CHICAGO—HP Inc., the largest maker of personal computers, unveiled its Metal Jet printer at the IMTS show here on Monday. Early customers include the engineering firm GKN Plc, which expects to print millions of production-grade Metal Jet parts for customers as early as next year.

Since its split from Hewlett Packard Enterprise Co., HP has redoubled efforts to expand beyond its core PC and paper printer businesses. 3D printing is a big part of this plan. The new steel-printing machine could open up new opportunities in the automotive, industrial and medical-equipment fields. Metal parts manufacturer Parmatech Corp. has also signed on as a partner.