MILL GRINDING

1. Mill (grinding)
From Wikipedia, the free encyclopedia
Attrition Mill
A tabletop hammer mill
Other names Grinding mill
Uses Grinding
Related items
Mortar and pestle
Expeller
Extruder
A mill is a device that breaks solid materials into smaller pieces by grinding, crushing, or
cutting. Such comminution is an importantunit operation in many processes. There are many
different types of mills and many types of materials processed in them. Historically mills were
powered by hand (e.g., via a hand crank), working animal (e.g., horse mill), wind (windmill) or
water (watermill). Today they are usually powered by electricity.
The grinding of solid matters occurs under exposure of mechanical forces that trench the
structure by overcoming of the interior bonding forces. After the grinding the state of the solid
is changed: the grain size, the grain size disposition and the grain shape.
Milling also refers to the process of breaking down, separating, sizing, or classifying
aggregate material. For instance rock crushing or grinding to produce uniform aggregate size
for construction purposes, or separation of rock, soil or aggregate material for the purposes of
structural fill or land reclamation activities. Aggregate milling processes are also used to
remove or separate contamination or moisture from aggregate or soil and to produce "dry fills"
prior to transport or structural filling.

2. Grinding may serve the following purposes in engineering:
• increase of the surface area of a solid
• manufacturing of a solid with a desired grain size
• pulping of resources
Roller mill
For rolling mills that roll metal into various shapes, see rolling (metalworking).
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 traditional millstone arrangements in gristmills. Roller mills for rock
complement other types of mills, such as ball mills and hammermills, in such industries as
the mining and processing of ore and construction aggregate; cement milling; and recycling.
• 6 References
Producing wheat flour
To produce refined (white) wheat flour,[1] grain is usually tempered, i.e. moisture added to the
grain, before milling, to optimize milling efficiency. This softens the starchy "endosperm"
portion of the wheat kernel, which will be separated out in the milling process to produce what
is known to consumers as white flour. The addition of moisture also toughens the bran and
ultimately reduces the energy input required to shatter the kernel, while at the same time
avoiding the shattering of bran and germ particles to be separated out in this milling process
by sieving or sifting.
The endosperm portion of the kernel makes up about 80% of the volume and is desirable
because the products produced by this white flour are often considered to have milder flavor,
smoother texture, and, in the case of bread, greater volume. The balance of the kernel is
composed of the bran and the germ which tend to be coarser. With the invention of the roller

3. milling system in the late 19th century, the bran and the germ were able to be removed,
dramatically improving the appeal of baked products to the public.
The moistened grain is first passed through the series of break rollers, then sieved to
separate out the fine particles that make up white flour. The balance are intermediate particles
of endosperm (otherwise known as product middling or farina) and coarse particles of bran
and germ. The middling then makes multiple passes through the reduction rolls, and is again
sieved after each pass to maximize extraction of white flour from the endosperm, while
removing coarser bran and germ particles.
To produce whole wheat flour, 100% of the bran and germ must be reintroduced to the white
flour that the roller milling system was originally designed to separate it from. Therefore, these
elements are first ground on another mill (usually a pin mill). These finer bran and germ
fractions are then reintroduced to the endosperm (white flour) to produce whole wheat
flour made of 100% of the kernel of wheat.
Gristmill conversion
In the 19th century roller mills were adapted to grist mills before replacing them. The mill used
either steel or porcelain rollers.[2] Between the years 1865 and 1872, the Hungarian milling
industry upgraded and expanded the use of stone mills combined with roller mills in a process
known as Hungarian high milling. Hungarian hard wheat so milled was claimed as integral to
the "First in the world" success of the Vienna Bakery of the 1867 Paris Exposition.[3]
Other applications
• Specialized for the high production of superfine pyrophyllite powder making in glass
fiber industry
• Specialized for the high production of gangue powder making in coal industry
• Specialized for the high production of various of chemical raw material powder making in
the chemical industry.
Working principle[edit]
While working, motor drives the hanger of the grinding roller to rotate through V pulley and
centre bearing. The roller, which is hung by bearing and pendulum shaft, will roll along the

4. inner circle of the roll ring while the hanger is rotating. A dust removal blower will
generate negative pressure at the inlet and outlet of the grinder to prevent dust and radiating
the heat in the machine.