Production of a high-quality casting is conditioned by an appropriate design implemented by a designer. When developing a design, designer has to take into account manufacturability of the casting, and respect the specific rules for the casting design. Manufacturability means that the proposed component must be suitable for casting production. A precondition for the successful production of high-quality castings is the cooperation between a part designer and a production engineer ever since the design stage. The basic steps for the casting production are performed in the frame of the production engineering department, in which the optimal production method is determined, and the production documentation of casting is processed. The fundamental documents include a “split casting drawing” and a “production procedure of the casting”. These documents are the essentials for the manufacture of the patterns and the mould. In some special cases, a separate pattern drawings are also prepared.
The split casting drawing is a design drawing of a part, supplemented by the additional data determining the requirements for the pattern and the moulding method. A special feature of the drawing documentation is that it is made in colour. The principles of graphical representation is prescribed by the STN 01 3061 Standard. The key step in the design is the correct selection of the casting position in the mould, which determines the selection of the parting line of the mould and of the pattern. The choice of the casting position and the parting line within the mould influences the final casting accuracy and the complexity of the pattern, while simultaneously determining the labour intensity, as well as the complexity of the moulding process and consumption of the liquid metal, and thus the total cost of the casting production. The overall solution of the gating system, the size and the distribution of feeders depend also on the position of the casting in the mould. Further step in the preparation of the casting drawing is to determine the number and position of the cores and the order of their insertion into the mould. All allowances, drafts, and fillets are included into the drawing. Its sizes are prescribed by the relevant standards (STN 01 4980, STN 01 4470, STN 04 2021, STN 01 4909) and depend on the following factors: degree of casting accuracy, dimensions and location of relevant surfaces, material of the pattern and thickness of the casting wall. Degree of the casting accuracy depends on the production method used for the mould (STN 01 4470). The gating system, feeders and vents are also drawn in and dimensioned in the split casting drawing. Special attention must be paid to the design and calculation of the gating and feeding systems to ensure the production of quality castings.
Production procedure of the casting is a summary of the binding directives and data that unambiguously determine the optimal conditions of the casting production. Besides the production of casting itself, it is also used as the basis for the economic analysis of production, determination of material consumption, number of employees, setting of performance standards, setting of demands for machinery and so on. The production procedure of a casting is worked out on a standard form, supplemented by the necessary number of attachments where necessary. The form also includes a draft of the casting situated in the mould, regarding various views and sections.
Computer-aided design and modelling, as well as modern techniques for Rapid Prototyping can provide powerful assistance in further reducing the costs and lead times during the casting design stages. Today, engineers have access to a lot of software assisting in the design, manufacture and management tasks associated with the casting projects. The maximum benefit can be achieved via the CAD/CAE/CAM software, if the pattern design, inspection, and manufacture are fully integrated. The CAD/CAE/CAM integrated system can shorten the cycle of the casting design and manufacture, and result in the production of high-quality castings in a shorter time. A design of an optimal construction of a casting is a complicated process requiring cooperation of a lot of specialists, a designer and a casting engineer in particular. Utilisation of the CAD/CAE/CAM software mostly facilitates and speeds up design revisions. The design revisions are expensive and time consuming. They are rather common, since the product designers’ knowledge of casting processes is quite limited. A lot of designers do not know how to evaluate manufacturability. In a conventional approach, the problems appear at the manufacturing stage, when it is much more expensive to incorporate changes than at the design stage. Just the application of the CAD/CAE/CAM system makes the communication between a designer and a casting engineer easier; it facilitates electronic exchange of information between stakeholders.
The first step of manufacturing engineering supported by the CAD/CAE/CAM systems is generating a geometric model of the component in a computer with CAD (Computer-Aided Design). There is a lot of software for modelling the components, such as AutoCAD, AutoDesk Inventor, CATIA, Solid Edge, SolidWorks, etc. Once the part model is generated, it can be used for many different applications. These include for example CAE analysis (Computer-Aided Engineering) for the simulation of stress, heat transfer, vibration, fatigue and fracture etc., used to optimize the functionality and weight of the component. This step is followed by the design of the pattern, cores, gating system and feeders. The design of the component is adapted regarding the manufacturability. All changes in size or shape of the components have to be consulted with stakeholders. After adjusting the shape and dimensions of the component, the computer model is used as an input for the casting simulation software (AutoCAST, FLOW-3D, MAGMASoft, Pro/CAST, SOLIDCast, etc.). The casting simulation may include mould filling and casting solidification, both useful for optimizing the design of gating and feeding systems. It allows predicting the filling and the solidification, and determining the places where shrinkage cavities and other defects may origin. After the casting simulation process, the pattern model is sent to a CAM (Computer-Aided Manufacturing) program to plan the CNC cutter paths and simulate the machining operation. Another possibility for rapid production of patterns is use of the Rapid Prototyping technologies.