Proto Labs is using existing injection molding machinery to cost effectively add overmolding to its prototyping and short-run production offerings.
The company uses a pick-and-place overmolding process to mold the substrate in one injection press, then move the substrate to a second injection press which molds a second, elastomeric layer onto it. The process capitalizes on Proto Labs' proprietary digital manufacturing approach to accomplish the overmolding job, explained Proto Labs global product manager Becky Cater in an email.
“The overmolding process has typically required a large financial investment, leading it to only be viable for very high volume applications,” Cater stated. “Our cost-effective, quick-turn overmolding service provides engineers and designers with a low-risk way to experiment with, and design-in, overmolding in a range of products.”
Proto Labs cited its work with liquid silicone rubber for overmolding when it announced the new capability Sept. 12 and has featured it at the International Manufacturing Technology Show in Chicago, Sept. 12-17.
Cater said her firm is offering LSR as well as thermoplastic elastomers for customers' product development. LSR, although more expensive, provides better chemical and high temperature resistance than TPEs, Cater said. LSR also maintains elastomeric properties at very low temperatures and has inherent lubricity. TPEs have become a key overmolding material for parts needing a soft touch or an additional color. Proto Labs is based in Maple Plain, Minn. In addition to its U.S. manufacturing sites, it operates plants in Europe and Japan.
Cater said bonding compatibility with the substrate resin is important when choosing the overmold polymer. With LSR, designers also need to pay special attention to thermal compatibility because LSR typically is molded at 300 to 400° F, a temperature range that can deform TPEs.
TPEs and LSR give equally quick turnaround times — 15 or fewer business days, according to Proto Labs.
Proto Labs builds all its molds in-house to ensure control from design to part finishing. The company usually uses aluminum for molds geared to prototyping and short runs.
“This is a game-changer,” Proto Labs CEO Vicki Holt said in a news release.
Proto Labs' United Kingdom office will be at K 2016 in Düsseldorf, Germany, next month, Hall 11/D59.