The rapid prototyping manufacturing of mold and the pouring production of sand castings will be carried out according to the early design scheme. The design scheme is verified and compared through actual production to determine the optimal design scheme. Analyze and solve the problems in the process of rapid prototyping manufacturing, and test the size, internal and external quality and mechanical properties of the final sand castings.
According to the three designed parting and sand mold manufacturing process schemes, the sand casting manufacturing and core assembly are compared. The advantage of design scheme 1 is that it has high integration, minimizes the positioning of sand core, and is conducive to improving the accuracy of sand castings. The disadvantage is that due to the high degree of integration, especially the water jacket core and airway core are concentrated in the base core, the sand core is easy to be cleaned in place, resulting in the decline of the surface quality of sand castings. In addition, due to the high integration of sand core, it is more difficult to clean. Once it is damaged, the processing cycle increases rapidly. In addition, design scheme 1 is inconvenient to work when implementing process measures such as cold iron and exhaust.
Design scheme 2 reduces the integration of sand core and can better complete the cleaning and the implementation of subsequent processes. However, No. 1 top core and No. 3 water jacket core are deformed during secondary curing, and additional support is required. The main problem is that the results of all sand molds and sand cores after parting are complex, which can not be manufactured by digital Moldless casting process, and the overall manufacturing cycle is long.
Design scheme 3 can use two processes to manufacture the casting sand mold at the same time, so the overall manufacturing cycle is shortened. And the subsequent process schemes such as cold iron and exhaust are easier to realize. The disadvantage is that the positioning times are increased, but through the test, the accuracy of core assembly meets the dimensional accuracy requirements of sand castings. Therefore, scheme 3 is finally selected.
| Casting name | Casting process | Mold name | Mold manufacturing process |
| Aluminum alloy cylinder head of engine | Sand core assembly gravity casting | Base core, water jacket core, oil duct core, inlet duct core and exhaust duct core Side core 1 / 2, end core 1 / 2 | Laser selective sintering coated sand Processing self hardening sand by digital Moldless casting |
| Cast iron engine block | Sand core assembly gravity casting | Upper mold and lower mold Crankcase 1 / 2 / 3, end core 1 / 2 Water jacket core, top cover core and oil passage 1 / 2 | Processing self hardening sand by digital Moldless casting Laser selective sintering coated sand 3D inkjet printing sand core |
| Aluminum alloy engine chain chamber cover | Gypsum mold precision casting | Integral wax model prototype | Waxing after selective laser sintering PS powder |
According to the previous simulation results, in the actual production process, the solutions of chill and exhaust channel of rapid prototyping sand mold are formulated, and the size control solutions of casting sand core and wax mold are formulated. The casting of cast iron cylinder block and aluminum alloy cylinder head is completed by sand casting process, and the casting of chain chamber cover is completed by wax mold casting process. The size, internal quality and performance of the casting are tested and analyzed, and qualified samples are obtained. See the table for the casting process adopted by the three sand castings and the scheme of rapid prototyping manufacturing process of the mold.