How to convert CATIA axis system changes into Settable User Frames for Siemens 840D

The following document outlines the procedure for generating Siemens 840D settable user frames from a regular axis system change in CATIA.

Normally, when an axis system change is set in CATIA, the resulting aptsource will only contain a series of commented-out lines which define the axis system transformation matrix.

For example:



    $$ Machining Axis Change.1


    $$ -0.93624 0.00000 0.35137 1755.92334


    $$ 0.34719 -0.15375 0.92511 1741.31883


    $$ 0.05402 0.98811 0.14394 475.88750

For Siemens 840D controls, this information is required to be passed to the NC program as a settable user frame.

For the example above, the user frame definition will be:












With CAM-POST, this can be handled quite easily using the following two steps:

1. The first step is to modify the CATIA PPTable. Change the START_NC_COMMAND sequence to the following:


*START_NC_COMMAND                                                     NC_MACHINING_AXIS

With the new PPTable loaded, the previously commented-out lines in the aptsource will be replaced by the following command:

MSYS / -0.93624, 0.00000, 0.35137, 1755.92334,$
0.34719, -0.15375, 0.92511, 1741.31883,$
0.05402, 0.98811, 0.14394, 475.88750

2. The second step consists in changing the post-processor by adding a User-Defined Syntax macro on the word MSYS. This macro will capture the 12 parameters of the MSYS command and generate the required $P_UIFR codes.

This macro will include logic to calculate the three rotation angles. If required, ICAM Technologies can provide you the actual contents of the macro so you can add it to your post-processor.

Benefit to User
Learn how to modify the CATIA PPTable in order to generate information that can be used by the post.

For more information or comments, please do not hesitate to contact Phil at