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Machine presses use pressure to shape or cut parts in manufacturing, with hydraulic, pneumatic, or mechanical power sources. They are used in various industries and can be automated, but safety concerns exist. Different types of presses include screw, laminating, arbor, and knuckle presses.
A printing press is a machine tool that uses pressure to cut or shape parts as part of a manufacturing process. Machine presses use a variety of means to apply pressure, including hydraulic, pneumatic, and mechanical, such as in screw or roller presses. The particular type of press used may depend on the material being shaped or cut, as well as the specifications of the final product. Examples of types of machine presses date back several centuries, although the specific methods of applying pressure have changed over the years with continuous innovation.
A variety of machine presses are used during manufacturing, from shaping sheet metal for use in automotive manufacturing to pressure shaping plywood to create curved pieces for furniture. Through the use of dies, a printing press can be used to cut shapes or punch holes in sheets of material. A single press, equipped with a variety of cutting and shaping pieces along its length, can be used in metal forming to shape and cut a single piece, such as the tab for a soda can, by advancing a sheet of metal each time the press is raised. With this method, each individual step in creating the part is completed by a separate mold along the length of the single press.
Two of the most popular types of machine presses used in industry are pneumatic and hydraulic presses, both of which depend on fluids to exert pressure. An air press depends on a pump to build air pressure in a tank, which is released as needed to apply pressure. A hydraulic press consists of two cylinders of different sizes joined by a tube, and the whole is filled with liquid, usually oil, and sealed. When pressure is exerted on the smaller piston, due to the law of conservation of energy, a greater force is applied over a smaller distance to the larger piston.
A pneumatic press is capable of moving much faster and can perform several cycles in the time it takes for a hydraulic press to complete a single cycle. The trade-off for speed is horsepower, as a hydraulic press may be capable of exerting multiple times the pressure of a comparably sized pneumatic press. While mostly automated, safety concerns exist as a pneumatic press can move too quickly for a human operator to react. A hydraulic press may be moving slowly enough to be stopped mid-cycle by cutting power, but the need for more operator interaction actually poses greater risks.
Other types of machine presses use a mechanical lever, such as the screw press, which applies pressure through the lever created by turning a screw. In the case of a laminating press, pressure is applied as the material passes through a series of rolls, as in a manual press, although the method is also used to cut and shape sheet metal. The arbor press has a notched rod which corresponds to a gear, and as the gear is rotated, the rod applies pressure. The knuckle press depends on the movement of a knuckle joint, with pressure applied in the classic fulcrum and lever configuration. All of these and other mechanical presses can use hydraulic or pneumatic pressure as their power source, or they can get energy from a mechanical motor.
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