Break for perfect formfitting

BMW manufactures its boxer cilinder rods in one piece. Then cracks them in two to assemble them onto the cilinderhead. By doing this they obtain a perfect match between the two pieces.

Almost every internal combustion engine uses connecting rods to convert the linear movement of the pistons into the rotational movement of the crankshaft. If split connecting rods are used, the connection rod eye lower end must be separated into the connecting rod saddle and bearing cap.

Until now, these two halves were produced separately and then matched up together at a later point. This process required numerous working steps during production and a high level of dimensional accuracy.

Cracking - the technology
This working process has been rationalized for high performance engines. The connecting rods used here are initially produced as single part precision forged parts. The connecting rod bearing is then broken apart at a predefined point by fracture splitting, so-called cracking.
Process monitoring

The entire cracking process only takes milliseconds. The quality of the fracturing process and the fracture can be determined from the force/time curve.

Source: hbm.comAdded: 20 February 2007