Mold is a very important process equipment in manufacturing industry. It is widely used in casting, forging, stamping, plastic, rubber, glass, powder metallurgy, ceramic products and other production industries. The mold can not only realize mass production, but also effectively avoid waste of redundant materials and produce in less time. Therefore, the mold can improve production efficiency, save raw materials, reduce costs, and ensure certain processing quality requirements, The "four high and two low" (high precision, high complexity, high consistency, high productivity, low energy consumption and low material consumption) achieved by using molds to produce parts makes the mold industry occupy an increasingly important position in the manufacturing industry. Therefore, many parts and components used in automobiles, aircraft, tractors, electrical appliances, instruments, toys and daily products are processed and manufactured with molds.

The main parts of the mold are:; Female mold, mandrel, die punch. First, the process analysis before pressing shall be carried out for the compact. After the process analysis and comparison, the unidirectional pressing process is applied. Through the calculation of the density, quality, height and outer diameter of the compact, the types of mandrel, female die and die punch are preliminarily determined. Secondly, the type of press for blank processing is analyzed. The design process of each working part of the mold is expressed, and finally the part drawings and assembly drawings of the mold are drawn.

Powder forming is one of the main processes of powder metallurgy, in which the basis of powder forming is mold design, and powder metallurgy mold is an independent type composed of metallurgy and machinery. Powder metallurgy mold design is related to the quality, cost, safety, productivity and automation of product production, so the basic principles of mold design are proposed:

(1) Three basic requirements shall be guaranteed: geometric shape, precision and surface roughness of the blank, density and distribution of the blank, etc.

(2) The die structure is reasonably designed and the die materials are selected from the best.

(3) Pay attention to the cost and machinability of mold structure and parts manufacturing.

Basic methods of powder metallurgy mold design:

(1) Collect relevant design data as the basis for mold design. Including technical requirements and product drawings, product batch production and process flow, process parameters, press type and technical parameters; Mold processing capacity and equipment; Be aware of the problems that have occurred in the application of the mold.

(2) Carry out the blank design through the product drawing, select the press and pressing method, design the mold structure drawing, and analyze whether the powder metallurgy method is suitable for production.

The mold structure design mainly considers the following aspects:

(1) The connection method of main parts is the connection of mandrel, female die and upper and lower die punch, taking full account of the safety guarantee in use, convenient installation and disassembly, simple and reliable structure, material saving and beautiful overall appearance.

(2) The floating structure often requires the floating of mandrels, female dies and upper and lower dies according to the requirements of different compensation charging and pressing methods. Spring, friction, pneumatic and hydraulic, etc. provide floating force. The design of floating structure should be more in line with the requirements and conditions.

(3) Demoulding reset structure The action of the press and the design of reset and demoulding according to the shape of the compact are often specified in a unified structural design scheme to strictly ensure the excellence of the compact, a series of actions should be safe and correct, and the reset action in the operation of the mechanical press should be accurate.

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When designing the structure of the forming die, proceed in the following order:

(1) The selection of the upper pressing side of the blank during pressing needs to be determined by comparing various factors.

(2) In consideration of the change of the pressing direction of the compensated powder loading, for example, when the pressing direction of the compact becomes, in order to make the density of different parts of the compact uniform during pressing, which combination structure should be used (select a reasonable fractal surface) to achieve the purpose of compensating powder loading, so that the compression ratio is basically the same.

(3) For the blank without steps, whether the demoulding method should be the pull down type (the lower die should not move, the female die should be pulled down, and the blank should be detached) or the ejecting type (the lower die should push the blank out of the female die). From the angle of die structure, the problems of parts with steps, helicoids, spherical parts, and parts with multiple parallel holes are solved.

(4) The structure scheme is determined according to the blank style, demoulding line, pressing mode, demand for compensating powder loading and specific action of the rolling mill.

(5) Calculate the powder loading height and the wall thickness of the female mold. Calculate the powder loading height and the wall thickness of the female mold according to the selected blank height and compression ratio. The calculation of the center is based on the structure or usage habits. Generally, the ratio of the outer diameter of the female mold to the inner diameter is 2-4; For larger female mold, it shall be calculated according to strength and stiffness conditions.

(6) To draw the general assembly drawing of the structure, first draw the blank drawing, and then take it as the center. First draw it vertically, then draw it horizontally, and gradually expand outward. First, draw the mandrel, female die, upper and lower die stamping and other parts, and then gradually draw other parts according to the established structural scheme and the needs of the overall structure.