Division of Labor, Assembly Line, Mass Production

Division of labour is the specialisation of cooperative labour in specific, circumscribed tasks and roles, intended to increase the productivity of labour. Historically the growth of a more and more complex division of labour is closely associated with the growth of total output and trade, the rise of capitalism, and of the complexity of industrialisation processes. Later, the division of labour reached the level of a scientifically-based management practice with the time and motion studies associated with Taylorism.
The productivity gains of the division of labor are important within any type of production process, ranging from pin manufacture to software production to legal practice and medical care.
The division of labor makes trade necessary and is the source of economic interdependence.

The assembly line concept was not "invented" at one time by one person, and no one person is the "father" of it. It has been independently redeveloped throughout history based on logic. Its exponentially larger development at the end of the 19th century and beginning of the 20th occurred among various people over decades, as other aspects of technology allowed. The development of toolpath control via jigs, fixtures, and machine tools (such as the screw-cutting lathe and milling machine) during the 19th century provided the prerequisites by making interchangeable parts a practical reality. Before the 20th century, the way that most manufactured products were made was that a single craftsman or team of craftsmen would create each part of a product individually by hand, using their skills and such tools as files and knives, and assemble them together into an assembly, making cut-and-try changes in the parts so that they would fit and work together (the so-called English System). The transition to other methods began as creativity and logic took advantage of the opportunities that the aforementioned machining developments presented. Thus, before the modern assembly line took shape, there were prototypical forms in various industries.

Mass production (also called flow production, repetitive flow production, or series production) is the production of large amounts of standardized products on production lines.
It was popularized by Henry Ford in the early 20th century, notably in his Ford Model T.
Mass production typically uses moving tracks or conveyor belts to move partially complete products to workers, who perform simple repetitive tasks to permit very high rates of production per worker, allowing the high-volume manufacture of inexpensive finished goods. Mass production is capital intensive, as it uses a high proportion of machinery in relation to workers. With fewer labour costs and a faster rate of production, capital is increased while expenditure is decreased. However the machinery that is needed to set up a mass production line is so expensive that there must be some assurance that the product is to be successful so the company can get a return on its investment. Machinery for mass production such as robots and machine presses have high installation costs as well. Thus, mass production is ideally suited to serve large, relatively homogenous populations of consumers, whose demand would satisfy the long production runs required by this method of manufacturing. As such, it is not surprising that, given a number of other factors, mass production first became prevalent in the United States.
One of the descriptions of mass production is that the craftsmanship is in the workbench itself, not the training of the worker; rather than having a skilled worker measure every dimension of each part of the product against the plans or the other parts as it is being formed, there are jigs and gauge blocks that are ready at hand to ensure that the part is made to fit this set-up. It has already been checked that the finished part will be to specifications to fit all the other finished parts - and it will be made quicker, with no time spent on finishing the parts to fit one another. This is the specialized capital required for mass production; each workbench is different and each set of tools at each workbench limited to those necessary to make one part. As each of these parts is uniformly and consistently constructed, interchangeability of components is thus another hallmark of mass produced goods.

Use of assembly lines in mass production
Mass production systems are usually organized into assembly lines. The assemblies pass by on a conveyor, or if they are heavy, hung from an overhead monorail.
In a factory for a complex product, rather than one assembly line, there may be many auxiliary assembly lines feeding sub-assemblies (i.e. car engines or seats) to a backbone "main" assembly line. A diagram of a typical mass-production factory looks more like the skeleton of a fish than a single line.