Prototype vs. production tooling in rapid product development

In the course of mechanical product development, the main purpose of prototyping is to verify the integrity of the proposed design. The design engineer wants to validate the entire design and its performance prior to committing resources to production tools. In order to provide useful and meaningful results, a prototype unit needs to simulate a production unit so that the test results are valid. If a design fails during the prototype stage, the design engineer is left to determine if the failure was due to a faulty design or a "prototype part" shortcoming. In the case of plastic parts, the most important mechanical properties are dimensional accuracy and material performance.