The service life of the mold restricts the application and development bottleneck of the precision punching technology. Therefore, we must pay attention to the service life of the mold. The following Xiaobian provides us with the factors that affect the service life of the mold, and tells everyone to improve the service life of the mold. What are the ways.
Factors affecting the service life of the mold:
1. The structure and craftsmanship of precision punching parts (sharp angle, thin wall, hanging wall, dimensional tolerance, etc.).
2. Fine blanking material (material, material thickness, hardness, plasticity, surface quality).
3, the structure of fine punching die (strength, stiffness, mold guide, small punch guide, exhaust and lubrication).
4, mold material (material, carbide size and uniformity, hardness, toughness).
5, mold manufacturing (die billet forging, processing technology, heat treatment, wire cutting, grinding, assembly).
6, production operations (modulation height, pressure, speed, feeding accuracy, billet cleaning, lubrication).
7, mold maintenance (reasonable storage, reasonable sharpening, cleaning, stress tempering, rust).
Improve the service life of the mold:
1. Review the craftsmanship of fine blankings. The craftsmanship (especially the fillet radius) of the fine-punched parts has a certain influence on the life of the fine die. For the poor craftsmanship (especially the sharp corners), suggestions for improvement should be made to the design department. Figure 1 shows the relationship between the corner radius of the part and the die life. Generally, R/t≥0.8 is better. If less than 0.25, it will lead to a lower die life.
2, fine blunt mold material selection and heat treatment. The material of the main working parts of the fine punching die is generally Cr12MoV. When the thickness of the workpiece is more than 4mm, the convex and concave die can be high-speed steel W6Mo5Cr4V2. For punches and dies with high working strength and severe stress, powder metallurgy steel (V4, ASP23, ASP30) or hard alloy GT30 is used. The heat treatment hardness of convex and concave molds is generally 58~62HRC. For molds with simple shape with wear as the main failure mode, 60~64HRC is desirable. For molds with complex shapes and with chipping as the main failure mode, it is desirable to use 56~ 60HRC, even 54~58HRC.
For the heat treatment of Cr12MoV mold, when the shape of the cutting edge is relatively simple and the thickness of blanking material is thin (t≤3mm), higher strength and resistance can be obtained by using a hardening process (1020°C quenching and 220°C tempering). Grinding. When the edge shape is more complex and the blank material is thicker (t>3mm), the use of two hardening processes (1080°C quenching, 520°C tempering) can obtain higher impact toughness and stability. For the heat treatment of W6Mo5Cr4V2 molds, a low temperature quenching process must be used to obtain high strength and good toughness.
3, attention should be paid to the structural design of fine die. The force state of the mold should be good to prevent partial load, cantilever, one-way force, etc.; the guide can be used to reduce the wear of the working parts, ensure the uniformity of the clearance, avoid the bruising of the mold and avoid the wrong center of the pressure center. effective. For example, when designing fine punching punches, punching jacket structure should be used reasonably. When designing some large molds, small guide posts should be considered in the internal structure to increase guide precision. The pressure plate and punch guide are also better. When the material thickness t≥4mm, the concave mold is better to add prestressed sleeve. Due to the relatively precise fit between the components of the fine blanking die, the lubricating oil used is very thick, and a sealed space is easily formed between the bottom surface of the die and the punch punch, and between the accurately fitting punch base and the base. During the movement of the mold, the air in the closed area is not easily drained away, so that the heat caused by the friction between the mold components is not easily carried away with the air, which will affect the movement of the ejector plate and the ejector rod, reduce the production speed, and may even cause artifacts. The phenomenon of unevenness will affect the normal life of the fine die. Therefore, the exhaust groove should be opened on the bottom of the convex and concave die, the punch fixing plate, and the base.
4, the fine die assembly. Apart from paying attention to the uniform gap between the upper and lower die edges, the coaxiality and the matching relationship between the parts, the assembly of the fine blanking die must pay special attention to the phase height of each working part to ensure the correct position of the die in the closed state and open state. To ensure the workability of its work.
5, production operation and maintenance. When installing the mold to adjust the pressure, under the premise of guaranteeing the quality of the fine stamping, the pressing force and back pressure should be as small as possible. When using the fine punching continuous mold, the first and last parts of the strip should pay special attention to the force of the mold. Balance, otherwise the punch is easily broken due to lateral forces. When feeding, care should be taken to set devices such as strip height restrictions to prevent waste weight. It is found that when the workpiece burr exceeds the standard, it should be sharpened in time. The amount of sharpening is generally 0.1~0.2mm, and attention is paid to eliminating internal stress.
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