wcm - group technology & cellular manufacturing

Mayuresh Unde

1st Feb, 2011

Group Technology & Cellular Manufacturing

Types of Manufacturing Layouts

Process Layout

Product Layout

Cellular Layout

Process Layouts

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

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 – heavy capital investment– Duplicate tooling is required for all cells– Difficult to alter flow rates / introduce new products as

line re-balancing would be required

Cellular Manufacturing

A manufacturing cell is a cluster of machines or processes located in close proximity and dedicated to the manufacture of a family of parts.

The parts are similar in their processing requirements, such as operations, tolerances, and machine tool capacities

Cellular Layout

Cell #2

Cell #3

Cell #1

D D M I

D ML L I

D

M

L

M

I

CELLULAR LAYOUT

Volume Vs Variety

TRANSFERLINE

SPECIAL SYSTEM

FLEXIBLEMANUFACTURING

SYSTEM

MANUFACTURINGCells

STD. AND GEN.MACHINERY

VO

LUM

E

HIGH

VARIETYLOW HIGH

Cellular Layout Characteristics

• Advantages

– Control is simplified

– Common tooling and fixtures

– Flexible -- can produce many different part types –(part families)

– Reduced cycle times

– Reduced inter-cellular movements

– Multi-skilled workers

Design of cellular manufacturing system is a complex exercise with broad implications for an organization.

The cell design process involves issues related to both system structure and system operation

11

Cell Design

Structural issues include:

• Selection of part families and grouping of parts into families

• Selection of machine and grouping of these into cells

• Selection of tools, fixtures, and pallets

• Selection of material-handling equipment

• Choice of equipment layout

12

Issues related to procedures include:

• Organization of supervisory and support personnel around the cellular structure

• Formulation of maintenance and inspection policies

• Design of procedures for production planning, scheduling, control, and acquisition of related software and hardware

• Modification of reward & incentive systems

• Outline of procedures for interfacing with the remaining manufacturing system (in terms of work flow and information, whether computer controlled or not)

Cell Design

Cell Cycle Time & Capacity

In an assembly cell, the actual cycle time is entirely a function of the cell Manual Time, which is the time required for the workers to perform their tasks and move between workstations. Thus, if only one person operates the assembly cell then,

Cell Cycle Time = Ʃ Operation Times + Ʃ Walk Times

Cell Capacity = Time Available Cell CT

Part Families & Groups

The word ‘Family’ is used as a name for any list of similar parts. The families used with group layout are lists of parts which are similar because they are all made on the same group of machines. This type of family is called a ‘Production Family’.

The other important features that is important choosing the families;Manufacturing tolerancesRequired quantities / volumesMaterialsSpecial features, which will require the use of different machines

A ‘Machine Group or Machine Cell’ is a list of machines, selected for layout together in one place, because it contains all necessary facilities to complete the processing of a given family of parts. A family of parts can only be defined by relating it to a particular group of machines, and a group by relating it to a family. Groups vary greatly in type and size, widely in the number of machines and different machines types.

Typical Part Families

Items that are made with the same equipment

Items that look alike –Physical characteristics, dimensions, geometric shapes etc.

Family 1

Family 2

Group Technology

Group technology begun by grouping parts into families, based on their attributes.

There are three methods that can be used to form part families:

Manual visual inspection: Uses Judgment

Classification and coding: Most widely used in the industry, time consuming and complicated at times

Production flow analysis: Production Flow / Route sheets are studied from a manufacturing process perspective

Group Technology or GT is a manufacturing philosophy in which the parts having similarities (Geometry, manufacturing process and/or function) are grouped together to achieve higher level of integration between the design and manufacturing functions of a firm. The aim is to reduce work-in-progress and improve delivery performance by reducing lead times.

Classification & Coding

FUNCTIONAL CLASSIFICATION

• coding based on part design attributes

• coding based on part manufacturing attributes

• coding based on a combination of design & manufacturing attributes

STRUCTURAL CLASSIFICATION

• Hierarchical Structure

• Chain Type Structure

Functional ClassificationEX

AM

PLE

The Optiz Classification System

Form Code:describes the primary design attributes

Supplementary Code:manufacturing attributes –dimensions, work material, accuracy, starting work piece shape

Secondary Code:Identifies production operation type and sequence

12345 6789 ABCD

Mono-code – Hierarchical Code

• The structure of mono-code is like a tree in which each symbol amplifies the information provided in the previous digit.

• A monocode (hierarchical code) provides a large amount of information in a relatively small number of digits. Useful for storage and retrieval of design-related information such as part geometry, material, size, etc.

Production Flow Analysis

A technique for forming part families based on Operation Routing Summaries

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}

Part No. Routing Times (min) Ave. Dem.

101 D1 -M1 - V1 9 - 12 - 14 100

102 D2 -M2- V1 5 - 11 - 14 250

103 D1 -M1 7 - 9 700

104 M2 - V2 - D2 8 - 12 - 5 100

105 V1 - M1 - D1 7 - 10 - 12 200

Operation Routing Summary

PFA Matrix

M =

Mac

hin

es

Parts

101 102 103 104 105

Drill 1 1 0 1 0 1Drill 2 0 1 0 1 0Mill 1 1 0 1 0 1Mill 2 0 1 0 1 0VB 1 1 1 0 0 1VB 2 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 16V 1 1 1 0 0 1 32V 2 0 0 0 1 0 64

42 52 10 84 42

1

Machine# (i)

23456

2 i

Generate 2i

=i

ij mw ij2

Sum: mi,j * 2i

for each column (wj)

(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

D 1 1 1 1 0 0D 2 0 0 0 1 1M1 1 1 1 0 0M2 0 0 0 1 1V 1 0 1 1 1 1V 2 0 0 0 0 0

10 42 42 52 84wj

101 105

104

102

103


#3. calculate the total row weight, wi

=j

ijj

i m2w

103 101 105 102 104

D 1 1 1 1 0 0 14D 2 0 0 0 1 1 48M1 1 1 1 0 0 14M2 0 0 0 1 1 48V 1 0 1 1 1 1 28V 2 0 0 0 0 1 32

2 4 8 16 322j

wi

Sum: mi,j * 2j

for each row (wi)

Generate 2j

1


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

ascend.

103 101 105 102 104110000

111000

111000

001011

000111

D 1

M1

V 1

V 2

D 2

M2

D2 V2

V1

M1

V2


103 101 105 102 104110000

111000

111000

001011

000111

D 1

M1

V 1

V 2

D 2

M2

#5 Stop and make Cells and Part families

Production Flow Analysis

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

Weakness:

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

Advantages

• 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

Benefits of Group Technology/ Cellular Mfg

1. Engineering design

• Reduction in new parts design

• Reduction in the number of drawings through standardization

• Reduction of drafting effort in new shop drawings

• Reduction of number of similar parts, easy retrieval of similar functional parts, and identification of substitute parts

2. Layout planning

• Reduction in production floor space required

• Reduced material-handling effort

Benefits of Group Technology

3. Specification of equipment, tools, jigs, and fixtures

• Standardization of equipment due to implementation of cellular manufacturing systems

• Significant reduction in up-front costs incurred in the release of new parts for manufacture

4. Manufacturing: process planning

• Reduction in setup time and production time

• Reduction in wait times, transfer times etc.


5. Manufacturing: production control

• Reduced work-in-process inventory

• Improved material flow and reduced warehousing costs (Semi-finished)

• Increased Inventory turns

• Improved through-put

6. Manufacturing: quality control

• Reduction in number of defects leading to reduced inspection effort

• Reduced scrap generation

• Better output quality

• Increased accountability of operators and supervisors responsible for quality production, making it easier to implement total quality control concepts.


7. Purchasing

• Coding of purchased part leading to standardized rules for purchasing leading to less supplier quality issues

• Economies in purchasing possible because of accurate knowledge of raw material requirements

• Reduced number of part and raw materials

• Simplified vendor evaluation procedures leading to just-in-time purchasing

8. Customer service

• Accurate and faster cost & time estimates

• More reliable operations leading to accurately meeting delivery deadlines – leads to improved customer satisfaction

wcm - group technology & cellular manufacturing

Documents