VOL. 12 July ISSUE YEAR 2011
in Vol. 12 - July Issue - Year 2011
A Solution For Higher Operating Loads. Dual Shotpeening Of Automotive Transmission Components
As an all-round supplier, Rösler GmbH is an international market leader in the production of surface finishing, shot blasting machines, painting systems and preservation lines as well as process technology for the rational surface finishing (deburring, descaling, sand removal, polishing, grinding…) of metals and other components. Besides the German plants in Untermerzbach and Bad Staffelstein, the Rösler Group has branches in Great Britain, France, Italy, The Netherlands, Belgium, Austria, Switzerland, Spain, Romania, Russia, China, India, Brazil, South Africa and USA.
Future generations of automotive transmissions will be exposed to higher operating loads. PSA Peugeot Citroën is meeting this technical challenge by a dual-stage shot peening process for transmission components with different blast media.
PSA Peugeot Citroën has stringent requirements, including the reduction of CO2 emissions and fuel consumption, as well as increased vehicle safety and comfort. The French car manufacturer is currently developing innovative power trains, which are characterized by their fuel efficiency and high performance. This requires parts – including transmission components -that are manufactured within very tight tolerances, and which can withstand extremely high operational loads. To improve mechanical strength, wear resistance and life expectancy of components exposed to very high loads (for example shafts and gears), PSA Peugeot Citroën has invested in an innovative Rösler shot peening system that allows the peening of components with two different blast medias.
A custom engineered shot blast process
The automatic rotary table peening system, specifically developed for PSA Peugeot Citroën, contains five work stations, separated from each other by manganese steel dividing walls. Each work station is equipped with two rotary satellite units. This configuration allows the simultaneous peening of ten transmission parts. The Almen readings for the various parts range from 0.45 to 0.6 mmA.
Per each satellite unit, four blast nozzles are initially throwing steel blast media (G2, 700 Hv), followed by a finer type of the same blast media. The average peening time for two parts is 30 seconds. After the final peening step, the parts are marked with an inkjet printer. This prevents the risk of installing parts that are not or are only partially peened.
In order to implement the dual shot peening concept, the shot peening system was equipped with two blast units, operating entirely independently of each other. The blast media is delivered by two dual-pressure vessels. The continuous monitoring of blast media quantity, blast pressure and compressed air consumption guarantees a high degree of process safety and repeatable results. For certain critical components, a special laboratory conducts measurements to verify that residual compressive stresses of a minimum 1,000 Mpa were induced on the parts surface.
Specially designed fixtures guarantee fast parts loading/unloading
Jointly with PSA Peugeot Citroën, Rösler designed the special holding fixtures for the different transmission parts with dimensions of 200 mm in diameter and 32 mm thickness up to 380 mm length and 60 mm diameter respectively. This special design ensures not only the absolutely precise positioning of the parts on the satellite stations, but also the loading/unloading of a complete batch of parts in only ten minutes.
Media cleaning and classification: a real challenge
The use of different blast media within the same shot peening system requires highly effective media classification. For this purpose, the steel media passes through an air wash separator, followed by a special screen separation unit. The dust collector system, specially designed for automotive applications, is equipped with an automatic fire alarm and fire extinguishing system and fully complies with the ATEX guidelines, category St1. In addition, the clean air outlet is equipped with a sensor that measures the dust concentration in the clean air.
Key factors in the customer’s decision for the shot peening system from Rösler were the tailor-made technical concept and Rösler’s experience and know-how in design dual shot peening systems. PSA Peugeot Citroën has also had an excellent track record with the seven Rösler systems that have been in operation at their facility.