The third edition of AP238, published in September 2022, maintains harmonization with AP242 third edition through shared use of the ISO 10303 resource parts collectively published as version nine of the STEP module and resource library. In particular, it contains several new entity definitions for model annotation leader lines.

This builds on the second edition, which harmonized with AP242 with new definitions for semantic tolerances, improved tesselated models and point cloud data, new types of hole features, many refinements identified during production testing, additive manufacturing support, extended CAM descriptions, kinematics for machine tool models, and digital twins of actual or simulated machining.

The first edition, which introduced the STEP-NC process descriptions, toolpaths, features, and technology for milling and turning. AP238 first edition was published in 2007 and predated AP242e1 (2014) and AP242e2 (2020) but was harmonized with the AP214 and AP203e2 definitions in use at that time.

Programming Notes

The schema name was updated after the first edition to indicate the link between AP242 and AP238 for model-based design and manufacturing. The second and third edition of AP238 is identified by the StplibSchemaType stplib_schema_ap238e2 enum, which matches the new "model-based" schema name. The stplib_schema_ap238 is still available to identify the older first edition name if needed.

RoseDesign * d;

stplib_put_schema (d, stplib_schema_ap238e2);

switch (stplib_get_schema(d)) {
case stplib_schema_ap238e2:
    // ap238 third or second edition

case stplib_schema_ap238:
    // ap238 first edition

The STEP-NC API is built on top of the EXPRESS library and provides higher-level operations to work with machining resources and concepts. There is also additional information on ap238.org and the STEP-NC area of the STEP Tools website.

Some recommended practice documents are available on the CAx-IF site for general STEP concepts and AP242 usage also applicable to AP238.

New Entity Definitions

The third edition adds the following new entity definitions for model annotation leader lines, and matches the other definitions provided by SMRL v9 and used in AP242 ed3.

The second edition added a number of new definitions to support machining process, as well as nine hundred new definitions introduced by all editions of AP242 for semantic tolerances and PMI, kinematics, tesselated models, scan data models, additive setup, high-level process plans, and new types of hole features.