Prototype testing

Prototype testing is the planned testing of physical product samples to verify that they meet the requirements for function, strength, durability, environmental resistance, safety and usability. It complements calculations and simulations with the real behavior of the part, including effects that are hard to model: friction, clearances, manufacturing variation, assembly and user behavior.

Depending on the goal, tests are functional (mechanisms, sealing, assembly, operation), mechanical (static load to failure, impact, drop), life and fatigue tests (repeated cycles, often accelerated by higher load or frequency), environmental (temperature, humidity, thermal shock, UV exposure, salt spray), vibration and shock tests, and IP rating tests to IEC 60529. User tests check ergonomics and how intuitive the controls are.

The foundation is a test plan: what is being verified, against which requirement, by what procedure, on how many samples and with what acceptance criterion. Results are recorded in a test report with a description of the sample (revision, material, manufacturing process), the test conditions and the measured values. Testing follows the design iterations: early prototypes prove the principle, while later samples made with a near-production process serve for validation and to prepare for certification tests.

Simpler tests can be run on in-house fixtures, while standardized tests for certification are usually handled by accredited test laboratories (accreditation to ISO/IEC 17025).

Testing makes sense at every stage where the result will drive a decision: after the first functional prototype is built, before ordering molds and tooling, after a significant change in design or material, and before certification. Pre-compliance tests (for example for the IP rating or EMC) reveal problems before an expensive certification test does.

For parts under cyclic loading, safety-relevant products and anywhere the calculation rests on uncertain assumptions (plastics, contacts, impacts), a physical test is essential.

The most common mistake is testing without criteria set in advance. The result is then debated only after the test, and "passed" means something different to everyone. The second mistake is drawing conclusions from a single sample: results, especially from fatigue and impact tests, show scatter, so plan for several samples in important tests. In accelerated tests, make sure the higher load or temperature does not trigger a different damage mechanism than real service does.

The prototype must be representative for the test in question. A part printed with FDM has different strength, stiffness and impact behavior than an injection-molded part, so for each test state what the result means for production. Record the sample revision and test conditions, photograph any damage and measure samples before destructive testing. With an external lab, ask about accreditation for the specific test and the format of the test report.