Investment casting :

Investment casting (lost-wax process) yields a finely detailed and accurate product, but mechanical properties are not good since the process involves slow cooling.

Polystyrene foam is also used in investment casting—see lost-foam casting.

After a variable lead time, usually weeks, 1–1000 pieces/hour-mold can be produced in the mass range 2.3–2.7 kg. Items up to 45 kg and as light as 30 g are possible for unit production.

The process starts by creating an injection die to the desired specifications. This die will be used to inject wax to create the patterns needed for investment casting. The patterns are attached to a central wax sprue, creating an assembly, or mold. The sprue contains the fill cup where the molten metal will be poured into the assembly.
The wax assembly is now dipped multiple times in a ceramic slurry, depending on the shell thickness desired. A layer of fine sand (usually zircon) is added on top of each ceramic layer. This process will be repeated until the desired shell is created.

After the shell is created to the specifications desired, the wax must be removed; this is normally achieved using an autoclave. This is where the name "lost-wax process" comes from. This leaves an impression of the desired castings, which will be filled with metal. Before being cast, however, the shells must be heated in a furnace so they do not break during the casting process.

Next, the desired metal is poured into the hot ceramic shell. The metal fills each part on the assembly, and the central sprue cavity and fill cup. The individual parts will be removed after the mold cools and the shell is removed. The shell is generally removed with water-blasting, although alternate methods can be used. What remains are the cast metal parts, but they are still attached to the sprue assembly. The individual parts are removed by cold-break (dipping in liquid nitrogen and breaking the parts off with hammer and chisel) or with large cutoff saws.

Most investment castings need some degree of post casting machining to remove the sprue and runners, and improve surface finish. Grinding operations are perfomed to remove the gate. Parts are also inspected to make sure they were cast properly, and if not are either fixed or scrapped. Depending on the investment casting facility and specifications, more finishing work can be done on-site, sub-contracted, or not done at all.

Investment casting yields exceedingly fine quality products made of all types of metals. It has special applications in fabricating very high-temperature metals such as alloy steels or stainless steels, especially those which cannot be cast in metal or plaster molds and those which are difficult to machine or work.

Investment casting is often used in the aerospace and power generation industries to produce single crystal turbine blade, which exhibit superior creep resistance to equiaxed castings. A combination of slow cooling rates, seed crystals, and an elaborate sprue and runner system referred to as a "pigtail" are used to produce single crystal castings.

Nonexpendable mold casting :

Nonexpendable mold casting differs from expendable processes in that the mold need not be reformed after each production cycle. This technique includes at least four different methods: permanent, die, centrifugal, and continuous casting.

Permanent mold casting :

Permanent mold casting (typically for non-ferrous metals) requires a set-up time on the order of weeks to prepare a steel tool, after which production rates of 5-50 pieces/hr-mold are achieved with an upper mass limit of 9 kg per iron alloy item (cf., up to 135 kg for many nonferrous metal parts) and a lower limit of about 0.1 kg. Steel cavities are coated with refractory wash of acetylene soot before processing to allow easy removal of the workpiece and promote longer tool life. Permanent molds have a life which varies depending on maintenance of after which they require refinishing or replacement. Cast parts from a permanent mold generally show 20% increase in tensile strength and 30% increase in elongation as compared to the products of sand casting.

The only necessary input is the coating applied regularly. Typically, permanent mold casting is used in forming iron-, aluminium-, magnesium-, and copper-based alloys. The process is highly automated.

Die casting :

Die casting is the process of forcing molten metal under high pressure into the cavities of steel moulds. The moulds are called dies. Dies range in complexity to produce any non-ferrous metal parts (that need not be as strong, hard or heat-resistant as steel) from sink faucets to engine blocks (including hardware, component parts of machinery, toy cars, etc). In fact, the process lends itself to making any metal part that:

must be precise (dimensions plus or minus as little as 50 µm--over short distances),
must have a very smooth surface that can be bright plated without prior polishing and buffing,
has very thin sections (like sheet metal--as little as 1.2 mm),
must be produced much more economically than parts primarily machined (multicavity die casting moulds operating at high speed are much more productive than machine tools or even stamping presses),
must be very flexible in design; a single die casting may have all the features of a complex assembly.
If several machining operations would be required or assembly of several parts would be required (to make a finished part), die casting is probably far more economical. This level of versatility has placed die castings among the highest volume products made in the metalworking industry.

Common metals used in die casting include zinc and aluminum. These are usually not pure metals; rather are alloys which have better physical characteristics.

In recent years, injection-molded plastic parts have replaced some die castings because they are usually cheaper (and lighter--important especially for automotive parts since the fuel-economy standards). Plastic parts are practical (particularly now that plating of plastics has become possible) if hardness is not required and if parts can be redesigned to have the necessary strength.

Process :

There are four major steps in the die casting process. First, the mould is sprayed with lubricant and closed. The lubricant both helps control the temperature of the die and it also assists in the removal of the casting. Molten metal is then injected into the die under high pressure. The high pressure assures a casting as precise and as smooth as the mold. Typically it is around 100 MPa (1000 bar). Once the cavity is filled then the pressure is maintained until the casting has become solid (though this period is usually made short as possible by water cooling the mold). Finally, the die is opened and the casting is ejected.

Equally important as high-pressure injection is high-speed injection--required so the entire cavity fills before any part of the casting solidifies. In this way, discontinuities (spoiling the finish and even weakening the casting) are avoided even if the design requires difficult-to-fill very thin sections.

Before the cycle can be started the die must be installed in the die casting machine (set up) and brought to operating temperature. This set-up requires 1-2 hours after which a cycle can take anywhere between a few seconds to a few minutes depending on the size of the casting. Maximum mass limits for magnesium, zinc, and aluminium parts are roughly 4.5 kg, 18 kg, and 45 kg, respectively. A typical die set will last 500,000 shots during its lifetime with lifetime being heavily influenced by the melting temperature of the metal or alloy being used. Aluminum and its alloys typically shorten die life due to the high temperature of the liquid metal resulting in deterioration of the steel mold cavities. Molds for die casting zinc last almost indefinitely due to the lower temperature of the zinc. Molds for die casting brass are the shortest-lived of all. This is despite, in all cases, making the mold cavities out of the finest "hot work" alloy steel available.

A shot occurs every time the die is filled with metal. Shots are different from castings because there can be multiple cavities in a die, yielding multiple castings per shot. Also the shot consists not only of the individual castings but also the "scrap" (which, unlike in the case of scrap from machining, is not sold cheaply; it is remelted) that consists of the metal that has hardened in the channels leading into and out of the cavities. This includes, for example, the sprue, runners and overflows. Also there is usually some unplanned-for thin scrap called flash, the result of molds not fitting together tightly.

Molding (process) :

Molding is the process of manufacturing by shaping pliable raw material using a rigid frame or model called a mold.
A mold or mould is a hollowed-out block that is filled with a liquid like plastic, glass, metal, or ceramic raw materials. The liquid hardens or sets inside the mold, adopting its shape. A mold is the opposite of a cast (see casting). The manufacturer who makes the molds is called moldmaker or mouldmaker. A release agent is typically used to make removal of the hardened/set substance from the mould easier.

Types of molding include:
	Powder metallurgy and ceramics		Compaction plus sintering
	Plastics		Injection molding
	Compression molding		Transfer molding
	Extrusion molding		Blow molding
	Rotational molding		Thermoforming
	Vacuum forming, a simplified version of thermoforming		Reaction Injection Molding
	Laminating		Expandable bead molding
	Foam molding		Rotomolding
	Vacuum plug assist molding		Pressure plug assist molding
	Matched mold