# Backward movement with external position offsets (P-CHAN-00275)

Program execution with offset overlapping
Movement with forward/backward control with offsets

## Attention

An active kinematic transformation which is especially dynamically different depending on the position, may cause a dynamic overload (or an incomplete loading) of the axes.

Background: If a backward movement has an offset, a deviation is made from the original path. However, dynamic planning was executed with the original path motion in forward direction without offset.

P-CHAN-00275 | Backward movement with external position offsets
Description | The programmed path contour can be shifted by external online influences. Subsequent synchronisation can signal this position offset to the entire NC channel (see #CHANNEL INIT[CMDPOS]). This deletes the offset, i.e. an absolute programmed position then does not include an offset.

During forward/backward movement, external offsets are not moved backward like other motions defined in NC program. If there is backward movement on a program position with an external offset, there are two options:

1. A further backward movement is not allowed since the positions specified in the NC program must also be reached in the backward direction without offset.
2. The offset is retained and backward movement is allowed to continue. The current absolute positions defined in NC program are no longer valid since they are shifted by the currently valid offset.

These offsets may be caused by:

- Manual mode actions
- Shifting the contour with 'Jog of Path' (see [FCT-C15])
- Compensations executed online (see [FCT-C20]

Parameter | forward_backward.with_offset
Data type | BOOLEAN
Data range | 0: No backward movement is possible over the program position of an external offset. The backward movement storage is cleared automatically (as for a #BACKWARD STORAGE CLEAR). 1: A backward movement is possible beyond the program position of an external offset is possible. The active offset at the time of reversal is retained.
Dimension | ----
Default value | 0
Remarks | The backward movement is stopped when the following online influences occur: - Measurement with G100 - Homing with G74 - Deselection of Online Tool Compensation with #OTC OFF