„Welding expertise that saves lives“
Airbag ignition wires: Machined with micrometer precision
The latest B 20K welding controller used in combination with a RM 40P stamping and forming machine is the ideal solution for joining ignition wires. The greatest advantage is the ability to precisely dose and fine-tune the energy input during resistance welding. This ensures that the wire fuses perfectly, thereby guaranteeing that the component will function correctly.
They are practically invisible in the passenger compartment, trigger in a fraction of a second and save lives: Airbags are one of the most important safety features in the car. It is therefore equally important that all the components are manufactured to the highest quality. This applies just as much to the crash sensors as it does to the plastic bags, which are deployed in just 20 to 50 milliseconds. However, the most important element of all is the airbag’s ignition mechanism. “The igniter is the heart of every airbag system,” explains Martin Ott from the Bihler Welding Technology Department. “If a crash occurs, it receives an electric pulse from the sensors and then immediately triggers airbag inflation.”
Constant resistance
The central component of the ignition unit is the ignition wire, which is only a few micrometers thick and has to remain securely and permanently attached to two connecting pins. Bihler has more than 40 years’ experience of applications just like this and has already successfully implemented numerous automation solutions that meet the high requirements, in particular with regard to joining the wires. Ott makes things clear: “The most important quality criterion for igniters is keeping the resistance constant in order to ensure that exactly the right amount of electricity is applied at the transitions of the connecting pins. Precisely dosed, targeted energy input is therefore essential.
In the high-frequency range
The B 20K welding controller represents the perfect response to these requirements. This is because it works at particularly high frequencies of between 1 and 20 kHz and consequently permits particularly precise adjustment of the energy input. At the same time, the B 20K allows users to make a large number of settings for high-frequency operation and intervene to monitor the welding process online, adapt it to the specific circumstances and consequently achieve optimum parts quality. The process is monitored by five integrated, freely programmable measurement channels. These capture all the relevant data, for example concerning current, voltage and distance, and are used to assess the final weld. In addition, users can choose between various current or power control modes that make it possible to implement individual welding profiles and ensure optimum process reliability. There is also an active power supply module for the network supply that ensures that the system is protected against network fluctuations.
Clamping and fusing
A RM 40P stamping and forming machine in combination with a B 20K welding controller is one example of a cutting-edge manufacturing solution for airbag igniters. Equipped with two welding heads, the system handles wire diameters of 11 to 23 µm and outputs 100 finished parts per minute. The two pins are prepared at the stamping and forming machine and the wire is then inserted in the two lugs provided and mechanically fixed in place. At the downstream welding station, the lugs are then securely and permanently resistance-welded to the wire.
Integrating relevant variables
This solution once again underscores Bihler’s outstanding competence in the manufacture of airbag igniters – an area of expertise that goes all the way back to 1984, when a MACH-1/7 was used in combination with the B 10 three-phase welding controller operating at 50 Hz. And in the future, Bihler will use NC technology and OPC-UA-based data transfer to incorporate information about parts preparation in the welding process. This solution will also include further-optimized stamping force management, and it will be possible to use information about a number of relevant variables, for example from resistance measurement systems, in a variety of control circuits in order to make the manufacture of airbag igniters and other demanding precision parts even more efficient and reliable.
