Partnering for lighting and moulds

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Very often tool makers work together with product manufacturers as development partners to fulfil the requirements of OEMs.

Porsche with integrated LED lights from Hella and Hofmann

Automotive lighting is an interplay of function and design. It should be functionally outstanding and contribute to the unique look of a vehicle. For the new Porsche Macan, Hella Slovakia Signal Lighting developed a completely new rear lighting system with light strips for guiding LED light. The patented “Edgelights” for a strip-form signal light are said to provide a new level of quality for the safety-related brake light function.

The heart of the brake light is a thickwall part made of PMMA, which is the so-called light module or light strip, using the two-component technology. This part, which has a complex prism geometry and reflective qualities for light guidance, was developed in partnership with tool maker Hofmann Innovation.

“Edgelights” are highly complex light strips for rear lighting systems. In combination with other individual parts, “Edgelights” are part of the safety-relevant functioning of the brake lights in the rear lighting system of a vehicle. The design for the Porsche Macan chosen by Hella consists of three component groups. In addition to the “Edgelight” light modules, the rear light component groups consists of other components usually found in rear lights. These include lenses made of PMMA in four colours (red transparent, grey transparent, black opaque and light red transparent), which are injection moulded using a three-step technology. The heavily-tiered external contour of the upper light lens is unusual.

Hofmann contributed to the design of series tools and production processes. Besides, the design, surface look and function, it is optimised for plastics and ensures process stability during production, and is said to be distortion-free. In this regard, Hofmann offers trial and pilot production in its technical centre in Lichtenfels.

Hella manufactures the series-production “Edgelights” from transparent PMMA on turning tools, as multi-component parts, using a two-step process. Each tool produces a left-hand and a right-hand component in each cycle. They are pre-injected and finish-injected using the two-component technology. Here, the challenge for production is in the correct geometrical forming and cleanliness of the “Edgelights”. These requirements are essential to allow the light beams to shine with the desired intensity. After cooling down, the light modules are delivered as individual parts to the rear light production facility.

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In order to achieve the required light values, the thickwall PMMA part, which is made of Altuglas HT 121 or Plexiglass 8N, requires high precision optical surfaces with a good surface quality, with the lowest possible distortion in the part. The geometry of the PMMA light strip is designed in such a way that the light entering and exiting at both ends is as focussed as possible. The illumination effect of the rear lights is homogenous and bright.

As part of tool development, it was the task of Hofmann to develop a 3D contour that would allow maximum light output at the point of emission and at the same time be manageable from a production technology point of view. This applied not only to the manufacture of the series-production tools, but also to the demoulding characteristics of the light module in the tool, as well as the manageability of the process in terms of strict absence of distortion.

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There are two types of model making in product development: rapid prototyping and industrial prototyping. With rapid prototyping, Hella needed prototypes from Hofmann in order to test them and for approval from Porsche. This process required constant adaptation to suit the design requirements. These prototype parts, which are equivalent to seriesproduction parts, are developed using model making methods. Initially they are built as individual components, and later as rear lights built into preproduction cars.

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The methods included pouring of the “Edgelight” light modules with PMMA, and CNC milling of the light entry and exit geometries, in order to achieve continuous improvement of the light parameters. EMU samples were made for the complete rear light module component group, using STL technology (stereo lithography), laser sintering for plastics, aluminium processing and vapourising of the reflectors. In addition, vibration welding was used and testing materials supplied for the subsequent small batch.

With regards to small batch production, after the development and modelling phase, industrial prototyping comes into play. Porsche needs demonstration vehicles from pilot production runs for presentation at trade fairs or for dealer presentations. These vehicles correspond to production vehicles in terms of function, but some model parts are used in them. In total, Hofmann delivered 300 sets of rear lights for this purpose.

Braun and Priamus work on perfecting filling of moulds

German pharmaceutical and medtech company B. Braun Melsungen and Swiss specialist for quality assurance and control systems Priamus System are teaming up to jointly develop technology for injection moulds.

The difficulty with different components, which are produced for example with 16 or 24-cavity moulds, results from the unbalanced filling of the cavities and therefore results in incompletely filled parts (short shots), which can damage a mould core. The consequences are high repair costs and downtimes.

Thus, Braun and Priamus have developed a process solution whereby small and highly sensitive cavity temperature sensors, placed at the end of the flow path of each cavity, provide information about the melt front. These sensors guarantee the simultaneous filling of the cavities by automatically balancing and recognising short shots in real-time in order to prevent damage of the cores. Furthermore, bad parts are automatically sorted through the monitoring of the measurement data, which is also documented.

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In addition, the use of the pressure sensors together with the temperature sensors can monitor deviations on viscosities.

Moulds manufactured at Braun in Germany are sampled and process validated so that all mould data for constant quality are laid down in Germany. During series production in global production facilities, the same quality is guaranteed by controlling this reference data, says the firm.

The Priamus systems used for this purpose are solely based on information from the cavity, such as the cavity pressure and cavity temperature signals, which are monitored and controlled themselves.

(IMA)

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