ABSL Power Solutions 2007 STM Quality LimitedSTM Quality
LimitedSTATISTICAL PROCESS CONTROLTOTAL QUALITY
MANAGEMENTIntroduction to S.P.C. STM Quality LimitedSTM Quality
LimitedWhat is meant by Statistical Process Control? STM Quality
LimitedSTM Quality LimitedThis is a control system which uses
statistical techniques for nowin!" all the time" chan!es in the
#rocess$%t is an e&ecti'e method in #re'entin! defects and
hel#s continuous quality im#ro'ement$Statistical Process Control
(S.P.C.) STM Quality LimitedSTM Quality LimitedWhat oes S.P.C.
mean?Statistical(Statistics are tools used to mae #redictions on
#erformance$There are a num)er of sim#le methods for analysin! data
and" if a##lied correctly" can lead to #redictions with a hi!h
de!ree of accuracy$ STM Quality LimitedSTM Quality LimitedWhat oes
S.P.C. mean?Process(The #rocess in'ol'es #eo#le" machines"
materials" methods" mana!ement and en'ironment worin! to!ether to
#roduce an out#ut" such as an end #roduct$ STM Quality LimitedSTM
Quality LimitedWhat oes S.P.C. mean?*ontrol(*ontrollin! a #rocess
is !uidin! it and com#arin! actual #erformance a!ainst a
tar!et$Then identifyin! when and what correcti'e action is
necessary to achie'e the tar!et$ STM Quality LimitedSTM Quality
LimitedS.P.C.Statistics aid in main! decisions a)out a #rocess
)ased on sam#le data and the results #redict the #rocess as a
whole$ STM Quality LimitedSTM Quality LimitedThe ProcessPeo#le
Machines MaterialMana!ement Methods +n'ironment,ut#ut STM Quality
LimitedSTM Quality LimitedS$P$*$ is statistical analysis of the
#redicta)ility and ca#acity of a #rocess to !i'e a uniform
#roduct$!e"nition STM Quality LimitedSTM Quality LimitedThe Aim o#
S.P.C. $ !etection Strate%y-etection(This focuses on identi.cation
of #ro)lems after #roduction" )y /000 ins#ection or )y customer
com#laints$%t is a historically1)ased strate!y$ STM Quality
LimitedSTM Quality LimitedThe Aim o# S.P.C. $ !etection
Strate%y-etection -raw)acs( Production is already made$ *ustomer
dissatisfaction$ %n2ated costs 1 rewor3 ins#ection$ 4e#etiti'e
#ro)lems$ 5e!lected im#ro'ements$ STM Quality LimitedSTM Quality
LimitedThe Aim o# S.P.C. $ Pre&ention Strate%yPre'ention(This
focuses on in1#rocess #roduction and identi.cation of #ro)lems
throu!h analysis of #rocess ca#a)ility$%t is a future1orientated
strate!y$ STM Quality LimitedSTM Quality LimitedThe Aim o# S.P.C. $
Pre&ention Strate%yPre'ention Bene.ts( %m#ro'ed desi!n and
#rocessca#a)ility$ %m#ro'ed manufacturin! quality$ %m#ro'ed
or!anisation$ *ontinuous %m#ro'ement$ STM Quality LimitedSTM
Quality LimitedThe S$P$*$ has to )e looed at as a sta!e towards
com#letely #re'entin! defects$6ith sta)le #rocesses" the cost of
ins#ection and defects are si!ni.cantly reduced$S.P.C. as a
Pre&ention Tool STM Quality LimitedSTM Quality LimitedAssesses
the desi!n intent$Achie'es a lower cost )y #ro'idin! an early
warnin! system$Monitors #erformance" #re'entin! defects$Pro'ides a
common lan!ua!e for discussin! #rocess #erformance$The 'ene"ts o#
S.P.C. STM Quality LimitedSTM Quality LimitedProcess
+lementVariable ExamplesMachine7777777777$Speed, operating
temperature, feed rateTools777777777777$$Shape, wear
rate8i9tures7777777777$$Dimensional
accuracyMaterials7777777777Composition,
dimensions,#erator7777777777Choice of set-up,
fatigueMaintenance7777777Lubrication,
calibration+n'ironment7777777Humidity, temperatureProcess
(ariations STM Quality LimitedSTM Quality Limited5o industrial
#rocess or machine is a)le to #roduce consecuti'e items which are
identical in a##earance" len!th" wei!ht" thicness etc$The
di&erences may )e lar!e or 'ery small" )ut they are always
there$The di&erences are nown as :'ariation;$ This is the
reason why :tolerances; are used$Process (ariations STM Quality
LimitedSTM Quality Limited*ommon causes are the many sources of
'ariation that are always #resent$A #rocess o#erates within :normal
'ariation; when each element 'aries in a random manner" within
e9#ected limits" such that the 'ariation cannot )e )lamed on one
element$6hen a #rocess is o#eratin! with common causes of 'ariation
it is said to )e sta)le$Stability STM Quality LimitedSTM Quality
LimitedThe #rocess can only )e termed :under control; if it !i'es
#redicta)le results$%ts 'aria)ility is sta)le o'er a lon! #eriod of
time$Process Control STM Quality LimitedSTM Quality Limitedcult to
see any #attern$6ithin the ta)le" num)ers ?0 and ?7 were outside
the tolerance @ but were they easy to spotA way of o)tainin! a
#attern is to !rou# the measurements accordin! to siAe$ STM Quality
LimitedSTM Quality Limited!ata Inter)retation * Tally ChartThe
tally chart !rou#s the measurements to!ether )y siAe as shown$The
two #arts that were out of tolerance are now easier to detect
B?C$?DmmE$36.3936.3836.3736.3636.3536.3436.3336.3236.3136.3036.2936.28
STM Quality LimitedSTM Quality LimitedTally Chart $ +re,-encyThe
tally chart shows #atterns and we can o)tain the 4A5
