Impact mills are one of two general classes of milling devices used to reduce the particle size of a material.

Description

The other class of

mills Mills is the plural form of mill, but may also refer to: As a name *Mills (surname), a common family name of English or Gaelic origin * Mills (given name) *Mills, a fictional British secret agent in a trilogy by writer Manning O'Brine Places Unit ...

are "attrition" or grinding mills. Impact mills pulverize the material upon impact. The feasibility of impact mills was greatly enhanced by the mechanization and engineering of the

Industrial Revolution The Industrial Revolution was the transition to new manufacturing processes in Great Britain, continental Europe, and the United States, that occurred during the period from around 1760 to about 1820–1840. This transition included going f ...

. Prior to the industrial revolution, milling was primarily done by attrition or grinding the material between two surfaces. Attrition milling continues to be the dominant milling class, particularly in the milling of agricultural products (i.e. grain into flour).

Roller mill Roller mills are mills that use cylindrical rollers, either in opposing pairs or against flat plates, to crush or grind various materials, such as grain, ore, gravel, plastic, and others. Roller grain mills are an alternative to traditiona ...

s and stone mills are two examples of attrition (grinding) mills.

Variations of impact mills

Impact mills either pulverize the material by simply employing gravity or they can mill dynamically upon impact with a high speed rotor,

hammer A hammer is a tool, most often a hand tool, consisting of a weighted "head" fixed to a long handle that is swung to deliver an impact to a small area of an object. This can be, for example, to drive nails into wood, to shape metal (as w ...

pin A pin is a device used for fastening objects or material together. Pin or PIN may also refer to: Computers and technology * Personal identification number (PIN), to access a secured system ** PIN pad, a PIN entry device * PIN, a former Dutch ...

Gravitational impact mills

Gravitational impact mills pulverize the material inside a rotating chamber. This is accomplished by a cascading motion of larger pieces repetitively impacting and compressively grinding the product into finer particles as it rotates in the chamber. These are generally referred to as " autogenous" impact mills. This action can be enhanced by placing steel balls in the chamber. The class of gravitational impact mills that incorporate steel balls in the chamber are appropriately referred to as "

ball mill A ball mill is a type of grinder used to grind or blend materials for use in mineral dressing processes, paints, pyrotechnics, ceramics, and selective laser sintering. It works on the principle of impact and attrition: size reduction is done ...

Dynamic impact mills

Dynamic impact would occur when material is dropped into a chamber where it receives a pulverizing blow from a

, rotor or pin. Pulverizing can be enhanced by engineering the rotor or hammer to pass close to a serrated fixed stator. Pin, unifine; and VSI mills are examples of dynamic impact mills.

References

{{reflist Industrial equipment Grinding mills