Prototyping has always been considered the “main” use for 3D printing. Building a design quickly, without the need to invest time and money in tooling, allowed for significant decrease in product development times, and provided new opportunities to refine designs based on testing and user feedback before committing to production tooling.
Today concept models, functional prototypes, and other early-stage applications are still the heart of 3D printing, but as the material properties, productivity, and fidelity of 3D printing technology has improved, users are finding that there are huge gains to be realized by applying 3D printing to later stages of the manufacturing process. By integrating 3D printing into manufacturing at the tooling stage, manufacturers can get production lines started more quickly and operate them more efficiently – without any of the tradeoffs in capability that are still an unfortunate part of direct manufacturing with 3D printing.
The quintessential example is undoubtedly injection molding. Purely traditional injection molding tooling paths are a major reason for the adoption of 3D printing for prototypes – 3D printed plastic parts are now very commonly used to evaluate designs that will eventually be produced via injection mold for applications in every sector of industry. Until fairly recently this was effectively the full extent of 3D printing use in injection molding processes – once the design was locked in, the rest of the manufacturing process was business as usual. There was and is, of course, a lot of interest in using 3D printing for direct production of these parts, skipping the molding process entirely, but in most cases this has proven to involve significant tradeoffs in material properties and part finish – and for producing parts in volume, even the most cost-effective forms of 3D printing are much more expensive per-part than injection molding. As a result, the productivity gains from 3D printing in this process have been limited.
What has recently been proven to be viable, however, is the use of 3D printing in the development of the injection mold tool itself. The latest generation of 3D printing resins are now durable and heat-resistant enough to produce prototype mold tools that allow parts to be built with true production material and process, allowing manufactures like Bi-Link to get initial runs of parts off the line, whether in lieu of a steel mold or while the steel mold is beginning to be cut.
There are still some tradeoffs to this process – the polymer molds are less durable and thermally conductive than steel, so they wear out quickly (lasting for hundreds of parts instead of tens of thousands) and require longer cycle times for the polymer to solidify; for most cases this limits their application to the early stages of production, but they still provide both large decrease in lead times and an opportunity to make further revisions early in production at low cost.
Others are using 3D printed metal tools for injection molds, but the benefits are slightly different. Due to the rougher surface finish achieved by current metal printing systems, these tools generally need to be finished with a CNC machine before use, so the decrease in lead time is not as significant as with resin 3D printed tools. However, the geometric freedom they provide has benefits on the tail end – whereas the polymer tools hold heat and require longer cycle times, a metal printed tool can be designed with conformal channels in the tool, allowing manufacturers to significantly decrease cycle times compared to traditional tools by using hydraulic cooling. A manufacturer taking advantage of both technologies could potentially get their first production parts within 24 hours of finishing their design, using a 3D printed polymer tool, and then achieve higher productivity by replacing it with a 3D printed metal tool when it wears out.
Injection molding is only one of the processes where 3D printed molds can be used, however, and one of the most demanding at that. In other processes involving lower temperatures, such as hydroforming, or lower pressures, such as vacuum forming, 3D printed mold tools can replace traditionally manufactured tools without drawbacks – granting these processes a huge portion of the flexibility and rapidity of the 3D printing process itself. Invisalign, for example, uses a vacuum forming process in combination with 3D printed tools to produce their translucent dental aids – providing them with the flexibility to produce millions of individually customized tools without compromising on their production material or quality.
At 3D Fixtures, we’re convinced that 3D printing is every bit as valuable to the tooling stage of manufacturing as it is to the design stage.