Precision auto parts mold design points

Car plastic zero most used injection molding, because the plastic itself is of high precision design, make the plastic parts can't adopt the conventional injection molding, precision injection molding process technology must be used. Precision plastic parts to ensure that the car's performance, quality and reliability, the injection molding of high quality and meet the requirements of the product design of plastic products, plastic materials, injection molding equipment and must be constantly to improve the mold and injection molding process. The main factors influencing the precision injection for determining precision injection is based on the precision of injection molding products, the products of the size tolerance, form tolerance and surface roughness. For precision injection there must be many related conditions, and the most essential is the plastic material, injection mold, injection molding process and injection molding equipment, the four basic factors. Design of plastic products, should be first selected engineering plastic material, and can perform a precision injection molding engineering plastics and must choose those high mechanical properties, dimension stability, good creep resistance, environmental stress cracking resistance of the material. Second should be based on the selected plastic materials, precision of finished product size, weight, quality requirements and expected mold structure selection of a suitable injection molding machine. In the process of machining, the factors influencing the precision of injection molding products mainly comes from the precision of the mold, injection molding shrinkage, and the change of environmental temperature and humidity range, etc. In precision injection mold is used to obtain one of the keys to meet the requirements of the quality of precision plastic products, precision injection used mold should be practical and meets the requirement of product size and shape, precision. But even if the precision of the mould, size is consistent, the molding plastic products the actual size may also be due to shrinkage difference and inconsistent. Effectively control plastic shrinkage rate, therefore, it is very important in precision injection molding technology. Mould design is reasonable or not will directly affect the plastic shrinkage rate, due to the mold cavity dimension is estimated by the plastic product size and shrinkage rate is obtained, and the shrinkage is or manual of engineering plastics as recommended by the plastic manufacturer of a range of values, it not only with the mold gate forms, gate location and distribution, and the crystal orientation of engineering plastics. Plastic products shape, size and the position and the distance to the gate. Influence mainly include thermal contraction of plastic shrinkage rate, phase change shrinkage, orientation, compression contraction with factors such as elastic recovery, and the influence factors and precision injection parts molding conditions or operating conditions. Therefore, these factors must be considered when designing the mold and injection molding conditions and the relationship between apparent factors, such as injection pressure and cavity pressure and mold filling speed, melt temperature and mold temperature, injection mold structure and gate forms and distribution of products as well as the gate area, wall thickness, plastic materials, plastic materials content of reinforcing filler in the impact of factors such as crystallinity and orientation. The influence of above factors for different plastic materials, and other processing conditions such as temperature, humidity, continue to crystallization, the change of the internal stress of after molding, injection molding machine. Due to the injection molding process is the plastic from the solid powder or granular materials to melt and liquid to solid products process. Expect the melt from grain, again by the melt to the products, through middle temperature field, stress field, flow field and density field, in the field, under the joint action of different plastic thermosetting or thermoplastic, crystalline or non-crystalline, enhanced or not enhanced with different polymer structure such as morphology and rheological properties. All affect the field's factors will affect the physical and mechanical properties of plastic products, size, shape, appearance quality and accuracy. So, technological factors and the performance of the polymer, structure form and inner links between plastic products through plastic products. Analysis clear these inner link, to reasonably to injection molding processing technology, reasonable design and manufacture of moulds according to the drawing, and choose the injection molding processing equipment has important significance. Precision injection with normal injection molding in the injection pressure and injection rate also has difference, precision injection often adopts high voltage or super high pressure injection, high-speed injection for smaller molding shrinkage rate. Comprehensive the above various reasons, the design of precision injection molds in addition to consider the general mold design elements, must also consider the following: (1) using appropriate mold size tolerance; (2) prevents molding shrinkage ratio error; (3) to prevent plastic deformation; (4) to prevent demoulding deformation; (5) to make the mold manufacturing to minimize error; 6. Prevent mold precision error; All landowners keep mould precision. To prevent to produce molding shrinkage ratio error. Due to the shrinkage rate will change due to the injection pressure, therefore, for a single cavity mould, the cavity pressure inside the cavity should be consistent as far as possible; As for multi-cavity mold, mold cavity pressure should be slightly different. In a single cavity more gate or multi-cavity gate, must be in the same injection pressure, injection cavity pressure. Therefore, must ensure that the gate location is balanced. In order to make the cavity pressure inside the cavity is consistent, consistent with pressure near the entrance to the gate. Gate of pressure equalization is associated with flow resistance in flow channel. So, before the gate pressure reaches equilibrium, equilibrium should first make circulation. Because the melt temperature and mold temperature affect the actual shrinkage rate, so in the design of precision injection mold cavity, in order to facilitate the forming conditions were determined, must pay attention to the arrangement of the cavity.