Intended learning outcomes: Identify the basic concepts of the Toyota Production System. Produce an overview on the so-called 3M: muri, mura, and muda.
The origin of the just-in-time concept is in the Toyota Production System. Here see [Toyo98].
The Toyota Production System (TPS) is a framework of concepts and methods for increasing productivity and quality.
The minimization of the so-called 3M, “muri”, “mura”, and “muda” is a basis of TPS.
Overstraining or excessive stress (Japanese “muri”) refers to an unreasonable overburdening of human beings (physically or mentally) or machines.
With human beings, “muri” can entail exhaustion, injuries, unplanned absence, diseases, and even burnout. With machines, “muri” can entail interruptions and decreased availability.
Variation (Japanese “mura”) describes unevenness in the production system.
“Mura” can result, for example, from discontinuous demand, but also from changing product mix, differing times required for individual operations, or badly organized workplaces. “Mura” can spread out to the whole supply chain, which can entail, among other things, the bullwhip effect (here see Section 2.3.5). Leveling of the production along the entire supply chain (Japanese “heijunka”) as an important tool for reducing “mura” requires a reduction of the lead time. For this, the following sections will deal with reduction of inventories, mixed-model and mixed production, as well as lot size reduction.
Waste, or useless effort (Japanese “muda”) is seen as all activities in development and manufacturing within the entire supply chain, extending to and including the consumer, that are non-value-adding from the customer’s point of view.[note 602].
Ohno’s seven wastes are overproduction, waiting, transportation, unnecessary inventory, unnecessary motion, making defects, inappropriate processing (e.g., physical work not suited to human beings or overprocessing that will not be paid by the customer). See [Ohno88].
The 3Ms interact mutually. Reducing “muda” without simultaneously reducing “mura” can result in “muri.” For example, reducing inventories and simultaneously satisfying heavily discontinuous customer demand will overburden the production system all too often. This will, among other things, decrease quality, and thus entail “muda.” Thus “mura” is a prerequisite of a durable reduction of “muda.” As “muri” entails, in general, “mura” and “muda,” avoiding “muri” has priority. An example is the famous cord, by which employees of Toyota’s assembly line can stop the line, not only because of defects (“muda”) but also if they cannot follow the takt time, for instance because of being overburdened. The short-term stop of the line will then not be considered as “mura” or “muda.” However, the reason for the overburdening as well as a feasible solution must be found quickly.
Continuation in next subsection (6.1.1b).
Course section 6.1: Subsections and their intended learning outcomes
6.1 Characterizing Lean / Just-in-Time and Repetitive Manufacturing
Intended learning outcomes: Explain Just-in-Time and Jidoka: Increasing productivity through reduction of overburdening, unevenness, and useless effort, or waste. Describe characteristic features for simple and effective planning & control techniques of repetitive manufacturing.
6.1.1 The Toyota Production System (TPS): Increasing Productivity through Reduction of Muri (Overburdening), Mura (Unevenness), and Muda (Useless Effort or Waste)
Intended learning outcomes: Identify the basic concepts of the Toyota Production System. Produce an overview on the so-called 3M: muri, mura, and muda.
6.1.1b The Toyota Production System (TPS): Just-in-Time and Jidoka
Intended learning outcomes: Produce an overview on just-in-time, Jidoka, lean production and a lean enterprise. Differentiate between the conventional view of inventory and the Japanese view.
6.1.2 Characteristic Features for Simple and Effective Planning & Control Techniques of Repetitive Manufacturing
Intended learning outcomes: Produce an overview on how the lean / just-in-time concept tends towards more simple techniques in place of more complicated techniques of materials and capacity management.
