Injection Molding vs 3D Printing: Complementary, Not Competing Technologies

Much has been written about how additive manufacturing can be a replacement for injection molding technology to mass produce end-use parts at scale. While it is true that advances in 3D printing have moved the quantity needle farther to the right, especially when using high speed extrusion technology on a fleet of 3D printers operating in parallel, it will be difficult for any 3D printing method—FDM, SLA, SLS or even high speed extrusion—to ever truly replace injection molding for high volume mass production applications. There are differences in surface finishes, material properties, and aspects of product design that may be optimized for injection molding versus 3D printing processes.

There are some instances in which 3D printing is favored, such as producing small runs of subcomponents, customized products emblazoned with a logo or serialized part number, or adding functionality or internal features that otherwise would be cost-prohibitive with other technologies. But generally, Essentium believes additive manufacturing technology should be viewed as a complement rather than a competitor to injection molding.

When to Use Injection Molding vs 3D Printing

Manufacturers use injection molding to achieve very low cost-per-part for very large volumes of identical units. But it usually takes multiple iterations over weeks or months and many thousands of dollars to get the mold design exactly right. Can a fleet of 3D printers produce hundreds of thousands of water bottles, Monopoly™ house and hotel game pieces, or automotive armrest panels? Perhaps, but that’s not the best use of the technology. For high volume mass production, there is simply no competing on cost or quantity against injection molding with tools designed to last for millions of shots.

That being said, there are several ways in which additive manufacturing can be used as an enabling technology to yield better injection-molded results:

Rapid prototyping and testing

A 3D printer can quickly and cost effectively print multiple prototype iterations until a final design is achieved before committing to an expensive mold. Further, today most injection molding material classes are also available as additive manufacturing filaments, and an interested manufacturer can have a specific IM production resin converted to filament. Parts printed from this end-use resin can then be tested for fit, strength, resistance to UV light, chemicals, solvents, and abrasives. 3D printed test parts can be exposed to weather elements, checked for color fastness, or subjected to different types of post-process surface finishing to gain predictable results for the final injection molded product. Here at Essentium, we did exactly that for the rapid development of face mask frames for front line workers in the COVID-19 pandemic.

Bridge to mass production

After the design is approved, 3D printers can immediately begin to create quantities of end-use parts for initial production runs. Get a head start on manufacturing and assembly during the time the mold is being produced—usually a lengthy process depending upon the complexity of the part. Or, immediately begin to design the next element to be used further down the lifecycle of the part, such as inspection or assembly fixtures. A recent example of 3D printing serving as a bridge to mass production is COVID-19 PPE production.

At the beginning of the pandemic, the 3D printing community banded together to print urgently needed face masks, shields, and ventilator parts. After the final designs were approved, traditional molds were made. A few months later, inventories exploded as large quantities of injection-molded face masks, shields, and ventilator parts rolled off production lines. However, in the interim, fleets of 3D printers were able to fill the void, continuing to pump out PPE for first responders until the injection-molded tools were ready.

Quality control and inspection

After each part is removed from the injection molding machine and has cooled, it must be checked for size and shape to make sure it is within spec. Go/No-Go gauges are used to ensure the part falls within established tolerances and/or is defect-free before moving into the assembly process. Assembly fixtures are another example, used for exact logo positioning, proper alignment with another part or tool, and countless other applications. Rather than machining these check fixtures out of blocks of metal or Delrin®, 3D printers are being used to quickly create less expensive tooling aids from lightweight polymers. Further, they can be printed using ESD-safe, non-marring materials to guard against scratching or damaging the part to be inspected or mounted.

Although 3D printing can indeed serve as a bridge to better injection-molded part production, it should be noted that additive manufacturing has matured to the point where it can be used to actually print volumes of end-use parts, and even create the molds for low quantity injection molding production runs. Those are topics for another blog. In the meantime, if you’d like to learn more about how Essentium high speed extrusion can complement your injection molding manufacturing processes, check out this webinar in which one of our materials experts takes a deeper dive into the capabilities of AM for tool production, criteria for suitable material selection, and basic design considerations.

Essentium, Inc. provides industrial 3D printing solutions that are disrupting traditional manufacturing processes by bringing product strength and production speed together, at scale, with an open ecosystem and material set. Essentium manufactures and delivers innovative industrial 3D printers and materials enabling the world’s top manufacturers to bridge the gap between 3D printing and machining to embrace the future of additive manufacturing. Contact us today.