Chapter 1: Introduction

By: Ermiyas T. [Msc.]02. 07, 2006 E.CCourse Number: MEng 5246Quality ManagementTarget Group : 5th year Mechanical Engineering Student

Presentations Overview 12Introducing the course outline Chapter One: IntroductionThis is another option for an Overview slide.

Course Objectives:The objective of the course is to introduce Quality control concept and techniques; The procedures for implementing quality engineering tools in industrial applications;Basic metrology and applied statistics for quality control applications in discrete-item manufacturing systems.Concept of quality and quality control; Probability distribution and histogram; Inference about process quality; type-I error (-error) and type II error (-error); Design of control chart, average run length for chart performance, control charts for variables, control charts for attributes, and control charts; Introduction to modern quality control techniques; Quality costs; Basic statistical tools; control charts; Process capability, use of quality control software.Course Description: Course Outline: 1. Introduction to Statistical Quality Control: The Meaning of Quality and Quality Improvement Dimensions of Quality Quality Engineering Terminology Statistical Methods for Quality Control and ImprovementApplications, organization, cost aspects2. Theory of Control Charts: Methods And Philosophy Of Statistical Process ControlControl Charts For VariablesControl charts for attributesProcess And Measurement System Capability Analysis3. Acceptance Sampling: Techniques Lot-By-Lot Acceptance Sampling For Attributes The Acceptance-Sampling Problem Advantages and Disadvantages of Sampling Types of Sampling Plans Lot Formation Random Sampling Guidelines for Using Acceptance Sampling Single-Sampling Plans for Attributes Definition of a Single-Sampling Plan The OC Curve Designing a Single-SamplingPlan with a Specified OC Curve Rectifying Inspection Double, Multiple, and Sequential Sampling Double-Sampling Plans Multiple-Sampling Plans Cont.Sequential-Sampling PlansOther Acceptance-SamplingAcceptance Sampling by Variables Advantages and Disadvantages of Variables Sampling Types of Sampling Plans Available Caution in the Use of Variables Sampling Designing a Variables Sampling Plan with a Specified OC CurveTQC and TQMStrategies for Implementing Quality Systems: General implementation strategies; The Malcom Baldridge Award; ISO 9000; The Deming Prize; Quality Function Deployment; Other strategies; ISO-14000.Reliability Study and Analysis: Design for reliability Cont.Chapter One: Introduction In todays increasingly competitive markets, quality has assumed a much larger role than its traditional meaning.

Quality has been adopted as an organizational or corporate philosophy where it can no longer be the sole responsibility of workers at the production floor to produce acceptable items.

The meaning of quality has stretched to include all employees from the top firms management through the entire organization as well as vendors.

Quality has become a tool of providing a continuous feedback to the organizational production and business systems with the objective of producing products with high quality and minimum cost, and thus finished products, but also to the quality of the processes that go into those products.

1.1. Definition of product quality

Complex products, such as many appliances, automobiles, or airplanes, will usually require some repair over their service life. For example, you should expect that an automobile will require occasional repair, but if the car requires frequent repair, we say that it is unreliable. This is an industry in which the customers view of quality is greatly impacted by the reliable dimension of quality.

The quality of a product can be evaluated in several ways. It is often very important to differentiate these different dimensions of quality. Garvin (1987) provides an excellent discussion of eight components of dimensions of quality. We summarize key points concerning these dimensions of quality as follows:1. Performance (will the product do the intended job?)Potential customers usually evaluate a product to determine if it will perform certain specific functions and determine how well it performs them.2. Reliability (how often does the product fail?)3. Durability (how long does the product last?)This is the effective service life of the product. Customers obviously want products that perform satisfactorily over a long period of time. Again, the automobile and major appliance industries are examples of business where this dimensions of quality is very important to most customers. 4. Serviceability (how easy is it to repair the product?)There are many industries where the customers view of quality is directly influenced by how quickly and economically a repair of routine maintenance activity can be accomplished. Examples include the appliance and automobile industries and many types of service industries (how long did it take a credit card company to correct an error in your bill?).5. Aesthetics (what does the product look like?)This is the visual appeal of the product, often taking into account factors such as style, color, shape, packaging alternatives, tactile characteristics, and other sensory features. For example, soft drink beverage manufacturers have relied on visual appeal of their packaging to differentiate their product from other competitors.

Cont.6. Features (what does the product do?) Usually, customers associate high quality with products that have added features; that is those that have features beyond this basic performance of the competition. For example, you might consider a spreadsheet software package to be of superior quality if it hand built-in statistical analysis features while its competitors did not.7. Perceived Quality (what is the reputation of the company or its product?) In many cases, customers rely on the past reputation of the company concerning quality of its products. This reputation is directly influenced by failures of the products that are highly visible to the public or that require product recalls, and by how the customer is reported. Perceived quality customers loyalty, and business trips using a particular airline, and the flight almost always arrives on probably prefer to fly on that carrier instead of its competitors.

Cont.8. Conformance to standards (is the product made exactly as the designer intended?)We usually think of a high-quality product as one that exactly meets the requirements placed on it. For example, how well does the hood fit on a new car? Is it perfectly flush with the fender height and the gap exactly the same in all sides? Manufactured parts that do not exactly meet the designers requirements can cause significant quality problems when they are used as the components of a more complex assembly. And automobile consists of several thousand parts. If each one is just slightly too big or too small, many of the components will not fit together properly, and the vehicle (or its major subsystems) may not perform as the designer intended. Cont.As value ( Feigenbaum)As conformance to requirements (Crosby) As fitness for use (Juran)As meeting and/or exceeding customers expectations (Buzzell & Gale)Other definitions of Quality Cont.We see from the foregoing discussion that quality is indeed a multifaceted entity. Consequently, a simple answer to questions such as what is quality? or what is quality improvement? is not easy. The traditional definition of quality is based on the viewpoint that products and service must meet the equipment of those who use them.

1.2. Steps to ensure qualityThe users and/or customers needsRequirements relating to product safety and health hazards provided for in the statutory and regulatory requirementsRequirements provided for national and/or international standardsThe competitors product specifications, in order to gain marketing advantages

A specification is the minimum requirement according to which a producer or service provider makes and delivers the product and service to the customer. In setting specification limits, the following should be considered:In designing the product, the capacity of processes and machines should be kept in mind. It is also necessary to maintain a balance between cost and value realization. The clearer the specification, the better the possibility of creating and delivering quality products.To achieve the above, those responsible for design, production and quality should be consulted from the sales negotiation stage onwards. The overall design of any product is made up of many individual characteristics. For example these may be:

Dimensions, such as length, diameter, thickness or area;Physical properties, such as weight, volume or strength;Electrical properties, such as resistance, voltage or current;Appearance, such as finish, color or texture;Functional qualities, such as output or kilometer per liter;Effects on service, such as taste, feel or noise level.

Cont.1.2.1. Preparing Product Design1.2.1.1. Preparing product designThe specifications and drawings produced by the designer should show the quality standard demanded by the customer or marketplace in clear and precise terms. Every dimension should have realistic tolerances and other performance requirements should have precise limits of acceptability so that the production team can manufacture the product strictly according to specification and drawings.Manufacturing drawings and specifications are prepared by the designers and these should indicate to the production team precisely what quality is required and what raw materials should be used Cont.1. 2.1.2. Preparation for manufactureDeciding on the method of manufacture. Providing the necessary machines, plant, tooling and other equipment.Obtaining satisfactory raw materials.Obtaining and training suitable operators.Planning inspection and shop floor quality control.After the design, including the manufacturing drawings, has been reviewed and finalized, it is time to plan for manufacture. This will include the following steps:

1. 2.1.3. ManufactureOnce the design and planning for manufacture have been completed, the manufacturing can begin. If the planning has been well done, there should not be too many problems. During manufacture the following are the most common factors that can affect quality:Set-up. Some processes, such as punching, cutting, printing and labeling, are so consistent that, if the initial set-up is correct, the whole lot will conform to the specifications. However, the initial set-up has to be checked by carrying out first-piece inspection;Machines and tools. From time to time changes can occur in machine or tool settings, which can then lead to defects. Processes of this type include machining, resistance welding and filling. Here it is necessary to carry out periodic checks by patrol inspection; Cont. Cont.Operator. There are some processes where the result depends on the skill and attention of the operator, such as welding, hand soldering and painting processes. For such processes it is necessary at the manufacture planning stage for the operators working methods to be decided upon;Materials and components. It is important to ensure the quality of raw materials and components by undertaking regular checks on the suppliers processes and also where necessary by carrying out incoming inspection1.2.1.4. Correction of quality deficienciesIn spite of all the efforts made, the required quality will sometimes not be attained and one may be faced with a pile of scrap and rework. This means that something has gone wrong during the manufacturing process. The reason for the trouble must be located and permanently corrected so that it cannot happen again. The following are obvious possibilities:The shop-floor operators had no clear idea what standard of quality was required;The method was such that it was very difficult to get the job right, but very easy to get it wrong;The machine and equipment were incapable of achieving the tolerances required;The incoming materials and components were unsatisfactory;The operators were untrained and not up to the job; Shop-floor quality control was either not properly planned or not properly executed, or both. Cont.1. 2.1.5. CoordinationIt is obvious from the above steps that everybody in the company, that is the sales-men, designers, purchasing, stores and methods staff, plant engineers, jigs and tool personnel, production planning and production staff, operators, inspection and testing staff, packaging, dispatch and so on, are responsible for product quality. Indeed, quality is ever bodys business. Unfortunately, if care is not taken, it ends up being nobodys business. It is therefore important to ensure that everyone is quality-conscious and that they all work together on matters related to quality. Cont. 1.3 Quality and competitiveness There is a strong underlying suggestion in the quality management literature that quality is the best and, in many instances, only dimension through which competitive advantage can be achieved [9,7]. Indisputably, quality as a competitive factor in the manufacturing sector has been largely enhanced over the past two decades. It is important to understand the role of quality to competitive position. The real magic formula of the seeming Japanese dominance simply lies in understanding the role of quality plays in their corporate strategy. Robert [10] stated that high quality not only puts a company on a much different competitive plane than its counterparts but it also makes a wider variety of strategic options accessible to the company. Moreover, [11] indicated that quality improvements benefit a company both in terms of costs and revenues. Quality has been cited as a competitive priority [12], an issue of strategic importance [4], and an ``order qualifier''- a means of survival [13]. Over the years, managers have witnessed it in different forms - statistical quality control (SQC), total quality control (TQC), total quality management (TQM), etc. Figure 1 below gives an insight on the link between quality effort and competitiveness.

Cont.Figure 11.4 Quality costsEvery time work is redone, the cost of quality increases. Examples include:

The reworking of a manufactured itemThe retesting of an assembly The rebuilding of a toolThe correction of a bank statementIn short, any cost that would not have been expanded if quality were perfect contributed to the cost of quality. Generally speaking, quality costs are those categories of costs that are associated with producing, identifying, avoiding or repairing products that do not meet requirements. Many manufacturing and service organizations use four categories of quality costs:1.4.1 Prevention costsThe costs of all activities specifically designed to prevent poor quality in products or services such as:New product reviewQuality planning Supplier capability surveysProcess capability surveysProcess capability evaluationsQuality improvement team meetingsQuality improvement projects Quality education and training1.4.2 Appraisal costsCosts associated with measuring, evaluating or auditing products or services to assure conformance to quality standard and performance requirements such as:

Cont.Incoming and source inspecting/test of purchased materialIn-process or service auditsCalibration of measuring and test equipmentAssociated supplies and material1.4.3 Failure costsCosts resulting from products or services not conforming to requirements or customers needs failure costs are divided into internal and external failure categories.

1.4.3.1 Internal Failure Costs Failure costs occurring prior to delivery of shipment of the product or the furnishing of service to the customer. Example of such costs: Cont.ScrapRework Re-inspectRe-testing Material reviewDown grading1.4.3.2 External Failure costs Failure costs occurring after delivery of shipment of the product and during or after furnishing of services to the customer such as:Processing customer compliant Customer returns Warranty claimsProduct recalls

Cont.1.5. Statistical Methods for Quality Control and ImprovementStop Producing Chaos a cry from the heart! When the great guru of quality management and process improvement W. Edwards Deming died at the age of 93 at the end of 1993, the last words on his lips must have been Management still doesnt understand process variation.A process as a system with a set of inputs and an output.

Figure 2

such as temperatures, pressures, feed rates, and other process variables. Cont.Figure 2

such as environmental factors or properties of raw materials provided by an external supplier. Cont.Figure 2Statistical process control is a methodology to monitor and benchmark a process to improve its variability, stability and capability. According to Douglas Montgomery (1985) states that Statistical methods play a vital role in quality assurance. They provide the principal means by which product is sampled, tested and evaluated and information in those data used to control and improve the production process. In any production process, regardless of how well designed or carefully maintained it is, a certain amount of natural variability will always exist.Production processes must perform consistently overtime to be capable of meeting production and design requirements.The output variable y is a quality characteristic, that is, a measure of process and product quality. This model can also be used to represent nonmanufacturing or service processesThe production process transforms the input raw materials, component parts, and subassemblies into a finished product that has several quality characteristics. Cont.A control chart is one of the primary techniques of statistical process control (SPC).A typical control chart is shown in Fig. 3. This chart plots the averages of measurements of a quality characteristic in samples taken from the process versus time (or the sample number).

Cont.Figure 3The chart has a center line (CL) and upper and lower control limits (UCL and LCL in Fig.3. The center line represents where this process characteristic should fall if there are no unusual sources of variability present. The control limits are determined from some simple statistical considerations. Cont.End?