Principles and Rules

In 1996, following the success of ‘The Machine…’ (Womack et al, 1990), the authors defined five principles of Lean in their book ‘Lean Thinking’ (Womack and Jones, 1996; 2003). The principles are described by the authors as ‘a sort of North Star… a dependable guide to action to help managers transcend the day to- day chaos of mass production’ (Womack and Jones, 2003:10). These five principles (Box 1) are considered probably the most widely cited in the academic literature (Radnor, 2010a). The authors assert that through understanding these

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principles and tying them all together, organisations can stay on course towards Lean operations.

Spear and Bowen (1999) also sought to codify and ‘demystify’ the Toyota Production System. Like Schönberger (2007), Spear and Bowen (1999) reflect with bemusement the failure and frustrations of hundreds of thousands of managers in successfully replicating the success of Toyota. The authors like others (eg. Roth, 2006), suggest that observers are mistaking the tools and techniques that they see as the system. Spear and Bowen (1999) propose that rigid work specification at Toyota is what provides the organisation with the impetus for continuous improvement.

“It [is] impossible for them to resolve an apparent paradox of the system - namely, that activities, connections, and production flows in a Toyota factory are rigidly scripted, yet at the same time Toyota's operations are enormously flexible

and adaptable. Activities and processes are constantly being challenged and pushed to a higher level of performance, enabling the company to continually

innovate and improve.” (Spear and Bowen 1999:97)

Spear and Bowen’s (1999) contribution to the literature entitled ‘Decoding the DNA of Toyota’ is to use their own observations to make the implicit, explicit. The authors propose four rules: three of design and one of improvement (See Box 2).

Box 1: Five Principles of Lean Source: Womack and Jones (1996, 2003) 1. Specify value from the perspective of the customer.

2. Identify the value stream for each product and challenge all of the wasted steps.

3. Make value flow continuously, without interruptions. 4. Let the customer pull value from the producer 5. Pursue perfection.

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According to Spear and Bowen (1999), the central tenet of the TPS is to create a ‘community of scientists’. The rigid specification of work exemplified in rule one is about testing hypotheses through action. The authors explain: “Performing the

activity tests the two hypotheses implicit in its design: first, that the person doing the activity is capable of performing it correctly and, second, that performing the activity actually creates the expected outcome…refuting at least one of these two hypotheses, indicates that the activity needs to be redesigned or the worker needs to be trained” (Spear and Bowen, 1999:100). Rules two and three denote the removal of ambiguity in communication and process pathways. An emphasis is placed on the use of clear, visual unambiguous signals that are precise, detailed, expressly designed and standardised in the manner outlined in rule one.

In common with the principles stipulated in Womack and Jones (1996), these rigid rules of design are central to achieving ‘flow’:

“A product does not flow to the next available person or machine, it should flow to a specified person or machine” (Spear and Bowen, 1999:104)

Box 2: The Four Rules that make up the DNA of Toyota (Source: Spear and Bowen, 1999)

Rule 1: All work shall be highly specified as to content, sequence, timing, and outcome.

Rule 2:Every customer supplier connection must be direct, and there must be an unambiguous yes-or-no way to send requests and receive responses.

Rule 3:The pathway for every product and service must be simple and direct.

Rule 4:Any improvement must be made in accordance with the scientific method, under the guidance of a teacher, at the lowest possible level in the organization

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If flow cannot happen according to its specification then Toyota will treat it as a problem. This rigid specification of the pathway is again testing hypothesis in action, i.e. a pathway designed according to rule 3 (see box 2) dictates that every supplier connected to the pathway is necessary, and any supplier not connected is not necessary. If for any reason, production is diverted to another supplier or if staff begin turning to others for help that are not designated helpers, Toyota would conclude that their actual demand or capacity did not match their expectations (Spear and Bowen, 1999:102). Thus, the authors identify that whenever Toyota defines a specification, it is establishing sets of hypotheses that can be tested, anything less than such scientific rigor they claim, would amount to little more than trial and error.

The fourth rule put forward by Spear and Bowen (1999) is about explicitly teaching people how to improve according to the scientific method of hypothesis testing, i.e. "If we make the following specific changes, we expect to achieve this specific outcome" (Spear and Bowen, 1999:104).

In summary, the principles defined by Womack and Jones (1996) and Spear and Bowen (1999) differ in their articulation of the principles but have a common pursuit of achieving continuous flow and continuous improvement. The five principles put forward by Womack and Jones place more emphasis upon defining value from the perspective of the customer, whereby Spear and Bowen’s rules place greater emphasis on unambiguous design, rigid specification and scientific testing in relation to continuous improvement. Essentially the two guides for implementation described above are both valuable contributions to an understanding of the central tenets of Lean and Lean implementation.