Surface quality at the Fraunhofer Institute IFAM

Bonding, painting and coating are work steps that are used in all branches of industry - for example, transport equipment construction, mechanical and plant engineering or the electrical industry, but also medical technology. They do not always run smoothly: during the often necessary pretreatment of the material surfaces, defects can occur that initially remain undetected.

In order to avoid resulting damage, it is advisable to continuously monitor the surface quality in the manufacturing process.

Pretreatment important and difficult
When bonded joints fail due to poor adhesion, experience shows that contaminated surfaces are the cause in about 70 percent of cases. Defects in paints and coatings are also often discovered after the fact. The source of the defect is predominantly the pretreatment of the materials. This plays a key role in the overall process:

Only the cleaning and activation of surfaces guarantees successful bonding, painting and coating in many cases. The decisive processes of the sometimes multi-stage pretreatments take place in the size range of a few nanometers. Until now, continuous monitoring of these processes has hardly been possible.

Quality assurance has generally only been carried out by destructive testing on random samples after the bonding, painting or coating has been produced. Impurities or incomplete pre-treatments - for example, fingerprints or incomplete activations - have often remained undetected until now because they are not visible.

In addition to modern test methods for production-integrated quality assurance (in the running process), the specialists at the Fraunhofer IFAM research locations also develop solutions for the areas of production-accompanying testing, maintenance and repair, this also still with the aid of hand-held measuring instruments.

Permanent quality controls
The field of activity "adhesive bonding technology" includes, for example, the development and characterization of adhesives and matrix resins, the design and simulation of adhesive, riveted and hybrid joints in accordance with the stresses involved, as well as their characterization, testing and qualification. The focus is also on planning and automating the industrial production of individual joints.

Researchers at the IFAM Institute are aware of the difficulty: The basis, but also the complex challenge of optimum quality assurance of highly sensitive manufacturing processes can only be provided by continuous monitoring of the surface condition. However, this is very difficult in ongoing production. This is why IFAM is working on methods which guarantee reliable defect detection.

The "Quality Assurance of Surfaces at the Fraunhofer Institute for Manufacturing Technology and Advanced Materials IFAM" group is developing new, state-of-the-art methods for permanent surface monitoring in the production process. For this purpose, procedures are being developed for various materials and applications which allow simple but efficient inspection of pretreated surfaces "before the next process step". A central point of view is the flexibility of the respective technical solution. This allows the continuous monitoring of the condition of component surfaces to be integrated into the customer's individual manufacturing processes.

Two control methods used at IFAM:

OSEE (Optically Stimulated Electron Emission), for example, exploits the photoelectric effect on surfaces to detect contamination or coatings. The method can be used on metallic surfaces, but also on CFRP surfaces, e.g. to detect residual contamination from grease on die-cast aluminum components.

Another example is aerosol wetting testing, which can be used to check the quality of surface pretreatment over a large area. Specially developed image acquisition systems as well as evaluation routines enable reliable statements and can be optimally integrated into ongoing production processes.

Focus on surface inspection
The institute is concerned with tailor-made surface modifications. Currently, more than 650 employees from 21 departments bundle their broad technological and scientific know-how in seven core competencies: Metallic Materials, Polymeric Materials, Surface Technology, Bonding, Shaping and Functional Materials, Electromobility, Automation and Digitalization.

These core competencies - each in its own right and in combination - are the basis of the Institute's strong position in the research market and form the basis for future-oriented developments for the benefit of society.

The products and technologies primarily address industries with special significance for future viability: aviation, automotive, energy technology, medical technology and life sciences as well as maritime technologies. However, solutions developed at the institute are also used in other sectors of industry such as mechanical and plant engineering, the electronics and electrotechnical industries, shipbuilding and rail vehicle construction, and the packaging and construction industries.

In the respective departments, the industrial application spectrum of many materials is made clear. Adhesion and Interface Research, for example, works on the early detection of degradation phenomena, the validation of aging tests and process-integrated surface control, among other things.

The Adhesive Bonding Technology and Surfaces department is certified according to DIN EN ISO 9001, the materials testing laboratory and the corrosion testing laboratory are additionally accredited according to DIN EN ISO / IEC 17025. The Adhesive Bonding Technology Centre is internationally recognised as an accredited personnel qualification centre for further training in adhesive bonding technology via DVS-PersZert in accordance with DIN EN ISO / IEC 17024. Like the Plastics Competence Center Bremen, it is certified according to AZWV.