Application Technology

The automation of cable set production for automobiles is gathering speed, with ITW Automotive’s Plastic Fasteners Division supporting the process with a fully automated and fully validated production concept for bonded fasteners. The concept is characterised by a high-level of standardisation, continuous validation of the process chain and numerous cost and process benefits. 

The vehicle electrical system is one of the last disciplines in automotive manufacturing that is not manufactured automatically. The size and complexity, as well as the vast number of varieties and flexible structure of vehicle electrical systems, were previously arguments against robot-assisted manufacturing. In addition, for a very long time, the element of cost was managed by shifting manual cable set production to best cost countries. 

However, things are changing. The economic and geopolitical upheavals that have taken place over the last few years have motivated automotive manufacturers and vehicle electrical system suppliers to bring cable set production closer to vehicle production again, in order to boost supply chain resilience. This requires automated systems, as they are only way to limit production costs while increasing process reliability. ITW is able to provide a decisive impetus for this type of automated production with a fully validated production concept for bonded fasteners. 

Reliable processes

ITW became aware early on that an innovative fastener for automated production can only be successful in combination with a validated production and assembly concept. Adhesive technology works well here, as it is already used across various applications in automotive engineering. 

ITW therefore developed a continuous process concept and safeguarded it with comprehensive concept validation, process reliability, and cost efficiency, a top priority. The geometry of the locator was also optimised for automated processing. 

ITW then set-up simplified automated prototype production with industrial partners for the proof of concept. Key steps in the fully automated process include separation of the locators delivered as bulk goods into a vibratory bowl; picking up of the locator by the setting head at the end of the in-feeding conveyor; plasma pre-treatment of the adhesive surface; application of the hot adhesive on the curved contact surface; as well as the placing of the locator on the taped wiring harness using a robot. 

Even during the early development of the concept, ITW integrated several design details that offer many advantages in the subsequent series process. For example, the locator has two standardised contact surfaces for its vacuum gripper – regardless of the geometry of the connecting element. Various locators can therefore be handled on one cable set, with a single standard setting head, without needing to put a lot of work into modifying the setting head.

In addition, the newly developed locators are suitable for both bonding and winding with tapes. As a result, cable set manufacturers can combine the ITW locators with manual winding technology in a first step, already in series production, and later either with an automated winding process or as a standalone bonded connection. Furthermore, ITW has selected an adhesive that produces an excellent bonded connection with all relevant winding tape variants. Depending on the materials of the winding tapes, holding forces of up to 600N can be achieved – far above the required values of around 100N – 150N. 

As an option, a tab can be attached to the locator to make it easier to replace damaged fixtures. The locator consists of 80% – 100% recycled material and thus improves the customer’s carbon balance. 

Modular expansion

Flexibility and modularity play a key role for cable set producers. With ITW adhesive technology, automated production lines can easily be expanded with separators, robots, and setting heads, to shorten cycle times or place additional locator variants on the same wiring harness. 

The automated locator production concept also offers additional advantages compared to previous fastener solutions – primarily cable ties and adhesive tapes. Bonding is therefore a relatively simple and fast process with a high-level of reliability and comparatively low investment costs. The small locators and the streamlined setting head can be easily inserted into narrow gaps between the mounting panel and the wiring harness, thereby ensuring good all round access to the wiring harness. Competing concepts require significantly more space here.

Furthermore, a bonded locator can be placed with significantly reduced distance to an interference contour when compared with competing processes. These are also significantly more complex and fragile when handling during bonding. 

When applied to the design and development of the wiring harness, ITW states its adhesive technology enables greater design freedom than competing concepts and is significantly cheaper. It also offers a fully validated process and represents a significant step towards automated cable set production. Furthermore, the concept complies with the basic recommendations of DIN 72036, which several OEMs, cable set manufacturers, and suppliers, have developed as part of ARENA 2036, which will be published soon. ITW has already presented the concept with bonded fasteners to premium OEMs in the south of Germany and is currently working together with one of them on the concept approval. If these tests are successfully completed, cable set manufacturers could integrate ITW adhesive technology into initial automated production concepts for this premium OEM.

ITW can support partners not only with its fasteners suitable for automation and setting head technology, but also with its expertise on the entire production concept in this process. This includes, for example, contact with adhesive and system suppliers. Customers may also choose to just use ITW’s concepts and industrialise them with their own partners.