Grupne Tehnoilogije

8/20/2019 Grupne Tehnoilogije

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Group Technology

Batch manufacturing is estimated to be the mostcommon form of production in the United States,

constituting more than 50% of total manufacturing

actiity!

There is a gro"ing need to ma#e batchmanufacturing more efficient and productie!$n addition, there is an increasing trend to"ard

achieing a higher leel of integration bet"een the

design and manufacturing functions in a firm!n approach directed at both of these ob&ecties

is group technology 'GT(!

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Group Technology

Group technology is a manufacturing philosophyin "hich similar parts are identified and grouped

together to ta#e adantage of their similarities in

design and production!

Similar parts are arranged into part families , "hereeach part family possesses similar design and/or

manufacturing characteristics!)or e*ample, a plant producing +0,000 different

part numbers may be able to group the ast

ma&ority of these parts into 0-.0 distinct families!

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Group Technology

The manufacturing efficiencies are generallyachieed by arranging the production euipment into

machine groups or cells, to facilitate "or# flo"!Grouping the production euipment into machine

cells, "here each cell specialies in the production ofa part family, is called cellular manufacturing.

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Group Technology

GT is most appropriately applied under thefollowing conditions:

The plant currently uses traditional batchproduction and a process type layout andthis results in much material handling eort,high in-process inentory, and longmanufacturing lead times!

The parts can be grouped into partfamilies. This is a necessary condition! "ach

machine cell is designed to produce a gien partfamily or limited collection of part families, so itmust e possile to group parts made in theplant into families!

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Group Technology

There are two ma$or tas%s that a companymust underta%e when it implements grouptechnology! These two tas%s representsigni&cant ostacles to the application of GT!

Identifying the part families.

'f the plant

ma%es 1(,((( dierent parts, reiewing all ofthe part drawings and grouping the parts intofamilies is a sustantial tas% that consumes asigni&cant amount of time!

Rearranging production machines into

machine cells.

't is time consuming andcostly to plan and accomplish thisrearrangement and the machines are notproducing during the changeoer!

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Group Technology - )art *amilies

Group technology oers sustantial ene&ts tocompanies that hae the perseerance toimplement it! The ene&ts include:

GT promotes standardi+ation of tooling,&turing and setups!

aterial handling is reduced ecause parts aremoed within a machine cell rather than withinthe entire factory!

)rocess planning and production scheduling aresimpli&ed!

.etup times are reduced, resulting in lower

manufacturing lead times!/or%-in-process is reduced!/or%er satisfaction usually improes when

wor%ers collaorate in a GT cell!0igher uality wor% is accomplished using

group technology! 8


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)art *amilies2 part family is a collection of parts that are

similar either ecause of geometric shape andsi+e or ecause similar processing steps arereuired in their manufacturing!

2 group of parts that possess similarities in

geometric shape and si+e, or in the processingsteps used in their manufacture

)art families are a central feature of grouptechnology

There are always dierences among parts in afamily

ut the similarities are close enough that theparts can e grouped into the same family

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Group Technology - )art*amiliesT"o parts that are identical in shape and sie but

uite different in manufacturing1'a(+,000,000 units/yr, tolerance 2 30!0+0 inch, +0+5

C4 steel, nic#el plate 'C4 2 Cold 4olled (

'b(+00/yr, tolerance 2 30!00+ inch, +- stainless

steel

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Group Technology - )art*amilies Ten parts that are dierent in si+e and shape, ut

uite similar in terms of manufacturing

2ll parts are machined from cylindrical stoc% yturning4 some parts reuire drilling and5or milling

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The biggest single obstacle in changing oer to

group technology from a conentional productionshop is the problem of grouping the parts into

families!There are three general methods for soling this

problem, "hich inole the analysis of much data

by properly trained personnel!

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Group Technology - )art*amilies

+( 6isual inspection - using best &udgment to group partsinto appropriate families, based on the parts or photos of the

parts7( 8roduction flo" analysis - using information contained

on route sheets to classify parts

( 8arts classification and coding - identifying similarities

and differences among parts and relating them by means of

a coding scheme

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Group Technology

+( The visual inspection method is the leastsophisticated and least e*pensie method! $tinoles the classification of parts into families

by loo#ing at either the physical parts or their

photographs and arranging them into groupshaing similar features!

lthough this method is generally considered to be the least accurate of the three, one of the first

ma&or success stories of GT in the United Statesmade the changeoer using the isual inspectionmethod!

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Group Technology

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Group Technology

2) Production flow analysis18arts that go through common operations are grouped

into part families!

The machines used to perform these common

operations may be grouped as a cell, conseuently this

techniue can be used in facility layout 'factory layout(

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Group Technology

'nitially, a machine6component chartmust e formed! This is an 7 matri,where

numer of machines

7 numer of parts* 2 + if part & has an operation on machine i9 0

other"ise!

'f the machine6component chart is small,parts with similar operations might egrouped together y

manually sorting the rows and columns!

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Parts Classication and Coding

3) Parts Classication and Coding

This is the most time consuming of thethree methods! 'n parts classi&cationand coding,

similarities among partsare identi&ed, and these similarities are

related in a coding system!

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Parts Classication andCodingost classi&cation and coding systems are one of the

following:.ystems ased on part design attriutes

.ystems ased on part manufacturing attriutes

.ystems ased on oth design and manufacturingattriutes

Part esign !ttributesa$or dimensions

asic eternal shape

asic internal shape

Length5diameter ratio

aterial type

)art function

Tolerances

.urface &nish

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Parts Classication andCodingPart "anufacturing !ttributesa$or process

9peration seuence

atch si+e2nnual production

achine tools

utting toolsaterial type

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Classification and coding systems are deised toinclude both a part:s design attributes and itsmanufacturing attributes! 4easons for using acoding scheme include1

;esign retrieal designer faced "ith the tas# ofdeeloping a ne" part can use a design retriealsystem to determine if a similar part alreadye*ists! simple change in an e*isting part "ouldta#e much less time than designing a "hole ne"

part from scratch!

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utomated process planning The part code for a ne" part

can be used to search for process plans for e*isting parts

"ith identical or similar codes!


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Coding methods1These are employed in classifying parts into part

families!

Coding refers to the process of assigning symbols to

the parts!The symbols represent design attributes of parts or

manufacturing features of part families!

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The ariations in codes resulting from theway the symols are assigned can egrouped into three distinct type of codes:

"onocode or hierarchical

codePolycode or attribute

#ybrid or mi$ed code

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"onocode or hierarchical code

Structure of Monocode 30


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"onocode or hierarchical code

A monocode 'hierarchical code( proides a largeamount of information in a relatiely small number ofdigits!

Useful for storage and retrieal of design related

information such as part geometry, material, size,etc!

$t is difficult to capture information on manufacturingseuences in hierarchical manner , so applicability ofthis code in manufacturing is rather limited!

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Poly CodeChain-type structure, #no"n as a polycode, in "hich

the interpretation of each symbol in the seuence isal"ays the same9 it does not depend on the alue of

preceding symbols, so symbols are independent of

each other!

=ach digit in specific location of the code describes auniue property of the "or#piece!

$t is easy to learn and useful in manufacturing

situations "here the manufacturing process hae to

be described!

The length of a 8olycode may become e*cessie

because of its unlimited combinational features!

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Poly Code

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Group Technology


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%ome of the importantsystems?pit classification system @the Uniersity of

achen in Germany, nonproprietary, Chain type!

Brisch System @'Brisch-Birn $nc!(

C?;= '


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Group Technology

The P!T" classification system#

$t is a mi$ed 'hybrid( coding system

;eeloped by pitz, Technical Uniersity of achen,

+EF0

$t is "idely used in industry

$t proides a basic frame"or# for understanding the

classification and coding process

$t can be applied to machined parts, non-machined

parts 'both formed and cast( and purchased parts

$t considers both design and manufacturing

information

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Group Technology

The &pit' coding system consists of three groups of

digits(

Form Supplementary Secondary

code code code

12345 6789 ABCD

part geometry

and feature

rele!ant to part

de"gn

"nformat"on

rele!ant to

manufactur"ng

#polycode$

%roduct"on

procee and

product"on

e&uence

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9pit+ .ystem

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*orm code in 9pit s stem for rotational parts in


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*orm code in 9pit+ system for rotational parts inclasses 3, and ;

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.upplemental code in 9pit+ system

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The &PIT classicationsystemExample: A part coded 20801< - )arts has L5= ratio > 3

( - 7o shape element ?eternal shapeelements@

8 - 9perating thread( - 7o surface machining

1 - )art is aial

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The &PIT classication systemExample

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The &PIT classicationsystem=*ample1 Gien the part design sho"n define the

form code using the ?pit system

Step +1 The total length of the part is +!F5, oerall

diameter +!75, A/; 2 +!. 'code +(

Step 71 =*ternal shape - a rotational part that isstepped on both "ith one thread 'code 5(

Step 1 $nternal shape - a through hole 'code +(

Step .1 By e*amining the dra"ing of the part 'code 0(

Step 51 o au*iliary holes and gear teeth 'code 0(

Code# %&%''

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Group Technology

S=A=CT$? ?) CASS$)$CT$? ; C?;$G SST=


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C*++,+!R "!,!CT,RIG

Cellular manufacturing is an application of grouptechnology in manufacturing, in "hich all or a

portion of a firmHs manufacturing system has been

conerted into cells!

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C*++,+!R "!,!CT,RIG

The primary ob&ecties in implementing acellular manufacturing system are to reduce1

Setup times 'by using part family tooling andseuencing(

)lo" times 'by reducing setup and moetimes and "ait time for moes and usingsmaller batch sies(

4educe inentories


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C*++,+!R "!,!CT,RIG

*unctional and ellular layouts of an electronics plant:

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C*++,+!R "!,!CT,RIG

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Cell esign;esign of cellular manufacturing system is a comple*

e*ercise "ith broad implications for an organiation!

The cell design process inoles issues related to both

(ystem structure and (ystem operation.

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*/aluation of Cell esign

ecisionsThe ealuation of design decisions can be categoried

as related to either

the system structure

or

the system operation!

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Typical considerations related to the systemstructure include:

=uipment and tooling inestment 'lo"(

=uipment relocation cost 'lo"(


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The system operation

=aluations of cell system design are incomplete

unless they relate to the operation of the system!

fe" typical performance ariables related to

system operation are1

=uipment utiliation 'high(

Ior#-in-process inentory 'lo"(

Jueue lengths at each "or#station 'short(

Kob throughput time 'short(Kob lateness 'lo"(

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ell =esign

ma&or problem throughout the cell design process is the necessity of trading off against each

other ob&ecties related to structural parameters

and performance ariables!

)or e*ample, higher machine utiliation can be

achieed if seeral cells route their parts through

the same machine! The dra"bac#s are increased

ueuing and control problems!

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ell =esign

System cost and performance are affected by eerydecision related to system structure and system

operation!

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C*++ &R"!TI&


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C*++ &R"!TI&!PPR&!C#*%

achine * Component +roup Analysis#


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)roduction Aow analysis

Stage +1 achine classification!


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Stage 71 Checing parts list and productionroute information.

)or each part, information on the operations to be

underta#en and the machines reuired to performeach of these operations is chec#ed thoroughly!

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Stage 1 -actory flow analysis.

This inoles a micro-leel e*amination of flo" of

components through machines! This, in turn, allo"s

the problem to be decomposed into a number ofmachine-component groups!

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) d ti A


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)roduction Aow

analysis

Stage .1achine*component group analysis. n intuitie manual method is suggested to

manipulate the matri* to form cells! >o"eer, as the problem sie becomes large, the manual approach

does not "or#! Therefore, there is a need to deelopanalytical approaches to handle large problemssystematically!

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"B2)L"


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"B2)L":

onsider a prolem of ; machines and C parts!

Try to group them!


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omponents


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Duantitatie 2nalysis in ellularanufacturing

Ean% 9rder lustering 2lgorithm:Ean% 9rder lustering 2lgorithm is a

simple algorithm used to form machine-part groups!

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Ean% 9rder lustering


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Ean% 9rder lustering2lgorithm.tep 1: 2ssign inary weight and calculate a decimal weight for

each row and column using the following formulas:

∑

∑

−n

+2 p

m

+2 p

p-m

ip

72 &columnfor"eight;ecimal

7 b2i ro"for"eight;ecimal

pn

pjb

Where “i” is ro no!" “#” is co$umn num%er" m is num%er of

co$umns" n is num%er of ros" p is the component&p'rt ro or

co$umn num%er

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.tep


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"B2)L": onsider a prolem of F machines and 1(parts! Try to group them y using Ean% 9rderlustering 2lgorithm!


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(in'r) ei*ht


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Binary"eight


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Binary"eight


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g g Techniue

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