Lean Thinking and Systems
Lean Thinking and Lean Systems
McGraw-Hill Education
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Learning Objectives
Describe the origins and evolution of lean thinking.
Describe the five tenets of lean thinking and the seven forms of waste in a lean system.
Explain how a stabilized master schedule is achieved for repetitive manufacturing.
Design a kanban system for a lean system.
Explain how setup time, lot size, layout and maintenance are related to lean thinking.
Differentiate how employees, quality, and suppliers are unique in lean systems.
Explain how to implement a lean system.
Evolution of Lean
Toyota Production System (TPS)
Developed in Japan following WWII (limited resources)
Also known as Just-in-Time (JIT) manufacturing
Came to U.S.- 1981 at Kawasaki motorcycle plant in Lincoln, Nebraska
Lean Production
Term coined in late 1980s
Popularized in 1990s by Womack, Jones & Roos’ “The Machine That Changed the World”
Lean Tenets
Create product/service value from customer perspective
Reduce waste – muda
Identify, study, improve the value stream
Observe the process – gemba
Ensure simple, smooth, error-free flow
Determine takt time
Produce only what is pulled by customer
Use kanbans
Strive for perfection
Hold kaizen events, 5S, 5 Whys
The Seven Forms of Waste
Overproduction: Producing more than the demand for customers, resulting in unnecessary inventory, handling, paperwork, and warehouse space.
Waiting time: Operators and machines waiting for parts or work to arrive from suppliers or other operations. Customers waiting in line.
Unnecessary transportation: Double or triple movement of materials due to poor layouts, lack of coordination, and poor workplace organization.
Excess processing: Poor design or inadequate maintenance or processes, requiring additional labor or machine time.
Too much inventory: Excess inventory due to large lot sizes, obsolete items, poor forecasts, or improper production planning.
Unnecessary motion: Wasted movements of people or extra walking to get materials.
Defects: Use of material, labor, and capacity for production of defects, sorting out bad parts, or warranty costs with customers.
Value Stream Mapping
Value stream is all processing steps to complete product/service
Extension of process flowcharting
Includes value-adding/non-value-adding activities
Requires direct observation of process – gemba
“Is this step or task necessary in creating value to the customer?”
Change and improve process
Value Stream Mapping
Inventory Covers Problems (Figure 7.2)
Unreliable
Inefficient
Water Level
Water level indicates level of inventory in the system
Water Level Lowered To Expose Problems
Unreliable
Inefficient
Water Level
Water level indicates level of inventory in the system
Water Flows Smoothly, once problems are resolved
Water Level
Water level indicates level of inventory in the system
Problems reduced/solved
5 Whys Technique
Explores cause-and-effect relationships that underlie problems (root causes)
Enables root causes to be identified/resolved
Example: Truck won’t start.
Why? Battery is dead.
Why? Alternator not functioning.
Why? Alternator belt is broken.
Why? Truck was not maintained as recommended.
Why? Truck is old; no replacement parts available.
Solution? Find source for parts, or purchase new truck.
5S Technique
Organize workspace to improve employee morale, safety, process efficiency.
Reduces time looking for “things.”
Seiri to Sort (keep, toss)
Seiton to Straighten or set in order
Seiso to Shine, sweep, or clean
Seiketsu to Standardize
Shitsuke to Sustain (maintain)
5S Technique example
Storage of chemicals in production area
Elements of Lean System
Stabilizing the master schedule
Controlling flow with kanban system
Reducing setup time (quick changeover)
Small lot sizes (goal lot size of single unit)
Efficient layout (linear flow, low inventories)
Preventive maintenance
Cross-training, rewarding workers
Quality and continuous improvement
Close relationships with suppliers (frequent deliveries)
Stabilizing the Master Schedule
Production horizon set according to demand
Production schedule repeated each day
Uniform load: level work load across workers/machines
Takt time: match supply (production rate) to demand rate
Produce planned quantity each day, and no more
Desirable, but not essential, to a lean system
Kanban System
Kanban: “marker” (card, sign)
“Pull” production system
Visual control system of cards and containers, or other type of signal
Number of containers:
D = Demand rate (at work center)
T = Time for container to complete circuit
C = Container size (# units)
The Kanban System
Signals the need for more parts
Uses simple cards or signals to control production/inventory
Each work center receives production order (card) from succeeding work center
Prevents the buildup of inventory
Reduces lead time
Extends to receiving orders from suppliers
Kanban System (Figure 7.3)
Reducing Setup Time and Lot Sizes
Reducing setup time:
increases available capacity
increases flexibility to meet schedule changes
reduces inventory
Setup types
Single (single digit minutes)
One-touch (less then 1 min; 2-step process)
Internal (while machine stopped)
External (while machine operating)
Lot size reduction
Goal: single unit production
Non-Lean Layout (Figure 7.4)
Stockrooms
Supplier A
Supplier B
Work Centers
Lean Layout
Supplier A
Supplier B
Work Centers
Lean Layout with Group Technology
(Cellular Manufacturing)
Supplier A
Supplier B
Engaging Workers
Multifunction, cross-trained workers
Flexibility to move to busy work centers
New pay system to reflect skills variety
Workers contribute individually and collaboratively
Perform own maintenance and inspection
Teamwork, problem solving
Suggestion systems
Quality in a Lean System
Quality is essential input into lean system
Defects are waste
No inventory to cover up mistakes
System designed to expose errors; correct them at their source (so not repeated in the future)
Continuous improvement of the process
Supplier Relationships
Viewed as the ‘external factory’
Co-location, frequent deliveries
Fewer suppliers
No inspection—high quality is assumed (required)
Integrated supplier programs
Early supplier selection
Family-of-parts sourcing
Long-term strategic relationship
Reduce paperwork and inspection
Implementation of Lean Systems
Establish a cross-functional team
Determine what customers value
Construct value stream map
Eliminate waste (non-value-adding activities)
Use customer demand to pull work thru process
Implement team ideas
Repeat the cycle on another process
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