Discover how Autodesk Fusion helps you customize CNC post processors—from quick edits to advanced configurations—and test safely before production.

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Overview: Post processors in Fusion

Post processors convert CAM toolpath data into machine‑specific code (G‑code), ensuring your program runs correctly on a given CNC machine.

Autodesk Fusion provides an online library with hundreds of free post processors that you can install and customize as needed. You can browse and install posts from the Fusion Online Post Library, store them in your cloud or local library, and edit them using the Fusion Post Extension for Visual Studio Code.

For simple adjustments, Post Properties can be edited directly from the NC Program or Post dialog, while more advanced changes require modifying the post configuration file itself.

If additional customization is needed, paid services are available through the Post Services Marketplace, and new post requests can be submitted via the Post Processor IdeaStation. Any changes should always be verified using a simulator or a dry run before running the program on a live machine.

How do I find and intall a post processor in Fusion?

• Where to look: Open the Online Post Library, it contains the most up-to-date posts, including some machine-specific posts with tailored properties and functionality.
• Install options:
  • Install to your personal cloud library to access posts across devices.
  • Install locally if you prefer local files.
• Quick steps:
  • Search the online post library for your machine/controller
  • Click install and choose cloud or local
  • Open Fusion and confirm the post appears in your post library

How do I edit a post processor in Fusion?

Most post processor customizations fall into two categories: simple configuration changes and advanced code modifications.

For quick adjustments, Fusion allows you to modify Post Properties directly from the NC Program or Post Process dialog. For machine-specific behavior changes, you’ll need to edit the post processor file itself using the Fusion Post Extension for Visual Studio Code.

Before making changes, always create a backup of the original post and validate any modifications using simulation or a dry run before sending code to a machine.

Editing a post processor: Step-by-step

Step 1: Locate and install the post processor

Start by finding the post processor that matches your machine controller in the Autodesk Online Post Library.

You can install posts directly into your cloud library to access them across multiple devices or save them locally on your workstation.

Step 2: Open the post processor in Visual Studio Code

Install Visual Studio Code and the Fusion Post Extension, then open the post processor’s CPS file.

The extension helps navigate large post files by providing code navigation, syntax highlighting, NC code previews, and easier access to editable sections.

Step 3: Make a small change first

When learning to edit posts, start with a low-risk change before modifying machine behavior.

Common beginner edits include:

• Customizing header comments
• Modifying footer information
• Adjusting formatting options
• Enabling supported post properties
• Exposing optional machine settings

Example: Modifying program header output

Many shops customize the information displayed at the top of every NC file.

For example:

JavaScript

1 writeComment(“PART: ” + programName);

2 writeComment(“SETUP: ” + currentSection.workOffset);

3 writeComment(“MACHINE: Haas VF-2”);Show more lines

While the exact implementation varies by post processor, modifications like these can help operators identify jobs more quickly on the shop floor.

Step 4: Generate test NC code

After saving the post, create a simple toolpath and run the post processor.

Compare the output against code generated by the original post to verify that the expected changes appear correctly.

Pay close attention to:

• Tool calls
• Work offsets
• Spindle commands
• Rotary motions
• Program headers and footers

Step 5: Validate before production

Never assume a modified post is production-ready.

Run the output through:

• Machine simulation
• NC code verification software
• Dry runs on the machine
• Air cuts when appropriate

Even simple edits should be validated before machining production parts.

Example: Modifying program header output in a post processor

Many first-time post processor edits involve changing the information output at the top of a CNC program.

For example, a shop may want to automatically include:

• Program number
• Part name
• Setup name
• Programmer name
• Machine name

A simplified example inside a post processor might look like:

JavaScript

Example: Modifying Program Header Output in a Post Processor

Many first-time post processor edits involve changing the information output at the top of a CNC program.

For example, a shop may want to automatically include:

• Program number
• Part name
• Setup name
• Programmer name
• Machine name

A simplified example inside a post processor might look like:

JavaScript

1 writeComment(“PART: ” + programName);

2 writeComment(“SETUP: ” + currentSection.workOffset);

3 writeComment(“MACHINE: Haas VF-2”);Show more lines

The exact implementation varies by post processor, but the general workflow is the same:

1. Open the post in Visual Studio Code.
2. Locate the section responsible for program header output.
3. Modify the desired text or variables.
4. Save the post.
5. Post-process a test program.
6. Verify the generated NC code.

Quick comparison: Post processor edit methods in Fusion

Common post processor customizations

The most common post processor edits typically focus on output formatting, machine-specific functionality, or workflow standardization.

If your goal is simply to modify output formatting or enable existing options, Post Properties are often the fastest and safest approach. More advanced machine behavior changes typically require direct CPS file modifications.

Can I enable 4th and 5th axes in a post?

• Many posts in the Online Post Library already support 4th- and 5th-axis code, but those axes are often disabled by default.
• Options to enable:
  • Often you can enable additional axes via Post Properties (simple toggle when available).
  • Some posts require edits to the configuration file itself to expose or map the additional axes.
• Guidance: See the written guide to enabling 4th and 5th axes for details on axis properties and examples. As always, proceed with caution and test thoroughly.

What are post properties and when should I use them?

• Post properties let you make many common “edits” without opening the post file.
• Where to find them: NC program or post dialog inside Fusion.
• Typical uses:
  • Change header/footer text in the output file
  • Enable or disable certain flags or axes (when supported)
  • Adjust feedrate or spindle formatting options exposed as properties
• Benefits:
  • No need to edit code
  • Reversible and low risk
  • Faster for quick configuration changes

Security, safety, and best practices

• Always validate edited posts in simulation or a safe dry run before executing on a machine.
• Keep backups of original posts and version your edits.
• Limit access to modified posts if they could affect production workflows.
• If in doubt, use the Post Services Marketplace to obtain professionally validated post customizations.

Ready to start editing your own posts? Download a free 30-day trial of Fusion and visit the Online Post Library to find posts and get started.

Autodesk Fusion post processor frequently asked questions (FAQs)