How to Generate Gerber Files from Mentor Expedition: The Complete PCB Engineer’s Guide

Mentor Expedition (now Siemens Xpedition) stands as one of the most powerful PCB design platforms in the industry. It handles complex high-speed designs, rigid-flex boards, and multi-board systems that would challenge lesser tools. But all that design sophistication means nothing if you can’t get clean manufacturing files out the door.

I’ve worked with Expedition on aerospace and medical device projects where fabrication requirements were unforgiving. Zero tolerance for errors. What I’ve learned is that Expedition’s manufacturing output system is incredibly flexible, but that flexibility comes with complexity. Understanding how to configure Gerber output correctly separates smooth production runs from frustrating rejection cycles.

This guide walks through the complete process of generating Gerber files from Mentor Expedition, from initial setup through verification. Whether you’re new to Expedition or looking to refine your existing workflow, you’ll find practical guidance that applies to real-world manufacturing scenarios.

Understanding Expedition’s Manufacturing Output Architecture

Before diving into step-by-step procedures, it’s worth understanding how Expedition approaches manufacturing output. This context helps you make better configuration decisions.

The Expedition CAM Flow

Expedition uses an integrated CAM (Computer-Aided Manufacturing) environment that’s more sophisticated than what you’ll find in mid-range PCB tools. Rather than simple “export” functions, Expedition provides a complete manufacturing preparation system including Gerber and drill output generation, design-for-manufacturing checks integrated into the output flow, panel and array creation capabilities, and output automation through job files.

The CAM output system pulls data from your design database and transforms it according to configurable rules. This means you have granular control over exactly what appears on each output layer, but you also need to configure those rules correctly.

Gerber Format Options in Expedition

Expedition supports multiple Gerber format variants. Extended Gerber RS-274X is the industry standard that embeds aperture definitions within the file. Gerber X2 is the enhanced format with layer-type metadata for automatic identification. X3 (Gerber Job) is the newest format that bundles layer files with job information.

For most fabricators, RS-274X remains the safest choice. It’s universally supported and well-understood by CAM operators worldwide. X2 offers advantages when your fabricator’s equipment supports it, but always confirm compatibility before switching formats.

Preparing Your Expedition Design for Gerber Generation

Manufacturing output quality depends heavily on design preparation. These verification steps catch issues before they become fabrication problems.

Design Verification Checklist

Run comprehensive design rule checks before generating any manufacturing files. In Expedition, access DRC through the Verify menu. Address all errors and carefully review warnings.

Critical checks include clearance violations between copper features, minimum feature size violations for traces and spaces, drill-to-copper spacing issues, acid trap detection, silk screen over pad violations, and net connectivity verification.

Don’t skip the warnings. What Expedition considers a warning might be a hard failure at your fabricator’s facility.

Layer Stackup Verification

Your layer stackup configuration directly affects Gerber output. Access stackup settings through Setup and then Cross Section. Verify that all layers are correctly defined with proper types (signal, plane, mixed), that layer pairing for drilling is accurate, that dielectric thicknesses match your fabrication specification, and that copper weights are correctly specified.

Stackup errors propagate through to manufacturing and can result in boards with incorrect impedance or structural problems.

Padstack and Via Audit

Review padstack definitions for manufacturing compliance. Expedition’s padstack editor provides detailed control over pad geometry, but this means incorrect definitions won’t be automatically corrected.

Check that minimum drill sizes meet fabricator capabilities (typically 0.2mm or larger), annular ring requirements are satisfied on all layers, thermal reliefs are properly defined for plane connections, and via-in-pad configurations are flagged if your process doesn’t support them.

Step-by-Step Process to Generate Gerber Files from Expedition

Now let’s walk through the actual Gerber generation process in Mentor Expedition.

Step 1: Accessing the CAM Output Environment

Open your design in Expedition PCB. Navigate to Output and then CAM Documents, or use the keyboard shortcut if configured in your environment. This launches the CAM Document Manager, your control center for all manufacturing outputs.

The CAM Document Manager displays existing output configurations and allows creation of new output documents. For a new design, you’ll typically start with a clean configuration or load a template from a previous project.

Step 2: Creating Output Document Definitions

Each manufacturing layer requires its own output document definition. Click “New” or “Add Document” to create a new output definition.

For a standard 6-layer board, you’ll need documents for Top Copper (Layer 1), Inner Layer 2 (signal or plane), Inner Layer 3 (signal or plane), Inner Layer 4 (signal or plane), Inner Layer 5 (signal or plane), Bottom Copper (Layer 6), Top Solder Mask, Bottom Solder Mask, Top Silkscreen, Bottom Silkscreen, Top Paste Mask, Bottom Paste Mask, Board Outline/Mechanical, and Drill outputs (typically multiple files).

Step 3: Configuring Gerber Output Parameters

Select a document and access its properties. The configuration dialog contains several critical sections.

For format settings, select Gerber RS-274X for maximum compatibility. Set units to match your design (inches or millimeters). Configure number format, which is typically 2:5 for imperial (inches with 5 decimal places) or 3:4 for metric. Set zero suppression to “Leading” for most fabricators. Choose “Absolute” coordinate mode unless specifically requested otherwise.

For layer content selection, choose which design layers contribute to this output. For copper layers, include the primary copper layer, relevant via layers, and any embedded component layers if applicable. For solder mask, select the mask layer corresponding to this board side. For silkscreen, select only the silk layer to avoid including unintended content.

For aperture handling, set aperture mode to “Automatic” for most applications. Expedition will generate appropriate apertures based on your design features. If your fabricator provides a specific aperture table, you can load it using the “Fixed” aperture mode.

Step 4: Configuring Film Settings

Film settings control how the output is generated. Set the plot origin, which is typically at the board origin (0,0). Configure any rotation if your fabricator requires specific orientation. Set mirroring options, which usually should be “None” for standard outputs (fabricators handle mirroring as needed). Define the film boundary, typically matching the board outline with appropriate margins.

Step 5: Defining Output File Names and Locations

Consistent file naming reduces fabrication errors. Configure meaningful output names for each document.

Layer Type	Recommended Name	Standard Extension
Top Copper	BoardName_Top	.GTL
Bottom Copper	BoardName_Bottom	.GBL
Inner Layer 2	BoardName_L2	.G2 or .GL2
Inner Layer 3	BoardName_L3	.G3 or .GL3
Inner Layer 4	BoardName_L4	.G4 or .GL4
Inner Layer 5	BoardName_L5	.G5 or .GL5
Top Solder Mask	BoardName_TSM	.GTS
Bottom Solder Mask	BoardName_BSM	.GBS
Top Silkscreen	BoardName_TSS	.GTO
Bottom Silkscreen	BoardName_BSS	.GBO
Top Paste	BoardName_TPM	.GTP
Bottom Paste	BoardName_BPM	.GBP
Board Outline	BoardName_Outline	.GKO or .GM1

Set the output directory to a dedicated manufacturing folder within your project structure. Keeping outputs organized simplifies revision management and fabricator communication.

Step 6: Generating the Gerber Files

With all documents configured, select the documents you want to generate. You can select individual documents or use “Select All” for batch generation.

Click “Generate” or “Run” to create the output files. Expedition processes each document and writes the corresponding Gerber files to your specified directory.

Monitor the output log for warnings or errors. Common issues include aperture generation warnings (usually informational), missing layer content warnings, and file write errors (typically permission-related).

Step 7: Creating NC Drill Outputs

Drill file generation follows a similar process but with drill-specific configuration.

Create a new document with type “NC Drill” or “Excellon Drill.” Configure drill parameters including units matching your Gerber outputs, coordinate format compatible with your Gerber number format, zero suppression matching your Gerber configuration, and tool ordering (typically ascending by size).

Expedition allows separation of drill outputs by type. For most designs, generate separate files for plated through-holes (PTH), non-plated through-holes (NPTH), and blind/buried vias if applicable.

The drill output includes a tool table header listing all drill sizes and their assigned tool numbers. Review this table for any unexpected drill sizes that might indicate design issues.

Advanced Gerber Generation Techniques in Expedition

Once you’ve mastered basic output generation, these advanced techniques improve efficiency and output quality.

Using Output Job Files

Expedition supports job files that automate output generation. A job file captures all your document configurations and can be executed with a single command.

To create a job file, configure all your CAM documents as described above. Save the configuration as a job file through File and then Save Job. For future designs with similar requirements, load the job file and modify only the design-specific parameters.

Job files are particularly valuable for organizations with standardized fabrication requirements. Create master job files for common board configurations (2-layer, 4-layer, 6-layer, etc.) and distribute them to your design team.

Embedded Component Considerations

For designs with embedded passive components, Gerber output requires additional configuration. Embedded component layers must be included in the appropriate copper layer outputs. Cavity information may require separate output documents. Your fabricator needs clear documentation of embedded component locations and specifications.

Work with your fabricator early in the design process to establish output requirements for embedded components. This technology is still specialized enough that standard output configurations may not apply.

Panel and Array Output

If you’re generating Gerber files for panelized production, Expedition offers several approaches. Design-level panelization means creating the panel in your Expedition design and outputting as a single “board.” CAM-level panelization means using Expedition’s CAM tools to create panels from single-board Gerber files. You can also defer to your fabricator and provide single-board Gerbers and letting them handle panelization.

For most prototype and low-volume production, letting the fabricator handle panelization is simplest. For high-volume production where you need specific panel layouts, handling it yourself provides more control.

Essential Gerber File Verification Steps

Never submit manufacturing files without independent verification. This step catches errors that are invisible within the source tool.

Using Expedition’s Built-in Viewer

Expedition includes viewing capabilities for generated outputs. After generation, use View and then Gerber Viewer to load and inspect your files. Check each layer individually for completeness. Overlay multiple layers to verify alignment. Compare drill output against copper layers.

External Gerber Viewer Verification

While Expedition’s viewer is useful, verification with an external tool provides an independent check. This catches any issues specific to Expedition’s output generation or viewing.

Recommended verification tools include GerbView from the KiCad project (free, handles Gerber and drill), ViewMate from Pentalogix (free, Windows-based with measurement tools), Ucamco Reference Gerber Viewer (free online, from the format maintainers), CAMtastic (included with Altium, but works standalone), and ZofzPCB (free, provides 3D visualization).

Critical Verification Points

During verification, systematically check layer-to-layer registration by overlaying copper layers to verify consistent alignment. Check drill-to-pad alignment to ensure every drill hit centers on its intended pad. Verify solder mask clearances to confirm adequate opening around all pads. Check the board outline to make sure it’s present and correctly defines the board boundary. Look for silkscreen violations to catch any text or graphics overlapping pad areas. Verify plane layers to confirm clearances and thermal reliefs appear correctly.

Manufacturing Package Completeness Checklist

Before submission, verify your manufacturing package includes all required files.

File Category	Typical Count	Critical Notes
Copper Gerbers	One per copper layer	All signal and plane layers
Solder Mask Gerbers	2 (top and bottom)	Verify polarity with fab
Silkscreen Gerbers	1-2 (top required, bottom optional)	Check for pad overlap
Paste Mask Gerbers	2 (top and bottom)	Required for SMT assembly
Drill Files	2+ (PTH, NPTH minimum)	Separate by hole type
Board Outline	1	Include any internal cutouts
Readme/Specification	1	Stackup, finish, special requirements
Pick and Place	1 (for assembly)	Component centroids
Bill of Materials	1 (for assembly)	Complete BOM with reference designators

Troubleshooting Common Expedition Gerber Issues

Even experienced engineers encounter output problems. Here are solutions to frequently occurring issues.

Missing Features in Output

When expected features don’t appear in Gerber files, check layer assignments in the CAM document configuration. Verify that the feature exists on the expected layer in your design. Check class/subclass filtering if configured. Look for conditional layer rules that might exclude the feature.

Aperture Flash Failures

If complex pads appear as outlines rather than filled shapes, check for pads exceeding the maximum aperture size (if fixed apertures are used). Verify that automatic aperture generation is enabled. Consider simplifying complex pad shapes that can’t be represented as single apertures.

Drill File Coordinate Mismatch

When drill holes don’t align with Gerber artwork, ensure identical origin points for both output types. Verify matching units between Gerber and drill configurations. Check for offset settings that might differ between outputs. Confirm number format consistency.

Incorrect Plane Layer Output

For power and ground plane issues, verify plane layer type assignment in the cross section. Check for correct negative/positive polarity settings. Ensure anti-pad and thermal relief definitions are correct. Look for isolated copper regions that might indicate connectivity issues.

Large or Corrupted Output Files

If output files are unexpectedly large or won’t load in viewers, check for excessive polygon vertices that could simplify. Verify arc interpolation settings. Look for data precision settings creating unnecessary detail. Ensure the design doesn’t contain corrupted geometry.

Best Practices for Expedition Manufacturing Output

These practices, developed over years of production experience, improve reliability and reduce manufacturing issues.

Template and Standards Management

Create standardized output templates for your organization. Document standard naming conventions. Establish standard format configurations (units, precision, zero suppression). Create templates for common board configurations. Review and update templates when fabricator requirements change.

Revision Control

Implement clear revision tracking for manufacturing outputs. Include revision identifiers in output directory names. Maintain a log of changes between output revisions. Archive previous output sets for reference. Consider integrating with your PLM/PDM system if available.

Fabricator Communication

Build relationships with your fabricators’ CAM departments. Obtain their preferred file format specifications. Ask about any special requirements or capabilities. Request feedback on output quality. Establish direct contacts for technical questions.

Useful Resources for Expedition Users

These resources provide additional support for Expedition manufacturing output.

For official documentation, Siemens Support Center at support.sw.siemens.com provides access to Xpedition documentation. The Xpedition CAM User Guide contains detailed output configuration information. The Siemens Knowledge Base includes technical articles on output issues.

For Gerber format references, Ucamco maintains the official Gerber format specification at ucamco.com/gerber. This includes RS-274X, X2, and X3 format documentation.

For verification and viewing tools, ViewMate is available at pentalogix.com, GerbView is part of the KiCad suite at kicad.org, and the Ucamco Online Gerber Viewer is at gerber-viewer.ucamco.com.

For community and peer support, the Siemens Xpedition community forum is accessible through Support Center. EDAboard.com hosts Mentor/Siemens tool discussions. The PCB Design subreddit at r/PrintedCircuitBoard includes Expedition users.

For training and learning, Siemens offers official Xpedition training courses. LinkedIn Learning includes courses covering Expedition workflows. YouTube contains tutorials on specific Expedition features.

Frequently Asked Questions

What Gerber format should I use when exporting from Expedition?

For maximum compatibility with PCB fabricators worldwide, use Gerber RS-274X (Extended Gerber). This format embeds aperture definitions directly in each file and is supported by virtually all fabrication equipment. Gerber X2 offers advantages like automatic layer identification, but verify your fabricator supports it before switching. When in doubt, ask your fabricator what format they prefer.

How do I generate separate drill files for plated and non-plated holes in Expedition?

In the CAM Document Manager, create two separate NC Drill output documents. For each document, use the hole type filter in the properties dialog to include only plated through-holes in one document and only non-plated holes in the other. Name the files descriptively (such as “BoardName_PTH.drl” and “BoardName_NPTH.drl”) so fabricators can easily distinguish them. This separation is important because plated and non-plated holes require different manufacturing processes.

Why do my inner plane layers look incorrect in the Gerber viewer?

Inner plane layers often appear confusing because of polarity settings. Plane layers are typically output as “negative” polarity, meaning the Gerber file shows copper removal (clearances and thermal reliefs) rather than copper presence. Some viewers display negative layers with inverted colors. Check your CAM document polarity settings, then verify your viewer is interpreting the polarity correctly. When overlaying with other layers, the clearances should align with pads and vias.

Can I automate Gerber generation for multiple designs with similar configurations?

Yes, Expedition supports job files that capture your complete CAM configuration. Create and configure all your CAM documents once, then save the configuration as a job file. For future designs with similar layer structures, load the job file and it will apply all your output definitions automatically. You may need to verify layer assignments if the new design has different layer names, but format settings and naming conventions carry over. This is especially valuable for organizations with standardized board configurations.

What additional files should I include with Gerber outputs for a complete manufacturing package?

Beyond Gerber and drill files, include a fabrication specification document detailing board thickness, copper weight, surface finish, solder mask color, and any special requirements. Include a layer stackup drawing or table showing layer order and materials. For impedance-controlled designs, provide the impedance specification with target values and tolerances. If ordering assembly services, include pick-and-place centroid data and a complete bill of materials with manufacturer part numbers. A readme file summarizing the package contents helps fabricators navigate your submission.

Conclusion

Generating Gerber files from Mentor Expedition requires more initial configuration than simpler PCB tools, but the result is precise control over your manufacturing outputs. The investment in proper setup pays dividends through reliable production and fewer fabrication issues.

Start with thorough design verification. Configure each output document carefully, paying attention to layer content, format settings, and file naming. Generate your outputs and verify them in an external viewer before submission. Build templates from successful configurations to streamline future projects.

The complexity of Expedition reflects the complexity of modern PCB designs. High-density interconnect, embedded components, rigid-flex constructions—these technologies demand sophisticated design tools and equally sophisticated manufacturing output capabilities. Master the output process, and you’ll confidently move even your most complex designs from concept to production.

When issues arise, and they will occasionally, approach them systematically. Check configuration settings, verify layer assignments, and compare against known-good outputs from previous projects. The Expedition user community and Siemens support resources can help with unusual problems.

Your design work deserves manufacturing files that accurately represent it. Take the time to configure Expedition’s CAM system correctly, and you’ll consistently deliver fabrication packages that work on the first submission.