Five basic ways to improve mold quality

Update:25-06-2021
Summary:

In recent years, competition in the manufacturing indus […]

In recent years, competition in the manufacturing industry worldwide has become increasingly fierce. The ability of companies to provide customers with personalized and high-quality products in the shortest possible time with high efficiency and low consumption has become a symbol of corporate competitiveness. . Mold is called the father of industry. The quality of mold will directly affect product quality, output, cost, the cycle of new product production and old product replacement, the speed of corporate product structure adjustment, and market competitiveness. Therefore, the economic situation The quality of the mold puts forward higher and higher requirements. So how can we improve the quality of the mold more reasonably? In other words, how can we make the mold produce qualified parts for a longer time and more mold times under the conditions of high precision, low cost, and high efficiency? This has increasingly become the focus of attention. Mold quality is not a simple topic, it includes the following aspects:
  ⑴Product quality: the dimensional stability and conformity of the product, the surface finish of the product, the utilization rate of the product material, etc.;
  ⑵Service life: under the premise of ensuring product quality, the number of work cycles that the mold can complete or the number of parts produced;
   ⑶ The use and maintenance of the mold: whether it is the most convenient to use, easy to demold, and the production auxiliary time as short as possible;
  ⑷Maintenance cost, maintenance periodicity, etc.
The basic way to improve mold quality:
  ⑴First of all, the design of the part should be reasonable, and the best structural plan should be selected as much as possible. The designer of the part should consider the technical requirements of the part and its structure must conform to the manufacturability and feasibility of mold manufacturing.
⑵The 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 the mold structure, the machinability of mold parts and the convenience of mold maintenance. At the beginning of the design, it should be considered as thorough as possible.
①The selection of mold materials must not only meet the customer's requirements for product quality, but also consider the cost of the material and its strength within the set period. Of course, it must also be based on the type of mold, working methods, processing speed, and main failure modes. And other factors to select materials. For example: the main failure mode of the punching die is the wear of the cutting edge, it is necessary to choose a material with high surface hardness and good wear resistance; the stamping die is mainly subjected to periodic loads, which is easy to cause surface fatigue cracks and cause surface peeling, then choose Materials with good surface toughness; materials with particularly low friction coefficient should be selected for drawing molds; materials with strong thermal fatigue properties should be selected for die-casting molds due to cyclic thermal stress; for injection molds, when the plastic parts are ABS, PP, PC For such materials, the mold material can be pre-hardened quenched and tempered steel. When the plastic parts are high-finish and transparent materials, corrosion-resistant stainless steel can be selected. When the products are large in batches, quenched and tempered steel can be selected. In addition, it is also necessary to consider the use of mold materials with less affinity with the parts to prevent mold sticking from aggravating the wear of mold parts, thereby affecting the quality of the mold.
②When designing the mold structure, try to be as compact as possible, easy to operate, and ensure that the mold parts have sufficient strength and rigidity; when the mold structure allows, the corners of the mold parts should be designed as rounded transitions as much as possible to avoid stress concentration ; For the concave mold, cavity and part of the punch and core, a combination or inlay structure can be used to eliminate stress concentration. For the slender punch or core, appropriate protective measures must be taken in the structure; for the cold die, it should be Equipped with devices to prevent clogging of parts or waste materials (such as ejector pins, compressed air, etc.). At the same time, it is also necessary to consider how to reduce the impact on mold quality caused by the wear of sliding fittings and frequent impact parts during long-term use.
  ③In the design, it is necessary to reduce the scope of disassembly and assembly when repairing a certain part, especially when the wearing parts are replaced, as far as possible to reduce the scope of disassembly and assembly.
   ⑶ The mold manufacturing process is also an important part of ensuring 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 accuracy of the equipment itself, it is necessary to improve the processing method of the parts and improve the technical level of the fitter in the mold grinding and matching process to improve the processing accuracy of the mold parts ; If the overall assembly effect of the mold does not meet the requirements, the probability of making the mold move in an abnormal state in the trial mold will increase, which will have a great impact on the overall quality of the mold.
Therefore, in order to ensure that the mold has a good original precision—the quality of the original mold, a reasonable high-precision processing method must be selected in the manufacturing process, such as EDM, wire cutting, CNC machining, etc., and attention should be paid to the accuracy of the mold. Including the machining accuracy and assembly accuracy of mold parts and comprehensive inspection of mold accuracy through mold trial acceptance work, high-precision measuring instruments should be selected as much as possible during inspection. For those mold parts with complex forming surface and curved surface structure, if you use ordinary straight The ruler and vernier card cannot achieve accurate measurement data. At this time, precision measurement equipment such as a three-coordinate measuring instrument must be selected to ensure the accuracy of the measurement data.
  ⑷ Surface strengthening of the main forming parts of the mold to improve the wear resistance of the surface of the mold parts, so as to better improve the quality of the mold. For surface strengthening, different strengthening methods should be selected according to different use molds. For example: the blanking die can be strengthened by electric spark, cemented carbide surfacing, etc., to improve the wear resistance and compressive strength of the surface layer of the mold parts; die-casting molds, plastic molds and other hot-processed mold steel parts can be nitrided (hard nitrogen Chemical) treatment to improve the wear resistance, heat fatigue resistance and corrosion resistance of parts; drawing dies and bending dies can be treated with sulphurization 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 developed in recent years can form a very strong, smooth, uniform and dense protective film on the surface of the part. This technology is particularly suitable for mold surface protection. Treatment is also an effective way to improve the quality of molds. Of course, if the part is a trial product or the production batch is quite small, it is not necessary to carry out the surface strengthening treatment of the mold part.
  ⑸ The correct use and maintenance of the mold is also a major factor in improving the quality of the mold. For example: mold installation and debugging methods should be appropriate, in the case of hot runners, the power supply wiring must be correct, the cooling water circuit must meet the design requirements, and the parameters of the injection molding machine, die casting machine, and press in the mold production must meet the design requirements and many more. When using the mold correctly, it is necessary to perform regular maintenance on the mold. The guide posts, guide sleeves and other parts of the mold should be filled with lubricating oil frequently. For forging molds, plastic molds, die-casting molds, etc. Lubricant or mold release agent should be sprayed on the surface of the molded part before molding. The planned protective maintenance of the mold and the data processing in the maintenance process can prevent possible problems in the mold production and improve the efficiency of maintenance work.
   In short, if you want to improve the quality of the mold, you must first consider the impact on the mold quality in every link, and secondly, you must cooperate with all departments. The quality of the mould is the true embodiment of the mould enterprise's own strength.

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