3-D design differs from 2-D design in a pivotal way: in 2-D, drawings are the master documents that define how each part in a tool assembly should be made and illustrate how the product comes together.

Drawings may be made on a drafting board or, more commonly, with 2-D CAD systems. Today, models are the master with 3-D CAD.

Injection mold builders have employed a combination of 2-D and older-generation 3-D CAD/CAM systems since the 1980s, but they haven’t reached their potential speed, efficiency and productivity. Models used for milling mold core and cavity surfaces have typically consisted of 3-D wireframe and surface models. However, today’s new CAD systems, which employ solid models, generally perform better for complex milling because they eliminate confusing lines that should be hidden. This makes it easier to visualize tool positions or ensure that only the right material is being removed.

Meanwhile, many moldmakers who use 3-D CAD/CAM for milling still employ 2-D drawings for designing the complete mold-base assembly. Mold assemblies contain hundreds of parts, and computer workstations have traditionally lacked the power to model all of these effectively in three dimensions. Yet, when mold assemblies are represented in 2-D, mistakes in drawings or in their interpretation are common and costly. Companies must rework, or even scrap, incorrectly made molds or tools.