Getting What You Want: How to Write a Product Specification

There is an art to getting what you want. If you don’t specify enough requirements, the product won’t perform as you need. If you specify too much detail, the cost may be high and you might exclude viable products.

When writing product specifications there are a few critical topics to cover:

• Performance
• Validation
• Quality

Specify Performance Not Design
Engineers can easily fall into the trap of specifying design requirements rather than performance criteria. However, the potential liabilities associated with specifying design and then having products that don’t meet performance requirements make it worth the effort to specify product performance rather than design.

Do specify critical size dimensions, but do not specify the shape. Specify temperatures the product needs to operate under, but do not specify the material that is used – unless there are environmental regulations you need to meet. Once your specification is written, perform a final review and consider whether each requirement is necessary or if it can be re-written as a performance specification.
Some performance-related specifications to consider include:

• Environmental conditions – temperature, moisture, pressure conditions under which the product needs to operate
• Operating demand – continuous versus intermittent operation
• Acceptable maintenance requirements - frequency and extent
• Mounting constraints
• Connection interfaces
• Disposal requirements particularly regarding recycling options and hazardous materials
• Material compatibility

Specify Validation of Performance
Include the validation requirements in the specification. This may affect both price and delivery schedules. The performance validation requirements for the final product or system affects the requirements for the part specification you are writing.

Products performing safety functions usually have strict performance validation requirements. Also, if failure of a product has significant financial implications, performance validation is important. Some options for performance validation include third-party testing, testing to a standard procedure, and statistical sampling. Validation of performance is also influenced by the quality requirements included in the specification.

Quality Supports Satisfaction
Quality requirements in a product specification warrant the same careful consideration given to performance validation. In addition to your own company quality process to consider, your customer’s quality expectations need to be assessed.

State Acceptance Criteria
This part of a specification is tied to both quality and validation. The specification needs to state what sort of documentation or actions you will accept to demonstrate that the product purchased meets the specification. For validation, you may require that the part be stamped by the testing organization. For quality, your company may send inspectors to audit the supplier’s manufacturing process and quality program. Be sure this is decided prior to issuing the specification as it will affect price and possibly delivery schedules.

Industry Standards Can Help
Referring to codes and standards in specifications simplifies the specification writing process. Engineers have a high degree of confidence in products known to meet standards. There are a few important points to successfully using standards in product specifications.

1. Be sure you know the content of the standard you are citing. Standards change over time and if you haven’t reviewed the current version of a standard the information you need may no longer be included.
   
   
2. Include a detailed citation when referring to a standard. This means not only the version or date of the standard but also the section of the standard. Many standards contain detailed information for a variety of scenarios, which may result in confusion regarding what is being specified.
   
   
3. Use industry standards rather than government standards. Industry standards are generally available and familiar. If they are international industry standards you are more likely to get a large number of potential suppliers. Additional government standards sometimes require a waiver before they can be used by commercial entities.
   
   
4. Once you include a standard in your product specification, stay current. Changes to standards after you have included it in a specification may require changing the specification. Also, many standards are revised to reflect improvements in industry.

IHS Provides Current Standards
IHS maintains the comprehensive databases of standards and employs proprietary processes and technology to collect, manage, and deliver a vast inventory of information. IHS is an ISO 9001 registered company. As a result, use of IHS standards solutions fits within even the most rigorous quality management systems.

IHS Offers Standards Products and Custom Solutions
Contact us at 800.716.3447 (US / Canada), 303.397.2896 (Worldwide) or visit our solutions portal to find out more about standards, standards-related products, and enterprise services applicable to the manufacturing industry.