Industrial bonding processes

From production planning to the industrial production of bonded products: Development of adhesive bonding processes

In adhesive bonding, the design of the manufacturing process plays a special role in ensuring controllable and consistent quality of the bond. The manufacturing process is of particular importance in the context of bonding. Upscaling from manual production to semi-automated or fully automated production requires in-depth knowledge of the right dispensing systems, mixers and suitable nozzles as well as the interfaces to downstream sub-processes.

The experts at Fraunhofer IFAM advise customers on each production step and even offer to set up a customized prototype adhesive bonding production or series production for their products. This is used to demonstrate to the customer what their production could look like in the future.

We also offer detailed analyses of adhesive bonding processes. The analysis can be carried out either for existing adhesive bonding processes or in advance of future manufacturing scenarios. Fraunhofer IFAM focuses directly on the needs of the customer. These are recorded in a detailed list of requirements before the start.

In the following, we present a first impression of our range of services based on individual process steps and application techniques. We would be pleased to analyze the adhesive bonding needs of your company together with you and develop a customized solution for you.

A holistic view: Adhesive bonding production concepts


The successful use of adhesive bonding technology in production cannot be ensured solely by selecting a suitable adhesive system that ensures that the mechanical requirements for the bonded joint are met. The large number of different adhesive systems also requires intensive consideration of the customer's entire manufacturing process. The process usually starts with the surface pretreatment of the components, followed by the application of the adhesive as well as the joining of the components, and ends with the curing of the adhesive system. Only a manufacturing process that is tailored to the adhesive system can ensure the lasting and successful use of adhesive bonding technology.

The development of these manufacturing concepts usually takes place in parallel with the adhesive selection and is backed up by empirical tests. The test concept required for this is individually adapted to the respective task. By means of this procedure, all relevant process parameters are recorded, thus enabling production-related planning of the subsequent process sequence.

The compatibility of the adhesive bonding production process can be checked in advance using various methods. Based on customer-specific requirements, we first develop possible manufacturing concepts and evaluate them in terms of customer benefit. We then test these concepts for technical suitability using prototype trials.

In the case of complex issues, the methods of manufacturing simulation allow a decided insight into the future manufacturing process. Furthermore, a self-developed software (IFAM-Calculation Tool) allows an exact estimation of the expected manufacturing costs and the necessary investment costs. Thus, it is already possible in early development stages to check the suitability with regard to the customer's requirements and to avoid undesirable developments.

Metering and mixing technology: Automated adhesive processing


For the processing and application of adhesives – depending on whether they are single-component (1-K) or two-component (2-K) adhesives – metering systems and mixers are required. The selection of a metering system for a process requires a multi-layered approach. On the one hand, material-dependent influences must be taken into account, e. g. the viscosity of the adhesive, as well as process-dependent influences, such as the application quantity in the desired cycle time.

We offer the customer individual support in the selection of dispensing equipment and suitable mixing systems – in addition to consulting services: A large number of systems for different types of containers – from cartridges (10 ml) to drums (200 l) – are available in the Fraunhofer IFAM technical center. In addition, for specific tests, equipment can be borrowed from the relevant manufacturers and tested in the technical center in Bremen for suitability according to the requirements of the adhesive used and the respective manufacturing process.

Application technology: Nozzles


The application of adhesives often requires specific nozzle concepts tailored to the particular application. The required adhesive bead with its individual dimensions results from the geometry of the substrates to be joined and the desired gap dimensions. A particular challenge here is the bonding of large components or three-dimensionally curved structures.

In order to be able to apply the adhesive bead to the component reliably, a suitable nozzle must be available. The nozzles available on the market for adhesive application are standard products for standard solutions.

For more specific adhesive application requirements, we offer the development and qualification of individual application nozzles that are matched to the adhesive system and the required bead shape of the specific application. The development of the application nozzles is carried out with the inclusion of flow simulation for the respective nozzle shape.

Application technology: Tapes


Flexible packaging, adhesive tapes, functional textiles and even web-shaped modules for the production of flexible solar cells for energy generation are products that are part of everyday life or are increasingly finding their way there. They are characterized by the fact that during their manufacturing process materials – for example adhesives – are applied to substrates over a large area.

Fraunhofer IFAM not only has a wide range of expertise in the area of manufacturing technology relating to linear adhesive application, but also in the area of two-dimensional coating. These are complemented by extensive experience in the use of adhesives and polymer coating materials in packaging, films, paper, and other flat materials.

A pilot plant for coating and bonding of web-shaped or large-area substrates enables the technology transfer of individual adhesive technology innovations directly to the customer's industrial production. The coating line enables the development of application-oriented special processes that go far beyond the laboratory scale.

Adhesive application in micro manufacturing


Particularly in microsystems technology, precision engineering, medical technology, microelectronics, optics as well as optoelectronics, adhesive bonding opens up new perspectives for companies in the production of the smallest components, which combine a wide range of functions in a small space. In this way, even complex designs can be bonded in individual configurations throughout the micro range.

Bonding in small dimensions is associated with a variety of new challenges, since the properties of polymers known from the macro range cannot be transferred to the micro range without restrictions. The experts in the Adhesive Bonding Technology department at Fraunhofer IFAM have the in-depth know-how and experience to deal with this problem. Therefore, they work together with the customer to develop customized solutions for bonding in the micro range.

Particularly for bonding processes in the range of a few micrometers, only the perfect coordination of the manufacturing processes guarantees success, because even the slightest deviations, which are hardly relevant in the macro range, can have significant effects here. Microfabrication techniques therefore include the reproducible application of the smallest adhesive volumes or the thinnest adhesive layers, the positioning and adjustment of the tiniest parts, force- or displacement-controlled joining, and low-stress curing with short cycle times.

A wide range of applications for microfabrication are available at the institute; otherwise they are developed individually according to customer requirements.

Polymer potting for the protection of electronic components


With the steady increase in electronic assemblies and their use, for example in motor vehicles and sensors, the demands on their long-term stability and functional reliability are also rising. Polymer potting is a suitable method for protecting these components. By potting or applying protective coatings, the components to be protected, for example a printed circuit board, are completely enclosed by a polymer to ensure their reliability. The potting leads to better heat dissipation, mechanical protection as well as protection against external influences and also electrical insulation, which means that the functionality of the components can be guaranteed even in harsh environments.

Flow simulation


The description of flow processes by numerical flow simulation CFD (Computational Fluid Dynamics) is already used in a wide variety of technical fields. The range of this method extends from the aerodynamics of various means of transport to the simulation of the filling process in injection molding and the description of engine combustion processes. In the field of mechanical adhesive processing, numerical flow simulation has so far been little used.

In contrast to air and water, adhesives are almost exclusively non-Newtonian fluids with complex flow behavior. For the manufacturer and the operator of adhesive dispensing and application systems, the flow of adhesives in these systems is therefore difficult to estimate. This can lead to unexpected flow effects, planning problems, or sudden operational disturbances.

Fraunhofer IFAM uses flow simulation on behalf of customers and in research projects with the aim of fully understanding the flow of the adhesive during adhesive bonding production. The basis for an accurate simulation is always the targeted rheological characterization of the flow behavior of the adhesives, the validation of the simulation on an instrumented application technique, and the detailed knowledge of the industrial production conditions.

Robot Technical Center: Automated Adhesive Bonding Processes


The robot technology center at the Fraunhofer IFAM in Bremen has successfully established itself as a test environment for the automated application of adhesives. It currently consists of two industrial robots with payloads of 125 and 60 kg respectively. One robot also has a linear axis to extend the working area. Furthermore, a large number of dispensing systems are available for a wide range of applications. When planning the robot technology center, care was taken at every stage to ensure that all dispensing equipment could be used flexibly on one of the robots or as a stand-alone system with a fixed nozzle. The experts in adhesive bonding production can carry out research and development work for customers from a wide range of sectors in the robotics technology center. One current issue is the integration of adhesive bonding technology into the Industry 4.0 environment. The researchers have already completed the "Bonding 4.0" project in this area. As part of the DigiKleb funding project, the bonding robot technology center is currently being expanded into a demo center for automotive bonding in Industry 4.0.