EngineeringManagement

MSE595LMLean 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

Continuous Flow changes everything:• 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

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) 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

Takt Time

Key Points About Takt Time

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

EngineeringManagement

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

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: The signal can be a:• Card• Square• Box• Pigeon hole• Light• Etc.• Electronic Signal• Racks• Shopping Carts• MRK ( Manufacturing Ready Kit)

• Authorizes production

• Authorizes movement

• Limits inventory

• Drives 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

Example

Leadtime 75Safety Time 14Total Time 89Number of months 3

Production monthly requirements 50Units in the Pipeline 148Cost of unit 20000Unit per kanban (container) 25

Number of Kanbans 5.933333

Pipeline inventory cost 2966667

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

Kanban Example

Who is full?

Who needs work?

Condo-ban!!

Kanban

Units ready for calibration

Unit in build

SMT Kanban

Kanban Light (More Work)

4-754 MRKManufacturing Ready Kit: The empty kit signals for replenishment

4-754 MRK

Homework Assignment 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?

Read Lean Thinking Chapter 4 - Pull

• Pages 67 - 89

Questions? Comments?