Fig.6.8 Shell mould ready for pouring
当得到一个所需厚度的壳型时，翻斗旋转180度以使多余的砂子回落到斗中，留下如图6.7（d）中所示的与模型紧密接触的壳型，平均的壳型厚度取决于模型的温度和腹膜砂与型板的接触时间，实际所需的壳型厚度取决于浇注金属的温度和铸件复杂程度。通常这可以通过试验和错误分析方法达到.
Since the shells are thin, they may require some outside support so that they can withstand the pressure of the molten metal. A metallic enclosure to closely fit the exterior of the shell is ideal, but is too expensive and therefore impractical. Alternatively, a cast iron shot is generally preferred as it occupies any contour without unduly applying any pressure on the shell. With such a backup material, it is possible to reduce the shell thickness to an economical level.
由于壳型很薄，它们需要一些外部的支持以承受熔融金属液的压力，在壳型的外部固定一个金属外壳十分的理想，但是由于太昂贵而不合实际。相比之下，通常使用一种铸铁金属丸，其占去了所有的轮廓，除去了壳型上不应有的压力。
6.2.2 Die Casting 6.2.2 压力铸造
Die casting involves the preparation of components by injecting molten metal at high pressures into a metallic die. Die casting is closely related to permanent mould casting, in that both the processes use reusable metallic dies. In die casting, as the metal is forced in under pressure compared to permanent moulding, it is also called
'pressure die casting'. Because of the high pressure involved in die casting, any narrow sections, complex shapes and fine surface details can be easily produced.
压力铸造涉及到将熔融金属在高压下射入到金属铸型中制备部件。压力铸造与金属型铸造密切相关，与金属造型相比由于金属在压力下注入，其也被称为压力模型铸造，由于压力铸造中涉及到高压，所以所有的窄小部分、复杂形状以及精密表面结构零件制作便容易实现。
In die casting, the die consists of two parts. One called the stationary die or cover die which is fixed to the die casting machine. The second part called the ejector die is moved out for the extraction of the casting. The casting cycle starts when the two parts of the die are apart. The lubricant is sprayed on the die cavity manually or by the auto lubrication system. The two die halves are closed and clamped. The required amount of metal is injected into the die. After the casting is solidified under pressure the die is opened and the casting is ejected.
在压力铸造中，模具由两部分组成，一部分固定在压铸机上的被称为固定模或者凹压模，第二部分称为凸压模，当其移动时，铸件才能取出。当模具的两部分分开时铸件循环开始，润滑剂通常由人工或自动润滑系统洒到型腔内。两个半模进行合模并夹紧。所需量的金属注入到模型中，铸件在压力下凝固后，模型打开，铸件随即被取出。
The die casting machines are of two types: hot chamber die casting, and cold chamber die casting. The main difference between these two types is that in hot chamber, the holding furnace for the liquid metal is integral with the die casting machine, whereas in the cold chamber machine, the metal is melted in a separate furnace and then poured into the die casting machine with a ladle for each casting cycle which is also called 'shot'.
Fig. 6.9 Operation sequence of hot chamber process
压铸机有两种类型：热室压铸法和冷压铸造。两种类型之间主要的不同在于，在热室中，液态金属所用的保温炉是和压铸机一体的，然而在冷室机中，金属在单独的炉子中熔炼，然后每次浇注过程中用一个浇包将其浇入到压铸机中，这一过程又称为压射。
6.2.3 Investment Casting 6.2.3 熔模铸造
This is the process where the mould is prepared around an expendable pattern. Casting processes in which the pattern is used only once are variously referred to as \of the desired form out of wax or plastics (usually polystyrene). The first step in this process is the preparation of pattern for every casting made. To do this, molten wax which is used as the pattern material is injected under pressure of about 2.5 MPa into a metallic die which has the cavity of the casting to be made. The wax when allowed to solidify would produce the pattern. To this wax pattern, gates, runners and any other details required are appended by applying heat. 这是围绕一个可消耗的模型制作铸型的工艺过程，在这种铸造工艺中模型只使用一次，通常被冠以不同名称为“失蜡铸造”或者“精密铸造”工艺。在所有情况
下，他们包括用蜡或塑料（通常为聚苯乙烯）制作需要形状的模型。工艺的第一步是将要制作的铸件的模型准备阶段。在这一步中，用于做模型材料的熔融蜡注射入有将要制作铸件的腔形状的金属型中，当蜡凝固时生产出模型。对蜡模来讲，内浇道、直浇道和其他需要的结构通过作用热悬挂上去。
The process has been described as the lost wax, precision casting, and investment casting process. The last-dimensional name has been generally accepted to distinguish the present industrial process from artistic, medical, and jewelry applications. The basic steps of the investment casting process are as follows (Fig. 6.11): 1. Production of heat disposable patterns, usually in wax or plastic. 2. Assembly of these patterns onto a gating system.
3. Investing, or covering the pattern assembly with ceramic to produce a monolithic mold. 4. Melting out the pattern assembly to leave a precise mold cavity.
5. Firing the ceramic mold to remove the last traces of the pattern material, to fire the ceramic and develop the high temperature bond, and to preheat the mold ready for casting. 6. Casting.
7. Knock-out, cut off, and finishing.
Fig. 6.11 Old but modern investment casting with many new developments 熔模铸造的工艺的基本步骤如下：
1、热量可支配模型的制作，通常用蜡或塑料。 2、装配这些模型到一个浇注系统上。
3、熔模，或者用陶瓷覆盖装配模来生产一个整体铸型。 4、熔融装配模已得到精密的型腔。
5、烘烤陶瓷型以除去模型材料最后的痕迹，烘烤陶瓷型并使其高温结合，提前加热铸型以为铸造做准备。 6、铸造过程
7、敲落，切断和表面清理。 8、
6.2.4. Squeeze Casting 6.2.4 挤压铸造