For camshafts and gear shafts, heat shrinking of the constituent parts ensures a compact design and high functional density, with the gears in direct contact with the shoulders.
The adjustments never end for manufacturers supplying automakers with components and systems – in particular as the OEMs strive to speed up their design processes and implement the changes in their products. For the suppliers, it’s no small thing to adjust to design changes, but they do what is expected, including adopting wholly new production processes.
For example, composite camshafts are a relatively new automotive design, and they continue to gain marketshare (for example, in commercial truck manufacturing) thanks to the considerable weight savings they bring, particularly in comparison to one-piece camshafts. In addition to the weight savings, the composite versions are less expensive, allow the designer to identify and apply different materials for the various constituents, provide greater flexibility in production, and invite designers to implement new cam geometries, such as negative radii. But most important, composite camshafts help to reduce fuel consumption – as well as CO2 emissions.
However, alternative processes for joining cams and shafts have one serious disadvantage: the two component parts cannot be joined with the necessary accuracy to avoid a subsequent finish grinding process. In many cases, joining a cam to a tube is carried out using a form-fit process like press-fitting, knurling, and/or spline/serrated gearing. The joining forces required for these processes can deform the components and result in unacceptable tolerances in cam position and orientation.