Every manufacturing project goes through rigorous testing at various stages in the design and manufacturing process. Some of this product testing is handled internally; some using third parties like independent testing labs.
The most important testing, of course, is for regulatory compliance.
Regulatory compliance tests are run by Nationally Recognized Test Labs (NRTL) which is qualified to decide how the standards are applied, which tests are to be run, and interpretation of the results.
The Regulatory Approval process can be complex. The tests are run by Nationally Recognized Test Labs (NRTL) who are qualified to decide how the standards are applied, which tests are to be run, and interpretation of the results.
The standards to be applied are published by various organizations, including some NRTLs (e.g., UL) and organizations whose charter is to determine, publish and maintain standards for design and test of products (e.g., ISO, ANSI, IEC), but who do not have an associated Test Lab. The requirements for how the standards are applied vary from country to country and market to market, so it is vital that you understand the product market and the countries you intend to market the product. The earlier in the product design cycle this information is known, the easier it will be to design the product for compliance with the required standards.
A good example of this process involves design and manufacture of products to be used in hazardous locations (areas with potentially explosive atmospheres – e.g., refineries). The most difficult location risks are Class I/II/III, Div 1, or Zone 0 locations (depending on the classification system), which have the potentially explosive conditions present most often (e.g., inside a chemical tank). The risk also varies based on the type of hazard present. Hydrogen or Acetylene are much riskier than Propane. There are other considerations, but suffice to say that the range of conditions have a huge impact on the standards the product must meet to be certified for use in those locations. If you design a product for that market without considering the design standards and testing required, it is almost guaranteed to fail regulatory approval and require very significant design changes. One interesting point, NRTLs don’t really care if your product works; they care that it will meet the standards.
The regulatory requirements of the market must be considered as design input for the product. Product Resources’ Product Requirements Document template includes a section on Regulatory Requirements just for this purpose. This issue is surprisingly difficult to pin down. Some of the standards are well known and easy for a reasonably experienced engineer to identify (e.g., IEC 61010 or 60601), but there may be more standards that apply to your product than you know, and it will pay you to engage with an NRTL early enough in the requirements-writing phase to identify all the relevant standards and tests. Note that this interaction occurs before product design begins.
With the knowledge of the standards that will need to be applied and the tests that the product will be subjected, the design can proceed, and the engineers can use techniques that will ensure the product will pass those tests. Still, some of the testing (e.g., Radiated Emissions) presents risk to the design because of the complexity and chaos of the physics. Good design technique will lower the risk, but it is not unlikely that the product may fail and need mitigation.
There are a few choices to be made here. One choice is to keep updating the design until the risk is made as low as possible. This will likely add cost to the project and the product. The other choice is to have a plan to implement those changes, but only if testing shows them to be necessary. This may add cost to the project but will minimize the cost to the product.
The secret to being cost and time efficient, is to hire the NRTL to do a “Pre-test”, but only on the portions of the test protocol which are at an elevated risk. Go to the lab with the product and work with the technician to evaluate the product. If you see test results that are borderline, make modifications right then and test again. Once you have confidence in the product, incorporate the changes into the product design. When you send the product to the NRTL for the official test, you will be much more confident that the product will pass. Depending on the differences between Beta Prototypes and Pilot Production, you may be able to utilize a Beta Prototype for the Pre-Test and still have confidence in the results. If the differences are too great to give you that confidence, grab the first Pilot unit developed, or build a Pilot unit special for the purpose and use that as the test product.
For official testing, the NRTL will test the product that you send to them for compliance to the standards required by the product type and the market. Therefore, you want to test with Pilot production units rather than Beta prototypes. For every change you make between the product that was approved by the NRTL and the product you intend to build, you will need to do a risk analysis to see if there is a significant impact on the test results if the unit were to be re-tested. For some products, there is no choice, and you must re-test if you make any changes. For others, the requirements are less strict.
All NRTLs will send a test report detailing the findings and their certification that the product passed the tests and standards noted. For products that receive an NRTL Mark, and depending on the standards used, there may also be a “Factory Audit Manual” or similar which details, by manufacturer and part number, exactly which components may be used as certain components and in many cases what tests must be performed. Understand that you may not substitute listed components without the permission of the NRTL, nor can you change any required test protocol without permission.
Many NRTLs will require, as a condition of you being able to place their mark on the product label, periodic audits of the manufacturing facility where they can verify that the approved components are being used in the product. If they find that you have made an unauthorized substitution, they have the power to stop you (legally) from applying their mark and they can also force a product recall to remove their mark from the product.