The second edition of AP238 is formally known as STEP Part 238: Application Protocol for Model-based Integrated Manufacturing, commonly referred to as STEP-NC. The standard was published as ISO 10303-238:2020(E). The title was updated to indicate the interaction between AP242 and AP238 for model-based design and manufacturing.

Programming Notes

The AP238 second edition schema 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 distinguish between the two editions if needed.

RoseDesign * d;

stplib_put_schema (d, stplib_schema_ap238e2);

switch (stplib_get_schema(d)) {
case stplib_schema_ap238e2:
    // ap238 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

AP238 first edition was published in 2007 and predated AP242e1 (2014) and AP242e2 (2020). The largest change in AP238 second edition is the addition of the nine hundred new definitions originally introduced by AP242 for semantic tolerances and PMI, kinematics, tesselated models, scan data models, additive setup, high-level process plans, and new types of hole features.

AP238 second edition also adds a few other new EXPRESS entities to support ARM concepts that were identified during production testing. These include assigning machining fixtures to a process, more efficient toolpath representation for high-speed machining, additive manufacturing operations, extended CAM descriptions, assigning machine tool models with kinematics to a process, capturing digital twins of actual or simulated machining.

There were also supertype changes to several EXPRESS entities to integrate with the AP242 process plan model, but the appearance of data in Part 21 files remains the same.

machining_process_executable (supertype change)
machining_rapid_movement (supertype change)
machining_touch_probing (supertype change)