Assembly Line

In mass production, products are usually produced on an assembly line. Many believe that the assembly line was the most significant technological development of the 20th century. Nearly everything that we have we would not have in the quantities we have it, and at the prices we have it, without the assembly line. The assembly line moves the world. It is a driving force behind every industrialized nation on earth.

An assembly line can be explained as workers and machines organized into a continuous flow of raw materials that are made into products in an unimaginable scale. Through the use of mass production methods and the assembly line, more goods can be produced in a given period of time, usually at a lower cost.

On assembly lines such as the one shown in this photo of a motorcycle factory, products move from one work station to the next. The production process is divided into steps. Each worker does one step, as the item moves by on the line.

Eli Whitney started one of the earliest assembly lines in 1789. Eli Whitney, you may recall, is also noted for his invention of the cotton gin. Whitney signed a contract with the U.S. Army to make 10,000 rifles (a huge number in those days) in only two years.

The normal procedure for making a rifle in those days was by the Craft System. Using the craft approach a skilled craftsman would make each part, one at a time, as he put the rifle together. That meant that parts would only fit that one rifle and no two rifles were exactly the same. If a part later broke, the replacement part had to be hand crafted to fit. It took great skill to make the parts and the process was very slow and expensive. Eli could never have fulfilled his contract on time by using the craft method.

A skilled craftsman does his work, one item at a time. The quality of the finished product depends upon the skill of the craftsman. More time is needed to complete a product, and the cost is usually much higher.

Eli succeeded by making a large number of each kind of rifle part at once and keeping the parts in separate bins. The parts were standardized, which means they were exactly alike. We call these parts interchangeable parts - any of them could be used in assembly. This not only cut the cost but also speeded up production tremendously.

Interchangeability of parts is one of the most important characteristics of an assembly line. One of the first moving assembly lines was at the Ford Motor Company in 1913. Henry Ford, founder of the company, had built his first car in 1896 and was unique among automobile inventors. Until this time, automobiles were being built one at a time and were quite expensive. Only rich people could afford to buy one.

Ford wanted to build a car for the common people. To do so he had to produce them at the lowest possible price. After he had developed the wildly successful Model T, Ford began experimenting with available production techniques. He could not keep up with the demand for his cars. By 1908 the nation was on the move, and Ford’s need for production speed was paramount.

In Ford's early assembly line, autos were pulled by rope from one worker to the next. This new technique allowed individual workers to stay in one place and perform the same task repeatedly on vehicles as they passed by. This reduced production time by about one-half. By applying the same principle to the assembly of a total car, Henry Ford speeded up car production even more. He later employed the use of conveyor belts to move the parts down the line. By now, a finished Model T came off the assembly line every ten seconds. As they were able to refine and improve the assembly line even more, Ford was able to cut the price for a Model T in more than half.

Henry Ford and his Model T

But there was a problem. The problem with Ford's assembly line idea was that workers were not allowed to think on the job. Workers were not even allowed to stop the assembly line if they knew the parts were wrong. They were only allowed to do their assigned tasks, and to do them as quickly as they could. For speed, their tasks were made so simple that they required almost no skill to perform. The repetitive and unfulfilling work caused many workers to became very bored and dissatisfied with their jobs. Plus, they were unhappy about continually being pushed to perform their jobs faster and faster.

Putting the finishing touches on a car body as it
moves down the assembly line on a conveyor belt.

As a result, absenteeism rose and the employee turnover rate became very high. This was unacceptable on an assembly line since every work station had to be filled in order for the line to work. Also, it was very expensive to train new workers to replace the ones that had quit. So, Henry came up with a plan. He decided to more than double employee wages to $5.00 per day. That was an unheard of amount for those days. He also cut the length of the working day from 9 hours to 8. It worked. Even though the workers were still bored with the work, and they still considered it dull and unfulfilling, for those high wages they were more than willing to work the long hours on the assembly line.

Then something unexpected happened. An added benefit to the higher wages was that the workers were now able to afford Model Ts for themselves. That meant more cars had to be made, which meant more work for the employees, and more profit for the Ford Motor Company. It's what we might call a win-win situation. Henry came out looking like a genius.

Below is a chart that compares the differences between Craft Manufacture and Assembly Line Production.

Craft Manufacture

Assembly Line

1. Workers are very skilled.

2. Workers make a product from start to
     finish by themselves.

3. Work is varied and interesting.

4. Craftspeople get satisfaction by seeing the
     finished product (like a completed chair).

5. Each part is hand crafted so no two are
     exactly alike.

6. Only one item is produced at a time.

7. It takes a long time to produce each item.

8. The cost of each item is high.

9. Quality depends mainly upon the skill of
     the craftsperson.

1. Workers need limited skill.

2. Workers work on only one part of the
      product.

3. Work is routine and often boring.

4. Factory workers see only the one part
     that they produce (like the chair leg).

5. Parts are machine made and are inter-
     changeable.

6. Many items are produced during the
     production run.

7. The average time it takes to produce
     each item is reduced.

8. The cost of each item is lowered.

9. Quality depends mainly upon the
     accuracy of the machines and how well
     they have been set up by people.

In using the assembly line to manufacture automobiles, Henry Ford brought about what we call a critical threshold in technological history. A critical threshold happens when a technology becomes so important in people's every day lives that the world is changed forever.

For the first time, Henry Ford made it possible for almost anyone to afford an automobile. It seems that almost everyone wanted one. Families moved from the farms to the high paying factory jobs in the cities. Roads had to be built. Gas and oil had to be produced. People began to take vacations. Motels, restaurants, and gas stations sprung up across the country.

Who knows if filling the planet with cars was a good idea? But there is no turning back now. We depend upon the automobile for our way of life. And it all started with Henry Ford and the assembly line.

The assembly line is often referred to as work in motion. Work in motion is as mesmerizing now as it was at the turn of the century. What might look like miles of mechanized mayhem is actually one of the most dependable and durable production techniques ever invented.

Boeing’s 21^st century assembly line reflects the same audacity
of scale found in assembly lines at the beginning of the century.

Today the assembly line is used to make everything from a two pound computer to a 94,000 pound aircraft. The Boeing 717-200, shown above, is the largest vehicle ever built on a moving assembly line. Three hundred yards long, the line moves the 100 seat aircraft ½ inch every minute, and delivers to customers at the rate of one airplane every four days.