STEP format

Standard for the Exchange of Product Data (STEP) is a ISO standard industrial automation systems product data representation and exchange format.

The file structure for a STEP file has a modular structure which makes it easier for developers to adapt the format to their own needs. The modules are called “classes” and are classified using numbers as follows:

11 to 13: Description methods: These classes describe the languages and methods that are used to create a STEP file. Right now, only two description method classes exit:
Part 11: The EXPRESS language reference manual.

Part 12: The EXPRESS-I language reference manual

The EXPRESS language is a data definition language that is used to represent the structure of data and any constraints that may apply to it. The information models contained in STEP Integrated Resources and Application Protocols are defined using EXPRESS.
21 to 26: Implementation methods: describe the correspondences between STEP and other formal languages. (text encoding, C++ binding, ...)
31 to 35: Conformity tests: used to check the degree of conformity of the software associated with the Application Protocol.
41 to 49: Integrated generic resources: the conceptual building blocks for STEP
101 to 106: Integrated application resources: contains the actual database, the building block of the file. divided into generic resources and Application resources
201 to 233: Application protocols: contain all the branch-specific classes.
301 to 332: Abstract test suites
501 to 518: Application interpreted constructs Descriptions methods

STEP Application protocols

+ 201: 2D explicit technical design
+ 202: 2D associative technical design
+ 203: configuration of mechanical parts and assemblies
+ 204: Brep 3D mechanical design
+ 205: Surface 3D mechanical design
+ 206: Wireframe 3D mechanical design
+ 207: Sheet Metal Die Planning
+ 208: Life Cycle Change Process
+ 209: Composite Structures
+ 210: PCA: Design & Manufacture
+ 211: Elect, Test, Diagnostics & Remfg
+ 212: Electrotechnical Plants
+ 213 : NC Process Plans
+ 214: Automotive design
+ 215: Ship Arrangement
+ 216: Ship Moulded Forms
+ 217: Ship Piping
+ 218: Ship Structures
+ 219: Inspection Process Plans
+ 220: PCA: Manufacturing Planning
+ 221: Functional Data & Schematic Rep. for Process Plants
+ 222: Design to Manufacturing for
Composite Structures
+ 223: Exchange of Design, and Manufacturing Product Information for Cast Parts
+ 224: Mechanical Products Definition for Process Planning Using Form Features
+ 225: Strctrl. Blg. Elements Using Explicit Shape Rep.
+ 226: Ship Mechanical Systems/Moulded Forms
+ 227: Plant Spatial Configuration
+ 228: Building Services: Heating, Ventilation, and AC
+ 229: Exchange of Design and Manufacturing Info for Forged Parts
+ 230: Building Structural Frame: Steelwork
+ 231: Process engineering Data: Proc Design & Proc Specs of Major Equipment
+ 232: Technical Data Packaging

Each AP has its own subset of entities specific for the industry branch the AP was developed for Alias (supports the AP203 and the AP214.)

Application protocol support for STEP formats

The geometric descriptions contained within ISO10303-203 and ISO10303-214 are identical and comprises the core of the implementation of the translator. The following table shows the mappings made by Alias.

STEP Entity	Alias Entity
Cartesian Point	Point
Line	B-spline Curve
Circle	B-spline Curve
Ellipse	B-spline Curve
Parabola	B-spline Curve
Hyperbola	B-spline Curve
PolyLine	B-spline Curve
Composite Curve	B-spline Curve (Grouped)
Trimmed Curve	B-spline Curve
B-spline Curve	B-spline Curve
Plane	B-spline Surface
Cylindrical Surface	B-spline Surface
Conical Surface	B-spline Surface
Spherical Surface	B-spline Surface
Toroidal Surface	B-spline Surface
Surface of Linear Extrusion	B-spline Surface
Surface of Revolution	B-spline Surface
B-spline Surface	B-spline Surface
Rectangular Trimmed Surface	Trimmed Surface
Curve Bounded Surface	Trimmed Surface
Offset Surface	B-spline Surface
Manifold Solid Brep	Shell (Closed)
Shell Based Surface Model	Shell (Open/Closed)

Pro/ENGINEER options for export and import

To make the import and export of IGES and STEP files easier for Alias to read.

In Pro/ENGINEER, select Utilities > Options
Add the following data to the configuration file.

IGES_OUT_ALL_SRFS_AS 128
IGES_OUT_SPL_CRVS_AS_126 YES
IGES_OUT_SPL_SRFS_AS_128 YES
IGES_OUT_MIL_D_28000 NO
IGES_OUT_TRM_SRFS_AS_143 NO
IGES_OUT_TRIM_CURVE_DEVIATION DEFAULT
INTF_OUT_BLANKED_ENTITIES NO
INTF3D_OUT_EXTEND_SURFACE YES
INTF3D_OUT_FORCE_SURF_NORMALS YES
IGES_IN_106_F2_AS_SPLINE NO
IGES_IN_DWG_LINE_FONT YES
IGES_IN_DWG_PNT_ENT YES
IGES_IN_DWG_COLOR YES 
FIX_BOUNDARIES_ON_IMPORT YES