Rapid Prototyping: There’s More Than One Way to Skin a CAD
The value of a physical prototype is hard to overstate.
Every product, whether it be hardware or software, starts as a prototype before it becomes a shippable product. Given the nature of software, it’s fairly simple to implement a change, test its performance, and iterate to the point of a final product. But with physical parts, the prototyping and development phase is further complicated by coordination with suppliers, selecting materials and processes, as well as regulatory approvals and certifications.
Despite the many software tools on the market that simulate part design and conduct an analysis of manufacturability, having a physical prototype that users can interact with is a necessary step in any successful product development cycle. Not only does it give users and customers a way to react to your potential design, but it also helps identify manufacturing issues early on in development—saving you from costly redesigns and delays as you near production.
What’s the best way to manufacture a prototype? The optimal manufacturing process will depend on where you are at in the development process and what attributes are most important. This can range from material properties such as flammability and tensile strength to testing the fit of a component within an assembly, and don’t rule out cosmetics. But with rapid manufacturing technologies, design changes can be made during prototyping and multiple iterations can be tested without adding significant development time and delaying market launch.
Concept Model and Early Design Validation
At the earliest stages of product development, when ideas are still in their infancy, so are the prototypes. Even if the initial product idea could use some additional thought, creating a physical model helps communicate an idea and get feedback from peers, customers, and any other stakeholders.
When fleshing out ideas and building concept models, manufacturing speed is extremely valuable since it will enable you to test and iterate more designs, without sacrificing time to market. For this reason, 3D printing is frequently used to validate early designs. Whether produced in-house or outsourced to a 3D printing service provider, additive manufacturing can quickly build concept models intended to spark conversation and gain design feedback.
In addition to manufacturing speed, cosmetic features like color and texture can play an important role when evaluating an initial product concept.
Testing Form and Fit within an Assembly
As the design moves along, the next step is often testing the assembly—rarely does part design occur in a vacuum. For example, simple design errors like placing two tabs at 1.5 inch spacing and the slots being at 1 inch can easily be spotted with a physical prototype. Testing form and fit will usually coincide with discussions on which material will be used for the final part as this can sometimes impact assembly.
Given the prototyping process, the exact material used in production may not be available, but choosing a similar material can pay dividends later on. If you’re prototyping a molded part, 3D printing offers a variety of thermoplastic-like materials that, despite not being identical to their production counterparts, can be suitable at this stage in development.
Designing for moldability is strongly encouraged, even if it’s early in the process and the current iteration will be fabricated using 3D printing, machining, or something other than molding. This can save you from needing to make any substantial design changes once the time for production arrives.
Stereolithography (SL), a 3D printing process that cures thermoset resins, is often recommended for prototypes that are intended to evaluate form and fit. The technology produces parts with exceptional detail and quality surface finishes, so they can easily mate with other components within an assembly and have the feel of a final product. And, like we mentioned earlier, SL offers a number of thermoplastic-like materials, perfect for injection molding prototypes.
Another 3D printing technology to consider is PolyJet. This process can produce flexible components like gaskets and seals as well as parts containing multiple colors or material hardnesses. This can be leveraged early in product development to prototype elastomeric and overmolding designs.
Don’t forget about CNC machining, though. You’ll find many product engineers swear by machined prototypes before moving to injection molding. Since you can manufacture the part from the same thermoplastic material used in production, a machined part will give a more accurate approximation of a molded part’s material properties like strength and durability.
If the goal of your prototype is to test tolerances, you will have to rely on your production manufacturing process to gain any worthwhile insights as tolerances can vary among manufacturing processes.
Now that you’ve ironed out most of your part design, it’s time to make sure it functions as intended. Functional testing usually involves some level of user testing as well as assessing the mechanical properties of your design. And, don’t forget about chemical and electrical properties, both can have an impact on part performance. This is when material selection will start to come into focus.
If quantities are still in the handful of parts, 3D printing and machining can be viable. Powder bed fusion processes like selective laser sintering (SLS), multi jet fusion, and direct metal laser sintering (DMLS) are capable of creating functional, durable prototypes. These processes build parts from thermoplastic and metal powders. Surface finishes can be rough compared to other 3D printing processes, but SLS and DMLS parts will have the strength necessary for functional testing. Multi jet fusion is a new additive technology that builds nylon parts with improved isotropic material properties and surface finishes compared to other powder-based 3D printing processes.
At this point, some product developers will move straight to injection molding, since rapid injection molding is a cost-effective solution for low volumes of parts. This is especially valuable when conducting market testing or pilot runs with select customers and volumes of prototypes needed is in the hundreds to a few thousand. Prototyping in production-grade materials and processes can be an enlightening exercise since you can accurately examine your material choice and tolerances will remain consistent once you move to production. Gaining these insights without needing to invest in traditional steel tooling can provide a significant competitive advantage.
The features in your design and materials will ultimately determine which manufacturing process will be most beneficial and economical for functional testing.
Regulatory Approval and Certification
Many products undergo regulatory testing prior to full-scale market launch to ensure performance and safety. Common approval processes include FDA, FCC, ISO, and UL. These tests will vary depending on the type of product and industry served, but some examples are electromagnetic interference properties, biocompatibility, or flammability.
For these tests, production parts are required. Rapid, on-demand injection molding can provide substantial value to companies wanting to get through regulatory approvals as fast as possible. With cost-effective aluminum tooling and production parts within days, regulatory testing can be completed in a fraction of the time compared to traditional molding.
Making the Most of a Prototype
The value of a physical prototype is hard to overstate. Prototyping helps product design and engineers make more informed decisions as it allows for usability and functional testing before finalizing design. Additionally, remaining mindful of the final manufacturing process and materials while prototyping will help you get through regulatory testing faster and ensure a smooth transition to your end goal, production parts and a market-ready product.