Design requirements for molds in plastic injection molding processing
The characteristics of plastic injection molding are determined by the characteristics of the raw material, and there are two main points: one is the filling activity of the plastic melt during injection, and the other is the shrinkage position of the plastic in the mold cavity when it is cooled and cured. These two points determine the difference of the injection mold and the difficulty of the injection mold design. When designing injection molds, it is necessary to inquire about the characteristics of the processed plastic raw materials, so that the designed injection mold is more reasonable, and the characteristics of plastics are usefully exercised in the design process. Therefore, the questions that need to be considered in the injection mold design process are as follows.
1. Deeply analyze the layout of plastic parts and their technical requirements. The layout of plastic parts determines the complexity of injection mold layout, and the technical requirements of plastic parts (dimensional accuracy, surface roughness, etc.) determine the difficulty of injection mold production and molding process, so for those who do not meet the additional requirements of plastic injection molding, the layout style of different principles, etc., should propose an improved design scheme for injection molded parts, otherwise it will increase the difficulty of injection mold design and production and injection molding process;
2. Familiar with the technical specifications of injection molding machines. The technical specifications of the injection molding machine limit the size of the injection mold and the limitations of the injection molded product that can be molded;
3. Inquire about the performance and process performance of plastic injection molding processing. Including the active position of the plastic melt, the larger activity interval ratio that the melt can reach: analyze the activity resistance of the runner and cavity, the discharge of the original air in the mold cavity, the crystallization that the plastic may produce in the injection mold, orientation and the internal stress caused by it, the cooling contraction and compensation questions of the plastic, the requirements of the plastic for the temperature of the injection mold, etc.;
4. Considering the design and production of injection molds, mainly handle the following questions:
(1) The dimensions of injection molded parts should be accurate. Molded parts are the crisp components that determine the style, size and surface quality of plastic parts, which are very relevant and require special attention. When calculating the size of molded parts, the equilibrium shrinkage method is generally accepted. For plastic parts with high accuracy and need to master the mold modification allowance, it can be calculated according to the small belt method, and for large plastic parts, although the analogy method can be used, the shrinkage rate of several styles of measured plastic parts in the difference is calculated to make up for the influence of certain components that are difficult to consider on the surface.
(2) The designed injection mold should be obedient to high, safe and reliable. This requirement affects many aspects of injection mold design, such as the filling of the pouring system, the closed module, the good results of temperature adjustment Xijong, and the naïve and reliable release mechanism.
(3) The layout of the injection mold should be reasonably selected. Credentials the drawings and technical requirements of plastic parts, research and select appropriate molding skills and equipment, link the manufacturer's mechanical processing talent, propose the layout scheme of the injection mold, fully solicit the opinions of relevant parties, and analyze and discuss, so that the designed injection mold layout is reasonable, the quality is reliable, and the manipulation is convenient. When necessary, the requirements for the design and processing of injection molds can be met, and the requirements for the drawings of the plastic parts can be put forward, but they need to be discussed by the user before implementation.
(4) The layout of the injection mold should adapt to the molding characteristics of the plastic. When designing injection molds, it is important to inquire about the molding characteristics of the plastics used and despite meeting the requirements, this is also a nervous mistake in obtaining high-quality plastic parts.
(5) The designed injection mold should be convenient for production. When designing injection molds, although the production of the designed injection molds is easy and cheap. Especially for those relatively complex molded parts, the demand consideration is to accept ordinary machining skills or accept special processing skills. If you accept the extra processing skills, how to assemble after the processing of the hot mo, similar questions need to be considered and handled when designing the injection mold, and the repair after the mold trial should also be considered, and there should be enough mold repair margin.
(6) Parts processed by plastic injection molding should be wear-resistant and resistant. The cost resistance of injection mold parts affects the application life of all injection molds, so in the design of such parts should not only put forward the necessary requirements for materials, processing skills, hot disposal, etc., such as pushrods and other pin pillars are also easily stuck, bent, broken, so the failure accounts for a large part of the injection mold failure. For this reason, it is also necessary to consider how to facilitate adjustment and replacement, but pay attention to the adaptation of part life to the injection mold.