Going back and forth trying to understand what each person needs to get a prototype can kill time, and waste budget. Knowing what you need and what to provide can be a challenge with the many processes used to build prototypes. We’ll walk through what’s needed to get your prototype, so you’ll be ready to hit the ground running with each new project.
About a 12-minute read
So, you reached the point in your project when you need a prototype. You know what you need, but aren’t sure how to have it made. Over the years, we’ve found some tips that have worked to improve workflow and streamline the process. There are six basic kinds of prototypes, which you can learn more about in complete prototypes:
- Foam Model
- Proof-of-Concept Model
- Appearance Prototype
- Engineering Prototype
- Electronic Prototype
- Functional Prototype
Each of these need a distinct type of information. We’ll cover the fundamentals, the type of information needed, level of detail, and examples for what we are looking for to build a prototype. The depth of information increases as your prototype complexity increases, from general to specific. As a rule of thumb, we’ll talk about the minimum amount of information needed for each prototype. Of course, we can always take in more detailed data, and more information is always better, but this time we’ll focus on what is required.
Let’s get started!
The foam model is an inexpensive, early prototype and typically requires the least amount of information. This is where you hear people talking about a “napkin sketch.”
A napkin sketch?
Ok, let me paint a picture. You’re sitting in a restaurant telling a friend all about your latest design, trying to explain it, but he isn’t getting it. You grab a pen, and the napkin on the table. You begin to sketch out your design, maybe you throw a couple of quick overall dimensions or a quick exploded view. Eureka! He gets it! Napkin sketch.
The thing to remember with a foam model is that you are moving fast. The starting point for a foam model can truly be a quick sketch with overall sizes. You are looking for proportions and general requirements. This is very early in the process, so don’t get bogged down in minute details. The details will likely change over time.
A basic orthographic sketch may help convey your ideas to your prototype specialist. A section drawing or two would also help for more complex areas. Your prototype specialist can take these overall shapes and dimensions and use them to start working on your model. We generally use materials that we can work with quickly, such as urethane foams, which can be cut with bandsaws, table saws, or we may even sculpt details by hand.
If you prefer working things out in CAD, the level of detail needed for a foam model is low. There isn’t a need for refinement, but should include outside surface CAD with primitive shapes. A CNC programmer will just need enough information to use it to write tool paths.
With a foam model, information is just used to communicate size and shape in simple, basic terms. You may create several foam models to evaluate concepts, and decide on a design direction.
"The thing to remember with a foam model is that you are moving fast. This is very early in the process, so don’t get bogged down in minute details. The details will likely change over time."
The idea behind a proof-of-concept model is to test functionality. This is still in the initial stages of development where the intent is exploring and learning. We’re not worried about finesse or final details just yet. When relaying information, determine what you want to learn. What details are important? The information that you need to provide depends on what type of mechanism you are developing, and what you want to test.
For example, let’s say that you are working out a trigger mechanism and you want to learn how much travel you need to activate the trigger. In this case we may use laser cut acrylic to create your trigger components with simple, two-dimensional parts. You can provide drawings with critical dimensions, Adobe Illustrator outlines (.ai or .eps) or a DXF file with outlined artwork.
If you’re working on a new device to administer CPR, for example, you may want to explore multiple ways of delivering chest compressions. With clearly defined explanations of what to test with each prototype, our team will find the solution, process, and material for the most quick and efficient way to produce that prototype to complete the test. This may mean hitting properties for strength for some parts, but not others. Or, it may mean producing a prototype not built to last, but will be able to complete the test with a short lifetime. Without a need for long term durability, we can save time and budget by creating a quick solution. The goal is to fail fast, and move on to the next step in the process.
In this case, we could combine several processes into one prototype. By looking at the properties needed for the parts being tested, a proof-of-concept prototype may consist of parts that have been CNC machined, 3D printed, laser cut or even simple wooden framework cut on a bandsaw.
No matter the product type, the goal is to rapidly ideate to test your concepts. After talking with a prototype specialist to determine the process for your parts, it may require simple 2D outlines for laser cutting, or CAD geometry for 3D printing. The most important thing is to begin by communicating the testing intent and properties needed, and the rest is determined throughout the process.
"No matter the product, the goal is to rapidly ideate to test your concepts. The most important thing is to begin by communicating the testing intent and properties needed, and the rest can be determined through the process."
An appearance prototype looks like the final product, but without the functionality. The goal here is to validate the industrial design direction, present the final concept to management or investors, and to get a jump on photography for catalogs or advertising.
The data needed for an appearance prototype is very detailed. CAD files for CNC programming or to run rapid prototype (RP) parts should be the starting point. For an appearance prototype, make sure that there are solid shapes with no gaps and eliminate parts that don’t fit or are not needed for the prototype. The simpler and direct the file can be, the better.
"For an appearance prototype, make sure that there are solid shapes with no gaps and eliminate parts that don’t fit or are not needed for the prototype. The simpler and direct the file can be, the better."
You need to make sure that the data you provide will work with the software your prototype house is using, and it is always a good idea to send over test files prior to sending over the final data. It’s better to resolve any issues early, as opposed to the end of your program when timing is tight. With Priority Prototypes, we prefer native files in Solidworks, but a neutral file like Step or Iges is also sufficient.
The parts in your CAD data should be broken into separate pieces, or parts should be sent as individual files. Make sure to check clearances, fit, interferences, and if your prototype specialist will be doing the assembly, be sure to send an assembly file. Rather than production breaks, parts should be separated for color and texture breaks. For example, for a part that will be co-molded in production, the prototype data should be split by color and texture so that you can get the look of a co-molded part. This technique of splitting up parts and reassembling them will give you crisp color and texture breaks. The detail will make your prototype look much more realistic when it is finished.
Sitting down and discussing the colors and finishes with your prototype specialist will save time. They need to understand exactly what you want, where you want it. Color renderings and exploded views are great to communicate your intent. The more visual information that you can provide the better. There is no such thing as too much information!
If possible, provide color samples with a 4”x 4” color square. This will allow for a good color scan and match. If you can’t provide an exact color sample, you will need to provide a color reference number such as a Pantone number. Or, we can use an actual part that can be used as reference. For texture reference, the best solution is to provide a Mold Tech (MT) number. This is an industry standard used for texturing injection molded tools. If you provide an MT number, your prototype specialist can match the texture you’re looking for.
Although color and texture can be very close, remember that with a prototype, it’s unlikely to be an exact match to production. Remember, you are dealing with paint as opposed to injection molded plastics. It will be close enough to convey the look and feel you want with your product, but it probably won’t be exact if evaluated with a spectrometer.
With an engineering prototype, the most important information is the intended production method and what you are planning to test with this prototype. Whereas a proof-of-concept prototype is intended to understand concepts and basic functionality, an engineering prototype is confirming functionality with near-production materials.
In most cases the information needed here will be in the form of 3D geometry. As a general rule, CAD should be set up for the material and processes of the parts being made. If you are unsure, or need assistance with file setup, a prototype specialist can help walk you through the specifics of your project. Your CAD model needs to reflect a production solution in order to prototype parts that reflect the production intent. You should include details such as wall thickness, parts, and bosses. This should also demonstrate how your design will be separated into its individual parts.
A great resource for prototyping parts with production materials is 3D printing. There are a variety of printers ranging from hobby grade to professional machines. The type of machine you use depends on the material and the quality of the part that you need. For an engineering prototype, 3D printing is ideal for parts that are not being tested for mechanical movement. To learn more about the distinctions and uses for different 3D printing machines, see “How to Navigate the Rapidly Changing World of 3D Printing“.
Other parts may need to be extremely strong, heat resistant, durable, etc. Casting, CNC machining, SLA, or a variety of other processes may be a better solution for your prototype. With production intent, detailed CAD and testing requirements, a prototype specialist will help produce the prototype need to verify functionality and move to a final, functional prototype.
Similar to the engineering prototype, the data needed for an electronic prototype is very specific. You will need to define the features of your prototype in terms of functional and non-functional requirements. This could be how long a wearable device needs to last on a charge, the modes of operation of a user interface, or the specific technologies that make your product unique. Combining the electrical hardware requirements with functional requirements, our electrical and software engineering team works together closely to get exactly what you need.
One example of this is how a product’s interface changes as it receives input from a user. Does an LED indicator change from blue to green as a knob turns? Does it flash or pulse? Does it convey an error or a state change? A clear storyboard of the product interaction and an outline of the use cases will help our electrical and software engineers achieve the correct modes of operation that you’re looking for.
In addition to how the prototype should function, our mechanical engineers and prototype specialists will need to understand how the electronics integrate into the system. Does it need to mount to a plastic enclosure? Or does it need to be in a compression molded housing? Where should the power source be? Communication of assembly details will ensure the products electronic and mechanical parts come together without a hitch.
With an electronic prototype in hand, you will be able to test and validate technologies, and evaluate the product’s functionality.
You made it! We have come to the end; the final, most fully developed prototype! The functional prototype is the last step before production and the most realistic prototype. It is a true representation of the final functional and aesthetic qualities of your design. After this model, you are ready for production. The information required for this model combines all the information needed from the previous models. You are taking what you learned, and the refined details to create the functional prototype.
At this point, part count is solidified, CAD is complete, material choices are finalized, and colors are selected. The prototype looks and preforms like the final production product, and production materials and finishes are utilized for this model.
Along with a with the data base of CAD and artwork files, you will want to provide a solid bill of materials or BOM. This calls out all the parts that make up your product with color specifications, materials and fasteners. The functional prototype takes learnings from all previous prototypes, makes adjustments, and creates a final realized prototype that gives you confidence to move to production.
No matter where you are in the development process, creating a prototype is exciting. The ideas that you have been researching, sketching and working through in CAD are being transformed into a real, physical thing! The information that you provide along the way is important. It is what gets your product built the way you need it. So, when you pick up the phone or send that email to your prototype specialist, remember that no detail is too much. The more information that you can provide at every step will help them understand what you want.
So, remember, your information builds as your prototype builds. You are always moving from general to specific. As a rule of thumb, for the most efficient prototype development that saves your time and budget, you can use this guide to have your information ready every step of the way. This won’t cover every scenario, but it will help you ask the right questions and get your project off to a strong start.
Chris Kanoski, Prototype Lab Coordinator/ Senior Prototype Specialist
The builder. Whether it’s at work or home, he’s building something. From pirate ships for his kids, historical replicas for himself or renovating his home, he never stops building. He specializes in small-scale, intricate projects in our model shop. Precision is his forte and it’s evident in everything he constructs.