8.24.2020

Lean in High-Mix Low-Volume (HMLV) Manufacturing -- Does it Work?

Lean thinking and methodology have resulted in many organizations instituting powerful initiatives and gaining major improvements, but most still associate Lean principles with low-mix high-volume (LMHV) manufacturers. There are, however, a gamut of high-mix low-volume (HMLV) manufacturers that wonder if the power of Lean is really applicable to them given their very different factors regarding volume, variety, and scheduling.

I recently spoke with Shahrukh Irani – who actually just published a book entitled Job Shop Lean:  An Industrial Engineering Approach to Implementing Lean in High-Mix Low-Volume Production Systems – and asked him the very specific question: “How is Lean applicable in High-Mix Low-Volume (HMLV) manufacturing?” Here is his detailed answer: 

Of all high-mix low-volume (HMLV) manufacturers, a job shop has the most complex production system.  The classification of different production systems that is shown in Figure 1 provides the simplest evidence that forcing a job shop to adopt a production system and tools that were designed to improve a repetitive assembly line’s performance is like fitting a square peg into a round hole. 

Figure 1: Comparison of an Assembly Plant and a Custom Fabrication Job Shop


Currently, nearly every job shop has failed to realize the full gains from Lean because they have stopped at implementing only the Lean tools listed in the left-hand column of Table 1.  In contrast, the Lean tools in the right-hand column of Table 1 are ineffective, often inapplicable, in any job shop.  So how does any Lean job shop reap additional benefits from Lean?  By implementing a new “Job Shop Lean Toolbox” in which the Lean tools in the right-hand column of Table 1 have been replaced with other tools that were developed for job shops!  

Table 1: A New “Job Shop Lean Toolbox” for High-Mix Low-Volume Manufacturers

Lean tools that will work in job shops also

Lean Tools that will not work in job shops

Strategic Planning

Pencil-and-Paper Problem Solving

Top-Down Leadership

Value Stream Mapping

Gemba Walks by Managers

Assembly Line Balancing

Employee Engagement

One-Piece Flow Cells

Workplace Design with 6S

Product-specific Kanbans

TPM (Total Productive Maintenance)

FIFO Sequencing of Orders

Setup Reduction (SMED)

Pacemaker Scheduling

Error-Proofing (Poka-Yoke)

Inventory Supermarkets

Quality At Source

Work Order Release based on Pitch

Visual Workplace

Production based on Level Loading

Product and Process Standardization

Mixed Model Production with Takt Time

Right-sized Flexible Machines

Right-sized Inflexible Machines

Standard Work

Pull-based Production Scheduling

Continuous Problem-Solving

Manual Scheduling with Whiteboards

 

If the Tool Works for High-Mix Low-Volume, Then Job Shop Lean Uses It!

In Table 1, the tools in the left-hand column will also work in HMLV production systems.  Top-down Leadership” and “Employee Involvement” are essential.  “Standard Work Instructions” and “Setup Reduction” are needed to minimize variation in setup times on any machine (or manufacturing cell) due to different parts having varying setup sequences, tooling packages, material sizes, tolerances, etc.  “Quality at Source” empowers employees to reduce costs, take pride in their workmanship and have ownership for their work.   “Right-sized Machines” appears in both columns of Table 1 because simple machines are easy to learn to use, setup, operate and maintain.    

If the Tool Does Not Work for High-Mix Low-Volume, Then Job Shop Lean Replaces It!

In Table 1, the tools in the right-hand column will almost never work in HMLV production systems because those tools are simply not applicable to MTO (Make-To-Order) HMLV production systems that do not operate like assembly lines.  It is these tools that have been replaced by a more effective set of tools, often enabled by software, to successfully implement Job Shop Lean.

What do you think of Shahrukh's observations? What are the experiences of those who work in a HMLV environment and have been part of a Lean initiative?

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