Thu Apr 27 14:58:21 CST 2023
The requirements for the design and production of moulds are: precise dimensions, clean surfaces; reasonable structure, high production efficiency, easy automation; easy manufacture, high life expectancy, low cost; design to meet the needs of the process, economic and reasonable.
The design of the mould structure and the selection of parameters must take into account factors such as rigidity, guiding, unloading mechanism, positioning method and clearance size. The wearing parts on the mould should be easy to replace. For plastic moulds and die-casting moulds, reasonable pouring systems, the flow of molten plastic or metal, the position and direction of entry into the cavity should also be considered. In order to increase productivity and reduce pouring losses in the runners, multi-cavity moulds can be used, where several identical or different products can be completed simultaneously in one mould. In mass production high efficiency, high precision and high life moulds should be used.
Stamping moulds should use multi-station progressive moulds, which can use carbide inserted block progressive moulds to improve the life. In small batch production and new product trial production, simple moulds with simple structure, fast manufacturing and low cost should be used, such as combination punching die, thin plate punching die, polyurethane rubber die, low melting point alloy die, zinc alloy die, super plasticity alloy die, etc. Moulds have begun to use computer-aided design (CAD), that is, through the computer as the centre of a set of systems to optimize the design of the mould. This is the development direction of mould design.
According to the structural characteristics, mould manufacturing is divided into flat punching and cutting moulds and cavity moulds with space. Punching and cutting dies make use of the precise size fit of the convex and concave dies, some even have a gapless fit. Other forging dies such as cold extrusion dies, die casting dies, powder metallurgy dies, plastic dies, rubber dies, etc. are all cavity dies and are used to form three-dimensional shaped workpieces. Cavity moulds have dimensional requirements in 3 directions: length, width and height, and are complex in shape and difficult to manufacture. The moulds are generally produced in small batches and in single pieces. The manufacturing requirements are strict and precise, and precision machining equipment and measuring devices are used.
Flat punching dies can be initially shaped by EDM, and then further improved in terms of accuracy by means of profile grinding and co-ordinate grinding. Form grinding can be carried out using optical projection curve grinders, or surface grinders with reduction and repair grinding wheel mechanisms, or on precision surface grinders using special form grinding tools. Coordinate grinding machines can be used for precision positioning of moulds to ensure precise apertures and hole distances. Computer numerically controlled (CNC) continuous trajectory coordinate grinding machines can also be used to grind convex and concave moulds of any curved shape. Cavity moulds are mostly machined using profiling mills, EDM and electrolytic machining. The combined application of profiling and CNC and the addition of a three-way flat head in EDM can improve the quality of the cavity. The addition of inflatable electrolysis to electrolytic machining can improve production efficiency.