The process of mold design is generally like this: from the user to the plastic product drawing (which may be two-dimensional or three-dimensional), the mold design engineer considers the appropriate structure according to the type, characteristics and shape of the product. That is, the plastic Pieces can be formed by using what kind of mold structure. In this process, the structural design engineer also needs to select the type, size, gate type, quantity, size, location of the runner and determine the number and size of the runner according to some specific requirements of the product. In addition to being structurally sound, the designed mold is also feasible in terms of casting and cooling systems.
Obviously, mold design is very demanding on structural design engineers. He not only has experience in structural design, but also has a lot of knowledge in molding materials and molding processes, or the success or failure of the design depends largely on the experience of the mold designer. Even though the design engineer has good experience in mold design, he still faces many new problems, because the actual product is often kaleidoscopic. Sometimes subtle changes or specific product requirements can make an existing experience unavailable, or even if available, it cannot be verified prior to actual testing. This leads to an important design-correction-redesign feature of the mold design process. How to reduce the number of cycles in the process so that the initial design achieves or approximates the combined result is of great significance in practice.
CAE analysis is an ideal tool to solve the above problems. The reason is that the tool is based on a relatively accurate mathematical model and thus can approximate the results of actual production practice. In addition, the computational speed allows multiple gating and cooling systems to be executed before the actual test. Evaluate until optimization, thereby shortening design and manufacturing cycles and improving quality.
This article presents some of the issues and practices noted in CAE analysis, with examples.
(1) Clear analysis requirements and priorities. The purpose of CAE analysis is different for different products. For appearance parts, injection molding defects that affect appearance such as welding marks are not allowed on the surface; for parts that do not appear, the position of sintering marks is not important, but if the product has a strict assembly relationship, the allowable warpage and deformation amount become the main pursuit The goal. In addition, it is generally required that all items meet the requirements of flow balance and uniform filling. In practice, it is difficult to satisfy multiple requirements at the same time. In most cases, it is mainly to satisfy a major requirement. On this premise, other requirements are met. Therefore, on the basis of clear analysis requirements, it is also necessary to distinguish which are the main requirements of this analysis.
After determining the requirements and priorities of the analysis, it is necessary to initially determine which parameters are modified or changed. For example, the main factors affecting the position of the weld marks are the position of the gate and the shape characteristics of the product. Generally, it is not allowed to change the shape of the product; the main factor affecting the warpage deformation is the shape of the product. From a process point of view, the injection pressure is too large. , Too long pressure holding time and uneven cooling will lead to excessive warpage. In addition to the characteristics of the product structure itself, the size of the gate and runner can directly affect the injection pressure in the cavity. The size and arrangement of the cooling channels directly affects the uniformity of cooling. These factors indirectly affect the deformation and warpage of the product.
(2) Analysis of product structure characteristics. Using professional CAE analysis software for injection flow simulation requires geometric modeling first. Generally, this process takes a long time. For this reason, the geometric model should be appropriately simplified to shorten the modeling time and improve the calculation efficiency. At present, some CAE software has the function of directly importing the solid model from professional CAD software, and then using the specific neutral extraction tool in the software to extract the neutral surface for calculation, but when the product structure is more complex, it will be generated. many problems. Therefore, it is still important to simplify details that do not significantly affect the computational results.
