S TEP NC AND I NTERNET M ANUFACTURING

(Steve Krar, Consultant – Kelmar Associates)

Fig. 10-8-1 STEP NC can change the way products are manufactured throughout the world. (Modern Machine Shop)

STEP-NC, a process under development since 1984, has the potential for dramatically changing the way products are manufactured in the world, Fig. 10-8-1. STEP-NC is a worldwide standard, developed by the International Standards Organization (ISO), to extend STEP (Standard for the Exchange of Product) model data, so that it can be used to define data for NC (numerical control) machine tools. STEP became a full ISO standard in 1994, and since then all leaing CAD software vendors, have implemented STEP data translation into their products. It has drawn the interest and support of the Department of Energy, Boeing, Lockheed Martin, General Electric, General Motors, and Daimler-Chrysler.

WHAT IS STEP?

STEP is an extensible, comprehensive, international data standard, for product data created by an international team of more than 200 product data experts. It is designed to give an explicit, and complete representation of product data throughout its entire life cycle. There has always been a mismatch between the lifetime of software systems, and the information they produce. To see this clearly, look at the number of outdated word-processing files in any computer. This problem is greatly magnified when comparing technical, design, and engineering software files. CAD and analysis systems change every two to three years, while technical prints and manufacturing plans for things such as aircraft, ships, and building must be kept for 30 to 50 years.

Working Steps

With the development of STEP NC, what’s happening is not simply the reshaping of CNC; it is the reshaping of manufacturing. In the vision that is emerging, the CNCmachine tool will be more important than ever. STEP-NC changes the way manufacturing is done, by defining data as working steps: a library of specific operations that might be performed on a CNCmachine tool, Fig. 10-8-2. In other words, it breaks down every machining operation into the steps required to perform the operation. In the past CNC machine tools had to be programmed using G and M codes, which were instructions that only told the machine what moves to make, without any details that referred to the part being processed. STEP-NC will make G and M codes obsolete.

Fig. 10-8-2 STEP defines data as working steps, a library of operations performed on a CNCmachine tool. (STEP Tools, Inc.)

Most numerically controlled machine tools are programmed using a language called RS274. This language, almost 40 years old, restricts the range of information that can be communicated to the machine tool controller. STEP-NC (ISO 14649) will replace RS274 with a rich data format, which integrates the manufacturing process plan, with the manufacturing features and geometry that were used to derive that process plan. Raising the level of the controller in this way, will allow both upstream and downstream applications to manage product data, in ways that are more intelligent and efficient.