Standard enables data flow between CNC, CAD/CAM
Troy, NY—To remedy the fact that NC programming has remained the only function in the design-to-manufacturing process that didn't use full-fidelity 3-D information, on, the official ISO STEP (STandard for the Exchange of Product model data) number for the STEP-NC standard, AP-238, was recently introduced.
Troy, NY— Developed 40 years ago, the ISO 6983/RS274D language for computerized numerical control (CNC) programs was designed in an era when paper tape was the most popular medium for moving data between computers. Back then, the logic necessary to process simple commands was barely affordable for a CNC machine. Until now, even though the average microprocessor can easily process 3-D data, NC programming remained the only function in the design-to-manufacturing process that didn't use full-fidelity 3-D information.
To remedy this situation, AP-238, the official ISO STEP (STandard for the Exchange of Product model data) number for the STEP-NC standard, was recently introduced. In AP-238, the information required to control a machine is linked to the information created by CAD and CAM systems to create an independent, fully documented CNC control file. This will make developing a CNC part program more efficient because the machining instructions can be defined more concisely.
CNCs can also use this richer information to optimize and check a part program for the tooling available at manufacturing time, instead of having it fixed during planning. An AP-238 data set describes all that the shop floor needs to know about the product and the process, including all the required tolerances, so drawings will no longer be required on the shop floor.
The activity model and information requirements behind AP-238 have been standardized separately as ISO 14649. These models were originally developed by a joint European and Japanese project. The first model they produced was for the data necessary to control milling machines. The leading developers of the milling model represented Siemens; Aachen and Stuttgart universities in Germany; Komatsu and Fanuc in Japan; and Heidenhein in Switzerland.
AP-238's draft international standard is now available on the TC184-SC4 documents Web site as wg3n1534, and will soon be circulated by the various national standards organizations. For those without access to the SC4 site, it can viewed at ftp://ftp.steptools.com/private/ap238/ap238_dis_package.zip .
Control Engineering Daily News Desk
David Greenfield, editorial director