A pharmaceutical cone mill trial should establish whether a proposed setup can deliver the required particle size distribution at a useful production rate. Before sending material, agree what will be measured, how results will be assessed and which production conditions the trial needs to represent.
A clear trial brief helps process engineers, production teams and equipment suppliers evaluate the same outcome. It also makes comparisons between tooling combinations more meaningful.
Start with the process requirement
Describe where milling sits in your process. Are you sizing wet granules before drying, processing dry granules before compression, or breaking down agglomerates in an incoming material? These applications can require different milling actions and different measures of success.
State the problem in measurable terms. “Reduce oversize material while controlling fines” is a useful starting point, but the trial needs agreed limits. Include the required batch size, available processing time and any known downstream constraints.
If tablet manufacture is the next stage, agree whether further assessment of the milled granules is needed. Particle size results alone do not demonstrate the performance of the complete formulation or manufacturing process.
Send material that represents production
Give the supplier a description of the sample and the conditions under which it was produced. Record its moisture condition, incoming particle size, storage history and any tendency to form lumps. Identify relevant handling hazards and temperature sensitivities before arranging shipment.
Discuss the quantity needed for the planned work rather than assuming one small sample will answer every question. Allow for alternative settings, sampling and a repeat of the preferred setup. If normal production material varies, agree which variations should be represented.
Set acceptance criteria before the trial
Use a brief like the following to define success. Set values for your application with the relevant process and quality teams; there is no universal pharmaceutical cone mill specification.
| Measure | Agree before testing | Record in the results |
|---|---|---|
| Particle size distribution | Target size range, permitted oversize and fines | Measured distribution using the agreed method |
| Throughput | Required processing rate or batch completion time | Mass processed, elapsed time and interruptions |
| Temperature | Acceptable limit and measurement location | Starting condition and temperatures during the run |
| Recovery | How retained material and samples will be accounted for | Input, collected product, samples and retained material |
| Repeatability | Which setup will be repeated and what variation is acceptable | Results from the repeat under documented conditions |
Agree the sampling procedure and particle sizing method as well as the target. When comparing results, use consistent sample preparation and measurement conditions. Otherwise, a change in the analysis can obscure whether the milling setup actually improved.
Evaluate the complete milling setup
A screen aperture is a tooling dimension, not a specification of the final particle size distribution. Material characteristics and the combination of screen, impeller, speed and feed conditions influence the result. Two runs using the same aperture should not be assumed to produce identical distributions.
Hanningfield offers a range of conical mill screens and impellers. A trial can help establish which combination suits the material and required outcome.
Document the machine model, screen identification, impeller profile, operating speed and feeding arrangement for every run. Start with an agreed reference setup, then use a planned sequence of changes. Avoid changing several settings without recording why: it becomes harder to identify what affected the result.
Assess size and throughput together. A configuration that reaches the target distribution but cannot complete the batch within the available time may need further development. Equally, a fast run is not successful if its product falls outside the agreed specification.
Connect the findings to production
A promising laboratory result is a starting point for specifying the production installation. Discuss how the selected conditions will transfer to the proposed machine size, feed system and batch duration, and identify what still requires confirmation.
The Hanningfield Uni-Mill under-driven range includes laboratory and production models, with a choice of screens and impellers for each model. Published maximum throughput figures are product dependent, so use material-specific trial evidence when assessing capacity.
Include practical installation questions in the review: available height, inlet and outlet connections, access for cleaning, product changeovers and containment needs. Agree which requirements can be assessed during the material trial and which need separate equipment or installation checks.
Prepare your cone mill trial brief
Hanningfield can carry out in-house trials using customer-supplied material to help identify suitable tooling before an order is placed. Bring a process description, representative material information, target distribution, required rate and relevant handling constraints.
Contact Hanningfield to discuss a cone mill trial and agree the sample requirements and scope. A useful trial should leave you with a documented setup, measured results and a clear list of the next steps needed to specify your milling process.