Cold Forging of a Silent Block Bush Steel Sleeve

    The object of this study was simulating and optimizing the cold forging process for a silent block bush steel sleeve. A block bush consists of two concentric steel sleeves with rubber securely bonded between them to fill up the void and absorb torsional, axial and radial loads. Silent block bushes are typically used in suspension systems in the automotive industry to absorb load and minimize suspensions. A silent block bush is traditionally used in the linkage system of a car suspension, in railway carriages and in agricultural machinery.

silent block

There were multiple objectives attached to this study. Specifically:

• optimize the material flow inside the dies and predict defects such as folds, cracks and underfills
• calibrate the press kinematics
• verify compliance with the original design blueprint
• estimate the maximum forging load at each forging stage
• and all of these while minimizing the costs and lead time
  
  
  
  springs

Setting up the Forging Simulation Parameters

Setting up the simulation environment could not have been easier. Transvalor ColdForm comes with a large reference database containing the properties of more than 200 steel, aluminum, brass and titanium materials. In fact, the material used in this study, CB4FF steel – UNI 7356, 1974 – at 20?C was already included and we, therefore, did not need to input any material properties.

Furthermore, the elasticity and plastic strain of the material were both accounted for by ColdForm; this enabled accurate residual stress and geometrical dimensions to be obtained after forming.

The simulation also took into account the heat transfer between the work piece and the dies, as well as the elastic spring back at each forging stage.

The Cold Forging Simulation Results

The objectives above were all met by the simulation, and the results are best expressed in the words of Gianfranco Marcandella, R&D technical lead at Altia Fontanafredda S.r.l. (see Raves section on the right column).