Stratasys Ltd. said Friday that it will buy certain assets of Interfacial Solutions, a plastics supplier based in River Falls, Wis., and its third acquisition of the week.

Interfacial Solutions provides thermoplastics research and development and production services and has been a supplier to Stratasys for three years.

Terms of the deal weren't disclosed.

The move came after Strata­sys announced Wednesday that it will buy two 3-D printing service firms that have more than 480 workers, mainly in California and Texas.

The purchases represent a broader direction for the Eden Prairie-based manufacturer. Its previous major purchases were of companies that, like itself, were hardware companies making 3-D printers. In 2012, Stratasys bought Israel-based Objet, a maker of commercial-grade 3-D printers, and last June it bought New York-based MakerBot, maker of consumer versions of 3-D printers.

Interfacial Solutions' thermoplastics include the systems and meltable material that are used in 3-D printers to form or duplicate objects. Taking instructions from software, 3-D printers disperse the heated plastic material into shapes that harden when they cool. A growing number of companies use 3-D printers to make prototypes of products or components. And some consumers use them in home workshops.

Stratasys CEO David Reis said Interfacial Solutions' research expertise and products will make Stratasys more vertically integrated and strengthen its own product development and manufacturing. "We expect to accelerate new materials development allowing us to introduce new products to the market faster," Reis said.

The deal is expected to close by the end of June.

On Friday, shares in Strata­sys fell 2.6 percent amid a broad sell-off in tech-related stocks. Stratasys shares were up 4.7 percent on the week.

In the other deals this week, Stratasys said it will pay about $295 million for Solid Concepts in Valencia, Calif., and an undisclosed sum for the smaller Harvest Technologies in Belton, Texas. Some Wall Street analysts estimated it was paying about $60 million for Harvest Technologies.

Those two acquisitions will greatly expand Stratasys' contract manufacturing business and will help it capture more medical and aerospace ­business, company officials said.

While Stratasys specializes in making commercial 3-D printers and does some 3-D contract manufacturing, Solid Concepts is the nation's largest 3-D printing contract manufacturer. It will add about $65 million to Stratasys' nearly $500 million in annual revenue.

The California company builds proto­types and production parts for its clients, from metal as well as the plastic parts most associated with 3-D printers.

Dee DePass • 612-673-7725