The wait function in KUKA robot programming is crucial. It enables the robot to pause during instruction execution. For example, WAIT SEC(x), where x represents the waiting time in seconds. It is used to ensure precise timing of robot actions, such as in welding operations.
- Overview
The waiting function in KUKA robot programming instructions is usually used to control the signal and time of the robot when performing tasks. The relevant instructions are:
WAIT FOR-a waiting function related to the signal.
WAIT-a waiting function related to time, the control system waits at this position in the program according to the input time. - The concept of computer advance
Computer advance is an important concept in the KUKA robot system, which is to read the motion statement in advance (invisible to the operator) so that the control system can design the trajectory when there is a trajectory approach instruction. But it is not only the advance motion data that is processed, but also the mathematical and peripheral control instructions. Some instructions will trigger a advance stop, including instructions that affect peripherals, such as OUT instructions (gripper closed, welding clamp open). If the advance pointer is paused, trajectory approach cannot be performed. - WAIT and WAIT FOR
The waiting function in the motion program can be easily programmed through an online table. In this case, the waiting function is divided into a time-related waiting function and a signal-related waiting function.
3.1 WAIT
Setting a time-dependent wait function allows the robot’s movement to be paused for a programmed time. However, WAIT always triggers a pre-advance stop.
3.2 WAIT FOR
Setting a signal-dependent wait function allows multiple signals (up to 12) to be logically connected if necessary. If a logical connection is added, columns for additional signals and other logical connections appear in the online table. - Logical connections
Logical connections are used when applying signal-dependent wait functions. Logical connections can be used to combine queries for different signals or states, e.g. to define dependencies or exclude specific states. A function with a logical operator always results in a logical value, i.e. it always gives “true” (value 1) or “false” (value 0) in the end.
The operators for logical connection include:
NOT: This operator is used for negation, i.e., the value is reversed (from “true” to “false”)
AND: The result of this expression is true when the two connected expressions are true
OR: The result of this expression is true when at least one of the two connected expressions is true
EXOR: The result of this expression is true when the expressions connected by this operator have different logical values.
- Processing with and without pre-feed (CONT)
The signal-related waiting function can be programmed in processing with or without pre-feed. No pre-feed means that the movement will stop at a certain point in any case and the signal will be detected there, that is, the point cannot be approached by trajectory.
The waiting function programmed with pre-feed and related to the signal allows the trajectory to be approached at the point created before the instruction line. However, the current position of the pre-feed pointer is not unique, so the exact time of signal detection cannot be clearly determined. In addition, signal changes cannot be recognized after signal detection.
- Operation steps for programming the waiting function
Position the cursor on the line where the logical instruction should be inserted.
Select the menu sequence “Command”, “Logic”, “WAIT FOR” or “WAIT”.
Set the parameters in the online table.
Click “Command OK” to save the settings.