Top Tips: Rapid Prototyping for Small Shops
Prototypes have traditionally been early versions of designs given three-dimensional solid form in order to test their appearance, ergonomics, fit, or performance in a real-world application. As the product design cycle becomes shorter, parts made using prototyping technology are increasingly used as stand-ins for parts made using more traditional manufacturing methods.
Read on for some tips on incorporating rapid prototyping technologies into your product development cycle.
The term rapid prototyping encompasses a variety of technologies, both recent and well-known. CNC machining, for instance, has been around for decades. Sheet-metal fabrication refers to bending, shaping, and joining sheets of aluminum or steel to create cost-effective and material-efficient parts.
3D printing covers a range of additive manufacturing processes in various stages of maturity. More established polymer injection molding can reliably create strong plastic parts that are not cost-effective to machine in quantities larger than 3D printing techniques can produce.
In today’s marketplace, many clients are looking for a part that is customized to their specific needs. In the medical arena, service providers are tailoring orthotics, prosthetics, and even surgical guides to each patient. Other examples come from specialty parts makers like Ring Brothers, a Spring Green, Wisconsin, auto shop specializing in restoring classic cars and making other parts customized to each client’s car.
When custom parts are required, smaller shops like these often have an advantage. RP technology can help them create the custom parts their customers need without having to invest in expensive tooling or fixtures.
A part produced using a manufacturing method is only as good as the data defining it. Designers creating RP parts start with robust 3D part definition. This can come from geometric dimensioning and tolerancing (GD&T) data detected using 3D scanners, from some CAT scans, or from 3D CAD drawings.
To preserve the agility of RP technology, the 3D data needs to easily update when changes are made to the design or to related parts. To ensure high-fidelity updates, designers often choose CAD software packages that can interact seamlessly with their scanners and other data sources.
Designers need a CAD file format that can easily translate into manufacturing data. For instance, many modern CAD packages integrate functions that were previously the province of CAM software, like the creation of CNC machining profiles. Software updates now allow engineers to visualize the machining path before material removal begins.
For polymer parts, designers need a CAD program that can generate models of mold surfaces from a 3D part model or that can seamlessly send their design to a 3D printer.
Although RP is the main production method for some products, other designers still use it for trial runs and plan to begin full-rate production using another manufacturing method. These designers need tools to estimate the cost of full-rate production and to catch any manufacturability problems. Some CAD software now offers modules that can generate instant quotes for traditional manufacturing methods or that can highlight design features that make manufacturing more difficult or costly.
When parts present manufacturing challenges, designers need to think outside the box. In 3D printing, for example, changing the build axis of the part can place the stronger axis of the material in the direction of greater stress or minimize the amount of support material or secondary operations required.
Designers can also move the parting lines of injection molded parts to improve part release and speed cycle times. Flipping or rotating a CNC machined part can highlight ways to reduce material waste or use more economical cutting methods.
Today’s rapid prototyping methods use a wide range of materials matching the range of roles prototypes play. For instance, the photo-curing polymers used in SLA are best suited for display and fit testing, but they don’t hold up to stress or UV light. On the other hand, sheet metal parts are capable of taking on full functional testing and production.
CNC machining is thought of as a metal fabrication technology, but it also works with many engineering plastics with less wear on cutting tools and less energy expended. The same is true of softer metals like brass or steels that are machined before a hardening heat treatment. On the flip side, 3D printing processes like direct metal laser sintering create parts from metal powders using additive manufacturing.
The small shop’s biggest advantage is its agility with regard to iterating designs. The right CAD program can help designers maintain this flexibility. Modern software platforms have cloud-based or file-sharing capabilities that enable collaboration and ensure automatic updates of linked products as the design iterates. Simulation modules also let designers virtually test part performance without having to export to another program.
Modern CAD packages also support another kind of virtual testing by letting designers see what the part would really look like in 3D on the screen. Many platforms also support augmented and virtual reality visualization. These methods give designers a feel for the actual appearance and ergonomics of the part before committing to a real-world prototype.