Also known as lean production or simply lean, lean manufacturing is simply a multi-dimensional approach encompassing a variety of management practices. These include quality systems, just in time, cellular manufacturing, work teams and supplier management among others. The main aim or goal of lean manufacturing is that all these practices exist and work harmoniously and synergistically to result in a high quality and streamlined system, capable of producing finished products at a pace that matches that of customer’s demand, thereby minimising or eliminating wastage [1]. This enables companies to deal with the increased challenges from competitors.

Background information

Lean can be best described as a revolution because once implemented, it completely changes the way a company conducts business. It originated in Japan in the 1940s within Toyota whose production system was anchored around the goal to have a continuous flow without relying on long productions lines in order to be efficient. It recognised that, of the total effort and time required to process a product, only a small fraction added value to the customer. This was in contrast to what was happening in the western world, where, based around complex computerised systems and material resource planning (MRP), mass production was developing alongside Henry Ford’s mass production philosophies of standardised products, minimal product changeovers and high volume production.

Taiichi Ohno, considered as the father of the Toyota production system which later became known as Lean continued developing the system into late 1980s without being restrained by computer advancements. Toyota’s supply base was lean by the 1970s and their distribution base by the 1980s. The lean system included the following tools and techniques;

  • Kanban
  • Visual control
  • Single minute exchange of dies
  • Poke yoke
  • 5 S’s

In the 1990’s, Womack et al. [3] compared and contrasted mass production and lean production as shown in Table 1.

Table 1: Comparison of Mass production and Lean production [2]
                                                 Mass production                Lean production
  • Henry Ford
  • Toyota
  • Narrowly skilled professionals
  • Teams of multi-skilled workers at all levels in the organization
  • Unskilled or semi-skilled workers
  • Teams of multi-skilled workers at all levels in the organization
  • Expensive, single-purpose machines
  • Manual and automated systems which can produce large
  • volumes with large product variety
Production methods
  • Make high volumes of standardized products
  • Make products which the customer has ordered
Organizational philosophy
  • Hierarchical—management take responsibility
  • Value streams using appropriate levels of empowerment—
  • pushing responsibility further down the organization
  • Aim for ‘good enough’
  • Aim for perfection

The Lean manufacturing process

Implementation of the lean manufacturing process involves the following main stages;

1. Waste identification
This stage is based on a commitment to continuously improve as embodied by Kaizen which says that everyone, from the CEO to the workers at the assembly or processing line, should engage in activities that continuously improve all functions of the company.
No matter how efficiently you are producing at the moment or no matter how good the process is at the moment, it can always be made better. Simply put, waste always exists.
This stage therefore involves techniques of identifying waste one of which is the Visual Stream Map (VSM). This technique displays how materials as well as processes flow through the organisation in a bid to deliver the product or service to the end user or customer.
In analysing VSM, it is possible to see the process that result in value addition by looking through the departments and establishing how actions are connected. This analysis helps you to come up with an updated VSM that includes as few non value addition activities as possible.

2. Waste analysis and root cause identification
The next question is why are we having some wastages? In answering this question, you must do a Root Cause Analysis. This helps you to identify the real cause of wastage which is sometimes different from the one that is easy to guess. For example, a frequent machine breakdown can easily be interpreted as a failure of the machine and therefore the necessity to buy a new one but a Root Cause Analysis can reveal something different, like improper usage due to inadequately trained operators. Brainstorming and Cause and effects diagrams are also used in this stage. A sample cause and effect diagram is shown in Figure 1.
Figure 1: Cause and Effect diagram [4]

3. Solve the root cause

Once you know the source of your wastage, you should employ tools that help you to reduce the wastage. These tools include;

  • Just in Time (JIT)
    • Based on the ‘pull’ model. JIT minimises stock and resources whereby you only purchase materials or produce products when required. It also focusses on small, continuous batches. In so doing, it makes it easy to monitor quality as well as correct any anomalies.
  • Kanban
    • This system supports JIT by reducing overproduction. The key is having what you need only when you need it.
  • Zero defects
    • Instead of spending time, money and energy in fixing products that are of a poor quality, get it right the first time. This is the real measure of quality.
  • Single minute exchange of dies
    • Design the machinery and the processes to support quick and efficient change overs, thereby minimising changeover times.
  • The 5S philosophy
    • These are 5 Japanese words that focus on standardisation and simplification of the workplace. This way, very few things can go wrong.

Advantages of Lean manufacturing

Advantages of lean include less process waste, less rework, reduced inventory, more profits, improved knowledge management and reduce lead time among others. These are illustrated in Figure 2 and altogether result in more customer satisfaction.

Figure 2: Typical benefits of Lean manufacturing

References/ important links
1. Shah, R., & Ward, P. T. (2003). Lean manufacturing: context, practice bundles, and performance. Journal of operations management, 21(2), 129-149.
2. Melton, T. (2005). The benefits of lean manufacturing: what lean thinking has to offer the process industries. Chemical Engineering Research and Design, 83(6), 662-673.
3. Womack, J. P., Jones, D. T., & Roos, D. (1990). Machine that changed the world. Simon and Schuster.
4. https://en.wikipedia.org/wiki/Ishikawa_diagram
5. https://www.mindtools.com/pages/article/newSTR_44.htm

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