Precision Force Control: Validating Load Cells And Burster Controllers In Pen Assembly

Assembling delicate medical devices like insulin pens requires exact force control to prevent damage and ensure functionality. This article explains how DROFEN MACHINERY utilizes load cells and Burster controllers for precise press-fit operations, and how these critical systems are rigorously validated during the Factory Acceptance Test (FAT).

 

In the automated assembly of injection pens, mechanical precision is only part of the equation. The force applied during assembly-such as pressing the cartridge holder onto the pen body or seating the dosing mechanism-must be meticulously controlled. Applying excessive force can cause micro-fractures in the glass cartridge or deform plastic components, while insufficient force can lead to loose assemblies and dosing inaccuracies.

 

To achieve this delicate balance at speeds of up to 160 units per minute, DROFEN MACHINERY integrates high-precision load cells and advanced force controllers (such as Burster systems) into our turnkey assembly lines. However, integrating these components is not enough; their performance and safety interlocks must be proven through rigorous validation during the Factory Acceptance Test (FAT).

 

In a typical press-fit station on our EcoLine assembly systems, the servo-driven press head is equipped with a load cell. As the press head descends, the load cell continuously measures the insertion force. This real-time data is fed into a dedicated Burster controller, which compares the force-displacement curve against a pre-defined acceptable envelope.

 

If the force curve falls outside the envelope (indicating, for example, a jammed component or an oversized part), the controller instantly signals the PLC to abort the pressing operation and flag the sub-assembly as a reject.

 

During the Operational Testing (OT) phase of our FAT, we do not merely check if the press station moves; we actively challenge the integrity of the force monitoring system itself.

 

1. Controller Readiness Verification

Before any pressing action can occur, the control system must confirm that the force monitoring equipment is online and calibrated. During the FAT (e.g., Test 1.01.16.02), we simulate a scenario where the Burster controller is disconnected or in a "Not Ready" state. We verify that the PLC correctly inhibits the press station from operating, ensuring that no unmonitored assemblies are produced.

 

2. Simulating Sensor Failure

What happens if a load cell wire breaks or the sensor fails mid-production? We simulate this exact scenario (e.g., Test 1.01.16.01 for Load Cell Failure on specific nests). The FAT protocol dictates that the system must immediately detect the signal loss, halt the affected station, trigger a specific HMI alarm, and ensure that the parts in the unmonitored nests are securely tracked and ultimately rejected.

 

3. Challenge Testing the Force Envelope

While not explicitly detailed in the basic OT failure checks, a comprehensive FAT also involves introducing challenge parts that are intentionally out of tolerance (e.g., slightly oversized diameter) to verify that the Burster controller correctly identifies the abnormal force curve and rejects the assembly.

 

By systematically validating these force control mechanisms, DROFEN MACHINERY provides CDMOs and pharmaceutical manufacturers with the assurance that their injection pen assembly lines will deliver consistent, high-quality products while protecting delicate components, making your manufacturing processes great again.