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Die life of cold stamping die and improvement - Part Three

Die life and Countermeasures

Die with the life of the workpiece by punching out the number of terns. Many factors affect the die life. There are stamping die structure design, manufacture molds used in the punch and stamping die materials, die quality and surface hardening heat treatment, precision die manufacturing parts and cold stamping materials selection. In addition, there are die installation, adjustment, use and maintenance.

1. Die Design on Life

a. Layout design of layout methods and take the boundary value a great impact on the die life, too small to take the boundary value, often causing rapid wear and convex mold, die bite wounds on the. Starting from material savings, take the boundary value smaller the better, but take the edge is less than some value, the cut surface of the mold and the quality of life adversely. There will be left behind in the blanking die Q-gap were to produce spare parts glitch, or even damage the die edge, reduce die life. Therefore, consider increasing the material utilization of the same time, parts must yield, quality and life expectancy to determine the layout methods and take the boundary.

b. Die structure prone to stress concentration on the cracking of the stamping die structure, composite structure can be used or mosaic structure, and prestressed structure to enhance the mold life.

c. The impact of clearance when the gap is too small, compressed extrusion of interest, increased friction, increased wear, the wear side of aggravated discharge and push pieces after blanking time, materials and convex, the friction between die will cause wear and tear than the end edge on the side of the grinding much, but also easily lead to convex, concave mold temperature is high, the adsorption of metal debris in the side edge to form a metal tumor, so that male and female die chipping or expansion occurs crack phenomenon. Therefore, the gap is too small to Die Life very bad. Gap is too large will increase the punch and the die face the edge of the concentration of stress, resulting in a sharp increase in stress, so blade edge quickly lose angular yield deformation. Therefore, addition of blanking force, thereby enabling faster edge edge wear, reduce die life. But in order to reduce the male and female die wear, extending mold life, while ensuring quality of stamping pieces under the premise that larger space designed properly it is necessary.

d. Die-oriented structure of the life of a reliable guide for the working parts reduce wear, prevent male and female die bite wound is very effective. In particular, non-small-Q gap Q gap or Die, compound die and multi-position progressive die even more important. To improve the stamping die life, must be based on processes and the demand of precision, the correct choice-oriented form and orientation accuracy, the choice should be higher than the accuracy-oriented convex, concave mold with precision.

e. The impact of cold stamping materials, cold stamping materials selected should meet the design requirements of workpieces and stamping process requirements, or easy to mold damage and reduce mold life. Poor surface quality of cold stamping, punching, cracking when the workpiece is also easy to scratch mold. Bad cold stamping plastic materials, deformation is small, easy to press when the workpiece rupture, but also easy to scratch mold. In addition, the material thickness tolerances shall comply with national standards. Die because of a certain thickness of material suitable for forming, bending, flanging, drawing die of the male and female die structure gap is directly determined by the thickness of the material. Therefore, uneven thickness, will result in waste generation and mold damage.

2. Die life

Die life of a mold material properties, chemical composition, structure, hardness and comprehensive reflection of metal lurgical quality. Among them, the material properties and heat treatment affect the quality of the most obvious. Mold material properties on the impact of stamping die life is great. If the same workpiece, using a different mold material of the bending test, the test results: The 9Mn2V material, the life of 5 million; with Cr I2Mov nitriding, the life of up to 40 million. Therefore, the choice of materials, the batch size should be based on workpiece, rational use of mold materials. The hardness of the die parts to Die Life a great impact. But not the higher hardness, longer die life. This is because the hardness and strength, toughness and abrasion resistance are closely related. Some die demands of high hardness, long life. Such as the use of T10 steel dies, hardness 54~58HRC, only washed thousands of times a burr on the workpiece great. If the hardness to 60~64 HRC, the grinding life of up to 2 to 3 million. However, if continue to improve hardness, fracture occurs earlier. Some die hardness should not be too high, as the die manufacturing using CrI2MoV 58~62HRC hardness, the general life of 2-3 million, invalid form of chipping and cracking, and if the hardness down to 54~58HRC, life expectancy increased to 5~60000, but decreased to 50~53HRC hardness appears easy to blunt the die edge phenomenon. Thus, mold hardness must be based on material properties and failure modes may be. Should enable the hardness, strength, toughness, and wear resistance, resistance to fatigue strength needed to achieve a particular stamping process the best match.

3. The surface of the mold heat treatment to strengthen the quality and impact on life.

Mold heat treatment the nature and quality of life of the mold a great impact. Practice shows that the die parts of the quenching distortion and cracking, early fracture during use, while the metallurgical and material quality, forging quality, mold structure and process related, but related more to stamping die of heat treatment. According to statistical analysis of failure causes of mold, heat treatment failure due to improper accounting for more than 50%. Practice shows that the mold material must be accompanied by high heat treatment process properly, can really play a materials potential. Parts surface hardening mold work purpose is to obtain the effect of external hard tough inside, so be hardness, wear resistance, toughness, good resistance to fatigue with. Many ways to die surface hardening, surface treatment technology of new technologies developed rapidly. In addition to Nitrocarburizing and ion nitride, boride, seepage niobium, vanadium permeability, hard chrome plated and spark strengthening, the chemical vapor deposition (CVD) and physical vapor deposition (PVD) has been gradually adopted. By CVD and PVD treatment, the mold surface covered with super-hard material, such as TiC, TiN, etc. High hardness, wear resistance, corrosion resistance, adhesion is very good, can improve the die life several times to several times.

4. Manufacturing precision of the die parts of die life

Precision die manufacturing and life in it in particular, mold surface roughness on the mold a great impact. If using CrI2MoV steel blanking die, if the surface roughness value R=1.6m, its life span is about 30,000. Such as polished by the precision, surface roughness value R=0.4m, life can be increased to 4-5million. Therefore, the working parts of the mold surface, the general must go through grinding, grinding, polishing and other finishing and fine processing.

5. Other aspects of the impact of die life

a. Press the accuracy is not high, but also easy to make die damage.

b. Die in the press or not installed properly and the operators technical level, on the tool life is also greatly affected.

c. Die in the custody and maintenance of good and bad, and the use of lubricant condition also affects mold life.

6. Conclusion

In actual production, sheet metal dies for use, rare case of non-normal wear and tear. But when the die plate was found prone to irregular wear, we always study for the problems summarized. Because of a cold die, from the design, manufacture, assembly, commissioning and installation and use, all spent many hours, while the convex die, stamping die material used, mostly high-quality alloy steel. Therefore, the die cost is relatively high. Therefore, in the production of understanding the factors that affect the die life and take the appropriate measures to guide the production of great practical significance.



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