Grinding and dispersing techniques

One of the keys to proper grinding is making a good premix. It is also one of the most neglected processes in the particle reduction industry. The better the dispersion before the product is sent to the mill, the more productive the mill cycle will be. Poor quality premix results in longer grinding times (higher production costs), clogged screens (more downtime and product loss) and greater wear on the mill (higher maintenance costs).

There are a few simple rules for making a good premix:

• High granular solids content. Keep the dry particulate content of the premix as high as possible. Resins and solvents can be added prior to the milling step. The premix viscosity should produce a "doughnut" shaped flow with small swirls and no splash.

• The blade diameter should not be less than one-third of the tank diameter.

• Tipping speed should be between 5000 and 5200 feet per minute. The formula for tip speed is: FPM = Cxrpm C = Лx(D÷12) FPM = Feet per minute C = Circumference RPM = Rotations per minute D = Inches diameter mixing stage is not optimized)

• Selecting the proper diffuser blade is the final step.