By Alwyn Scott SEATTLE (Reuters) - Boeing Co has hired a small company to make about 600 3D-printed parts for its Starliner space taxis, meaning key components in the United States manned space program are being built with additive manufacturing. The company, privately held Oxford Performance Materials, will announce a $10 million strategic investment from advanced materials company Hexcel Corp as early as Friday, adding to $15 million Hexcel invested in May and lifting Hexcel's equity stake to 16.1 percent, Oxford and Hexcel said.