Sunday, November 24, 2013

Lean Production - Toyota System - Womack, Jones, and Roos

Content in Chapter 3

Chapter 3. The Rise of Lean Production

Example of Lean Production

In American Companies, die changes required a full day. The American companies dedicated die presses to each part. To Ohno of Toyota, that was not the solution. He has to stamp all the parts he needed from only few press lines. Hence he decided to decrease the die change time and he went on decreasing the die change time to 3 minutes and he also eliminated the need for die change specialists. The operators only will change the die. In the process he made the unexpected discovery - it actually cost less per part to make small batches of stampings than to run off enormous lots (due to  small setup costs).

Making only a few parts before assembling them into a car cause stamping mistakes to show up instantly. It made the production people more concerned about quality and that eliminated defectives significantly. But to make the system a success, Ohno needed both an extremely skilled and a highly motivated work force. Workers have take the initiative to maintain quality production. Otherwise, the whole factory will come to a halt.

Ohno organized his assembly workers into teams. The teams were given a set of assembly steps, their piece of line and told to work together on how best to perform the necessary operations. They work under a team leader, who would do assembly tasks, as well as coordinate the team and would  fill in for any absent worker. In mass production plans there were foremen and utility workers used to take the place of absentees. Ohno next gave the teams the job of housekeeping, minor tool repair, and quality checking. Finally, he gave them responsibility for process improvement also. This continuous, incremental improvement process, kaizen in Japanese, took place in collaboration with the industrial engineers, who still existed in much small number.

Ohno reasoned that rework at the end of assembly due to finding errors in final inspection is a waste. He wanted even assembly workers to pass on the work only if it is defect free and in case there is a defect which they could not rectify, they can stop the line and take the time to rectify the defect even with the help of other workers. Also, problem solving through 5 Whys methods is also used to avoid recurrence of the problem. In the initial days of this practice, the line was stopped  many times and workers got frustrated, with practice, the stoppages decreased significantly. Today, in Toyota plants,  yields approach 100 percent. That is the line practically never stops.  The extra benefit due to this method was that quality of shipped cars steadily improved. You cannot build quality by inspection, you have to build quality at the production centers only.  Today, Toyota assembly plant have practically no rework areas and perform almost no rework on assembled cars. In contrast, mass-production plants devote 20 percent of plant area and 25 percent of their total hours of final-assembly effort to fixing mistakes. American buyers report that Toyota's vehicles have among the lowest number of defects of any in the world, comparable to the very best of the German luxury car producers, who devote  many hours of assembly effort to rectification.

Chapter 4. Running the Factory

Classic Lean Production - Description of  Toyota Takaoka Plant

Toyota Takaoka plant was started in 1966.

The army of indirect workers so visible in General Motors plant are not there. Practically every workers in the plant is adding value. Toyota believes in face-to-face communication and hence facilities are located close together.  Less than an hour's worth of inventory was next to each worker. The line is well balanced and every worker worked at the same pace. If a defective part was found, worker carefully tagged it and send to quality control area of replacement.  Five why method is followed for every defective piece found.  Every worker has facility to stop the line. But the line is rarely stopped. There is no rework area for the assembled cars. Almost every car was driven direct from the line to the boat or truck.

There were practically no buffer between paint and final assembly. There were no parts warehouses. The work place was harder but there was a sense of purposefulness.

Mass Production versus Lean Comparision

Gross assembly hour per car was only 18 hours in comparison to 40.7 in GM Famingham plant.

Takaoka was almost twice as productive, three times as accurate as Framingham, but uses only 60% space. Its parts inventory was only 2 hours in comparison to 2 days of GM plant. It is a revolution because the change/improvement was in many dimensions. Also, the line can be changed to a new model a few days only.

Getting to Lean

Important organizational features of lean plants are responsible for half of the overall performance difference among plants of the world. The other two are automation and manufacturability.

The truly lean plant has two key organizational features.

It transfers the maxium number of tasks and responsibilities to those workers actually adding value to the car on the line.

It has in place a system for detecting defects that quickly traces  every problem, once discovered, to its ultimate cause.

In a lean plant all information of plant are displayed on andon boards.  Every time something goes wrong in the plant, every employee knows it and any employee who knowns how to help runs to lend a helping hand.

It is the dynamic work team that is at the heart of the lean factory.  To build efficient teams number of steps are necessary.  Firsr workers, who are team members, need to be taught a wide variety of skills. - in fact, alla the jobs in their work group or team so that tasks can be rotated and workers fill in for each other. Apart from production jobs, workers have to acquire many additional skills: simple machine repair, quality checking, housekeeping, and materials-ordering. They need encouragement to think proactively to solve problems before they become serious.

The authors say that workers respond only when they feel management values skilled workers, makes sacrifices to retain them and is willing to delegate responsibility to them.

The tools used in lean production system as covered by various authors on lean system are consolidated in
Lean Production System Tools - Categorization - Industrial Engineering

Taiichi Ohno specially praises and appreciates the role of industrial engineering in making Toyota, a success.
Taiichi Ohno on Industrial Engineering - Toyota Style Industrial Engineering

Explanation of the Toyota Production System by Taiichi Ohno in the book on Toyota Production System - Summary
Toyota Production System - Origin and Development - Taiichi Ohno

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