Mikron achieves zero defects in high-speed assembly of gas generators for TRW airbag systems

Citation

(2002), "Mikron achieves zero defects in high-speed assembly of gas generators for TRW airbag systems", Assembly Automation, Vol. 22 No. 4. https://doi.org/10.1108/aa.2002.03322daf.001

Mikron achieves zero defects in high-speed assembly of gas generators for TRW airbag systems

Mikron achieves zero defects in high-speed assembly of gas generators for TRW airbag systems

Keywords: Assembly, Automotive

The assembly of gas generators for the inflation of automotive air bags demands the highest standards of reliability and process accountability: zero defects in every component at every stage of manufacture is essential. International manufacturer TRW selected Mikron Assembly Technology to develop a system to meet the challenge.

An air bag must fully inflate within a fraction of a second if it is to protect the vehicle’s occupants in the event of an accident. There are no second chances, and 100 per cent reliability is vital (see Plate 1).

Europe’s leading air bag manufacturer TRW Airbag Systems has developed the PP13 gas generator, a pyrotechnic inflator offering improved ignition control and application versatility.

Plate 1 No second chances. An air bag must fully inflate in a fraction of a second to protect the vehicles occupants in the event of an accident

TRW appointed Mikron Assembly Technology to develop an assembly system capable not only of assembling the components accurately at high speed, but also with the ability to guarantee zero defects and provide traceable documentation for archiving.

Simultaneous engineering

From the outset Mikron planned the development of the assembly system using their technique of “simultaneous engineering”, a management tool which allowed the design of the assembly equipment to take place in parallel with the development of the product at TRW. By co-ordinating the project in this way, Mikron was able to meet the critical time-to-market criteria required by TRW.

Flexifactor high speed assembly system

Mikron used their linear feed high-speed Flexifactor system with individual cam driven assembly cells connected by conveyors to assemble the PP13. The construction of air bag gas generators demands the integration of highly complex assembly processes. Mikron designed special laser welding cells for the TRW project to carry out the task of welding the pre-pressed disks that separate the air- tight generator chambers. The completed system incorporated five of these cells alternately actuated by powerful laser units.

Filling quantity critical

The response and behaviour of an air bag can be substantially influenced by the fuel composition of the filling as well as the quantity of fuel used. To accurately monitor the critical filling of the gas generators, a system of weighing the units both before and after filling was incorporated in the assembly process. The exact weight of the filling used in each chamber is automatically calculated and electronically recorded.

All assembly data stored

Data for each component must be stored and be traceable for a period of at least 15 years. To achieve this Mikron used a system of bar coding and permanent laser marking to identify each component during assembly. All data were then automatically transferred to TRW’s master computer for archiving.

Zero defects

As functionally testing the completed unit would result in its destruction, it was necessary for Mikron and TRW to develop a perfect test program that could be incorporated into the Flexcell assembly system. During assembly, any deviation from the required standard had to be identified at every step of production rather than by inspecting the completed product at the end of the line. This was achieved by incorporating vision recognition systems, leak testing, laser monitoring devices, weight and force measuring systems and other inspection equipment within the production cells to guarantee zero defects.

Reliability and versatility

In addition to stringent quality safety requirements, TRW demanded the highest standards of reliability from the Mikron system. Air bag production continues day and night year in year out and reliability is vital.

Many different gas generators are assembled on the Mikron installations, corresponding to air bag sizes from 8 to 160l(see Plate 2). In developing the assembly equipment, the Mikron engineers carefully considered the need to minimise the set-up complexity during product changeover and keep down-time to a minimum.

Plate 2 Two stage PP13 airbag gas generator for the inflation of a 103l airbag

Seven Flexifactor high-speed assembly systems with a total of 25 Flexcell assembly cells are now in continuous operation at the TRW factory with additional units installed at the company’s plant in the USA.

Technical information from: Richard Krusts (Regional Sales Manager), Mikron Assembly Technology, 74 Newland lane, Ash Green, COVENTRY, CV7 9BA, Tel: 02476 366071; Fax: 02476 366084; E-mail: r.krusts@ch.mikron-tg.com