Are 3D printed molds ready for prime time?

With the additive manufacturing (AM) or 3D printing process, there's almost nothing that can't be printed from human ears to end-use aircraft components thanks to an ever increasing range of materials, both polymers and metals. So what's been holding back the 3D printing of molds cores and cavities?

Primarily, cores and cavities for the injection molding process need to hold up under the heats and pressures of that environment. Additionally, the surface finish of 3D printed cores and cavities typically is not suitable for the parts and requires some finishing work. So, for years prototype parts have been built using the various 3D processes to evaluate the geometry, look and feel prior to a one- or two-cavity pilot mold being built in which to run actual pre-production parts.

That is changing however, with an announcement from Stratasys Ltd. with headquarters in Minneapolis, MN, and Rehovot, Israel, that Robert Seuffer, GmbH & Co. KG ( Seuffer), a German supplier of parts for household appliances and commercial vehicles, is using Stratasys 3D printing to manufacture cores and cavities to produce injection molded sample parts.

This may be a game-changer for mold manufacturers, whose customers typically require prototype parts to evaluate part design for performance and fit before making the production mold. Even the fastest machined cores and cavities for a "pilot" mold can take up to two weeks to make. That means the ability to dramatically streamline the tool creation process for producing these prototype parts is another concrete example of how Stratasys 3D printing is revolutionizing manufacturing.

 "Working with the automotive industry, sample parts need to be tested in the environment of moving mechanical parts as well as in high temperature environments," explained Andreas Buchholz, Head of R&D at Seuffer. "With Stratasys 3D printing, we can design first drafts of the injection mold within a few days and 3D print them in less than 24 hours for part evaluation. Traditionally, it would take eight weeks to manufacture the tool in metal using the conventional CNC process. And while the conventional tool costs us about 40,000 euros, the 3D printed tool is less than 1000 euros, a saving of 97%."

Using Stratasys 3D printing technology, Sueffer also produces 3D printed molds for its hot melt process. These molds, which are used to overmold low melting point polyamide over electronic circuit boards, are created with Stratasys' rigid, opaque Vero materials.

Rob Winkler, supervisor for FDM (Fused Deposition Modeling) applications for Stratasys, provided an interesting technical presentation at the SPE Thermoforming Conference in September. "Thermoforming is possible using an FDM-built tool with pressures up to 10,000 psi and for most sheet thicknesses," Winkler said. "FDM tooling success is dependent on forming pressures and those are dependent on the type of sheet being formed, the thickness, and the bend radii, draft and draw depth.

The most common material used that provides optimum tool life is ABS, which is also easiest to finish and bond. Polycarbonate is preferred for low-volume manufacturing, because it has a higher heat deflection temperature (HDT) and the sheet material doesn't stick to

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