Technology & Engineering
Design Specification
A design specification is a detailed description of the requirements and characteristics of a product, system, or component. It outlines the parameters, features, and performance criteria that the design must meet. This document serves as a guide for engineers and designers to ensure that the final product aligns with the intended functionality and quality standards.
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eBook - ePub- Peter Childs(Author)
- 2013(Publication Date)
- Butterworth-Heinemann(Publisher)
Design usually starts with a need or requirement which, when satisfied, will allow a product or process to be offered to an existing market or new market. The market need may be to meet competition, a response to social changes, opportunities to reduce hazards, inconvenience or costs, or exploitation of a new market opportunity. This is the “front end” of design. People with front-end skills, such as market researchers and information scientists, are fundamental to the design process. The starting point for the majority of design activities in industry is the establishment of the market need situation. Common practice is to produce a document or statement of need, called “the brief” or “market brief,” at this initial stage. The brief varies from a simple statement of the requirements to a comprehensive document that describes the true needs of the user.Specification is usually critical to effective design. Thorough specification provides limits defining the attributes and functions that are requisites of a design. Common practice is to develop a product Design Specification (PDS) where each attribute and function required of the product or system is described and quantified. An alternative is the use of quality function deployment (QFD), where matrices are used to capture the attributes, functions, and features associated with a product or system with a particular focus on ensuring that the voice of the customer (VOC) is captured in the specification—geared toward ensuring that the product development cycle results in an outcome that matches the customer requirement.There are many variants and forms of specification. Specification can represent a significant undertaking. The specification documentation associated with a new turbofan engine for an aviation application, for example, may occupy over 500 pages. The precise form used will likely depend on precedence within a particular organization. The automotive industry, for example, has tended to use QFD over the last few decades, and such approaches may demand more resources than available and simpler pro formas may enable a more timely and accessible approach to specification.Specification is usually incorporated as a fundamental part of new product development project management. It is not always possible to produce a complete specification at the outset of a project. It may be necessary to take an iterative approach to the specification with elaboration of details as a result of initial phases of design activity and concept ideas with these providing insights to what attributes and functions for a product or system are possible and desirable. In essence, the early concepts and designs serve to inform the specification. Such an approach fits well with stage gated project management processes, perhaps with phases of system design review, performance design review, and technical design review, with each referring back to an original specification and enabling the development of an agreed technically feasible specification that provides a design that is fit for purpose. A common occurrence in industry is the use of an agreed specification to provide the basis for contractual negotiation, enabling the associated parties to be able to define the completion of tasks. Any variation on the specification should be addressed by a change management process, where changes to the specification need to be agreed upon by all associated parties. When agreement cannot readily be obtained, these changes must be managed by an arbitration process.
eBook - ePub- Peter Childs(Author)
- 2018(Publication Date)
- Butterworth-Heinemann(Publisher)
Design usually starts with a need or requirement which, when satisfied, will allow a product process or system to be offered to an existing or new market. The market need may have arisen to address increased competition, a response to social changes, opportunities to reduce hazards, inconvenience or costs, or exploitation of a new market opportunity. This is sometimes known as the ‘front end’ of design. People with front-end skills, such as market researchers and information scientists, are fundamental to the design process. The starting point for the majority of design activities in industry is the establishment of the market need situation. Common practise is to produce a document or statement of need, called ‘the brief’ or ‘market brief’, at this stage. The brief varies from a simple statement of the requirements to a comprehensive document that describes the criteria that are understood to meet the users’ true needs.Specification is usually critical to effective design. Thorough specification provides limits defining the attributes and functions that a design should have. Common practice is to develop a product Design Specification (PDS) where each attribute and function required of the product, service or system is described and quantified. An alternative is the use of quality function deployment (QFD), where a series of matrices are used to capture the attributes, functions and features associated with a product or system, with a particular focus on ensuring the voice of the customer is captured in the specification with a view to ensuring that the product development cycle results in an outcome that matches the customer requirement.There are many variants and forms of specification. Specification can represent a significant undertaking. The specification documentation associated with a new turbofan engine for an aviation application, for example may occupy over 500 pages. The precise form used to capture the specification required will likely depend on precedence within a particular organisation. The automotive industry, for example has tended to use QFD over the last few decades (see, e.g. Miller et al., 2005 ; Sugumaran et al., 2014
eBook - ePub- K. L. Richards(Author)
- 2020(Publication Date)
- CRC Press(Publisher)
4Product Design Specification
4.0 IntroductionA critical document in the design process that is usually overlooked is the Product Design Specification or PDS. When it is used correctly, it will save a lot of embarrassment in reducing items overlooked and could cost the company a heavy financial cost to correct the problem.The PDS is essentially a contract between the manufacturer and the customer. The manufacturer knows what he is going to produce and the customer knows what they are going to receive. The problem of converting the frequently non-technical, non-quantifiable customer requirements to a set of product characteristics expressed in engineering terms leads to the PDS.The PDS defines the customer requirements as completely as possible. When the document is completed, the design team can then commence to undertake the design activity of proposing product arrangements to meet the customer’s needs. It is inevitable that a number of alternative designs will be generated in this exercise. It is more than likely that one of the designs will be able to offer the best options when assessed against the requirements as stated in the PDS. This is the concept generation phase as identified at stage 3 in Figure 4.1 . Those concepts that do not meet the Design Specification will either be rejected or after a degree of rework will be reconsidered.A number of techniques will be discussed in the next conceptualisation stage in which other attributes identified such as reliability, cost, ease of manufacture, etc., will be discussed. A typical PDS covers the following details.FIGURE 4.1Information flow for the compilation of a PDS.
This provides an overview of the proposed product being specified. This is NOT intended to be a requirement section.4.1 Description of the ProductThe starting point of any PDS is the brief that is put together by the marketing department and describes what the customer is requiring. If the product is specific to one customer, it will describe in detail exactly what the product is expected to fulfil. In case the product is more generally commercially orientated, the data would usually have been obtained from ‘focus groups’ or other marketing techniques. In this case, the brief will be couched in more general terms giving the designer a little more latitude to how he will approach the design.
eBook - ePub- Stephen Emmitt(Author)
- 2012(Publication Date)
- Wiley-Blackwell(Publisher)
Chapter 8The Art of Specifying
Detailing a building is a process of continual evolution grounded in what the designer (and his or her employer) believes to be best practice. Interwoven with detailing is that of specifying the quality of materials, components and products that make up a building’s assembly. Drawings indicate the spatial relationship of components to each other. It is the written specification that describes the quality of the workmanship, identifies the materials and products (or performance requirements of materials and products) to be used, and the manner in which they are to be assembled. The process of selecting the most appropriate material or product for a given situation is known as specifying, and the resultant set of documents is known as the written specification.At first glance, the selection of materials and products to meet a specific purpose would appear to be a relatively straightforward activity. However, both the issues to be considered and the actual process are complex and one of the central problems facing designers is that of determining priorities (see Emmitt & Yeomans, 2008). Resources are not infinite, so to achieve the given objectives within the constraints of time, finance and expertise, the number of variables considered has to be limited and prioritised for each project. The selection of one product over another will affect the selection of others and how the building is detailed because no architectural component can be considered in isolation. Designers must constantly appraise and re-appraise the product in relation to the building assemblage, and future disassembly, as a whole.Specification methods
The written specification is an important document in ensuring a quality building. It is an essential part of the design process that requires particular skills in researching different product characteristics and being precise. In the USA it is a job carried out by qualified specification writers. In the UK the majority of design practices are small and so the specification is often written by the same person who carried out the design and detailing of the scheme. For larger and more complex projects it is common for the design architects and engineers to hand over the tasks of detailing and specification writing to others within the office. In this case it is critical that the interface between the conceptual designer(s) and specification writer(s) is as seamless as possible.
eBook - ePubSystem Verification
Proving the Design Solution Satisfies the Requirements
- Jeffrey O. Grady(Author)
- 2016(Publication Date)
- Academic Press(Publisher)
Section 2 of a specification is essentially a bibliography containing a listing of all documents referred to in the specification, giving in each case the precise identification of these documents. There exist many broadly recognized and respected standards prepared by large customer organizations, government agencies, or industry societies. These external documents commonly take the form of standards and specifications that describe a preferred solution or constrain a solution with preferred requirements and/or values for those requirements. Often the content of these documents will coincide with the needs in a program specification. For example, the product may need a valve with characteristics that many other applications share and there has been a standard prepared for that kind of valve. Rather than preparing the detailed performance requirements for this valve, we could simply refer to the standard.The downside is that one has to be very careful not to import unnecessary requirements through this route. If a complete document is referenced without qualification, the understanding is that the product must comply with the complete content. There are two ways to limit applicability. First, we can state the requirement such that it limits the appeal, and therefore the document applies only to the extent covered in the specification statement. The second approach is to tailor the standard using one of two techniques. The first tailoring technique is to make a legalistic list of changes to the document and include that list in the specification. The second technique is to mark up a copy of the standard and gain customer acceptance of the marked-up version. The former method is more commonly applied because it is easy to embed the results in contract language, but it can lead to a great deal of difficulty when the number of changes is large and their effect is complex.Section 6 should include a traceability table listing the applicable documents and identifying the specification paragraph where they are called.2.4 Detail Specification Structure
The item detail specification structure is very similar to the item performance specification. The content of that structure will commonly be significantly different, however, in that the performance specification is defining requirements for the design of the product entity and the detail specification is identifying characteristics that are expected of a delivered product entity. The verification requirements will also reflect a different situation. The performance specification will call for clear proof that the design complies with requirements even to the extreme of damaging the item qualification test article, while the product completing acceptance test in response to the content of the detail specification must have a full life upon delivery.
eBook - ePubMedical Device Design
Innovation from Concept to Market
- (Author)
- 2012(Publication Date)
- Academic Press(Publisher)
We also saw that we need to document the process fully. This was suggested for two main reasons: the first being that you may not be the final designer; the second being that you may leave the project either intentionally or through accident. In both situations future designers need the information stored in you head.References
1. Bicheno J, Catherwood P. Six sigma and the quality toolbox Buckingham: PICSIE Books; 2005.2. British Standards (2001). Product specifications. Guide to identifying criteria for a product specification and to declaring product conformity , BS 7373-2:2001.3. Enderle J, Bronzino J. An introduction to biomedical engineering 3rd ed. Academic Press 2011.4. European Community (1993). Medical Devices Directive . 93/42/EC.5. FDA. Design control guidance for medical device manufacturers FDA 1997. 6. FDA (2010). 21 CFR Subchapter H, Part 860.7. ISO (2003). BS EN ISO 13485:2003 Medical devices – Quality management systems – Requirements for regulatory purposes .8. ISO (2008). ISO 9001:2008 Quality management systems .9. Hurst K. Engineering design principles London: Arnold Publishers; 1999. 10. Pugh S. Total design: Integrated methods for successful product engineering Prentice Hall 1990. 11. Ulrich KT, Eppinger SD. Product design and development McGraw Hill 2003. 12. Webster J. Medical instrumentation: Application and design J Wiley and Sons Ltd 2009.1 City Slickers , MGM Studios, 1991 – a hit comedy in the early 1990s.2 When you machine a material some of the machined material resides on the tool itself. Hence if you machine titanium one morning and then stainless steel in the afternoon you may impart some titanium on the workpiece – hence contamination is possible.3
eBook - ePubDesigning for the Digital Age
How to Create Human-Centered Products and Services
- Kim Goodwin(Author)
- 2011(Publication Date)
- Wiley(Publisher)
If you think the engineers may have a harder time building the application than they expect to, you can also add some thoughts—either in a single section or woven throughout the document—about how to scale back. Indicate the aspects of the design that you believe are most critical to meeting the personas’ needs and the components that could be temporarily replaced by a more economical option.Qualities of an Effective Spec
The effectiveness of your specification is not determined only by its content and structure, but also by how you express the content. A good spec is prescriptive, clear, explanatory, efficient to read, and appropriately formatted. It also stands alone, with no need for readers to be familiar with earlier documents.Prescriptive, not suggestive
Many product managers write requirements documents using the terms “must” and “should”—anything with the word “must” in front of it is presumably nonnegotiable, and anything with the word “should” in front of it can fall by the wayside if the engineers run out of time.However, everything in the form and behavior specification is a prescription that’s meant to be implemented, not a collection of suggestions. The contents are not open to interpretation, so your language should not imply that they are. Write with confidence and conviction about the product and the people who will use it. Avoid saying what the product should, could, or might do; say what it will do.Clear and professional, not pretentious
The form and behavior spec is a professional business document, so appropriateness, organization, grammar, and spelling all count. If you’re sloppy about these, some readers will wonder if you were similarly sloppy in your design thinking. As discussed in Chapter 13, use active voice and simple sentences, and don’t feel compelled to show off your prodigious vocabulary. Have a good copy editor take a look at it. Likewise, ask your teammates to give the document an editing pass; see the “Technical review and document QA” section later in this chapter for guidance on this topic.
