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Mold control enables precise injection molding. Precise injection molding is influenced by many related factors and environmental conditions, with the most fundamental ones being the plastic material, the injection mold, the injection molding process, and the injection molding equipment. In the early stage of designing plastic products, it is necessary to first select the engineering plastic with the required properties based on its application environment. Secondly, an appropriate injection molding machine should be selected based on the chosen plastic material, the required dimensional accuracy of the finished product, the weight of the parts, the quality requirements, and the intended mold structure. Among the factors affecting precision injection molding, the mold is key to producing precision plastic products that meet quality requirements. Mold design: The rationality of mold design has a direct impact on the quality of plastic products. Since the dimensions of the mold cavity are determined by the required dimensions of the plastic product plus the shrinkage rate of the material used, and the shrinkage rate is usually a value within a range recommended by plastic manufacturers or engineering plastic manuals, it depends not only on the type, position, and distribution of the mold gates but also on the crystalline orientation (anisotropy) of the engineering plastic, as well as on the shape and size of the plastic product, as well as the distance and position from the gates. The main factors affecting plastic shrinkage include thermal shrinkage, phase transition shrinkage, orientation shrinkage, compression shrinkage, and elastic recovery, and these factors are related to the molding conditions or operating conditions of precision injection-molded products. Therefore, the designer of the mold must have extensive experience in design and injection molding, and must take into account the relationship between these influencing factors and the injection molding conditions, as well as various apparent factors such as injection pressure and cavity pressure along with filling speed, the temperature of the injected melt and the temperature of the mold, the mold structure and the shape and distribution of the gates, as well as factors like the gate cross-sectional area, the wall thickness of the product, the content of reinforcing fillers in the plastic material, and the crystallinity and orientation of the plastic material. The impact of the aforementioned factors also varies depending on the type of plastic material, or other molding conditions such as temperature, humidity, continued crystallization, internal stresses after molding, and variations in the injection molding machine. The injection molding process is a process in which plastic is transformed from a solid state (powder or pellets) to a liquid state (melt), and then back to a solid state (finished product). From granules to melt, and then from melt to the final product, various factors such as temperature fields, stress fields, flow fields, and density fields come into play. Under the combined effect of these fields, different plastics (therosetting or thermoplastic, crystalline or amorphous, reinforced or unreinforced, etc.) exhibit distinct polymer structural forms and rheological properties. Any factor that affects the aforementioned \"field\" will inevitably impact the physical and mechanical properties, dimensions, shape, precision, and appearance quality of plastic products. In this way, the intrinsic relationship between processing factors and the properties, structural morphology of polymers, as well as plastic products, is manifested through those plastic products. Understanding these internal relationships is of great significance for properly formulating injection molding processes, designing and manufacturing molds according to drawings, and even selecting appropriate injection molding equipment. Precision injection molding also differs from conventional injection molding in terms of injection pressure and injection speed; precision injection molding often employs high or ultra-high pressure along with fast injection speeds to achieve a lower degree of shrinkage during molding. For the above reasons, when designing precision injection molds, in addition to considering the general design factors for molds, the following points must also be taken into account: 1. Adopt appropriate mold dimension tolerances ； 2 Prevent generation of warpage shrinkage errors ； 3 Prevent injection molding deformation ； 4 Prevent demolding deformation ； 5 Minimize mold manufacturing errors ； 6 Preventing errors in mold precision ； 7 Maintain mold accuracy. To prevent errors in shrinkage rates, since the shrinkage rate can vary depending on the injection pressure, for single-cavity molds, the cavity pressure within the cavity should be as consistent as possible. As for multi-cavity molds, the cavity pressure between the cavities should differ very little. In the case of single-cavity multi-gate or multi-cavity multi-gate configurations, injection must be carried out at the same injection pressure to maintain uniform cavity pressure. To this end, it is necessary to ensure that the gate positions are balanced. To maintain uniform cavity pressure within the mold cavity, it is best to keep the pressure at the gate inlet consistent. The balance of pressure at the gate is related to the flow resistance in the runner. Therefore, the runner should be balanced first before the gate pressure reaches equilibrium. Since the melt temperature and mold temperature affect the actual shrinkage rate, when designing the cavities of precision injection molds, attention must be paid to the arrangement of the cavities in order to facilitate the determination of the molding conditions. This is because the molten plastic brings heat into the mold, and the temperature gradient within the mold generally surrounds the cavity in a concentric circular pattern centered on the sprue. Therefore, design measures such as flow channel balancing, cavity arrangement, and concentric circular arrangement centered on the main flow channel are necessary to reduce shrinkage rate differences among the cavities, expand the allowable range of molding conditions, and lower costs. The arrangement of cavities in precision injection molds must meet the requirements of balanced flow channels and an arrangement centered around the main flow channel; moreover, a cavity arrangement with the main flow channel as the symmetry axis must be used. Since mold temperature has a significant impact on the molding shrinkage rate, it also directly affects the mechanical properties of the injection-molded products and can cause various molding defects such as surface roughness; therefore, it is necessary to maintain the mold within a specified temperature range, and to ensure that this temperature does not change over time. The temperature difference between the various cavities of a multi-cavity mold must also remain constant. To this end, temperature control measures for heating or cooling the mold must be implemented in mold design, and attention must be paid to the design of the temperature control-cooling circuit in order to minimize the temperature difference between the various cavities of the mold. In the temperature control circuits for cavities and cores, there are mainly two connection methods: series cooling and parallel cooling. In terms of heat exchange efficiency, the flow of cooling water should be turbulent. However, in a parallel cooling circuit, the flow rate in one of the branches that divide the flow is lower than that in a series cooling circuit, which may result in laminar flow; moreover, the actual flow rate entering each branch is not necessarily the same. Since the temperature of the cooling water entering each circuit is the same, the temperature of each cavity should also be the same. However, in reality, due to differences in flow rates within each circuit as well as variations in the cooling capacity of each circuit, it is not possible for the temperatures of the various cavities to be identical. The disadvantage of using a series cooling circuit is the high flow resistance of the cooling water, resulting in a significant difference between the temperature of the cooling water at the inlet of the first cavity and that at the inlet of the last cavity. The temperature difference at the cooling water inlet and outlet varies depending on the flow rate. For small, precision injection molds, it is generally more appropriate to use a series cooling circuit in order to reduce mold costs. The mold cavity and core should each have their own cooling water circuit system. In the design of the cooling circuit, due to the different amounts of heat absorbed from the cavity and the core, the thermal resistance of the circuit structure varies as well, resulting in a large temperature difference between the water temperatures at the entrances of the cavity and the core. If the same system is used, the design of the cooling circuit also becomes more difficult. Furthermore, when taking measures to prevent warping in injection-molded products, it is also desirable to maintain a certain temperature difference between the cavity and the core. Therefore, when designing the cooling circuits for the cavity and core, it should be possible to adjust and control their temperatures separately. Maintaining mold precision: To maintain mold precision under injection pressure and clamping force, it is necessary to consider the feasibility of performing operations such as grinding, lapping, and polishing on the cavity components when designing the mold structure. Although the machining of the cavities and cores has achieved high precision levels, and the shrinkage rate is as expected, due to centering errors during molding, it is difficult for the relevant dimensions on the inner and outer sides of the molded parts to meet the design requirements for plastic components. To maintain the dimensional accuracy of the moving and fixed mold cavities at the parting line, in addition to using the guide posts and guides commonly employed in standard molds for centering, it is also necessary to install positioning elements such as tapered dowels or wedge blocks to ensure accurate and reliable positioning. For manufacturing precision injection molding molds, high-quality alloy tool steels with excellent mechanical properties and low thermal creep should be selected. For the materials used to create the mold cavities and runners, materials that have undergone rigorous heat treatment and possess high hardness, good wear resistance, strong corrosion resistance, and resistance to thermal deformation are required. At the same time, the ease of machining and electrical processing, as well as cost considerations, must also be taken into account. To prevent changes in dimensional accuracy due to aging, it is necessary to specify, during mold design, a tempering or low-temperature treatment to reduce the residual austenite structure in the mold material. For the vulnerable components of precision injection molding molds, especially those such as cavities and cores, the possibility of repair should be considered during design, so as to maintain high precision even after the mold is repaired. Whether the mold venting design is reasonable is also a key factor in determining the maintenance of mold precision. Most precision products are molded using engineering plastics; during the molding process, to ensure good fluidity of the plastic as well as consistent shrinkage of its molecules, it is generally necessary for the mold temperature to be within a certain range in order to carry out the molding. When the mold temperature is too high, the expansion of the mold components makes it difficult to expel gases from within the mold, resulting in defects such as trapped air, scorching, and insufficient material in the product. Therefore, the cavity area of the mold should be designed with insert components, and exhaust grooves should be provided on the friction surfaces of the ejection components to prevent needle scorching. Reasonably designing precision injection molds is the foundation and essential prerequisite for obtaining precision products. By properly determining the dimensions and tolerances of the mold, taking technical measures to prevent issues such as shrinkage errors, injection deformation, demolding deformation, and flash in the injection-molded products, as well as ensuring mold precision, and by employing the correct precision injection molding processes, suitable engineering plastic materials, and high-quality injection molding equipment to achieve an optimal balance, it is highly important for improving the quality, reliability, and performance of precision plastic parts, reducing production costs, and increasing production efficiency.