This diploma thesis deals with the evaluation of the capability of a specific production process. The theoretical part of the work contains a description of statistical process control, types of control charts and evaluation of process capability. The practical part is focused on evaluating the capability of a specific process. The method of dataset collection is described at first, then this data are analyzed and the capability of this process is evaluated.

Master’s thesis is point to the innovation the data collecting of testing machine of selective circuit breakers. New solution of data collection don’t affect the operations of testing machine. The cost calculation of new solution is included. Master’s thesis also included program solution of SPC methods and application of it to the process of testing the selective circuit breakers.

The thesis deals with implementing of statistical process control (SPC) on CNC cut center into the mechanic production. One part of the project is engaged in theoretical information gathering, process monitoring and data collection. Second part deals with stabilization, regulation and improvement of the process using right statistical instruments. As a result is implementing measuring station from where will be the process data transferred to a server and evaluated. On the basis of that is possible to implement a correction in the right time if the process isn´t stabilized. The main objectives of the thesiss are cost reduction, scrap reduction and modernization of the process.

This thesis aims to evaluate a new manufacturing process by using statistical methods SPC. In the theoretical part provides the basic methods and rules applied in the assessment of control charts. The next part evaluates the current state of the company Hanhart Morkovice s.r.o. analysis and production of coils. The analytical part deals with control charts for reference and quality characters using statistical software process capability indexes and control charts. Based on information from the analytical part, conclusions are drawn and designed for long-term steps using established methods of SPC for quality characters.

The thesis is focused on the production management company XY. In the first part, there is the theoretical knowledge required for the understanding of this problem and diploma thesis. In the second part there is the analysis of company processes. Based on the identified problems the methodology of improvement is designed in this section.

The diploma thesis deals with usage of statistical methods to assure capability of production process. The theoretical part includes the definition of quality management, basic statistical concepts and statistical process control. The practical part presents basic information about the company P & L, spol. s r. o. and analyzes the production process of selected parts. The tools of statistical process control are applied and measures to assure capability of production process are proposed.

[pt] A maioria dos trabalhos que propõem esquemas de Controle Estatístico de Processos Multivariados (CEPM) e que analisam o desempenho desses esquemas considera alterações nas variáveis observadas. Alguns autores mostraram que, quando alterações no vetor de médias de um processo multivariado ocorrem tipicamente em direções previsíveis, a estatística mais eficaz para o monitoramento do processo é o valor da projeção do vetor de observações (ou de sua média amostral) em cada uma dessas direções. Este trabalho propõe um método para o monitoramento de processos multivariados nos quais alterações nos parâmetros do processo são devidas a causas especiais que afetam variáveis não observáveis e ocorrem em direções conhecidas (ortogonais), e compara seu desempenho com o de gráficos de Shewhart nas variáveis observadas, nas componentes principais, e com o de gráficos de T2 no vetor de variáveis observadas. Além disso, é proposto um esquema complementar de monitoramento para detectar alterações em novas direções fora do hiperplano formado pelas direções conhecidas. Resultados obtidos por simulação mostram que o esquema proposto, de gráficos de controle em variáveis transformadas (projeções do vetor de variáveis observadas nas direções conhecidas), tem melhor desempenho na maior parte dos casos analisados. A análise de desempenho é feita supondo deslocamentos da média nas direções conhecidas (já que estes é que são as alterações conhecidas, ocasionadas pelas causas especiais) e/ou aumentos da variância nessas mesmas direções. A comparação é baseada nas probabilidades de alarme falso e de alarme verdadeiro. / [en] Most of the works that propose schemes of Multivariate Statistical Process Control (MSPC) and that analyze the performance of these schemes consider changes in the observed variables. Previous authors have shown that when the shifts in the mean vector of a multivariate process typically occur in predictable directions, the most effective statistics for process monitoring are the values of the projections of the vector of observations (or of the sample average vector) in each of these directions. This paper proposes a method for the monitoring of multivariate processes in which changes in the process parameters are due to special causes that affect non-observable variables and occur in (orthogonal) known directions, and compares its performance with that of Shewharts charts on the observed variables, on the principal components, and with that of T2 charts on the vector of observed variables. In addition, it is proposed a supplementary scheme of monitoring to detect changes in new directions outside of the hyperplane formed by known directions. Results obtained by simulation show that the proposed scheme, consisting of control charts on the transformed variables (projections of the vector of observed variables on the known directions), has better performance in most of the cases analyzed. The analysis of performance is done assuming shifts in the mean of the known directions (since these are the known changes associated to special causes) and/or increases of the variance in these same directions. The comparisons are based on the in-control and out-of-control probabilities of signal.

Rechargeable lithium-ion batteries (LIBs) have generated a shift in the automotive industry towards electric vehicles (EVs) instead of vehicles powered by fossil fuels. As a result, the demand for LIBs is only expected to grow in the future due to an increased demand for passenger EVs. Consequently, LIB manufacturers have to increase their production to meet the increasing demand. Northvolt is a Swedish LIB manufacturer founded in 2016, aiming to start the production of LIBs at the Northvolt Ett factory in Skellefteå during 2021. The Northvolt Ett factory will be one of the largest battery plants in Europe, supplying battery cells for both commercial and domestic use. Poorly manufactured battery cells can potentially cause hazardous events, such as fires or explosions, further supporting the need for high quality batteries. Consequently, requirements from customers and industry standards are high in terms of product quality control through e.g. measurement system analysis (MSA), statistical process control (SPC), and capability analysis. Furthermore, previous research has highlighted issues during commissioning and ramp-up of production, potentially occurring at Northvolt Ett.  The purpose of this study has been to describe how high-quality production can be ensured and maintained during and after commissioning. The study has been conducted as a qualitative case study at Northvolt Ett, focusing on qualification of the coating process. The basis for the study was to examine previous research on quality assurance from other industries, analyze automotive standards, and gather learnings from the pilot production at Northvolt Labs in Västerås. Unstructured interviews were conducted with Northvolt staff to understand what had previously been done related to quality assurance for Coating.  The learnings from Northvolt Labs highlighted a clear focus on preventive actions, such as establishing a Design-FMEA, Process-FMEA, and a Control Plan for the coating process. However, room for improvement was identified in terms of process improvement and control, since the lack of SPC has yielded unreliable results from the performed capability analysis. In addition, previous research has shown that preventive actions should be combined with actions for process improvement to reach full-scale production quickly. Thus, recommendations have been made for Northvolt to implement a clear strategy for product qualification through SPC and capability analysis, as a complement to the preventive actions. The recommendations include specific propositions for validation of the coating process and a general framework for process validation through MSA, SPC, and capability analysis. The presented recommendations can help Northvolt perform successful commissioning of the processes at Northvolt Ett and can also be useful for process validation in other manufacturing industries. / Laddningsbara litium-jon-batterier (LIB:s) har skapat en omställning i bilindustrin mot eldrivna fordon istället för fordon som drivs av fossila bränslen. Som en konsekvens väntas efterfrågan av LIB:s bara att öka i framtiden på grund av en ökad efterfrågan på eldrivna passagerarfordon. LIB-tillverkare måste därför öka sin produktion för att möta den växande efterfrågan. Northvolt är en svensk LIB-tillverkare som grundades 2016, med sikte på att starta produktionen av LIB:s vid fabriken Northvolt Ett i Skellefteå under 2021. Fabriken Northvolt Ett kommer att vara en av de största batterifabrikerna i Europa och leverera battericeller för både kommersiell och privat användning. Dåligt tillverkade battericeller kan potentiellt orsaka allvarliga händelser som bränder eller explosioner, vilket vidare stödjer behovet av batterier med hög kvalitet. Till följd av detta är kraven från standarder och tillverkare inom bilindustrin höga i termer av kvalitetskontroll av produkter genom t.ex. mätsystemanalys (MSA), statistisk processtyrning (SPS), och duglighetsanalys. Vidare visar tidigare forskning på problem som kan uppstå under driftsättning och upprampning av produktion, vilka potentiellt kan uppstå för Northvolt Ett.  Syftet med denna studie har varit att beskriva hur högkvalitativ produktion kan säkerställas och upprätthållas under och efter driftsättning. Studien har genomförts som en kvalitativ fallstudie vid Northvolt Ett med fokus på kvalifikation av coating-processen. Utgångspunkten för studien har varit att undersöka tidigare forskning inom kvalitetssäkring från andra industrier, analysera standarder från bilindustrin, och hämta in lärdomar från pilotproduktionen vid Northvolt Labs i Västerås. Ostrukturerade intervjuer genomfördes med anställda på Northvolt för att öka förståelsen för vad som tidigare gjorts relaterat till kvalitetssäkring för Coating.  Lärdomarna från Northvolt Labs visade ett tydligt fokus på förebyggande åtgärder, som upprättande av en Design-FMEA, Process-FMEA, och en kontrollplan för coating-processen. Dock identifierades ett förbättringsområde inom åtgärder för processförbättring och kontroll, då avsaknaden av SPS har genererat opålitliga resultat från den genomförda duglighetsanalysen. Vidare har tidigare forskning visat att förebyggande åtgärder borde kombineras med åtgärder för processförbättring för att snabbt uppnå fullskalig produktion. Rekommendationer har därför tagits fram till Northvolt för att implementera en tydlig strategi för produktkvalifikation genom SPS och duglighetsanalys, som ett komplement till de förebyggande åtgärderna. Dessa rekommendationer inkluderar specifika förslag för validering av coating-processen samt ett generellt ramverk för processvalidering genom MSA, SPS, och duglighetsanalys. De presenterade rekommendationerna kan hjälpa Northvolt att genomföra en framgångsrik driftsättning av processerna på Northvolt Ett och kan även vara användbara för processvalidering i andra tillverkningsindustrier.

Statistical process control (SPC) is a collection of scientific tools developed and engineered to diagnose unnecessary variation in the output of a production process and eliminate it or perhaps accommodate it by adjusting process settings. The task of quality control (QC) is of fundamental importance in manufacturing processes when a change in the process causes misleading results, this alteration should be detected and corrected as soon as possible. Statistical QC charts originated in the late 1920s by Dr. W. A. Shewhart provide a powerful tool for monitoring production lines in manufacturing industries. They are also have been implemented in various disciplines, such as sequential monitoring of internet traffic flows, health care systems, and more. Shewhart-type charts are effective in detecting large shifts in the process but ineffective in detecting small to moderate shifts. This blind spot allows small shifts (smaller than one standard deviation) to continue undetected in the process, thereby incurring larger total costs for manufacturers. This thesis addresses this issue by augmenting current time-weighted charts (charts that use all the information from the start of a process until the most recent sample/observation) with a Double Generally Weighted Moving Average (DGWMA) chart, leading to more effective process monitoring. The objective of this thesis is to provide the fundamentals and introduce the researcher/practitioner to the essentials of the univariate DGWMA chart from both parametric and nonparametric perspectives. Numerous concepts and characteristics of proposed DGWMA charts are discussed comprehensively. Theoretical expressions and detailed calculations have been provided to aid the interested reader to familiarize and study the topic more thoroughly. This thesis paints a bigger picture of the DGWMA chart in a sense that other time-weighted charts such as the Generally Weighted Moving Average (GWMA), Exponentially Weighted Moving Average (EWMA), Double Exponentially Weighted Moving Average (DEWMA) and Cumulative Sum (CUSUM) fall under this umbrella. Both real-life data and simulated examples have been embedded throughout the thesis. We make use of R and Mathematica software packages to calculate numerical results related to the run length distribution and its associated characteristics in this thesis. We only consider control charts for monitoring the process location parameter. However, our conclusions and recommendations are extendable for the process dispersion parameter. In this thesis, we consider the DGWMA chart as the main chart and the EWMA, DEWMA, GWMA, and CUSUM charts as special cases. The thesis consists of the following chapters with a short description for each chapter as follows: Chapter 1 provides a brief introduction to SPC concepts and gives a literature review in terms of background information for the research conducted in this thesis. The scope and objectives of the present research are highlighted in detail. Chapter 2 provides an overview and a theoretical background on the design and implementation of the DGWMA chart derived from the SPC literature review. The properties of the DGWMA chart, including the plotting statistic, the structure for the weights, the control limits (exact/steady-state), etc. are considered in detail. The weighting structure of the DGWMA chart and its special case are discussed and pictured to emphasize the impact of weights in increasing the detection capability of time-weighted charts. Three approaches are described and investigated for calculating the run length distribution and its associated characteristics for the DGWMA chart and its special case the DEWMA chart; this includes: (i) exact approach; (ii) Markov chain approach; (iii) Monte Carlo simulation. In Chapter 3 we develop a one-sided generalized parametric chart (denoted by DGWMA-TBE) for monitoring the time between events (TBE) of nonconformities items originating from the high-yield processes when the underlying process distribution is gamma and the parameter of interest is known (Case K) and unknown (Case U). A Markov chain approach is implemented to derive the run length distribution and its associated characteristics for the DGWMA and DEWMA charts. An exact approach is also used to derive closed-form expressions for the run length distribution of the proposed chart. Performance analysis has been undertaken to execute a comparative study with several existing time-weighted charts. The proposed chart encompasses one-sided GWMA-TBE, EWMA-TBE, DEWMA-TBE, and Shewhart-type charts as limiting or special cases. The CUSUM-TBE chart is also included in the performance comparison. The necessary design parameters are provided to aid the implementation of the proposed chart and finding the optimal design and near optima design that is useful for practitioners. Alternative discrete distributions are considered for the weights of the GWMA-TBE chart and a discussion is provided to address the connection between new weights originating from the suggested distributions and the chart’s capability in detecting shifts. As a result, one can design an optimal GWMA-TBE chart by replacing weights from the discrete Weibull distribution without the implementation of the double exponential smoothing technique. Chapter 4 focuses on developing a two-sided nonparametric (distribution-free) DGWMA control chart based on the exceedance (EX) statistic, denoted as DGWMA-EX when the parameter of interest is unknown (Case U) and the underlying process distribution is continuous and symmetric. An exact approach and a Markov chain approach are considered to calculate the run length distribution and its associated characteristics for the proposed chart. A performance comparison has been undertaken to execute analysis with other nonparametric time-weighted charts available in the SPC literature. The proposed chart en-compasses two-sided GWMA-EX, EWMA-EX, DEWMA-EX, and Shewhart-type charts as limiting or special cases. The CUSUM-EX chart is also included in the performance comparison Also, the performance of the proposed DGWMA-EX chart has been evaluated under different symmetric and skewed distributions in comparison with its main counterparts, and the necessary results and recommendations are provided for practitioners to design an optimal chart. Chapter 5 encloses this thesis with a summary of the research conducted and provides concluding remarks concerning future research opportunities. / Thesis (PhD (Mathematical Statistics))--University of Pretoria, 2020. / This research was supported in part by the National Research Foundation (NRF) under Grant Number 71199 and the postgraduate research bursary supported by the University of Pretoria. Any findings, opinions, and conclusions expressed in this thesis are those of the author and do not necessarily reflect the views of the parties. / Statistics / PhD (Mathematical Statistics) / Unrestricted

Intern materialförsörjning ställer höga krav på leveransservice, exempelvis i form av leverans av rätt material i rätt kvantitet och kvalitet. En del av den interna materialförsörjningen på Saab Surveillance, ett företag som tillverkar högspecialiserade och avancerade produkter, består av materialbrister. Det finns höga krav på effektiv hantering av materialbrister med avseende på tid såväl som flexibilitet, som i nuläget inte uppfyller produktionens behov.  För att undersöka möjligheten att öka effektiviteten i logistikflöden med hjälp av kvalitetskoncept, genomfördes en fallstudie på Saab Surveillance. Studiens syfte var att utveckla en förbättrad hantering av materialbrister hos Saab Surveillance som bidrar till en effektivare intern materialförsörjning från lager till produktion genom tillämpning av kvalitetskoncept. För att uppnå studiens syfte besvarades tre frågeställningar. Den första frågeställningen, ”Hur är den interna materialförsörjningen av materialbrister utformad i nuläget?”, besvarades genom kvalitativa data från intervjuer och observationer. Därutöver bidrog kvantitativa data med ytterligare information, exempelvis ledtider och orsaker till materialbrister. Därefter analyserades den nuvarande interna materialförsörjningen av materialbrister utifrån olika teman och statistisk processtyrning för att besvara andra frågeställningen, ”Vilka möjligheter finns för effektivisering av den interna materialförsörjningen av materialbrister?”. Den tredje frågeställningen, ”Hur bör den interna materialförsörjningen av materialbrister hanteras för att öka effektiviteten?”, besvarades utifrån resultatet från den första och andra frågeställningen, referensramen samt intern benchmarking.  Studiens resultat visade att den nuvarande interna materialförsörjningen av materialbrister kan sammanfattas med sju övergripande aktiviteter: registrering i materialbeställningslista, uppdatering i affärssystemet, skicka information, prioritering av plockning, plockning, leverans och mottagning. Vidare identifierades flera möjligheter för ökad effektivitet i material- och informationsflödet. Till exempel fanns variation i ledtid, slöseri i form av väntetid samt bristande kommunikation. Möjligheterna för ökad effektivitet utgjorde grunden för förbättringsförslagen.  Samtliga sju förbättringsförslag utgick från produktionens behov och förväntningar. Förbättringsförslagen bestod till exempel av att införa en produktionsbuffert för att reducera antalet materialbrister som hanteras i lagret. Genom att skapa förståelse för produktionens förväntningar och lagrets förutsättningar kan det interna kundfokuset öka samt bidra till att en förväntad ledtid för leverans av materialbrister bestäms. Vidare kan införandet av ett materialbristverktyg för beställning av materialbrister standardisera kommunikationen mellan produktionen och lagret. Dessutom var ett förbättringsförslag att tillämpa sekventiell zonplockning av materialbrister för att undvika väntetid som uppstår vid konsolidering. Effektivare leveranser av materialbrister kan också uppnås genom att ha fasta tider för mjölkrundor samt ta bort leveransalternativet till upphämtningshyllan. Ytterligare förbättringsförslag syftade till att reducera väntetid genom omfördelning av ansvar, där montören tillåts beställa materialbrister och senare hämta det från en bestämd plats för materialbrister, istället för produktionsplaneraren. Avslutningsvis resulterade studien i ett förbättringsförslag om att tillämpa statistisk processtyrning för att kunna följa upp effekterna av de föreslagna förbättringarna.  Slutligen visade studien att tillämpning av kvalitetskoncept som kundfokus och statistisk processtyrning kan bidra till effektivisering av intern materialförsörjning av materialbrister. Vidare kan det också vara intressant att undersöka möjligheten att tillämpa kvalitetskoncept i andra logistikflöden för att uppnå ökad effektivitet. / Internal materials supply sets high demands on delivery service, for example in the form of delivery of the right material in the right quantity and quality. A part of the internal materials supply at Saab Surveillance, a company that manufactures highly specialized and advanced products, consists of material shortages. There are high demands on efficient handling of material shortages regarding time as well as flexibility, which currently does not fulfil the needs of the production.  To examine the possibility to increase the efficiency in logistics flows using quality concepts, a case study was performed at Saab Surveillance. The aim of the study was to develop an improved handling of material shortages at Saab Surveillance which contributes to a more efficient internal materials supply from warehouse to production by applying quality concepts. To achieve the aim of the study, three research questions were answered. The first research question, “How is the internal materials supply of material shortages currently designed?”, was answered through qualitative data from interviews and observations. In addition, quantitative data contributed with further information, for example lead times and causes to material shortages. Thereafter, the current internal materials supply of material shortages was analyzed based on different themes and statistical process control to answer the second research question, “What possibilities are there for making the internal materials supply of material shortages more efficient?”. The third research question, “How should the internal materials supply of material shortages be handled to increase the efficiency?”, was answered based on the result of the previous research questions, the theoretical framework and internal benchmarking.  The results of the study showed that the current internal materials supply of material shortages could be summarized with seven overall activities: registration in list of material orders, updating the enterprise resource planning system, sending information, prioritizing of picking, picking, delivery and receiving. Furthermore, several possibilities for increased efficiency in the material and information flow were identified. For example, there was variation in lead time, waste in terms of waiting time and insufficient communication. The possibilities for increasing efficiency formed the foundation for the suggestions of improvement.  All seven suggestions for improvement originated from the needs and expectations of the production. The suggestions for improvement consisted of, for example, implementing a production buffer stock to reduce the number of material shortages which are handled in the warehouse. By creating an understanding of the expectations of the production and the prerequisites of the warehouse, the internal customer focus could increase as well as contribute to determining an expected lead time for the delivery of material shortages. Furthermore, the introduction of a material shortages tool for ordering material shortages could standardize the communication between the production and the warehouse. Additionally, a suggestion for improvement was to apply sequential zone picking of material shortages to avoid waiting time which occurs at consolidation. More efficient deliveries of material shortages could also be achieved by having set times for milk runs as well as removing the delivery option to the pickup shelf. Further suggestion of improvement aimed at reducing waiting time by redistribution of responsibility where the assembler is allowed to order material shortages and later pick it up from a specific location for material shortages, instead of the production planner. Finally, the study resulted in a suggestion for improvement to apply statistical process control to be able to follow up the effects of the suggested improvements.  Finally, the study showed that application of quality concept, such as customer focus and statistical process control, could contribute to increased efficiency of the internal materials supply of material shortages. Furthermore, it would be interesting to examine the possibility of applying quality concepts in other logistics flows to achieve increased efficiency.