A functional prototype is the most basic working prototype built to validate a product design, which can be regarded as the initial model of the final product, and already contains the functions and appearance required by the design. Additionally, it is an integral part of the assembly, testing, piloting, and market research process that evaluates design, materials, strength, tolerances, assembly, work mechanisms, manufacturability. Functional prototype can be manufactured with several prototyping techniques and engineering-grade materials, which can work under simulating real working conditions, and purpose for validate the design and improve the design by testing the form, fitness, and functionality.