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Good things come in small packages
Filling in the µl range for diagnostic products
The product range of this young, ambitious producer of diagnostics is rapidly expanding and also includes small batch sizes, depending on the segment. A broad range of plastic containers are processed, including non-freestanding Sarstedt tubes in formats of 0.5 and 2 ml as well as various shapes of plastic bottles with volumes of 20, 60 and 130 ml.
The main challenge in this project was to achieve a long-term absolute filling accuracy of +/- 2% for small quantities starting at 50 µl. To clarify: a deviation of max. 1 µl is permissible for a target filling volume of 50 µl! The filling tubes and needles have an inside diameter of 0.2 mm. In this range, not only is precise dosing a technical challenge; weight checking is also at the limit of detection accuracy. Some 2,000 random measurements were carried out for the customer in advance to document the process stability of the peristaltic filling system and the reproducibility of the results.
Precision at the limits of measurability
The non-freestanding containers are transported from a bin into a sorting bowl. The tubes feature the typical Sarstedt collars, which allow them to be transferred from the sorting bowl to a linear suspended transporter. The freestanding bottles take another path: a disc sorting unit orients the containers for the linear transport system. All containers undergo processing on the same intermittent cycle rotary filling machine.
The dosing station consists of two peristaltic pumps: an OPTIMA OP 45 peristaltic pump system for the smallest volumes of 50 µl to 10 ml, and an OPTIMA OP 75 for the larger formats. Filling of both containers takes place at a single filling position, after which the plastic caps are individually fed from a sorting bowl connected to a supply bin. A swivel arm with a grabber picks one screw closure, places it on the container, and closes it with a specified torque.
Labels are affixed to the containers at the next station, the information for which is entered on the central HMI of the KUGLER FLEXOFILL system. The only thing that varies from container to container is the product discharge: Sarstedt tubes that pass inspection are actively discharged via a chute for further processing. Tubes that do not pass inspection are rejected via a second outlet on the rotary filler and a chute. Freestanding plastic bottles are discharged using the same system, but are pushed to a conveyor and transported to a manual removal station. Format changeovers can be completed in 30 to 40 minutes.
Optima Pharma has installed an external in-process weight control system to achieve the necessary filling accuracy, which in this case is especially challenging considering the tiny volumes. The equipment operator independently decides the frequency at which inspection needs to take place. This function is protected at a high level by a password. The control system automatically prompts the operator to perform in-process control. The machine first clears the machine transport, and informs the operator how to proceed.
First, pre-weighed containers are placed in the system at a predefined position. After the completion of this procedure is confirmed by the operator, the machine processes the three to five containers that have been inserted. The containers are manually removed and their gross weight determined at the external weighing station in the immediate vicinity of the filling and closing unit.
Regular production mode cannot continue until the net weights are entered into the control system and confirmed by the operator. The recorded net weights are used to control the filling system and optimize filling accuracy. Another advantage of this system is that the process is documented. The measured and transferred sample information is logged in the batch record by the control system in the Optima machine. The documentation then includes both the number of samples and the measured weights, which are included in the batch documentation provided to the customer by the equipment operator.
“Entry-level” system with superior quality
The customer requested three expansion stages to allow it to flexibly react to growing demand. The output of the KUGLER FLEXOFILL in its current basic version is 200-600 containers/h, depending on format. Higher outputs can be achieved at any time.
Possible upgrades: The manual entry of the filling weights can be automated by connecting the scale to the Optima machine’s control system. Furthermore, manual torque control can be replaced by a measuring unit in the capping head to measure the tightening value and document it. Both options are already available should they be needed.
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