Fixing the Gripper Missaligment Issue

Today’s development session focused on resolving a persistent issue in the pick-and-place station: the gripper was consistently picking up lids at a slight angle, which caused misalignments during placement. Despite multiple attempts to correct the collision zones, joint constraints, and signal timing in Siemens NX, the issue persisted.

However, considering the physical characteristics of the real system, where the gripper's end is flexible and can adjust to the surface of a tilted lid, I devised a new solution tailored for the simulation environment. Instead of trying to perfect the virtual grip dynamics, I repositioned the lid feeding slide so that lids are now presented in a more favourable orientation. With this modification, the gripper now consistently picks up lids horizontally and places them accurately on the workpieces, effectively replicating the real-world behaviour, just by simulating the outcome differently.

Improving Dismantling Station

With this issue resolved, I was able to progress on the Dismantling Station. I began by adding a new sensor to check whether a workpiece queued for recycling has a lid attached. Depending on the presence or absence of a lid, two separate sequences are now triggered: one for recycling complete workpieces with lids and another for those without. This conditional branching works seamlessly and reflects a more realistic dismantling logic.

To further optimise flow, I also implemented a stopper mechanism that releases workpieces only when the dismantling station is available. This small change has a significant impact — it prevents pile-ups, reduces unnecessary waiting time, and ensures smoother transitions between modules.

Smart Sorting Station enhancement

Encouraged by the success of conditional logic at the dismantling station, I applied the same principle to the sorting station. Now, before any colour detection occurs, the system checks whether the workpiece has a lid. If it does, the workpiece proceeds to the sensor for colour detection and is sorted to the correct slide. If not, it is immediately redirected to the dismantling station for recycling. This improvement ensures that only complete, correctly assembled workpieces are counted towards the user’s order, while incomplete ones are efficiently removed from the workflow.

// -------------------- LID Detection --------------------

// check if workpiece has lid - if YES, follow sequence, if NOT - send to dismantle station

21:

        IF "SORT_SENSOR_LID" THEN

            #Step := 30;

        ELSIF NOT "SORT_SENSOR_LID" THEN

            #Step := 300;

        END_IF;

Conclusion

Overall, significant progress was made in improving both the pick-and-place functionality and the dismantling workflow. By rethinking component placement and simulating real-life flexibility, the gripper issue was effectively resolved, enhancing lid alignment during placement. Similarly, dual-sequence logic in both the dismantling and sorting stations has improved process flexibility and accuracy.

While the system now operates reliably, some minor adjustments to sensor placement and position control values may still be required to improve detection precision and reduce false triggers. These refinements do not critically affect the simulation but contribute to a more stable and responsive digital twin environment.