Although injection molding is the most-used production method for plastics in the world, producing very strong, durable parts, 3D printing produces plastic parts with comparable strength and that are suitable for most applications. For example, industrial automation provider Melton Machine & Control Company uses SLS Nylon 12 to create fixtures that go into welding machines. These parts withstand daily high heat and spatter for a few years at a time. Other times, 3D printed parts are the best choice for end-use parts because of their ability to be lightweighted. BMW uses 3D printed parts with a light infill to make custom jigs much easier to lift on the assembly line.
What makes 3D printing a clear choice for production, however, is the ability for parts to have complex features. BMW’s jigs feature complex features that mimic the organic curves of an automobile front or back end to ensure the proper alignment of decals. Geometries like these, as well as undercuts and “impossible shapes” like lattice structures, must be approached at multiple angles. 3D printing can easily print these multi-angled features on multiple axes through a combination of layer-by-layer cross-sections and support structures. With injection molding, however, complex shapes may be impossible to mold because of a nonviable machining path when making the mold tool, or during molding, may create a die lock condition. If the feature is complex but possible with molding, it may require costly side actions. These factors mean that the required geometry for a part may not be achievable with injection molding production, or that the cost of molding is less cost-effective than 3D printing production.
When it comes to cosmetics, 3D printed plastic parts can rival the superior quality of injection molded surface finishes through post-processing options. While standard injection molded parts come out with a completely smooth surface, with the exception of small parting lines or ejection rings, 3D printed parts may have layers (for extruded processes) or a slightly grainy surface texture (for sintered processes). Finishing options like sanding, media tumbling, painting, dyeing, and plating can make parts production-ready.
Oftentimes, the answer is that 3D printing is good enough, and certainly cheap and fast enough, to use as end-use parts and for an end-customer. Especially at fast-moving startups and with projects experiencing delays, 3D printed parts can withstand a high level of environmental stress, making them perfectly suitable for 3D printing production.