# Limits of TRC

The TRC takes into account the current and two further relevant NC blocks to calculate interim blocks. "Relevant” here means: motion blocks in the selected main plane in which tool radius compensation takes place. "Non-relevant" would refer to techno blocks, time delays (G04) or path motions with one axis perpendicular to the main plane. If an interim block running in the opposite direction to the programmed contour is calculated within these three blocks, a contour violation is detected. The figure below shows an example of this.

If a bottleneck position is caused by one or more blocks which are more than 3 blocks away from current block, this contour violation is not detected by the TRC. The figure on the next page shows an example of this.

Example of detected contour violation
Example of undetected contour violation