A round hole screen is designed for the standard milling applications and is used to size product before it leaves the screen. As the impeller rotates, it forces the material through the holes in the screen, reducing the size of the particles. It should be noted that the particles exiting through the hole will be smaller than the hole itself, as the particle exits at a diagonal trajectory, rather than head-on. Therefore the speed of the impeller will impact particle size (faster speed, smaller particle).
Typical applications for a round hole screen include easily friable materials or those which do not require an aggressive milling action (for milling hard materials, see grater screens). Common round-hole applications include most powders, APIs or most other dry, friable materials.
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