharmaceutical manufacturing, milling presents three core challenges that conventional equipment frequently fails to address simultaneously:
Containment: Open milling operations generate respirable dust, creating occupational exposure risks for operators and cross-contamination risks for other products. High-potency APIs (HPAPIs) require OEB 3, 4 or 5 containment strategies.
Changeover time: A mill that requires extensive disassembly, component replacement or dedicated tooling to change particle size targets adds significant downtime to a production schedule and increases cleaning validation complexity.
Scalability: A particle size target achieved on a lab-scale mill must be replicable at production scale — and the scaling parameters must be predictable and documentable for regulatory submissions.
The Uni-Mill addresses each of these challenges through its core design philosophy.
How the Uni-Mill Achieves Contained, Flexible Milling
Screen and impeller selection: The Uni-Mill’s particle size output is controlled entirely by the combination of screen aperture and impeller geometry — no mechanical adjustment of the drive is required. Changing from 500 µm to 800 µm output is a matter of swapping one screen; changing from gentle de-agglomeration to aggressive size reduction requires changing the impeller type. Both components are tool-free, GMP-cleanable and individually validated as product-contact parts.
Closed-loop integration: The Uni-Mill integrates directly with Hanningfield’s Uni-Vac vacuum conveying system. Material is drawn in from an upstream vessel (IBC, drum or hopper), milled inline, and transferred directly to a downstream process vessel — without opening the system. This fully closed loop eliminates operator dust exposure and reduces airborne cross-contamination to zero.
Low heat generation: Unlike hammer mills or pin mills operating at very high tip speeds, the Uni-Mill’s controlled impeller speed generates minimal heat during the milling cycle. This protects heat-sensitive APIs and excipients where thermal degradation would compromise product quality or stability.
The Uni-Mill Model Range
M05-U: Tabletop or isolator-mounted unit, suitable for R&D, laboratory-scale formulation development and small-batch clinical production.
M10 – M100: Scale-up models for clinical batch manufacture, technology transfer and low-volume commercial production.
M200 – M600: Full commercial production models for high-throughput API milling, granule sizing and excipient processing.
Because the milling mechanism is identical across the range, particle size data and process parameters generated on the M05 translate directly to the M600 — supporting regulatory submissions and technology transfer dossiers without the need to repeat extensive milling studies.
Validation Documentation
For pharmaceutical customers, equipment validation is a non-negotiable requirement. Hanningfield supplies the Uni-Mill with a full validation documentation package as standard:
- FDS – Functional Design Specification
- FAT – Factory Acceptance Testing
- SAT – Site Acceptance Testing
- IQ – Installation Qualification
- OQ – Operational Qualification
- 3.1 Mill Certificates for all product-contact stainless steel components
This documentation package reduces the validation engineering burden for the end user and accelerates regulatory approval timelines across FDA, EMA, TGA and Medsafe markets.
Applications in Pharmaceutical Manufacturing
Granule sizing: De-agglomeration of wet or dry granules before fluid bed drying or tablet compression, ensuring consistent particle size distribution across the batch.
API milling: Particle size reduction of active pharmaceutical ingredients to achieve target dissolution profiles or improve content uniformity in low-dose formulations.
Tablet rework: Milling of out-of-specification tablets or rejected granulate for re-compression, recovering valuable API from waste material.
Excipient processing: Milling of microcrystalline cellulose, lactose, HPMC or other excipients to specification prior to blending.
ATEX-Rated and High-Potency Configurations
For applications involving explosive dust characteristics (ATEX Zone 21 or Zone 22) or high-potency compounds requiring OEB 3–5 containment, Hanningfield offers ATEX-certified Uni-Mill configurations and closed-loop containment systems. These are engineered in conjunction with the Uni-Vac vacuum conveyor and isolator interfaces to provide a complete contained milling solution validated to the required OEL (Occupational Exposure Limit).
What to Consider When Specifying a Pharmaceutical Cone Mill
Target particle size distribution: Define the D50 and D90 targets for the milled product, as these determine screen aperture selection and impeller type.
Throughput requirement: Calculate the required kilograms per hour or per batch to confirm the appropriate Uni-Mill model size.
API potency and OEL: Determine the containment category required to inform whether a standard or closed-loop configuration is needed.
Cleaning validation: Smooth surface finishes, tool-free disassembly and crevice-free design all contribute to cleaning validation efficiency and reduced CIP downtime.
Regulatory market: Confirm whether FDA, EMA, TGA or Medsafe compliance documentation is required, and agree the validation package scope with the supplier prior to order.
Sourcing the Uni-Mill in New Zealand
Advanced Packaging Systems (APS) is the exclusive New Zealand agent for Hanningfield Process Systems, providing application consultation, technical specification support and post-installation service. APS supports pharmaceutical, nutraceutical and food manufacturers across New Zealand with access to Hanningfield’s full range of powder processing and containment equipment.
To discuss a milling requirement or request a technical data sheet, contact APS.
