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    Gerteis® Small Scale Mill for laboratory applications

    products-servicesGerteis Maschinen + Processengineering AG
    December 7th 2021

    Gerteis® of Switzerland has leveraged its three decades of experience in the roller compaction of pharmaceutical powders into the design of its Small Scale Mill, a highly accessible and easy to use laboratory tool for producing pilot and test batches of powders.

    Built for milling small amounts of a roller compacted pharmaceutical material, the manually operated Small Scale Mill allows powder batches ranging from a few grams to 50g to be milled in one pass.

    Small Scale Mill Design and Features

    Gerteis® research studies indicated that existing laboratory scale or domestic mills were unable to reproduce the same PSD as full scale roller compactors. Therefore it developed the Small Scale Mill specifically to reproduce the grinding principles of the PACTOR® line.

    The Small Scale Mill reproduces the same milling steps as the renowned Gerteis® PACTOR® roller compaction machines with almost identical particle size distribution (PSD), making it a highly useful tool for developing dry granulates during first phase R&D.

    Gerteis® engineered the Small Scale Mill to be compact and simple, using manual operation for minimal footprint and low cost. The tool uses different screens with various apertures to vary and modify the PSD of the achieved granules of the pharmaceutical formulation.

    The rasping screen and various meshes are easily fitted and changed, allowing a very wide range of screening patterns to meet different specifications. The manually operated milling bars push material – either in roller compacted ribbon or tablet piece form – through the screens in the milling chamber, with fully processed granules collected in a drawer.

    The overall design emphasizes ease of use with fast and simple fitting and cleaning of all components. Materials used comply with all pharma regulatory guidelines.

    Small Scale Mill Results

    Gerteis® has compared Small Scale Mill performance against the benchmark MACRO-PACTOR® production scale roller compactor in tests at the University of Bonn, using four different excipients; Vivapur® 101, Ecompress® prem, Neosorb® 300 DC and FlowLac® 100. Each excipient was milled with the Small Scale mill and the MACRO-PACTOR®  fitted with pocketed rotor.

    Results for all tested excipients (see Figure 1) showed close PSD correlations between Small Scale Mill and MACRO-PACTOR®.  All followed typical PSDs for dry granulates with a maximum 20 per cent proportion of <100 µm ‘fines’. Small differences between the two machines were observed for the strongest particle fraction (1000 µm-1400 µm), slightly tilting PSD for the Small Scale Mill towards coarser particles. The extent of this small deviation seems to depend on material and caused by those MACRO-PACTOR® features, such as granulator settings, that are not replicated by the manually operated Mill. Such process parameters can be optimized in scale-up and so can safely be ignored during development.

    The Small Scale Mill shows very close PSD correlation with Gerteis® production-scale roller compactors, thereby providing an ideal tool for the research of milled granulates at lab scale.


    Click on Gerteis Knowledge Hub for more on Small Scale Mill and other granulation resources.
    Click on Contact Gerteis for queries about Small Scale Mill.


    Dry granulation and its application in dietary supplements manufacturing

    Gerteis® Small Scale Mill for laboratory applications

    Gerteis®  Small Scale Mill.

    Gerteis® Small Scale Mill for laboratory applications

    Figure 1: PSD-curve comparisons of four excipients milled on Gerteis® Small Scale Mill and MACRO-PACTOR®.

    Gerteis® Small Scale Mill for laboratory applications

    Gerteis®  MACRO-PACTOR®: flagship pharma roller compactor.

    Gerteis® Small Scale Mill for laboratory applications

    Table 1: Excerpt of APIs processed by roller compaction.

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