Lean manufacturing

Lean manufacturing is a generic process management philosophy derived mostly from the Toyota Production System (TPS), but also from other sources. It is renowned for its focus on reduction of the original Toyota 'seven wastes' in order to improve overall customer value. Lean is often linked with Six Sigma because of that methodology's emphasis on reduction of process variation (or its converse smoothness). Toyota's steady growth from a small player to the most valuable and the biggest car company in the world has focused attention upon how it has achieved this, making "Lean" a hot topic in management science in the first decade of the 21st century.

For many, Lean is the set of TPS 'tools' that assist in the identification and steady elimination of waste (muda), the improvement of quality, and production time and cost reduction. To solve the problem of waste, Lean Manufacturing has several 'tools' at its disposal. These include continuous process improvement (kaizen), the "5 Whys" and mistake-proofing (poka-yoke). In this way it can be seen as taking a very similar approach to other improvement methodologies.
There is a second approach to Lean Manufacturing which is promoted by Toyota in which the focus is upon implementing the 'flow' or smoothness of work (opposite of mura, unevenness) through the system and not upon 'waste reduction' per se. Techniques to improve flow include production levelling, "pull" production (by means of kanban) and the Heijunka box.
The difference between these two approaches is not the goal but the prime approach to achieving it. The implementation of smooth flow exposes quality problems which always existed and thus waste reduction naturally happens as a consequence. The advantage claimed for this approach is that it naturally takes a system-wide perspective whereas a 'waste' focus has this perspective assumed. Some Toyota staff have expressed some surprise at the 'tool' based approach as they see the tools as work-arounds made necessary where flow could not be fully implemented and not as aims in themselves.

Overview

Both Lean and TPS can be seen as a loosely connected set of potentially competing principles whose goal is cost reduction by the elimination of waste. These principles include:

• Pull processing: products are pulled from the consumer end (demand) just-in-time to be used, not pushed from the production end (Supply)
  Perfect first-time quality - quest for zero defects, revealing & solving problems at the source
• Waste minimization – eliminating all activities that do not add value & or are safety nets, maximize use of scarce resources (capital, people and land)
• Continuous improvement – reducing costs, improving quality, increasing productivity and information sharing
• Flexibility – producing different mixes or greater diversity of products quickly, without sacrificing efficiency at lower volumes of production
• Building and maintaining a long term relationship with suppliers through collaborative risk sharing, cost sharing and information sharing arrangements
• Autonomation - if an abnormal situation arises then a machine or person must stop production in order to avoid defective products and other waste
• Load levelling and Production flow - fluctuations in product flow increase waste because process capacity must always be prepared for peak production
• Visual control - where the actual progress of work in comparison to daily production plans is clearly visible.

The disconnected nature of some of these principles perhaps springs from the fact that the TPS has grown pragmatically as it responded to the problems it saw within its own production facilities. The TPS has been under development since about 1948 and continues to develop today. Thus what one sees today is the result of a 'need' driven learning to improve where each step has built on previous ideas and not something based upon a theoretical framework. Toyota's view is that the methodology is not the tools but the method of application of muda, mura, muri to expose the things the tools can address. Thus the 'tools' are adapted to different situations which explains any apparent incoherence of the 'principles' above.
Lean production, alternatively gaining distinction as the Toyota Product Development System (TPDS), is aimed at defining value, creating flow, and eliminating waste in every area and stage of work including customer relations, product design, supplier networks and factory management. Its goal is to incorporate less low-value human effort, less inventory, less time to develop products, and less space to become highly responsive to customer demand while producing top quality, error-proofed products in the most efficient and economical manner possible.'
The TPS has two pillar concepts: JIT (flow) and autonomation (smart automation).[3] Adherents of the Toyota approach would say that 'flow' delivery of 'value' does all these improvements as a side-effect. If production 'flows' perfectly then there is no inventory, if customer valued features are the only ones produced then product design is simplified and effort is only expended on features the customer values. The other of the two TPS pillars is the very human aspect of 'autonomation' whereby automation is achieved with a human touch.[4] This aims to give the machines enough 'intelligence' to recognise when they are working abnormally and flag this for human attention. Thus humans do not have to monitor normal production and only have to focus on abnormal, or fault, conditions. A reduction in human workload that is probably much desired by all involved.
Lean is focused on getting the right things, to the right place, at the right time, in the right quantity to achieve perfect work flow while minimizing waste and being flexible and able to change. These concepts of flexibility and change are principally required to allow production levelling, using tools like SMED, but have their analogues in other processes such as R&D. The flexibility and ability to change are not open-ended, and therefore often expensive, capability requirements. More importantly, all of these concepts have to be understood, appreciated, and embraced by the actual employees who build the products and therefore own the processes. The cultural and managerial aspects of lean are just as important as the actual tools or methodologies of production itself. There are many examples of Lean tool implementation without sustained benefit and these are often blamed on weak understanding of Lean in the organisation. Lean aims to make the work simple enough to understand, to do and to manage. To achieve these three at once there is a belief held by some that Toyota's mentoring process (loosely called Senpai and Kohai relationship), so strongly supported in Japan, is one of the best ways to foster Lean Thinking up and down the organizational structure. The closest equivalent to Toyota's mentoring process is the concept of Lean Sensei, which encourages companies, organizations, and teams to seek out outside, third-party "Sensei" that can provide unbiased advice and coaching, (see Womack et al, Lean Thinking, 1998).

Lean implementation

System engineering
Lean is about more than just cutting costs in the factory. One crucial insight is that most costs are assigned when a product is designed, (see Genichi Taguchi). Often an engineer will specify familiar, safe materials and processes rather than inexpensive, efficient ones. This reduces project risk, that is, the cost to the engineer, while increasing financial risks, and decreasing profits. Good organizations develop and review checklists to review product designs.
Companies must often look beyond the shop-floor to find opportunities for improving overall company cost and performance. At the system engineering level, requirements are reviewed with marketing and customer representatives to eliminate costly requirements. Shared modules may be developed, such as multipurpose power-supplies or shared mechanical components or fasteners. Requirements are assigned to the cheapest discipline. For example, adjustments may be moved into software, and measurements away from a mechanical solution to an electronic solution. Another approach is to choose connection or power-transport methods that are cheap or that used standardized components that become available in a competitive market.

A summary, An Example program:

With a muda or tools based approach

• Senior management to agree and discuss their lean vision
• Management brainstorm to identify project leader and set objectives
• Communicate plan and vision to the workforce
• Ask for volunteers to form the Lean Implementation team (5-7 works best, all from different departments)
• Appoint members of the Lean Manufacturing Implementation Team
• Train the Implementation Team in the various lean tools - make a point of trying to visit other non competing businesses which have implemented lean
• Select a Pilot Project – 5S is a good place to start
• Run the pilot for 2-3 months - evaluate, review and learn from your mistakes
• Roll out pilot to other factory areas
• Evaluate results, encourage feedback
• Stabilize the positive results by teaching supervisors how to train the new standards you've developed with TWI methodology (Training Within Industry)
• Once you are satisfied that you have a habitual program, consider introducing the next lean tool. Select the one which will give you the biggest return for your business.

With a muri or flow based approach

• Sort out as many of the visible quality problems as you can, as well as downtime and other instability problems, and get the internal scrap acknowledged and its management started.
• make the flow of parts through the system/process as continuous as possible using workcells and market locations where necessary and avoiding variations in the operators work cycle
• introduce standard work and stabilise the work pace through the system
• start pulling work through the system, look at the production scheduling and move towards daily orders with kanban cards
• even out the production flow by reducing batch sizes, increase delivery frequency internally and if possible externally, level internal demand
• improve exposed quality issues using the tools remove some people and make it all work again