Welding-

In welding, two pieces of metals are permanently joined together by coalescence resulting from application of temperature and pressure. Depending upon the range of temperature and pressure used a wide variety of welding and allied processes are now available and used in manufacturing. The most commonly used welding methods are arc welding and gas welding.

Machining-

Machining essentially involves removal of excess material to get the desired shape, size, accuracy and finish of the product. In conventional machining processes, material removal is achieved through tool-work interaction. The tool used may be a single-point tool such as those used in turning, shaping and planning operations, or a multi-point tool like those used in milling and drilling operations. When bonded abrasives are used as a tool, the process is known as grinding.
A number of new machining methods have been developed which use new energy modes for achieving material removal. These machining methods have come to be known as unconventional machining processes and include electro discharge machining, electrochemical machining, ultrasonic machining and laser beam machining.

Forming-

In forming operations, the desired shape and size are obtained by plastically deforming the material in solid state. It basically makes use of the ability of materials, usually metals, to flow plastically when subjected to high stresses. Primary forming operations include forging, rolling, extrusion, wire drawing and deep drawing. These opertions are carried out either above the recrystallization temperature of the material being deformed.

Casting-

In casting processes the liquid metal is poured into the mould cavity of desired shape which on solidifying takes the shape of the cavity. Sand casting, investment casting, die casting and continuous casting are some of the commonly used casting processes.

1) Process-type manufacturing-

It involves continuous processing, that is the material goes through a series of process steps in a continuous manner which eventually gives the finished product. This type includes production of raw material and chemical products. The fabrication-type manufacturing involves production of discrete components and is achieved by changing the raw material into a final product using manufacturing processes and assembly operations.
The manufacturing processes that are used in fabrication-type manufacturing can be classified into five broad categories-
a) Casting
b) Forming
c) Machining
d) Welding
e) Heat treatement