What is CAM postprocessor ? SolidCAM as an example

In CNC manufacturing, efficiency depend on how well the CAM software communicates with the machine. In CAM software, this bridge is called a postprocessor — a critical piece of the workflow that transforms generic toolpaths into machine-ready NC code. In this blog post, we’ll explore what a postprocessor is, why it’s essential, and how it works in SolidCAM.

In this blog post, you’ll find

1. What is CAM postprocessor?

2. Why do you need a postprocessor?

3. How postprocessors work in SolidCAM?

4. Why a Quality Postprocessor Makes All the Difference

1. What is CAM postprocessor?

In CAM, a post-processor translates toolpaths generated by the CAM system into machine-specific G-code. It acts as a bridge between the CAM software and the CNC machine, converting the abstract toolpaths into a language the machine can understand and execute.

2. Why do you need a postprocessor?

In CAM software, we define various parameters directly on the 3D CAD model. Usually, we add multiple operations in which we define geometry, choose tools, and set machining parameters. After this, we generate toolpath data, which is machine-independent. Toolpath data does not depend on a specific machine — it contains only information about tool movements and machining parameters.

These general data must then be converted into NC code in order to run on the desired CNC machine. The input to the postprocessing stage is the general toolpath data, and the output is a NC file in the required format for a specific machine.

The structure of a postprocessor depends on the CNC controller type, the machine kinematics, the machine’s own configuration, and the preferences of each individual user.

The type of CNC controller has a major influence on the output format, command structure, and available functions. Some of the most common controllers in use today include Fanuc, Sinumerik, Haas, Heidenhain, etc. - each with its own syntax, supported cycles, and formatting rules.

Klartext Heidenhain Code

Machine kinematics must be precisely defined within the postprocessor. Examples of possible kinematics include:

• 3-axis milling

• 4-axis milling (table or head rotation)

• 5-axis head-head configuration

• 5-axis table-table configuration

• 5-axis head-table configuration

• Mill-turn machines

• Multi-tasking machines with sub-spindles

• ...

  
  

Even if we have the same machine model and controller, the postprocessor might not be fully compatible. Why? Because of differences in machine settings.

For example, with the Heidenhain controller’s CYCLE19 coordinate system transformation cycle, the behavior can vary. On one machine, calling CYCLE19 will also physically rotate the table, while on another it will only perform the coordinate system transformation, and the table rotation must be programmed in a separate block.

Another example is the metric vs. imperial measurement system. Even two identical machines with the same kinematics can be configured to work either in metric units or in imperial (inch) units. In the metric system, outputting coordinates to 3 decimal places is usually sufficient, while in the imperial system, 4 decimal places may be required for the same level of precision.

Furthermore, even if we have two identical machines with the same kinematics, the same controller, and the same machine settings, the postprocessor can still differ. The last variable is the output preferences of each user. For instance, one user might want the safe retract position to be at one set of coordinates, while another might prefer a different position, request different comment formats, customized tool lists, or specific header or footer structures in the NC program, etc.

Because of all these factors, there is no universal list of generic postprocessors that would satisfy all possible requirements.

3. How postprocessors work in SolidCAM?

In SolidCAM, postprocessors are built using an open and highly configurable architecture. They are typically composed of GPPL (Generic Post Processor Language) files, which define the logic and output structure, and VMID (Virtual Machine ID) files, which store machine-specific parameters such as kinematics, axis limits, and rotation points.

When a toolpath is generated, SolidCAM passes the machine-independent data to the postprocessor, which then applies the rules, formats, and sequences defined in the GPP and VMID files to produce the final NC program for the target CNC controller. Because of this open structure, postprocessors in SolidCAM can be extensively customized to match any combination of controller type, machine kinematics, and user-specific output preferences.

4. Why a Quality Postprocessor Makes All the Difference

There’s nothing worse than having to manually edit G-code every single time. Over time, a person gets used to it, develops a routine, and might even do it almost automatically — but that doesn’t mean they should get used to it. Every manual change is a potential error, a waste of time, and a sign that the communication between CAM and the machine isn’t fully optimized. A quality postprocessor eliminates this habit at its root, turning program generation into a consistent and reliable step without the need for post-run “patching” of the code.

The best postprocessor is one that produces G-code that never needs manual editing.

Conclusion

In practical terms, an effective postprocessor ensures that the generated G-code matches the machine’s configuration, control capabilities, and shop standards without requiring subsequent manual modifications. This alignment between CAM output and machine execution minimizes error potential, maintains process consistency, and improves overall production efficiency. With SolidCAM, an additional advantage is the open postprocessor structure, which allows end users to make their own adjustments if any specific requirements or changes arise.

If you require a custom postprocessor, feel free to contact us at info@campostprocessor.com or through the Postprocessor Request Form below.