Lean Systems – Important Points – Summary – Krajewski – 12th Edition

Learning Goals

Continuous Improvement Using A Lean Systems Approach

  • Describe how lean systems can facilitate the continuous improvement of processes.
Strategic Characteristics of Lean Systems
  • Identify the strategic supply chain and process characteristics of lean systems.
Designing Lean System Layouts
  • Explain the differences between one-worker, multiple machine (OWMM) and group technology (GT) approaches to lean system layouts.
Value Stream Mapping
  • Understand value stream mapping and its role in waste reduction.
The Kanban System
  • Understand kanban systems for creating a production schedule in a lean system.
Operational Benefits and Implementation Issues
  • Explain the implementation issues associated with the application of lean systems.

Chapter 6.  LEAN SYSTEMS

ALDI mini case

Continuous Improvement Using A Lean Systems Approach

In terms of waste elimination of principle of industrial engineering (principles of industrial engineering, Narayana Rao), Toyota Production System as described by Ohno identifies 7 wastes. The eighth waste is also added as underutilization of employees knowledge and creativity, The ninth waste is also added in the OEE explanation, underutilization of speed. Actually underutilization of speed of machines and men is the prime focus of Taylor’s productivity improvement effort.
Krajewski et al. described eight wastes. The goal of lean system is to eliminate these eight types waste and continuously improve the value-added benefits of the operation. Lean systems focus on both quality and productivity to facilitate low inventories and the opportunities to improve are observed, identified and efforts are made to improve activities, operations and processes on a continuous basis to achieve zero waste (muda).  The japanese term for process or operation improvement is kaizen.  One of the ways, waste is brought into spotlight is by decreasing inventory between process steps. This brings into focus problem areas and demands improvement.

Strategic Characteristics of Lean Systems
Supply Chain Considerations in Lean Systems
Process Considerations in Lean Systems
Managerial Practice 6.1 Alcoa
Toyota Production System

Close supplier ties: Lean systems operate with low inventories and suppliers have to supply at frequent intervals. Let us first start with a daily delivery and later move to multiple deliveries in a day. The leadtime is short. The information of consumption during the day,  let us say is given during the working day and by evening the entire stock consumed in the day has to be replenished by the supplier. Supplies have to arrive on schedule without fail and there cannot be any defects. To ensure this supplier are treated as partners in the supply chain venture. The partner share in the supply chain profit and efforts are made to increase profit as much as possible by eliminating waste in the supply chain practices. Ohno described in his book that industrial engineering is profit engineering. Elimination of waste is profit creation.

Small lot sizes and brief setup times: Another important strategic characteristic of lean system is the small lot size. It is brought into the system profitably by first reducing the setup times. Setup time reduction requires the cooperation between engineering, industrial engineering, management and operators. While in the case of dies SMED is a popular idea, in case of tool changes in CNC machines we have to think of SSET – subsecond exchange of tools.

Operations in the processes are activated through pull systems.

Quality at the source and zero defects is promoted. Jidoka is an idea of Toyota’s founders in automatic  textile machinery wherein they developed a machine that will stop if a defect likely to be produced and calls for operator attention.

Lean systems also try to make the load uniform every day by producing multiple products and taking steps to smoothen demand with close ties with customers also.

5S practices, standardized work methods communicated through visual means, flexible workforce with multiple skills as required by the process, jidoka automation, and total productive are other important characteristics of lean system (TPS).

Toyota Production System   Toyota Production System – Origin and Development – Taiichi Ohno
Toyota Production System – Industrial Engineering Component – 1- Shigeo Shingo
Toyota Production System – Industrial Engineering Component – 2- Shigeo Shingo

Designing Lean System Layouts
One Worker, Multiple Machines
Group Technology

Line flows are used in lean systems. In lean systems, line layouts are made to accommodate multiple products in parts making or in assembly. In assembly it is called mixed-model assemble line. In machine shops it called group technology or cellular manufacturing. In these layouts, one worker – multiple machines system is employed when one worker can man multiple machines without extra burden.

The Kanban System
General Operating Rules
Determining the Number of Containers
Other Kanban Signals

The kanban is a visual card authorizing further production of the component. As an assembly line lifts parts from a supermarket rack, it detaches the kanban attached to the container and leaves at that place. This acts the authorization for the parts producing department to produce another container of components.

Kanban system operators on simple rules or principles,.

1. Each container has a kanban attached to it along with parts.
2. Assembly line withdraws components when it needs from the supermarket rack. They pull the parts as per their need.
3. Assembly area cannot take the container without removing the kanban card and leaving it at the place.
4. The container has the specified number of parts only.
5. All the parts in the container have to be good. Quality assured by the production operator.
6. Production of components in day cannot exceed the quantity indicated by the kanbans.

Value Stream Mapping
Current State Map
Future State Map

 Value stream mapping is recommended as the main process map or flow map for the development and improvement of lean system. Shigeo Shingo or Taichi Ohno did not indicate the value stream map as the main instrument. But now it is popular in lean literature.

Value stream map spans the supply chain from the firm’s suppliers of  raw materials to the delivery of the finished good to the customer.This visual picture helps managers to identify the source of wasteful non-value added activities and lean tools or lean system improvement tools are used to eliminate waste.

First a current state map is prepared and analyzed. Possible improvements are identified and the required engineering and management modifications are identified. Based on the proposals selected for implementation, a future state map is prepared and the whole project is sent to higher level managers for approvals.

As a part of mapping, cycle time (C/T), setup or changeover time (C/O), uptime, production batch sizes, number of operators in the operation/process,  working time, scrap rate, etc. are measured and indicated in the map.

Operational Benefits and Implementation Issues
Organizational Considerations
Process Considerations
Inventory and Scheduling

Lean system can be a decision during manufacturing strategy determination as it yields multiple benefits compared to line systems or batch systems.

Lean systems are giving rise to some operational problems as many companies are trying to implement them and they need attention and managerial creativity to solve the problems in the context of the firms. While, Toyota is a standing testimony to the feasibility of a lean system, the managers of each company have to do problem solving in the context of their own company.

The problems indicated in the Krajewski’s book are human reactions, issues of continued trust between persons and partner firms, reward system issues, maintaining stability of schedules, difficulty of setup time reductions in some operations and machines, and supplier coordination issues,

Learning Goals in Review

Video Case Lean Systems at Autoliv
Case Copper Kettle Catering

Process Improvement – Process Industrial Engineering – Relevant Chapters in Operations Management

Process Strategy and Analysis – Important Points – Operations Management – Krajewski – 12th Edition

Quality and Performance – Important Points – Summary – Krajewski – 12th Edition

Lean Systems – Important Points – Summary – Krajewski – 12th Edition

Constraint Management – Important Points – Summary – Krajewski – 12th Edition

Index to Summaries of all Chapters of Krajewski’s Book

Operations Management – Krajewski – 12th Edition – Chapter Summaries – Important Points