Verification and validation are distinct, but related activities that combined demonstrate through objective evidence that the medical device meets the design requirements defined and the medical device meets user needs and intended use. Before talking about timing of V&V, it is important to differentiate between PROCESS validation and DESIGN validation.
Per FDA, process validation is defined as the collection and evaluation of data, from the process design stage through commercial production, which establishes scientific evidence that a process is capable of consistently delivering quality product. While Design Validation is the establishment by objective evidence that specifications (specified requirements) conform with user needs and intended use(s). Typically, based on my experience, some process validation will occur followed by design verification. Then depending whether there is scale-up required, process that will be leveraged for commercial will also go through process validation. The design validation is typically the last part of these three activities. Depending on the strategy of the company, samples from small scale or large scale production can be used for design validation, but they must be representative of the image that will be marketed, otherwise the regulatory agencies may require some kind of bridging study. In terms of timing, typically process validation can occur around 2/4 of the project while design verification will occur around ¾ and final stage of the project.