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Story 193 – 2015 – Innovation

When the smallest detail matters

A new process for manufacturing connecting rod bushings for truck engines

Enormous development work at Wieland has resulted in a revolutionary process for the production of connecting rod bushings: without machining, highly loaded slide bearings can be produced in large series with high precision in almost any conceivable geometry.

Truck engines operate at comparatively low rotational speeds, which are generally below 2,000 rpm. With one challenging consequence: the connecting rod bearings, through which the force of the pistons is transmitted to the crankshaft, are almost exclusively loaded with compressive forces, while the tensile forces are very low. For this reason, the slide bearings used at this point - the connecting rod bushings - are designed in a stepped or slanted design; this is the only way to achieve optimum load distribution.

In order to be able to produce such complex geometries as precisely, durably and economically as possible, Wieland implemented a completely new process for the production of rolled connecting rod bushings in large series in 2015. The patented, unique principle works with predetermined breaking points which are stamped onto the blank according to the desired contour – even before rolling.

Once the bushing is calibrated after the rolling process, the final profile is achieved by "cracking", i.e. breaking off the pre-stamped surfaces. At the same time, at the predetermined breaking points no fibres are let on the high-precision bushings, which can thus be realised without machining and in almost any shape.

This requires a material that can cope with the high specific performances. Wieland has therefore developed and patented the alloy Wieland L66 especially for this application.

After intensive and thorough tests, in which important Wieland customers were involved, the crack bushing is now successfully in series production at several manufacturers of truck engines. And: The revolutionary process now allows large-scale series production and can be adapted to all conceivable geometries – such as trapezoid or step. With this in mind, the business unit Engineered Products continues to work on new material variants and process optimisations – with the promising goal of winning further markets and customers for the unique crack bushings.

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Crack bushings

The asymmetrical shape of a connecting rod bushing for truck engines, produced by the cracking process, is clearly visible.