RAPID ROTARY UTILITY

This program converts G-code from G94 (units per minute feed rate mode) to G93 (Inverse time mode). The main difference between these two modes is that in G93, for every linear or arc move (G1, G2, or G3), that command must also specify how much time it should take to make that move. Using G93 is advantageous when a move has both linear and rotary components. The reason is that linear moves have units of distance while rotary moves are measured in degrees and many CAM software packages only specify feed rates in distance units. However, if you had a rotation move at the same time as a linear move, the controller (e.g., LinuxCNC) would move both axes at the same rate. For this reason, inverse time mode is used.

This application does not alter any of the positions in the G-code movement commands. Instead, it converts from G94 to G93 by calculating the distance the tool travels for each line and using the last feed rate specified to calculate the time it should take the tool to complete that movement. For rotary moves, the program uses the Z-axis position (as the radius value) to convert from rotational units (angles) to distance. This allows for constant tool tip feed rates even for complex geometries and results in slower A-axis rotations when machining larger diameter sections of a part and faster A-axis rotations when machining smaller diameter sections.

Typical Workflow

Features

Limitations