Ask the Engineer

Specification Requirements to Ensure Regulatory Compliance

By Julie Cameron
August 15, 2012


• Categories: Ask the Engineer

Q: What types of requirements do I need to call out on my specification or drawing to ensure regulatory compliance?

A: Over the past couple of years, we’ve seen a sharp increase in regulatory oversight in the medical device industry. If your manufacturing requirements aren’t specific enough, your contract manufacturer might unknowingly make a problematic substitution. Of course, the types of requirements you should call out will vary based on your manufacturing process — so how do you know which ones are most important for your product? We’ll review some of the most critical requirements in our next few e-newsletters to help you avoid costly mistakes. We’ll start here with material type.

Material requirements

Clearly defining your material requirements helps eliminate variability in your manufacturing process because it ensures that the same raw material — from the same manufacturer, using the same formulation and manufacturing specifications — is always used to produce your part. Specifying the exact material also allows for traceability back to the raw material lots of both the base material and any additives you specify, and prevents misinterpretations and substitutions of raw materials or additives. Consider specifying the following:

• Material manufacturer or trade name;
• Material designation; and
• Formulation, including pigments, radiopacifiers, additives and actives.

It’s always best to work closely with your contract manufacturer to ensure that your design requirements are properly documented in your specification or drawing.

Critical features

When designing a medical device, it’s important to determine which features are critical to its design and overall performance. Critical features are chosen subjectively based on the function and fit of your particular component. In contrast, non-critical dimensions may be areas of the part that are not close to mating assembly components, and do not affect the design intent or the overall performance of the device. Each critical feature needs to be properly detailed in your specifications. This includes nominal values and acceptable tolerances that define size, shape and sometimes physical properties.

Measurement methods

Clearly defining how specified parameters of critical components are to be measured is as important as determining the critical dimensions themselves. Dimensions can be measured by contact methods such as mandrels and gauges, or by non-contact methods involving optical measuring devices. Results can vary depending on the method.

For example, when measuring the inner diameter of a tube with a pin gage or mandrel, you must consider that the inner diameter of the tube may not be perfectly round. The pin gauge or mandrel will measure the smallest diameter. When measuring that same tube with a non-contact system, the diameter on multiple axes are measured and then averaged. Which method is preferred? It depends on how your component is going to be used. It’s best to choose a measurement method that correlates to the function and fit of your component in use.

Precisely defining both critical dimensions and measurement methods will ensure proper process control, change control and document traceability in the manufacturing of your device. It’s always best to work closely with your contract manufacturer to ensure that your design requirements are properly documented in your specification or drawing.