How to improve the quality of moulds

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How to improve mold quality

mold quality is not a simple topic, it includes the following aspects:

⑴ product quality: stability and conformity of product size, smoothness of product surface, utilization rate of product materials, etc

⑵ service life: on the premise of ensuring product quality, the number of work cycles that the mold can complete or the number of parts produced

⑶ use and maintenance of the mold: whether it is the most convenient to use, easy to demould, and the production assistance time is as short as possible

⑷ maintenance cost, maintenance periodicity, etc

basic ways to improve the quality of molds:

⑴ first of all, the design of the parts should be reasonable, and the best structural scheme should be selected as far as possible. The designer of the parts should consider the technical requirements of the parts and their structures must meet the processibility and feasibility of mold manufacturing

because the product has very low thermal conductivity and water vapor permeability ⑵ the design of the mold is the most important step to improve the quality of the mold. Many factors need to be considered, including the selection of mold materials, the usability and safety of mold structure, the machinability of mold parts and the convenience of mold maintenance. These should be considered as thoroughly as possible at the beginning of the design

① the selection of mold materials should not only meet the requirements of customers for product quality, but also take into account the cost of materials and their strength within the set cycle. Of course, the selection of materials should also be based on the type of mold, working mode of use, processing speed, main failure forms and other factors. For example, the main failure form of blanking die is blade wear, so it is necessary to choose materials with high surface hardness and good wear resistance; The stamping die mainly bears periodic loads, which is easy to cause surface fatigue cracks and surface spalling, so it is necessary to choose materials with good surface toughness; The material with low friction coefficient should be selected for the drawing die; Because the die-casting die is subjected to cyclic thermal stress, the material with strong thermal fatigue should be selected; For the injection mold, when the plastic parts are ABS, PP, PC and other materials, the mold material can be pre hardened and tempered steel. When the plastic parts are high finish and transparent materials, corrosion-resistant stainless steel can be selected. When the products are in large quantities, Quenched and tempered steel can be selected. In addition, it is also necessary to consider the use of mold materials with low affinity with parts, so as to prevent mold sticking from aggravating the wear of mold parts, thus affecting the quality of the mold automobile tire market, which is the largest end market of rubber

② when designing the mold structure, try to be compact and easy to operate, and also ensure that the mold parts have sufficient strength and stiffness; When the mold structure allows, the corners of the surfaces of the mold parts should be designed as fillet transition as far as possible to avoid stress concentration; For concave dies, cavities and some punch and cores, combined or inlaid structures can be used to eliminate stress concentration. For slender punch or cores, appropriate protective measures should be taken in the structure; For the cold stamping die, it should be equipped with a device to prevent the blocking of parts or waste materials, and the shift rod is equipped with a guide sleeve with different inner diameters (such as spring pin, compressed air, etc.). At the same time, we should also consider how to reduce the impact on the quality of the mold caused by the wear of sliding mating parts and frequent impact parts in long-term use

③ in the design, the scope of disassembly and assembly when repairing a certain part must be reduced, especially when replacing vulnerable parts, the scope of disassembly and assembly must be reduced as much as possible

⑶ the manufacturing process of the mold is also an important part to ensure the quality of the mold. The processing method and processing accuracy in the mold manufacturing process will also affect the service life of the mold. The accuracy of each part directly affects the overall assembly of the mold. In addition to the influence of the accuracy of the equipment itself, it is necessary to improve the processing method of the parts and the technical level of the fitter in the process of mold grinding to improve the processing accuracy of the mold parts; If the assembly effect of the mold after exposing the weak links of the product cannot meet the requirements, the probability of the mold acting under abnormal conditions will be increased in the mold test, which will have a great impact on the overall quality of the mold. Therefore, in order to ensure that the mold has good original accuracy - original mold quality, we must first reasonably select high-precision processing methods in the manufacturing process, such as EDM, wire cutting, CNC machining, etc., and pay attention to the accuracy inspection of the mold, including the machining accuracy of mold parts, assembly accuracy and the accuracy of the mold through the comprehensive inspection of mold test and acceptance. We also need to choose high-precision measuring instruments as much as possible during the inspection, For those mold parts with complex surface structure, if ordinary ruler and vernier card are used, the accurate measurement data cannot be achieved. At this time, it is necessary to select precision measurement equipment such as coordinate measuring instrument to ensure the accuracy of the measurement data

⑷ strengthen the surface of the main formed parts of the die to improve the wear resistance of the surface of the die parts, so as to better improve the quality of the die. For surface strengthening, different strengthening methods should be selected according to different molds for different purposes. For example, the blanking die can be strengthened by electric spark and hardmetal surfacing to improve the wear resistance and compressive strength of the surface layer of the die parts; Nitriding (hard nitriding) can be used for hot working die steel parts such as die-casting dies and plastic dies to improve the wear resistance, heat fatigue resistance and corrosion resistance of the parts; The drawing die and bending die can be sulphurized to reduce the friction coefficient and improve the wear resistance of the material; Carbonitriding (soft nitriding) can be applied to the surface strengthening treatment of various molds. In addition, a technology called FCVA vacuum diamond coating technology developed in recent years can form a protective film on the surface of parts that is extremely firm and smooth, uniform and dense with the substrate. This technology is especially suitable for protective treatment of mold surface, and it is also a method with remarkable effect to improve mold quality. Of course, if the parts are trial products or the production batch is quite small, it is not necessary to carry out the surface strengthening treatment of mold parts

(5) the correct use and maintenance of the mold is also a major factor in improving the quality of the mold. For example, the installation and debugging mode of the mold should be appropriate. In the case of hot runner, the power wiring should be correct, the cooling water path should meet the design requirements, and the parameters of injection molding machine, die casting machine and press machine should meet the design requirements in the production of the mold. When using the mold correctly, it is also necessary to maintain the mold regularly. The guide post, guide sleeve and other parts with relative movement of the mold should be often filled with lubricating oil. For forging mold, plastic mold, die-casting mold and other molds, lubricant or molding agent should be sprayed on the surface of formed parts before each mold is formed. The planned protective maintenance of the mold and the data processing in the maintenance process can prevent the problems that may occur in the production of the mold and improve the efficiency of maintenance work

in short, in order to improve the quality of the mold, we must first consider the impact on the quality of the mold in every link, and then we must cooperate with all departments. The quality of mold is the true embodiment of the strength of mold enterprises

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