Testing interior door panels efficiently and safely

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Door interior trim panels are complex products with highly functional density that demand complex, reliable testing technology. This is an area of expertise for specialist ITgroup, which outlines here the processes and equipment used for testing of these components.

The days when the interior linings of the side doors were mainly used to seal the vehicle interior due to acoustics, humidity and air permeability are long gone. In modern vehicles, door panels are important functional units. They contain both mechanical components such as locks as well as a large number of electronic elements, such as switches for window lifters and mirror adjusters, central locking systems, loudspeakers, ambient lighting, and much more. Decorative elements such as trim strips and panels are also standard for many manufacturers. The high density of functions is increasing, especially in luxury class vehicles.

Due to the constantly growing number and variety of components in door panels, they must be designed so that they can be installed quickly and easily. Because of the trend toward more and more individualized products, challenges arise for manufacturers regarding development and production. Demands on inspection and testing are growing correspondingly, particularly with regard to process reliability and complexity.

In order to cost-effectively produce such complex components, automobile manufacturers rely on modular concepts. For example, the technical inner workings of a door are combined as far as possible into assemblies with corresponding modules, which can mean cross-platform savings in development and assembly, while at the same time retaining the individuality of the particular components.

Complex testing processes
The ITgroup also follows this principle of modularity; currently four powerful test stations for complex door panels of the luxury class have been assembled and delivered according to a modular concept.

“During development and design, we do not stubbornly look at the specifications, but study the processes at our various customers’ sites in detail so that the systems can be optimally integrated into the respective production environment and meet all requirements. Thanks to our modular testing technology, future modifications or expansions can also be implemented quickly and easily while maintaining high quality standards,” summarizes Tobias Kempe, account Manager at ITgroup.

The company offers various options for handling the test objects. From manual to semi-automated to fully automated solutions, everything is possible. The method of handling mainly depends on the required cycle time.

Each of the four limousine doors has its own production line, so the four new test stations are used at the end of each line, for so-called end-of-line testing. This means that the doors are tested 100% in just-in-sequence cycles.

Due to the numerous electronic and non-electronic components used in these test stations, several modules of the modular ‘Customize iT’ system in the company’s ‘MidiAdvanced’ range are used. In addition to a module for pure presence control and communication with electronic components, modules for photo documentation and optical camera control are also integrated. This covers a very wide range of door panel testing tasks, helping the manufacturer to maintain quality standards and to meet the obligation to provide proof and documentation to the end customer.

“No matter how varied the test requirements are, the test stations are developed completely in our company and, with the exception of the mechanical fixtures, are manufactured in Erdmannhausen. Our ‘one-stop-shop concept’ saves the customer from having to deal with an often complex and very changeable test environment despite the wide variety of components,” says Kempe. The customer thus has a comprehensive overall system, which makes life easier for the operator and secures production.

Future-oriented test stations
In the times of Industry 4.0, with increasing customer requirements and decreasing batch sizes, flexible test stands are required. For example, if customers require various colors of leather, ITgroup service technicians can access the test station via remote maintenance system and adapt the system quickly and easily. The system is not a rigid tool, but can be expanded if necessary thanks to the high-quality construction of the test stand, and can thus be reused in subsequent projects.

“Through many years of experience in developing test techniques for system suppliers of the installed sensor technology and electronics, we have a sound knowledge of the individual electronic components, starting with the test procedures and types of communication, through technical know-how for the optical inspection of even non-electronic components,” summarizes Kempe.

Diverse test landscape
For many electronic components, a mere presence check via current consumption or simple resistance measurement is often not sufficient. Communication via the component-specific bus system is required to differentiate which variant is installed with which hardware, software and serial number. To check switch functions, it is often necessary for an operator or robot to actuate the switch, so that the test system can evaluate the corresponding signals and functions at the same time. During this electronic test, the installation check can be carried out fully automatically using various camera test features and photo documentation of the complete inside and outside of the door.

After the test has been completed, these results, including the images, must be locally stored and transferred to the respective customer system. In the event of a complaint, this allows the perfect condition of the door panel to be verified at the end of production.

Ergonomically optimized test stand
The height-adjustable test table has a swivel frame in which the interior door panel to be tested is fixed for the entire test sequence. This includes a hand scanner for reading the barcode of door panels and cable harness and three cameras below the test table.

For testing, the operator places the inner door panel to be tested in the test table with the inside facing upward. He then scans the construction order and connects the coupling points with the contacting adapters and starts the electronic component test. Thanks to the swivel frame, the operator can swivel the door lining 180° and test the switches and ambient lighting for full function. In both positions, different variant and installation features are inspected and documented by several cameras. The tests are, of course, based on the manufacturer’s specifications. The tests also incorporate an optical check to ascertain whether the trim strips, switch types (variant check), chrome parts and plastic clips correspond to the order profile.

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