Innovations in precision optics

Injection moulding polymer optics requires a high degree of precision in terms of mechanical engineering, tooling and process engineering, combined with a high level of reproducibility and cleanliness of the production environment. Managing Director of Sumitomo (SHI) Demag UK Nigel Flowers outlines how the market is evolving in technically demanding optical applications, including new generation lighting and industrial technologies.

Matrix LED automotive lights are just one 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 headlights 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 aren’t blinded by a full beam or to highlight a particular road obstacle. Right now the technology is confined to premium vehicles, but it’s anticipated that these headlights could become more mainstream in the near future.

The future development of autonomous vehicles is also prompting demand for more integrated LSR electronic components. Battery and fuel cell EV technology is another critical area that requires new generations of parts, and consequently new supply chains. It is an area where Sumitomo (SHI) Demag is regarded as a strong development partner, working with customers to determine the best solution.

Optics know-how

Injection moulding polymer optics requires extensive processing expertise, specifically knowledge of  processing parameters and tolerance limits. Yet, it is a rapidly growing market.

Between now and 2026, the global silicone market size is projected to expand from USD 16.7 billion in 2021 to USD 23.4 billion by 2026, at a CAGR of 7.0%.[i] This rapid growth means that LSR is fast becoming the material of choice for specific applications in the digital electronics and automotive segments. Other end-use industries include building & construction, industrial & mechanical processes, aerospace, personal care & consumer goods, healthcare and transportation.

LSR is probably where the most significant developments are happening in optical injection moulding currently. LSR is especially well suited for injection moulding due to its liquidity.

Consequently, 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.

Performance enhancing characteristics

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. Far lighter than glass, and most other plastics too, LSR is especially valuable in automotive applications due to vehicle vibrations. It’s UV stability also makes it good for outdoor applications.

LSR is also starting to be used more extensively in encapsulated electronic components, cables etc. where insulation is required for user safety.

In order to mix and process LSR material, moulders do 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 efficiency is compromised.

To achieve the extremely precise shot control needed and to handle the low-viscosity material, Sumitomo (SHI) Demag has launched a fully-integrated precision IntElect LSR injection moulding package. Units feature a specially designed screw, ranging from 14mm to 45mm, 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 and avoid uncontrolled backflow of material. It also features a shut off system specifically designed for LSR, plus a pressure controlled vacuum sequence 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. While the robust linear guidance system controls the mould opening and closing sequence with a built-in staged clamp force, further reduces 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.

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 individual materials into one seamless, robust component, which offers vehicle designers huge opportunities.

[i] https://www.marketsandmarkets.com/Market-Reports/silicone-market-709.html?gclid=EAIaIQobChMI6KPRgKae8QIVkaZ3Ch1C3Q_iEAAYAiAAEgIn5PD_BwE