The mold consists of pouring molten metal into the mold (same as ingot process), and the mold cavity provides the final useful shape, after which only processing and welding are required according to specific application. Molds are usually classified according to the methods of making molds, the materials of making molds or the methods of entering molds. There are four basic types of casting processes:, permanent casting, die casting and centrifugal casting. Considering its economy, rationality and technology, sand casting is adopted in this design.
There are four types of sand casting mold: wet mold, dry mold, surface dry mold and self hardening mold. The selection of each mold needs to be determined according to the casting weight, structure and quality requirements, production batch and workshop production conditions and other factors. Wet mold is the most widely used mold. The basic characteristic of wet casting is that the sand mold does not need to be dried and there is no hardening process. Its main advantages are high production flexibility, high productivity, short production cycle, easy to organize flow production, easy to realize mechanization and automation in the production process, and low material cost. Generally, the medium and small-sized castings should choose the wet type as much as possible. Therefore, the design adopts the wet casting method.
Due to the high moisture content and low strength of the wet casting method, the defects such as scab, rat tail, sand sticking, air hole, sand hole and sand expansion are easy to occur in the casting. The following situations should be paid attention to when using the wet casting method:
1.When the casting has a large horizontal wall during pouring, sand inclusion defects are easily caused by using wet mold. Other sand mold shall be considered.
2.When the casting is too high and the static pressure of metal exceeds the compressive strength of wet mold, dry sand mold or self hardening sand mold shall be considered.
3.When too much cold iron is placed in the mold, wet mold should be avoided. Because the cold iron is rusted or cooled, the “water drop” will condense, which will cause pore defects after pouring. If it is necessary to use cold iron, the cold iron shall be preheated in advance, and the mold shall be closed and poured in time after being put into the mold.
4.The sand mold with a long molding process or a long time to wait for pouring should not be wet mold, because the wet mold will be air dried if placed for a long time, which will reduce the surface strength and prone to sand washing defects.
The parts of the support table are of rotary structure and have flat parting surface, so it is suitable for parting modeling. Due to its small production batch, it adopts manual molding and core making.
To sum up, the design adopts wet sand manual parting molding.