More Widely Adopting the 3D Printing of Injection Molds
Full-service design and mold delivery, moldmaking materials and a low-cost, high-precision printer minimize the technical risk of 3D-printed mold tryout.
Bob Zollo is a founder and CEO of Avante Technology, which focuses on educating and assisting companies seeking to incorporate desktop fused deposition modeling (FDM) 3D printing as part of their work process. Zollo has developed 3D printing materials, technology and design guidelines specifically for 3D-printed injection molds. His experiences led him to developments and insights on 3D-printed moldmaking:
Design. Zollo believes that the next major obstacle to broader adoption of 3D-printed molds is overcoming the lack of know-how in designing these molds. He says that printed plastic molds differ from metal molds in their surface energy, mechanical strength and heat conductance. He says, for example, “Increase the draft of internal pins and structures to ensure smooth movement between mold halves. If 3 percent draft was specified in the CAD drawing for metal molds, revise this to 4 to 5 percent for printed plastic molds.” Holes should be printed slightly smaller in diameter, so they can be postprocessed to smooth the interior. Other examples of principles that need to be learned and applied include how to adapt the infill and outer layer print strategy to optimize mechanical strength.
Zollo believes that the next major obstacle to broader adoption of 3D-printed molds is overcoming the lack of know-how in designing these molds.
Materials. “Engineers designing a part usually begin with mechanical and other physical characteristics and then select material based on these requirements. For me, it seemed logical to start with the mechanical and chemical properties required to create high-performance parts and molds, and formulate the material to meet these requirements,” Zollo says. After coming to this realization, he began to focus on developing materials for finely extruded parts. He went back to the lab and worked with a few of his previously developed materials and discovered that some of the compounds worked well for 3D printing. The result of Zollo’s R&D was a carbon nanotube reinforced, high-performance composite filament for plastic composite molds. This composite material can handle the required stress and is resilient in the molding process. “It also possesses low surface energy (like Teflon), which means the injected material comes in and just glides over the surface,” Zollo says.
The 3D printer. When Zollo tested printing precision molds and parts on a range of open-source printers, he was not satisfied with the precision, reliability and quality of any third-party printers. So, he and CTO Ron Aldrich set out to develop a proprietary high-precision desktop printer. The approach was to develop and optimize a printer for the material, not the other way around.
“Our high-precision 3D printer looks like a conventional FDM printer,” Zollo says. Several subtle features enable precision printing, like the 25-point measurement of the entire print bed before each print job to create a 3D profile of any deviation in flatness, an ARM Cortex processor-based controller board and proprietary printer driver controls of the stepper motors. The STL file-slicing engine software has also been customized to deliver more consistent plastic flow for a denser, smoother finish. When Zollo tested printing molds in his lab, he was surprised to learn that his printed molds could easily support 100+ cycles, depending on the design of the mold and the material being molded.
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