Mouldmaking for medical products State-of-the-art glass: mould platforms for IVD consumables

Editor: MA Alexander Stark

Germany — Disposable in-vitro diagnostics (IVD) articles such as pipette tips, reaction vessels, or petri dishes must be manufactured to strict precision and efficiency standards. Otto Männer developed a product-group cluster in order to define mould-construction specifications for this type of IVD article.

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Mould platforms for four IVD categories
Mould platforms for four IVD categories
(Source: Männer)

Reliable diagnostics — whether secretions or tissue samples — require that the reaction vessels used are absolutely sterile. This is why clinics and physicians’ practices generally rely on disposable products in sterile packaging. GMP and FDA regulations specify the quality requirements for their manufacture, as will the EU Medical Devices Regulation beginning in May 2021. These disposable products are elaborate and highly varied, as units can be thin-walled, transparent, delicate, or have a complex shape. A typical requirement for in-vitro applications is very strict tolerances because functions such as dosing accuracy, snap-in catches, or seals are indispensable in diagnostics.

In mouldmaking, this means technical feasibility must be combined with high output volume and low unit costs. There are unique specification profiles for toolmaking, including short cycle times, multiple cavities, highly polished, refined surfaces, sophisticated hot runner technology, integration of sensors, and automation systems. Due to the process-related requirements of in-vitro products, it is important to have a classification system that leads to a platform strategy for the manufacturing moulds. Männer has developed the following modular systems for this area:

  • Group 1: Pipette tips
  • Group 2: Sample and reaction tubes, cuvettes, or microcentrifuge tubes
  • Group 3: Petri dishes, cell culture dishes, bottles, or plates
  • Group 4: Deep-well plates, PCR plates, microtiter plates, racks, or cassettes

Each group poses specific challenges in mould construction. For example, in Group 1, the filling volume of IVD articles is determined by the geometry of pipette tips. This makes achieving part-to-part consistency through uniform balancing and individual cavity control the highest priority. Reaction vessels in Group 2 cover a more varied geometric and functional range. Common features of reaction tubes include a specified liquid volume and closure by means of a separate cap or a one-shot flip closure. Männer typically equips its tools with multi-point nozzles that can be installed in space-saving highcavitation moulds of up to 64 cavities. Challenges that arise in these types of mould processes include air entrapment in the sealing area or the specified lid opening force.

For articles in Groups 3 and 4, flatness of the base and high visual quality (from transparent to mirror-polish surfaces) must be achieved. A precisely defined fit of the lid and tray are also required for articles with a cover. In Group 3, where demand is strongest for petri dishes made of PS (polystyrene), wall thicknesses generally range from 0.6 to 0.75 mm and are produced in stack molds with 4+4 to 8+8 cavities. There is currently a high demand for Group 4 articles for Sars-Cov-2 test kits. The company's approach for 2- to 4-cavity moulds is paying off in this area. By applying special materials and cooling that closely matches part contours, cycle times in rack production can be reduced by up to 25 %.

Männer can support customers throughout every phase of the process, including the early design stage when articles are optimized for series production. The Barnes Molding Solutions network makes it possible to perform validation and qualification testing at four test centers in China, Germany, and the US, while adhering to consistent global standards. Since the outbreak of the pandemic, online validation has been available as well. Beginning in April, the Männer Test Center will have a complete production cell dedicated to the manufacture of pipette tips and related handling.

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