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technology | Medical

Above: Pipette tips produced on a 128-cavity mould by Tanner on a Netstal Elion 2800 moulding machine

capabilities being a major topic in this context. Arburg has recently been involved with German

company Biovision in developing special resorbable implants made from PLA for use as screws or pins to fix bones or tissue. A major advantage of resorbable implants is that, as the material degrades over time, they do not have to be removed surgically once healing is complete. Biovision has used an Allrounder 270 A machine and a micro-module to manufacture PolyPIN bone pins with lengths of between 25-60 mm. The PolyPIN implants are being used for surgical fixation of fractures subject to low biomechanical stresses. The implants fully degrade after around two years. A further interesting area of application is additive

manufacturing of individualised PLA implants, which can be designed precisely for the specific patient. “Owing to their toughness, PLA plastics are complex to process and they require the appropriate injection moulding expertise,” explains Kitzlinger. “At a purchase price of several thousand Euros a kilo, the material is rather expensive, as well as being sensitive to high tem- peratures and long dwell times. So there is no scope for error during injection moulding. High shearing during preparation would also damage the material and lead to premature biodegrading in the body. For gentle material preparation and short dwell times, we therefore use a special 15mm screw with widened flights and a chrome nitride (CrN) coating. This reliably prevents the formation of undesirable deposits and microfretting.”

Dental collaboration Engel has been involved in a collaborative venture for production of interdental brushes developed by German company Pheneo. The product – named Scrub! - will soon be introduced to the market. The manufacturing process involves incorporation of up to 500 bristles moulded directly in a single-component injection moulding process together with the core and the grip.

16 INJECTION WORLD | September 2016

The high-performance precision mould with eight cavities, which is extremely delicate in the bristle area, has been developed by Hack Formenbau of Germany. Hekuma, also of Germany, is responsible for the process automation using a highly integrated, automated production cell from the company’s modular HEKUflex range. Immediately after injection moulding, the parts are camera inspected and good parts automatically packed into retail sales bags with 16 pieces each. One bag leaves the production cell every four seconds. The companies say that the single-component design and the high process integration level achieves a significant increase in production efficiency compared with well-established products and methods on the market. Up to now, they say interdental brushes have consisted of three components which are typically produced in separate processes: the grip, a wire mesh and the filaments. This new technological solution makes it possible to produce brushes with small cores and numerous fine bristles using single-component injection moulding for the first time. The plastic compound used also makes an important

contribution to the manufacturing process, with the length of the glass fibre selected so that the fibres provide stability for the grip and core, but do not penetrate the very delicate bristle areas. Engel says that to completely fill the eight cavities

with up to 500 bristles at a total shot weight of only 1.93 grams not only places extremely high demands on the mould, but also on the injection moulding machine. The all-electric drive technology ensures high precision of set machine movements but, in order to also compensate for fluctuations in the ambient conditions or raw material, the iQ products from Engel’s inject 4.0 programme come into play. Shot by shot, iQ weight control analyses the pressure

profile and adjusts both the switchover point and the injection profile to the current conditions. At the same time, iQ clamp control monitors the mould breathing for each shot separately and adjusts the clamping force automatically. As the third assistance system, Engel e-flomo keeps temperature control conditions in the mould constant. The company says the decentralised intelligence directly on the machine guarantees maxi- mum process consistency in this application, preventing rejects and thus ensuring competitive unit costs.

Pipettes in volume Netstal - part of the KraussMaffei Group - has devel- oped a 128-cavity pipette tip production line with highly efficient handling solution with partners Tanner and Zubler Handling. The system incorporates an all-elec- tric Elion 2800-870 moulding machine producing tips on

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