From the Lab to the Line: Mastering Particle Size with Wet Grinding

The smoothness of a product is not simply for aesthetic appeal, but is essential in industries such as paint, pharmaceuticals, inks and cosmetics where product performance relies on particle size. A cough syrup that separates easily or car paint that shines like glass should have a high surface-area-to-volume ratio and that can be achieved through the grinding method known as Wet Grinding System. Wet Grinding Systems may be complicated to understand when setting up a new manufacturing facility and conducting research in the laboratory; however, we will try to explain how to properly operate the Wet Grinding System from mixing to final microscopic grinding.

Phase 1: The Pre-Mixed Liquid

The first step in the fine grinding process is creating a slurry or mixture of the solid powders with the chemical liquids to prevent the solid powders from forming clumps when poured directly into the fine mill. This is accomplished by using a High-Speed Agitator Dispersor, which is similar to a powerful blender that utilizes a rapidly rotating disc blade to create a tornado-like effect or vortex in the mixing container. In addition to mixing the powders and liquids together, the High-Speed Agitator will also apply enough shear force to break apart the large clumps of powders and fully coat them with the liquid. When the pre-mix is an even, uniform suspension, it is then ready for fine grinding.

Phase 2: Fine Milling

You’ll want to pulverize the particles in your flowable slurry to a particle size between 1-micron and 2-nanometer. While production uses very large machines to accomplish this task, you should consider using Laboratory Bead Mills if you are developing a new formulation or producing a very expensive small batch of medicine.

A Laboratory Bead Mill can be thought of as a scaled-down mill of the larger production-sized machines but designed for precision, ease of cleaning, and efficient operation, allowing only small amounts of product to be milled at a given time. Laboratory Mills allow researchers to assess how different flow rates and speeds affect the process without wasting hundreds of gallons of raw materials. This data is essential to successfully "scale-up" the process from the Laboratory Mill to production. If you can achieve a desirable process on a Laboratory Mill, you will usually be able to duplicate it in production.

Phase 3: How the Fun Starts!

What is going on within that molar? The design is the same for a lab-scale or large production scale Wet Bead Mill; thus, the operation is similar.

The shaft is located within the grinding room. The shaft has discs or pins that rotate as it moves around. The grinding chamber holds thousands of small solid beads (ceramics, glass or steel). As the shaft turns, the beads are misaligned with each other.

You guide your pre-mixed slurry through the grinding room; as the liquid flows into the chamber, the particles become "trapped" in between the disrupting beads. The combination of impact (beads hitting into the particulate matter) and shear (beads moving laterally along the particulate matter) both grind and crush the solids down to their desirable size. The Wet Bead Mill uses liquid as the medium for moving the product through and helps prevent overheating (often allowing a cooling jacket to maintain the appropriate temperature), thereby preventing any degradation of the product or damage to the equipment.

Final thoughts

To achieve optimal dispersion requires a process. The first step of that process is mixing materials together in a High Speed Agitator Disperser. The second step is precision through Wet Grinding. Laboratory Bead Mills can be used during testing R&D to help guarantee that the end product will be stable, glossy and optimally ground. When combined, these two components create our smooth colourful modern world through a simple principle of Physics and well-designed engineering.