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Knowledge of Dies and Moulds

update:06-09-2019
abstract:

The requirements of die design and manufacture are: pre […]

The requirements of die design and manufacture are: precise size, smooth surface; reasonable structure, high production efficiency, easy automation; easy manufacturing, high life, low cost; design meets the needs of technology, economic and reasonable.

The factors such as rigidity, directivity, unloading mechanism, positioning method and clearance size should be taken into account in die structure design and parameter selection. The vulnerable parts on the die should be easily replaced. For plastic and die casting moulds, reasonable pouring system, flow state of molten plastics or metals, and the position and direction of entering the cavity should also be considered. In order to improve productivity and reduce runner pouring loss, a multi-cavity die can be used to complete multiple identical or different products simultaneously in one die. In mass production, high efficiency, high precision and long life die should be adopted.

Stamping die should adopt multi-position progressive die and carbide insert progressive die to improve service life. In small batch production and trial production of new products, simple dies with simple structure, fast manufacturing and low cost should be adopted, such as combined die, sheet die, polyurethane rubber die, low melting point alloy die, zinc alloy die, superplastic alloy die, etc. Computer aided design (CAD) has been used in die design, that is, the optimal design of die has been carried out through a computer-centered system. This is the development direction of die design.

According to the structure characteristics, die manufacturing can be divided into planar blanking die and cavity die with space. Punching dies are precisely matched with the dimensions of punches and dies, and some even have no clearance matching. Other forging dies, such as cold extrusion dies, die casting dies, powder metallurgy dies, plastic dies, rubber dies and so on, belong to cavity dies and are used to form workpieces with three-dimensional shapes. Cavity die has dimension requirements in three directions of length, width and height, and its shape is complex and difficult to manufacture. Mould production is generally single-unit and small-batch production, which requires strict and accurate manufacturing. Precision processing equipment and measuring devices are mostly used.

Planar blanking dies can be formed by EDM, then formed grinding, coordinate grinding and other methods to further improve the accuracy. Forming grinding can be carried out by optical projection curve grinder, surface grinder with abnormal and polishing wheel mechanism, or by special forming grinding tool on precision surface grinder. The coordinate grinder can be used for precise positioning of the die to ensure precise aperture and spacing. The convex and concave dies of any curve shape can also be grinded by CNC continuous trajectory coordinate grinder. Profile milling machine, EDM and electrochemical machining are widely used for cavity die. Combining profiling milling with numerical control and adding three-way translational head device in EDM can improve the processing quality of the cavity. Increasing aerated electrolysis in ECM can improve production efficiency.

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