Toyota Production System (TPS): the house, the pillars and the tools

In one line

The Toyota Production System (TPS) is a production management system that aims to make only what the customer orders, when the customer orders it, with quality assured at every step and continuous improvement carried out by the people who run the process.

What it is

Niebel and Freivalds explain that the TPS was developed by Toyota Motor Corporation as a way to eliminate waste, and that its main purpose is to improve productivity and reduce costs. It applies Taylor's scientific management and Ford's mass assembly line, but with a broader scope: it also targets sales, administrative and capital costs. Toyota considered it dangerous to blindly follow Ford's mass production system, which worked well in times of heavy growth. In the United States this approach is known as lean manufacturing.

The sources do not agree on the starting point. Niebel and Freivalds link it to the oil crisis of 1973; the University of Azuay thesis places Taiichi Ohno's decisive influence in the 1950s, with the development of the just-in-time and jidoka principles. The reasonable view is to think of it as a system built over decades.

The house of the TPS

The University of Azuay thesis represents it as a house:

• Roof: the long-term goals (quality, cost and delivery time), without compromising the integrity of the workers.
• Pillars: just-in-time and jidoka, which make it possible to correct any anomalies that appear with people, machines or materials.
• Foundation: standardization of production and continuous improvement, together with heijunka, the leveling of the workload and the flow to keep pace with demand without overproducing.

The elements of the system

Niebel and Freivalds list the key elements: keiretsu (integrated suppliers that deliver quality parts on time), poka-yoke, just-in-time with its associated jidoka, the kanban system, the flexible workforce, kaizen and respect for the worker with a suggestion system. As a corollary of the seven wastes come the 5S, and as a requirement of just-in-time, quick die changeover (SMED).

Real example

The origin of the TPS is a story of scarcity. According to the Icesi University article, after World War II Japanese companies had no working capital to buy large quantities of raw material nor space in their plants to store it, and Toyota was asked to produce every kind of vehicle for the local market, from cars to medium-duty trucks, so a giant factory specialized in a single model, American style, made no sense. In 1949 the company went through a financial crisis that left it close to bankruptcy: the banks demanded that it cut staff and adjust the number of cars produced to the number actually sold.

A current application case appears in the University of Azuay thesis on a dairy plant, LACPRIMA. Its diagnosis found problems in each area and assigned one tool to each: lack of time records in pasteurizing (value stream mapping), loss of time and product when filling the molds (poka-yoke), molds stored in two different places in the plant (spaghetti diagram) and clutter on shelves and in work areas (5S). The diagnosis concludes that the underlying problem was the lack of records and procedures, which generated a lot of waste. The travel distance per cycle of the two operators at the molding station dropped from 200 to 110 meters and from 150 to 80 meters, as detailed in the article on the spaghetti diagram.

Benefits

• It reduces inventories, lead times and waste without depending on a large investment.
• It builds quality into the process: whoever detects the problem can stop the line.
• It adapts to short runs and product mix.

Limitations to keep in mind

• It is a system, not a toolkit: copying kanban without production leveling or quick die changeover usually fails. The LACPRIMA thesis puts it in its own way: it implemented the basic tools to lay out the pillars and allow other philosophies to be developed later, without compromising the stability of the system.
• It requires reliable suppliers and a culture of problem solving at the workstation.
• There are fewer documented cases of pure TPS than of Lean; the thesis itself points this out.

In summary

The TPS is the source of almost everything that is taught today as Lean. Its logic fits in one sentence: the two pillars (just-in-time and jidoka) rest on a foundation of standardized, leveled work under continuous improvement, and everything aims at eliminating waste.