PCS defines the origin and orientation of a part or component within an assembly. In STEP files, PCS is typically represented by an AXIS2_PLACEMENT_3D entity, which specifies the X, Y, and Z directions relative to the global coordinate system. This system ensures that each part maintains its intended position and orientation when imported into different CAD or CAM environments.
PCS is critical for modular assemblies and tool data exchange because it provides a stable reference for geometry, tolerances, and machining features. When exporting to DXF or STEP, PCS helps maintain consistency between design and manufacturing stages, reducing errors caused by misaligned components.