What Makes a Mill Ideal for Lab Work?

Considering most material research and development is completed on a small scale, laboratory-size milling equipment offers a unique advantage in testing new processes and materials with minimal financial investment. Development work can require many trials to find the proper mill configuration and operating parameters, so the technology selected needs to be suitable to provide the following:

Versatility/Flexibility
What good is a lab mill, if it only has one type of grinding mechanism?  Most lab scale size reduction equipment is designed around a single grinding mechanism, which is a major limiting factor in a lab environment. The ideal equipment should combine as many of the technologies available on the market from jet milling, impact milling, media milling, and even classification or mixing into a single system.  On the other hand, if a majority of the testing is going to be completed with impact type milling, it is again crucial to obtain equipment that combines all of the grinding principles, including shear, attrition, compression, and impact, to produce a wide variety of particle size distributions with differing materials. The last thing an operator needs to do is to spend hours switching technologies. So if this particular equipment allows for a quick conversion by a simple rotor change out, it will provide an effective use of the available development time.

Scalability
What good is a lab mill, if it is the only machine size available with no way of scaling up? When scaling there are two factors to consider: particle size distribution (PSD) and throughput rate (lb/hr). It is crucial to know that the equipment selected will produce the same PSD on the production unit and the throughput rate achieved would provide some idea on the energy required for the production scale equipment.

Cleanability
What good is a lab mill, if it takes massive effort to disassemble and clean? Since product development means lots of short runs in a given period of time, it is essential to be able to clean lab equipment in a short period of time to prevent any cross contamination between product runs, while maintaining the project schedule. Quick-connect clamps, slide out internals, and proper sealing to isolate the product zone from the drive components are critical in reducing downtime.

Durability
What good is a lab mill, if it breaks down every time you run material? Even the most basic laboratory mills are not inexpensive, as such the selected equipment should be durable enough to withstand years of processing without significant maintenance required. This requires proper design of the equipment with the most appropriate materials of construction for the expected service while keeping costs in check.

Efficiency
What good is a lab mill, if you only recover half of what you feed? During research and development trials, material may be expensive to produce or difficult to find, so every gram counts. The ideal lab mill should provide a design for the high recovery of processed materials, where material recovery after processing should be no less than 95%. To achieve these high yields your lab scale mill internal surface areas should be minimized so that material cannot accumulate in the mill during processing and special venting designs incorporated to prevent material from escaping the system.

Summary
We have listed five critical categories that explain the ideal requirements in the selection of a laboratory scale mill. Equipment with similar features might be misleading, so a detailed discussion with your equipment vendor, as well as material testing, is recommended to make sure that the above five categories are addressed to meet your requirements.  

    Greg Boyer is the marketing manager for Hosokawa Micron Powder Systems, Summit, NJ. Hosokawa specializes in size reduction systems and powder processing solutions for the chemical, food, pharmaceutical, and mineral industries.

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