A Fundamental Limitation of Lean

     

For every OEM like Toyota, there are thousands of small-to-medium manufacturers (SMM) whose operations simply do not match those of an assembly line.  Most SMMs tend to be HMLV (high-mix low-volume) custom manufacturers, or worse, they operate like job shops.  The Toyota Production System (TPS) is not the complete solution for these HMLV (high-mix low-volume) manufacturers because many of the revolutionary operational strategies of the TPS are primarily suited for assembly line production.  The majority of the popular Lean tools were never designed to handle the operating conditions and constraints of high-mix low-volume (HMLV) manufacturing facilities, as shown in Table 1.  

It is essential that HMLV manufacturers embrace the philosophy and follow the 5-step process — Principles of Lean — when implementing Lean.  But, they must also carefully select a manufacturing strategy that suits them.  In turn, their choice of manufacturing strategy will force them to significantly change the methods and tools they use to implement that strategy.  Today, there is a clear-cut need for a viable production system model that could be implemented by the thousands of high-mix low-volume (HMLV) manufacturers in the US alone, ranging from machine shops to ship yards!

Advancing Lean to High-Mix Low-Volume (HMLV) Manufacturing

Job Shop Lean is essentially a modification of the five-step process for implementing Lean proposed by James Womack and Daniel Jones in their bestseller book published in 2003, Lean Thinking.  Unfortunately, while the Womack-Jones process for implementing Lean may be universally applicable in bits and pieces, many of the Lean tools that are used to implement that process are unsuitable for HMLV environments.  In the case of any HMLV manufacturer, such as a CNC machine shop, fabricator or custom forge shop, the TPS/Lean tools are incapable of implementing the three major steps in the Womack-Jones process for implementing Lean:

  1. Map the value stream: Identify all the steps in the value stream for each product family, eliminating whenever possible those steps that do not create value.
  2. Create flow: Make the value-creating steps occur in tight sequence so the product will flow smoothly toward the customer.
  3. Establish pull: As flow is introduced, let customers pull value from the next upstream activity.    

How Job Shop Lean Differs from Lean

Job Shop Lean is similar to, but also differs from, Lean as follows:

  1. It completely embraces the human resource aspects of the Toyota Production System such as management involvement and engagement with employees, cross-training of employees, kaizen events executed by employee teams, etc.
  2. Its toolkit includes the TPS/Lean tools listed in the left-hand column of Table 1.
  3. Its toolkit replaces the TPS/Lean tools listed in the right-hand column of Table 1 with tools that are appropriate for design and operation of an HMLV production system in the 21st Century.
  4. It requires that the ERP system being used by an HMLV manufacturer have the capabilities/functions to plan, schedule and control shop floor (and office) operations that do not have the cadence that exists in assembly line manufacturing.  
  5. It emphasizes major revision of university curricula so that the education and training of future Industrial Engineers and Operations Managers gives them real-world knowledge and industry experience in implementing Lean, Six Sigma, Theory Of Constraints, etc. before they enter the workforce.

For Further Information on Job Shop Lean

Please click here to listen to an online lecture Job Shop Lean vs. Toyota Lean: Why the Toyota Production System is Unsuitable for Job Shops. 

Please click here to access the article Adapting Lean for Hgh-Mix Low-Volume Manufacturing Facilities. Gear Technology, (2012, August), 10-12.

Please click here to access the article A Quick-Start Approach for Implementing Lean in Job Shops. Gear Technology, (2012, October), 10-12.

Please click here to access the report Recession-Proof your Shop the Lean Way.

Please click here to access other Job Shop Lean videos available on my YouTube Channel.

Please click here for more information on the book Job Shop Lean: An Industrial Engineering Approach to Implementing Lean in High-Mix Low-Volume Production Systems.