STEP vs IGES — 모던 vs 레거시 CAD 교환

STEP (ISO 10303) is a modern (1994 onward, AP214 in 1998, AP242 in 2014) standard with explicit support for product data: assemblies, hierarchy, materials, color, kinematic, GD&T, PMI annotations. IGES (Initial Graphics Exchange Specification, ANSI Y14.26M, last updated 1996 as IGES 5.3) is older and primarily geometry-only — surfaces, curves, points, with limited support for assemblies and metadata. STEP is actively maintained; IGES is frozen. STEP is the modern default, IGES is the legacy fallback when STEP isn't supported.

Two reasons. First, legacy CAD systems (some industrial CNC machines, older CAM software, very old CATIA versions) still only read IGES. Second, IGES tolerates ambiguity better — when CAD systems disagree on geometry interpretation, IGES sometimes succeeds where STEP fails because IGES has fewer strict rules. For new work, always export STEP. For sending data to a customer with a 1990s-vintage CAD system or specific aerospace defense workflows, IGES may be the only working option. The conversion is one-way: STEP-to-IGES loses metadata, IGES-to-STEP recovers nothing that wasn't there.

STEP, especially STEP AP242. AP242 includes PMI (Product Manufacturing Information): GD&T tolerances, surface finish callouts, weld symbols, datum identifiers — the same engineering metadata that appears on a 2D drawing. Aerospace and automotive workflows leverage AP242 to ship 'drawingless' designs where all manufacturing intent is in the 3D model. IGES has no equivalent — annotations are at best loose text labels with no machine-readable semantics. For modern design intent transfer, STEP AP242 is the standard.

STEP files are typically 20-40% smaller than equivalent IGES files for the same geometry, partly because STEP's data structure is more efficient and partly because STEP allows compression-friendly representations. For a typical mechanical part, STEP is 1-5 MB vs IGES at 1.5-7 MB. For large assemblies (thousands of parts), STEP's hierarchical assembly structure means even bigger savings — IGES has to flatten everything into a single file. Both formats are ASCII (human-readable) by default, which inflates size 3-5× compared to a binary equivalent. STEP has a binary variant (Part 28, XML-based) but it's rarely used in practice.

MakerSuite 3D currently uses occt-import-js (OpenCASCADE WebAssembly build) which supports STEP natively but not IGES out of the box. To view IGES in our viewer, convert it to STEP first using FreeCAD (File > Open .iges, then File > Export .step) or any CAD with IGES read + STEP write capability. The conversion is lossless for geometry. For mechanical CAD work, exporting STEP from your design tool directly is recommended — avoid IGES as an intermediate format because it loses metadata that other workflows depend on.