Four key factors affect the failure of stamping dies

Stamping mold is the main process equipment for stamping processing, and it is a relatively critical mold in industrial production. There are many factors that affect the service life of stamping dies. Stamping die failure is one of them. The main forms include wear failure, deformation failure, fracture failure and gnawing failure. Below we will give a detailed introduction to these. I hope everyone can understand this and make corresponding improvement measures.

1 Stamping equipment

The accuracy and rigidity of stamping equipment (such as presses) have an extremely important impact on the life of the die. The stamping equipment has high precision and good rigidity, and the die life is greatly improved. For example: the die material of complex silicon steel sheets is Cr12MoV. When used on ordinary open presses, the average regrinding life is 10,000 to 30,000 times. However, when used on new precision presses, the regrinding life of the die can reach 60,000 to 120,000 times. Especially for dies with small or no gaps, carbide dies and precision dies, presses with high precision and good rigidity must be selected. Otherwise, the life of the mold will be reduced, and in severe cases, the chess set will be damaged.

2 Stamping mold design

(1) The accuracy of the mold guide mechanism. Accurate and reliable guidance has a great impact on reducing the wear of the working parts of the mold and avoiding the gnawing of the convex and concave dies. It is especially effective for blanking dies with no gaps and small gaps, composite dies and multi-station progressive dies. In order to improve the life of the mold, it is necessary to correctly select the guide form and determine the accuracy of the guide mechanism based on the nature of the process and the accuracy of the parts. Generally speaking, the accuracy of the guide mechanism should be higher than the matching accuracy of the convex and concave molds.

(2) Mold (convex and concave mold) cutting edge geometric parameters. The shape, fitting clearance and fillet radius of the convex and concave molds not only have a great impact on the forming of stamping parts, but also have a great impact on the wear and life of the molds. For example, the matching gap of the mold directly affects the quality of the blanking parts and the life of the mold. If the accuracy requirements are high, a smaller gap value should be selected; otherwise, the gap can be appropriately increased to increase the life of the mold.

3 stamping process

(1) Raw materials for stamping parts.

In actual production, due to the excessive thickness tolerance of raw materials for external pressure parts, fluctuations in material properties, poor surface quality (such as rust) or uncleanness (such as oil stains), etc., it will cause the mold working parts to wear more and become prone to chipping and other defects. as a result of.

For this reason, attention should be paid to:

① Use raw materials with good stamping processability as much as possible to reduce stamping deformation force;

② Before stamping, the grade, thickness and surface quality of the raw materials should be strictly checked, and the raw materials should be wiped clean. If necessary, surface oxides and rust should be removed;

③According to the stamping process and the type of raw materials, softening treatment and surface treatment can be arranged if necessary, as well as selecting appropriate lubricants and lubrication processes.

(2) Layout and edging.

Unreasonable reciprocating feeding and layout methods and too small edge values will often cause rapid wear of the mold or damage to the convex and concave molds. Therefore, while considering improving material utilization, the layout method and edge value must be reasonably selected according to the processing batch size, quality requirements and mold fit clearance of the parts to increase the life of the mold.

4 stamping die materials

The impact of mold materials on mold life is a comprehensive reflection of material type, chemical composition, organizational structure, hardness and metallurgical quality. Molds made of different materials often have different lifespans.

To this end, two basic requirements are put forward for the materials of die working parts:

① The material’s performance should have high hardness (58~64HRC) and high strength, high wear resistance and sufficient toughness, small heat treatment deformation, and certain thermal hardness;

②The process performance is good. The processing and manufacturing process of die working parts is generally complex. Therefore, it must be adaptable to various processing techniques, such as forgeability, machinability, hardenability, hardenability, quenching crack sensitivity and grinding processability, etc. Usually, mold materials with excellent performance are selected based on the material characteristics, production batch size, accuracy requirements, etc. of the stamping parts, while taking into account its craftsmanship and economy.

Toolox series materials are a new type of pre-hardened tool steel with high toughness, high wear resistance and basically no internal stress. The processing stability is particularly good. Compared with the corresponding materials under the same conditions, the processing efficiency is increased by about 20%. It also has very high purity, very fine grain size, very low S and P content, low precipitated carbide content, and is very uniform. Due to the special composition design, Toolox series materials have very excellent surface treatment properties, among which After nitriding, the surface hardness of Toolox44 can reach above HRC65, the surface hardness of Toolox40 can reach above HRC62, and the surface hardness of Toolox33 can reach above HRC58. The maximum depth is 1.8mm. Therefore, TOOLOX series materials have special advantages in stamping molds.

6 ways to improve the service life of stamping dies

Stamping molds are necessary process equipment in the stamping production process and play a decisive role in improving product quality, extending product life, and improving production efficiency. However, since stamping dies lose working dimensions due to frequent wear during the production process, it is difficult to meet production needs. Therefore, it is critical to improve the durability (service life) of stamping dies.

Methods to improve the durability of stamping molds generally include the following:

1. Improve the design of stamping molds

Whether the stamping die design is reasonable is the basis for improving the durability of the stamping die. Therefore, when designing stamping dies, effective measures should be taken against adverse conditions in product forming to improve the durability of the stamping dies. For example, the life of a small-hole stamping die is often reflected in the punch that punches small holes. For this type of stamping mold, the length of the small punch should be shortened as much as possible during design to increase the strength. At the same time, guide sleeves should be used to strengthen the small punch for protection. In addition, in the design of stamping molds, factors such as the form of the mold base, the fixing method and guide form of the convex and concave molds, the determination of the pressure center, and the rigidity of the upper and lower templates should be fully considered. Especially for punching dies, the selected gap value has a great impact on durability. During design, the gap of the stamping die must be selected reasonably, and the gap value cannot be too small, otherwise it will affect the service life and durability of the stamping die. Practice has proven that without affecting the quality of stamped parts, appropriately enlarging the gap can greatly improve the durability of the stamping die, sometimes even several times or dozens of times.

2. Correctly choose stamping die materials

Different stamping die materials have different strengths, toughness and wear resistance. The use of advanced materials under certain conditions can increase durability several times. Therefore, in order to improve the durability of the stamping die, good materials must be selected.

The Toolox series of materials is a new type of pre-hardened tool steel with high toughness, high wear resistance and basically no internal stress. It also has very high purity, very fine grain size, and very high S and P content. Less, the precipitated carbide content is less and very uniform. Due to the special composition design, Toolox series materials have very excellent surface treatment properties. Among them, the surface hardness of Toolox44 after nitriding can reach above HRC65, and the surface hardness of Toolox40 can reach above HRC62. The surface hardness of Toolox33 can reach above HRC58, and the depth can reach up to 1.8mm.

The above characteristics of Toolox series materials make Toolox series materials have special advantages in some stamping dies.

1) Stamping molds for thicker steel plates (the punching thickness of typical cases is 35mm steel plates), stainless steel plates, and non-ferrous metal plates, typically air-conditioning fin molds, etc.

2) Stretching mold, stainless steel drawing mold.

3) Cold extrusion mold. Cold extrusion 304 stainless steel, thickness above 0.5mm, replaces DC53 and other materials, and the effect is very good.

4) Large stamping templates with high dimensional stability requirements.

3. Properly carry out forging and heat treatment of stamping die parts

While selecting high-quality stamping die materials, reasonable forging and heat treatment are required for materials of the same material and different properties, which is one of the main ways to improve the durability of the stamping die. For example, during quenching, if the workpiece is overheated during heating, it will not only make the workpiece too brittle, but also easily cause deformation and cracking during cooling, reducing the durability. Therefore, when manufacturing stamping dies, the heat treatment process must be properly mastered. Toolox material is quenched and tempered steel that is directly pre-hardened by steel mills. It no longer requires heat treatment. With appropriate surface treatment (such as nitriding), the high toughness of Toolox base material and the high hardness of the upper surface layer can achieve excellent results. effect.

4. Reasonably arrange the stamping mold manufacturing process and ensure processing accuracy

The processing accuracy of stamping molds has a great influence on the durability of stamping molds. For example, due to uneven assembly gaps in the punching die, the die is often chewed up under the action of shearing force and affects the life of the stamping die. At the same time, if the surface finish of the stamping mold is too low, the durability of the stamping mold will also be reduced. Therefore, during processing, sufficient attention must be paid to the size of the hole spacing, the verticality of the punch to the fixed plate support surface during assembly, the uniformity of the spacing between the stamping dies, and the guidance accuracy level of the guide bushes and guide posts. The higher the manufacturing and assembly precision and the higher the surface roughness level of the working part, the higher the durability of the stamping die.

5. Choose the press correctly

In order to improve the durability of the stamping die, a press with higher precision and higher rigidity should be selected, and its stamping tonnage should be at least 30% greater than the stamping force. Normally, using a servo punch press can increase the mold life by more than dozens of times.

6. Proper use and maintenance of stamping dies

In order to improve the durability of the stamping mold, the operator must use and maintain the stamping mold reasonably, and the stamping mold should be repaired frequently to prevent the stamping mold from working with diseases.

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