Mechanical milling is a modern marvel. It used to be that if you wanted anything ground or pulverized, you had to lay it on top of a horizontal, circular stone, and then a mule or other beast of burden would walk in a circle pulling a vertical circular stone over the top of the horizontal one. Anything left on the horizontal stone was instantly crushed and ground by the movement of the vertical stone over the top of it. Now, hundreds of years after the process has been fully automated and mechanized, it does not resemble the old stone wheels and animal power anymore. It looks more like the following.
Lots of Weird "Marbles"
Every milling machine that grinds and pulverizes has "marbles" in it. These pellets or marbles are of varying sizes and different materials, each type and size creating a different effect on the material to be ground. The pellets or marbles may be steel, plastic resin, ceramic, or sand, depending on the milling process and effect desired. To some extent, you probably could say that stones are still involved in the milling/grinding process, but they are nowhere near the couple of tons of limestone used centuries ago.
Rotating Horizontal Cylinders
In a modern mechanical milling machine, you have one exterior cylinder and one interior cylinder. The exterior one remains still, while the interior one rotates with intense acceleration. There are also controls on the outside of the primary, stationary cylinder that allow the millers to control how fast the interior cylinder spins. Faster spinning plus large grain pellets or marbles for grinding equals a powdery fine product. Slower spin plus smaller grain pellets or marbles gets you a coarser grain material. As the interior chamber is rotated and spun, the pellets or marbles fly around and pound the material to be crushed, ground, sanded, or pulverized. The material is then sifted out of the pellets or marbles before moving on in the manufacturing processes.
Washing the Milling Machines
Centuries ago, millers would simply use buckets of water to wash away residues from whatever was ground on the millstones. Now, the process is a little more labor-intensive. Everything has to be removed from the inside chamber before it is all pressure-washed by hand and expressed out of the machines. This has to be done every time a different material needs to be loaded into a machine and milled.
Contact a company like Allied High Tech for more help.