A fixed external gripper can take a workpiece from a robot in KUKA Sim Pro without being mounted on that robot. Add grasping behavior with the Grasp Action Wizard, connect the robot output to the generated GraspSignal, and align the gripper’s GraspContainer link with its TCP/detection frame. Incorrect container-link placement can let the signal execute while leaving the workpiece suspended in space.
Supported Grasping Mechanism
The Grasp Action Wizard adds robot-like grasp and release behavior to an independent component. It is intended for simple actuators or devices created with the IO Control Wizard and does not require the gripper to be connected mechanically to a robot. The wizard requires access to the Modelling tab in a Professional or Premium installation.
| Element | Function | Required relationship |
|---|---|---|
GraspSignal |
Triggers the external gripper’s grasp action | Connect it to an output from the robot or controller |
| TCP/detection frame | Defines the detection location used to find a workpiece | Place it at the gripping pads or vacuum surface |
GraspContainer |
Attaches the detected workpiece using the container grasp behavior | Align its link position with the TCP/detection frame |
| IO-controlled joint | Moves or rotates the external gripper after capture | Configure it separately with the IO Control Wizard |
Choose the Container Behavior
A static GraspContainer retains the captured part’s location relative to its parent hierarchy. It does not prevent the external gripper from moving the part. If the container belongs to a node attached to a rotating link, the captured part follows that link when the joint rotates.
Use a dynamic container such as OneWayPath only when path behavior is required. A path can retain a part offset, although its default behavior snaps the part to the interpolated path. The path must remain under the moving gripper link if the part must follow that link.
Configure the External Gripper
- Model the fixed gripper component, including any link and joint used to rotate or translate its pads.
- Run the Grasp Action Wizard on the gripper and assign the TCP/detection frame at the physical gripping location.
- Move the
GraspContainerlink to the TCP/detection-frame position. Merely placing the workpiece close to the frame does not correct a displaced container link. - Connect a robot or controller output to the gripper’s
GraspSignal. Command the output when the robot has placed the workpiece inside the detection volume. - Use the IO Control Wizard to assign signals to the gripper joint when the captured part must rotate or move with the external mechanism.
If parts can arrive at different pad positions, program the robot to place each part at a detectable location or enlarge the detection volume enough to find the part from the configured TCP frame. Confirm that the enlarged volume does not select an unintended component.
Coordinate the Robot Handoff
A supported handoff sequence is: the robot grasps a part from the conveyor, moves it into the external gripper’s detection region, and then triggers the external gripper’s grasp action. The external gripper can rotate its axis while holding the part. The robot subsequently executes its own grasp action to recover the part, then executes its release action when placing the part on the conveyor.
Attach a robot base frame such as BASE_1 to the external gripper when robot motions to and from the gripper must follow different gripper configurations. Reference that base frame in the associated robot motions.
Diagnose Failed Grasping and Version Mismatch
| Observed condition | Evidence-supported cause | Corrective action |
|---|---|---|
| The pads rotate but the cube remains suspended | The GraspContainer link is not positioned at the TCP/detection frame, or the part is outside the detection volume |
Align the container link with the frame, place the part inside the detection region, and trigger GraspSignal again |
| The grasp works, but pad-to-pad placement varies | The robot placement and detection region do not cover the required locations | Teach the placement locations or adjust the detection volume while checking for unintended detections |
| “Component or layout file is newer than application.” | The layout was created in a newer Visual Components environment than KUKA Sim Pro 3.1 | Use a layout compatible with KUKA Sim Pro 3.1.2 or rebuild the program and components in that version |
| The Job Map is empty after opening a layout | The imported program contains Visual Components statements rather than KRL/KUKA statements | Exchange the robot for the appropriate KUKA eCatalog robot and recreate the program in the Job Map using KUKA-compatible statement types |
In the documented KUKA Sim Pro 3.1.2 conversion, exchanging the robot for one from the KUKA eCatalog supplied RCS and additional properties while preserving tool-frame, base-frame, and signal mappings. The motion program still had to be recreated because the statement types differed.
Verify the Completed Model
- Move the robot-held workpiece into the external gripper’s TCP/detection region.
- Set the connected robot output and confirm that
GraspSignalexecutes the external grasp action. - Move or rotate the external gripper joint and confirm that the workpiece follows the gripper link instead of remaining in world space.
- Return the robot to the handoff position, execute the robot grasp action, and confirm that it can retrieve the part.
- Run the entire sequence repeatedly and check that frame references, detection, attachment, joint motion, and final placement remain consistent.
FAQ
Why does my KUKA Sim external gripper rotate without moving the part?
The external gripper has not attached the part, commonly because the GraspContainer link is displaced from the TCP/detection frame. Align the link with that frame, place the part within the detection volume, and trigger GraspSignal.
Can a static GraspContainer move a captured component?
Yes. The captured component retains its location relative to the container and follows the parent node; if that node is attached to a rotating gripper link, the component rotates with it.
Why is the Job Map empty when I open a layout in KUKA Sim Pro 3.1.2?
A layout created with Visual Components statements can open without a usable KRL/KUKA program. Exchange the robot for the appropriate KUKA eCatalog robot if required, then recreate the program in the Job Map with KUKA-compatible statements.
