Overview of the Various Types of Hardware Prototypes

There are many types of prototypes that you will hear about when developing a new hardware product. Each stage of bringing your product to market has different prototype requirements.

Unfortunately, a single prototype is never sufficient for bringing a commercial product to market. No matter how advanced computer-aided-design has become any new product will require multiple prototype iterations.

You always want to start off with the simplest, lowest cost type of prototype. Then, gain as much information as you can from that prototype before transitioning to a more expensive category of prototype.

In this article I’m going to review all of the different types of prototypes you may need along the path to market.

Keep in mind that as an entrepreneur you will rarely fund all of these prototypes yourself. At some point you will likely need outside funding to help finance some of the later stage prototypes. The ideal stage to begin seeking outside funding is something I will discuss as well.

NOTE: This is a long, very detailed article so here’s a free PDF version of it for easy reading and future reference.

A proof-of-concept (POC) prototype is, as it’s name implies, an early stage prototype for proving the basic concept of the product. Rarely will a POC prototype function identically to the final product, and it will never look like the final product.

A POC has only one goal — to prove the fundamental concept of the product at the lowest cost possible.

For the majority of electronic hardware products, a POC prototype will be built on an electronics development kit such as an Arduino or Raspberry Pi.

A proof-of-concept prototype is usually only used to determine the practicality of a new product idea. It will rarely be seen by customers. In most cases, a prototype much closer to a production version will be necessary for presenting to customers and investors.

Creating a proof-of-concept prototype makes the most sense if you have fundamental questions about whether your product can actually solve the intended problem.

Figure 1 — A proof-of-concept (POC) prototype is built from off-the-shelf components and is commonly based on an Arduino or Raspberry Pi.

If there are multiple ways to solve a target problem, but you are unsure of which solution is best, then a proof-of-concept prototype can provide a lot of insight. Fundamental questions, such as the basic solution option, are much better determined by a POC prototype than with a custom Printed Circuit Board (PCB).

If you are technical enough to create your own POC prototype then it makes even more sense. You may not have the engineering skills to develop your own custom PCB design for the production version of your product, but many of you can learn the skills necessary to build your own POC prototype with an Arduino or Raspberry Pi.

If you don’t have the skills to create your own POC prototype, and/or you have no major questions about the feasibility of your solution, it is probably better to skip the POC prototype altogether. Instead, focus on outsourcing the development of the production version of your product.

Most large tech companies bypass the POC stage primarily because they know it’s a quicker path to market if they instead focus all their efforts on developing the production version. They also have a lot more money than you do allowing them to take expensive shortcuts that you likely shouldn’t take.

Some design engineers also scoff at the concept of a POC prototype because they know they are rarely similar to the final production version.

Regardless, if you have fundamental questions or concerns about your solution, and you have a limited budget, then creating a POC prototype will be time well spent. The downside is it may increase the time it takes to get your product to market.

When first prototyping a new product it’s usually necessary to split the task into two parts each with its own purpose. For most products you will initially want to separate the appearance of the product from the function of the product.

These are commonly referred to as looks-like prototypes and works-like prototypes.

A looks-like prototype is for the exterior of a product which will be made of plastic or metal, whereas a works-like prototype is usually focused on the internal electronics.

Optimizing the look, form, feel, and aesthetics of a product is the purpose of a looks-like prototype.

Most looks-like prototypes are created with 3D printing technology which is an additive process. This means material is added in layers to form the final shape.

Figure 2- 3D printing is the most common method of producing looks-like prototypes. But CNC machining and even simple options like clay and foam should be not be neglected.

However, for some products CNC machining is a better solution. CNC (Computer Numerical Control) machining is a subtractive process.

CNC machining starts with a solid block of the chosen material (usually plastic or metal) and then the final shape is carved out from that block by removing material.

One key advantage of CNC machining compared to 3D printing is that you can use the desired production plastic instead of 3D printer resins that only simulate the production plastic.

Different plastics have different characteristics so for many products the plastic type is critical to appearance and/or function of the final product.

Also, don’t neglect old techniques like foam and clay which can be very helpful in the beginning stages. Both of these “technologies” allow you to quickly and cheaply transform a concept into something you can hold in your hand.

For my own hardware product my earliest prototypes where made of clay which provided me critical feedback on how the product felt in a user’s hands.

Always start out with the simplest, cheapest methods of prototyping. Learn as much as you can from these low cost prototypes before migrating up to more advanced prototyping technologies.

It is much easier (and cheaper) to iterate a foam or clay prototype than a 3D printed prototype. Starting with clay prototypes may even reduce the number of prototype iterations required once you upgrade to 3D printing.

As you work your way up the prototyping technology hierarchy you will find that design changes become more and more complicated.

Clay prototypes are trivial to change, 3D printed prototypes are moderately complex/expensive to modify, and injection molded prototypes are the most complex to upgrade.

Now it’s time to focus on the functionality of the product, which for most hardware products means the internal electronics.

For a Proof-of-Concept prototype you will usually build the electronics entirely from off-the-shelf components and development kits such as an Arduino or Raspberry Pi.

In fact, a POC prototype can be considered an early version of a works-like prototype.

But for your production works-like prototype you will need to develop a custom Printed Circuit Board (PCB) to hold and connect all of the discrete electronic components.

Because of this, there is typically a big jump in technical skills required to go from a POC to a production-level, works-like prototype.

Figure 3 — There is a drastic jump in the technical skill to develop a custom PCB compared to the skill needed to make a POC using off-the-shelf components.

Many founders have the skills (or can learn them) to develop a Proof-of-Concept prototype, but to develop a custom PCB for your works-like prototype requires significant engineering design experience.

If you are fortunate enough to have these skills then you will save thousands of dollars on development fees. Engineers are expensive and the development of this custom PCB is commonly the most expensive development cost you will face.

An engineering prototype (also sometimes called a works-like-looks-like prototype) is the first time that appearance and functionality come together in a single prototype.

Once you have an engineering prototype you finally will have something of sufficient quality to show customers and investors.

Figure 4 — An engineering prototype merges the works-like and looks-like designs together into a single prototype.

This is the point where seeking outside investors becomes a bit more practical. By getting to this stage you’ve essentially removed most of the engineering and manufacturing risk. Investors obviously love this reduction in risk.

For my own hardware product I funded the development myself up to this stage. I was then able to use my prototype to get a large, national retailer interested in my product.

From there, I leveraged that success to find a manufacturer willing to fund the remaining prototype stages.

With an engineering prototype you are finally getting close to the production prototype, but it still hasn’t been tested or prepared for mass production.

This is a works-like-looks-like prototype that has been optimized for manufacturing. This is very close to the final product your customers will see. In most cases, it should also include the retail package if the product will be sold via retail outlets.

Although the pre-production prototype may look and function very similar to the works-like-looks-like prototype, the key difference is manufacturability.

During product development many entrepreneurs underestimate the work needed to migrate from a prototype to a product which can be efficiently manufactured.

Making a few prototypes is completely different than manufacturing millions of units. In most cases, considerable additional design effort is required to prepare the design for mass manufacturing.

For example, 3D printing or CNC machining are typically used when prototyping the product’s enclosure. For mass manufacturing, high-pressure injection molding will be the technology used to produce the enclosure.

3D printing and CNC machining are very forgiving technologies and you can prototype just about any shape of plastic you can imagine. This is not the case with injection molding.

Injection molding has very strict production requirements. After you finalize your 3D printed prototypes it will be necessary to further upgrade the design for injection molding.

Once you have a finished engineering prototype it’s time to begin testing it to validate that it works exactly as specified.

Figure 5 — The goal of the EVT stage is to prove that your product design meets the functional, performance, and reliability requirements.

The first stage of this testing is called Engineering Validation Testing (EVT). This stage of testing focuses on the electronics. Typically between 10–50 units will be tested during EVT.

EVT will include testing the basic functionality but also doing various stress tests to ensure there are no hidden problems. This includes power, thermal and EMI testing.

The goal of EVT is to validate that your prototype meets the functional, performance, and reliability specifications.

The Design Validation Test (DVT) is one of the most complex stages. It’s goal is to ensure the product meets any necessary cosmetic and environmental specifications.

A significantly larger number of units will be needed than for the EVT stage, typically 50–200 units.

These units will be very aggressively tested including drop, fire, and waterproof testing. Validating that the product is durable enough to withstand day to day use is one of the primary goals of design validation testing.

This is also commonly the stage at which electrical certifications are obtained. This includes certifications such as FCC, CE, UL, and RoHS to name a few.

Because of the cost and time required to obtain the necessary electrical certifications, the process is usually delayed until the DVT stage. This is to ensure that no other design changes are required after certification testing begins.

Of course, if any problems are found during the certification testing process then design modifications may be necessary to correct them.

The PVT stage will be your first official production run. You will establish a pilot production line with the priority of optimizing your production process.

The focus here will be on improving your scrap rate, assembly time, and quality control process by optimizing your production line, but not by making any further product design changes (unless a serious design issue is discovered).

A small pilot production run of several hundred units is typical. And if no problems are found these can be your first units that can be sold!

Don’t be in a rush to move up to more advanced prototyping technologies until you have gained all of the information you can from less complex, lower cost technologies.

The idea that you simply create a single prototype (or two) and then just jump into full production should now be clearly seen as a myth.

Are you frustrated and overwhelmed trying to develop and bring your own hardware product to market? If so, now you can finally get the help you need to succeed in the Hardware Academy.

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Author: John Teel

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