© Strojni{ki vestnik 50(2004)3,157-167 © Journal of Mechanical Engineering 50(2004)3,157-167 ISSN 0039-2480 ISSN 0039-2480 UDK 658.512.4:658.562 UDC 658.512.4:658.562 Kratki znanstveni prispevek (1.03) Short scientific paper (1.03) Šest sigm” v razvoju postopka izdelave Six Sigma in Process Design Du{ko Pavleti} - Sandro Fakin - Mirko Sokovi} Prispevek se ukvarja z uporabo metodologije »sest sigm« v razvoju postopka izdelave. Na primeru obdelave okrova kompresorja je razložen razvoj postopka v Cimosovi tovarni v Buzetu in možnosti uporabe nekaterih orodij »sest sigm«, predvsem mape postopka in vzročno-posledične matrike. Prikazan je prilagojen razvoj poteka postopka z vgrajeno uporabo omenjenih orodij, narejena je primerjava sedanjega in novega načina poteka postopka in pojasnjeni so doseženi rezultati. © 2004 Strojniški vestnik. Vse pravice pridržane. (Ključne besede: metodologija šest sigma, razvoj postopkov, mape postopkov, matrike vzročno-posledične) This paper deals with the application of Six Sigma methodology in process design. Using an example of compressor-housing machining the process design and development at the Cimos facility in Buzet and the possibilities for some Six Sigma tools’ applications are explained. The primary tools are the process map and the cause-and-effect matrix. A modified process design flow with incorporated applications of the mentioned tools are shown, a comparison of the old and the modified process-design flow is made and the obtained results are discussed. © 2004 Journal of Mechanical Engineering. All rights reserved. (Keywords: Six Sigma methodology, process design, process maps, cause-and-effect matrix) 0 UVOD »Šest sigm« je program izboljšanja kakovosti z namenom zmanjšati število napak pod 3,4 kose na milijon izdelanih. Pri tem se uporablja običajna porazdelitev in močna povezava med neustreznostmi izdelka oziroma napakami in številom izdelanih kosov, zanesljivostjo, časom izdelave, opremo, načrti itn. [1]. »Šest sigm« poudarja inteligentno mešanico modrosti organiziranja s preizkušenimi statističnimi orodji za izboljšanje tako učinkovitosti kakor zmožnosti organizacije pri upoštevanju potreb odjemalcev. Končni cilj ni izboljšanje zaradi izboljšanja, ampak bolj ustvarjanje ekonomske blaginje za odjemalca in prav tako dobavitelja [2] in [3]. To nakazuje, da “šest sigm” ne nadomešča znane in trajajoče pobude za kakovost v organizaciji, ampak da se najvišje vodstvo osredotoča na tiste postopke, ki so prepoznani kot ključni za kakovost v očeh odjemalcev. Ti kritični sistemi so nato predmet natančnih pregledov in močnih naporov za izboljšanja; uporaba najmočnejših “mehkih” in “trdih” veščin organizacije lahko pripelje do napredka [4]. »Šest sigm« projekti neprekinjenega postopka izboljšav so vodeni od zasnove do izvršitve, 0 INTRODUCTION Six Sigma is a quality-improvement program that aims to reduce the number of defects to as low as 3.4 parts per million. It uses the normal distribution and the strong relationship between product nonconformities, or defects, and product yield, reliability, cycle time, inventory, schedule, etc. [1 ]. Six Sigma emphasizes an intelligent blending of the wisdom of an organization with proven statistical tools to improve both the efficiency and the effectiveness of the organization when it comes to meeting customer needs. The ultimate goal is not simply improvement for improvement’s sake, but rather the creation of economic wealth for the customer and the provider alike. This does, not imply that Six Sigma replaces existing and ongoing quality initiatives in an organization, rather that senior management focuses on those processes identified as critical-to-quality in the eyes of customers. Those critical systems are then the subject of intense scrutiny and improvement efforts, using the most powerful soft and hard skills that the organization can bring to bear [2]. Six Sigma projects of continuous process improvement are led, from concept to completion, gfin^OtJJIMISCSD 04-3 stran 157 | ^BSSITIMIGC Pavleti} D., Fakin S., Sokovi} M.: “[est sigm” v razvoju postopka - Six Sigma in Process Design skozi pet projektno usmerjenih korakov ali faz, imenovanih DIAIK (definiraj, izmeri, analiziraj, izboljšaj in krmili) [5]. 1 RAZVOJ IN PRIPRAVA POSTOPKA Postopek razvoja in priprave postopka izdelave bodo razloženi na primeru obdelave okrova kompresorja, prikazanega na sliki 1. Ulitke naredijo v Cimosovi livarni v Roču iz aluminijeve zlitine. Celotna mehanska obdelava pa je opravljena v Cimosovi tovarni v Buzetu na Hrvaškem. Običajno je razvoj postopka izdelave v Cimosovi tovarni v Buzetu razdeljen na pet korakov [6]: -študij izvedljivosti postopka, - načrtovanje postopka, - priprava postopka, - preizkusna proizvodnja in - kvalifikacija postopka. Postopki, ki imajo neposredni vpliv na kakovost izdelka, morajo biti natančno določeni. Zato je pri načrtovanju postopka izdelave treba prepoznati in utemeljiti ustrezne zahteve kakovosti. Za dosego teh pogojev je med drugim treba določiti: - načrt razvoja postopka za nove ali spremenjene izdelke, skupaj z jasno dokumentiranimi proizvodnimi koraki in tokom materiala; ustrezno proizvodno opremo in delovno okolje; vzdrževanje in preventivno vzdrževanje opreme in delovnega okolja za zagotavljanje stalne razpoložljivosti proizvodnega sistema; postopke in metode za zagotavljanje kakovosti postopka izdelave; skladnost opravil s predpisi in standardi, zakoni, definiranimi odgovornostmi, načrtom menedžment kakovosti (MK) kakor tudi z zahtevami odjemalcev glede kakovosti; through five project-management steps or phases named DMAIC (Define, Measure, Analyze, Improve, Control) [5]. 1 PROCESS DESIGN AND DEVELOPMENT The process design and development will be explained using the example of the compressor housing shown in Fig. 1. The castings are made in Cimos foundry Roč from aluminum alloy. All the machining is done in Cimos’s facility in Buzet, Croatia. At the Cimos facility in Buzet there are five basic steps in process design and development [3]: - feasibility study of the process, - process planning, - process preparation, - trial production, - process qualification. The processes with a major influence on product quality have to be identified. Therefore, in process planning it is necessary to recognize and establish relevant quality requirements. And in order to determine quality requirements it is first necessary to determine: - A process developments plan for new and modified products, along with comprehensive documented production steps and material flow - The production equipment and the working environment. - Maintenance and preventive maintenance for the equipment and the working environment to ensure the availability of the production system. - The procedures and methods for process quality assurance. - That the operation is in accordance with production rules and standards, laws, defined responsibilities, quality management (QM)-plans, as well as customer quality requirements. Sl. 1. Obdelan okrov kompresorja Fig. 1. Machined compressor housings VH^tTPsDDIK stran 158 Pavleti} D., Fakin S., Sokovi} M.: “[est sigm” v razvoju postopka - Six Sigma in Process Design - opazovanje in dokumentiranje vseh parametrov postopka in karakteristik izdelka, ki mora biti na voljo vsem pristojnim službam in oddelkom; - odobritev postopkov in opreme od vseh pristojnih oseb. V fazi načrtovanja postopka je močno razširjena uporaba metode Analize izvora in vpliva napak (AIVP). Metoda AIVP ima velik vpliv na pripravo postopka, zato ker se izhodne veličine iz analiz AIVP uporabljajo za določanje, katere napake bi se verjetno pojavile ter kakšni popravni ukrepi so potrebni za njihovo preprečitev. Da bi postopek razvoja in priprave postopka izdelave bil učinkovit, je treba v fazi načrtovanja postopka uporabiti še nekatera dodatna orodja, ki izhajajo iz metodologije »šest sigma«. 2 METODA »ŠEST SIGM« PRI RAZVOJU POSTOPKA V fazi načrtovanja postopka v podjetju Cimos uporabljajo metodo AIVP. Problem, ki se pri tem pojavlja pri izvajanju postopka AIVP, je v tem, da se običajno obravnava preveliko število KVSP (ključne vstopne spremenljivke postopka), ki nimajo velikega vpliva, včasih pa sploh ne vplivajo, na KISP (ključne izstopne veličine postopka). Da bi razvoj in načrtovanje postopka potekala hitreje, je treba v fazi načrtovanja postopka uporabiti še nekatera dodatna orodja. Metodologija “šest sigm” prinaša orodja in metode, s katerimi je mogoče število KVSP zmanjšati na minimum oz. le na tiste veličine, ki imajo velik vpliv na KISP. Orodja in metode, ki pomagajo zmanjšati število KVSP ter doseganje optimalnega postopka, so prikazani na sliki 2. V prispevku je predlagana uporaba postopkovnega mapiranja in izdelava vzročno-posledične matrike. 2.1 Mapa postopka izdelave Mapa postopka izdelave je grafični prikaz poteka postopka s posameznimi koraki postopka, ki prikazuje vstopne in izstopne parametre postopka ter priložnosti za njegovo izboljšanje. Vsaka postopkovna mapa naj bi bila rezultat skupinskega dela, ker je nemogoče, da bi le ena oseba imela vsa znanja o postopku. 2.2 Vzročno-posledična matrika Vzročno-posledična matrika podaja zvezo med ključnimi vstopnimi ter ključnimi izstopnimi veličinami (zahteve kupcev) pri čemer uporablja mapo postopka kot osnovni vir za vstopne informacije. Ključne izstopne veličine so razvrščene glede na njihovo pomembnost, medtem ko so ključne vstopne veličine izračunane iz medsebojnih odvisnosti vstopnih in izstopnih veličin [6]. - The monitoring and documenting of all process parameters and product characteristics, available to all competent services and departments. - The approval for processes and equipment from all the responsible persons. In the process planning stage the Failure mode and effect analysis (FMEA) method is widely used. The process FMEA method has great influence and significance on process preparation because outputs from the FMEA analysis are used to determine which failures are likely to appear and what corrective actions are necessary for failure prevention. In order to have efficient process design and development some additional tools and methods should be used in the process planning phase. These tools can be derived from Six Sigma methodology. 2 SIX SIGMA METHODS IN PROCESS DESIGN In the process planning phase in Cimos facilities the FMEA method is widely used. The problem that emerged with the application of the FMEA method is the large number of KPIV (Key Process Input Variables) that do not have a significant influence or have no influence on KPOV (Key Process Output Variables). To have faster and more effective process design and development in the process planning stage it is necessary to apply some additional tools. Six Sigma methodology brings tools and methods with which the number of KPIV can be reduced to a minimum, or to those variables which have a major influence on KPOV. Tools and methods that help to decrease the number of KPIV and achieve an optimized process are shown in Fig. 2. In this paper the applications of process map and the cause-and-effect matrix are proposed. 2.1 Process map In general, a process map is a graphical representation of a process flow that identifies the steps of the process, the input and output variables of a process and the opportunities for improvements. Every process map should be the result of teamwork, because it is impossible that just one person could have all the knowledge about the process. 2.2 The cause-and-effect matrix A cause-and-effect matrix relates the key inputs to the key outputs (customer requirements) using a process map and a cause-and-effect diagram as the primary source of the input information. The key outputs are rated according to their importance, while the key inputs are scored in terms of their relationship to the key outputs [6]. | lgfinHi(s)bJ][M]lfi[j;?n 04-3_____ stran 159 I^BSSIfTMlGC Pavleti} D., Fakin S., Sokovi} M.: “[est sigm” v razvoju postopka - Six Sigma in Process Design Izmeri Measure Analiziraj Analyze Izboljšaj in upravljaj Improve and Control m ape (miselna, postopkovna) measuring systems analize zmožnosti capability analysis - histogram / histograms nadzorna karta / control charts Ä - vzročno - posledični diagram - cause-and-effect diagram - vzročno - posledično matriko - cause-and-effect matrix ^s. - AIVP / FMEA - multivariacijske analize - multi-vari analyses - načrtovanje preizkusov (NP) - design of experiments (DoE) - NP / razvoj operacij - DoE / EVOP - načrt nadzora - control plan - SPC Optimiran postopek / Optimized process Legenda / Legend: KVSP - ključne vstopne spremenljivke postopka / KPIV - key process input variable KISP - ključne izstopne veličine postopka/ KPOV - key process output variable Vodi k razumevanju x za y = f(x) Leads to understanding of x for y = f(x) Sl. 2. Orodja in metode za optimizacijo postopka izdelave Fig. 2. Tools and methods in process optimization Pri uporabi vzročno-posledične matrike sta značilni dve fazi. V prvi fazi so vstopni parametri povezani z izstopnimi, kar določa osnovo za analizo Pareto. V drugi fazi pa oblikujemo novo vzročno-posledično matriko s tremi oz. štirimi kritičnimi vstopnimi parametri iz matrike v prvi fazi. V matriki je faktor pomembnosti za vsak parameter posebej razvrščen, vsak našteti vstopni parameter pa je povezan z vsakim izstopnim parametrom. Končna vrednost za vsak parameter je dobljena z množenjem nivoja pomembnosti z vrednostjo, ki je bila pripisana posameznim parametrom, ter s seštevanjem (vodoravno) prek vseh parametrov. Da se prepričamo o nivoju vpliva parametrov, bo v nadaljevanju uporabljena analiza Pareto. Diagram Pareto jasno prikaže informacijo o relativni pomembnosti parametrov obravnavanega problema. Ta informacija pomaga razpoznati najpomembnejše parametre, ki bodo analizirani najprej. V diagramu Pareto se tudi jasno pokažejo področja mogočih izboljšav. Pri uporabi vzročno-posledične matrike so vsi KVSP razvrščeni glede na pomembnost spremenljivke. Rezultati, dobljeni z vzročno-posledično matriko, se lahko uporabijo za različne analize in optimizacije, kakor so AIVP, multivariacijska analiza ter načrtovanje preizkusov. In the application of a cause-and-effect matrix there are two phases. In the first phase the inputs are correlated to the outputs that provide the basis for a Pareto analysis. In the second phase, a new cause-and-effect matrix is started with three or four critical inputs from the first-phase matrix. In the matrix a factor of importance for each parameter is rank ordered and every listed input parameter is correlated to every output parameter. Finally, a total value for each parameter is obtained by multiplying the rating of importance with the value given to the parameters and adding across for each parameter. To be very certain about the level of a parameter’s influence an additional Pareto analysis is applied. The Pareto diagram clearly displays information about the relative importance of the factors of a certain problem. This information helps to identify the most important factors, which will be analyzed first. With the help of the Pareto diagram domains, of possible improvement are clearly identified. Using a cause-and-effect matrix all the KPIV can be rank ordered with respect to the importance of the variable. The results obtained with the cause-and-effect matrix can be used for other analyses and optimizations such as FMEA, multi-vari analysis and design of experiments. VBgfFMK stran 160 Pavleti} D., Fakin S., Sokovi} M.: “[est sigm” v razvoju postopka - Six Sigma in Process Design 2.3 Prilagojena oblika poteka postopka 2.3 Modified process design flow Predlog prirejenega sinoptika načrtovanja postopka izdelave je prikazan na sliki 3. By applying the presented method at the process planning stage the process-design flow is modified, Fig. 3. popravni ukrepi corrective actions DOSJE PO OPOMNIKU ŠT.C - 5744 DOSSIER No. C-5744 ZGODOVINA NAPAK PODOBNEGA IZDELKA / HISTORY OF FAILURES FOR SIMILAR PRODUCT NAČRTOVANJE POSTOPKA PROCESS PLANNING EMS zakoni laws predpisi regulations standardi standards popravni ukrepi corrective actions zasnova terminskega plana (TP) postopka drafts of process schedule (PS) terminski plan schedule I porazdelitev nalog tasks distribution I zasnova TP (SN 04 58) PS project (SN 04 58) osnutek TP plana pregled postopka drafts of TP plan \ synoptic of process zasnovaMK plana(SN10 01) QMplan project (SN 10 01) PLANIRANJE KAPACITET IN LOGISTIKE / CAPACITY AND LOGISTICS PLANNING -prostor, stroji, orodja, naprave/ place, machines, tools, devices -materiali / materials - kadri /cadres - embalaža / packing pregled log. post. synoptic of log. process SN 04 54 izdelava vzročno - posledične matrike cause-and-effect matrix elaboration vzročno-posledična matrika cause-and-effect matrix AIVP postopka (SN 04 53) process FMEA (SN 04 53) izsledki FMEA *\ results of FMEA dopolnitev TP in MK plana z izsledki iz AIVP / accomplishing of the PS and QM plan with results of FMEA dopolnjen MK načrt *| accomplished QM plan Sl. 3. Modificirana oblika poteka postopka izdelave Fig. 3. Modified process-design flow Pavleti} D., Fakin S., Sokovi} M.: “[est sigm” v razvoju postopka - Six Sigma in Process Design Nova, prilagojena mapa postopka za potek izdelave okrova kompresorja, skupaj z vsemi KVSP in KISP, je prikazana na sliki 4. A new, modified process map for compressor-housing production is developed and shown in Fig. 4, along with all the KPIV and KPOV. KVSP / KPIV - nasloni na ulitku / position points on workpiece - homogenost ulitka / homogenity of casted part - vpenjalne čeljusti / clamping jaws -rezalno orodje / cutting tool -NC-program/ NC-program - koncentracija emulzije / concentration of emulsion -operater/ operater ZAČETEK START OP 02 STRUŽENJE SESALNE STRANI / TURNING OF SUCTION SIDE KISP / KPOV - notranji premeri / inner diameters - zunanji premeri / outer diameters -tehnološka kota 56,1 ±0,15 mm/ technological measure 56.1 ±0.15 mm - hrapavost površine / surface roughness - površinska poroznost / surface porosity - čas cikla / time of cycle -tehnološka kota 56,1 ±0,15 mm/ technological measure 56.1+0.15 mm - homogenost ulitka / homogenity of casted part - vpenjalne čeljusti / clamping jaws -rezalno orodje / cutting tool - program za RK / NC-program - koncentracija emulzije / concentration of emulsion -operater/ operater - kota 2,68 ± 0,25 mm / measure 2,68 ± 0,25 mm - homogenost ulitka / homogenity of casted part - vpenjalne čeljusti / clamping jaws -rezalno orodje / cutting tool - program za RK / NC-program - koncentracija emulzije / concentration of emulsion -operater / operater - livarski pesek v ulitku / sand in the casted part - masten obdelovanec / oily workpiece - parametri pranja / parameters of washing OP 04 STRUŽENJE KRIVULJE TURNING OF CURVE - homogenost ulitka / homogenity of casted part - parametri stroja / parameters of machine - tesnilni elementi / sealing elements - notranji premeri / inner diameter - oblika in lega krivulje / shape and position of curve - vse izmere v smeri z-osi / all measures in z-axis direction - hrapavost površine / surface roughness - površinska poroznost / surface porosity - čas cikla / time of cycle - višina frezanja površine za graviranje / hight og milling - globine navojev / depth of threads - prehodnost navojev / threads transition - poroznost v navoji / threads porosity - hrapavost površine / surface roughness - čas cikla / time of cycle - čistost obdelovanca / workpiece cleanness - čas cikla / time of cycle - tesnost ustrezna z zahtevami / leakage according to requirements - čas cikla / time of cycle - obdelovanci / workpieces -embalaža / packing -operater/ operater OP 12 PAKIRANJE PACKING - pakiranje ustrezno z zahtevami / packing according to requirements SKLADIŠČENJE IZDELKOV STORAGE OF FINAL PARTS KONEC END Sl. 4. Modificirana mapa postopka za potek izdelave okrova kompresorja Fig. 4. Modified process map for compressor-housing production VH^tTPsQDIK stran 162 Pavleti} D., Fakin S., Sokovi} M.: “[est sigm” v razvoju postopka - Six Sigma in Process Design Na sliki 4 so KVSP našteti na levi strani diagrama, medtem ko so KISP podani na desni strani diagrama. Včasih so KISP pri enem opravilu obenem tudi KVSP za naslednje opravilo, kakor v primeru opravil OP 02 in OP 04. Našteti KVSP in KISP v mapi postopka bodo uporabljeni kot vstopni parametri za analizo v vzročno-posledični matriki (sl. 5). Rezultati iz vzročno-posledične matrike so v nadaljevanju analizirani v diagramu Pareto. KISP so razvrščeni v skladu s številom točk iz vzročno-posledične matrike. Diagram Pareto za najbolj vplivne KISP je prikazan na sliki 6. KVSP so analizirani na enak način kakor KISP (sl. 7). In Fig. 4 the KPIV are listed on the left-hand side, while the KPOV are listed on the right-hand side of the diagram. In some cases the KPIV from one step are the KPOV for the next step, for example OP 02 and OP 04. The KPIV and KPOV listed in the process map will be used as inputs for the analysis in the cause-and-effect matrix, shown in Fig. 5. The results the cause-and-effect matrix are further analyzed with the Pareto diagram. The KPOV are rank ordered in accordance with the number of points from the cause-and-effect matrix. The Pareto diagram for the most influential KPOV is shown in Fig. 6. The KPIV are analyzed in the same manner as the KPOV, Fig. 7. Ocena pomembnosti za odjemalca procesa / Importance of estimation for process customer Tek. štev. / cur. No. 335313351133555 1 2 3 4 5 6 7 8 9 10 Skupaj Sum nasloni na ulitku / position points on workpiece 0 0 5 0 0 0 0 5 0 0 0 0 0 0 0 50 homogenost ulitka / homogenity of casted part________________ vpenjalne čeljusti / clamping jars 0 0 1 3 5 0 0 0 0 0 0 0 0 5 0 44 5 5 5 1 0 0 0 3 0 0 0 0 0 0 0 73 rezalno orodje / cutting tool 551311030000000 program za RK / NC-program koncentracija emulzije / emulsion concentration 3 3 3 3 0 5 0 3 0 3 0 0 0 0 0 75 1 1 0 3 0 0 0 0 0 0 0 0 1 0 0 20 operater / operator tehnološka kota 56,1 mm / technological measure 56.1 m 0 0 0 0 0 3 0 0 0 0 0 0 1 0 0 14 0 0 0 0 0 0 5 5 0 0 0 0 0 0 0 40 homogenost ulitka / homogenity of casted part 0 0 0 3 5 0 0 0 0 0 0 0 0 5 0 39 10 04 vpenjalne čeljusti / clamping jars 5 0 0 0 0 0 5 3 0 0 0 0 0 0 0 45 rezalno orodje / cutting tool program za RK / NC-program 5 0 0 3 0 1 5 3 0 0 0 0 0 0 0 57 3 0 0 3 0 5 5 3 0 0 0 0 0 0 0 63 13 04 koncentracija emulzije operater / operator kota 2,68 mm / measure 2.68 mm 100300000000100 0 0 0 0 0 3 0 0 0 0 0 0 1 0 0 14 000000000500000 5 16 06 homogenost ulitka / homogenity of casted part 000350000005050 17 06 vpenjalna naprava / clamping device 000000001100000 2 18 06 rezalno orodje / cutting tool program za RK / NC-program koncentracija emulzije / emulsion concentration 000000001300000 4 21 0 0 0 3 0 5 0 0 3 3 0 0 0 0 0 30 000000000000100 5 06 operater / operator livarski pesek v ulitku / sand in the casted part 000000000050100 22 08 0 0 0 0 0 0 0 0 0 0 0 0 5 0 0 25 23 08 masten obdelovanec / oily workpiece 0 0 0 0 0 0 0 0 0 0 3 0 5 1 1 44 parametri pranja / washing parameters homogenost ulitka / homogenity of casted part 0 0 0 0 0 3 0 0 0 0 1 0 5 1 3 57 0 0 0 0 0 0 0 0 0 0 0 0 0 5 0 25 parametri tesnosti / leakage parameters tesnilni elementi / sealing parameters 0 0 0 0 0 3 0 0 0 0 0 0 0 5 0 34 0 0 0 0 0 1 0 0 0 0 0 0 0 3 0 18 končani obdelovanci embalaža / packing 000000000000005 000000000000005 25 25 30 12 operater / operator 000000000000005 Skupaj / Sum 42 42 75 39 48 15 95 12 85 100 95 Sl. 5. Vzročno-posledična matrika za postopek izdelave okrova kompresorja Fig. 5. Cause-and-effect matrix for compressor-housing production 6 1 9 0 Pavleti} D., Fakin S., Sokovi} M.: “[est sigm” v razvoju postopka - Six Sigma in Process Design 120 110 100 90 80 70 60 50 40 30 20 10 100 95 95 KISP-i / KPOV-s 48 42 42 39 15 Sl. 6. Diagram Pareto za KISP Fig. 6. Pareto diagram for the KPOV 85 75 65 55 45 35 25 Sl. 7. Diagram Pareto za KVSP Fig. 7. Pareto diagram for the KPIV 3 PRIMERJAVA SEDANJEGA IN NOVEGA 3 COMPARISON OF THE OLD AND THE MODI- POTEKA POSTOPKA FIED PROCESS-DESIGN FLOW Za primerjavo med sedanjim in novim načinom razvoja postopka bodo v nadaljevanju analizirani parametri, to so: število KVSP, število vzrokov napak v AIVP-postopku ter faktor ocene kritičnosti “C”. S slike 8 je razvidno, da je pri sedanjem načinu razvoja postopka obravnavano večje število KVSP. Pri tem je to število KVSP zajelo celo manjše število vzrokov napak kakor pri novem načinu. Pri primerjavi se še opaža, da je To compare the old and the modified process-design flow, the number of KPIV, the number of failure causes in the FMEA analysis, and the criticality factor, both in the old and the modified process-design flow, will be analyzed. As shown in Fig. 8, in the old process-design flow there were greater numbers of KPIV. At the same time the number of failure causes analyzed in the old process-design flow was significantly lower than in the modified one. Furthermore, the criticality factors VBgfFMK stran 164 Pavleti} D., Fakin S., Sokovi} M.: “[est sigm” v razvoju postopka - Six Sigma in Process Design 30 i 60 n obstoječi način prilagojeni način razvoja postopka razvoja postopka old process modified process design flow design flow 1600 obstoječi način prilagojeni način razvoja postopka razvoja postopka old process modified process design flow design flow 1500 ¦ 1400 1300 - 1200 1100 1000 obstoječi način prilagojeni način razvoja postopka razvoja postopka old process modified process design flow design flow Sl. 8. Primerjava parametrov med sedanjim in novim razvojem poteka postopka Fig. 8. Comparisons of the old and the modified process-design flow vsota ocen kritičnosti “C” pri novem načinu razvoja postopka večja. To pomeni, da je z manjšim številom KVSP odkritih več mogočih vzrokov za napake, na katere lahko preprosto korektivno delujemo in s tem preprečimo dejansko nastajanje napak v postopku proizvodnje. Če primerjamo uporabljen čas in stroške, lahko ugotovimo, da so razmere malo drugačne. Analiza porabljenega časa za oba poteka postopka je prikazana na sliki 9, medtem ko slika 10 prikazuje analizo stroškov. S slike 9 je razvidno, da je za pripravo po novem načinu razvoja postopka uporabljeno več časa, približno 42,5 %. Hkrati so po novem načinu (sl. 10) stroški večji. Dejansko sliko novega načina poteka postopka dobimo, če le-tega projeciramo na enomesečno proizvedeno količino. Na sliki 11 so podani dejanski stroški slabe kakovosti za enomesečno proizvodnjo okrovov kompresorja. are greater in the modified than in the old process-design flow. In the modified process-design flow with a smaller number of KPIV there are a greater number of failure causes determined which could be easily acted upon, corrective action defined and the appearance of failure in production prevented. The results of these analyses are slightly different if we analyze the times spent and the costs. Time analyses for both process-design flows are shown in Fig. 9, while the cost analyses are shown in Fig. 10. From Fig. 9 it can be concluded that in the modified process-design flow more time is used: approximately 42.5 %. At the same time, in the modified process-design flow more money is spent. The costs were greater in the modified than in the old process-design flow. A true picture can be obtained by projecting a modified process-design flow on a one-month production volume. Fig. 11 shows the real poor-quality costs of one month’s compressor-housing production. gfin^OtJJIMISCSD 04-3 stran 165 | ^BSSITIMIGC Pavleti} D., Fakin S., Sokovi} M.: “[est sigm” v razvoju postopka - Six Sigma in Process Design 600 500 400 300 200 100 0 obstoječi način / old process design prilagojeni način / modified process design dejavnosti / activities skupaj / sum 456 izdelava vzročno- cause-and matrike ct / izdelava pregleda izvajanje FMEA izdelava mape marix predvidenega process FMEA postopka / process poteka / project map 180 review 120 00 Sl. 9. Analiza porabljenega časa za sedanji in novi način poteka postopka Fig. 9. Spent-time analysis of the old and the modified design flow 60000 50000 40000 30000 20000 10000 obstoječi način old process design 38000 54000 prilagojeni način modified process design načini razvoja postopka process design flow Sl. 10. Analiza stroškov za sedanji in novi način poteka postopka Fig. 10. Costs analysis of the old and the modified design flow 400 300-200 100- 0l I obstoječi način / old process design I prilagojeni način / modified process design materialni izmet material scrap 238 obdelovalni izmet machining scrap 51 38 izmet / scrap stroški / costs Sl. 11. Stroški slabe kakovosti pri enomesečni proizvodnji okrovov kompresorja Fig. 11. Poor-quality costs of one months compressor-housing production Ob upoštevanju večjih stroškov novega načina poteka postopka ter prihrankov na račun manjšega obdelovalnega in materialnega izmeta v proizvodnji lahko dosežemo znaten celoten prihranek pri uvajanju novega načina. Taking into account the higher costs of the modified process-design flow and the savings in machining and materials scrap in production, a significant overall saving can be achieved by the application of the modified process-design flow. VH^tTPsDDIK stran 166 0 Pavleti} D., Fakin S., Sokovi} M.: “[est sigm” v razvoju postopka - Six Sigma in Process Design 4 SKLEPNE UGOTOVITVE Razvoj postopka, posebej faza načrtovanja postopka je zelo pomembna faza v pripravi proizvodnje avtomobilskih delov. Zaradi velikih serij izdelkov tudi majhni odstotki izmeta povzročajo ogromne stroške. Najmanj, kar lahko naredimo v fazi načrtovanja postopka, je, da uporabimo orodja za izboljšanje postopka, tj. mapo postopka izdelave in vzročno-posledično matriko. Iz pričujočega prispevka je razvidno, da uporabljeni orodji odkrivata veliko število možnih vzrokov za napake, na katere se lahko deluje in s tem prepreči nastajanje napak v postopku proizvodnje. Za uporabo metode AIVP po novem načinu poteka postopka je bilo porabljeno več časa kakor pri sedanjem načinu. Poleg tega sta bila tudi razvoj in priprava novega poteka postopka precej dražja. Vendar je ocena, da bi z zmanjšanjem stroškov obdelovalnega ter materialnega izmeta (v takšnem obsegu) pokrili vse dodatne stroške v fazi priprave; še več, dosegli bi prihranke, ki bi bili nekajkrat večji, kakor je začetno povečanje stroškov. Sklenimo z ugotovitvijo, da celo uporaba posameznih, izoliranih orodij iz metodologije »šest sigm« zagotavlja koristi v izboljšanju postopka. Ti rezultati bodo še boljši s širšo uporabo orodij »šest sigm« in metodologije v celoti. 4 CONCLUSION Process design and development, especially the process planning stage, is a very important phase in the preparation or automotive-part production. Due to the very high production volume, even low scrap levels result in high costs. What we can do in the process planning stage is to apply process-improvement tools such as a process map and a cause-and-effect matrix. From this study it is evident that the applied tools detect a greater number of possible failure causes, so that failures in the production process can be prevented. With the application of the FMEA method more time is spent in the new than in the old process flow. Furthermore, the new process design and development is more costly than the old one. Hence, due to better production preparation the machining and material scrap will be decreased to such a level as to cover all the additional costs in the preparation stage and, furthermore, to produce savings that are several times greater than the initial cost increase. In conclusion, even the application of some isolated tools from Six Sigma methodology provide benefits in process improvement. These results could be improved with more widespread use of Six Sigma tools and methodology. 5 LITERATURA 5 REFERENCES [1] Tadikamala, P. (1994) The confusion over Six Sigma quality, Quality Progress, No 11. [2] Smith, G. (1993) Benchmarking success at Motorola, Copyright Society of Management Accountants of Canada. [3] Breyfogle III, F. W., et al. (1999) Managing Six Sigma, John Wiley & Sons, Inc., New York. [4] Fortenot, F, et al. (1994) Six Sigma in customer satisfaction, Quality Progress, No 12. [5] Pavletič, D., M. Sokovič (2002) Six Sigma: A complex quality initiative, J. of Mech. Eng, Vol. 48, No 3. [6] Fakin, S., M. Sokovič (2001) Use of Six sigma method in the automotive parts production development process, Diploma thesis No. S-556, Faculty of Mechanical Engineering, University of Ljubljana (in Slovene). Naslovi avtorjev: mag. Duško Pavletič Univerza v Rijeki Tehnična fakulteta Vukovarska 58 HR-51000 Rijeka, Hrvaška Sandro Fakin CIMOS dd. PC1 Buzet, Hrvaška doc.dr. Mirko Sokovič Univerza v Ljubljani Fakulteta za strojništvo Aškerčeva 6 1000 Ljubljana mirko.sokovic@fs.uni-lj.si Authors’ Addresses: Mag. Duško Pavletič University of Rijeka Faculty of Engineering Vukovarska 58 HR-51000 Rijeka, Croatia Sandro Fakin CIMOS Ltd. PC1 Buzet, Croatia Doc.Dr. Mirko Sokovič University of Ljubljana Faculty of Mechanical Eng. Aškerčeva 6 1000 Ljubljana, Slovenia mirko.sokovic@fs.uni-lj.si Prejeto: Received: 14.8.2003 Sprejeto: Accepted: 8.4.2004 Odprto za diskusijo: 1 leto Open for discussion: 1 year gfin^OtJJlMlSCSD 04-3 stran 167 | ^BSSITIMIGC