A cylindrical metal part that guides the piston to stop its linear reciprocating motion in the cylinder. Air in the engine cylinder through the contraction of heat energy into mechanical energy; gas in the compressor cylinder to withstand piston compression progress pressure. The casing of a turbine, rotary piston engine, etc., is often referred to as a "cylinder.". Application fields of cylinder: printing (tension control), semiconductor (spot welding machine, chip grinding), automatic control, robot, etc.

The cavity in which the piston is placed on the cylinder block of an internal combustion engine. It is the track of piston movement, in which the gas goes out shrinks. After passing the cylinder wall, part of the waste heat the gas can be dissipated, making the engine stick to the normal working temperature. There are two types of cylinder: integral type single casting type. Single casting can be divided into dry type wet type. When the cylinder the cylinder block are cast as a whole, they are called integral cylinders; when the cylinder the cylinder block are distinguished cast, the single cast cylinder barrel is called cylinder sleeve. The cylinder liner which is in direct contact with cooling water is called wet cylinder liner; the cylinder liner which is in direct contact with cooling water is called dry cylinder liner. In order to adhere to the tightness of the contact between the cylinder the piston increase the friction loss of the piston in its movement, the inner wall of the cylinder should have high machining accuracy accurate external dimension.