James Magos has been appointed senior vice president of sales at LightPath Technologies Inc., an Orlando, Fla.-based manufacturer of precision-molded aspheric optics, fiber optic collimators, isolators and manufacturing technologies.   . . .   3D Systems Corp., of Valencia, Calif., announced that Brian K. Service has resigned as an officer and director of the board. He will continue to assist with various clients and transactions for two years. The company said the board has decided to put a long-term management team in place, and has named co-founder and CTO Charles W. Hull as interim CEO. Hull will continue to serve as CTO. Kevin M. McNamara has been named acting CFO, effective August 15. 3D Systems develops stereolithography apparatus systems and other machines to create 3-D manufacturing prototypes in a process called solid imaging (using a laser to cut successive layers from resin to form a physical model).