Die is a tool used to make blanks into parts with specific shapes and sizes under the action of external force in blanking, forming stamping, die forging, cold heading, extrusion, powder metallurgy parts pressing, pressure casting, and compression molding or injection molding of engineering plastics, rubber, ceramics and other products. The die has a specific contour or cavity shape, and the contour shape with cutting edge can make the blank separate according to the contour shape, that is, punch; The shape of the inner cavity can make the blank obtain the corresponding three-dimensional shape. Mold is generally divided into two parts: moving mold and fixed mold, or male mold and female mold, which can be separated and combined. When separated, the blank is loaded or the workpiece is taken out, and when closed, the workpiece is separated or shaped from the blank. In the process of blanking, forming stamping, die forging, cold heading, pressing and compression molding, the external force required for separation or forming is applied to the blank through the die; In the process of extrusion, die casting and injection molding, external force is exerted on the blank by air pressure, plunger and punch, and the die bears the expanding force of the blank. In addition to itself, a mold needs a mold base, a mold frame, a guide device and a product ejection device, etc. These components are generally made into universal types to be suitable for a certain range of different molds. Moulds are widely used. A large number of moulds are used in the manufacture of electromechanical products, such as automobiles, bicycles, sewing machines, cameras, motors, electrical appliances, meters, etc., as well as household appliances. Mold is basically produced in one piece, and its shape is complex, which requires high structural strength, stiffness, surface hardness, surface roughness and machining accuracy, so mold production needs a high technical level. The timely supply and quality of molds directly affect the quality, cost and development of new products. Therefore, the level of mold production is one of the important signs of mechanical manufacturing level. Moulds for processing metals are classified according to the processing technology adopted, and commonly used are: stamping dies, including blanking dies, bending dies, drawing dies, hole-turning dies, shrinkage dies, undulating dies, bulging dies, shaping dies, etc. Forging dies, including forging dies for die forging and upsetting dies; As well as extrusion dies and die casting dies. The molds used for processing nonmetals and powder metallurgy are named and classified according to the processing objects, including plastic molds, rubber molds and powder metallurgy molds. Stamping die is a die used for sheet metal stamping and separation. The mold for forming has a cavity, and the mold for separating has a cutting edge. The most commonly used stamping die has only one station to complete a production process. This kind of mould is widely used, simple in structure and easy to manufacture, but its production efficiency is low. In order to improve productivity, multiple stamping processes, such as blanking, drawing, punching and trimming, can be arranged on one die, so that the blank can complete multiple stamping processes on one station. This die is called compound die. In addition, blanking, bending, drawing, punching and trimming are arranged at different stations of a die. In the stamping process, the blank is continuously stamped and formed through multiple stations in turn, and finally becomes a part at the last station. This die is called progressive die, also known as continuous die. The characteristics of stamping die are: high precision, accurate size, and the gap between punch and die of some stamping dies is close to zero; The stamping speed is fast, and it can be punched dozens to thousands times per minute; The die life is long, and the life of some silicon steel sheet blanking dies is more than several million times. Forging die is a die used for forging hot metal. In die forging, the blank is often deformed many times before it can be made into forgings, which requires carving several cavities on a module. Metal is sent to each cavity in turn, and flows plastically in the cavity, and finally fills the cavity to make forgings. In die forging, it is difficult for the blank to be equal to the cavity volume during final forging. In order to avoid waste, a slightly larger blank is often selected. Therefore, a flash groove is set around the cavity of the interface between the upper and lower dies of the final forging die to store excess metal, and the flash is cut off after forming. The technical characteristics of forging die are: there are many complicated cavities; The working conditions are bad, and the red-hot steel above 1℃ deforms and flows in the mold cavity; The die should bear the high-speed impact of the forging hammer or the reduction of heavy load; In the process of use, it is often in a state of rapid cooling, rapid heating and alternating cold and hot. Therefore, the mold material should have high strength, toughness and wear resistance. Hot forging must also have high temperature strength and hardness, and undergo toughening heat treatment. Extrusion die is a die used to extrude metal. The positive extrusion die has a static female die, an extrusion cylinder for placing the blank, and a punch for applying pressure to the blank. The extrusion barrel of the reverse extrusion die is a female die and the punch is a male die. Because the metal needs to be extruded from the female die under great pressure, the extrusion cylinder and the female die for reverse extrusion need high strength, so the multi-layer prestressed composite structure is often adopted. The working length of punch and punch should be short to avoid instability and bending under high compressive stress. Die casting die is installed on the die casting machine, which can inject liquid metal into the cavity under high pressure and keep the pressure until the metal solidifies and forms. It is mainly used for aluminum, zinc and copper parts, and can also be used for steel parts. The structure of the die casting mold is similar to that of the plastic injection mold. It consists of a moving mold and a fixed mold, and the core is used as the cavity of the casting. After the metal is cooled and solidified in the cavity, the core is drawn out and the mold is separated. Die-casting parts are generally thin and hollow, with many platforms and ribs, complex shape and structure, accurate size requirements and smooth surface. Because the metal is formed at high temperature, the die casting die needs to be made of high temperature resistant materials. Plastic mold is a mold used for plastic forming. With the development of plastic industry, the demand for plastic molds is increasing day by day, and its output has occupied the first place in all kinds of molds. Commonly used plastic molds include injection mold, compression mold and extrusion mold. When the plastic mold works, the pressure and temperature it bears are not high, but the number of parts is large, and the surface requirements are particularly smooth. Therefore, the die material can be pre-hardened steel, that is, the die is heat-treated first, and then cut to prevent deformation after heat treatment, and finally polished to improve surface quality. Rubber mold is mainly used for forming rubber products such as tires, automobile battery cases and soles. Generally, rubber material is sandwiched into a mold and shaped by steam heating. There are also rubber injection molds similar to plastic injection molds. Powder metallurgy die is a die for powder pressing of solid metal. When working, metal powder is quantitatively poured into the lower die, then the upper die is pressed down, closed and shaped, and then the preform is ejected by the ejector and sent to the sintering furnace for sintering, thus making powder metallurgy parts. Generally speaking, powder metallurgy parts have a large gap, accounting for about 15% of the total volume, low forming pressure, simple die structure and general requirements for precision and surface roughness, so there is no special requirement for the die. In order to reduce the gap and improve the density and strength, the sintered blank is hot forged again, which is called powder forging. The die used is similar to the die forging die. Because the mold is a tool for molding, it requires accurate size, smooth surface, reasonable structure, high production efficiency and easy automation. But also has the advantages of easy manufacture, long service life and low cost; In addition, it is necessary to consider that the design meets the needs of the process and is economical and reasonable. Factors such as rigidity, guidance, unloading mechanism, positioning method and gap size must be considered in the structural design and parameter selection of the die, and the wearing parts on the die should be easy to replace. For plastic mold and die casting mold, we should also consider the reasonable gating system, the flow state of molten plastic or metal, and the position and direction of entering the cavity. In order to improve the productivity and reduce the pouring loss of runner, multi-cavity mold can be used, that is, multiple identical or different products can be completed in one mold at the same time. Mold production is generally single piece and small batch production, which requires strict and accurate manufacturing. Therefore, precision processing equipment and measuring devices are often used. According to the structural characteristics, dies are generally divided into flat blanking dies and cavity dies with space. Plane blanking die can be initially formed by EDM, and then the accuracy can be further improved by means of form grinding and coordinate grinding. Coordinate grinding machines are generally used for precise positioning of molds to ensure precise aperture and hole spacing. You can also use the computer numerical control continuous trajectory coordinate grinder to grind any curved punch and die. Cavity die is mainly used for forming three-dimensional workpieces, so it has size requirements in three directions: length, width and height, and its shape is complex and it is difficult to manufacture. Such as cold extrusion die, die casting die, powder metallurgy die, plastic die, rubber die, etc. all belong to cavity die, and the cavity die is mostly machined by copying milling machine, EDM and electrolytic machining. Combining copying milling with numerical control and adding three-way translation head device in EDM can improve the machining quality of cavity. Computer numerical control multi-axis milling machine, coordinate grinding and machining center machine tool are important equipment for cavity die machining. Generally, electric or pneumatic tools are used to grind and polish the surface of cavity, with various grinding, polishing wheels and grinding paste powder, or ultrasonic grinding, extrusion honing, chemical polishing and other methods are used. Coordinate measuring machine and optical projection comparator are commonly used precision measuring equipment in mold manufacturing. Mould is a precision tool, which is expensive, and its service life must be improved as much as possible. The normal failure forms of molds are mainly wear, collapse and fracture, adhesion, etc. The failure forms of molds for different purposes are also different. The ways to improve the service life of dies are mainly to reasonably select die steel and determine the heat treatment specification according to the application conditions. Selecting materials with high strength at service temperature can prevent collapse; Increasing die hardness can reduce wear rate; High toughness and fatigue resistance, as well as the elimination of hardened layer and machining residual stress, can hinder the generation and development of cracks and prevent cracking. Surface treatment, lubrication and selection of mold materials with good adhesion resistance are important measures to prolong the life of mold. The requirements of the working surface and the matrix of the die are quite different, so it is difficult to meet them completely and reasonably with one material. However, the comprehensive performance of the die can be improved by inserting, surfacing, spraying and local strengthening. In addition, reasonable operation and use is another way to eliminate abnormal failure and slow down normal failure.