By Paul Vizzio
The manufacturing world is filled with acronyms, among them being EVT, DVT, PVT, and MP; these describe the stages of manufacturing from least to most mature. Full mass production cannot occur at the conclusion of design, rather there are several steps along the way that exist to minimize risk. There will be flaws in both design and process that get uncovered in these stages and it is very important to catch them early and to catch them before you manufacture thousands of unusable units. The first set of stages after finalizing your design occurs in validation testing, which is then followed by mass production.
EVT: Engineering Validation Test
EVT is the first of the validation tests. At this point in the lifecycle you have already gone through design iterations + prototypes and have an overall design that you are comfortable in going into production with. At this stage, the parts are made on hard tools that will be used in production (injection molds, blow molds, etc..). Some exceptions on tools can be made provided the part is low risk. The parts are gone over and put together by the engineering team of the design agency; this may also be done in parallel by the moldmaker and any contracted firms you are working with that will put together or run quality assurance on your product. The parts typically consist of T1 and/or T0 shots. T0 shots being the first off tool shots in the mold and T1 being the shots off the mold after the moldmaker corrects parts to be in spec with the engineering drawings. T0 shots are usually very coarse and intended to just show that parts can be made using the molds, not necessarily that they will be accurate. The moldmaker will use the T0 shots to make T1 shots, which should in theory make them in spec with the engineering drawings; in reality this rarely happens and the part coming off the mold has some issues that will need to be addressed either by altering the design or mold parameters.
The main outcome of EVT is for the design agency to see how their design looks and fits together; this will drive any and all changes that need to happen. It is very important to start analyzing the tolerance stackups that your vendors can produce as they will likely be different from the drawings. It is important to know exactly where every product stands on its dimensional deviations and to plan on fixing the parts, or altering the design such that you can minimize your failure rate. That makes it very important for every piece to be looked over thoroughly by the engineering team. This is the stage for full product testing as well as unforeseen issues will pop up that need to be designed for. Testing may include IP rating, drop testing, stress testing, shock testing, environmental testing, and many others. The production line must also be thought out at this point to finalize assembly drawings and any testing or programming steps that will need to occur.
It is critical to figure out as much about the production design at this stage, as time goes on changes become more expensive and time consuming as the product matures. Depending on the amount of changes required, another EVT round may be initiated using T2 plastics, or you can proceed on to DVT if the changes are minimal.
The large majority of these final assemblies will be used for testing, hence the “engineering validation” part of the acronym. While some of these may be used to show investors or if you are very lucky, Alpha testers, you should not plan to have any working products that leave the hands of the development team(s).
Estimated quantity output: < 100, depending on your projections
DVT: Design Validation Test
This is the stage where the final design really starts taking shape and you start getting feedback from your proposed production line. Whereas in EVT, the engineering/development teams put together the assemblies, this stage hands that off to the actual factory. The factory will have a much more in-depth knowledge of their skills, production level processes and line layout than the designer’s engineering team will. It’s one thing for an engineering team to optimize for 100 units, and a completely different story for a factory to optimize for thousands to millions of units. The engineering team should be on hand at the factory as the factory starts to include their own proposals for increasing output and reliability; sometimes these proposals are as easy as re-arranging steps, while sometimes it requires slight retooling of parts. The majority of the time, there will be some retooling that needs to occur to increase yield and this should be reflected in your initial timeline projections. At this stage, you likely will not be running on the final production line, but by the end you should have a clear plan forward on how to build and manage the line(s).
This stage may produce fully functional units, but the quality assurance (QA) checking will likely not be up to par yet. It will take time and experimentation for the factory to optimize their line and many unexpected issues may get through that weren’t initially thought of for QAing. That being said, these assemblies will have unforeseen issues and should not go to final consumers; these units could be perfect for Beta customers, provided that they understand there will be hiccups.
Estimated quantity output: < 500 depending on your projections
PVT: Production Validation Test
This is the final stage before mass production and the one where, if lucky, you should be able to send out to first customers. This stage is where the factory executes the planned production line(s) using all the final fixtures, processes and QA stages. This serves as the trial run to ensure that everything will be ready for mass production. It is very common at this stage to find issues and optimizations with the factory lines and fixtures; sometimes this can include design changes to plastics and PCBAs to minimize yield scrap. All components and processes should be in their intended mass production stage, this includes packaging, third party logistics, freight forwarding and quality assurance checks.
Estimated quantity output: < 2000, depending on your projections
MP: Mass Production
This is the stage you’ve been waiting for. This is when all of the preparation and hard work pays off to be able to hand money over to your factory, and get final products sent out the door to your customers. This stage is often divided into three sub-stages based on maturity: red, yellow and green. Red comes first and means that the mass production line has started, but still not running at 100% while kinks get worked out. Yellow is when products have been coming off the line for some time and optimizations are being put in place and tested, but yield is still not where it could be. Green is when everything is running as a well-oiled machine. There will always exist opportunities for yield improvement, but those opportunities are plateauing. At this stage, design effort is minimal, while continuous process improvement becomes the main driver of cost reductions moving forward (along with any cost restructuring due to higher and/or more regular part buys with your suppliers).
Estimated quantity output: your projections
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