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High-end injection molding for in-vitro diagnostics
| Reinhard Bauer
Highest precision at the limit
The quick and precise analysis of tiny tissue samples is of the utmost importance for the diagnosis of life-threatening illnesses. The sample carrier being used is one of the analysis system's precision components.
Despite their conventional appearance, the carrier plates for human sample analysis produced by STRATEC Consumables GmbH in large series are nevertheless high-precision plastic parts on which extreme demands are placed.It is a rectangular platelet in the microscopic format of 75 x 25 x 2 mm. These and other consumables with a similar accuracy class are produced by STRATEC Consumables GmbH in Salzburg/Anif. In order to be prepared for the quality levels of future device generations in this product segment, STRATEC chose Netstal injection molding machines for the last capacity expansion.
ELION MED
Production cell based on an ELION 800 in clean room design
Tightest manufacturing tolerances
In the concrete case, 48 deposition points for molecular samples (12 x 4 matrix) are located on a sample carrier, all of which must provide the same starting point for the analysis process. For the process, analytical instruments are used in which a laser evaporates human specimens and turns them into a mixture of molecules. That mixture is then accelerated linearly in an electric field and fed into a detector unit. The mass spectrum recorded there allows the comparison of benign and malignant cells or serves to identify different types of bacteria. This is only possible if the sample carriers remain dimensionally stable without distortion within narrow tolerances – both during the analysis process as well as during the optional low temperature archiving (-80°C) for reference purposes.
STRATEC uses the know-how and processes developed by Sony DADC for the production of optical storage media such as CDs, DVDs and Blu-ray disks, in particular precision injection molding in a cleanroom, thin-wall metal coating or printing.
Injection molding precision thought ahead
How did Netstal score points? Dr. Christoph Mauracher, the managing director of STRATEC Consumables, has the answer: "As the requirements of our customers have grown with each new generation of analytical instruments, we have to keep up on the production side and systematically explore potential for improvement. That is why we had to find an injection molding technology that operates at the limit of what is currently possible. After extensive comparisons, the all-electric Swiss Netstal ELION injection molding machines ended up very high on our shortlist.
"The high shot-to-shot consistency allows continuous production within the narrowest tolerances while virtually eliminating rejects."Dr. Christoph Mauracher, CEO Stratec Consumables
Specific controller architecture ensures maximum precision
Because the necessary dimensional and shape precision makes the highest demands on metering, pressure control and pressure changeover. In order to meet this requirement, Netstal generally relies on pressure sensors for all machines, which are optimized by its own development contributions and used in combination with a controller architecture that is matched to this. In addition, this technology package is not used as standard for all machines in the same configuration, but is matched to their size.
Netstal's control architecture
The sensors adapted by Netstal in combination with a specifically adapted control architecture and stable temperature control provide the prerequisites for ultra-precise process control.
Highest shot-to-shot consistency
Netstal injection control allows a force-dependent pressure change-over, independent of the material properties and thus guarantees a very stable part weight.
This ensures the currently highest dynamics during injection and ultra-precise process control. The stable gearbox design and a plasticizing unit with a temperature stability of +/- 0.25 °C guarantee that identical parts are continuously produced without the need for additional control algorithms to compensate for external influences.
Successful partnership
Horst Bar (left), the project manager responsible at Luger GesmbH, Thomas Aschenbrenner from Netstal Application Technology and STRATEC Consumables CEO Dr. Christoph Mauracher (right) can look back on a successful production start-up of the Netstal production cells.
Efficiency targets achieved
Dr. Mauracher added: “The high overall system efficiency and reliability of the ELION machines enable consistently high part quality at the lowest unit costs. The high shot-to-shot consistency allows continuous production within the narrowest tolerances while virtually eliminating rejects. It is also good to know that the machine could run faster than it has to do with the described product because the technical data lists a theoretical dry running time of 1.3 s at a stroke of 287 mm. We also appreciate the smooth running of the machine. From this point of view, the slightly higher acquisition costs were more than justified."
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