Sigma Tool & Molding Inc. is an Erie, Pennsylvania, tool-and-die shop that builds complex core-and-cavity plastic injection molds for domestic and offshore production. Its in-house capabilities extend from mold design and repair to laser welding, polishing, and engraving, with hot-half manifold repair standing out as a specialty the company says many competitors do not offer. Sigma also supports customers with prototype 3D-printed parts and ongoing service after a tool enters production.