Production line for airbag gas generators
PIA Fact Check
- Cycle time improved by 50%
- Best possible flexibility
- Safety standards due to pyro material
From production with very little partial automation to full automation
Gas generators are required to inflate an airbag in a controlled manner - using pyro material - in the event of a collision. There are different airbag variants (e.g. for driver or passenger seats) and in ignition stages (single and double). PIA Automation developed a complex assembly concept for the production of airbag gas generators for a well-known customer in the automotive supply industry. The challenges include complying with high safety standards (particularly due to the highly flammable pyro material), reducing the cycle time by half while maintaining the maximum flexibility.
PIA Automation’s challenge here was to integrate customer’s highly flexible (but partially automated) production method into a fully automated assembly system. Previously, the assembly line relied on manual workstations for many steps, with logistics processes also handled by operators. While the goal was to retain as much flexibility as possible, automation was expected to significantly improve efficiency – reducing the cycle time from 12 seconds to just 6.
Large system in six-second cycles
Previously, five to eight employees were required to produce a single gas generator. Now, thanks to full automation, the machine runs automatically for extended periods - stopping only when material needs replacement or refill - with just one operator overseeing the process. The entire production runs automatically, including:
- Feeding and component transport (via workpiece carriers)
- Assembly processes (pressing, welding - both laser and friction welding and gluing)
- Pyro material filling in multiple stages
- Quality control (including helium leakage testing)
All of this is achieved in a six-second cycle – a major challenge, as some processes take longer than others. To meet this target, longer process steps were parallelized: within each module, two identical stations run simultaneously, ensuring the total cycle time remains 6 seconds for the production of each generator.
Sensitive handling of the pyro material
Various examples with PIA-specific solutions show just how complex the implementation of the system was. Existing concepts were adapted and optimized to meet customer requirements. These include the integration of the laser rotary indexing table, the patented PIA quick-change system clictec, special flexible feeders as a magazine solution, and high safety standards with regard to the pyro material. The system was realized in accordance with the globally applicable CE directives and in compliance with explosion protection safety measures. This means that the system concept works worldwide and can also be adapted for other countries.
To illustrate the sensitive handling of the pyro material, the complex inflation mechanism of an airbag is described: The initial electrical impulse first ignites a preliminary stage with its own pyro material. This in turn ignites the actual mass of pyro-material, which then inflates the airbag. There is also the option of a second ignition, so that after the first impact of the head on the airbag, the airbag remains filled and absorbs the new movement if the head is thrown back and hits the airbag again. Up to three chambers in the system must therefore be filled with pyro material to an accuracy of 0.07 grams. This is ensured by weighing all three chambers. In addition, it must be checked whether the electric detonators are actually functional at a certain resistance. The system also performs this with an electrical function test. Production stops are also a particular challenge with regard to the moisture-sensitive pyro material. In this case, the pyro material must be moved from production to a controlled environment. This was solved semi-automatically. Partially assembled products must then be removed from the system and re-introduced later at the same location. The machine control system checks that this is correct. All semi-finished products already have identification codes so that complete traceability of the products is always guaranteed.
PIA solution for a safe laser process
For the laser processes, the customer benefited from PIA's own solution, a laser rotary indexing table, which was adapted for this system. This has two advantages: safety for the operator and lower maintenance costs. The module consists of a large and a smaller rotary indexing table. The larger one transports all parts between the individual stations. The laser work is carried out on the smaller rotary indexing table. This chamber is locked in such a way that the door can only be opened with tools. This offers employees a high level of safety during operation. The larger rotary indexing table can be opened independently of the laser rotary indexing table, while the laser itself is still ready for operation and does not have to be switched off completely. If the laser is not constantly switched on and off, production times are increased and maintenance costs are significantly reduced.
Complete traceability
Another PIA product that customers can use when setting up an assembly system is the line controller. The software is directly compatible with the machine control system and the existing interfaces. The line controller monitors all process parameters and enables comprehensive traceability. Each product is traceable and stored in a database. The line controller also specifies the production data for each variant from the job management system and instructs the stations to manufacture according to a specific data series. The line controller also communicates with the customer's higher-level systems: for example, to report back how much waste was produced in the last variant, how much material was used and how many new materials need to be ordered.
Individual magazine solution
A tricky detail of the system was the realization of a form-flexible feed. Falc Borchard explains: "You have to imagine a material like a cosmetic pad. Feeding and precise separation of the individual "pad" is difficult due to the lack of stability. We have developed a magazine solution that can reliably and reproducibly feed these flexible noise damping components made of fiber composite material individually." The components are later used in the generator to dampen the noise generated by the car's vibrations
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