Thread forming screws cut costs while improving safety

Engineering students are discovering that finding the right balance between good engineering design practice, racing car performance and financial planning, is not easy. Dean Palmer investigates

Direct fastener technology is gaining increasing acceptance, particularly in the automotive industry, where high volume manufacturing and assembly occurs. Thread forming screws, for example, are particularly useful when used to join plastic parts together.

But the functional capabilities of direct fasteners are being thoroughly tested in low volume production too. The Wolfsburg University of Technology in Germany has entered a team in the popular 'Formula Student' programme recently, which provides engineering students with an opportunity to get to grips with the demands of engineering practice at an early stage of their careers. The competition is not simply a matter of building the fastest car, but of finding a compromise between engineering design, race performance and financial planning.

Students at the Wolfsburg University of Technology set up the 'Wob Racing Team' in 2003, and has designed and manufactured a competition racing car in the Formula SAE class.

"The vehicle must not cost too much, and must be reliable and easy to drive," explained Steffen Niemann, project technical manager of Wob Racing.

Following initial successes at the Formula Student competitions in the UK and in Germany, the students are now building the vehicle for 2006. Fastener manufacturer Arnold Umformtechnik is now the development partner, who is supporting the project, both financially and by offering its technical expertise.

"The use of Arnold's thread forming Remform screws is helping our work in every discipline required," argued project manager Niemann. "By using Remform, we've shortened the process chain, reduced assembly costs and parts, and are creating an extra safety cushion."

Professor Paul Wollschl├Ąger, deputy director of the Vehicle Construction Institute commented: "The principle of direct screwing is that, as it is screwed in, the screw takes over some of the steps of the manufacturing process that, in conventional manufacturing, would need to be carried out as separate work procedures. As the fastener is screwed in, a gimlet incorporated into the tip, first forms the appropriate through-hole diameter, after which the screw taps into the bore thread with its own thread. There is no need to drill the hole and cut the thread, so assembly time is less. We save machining costs too, and on wear, so assembly costs go down."

The intake system on Wob Racing's WR01 model is manufactured as a rapid prototyping part from PA-6. It is not just the injection strip that is screwed to it, but the temperature sensor also has to be fastened to it. Remform screws solved this problem. The patented thread geometry provides the fastening with a considerably higher strip load and offers a greater difference between screw-in torque and overturn torque than the traditional 30┬░ low angle screws. The screws, which are therefore consistently tight, provide additional safety room - particularly necessary under the extreme conditions of motor racing.

Tom Shelley

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Interesting article.

Comment James Cherry, 06/09/2012

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