Editing Mastercam post processors (the files) is a powerful way to tailor G-code output to your specific CNC machine. While there isn't one "perfect" article, several high-quality resources and expert tips provide a comprehensive guide to the process. The Best Tool for Editing: Mastercam Code Expert Most pros agree that the Mastercam Code Expert is the best environment for editing posts. eMastercam.com Why use it: It includes built-in recognition for predefined variables and operators, color-coding them to help you avoid typos. How to access: File > Edit/Open external within Mastercam and select your eMastercam.com Essential Editing Tips from the Pros Always Backup First: Never edit your "live" post without a safety copy. Rename your working file (e.g., Post_v1_Edited.pst ) so you can always revert if the code breaks. Use the Post Debugger: To see exactly which line of the post processor is generating a specific line of G-code, enable the Post Debugger . In Mastercam, go to File > Configuration > Post Dialog Defaults and check "Enable post debugger". When you post code, click the ladybug icon to step through the logic. Check "Post Switches" First: Many common changes (like turning off tool pre-calls or changing G-code formats) are already built-in. Look at the top of the file for a "switches" table where you can simply change a to toggle features. Note Your Changes: Use a unique character (like a pound symbol or your initials) to mark every change you make. This makes it easy to search for your modifications later. Top Resource Links adding / editing tool comments - eMastercam.com Register now to participate in the forums, access the download area, buy Mastercam training materials, post processors and more. * eMastercam.com Opening a post for editing - eMastercam.com
Mastering the Art of Mastercam Post Processor Editing: From G-Code to Control Introduction: The Final Link in the CAM Chain In the world of CNC machining, Mastercam is the brains—the place where toolpaths are born from solid models. But the voice that speaks to your machine tool is not Mastercam itself; it is the Post Processor . The post processor is a translator. It converts the generic, neutral toolpath data (NCI - Numerical Control Interface) into the specific, dialect-heavy G-code that your Haas, DMG MORI, Mazak, or Fanuc control understands. Editing a post processor is not a luxury; it is a necessity for any shop that demands efficiency, safety, and customized output. A poorly edited post can crash a spindle. A masterfully edited post can shave seconds off every cycle and eliminate manual editing at the control. The Anatomy of a Mastercam Post (.PST and .PSB) Before editing, you must understand the files:
The .PST File (Post Text): This is the human-readable, editable text file containing the logic, variables, and string definitions. This is where 90% of your editing will occur. The .PSB File (Post Binary): This encrypted file contains proprietary logic from Mastercam or your machine builder. You cannot edit this directly. If you lose the .PSB, you lose the core functionality of advanced 5-axis or specialized posts.
Golden Rule: Always make a backup copy of your original .PST and .PSB before making any changes. mastercam post processor editing
Common Reasons to Edit a Post Processor
Formatting Output: Changing G21 (Metric) to G20 (Inch), or ensuring decimal points follow your shop standard (X1.5000 vs X1.5). Adding Safety Blocks: Forcing a G28 home reference, a G90 absolute positioning, or a tool length measure G43 H on every tool change. Custom Cycles: Modifying the output of drilling cycles (G81, G83) to include dwells ( P ), chip breaking, or custom M-codes. Coolant Control: Changing from flood M08 to through-spindle coolant M88 or mist M07 based on operation type. Renumbering: Customizing N-block numbering (e.g., N100, N200 instead of N1, N2). Eliminating Manual Edits: Removing the need for operators to delete or change lines at the machine.
The Core Editing Environment Do not use Notepad. It lacks syntax highlighting and line numbers. Use a proper code editor like Visual Studio Code , Notepad++ , or CIMCO Edit . The post language is a hybrid of MP Language (Mastercam’s proprietary scripting) and standard logic structures (if/else, while, switch). Key Sections to Edit 1. The Header (Machine Definition Variables) At the top of the .PST file, you will find critical switches: # General Output Settings progname$ : 1 # Use program name from Mastercam spaces$ : 0 # Add spaces between addresses (0=no, 1=yes) omitseq$ : yes # Omit sequence numbers? seqno$ : 2 # Start sequence number at N2 Editing Mastercam post processors (the files) is a
Example Edit: To force an imperial output, find fastmode$ and metrictool$ and set them appropriately. 2. The Start of File (SOF) Block – pheader$ and psof$ This is the most critical safety zone. This controls what appears before the first movement. Original: psof$ # Start of file for non-zero tool pbld, n$, "G00 G17 G40 G80 G90", e$
Edited (Adding a custom safe start): psof$ pbld, n$, "G20" (Inch mode) pbld, n$, "G90 G80 G40 G17" (Absolute, cancel canned cycle/cutter comp) pbld, n$, "G91 G28 Z0." (Send Z home) pbld, n$, "G90 G54" (First work offset) pbld, n$, "M01" (Optional stop for operator check) e$
3. Tool Change Routine – ptlchg$ and ptlchg0$ eMastercam
ptlchg$ : Called when a new tool is used. ptlchg0$ : Called when the same tool is used for a new operation (null tool change).
Common edit: Force a tool length measure on every tool change. ptlchg$ # Tool change pbld, n$, "M06", "T", t$, e$ pbld, n$, "G43", "H", t$, "Z0.1", "M08", e$ # Add H offset and coolant