Arthur B. Sims has been elected chairman...

Arthur B. Sims has been elected chairman and chief executive of 3D Systems, a Valencia maker of machines that combine a laser, computer and chemicals to rapidly produce models that are used as prototypes by manufacturers.

Sims, the former president of Quadratron Systems Inc., was also named chief executive of 3D’s parent, 3-D Systems Inc., a Canadian-based holding company. Sims succeeded Robert B. Fletcher, who served in the posts on a temporary basis. Fletcher remains chairman of the holding company.