Cause analysis of die burst:
1. Mould material is not good and easy to crack in subsequent processing.
2. Thermal Disposal: Deformation due to improper quenching and tempering process
3. The flatness of the grinding die is insufficient, resulting in flexural deformation.
4. Design process: die strength is not enough, knife edge spacing is too close, die structure is unreasonable, the number of template blocks is not enough, no cushion plate cushion foot.
5. Improper disposal of wire cutting: pulling wire cutting, wrong clearance, no angle clearance
6. Selection of punch equipment: tonnage of punch, insufficient punching force, too deep die adjustment
7. Unsmooth stripping: no demagnetization disposal before consumption, no stripping tip; broken needle, broken spring and other stuffing in consumption
8. Dropping is not smooth: there is no leakage of feces when assembling moulds, or rolling and blocking feces, padding and blocking feces
9. Consumption awareness: laminated stamping, inadequate positioning, no use of air guns, template cracks continue to consume
How to prevent die burst?
1 stamping equipment
The accuracy and rigidity of stamping equipment (such as press) are very important to the life of stamping die. Stamping equipment has high precision and good rigidity, and die life has been greatly improved. Especially for small clearance or no clearance dies, carbide dies and fine dies, it is necessary to select a press with high precision and good rigidity. Otherwise, die life will be reduced and chess pieces will be damaged seriously.
2. Die Design
(1) The precision of the guide mechanism of the die. In order to improve the service life of the die, it is necessary to select the correct guiding mode and confirm the accuracy of the guiding mechanism according to the requirements of the process nature and the accuracy of the parts.
(2) Geometric parameters of die edge (convex and concave die). The shape, fit clearance and fillet radius of convex and concave dies not only have a great influence on the forming of stamping parts, but also on the wear and life of dies. If the precision requirement is high, the smaller clearance value should be chosen; otherwise, the clearance can be increased appropriately to improve the service life of the die.
3 Stamping Technology
(1) Raw materials of stamping parts.
(1) The original materials with good stamping technology should be used as far as possible to reduce the stamping deformation force; (2) Before stamping, the grade, thickness and appearance quality of the original materials should be strictly checked, and the original materials should be wiped clean, and the surface oxides and rust should be removed if necessary; (3) According to the stamping process and the varieties of the original materials, softening points can be arranged when necessary. Placement and surface disposal, as well as the selection of appropriate smoothing agent and smooth process.
(2) Layout and lapping.
Irrational reciprocating feeding layout method and too small lapping boundary value often lead to sharp wear or convex and concave die gnawing. In order to improve the service life of the die, the layout method and lapping boundary value must be reasonably selected according to the processing batch, quality requirement of the parts and the clearance of the die.
4 Mould Information
The data should have high hardness (58 ~ 64HRC) and high strength, high wear resistance and enough toughness, small heat treatment deformation, and a certain degree of thermo-hardness; and the process performance is good.
5 Hot Processing Technology
The hot working quality of the die has a great influence on the performance and service life of the die.
(1) Forging process. This is an important link in the manufacturing process of working parts of dies and moulds. The range of forging temperature should be strictly controlled, the correct heating standard should be formulated, the correct forging force method should be adopted, and the slow cooling or timely annealing after forging should be adopted.
(2) Preparing for thermal treatment. In order to improve the structure, eliminate the structural defects of forging blank and improve the processing technology, annealing, normalizing or tempering should be adopted respectively according to the different information and requests of die working parts.
(3) Quenching and tempering. This is the key link in the heat treatment of die. When the die is quenched and heated, special attention should be paid to avoiding oxidation and decarbonization. The standard of heat treatment process should be strictly controlled. Vacuum heat treatment can be adopted when conditions permit. After quenching, it should temper in time and adopt different tempering processes according to technical requirements.
(4) Stress relief annealing. As for the mould with high precision requirement, after grinding or electro-machining, stress relief and tempering are needed, which is beneficial to stabilizing the precision of the mould and improving its service life.
6. Processing Appearance Quality
It is necessary to avoid the appearance of burned parts in the process of working parts of dies and moulds, strictly control the grinding process conditions and methods (such as grinding wheel hardness, particle size, coolant, feed rate and other parameters); and avoid the knife marks on the surface of working parts of dies and moulds in the process of processing. Macroscopic defects such as interlayer, crack, impact scar, etc. The existence of these defects will cause stress concentration, become the source of fracture, and form the early failure of the die; Third, the use of grinding, grinding and polishing and other finishing and precision processing, to achieve a smaller surface roughness value, improve the service life of the die.
7 Apparently Intensified Disposal
In order to improve the performance and service life of the die, the application of strengthening the appearance of the working parts of the die is more and more widespread. Commonly used surface strengthening treatment methods include liquid carbonitriding, ion nitriding, boronizing, vanadizing and spark strengthening, chemical vapor deposition (CVD), physical vapor deposition (PVD) and carbide dipping into the workpiece surface in salt bath (TD).
Control of Metamorphic Layer in Wire Cutting
The cutting edge of punching die is mostly processed by wire cutting. Because of the thermal effect and electrolysis effect of WEDM, a certain thickness of metamorphic layer is produced on the surface of the die, which results in the decrease of the surface hardness and the appearance of micro-cracks. The early wear of the die in WEDM is prone to occur, which directly affects the maintenance of the blanking clearance of the die and the easy collapse of the edge, and shortens the service life of the die. 。 Therefore, reasonable electrical regulation should be selected in WEDM to minimize the depth of metamorphic layer.
9 Correct Use and Reasonable Maintenance
In order to maintain normal consumption, improve stamping quality, reduce cost and prolong die life, it is necessary to correctly use and reasonably maintain the die, strictly implement the "three inspection" system of die (pre-operation inspection, inspection and post-operation inspection) and do a good job in die maintenance and repair.
These are the related contents shared by Shandong Mold Manufacturers. For more information, please visit the website: http://www.jnhjgs.cn.