Hot runner technology works towards quality surfaces in auto sector

With the automotive sector demanding high surface quality, hot runner technology provider Oerlikon HRSflow, together with companies such as film technology provider Leonhard Kurz, Austrian machinery maker Engel and Austrian moulding firm Schöfer worked on a "smart" car rear panel in 2K technology.

The companies contributed to the success of this innovative project, which required, among other things, extensive rheological calculations due to the complex requirements.

The project also included injection-moulded light guide elements for which Oerlikon HRSflow’s new, patent-pending CTC gate insert is used.

Beyond, the advantages of the company's FLEXflow technology with servo-controlled needle positioning are demonstrated by the cascade injection moulding of headlight covers and the back moulding of films in a lightweight construction application.

The supporting element of a "smart" car rear panel using 2K technology is a frame made of PC/ABS. In the first step, this is injection moulded using a hydraulic 2-drop hot runner system from Oerlikon HRSflow.

In the second step, the part is overmoulded with PMMA or alternatively PC using a single nozzle from the Ga series. Finally, the part is decorated directly in the mould with a capacitive yet aesthetically pleasing film.

For the injection molding of an automotive light guide element, Oerlikon HRSflow’s new patent-pending CTC gate insert provides optimum properties. It is made of steel with mechanical properties and wear resistance.

In addition, flash formation is completely avoided thanks to optimum thermal control in the gate area in conjunction with a cylindrical shut-off. Both factors help optimise productivity in the manufacture of the light guide element.

Forgiving dimensional requirements simplify machining of the nozzle seat, and a smart solution that allows the gate opening to be renewed with minimal effort facilitates maintenance work.

In general, injection moulded parts that require a wide process window due to difficult conditions such as low shot volumes, long packing times and high holding pressure values are among the typical applications for the new CTC.

LED headlight bars made of crystal-clear polycarbonate (PC) are a proven application of Oerlikon HRSflow's FLEXflow technology. The systems' servo motors enable synchronised needle movements for precisely controlled flow front progression during sequential injection moulding.

Sudden pressure drops that occur when additional gates are opened are perfectly damped, so that the cavities are filled evenly and residual stresses in the moulded part are minimised. There is also a high degree of flexibility during the holding pressure phase because the needle closing profile (speed and stroke) can be adapted to meet product dimensional requirements.

In another example, the possibilities of hot runner technology in the design of future cockpits are illustrated by a joint project between the Koller Group, Dietfurt, and Oerlikon HRSflow using the example of a laptop housing demonstrator part.

A prefabricated and preformed film is back-injection moulded with PC using the FIM (Film Insert Moulding) process.

Mould development was carried out jointly with Koller Formenbau, while the back moulding process was developed with the automotive lightweight specialist Koller Kunststofftechnik. While the film was initially displaced below the injection point, this washout effect could be reliably avoided by using and optimising Oerlikon HRSflow’s electrically controllable FLEXflow hot runner system.

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