MEDICAL | INNOVATION
of miniature parts as light as 0.0003 g, with walls as thin as 0.0004 inches and dimensional tolerances to ±0.0005 in. Typical items being moulded using the technology include catheter components, implants, blade holders, dental prosthetics and hearing aids. A new generation of all-electric machines have
Above: At its 2018 Technology Days event, Arburg presented an All- rounder injection moulding machine from the high-performance electric Alldrive series and a Freeformer for additive manufacturing with medical technology applications in the cleanroom laboratory
Technik removes 32 pipette tips from the mould in sync with the injection moulding process and loads groups of 96 pipette tips, sorted by cavity, into racks. Every 18 seconds, 96 pipette tips are discharged from the production cell, which is enclosed to create a cleanroom environment. Arburg highlighted high-end cleanroom solutions for medical applications during its Technology Days event. One high-end injection moulding solution for the cleanroom was a GMP-compliant, stainless steel version of the Allrounder 370 A with a clamping force of 600 kN. Equipped with a mould from Ernst Rittinghaus, this high-performance machine produced two biotechnology columns (syringe barrels) from PP with a dosage volume of 2 mm. The cycle time was 8s. Outside the cleanroom, a hybrid Allrounder 470 H with a clamping force of 1,000 kN also produced medical technology parts; on a 24-cavity mould featuring a hot runner system, 24 overcaps were produced from HDPE in a cycle time of 7s. The company also demonstrated its Arburg
Right: A micro-injection unit installed on a Sumitomo (SHI) Demag 250kN machine
Plastic Freeforming technology to additively manufacture functional components from qualified original materials. One innovation was the process- ing of PMMA, as well as a medical-grade SEBS with a Shore A hardness of 28. A Freeformer also manufactured cranial implants made from medical- grade PLLA in the cleanroom laboratory. Micro-injection moulding (micro-IM) relates to the manufacture of injection moulded plastic parts that have a shot weight of less than 1 g and offers great potential in medical applications. Sumitomo (SHI) Demag says that its all-electric moulding machines can be easily adapted to allow micro-IM
24 INJECTION WORLD | September 2018
www.injectionworld.com
brought vastly increased levels of precision, made possible due to advanced direct drive technology. “We are now able to achieve very high levels of repeatability while a specific 14 mm screw design improves the dosing, which is critical in micro-IM,” says Nigel Flowers, Managing Director of Sumi- tomo (SHI) Demag UK. “Working with shot weights of between 0.1-1 g means that designers can now consider miniaturisation of components as it is now more cost-effective.” Using the 14 mm screw, traditional 50- and 75-tonne IntElect electric machines from Sumitomo (SHI) Demag can be deployed. The screw design is the smallest screw capable of processing standard plastic resins. The 14 mm tool enables moulders to limit the amount of material used by adapting nozzle body length and diameter to minimise residual time of material in the barrel. The 14 mm plasticising unit contains around 8 cm3
of plastic
material at the screw. “Traditionally, they would be used to run all sorts of different components with shot weights that were much larger than 1 g, but the 14 mm screw gives us small shot weights and the fine control that we need,” says Flowers. The trend for implantable devices in the medical industry is a significant advance for the sector. While the overall production process is not altogether different, the type of material used could be, says Flowers. “Almost every material you would expect in medical could crop up in micro moulding – there is no specific material of choice for implantable devices,” he says. “It is dependent on what the part is being used for – there have been cases where the plastic is coated in gold for
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