Reliable Capping and Decapping – One Tube at a Time

Automated opening and closing of screw-capped laboratory tubes with controlled torque.

Automated Capping and Decapping of Laboratory Tubes and Vials

Opening and closing screw-capped laboratory tubes is required in many laboratory workflows. Whether caps need to be removed for subsequent process steps, tubes must be weighed without caps, liquids are dispensed into closed vials, or open vessels need to be sealed with new caps, reliable capping and decapping operations are essential.

Providing open tubes manually for downstream processes such as pipetting is time-consuming and labor-intensive. In particular, the consistent closing of tubes and vials with defined torque is critical to ensure proper storage and safe transport conditions.

Combining temporary opening for process execution—such as weighing or liquid filling—with immediate re-capping offers significant advantages. This approach improves process stability, cleanliness and product protection while also enhancing operator safety and reducing risks related to evaporation or contamination.

How Automated Screw Capping and Decapping Works

Coordinated Multi-Axis Tube Handling

For screw capping and decapping operations, the Lab-Bot transports the tube or vial to the multifunction unit. There, the tube body is clamped securely between three rollers. These motor-driven rollers rotate the tube body while the screw cap is held stationary by the gripper arm. This relative motion enables controlled opening and closing of screw caps.

Minor height differences between tube and cap threads are compensated by a controlled movement of the vertical axis (Z-axis). The clamping force applied by the three rollers can be precisely adjusted to match the specific tube type, ensuring secure fixation without deformation. In addition, the torque applied during capping is finely adjustable, allowing tubes and vials to be closed with a defined and reproducible closing torque.

Any irregularities during the screwing process, such as thread misalignment or abnormal torque behavior, are reliably detected by the control system. In such cases, the process is stopped automatically to prevent damage or incorrect sealing.

All motor parameters, torque limits and positional values required for screw capping and decapping are predefined and stored within the corresponding vessel definition file. This ensures consistent process execution and reproducible results across different tube types and applications.

Cap Handling and Storage

Temporary Cap Storage

The multifunction unit includes an integrated cap storage area located within its protective enclosure. During decapping operations, screw caps can be temporarily placed in this dedicated holder, for example when tubes are opened for intermediate process steps such as weighing. This ensures controlled handling of caps without manual intervention.

Automated Cap Feeding

For applications requiring the use of new caps, an optional cap feeder is available. The cap feeder supplies fresh screw caps for micro screw tubes and HPLC vials and enables fully automated re-capping without reusing the original cap.

Cap Disposal

If caps are not required for further processing, removed caps can be discharged automatically into a defined waste position. This allows clean separation of tubes and caps and supports workflows where caps must be discarded for quality or contamination control reasons.