Rapid prototyping with solid free-form fabrication (SFF) is a key innovation that makes it possible to rapidly produce physical parts directly from a CAD model. Recent research focuses on SFF systems which directly fabricate metal parts. This paper introduces the Stanford Solid Plotter (SSP), a new SFF system that forms prototypes using metal-deposition. Since many critical problems in metal deposition relate to heat transfer issues, the main focus of the paper is on key aspects of the thermal behavior of the SSP part fabrication process, namely the deposition, freezing and cooling of a workpiece. Predictions from a finite difference heat transfer model are used to improve both the precision and strength of actual workpieces made with the SSP. Lab experiments using thermocouples confirm the behavior of the finite difference model.