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Lean Manufacturing
Chapter 3Flow
Flow - Definition
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
What happens when you go to your doctor?• 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
What happens when you take a flight? What happens when you build a custom home?
• 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?
Think about ways to:• 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
The Techniques of Flow
Step 1: Focus on the actual object• The specific design• The Specific order• The product itself
Step 2: Ignore traditional boundaries of • 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
All three steps must be taken together
Example: From Batch to Flow in BicyclesThe Design Step
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
Create truly dedicated product teams with all the skills required to conduct the following in one room in short period of time:• 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 BicyclesDesign Using The Lean Approach
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 BicyclesOrder-Taking
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!
Example: From Batch to Flow in BicyclesOrder-Taking Using the Lean Approach
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
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) • andon boards: status-display station: Japanese name for a visual
production-control device (usually a lighted overhead display) that continuously shows changing status of the production line and sounds alerts if a problem is imminent.
Lean technique – transparency or visual control – everyone can see where production stands at every moment
Takt Time
N u m b er o f B ik es O rd ered
N u m b er o f H o u rs A v ailab le
B ik es
H o u rs
B ik es
H o u r
B ik e
M in u tes
4 8
8
6 1
1 0
Historic practice was to differentiate production activities by type and to create departments for each type of activity.
Frame and handle bars:• 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
Example: From Batch to Flow in BicyclesProduction
Bicycle Plant Layout and Flow
STARTTUBE
CUTTINGDEBURR
TUBEMITERING
TUBESTO CK
STO RAG E
TUBEBENDING
FRAMEW ELDING
1
1 FRAMEPARTS
STO RAG E
FRAMEW ASHING
2
2FRAME
PAINTINGFINAL
ASSEMBLYFRAMESTO RAG E
FINISHEDSTO RES/SHIPPING
END
CO MPPARTS
STO RAG E
Continuous Flow Factory
Continuous Flow Production
Remember!
• Make It Flow
• Feed the Flow
• Link the Flow
Continuous Flow Production
Definition
• 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)
FLOW:Production: Pipeline with fast-flowing water or product
The right Job and it must keep moving
2 WEEKS!When do we get our Parts?
Connected Lines
Layout change
Before GearHobbing
CNC LatheBoring Chamfer
GearShaver
Dbur.
HoleBoring
ManualDeburring
ToothChamfer
Gear ShavingAfter
CNC LatheC
NC
Lathe
Honin
g
CNC Mill
Mill DrillBoring
Dbur.
Ho
b
Chamfe
r
GearShaver
CNC Lathe
Honing CNC MillMill
Drill
Boring
Hob
ChamferGear
Shaver
Dbur.
Blank Machining
Blank MachiningBore Honing
Drive SlotMilling Lube Slot
Milling
HoleDrilling
HoleBoring
ManualDeburring
GearHobbing
ToothChamfer
Gear Shaving
In Out
Summary of Benefits
Work flow levels are reduced and progress is visible at a 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
Eight Wastes
TABLE 8.1 | THE EIGHT TYPES OF WASTE OR MUDA
Waste Definition
1. Overproduction Manufacturing an item before it is needed.
2. Inappropriate Processing
Using expensive high precision equipment when simpler machines would suffice.
3. Waiting Wasteful time incurred when product is not being moved or processed.
4. Transportation Excessive movement and material handling of product between processes.
5. Motion Unnecessary effort related to the ergonomics of bending, stretching, reaching, lifting, and walking.
6. Inventory Excess inventory hides problems on the shop floor, consumes space, increases lead times, and inhibits communication.
7. Defects Quality defects result in rework and scrap, and add wasteful costs to the system in the form of lost capacity, rescheduling effort, increased inspection, and loss of customer good will.
8. Underutilization of Employees
Failure of the firm to learn from and capitalize on its employees’ knowledge and creativity impedes long term efforts to eliminate waste.
Continuous Improvement
Figure 8.1 – Continuous Improvement with Lean Systems
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.
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
Pull Production System
Definition• A customer driven system that produces
and moves a product/service only when the customer needs it.
Work Flow
Kanban1
Kanban2
Kanban3
WorkCenter A
WorkCenter B
Customer
Pulls
The Kanban System
Receiving postKanban card for product 1
Kanban card for product 2
Fabrication cell
O1
O2
O3
O2
Storage area
Empty containers
Full containers
Assembly line 1
Assembly line 2
Figure 8.4 – Single-Card Kanban System
The Kanban System
Storage area
Empty containers
Full containers
Receiving postKanban card for product 1
Kanban card for product 2
Fabrication cell
O1
O2
O3
O2
Assembly line 1
Assembly line 2
Figure 8.4 – Single-Card Kanban System
The Kanban System
Storage area
Empty containers
Full containers
Receiving postKanban card for product 1
Kanban card for product 2
Fabrication cell
O1
O2
O3
O2
Assembly line 1
Assembly line 2
Figure 8.4 – Single-Card Kanban System
The Kanban System
Storage area
Empty containers
Full containers
Receiving postKanban card for product 1
Kanban card for product 2
Fabrication cell
O1
O2
O3
O2
Assembly line 1
Assembly line 2
Figure 8.4 – Single-Card Kanban System
The Kanban System
Storage area
Empty containers
Full containers
Receiving postKanban card for product 1
Kanban card for product 2
Fabrication cell
O1
O2
O3
O2
Assembly line 1
Assembly line 2
Figure 8.4 – Single-Card Kanban System
The Kanban System
Storage area
Empty containers
Full containers
Receiving postKanban card for product 1
Kanban card for product 2
Fabrication cell
O1
O2
O3
O2
Assembly line 1
Assembly line 2
Figure 8.4 – Single-Card Kanban System
The Kanban System
Storage area
Empty containers
Full containers
Receiving postKanban card for product 1
Kanban card for product 2
Fabrication cell
O1
O2
O3
O2
Assembly line 1
Assembly line 2
Figure 8.4 – Single-Card Kanban System
The Kanban System
KA
NB
AN
Part N
um
ber:
1234567Z
Location
:A
isle 5B
in 47
Lot Q
uan
tity:6
Su
pp
lier:W
S 83
Cu
stomer:
WS
116
1. Each container must have a card
2. Assembly always withdraws from fabrication (pull system)
3. Containers cannot be moved without a kanban
4. Containers should contain the same number of parts
5. Only good parts are passed along
6. Production should not exceed authorization
Number of Containers
Two determinationsNumber of units to be held by each container
Determines lot size
Number of containers Estimate the average lead time needed to produce a container of
parts
Little’s law Average work-in-process inventory equals the average demand
rate multiplied by the average time a unit spends in the manufacturing process
Number of Containers
WIP = (average demand rate) (average time a container spends in the manufacturing process)+ safety stock
WIP = kc
kc = d (w + p )(1 + α)
k = d (w + p )(1 + α)
cwhere
k =number of containersd =expected daily demand for the partw =average waiting timep =average processing timec =number of units in each containerα =policy variable
Number of Containers
Formula for the number of containers
k =Average demand during lead time + Safety stock
Number of units per container
WIP = (average demand rate)(average time a container spends in the manufacturing process) + safety stock
Determining the Appropriate Number of Containers
EXAMPLE 8.1 The Westerville Auto Parts Company produces rocker-arm
assemblies A container of parts spends 0.02 day in processing and 0.08 day
in materials handling and waiting Daily demand for the part is 2,000 units Safety stock equivalent of 10 percent of inventory
a. If each container contains 22 parts, how many containers should be authorized?
b. Suppose that a proposal to revise the plant layout would cut materials handling and waiting time per container to 0.06 day. How many containers would be needed?
Determining the Appropriate Number of Containers
SOLUTION
a.If d =2,000 units/day, p =0.02 day, α =0.10, w =0.08 day, andc =22 units
k =2,000(0.08 + 0.02)(1.10)
22
= = 10 containers22022
b. Figure 8.5 from OM Explorer shows that the number of containers drops to 8.
Figure 8.5 – OM Explorer Solver for Number of Containers
Application 8.1
Item B52R has an average daily demand of 1000 units. The average waiting time per container of parts (which holds 100 units) is 0.5 day. The processing time per container is 0.1 day. If the policy variable is set at 10 percent, how many containers are required?
k = d (w + p )(1 + α)
c
= 6.6, or 7 containers
=1,000(0.05 + 0.01)(1 + 0.1)
100
Kanban Light (More Work)
![[1913] #2.12 Armour's Monthly Cook Book - October 1913](https://img.dokumen.tips/doc/110x75/577d2da61a28ab4e1eae0102/1913-212-armours-monthly-cook-book-october-1913.jpg)
