Today every industry all over the world is facing different types of challenges. Among them the most critical challenge is satisfying unlimited human wants by limited resources. This is the greatest concern of all the industries. The development of an industry depends on how they can cope up with this challenge. To cope up with this situation is not an easy task at all. For this regards at first we have to ensure proper utilization of our resources by reducing wastage at minimum possible rate. At the same time, we have to keep in mind another important thing, is that quality of our products. Without this, we will not achieve sustainable development. From this concern, lean is emerged. Simply, lean means creating more value for customers with fewer resources.

Lean manufacturing is a systematic approach to identifying and eliminating wastes through continuous improvement by flowing the product at the pull of the customer in pursuit of production. In a more basic term, more value with less work. It is also known as “Toyota Production System”.

Lean is a term to describe a system that produces what the customer wants, when they want it, with minimum waste. Lean thinking focuses on value-added lean consists of best practices, tools and techniques from throughout industry with the aims of reducing waste and maximizing the flow and efficiency of the overall system to achieve the ultimate customer satisfaction.

Another way of looking at lean is that it aims to achieve the same output with less input, less time, less space, less human effort, less machinery, less material, less costs.

When a U.S equipment manufacturing company ‘Lantech’ completed the implementation of lean in 1995, they reported the following improvements compared to their batch-based system in 1991:

  1. Manufacturing space per machine was reduced by 45%
  2. Defects were reduced by 90%
  • Production cycle time was reduced from 16 weeks to 14 hours-5 days
  1. Product delivery lead time was reduced from 4-20 weeks to 1-4 weeks.

Lean for Production and Services:

A popular misconception is that lean is suited only for manufacturing. Not true. Lean applies in every business and every process. It is not a tactic or a cost reduction program, but a way of thinking and acting for an entire organization.

Businesses in all industries and services, including healthcare and governments, are using lean principles as the way they think and do.

Purpose, Process, People:

Lean thinks about three fundamental business issues that should guide the transformation of the entire organization:

Purpose: What customer problems will the enterprise solve to achieve its own purpose of prospering?

Process: How will the organization assess each major value stream to make sure each step is valuable, capable, available, adequate, flexible, and that all the steps are linked by flow, pull, and leveling?

People: How can the organization insure that every important process has someone responsible for continually evaluating that value stream in terms of business purpose and lean process? How can everyone touching the value stream be actively engaged in operating it correctly and continually improving it?

Principles of lean manufacturing:

Key principles behind lean manufacturing can be summarized as follows:

  • Recognition of waste: the first step is to recognize what does and does not create value for the customer’s perspective. Any material, process or feature which is not required for creating value from the customer’s is waste and should be eliminated.
  • Standard processes: lean requires an implementation of very detailed production guide lines, called standard work, which clearly state the content, sequence, timing and outcome of all actions by workers.
  • Continuous flow: lean usually aims for the implementation of a continuous production flow free of interruption, detours, backflows or waiting.
  • Pull-production: pull production aims to produce only what is needed, when it is needed.
  • Quality at the source: lean aims for defects to be eliminated at the source and for quality inspection to be done by the workers as part of the in line production processes.
  • Continuous improvement: it means incremental improvement of products, processes of services over time, with the goal of reducing waste to improve workplace functionality, customer service of product performance.
  • Customer focus: a lean manufacturing enterprise thinks more about its customers than it does about running machines fast to absorb labor and overhead.
  • Value: the product must meet the customer’s needs at both a specific time and price. Identifying the value in lean production means to understand all the activities required to produce a specific product, and then to optimize the whole process from the view of the customer.
  • Perfection: the systematic elimination of waste will reduce the cost of operating the extended enterprise and fulfills customer’s desire for maximum value at the lowest price.

Lean manufacturing concepts:

In lean manufacturing, the value of a product is defined only based on what the customer actually requires and is willing to pay for. Production operations can be grouped into following three types of activities:

Value-added activities: these are activities which transform the materials onto the exact product that the customer requires.

Non-value-added: these are the activities that aren’t required for transforming the materials into the product that the customer wants. Anything which is non-value-added may be defined as waste. Anything that adds unnecessary times, effort or cost is considered non-value-added. Another way of looking to waste is that it is any material or activity for which the customer is not willing to pay.

Necessary non-value-added: these are activities that don’t add value from the perspective of the customer but are necessary to produce the product unless the existing supply or production process is radically changed.

Research at the “Lean Enterprise Research Center” (LERC) in the United Kingdom indicated that for a typical manufacturing company the ratio of productivities could be broken down as follows:

Value-added activities                             5 %

Non-value-added activities                    60 %

Necessary non-value-added activities     35 %

Total activities                                                100 %


Waste is anything that does not contribute to transforming a part to the customer’s needs. The aim of lean manufacturing is the elimination of waste in every area of production including customer relations, product design, supplier networks and factory management. Its goal is to incorporate less human effort, less inventory, less time to develop products and less space to become highly responsive to customer demand while producing top quality products in the most efficient and economical manner possible. Essentially, a waste is anything that the customer is not willing to pay for.

Types of waste:

There are three broad types of waste:

  1. Muda
  2. Muri
  3. Mura

It should be noted that for many lean implementations this list shrinks to the first waste type only with reduced corresponding benefits. To illustrate the state of this thinking it is observed that only the last turn of a bolt tightens it—the rest is just movement.

Firstly, Muri focuses on the preparation and planning of the process, or what work can be avoided proactively by design. Next, Mura then focuses on how the work design is implemented and the elimination of fluctuation at the scheduling or operations level, such as quality and volume. Muda is then discovered after the process is in place and is dealt with reactively. It is seen through variation in output. It is the role of management to examine the Muda, in the processes and eliminate the deeper causes by considering the connections to the Muri and Mura of the system. The Muda and Mura inconsistencies must be fed back to the Muri, or planning, stage for the next project.

Seven Deadly Wastes:

Overproduction: It means making something before it is truly needed. This is a particularly serious form of waste because it leads to excess inventory that is often used to mask other underlying problems and inefficiencies. Causes for overproduction waste include:

  • Misuse of automation
  • Long process setup
  • Over engineered
  • Redundant inspection

Waiting: When work-in-process is waiting for the next step in production (no value is being added). It can be truly illuminating to look at the time from order to shipment and ask – how much of that time is actually spent on true value-added manufacturing. Causes of waiting waste include:

  • Unbalanced work load
  • Unplanned maintenance
  • Long process set-up times
  • Misuse of automation

Transport: Unnecessary movement of raw materials, work-in-process or finished goods. The lean demands so that the material can be shipped directly from the vendor to the location in the assembly line where it will be used. The lean term for this technique is called point-of-use-storage (POUS). Causes of transportation waste include:

  • Poor plant layout
  • Poor understanding of the process flow for production
  • Large batch sizes, long lead times and large storage areas3

Motion: Unnecessary movement of  the workers, machines and transport due to the inappropriate location of tools and parts is waste. Causes of motion waste include:

  • Poor people/machine effectiveness
  • Inconsistent work methods
  • Unfavorable facility or cell layout
  • Poor workplace organization and housekeeping

Over processing: It is the extra processing than it is needed to produce what the customer requires. This is often one of the more difficult wastes to detect and eliminate. Causes for processing waste include:

  • Product changes without process changes
  • True customer requirements undefined
  • Over processing to accommodate downtime
  • Lack of communication
  • Extra copies/excessive information

Inventory: Product (raw materials, work-in-process, or finished goods) quantities that go beyond supporting the immediate need. Work in process (WIP) inventory is material between operations due to large lot production or processes with long cycle times. Material sits taking up space, costing money and potentially being damaged. Causes of excess inventory include:

  • Product complexity
  • Poor market forecast
  • Misunderstood communications
  • Unreliable shipments by suppliers

Defects: Production that is scrap or requires rework. Making defective products is pure waste. Production defects and service errors waste resources in four ways. First, materials are consumed. Second, the labor used to produce that part (or provide the service) the first time cannot be recovered. Third, labor is required to rework the product (or redo the service). Fourth, the labor is required to address any forthcoming customer complaints. Causes of processing waste include:

  • Weak process control
  • Poor quality
  • Unbalanced inventory level
  • Deficient planned maintenance
  • Customer needs not understood4

Some Essential Lean Tools:

Lean has a very extensive collection of tools and concepts. Surveying the most important of these, understanding both what they are and how they can help is an excellent way to get started.

·       The 5 S’s:

The 5 S’s are some rules for workplace organization which aim to organize each worker’s work area for maximum efficiency:

  1. Sort: sort what is needed and what is not needed so that the things that are frequently needed are available nearby and as easy to find as possible.
  2. Set in order: arrange essential things in order for easy access. The objective is to minimize the amount of motion require for workers to do their jobs.
  3. Shine: keep machines and work areas clean so as to eliminate problems associated with un-cleanliness.
  4. Standardize: make the first 3 S’s a routine practice by implementing clear procedures for sorting, setting order and shining.
  5. Sustain: promote, communicate and train in the 5 S’s to ensure that it is part of the company’s corporate culture. This might include assigning a team to responsible for supervising compliance with the 5 S’s.5

How does it help?6

Eliminates waste that results from a poorly organized work area (e.g. wasting time looking for a tool).

  • Just-In-Time (JIT):

Pull parts through production based on customer demand instead of pushing parts through production based on projected demand.8

How does it help?

It is highly effective in reducing inventory levels. Improves cash flow and reduces space requirements.


Toyota is considered by many to be the poster child for JIT success. The Toyota production strategy is highlighted by the fact that raw materials are not brought to the production floor until an order is received and this product is ready to be built. No parts are allowed at a node unless they are required for the next node, or they are part of an assembly for the next node. This philosophy has allowed Toyota to keep a minimum amount of inventory which means lower costs. This also means that Toyota can adapt quickly to changes in demand without having to worry about disposing of expensive inventory.

Important Factors to Toyota Success:

  1. Small amounts of raw material inventory must be kept at each node in production, so that production can take place for any product. These parts are then replenished when they are used.
  2. Accuracy of forecasting is important so the correct amount of raw materials can be stocked.9
  • Root Cause Analysis:

A problem solving methodology that focuses on resolving the underlying problem instead of applying quick fixes that only treat immediate symptoms of the problem. A common approach is to ask why five times – each time moving a step closer to discovering the true underlying problem.10

How does it help?

It helps to ensure that a problem is truly eliminated by applying corrective action to the “root cause” of the problem.11

  • Kaizen:

Kaizen is a Japanese term for “continuous improvement”. It is a strategy where employees work together proactively to achieve regular, incremental improvements in the manufacturing process. A main theme of kaizen is to create a culture of continuous improvement, largely by assigning responsibilities on workers and encouraging them to identify opportunities for improvement.12

How does it help :

It combines the collective talents of a company to create an engine for continually eliminating waste from manufacturing processes.13

  • Batch size reduction:

Lean manufacturing aims for materials to flow on the factory floor in the smallest batch sizes possible, with the ideal being one piece flow, so that work-in-progresses between processing stages can be minimized, the smaller the batch size, the more likely that each upstream workstation will produce exactly what it’s customer needs, exactly when it’s customer needs it.Therefore, instead a few large production lines with large batch sizes, lean manufacturing usually favors a larger number of production lines with small batch sizes.14

How does it help:

  • Less WIP (work is process) between processing stages
  • A large number of production lines with smaller batch sizes allows for a bigger range of products to be made concurrently, therefore reducing downtime and disruptions due to changeovers.
  • Requires fewer workers and provides greater accountability.

 Kanban :

It is a method of regulating the flow of goods both within the factory and with outside suppliers and customers. Kanban is a pull based material replenishment system that uses visual signals, such as color coded cards, to signal to upstream workstations when inputs are required at the downstream workstation. Actually kanban is a communication tool for pull based production. A kanban could be an empty bin, a card an electronic display or any suitable visual prompt that indicate when more goods are needed. Typically there are two types of kanban:

  1. Production kanban
  2. Withdrawal kanban15

16How does it help:

It eliminates waste from inventory and overproduction. It can eliminate the need for physical inventories (instead relying on signal cards to indicate when more goods need to be ordered).17

There are even some more important tools in lean. They include Andon, Bottleneck Analysis, Continuous Flow, Gemba (The Real Place), Heijunka (Level Scheduling), Hoshin Kanri (Policy Deployment), Jidoka (Autonomation), KPI (Key Performance Indicator), Overall Equipment Effectiveness (OEE), PDCA (Plan, Do, Check, Act), Poka-Yoke (Error Proofing), Single Minute Exchange of Die (SMED), SMART Goals, Standardized Work, Takt Time, Total Productive Maintenance (TPM), Value Stream Mapping (VSM) etc. Discussions on  them will come later.

Lean has become a key tool for the development of almost all the companies in the present world. In order to develop any company/service/product one has to know specifically about lean and implementation of it’s tools as an industrial engineer. So, good skill in lean has almost priority to make a strong and successful career in industrial engineering.