Engineering
Management
MSE595LM
Lean Manufacturing
Chapter 3
Flow
Flow - Definition
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The production system Henry Ford introduced at his Highland
Park, Michigan plant in 1913.
The objective of flow production was to drastically reduce
product throughput time and human effort through a series of
innovations.
Consistently interchangeable parts so that cycle times could be
stable for every job along an extended line
The line itself
The reconfiguration of part fabrication tasks so that machines
were lined up in process sequence with parts flowing quickly
and smoothly from machine to machine
Production control system insuring that the production rate in
parts fabrication matched the consumption rate of parts in final
assembly.
The World of Batch-and-Queue
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What happens when you go to your doctor?
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Make appointment days ahead
Arrive on time and wait in waiting room
Doctor behind schedule
Referral to a specialist
Laboratory tests
Wait for results
Treatment or medication given
Trip to pharmacy or to specialist
Hospitalization – whole new disconnected processes and waiting
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What happens when you take a flight?
 What happens when you build a custom home?
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As the customer, you pay for all the waiting and rework
The creation, ordering, and provision of any good or any
service can be made to flow.
How to Obtain Flow?
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Think about ways to:
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Line up all of the essential steps needed to get a job done
Obtain a steady, continuous flow
No wasted motions
No interruptions
No batches
No queues
Continuous Flow changes everything:
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How we work together
The kinds of tools we devise to help with our work
The organizations we create to facilitate the flow
The kinds of careers we pursue
The nature of business firms and their linkage to each other
The society
The Techniques of Flow
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Step 1: Focus on the actual object
• The specific design
• The Specific order
• The product itself
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Step 2: Ignore traditional boundaries of
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Jobs
Careers
Functions and
Firms
Form lean enterprise removing all obstacles to the continuous flow
Step 3: Rethink specific work practices and tools
• Eliminate backflows, scrap, and stoppages so that the design,
order, and production of the specific product can proceed
continuously
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All three steps must be taken together
Example: From Batch to Flow in Bicycles
The Design Step
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Marketing department determined a “need”
Product engineers design a product to serve the need
Prototype department built a prototype to test the design
Tooling department designed tools to make a high-volume
version of the approved prototype
Production engineering figured out how to use the tools to
fabricate the frame and to assemble the component parts into a
completed bike
Purchasing department arranged to buy the necessary
component parts for delivery to the assembly line once the
design was finalized
The design moved from department to department waiting in
the queue
Frequent reworked or secretly reengineered to deal with
incompatibilities between the process steps
Example: From Batch to Flow in Bicycles
Design Using The Lean Approach
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Create truly dedicated product teams with all the skills required
to conduct the following in one room in short period of time:
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Value specification
General design
Detailed engineering
Purchasing
Tooling
Production planning
Quality Function Deployment (QFD): decision-making
methodology utilizing “standardized work” to ensure process
repeatability
 Throughput time accurately measured
 Design methodology continuously improved
Example: From Batch to Flow in Bicycles
Order-Taking
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Sales department obtain orders from retailers
Scheduling department in Operations or Manufacturing work the
production schedules for the various products
Customers call the Sales department to status late orders
Sales calls Scheduling
When customers threaten to cancel orders, Sales and
Scheduling expedite the orders
Sales and Scheduling had been combined in the early 1990’s
Computerized systems make instantaneous order changes and
sometimes electronically transmitted to the customers
Example: From Batch to Flow in Bicycles
Order-Taking Using the Lean Approach
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Sales and Production Scheduling are core members of the
product team
In a position to plan the sales campaign as the product design
is being developed
Sale with a clear eye to the capabilities of the production
system so that both orders and the product can flow smoothly
from sale to delivery
No stoppages in the production system
Products are built to order
Only few hours elapse between the first operation on raw
materials and shipment of the finished item
Orders can be sought and accepted with clear and precise
knowledge of the system’s capabilities
There is no expediting!
Takt Time
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Precisely synchronizes the rate of production to the rate of
sales to customers
 Takt Time Calculation Example:
• Customers are placing orders at the rate of 48/day
• Bike factory works a single eight-hour shift
Number of Bikes Ordered
48 Bikes 6 Bikes
1 Bike
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Number of Hours Available 8 Hours
Hour
10 Minutes
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Takt time adjusted as orders increase or decrease over time
 The production slots created by the Takt Time are clearly posted
on whiteboard or electronic displays (andon boards)
 Lean technique – transparency or visual control – everyone
can see where production stands at every moment
Takt Time
Key Points About Takt Time
Example: From Batch to Flow in Bicycles
Production
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Historic practice was to differentiate production activities by type and
to create departments for each type of activity.
Frame and handle bars:
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Tube cutting
Tube bending
Mitering
Welding
Washing
Painting
Final Assembly of complete bike
Over time, higher speed machines with higher levels of automation
were developed for cutting, bending, welding, and painting
Assembly lines to assemble a mix of high-volume models
Large batches made before changing over to run the next part
Large inventory
Bicycle Plant Layout and Flow
TUBE
STOCK
STORAGE
START
COMP
PARTS
STORAGE
2
1
FRAME
WASHING
TUBE
CUTTING
DEBURR
FRAME
WELDING
FRAME
PAINTING
TUBE
MITERING
TUBE
BENDING
FRAME
PARTS
STORAGE
FRAME
STORAGE
FINAL
ASSEMBLY
1
2
FINISHED
STORES/
SHIPPING
END
Engineering
Management
Continuous Flow Factory
Continuous Flow Production
Remember!
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Make It Flow
Feed the Flow
Link the Flow
Continuous Flow Production
Definition
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Flow of products in a level manner through the
production operations. The ideal situation is one
piece flow at and between processes.
The intent of flow production is to increase
the velocity of products and make the
production cycle predictable.
Steady Velocity
Traditional: Batch Production (like a meandering stream with many stagnant pools, waterfalls, and eddies)
When do we get our Parts?
FLOW:Production: Pipeline with fast-flowing water or product
The right Job and it must keep moving
2 WEEKS!
Connected Lines
Layout change
Before
Bore Honing
Blank Machining
Honing
Drive Slot
Milling
Lube Slot
Milling
CNC Mill
Gear
Hobbing
Hole
Drilling
Drill
Hob
Mill
Dbur.
Dbur.
CNC Lathe
Lathe
CNC
Blank Machining
Manual
Manual
Deburring
Deburring
After
Boring
CNC Lathe In
Drill
Out
Gear
Gear
Shaver
Shaver
Tooth
Tooth
Hole Chamfer
Hole
Chamfer
Boring
Boring
Gear
Shaving
CNC Mill
Mill
Chamfer
Chamfer
Boring
Gear
Shaver
Gear
Hobbing
Summary of Benefits
 Work flow levels are reduced and progress is visible at a
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glance
The ability to cross train is enhanced
Work team members take ownership of full process and can
help each other
Quick problem identification and feedback
Reduced Cycle Time
Improved quality through cycle of learning
Information flow and decision making enhanced
Value-added ratio improved
Reduces transportation waste
Reduces material handling
Helps to identify root causes of quality problems
Allows for equipment dedication
Drives set-up times down
Rules for Kanban Systems
1) Pull from the downstream process (or customer)
drives the system.
2) All product or inventory is under kanban control.
3) Only an “empty” kanban authorizes production.
4) Never pass a known defect downstream.
5) Use gradual kanban reductions to drive
improvement.
Purpose of a Kanban System
1) Authorize production
2) Authorize movement.
3) Limits amount of inventory in the system.
4) A tool for driving continuous improvement.
Kanban
Is a “signal” that:
• Authorizes production
• Authorizes movement
• Limits inventory
• Drives continuous
improvement
The signal can be a:
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Card
Square
Box
Pigeon hole
Light
Etc.
Electronic Signal
Racks
Shopping Carts
MRK ( Manufacturing Ready Kit)
How Many Kanbans?
(Lead Time + Safety Time) = Total Time
Total Time x Production Requirement = Units in Pipeline
Units in Pipeline
Units per Kanban
= Number of Kanbans
Example
Leadtime
Safety Time
Total Time
Number of months
Production monthly requirements
Units in the Pipeline
Cost of unit
Unit per kanban (container)
Number of Kanbans
Pipeline inventory cost
75
14
89
3
50
148
20000
25
5.933333
2966667
Pull Production System
Definition
• A customer driven system that produces and
moves a product/service only when the
customer needs it.
Kanban
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Work
Center A
Kanban
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Work Flow
Work
Center B
Kanban
3
Customer
Pulls
Kanban Example
Condo-ban!!
Who is full?
Who needs work?
Kanban
Unit in build
Units ready for calibration
SMT Kanban
Kanban Light (More Work)
4-754 MRK
Manufacturing Ready Kit: The empty kit signals for replenishment
4-754 MRK
Homework Assignment
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Questions:
1. Explain what is meant by Continuous Flow Production
2. What is Takt Time? What is Takt Rate? Why is it important
to know them?
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Read Lean Thinking Chapter 4 - Pull
• Pages 67 - 89
Questions? Comments?