QUALITY PLANNING II. Study supports

Transcription

1 PROJECT IRP Creation of English Study Supports for Selected Subjects of the Follow-up Master Study in the Quality Management Study Field IRP/2015/104 QUALITY PLANNING II Study supports Jiří Plura

2 Language review: Mark Landry Title: Author: Prof. Ing. Jiří Plura, CSc. Edition: first, 2015 Number of pages: 108 Study materials for the study support of, the Faculty of Metallurgy and Material Engineering. Intended for the IRP project of: Creation of English Study Supports for Selected Subjects of the Follow-up Master Study in the Quality Management Study Field Number: IRP/2015/104 Eecution: VŠB Technical University of Ostrava The project is co-financed by the Ministry of Education, Youth and Sports of the Czech Republic ISBN

3 INSTRUCTIONS FOR STUDY You have received a study support containing the main topics covered by the course of the taught in the 2nd semester of the follow-up master's degree of the study programme of Quality Management study field at the Faculty of Metallurgy and Material Engineering. Subject aims and outputs of learning The aim of the course is to learn advanced techniques and the methods of quality planning. The course builds on the knowledge gained in the course "Quality Planning I". Attention is paid to modern methodological approaches to product quality planning, the requirements of production part approval processes, to the advanced procedures of process capability analysis, to the procedures of measurement system analysis and other specialized methods. Knowledge outputs: to characterize and classify advanced methods of quality planning to identify appropriate methods for different situations Skill outputs: to apply selected advanced procedures and the methods of quality planning to interpret the results of the application of methods and propose appropriate actions. Who is the course intended for The course is included in the follow-up master's study of the field of study of Quality Management, but it can be studied by an applicant from any other field of study, provided that he/she meets the required prerequisites. This study support is divided into chapters, which logically divide the studied matter, but are not equally comprehensive. The estimated study time of the chapters may vary considerably, which is why large chapters are further divided into numbered sub-chapters and they correspond to the structure described below. Method of communication with the educator This matter is presented to students within the frame of their lectures and practical eercises, where they practically learn the topic discussed during the theoretical lectures. But selected topics suppose self-learning and elaboration of the written seminar works discussed with the lecturer during the consultations and via internet. 3

4 STRUCTURE OF THE CHAPTERS Time to study The time necessary to study the subject matter is given at the beginning of every chapter. The time is approimate and can serve as a rough guide for the study layout of the entire subject. The time may seem too long to some people or, on the contrary, too short to other ones. There are students who have never encountered this issue and, on the other hand, those who already have etensive eperience in this field. Goal There are defined objectives given for you to achieve after reading the chapter and studying the topics - concrete skills, knowledge. Lecture This part is the actual presentation of the studied subject matter, the introduction of new terms, their definitions and eplanation of the principles of the studied subject matter. All is accompanied by pictures, tables, solved eamples. Summary of terms The main terms you should learn are repeated at the end of the chapter. If you still do not understand any of the terms, go back to them again. Questions There are several theoretical questions to verify that you have fully and well mastered the subject matter of the chapter. References There is a list of the used reference sources, from which you can draw additional information on the issue in question, at the very end of every chapter. The author of this educational material wishes you a successful and pleasant study using this tetbook. Prof. Ing. Jiří Plura, CSc. 4

5 CONTENTS INSTRUCTIONS FOR STUDY... 3 STRUCTURE OF THE CHAPTERS ADVANCED APPROACHES TO PRODUCT QUALITY PLANNING Advanced Product Quality Planning (APQP) Planning Product design and development Process design and development Product and process validation Feedback, assessment and corrective action Production Part Approval Process PPAP FAULT TREE ANALYSIS (FTA) Fault tree analysis procedure ADVANCED APPROACHES TO PROCESS CAPABILITY ANALYSIS Procedure of process capability analysis Process Capability Indices The influence of process changes to capability indices Sensitivity of capability indices to the quality characteristic variability Sensitivity of capability indices to the quality characteristic position Ambiguity of process capability indices in relation to the distribution of the quality characteristic Factors affecting the results of process capability analysis Confidence intervals of process capability indices THE PROCEDURES OF PROCESS CAPABILITY ANALYSIS IN NON- STANDARD SITUATIONS Procedures of process capability analysis in the cases, when a process is out of control Procedures of process capability analysis when data normality is not met PROCESS CAPABILITY ANALYSIS IN THE CASE OF NON- MEASURABLE CHARACTERISTICS Process capability indicators in the case of monitoring nonconforming products Process capability indicators in the case of monitoring nonconformities MEASUREMENT SYSTEM ANALYSIS. ANALYSIS OF DRIFT, BIAS AND LINEARITY Statistical properties of measurement systems Analysis of measurement system drift

6 6.3 Analysis of measurement system bias Analysis of measurement system linearity MEASUREMENT SYSTEM ANALYSIS. REPEATABILITY AND REPRODUCIBILITY ANALYSIS (GRR ANALYSIS) Range method Average and Range Method ANOVA MEASUREMENT SYSTEM ANALYSIS. ATTRIBUTE MEASUREMENT SYSTEMS ANALYSIS Evaluation of agreement between operators Evaluation of the agreement between individual operators and reference values Effectiveness of attribute measurement system

7 1. ADVANCED APPROACHES TO PRODUCT QUALITY PLANNING Time for learning 3 hours Goal After studying this chapter you will be able to: Eplain the methodology of advanced product quality planning (APQP) Describe the various inputs and outputs of APQP stages Eplain the course of the Production Part Approval Process and describe individual requirements. Lecture 1.1 Advanced Product Quality Planning (APQP) Present development in the all fields of human activity is connected with increased requirements for product quality. Quality planning has a total essential influence on a product s quality. According to the terminological standard of ISO 9000 s standards family (ISO 9000, 2006) quality planning is defined as part of quality management focused on setting quality objectives and specifying necessary operational processes and related resources to fulfill the quality objectives. Quality planning represents many activities, which decide about resulting quality. For eample these partial activities are included in quality planning [1]: Quality objectives identification and their development in an organization Product quality characteristics planning (the development of products, which meet customer (and other stakeholders) requirements Quality plan processing 7

8 Planning of methods, which will be used for the achievement of required product quality Processes quality planning (the development of processes, which will be able to assure the required product quality and verification of their capability) Planning preventive actions for possible problem risk minimization Planning the methods of measuring and monitoring product and process quality Planning measurement systems and verifying their suitability Planning data collection and the necessary quality records, etc. Quality planning is realized especially in the pre-production phase. Activities in these phases decide about customer satisfaction, product competitiveness and an organization s profit. While in the past the production phase was regarded as a key phase for product quality, at present it is generally recognized that the pre-production phase contributes to final product quality approimately by eighty percent. This state is considerably influenced by the increasing compleity of present products and the technologies used, competitive market conditions and enhanced customer requirements. The importance of quality planning is also connected with the fact that in preproduction phases many more nonconformities arise than in production and other phases. In addition, the removal of nonconformities during pre-production phases is much cheaper than their removal after launching production. However, up to now many organizations pay insufficient attention to these phases. Often there is a lack of time and money for sufficient design processing and quality planning, but later there must be much more time and money for the removal of problems occurring in the implementation phase. Arguments for focusing on quality planning can be summarized by these points: Quality planning principally influences customer satisfaction. The way of product quality planning is an important attribute of an organization s competitiveness. Product quality planning is a way to prevent nonconformities during product implementation and use. Most of nonconformities arise in the pre-production phases, where product quality planning activities are especially done. The removal of nonconformities in the pre-production phases requires the lowest costs and the shortest time. By using the procedures and methods of product quality planning an organization proves that it has utilized all means for achieving customer satisfaction and for preventing nonconformities. Product quality planning results in increased customer reliance on the products of an organization. 8

9 The success of product quality planning is significantly affected by the methodology used. At present, methodologies used in the automotive industry are best processed. An eample is the APQP (Advanced Product Quality Planning and Control Plan) methodology. This methodology was developed jointly by Chrysler, Ford and General Motors as part of the Standard QS In this methodology, product quality planning is defined as a structured method of defining and establishing the steps necessary to assure that a product satisfies the customer. These main benefits of product quality planning are emphasized: directing resources to satisfy a customer promoting an early identification of the required changes avoiding late changes. Using APQP methodology simplifies the scheduling of product quality planning and facilitates communication with suppliers. Product quality planning, using APQP methodology is divided into five overlapping stages (see Fig. 1.1). 1. Planning 2. Product design and development 3. Process design and development 4. Product and process validation 5. Feedback assessment and corrective action. Before the APQP application preparatory phase is completed, it is necessary to provide training for personnel who will be involved in product quality planning and establish an interdisciplinary team of product quality planning. Members of the team should be, in addition to representatives of the quality department, also representatives of design and development, production, technical inspection, supply, sales, service, contractors, customers, etc. An important part of the preparatory phase is defining the action area of the team, defining the methods of communication with other customer and supplier teams, establishing a timetable for product quality planning and determining the necessary costs. 9

10 Fig. 1.1 Product quality planning timing chart according to APQP methodology Planning This initial phase of product quality planning should ensure a full understanding of the requirements and epectations of customers. All activities must be carried out with respect to the customer and to provide better products and services than the competitors. Inputs: Voice of a customer The voice of the customer creates information obtained from internal and eternal customers. When collecting this information there can be used, for eample: Market research Historical warranty and quality information Team eperience. 10

11 Business plan and marketing strategy A business plan and marketing strategy set certain limitations that may affect product quality planning (e.g. cost, schedule, resources for research and development, etc.). Marketing strategy defines target customers, the main selling points and key competitors. Product and process benchmark data The use of benchmarking provides inputs in establishing product/process performance targets. Product and process assumptions It is necessary to include among the inputs product and process assumptions (such as the application of technical innovations, advanced materials, new technologies, etc.). Product reliability studies This data considers the frequency of repairs or the replacement of components within designated periods of time and the results of reliability tests. Customer inputs Valuable information about their needs and epectations can provide future users of the product. This information should be used in developing criteria for evaluating customer satisfaction. Outputs: Design goals Design goals are a translation of the Voice of a Customer into measurable design objectives. The proper selection of design goals assures that the Voice of a Customer is not lost in subsequent design activities. The Voice of the Customer also includes regulatory requirements. Reliability and quality goals Reliability goals are based on customer wants and epectations, program objectives and reliability benchmarks. Quality goals should be based on metrics such as parts per million or scrap reduction. 11

12 Preliminary bill of material The team should establish a preliminary bill of material. Part of it should be a list of potential suppliers. Preliminary process flow chart chart. The anticipated process of production should be described using a process flow Preliminary listing of special product and process characteristics On the basis of information from the customer and on the knowledge of the supplier about the product and the process there should be established special characteristics of the product and the process, which will require special attention. Product assurance plan This plan translates design goals into design requirements. It should include e. g. outlining of program requirements, reliability goals and requirements, the assessment of new technology, material, environment, packaging, service and manufacturing requirements, etc., use of FMEA, the development of engineering requirements. Management support The final output of this phase is Management Support which can be understood as "to inform management about the results and to obtain its support." It is one of the key factors in the success of the product quality planning team. The team should officially inform management about the results after completion of each phase of product quality planning (or more often if necessary). The aim is to demonstrate that all quality planning requirements have been met and all remaining problems are documented and solutions are planned. The result should be the adoption of these results and obtaining support for the net phase (release to the product design and development phase) Product design and development This phase is dealing with the elements of the planning process during which design features and characteristics are developed into a near final form. A feasible design must permit meeting production volumes and schedules, and be consistent with the ability to meet engineering requirements, along with quality, reliability, investment cost, weight and timing objectives. Inputs to this phase correspond to the outputs of the previous phase. 12

13 a) Design Outputs: Design Failure Modes and Effects Analysis (DFMEA) Using the DFMEA application potential failures of a designed product are analysed and their risks are evaluated. In the cases when the risk of potential failure is not acceptable suitable actions for design quality improvement are proposed and implemented. Design for manufacturability and assembly Design for manufacturability and assembly is a simultaneous engineering process designed to optimize the relationship between design function, manufacturability and assembly. During this optimization, a product quality planning team should consider e. g. the sensitivity to the variability of production conditions, dimensional tolerances, the number of components, material handling, etc. Design verification Design verification confirms that product design meets a customer s requirements defined in the previous phase. Design review Design reviews are regularly scheduled meetings led by the organization s design engineering activity and must include other affected areas. Design reviews should include e.g. an evaluation of design requirement considerations, reliability goals, component or system duty cycles, computer simulations and bench test results, the review of design for manufacturability and assembly, test failures, design verification progress, etc. Prototype build Control plan The manufacture of prototype parts provides an opportunity for assessing how well the product meets the voice of customer objectives. A prototype control plan is a document which defines all measurements and material or functional tests applied during prototype creation. Engineering drawings (including mathematical data) A product quality planning team should review whether drawings contain sufficient information about the dimensions and other parameters of the individual parts. Drawings can contain special (set by law or safety regulations) characteristics that must be put into the control plan. Control and inspection points should be clearly defined, in order to propose suitable measuring instruments and products. The dimensions on the drawings should be 13

14 assessed in terms of manufacturability and compatibility with standards for production and measurements. Engineering specifications A detailed review and understanding of the controlling specifications will help a product quality planning team to identify the functional, durability and appearance requirements of the subject component or assembly. Sample size, frequency, and acceptance criteria of these parameters are generally defined as part of the engineering specification. Otherwise, the sample size and frequency are to be determined by the organization and listed in the control plan. Material specifications Material specifications should be reviewed for special characteristics relating to physical properties, performance, environmental, handling, and storage requirements. These characteristics should also be included in the control plan. Drawing and specification changes Where drawing and specification changes are required, the team must ensure that the changes are promptly communicated and properly documented in all affected areas. b) APQP outputs New equipment, tooling and facilities requirements The product quality planning team should include new equipment and facilities requirements in the timing chart. The team should assure that there is a process to determine that new equipment and tooling are capable and delivered on time. Facilities progress should be monitored to assure completion before the start of the pilot production. Special product and process characteristics In the planning stage, the team identifies a preliminary list of special product and process characteristics. The product quality planning team should build on this listing and reach a consensus through the evaluation of the technical information. The organization should refer to the appropriate customer-specific requirements for additional details on the use of special product and process characteristics. 14

15 Gages and testing equipment requirements The product quality planning team should identify gages and testing equipment requirements, add these requirements to the timing chart and monitor that the required timing is met. Team feasibility commitment and management support The product quality planning team must assess the feasibility of the proposed design (also in the cases when the design was submitted by a customer). The team must be satisfied that the proposed design can be manufactured, assembled, tested, packaged, and delivered in a sufficient quantity on schedule at an acceptable cost to the customer. The team consensus that the proposed design is feasible should be documented as the Team Feasibility Commitment Process design and development This stage should ensure the comprehensive development of an effective manufacturing system, which must assure that customer requirements, needs and epectations will be met. The inputs to this stage are corresponding to the outputs of the product design and development stage. Outputs: Packaging Standards and Specifications Packaging Standards are usually defined by the customer, if not, the product quality planning team should ensure that individual product packaging is designed and developed. Packaging design should assure that the product characteristics remain unchanged during packing, transit, and unpacking. The packaging should have compatibility with all identified material handling equipment. Product/Process Quality System Review A product quality planning team should review the quality management system of the manufacturing site. Any additional controls or procedural changes required to produce the product should be updated, documented and included in the manufacturing control plan. This is an opportunity for the improvement of an eisting quality management system. 15

16 Process Flow Chart The process flow chart helps the team to analyze and optimize the proposed process. It is especially useful in the implementation of the FMEA process and in developing a control plan. It can be used to analyze the sources of variations of machines, materials, methods, and manpower from the beginning to the end of a manufacturing or assembly process. Floor Plan Layout The floor plan should be developed and reviewed to determine the acceptability of important control items, such as inspection points, control chart location, the applicability of visual aids, interim repair stations, and storage areas to contain nonconforming material. Characteristics Matri To analyze the relationship between the characteristics of the product and manufacturing operations, it is recommended to apply the characteristics matri. In this matri rows represent individual product quality characteristics and the columns individual production operations. In the matri cells there are used graphical symbols for identifying whether a given operation decides about a given quality characteristic or whether a given quality characteristic is important for a given operation performance. The more relationships the given quality characteristics to the operations has, the more important is its control. Process Failure Mode and Effects Analysis (PFMEA) Within the process design and development the Process FMEA should be performed. It is a team analysis of the proposed process, whose aim is to identify possible failures that may arise during the production of the product and to analyze and minimize their risks. Pre-Launch Control Plan A pre-launch control plan specifies measurements and tests that will be done after a prototype and before full production (especially during pilot production). The purpose of the pre-launch control plan is to detect potential nonconformities during or prior to initiating the production run. e.g. by the means of more in-process and final check points, more frequent inspections, statistical evaluations, enhanced audits or identification of error-proofing devices. Process instructions The product quality planning team should ensure that process instructions provide sufficient understanding and detail for all personnel who have direct responsibility for the 16

17 operation of the processes. These instructions should be developed on the basis of the following sources: FMEA results, control plans, the process flow chart, engineering drawings and material specifications, floor plan layout, the characteristics matri, packaging specifications, process parameters, eperience and knowledge of the processes and products, handling requirements, industry standards and operators qualification. The process instructions for standard operating procedures should be published and should include set-up parameters such as: machine speeds, feeds, cycle times and tooling, and should be accessible to the operators and supervisors. Measurement Systems Analysis Plan The product quality planning team should ensure that a plan to accomplish the required measurement systems analysis is developed. This plan should include e.g. the responsibility to ensure bias, linearity, the repeatability and reproducibility of measurement systems. Preliminary Process Capability Study Plan The product quality planning team should ensure the development of a preliminary process capability analysis plan. More information can be found in PPAP (Production Part Approval Process) [2] and SPC (Statistical Process Control) [3] methodologies. Management Support The product quality planning team should schedule a formal review designed to reinforce management commitment at the conclusion of the process design and development phase. This review is critical for keeping upper management informed as well as gaining assistance in resolving any open issues. Management support includes the confirmation of planning and providing the resources for product and process validation Product and process validation Validation of the product and process is based on the evaluation of a significant production run (pilot production). During a significant production run the product quality planning team should validate that the control plan and process flow chart are being followed and the products meet customer requirements. A significant production run may uncover additional problems, which should be investigated and solved before starting serial production. Inputs to this stage are corresponding to outputs from the stage "Process Design and Development". 17

18 Outputs: Significant Production Run The significant production run must be conducted using production tooling, production equipment, the production environment (including production operators), facility, production gages and production rate. The minimum quantity of products for a significant production run is usually set by the customer. Outputs of the significant production run are used e. g. for: Measurement systems analysis Preliminary process capability study Process review Production validation testing Production part approval Packaging evaluation Quality planning sign-off Sample production parts. Measurement Systems Analysis Measurement of characteristics identified in the control plan should be performed using specified measurement systems. The acceptability of these measurement systems should be verified by the means of measurement system analyses during or before significant production run. Preliminary Process Capability Study A preliminary process capability study should be performed on characteristics identified in the control plan. The study provides an assessment of the readiness of the process for production. Production Part Approval The Purpose of Production Part Approval Process (PPAP) is to provide evidence that all customer engineering design records and specification requirements are properly understood by the organization and that the manufacturing process has the potential to produce a product consistently meeting these requirements during an actual production run at the quoted production rate. 18

19 Production Validation Testing Production validation testing refers to engineering tests that validate that products made using production tools and processes meet customer engineering standards including appearance requirements. Packaging Evaluation All test shipments and test methods must assess the protection of the product from normal transportation damage and adverse environmental factors. The product quality planning team deals with evaluating the effectiveness of the packaging also in the cases when packaging is defined by a customer. Production Control Plan The production control plan is a written description of the systems for controlling production parts and processes. The production control plan is a living document and should be updated to reflect the addition or deletion of controls based on eperience gained by producing parts. Approval of the authorized customer representative may be required. Quality Planning Sign-Off and Management Support The product quality planning team should perform a review at the manufacturing locations and coordinate a formal sign-off. The product quality sign-off indicates to management that the appropriate APQP activities have been completed. The sign-off occurs prior to first product shipment and includes a review of the following: Verification that process flow charts eist and are being followed Verification that control plans eist, are available and are followed at all times for all affected operations Verification that process instructions contain all the special characteristics specified in the control plan and all PFMEA recommendations have been taken into consideration Verification which special monitoring and measuring devices are required by the control plan, verification gages, repeatability and reproducibility and their proper usage Demonstration of the required capacity. Upon completion of the sign-off a review with management should be scheduled to inform management of the program status and gain their support with any open issues. The 19

20 Product Quality Planning Summary and Approval Report is an eample of the documentation required to support an effective quality planning sign-off Feedback, assessment and corrective action Quality planning does not end with the process of validation and installation. It is a component of the manufacturing stage where output can be evaluated when all special and common causes of variation are present. This is also the time to evaluate the effectiveness of the product quality planning efforts. Inputs to this stage are corresponding to outputs from the stage "Product and Process Validation". Outputs: Reduced Variation Control charts and other statistical techniques should be used as tools to identify process variation. Analysis and corrective actions should be used to reduce variation. Continual improvement requires attention, not only to the special cause of variation, but in understanding common causes and seeking ways to reduce these sources of variation. Proposals should be developed including costs, timing, and anticipated improvement for a customer review. Improved Customer Satisfaction Quality planning activities and the demonstrated process capability are important for customer satisfaction, however, the product or service still has to perform in the customer s environment. The effectiveness of product quality planning can be evaluated up to the stage of the use of the product. The organization and customer should be partners in making the changes necessary to correct any deficiencies and in improving customer satisfaction. Improved Delivery and Service There is continual improvement during the delivery and service stage of product quality planning in which the organization and customer partnership solves problems. The eperience gained at this stage provides the customer and organization with the necessary knowledge to reduce process variability, inventory, and quality costs and to provide the right component or system for the net product. 20

21 Effective Use of Lessons - Learned/Best Practices A lessons learned or best practices portfolio are beneficial for capturing, retaining and applying knowledge. Input to lessons learned and best practices can be obtained through a variety of methods including: Review of Things Gone Right/Things Gone Wrong (TGR/TGW) Data from warranty and other performance metrics Corrective action plans Comparison with similar products and processes DFMEA and PFMEA results Production Part Approval Process PPAP The Production Part Approval Process (PPAP) [4] defines the generic requirements for production part approval, including production and bulk materials. It is applied in the automotive industry within Standard QS The purpose of PPAP is to determine if all customer engineering design records and specification requirements are properly understood by the organization and that the manufacturing process has the potential to produce a product consistently meeting these requirements during an actual production run at the quoted production rate. Within the framework of this process, the supplier presents to the customer a range of evidence showing his readiness to begin serial production. The production part approval process should be applied in the following situations: a new part or product correction of the discrepancy of a previously submitted part product modified by an engineering change (in design, specifications or materials) production using new or modified tools production after changing production equipment production in another manufacturing site change of subcontractor changing test methods tools for serial production were not used for more than a year. Fulfillment of a number of requirements of the production part approval process into serial production must be documented on the basis of the products produced during a significant production run. A significant production run must be from a production, which lasts from one to eight hours in which at least 300 consecutive parts must be made, unless 21

22 otherwise specified by the authorized customer representative. A significant production run must be manufactured under conditions corresponding to series production; at the production site, at the production rate, using production tools, materials, gages and workers. PPAP requirements Fulfillment of the following requirements must be demonstrated within the framework of the production part approval process: 1) Design Record An organization must have the engineering documentation of a part, and must provide proof of its material composition (IMDS = International Materials Data System can be used). 2) Authorized Engineering Change Documents In the case of any technical changes of a part that were not still reflected in the design documentation relevant documents demonstrating the approval of these changes is required. 3) Customer Engineering Approval If customer engineering approval is required, it must be documented as evidence. 4) Design Failure Mode and Effects Analysis (Design FMEA) In the case when an organization is responsible for the design of the product, it must apply the Design FMEA and document the results. Design FMEA can be processed for a group of similar parts. 5) Process Flow Diagram(s) The organization must show a process flow chart. 6) Process Failure Mode and Effects Analysis (Process FMEA) The organization must apply the Process FMEA and document the results. Process FMEA can be performed for a process producing a group of similar parts or materials. 22

23 7) Control Plan The organization must process a control plan that defines all methods used for process control and is in accordance with customer requirements. 8) Measurement System Analysis Studies The organization must perform measurement systems analysis (e.g. repeatability and reproducibility, bias, linearity, stability) for all new or modified measurement systems. 9) Dimensional Results The organization shall provide evidence that dimensional verifications required by the design record and the control plan have been completed and the results indicate compliance with specified requirements. Dimensional results must be for each unique manufacturing process, e.g. for all production lines, cavities, molds, dies, etc. The organization shall identify one of the measured parts as a master sample. 10) Records of Material / Performance Test Results The organization must keep records of the tests prescribed in the design documentation or control plan. 11) Initial Process Studies (preliminary (initial) process capability studies) A preliminary process capability study is performed on the basis of data about the quality of products produced during a significant production run. An acceptable level of preliminary process capability must be achieved for all special characteristics. If no special characteristics were identified, a customer reserves the right to request proof of a sufficient level of preliminary process capability for other selected characteristics. To evaluate the preliminary process capability at least 100 data in 25 subgroups should be obtained from a significant production run. In some cases a process capability study can be performed, with the consent of the customer, on the basis of long-term data from the same or a similar process. In the case of out of control processes the organization must identify, evaluate, and if possible, eliminate the effect of special causes of variation prior to PPAP submission. The 23

24 organization shall notify the authorized customer representative of any unstable processes and shall submit a corrective action plan. Criteria of preliminary process capability: Results C pk >1,67 1,33 <= C pk <=1,67 C pk < 1,33 Interpretation The process currently meets the acceptance criteria. The process may be acceptable. Contact the authorized customer representative for a review of the study results. The process does not currently meet the acceptance criteria. Contact the authorized customer representative for a review of the study results. In the event that the acceptance criteria are not achieved, the organization must submit a plan of corrective actions and modified control plan ensuring a hundred percent inspection. 12) Qualified Laboratory Documentation Inspection and testing for PPAP must be performed by a qualified laboratory as defined by customer requirements (e.g. an accredited laboratory). This laboratory shall have documentation that it is qualified for the type of measurements or tests conducted. 13) Appearance Approval Report (AAR) In the case when design documentation includes requirements for appearance an Appearance Approval Report (AAR) must be processed for each part (or a series of parts). 14) Sample Production Parts The organization shall provide a sample products as specified by a customer. 15) Master Sample The organization shall retain a master sample for the same period as production part approval records. The master sample must be identified and must show the customer an approval date on the sample. 24

25 16) Checking Aids If the customer requests it, the organization must submit checking aids (fitures, gages, templates, etc.) for each part. The organization must certify that all aspects of these checking aids agree with the requirements for dimensional requirements. The organization shall provide preventive maintenance using checking aids for the life of the part. 17) Customer-Specific Requirements The organization shall have records of compliance to all applicable specific requirements of a customer. 18) Part Submission Warrant (PSW) After fulfillment of all PPAP requirements the organization shall complete the Part Submission Warrant (PSW). The organization shall verify that all of the measurement and test results show conformance with customer requirements and that all required documentation is available. Organizations must fulfill all applicable requirements for part approval for serial production. The way of submission can be different, because it depends on past eperience with a given supplier. They are used five levels of evidence of submitting within PPAP (see Tab. 1.1). Level 3 is used as a starting level. Based on the evaluation of the evidence submitted to meet the requirements of PPAP there are three basic states of PPAP for the customer: a) Approved b) Interim approval (it permits the shipment of parts for a limited time or a limited number of pieces) c) Rejected. In the case of interim approval or rejection the organization must remove the shortcomings within the set deadline and submit new evidence of compliance. Records of PPAP must be maintained for a period, when a given part is active plus one year. 25

26 Release of the production process and the product (PPF) Similar to the Production Part Approval Process (PPAP), which is used within Standard QS-9000, there is the Release of the Production Process and the Product (PPF) applied within the VDA standard. PPF is a part of the VDA 2 "Quality Assurance of Supply" (5th edition 2012). It defines a total of 22 requirements which approimately correspond to the requirements of PPAP. Tab. 1.1 PPAP submission levels. Level 1 Level 2 Level 3 Level 4 Level 5 Warranty only (and for designated appearance items an Appearance Approval Report) submitted to the customer Warranty with product samples and limited supporting data submitted to the customer Warranty with product samples and complete supporting data submitted to the customer Warranty and other requirements as defined by the customer Warranty with product samples and complete supporting data reviewed by the organization manufacturing location Summary of terms Quality planning - part of quality management focused on setting quality objectives and specifying necessary operational processes and related resources to fulfil quality objectives APQP (Advanced Product Quality Planning and Control Plan) product quality planning methodology developed jointly by Chrysler, Ford and General Motors as part of Standard QS APQP stages - methodology APQP divides product quality planning into five overlapping stages: 1) Planning, 2) Product design and development, 3) Process design and development, 4) Product and process validation, 5) Feedback assessment and corrective action. 26

27 Design for manufacturability and assembly - a simultaneous engineering process designed to optimize the relationship between design function, manufacturability and assembly. Control plan - a document which defines all measurements and material or functional tests applied during prototype creation or a significant production run or serial production (Prototype control plan or Pre-launch control plan or Production control plan). Special product and process characteristics the designation of key product or process characteristics used in the automotive industry. Team Feasibility Commitment - a document which declares product quality planning team consensus that the proposed design is feasible (can be manufactured, assembled, tested, packaged, and delivered in a sufficient quantity on schedule at an acceptable cost to the customer) Significant Production Run - production run before series production under conditions corresponding to the series production; at the production site, at the production rate, using production tools, materials, gages and workers. A significant production run must be from a production, which lasts from one to eight hours in which at least 300 consecutive parts must be made, unless otherwise specified by the authorized customer representative. PPAP (Production Part Approval Process) a process which defines the generic requirements for production part approval applied in the automotive industry. The purpose of PPAP is to determine if all customer engineering design records and specification requirements are properly understood by the organization and that the manufacturing process has the potential to produce a product consistently meeting these requirements during an actual production run at the quoted production rate. Questions 1. Which activities are included in quality planning? 2. Why is quality planning a very important part of quality management? 3. What is the difference between APQP and PPAP? 4. What are main inputs of the APQP stage Planning? 5. What are DFMEA and PFMEA and what is the purpose of using them? 6. What is the content of the Pre-launch control plan? 7. In which situations should PPAP be applied? 27

28 8. How many products should be produced during a significant production run? 9. What are the PPAP acceptance criteria for preliminary (initial) process capability analysis? 10. How many submission levels are used in PPAP? References [1] PLURA, J. Do you Plan Product Quality Effectively? Conradi Research Review, 2003, No. 2, pp , ISSN [2] APQP. Advanced Product Quality Planning and Control Plan. 2nd edition. Chrysler Corporation, Ford Motor Company, General Motors Corporation, 2008 [3] PPAP Production Part Approval Process. 4th edition. AIAG, 2006 [4] GRYNA F. M., CHUA, R. C. H., De FEO, J. A. Juran's Quality Planning and Analysis: for Enterprise Quality. 5th ed. New York: McGraw-Hill Higher Education, 2007, 774 pp., ISBN

29 2. FAULT TREE ANALYSIS (FTA) Time for learning 2 hours Goal After studying this chapter you will be able to: Eplain the principle of Fault Tree Analysis (FTA) Eplain the principles of Gate AND and Gate OR Process a fault tree Propose suitable actions for decreasing the probability of a fault event. Lecture Fault Tree Analysis (FTA) is a method of reliability analysis of comple systems, which is based on the logical decomposition of a certain undesirable event (fault) on partial (intermediate) or elementary (primary) events. Processing the fault tree analysis enables us to analyse the mechanism of faults and to optimize the system with the objective to reduce the probability of the undesirable event. Fault Tree Analysis can be used as a tool of prevention or for the comprehensive analysis of eisting problems. The preventive use of Fault Tree Analysis is a recommended part of a design review. Its application usually follows after FMEA, which represents basic tool for the analysis of system behaviour. FTA was firstly used in Bell Laboratories at the beginning of Sities and later was developed at the company Boeing. Initially it was mainly applied in the aerospace industry and in nuclear energetics. 29

30 The main objectives of fault tree analysis are: The identification of a cause or combination of causes leading to an undesirable (top) event The identification of causes, which can have the largest share on top event occurrence Estimating probability of events An assessment whether the reliability of an analysed system is corresponding to the requirements Finding suitable actions for decreasing the probability of top event. The basic tool of FTA is a fault tree which represents a graphical epression of the relationships between partial events (partial failures) and specifically a final undesirable event (top event). For fault tree processing there are used specific graphical symbols. At present these graphical symbols are not unified, and also the standard for FTA permits the use of various symbols depending on user preferences or the software used [1]. The selected symbols for fault tree processing are given in Fig Fault trees are displayed vertically or horizontally. In the case of vertical orientation the top event is on the top and elementary events are lower, in the case of a horizontal arrangement the top event can be on the left side or on the right side. The basic elements of a fault tree are gates, which epress the hierarchy of undesirable events and define if a given event occurs only in the case of all input events occuring or it occurs in the case of the occurence of any input event. AND Gate The AND gate is used in the cases when a given output event occurs only in the case of the occurence of all input events together (logical product). The resulting probability of an output event can be calculated (in the case when the input events are independent) on the basis of the probability of the input events according to the formula: where: B PB PB P P" AND" P B n (2.1) P AND - the probability of an event eiting from AND gate 30

31 B i P(B i ) - events entering the AND gate - the probabilities of events entering the AND gate With regard to the fact that the probabilities are epressed by values from 0 to 1, it is possible to derive on the basis of this relationship that in the case of AND gate the probability of an output event is lower or maimally equal to the probability of an input event which is least probable: P min P B " AND" i (2.2) i From this inequality it is evident that the presence of gates AND in the fault tree has a positive effect on decreasing the probability of an undesirable event. OR Gate The OR gate is used in the cases, when an eiting event occurs in the case of the occurence of any entry event (the logical sum). The resulting probability of an eiting event can be calculated (in the case when the entry events are independent) on the basis of the probability of entry events according to the formula: P 1 PC 1 PC 1 PC P OR" C n " (2.3) where: P OR C i - the probability of an event eiting from OR gate - events entering the OR gate P(C i ) - the probabilities of events entering the OR gate. From the given relationship it can be derived that in the case of the OR gate the probability of an eiting event is greater or minimally equal to the probability of the most probable entry event: P ma P C " OR" i (2.4) i From this inequality it is evident that the presence of OR gate in the fault tree has a negative effect on the probability of an undesirable event. 31