HOW HAMMER MILLS WORK
Hammer mills consist of a rotating shaft that has hammers attached to it. The hammers rotate at a reasonable high speed close to a milling chamber that is equipped with a screen. The main product is fed into the milling chamber and the hammers mill the product until it has reached a size that is small enough to escape out of the milling chamber through the screen. If the operator wants to change the size of the product, then the size of screen must be changed. Within certain criteria the same hammer mills can be used to mill grain as well as plant materials such as lucerne.
In this aggressive milling process a large percentage of the product will be reduced to a size that is much smaller than the screen size that has been installed in the milling chamber, resulting in a product that is not very homogeneous. If the desired product is very fine, usually below 500 microns, then it should not be a problem. However, if the desired product must be, for example, smaller than 2000 microns, but the feed expert doesn’t want a large percentage below 500 microns, then a hammer mill is probably not the best option to mill with. It’s also worth considering that hammer mills are commonly considered energy guzzlers and can cause a fairly large kW/ton energy product ratio if not monitored closely. These mills can be dusty and create an unfavourable working environment if not applied correctly. In spite of this the hammer mill does have its place in milling and it can be effective when used in the right environment and for the right job.