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Investment casting has many advantages, but it also has the disadvantages of multiple processes, complicated process, long production cycle, and many factors affecting the quality of castings. It restricts the application and development of precision casting to some extent. With the rapid development of computer technology, the application of computer technology in precision casting, from the structural design of the precision casting, the formulation of the process to the design and manufacture of press-type, wax molding, shell manufacturing, core manufacturing, etc. The production has brought about great changes.
1. Application of numerical simulation technology of computer technology in structural design and process planning of investment castings
Investment castings have evolved toward lighter, thinner, and finishing. In recent years, net-shape or near-net-shape castings have been proposed to take advantage of investment casting to meet the demands of modern industry for high-quality parts. This requires that the structure of investment castings is more reasonable, the developed process plan is more optimized, and higher and higher requirements are placed on the precision casting technology.
2. The traditional fine casting production process includes the following five steps:
(1) The casting user gives the design blueprint to the foundry;
(2) The foundry makes a budget and proposes improvements to the design from the perspective of facilitating production and reducing costs;
(3) foundry design casting process equipment;
(4) The foundry has issued tooling drawings to the mold shop or modeling workshop;
(5) casting castings, casting inspection.
In the process of casting structure design, pressure design, injection wax process parameter formulation, and gating system, the traditional production mainly depends on the actual work experience of engineering technicians and lacks scientific theoretical basis. Especially for complex parts and important parts, it is often necessary to repeatedly modify the casting structure, press-type or casting process scheme to achieve the final technical requirements in the production. The computer has a powerful computing capacity and graphic processing capabilities, and can be numerical analysis technology, database technology The visualization technology combines classical heat transfer, flow, and solidification theories. By simulating the filling, solidification, and cooling of castings, the flow field, temperature field, and stress field of the precision casting process are analyzed to predict the casting organization and many casting defects such as cold septum and shrinkage cavities. , thermal cracking and deformation. Therefore, through parallel engineering, computer technology can be used to simulate the structural and casting process of castings, and provide effective basis for technicians to design reasonable casting structures and determine reasonable process schemes, thus avoiding the traditional structure of relying on experience. The blindness of design and process development can shorten the production preparation cycle and save test production costs. The numerical simulation process is shown below:
2. Application of Rapid Prototype Manufacturing Technology in Pressure Forming and Investment Manufacturing
With the advent of rapid prototyping technology, the manufacturing cycle of press-type and investment molds has been greatly shortened. The so-called rapid prototyping is to first form a three-dimensional CAD data file of a investment casting on a computer, cut it into many thin slices along the height direction, and then manufacture and combine them in order to form a three-dimensional shape product.
(1) Fabrication of pressure profile by rapid prototyping
According to the molding method, the rapid prototyping molding method can be divided into two types: one is to use a rapid prototyping method to make a resin or wax master (prototype), and then use it to make epoxy resin. Or silicone rubber pressure type. This method can produce compaction to meet the production of small batch castings. For example, the surface of the plastic master mold produced by the SLA method is sprayed with a metal layer of about 2 mm in thickness, and epoxy resin is filled in the back to make a metal-epoxy resin composite pressure type, which can satisfy the production of precision castings with hundreds of batches.
Another method is based on the geometric model of the compression-type block produced by the CAD system, and the resin pressure type is directly made by SLA, SLS and other methods. The SLS method is used to make the press model by changing the processing object from resin powder to steel powder with a thin layer of thermosetting resin on the surface. After laser sintering, it is bonded into a pressure type, and then the product is baked, the resin is burned off, and the copper solution is finally used. When infiltrated, a pressure profile similar to that of metal can be obtained.
(2) Rapid Prototyping Method Manufacturing Investment Model
Rapid prototyping methods—SLA method, SLS method, FDM method, and LOM method—can all be used to rapidly manufacture the investment model. Wax molds made using SLS method and FDM method can be used directly for the investment mold used for casting production; paper products produced by LOM method need to be coated with polyurethane on the outer surface before being used as a "fusing mold" for shell making. Or coat the paper product directly with a ceramic shell and then burn the paper mold. The SLA method uses a new type of resin to produce a resin pattern. The uncured resin is poured out to form a hollow mold. After hardening, the resin outlet is sealed with wax, and then a wax casting system is installed to make a shell.
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