Analysis and comparison of direct casting manufacturing process

Direct casting manufacturing process and traditional casting manufacturing technology, compared to direct casting manufacturing process has unparalleled superiority, it not only makes the casting process highly automated, flexible, agile, reduce the labour intensity of workers, but also technically breaks through many barriers of the traditional process, so that the design, manufacturing constraints are greatly reduced, especially in the following aspects: 

1.No model. In traditional casting production, pattern making is an important link. Models are generally made of wood, plastic, metal and other materials processed by hand or machine, sometimes need to be repaired by pliers, which is time-consuming and costly, and precision is not easy to guarantee. For some of the complex shape of castings, such as engine blades, ship propellers, automobile cylinder block, cylinder head, etc, Although some of the mould processing using CNC machine tools, profiling milling and other advanced equipment and technology, but due to the complexity of programming and tool interference on the geometric constraints have made it more difficult to increase the cost, resulting in a high, long cycle time; and the direct casting manufacturing process is completely avoided by the traditional casting manufacturing technology of the biggest defects, thus reducing the time required to shorten the production time of castings, thus reducing the time required to shorten the production time of castings. The largest defects, thus shortening the sand manufacturing time, reducing the cost of sand manufacturing and many other aspects, have made a qualitative leap in sand manufacturing technology.

2. Short production time. The manufacturing time of casting is from the end of casting design to the completion of manufacturing for casting before this period. The traditional method of manufacturing castings must be processed first mould, whether ordinary machining or CNC machining, the manufacturing cycle of the mould is relatively long. For large and medium-sized castings, the mould manufacturing cycle is usually calculated in months. Through the use of automatic computer processing, direct casting manufacturing process of information processing generally spends a few hours to tens of hours. In relation to the entire casting process, this period of time can be ignored.

3.Integrated modelling. Conventional moulding due to the need to remove the model from the casting, so it must be separated along the casting of the largest cross-section (parting surface), that is, the use of parting moulding. This often limits the freedom of casting design, some profiles and cavities complex casting had to use more than one parting surface, so that modelling, combined with the difficulty of the process greatly increased, easy to make the casting wrong box, flying edge and other defects, increasing the cleaning workload and machining. Direct casting manufacturing process using stack forming principle, there is no moulding process, so the design of the parting surface is not a major obstacle. In fact, the design of the parting surface can be adjusted as required, not in the casting with the largest cross section, but in the casting of non-critical parts. For some castings it is possible to use the integrated moulding method, i.e. the top and bottom moulds are formed at the same time. Integration of the main advantage of moulding is the elimination of the box, reduce the design constraints and machining, so that the casting of the dimensional accuracy is easier to control.

4. Type, core forming at the same time. As a result of discrete / stacking forming principle, so direct casting manufacturing process is easy to achieve the type, core forming at the same time. Traditional process for the mould considerations, some structural design within the cavity forming core, type, core separate manufacturing, and then under the core will be assembled together, the assembly process requires accurate positioning, but also must take into account the stability of the core. Direct casting manufacturing process to produce the casting, the core can be stacked at the same time, without the core assembly, positional accuracy is easier to ensure.

5. No pulling mould inclination. Since the direct casting manufacturing process is a direct stacking modelling without moulds, there is no mould pulling problem, so the constraints such as mould pulling slope, which are essential for the traditional casting design, lose their significance, and the weight of the casting can be reduced as a result.

6. Free-form (curved) moulds can be produced. In the traditional process, it is difficult to ensure the accuracy of the mould produced by ordinary machining methods; the programming of CNC machining is complicated, and the obstacles such as tool interference cannot be overcome. Therefore, it is not easy to guarantee the accuracy of castings with free-form surfaces or curves. And based on the principle of discrete / stacked forming direct casting manufacturing process, there are no forming geometric constraints, and thus can easily achieve any complex shape of modelling, and easy to ensure accuracy.

7. Can produce a combination of parts (functional parts). Due to the limitations of the traditional casting process, in the parts design and manufacturing process, a functional part must be divided into several parts, respectively, casting and processing, and then assembled. And based on the principle of discrete / stacked forming direct casting manufacturing process, no model, there is no mould problem on the shape of the parts limitations, can be combined with multiple parts under the traditional process can be able to parts of the one-time forming, reducing the machining and assembly workload, completely eliminated the machining and assembly errors caused by the loss of precision. It can be seen that this new process can also bring about changes in design thinking, can greatly improve production efficiency, reduce manufacturing costs.

8.Casting CAD body. In the casting CAD model based on computer drawing casting: compensation for shrinkage of the size of calibration, add rounded corners; at the same time to determine the number of casting and casting system type. Shrinkage, deformation of the casting manufacturing process through finite element simulation and error data statistics, you can achieve early, multi-loop, closed-loop control of the error feedback system; further available flow / hardening software to simulate the original CAD model to check the design and process parameters to determine whether it is reasonable, in order to predict, find and solve a variety of problems in the casting process. This is the realisation of the casting process of computer-integrated manufacturing.

In today's technological innovation, technological integration of the background, the rapid prototyping method into the traditional casting production, will produce a more adaptive to the modern economic and social development of the new casting process, but also the upgrading of the traditional casting process to improve play a good role in helping the casting industry to achieve scientific development, sustainable development.