What is lean manufacturing?

In times when high competitiveness is of particular importance, a manufacturing company should have the key ability to reduce operating costs while simultaneously increasing efficiency. This need has led to the development of many new management concepts, one of the most popular methods being lean manufacturing. What is lean manufacturing? And how does it affect the increase in competitiveness of manufacturing enterprises?

Lean manufacturing – lean manufacturing definition and philosophy

The concept of lean manufacturing is based on management that improves the quality of products and processes and eliminates waste. Lean means less human effort, less space in the plant, fewer tools, half the investment, and time to design a product manufactured twice as fast. It involves eliminating unnecessary activities and performing necessary ones in the correct sequence.

Activities consistent with the philosophy of lean manufacturing make it possible to reduce the consumption of everything needed in the production process. As a result, we get a product better suited to customer needs and additionally manufactured at a much lower cost compared to mass production. The concept of lean manufacturing, therefore, consists of improving the operation of the production system by eliminating all kinds of waste to produce exactly as much as customers need. Every unsold product is treated as a loss.

History and main assumptions of lean manufacturing

Although elements of lean production were used as early as the 16th century, the automotive company Toyota is considered the precursor of the concept of lean manufacturing. In the 1940s, Japanese engineer Taiichi Ohno began a series of changes in production organisation. These activities transformed Toyota from a local factory into a global leader in the automotive industry. The production system introduced became an alternative to the model of mass production. Interestingly, the tools and techniques used were discovered and described relatively late, only in the 1980s, when the automotive crisis in the United States intensified due to the growing competitiveness of Japanese manufacturers. The result of investigating the causes of the crisis was the 1990 book “The Machine That Changed the World,” in which the concept of lean manufacturing was described for the first time.

The most commonly used graphical form that presents a summary of the most important assumptions of lean production is the so‑called Toyota Production System (TPS) house.

The TPS house consists of elements such as:

• the roof, i.e., the company’s goals,
• the pillars, thanks to which the goals are achieved,
• the foundations, which constitute the assumptions and practices of the entire company.

In the simplest terms, it is assumed that to achieve the goal (in this case, the roof), you must start by building solid foundations on which to place the appropriate pillars. It is also assumed that the improper functioning of any element in the system weakens the entire structure.

Currently, the lean manufacturing definition goes beyond the scope of Toyota’s production system, which makes it possible to adapt it to enterprises with a different operating profile. Lean is now a more universal model described in three categories:

Goals of the lean manufacturing concept

SQDC is an acronym defining the main goals of lean manufacturing:

• S – Safety
• Q – Quality
• D – Delivery
• C – Costs

Enterprises consistent with the lean philosophy also strive to eliminate the so‑called 3 Mu, i.e., Mura (unevenness), Muri (overburden), and Muda (waste). These factors are interrelated, which can pose numerous problems in an enterprise. For example, unevenness of deliveries from suppliers or variability in production plans can cause inefficient use of human and machine resources, which may stand idle or work at too fast a pace. Excessive overburden leads to quality declines and more errors. In the context of lean manufacturing, the most attention is focused on Muda, i.e., waste, which is very often visible in production processes. Currently, eight basic types are distinguished, of which Taiichi Ohno identified the first seven.

These are:

• Overproduction – when the quantity of goods or services produced exceeds customer demand. This is currently presented as the most significant type of waste.
• Production defects – the product does not meet customer requirements, necessitating corrections or part scrapping.
• Excess inventory – storing too many materials in the company, i.e., raw materials, semi‑finished products, spare parts. In the office, there are excessive amounts of received emails, printed documents, and office supplies.
• Waiting – caused by material shortages, non‑functioning IT systems, breakdowns, and machine changeovers.
• Over‑processing – focusing on activities that do not increase product value, e.g., excessive machining of parts.
• Transport – concerns the distances that products, semi‑finished products, or tools travel between, for example, the warehouse and the workstation.
• Unnecessary motion – unnecessary movements must be made to complete a task.
• Lost employee creativity – a situation in which the ideas of members of the organisation are ignored. Task repetition enables an employee to become an expert in a given field, which can then be leveraged to improve processes.

TPS methods and techniques

Lean manufacturing currently provides a pervasive system of tools aimed at eliminating the 3 Mu, i.e., waste, unevenness, and overburden of employees. Some methods come from the Toyota Production System, which, along with the popularisation of the lean concept, has been expanded with additional techniques.

The classification of tools was defined by M. Ćwikliński and H. Obra, who introduced a division into those that serve:

• Improving organisation, e.g., JIT (Just In Time), internal pull system/supermarkets – Kanban system, One Piece Flow, 5S, TPM, Standardised Work, Production Levelling (heijunka), Jidoka, Self‑inspection at the workstation, Teamwork, Nemawashi decision‑alignment system, Kaizen, Hoshin Kanri.
• Problem-solving, e.g., Andon, Poka‑Yoke, problem‑solving at the point of occurrence (Genchi Genbutsu), Brainstorming, PDCA, Pareto charts, Ishikawa diagram, 5 Whys.

However, it should be remembered that simply using lean production tools will not make a company operate according to this concept. It is necessary to make more profound changes by implementing the philosophy of Lean Thinking.

Lean manufacturing tools – examples

5S tool – used to create an optimal workplace through:

• Seiri (sort, selection): identifying and removing all unnecessary items at the workstation.
• Seiton (set in order, systematisation): designating places for all items to limit unnecessary motion and effort.
• Seiso (shine, cleaning): keeping workstations clean by defining who, when, and what to do.
• Seiketsu (standardize): developing and implementing standards for the first three steps of 5S—these should be simple and visual.
• Shitsuke (sustain, self‑discipline): maintaining implemented improvements at the workstation by constantly promoting 5S in the workplace, communicating results, and training employees.

Kaizen – continuous improvement by constantly introducing changes and enhancements through small steps. The goal is to shorten process lead time and improve quality. The rule is the involvement of employees at all levels. The thought process occurs at every stage of production, i.e., it is a response to the traditional approach to mass production. It strives to reduce costs and improve the ergonomics of workstations.

Kanban – in Japanese, means a visual board. This method involves controlling production through events that occur directly on the shop floor. The benefits of the tool include short processing time, low inventory, on-time delivery, and quality control at all stages of production.

SMED – sets a goal to reduce machine changeover time to a maximum of 10 minutes.

Characteristics of the Lean Thinking philosophy

A key element of lean manufacturing is the Lean Thinking philosophy. According to it, the elimination of waste is not an end in itself, but the setting of a path along which the enterprise should move. This thinking is not about implementing more and more methods and tools; the key is to strive for excellence by shaping the right attitudes among employees. These principles are presented as a five‑step process:

• Define value – correctly define all activities performed by the company for which the customer is willing to pay. Eliminate those that do not add value, i.e., are waste.
• Identify the value stream – the flow of materials and information through all parts of the enterprise, from order to product delivery, should be controlled to ensure that every activity in a specific department adds value.
• Create flow – optimise activities to achieve a stable flow. Eliminate downtime, waiting between processes, and any disturbances.
• Establish pull – the pull system should connect product manufacturing with demand so that production processes occur at a matched pace and in required quantities.
• Pursue perfection – assumes that the company’s improvement process is continuous; thus, we achieve higher quality, lower costs, and shorter delivery times.

In addition to the methods and tools used to manage production, Toyota placed great emphasis on developing organisational culture. Building values and the right attitudes among employees is what distinguishes this Japanese company from competitors who introduced the Toyota production system. The advantage of lean manufacturing over other management styles did not lie in a set of tools, but in a specific philosophy of thinking and acting.

Lean Management vs. Lean Manufacturing – differences

Although these terms sound similar, they refer to different areas of a company’s operation. What differentiates the two concepts is the scope of activities undertaken. Lean Management is broader and involves improving the functioning of the enterprise in all its areas—from production, through the sales department, to accounting and controlling. It assumes that the enterprise operates properly when the harmonious operation of all these elements is ensured. The goal of lean manufacturing is also the continuous development and improvement of operations; however, its scope is much narrower. It focuses primarily on the activities of operational (production) departments, while other areas such as accounting or procurement take a back seat.

Efficient production management is currently the basis for cost reduction in a manufacturing company. The right system allows you to plan multi‑stage production while ensuring its real‑time monitoring.