With the Distribution Station logic completed, I shifted focus to finalising the Pick and Place Station—the following essential link in the automated assembly line. This station is responsible for picking up the lid workpiece and accurately placing it onto a base part that was delivered earlier.

The logic for this station was developed using TIA Portal (SCL), and all mechanical behaviour was modelled and tested within Siemens NX MCD. Overall, the system works well, though I encountered an unexpected challenge with gripper orientation during lid pickup.

Pick and Place Station

I started by adjusting and verifying all sensors and position control elements in Siemens NX, ensuring accurate detection and actuator feedback during the simulation. I then created all required control signals for this station, which included movement, suction, and gripper handling.

For logic handling, I created a dedicated SCL block within TIA Portal for the Pick and Place Station, along with its own data block to keep the variables organised and isolated. The modular structure I’ve been following makes it easy to manage each station independently.

The Pick and Place station features a vertical suction head mounted on a horizontally actuated slider. It also includes:

• Suction cup with gripping and release signals.

• Slider mechanism to move the suction head in and out.

• A stopper is used to hold the base workpiece in place temporarily.
  Sensors to track:

• Suction cup up/down

• Slider extended/retracted

• Workpiece presence

• Lightgate for part departure

The lid workpieces are delivered at a slight angle on a slide. This introduced a complication: when the suction head engages, the lid is picked up at an angle, whereas a flat pickup is ideal. This angle affects the precision of lid placement.

TIA Portal Programming Overview

The station logic is handled with a step-based CASE structure. Each stage handles specific movements, checks, or delays.

Step 0 – Initialisation

The system resets timers and actuators:

• Starts conveyors.

• Positions the slider and suction head.

• Resets gripper state.

Step 10 – Workpiece Detection

When the Workpiece reaches the stopper, and the system is idle, the suction cup lowers into position.

Step 20 – Grip

If the suction cup is down and the workpiece is still in place, the gripper engages:

"PICK_Gripper_GRIP" := TRUE;

A short delay ensures a solid grip. 

Step 30 – Lift

Once the delay finishes, the cup retracts vertically.

Step 40 – Extend Slider

If workpiece still detected and suction cup retracted the slider extends into position above the base.

Step 50 – Drop for Placement

The cup lowers down to place the lid on the base. The position is monitored by sensors and delay timers.

Step 60 – Release Lid

The gripper releases the lid:

"PICK_Gripper_GRIP" := FALSE;

"PICK_Gripper_Release" := TRUE;

Step 70 to 100 – Reset

The suction cup retracts, the slider moves back, and the stopper opens allowing the finished part to leave the station.

Conclusion

The Pick and Place Station logic is now nearly complete, and the gripper mechanism has been successfully implemented after initial issues. With all major motions, actuators, and sensors functioning as expected, only minor refinements like lid orientation remain. Solving this will bring the station to full operational status within the digital twin environment.