Chapter 23
House of Quality in the starting matrix
- 1st matrix: these inputs are the needs and desires of the customer. The input requirements are translated into output technical requirements - 2nd matrix: These technical requirements indicate how the input requirements are to be satisfied in the new product or service - 3rd matrix: depicts technical correlations among the output technical requirements. This section of the matrix uses a diagonal grid to allow each of the output requirements to be compared with all others. - 4th matrix: the relationship matrix; it indicates the relationships between inputs and outputs - 5th matrix: is used for comparative evaluation of inputs -6th matrix: used for comparative evaluation of output requirements
Engineering Analysis
- After a particular design alternative has been developed, some form of engineering analysis must often be performed as part of the design process. - The analysis may take the form of stress-strain calculations, heat transfer analysis, or dynamic simulation - The availability of software for engineering analysis on a CAD system greatly increases the designer's ability and willingness to perform a more thorough analysis of a proposed design. - Examples of computer-aided engineering(CAE) software in common use on CAD systems include: + Mass properties analysis- involves the computation of such features of a solid object as its volume, surface area, weight, and center of gravity. It is especially applicable in mechanical design + Interference checking- examines 3-D geometric models consisting of multiple components to identify interferences between components. It is useful in analyzing mechanical assemblies, and chemical plant piping systems + Tolerance analysis- analyzing the specified tolerances of a product's components is used (1) to assess how the tolerances may affect the product's function and performance, (2) to determine how tolerances may influence the ease or difficulty of assembling the product, and (3) to assess how variations in component dimensions may affect the overall size of the assembly + Finite element analysis- to aid in stress-strain, heat transfer, fluid flow, and other computations. +Kinematic and dynamic analysis- analysis studies the operation of mechanical linkages and analyzes their motions + Discrete-event simulation- is used to model complex operational systems, such as a manufacturing cell or a material handling system, as events occur at discrete moments in time and affect the status and performance of the system
Automated Drafting
- CAD systems can be used to prepare highly accurate engineering drawings when paper documents are required. - It is estimated that a CAD system increases productivity in the drafting function by about fivefold over manual preparation of drawings.
Computer-aided design (CAD)/ Computer-aided manufacturing(CAM)
- CAD/CAM denotes the integration of design and manufacturing activities by means of computer systems - CAD/CAM establishes a direct link between product design and manufacturing engineering. - It is the goal of CAD/CAM not only to automate certain phases of design and certain phases of manufacturing, but also to automate the transition from design to manufacturing
Computer-Aided Manufacturing (CAM)
- Computer-aided manufacturing (CAM): involves the use of computer technology in manufacturing planning and control. - The applications of CAM can be divided into two broad categories: (1) manufacturing planning and (2) manufacturing control. - Manufacturing Planning. CAM applications for manufacturing planning are those in which the computer is used indirectly to support the production function, but there is no direct connection between the computer and the process. - Applications of CAM in Manufacturing Planning +Computer-aided process planning (CAPP): Process planning is concerned with the preparation of route sheets that list the sequence of operations and work centers required to produce the product and its components. CAPP systems are available today to prepare these route sheets. +CAD/CAM NC part programming: represents a much more efficient method of generating the control instructions for the machine tool than manual part programming. +Computerized machinability data systems: Computer programs are available to recommend the appropriate cutting conditions for different materials and operations +Computerized work standards: These computer programs use standard time data that have been developed for basic work elements that comprise any manual task. The program sums the times for the individual elements required to perform a new job in order to calculate the standard time for the job. +Cost estimating: The task of estimating the cost of a new product has been simplified in most industries by computerizing several of the key steps required to prepare the estimate. . The computer is programmed to apply the appropriate labor and overhead rates to the sequence of planned operations for the components of new products. The program then adds up the individual component costs from the engineering bill of materials to determine the overall product cost +Production and inventory planning: include maintenance of inventory records, automatic reordering of stock items when inventory is depleted, production scheduling, maintaining current priorities for the different production orders, material requirements planning, and capacity planning +Computer-aided line balancing: Finding the best allocation of work elements among stations on an assembly line is a large and difficult problem if the line is of significant size. Computer programs are available to assist in the solution of the line balancing problem - Manufacturing Control is the second category of CAM applications which is concerned with computer systems to control and manage the physical operations in the factory. These applications include the following: +Process monitoring and control: is concerned with observing and regulating the production equipment and manufacturing processes in the plant +Quality control: includes a variety of approaches to ensure the highest possible quality levels in the manufactured product +Shop floor control: refers to production management techniques for collecting data from factory operations and using the data to help control production and inventory in the factory +Inventory control: is concerned with maintaining the most appropriate levels of inventory in the face of two opposing objectives: minimizing the investment and storage costs of holding inventory, and maximizing service to customers +Just-in-time production systems: refers to a production system that is organized to deliver exactly the right number of each component to downstream workstations in the manufacturing sequence just at the time when that component is needed. JIT is one of the pillars of lean production
Computer-Integrated Manufacturing (CIM)
- Computer-integrated manufacturing includes all of the engineering functions of CAD/ CAM, but it also includes the firm's business functions that are related to manufacturing - The ideal CIM system applies computer and communications technology to all the operational functions and information-processing functions in manufacturing from order receipt through design and production to product shipment - In this integrated computer system, the output of one activity serves as the input to the next activity, through the chain of events that starts with the sales order and culminates with shipment of the product
Product Design and CAD
- Design and manufacturing cannot be separated in the production system. They are bound together functionally, technologically, and economically - The general process of design is characterized as an iterative process consisting of six phases: 1. recognition of need-involves the realization by someone that a problem exists which could be solved by a thoughtful design 2. problem definition-involves a thorough specification of the item to be designed 3. synthesis-Each of the subsystems of the product must be conceptualized by the designer, analyzed, improved through this analysis procedure, redesigned, analyzed again, and so on. The process is repeated until the design has been optimized within the constraints imposed on the designer. The individual components are then synthesized and analyzed into the final product in a similar manner 4. analysis and optimization-(same as synthesis both are closely related) 5. evaluation-concerned with measuring the design against the specifications established in the problem definition phase 6. presentation-concerned with documenting the design by means of drawings, material specifications, assembly lists
Computer-aided design(CAD) and management systems provide many advantages
- Increased design productivity: helps the designer conceptualize the product and its components, which helps reduce the time required by the designer to synthesize, analyze, and document the design. The result is a shorter design cycle and lower product development costs - Increased available geometric forms in the design: permits the designer to select among a wider range of shapes, such as mathematically defined contours, blended angles, and similar forms that would be difficult to create by manual drafting techniques - Improved quality of the design: permits the designer to do a more complete engineering analysis and to consider a larger number and variety of design alternatives. The quality of the resulting design is thereby improved. - Improved design documentation: results in better documentation of the design than what is practical with manual drafting. The engineering drawings are superior, with more standardization among the drawings, fewer drafting errors, and greater legibility. - Creation of a manufacturing database: In the process of creating the documentation for the product design much of the required database to manufacture the product is also created. - Design standardization: Design rules can be included in CAD software to encourage the designer to utilize company-specified models for certain design features— for example, to limit the number of different hole sizes used in the design. This simplifies the hole specification procedure for the designer and reduces the number of drill bit sizes that must be inventoried in manufacturing
Quality Function Deployment(QFD)
- Is defined as a systematic procedure for defining customer desires and requirements and interpreting them in terms of product features, process requirements, and quality characteristics - The objective of QFD is to design products that will satisfy or exceed customer requirements. - QFD can be applied to analyze the delivery of a service as well as the design and manufacture of a product. It can be used to analyze an existing product or service, not just a proposed new one
Managing the Product Design
- Product data management (PDM): system consists of computer software that provides links between users (e.g., designers) and a central database, which stores design data such as geometric models, product structures (e.g., bills of material), and related records - The software also manages the database by tracking the identity of users, facilitating and documenting engineering changes, recording a history of the engineering changes on each part and product, and providing similar documentation functions. - product lifecycle management (PLM): concerned with managing the entire life cycle of a product, starting with the initial concept for it, continuing through its development and design, prototype testing, manufacturing planning, production operations, customer service, and finally its end-of-life disposal. Implementing PLM involves the integration of product and production data, business procedures, and people.
Design Evaluation and Review
- Some of the CAD features that are helpful in evaluating and reviewing a proposed design include the following: + Automatic dimensioning- These routines determine precise distance measures between surfaces on the geometric model identified by the user + Error checking- refers to CAD algorithms that are used to review the accuracy and consistency of dimensions and tolerances and to assess whether the proper design documentation format has been followed. + Animation of discrete-event simulation solutions- Displaying the solution of the discrete-event simulation in animated graphics is a helpful means of presenting and evaluating the solution. + Plant layout design scores- A number of software packages are available for facilities design, that is, designing the floor layout and physical arrangement of equipment in a facility. Some of these packages provide one or more numerical scores for each plant layout design, which allow the user to assess the merits of the alternative with respect to material flow, closeness ratings, and similar factors. - Rapid prototyping (RP): is a family of fabrication technologies that allow engineering prototypes of solid parts to be made in minimum lead time; the common feature of these technologies is that they produce the part directly from the CAD geometric model. - Virtual prototyping: based on virtual reality technology, involves the use of the CAD geometric model to construct a digital mock-up of the product, enabling the designer and others to obtain the sensation of the real product without actually building the physical prototype.
CAD Workstations
- The CAD workstation and its available features have an important influence on the convenience, productivity, and quality of the designer's output - Two CAD system configurations: + engineering workstation: is a stand-alone computer system that is dedicated to one user and capable of executing graphics software and other programs requiring highspeed computational power + PC-based CAD systems: are the most widely used CAD systems today. They consist of a personal computer with a high-performance CPU and high-resolution graphics display screen.
Manufacturing support systems
- The procedures and systems used by the firm to manage production and solve the technical and logistics problems associated with designing the products, planning the processes, ordering materials, controlling work-in-process as it moves through the plant, and delivering products to customers - computer-aided design (CAD): uses the computer to support the design engineering function - computer-aided manufacturing(CAM): uses the computer to support manufacturing engineering activities. - The combination CAD/CAM is symbolic of efforts to integrate the design and manufacturing functions of a firm into a continuum of activities rather than to treat them as two separate and disparate activities - computer-integrated manufacturing(CIM): includes all of CAD/CAM but also embraces the business functions of a manufacturing firm
Geometric Modeling: involves the use of a CAD system to develop a mathematical description of the geometry of an object.
- These operations include creating new geometric models from basic building blocks available in the system, moving and reorienting the images on the screen, zooming in on certain features of the image - Two-dimensional models are best utilized for designing flat objects and building layouts - Three-dimensional CAD systems are capable of modeling an object in three dimensions according to user instructions - can also be classified as wire-frame models or solid models. wire-frame model uses interconnecting lines (straight line segments) to depict the object
Computer-Aided Design(CAD)
- is defined as any design activity that involves the effective use of computer systems to create, modify, analyze, optimize, and document an engineering design
Steps in Quality Function Deployment(QFD): House of Quality
1. Identify customer requirements: Often referred to as the "voice of the customer," this is the primary input in QFD. Capturing the customer's needs, desires, and requirements is most critical in the analysis. 2. Identify product features: These are the technical requirements of the product corresponding to the requirements and desires expressed by the customer. In effect, these product features are the means by which the voice of the customer is satisfied. Mapping customer requirements into product features often requires ingenuity, sometimes demanding the creation of new features not previously available on competing products. 3. Determine technical correlations: The various product features will likely be related to each other. The purpose of this chart is to establish the strength of each of the relationships between pairs of product features. These numerical scores indicate how significant (how strong) the relationships between respective pairs of requirements are. 4. Develop relationship matrix: The function of the relationship matrix in the QFD analysis is to show how well the collection of product features is fulfilling individual customer requirements. 5. Comparative evaluation of input customer requirements: the relative importance of each customer requirement is evaluated using a numerical scoring scheme. High values indicate that the customer requirement is important. Low values indicate a low priority. This evaluation can be used to guide the design of the proposed new product. Second, existing competitive products are evaluated relative to customer requirements. This helps to identify possible weaknesses or strengths in competing products that might be emphasized in the new design. A numerical scoring scheme might be used as before 6. Comparative evaluation of output technical requirements: In this part of the analysis, each competing product is scored relative to the output technical requirements. Finally, target values can be established in each technical requirement for the proposed new product.