Use and maintenance of CNC punching die (5)

(5) mold Spring fatigue damage

One problem that is easy to be neglected in the use of punching molds is the service life of the mold springs. The mold springs also need to be regularly maintained or replaced. However, many domestic users can maintain the equipment and molds, but often ignore the maintenance of the mold springs, and even The user's spring has not been replaced for many years. The same station or mold often has damage or stamping, but it is impossible to find the cause. After replacing the mold spring, the problem is completely solved. The type of mold spring is also different for different punching equipment and molds. If improperly maintained, it is easy to produce mold strips and may damage the mold or guide sleeve, causing unnecessary losses.

4. Measures to improve the life of the mold

(1) Adopt new materials

With the continuous development of metallurgical technology, new materials for manufacturing molds have emerged. The rapid promotion and adoption of these new materials has achieved remarkable results in improving mold life. Several new materials that can improve the life of molds are as follows:

Compared with Cr12 steel, 1Cr4W2MoV Cr4W2MoV is characterized by fine eutectic carbides, uniform distribution, high hardenability and hardenability, higher mechanical properties and wear resistance, and increased steel due to the addition of alloying elements. Stability.

2Cr2Mn2SiWMoV is an air-cooled micro-deformed steel with high hardenability, low quenching temperature, low deformation and low Cr content, good carbide uniformity, high mechanical properties and wear resistance, and is suitable for high precision and long life. A mold with a complex shape.

36W6Mo5Cr4V is an alloy steel for cold extrusion. It has high strength, hardness, toughness, wear resistance and tempering resistance. It is suitable for cold extrusion process and has fewer applications for CNC molds.

46W6Mo5Cr4V2 is mainly used for cold extrusion die. It has low carbon content and easy spheroidizing annealing. It has good machinability and excellent comprehensive performance. Compared with Cr12 and high speed steel, the die life can be increased several times.

5W6Mo5Cr4V2Al has high hardness and can be hardened to 66-67HRC. It has good wear resistance and is suitable for punching materials with special wear on the mold, such as stainless steel and laminated fiberglass board. The life of the mold is 4 times higher than that of ordinary alloy steel.

(2) using steel bonded gold and cemented carbide

1 steel combined gold

It has good wear resistance. After annealing, the hardness is 32~43HRC. It can be machined by milling, milling, planing and grinding. The hardness after quenching can reach 68~72HRC. The heat treatment is basically not deformed and the impact resistance is good. It is widely used in production, and its life can be increased by more than 10 times compared with alloy steel molds, which is suitable for mass production.

2 hard alloy

With the continuous improvement of the processing technology, the application of cemented carbide molds is more and more extensive, its hardness is very high, up to 86HRC, the wear resistance is excellent, the die life is 30~50 times higher than the general tool steel, but it is impacted. The ability is poor. If the mold structure can be reasonably designed, the superiority of the cemented carbide can be better utilized and the service life of the mold can be improved.

(3) Reasonable design of mold structure

It is also an effective way to improve the service life of the mold by improving the structural form of the mold. E.g:

1 Prevent the anti-band die designed by the mold strip.

2 Improve the centering of the mold to design the full-guided mold, and improve the lead length to prevent the mold from being eccentric.

3 Improve the mold replacement efficiency, the United States MATE company designed the ULTRA super mold, the mold removal process can be completed without tools.

4 Reduce the cost of the mold, the large-station mold adopts the split structure, only need to replace the punch and the guide plate, saving the mold material.

5 Improve mold lubrication and prevent stripping. Japan AMADA Company specially designed air-blowing injection mold.

6 In order to improve production efficiency and machine tool processing range, special molds such as forming molds, combined molds and mother-child molds were designed.

(4) mold surface treatment

1 electric spark reinforcement

It is mainly used for surface treatment of cold die and super-hard tools. It can also be used for repairing the dimensions of molds or workpieces after wear. The working principle is to use conductive materials such as cemented carbide as electrodes to generate spark discharge between air and metal workpieces. The electric energy released by the spark discharge is used to infiltrate and transfer the electrode material to the surface of the workpiece, thereby forming a strengthening layer on the surface of the workpiece, improving the hardness and wear resistance of the surface of the mold, and prolonging the service life of the mold.

2 nitriding treatment

Nitriding methods include liquid nitriding, gas nitriding, and glow ion nitriding. The metal surface forms a hard nitride layer by nitriding, and the hardness can reach 65-69HRC. The surface of the mold after nitriding has higher hardness, wear resistance, heat resistance, fatigue strength and corrosion resistance, and the mold life can be Increase by 2 to 3 times.

3 surface coating treatment

The surface coating method improves the life of the mold by combining the high strength and toughness of the base material with the high hardness and wear resistance of the coating material. The coating types mainly include titanium carbide, titanium nitride, aluminum nitride titanium, etc., using advanced coating equipment, coating a special layer of 2~3μm on the surface of the mold under vacuum, thereby increasing the hardness of the mold to 60. ~90HRC, and the special coating can also play a heat insulation effect, which greatly increases the life and use times of the mold by 3 to 6 times and reduces the production cost. This surface treatment method is also often used on various cutting tools, which can greatly improve the wear resistance and service life of the tool.

4 special treatment methods

In order to improve the service life of the mold, AMADA Japan developed a powder material with a special coating of APH mold, and applied for a patent. By using this coating to improve the surface hardness of the mold and reduce the roughness value, it is an ideal mold. .

5 Conclusion

Punch molds encounter various problems in use, and it is impossible to give detailed explanation here. Only by correct use and maintenance, the operator's sense of responsibility can be improved, and the service life of the mold can be improved and the mold use cost can be reduced.

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