At thinXXS Microtechnology AG an in-house mould department manufactures intricate disposable quick-tests to diagnose medical conditions ranging from bacterial infections to cancer cells.
Producing such macroscopic parts with microstructures on a device that’s no larger than a credit card requires high repeatability precision and this is exactly what Sumitomo (SHI) Demag has helped the Zweibrücken facility to conquer.
Medical professionals and diagnostic laboratories from all over the world regard thinXXS, located on the German/French border, as the micro-mould engineering experts. Using ultra-fine precision milling machines, the German engineering team produces moulds featuring intricate channels and microstructures that are not visible to the naked eye. Drops of fluid, such as blood, are mixed in a reservoir in the moulded clinical test devices to create a reaction, which can reveal an infection within minutes. “We are dealing with dimensions less than a hair’s breadth in combination with highly complex geometries,” emphasises Tobias Lacroix, Head of Micro Injection Moulding at thinXXS
An all-electric Sumitomo (SHI) Demag IntElect 100-180 injection moulding machine was selected by thinXXS to manufacture the disposable bacterial quick tests. The final test device comprises three different components, all of which are produced on the IntElect in 4-cavity moulds and assembled in-house.
With a shot weight of approximately 12g, two of the individual components are made from uncoloured PMMA, the third from blue coloured polypropylene. Accurate reproduction of surface detail, high repeatability and part tolerances in the micrometre range were all critical considerations when selecting the machine, highlights Tobias. “Sumitomo’s well thought-out concept was the most convincing and the project timeline adhered to our tight schedule.” In addition to installing the injection moulding machine, Sumitomo supplied the downstream handling and automation system.
Behind closed doors
To prevent particles of dust and other contaminants entering the production process, the machine operates in a class 8 clean room environment. It can only be observed through a glass window in the cleanroom cabin.
As an added safeguard, the entire cleanroom cell is fully enclosed in a class 7 containment area. A six-axis Stäubli articulated arm robot removes the finished test components from the 4-cavity mould and places them onto a small load carrier. When the carrier is full, these are transported on a conveyor to the assembly and packing hall. Here, thinXXS staff members wear protective masks and clothing to maintain the class 7 cleanroom conditions and assemble the components into the finished test devices.
With an L/D ratio of 20 and a clamping force of 1,000 kN, the IntElect produces the device’s components within 16 seconds. The injection moulding process involves dispensing dried pellets into the IntElect’s plasticisation unit via the feeder and metering unit. The mould is then heated using water to 90 °C. A temperature control device is connected to the injection moulding machine via a CAN Bus interface and the controllable activeLock non-return function ensures that no melt flows back into the screw channels after the injection phase has started.
Each phase of the moulding process is designed to maintain the highest precision in order to accommodate the quick test’s fluidic functional design, explains Tobias. “Only a highly accurate part can guarantee a 100% reliable diagnostic result. We expected our injection moulding machine to achieve an extremely accurate reproduction of surface detail, a high repeatability and part tolerances in the micrometre range.”
Reflecting on Sumitomo (SHI) Demag’s approach to this project, Tobias is quick to confirm that the complete system is operating with precision and repeatability, adding: “Sumitomo fully supported us during the GMP validation and we passed the assessment without problems. I found it particularly helpful that our contacts looked after all technical and administrative matters concerning the complete line. I am really happy with everything!”