In a nutshell, STEP defines a standard for CAD product design data including geometry, topology, tolerances, relationships, attributes, assemblies, configuration and more. STEP-NC is an extension of STEP that annotates product design information with manufacturing information such as tooling, stock, manufacturing features and process sequence.

The result is full fidelity 3-D design data or a “super model” that is ready for downstream production.

STEP-NC is an interface or data input standard for Computerized Numerical Control (CNC) systems. Using STEP-NC, an external system – such as a process planning system or an integrated CAD/CAM system – can create instructions for making a part on a machine tool and send those instructions (via DNC, LAN, WAN or the Internet) to a CNC milling machine containing an embedded CAM system. The manufacturing process is streamlined because STEP-NC defines data as “working steps,” which is a library of specific operations that might be performed on a CNC machine tool. The newly enabled machine tool can receive STEP-NC data, “understand” what it means, and begin milling the piece without any more instructions.

In contrast, today’s machine tools are driven by G and M codes, a 40-year-old language used to describe part programs for CNC controls. It was designed for an era when paper tape was the most popular medium for moving data between computers and the logic necessary to process simple commands was just about affordable for a CNC machine. Today, the average microprocessor can easily process 3-D data.

NC programming is the only function in the design-to-manufacturing process that is not using full fidelity 3-D information. As a result, CAM programmers go through a lengthy process to translate part geometry, generate toolpaths, determine feeds and speeds, and select tool sizes. In effect, they have to think for the machine tool, an extremely high-tech product driven by very low-tech codes. STEP-NC will ultimately make G and M codes obsolete, and more than 4,500 post processors will be eliminated in the process.