Cellular Manufacturingand Facilities Layout

Dr. Richard A. Wyskrwysk@psu.edu

http://www.engr.psu.edu/cim

Outline of Activities

• Fundamentals of layout

• Advantages of various layouts

• Creating part families

• Economics of Cellular layout– scheduling– setup reduction

• Other issues

Readings• Chapter 18 of Computer Aided Manufacturing, Wang,

H.P., Chang, T.C. and Wysk, R. A., 3rd Edition (2004 expected) http://www.engr.psu.edu/cim/active/chapter18.pdf

ExerciseReadiness Assessment Test A.K.A. RAT

AS AN INDIVIDUALAS AN INDIVIDUAL,

Describe what you think a “part family” is.

Describe what you think a “process family” is.

Which is the best way to cluster products in a manufacturing facility: a) the way a part looks, b) the function of the part, 3) the way the part is made. Why?

Open Book / Open Notes

ExerciseReadiness Assessment Test A.K.A. RAT

AS A TEAMAS A TEAM, take 5 minutes

• Compare and discuss the efficiencies and the uses of the various ways to group “stuff” in a shop.

• Try to chalk out a ‘best practice’.• List the criterion you used.

Open Book / Open Notes

Objectives

• To apply the principles of flow to a complex manufacturing system

• To design the layout of process, product and cellular manufacturing systems

• To form cells in a manufacturing environment

• To analyze efficiencies of reduced batch sizes

Types of Manufacturing Layout

• Process Layout

• Product Layout

• Cellular Layout

FUNCTIONAL LAYOUTS ARE INEFFICIENT

PROCESS-TYPE LAYOUT

Lathe Milling Drilling

Grinding

Assembly

Receiving andShipping

L

L L

L

L

L

L

L M

MM

M M

M

A A

A A

D

D D

D

G

G

G

G G

G

Process Layout Characteristics

• Advantages– Deep knowledge of the process

– Common tooling and fixtures

– Most Flexible -- can produce many different part types

• Disadvantages– Spaghetti flow -- everything gets all tangled up

– Lots of in-process materials

– Hard to control inter-department activities

– Can be difficult to automate

PRODUCT LAYOUT

Shipping

L L M D

L M D

G

L M GG

A A

Receiving

Part #1

Part #3

Part #2

Product Layout Characteristics

• Advantages– Easy to control -- input control– Minimum material handling -- frequently linked to the

next process– Minimal in-process materials– Can be more easily automated

• Disadvantages– Inflexible -- can only produce one or two parts– Large setup– Duplicate tooling is required for all cells

Cell #2

Cell #3

Cell #1

D D M I

D ML L I

D

M

LM

I

CELLULAR LAYOUT

Cellular Layout Characteristics

• Advantages– Control is simplified

– Common tooling and fixtures

– Flexible -- can produce many different part types - a part family??

• Disadvantages– Setup ??

– Need to know about many different processes

FLEXIBILITY

PRODUCTION CAPACITY

TRANSFERLINE

SPECIAL SYSTEM

FLEXIBLEMANUFACTURING

SYSTEM

MANUFACTURINGCells

STD. AND GEN.MACHINERY

VO

LU

ME

HIGH

VARIETYLOW HIGH

How are Cells Formed

• Good intuition• Careful study• Group Technology (GT)• Production Flow Analysis (PFA)

Typical Part FamiliesItems that are made with the same equipmentItems that look alike

A FAMILY OF PARTS

PRODUCTION FAMILY

Items that are made with the same equipment - Production Flow Analysis

PFA is a technique that uses Operation Routing Summaries as input. It clusters the parts that require the same processes. These parts can then be assembled into a part family. The processes can be grouped into a cell to minimize material handling requirements.

Items that look alike

Most products that look similar are manufactured using similar production techniques. If parts are grouped because they have similar geometry (about the same size and shape), then they should represent a part family.

Grouping based on geometry or function

THREE TECHNIQUES TO FORM PART FAMILIES

2. CLASSIFICATION & CODING BY EXAMINTAION OF DESIGN & PRODUCTION DATA

• MAY USE PHOTOS OR PART PRINTS• UTILIZES SUBJECTIVE JUDGMENT

• MOST COMMON IN INDUSTRY• MOST TIME CONSUMING & COMPLICATED

Cont’d

1. TACIT JUDGMENT OR VISUAL INSPECTION

THREE TECHNIQUES TO FORM PART FAMILIES

3. PRODUCTION FLOW ANALYSIS

• USES INFORMATION CONTAINED ON THE ROUTE SHEET (THEREFORE ONLY MFG. INFO)• PARTS GROUPED BY REQUIRED PROCESSING

Classification & Coding by Examination of Design & Production Data

Many systems have been developed but none is universally applicable and most implementations require some customization

Identifying Manufacturing Cells Using Production Flow Analysis

Production Flow Analysis

• A technique for forming part families based on Operation Routing Summaries

• Several methods available. We will discuss 2 algorithms for PFF (Part Family Formation)

Let’s consider 5 parts (n) and 6 machines (m):

n = {101, 102, 103, 104, 105}

m = {Drill1, Drill2, Mill1, Mill2, Vbore1, Vbore2} = {D1, D2, M1, M2, V1, V2}

Operation Routing Summary

Create a PFA matrix, M

M =

Mac

hine

sParts

101 102 103 104 105Drill1 1 0 1 0 1Drill2 0 1 0 1 0Mill1 1 0 1 0 1Mill2 0 1 0 1 0VB1 1 1 0 0 1VB2 0 0 0 1 0

King’s Algorithm (Rank Order Clustering) Step#1Calculate the total column width for each column

Part# (j) 101 102 103 104 105

D1 1 0 1 0 1 2D2 0 1 0 1 0 4M1 1 0 1 0 1 8M2 0 1 0 1 0 16V1 1 1 0 0 1 32V2 0 0 0 1 0 64

42 52 10 84 42

1

Machine# (i)

23456

2i

Generate 2i

i

ij mw i2

Sum: mi,j * 2i

for each column (wj) Done!(wj)

#2. If Wj is in ascending order, go to step #3; otherwise, rearrange the columns to make Wj fall in an ascending order.

103 101 105 102 104 i

D1 1 1 1 0 0 14D2 0 0 0 1 1 48M1 1 1 1 0 0 14M2 0 0 0 1 1 48V1 0 1 1 1 1 28V2 0 0 0 0 0 32

10 42 42 52 84wj

101 105

104

102

103

#3. i, calculate the total row weight, wi

j

ijj

i m2w

103 101 105 102 104

D1 1 1 1 0 0 14D2 0 0 0 1 1 48M1 1 1 1 0 0 14M2 0 0 0 1 1 48V1 0 1 1 1 1 28V2 0 0 0 0 0 32

2 4 8 16 322j

wi

Sum: mi,j * 2j

for each row (wi)

Generate 2j

Done!

#4. If wi is in ascending order, stop. Otherwise, arrange rows to make Wi ascend.

103 101 105 102 104110000

111000

111000

001011

000111

D1

M1

V1

V2

D2

M2 D2 V2

V1

M1

V2

103 101 105 102 104110000

111000

111000

001011

000111

D1

M1

V1

V2

D2

M2

#5 Stop and make Cells and Part families

Discussion

• Good rectangles mean that you have very distinctive part families

• Do Parts no 103, 101, 105 have a distinct code so that a can be made to distinguish them from #102, 104.

• Cell formation

• Volume / Floor space

• Size of problems

• How about King’s algorithm? Will it always work?

• Are there problems with it?

F

DIRECT CLUSTER ALGORITHM

101 102 103 104 105D1 1 0 1 0 1D2 0 1 0 1 0M1 1 0 1 0 1M2 0 0 0 1 0V1 1 1 1 0 1V2 0 0 0 1 0

wi

323141

Step #1. For I, calculate the total no. of positive cells in row, i

j

ijMiw

all

101 102 103 104 105V1 1 1 1 0 1D1 1 0 1 0 1M1 1 0 1 0 1D2 0 1 0 1 0M2 0 0 0 1 0V2 0 0 0 1 0

wi

433211

3 2 3 3 3 1

Sort rows in descending order of the wi values

D1

M2

V1D2 No Change

No Change

Done!

Step #2. j, calculate the total # of positive cell in each column, j

i

ijj mwall

101 103 105104102V1 1 1 101D1 1 1 100M1 1 1 100D2 0 0 011M2 0 0 010V2 0 0 010

Sort Complete!

Sort columns in ascending order.

3 2 3 3 3

Step #3. For i = 1 to n, move all columns j where mij = 1 to the left maintaining the order of previous rows.

101 103 105104102V1 1 1 101D1 1 1 100M1 1 1 100D2 0 0 011M2 0 0 010V2 0 0 010

Move Column 105 to the left and push column 104 back

Observe Elements of Row 1

101 103 105 104102V1 1 1 1 01D1 1 1 1 00M1 1 1 1 00D2 0 0 0 11M2 0 0 0 10V2 0 0 0 10

For Rows 1,2 & 3: Move the 1’s to the left and push the columns with the zeroes back

Observe Elements of Rows 2 & 3

Move Columns 101, 103 & 105 to the left and push column 102 back

101 103 105 104102V1 1 1 1 01D1 1 1 1 00M1 1 1 1 00D2 0 0 0 11M2 0 0 0 10V2 0 0 0 10

Observe Elements of Row 4

Move Column 102 to the left and push column 101 back

101 103 105 104102V1 1 1 1 01D1 1 1 1 00M1 1 1 1 00D2 0 0 0 11M2 0 0 0 10V2 0 0 0 10

Observe Elements of Rows 5 & 6

Move Column 104 to the left and push column 102 back

101 103 105104 102V1 1 1 10 1D1 1 1 10 0M1 1 1 10 0D2 0 0 01 1M2 0 0 01 0V2 0 0 01 0

Step #

3 Com

plete

!!

Step #4. For j = m to 1, move all rows I, where mij = 1 to the top maintaining the order of the previous columns, wij

101 103 105104 102V1 1 1 10 1D1 1 1 10 0M1 1 1 10 0D2 0 0 01 1M2 0 0 01 0V2 0 0 01 0

Observe Elements of Column 102Observe Elements of Columns 101, 103 & 105: No Change can be made!!

Move Row D2 upwards and push row D1 down

101 103 105104 102V1 1 1 10 1

D1 1 1 10 0

M1 1 1 10 0

D2 0 0 01 1

M2 0 0 01 0V2 0 0 01 0

Observe Elements of Column 104

Move Row D2 to the top and push row V1 down

101 103 105104 102

V1 1 1 10 1

D1 1 1 10 0

M1 1 1 10 0

D2 0 0 01 1

M2 0 0 01 0V2 0 0 01 0

Observe Elements of Column 104

Move Rows M2 & V2 upwards and push row V1 down

101 103 105104 102

V1 1 1 10 1

D1 1 1 10 0

M1 1 1 10 0

D2 0 0 01 1M2 0 0 01 0V2 0 0 01 0

Step #

4 Com

plete

!!

Step #5. If current matrix is the same as the previous, stop; else to go 3.

101 103 105104 102

V1 1 1 10 1

D1 1 1 10 0

M1 1 1 10 0

D2 0 0 01 1M2 0 0 01 0V2 0 0 01 0

Identify Cells or potential Cells

Cell #1

Cell #2

Part Family #1 Part Family #2

Production Flow Analysis-SCOPE-

We learned two (and probably the most common) methods/algorithms for performing a Production Flow Analysis.

There are a host of other algorithms and methods which are used in Academics and in the Industry.

(contd..)

Production Flow Analysis -Organizational View-

Production Flow Analysis consists of 5 different analyses:

1. Company Flow Analysis

2. Factory Flow Analysis

3. Group Analysis

4. Line Analysis

5. Tooling Analysis

Company Flow Analysis

• A Planning technique used for the division of large companies into factory components. It aims to simplify the flow of materials between factories.

• Uses FROM-TO charts and frequency charts and a flow analysis (similar to the one discussed in slides 29 – 41).

• Is not a decision making model, but presents data in a way that decisions can be made based on a company’s goal.

CFA (Analysis)CFA (Analysis) Company’s Goals

Company’s Goals

We get a SCHEME for the division of products and components, machines and facilities into factory sets

Factory Flow Analysis

An attempt is made at this stage to find major groups of departments, and major families of components which can be completely processed in these departments.

The Goal is to change factories from process organization to product organization and to minimize interdepartmental material flow

(Contd.. FFA Methodology )

• Study and map the existing flow system• Identify the dominant material flows between shops

(or buildings)• Determine the Process Route Number (PRN) for each

part• Analyze the part by PRN.• Combine closely associated processes at departments

that complete most of the parts they make• If parts are observed to backtrack then such flows are

eliminated by minor redeployment of equipment

Factory Flow Analysis-Methodology-

Factory Flow Analysis-An Example-

Group Analysis

The flows in each of the individual shops (identified by FFA) are analyzed.

Operation sequences of the parts that are being produced in a particular shop are analyzed to identify manufacturing cells.

Loads are calculated for each part family to obtain the equipment requirements for each cell

Group Analysis

Essentially, while forming and rearranging the PFA matrix (slides 29-41) we were performing Group Analysis.

Those same algorithms are also employed in PFA activities other than Group Analysis (namely CFA, FFA etc..)

Choice of algorithm or technique that is best suited is, for the most part, a problem specific issue

Line Analysis

A linear or U-layout is designed for the machines assigned to each cell.

The routings for each part assigned to the cell and the frequency of use of each routing are used to develop a cell for: – Efficient transport, &– Minimum material handling and travel by

operators.

Line Analysis Example

Tooling Analysis

A Tooling Analysis helps to schedule the cell by identifying families of parts with similar operation sequences, tooling and setups.

It seeks to sequence parts on each machine to sequence all the machines in the cell to reduce setup times and batch sizes.

This increases available machine capacity on bottleneck work canters in the cell.

PFA: Assumptions

• Each component is equally important in terms of cost

• Lot size & its associated cost are not directly related to grouping procedure

• Routing is assumed to be optimal

PFA is suitable mostly for small sized applications, but it has difficulties coping with some large cell formation problems when the Machine-Part Matrix becomes more complex because of problem size

PFA: Weakness

• Reduces flow distances

• Better suited to JIT and “pull” manufacturing as the overall flow is much straighter

• Simple and Easy to implement

• Experience: Lots of Research and Background and support software

PFA: Advantages

Questions?!?

Could you use this for a “real-world” problem?

What problems arise from using PFA?