Product Generation
· Products must be developed from concepts through concurrent development of form, material, and production methods. This process is driven by the functional decomposition discussed in Chap. 7.
· Form is bound by the geometric constraints and defined by the configuration of connected components.
· The development of most components and assemblies starts at their interfaces, or connections, since for the most part function occurs at the interfaces between components.
· Product development is an iterative loop that requires the development of new concepts, the decomposition of the product into subassemblies and components, the refinement of the product toward a final configuration, and the patching of features to help find a good product design
Concept Evaluation
· The feasibility of a concept is based on the design engineer's knowledge. Often it is necessary to augment this knowledge with the development of simple models.
· In order for a technology to be used in a product, it must be ready. Six measures of technology readiness can be applied.
· A go/no-go screening based on customers' requirements helps filter the concepts.
· The decision-matrix method provides means of comparing and evaluating concepts. The comparison is between each concept and a datum relative to the customers' requirements. The matrix gives insight into strong and weak areas of the concepts. The decision-matrix method can be used for subsystems of the original problem.
· The advanced decision matrix method leads to robust decisions by including the effects of uncertainty, incompleteness, and evolution in the decision-making process.
· Belief maps are a simple yet powerful way to evaluate alternatives and work to gain team consensus.
· Product safety implies concern for injury to humans and for damage to the device itself, other equipment, or the environment.
· Safety can be designed into a product, it can be added on, or the hazard can be warned against. The first of these is best.
· A hazard assessment is easy to accomplish and gives good guidance.
Understanding the Problem and the Development of Engineering Specifications
· Understanding the design problem is best accomplished through a technique called quality function deployment (QFD). This method transforms customers' requirements into targets for measurable engineering requirements.
· Important information to be developed at the beginning of the problem includes customers' requirements, competition benchmarks, and engineering specifications complete with measurable benchmarks.
· Time spent completing the QFD is more than recovered later in the design process.
· There are many customers for most design problems.
· Studying the competition during problem understanding gives valuable in-sight into market opportunities and reasonable targets.
Wednesday, January 3, 2007
Product Evaluation for Cost, Manufacture, Assembly, and Other Measures
· Cost estimation is an important part of the product evaluation process.
· Features should be judged on their value—the cost for a function.
· Design for manufacture focuses on the production of components.
· Design for assembly is a method for evaluating the ease of assembly of a product. It is most useful for high-volume products that have molded components. Thirteen guidelines are given for this evaluation technique.
· Functional development gives insight into potential failure modes. The identification of these modes can lead to the design of more reliable and easier-to-maintain products.
· Design for the environment emphasizes concern for energy, pollution, and resource conservation in processing raw materials for products. It also emphasizes concern for recycling, reuse, or disposal of the product after its useful life is over
· Features should be judged on their value—the cost for a function.
· Design for manufacture focuses on the production of components.
· Design for assembly is a method for evaluating the ease of assembly of a product. It is most useful for high-volume products that have molded components. Thirteen guidelines are given for this evaluation technique.
· Functional development gives insight into potential failure modes. The identification of these modes can lead to the design of more reliable and easier-to-maintain products.
· Design for the environment emphasizes concern for energy, pollution, and resource conservation in processing raw materials for products. It also emphasizes concern for recycling, reuse, or disposal of the product after its useful life is over
Product Evaluation for Performance and the Effects of Variation
· Product evaluation should be focused on comparison with the engineering requirements and also on the evolution of the function of the product.
· Products should be refined to the degree that their performance can be represented as numerical values in order to be compared with the engineering requirements.
· P-diagrams are useful for identifying and representing the input signals, control parameters, noises, and output response.
· Physical and analytical models allow for comparison with the engineering requirements.
· Concern must be shown for both the accuracy and the variation of the model.
· Parameters are stochastic, not deterministic. They are subject to three types of noises: the effects of aging, of environment change, and of manufacturing variation.
· Robust design takes noise into account during the determination of the parameters that represent the product. Robust design implies minimizing the variation of the critical parameters.
· Tolerance stacking can be evaluated both by the additive method and by statistical means.
· Both analytical and experiment methods exist for finding the most robust design
· Products should be refined to the degree that their performance can be represented as numerical values in order to be compared with the engineering requirements.
· P-diagrams are useful for identifying and representing the input signals, control parameters, noises, and output response.
· Physical and analytical models allow for comparison with the engineering requirements.
· Concern must be shown for both the accuracy and the variation of the model.
· Parameters are stochastic, not deterministic. They are subject to three types of noises: the effects of aging, of environment change, and of manufacturing variation.
· Robust design takes noise into account during the determination of the parameters that represent the product. Robust design implies minimizing the variation of the critical parameters.
· Tolerance stacking can be evaluated both by the additive method and by statistical means.
· Both analytical and experiment methods exist for finding the most robust design
Designers and Design Teams
· The human mind uses the long-term memory, the short-term memory, and a controller in the internal environment in problem solving.
· Knowledge can be considered composed of chunks of information that are general, domain-specific, or procedural in content.
· The short-term memory is a small (seven chunks, features, or parameters) and fast (0.1 second) processor. Its properties determine how we solve problems. We use the external environment to augment the size of the short-term memory.
· The long-term memory is the permanent storage facility in the brain. It is slow to remember, it is fast to recall (sometimes), and it never gets full.
· Creative designers are people of average intelligence; they are visualizers, hard workers, constructive nonconformists with knowledge about the problem domain. Creativity takes hard work and can be aided by a good environment, practice, and design procedures.
· Because of the size and complexity of most products, design work is usually accomplished by teams rather than by individuals.
· Working in teams requires attention to every team member's problem-solving style (including yours)—introverted or extroverted, fact- or possibility-oriented, objective or subjective, decisive or flexible.
· Knowledge can be considered composed of chunks of information that are general, domain-specific, or procedural in content.
· The short-term memory is a small (seven chunks, features, or parameters) and fast (0.1 second) processor. Its properties determine how we solve problems. We use the external environment to augment the size of the short-term memory.
· The long-term memory is the permanent storage facility in the brain. It is slow to remember, it is fast to recall (sometimes), and it never gets full.
· Creative designers are people of average intelligence; they are visualizers, hard workers, constructive nonconformists with knowledge about the problem domain. Creativity takes hard work and can be aided by a good environment, practice, and design procedures.
· Because of the size and complexity of most products, design work is usually accomplished by teams rather than by individuals.
· Working in teams requires attention to every team member's problem-solving style (including yours)—introverted or extroverted, fact- or possibility-oriented, objective or subjective, decisive or flexible.
Describing Mechanical Design Problems and Process
· A product can be divided into functionally oriented operating systems. These are made up of mechanical assemblies, electronic circuits, and computer programs. Mechanical assemblies are built of various components.
· The important form and function aspects of mechanical devices are called features.
· Function and behavior tell what a device does; form describes how it is accomplished.
· Function relates desired behavior.
· One component may play a role in many functions, and a single function may require many different components.
· There are many different types of mechanical design problems: selection, configuration, parametric, original, redesign, routine, and mature.
· Mechanical objects can be described semantically, graphically, analytically, or physically.
· The design process is a continuous constraining of the potential product designs until one final product evolves. This constraining of the design space is made through repeated comparison with the design requirements.
· Mechanical design is the refinement from abstract representations to a final physical artifact.
· The most valuable information is the decisions that are communicated to others.
· The important form and function aspects of mechanical devices are called features.
· Function and behavior tell what a device does; form describes how it is accomplished.
· Function relates desired behavior.
· One component may play a role in many functions, and a single function may require many different components.
· There are many different types of mechanical design problems: selection, configuration, parametric, original, redesign, routine, and mature.
· Mechanical objects can be described semantically, graphically, analytically, or physically.
· The design process is a continuous constraining of the potential product designs until one final product evolves. This constraining of the design space is made through repeated comparison with the design requirements.
· Mechanical design is the refinement from abstract representations to a final physical artifact.
· The most valuable information is the decisions that are communicated to others.
Why Study the Design Process?
The design process is the organization and management of people and the information they develop in the evolution of a product.
· The success of the design process can be measured in the cost of the design effort, the cost of the final product, the quality of the final product, and the time needed to develop the product.
· Cost is committed early in the design process, so it is important to pay particular attention to early phases.
· Concurrent engineering integrates all the stakeholders from the beginning of the design process and emphasizes both the design of the product and concern for all processes—the design process, the manufacturing process, the assembly process, and the distribution process.
· All products have a life cycle beginning with establishing a need and ending with retirement. Although this book is primarily concerned with planning for the design process, engineering requirements development, conceptual design, and product design phases, attention to all the other phases is important.
· The mechanical design process is a problem-solving process that transforms an ill-defined problem into a final product.
· Design problems have more than one satisfactory solution.
· In problem solving there are seven actions to be taken: establish need, plan, understand, generate, evaluate, decide, and communicate.
· The success of the design process can be measured in the cost of the design effort, the cost of the final product, the quality of the final product, and the time needed to develop the product.
· Cost is committed early in the design process, so it is important to pay particular attention to early phases.
· Concurrent engineering integrates all the stakeholders from the beginning of the design process and emphasizes both the design of the product and concern for all processes—the design process, the manufacturing process, the assembly process, and the distribution process.
· All products have a life cycle beginning with establishing a need and ending with retirement. Although this book is primarily concerned with planning for the design process, engineering requirements development, conceptual design, and product design phases, attention to all the other phases is important.
· The mechanical design process is a problem-solving process that transforms an ill-defined problem into a final product.
· Design problems have more than one satisfactory solution.
· In problem solving there are seven actions to be taken: establish need, plan, understand, generate, evaluate, decide, and communicate.
Tuesday, December 12, 2006
An Overview of the Design Process
Design
Design is the process by which the needs of the customer or the marketplace are transformed into a product satisfying these needs. It is usually carried out a designer or engineer but requires help from other people in the company.
Design essentially is an exercise in problem solving. Typically, the design of a new product consists of the following stages:
Product Design Specification ---> Concept Design ---> Detail Design ---> Manufacturing and Testing ---> Sales
The development of a new product may also require the development of a prototype to prove that new technologies work before committing resources to full-scale manufacture.
The traditional view of the design to manufacture process is that it is a sequential process, the outcome of one stage is passed on to the next stage.
This tends to lead to iteration in the design. I.e. having to go back to an earlier stage to correct mistakes. This can make products more expensive and delivered to the marketplace late. A better approach is for the designer to consider the stages following design to try and eliminate any potential problems. This means that the designer requires help from the other experts in the company for example the manufacturing expert to help ensure that any designs the designer comes up with can be made.
So what factors might a designer have to consider in order to eliminate iteration?
Manufacture - Can the product be made with our facilities?
Sales - Are we producing a product that the customer wants?
Purchasing - Are the parts specified in stock, or do why have to order them?
Cost - Is the design going to cost too much to make?
Transport - Is the product the right size for the method of transporting?
Disposal - How will the product be disposed at the end of its life?
Design Brief
The design brief is typically a statement of intent. I.e. "We will design and make a Formula One racing car". Although it states the problem, it isn't enough information with which to start designing.
Product Design Specification (PDS)
To produce the PDS it is likely that you will have to research the problem and analyse competing products and all important points and discoveries should be included in your PDS.
Concept Design
Using the PDS as the basis, the designer attempts to produce an outline of a solution. A conceptual design is a usually an outline of key components and their arrangement with the details of the design left for a later stage. For example, a concept design for a car might consist of a sketch showing a car with four wheels and the engine mounted at the front of the car. The exact details of the components such as the diameter of the wheels or the size of the engine are determined at the detail design stage. However, the degree of detail generated at the conceptual design stage will vary depending on the product being designed.
It is important when designing a product that you not only consider the product design specification but you also consider the activities downstream of the design stage. Downstream activities typically are manufacture, sales, transportation etc. By considering these stages early, you can eliminate problems that may occur at these stages.
This stage of the design involves drawing up a number of different viable concept designs which satisfy the requirements of the product outlined in the PDS and then evaluating them to decide on the most suitable to develop further. Hence, concept design can be seen as a two-stage process of concept generation and concept evaluation
Concept generation
Typically, designers capture their ideas by sketching them on paper. Annotation helps identify key points so that their ideas can be communicated with other members of the company.
There are a number of techniques available to the designer to aid the development of new concepts. One of the most popular is brainstorming.
This technique involves generating ideas, typically in small groups, by saying any idea that comes into your head no matter how silly it may seem. This usually sparks ideas from other team members. By the end of a brainstorming session there will be a list of ideas, most useless, but some may have the potential to be developed into a concept. Brainstorming works better if the members of the team have different areas of expertise.
Concept evaluation
Once a suitable number of concepts have been generated, it is necessary to choose the design most suitable for to fulfil the requirements set out in the PDS. The product design specification should be used as the basis of any decision being made. Ideally a multifunction design team should perform this task so that each concept can be evaluated from a number of angles or perspectives. The chosen concept will be developed in detail.
One useful technique for evaluating concepts to decide on which one is the best is to use a technique called 'matrix evaluation'
With matrix evaluation a table is produced listing important the features required from a product - usually this list is drawn up from the important features described in the product design specification. The products are listed across the table. The first concept is the benchmark concept. The quality of the other concepts are compared against the benchmark concept for the required features, to help identify if the concept is better, worse than, or is the same as the benchmark concept. The design with the most 'better than' is likely to be the best concept to develop further.
Most people who use the matrix technique will assign points, rather than simple, better, worse, same, so that it is easier to identify which concepts are the best. It is also likely that some features of the design will be more important than others so a weighting is used.
Detail design
In this stage of the design process, the chosen concept design is designed in detailed with all the dimensions and specifications necessary to make the design specified on a detailed drawing of the design.
It may be necessary to produce prototypes to test ideas at this stage. The designer should also work closely with manufacture to ensure that the product can be made.
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