INNOVATION | OPTICAL MOULDING
Right: The precision and process stability offered by IntElect
machines make them an ideal injection moulding
solution for LSR applications, says Sumitomo (SHI) Demag
and process engineering. Moulding LSR requires
greater precision and process stability. “The latest IntElect systems are designed to achieve extremely precise shot control and also handle the low-viscosity material,” says Flowers. “Units feature a specially designed screw, ranging from 14 mm to 45 mm, a modified plasticising unit, a shut off system specifically designed for LSR and a spring loaded non-return valve to achieve the highest processing consistency.” In addition, he says: “Being able to combine LSR with technical plastics to create one fully bonded component is another exciting development. It will be feasible to combine two, three or more individu- al materials into one seamless, robust component, which offers vehicle designers huge opportunities.” In his view: “LSR is probably where the most significant developments are happening in optical injection moulding right now. LSR is replacing glass and traditional polymers in more technically demanding industrial optical applications such as thick-walled optical fibres, prisms or lenses. In these applications, optical function can be compromised if the contours are inaccurate. For automotive optics, this could impact road user safety. The reason why LSR is a good material for automotive optics is it enables manufacturers to achieve component geometries and technical features not previously possible, such as the moulding of complex optical surfaces onto a light guide for a matrix headlight. LSR is a fairly unique material in that it remains flexible and elastic down to -50°C, yet also retains its properties up to 200°C. As a result, LSR is starting to be used more extensively in encapsulated electronic components and cables, for example, where insulation is required for user safety.” Flowers adds that matrix LED automotive lights
are just one LSR application where significant growth is forecast. The adaptive headlight segment is expected to grow at the fastest rate between now and 2023, driven by high demand in Europe and Asia-Pacific. Adaptive headlighting is a highly sophisticated technology, comprising complex optical surfaces where light is guided through the micro-milled polished surfaces. Connected to a camera control system, individual LEDs are switched on and off to ensure road users are not blinded by a full beam or to highlight a particular road obstacle. Currently the technology is confined to premium vehicles, but it is anticipated that these headlights could become more mainstream in the near future. The company adds that in order to mix and
28 INJECTION WORLD | July/August 2021
IMAGE: SUMITOMO (SHI) DEMAG
process LSR material, moulders need specialist equipment that can deliver the stability required to handle an optical grade silicone material. Although there are examples where traditional moulding machines have been adapted with an LSR injection unit, moulders may find that part quality or efficien- cy is compromised. For this reason, Sumitomo (SHI) Demag has launched a fully-integrated precision IntElect LSR injection moulding package equipped with a special screw, a non-return valve, vacuum pump and toggle technology. This cell was developed in collaboration with a number of partners that are dedicated to the LSR marketplace. Currently, the Sumitomo (SHI) Demag LSR
package is available on IntElect machines ranging from 50 to 180 tonnes. Being able to form complex geometries and perfectly replicate micro-struc- tured surfaces is a key advantage of LSR. However, there is a tendency for flash caused by excess material to occur at parting lines of the mould (where the two mould halves meet), or other shut off areas. To address these, the LSR package comprises special features, including a spring-load- ed non-return valve to avoid uncontrolled backflow of material, a shut off system specifically designed for LSR, plus a pressure controlled vacuum se- quence to extract air and to prevent flash occurring during the filling of the mould. Additionally, the Centre Press Platen ensures high rigidity and uniform distribution of the clamp force to ensure more balanced pressure distribution. The robust linear guidance system controls the mould open- ing and closing sequence with a built-in staged clamp force, further reducing the risk of flash. As an IntElect system, the machine features an advanced mould sensor safety system (activeProtect). Additionally, IntElect users benefit from enhanced ejector control technology. The company is also currently supporting
several projects to establish new market concepts, including the development of a new LSR system. This technology can be utilised in combination with others to produce parts for hybrid vehicle fuel cells. “In the future, components of all types will
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