Firstly, the main material consumption of single casting technology and composite forming method in unit casting production is analyzed, as shown in Figure 1.
It can be seen from the figure that metal materials and molding materials are the main components of material resource consumption because they directly act on the forming of mold and castings. On the contrary, auxiliary materials and energy materials account for a relatively small proportion. Compared with traditional pattern modeling, sand mold 3D printing and optimized composite forming method reduce the total consumption of material resources to a certain extent. Specifically, in terms of metal materials, the design of different process parameters and the machining allowance of castings make the casting net weight different after casting. The net weights of traditional casting, sand mold milling, sand 3D printing and compound forming method (pre optimization) are 46.847kg, 43.414kg, 39kg and 42.159kg respectively.
The consumption of metal materials depends on the amount of molten iron. Compared with the traditional pattern modeling, the three methods reduce the consumption of metal materials respectively, resulting in the difference of final metal material consumption. Compared with the traditional pattern modeling, sand mold NC milling, sand mold 3D printing and composite forming methods reduce the consumption of metal materials by about 7.33%, 16.75% and 10.01% respectively. It should be noted that although recycled iron and scrap can be recycled, they are consumed for casting forming in the production process of unit castings, so they should also be counted as the consumption of metal materials. The optimized compound forming method further reduces the machining allowance of the casting and improves the yield of the casting to 85.52%. Therefore, the consumption of metal materials is reduced by about 5.04% compared with that before optimization.
In terms of molding materials, 468.155kg, 485.263kg and 413.881kg furan resin sand are invested in traditional pattern modeling, sand mold NC milling and sand mold 3D printing respectively. The actual consumption of molding sand is related to the enterprise’s old sand recovery process under the corresponding casting method. The recovery rate of old sand is 96.75%, 90% and 95%. The figure shows the actual consumption of molding sand. In the NC milling of sand mold, the sand block is prepared with the sand box as the forming carrier. The amount of molding sand depends on the specification and internal size of the sand box, and the milled molding sand also needs to be recycled. Combined with the old sand recovery rate, the modeling material consumption of sand mold NC milling is greatly increased compared with the traditional pattern modeling. The sand mold 3D printing gets rid of the limitation of the sand box, reduces the sand consumption between the mold and the sand box while controlling the mold wall thickness, so it reduces the investment of molding sand. In the original process design scheme of composite mold, furan resin sand and green sand are used at the same time, and based on 660mm × 660mm × The molding is completed under the specification of 300mm sand box. On the basis of ensuring that the mold strength reaches 3Mpa, the specification of sand box is reduced. Therefore, the input of molding materials is reduced by about 24.71% and 14.84% respectively compared with traditional pattern modeling and sand 3D printing, but the actual consumption of molding sand is increased, which is due to the recovery rate of old sand of molding sand. In the composite mold optimization process design scheme, the wall thickness and size of the mold module are further reduced. The reduced sand eating part in the sand box is filled with green sand. The green sand is not in direct contact with the liquid metal, and the actual consumption is 3.161kg under the recovery rate of 98.5%. In addition, the actual consumption of furan resin sand is 7.578kg, which is about 38.84% less than that of traditional pattern molding.
In terms of auxiliary materials, the steel shot, coating and inoculant consumption of the three casting methods are reduced to a certain extent compared with the traditional pattern modeling. Among them, the consumption of steel shot belongs to a long-term and slow process, and the amount of steel shot consumed by shot peening cleaning is evenly distributed to the unit casting, which is also a very small value. Disposable thermocouples are used as temperature measuring components to measure the temperature of molten iron, and the consumption is the same. The composite forming method consumes 0.006kg of wood mold resources per unit casting, accounting for only about 11% of the traditional pattern modeling. At least 140kg of wood can be saved in mass production of 3000 castings. The consumption of other auxiliary materials is mainly concentrated in the melting of molten iron and the covering process of coating layer. In addition, the water content in green sand has a direct impact on the compactness and strength of green sand, and its mass fraction is about 4.5%. Therefore, the demand for cooling water for the optimized composite mold is greatly increased to 9.482kg. In addition, the consumption of alcohol, natural gas and coke as input energy materials in the casting process is reduced to varying degrees compared with the traditional pattern modeling.