Technology & Living Standards - Mass Production, Automation, and Assembly Lines

Assembly Line

Introduction

This is the story of how the modern assembly line developed in the United States to reduce the costs and increase the numbers of affordable products available to Americans and many people around the world. Assembly lines, which include automation (mechanization & electrification), make products in large quantities ("mass production") with high labor productivity (quantity and quality of products made ÷ amounts of labor used). Assembly lines depend a large number of buyers ("the market") and on 8 technologies developed first in Great Britain and then in west Europe, and the United States beginning in the 18th century and continuing today. These technologies include advances in (1) materials processing, (2) power, (3) transportation, (4) machine tools, (5) special purpose machines, (6) division of machine and labor operations, (7) interchangeable parts, and (8) measurement standards and accuracy. These technologies culminated in the invention of the assembly line in the United States. However, new technologies depend on ingenious men who invent them and great numbers of workers who apply them. This is their story too.

Assembly lines are moving conveyors that carry parts to one area for assembly by machine and worker. They reduce the time to carry parts to the assembly areas by alternate hoists and carts and reduce the time to assemble parts into a finished product. Assembly lines depend markets, technologies and people, so they could not be envisaged until other technologies became available. Therefore, the history of the assembly line is built on the histories of markets, technologies and people.

Markets are people who want manufactured products and who have the money to buy them. Early in U.S. history, the population was small and money scarce, so manufacturing was focused on local populations.

Manufacturing means making useful things from less useful things, such as cloth from cotton, steel from iron ore, gasoline from petroleum, and houses from wood, metals and other materials. The place where manufacturing occurs is called a factory, mill or "works". Manufacturing is an ancient industry. When neolithic people made simple tools from stone by striking stones upon other stones to chip and shape them into useful objects, such as knives, axes, spears and hammers, from useless objects, they were manufacturing. They cut wood from tree limbs and bound stone to wood with small roots to assemble larger tools, which amounted to more complex manufacturing. This kind of manufacturing exists today among primitive peoples in many parts of the world. However, the history of the assembly line need not go back that far. It can be understood by reviewing manufacturing methods that existed in Europe and the United Stated from the late 18th century to the present day.

Mass production means manufacturing products in large quantities, thus reducing the cost of each product. The reason for this reduction is that costs are of two kinds: (a) variable, which vary in proportion to the number of units produced, and (b) fixed, which do not vary with the number of units produced. Therefore, the larger the number of units produced, the smaller the fixed cost per unit and the smaller the total (variable + fixed) cost per unit. However, large quantities cannot be made unless there are large numbers of consumers to buy them, power sources available to make the products and transportation modes available to bring materials, people and machines to the factory and bring the products to the consumer.

Power is required to do any kind of sustained work. Natural sources are muscle, waterfalls, wind and tides. Waterwheels, water turbines, steam engines and electrical generators are man-made power sources that free some people from brute labor, which they can use to figure out how to do things better and accumulate money to do them.

Transportation is required to move materials, equipment, supplies, and laborers to the factories. It is also necessary to move the products made in factories to markets.

Materials processing are required to make more usable materials from natural materials. Of special importance to mass production are iron, steel and copper. Limestone, firebricks, iron ore, wood and coal are required to make iron from iron ore. Clay is required to make firebricks for kilns and furnaces. Stone and cement are required to build foundations and walls.

Machine tools are general purpose machines that make all other machines, including themselves. They augment hand tools to make human labor more productive.

Special purpose machines are used in place of human and animal muscle to make parts and assemble them into useful products. Machines never tire and don't complain, so they can work around the clock when properly maintained. Although they are costly to purchase (the initial investment) compared to animals and hired labor, they are often are less expensive to operate over the life of the parts being made.

Division of machine and labor operations means separating the operations to make each part into simpler repetitive operations, thus reducing the time to change from operation to operation. It is often called the "division of labor".

Interchangeable parts are parts made so that any one of them at random can be fitted to another part in subassembly and final assembly. These parts must have dimensions that are almost identical with each other , which in turn, means that each dimension must be accurate within close tolerances (e.g., .001 inch). An inaccurate part (one outside its tolerance limits) won't fit with another part, thereby preventing assembly. It will have to be reworked or discarded, thereby increasing time and cost. In the case of small arms production (rifles and pistols), non-interchangeable parts can have deadly consequences when parts malfunction, so it is not surprising that the arms industry was the first one in which men sought to develop nterchangeable parts. Interchangeability, in turn, requires accuracy and precision in machining and accurate measurement. Interchangeable parts are made by more accurate, precise and faster machines.

Measurement standards and accuracy enable parts to be made to specifications with little error and with known error limits, called tolerances. At each part operation center, measuring and testing is performed to assure that the parts and subassemblies conform to predetermined physical and functional specification standards, so that they will work with other parts assembled with them.