Form, Fit, Function, and Proof Testing

Form and fit of prototype designs was the original function of 3D-printed parts. The ability to visualize and handle a 3D part, rather than crowd around a set of blueprints or a computer-generated model, has advantages, especially for customers and stakeholders not intimately associated with the technical design phase. The same goes for fitting a 3D model into a prototype system. While 3D CAD models can be assembled into virtual systems to simulate part and system function, there is great value in someone actually bolting up a part and confirming they can swing a wrench at it. The prototype does not need to be metal to add value to the form and fit stage of prototype development.

Composite materials are blurring the boundaries of plastic and metal used in prototypes for fit testing and functional testing. Advances in materials offering high temperature and strength, such as metal filled plastic composites, have been applied to offer an increasingly wide range of functional testing. The benefit of these hybrid materials is primarily their lower cost. Metal prototypes go one better by potentially offering the testing of the full functional range of part performance albeit at a greater cost. Metal prototype parts may also be used in short run production such as in molds, dies, tooling, and inserts used to produce other prototypical parts by conventional means such as injection molding or casting without incurring the high cost of large production run tooling.

Full functional testing of rapidly produced prototypes, saving both time and money, has been the primary function of AM technology. Although many applications are moving into full production, prototyping will still demonstrate the technology. Large corporations with highly skilled technical teams are routinely using this technology for larger and larger parts in an increasingly wider range of materials. The boundaries of what the technology can do are being pushed at a very rapid rate. Smaller businesses are finding they need to rely on service providers to tap into this market to stay competitive. Applications are emerging where full production of small lot size components is possible, but for now, keeping up with the competitor’s rush to market by using AM is sufficient motivation for small businesses to explore the use of AM. Due to cost and limited availability of engineering skills, AM machines, and specialized facilities, small- and medium-sized businesses are turning to established service providers to meet their needs. In some cases, large corporations are acquiring or merging with these service providers to establish in-house skills or to deny access to these services by their competition.

Proof testing is a way to subject a prototype part, a process qualification lot, or a random sample taken from a production lot, to a mockup testing of the part within an in-service environment. As an example, this is the testing stage where you tire up the rocket engine nozzle, take the car to the race track, or pressurize the storage vessel to see how well it works. Often the component is subjected to an extended range of standard operating conditions to prove functional performance beyond that typically seen in service. Elaborate machines to perform these tests have been used for years to evaluate test parts destined for manufacture. We have all seen the so-called shake, rattle, and roll systems where you bolt up the car and subject it to high cycle fatigue for tens of thousands of loading cycles and we all know the fate of the crash test dummies. It will probably not be too long before these machines and dummies feature 3D-printed parts.