Advent of One-Piece Flow In Machining Operations

Posted by on Sep 19, 2021 in Henry Ford, Lean, One-Piece Flow | 0 comments

Everyone will agree that Henry Ford developed the automobile assembly line. Back in Ford’s day, there were two ways to assembly automobiles. One way was to keep cars stationary while moving the assembly workers around; the other was to keep the assembly workers stationary while shuttling the vehicles around.

Realizing how bulky and heavy automobiles were, Ford initially thought it better to follow the first concept. But one day, while looking for ways to eliminate waste, he noticed the following:

  • waste in the scattered movement of workers
  • waste in searching for and finding objects
  • waste in conveying objects

Ford thought long and hard about how to eliminate them. Finally, he came upon the idea of mounting cars on a row of carts that could be pulled along by a rope and winch. With this discovery, he issued the following instructions:

  1. Set up a large winch and a long, thick rope to pull the automobiles along the assembly line.
  2. Divide the assembly line into 15 one-hour processes. This division would allow the rope to pull all automobiles to the following process once per hour.
  3. Distribute the assembly parts to their corresponding processes before they are needed.
  4. Assign three or four workers to each process and work out the balance of labor by observing the assembly line.

This experiment turned out to be a great success. It reduced the assembly time per vehicle from 13 hours to just 5 hours and 50 minutes. Within three months, his workers had improved their skills and reduced the time to 2 hours and 38 minutes.

Although Ford had success establishing one-piece flow for his automobile assembly operation, he was not able to achieve one-piece flow for his machining operations for three reasons:

  1. Maximizing the capacity utilization of the equipment was emphasized since the equipment was costly.
  2. The craft-oriented labor unions taught workers to stick to specific skills and not “invade the territory” of workers with other skills.
  3. Conventional wisdom emphasized by Frederick Tayor and others said that things are always “cheaper by the dozen.”

When Toyota studied Ford’s production system, they decided they would apply the principle of one-piece flow to the machining process as well. As a result, this meant they had to reduce their machining changeover time to zero. Their attempts resulted in what we now know as U-shaped cells for machining operations.

Next week, we will review the rules and conditions for one-piece flow using U-shaped cells.

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