What are the factors that affect the life of stamping dies?
发布时间：2018-09-05 浏览次数：1099次
Cause of mold burst
1. The mold material is not good and is easy to crack in subsequent processing
2. heat treatment: deformation due to improper quenching and tempering process
3. The mold grinding flatness is not enough, resulting in deflection deformation
3. Design process: die strength is not enough, blade spacing is too close, die structure is not reasonable, number of template blocks is not enough without pad feet
4. Improper handling of wire cutting: wire cutting with incorrect clearance and no corner clearing
5. Selection of punch equipment: Punch tonnage, insufficient punching force and too deep adjustment of die
6. Material removal is not smooth: there is no demagnetization treatment and no material removal tip before production; In production, there are blocking materials such as broken needles and broken springs
7. Material falling is not smooth: there is no leakage of excrement when assembling the mold, or the excrement is rolled and blocked, and the excrement is blocked by padding feet.
8. Production consciousness: lamination stamping, positioning is not in place, blowing gun is not used, and the template is cracked and still continues to be produced
Die failure mode
Die failure forms mainly include wear failure, deformation failure, fracture failure and gnawing failure. However, due to different stamping processes and working conditions, there are many factors affecting the service life of the die. The following is a comprehensive analysis of the influencing factors of die life in terms of die design, manufacture and use, and the corresponding improvement measures are taken.
1. Stamping equipment
The accuracy and rigidity of stamping equipment ( such as press ) are very important to die life. The stamping equipment has high precision and rigidity, and the service life of the stamping die is greatly improved. For example, the die material of complex silicon steel sheet is CRL 2 MOV, which is used on ordinary open press with an average regrinding life of 10 - 30,000 times, while the new precision press can have a regrinding life of 60 - 120,000 times. In particular, press machines with high precision and good rigidity must be selected for small-gap or gapless dies, cemented carbide dies and precision dies, otherwise, die life will be reduced and chess tools will be damaged.
2. Die Design
( 1 ) Precision of guiding mechanism of die. Accurate and reliable guidance can greatly reduce the wear of the working parts of the die and avoid the gnawing of the male and female dies, especially the blanking die, the compound die and the multi-position progressive die without clearance and with small clearance are more effective. In order to improve the service life of the die, it is necessary to correctly select the guide form and determine the precision of the guide mechanism according to the requirements of process properties and part precision. In general, the precision of the guiding mechanism should be higher than that of the male and female dies.
( 2 ) geometric parameters of the cutting edge of the die ( male and female ). The shape, fit clearance and fillet radius of the male and female dies not only have a great influence on the forming of stamping parts, but also have a great influence on the wear and service life of the dies. For example, the fit clearance of the die directly affects the quality of the blanking part and the life of the die. If the precision requirement is higher, a smaller clearance value should be selected. On the other hand, the gap can be appropriately increased to improve the service life of the mold.
3. Stamping process
( 1 ) raw materials for stamping parts.
In the actual production, due to the excessive tolerance of the thickness of the raw materials of the externally pressed parts, fluctuation of the material properties, poor surface quality ( such as rust ) or unclean ( such as oil stain ), etc., the wear of the working parts of the mold will increase and the blade will easily collapse. For this reason, we should pay attention to: ① adopt raw materials with good stamping manufacturability as far as possible to reduce stamping deformation force; ( 2 ) before stamping, the brand, thickness and surface quality of raw materials shall be strictly checked, and the raw materials shall be wiped clean, and surface oxides and rust shall be removed if necessary; ( 3 ) according to the stamping process and raw material types, softening treatment and surface treatment can be arranged when necessary, and appropriate lubricant and lubrication process can be selected.
( 2 ) Layout and lapping.
Unreasonable reciprocating feeding and layout method and too small lapping value often result in sharp wear of the die or gnawing of the male and female dies. Therefore, while considering the improvement of material utilization, it is necessary to reasonably select the layout method and edge value according to the processing batch of parts, quality requirements and mold fit clearance to improve the mold life.
4. Mold materials
The influence of mold material on mold life is a comprehensive reflection of material type, chemical composition, microstructure, hardness and metallurgical quality. Die life is often different for different materials. For this reason, two basic requirements are put forward for the material of die working parts: ① the material should have high hardness ( 58 - 64 HRC ) and high strength, high wear resistance and enough toughness, small heat treatment deformation and certain thermal hardness; ( 2 ) the process performance is good. The processing and manufacturing process of die working parts is generally complicated. Therefore, it is necessary to have adaptability to various processing technologies, such as malleability, machinability, hardening capacity, hardenability, quenching crack sensitivity and grinding workability. Generally, according to the material characteristics, production batch and precision requirements of stamping parts, mold materials with excellent performance are selected, while their manufacturability and economy are taken into account.
5, hot processing technology
Practice has proved. The hot working quality of the die has a great influence on the performance and service life of the die. From the analysis and statistics of die failure causes, it can be seen that die failure " accidents" caused by improper heat treatment account for more than 40 %. The quenching deformation and cracking of the working parts of the mould, as well as the early fracture in the use process, are all related to the hot working process of the mould.
( 1 ) Forging process, which is an important link in the manufacturing process of die working parts. For the dies of high alloy tool steel, technical requirements are usually put forward for the metallographic structure such as carbide distribution of the material. In addition, the forging temperature range should be strictly controlled, the correct heating standard should be formulated, the correct forging force method should be adopted, and the forging should be slowly cooled or annealed in time.
( 2 ) Preparation of heat treatment. Depending on the materials and requirements of the working parts of the die, annealing, normalizing or quenching and tempering should be adopted to improve the structure, eliminate the structural defects of the forged blank and improve the workability. The high carbon alloy die steel can eliminate the network secondary cementite or chain carbide, spheroidize and refine the carbide, and promote the uniformity of carbide distribution after proper preliminary heat treatment. In this way, the quality of quenching and tempering can be guaranteed and the service life of the die can be prolonged.
( 3 ) quenching and tempering. This is the key link in die heat treatment. If overheating occurs during quenching and heating, not only will the workpiece cause greater brittleness, but also it will easily cause deformation and cracking during cooling, seriously affecting the life of the mold. During die quenching and heating, special attention should be paid to preventing oxidation and decarburization. Heat treatment process specifications should be strictly controlled, and vacuum heat treatment can be adopted if conditions permit. Tempering shall be carried out in time after quenching and different tempering processes shall be adopted according to the technical requirements.
( 4 ) stress relief annealing. After rough machining, die working parts should be annealed to eliminate the internal stress caused by rough machining, so as to avoid excessive deformation and cracks caused by quenching. For molds with high precision requirements, stress relief tempering treatment is required after grinding or electrical machining, which is conducive to stabilizing mold precision and improving service life.
6, processing surface quality
The advantages and disadvantages of the working parts and the surface quality of the mold have a very close relationship with the wear resistance, fracture resistance and adhesion resistance of the mold, which directly affects the service life of the mold. In particular, the surface roughness value has a great influence on the service life of the die. If the surface roughness value is too large, stress concentration will occur during work, and cracks will easily occur between its peaks and valleys, affecting the durability of the die, as well as the corrosion resistance of the workpiece surface and directly affecting the service life and precision of the die. Therefore, the following matters should be paid attention to:
( 1 ) in the process of machining die working parts, it is necessary to prevent the surface of the parts from being burnt by grinding, and the grinding process conditions and process methods ( such as grinding wheel hardness, grain size, coolant, feed rate, etc. ) should be strictly controlled;
( 2 ) in the process of processing should prevent the die working parts surface with knife marks. Macroscopic defects such as interlayers, cracks, impact scars, etc.
1. The mold material is not good and is easy to crack in subsequent processing
2. heat treatment: deformation due to improper quenching and tempering process
3. The mold grinding flatness is not enough, resulting in deflection deformation
3. Design process: die strength is not enough, blade spacing is too close, die structure is not reasonable, number of template blocks is not enough without pad feet
4. Improper handling of wire cutting: wire cutting with incorrect clearance and no corner clearing
5. Selection of punch equipment: Punch tonnage, insufficient punching force and too deep adjustment of die
6. Material removal is not smooth: there is no demagnetization treatment and no material removal tip before production; In production, there are blocking materials such as broken needles and broken springs
7. Material falling is not smooth: there is no leakage of excrement when assembling the mold, or the excrement is rolled and blocked, and the excrement is blocked by padding feet.
8. Production consciousness: lamination stamping, positioning is not in place, blowing gun is not used, and the template is cracked and still continues to be produced
Die failure mode
Die failure forms mainly include wear failure, deformation failure, fracture failure and gnawing failure. However, due to different stamping processes and working conditions, there are many factors affecting the service life of the die. The following is a comprehensive analysis of the influencing factors of die life in terms of die design, manufacture and use, and the corresponding improvement measures are taken.
1. Stamping equipment
The accuracy and rigidity of stamping equipment ( such as press ) are very important to die life. The stamping equipment has high precision and rigidity, and the service life of the stamping die is greatly improved. For example, the die material of complex silicon steel sheet is CRL 2 MOV, which is used on ordinary open press with an average regrinding life of 10 - 30,000 times, while the new precision press can have a regrinding life of 60 - 120,000 times. In particular, press machines with high precision and good rigidity must be selected for small-gap or gapless dies, cemented carbide dies and precision dies, otherwise, die life will be reduced and chess tools will be damaged.
2. Die Design
( 1 ) Precision of guiding mechanism of die. Accurate and reliable guidance can greatly reduce the wear of the working parts of the die and avoid the gnawing of the male and female dies, especially the blanking die, the compound die and the multi-position progressive die without clearance and with small clearance are more effective. In order to improve the service life of the die, it is necessary to correctly select the guide form and determine the precision of the guide mechanism according to the requirements of process properties and part precision. In general, the precision of the guiding mechanism should be higher than that of the male and female dies.
( 2 ) geometric parameters of the cutting edge of the die ( male and female ). The shape, fit clearance and fillet radius of the male and female dies not only have a great influence on the forming of stamping parts, but also have a great influence on the wear and service life of the dies. For example, the fit clearance of the die directly affects the quality of the blanking part and the life of the die. If the precision requirement is higher, a smaller clearance value should be selected. On the other hand, the gap can be appropriately increased to improve the service life of the mold.
3. Stamping process
( 1 ) raw materials for stamping parts.
In the actual production, due to the excessive tolerance of the thickness of the raw materials of the externally pressed parts, fluctuation of the material properties, poor surface quality ( such as rust ) or unclean ( such as oil stain ), etc., the wear of the working parts of the mold will increase and the blade will easily collapse. For this reason, we should pay attention to: ① adopt raw materials with good stamping manufacturability as far as possible to reduce stamping deformation force; ( 2 ) before stamping, the brand, thickness and surface quality of raw materials shall be strictly checked, and the raw materials shall be wiped clean, and surface oxides and rust shall be removed if necessary; ( 3 ) according to the stamping process and raw material types, softening treatment and surface treatment can be arranged when necessary, and appropriate lubricant and lubrication process can be selected.
( 2 ) Layout and lapping.
Unreasonable reciprocating feeding and layout method and too small lapping value often result in sharp wear of the die or gnawing of the male and female dies. Therefore, while considering the improvement of material utilization, it is necessary to reasonably select the layout method and edge value according to the processing batch of parts, quality requirements and mold fit clearance to improve the mold life.
4. Mold materials
The influence of mold material on mold life is a comprehensive reflection of material type, chemical composition, microstructure, hardness and metallurgical quality. Die life is often different for different materials. For this reason, two basic requirements are put forward for the material of die working parts: ① the material should have high hardness ( 58 - 64 HRC ) and high strength, high wear resistance and enough toughness, small heat treatment deformation and certain thermal hardness; ( 2 ) the process performance is good. The processing and manufacturing process of die working parts is generally complicated. Therefore, it is necessary to have adaptability to various processing technologies, such as malleability, machinability, hardening capacity, hardenability, quenching crack sensitivity and grinding workability. Generally, according to the material characteristics, production batch and precision requirements of stamping parts, mold materials with excellent performance are selected, while their manufacturability and economy are taken into account.
5, hot processing technology
Practice has proved. The hot working quality of the die has a great influence on the performance and service life of the die. From the analysis and statistics of die failure causes, it can be seen that die failure " accidents" caused by improper heat treatment account for more than 40 %. The quenching deformation and cracking of the working parts of the mould, as well as the early fracture in the use process, are all related to the hot working process of the mould.
( 1 ) Forging process, which is an important link in the manufacturing process of die working parts. For the dies of high alloy tool steel, technical requirements are usually put forward for the metallographic structure such as carbide distribution of the material. In addition, the forging temperature range should be strictly controlled, the correct heating standard should be formulated, the correct forging force method should be adopted, and the forging should be slowly cooled or annealed in time.
( 2 ) Preparation of heat treatment. Depending on the materials and requirements of the working parts of the die, annealing, normalizing or quenching and tempering should be adopted to improve the structure, eliminate the structural defects of the forged blank and improve the workability. The high carbon alloy die steel can eliminate the network secondary cementite or chain carbide, spheroidize and refine the carbide, and promote the uniformity of carbide distribution after proper preliminary heat treatment. In this way, the quality of quenching and tempering can be guaranteed and the service life of the die can be prolonged.
( 3 ) quenching and tempering. This is the key link in die heat treatment. If overheating occurs during quenching and heating, not only will the workpiece cause greater brittleness, but also it will easily cause deformation and cracking during cooling, seriously affecting the life of the mold. During die quenching and heating, special attention should be paid to preventing oxidation and decarburization. Heat treatment process specifications should be strictly controlled, and vacuum heat treatment can be adopted if conditions permit. Tempering shall be carried out in time after quenching and different tempering processes shall be adopted according to the technical requirements.
( 4 ) stress relief annealing. After rough machining, die working parts should be annealed to eliminate the internal stress caused by rough machining, so as to avoid excessive deformation and cracks caused by quenching. For molds with high precision requirements, stress relief tempering treatment is required after grinding or electrical machining, which is conducive to stabilizing mold precision and improving service life.
6, processing surface quality
The advantages and disadvantages of the working parts and the surface quality of the mold have a very close relationship with the wear resistance, fracture resistance and adhesion resistance of the mold, which directly affects the service life of the mold. In particular, the surface roughness value has a great influence on the service life of the die. If the surface roughness value is too large, stress concentration will occur during work, and cracks will easily occur between its peaks and valleys, affecting the durability of the die, as well as the corrosion resistance of the workpiece surface and directly affecting the service life and precision of the die. Therefore, the following matters should be paid attention to:
( 1 ) in the process of machining die working parts, it is necessary to prevent the surface of the parts from being burnt by grinding, and the grinding process conditions and process methods ( such as grinding wheel hardness, grain size, coolant, feed rate, etc. ) should be strictly controlled;
( 2 ) in the process of processing should prevent the die working parts surface with knife marks. Macroscopic defects such as interlayers, cracks, impact scars, etc.
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