STEP Export-Import Support in Altium NEXUS

Altium NEXUS offers advanced capabilities for interacting with mechanical design systems and software (MCAD) through the active exchange of physical design data. The range of systems and interfaces that bridge the ECAD-MCAD domains also rely on standardized data formats such as the industry ratified STEP protocol (Standard for Exchange of Product model data), which provides an information-rich, clear text encoded file format for 3D model design data.

The STEP file format itself (*.step or *.stp) is defined in the ISO 10303-21 (International Organization for Standardization) specification for CAD data exchange and is supported by the majority of MCAD tools and systems. At the fundamental file exchange level, Altium NEXUS offers both export and import capabilities for 3D STEP files.

This provides the basis for the free exchange of high-quality, standardized 3D modeling data between software domains, which simplifies ECAD-MCAD design collaboration and enhances both the quality and accuracy of 3D model data. Note that both the STEP AP214 and the legacy AP203 formats are supported by Altium NEXUS – exported files are ISO-10303-21 -compliant (AP214).

► See the the ISO 10303-21 specification web page.
► Read information on the STEP file format.

Export STEP files

An important function in the data exchange relationship between the ECAD and MCAD worlds is the ability to port the PCB assembly into mechanical design software for the purposes of physical clearance checking. This is particularly crucial where the design is intimately matched with a product enclosure that also exposes PCB peripherals such as controls, switches, connectors, and displays.

In this case, the inherent universality and accuracy of the STEP file format allows comprehensive PCB modeling data to be transferred from Altium NEXUS to MCAD software with a high degree of confidence in the dimensional relationships. The MCAD designer can then import and place the PCB assembly 3D STEP model into the mechanical design to check and/or modify accordingly.

Enabling the Exporter

This board export capability is available through Altium NEXUS’s STEP Export feature, which also includes a broad range of data and object filtering options.

If not already enabled, the STEP exporter checkbox should be selected in the Configure Platform page in Altium NEXUS’s Extension & Update view. For access to the view, click the user button () at the top right of the application and select Extensions and Updates, then the  button under the view’s Installed tab.

If not enabled during Altium NEXUS's installation, the STEP Exporter can be activated from the Importers\Exporters page in Extensions & Updates.

Using the Exporter

To export the currently active board design as a STEP file, select File » Export » STEP 3D from the main menus, then nominate a target file name and location. The following Export Options dialog provides a range of selections that include options to determine which board objects will be included in the generated file.

Exported STEP files displayed in a MCAD application, where the upper image file includes no pad holes or 3D bodies and the lower image file includes all objects.

► See the Export Options dialog for more information on STEP file export settings.

Notes on Exported files

• If the Export Selected options (3D Bodies and Pad Holes) have been enabled in the Export Options dialog but no objects are currently selected in the PCB editor, then the generated STEP files will not include any of those object types.

• A STEP file may also be exported as part of an Altium NEXUS Output Job, by adding an Export STEP generator to the Export Outputs category in a project OutJob. See the Export Options dialog for the settings that apply to this export method.

• When the Export as Single Part option is selected, the generated STEP model will be saved as a single part, rather than an assembly of component models. This simplifies the exported STEP model but prevents individual components from being selected in the receiving MCAD application.

• STEP files generated by the Export 3D feature position the model graphic relative to the origin point in the source PCB design. The software used to import that file may or may not respond to the included location instruction – if the imported model is not displayed, it may be off screen at the current zoom level.
• If you do not have access to mechanical drawing/viewing software, the exported STEP file can be checked by importing it back into a placed 3D Body object in Altium NEXUS.

Save from the IPC Component Wizard

The automated IPC Compliant Footprint Wizard, which creates an IPC-compliant footprint in the PCB Library editor, provides the additional option of saving (and previewing) the generated footprint model as a 3D STEP file. The STEP based model can be embedded in the generated IPC-compliant footprint and also saved as a *.step file in a nominated location, where the latter option will allow the 3D model to be reused or distributed as needed.

The IPC Component Wizard is launched from the PCB Library editor (Tools » IPC Compliant Footprint Wizard) and the STEP export option enabled in the wizard’s penultimate Footprint Destination page. The generated STEP file model will accurately match the component dimensions that have been entered in the wizard.

Along with the option to generate and embed a STEP model for the component, the wizard also allows this to be saved as a STEP 3D model file.

Import STEP files

STEP files can be imported and used in Altium NEXUS through two distinct approaches, both of which use the same mechanism. The approach used is essentially dependent on how a STEP file will be applied in a design:

• A STEP file that represents mechanical elements of the final product design, such as an enclosure generated by an MCAD application, is generally imported into the PCB layout.
• A STEP file that represents a 3D component body (downloaded from the internet or created locally) is generally imported into a PCB Library component.

Import into the PCB

Within both the PCB and PCB Library domains in Altium NEXUS, STEP files are imported into a dedicated 3D Body object that is placed and aligned as required.

To place a 3D Body and populate its contents in the PCB Editor, select Place » 3D Body from the main menu, create its object shape and choose the Generic option as the 3D Model Type in the Properties panel. The Souce section in the panel will then offer three alternative source options for importing a STEP file:

1. Vault – Browse to a connected Altium managed content server and select a 3D model file revision. Altium NEXUS detects if this file is updated.
2. Embed Model – Browse and load a suitable file from disk. The model data is stored (embedded) in the PCB file.
3. Link to Model – Select a Model file from a folder registered in the Choose Model dialog – typically, the file might be shared with an MCAD designer. This file will be linked to the 3D Body, so any file updates made in the MCAD domain will be detected by Altium NEXUS when the file is opened.
   

► See 3D Body Properties for more information on the 3D Body object options.

The placed 3D Body (including its imported/linked STEP file) will appear as a simple body area in the editor's 2D display mode, and as a fully rendered 3D model in the 3D display mode (shortcut keys 2 and 3).

One of the most important STEP files that can be brought into the PCB space is a 3D model of the design’s host enclosure. Typically developed and then exported from the MCAD domain, the imported enclosure model can be placed and precisely aligned in the board design to check for clearance violations and accuracy.

In the image below, the design’s 3D enclosure model has been imported into the PCB as an embedded model. The imported model’s positioning and snap reference points are configured in the 3D Body mode of the Properties panel.

The 3D Body mode of the Properties panel.

Import into a Component

Using the same mechanism outlined above, a 3D STEP model file can be imported into a component footprint definition to provide a fully rendered 3D component body for that component. The STEP model can replace, or co-exist with, an existing 3D component body constructed from simple 3D shapes (Extruded, Cylinder, Sphere).

A 3D STEP file model is applied to a component footprint in an Altium NEXUS PCB Library by selecting Place » 3D Body from the main menu then choosing the Generic option for the 3D Model Type in the Properties panel. The STEP model is then loaded into the 3D Body using the Vault or Embedded import option as detailed above. Note that the File linking option is not available in the PCB Library editor.

Alternatively, to replace an existing 3D Body shape applied to a footprint (such as a Cylinder, for example), simply select its 3D Body object and load the STEP file using the Generic 3D Model option – this type of change is easiest to perform with the editor in 3D display mode.

A polarized capacitor footprint shown in the PCB Library editor. The center image is the 3D body made from 3D Shapes, while the right image shows its replacement STEP file model.

► See Including a 3D Model of the Component for more information on placing 3D footprint models.
► See 3D Content Central and component manufacturer websites for access to downloadable STEP models.