Analysis of process parameters of sand casting compound mold

The analysis of the process parameters of the composite mold is the basis for the subsequent optimization design of the composite mold. Selecting the appropriate process parameters can ensure the forming quality of the casting and improve the casting productivity. Among them, the selection of casting process parameters is related to many factors, including casting alloy, casting size and casting acceptance conditions, which is embodied in the design of casting dimensional tolerance, machining allowance, casting shrinkage and other parameters. In the process design stage of casting, it is equally important to design the process parameters of mold reasonably.

The factors affecting the resource demand of Moldless sand casting have been analyzed, in which the discussion on the inherent properties of mold and mold casting coupling reflects the characteristics of process parameters to a certain extent. Specifically, the heat storage coefficient of the mold, the material of the molding sand, the proportion of the molding sand composition and the compactness of the molding sand are related to the mold itself. The setting of these process parameters is related to the selection of the casting method and the structural characteristics of the casting, and depends on the production process of the enterprise. In addition, the negative number of parting and sand core are the factors to be considered in the early stage of modeling. In order to avoid mold deformation during mold repair and drying, which leads to loose mold closing, it is usually necessary to set fire-resistant mud strips on the parting surface of the mold, which will increase the height of the mold cavity. Therefore, it is necessary to reasonably design the negative parting number of the mold and correct the height of the mold cavity. At the same time, in order to avoid the increase of sand core size and the decrease of casting wall thickness due to the self weight sinking of sand core during drying, it is necessary to reduce the size of core box. Because the composite mold is a mold design scheme based on the composite forming method, the sand core can be completed by the traditional core making process when necessary, so these factors also need to be taken into account. In addition, the mold process parameters related to the casting structure, such as the mold size, the minimum wall thickness of the mold, the machining allowance reserved by the mold for the casting and the division number of mold modules, need to be designed on the basis of completing the design of casting process parameters, which has high coupling.

In conclusion, according to the analysis of the characteristics of various process parameters of composite mold and the attribute relationship of mold process parameters, the process parameters of composite mold can be divided into three categories: independent process parameters of composite mold, correction process parameters of composite mold and coupling process parameters of composite mold, and are defined as follows:

Definition 1: independent process parameters of composite mold: a kind of parameters related to the properties of the mold are called independent process parameters of composite mold, such as mold heat storage coefficient, molding sand material, molding sand composition ratio and molding sand compactness.

Definition 2: composite mold correction process parameters: a kind of parameters with correction significance for mold cavity and sand core are called composite mold correction process parameters, such as negative parting number and negative sand core number.

Definition 3: compound mold coupling process parameters: in mold design, a kind of parameters related to casting structure are called compound mold coupling process parameters, such as mold size, minimum wall thickness of mold, machining allowance and division number of mold modules.