Ball mills are used for grinding things down or for mixing things up. They grind ores down to powders before they are chemically processed, they grind grains down to flours for baking and they mix up paints so they are smooth enough to apply. All ball mills consist of rotating cylinders that contain hard (usually metallic) balls that do the grinding. There are three types of ball mills: horizontal, vertical and industrial.
Horizontal Ball Mills
Horizontal ball mills are the most common type. The basic design is the same but the details can vary slightly. A drum, which is usually detachable, has a door that can be used to load in the material to be processed. Sometimes -- like for paint mixers -- there will be a screen that keeps the metal balls in place. When the substance to be processed (and the balls) are in the drum, the door is closed and the drum is reinstalled -- horizontally -- on the mill where it is rotated until the job is done. Some ball mills have a timer and some have a window where the processed material can be viewed.
Vertical Ball Mills
Small vertical ball mills are about the size of a blender and are intended for laboratory or shop use. They are small enough to fit on a lab table or workbench and only big enough to process the small quantities need for desktop applications -- they are not intended for commercial or industrial use. These ball mills are often called planetary ball mills. The rotating drums are not usually detachable -- the material is poured into the top and the cap is replaced, like a kitchen blender. Like all ball mills, the speed and ball size have an effect on how the vertical ball mill works. Vertical ball mills often come with a variety of ball sizes (and have variable speed settings) for more efficient processing.
Industrial Ball Mills
Industrial ball mills are much larger than the other types of ball mills. They vary in size from approximately the size of a refrigerator to approximately the size of a bus. They are always horizontal. What distinguishes the industrial ball mill (besides its large size) is that they have multiple chambers and have a forced-air system constantly moving material through the rotating drum. The different chambers are separated by screens of progressively smaller mesh. The chambers contain balls of progressively smaller size. The size of the balls and the screen mesh keeps the balls in their own chamber. Material is forced from one chamber to the next as it is ground small enough to fit through the mesh screens.