Bonding of Automotive Displays

 

The digitization of the car for modern mobility requires interfaces that offer a more individualized and interactive approach to road users. With increased development of self-driving vehicles, multidimensional infotainment and safety functions are required to accommodate networking. In addition to creating a comfortable cockpit environment, automotive displays support driver safety by providing up-to-date information about traffic events and car functionality.

Automotive infotainment systems provide audio or video entertainment for all occupants via their displays. Advanced driver-assistance systems (ADAS) provide graphical visualization of driver information such as parking assistance, navigation, traffic assistance, control functions and internet connectivity. All setting options in the car can be operated via touch displays.

Freeform and curved automotive displays are the future, enabling larger and more attractive dashboard displays. Housing designs are evolving to better utilize interior space and accommodate these larger and more responsive screens. 

 

Our solutions for structural bonding of automotive displays meet the needs of market trends, such as the increasing demand for design flexibility. High-precision metering with Henkel’s fully automatic mixing and dosing systems ensure high contour accuracy during adhesive application.

How do you ensure perfect display bonding when cost and design considerations are increasingly narrowing the bonding surfaces of the display housing?

What can you do to compensate for component tolerances during adhesive application, so as to achieve an adhesive bead of uniform width after joining?

We provide the solution for you, with Active Quantity Adjustment (AQA). This method makes it possible to adapt the dosing quantity during application of the adhesive to the part contour. This compensates for production-related differences and irregularities in the bonding surfaces as well as applies a precisely calculated and accurately metered quantity of adhesive. To achieve this, a 3D line scanner measures the part geometry and compares the data with the previously defined CAD reference of the part before the adhesive is dispensed. The result after joining is an adhesive seam that is consistent in height and width.

The trend towards larger displays in vehicles, combined with the need for space-saving installation, has led to narrow-edged display solutions. The challenge is to still achieve strong adhesive bonding with narrow bonding surfaces and thus thin bonding lines.

The adhesive must not protrude at the edges once joining the display to the housing. Fully automatic adhesive application and tolerance compensation are handled by Henkel’s mixing and dosing systems.

 

Strong adhesive bonds on narrow bonding surfaces

 

Very fast curing 2-component adhesives for high initial strength

Freeform and curved automotive displays designs dominate the interiors of modern cars. They are fully integrated into the overall interior design.

The design and manufacture of automotive displays requires a variety of material features, ranging from ensuring the strength of the display housing structure to bonding the cover glass onto the TFT / LCD display.

For bonding the automotive display to the housing, structural 2C adhesives based on MS polymer and silicone are used for elastic bonding with high / medium strength. They are suitable for the multi-substrate bonding of freeform and curved display designs.

This can include the bonding of different substrates, such as plastic to plastic; plastic to glass; and glass to glass. Thanks to its very fast curing properties, the adhesive used achieves a high initial strength at room temperature shortly after the components are joined.

Display housing with adhesive bead before attaching the transparent cover

 

Cross section of the display housing after joining

Flexibly adjustable dosing quantity for compensation of component tolerances

 

With the Active Quantity Adjustment (AQA) process developed by Henkel, it is possible to control the amount of adhesive dispensed for bonding displays to the housing. This ensures the correct quantity dosage at all times based on the respective height profile of the component. This method makes it possible to adapt the dosing quantity during application of the adhesive to the part contour. This compensates for production-related differences and irregularities in the bonding surfaces as well as applies a precisely calculated and accurately metered quantity of adhesive.

Before dispensing, a 3D line scanner scans the geometry of the components. The scanned data are transmitted to the dosing machine’s programmable logic controller (PLC) and compared with the predefined CAD reference of the component. Any deviations detected are used to adjust the dosing program in advance for the next adhesive application.

Wavy unevenness of the bonding surfaces can occur during the injection molding of the display housing. In order to compensate for this, the robot travels more slowly over slightly recessed application areas so that more adhesive is applied there, and travels faster over the slightly raised areas so that less adhesive is dispensed there.

Wavy unevenness of the bonding surfaces can occur during the injection molding of the display housing. In order to compensate for this, the robot travels more slowly over slightly recessed application areas so that more adhesive is applied there, and travels faster over the slightly raised areas so that less adhesive is dispensed there.

The AQA process can compensate for differences in the dimensional tolerances of the component. With a target glue gap of 1 mm, the specified tolerance for pressing the glue line is +/- 0.5 mm when the display and frame are joined. Since cost and design factors are increasingly resulting in narrower display housing bonding edges, the AQA process ensures that the adhesive trace on the housing contour, despite possible dimensional tolerances, remains uniform after the display glass is attached.


Mixing and dosing systems with 6-axis robot and shuttle table for bonding display housings

 

Efficient and fully automatic – to meet your exact requirements

In the reference configuration shown, the fully automatic adhesive application process for bonding the automotive displays to the housing is carried out using the DM 502 mixing and dosing machine with a 6-axis robot guiding the MK 825 PRO precision mixing head and using WT 1-LEVEL shuttle table for the parts handling. The display housings are attached to the two pick-up plates, and are positioned within range of the robot in shuttle mode utilizing a single plane.

This ensures a continuous adhesive application process. Depending on the plastic used for the display housing, it may be necessary to apply plasma to the contour of the display housing beforehand in order to achieve an improved adhesive effect. For this purpose, the robot can optionally be equipped with a plasma nozzle.

To check and measure part tolerances of the display housing, a separate pre-dispensing process step scans the surface of the housing using a 3D line scanner. The measured data are transmitted to the dosing system’s programmable logic controller (PLC) and compared with the predefined CAD reference of the component. The detected deviations are used to adjust the dosing program in advance for the next adhesive application.

The mixing head mounted on the robot arm moves over the contour of the display housing and applies a precise, narrow bead of adhesive to the contour. Thanks to the AQA process, it is possible to automatically adjust the adhesive discharge quantity to match the dimensional deviations of any component tolerances.

Wavy unevenness of the bonding surfaces can occur during the injection molding of the display housing. In order to compensate for this, the robot travels more slowly over slightly recessed application areas so that more adhesive is applied there, and travels faster over the slightly raised areas so that less adhesive is dispensed there.

The result is a bead of adhesive that compensates for the height tolerances and will remain consistent after the display glass is joined to the housing.

Open Supply Tap Open Elevator Open Control cabinet Open Mixing head 825 PRO Open WT 1-LEVEL shuttle / sliding table Open CONTROL 2 Open MP 2 mobile panel Open Material pressure tanks Open Dosing machine cabinet

Supply Tap

Optional: Automatic SUPPLY TAP drum refilling station for low-viscosity products, e.g. isocyanate (B-component)

More information to our refilling stations

Elevator

Optional: Automatic ELEVATOR drum refilling station for the A-component with pneumatic lift and agitator

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Control cabinet

The control electronics, safety engineering and industrial PC are installed in the control cabinet.

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Mixing head 825 PRO

MK 800 PRO precision mixing head with high-pressure water rinsing or alternative component rinsing system

More information to our mixing heads

WT 1-LEVEL shuttle / sliding table

Two pick-up plates operating in pendulum mode in one plane

More information to our shuttle tables

CONTROL 2

Optionally available: CONTROL touchscreen operating panel (21.5“) for operating the dosing system

More information to our operating panels

MP 2 mobile panel

The multifunctional MP 2 mobile panel (10.1” WXGA TFT) enables convenient operation of the dosing system.

More information to our operating panels

Material pressure tanks

Material pressure tanks (24 l or 44 l, single-walled or double-walled) with minimum level sensors, on a grating platform with adjustable leveling feet

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Dosing machine cabinet

The dosing machine cabinet contains the components of the dosing periphery, e.g. the dosing pumps.

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