An Introduction to Prototype Stages & Phase Gates

Hardware product development can be a long and arduous process. It is rife with pitfalls that can easily skyrocket costs to reaching production and cause months or even years of delays. Many of these pitfalls are the result of attempting to rush to full scale production without understanding everything that needs to be done to get there. Therefore, it is important to understand the entire process and ensure that each step is completed to the point of acceptable risk tolerance to move forward. Developing a new product is always a risky venture, and taking too long to reach the market is another danger, but there is considerable value in determining which steps entail the most risk for your particular product and paying commensurate attention to them.


Concept Stage

There are 3 major phases that hardware product development can be broken down into. The first is the Concept Stage, which entails the research and development into the fundamental functionality required for the product to meet customer requirements. This can mean many different things depending on the technology being developed, but, for the case of manufacturing capability, this is simply connecting a customer problem to a piece of technology and validating that the technology works. For example, you might be looking at customers that need faster charging batteries and developed a new and improved battery that can meet that charging requirement. All that’s required for this stage is customer research into the problem space and a proof of concept prototype showing that the technology works. Little of the exploratory work put into developing a new technology is relevant to manufacturing.


Prototyping Stage

The second stage is the Prototyping Stage. Neglecting the work required to complete this stage and validate that completion is one of the biggest sources of unexpected costs in hardware product development. Here we iterate through the simultaneous development of two different kinds of prototypes, the Works-like Prototype and the Looks-like Prototype, to refine the concept technology into a sellable product. This process of iteration is important because a certain amount of trial and error is required to advance development, but this iteration should be contained within the Prototyping Stage. Once this stage is completed there should exist several nearly finalized documents that detail the product for both internal and external communication. These include things like the Product Requirements Document(PRD), Bill of Materials (BOM), Bill of Process (BOP, etc. Any changes made past this point should only be the result of requirements coming from manufacturing resources, either contract manufacturers (CMs) or internally, and not from new customer requirements or other improvements to the design unrelated to manufacturing. Ideally conversations with CMs will begin during this stage to minimize issues down the line.

Works-like Prototype

The Works-like Prototype does what the product needs to do, but doesn’t necessarily look like the final product. It should be capable of most functions required for the customer, but there are details remaining to be completed and layout / parts are not finalized. These prototypes are often built with off the shelf parts like Arduinos and use low volume manufacturing techniques like 3D printing. These are built primarily so users can validate assumptions about functionality and provide input in the design process. This input can then be incorporated, alongside any desired engineering or design changes, into the next iteration of the prototype and the process of sourcing feedback and identifying issues internally can begin again. This should be repeated continuously alongside development of the Looks-like Prototype until a satisfactory level of fidelity is achieved and risks to the following stages of development are acceptably minimized.


Looks-like Prototype

The Looks-like Prototype is meant to resemble the final product, but doesn’t necessarily have the functionality of the final product. It is primarily focused on the customer’s aesthetic and usability concerns and serves as a second means of sourcing customer feedback. These are also built using low-fidelity techniques, but can often be done even more cheaply than the Works-like Prototype, with foam boards for example. As with the Works-like Prototype, once customer feedback has been sourced, this should be incorporated into the next iteration. This process should repeat until the desired level of fidelity is achieved and risks to the following stages of development are acceptably minimized.


Prototyping Stage

The purpose of this stage is to shape the product from the original proof of concept prototype to something that more closely resembles what the customer wants to purchase and use. The goals for this stage are validating the technology works as intended, incorporating customer feedback into the product, determining the important aspects of the final product in regards to form and function, and validating each incremental step with the customer. Ideally the final iteration of each prototype, Works-like and Looks-like, would reveal no further changes that need to be made to the design. Realistically, this isn’t economically feasible, but anything more than minor changes should be considered a significant risk to moving onto the next stage. During the Prototyping Stage, problems and changes with the product are expected. Resolving these issues and finalizing any changes will form an important foundation for moving on to manufacturing concerns. Any remaining issues can easily set back costly progress in manufacturing and can lead to an overwhelming amount of complexity from having to deal with both issues in the Prototyping Stage as well as the Validation Stage simultaneously.


Validation Stage

Once both the Works-like and Looks-like Prototypes have been completed and validated with low volume components, the Validation Stage can begin. At this point, conversations with CMs should increase significantly to leverage their expertise in Design for Manufacturing (DFM). In addition to DFM other Design for X (DFX) processes should begin. These include designing for assembly, testing, repair, upgrade, sustainability, etc. Each DFX process encompasses its own iteration cycles to test and validate performance indicators. These performance indicators will be specific to the product being developed and include not just material properties, but other business considerations as well, quality, assembly time, component availability, etc. Additionally, not every DFX process will be required for every product, many products don’t require upgrades or repairs. Every product will require DFM, however, and it is generally a good place to start.


Design for Manufacturing

DFM first requires identifying manufacturing processes for each component. During the Prototyping Stage, low volume manufacturing processes, like 3D printing, are used to iterate quickly and cheaply. These processes don’t often scale to larger orders cost effectively, and a higher upfront cost for tooling can enable much lower costs down the line. Each of these manufacturing processes will have their own considerations that must be navigated, for example, injection molding requires mold flow analyses and consideration of materials. Many of these decisions will be driven by business in addition to engineering concerns. Tooling in particular can be a cashflow hazard and may force a more steady adoption of high volume manufacturing techniques.


Design for Test

Design for Test is another important process for many hardware products. For more complicated products, breaking the product down into subassemblies can be enormously helpful in testing. Faulty components can then be caught at the subassembly level and prevent wasting an entire build on a single faulty part. This can also save significant time when debugging a production line by narrowing down where the failure happened. For electronics, it can be beneficial to design circuit boards with additional space for use with a testing jig to test the boards as a standalone subassembly.


Validation Stage

These are only a couple examples of the DFX processes that will come up over the course of hardware product development. Bringing a product to market will require careful consideration of many DFX processes and with much greater detail than presented here.

Once all of the DFX processes have been completed, there should be a finalized set of documents, PRD, BOM, DOP, etc., that can be handed over to manufacturing resources, either CMs or internal assembly, to begin production testing. This involves a series of generally escalating production runs with deescalating oversight and control. Initial runs may only run at a hundredth of their potential capacity and will have oversight from skilled engineers to identify and resolve any issues. As these runs scale in size, they will also gradually shift from skilled engineers to technicians operating the line to ease into standard operating procedures. Automation, QA/QC, packaging and shipping processes will come into play here as well. It’s worth noting that many companies will use the output of early production runs as samples for customers and partners to trial. Any significant changes that need to be made to the product at this point have the potential to be very costly as previous work may need to be redone. 



The path to mass manufacturing is a complicated process and requires different mindsets and expertise at each step. The Concept Stage generally starts long before the realization of a potential product and market fit begin, and results in a proof of concept prototype that is far from manufacturing ready. The Prototyping stage then involves the parallel and iterative processes of developing Works-like and Looks-like Prototypes, resolving both customer and engineering issues along the way. Once these are complicated, merging them into a single prototype and going through various DFX processes can begin. These will include different things for each product, but will always center on DFM and working with manufacturing resources to determine how best to build the product. This culminates in a series of scaling production runs towards mass manufacturing where any final considerations are handled. 

If you haven’t already, consider taking our Product Stage Assessment to determine where you are in the scale manufacturing process and check out our other articles on manufacturing to find more information.

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