Casting process design is the core link in casting production. To complete casting process design tasks reasonably and effectively, casting process designers must not only be familiar with the production process equipment conditions of the enterprise but also apply their basic knowledge of casting process design to analyze the castability of the part structure. Only when the part structure meets the casting process requirements and advanced and reasonable casting processes and equipment are adopted can high-quality castings be produced.
For sand casting, it is essential to select appropriate molding and core-making methods, as well as the pouring position and parting surface, based on the structural characteristics and technical requirements of the part, considering the production batch of the casting. The casting process plan should be determined, sand cores designed, and appropriate process parameters such as machining allowance and casting shrinkage rate selected. This ensures the reliability and stability of casting quality, striving to achieve the goals of high quality, high efficiency, low cost, and minimal pollution.
Castability of Part Structure
The castability of a part structure refers to the extent to which the part's structure meets the requirements of the casting process, facilitates ensuring casting quality, and simplifies production operations. The analysis of the castability of a part structure primarily focuses on two aspects: avoiding defects and simplifying the process. It involves reviewing the product structure and technical economy based on the part drawing to ensure the reliability and stability of casting quality while reducing production costs. Examining the castability of a part structure serves two main purposes. First, it checks whether the part structure itself meets the casting process requirements. Designers often consider the part's function but overlook casting process requirements. If structural design issues are identified during review, communication with relevant personnel from the design and user units is necessary to improve the structure while ensuring usability. Second, under the given part structure conditions, it considers potential casting defects that may arise during production and implements corresponding preventive measures during process planning and detailed design.
The steps for designing cast parts mainly include:
- Functional design;
- Modification and simplification of the design based on casting experience;
- Metallurgical design (selection and suitability of casting materials);
- Economic considerations.
In some cases, the technical and economic benefits brought by improving structural manufacturability can be comparable to the effects of rationalization, mechanization, and automation of production processes. However, when analyzing the castability of a part structure, priority must be given to ensuring casting quality and usage requirements, avoiding a one-sided focus on simplifying the process. The requirements for castability are closely related to the type of alloy and casting method. Special casting methods, such as investment casting and die casting, have both similarities and differences with sand casting in terms of structural castability requirements. Similarities include requirements for reasonable wall structures, minimum wall thickness, and minimizing or eliminating thermal influences in wall connections. Special requirements arise from the unique characteristics of these processes. This chapter primarily analyzes the castability of part structures in sand casting. For requirements related to special casting methods, please refer to relevant materials.
