Mastercam Post Processor Editing

A Post Processor is a translator. Mastercam speaks an internal, generic language called NCI (Numerical Control Intermediate). Your Haas, DMG MORI, or Mazak speaks a unique dialect of Fanuc, Heidenhain, or Siemens.

The Post takes the NCI data (e.g., "cut a 0.5" hole at X1.0 Y1.0") and converts it into a line of G-code specific to your machine.

Example translation:

If the Post is wrong, the G-code is dangerous. mastercam post processor editing

Most users don't need to build a post from scratch. They need to modify 20% of the file to handle 80% of their daily annoyances. The most common edits fall into five categories:

Let's walk through how to edit these.

In the world of Computer-Aided Manufacturing (CAM), Mastercam holds a throne. It allows machinists and engineers to create complex toolpaths with a few mouse clicks. However, the toolpath inside Mastercam is just a ghost. It is a theoretical set of instructions that exists purely in the digital realm. A Post Processor is a translator

To make that ghost cut metal, you need a translator. That translator is the Post Processor.

Out of the box, Mastercam comes with generic post processors (MPFAN, MPLFAN, etc.). These are fantastic for general use, but they are precisely that: generic. If you run a Haas VF-2 with a 4th axis rotary, a laser cutter, a waterjet, or a Okuma Multus B-axis lathe, the generic post will fail. It might output the wrong G-code, ignore your coolant commands, or, worst of all, crash your spindle.

This is why Mastercam Post Processor Editing is the single most valuable skill for a serious CAM programmer. This article will serve as your deep-dive guide into understanding, editing, and mastering the .pst and .psb files that drive your shop. If the Post is wrong, the G-code is dangerous

Let’s solve specific shop-floor problems.

Some shops fall into the trap of "post editing as a workflow." If you are:

…don’t edit the PST. Use Mastercam’s Control Definitions or a Miscellaneous Operation (Misc Op) instead. If every part is different, the post is the wrong place for that logic.