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Success with fastenings
Early cooperation is a factor of success – proven cost reduction throughout the value added chain – quality increased by greater process reliability.(PresseBox) ( Forchtenberg, Germany, )
Confirming this philosophy, Mario Metzger, Product Manager at screw specialist Arnold Umformtechnik GmbH, Ubrig & Sohne’s longstanding development partner, said: “throughout the 15 years we have worked with Ubrig & Söhne we have been involved at the earliest possible stage with new development projects.” Since the beginning of the 1990s Ubrig & Söhne has been using Arnold Remform threadforming screws for its fastenings. It was then that Ubrig started to carry out its component assembly with traditional screw fastenings on a bigger scale. Remform screws became the obvious choice due to their low screw-in torque and high overtorque. They complied with the specified requirements profile to the fullest extent. And they are much less expensive than metric screw/nut fasteners. “At present around 80 percent of our screw fastenings are Remform products from Arnold,” said Peter Langer of Ubrig Industrial Engineering.
Plastic gains recognition
Together with Arnold Umformtechnik, Ubrig & Söhne has made its mark on the process of direct fastening into plastics. As they worked together, both companies had recognised at an early stage that plastic was increasingly in use as a material in the automotive industry. Its moulding capacity, the weight, and recyclability are all positive points in favour of the synthetic material. “The comparatively flexible material is particularly suitable for direct screw fasteners,” commented Langer, explaining the decision to buy fasteners from Arnold. “Thread-forming screws are particularly advantageous where the core hole is pre-cast.”
In close cooperation with the design engineers at Arnold, Ubrig & Söhne soon recognised that Remform fasteners in particular have a positive effect on costs. There is no need for inserts or inlays, so the cost of materials goes down. The high screw-in speed achieved and the fully automated casting of parts means that cycle times are short. Plant utilisation and productivity increase consistently. “The reduction in costs is running at over 60 percent compared with traditional fasteners”, stated Langer, as he justified the decision to go for this type of fastener technology.
Such effects are the result of the special capacity of Remform screws to form the thread itself. The asymmetric thread geometry of Remform screws is constantly opening up new application fields on the product line at Ubrig & Söhne. The patented profile reduces the edge stresses that occur as the thread is formed. The flank angles, which diminish towards the crest of the thread, ensure that radial stress is reduced. This considerably reduces the risk of the boss splitting; at the same time Remform screws increase the safety of the joint. The flank that is averted away from the screw head has been provided with a radius. The steep side that has moved towards the head retains the plastic and raises the flank overlap. This guarantees high cross-thread forces while maintaining tensile force and torque. And the steep flank also ensures that the driving forces are transmitted axially - in the correct direction. Compared with 30-degree low angle screws the engineers at Ubrig & Söhne were able to prove strip load measurements and the difference between minimum overturn torque and maximum screw-in torque can often be well over 30 percent.
“Overall we are using a proportion of around 80 percent of direct screw fastenings in plastic – and it is rising”, continued Peter Langer. “This development will continue.” Together with the specialists at Arnold we are able to comply with the quality parameters set by the manufacturers, even under heavy cost pressure.”
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