 Cutting: reduce material size using a sharp on one side. The results is to get uniform cut and minimal damage.

 Crushing: Grinding: reduce material size by emphasizing the blunt object to the materials so its broken to all direction with irregular shape. The level of damage to the materials is high.

 Shearing: reduce material size with a tool that has sharp edge on one side and blunt side in other side. This procedure is a combination of cutting and crushing.  Is the machine to grind materials into smaller parts. Some industries that use a hammer mill : . Ethanol industries (corn grinder) . A farm machine, which mills grain into coarse to be fed to livestock . Fluff pulp industries . Fruit juice industries . Shredding paper . Shredding yard and garden waste for composting . Crushing large rocks

 Hammer mill is basically a drum or cylinder with vertical or horizontal knives or hammers that mounted in drums or cylinders. The hammers are free to swing on the ends of the cross, or fixed to the central rotor. The rotor is spun at a high speed inside the drum while material is fed into a feed hopper. The materials will be milled or cut by hammer and materials that were smaller than the filter under the drum will come out of the machine.

 Hammer mill : . The parts hammer mill: hopper, hammer, walls, and filter. . Mechanism : • The milled material is inserted into the mill through a hopper • Materials that enter mill will hit by rotating hammer. Materials will have impact from hammer and wall so it will destroyed. The smaller materials than filter/ holes will going out and the larger will continue to impact the hammer and wall. • Materials will be exposed to a hammer randomly, either head or handle of a hammer so that fractions of material size is not uniform.

 Hammer mills work on the principle that most materials will crush, shatter, or pulverize upon impact using a simple four step operation:  Material is fed into the mill’s chamber typically by gravity.  The material is struck by ganged hammers (generally rectangular pieces of hardened steel) which are attached to a shaft which rotates at a high speed inside the chamber.  The material is crushed or shattered by the repeated hammer impacts, collisions with the walls of the grinding chamber as well as particle on particle impacts.  Perforated metal screens, or bar grates covering the discharge opening of the mill retain coarse materials for further grinding while allowing properly sized materials to pass as finished product.  Hard, heavy materials such as glass, stone or metals exit the mill via gravity. Pneumatic suction us used to assist in the discharge of lighter materials such as wood, paper or other low bulk density products . Advantages of hammer mill : ▪ Easy to install and to operate ▪ Not broken when operating empty ▪ Not over increase the material temperature ▪ Maintenance costs are relatively cheaper ▪ Low power . Disadvantages of hammer mill : ▪ Investment costs are relatively high ▪ The results are not uniform  The hammermill can be used as a primary, secondary, or tertiary crusher.  Small grain hammermills can be operated on household current. Large automobile shredders can use one or more 2000 horsepower (1.5 MW) diesel engines to power the hammermill.  The Screenless hammer mill uses air flow to separate small particles from larger ones. It is designed to be more reliable, and is also claimed to be much cheaper and more energy efficient than regular hammermills.  A or burr grinder is a device to grind hard, small food products between two revolving abrasive surfaces separated by a distance usually set by the user.  When the distance is larger, the resulting ground material is coarser. When the two surfaces are set closer together, the resulting ground material is finer and smaller. Usually the device includes a revolving screw that pushes the food through. It may be powered electrically or manually.

 Devices with rapidly rotating blades which chop repeatedly (see food processor) are often described as grinders, but are not burr grinders. Burr mills do not heat the ground product by friction as much as blade grinders, and produce particles of a uniform size determined by the separation between the grinding surfaces.  Food burr mills are usually manufactured for a single purpose: beans, dried peppercorns, coarse , , or poppy seeds, for example. Coffee mills are usually powered by electric motors; domestic pepper, salt, and mills, used to sprinkle a little seasoning on food, are usually operated manually, sometimes by a battery-powered motor.  Burr mill : . The part of burr mill: hopper, cylinder, wall plate . Mechanism : the material get into hopper which then enter into the gap between the cylinder and the wall plate . Materials will be milled and screw over into unloading. • Advantages of burr mill : ▪ The results are more uniform ▪ Investment costs are cheaper . Disadvantages of Burr Mill:: ▪ Thermal effects on materials ▪ If empty operation, the cylinder will wear out/broken ▪ Required skilled operator to adjust the distance between cylinder and wall ▪ Require relatively high energy ▪ Standard of smoothness and uniformity ▪ Smoothness and uniformity are measured by the modulus of smoothness and uniformity index Sieve Retained Percentage of Multiple number Material (g) Retained Percentage of Material Retained Material and Sieve number 7 20 20 140 6 30 30 180 5151575 4101040 3101030 2101020 1555 Pan 0 0 0 Total 100 100 490 . Smoothness modulus (MK): 490/100: 4.9 . If all the material retained in pan, so MK = 0 means a very smooth . If all the material retained on sieve No. 7, so MK = 7 means very rough. . MK = 4.9 means rough

. Uniformity index (IK): . Sieve 5-7: roughly categorized . Sieve 3-4: rather rough categorized . Sieve 1, 2, and pans : smooth categorized . From the table above showed that IK results are: 65: 20: 15 or 6.5: 2.0: 1.5  History: . The first rice mill in England about 140 years ago . Modern rice milling machine 35 years later in Japan . Modern rice milling 40 years later  Primary Technical Criteria: . Produce maximum head rice yield . Rice husker uniformly so rice color according to desired

 Secondary Technical Criteria: . Maximum milling capacity . Minimal energy consumption . Lower consumable parts . Productivity of operator maximum Potential milled grain is determined by:  Characteristic of varieties : . Percent husk: 17-24% of the grains . Grain shape (ratio of length and width). Slender grain is easily broken than round grain. . Hardness degree: Hardness of rice is varieties characteristic. Rice that has a hard layer tends to produce the high quality and yield. . Calcification: can be a characteristic of the variety or because of the environment. Calcification effect on yield and quality.  Grain Quality : . Moisture content: The optimum moisture content of grain for milling is 14% . Percent of empty grains: standard <3% . Cracked grains: Late harvest or too mature grains cause cracking. This will result in a lower yield of milled rice and head rice. . Green grains: immature green grain and when it milled tends to be small, green, calcify and will give broken or destroyed rice . . Yellow grains and damage grains: yellow grains occur because it can not be dried. Damaged grain generally occur because fungus attack. Often produce rice with black spots.  Mechanical Cleaning Machine: . to remove impurities: pieces of rice straw, dust, stone, metal, glass, insect . . Paddy Cleaner . Tool consists of a filter/sieve and an aspirator. Material moves down across the screen because filter is installed sloping. The larger impurities are filtered out in the first filter, while the smaller than grain will be filtered in the filter after the grain. The lighter impurities than grain will be separated with aspirator.

. Distoner. Separates grains from stone, clay, glass, or heavier objects. Distoner is gravity separator. Heavy objects (dirt) flow to the top of the slope, while the grain tends to bottom. Objects that have higher density than grain will separate with different flow directions.

 Precleaning ▪ Precleaning machine is responsible for cleanup of dust that can be cause problems at mill ▪ In small mills used Distoner (gravity separator) ▪ At the big mill or all types miller made in Japan coupled with aspirator and precleaning machine that separates empty grain and green grain. Doble Action Rough Rice Cleaning Machine

Type of Engelberg  Grain enter into gap between the two rubber roll that rotate with different speeds and inopposite directions.  Friction and pressure of the two rubber roll will release brown rice (PK) from the husk, and will be mixed after going through the roller gap.  Furthermore, a mixture of brown rice and husk enter into aspirator. In aspirator, a mixture of brown rice and husk will pass through a thin layer and fall into column with flow and arranged air .  Furthermore, husk blown out and separate with brown rice.

 The factors that determine Efficiency of the Brown Rice Milling : . Grain moisture content, generally too wet causing no peeling grain . The uniformity of incoming grain into rubber roll husker. . Ratio of Two rubber roll speed : lower the difference rotational speed between the two roll causes low efficiency of milling. . Pressure between two rubber roll. Higher pressure make more grain peeling, but will cause a broken rice and roll wear faster. . The uniformity of incoming grain to aspirator.