NX Configuring a Post Builder Post to Output Inverse Time Feed Rate (FRN)

Inverse Time Feed Rate (FRN) is a CNC G-code option that converts linear feed rate into a value that accounts for rotary motion.The picture below shows this NC output. Notice that the linear feed rate F250 is output with the G94 command. FRN G93 is activated when the the C axis is rotated. How is this option enabled in a multi-axis Post Builder post?

Solution

1. Add the G-FEED block for G94-Feed Rate Mode to the Program and Tool Path -> Program -> Motion -> Linear Move event and the Circular Move event.  If this G_feed command is not available from the Post Builder pull down menu then go to Program & Tool Path -> Word Sequencing and toggle on the G94 block.

2. On the Program and Tool Path -> Program -> Machine Control -> Feedrates -> Feedrate Modes menu set Rotary Only and Linear and Rotary to FRN. Verify that the Minimum and Maximum feed rate values that are specified are correct. This is especially true of the DPM. If the DPM Maximum value is too small than the FRN values will be too small also.

3. Import the pb_cmd_feeds_and_speeds_utils.tcl Custom Command, select only the PB_CMD_force_FRN_F_code file and add this as the first block of the Linear Move event.

4. If it is found that the FRN F values that are output are too small than edit the PB_CMD_FEEDRATE_NUMBER Custom Command and alter the set mom_sys_frn_factor 1.0 to a higher value.

5. If it is found that the feed values that are output are not consistent then import the Custom Command pb_cmd_fix_frn.tcl noting the installation directions. This command only pertains to posts created in older versions of Post Builder.

Notes and References

Please be aware that any code provided by GTAC is intended to be used for sample purposes only. It is the user's responsibility to determine whether the code is suitable for the purpose.

Hardware/Software Configuration

Platform: all
OS: n/a
OS Version: n/a
Product: NX
Application: CAM
Version: V1915
Function: POSTBUILDER

Ref: 002-8014860