İstatistiki proses kontrol (spc) ve bir fabrikada uygulanması
Başlık çevirisi mevcut değil.
- Tez No: 39635
- Danışmanlar: PROF.DR. İRFAN SAYGILI
- Tez Türü: Yüksek Lisans
- Konular: Makine Mühendisliği, Mechanical Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 1994
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Belirtilmemiş.
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 71
Özet
SUMMARY in this thesis , main subject is more than a direct theory , but a system change , a tool for a system change as vvell.ln order to explain the use of this tool , the SPC where , it is the abbraviation of Statistical Process Control , the short history about quality is given first, also to understand the need to use SPC is tried to be given by the Japanese system , and the idea of“ Need For Change ”.And finally the index , the helpfull tools for making SPC , commands for the system and an ımplementatıon example in a nevvly changed automative plant is given in the follovving pages of the thesis. in the summary part the flow of action will be the same as the thesis.SPC is though , not a very nevvly introduced tool , it is somehovv nevvly understood as a very usefull tool especially for the European , American and Japanese Automotive industries . Now ı belive it will be a very popular tool also in Türkiye , during the new mentatlity and trying to get quality certificates and avvards such as ISO 9000 , Q1 , ete. As indicated above SPC is the abbreviation of the word Statistical Process Control and can be summarised as using Statistical methods for controlling the proses from the basis of the process outputs , but specially interested in the procecc not the product. SPC is a usefull tool , but like every tool a sufficent management idea and company philosophy is required to transfer it to a living helpfull tool , othervvise it will only be usefull tool in the theory.For this the phlosphy of FORD Motor Company is herebelovv given.The same philosophy is accepted by OTOSAN. Ford Motor Company Operating Philosophy THE OPERATİNG PHİLOSOPHY OF FORD MOTOR COMPANY IS TO MEET CUSTOMER NEEDS AND EXPECTATIONS BY ESTABLISHING AND MAINTAINING AN ENVIRONMENT VVHICH ENCOURAGES ALL EMPLOYEES TO PURSUE NEVER - ENDING IMPROVEMENT İN THE OUALITY AND PRODUCTIVITY OF PRODUCTS AND SERVICES THROUGHOUT THE CORPORATION , ITS SUPPLY BASE AND , ITS DEALER ORGANIZATIONS. The Ford Operating Philosophy of“ Never Ending Improvement ”is applicable to ali forms of manufacturing operations.An integral part of that philosophy is the use of Statistical techniques to control manufacturing processes. IXThe last word“Never Ending Improvement”is the key point , not only for SPC but for every tool such as QFD , DOE , FMEA and ete. The levels of Ouality in the vvorld has mainly been divided into 4 categories: 1-The Product Orientation , vvhere only the final product is controlled and the idea of“DETECTION”is the king.ln this system it is allovved and accepted to make some % of rejected , serap parts.Because control of the parts is after the production it is like counting the dead soldiers after the war. 2-System Orientation , a more povverfull detection system , can also be considered as filtering , controls are made during raw-material income and betvveen operations Stili 100 % inspection is required to protect the customer from the scraps 3-Process Orientation , the beginning of the“Prevention Techniques”, also the starting point of SPC , if compared the previous step , item 2 was like filtering the river not avoiding it to be vvasted , so the more vvaste mixed with river, requires the more filtering units. But in this step the idea is to control the“ 5 ”main inputs of the process by examining the products and making an on-line feedback system. in this step , SPC , FMEA , QFD and other tools are used for this feedback reseting system. 4-Customer Orientation , the problem in the third step was , the ansvver of the question“ Who is the king ? , Who will decide what to do ? , Who determines the quality level ? ”. The ansvver of this question for step 3 is the Management, (Plant Mangers - General Manager) , vvhich is not enough , the point of vievv , the requirements of the customer should be inciuded in the system. in step 4 the cycie is now been closed by the idea“ Customer is the King ”, so the circle is now been closed and this is therefore might be called as“ Total Ouality Management”. After a gaze at the quality levels in the history , we can talk about a seperation , mentality based on the idea of“ Prevention ”versus“ Detection ”. For a classic engineer , generally considered as an American , the limits are the specification limiti , called also as tolerances.lf a part is in tolerance it is good , but if it is out of tolerance it is not only bad but also a scrab , a vvaste. Here we come to the difference point betvveen the Control Limits and the Specification Limits , vvhich vvill be shovvn as CL and SL respectively.For a Japanese engineer the limit is the CL , here also we should explain the meaning of the CL , according to Gauss in the planet called earth , everything happens in a random probability system vvhich can be resumed as the Normal Distribution , as if we gather data about the heights of the male people in a country , the distribution vvill be a normal öne vvhich means we vviil have for example lot of man , tali is 1.70 m , vvhilst less man , tali is 1.80 m ör 1.60 m . If we have a very mixed data such as for every height we have the same number of man , it is not logical the cause is ; the man we gather data are from mixed nations.So for the statistical point of vievv the distribution in normal conditions can be resumed as the average +/- 3 standart deviation.VVhich corresponds to nearly 99.7 % . xit is the same for a process , if we can control the cahnges in a process for the general causes , which are the allovved. changes for process , the outputs will be as in the previous example , and by the formula X +/- 3s , we can reach the control limits for the process in normal conditions , in the first part of the development of thesis , the subject called Capability is given , according to this the CL found should be smaller than the SL given in order to have accepted parts and to have Capability.So it will be clear that we will have some smaller limits called CL.In normal conditions the outputs of the process is accepted to be in this limits , 99.73 % A Japanese engineer will take precautions when he see a part below the CL , though it is stili an accepted part according to SL, but a sympthom of not normal condition.He will reset his process before having rejected parts , having no vvaste while the classical engineer will wait for resetting his process till he recognizes the rejected part ör parts.Japanese people cali such plants producing rejected parts as BLACK FACTORY. The need for change is simple“ To reduce the cost, to reach the customer with lower price , higher profit than the rivals in the market ”.Can we do that only with SPC , the ansvver is also simple“No”, but it is a tool to be better than the rivals.The story given herebelovv can make the subject easier to be seen.One Japanese and öne American boy was making a camp and were vvaiking in the forest when they heard the groaning voice of a lion , Japanese guy quickly sat down and began to wear his sport shoes , naturally the American asked him with a mocking manner“Do you think you can run faster than the lion with these shoes ?”, the ansvver was simple but not expected , he said“ l only expect to run faster than you ! ”The first step in the never ending improvement philosophy is to be better than the rivals , the second step is to be the best for the point of the customer. After trying to talk about the Need For Change and Need For SPC , we can talk about the steps of SPC.The first step is the choose of the points to be controlled by SPC.This is done by a team , called the SPC team , öne of the nevvly introduced subject is the team work not öne man show .The concerns , problems gathered from the customer complaıns , in plant concerns , both real and potential ; are put on the table , from this concerns the SPC team selects the points and the characteristics in the process vvhich is the cause for the concern , after selection for example a torque opreration , data are been collected for the capability vvorks , first the Machine Capability, an than the Process Capability, is calculated with the formulae of the indices Cm , Cmk , Pp , Ppk , Cp , Cpk. If this indices show an acceptable value , Control Chart implementation is carried on by calculating the control limits, average value. The improvements to the process should only be thought after the process is stable and in the control limit area.VVhen a process is stable and inthe limits of control vvhich in short means process under control; there is few ör no special causes affecting the process , the change is purely random because of the general causes. The commands on the control charts and on the data collected during the capability vvorks are analysed and problems are solved according to the problem solving techniques vvhich are also shortly described in the thesis.Some of these techniques are ;Check Sheets , Pareto Analysis , Flovv Charts , Brainstorming , xıNominal Group Technique , Histogram , Cause & Effect Diagrams (Fishbone Diagrams), Stratification and ete. in the analysıs of the Control Charts after calculating the control limits and passing to the on-going studies , some steps are highiy recomended in an order.These techniques vvhich are the messagers of the things göne vvrong and things probably can go vvrong are resumed with examples in the final-conclusion part of the thesis.Main keys are the points out of the control limits, runs of 7 points , and obvious non-random runs. One of the most important things in SPC is the calculation of the Control Limits ; in SPC there are 2 Control Limits ; öne is for the maximum value and knovvn as Upper Control Limit, the UCL index is used for it and the other öne is as expected for the minimum value and called as Lovver Control Limit, shovvn as LCL. it is very important that , after how many values , öne calculates the limits ; miscalculated limits are very dangerous in the analysis of the data vvhich will lead the engineer to unnecessary points, take a lot of time to realize it is wrong.lt is highiy recomended to calculate the UCL and LCL as follovvs ; First do the machine capability if it is acceptable pass to the process capability works ; initially calculate Pp and Ppk ( Proses Preliminary Potential - Real Capabiliy indices) ; this work requires 100 data from a process vvithout any interval, by this öne can calculate the limits for a process in a small time interval vvhich will not be the real Control Limits since in the real process time will affect a lot of factors , after analysing the data ; from the same process data should be collected in a 20 days time , again the same amount and the final Control Limits should be calculated also this period is for the calculation of Cp - Cpk ; prior to the exact CL calculations nearly 3 control charts shoul be filled and analysed ; only after that the CL calculated can be the mirror of the real process , change in time because of the 5 main key points ; the input material, vvorker, method, machine, environment. There are two main indices , shovvs the scrab % and the capability in terms of numbers , practically values greater than 1 is accepted but the target is minimum 1.33 - 1.67 for the Cp - Cpk.The formulae neccesary for the indices and the comments according to the values that , those indices have ,has been expiained detailly inside this thesis. One of the other critical point in SPC is the education of the vvorkers , SPC has been popular in industry because it can be used by the vvorkers easily .But this is only valid if the vvorker is trained enough and the personel in a factory is also well trained.For this also in Otosan , the first goal was to train people beginning from the Process Engineer who will aftervvards train their vvorkers.Also it is important to take the Management Support for to make a tool alive as told before.For this a seminary was given to the management comitee of Otosan .After completing the training , the capability vvorks vvere completed and by the help of the Control Charts the control is given to the real vvorkers.Also in the implementation part of tis thesis , the evidence for the trainings given by the author of this thesis and the control charts projecting the real process conditions of a factory , can be seen. XIIThe shortest word for SPC is the Change of mentality from Detection to Prevention.After supplying the Prevention techniques a further step is the Never Ending Improvement Philosophy , vvhich will lead our industry to be capable to take a part in the great market war of the world. Tarkan Uçüncüoğlu İstanbul 1994 MISSION Ford Motor Company is a worldwide leader in automotive and automotive-related products and services as well as in newer industries such as aerospace. Communications, and financial services. Our mission is to improve continualiy our products and services to meet our customers' needs. allowing us to prosper as a business and to provide a reasonable retum for our stockholders, the owners of our business. VALUES How we accomplish our mission is as important as the mission itself. Fundamental to suçcess for the Company are these basic values: People -- Our people are the source of our strength. They provide our corporate intelligence and determine our reputation and vltaiity. Involvement and teamwork are our core human values. Products -- Our products are the end result of our efTorts, and they should be the best in serving customers worldwide. As our products are vievved. so are we vievved. Profits -- Profits are the ultimate measure of how efficiently we provide customers with the best products for their needs. Profits are required to survlve and grow. GUIDINGPRINCIPLES Quality comes flrst -- To achieve customer satisfaction, the quality of our products and services must be our nurnber öne priority. Customers are the focus of everything we do -- Our work must be done with our customers in mind. provlding better products and services than our competition. Continuous tmprovement is essential to our success -- We must strive for excellence in everything we do: in our products, in their safety and value -- and in our services, our human relations, our competitiveness, and our profitability. Employee involvement is our way of life -- We are a team. We must treat each other witn trust and respect. Dealers and suppliers are our partners -- The Company must maintain mutually beneficial relationships with dealers. suppliers. and our other business associates. Integrity İS never compromised -- The conduct of our Company worldwide must be pursued in a manner that is socially responsible and commands respect for its integrity and for its positive contributions to society. Our doors are öpen to men and women alike without discrimination and vvithout regard to ethnic origin ör personal beliefs. XIİ)
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