Lean Manufacturing

In this article, you will explore the 5S method of workplace organization and how it enables workers to focus on the elimination of waste. It also discusses the Kaizen approach, which focuses on continuous improvement. A lean strategy enables companies to respond to consumer demand, take a long-term view, eliminate mistakes, all while valuing the input of the employee.

Objective

After reading this page, you should be able to:

  • Apply 5S in any machine shop.
  • Describe the concept of Kaizen.
  • Describe how to implement Lean in manufacturing.


Lean 5S

"5S" is a method of workplace organization that consists of five words: Sort, Set in order, Shine, Standardize, and Sustain. These five components describe how to store items and maintain the new order. When making decisions, employees discuss standardization, which will make the work process clear among the workers. By doing this, each employee will feel ownership of the process.

Phase 0: Safety

It is often assumed that a properly executed 5S program will improve workplace safety, but this is false. Safety is not an option; it's a priority.

Phase 1: Sort

Review all items in the workplace, keeping only what is needed.

Phase 2: Straighten

Everything should have a place and be in its place. Items should be divided and labeled. Everything should be arranged thoughtfully. Employees should not have to bend over repetitively. Equipment should be placed near where it is used. This step is a part of why lean 5s is not considered "standardized cleanup".

Phase 3: Shine

Make sure that the workplace is clean and neat. By doing this, it will be easier to be aware of where things are and where they should be. After working, clean the workspace and return everything to its former position. Keeping the workplace clean should be integrated into the daily routine.

Phase 4: Standardize

Standardize work procedures and make them consistent. Every worker should be aware of what their responsibilities are when following the first three steps.

Phase 5: Sustain

Assess and maintain the standards. The aforementioned steps should become the new norm in operation. Do not gradually revert to the old ways. When taking part of the new procedure, think of ways to improve. Review the first four steps when new tools or output requirements are presented.


KAIZEN

While the lean 5S process focuses on the removal of waste, Kaizen focuses on the practice of continuous improvement. Like lean 5S, Kaizen identifies three main aspects of the workplace: waste, inconsistency, and strain (on people and machines). However, the Kaizen step-by-step process is more extensive that the lean 5S process.

The Kaizen process overview:

  1. Identify a problem.
  2. Form a team.
  3. Gather information from internal and external customers and determine goals for the project.
  4. Review the current situation or process.
  5. Brainstorm and consider seven possible alternatives.
  6. Decide the three best alternatives of the seven.
  7. Simulate and evaluate these alternatives before implementation.
  8. Present the idea and suggestions to managers.
  9. Physically implement the Kaizen results and take account of the effects.

Lean manufacturing improves as time goes one, so it is important to continue education about maintaining standards. It is crucial to change the standards and train workers when presented with new equipment or rules.


LEAN

Think of a maintenance department as serving internal customers: the various departments and workers in the company.

Lean is different from the traditional western, mass production model that relies on economies of scale to create profits. The more you make the cheaper the product will become, the greater the potential profit margin. It is based on predictions of customer needs, or creating customer needs. It has difficulty dealing with unusual changes in demand.

Lean production responds to proven customer demand. Pull processing – the customer pulls production. In a mass system the producer pushes product onto the market, push processing.

Building a long-term culture that focuses on improvement.

Respect for workers better trained and educated, more flexible

Lean is a philosophy that focuses on the following:

  1. Meeting customer needs
  2. Continuous, gradual improvement
  3. Making continuously better products
  4. Valuing the input of workers
  5. Taking the long term view
  6. Eliminating mistakes
  7. Eliminating waste

Wastes arise when too many resources are used (such as materials, time, energy, space, money, human resources, poor instructions).

Common wastes are:

  1. Overproduction
  2. Defects
  3. Unnecessary processing
  4. Waiting (wasting time)
  5. Wasting human time and talent
  6. Too many steps or moving around (excessive transportation)
  7. Excessive inventory

Lean production includes working with suppliers, sub contractors, and sellers to streamline the whole process. The goal is that production would flow smoothly avoiding costly starts and stops. The idea is called just in time "produce only what is needed, when it is needed, and only in the quantity needed." Production process must be flexible and fast.

Inventory = just what you need

In mass production = just in case. Extra supplies and products are stored just in case they are needed.

Terminology:

Defects – the mass production system inspects items at the end of production to catch defects before they are shipped. The problem is that the resources have already been "spent" to make the waste product. Try to prevent problems immediately, as they happen, by inspecting during production, at each stage of production.

Safety – hurt time is wasted time

Information – need the right information at the right time (not too much, too little, or too late)

Principles:

Poka-yoke – determine the cause of problems and then remove the cause to prevent further errors

Informative inspections – analyzing data from inspections during the process

Source inspections – inspect before the process begins to prevent errors


MEAN LEAN

One of the terms applied to a cost-cutting or job-cutting interpretation of Lean is Mean Lean. Often, modern managers think they are doing lean without understanding the importance of workers and long term relationships.


RELIABILITY-CENTERED MAINTENANCE

Reliability-centered maintenance is a system for designing a cost effective maintenance program. It can be a detailed, complex, and statistically-driven, but at its base is fairly simple. Its ideas can be applied to designing and operating a PM system and can also guide your learning as you do maintenance, troubleshooting, and repair.

These nine fundamental concepts of RCM are:

  • Failures happen
  • Not all failures are equally likely
  • Not all failures have the same consequences
  • Simple components wear out; complex systems break down
  • Good maintenance provides required functionality for lowest practicable cost
  • Maintenance can only achieve the inherent design reliability of the equipment
  • Unnecessary maintenance takes resources away from necessary maintenance
  • Good maintenance programs undergo continuous improvement

Maintenance consists of all actions taken to ensure that components, equipment, and systems provide their intended functions when required. An RCM system is based on answering the following questions:

  1. What are the functions and desired standards of performance of the equipment?
  2. In what ways can it fail to fulfill its functions? (What are the most likely failures? How likely is each type of failure? Will the failures be obvious? Can it be a partial failure?)
  3. What causes each failure?
  4. What happens when each failure occurs? (What is the risk, danger, etc.?)
  5. In what way does each failure matter? What are the consequences of a full or partial failure?
  6. What can be done to predict or prevent each failure? What will it cost to predict or prevent each failure?
  7. What should be done if a suitable proactive task cannot be found ( if no task is available, or if it might be too costly for the risk involved)?

Equipment is studied in the context of where when and how it is used. All maintenance actions can be classified into one of the following categories:

  • Corrective Maintenance – Restore lost or degraded function
  • Preventive Maintenance – Minimize the opportunity for function to fail
  • Alternative Maintenance – Eliminate unsatisfactory conditions by changing a system's design or use

Within the category of preventive maintenance, all tasks belong to one of five (5) major categories:

  • Condition-Directed – Renew an item's life based on measured condition compared to a standard
  • Time Directed – Renew an item's life regardless of condition
  • Failure Finding – Determine whether a failure has occurred
  • Servicing – Add/replenish consumables
  • Lubrication – Oil, grease, or otherwise lubricate

We do maintenance because we believe that hardware reliability degrades with age, but that we can do something to restore or maintain the original reliability that pays for itself.

RCM is reliability-centered. Its objective is to maintain the inherent reliability of the system or equipment design, recognizing that changes in inherent reliability may be achieved only through design changes. We must understand that the equipment or system must be studied in the situation in which it is working.


IMPLEMENTING LEAN MANUFACTURING

Analyze each step in the original process before making a change.

Lean manufacturing's focus is on cost reduction and eliminating activities that do not add value to the manufacturing process. Basically, what lean manufacturing does is help companies to achieve their targeted production rates by introducing tools and techniques that are easy to apply and maintain. These tools and techniques reduce and eliminate waste, which is anything that is not needed in the manufacturing process.

For example, manufacturing engineers set out to use the six-sigma DMAIC (Design, Measure, Analyze, Improve, Control) methodology in conjunction with lean manufacturing to meet customer requirements related to the production of tubes. Manufacturing engineers were charged with designing a new process layout of the tube production line. The objectives for project were:

  • Improved quality
  • Decreased scrap
  • Delivery to the point of use
  • Smaller lot sizes
  • Implementation of a pull system
  • Better feedback
  • Increased production
  • Individual Responsibility
  • Decreased WIP
  • Dine flexibility

Before making changes, the team analyzed each step in the original layout of the tube production line process, and aimed to:

  1. Try to understand the original state process, identify the problem area, any unnecessary steps, and any "non-value added".
  2. After mapping the process, the lean team collected data from the Material Review Board (MRB) bench to measure and analyze major types of defects. To better understand the process, the team also did a time study for 20 days on a production run.

In the original state, the tube line consisted of one operator and four operations, separated into two stations by a large table using a push system. The table acted as a separator between the second and third operation.

The first problem that the team discovered was that the line was unbalanced. The first station was used about 70% of the time. Operators at the second station were spending a lot of their time waiting between cycle times. By combining stations one and two, room for improvement became evident with respect to individual responsibility, control of inventory by the operator, and immediate feedback when a problem occurred. The time study and the department layout reflect these findings.

They also recognized a second problem. Because of the process flow, the production rate did not allow the production schedule to be met with two stations. Because operators lost track of machine cycles, machines were waiting for operator attention. Operators also tried to push parts through the first station (the bottleneck operation in the process) and then continued to manufacture the parts at the last two operations. Typically, long runs of in-progress items built up, and quality problems were not caught until a lot of defective pieces were produced.

The original state data was taken from the last 20 days before the change. The teams analyzed each step in the original and made changes. The time study on the original process was used as the basis for reducing cycle time, balancing the line, and re-designing the line using Just-In-Time kanbans and scheduling. This was aimed at improving quality, decreasing lot size and in-progress items, and improving flow. New process data was taken starting one month after implementation. This delay gave the machine operators an opportunity to train and get to with the new process layout system.

With a U-shaped cell design instead of the two-table system, the new parts met the team's needs. The table in the original process was removed, which almost eliminated the backlog in in-progress items. With this reduction in in-progress items, production increased.

Some of the concepts used to improve the process included total employee involvement (TEI), smaller lot sizes, scheduling, point of use inventory, and improved layout. All employees and supervisors in the department were involved in all phases of the project. Their ideas and suggestions were incorporated in the planning and implementation process to gain wider acceptance of the changes to the process. Smaller lot sizes were introduced to minimize the number of parts produced before defects were detected. Kanbans were introduced (in the form of material handling racks) to control in-progress items and to implement a pull system. And the cell layout decreased travel between operations. Operators were authorized to stop the line when problems arose. In the original design, the operators continued running parts when a operation was down. With kanban control, the new layout eliminated the ability to store in-progress items, requiring the operator to shut down the entire line. The cell layout provided excellent opportunities for improving communication between operators about problems and adjustments that led to better quality.

Day-to-day inspection of the original-state process showed that operators spent a lot of time either waiting for someone to handle materials, or acting as material handlers themselves. With U-shaped cells, delivery to the point of use allowed the operators to be much more efficient. The operator placed boxes of raw material on six movable roller carts, which made them easy to access. These six boxes were enough to last for 24 hours. To reduce setup times, tools needed for machine repair and adjustments were located in the cell. The screws were not standardized, and tools were set up in order of increasing size. This allowed workers to quickly identify the proper tool.

The process was monitored for three months to verify that it was sustainable. Comparing time studies from the original-state with the new layout demonstrated an increase in production from 300 to 514 finished products per shift. The new layout eliminated double handling between the second and third operations, as well as at the packing step. It also reduced throughput time by making it easier to cycle all four operations in a pull-system order. Customer demand was met by two shifts, which reduced the labor cost.

The results of the redesign are as follows:

  • In-progress items decreased by 97%
  • Production increased 72%
  • Scrap was reduced by 43%
  • Machine utilization increased by 50%
  • Labor utilization increased by 25%
  • Labor costs were reduced by 33%
  • Sigma level increased from 2.6 to 2.8

This project yielded reduced labor and scrap costs, and allowed the organization to do a better job of making deliveries on time, while allowing a smaller finished-goods inventory. Daily production numbers and single-part cycle time served as a benchmark for monitoring progress towards the goal. This led to a sigma level increase, 43% reduction in defects, 97% reduction in in-progress items, and a production increase of 72%.

Implementing lean is a never-ending process: it is continuous improvement, after all. When you get one aspect of lean implemented, it can always be improved. Don't get hung up on it, but don't let things slip back to the starting point. There will always be time to go back and refine some of the processes.

Before Lean Manufacturing was implemented at this plant, it operated using traditional manufacturing. Traditional manufacturing consists of producing all of a given product for the marketplace so as to never let the equipment idle. These goods then need to be warehoused or shipped out to a customer who may not be ready for them. If more is produced than can be sold, the products will be sold at a deep discount (often a loss) or simply scrapped. This can add up to an enormous amount of waste. After implementing Lean Manufacturing concepts, the company started to use just-in-time. Just-in-time refers to producing and delivering a good in the amount required when the customer requires it and not before. In lean manufacturing, the manufacturer only produces what the customer wants, when they want it. This often a much more cost-effective way of manufacturing when compared to high-price, high-volume equipment.


Knowledge Check:

  1. What is 5S?
  2. Explain each "S" of the 5S.
  3. Explain the Kaizen concept.
  4. What is pull processing?
  5. What is poka-yoke?
  6. What is six-sigma DMAIC?
  7. What are the objectives for a new process layout of the tube production line described above?
  8. Before making changes, what do the team of manufacturing engineers do first?
  9. List the results of the redesign.
  10. What is the key to implementing a Lean new idea or concept?

Source: Adapted from LamNgeun Virasak; https://openoregon.pressbooks.pub/manufacturingprocesses45/chapter/chapter-7-lean-manufacturing/
Creative Commons License This work is licensed under a Creative Commons Attribution 4.0 License.

Last modified: Tuesday, 9 April 2019, 12:09 PM