Introduction to lean manufacturing

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The term ‘Lean Manufacturing' is a generic term which focuses on cut out of the "fat" or waste in the manufacturing process. Waste(elaborated as under) is as such defined as anything that does not add value to the customer or the customer is unwilling to pay for. This type of manufacturing system and philosophy was originally developed by Toyota and is now used by many manufacturers throughout the world. Other manufacturers have adapted the system to meet their own needs and assigned a proprietary name to it, such as Delphi Automotive's Delphi Manufacturing System.


If a customer orders a shirt to be custom made, it may take 6 weeks. However the actual time the tailors or seamstresses are working on the shirt is only 5 hours. The rest of the time is taken up by such things as material ordering, waiting between processes and inefficient shipping practices. This extra time does not add value to the customer. As Lean Manufacturing principals are applied to the shirt-making process, one would see a reduction in delivery time from 6 to 5 to 4 weeks and even less. The ideal shirt-making operation would be streamlined to give the customer, what they want, when they want it at the lowest possible cost within the least amount of time.

Though they may not call it Lean, the "Eyeglasses in About an Hour" companies have applied many Lean principles to their operation. What used to take weeks is now done in about an hour, adding value to the customer. It is no surprise that these operations have opened up all over the country. What was once thought of as impossible speed of delivery is now commonplace. Applying Lean Manufacturing principles gives manufacturers these types of results on a routine basis.


Lean manufacturing deals with the reduction or elimination of many types of waste with lowest cost and customer defined quality as driving forces. In Lean technology, identifying and eliminating waste is so important that it even has its own terminology. In Lean, waste is called MUDA, which comes from the Japanese term for waste. They are as follows:


  • bviously a product that cannot be sold or has to be dumped at a reduced price is wasteful. Also producing product before the customer needs it requires the part to be stored and ties up money in inventory.


Excess Inventory ties up a great deal of cash, which is wasteful. Stockpiling inventory between processes is wasteful.

Conveyance -

Unnecessarily moving a part during the production process is wasteful. It can also cause damage to the part, which creates wasteful rework.


Having to re-work parts because of manufacturing errors is a large source of waste. Additionally, sorting and inspecting parts is wasteful and can be eliminated by error proofing (designing your processes so that the product can only be produced one way, which is the correct way, every time).


Unnecessary or awkward operator motions put undue stress on the body and cause waste. Improvement in this area should result in reduced injury and workman's compensation claims.


Unclear customer requirements cause the manufacturer to add unnecessary processes, which add cost to the product.


The operator being idle between operations is wasteful. It is acceptable for the machine to wait on the operator, but it is unacceptable for the operator to wait on the machine.


As a consequence of eliminating the above 7 types of ‘waste', leads to an overall optimized output with:

  • Less capital equipment
  • Less floor space
  • Less operator effort
  • Less direct labor
  • Less indirect labor
  • Less inventory
  • Less lead time

Now, while the standard definition of Lean manufacturing is certainly accurate, the specific benefits that Lean will have on individual processes and eventually entire companies are achieved after much waste has been eliminated from a shop floor, notably single piece flow which is described as an ideal state of efficient operations, where batch sizes and lot production are replaced by working on one product at a time. While not practical for operations which very low processing times and correspondingly high change-over times ,it is nevertheless a Lean Manufacturing goal to achieve single piece flow in every operation possible.

As a company reduces the wastes mentioned earlier and strives for single piece flow, many other benefits will follow. Some of these benefits include

Improved quality and fewer defects:

When batching and lot production are eliminated, there are lesser chances for manufacturing defects. Since the batch size will be just one, there will not be mountains of inventory to count, move, store and pick. Furthermore, single piece flow ensures that if there is a quality problem, we know that the defect has affected only that single part. We do not need to dedicate hours isolating and testing other material in the same production run to determine if it meets quality standards.

  • f course, if a defect is caught in a single piece flow environment, this should not mean that we do not take the appropriate corrective actions to ensure that the problem will not reoccur. In this case, the manager or supervisor must determine if standard work was followed and if so, what changes need to be made to the standard in order to ensure that the problem will never resurface again. Kaizen!

Reduced Inventory:

Implementing single piece flow will require each operation to only produce what is needed by the next operation. When followed properly, the process will eliminate any opportunity to build ahead. Consequently, inventories will not be allowed to build up.

Requires less space:

As inventory levels are reduced, less space and manpower will be required to manage (receive, count, stock, store, pick and deliver) it. In addition, single piece flow usually results in manufacturing cells which squeeze machines close together so that a single operator can oversee many pieces of equipment with the least amount of walking motion.

Enhances overall manufacturing flexibility:

In a single piece flow environment, since we operate with less inventory, lead-times will also drop, thereby giving us more time to react to customer orders (unless the strategic decision is made to pass off the lead-time gains to the customer in order to beat competitors).

Makes identifying future kaizens simpler:

We have already discussed that in a single piece flow environment, defects and WIP inventories fall. As this happens, the shop floor will open up and it will become easier to see production problems. For example, if a particular process can not keep up with takt time and WIP is not allowed to be incurred, it will quickly become apparent to even the casual observer that something is wrong. In this case, it will be easy to decide where to focus the next improvement activity.

Ensures a safer work environment:

Less inventory means less clutter, more light in the darkest corners of the factory and the opportunity to better lay out equipment and tools. Also, since manufacturing cells are occupied by a set number of employees who each know their repeating tasks (as defined by standard work), there is less opportunity for unexpected movements, which increase the chances of accidents.

Improves employee morale:

Since single piece flow results in production problems being identified and solved right away, team members will receive immediate feedback on their work. This in turn will give everybody more ownership in their production area. Also, provided they lead problem solving efforts by focusing on processes and not individuals, more trust will be gained in managers.


Lean manufacturing organizations focus on four thrusts to support their lean manufacturing designs:

I.Solid leadership that:

  • Communicates the vision.
  • Facilitates and models the behaviors of lean manufacturing.
  • Sets the standards for the organization.
  • Assists the workforce in adapting to the change.
  • Builds trust and inspires commitment.
  • Coaches and develops the workforce.
  • Constantly challenges the system.

II.Team-based cultures that:

  • Use project-oriented, team-based structures that focus on empowerment concepts.
  • Leverage knowledge by using highly skilled workers.
  • Promote employee accountability and responsibility for work.
  • Advocate the continual development of the workforce.
  • Value diversity.
  • Believe that employee ownership of the final product is shared throughout the process.

III.Communication systems that:

  • Advocate and develop processes to identify critical design issues as early in the process as possible.
  • Encourage “on-the-spot” decision-making processes that use the fewest resources to resolve critical design issues.
  • Promote knowledge sharing between hourly workers, management, and design personnel.
  • Drive the behaviors of internal operations, as well as focus on the behaviors of suppliers and customers.
  • Accept formal and informal communication behaviors.

IV.Simultaneous development and continuous improvement processes that:

  • Design the product right the first time.
  • Use continuous improvement processes to identify the non-value-added problems.
  • Drive commitment to eliminating problems (controlling them is not enough).
  • Advocate just-in-time material control systems.
  • Promote constant improvement throughout the supply chain.
  • Leverage the knowledge of the organization with the knowledge bases of suppliers and customers.
  • Continually train and develop highly skilled workers.
  • Use scoreboards or measurement systems to monitor progress.


  • To significantly improve overall productivity
  • To increase market share
  • To improve speed-to-market with new products
  • To reduce manufacturing and engineering labour costs
  • To eliminate non-value-added operations and processes Lean manufacturing techniques


The basics of lean manufacturing, which is a performance-based process, employ continuous improvement processes to focus on the elimination of waste or non-value added steps within an organization. The challenge to organizations utilizing lean manufacturing is to create a culture that will create and sustain long-term commitment from top management through the entire workforce. Lean manufacturing techniques are based on the application of five principles to guide management's actions toward success:

1. Value: The foundation for the value stream that defines what the customer is willing to pay for.

2. The Value Stream: The mapping and identifying of all the specific actions required to eliminate the non-value activities from design concept to customer usage.

3. Flow: The elimination of all process stoppages to make the value stream “flow” without interruptions.

4. Pull:The ability to streamline products and processes from concept through customer usage.

5. Perfection: The ability to advocate doing things right the first time through the application of continuous improvement efforts.

The key effects of using lean manufacturing techniques are as follows:

  • Equipment reliability
  • Balanced or level production
  • Just-in-time material control techniques
  • Stop-the-lineto correct the problem and in-station process control
  • Continuous improvement processes
  • Statistical Process Control techniques for quality consistency
  • Developing human systems to support the technical processes