Ch6 Group Technology and Cellular Manufacturing
Transcript of Ch6 Group Technology and Cellular Manufacturing
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
1/108
1
GROUP TECHNOLOGY ANDCELLULAR MANUFACTURING
MIDDLE EAST TECHNICAL UNIVERSITY
Mechanical Engineering Department
ME 445 ME 445 Integrated Manufacturing SystemsIntegrated Manufacturing Systems
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
2/108
2
BATCH MANUFACTURING
IS A DOMINANT MANUFACTURING ACTIVITY IN THE WORLD,
GENERATING A GREAT DEAL OFINDUSTRIAL OUTPUT
IT ACCOUNTS60% - 80%
OF ALL MANUFACTURING ACTIVITIES
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
3/108
3
CHARACTERISTICS OFBATCH MANUFACTURING:
High level of product variety Small manufacturing lot size
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
4/108
4
Time onmachine
5%
Moving and waiting9 5%
Cuttingless than
30%
Positioning, loading, gauging,idle, etc.
70%
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
5/108
5
WHAT IS GROUP TECHNOLOGY?
Group technology (GT) is a philosophy thatimplies the notion of recognizing and exploitingsimilarities in three different ways:
1. By performing like activities together 2 . By standardizing similar tasks3 . By efficiently storing and retrievinginformation about recurring problems
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
6/108
6
Large manufacturing system can bedecomposed into smaller subsystemsof part families based on similarities in
1. design attr ibu t es and2 . m a nuf act u r ing fe at u r es
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
7/108
7
DESIGN ATTRIBUTES:part configuration ( round or prismatic)dimensional envelope (l ength to diameter
ratio)surface integrity ( surface roughness,
dimensiona l to l erances)material typeraw material state ( casting, forging, bar
stock, etc.)
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
8/108
8
PART MANUFACTURING FEATURES:
operations and operation sequences( turning, mi ll ing, etc.)batch sizes
machine toolscutting toolswork holding devices
processing times
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
9/108
9
An essential aspect of theintegration of CAD and CAM isthe integration of information usedby engineering and manufacturingand all the other departments in afirm.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
10/108
10
Gro up t e ch n olo gy emphasis onpart families based on similaritiesin design attributes and
manufacturing, thereforeGT
contributes to the integration of CAD and CAM.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
11/108
11
The Basic Key Features for a Successful GroupTechnology Applications:
Group Layout
Short Cycle Flow Control
A Planned Machine Loading
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
12/108
12
Group Layout
In most of todays factories it is possible todivide all the made components into familiesand all the machines into groups, in such a way
that all the parts in each family can becompletely processed in one group only.
The tree main types of layout are
Line Layout
Group Layout
Functional Layout
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
13/108
13
Line Layout
Line Layout is used at present in simple process industries, in continuous assembly, andfor mass production of components required in
very large quantities.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
14/108
14
Functional LayoutIn Functional Layout, all machines of the
same type are laid out together in the samesection under the same foreman. Each foreman
and his team of workers specialize in one process and work independently.This type of layout is based on process specialization.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
15/108
15
Group Layout
In Group Layout, each foreman and his teamspecialize in the production of one list of partsand co-operate in the completion of common
task. This type of layouts based on componentspecialization.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
16/108
16
The Difference between group and functional layout:
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
17/108
17
FamiliesThe word Fa mi ly is used as a name for
any list of similar parts. The familiesused with group layout are lists of parts
which are similar because they are allmade on the same group of machines.This type of family is called aPro du ct io n Fa mi ly. However, not allparts which are similar in shape willappear in the same family.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
18/108
18
The other important features that isimportant choosing the families;Manufacturing tolerances
Required quantitiesMaterialsSpecial features, which will require the
use of different machines
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
19/108
19
Groups
A group is a list of machines, selected for layout together in one place, because itcontains all necessary facilities to complete
the processing of a given family of parts. Afamily of parts can only be defined by relatingit to a particular group of machines, and agroup by relating it to a family. Groups vary
greatly in type and size, widely in the number of machines and different machines types.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
20/108
20
As group size is reduced, more types of machine will be needed in more than onegroup and there is an increased risk thatsome new machines must be purchased.
Another factor in choosing the size of group is the number of people who will beemployed in them.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
21/108
21
Group technology begun by grouping partsinto families, based on their attributes.There are three methods that can be usedto form part families:
Ma nue l v isu al inspe ct io n Pro du ct io n f low a n al ysis
Cla ssifi cat io n a nd co ding
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
22/108
22
Ma nu al v isu al inspe ct io ninvolves arranging a set of partsinto groups known as part families by visually inspecting thephysical characteristics of the
parts.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
23/108
23
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
24/108
24
Ma nu al v isu al inspe ct io n incorrect results human error different judgment by different people inexpensive least sophisticated
good for small companies havingsmaller number of parts
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
25/108
25
Pro du ct io n f low a n al ysis : Parts that gothrough common operations are groupedinto part families.
The machines used to perform thesecommon operations may be grouped as acell , consequently this technique can beused in facility layout ( factory l ayout )
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
26/108
26
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
27/108
27
Co ding me tho ds : are employed in
classifying parts into part families
C oding refers to the process of assigning
symbols to the parts
The symbols represent design attributes
of parts or manufacturing features of part families
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
28/108
28
The variations in codes resulting from the
way the symbols are assigned can begrouped into three distinct type of codes:
Mo n oco de or h ie rarch ical co de Pol yco de or attr ibu t e H yb r id or mixed co de
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
29/108
29
MONOCODE (HIERARCHICAL CODE)
This coding system was originallydeveloped for biological classification in18 th century.
The structure of m o n oco de is like a treein which each symbol amplifies theinformation provided in the previous digit.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
30/108
3 0
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
31/108
3 1
The following figure illustrates the structure
of a monocode:
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
32/108
32
A m o n oco de (hierarchical code) providesa large amount of information in arelatively small number of digitsuseful for storage and retrieval of design-related information such as p artge o me tr y, m at e r ial , size , etc.it is difficult to capture information on
manufacturing sequences in hierarchicalmanner, so applicability of this code inmanufacturing is rather limited
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
33/108
33
POLYCODE (ATTRIBUTE CODE):
The code symbols are independent of eachother
Each digit in specific location of the codedescribes a unique property of the workpiece it is easy to learn and useful in manufacturing
situations where the manufacturing process have tobe described
the length of a polycode may become excessivebecause of its unlimited combinational features
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
34/108
34
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
35/108
35
Differences in information storage capacitybetween m o n oco de and p ol yco de :
A ssume that a code consists of a fivesymbo l s and that in each of the five code
fiel ds the digits 0 to 9 are used. Determinehow many mutua ll y exc l usivecharacteristics can potentia ll y be stored inthe monocode and the polycode
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
36/108
36
N umber of characteristics may be stored in a monocode:
10 1 + 10 2 + 10 3 + 10 4 + 10 5 = 111110
N umber of characteristics may be stored in a po l ycode:
10 + 10 + 10 + 10 + 10 = 5 0
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
37/108
37
MIXED CODE (HYBRID CODE):
It is the mixture of both m o n oco de and
p ol yco de systems. Mixed code retains theadvantages of both systems. Most codingsystems use this code structure.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
38/108
38
MIXED CODE (HYBRID CODE):
The first digit for example, might be used todenote the type of part , such as gear. The nextfive position might be reserved for a shortattribute code that would describe the attribute of the gear. The next digit ( 7 th digit) might be used
to designate another subgroup, such asmateria l , followed by another attribute code thatwould describe the attributes.
A code created by this manner would berelatively more compact than a pure attributecode while retaining the ability to easily identifyparts with specific characteristics.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
39/108
39
Th e OPITZ cla ssifi cat io n sys t em :
it is a mixed (hybrid) coding systemdeveloped by O pi t z , Technical University of
Aachen, 1 97 0
it is widely used in industryit provides a basic framework for understandingthe classification and coding processit can be applied to machined parts, non-machined parts (both formed and cast) andpurchased partsit considers both design and m a nuf act u r inginformation
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
40/108
4 0
The Opitz coding system consists of three groupsof digits:
Form Supplementary Secondarycode code code12345 6789 ABCD
part geometry and
features re l evant to part design
information
re l evant tomanufacturing ( po l ycode)
Production
processes and productionsequences
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
41/108
4 1
PART FAMILY FORMATION
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
42/108
42
PART FAMILY FORMATION:One of the primary uses of coding systems is todevelop part families.
Example: Consider the family of ferrous partsformed by first three digits of Opitz form code; 1 3 1.
This implies that the attributes associated with thefamily members are length/diameter ratio in therange 0. 5 to 3 .0, all parts stepped to one end andinternal shape elements with threads.
A number of mathematical approaches have alsobeen developed to form part families usingclassification and coding system.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
43/108
43
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
44/108
44
For the purpose of selecting or developingyour own code, it is important to understandthe attributes of classification and codingsystems.
SELECTION OF CLASSIFICATION ANDCODING SYSTEMS
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
45/108
45
Some of the important classification and coding systemattributes include:
1. Flexibility for various applications such as part family
formation, process planning, costing, and purchasing2 . Accuracy, to provide correct information on parts3 . Expandability, to accommodate information on more partattributes deemed important later on4 . Ease of learning5 . Ease of retrieval6 . Reliability and availability of software7 . Suitability for specific applications
SELECTION OF CLASSIFICATION AND CODINGSYSTEMS
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
46/108
46
Matching these attributes with theobjectives of an organization would behelpful in selecting or developing acoding system to meet organizational
needs.
SELECTION OF CLASSIFICATION AND
CODING SYSTEMS
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
47/108
47
Group technology is a m a n a gemen tstrategy to help eliminate waste caused byduplication of effort.
BENEFITS OF GROUP TECHNOLOGY
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
48/108
48
BENEFITS OF GROUP TECHNOLOGY
It affects all areas of a company, including:
engineeringequipment specificationfacilities planningprocess planningproduction controlquality controltool designpurchasingservice
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
49/108
49
BENEFITS OF GROUP TECHNOLOGY
Some of the well-known tangible and intangible benefitsof implementing GT :
1. Engineering design
Reduction in new parts designReduction in the number of drawings through
standardizationReduction of drafting effort in new shop drawings
Reduction of number of similar parts, easy retrievalof similar functional parts, and identification of substitute parts
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
50/108
5 0
BENEFITS OF GROUP TECHNOLOGY
2 . Layout planning
Reduction in production floor spacerequiredReduced material-handling effort
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
51/108
5 1
BENEFITS OF GROUP TECHNOLOGY
3 . Specification of equipment, tools, jigs, andfixtures
Standardization of equipmentImplementation of cellular manufacturingsystems
Significant reduction in up-front costsincurred in the release of new parts for manufacture
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
52/108
52
BENEFITS OF GROUP TECHNOLOGY
4 . Manufacturing: process p l anning
Reduction in setup time and productiontimeAlternative routing leading to improvedpart routing
Reduction in number of machiningoperations and numerical control (NC)programming time
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
53/108
53
BENEFITS OF GROUP TECHNOLOGY
5 . Manufacturing: production contro l
Reduced work-in-process inventory
Easy identification of bottlenecksImproved material flow and reducedwarehousing costsFaster response to schedule changesImproved usage of jigs, fixtures, pallets, tools,material handling, and manufacturing equipment
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
54/108
54
BENEFITS OF GROUP TECHNOLOGY
6 . Manufacturing: qua l ity contro l
Reduction in number of defects leading to
reduced inspection effortReduced scrap generationBetter output qualityIncreased accountability of operators andsupervisors responsible for quality production,making it easier to implement total quality controlconcepts.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
55/108
55
BENEFITS OF GROUP TECHNOLOGY7
. Purchasing
Coding of purchased part leading tostandardized rules for purchasingEconomies in purchasing possiblebecause of accurate knowledge of rawmaterial requirements
Reduced number of part and raw materialsSimplified vendor evaluation proceduresleading to just-in-time purchasing
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
56/108
56
BENEFITS OF GROUP TECHNOLOGY
8 . Customer service
Accurate and faster cost estimatesEfficient spare parts management, leadingto better customer service
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
57/108
57
CELLULAR MANUFACTURING
Cellular manufacturing is an application of group technology in manufacturing inwhich all or a portion of a firmsmanufacturing system has been convertedinto cells.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
58/108
58
CELLULAR MANUFACTURING
A manufacturing cell is a cluster of machines or processes located in closeproximity and dedicated to themanufacture of a family of parts.
The parts are similar in their processingrequirements, such as operations ,to l erances , and machine too l capacities
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
59/108
59
The primary objectives in implementing acellular manufacturing system are toreduce:
setup times (by using part family tooling
and sequencing)flow times (by reducing setup and movetimes and wait time for moves and usingsmaller batch sizes)reduce inventoriesmarket response times
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
60/108
6 0
In addition, cells represent sociologicalunits that have more tendency toteamwork. This means that motivation for process improvements often arisesnaturally in manufacturing cells.
Manufacturing cells are natural candidatesfor just-in-time (JIT) implementation.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
61/108
6 1
Functional and cellular layouts of an electronics plant:
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
62/108
62
C e ll D esign
Design of cellular manufacturing system isa complex exercise with broad implicationsfor an organization.
The c e ll design p roc ess involves issuesrelated to both system structure andsystem operation
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
63/108
63
Structural issues include:
Selection of part families and groupingof parts into families
Selection of machine and processpopulations and grouping of these intocells
Selection of tools, fixtures, and pallets
Selection of material-handlingequipmentChoice of equipment layout
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
64/108
64
Issues related to procedures include:
Detailed design of jobsOrganization of supervisory and supportpersonnel around the cellular structureFormulation of maintenance and inspectionpoliciesDesign of procedures for production p l anning ,
schedu l ing, contro l , and acquisition of re l ated software and hardwareModification of cost control and reward systemsOutline of procedures for interfacing with theremaining manufacturing system (in terms of work flow and information, whether computer controlled or not)
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
65/108
65
Eval u at io n o f C e ll D esign D
ec
isio
ns
The evaluation of design decisions can be
categorized as related to either the system structureor
the system operation .
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
66/108
66
Typical considerations related to thesystem structure include:
Equipment and tooling investment (low)
Equipment relocation cost (low)Material-handling costs (low)Floor space requirements (low)
Extent to which parts are completed in acell (high)Flexibility (high)
l i f ll d i
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
67/108
67
Evaluations of cell system design areincomplete unless they relate to the
operation of the system .
A few typical performance variablesrelated to system operation are:
Equipment utilization (high)Work-in-process inventory (low)
Queue lengths at each workstation (short)Job throughput time (short)Job lateness (low)
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
68/108
68
A major problem throughout the celldesign process is the necessity of trading off against each other objectivesrelated to structural parameters and
performance variables .
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
69/108
69
For example, higher machine utilizationcan be achieved if several cells route their parts through the same machine. Thedrawbacks are increased queuing andcontrol problems .
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
70/108
7 0
System cost and performance are affected byevery decision related to sys t em s tr u ct u r e and
system
ope
ratio
n .
It is necessary to evaluate each importantdesign parameter and relate its performance topre-established criteria.
For example, structural variables such asnumber of machines must be balanced againstoperational variables such as machineutilization and throughput time usinganalytical and simulation approaches.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
71/108
7 1
CELL FORMATION APPROACHES
Mach ine - Co mp o nen t Gro up A n al ysis :
Machine - Component Group A na l ysis isbased on production flow analysis
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
72/108
72
Production f l ow ana l ysis involves four stages:
Stage 1: M achine classification .
Machines are classified on the basis of operations that can be performed on them.
A machine type number is assigned tomachines capable of performing similar
operations.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
73/108
73
Stage 2 : C hecking parts list and production route information .
For each part, information on theoperations to be undertaken and themachines required to perform each of
these operations is checked thoroughly.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
74/108
74
Stage 3 : F actory flow analysis .
This involves a micro-level examination of flow of components through machines.
This, in turn, allows the problem to bedecomposed into a number of machine-component groups.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
75/108
75
Stage 4 : M achine-component group
analysis .
An intuitive manual method is suggested
to manipulate the matrix to form cells.However, as the problem size becomeslarge, the manual approach does not work.Therefore, there is a need to developanalytical approaches to handle largeproblems systematically.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
76/108
76
EXAMPLE:
Consider a problem of 4 machines and 6 parts. Try to group them.
Machines 1 2 3 4 5 6
M 1 1 1 1
M 2 1 1 1
M 3 1 1 1
M 4 1 1 1
Components
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
77/108
77
Machines 2 4 6 1 3 5
M 1 1 1 1
M 2 1 1 1
M 3 1 1 1
M 4 1 1 1
Components
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
78/108
78
Ra nk Or de r Cl us t e r ing Al g or ith m :
R ank Order C lustering Algorithm is a
simple algorithm used to form machine- part groups.
Step 1: Assign binary weight and
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
79/108
79
Step 1: Assign binary weight andcalculate a decimal weight for each row andcolumn using the following formulas:
Decimal we
Decimal we b pj n p
ight for row i = b
ight for column j =
ip m-p p= 1
m
p= 1
n
2
2
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
80/108
8 0
Step 2 : Rank the rows in order of decreasing decimal weight values.
Step 3 : Repeat steps 1 and 2 for eachcolumn.
Step 4 : Continue preceding steps untilthere is no change in the position of eachelement in the row and the column.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
81/108
8 1
EXAMPLE:Consider a problem of 5 machines and 10 parts. Try to
group them by using R ank Order C l ustering A l gorithm.
Machines 1 2 3 4 5 6 7 8 9 10
M 1 1 1 1 1 1 1 1 1 1M 2 1 1 1 1 1
M 3 1 1 1 1
M4
1 1 1 1 1 1M 5 1 1 1 1 1 1 1 1
Components
Table 1
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
82/108
82
Machines 1 2 3 4 5 6 7 8 9 10 D ecimalequivalent
M 1 1 1 1 1 1 1 1 1 1 1007M 2 1 1 1 1 1 451
M 3 1 1 1 1 568
M 4 1 1 1 1 1 1 455
M 5 1 1 1 1 1 1 1 1 1020
2 9 2 8 2 7 2 6 2 5 2 4 2 3 2 2 2 1 2 0
Binary weight
Components
Table 2
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
83/108
83
Binaryweight
Machines 1 2 3 4 5 6 7 8 9 10
2 4 M 5 1 1 1 1 1 1 1 12 3 M 1 1 1 1 1 1 1 1 1 12 2 M 3 1 1 1 1
21
M 4 1 1 1 1 1 12 0 M 2 1 1 1 1 1
D ecimalequivalent 28 27 27 27 28 20 28 26 11 11
2 9 2 8 2 7 2 6 2 5 2 4 2 3 2 2 2 1 2 0
Binary weight
Components
Table 3
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
84/108
84
Binaryweight
Machines 1 5 7 2 3 4 8 6 9 10 D ecimalequivalent
2 4 M 5 1 1 1 1 1 1 1 1 10202 3 M 1 1 1 1 1 1 1 1 1 1 10192 2 M 3 1 1 1 1 9002 1 M 4 1 1 1 1 1 1 1232 0
M2
1 1 1 1 1 115D ecimal
equivalent 28 28 28 27 27 27 26 20 11 11
2 9 2 8 2 7 2 6 2 5 2 4 2 3 2 2 2 1 2 0
Binary weight
Components
Table 4
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
85/108
85
S imi lar it y Co effi c ien t- Ba sed
A pp roach es
In similarity coefficient methods , the
basis is to define a measure of similaritybetween machines, tools, design features,and so forth and then use it to form partfamilies and machine groups.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
86/108
86
S ing le -L ink a ge Cl us t e r A n al ysis
( SLC A ):
It is a hierarchical machine grouping
method known as single-linkage cluster analysis using similarity coefficientsbetween machines.
The procedure is to construct a treecalled a dendrogram .
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
87/108
87
The similarity coefficient between two machines is defined as theratio of the number of parts visiting both machines and the number of parts visiting one of the two machines :
S =+ Z - X
ijk=1
N
jk ijk
X
Y
ijk
ik
k
N
!
( )1
where: X ijk = operation on part k performed both on machine i and j ,Y ik = operation on part k performed on machine i ,Z jk = operation on part k performed on machine j.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
88/108
88
SLCA ALGORITHMS
It helps in constructing dendrograms .
A dendrogram is a pictorialrepresentation of bonds of similaritybetween machines as measured by thesimilarity coefficients.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
89/108
89
The steps of algorithm are as follows:
Step 1: Compute similarity coefficients for allpossible pairs of machines,
Step 2 : Select the two most similar machines to
form the first machine cell,Step 3 : Lower the similarity level (threshold) andform new machine cells by including all themachines with similarity coefficients not less
than the threshold value,Step 4 : Continue step 3 until all machines are
grouped into a single cell.
EXAMPLE:
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
90/108
9 0
EXAMPLE:Consider the matrix of 5 machines and 10 componentsgiven below.
Machines 1 2 3 4 5 6 7 8 9 10
M 1 1 1 1 1 1 1 1 1 1
M 2 1 1 1 1 1M 3 1 1 1 1
M 4 1 1 1 1 1 1
M 5 1 1 1 1 1 1 1 1
Components
Develop a denrogram and discuss the resulting cell structures.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
91/108
9 1
Step 1: Determine similarity coefficients between all pairsof machines.
C 59 + 5 - 5
0.556 12
Machine pairs
M1M2
M1M3
M1M4
M1M5
M2M3
M2M4
M2M5
M3M4
M3M5
M4M5
SC 0.55 0.30 0.67 0.70 0.00 0.83 0.30 0.00 0.50 0.40
Similarity coefficients of machine pairs
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
92/108
92
Step 2 : Select machines M 2 and M 4 , havingthe highest similarity coefficients of 0.83 to form the first cell.
Step 3 : The next lower coefficient of similarity is between machines M1 andM5 . Use these machines to form the
second cell.
Step 4 : The next lower coefficient of similarity is now 0. 67
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
93/108
93
between machines M1 and M 4 . At this threshold valuemachines M1, M 2 , M4 , and M 5 will form one machine
group. The other possible groups will be evaluated by thesame way.
0.00
0.50
0.670.70
0.83
M4 M1M2 M3M5
Dendrogram
EXCEPTIONAL PARTS & BOTTLNECK
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
94/108
94
EXCEPTIONAL PARTS & BOTTLNECKMACHINES:
One of the important goal in cell design is tocreate mutually independent machine cells.However, it may not always be economical or practical to achieve this goal.
In practice, therefore, some parts need to beprocessed in more than one cell. These areknown as exceptional parts and the machinesprocessing them are known as bottleneck machines.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
95/108
95
The problem of exceptional elements canpossibly be eliminated by:
Generating a l ternative process p l ansDup l ication of machinesSubcontracting these operations
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
96/108
96
EVALUATION OF CELL DESIGN:
In design of cells, there will be more than
one alternative solution. The objective is tofind the best alternative.
Assume we have the following alternative
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
97/108
97
Assume we have the following alternativecell configuration:
Similaritycoefficient
Number of cellsformed
ell configuration
1.00 5 (M1) , (M2) , (M3) , (M4) , (M5)0.83 4 (M2 , M4) , (M5) , (M1) , (M3)
0.70 3 (M2 , M4) , (M1 , M5) , (M3)
0.67 2 (M1 , M2 , M4 , M5) , (M3)
0.50 1 (M1 , M2 , M3 , M4 , M5)
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
98/108
98
The criteria is to minimize the distance thatthe parts should travel during theprocesses; in other words, to minimize thematerial handling costs of in t e rc e ll
(between cells) and in trac e ll (within cell)movements of the parts.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
99/108
99
The following factors affect the cost of in t e rc e ll and in trac e ll movements of parts.
1 . The l ayout of machines in a group2. The l ayout of machine groups3. The sequences of parts through machines
and machine groups
The total distances moved by a componentvisiting a number of machines in a cell hasto be determined.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
100/108
100
Assumptions:
1. In the absence of the real data on thesequences in which the components visitthe machines, it is assumed that the
machines are laid out in a randommanner.2 . There is one unit distance between each
machine in a group of N machines.3 . A part has to visit two machines in a
group of N machines.
E t d di t f t ight li l t N +1
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
101/108
101
Expected distance for a straight-line layout: N +13
Expected distance for a rectanglelayout of M rows of L machines:
M + L2
Expected distance for a square layout: 2 N
3
The total distance moved in j th cellfor the i th configuration: k i
m
d iwhere:
d ij = expected distance moved between two machinesfor i th configuration in j th ce ll
k ij = number of moves between two machines by a ll the parts for i th configuration in j th ce ll
The total cost of i t ll l and i t ll l movements
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
102/108
10 2
The total cost of interce ll ul ar and intrace ll ul ar movements(TCi) for the ith configuration:
where:C 1 = cost of an intercell movement
C 2 =
cost per unit distance of an intracell movementN i = number of intercell movements for ith configuration
T = +i 1 2 N d k i ij ij j
m
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
103/108
10 3
EXAMPLE:
Consider the following cell configuration.
Machines1 5 2 3 4 7 8 9 10 6
M 1 1 1 1 1 1 1 1 1 1
M 5 1 1 1 1 1 1 1 1
M 2 1 1 1 1 1
M 4 1 1 1 1 1 1M 3 1 1 1 1
Components
Consider 3 -cell case:
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
104/108
10 4
Consider cell case:
Expected movement distance,
in cell (M1, M 5 ) =
in cell (M2 , M4 ) =
in cell (M3 ) = 0
2 1
31!
2 13 1!
The number of moves passing through two
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
105/108
10 5
The number of moves passing through twomachines by all the parts,
in cell (M1, M 5 ) = 7in cell (M2 , M4 ) = 5in cell (M3 ) = 0
The total distance for all intercell moves for 3 -cell configuration:
1 x 7 + 1x 5 + 0 = 12
The number of intercell moves in 3 -cellconfiguration is 10.
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
106/108
10 6
Assume:
C1=
$2
.00 ( cost of intercell unit movement)C2 = $1.00 ( cost of intracell unit movement)
The total cost of in t e rc e ll and in trac e llmovements in 3 -cell configuration:
2 .00 $ x 10 + 1.00 $ x 1 2 = 32 .00 $
The summary of cost calculation for all possible cellconfiguration is given in the following table:
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
107/108
10 7
configuration is given in the following table:C ell
configuration
Number of
intercellmoves
Total distance of
intracellmoves
Total cost of
intercell andintracellmoves
5-cells (M1) , (M2) ,(M3) , (M4) ,(M5)
22 0 2 x 22 +1 x 0 = 44
4-cells (M2 , M4) , (M5) ,(M1) , (M3)
18 5 2 x 18 +1 x 5 = 41
3-cells (M2 , M4) , (M1 ,M5) , (M3)
10 12 2 x 10 +1 x 12 = 32
2-cells (M1 , M2 , M4,M5) , (M3) 4 30 2 x 4 +1 x 30 = 38
1-cells (M1 . M2 , M3,M4, M5)
0 44 2 x 0 +1x 44 = 44
-
8/8/2019 Ch6 Group Technology and Cellular Manufacturing
108/108
A survey of 53 show that the use of GT andcellular manufacturing in US industries has metwith success. The benefits reported from thesestudies include:
Reduction in throughput time by 4 6%Reduction in work-in-process inventory by 41 %Reduction in material handling by 39%Reduction in setup time by 32%Improvement in quality by 29 . 6%