The general guiding ideology of precision mold parts processing is to carry out adaptive processing for different mold parts, different raw materials, different shapes and different skill requirements, and there are many options. However, through the control of the processing process, to achieve the best processing effect and economy is the main point of our attention. According to the appearance and shape of precision mold parts, the parts can be mainly divided into three categories: shafts, discs, plates and shaped parts. The mold accessories manufacturers will tell you that the process of these three types of parts is generally: rough machining - semi-finishing - (quenching, quenching and tempering) - fine grinding - electrical machining - fitter trimming - assembly processing.
(1) Heat treatment of mold parts
In order to obtain the required heat treatment hardness of the mold parts, it is necessary to control the internal stress of the heat treatment of the parts, so that the dimension and shape and position of the parts can be stabilized during and after processing. There are different heat treatment methods for the effect of different raw materials. The process to consider is economy, material hardenability, hardenability, overheat sensitivity and decarburization sensitivity. After quenching, the general workpiece retains internal stress, which easily leads to subsequent finishing or cracking during work. After quenching, the parts should be tempered while hot to eliminate the quenching stress. For workpieces with complex shapes and many internal and external corners, tempering is sometimes not enough to eliminate quenching stress, and stress relief annealing or multiple aging treatments are required before finishing to fully release stress. Different methods are adopted according to different requirements.
(2) Grinding of mold parts
There are three main types of machine tools used for grinding: surface grinders, internal and external cylindrical grinders, and east-west forming grinding machines. During finishing grinding, the appearance of grinding deformation and grinding cracks should be strictly controlled, even if it is a microscopic crack on the surface of the workpiece, otherwise it will gradually appear in the subsequent work. Therefore, the feed amount during fine grinding should be small, the cooling during grinding should be sufficient, the coolant medium should be selected as much as possible, and the parts with machining allowance within 0.01mm should be ground at constant temperature as much as possible. When grinding workpieces, the grinding wheel must be carefully selected. During the grinding process, the grinding wheel should be trimmed in time to maintain the sharpness of the grinding wheel. When the grinding wheel is passivated, it will be rubbed, scratched and kneaded on the surface of the workpiece, causing burns, micro-cracks or grooves on the surface of the workpiece. Most of the parts are processed by surface grinders, and it is difficult to process long and thin sheet parts. Before processing, under the strong attraction of the magnetic table of the grinder, the workpiece originally had some kind of tortuous deformation to produce straight deformation, which was close to the surface of the worktable. After grinding, the workpiece was deformed and recovered under the effect of the original stress, and the thickness of the plate was uniformly measured. , but when there are strict requirements on the thickness of the plate, it is necessary to properly add the thickness allowance according to the workpiece material, shape, cutting method, heat treatment method and other factors.
(3) Electric machining of mold parts
Modern mold companies have almost no shortage of electric machining. Because electric machining can effectively process various special-shaped, various types of cavities or high-hardness parts, it has become an indispensable processing method in the mold making and metal processing industries. The slow-moving wire cutting processing skills are known from the feedback information of the enterprise: the accuracy has reached ±0.002mm, and the roughness Ra=0.4μm. In order to seek machining accuracy, after the rough machining is completed, the machining stress needs to be released. To deal with stress concentration, the principle of vector translation can be used. Before finishing, leave a margin of 0.8 to 0.9 mm, pre-machine the rough shape of the cavity, and then perform heat treatment to release the machining stress as much as possible before finishing to ensure thermal stability. stability. In EDM processing, rough and fine electrodes are produced respectively. Finishing electrodes are required to fit well in the shape of the cavity, and good finishing electrodes have been processed by CNC machine tools. For mold parts with different raw materials, electrode raw materials should be properly selected. When designing electrodes, calculate the amount of voids and the number of electrodes. When machining large areas or heavy electrodes, both the workpiece and the electrode must be stable and have a certain strength to prevent loosening during machining. However, the surface after EDM is more difficult to grind than the surface after general machining or heat treatment. Therefore, before the end of EDM, precise trimming should be used to remove the hardened thin layer formed on the surface.
(4) Surface treatment of mold parts
The content of forming surface treatment includes no pores on the surface of the steel, uniform hardness, small difference in anisotropic properties, low inclusions, and places where the surface of the parts leaves knife marks, wear marks and other stress concentrations during processing. Therefore, after the processing is completed, the parts need to be strengthened on the surface, and processed by mechanical polishing, fitter grinding, and polishing to deal with the processing hazards. Blunt the useless edges, sharp corners and holes of the workpiece. Generally, there will be a metamorphic hardened layer of about 6-10μm on the surface of the EDM, which is gray-white in color. This layer is brittle and has residual stress. Before use, the hardened layer should be fully eliminated. The method is surface polishing, and the hardened layer is polished off. In order to achieve high-quality polishing results, the raw material, shape, hardness and surface quality of the workpiece must be fully considered. There must be high-quality polishing tools, high-quality polishing materials, correct polishing procedures, and careful and consistent personnel. Quality, outstanding clean environment.
Conclusion: Many practices have proved that mold enterprises attach importance to the control of the finishing process of mold parts, which is a long-term and effective way for mold enterprises to survive and develop. It is of far-reaching significance to effectively improve the life of the mold in production and use, and to stabilize the quality of the product.
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