Underscoring interest by big companies in the technology. : Porsche and the venture capital arms of Microsoft msft and Siemens have invested $30 million in 3-D printing startup Markforged, highlighting how big companies are betting that the emerging technology will transform manufacturing. Although initial excitement over 3D printing has cooled recently with slower than expected sales to consumers, manufacturers appear to be interested in using the technology to more quickly build custom prototypes. With the new investment, Markforged has raised $57 million in total funding.