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Product Definition and Specifications

By: Dan Lockton - Updated: 27 Sep 2012 | comments*Discuss
Inventor Inventing Inventions Design

Established manufacturers and design consultancies usually follow a formal process defining the specification of a new product and it’s worth inventors thinking along these lines too, once the initial concept is established. While much inventing may appear ‘trial and error’ to an uninformed observer, that experimentation is mostly directed towards specific ends (a functional, marketable, manufacturable product), and having a specification to guide the process makes sure that the important issues are borne in mind at each stage.

Explain Your Invention

You probably already have an idea about the ‘elevator pitch’ for your invention: what you would say to someone you met in a lift, in a couple of sentences, to explain your invention. This might well start with “I’ve invented something which does X” and go on with “This will help people do Y”, or “This is better than anything else because of Y”. This sort of thinking is the basis of developing a specification: you need to consider not just what the product will do, but the context of the market and customers’ needs — these too are ‘problems’ which your product will address.

Product Design Specification

The Product Design Specification (PDS) method, articulated by Loughborough’s Professor Stuart Pugh, aims to be ‘a total description of a product at any given time in its development’, and is thus especially suitable for inventors who will be following a product’s development through from conception to production. The method is not complicated, but does require that you think carefully about many aspects of your invention, and see it as a product, with customers and users rather than simply your ‘baby’. Effectively, a PDS sets out all the requirements that a product has to fulfil — a set of necessary conditions for success, if you like. It doesn’t explain how you will achieve those conditions, merely that they need to be achieved — hence the ‘true at any time in development’ aspect. As your product evolves, you may well alter the PDS to reflect this, but they should agree with each other at every stage.

Pugh’s PDS method covers the following aspects: Performance, Economy, Target production cost, Quantity, Manufacturing facilities, Product life span, Customers, Competition, Service life, Environment, Size, Weight, Maintenance, Materials, Special processes, Ergonomics, Appearance, Finish, Quality and reliability, Packing, Shipping, Industry standards, Shelf or storage life, Testing, Safety, Personnel, Market constraints, Political and social factors and Design time. For each aspect, you will write a brief description of the conditions which the product will fulfil. In some cases this may be a numerical figure, but in others it will be a few sentences.

This sounds like an awful lot of aspects to consider, and you may feel that not all of them apply to your invention. Certainly at an early stage, you will be unable to say much about many of these aspects, but it is important to remember that at some point, each will be important to your product’s success. Depending on the product and market, some will be more important than others, but each will play a part.


Performance is the most obvious place for an inventor to start. What must your invention be able to do reliably and consistently? Then, going on to Economy: what resources (fuel, electricity, consumables) will your product use to achieve the performance specified? Target production cost: what price must the product be manufactured for? And so on. You may include information arising from your patent research under the Competition heading, alongside details of actual marketplace competitors; things to consider such as environmental legislation probably belong under Safety or Political and social factors, since Environment in Pugh’s PDS description implied the environment in which the product is going to be used, rather than ecological considerations.

Aside from helping you address important issues in your product’s development, having a PDS will show potential collaborators, investors and early customers (particularly retailers buying in bulk) that you have gone about developing your invention in a professional manner, and by taking account of issues that will affect them (such as shelf life and shipping), you have made their job easier.

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