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Pre-Production Milestones 101: EVT, DVT, PVT

By now, you are likely aware that the order of operations to deliver electromechanical products to customers is complex and elaborate. Mixed messaging and confusing or contradictory terminology makes the manufacturing process even more perplexing. To get you up to speed, we’ll start by demystifying these pre-production milestones: EVT, DVT, and PVT.

Terminology, Sorted.

In any industry, a strong command of the specific abbreviations, terminology, and acronyms signals field expertise. Use of industry short-hand is an asset in streamlining communication between experts. On the flip side, the learning curve to grasp all these abbreviations, terms, and acronyms can be frustrating and may hinder those new to a particular field; and, experts may not agree all the time!

In manufacturing, some of the most common acronyms needing untangling are those used to describe the phases of NPI (New Product Introduction) that cover the process of ramping up from a production-ready prototype to mass production. After selecting your CM (Contract Manufacturer), signing an MSA (Manufacturing Services Agreement), and completing the Design for Manufacturing (DFM), pre-production engineering, and tooling phases, you couldn’t (and wouldn’t!) immediately roll 10,000 units off the line the next day. There are distinct phases of production ramp to ensure that by the time you start manufacturing at scale, each unit will meet all your expectations and specifications, as well as any mandated safety and regulatory requirements indicated by your particular product category and industry. These phases are commonly referred to as EVT, DVT, and PVT.

Dragon Innovation: Production Milestones timeline: EVT, DVT, PVT

A note on terminology: while EVT, DVT, and PVT, outlined in this post, are commonly employed to describe production phases, the alternative “EP acronyms” (Engineering Pilot), EP, FEP, and PP, are frequently used as well. We’ll explore the EP alternative terminology more in-depth in future posts.

From One to Many

Overall, in the process of going from a production-ready prototype to mass production, the following steps take place:

  • Design documentation is transferred from you to the CM and reviewed by the CM.
  • Tools, dies, and other fixtures are manufactured by the CM.
  • Multiple rounds of production-intent prototypes (samples) are built and tested.
  • Your product is tested and certified to the required regulatory standards.
  • Test procedures and fixtures and quality control plans are developed and tested on the prototypes.
  • The assembly line is set up, work instructions are created, and the workers are trained.
  • A pilot run of perhaps 500 to 1000 saleable units are built on the assembly line to prove out the manufacturing process.

Although this process (and how long it takes!) can be frustrating, try to keep in mind that “It’s better to do it right than to do it over.” Dragon typically advises customers to allocate a bare minimum of 17 weeks for EVT, DVT, and PVT combined.

EVT, DVT, and PVT: What do they mean, and what is the goal of each phase?

Diving in more deeply, after the DFM (Design for Manufacturing) stage, there are typically three pre-production phases to go from one (production-ready prototype) to many (stable mass production):

  • EVT: Engineering Validation Test
  • DVT: Design Validation Test
  • PVT: Production Validation Test

EVT: Engineering Validation Test

The high-level goal of this phase is to assemble the parts for fit, and test the product for function; that is, make sure the parts go together and the device works as intended, even though the units may not look beautiful or work for very long. You are testing the hypothesis that the core product engineering functions as expected. Units built in EVT (“EVT samples”) are made by production tools (for example, the steel molds for plastic parts) that may or may not have been finalized (for example, the final textures may not have been applied). During EVT, the design engineers (ideally) are teaching the production line managers. During EVT, a typical company might expect to build 20 to 50 units (this can increase due to a number of factors). Due to the small lot size of EVT samples, each sample may cost 3-4 times the final per-unit cost, because some components may be sourced from lower minimum order quantity (MOQ) sources. Dragon typically advises customers to allocate at minimum 5 weeks for EVT phase (this can increase greatly due to a number of factors).

DVT: Design Validation Test

The high-level goal of this phase is to build out the production line. You are testing the hypothesis that each stage the production line functions so as to produce an end unit that meets all of your product requirements. During this phase, you will also test the h*ll out of the product. The more testing you can do in DVT, the better: Typically, you can either test one unit for a long time or many units, each for a shorter amount of time. (To state the obvious, therefore, the latter choice can speed up the overall timeline for DVT, if you have access to more units.) During DVT, a typical company might expect to build 50 to 100 or more units. During DVT, the production line managers are teaching the production line workers. DVT samples may take much longer to make, per unit, than in the final production process, as the production line itself is being tested. Material and component procurement for DVT samples will be at much higher quantities than the required DVT sample totals, due to the much higher scrap rate (due to higher failure rate) during assembly fixture validation. DVT samples are the ones typically used for any certifications or regulatory testing required, such as UL or FCC. (Note that DVT samples are not saleable, as they do not yet have the proper regulatory certification.) DVT samples also may not have final texture and finish. DVT is your last chance to make any alterations to production tools and test fixtures. Dragon advises customers to allocate at minimum 8 weeks for DVT phase (this can vary greatly due to a number of factors).  

PVT: Production Validation Test

The high-level goal of this phase is to make sure the production line can be properly run at scale. You are testing the hypothesis that your production process works at scale. During PVT, the production line workers will start to run the assembly line as expected for scale with all associated fixtures and test stations. The production line will begin to run slowly; ramping up to full production speed, and begin to build saleable production units. PVT is the time to analyze the production process metrics to make baseline predictions about mass production yields, volumes, times, rework times, etc. More units will be made during PVT; typically ~500; however, assuming all goes well, these units will be saleable. Dragon advises customers to allocate a minimum of 4 weeks for PVT phase (this can vary greatly due to a number of factors).

VAV or V&V: “Verification” and/or “Validation”?

We’ve seen some further acronymic confusion in the “V” of EVT, DVT, and PVT. Some sources will define the “V” in EVT, DVT, PVT as “Verification” rather than “Validation”. The disagreement boils down to whether you are validating or verifying (or, validating AND verifying). 

In a typical design thinking framework, determining whether you are building the right product for your business and customers (Validation) should come much earlier in the product development process than when you’re ready for mass production. However,  there are elements of both Validation and Verification (Verification defined as determining whether your products are built the right way) -- in the EVT, DVT, and PVT phases.

Dragon Innovation: verification vs. validation

V&V (or VAV, both of which stand for “Validation and Verification”) is an acronym used in manufacturing to describe the efforts and planning that go into the design stages, to prepare to confirm the product’s functional requirements and specifications that will be tested in production. V&V in medical devices is particularly well-documented (for example, see “Validation and Verification in Medical Devices” by ASME). Further, we can define these terms as follows: 

  • Validation - confirming the physical product meets the predetermined functional requirements. Does it meet the user needs?
  • Verification - confirming that the physical product, as manufactured, meets the specifications of the product (such as quality inspections, test inspections, some analysis). Does it meet the specifications?

Great! How do I learn more?

While approaching manufacturing at scale can feel like diving into the deep end without a life jacket, untangling the terminology that the manufacturing industry employs is a great first step to getting up to speed, and demystifying pre-production milestones. Here are some additional resources to help you learn more:

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