A prototype that works on your desk is not yet a product. Between the first working unit and a production line that ships thousands of identical units, most hardware teams go through three structured build stages: EVT, DVT and PVT. The names come from consumer electronics, but the logic applies to almost any engineered product.
The stages at a glance
| Stage | Question it answers | Typical build | Made with |
|---|---|---|---|
| Prototype / POC | Can it work at all? | 1–5 units | 3D printing, dev boards, hand assembly |
| EVT — Engineering Validation Test | Does the design meet its functional requirements? | Tens of units | Near-final electronics; printed or machined mechanics |
| DVT — Design Validation Test | Does the final design pass reliability, safety and certification tests? | Tens to a few hundred | Production tooling (T1/T2 molds), production materials |
| PVT — Production Validation Test | Can the factory build it consistently at rate? | Hundreds or more | Final tooling, production line, final test stations |
| MP — Mass production | Ship it | Ongoing | Approved process and golden sample |
Quantities are typical ranges only; a small industrial product may run EVT with five units, while a consumer device may build hundreds in DVT.
EVT: prove the engineering
EVT units should be functionally complete: the real circuit design, firmware that exercises every feature, and mechanics close to the final shape. Enclosures are often still 3D printed or CNC machined so they can change quickly.
- Every function tested against the requirements list
- Power consumption, thermal behaviour and RF performance measured
- Assembly attempted by someone other than the designer
- Design-for-manufacturing (DFM) review of parts that will be tooled
DVT: freeze and validate the design
DVT is where money becomes hard to recover: injection molds are cut, and parts come from production materials and processes. The goal is to prove that the final design survives real-world use and passes the certifications your markets require.
- Reliability tests: drop, vibration, temperature cycling, humidity, ingress (IP rating) as applicable
- Pre-compliance and formal certification testing at accredited labs (for example CE, FCC, UKCA)
- Cosmetic standards agreed and a golden sample approved
- Packaging and transit testing
Design changes after DVT usually mean tool modifications and repeated tests — plan the schedule with that risk in mind.
PVT: prove the process
PVT runs on the production line with production operators, fixtures and test stations. The design should no longer change; the focus is yield, cycle time and consistency.
- First-pass yield measured at each test station
- Work instructions and fixtures validated
- Incoming inspection of critical components in place
- Pre-shipment inspection plan agreed (see our quality control guide)
Common reasons launches slip
- Skipping DFM before tooling — undercuts, thin walls or tight tolerances discovered after the mold is cut.
- Certification treated as a final step — a failed EMC test can force a board re-spin late in DVT.
- Long-lead components not ordered early enough.
- Undefined acceptance criteria — “looks good” is not a cosmetic standard.
- Changing the design during PVT, which resets validation.
Small companies can compress the stages — carefully
Low-volume and industrial products often merge EVT and DVT, or use small batch manufacturing methods such as machined parts and bridge tooling to delay large tooling investments. What should never be skipped is a written requirements list, a DFM review before tooling and an approved sample before production.
If you are planning a hardware product, our product development and rapid prototyping pages explain how we support each stage.