Committed to safety

Efficient assembly of airbag control sensors

TRW Systems in the county of Durham, UK, is one of the market leaders in the manufacture of intelligent safety systems and has made a name for itself as a reputable supplier of airbag control sensors. Until recently, the production of airbag modules at TRW in Peterlee relied to a large extent on manual labor.

Rising demand and the desire to bring more of the supply chain in-house generated the need for new investment in a dedicated manufacturing line. TRW called in Stäubli Robotics as well as its system integrators Grohmann and IPTE to advise on the best way of directing the available funds. A preliminary analysis revealed that an expansion of the manual assembly line would not be able to compete with a fully automated robotic solution in terms of either output or cost benefit. The decision went in favor of a new fully automated assembly line based on four-axis and six-axis robots supplied by Stäubli Robotics.



New assembly line with Stäubli robots

The new assembly line consists of several cells connected in series, all of which are equipped with Stäubli industrial robots. In the first step, two Stäubli TS60 SCARAs insert a metal contact into a printed circuit board. This is followed by the soldering of electrical contacts on the board. During the subsequent quality inspection, another SCARA TS60 manipulates the components.

The next stage is the overmolding of the PCB. This is carried out by two six-axis RX160 chosen for their exceptional range and outstanding dynamics. These two industrial robots perform the complete handling of the components with the utmost speed and precision.

They subsequently transfer the module to the final quality assurance station. This is where it is tested for correct triggering in case of an accident. In order to pass the test, the response time for the airbag signal must not exceed 19 milliseconds. The failure rate in these tests has been drastically reduced by the new assembly line and now stands at under 0.1 percent – a remarkable improvement on the manual system which used a higher proportion of outsourced components. At the last station on the line, the product is marked and labeled to ensure 100% traceability.



Flexibility, quality and output

With its initial investment in a robot-assisted assembly line, TRW Peterlee was able to dispel initial concerns about operation and the cost of training. Indeed, such fears quickly turned out to be unfounded. In a very short period of time, the operators were able to utilize to the full the advantages of the new assembly line with its Stäubli robots. The production line was running 24 hours a day, six days a week, within its first seven months. There were no significant problems.

Due to the flexibility of the line, different variants of the airbag module can be produced. Shortly after it went into operation, they already had twelve models in production. Compared to the manual system, the automated solution gets by with twelve fewer human operators. In addition, the line is ideally suited for lean, just-in-time production. The senior management at TRW were impressed by the performance of the system, especially the Stäubli robots and the sensationally short amortization period of less than one year.