In the world of CNC machining, the conversation often revolves around spindle speeds, toolpaths, and cycle times. But for the programmer at the workstation—and the machinist on the shop floor—the unsung hero of productivity is the post processor.
When pairing Mastercam, one of the world’s most versatile CAM systems, with the Siemens 828D, one of the most feature-rich yet complex compact CNC controllers, the post processor isn't just a translator. It is the bridge between digital geometry and physical precision.
Here is why the Mastercam post for Siemens 828D has become a focal point for job shops and OEMs alike.
For advanced 5-axis machining, Siemens uses the TRAORI command to activate transformation. The post processor must calculate the tool vector (A, B, C or I, J, K) and output it correctly. siemens 828d post processor for mastercam
The 828D excels with local subprograms (LBL). A sophisticated post will output repeated features (bolthole patterns, pockets) as LBLxxx called with different zero offsets (G54, G55), rather than absolute reposted code. This reduces file size and allows on-machine edits.
Standard posts output long-hand G81, G83, etc. A proper 828D post converts these into Siemens CYCLE81 (Drilling), CYCLE83 (Deep hole pecking), and CYCLE84 (Tapping). This reduces line count from hundreds to a few lines and allows operators to edit parameters directly on the 828D panel.
You have three routes:
Before editing the post processor, the developer must identify the machine configuration:
Mastercam installs a generic "Siemens 840D" post by default. You can tweak this for the 828D.
.pst and .psb files using a text editor—advanced skill required.The turning center was meant for complex contours. In Mastercam, I used "Turning" cycles to rough out a shape. Siemens has a powerful command called CYCLE 95 (Turning Cycle), but it demands data in a very specific order. Bridging the Gap: The Critical Role of the
The standard Mastercam post wanted to output line-by-line G1 moves (point-to-point machining). While this works, it creates massive files and ignores the Siemens controller's ability to optimize feed rates on the fly. I wanted to use the controller's native cycles.
This required modifying the "Custom Cycles" section of the post. I had to map the Mastercam parameters—stock remaining, cutting depth, retract distance—into the Siemens format.
I remember staring at the logic:
CYCLE95( "Contour_Name", DP, DPP, ...) Kinematics: The Mastercam Machine Definition must match the
Mastercam didn't naturally name contours. I had to write a script in the post processor that would define the contour sub-routine before the cycle call. After three hours of debugging bracket errors and misplaced commas, the controller finally accepted the cycle. The machine roared to life, cutting steel in a smooth, rhythmic motion that looked just like the simulation.