Contents of DIN 2304 and DIN 6701

Adhesives are quality products that are manufactured in a reproducible way. Bonding faults in industrial products arise mostly due to adhesive application errors. These faults can be prevented by complying with the DIN 2304 standard "Adhesive bonding technology – Quality requirements for bonding processes" for general industry and the handicrafts sector or the DIN 6701 standard "Manufacture of adhesive bonds on rail vehicles and parts of rail vehicles". These standards aim to manage the organization of the whole bonding process. DIN 6701 applies for all bonded joints, classes of adhesives, and material combinations in the rail vehicle manufacturing industry whereas DIN 2304 applies for all load-bearing bonded joints in other sectors of industry. Both standards represent a paradigm shift for the use of adhesives, putting more responsibility on adhesive users and specifying a binding state-of-the-art in product safety regulation for the correct implementation of bonding processes. They stipulate both the requirements for manufacturing quality bonded joints and the general organizational, contractual and technical-production basis for manufacturing bonded joints.

The standards define three core concepts:

• Classification of bonded joints in accordance with safety requirements
• Appointment of supervisors in charge (SICs) of adhesive bonding work
• Verification: Actual load < Load limit of the bonded joint

DIN 2304 and DIN 6701 stipulate that users must classify all bonded joints into the safety classes S 1 – S 4 (DIN 2304) or A 1 to A Z (DIN 6701). This classification is exclusively based on the simple question:

What happens if the bonded joint fails?

The relevant designer or the person responsible for providing the component must answer this question and must classify the bonded joint in consultation with the supervisor in charge of the bonding work (SIC, core concept 2). The classification of the bonded joint here is independent of the strength and deformation properties and solidifying mechanism of the relevant adhesive.

Other requirements such as suitability for use with foods, fire protection regulations, emission regulations, and work safety when manufacturing bonded joints are not considered for the classification of bonded joints within these standards. There are already other standards and regulations for these aspects.

With regards to the appointment of a supervisor in charge (SIC) of adhesive bonding work by the user-company, suitable persons are employees having responsibility at the company for the adhesive bonding and related tasks. Their suitability and technical knowledge (obtained via training, education, and /or relevant experience) must be verified and documented.

The supervisor in charge (SIC) of adhesive bonding work at the company is the main contact person for all quality matters relating to the so-called "special process" of adhesive bonding, from the planning stage through to production and maintenance/repair. In accordance with DIN 2304 the user-company must assign a sufficient number of trained personnel for the relevant tasks and document their appointment. Depending on the class of bonded joint, a suitable professional qualification (carpenter, floor layer, decorator, etc.) or professional training such as DVS^®/EWF - European Adhesive Bonder, DVS^®/EWF - European Adhesive Specialist, DVS^®/EWF - European Adhsive Engineer can be used as suitable qualifications for appointment as SIC.

Further information about workforce training courses in adhesive bonding technology can be found at www.bremen-bonding.com.

It is standard practice to size a bonded joint such that the actual loads/stresses to which it is exposed are always less than the load/stress limit of the bonded joint. This is so not just for adhesive bonding but also for all other joining technologies. New in DIN 2304 and DIN 6701 is that assurance of this must be given by the supervisor in charge (SIC) of adhesive bonding work and demonstration of this must be clearly documented.

The demonstration of this can be carried out in four ways:

1. Measurements
2. Component testing
3. Documented experience
4. Combinations of 1 to 3

Besides the three mentioned core concepts, the following aspects are also covered in the standards:

• Contract reviews and subcontracting
• Development processes and process planning
• Infrastructure
• Production and maintenance
• Storage and logistics
• Monitoring/inspection of measuring equipment, testing devices, and auxiliary production equipment
• Quality management