Moving from the stationary frame to the moving parts, the monoblock filling machine operates through a tightly timed sequence.
The process begins with getting the bottles onto the line. For many of my clients in the IVD (In-Vitro Diagnostics) industry, the bottles are small, light, and often irregularly shaped, which makes them prone to tipping over. To solve this, we often use “activity molds” or custom fixtures. Instead of the bottle sliding along a rail, it sits securely inside a CNC-machined block that travels through the machine.
In some setups, we use a vibrating bowl or a storage bin that can hold dozens of bottles at once. For more specialized tasks, such as handling culture media, I’ve designed systems where a technician manually places bottles into the fixtures under a laminar flow hood to maintain a “Class 100” clean environment. This ensures that even before the liquid touches the bottle, the environment is controlled and the bottle is perfectly positioned for the next step.
Once the bottle is positioned, it moves under the filling heads. This is where the real engineering happens. For reagents and biological liquids, I almost always specify peristaltic pumps (often from brands like Lange).
I prefer peristaltic pumps for several reasons:
- Zero Contamination: The liquid only touches the medical-grade silicone tubing, not the pump’s internal gears.
- Easy Cleanup: To switch products, you simply swap the tube rather than dismantling the entire pump.
- High Accuracy: We can achieve incredible precision—When processing low-viscosity liquids (such as medicated oil, 20°C), the equipment can achieve a filling accuracy of ±0.5ml for 8ml bottles at a rate of 3300 bottles/hour.
To prevent bubbles or splashing, the monoblock filler uses “bottom-up” filling. The filling nozzle (made of non-reactive PP or PTFE) actually dives into the bottle and rises slowly as the liquid rises. This “diving” motion is controlled by a servo motor or pneumatic cylinder to ensure there are no drips on the bottle rim, which would ruin the seal later.
After filling, the bottle moves to the capping station. A mechanical arm or manipulator picks up a cap—often sorted by another vibrating plate—and places it onto the bottle mouth. For products that require a two-step seal, such as a plug followed by a screw cap, the monoblock filling machine handles both in consecutive stations.
The most critical part of this step is “torque control”. If a cap is too loose, the product leaks; too tight, and the consumer can’t open it. We use servo-driven capping heads where the twisting force (torque) can be adjusted digitally on the touch screen. I once worked on a project for medicated oil where the bottles were very small. We implemented a dual-station capping system that achieved a qualification rate of over 99% because the servo motors could detect exactly when the cap was seated correctly.