Milling and Micronisation

Pharmaceutical milling and micronisation to achieve your target particle size

We deliver the milling and micronisation technology to support your API’s physical characteristics for drug product formulation.

Milling and micronisation services at Sterling

Particle size reduction can be critical to optimising your API’s physical properties and its ability to be properly formulated as a finished drug product. As part of our material science capabilities at Sterling, we offer pharmaceutical milling and micronisation services to achieve your desired particle size distribution at any stage of development. ... Read more

Our team of specialists work in partnership with you to achieve your required particle size parameters, preparing your API for successful formulation. We have experience meeting particle size requirements with repeatable quality, at both small and commercial scale.

We are committed to providing our customers full visibility and transparency, enabling them to observe their programmes in motion. Our processing suites are equipped with state-of-the-art camera systems that offer customers the opportunity to view milling operations performed in the Material Science Centre, remotely. Read less

Fast Facts

Flexible equipment:

Our equipment enables us to offer different types of particle size reduction of your API depending on your desired particle size and requirements.

State-of-the-art milling capabilities:

A variety of mills, totalling 16 across our global network, to meet your product requirements, utilising a variety of containment solutions.

Expert teams:

Our specialists will help you develop the particle size reduction strategy best suited to your material and requirements.

Full visibility:

CCTV monitoring enables customers to view milling operations remotely.

State-of-the-art equipment:

We can utilise mechanical milling, micronisation technology or a combination of both to achieve your required particle size distribution.



Our mechanical milling capabilities enable us to achieve a particle size down to 30 microns. Our equipment offers the flexibility to support different modes of milling, and our team will help determine which approach, or combination of approaches, will achieve your particle size requirements.

Our mechanical milling equipment includes:

  • Two Frewitt Fredrive units with interchangeable heads. One of the units spans three floors of our Dudley site’s Material Science Centre and can offer containment up to OEB4. This can be utilised for hammer, knife, conical and sieve milling based on project requirements.
  • A Fredrive lab for milling development that supports hammer, knife, sieve, and pin milling.
  • Fitzpatrick mill that supports hammer and knife milling.
  • Two Hosokawa UPZ mills of differing sizes and capabilities. This includes pin milling and plate beater milling adaptors to allow for a fine and medium fineness material in a single step.
  • Two Frewitt Coniwitt cone mills which are high performance conical sieve mills which allow materials to be produced as low as 150 microns.
  • Two Quadro cone mills which are high capacity, compact design conical mills that can produce materials as low as 150 microns, with a lab sized unit which is scalable to the production scale unit and capable of handling materials to OEB3/4.
  • Two IKA wet mills which utilise twin rotor and stator technologies. They can produce wet materials to a D90 of around 1n microns with a lab sized unit which is scalable to the production unit.
  • A Hosokawa UPZ pin mill with one static pin disc and one rotating pin disc. This offers a finer particle size distribution than a hammer mill and is capable of handling materials that are OEB 4/5 level.
  • A Frewitt lab fitted with the HW1 module and is a high-performance hammer mill capable of producing small batches from 50g to a potential particle size as small as 30 microns.

When an even smaller particle size distribution is required, we can utilise micronisation technology. Micronisation of an API, or spiral jet milling, enables us to achieve a particle size down to 2 to 5 microns.

Our micronisation equipment includes:

  • A Hosokawa AS jet mill capable of larger volume production runs between 25kg and 150kg.
  • A Surtevant 1-inch microniser which enables us to micronise small amounts of material from 50 to 500 grams at a throughput which is governed by the particle characteristics of the supplied API.

API uniformity is paramount in drug formulation, whether the material is free flowing or more difficult to handle. At Sterling we have the capabilities to utilise both high shear and low shear options to meet your specific requirements.

Our blending equipment includes:

  • A Mueller GMBH tumble blender which utilises a rotation method for low shear blending.
  • An Amixon vertical blender which utilises a three-dimensional flow for a more aggressive, higher shear mixing capability.

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