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What are the important factors affecting the quality of injection molds?

Mold manufacturing is a complex process, from design, processing, assembly, debugging and other steps to the final actual use. During the entire life cycle, the factors that affect the quality of the mold are mainly the following.

  1. Mold steel
    Steel is the decisive factor in mold quality, and choosing reasonable steel is the top priority. The criteria for selecting steel are:

① Requirements for injection molding materials
Different plastics should use different steels, such as requirements for high polishing, corrosion resistance, etc.;

② Price
Steel is good as long as it can be used, not the more expensive the better; considering the cost factor of the mold, the mold steel should be selected according to the mold life to avoid unnecessary waste; generally, the life of P20 material is about 300,000; 2738 material is no problem at 500,000, and H13/2344 is usually more than 800,000-1 million, which can be selected according to the situation;

③ Surface treatment
The surface treatment of the mold is also very important. Nitriding can enhance the surface hardness of steel and effectively extend the life of the mold; electroplating can effectively modify the mold steel. For some plastic parts that require high brightness and corrosion resistance, electroplating can be used to enhance and improve the performance of steel.

  1. Structural design
    Mature mold structure not only takes into account the product material properties, shrinkage, molding temperature, elastic tensile deformation coefficient, etc., but also takes into account the cooling water circuit, the speed of opening and closing the mold, etc. Reasonable mold structure can effectively extend the life of the mold and ensure the smooth production of the mold, improve efficiency, and reduce costs.
  1. Mold processing
    If you want to do your job well, you must first sharpen your tools. The arrangement of mold technology is particularly important. Reasonable process arrangement can speed up the production cycle, shorten processing time, and effectively save costs. What’s more important is that accurate and reasonable processing can ensure the stability of the mold in the production process and extend its life. Some processing errors will cause mold welding. No matter how good the welding is, it is a loss for the mold; in addition, poor processing may also affect the mold movement, reduce the mold life, and cause the mold to crack or even break during the production process.
  2. Standard parts
    The lowest wooden strip determines the capacity of the bucket. Everyone understands this principle, but often does not pay attention to it when doing it. The same is true for molds. Although standard parts do not directly participate in molding, they control the operation of the entire mold. Good standard parts should be wear-resistant, hard enough, high precision, and not easy to deform. The price difference of standard parts of different brands is very large, so don’t bargain blindly when making molds. If you bargain, your mold will drop from Mercedes-Benz to Volkswagen.
  3. Collision (flying mold)
    Collision relies on the experience of mold fitters. It seems to be a simple job, but it is the most technical job. Complex molds mainly depend on this skill. Flat molds are the simplest, and as long as there is no flash on the fractal surface, it is basically ok. Auto parts molds are very troublesome, not only are the fractal surfaces relatively irregular, but they often include multiple sliders and top blocks. At the same time, other problems of the mold can be improved and perfected through collision, so it is a comprehensive work.
  1. Polishing/leather grain
    The polishing of the mold is the last link in the manufacturing of the mold. Polishing is directly reflected on the plastic parts, so this is the most face-saving job. Polishing can also help and supplement the mold movement, especially for demolding. Often, some mold production is not smooth because of inadequate polishing, excessive resistance, difficulty in demolding, and even whitening and cracking.
  2. Mold assembly
    Mold assembly is like assembling a machine. Every component and every screw must be correct, otherwise the consequences will be quite serious. At the least, it will lead to product defects and affect production, and at the worst, the mold will be completely damaged and scrapped. Therefore, the assembly work must be very meticulous. During the assembly process, special attention should be paid to the cleaning of the mold, especially the water channel and screw holes. The iron filings inside must be blown clean.
  3. Hot runner or cold runner
    This actually has the least impact on the quality of the mold, because the hot runner is generally a brand specified by the customer, especially some large customers. Foreign well-known brands are very good in both quality and after-sales service, so there is generally no problem with quality. It’s just that the quality of some domestic hot runners varies greatly. In order to save costs and gain price advantages, some small enterprises use some unreliable heating and conduction accessories, which are prone to problems. The main problem of cold runners is how to ensure the balance of injection molding, gate size, injection pressure, etc.
  4. Cooling water channel
    Anyone who has experience with molds knows how important cooling is to a mold. Due to the increase in prices and labor wages, when mass-producing products, the profit brought by not reducing the injection cycle by one second is unimaginable. However, while speeding up the production cycle, the mold temperature will rise. If it is not effectively controlled, the mold will be too hot to form, and even cause the mold to deform and fail. Therefore, excellent water channel design is particularly important, including the arrangement density, diameter, and mutual connection of the water channel.
  5. Mold maintenance
    Mold maintenance is mainly maintenance and maintenance during the production process. Molds are like cars. If they are not used for a long time and not maintained, they may cause the mold to be scrapped. Therefore, comprehensive maintenance should be carried out after each use of the mold, especially the rust prevention of the molding part and the rust prevention of the main moving parts. Because the mold needs to be exposed to water during the production process, it may get water on the mold during installation or disassembly, so be sure to ensure that the mold is dry, and then apply a layer of oil for protection.
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