Inverse Time Feed Rate

In 4/5X machines, it is sometimes required to use the Inverse Time feed rate mode, which helps the controller maintain a constant feed rate at the cutting point, regardless of the axes moved and the distance between the cutting point and the rotation axis.

In order to use this mode, it is necessary to know the actual distance of each feed-rate cutting motion (linear or circular) and to divide the required feed rate by that length.

GPP2 provides two new variables to allow the EX2 program to use this mode whenever desired:

  MOTION_LENGTH     // actual length of motion

  INVERSE_TIME_FEED // value of MCH_FEED divided by motion length

GPP2 verifies that the value assigned to the INVERSE_TIME_FEED variable is never larger than the maximum value that can be formatted for output for the FEED format. This abnormal situation could happen if the motion length is extremely small.

Whenever the EX2 program needs to use the Inverse Time mode, it can simply output the value of INVERSE_TIME_FEED instead of MCH_FEED. The MOTION_LENGTH variable is not absolutely necessary, and is given mostly for reference.