1 Rapid investment casting
Investment casting, also known as “lost wax casting”, has a long history in China. It is a kind of casting technology with little or no cutting. It is an excellent technology in the casting industry and a special casting method without parting surface. 3D printing technology is combined with traditional investment casting to form rapid investment casting (RIC). Since the advent of 3D printing technology, foundry workers have combined it with investment casting to innovate theand obtain good benefits. At present, three-dimensional printing technology can be used to produce die, pattern and shell respectively, forming different rapid investment casting technology routes.
The process of casting gas turbine blades with traditional casting technology is complex, long cycle and high cost. Chen Junyu et al. Used 3D printing melt deposition technology to print ABS model to obtain a complete blade shell, and used industrial endoscope to test the inner part of the cavity before pouring metal liquid, Three dimensional optical scanning method is used to detect the deviation value of the overall dimension of the casting and the key dimension of its blade section, and finally the parts that meet the design requirements are cast, which provides a new method with short time, low cost and high reliability for the investment casting of gas turbine blade samples. Liu et al. Used the method of light curing 3D printing to build the shell making method of investment casting and integral shell injection mold to prepare titanium alloy implants . The titanium alloy implants customized by this method can accurately reflect the individual characteristics of patients. The chemical composition, mechanical properties and precision of the customized implants meet the corresponding national standards and pharmaceutical industry standards, More than 100 clinical cases have been completed. Altaf khurram et al. Used the combination of thermal spray 3D printing and investment casting technology to manufacture polycrystalline diamond bit, so as to achieve faster manufacturing of polycrystalline diamond bit without affecting the mechanical properties of the bit. From left to right, optimized polycrystalline diamond bit CAD model, top and bottom wax mold, assembly wax mold and manufactured polycrystalline diamond bit are respectively used. The traditional manufacturing process may be a long time and high cost for the development of PCD bits. Through rapid investment casting, the rapid, low-cost and high-quality PCD bit manufacturing can be realized.
Sand casting is a rapid sand casting (RSC) formed by combining 3D printing technology with traditional sand casting. The manufacturing process includes direct casting and one-time conversion. The one-time conversion process is shown in Figure 5, including three steps of prototype design and manufacturing, sand mold modeling and pouring. Direct sand casting is usually made by 3DP or SLS direct forming sand mold for. Yang Yongquan et al. Studied the inkjet sand mold 3D printing process, and cast the four cylinder engine cast iron cylinder block. The inkjet sand mold 3D printing process has the advantages of high efficiency, low cost, low gas output and good permeability. Zhao Kaifa et al. Used SLS technology to directly form sand core, which has the advantages of fast response, short manufacturing cycle, high flexibility, good stability, integrated manufacturing of sand mold and sand core and the ability to produce any complex shape, etc., and has a significant role in promoting the rapid trial production and manufacturing level of large-scale complex castings, It shows great potential to solve the production of some key castings in the fields of aerospace and automobile.
Snelling et al. Studied 3D printing combined with sand mold casting to produce light honeycomb structure metal materials. Honeycomb structure can provide high specific strength, good impact absorption, heat insulation and sound insulation performance, and has a wide range of applications in aerospace, industry, medicine and other fields. However, the traditional manufacturing process has a stress concentration area at the metal joint, which has a great impact on the material performance, The author can overcome this shortcoming by making light honeycomb structure metal material by 3D printing sand mold casting. The casting can be used in the applications of light weight, high strength, impact resistance and heat insulation. Fresques et al. Summarized the development of the combination of 3D printing and sand casting, which has guiding significance for the development of rapid sand casting.