Define the Specifications: The Critical First Step in Any Product Design Project

Before anything else, every design project or product must comply with a set of functional requirements. It is a defined plan. Otherwise, it isn’t a product at all. Perhaps it’s simply a useless object or trash. Or maybe it is artwork.

The first, and most critical step, in any product design project is to define the specifications in detail. This establishes the common foundation upon which all subsequent decisions will be made as the project evolves.

A well-written set of product specifications not only outlines the definition of the product but also provide a framework for setting priorities and performance criteria.

Therefore, the first phase of your work as a designer begins with understanding and documenting the product application. This study provides a comprehensive understanding of the product’s purpose. Further, you’ll define the parameters associated with its intended use, as well as its potential unintended use. (Understanding unintended use can avoid result problems, premature failure or serious safety risks.)

These criteria can then be documented as specifications that define the product based on various parameters. Thus, your specification document describes and directs how all the subsequent decisions made throughout the design development process.

The product designer has no standard rules for creating product specifications. Some products require extensively detailed documents that could include hundreds of pages of specifications while others may be as brief as a page or two. It doesn’t matter how “simple” a product is, some form of documentation is always required to establish how that part or product is to perform, based on one or more sets of conditions. (As a starting point, a specification outline follows below.)

Specifications Avoid Costly Rework or Product Failures in any Product Design Project

This guidance may appear to be sensible and obvious. But, surprisingly—perhaps alarmingly—product specifications are often overlooked or omitted from the design process. Omissions typically lead to confusion during product development. And typically this results in costly rework, or catastrophic product failures.

Think of specifications as a contract between the development team, the company for which the product is being designed, and the end-user. Specifications not only influence the product design but also user manuals, compliance with regulatory bodies, and legal ramifications.

Specifications should be written with careful consideration of sound engineering principles, user requirements, cost considerations, manufacturing parameters and marketing requirements. Omissions or incorrect assumptions invariably lead to costly recalls or unnecessary complications throughout the design process.

Every product requires a unique set of specifications, but there is no universal answer. The following, however, is an abbreviated general list of specification categories that could pertain to many products.


  • User requirements
  • Appearance
  • Forecasted sales


  • Structural
  • Mechanical
  • Functional
  • Life cycle/reliability
  • Performance
  • Testing and verification


  • Return on investment\amortization
  • Capital availability
  • Risk
  • Vendor selection


  • Location for production
  • Supply chain
  • Design for manufacture
  • Number of parts
  • Tooling design


  • Recycling
  • Compliance with any regulatory body; UL, CSA, FDA, RoHAS, etc.


  • Lead times
  • Project risks
  • Project schedule
  • Available resources

A subset of this list can serve as an example of how these parameters are tightly interrelated. Material selection, for example, is dictated by designers and is critical to several factors. These include overall product performance, cost, reliability, appearance, manufacturability, compliance with regulatory bodies, and, in some cases, lead times.

As the person making significant decisions, your role requires a thorough understanding of static and dynamic structural requirements for a product during short-term as well as long-term performance.

For example, you should understand the significance of tensile strength, tensile modulus, fatigue resistance, creep and impact strength during the material selection process based on structural analyses. This insight will provide you with a sound basis for selecting optimal materials for a particular application.

Your list may be further truncated based on thermal conditions, chemical resistance, UV resistance, clarity requirements, etc. Other factors including availability, cost, and lead times for delivery may further reduce the selection.

Structural analyses, testing and all the associated performance evaluations that affect material selection are based on the specifications. If they omit potential exposure to harsh chemicals or thermal conditions, the analysis and selection will be based on erroneous premises that could lead to premature failure.

Omissions in specifications typically arise from ignorance of the effects certain environmental conditions. It is, therefore, crucial to test parts under anticipated environmental conditions as stated in the specifications to uncover potential failure. Rapid time to market often force industrial and product designers to omit long-term testing or simply ignore it all together…and introduce high risks in a project. In such cases, it is advisable to include a materials specialist to review the specifications and assess the potential risks.

Material selection will influence wall thickness, design features such as ribs, bosses, snaps, etc, and appearance for the designer. It will also affect the choice of tooling material, gate location and shrinkage rate and many other factors influencing tool cost.

Material selection is only one of the many parameters that are dictated by product specifications. An insightful designer can extrapolate other important decisions influenced by this important document. Your insight could prevent major setbacks or financial losses.

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