With ever more-complex constituent components and increasingly smaller batch sizes, power-train production is facing many challenges, but for a large number of applications in this sector the heat-shrink assembly process is paying dividends;
Where control cams and/or gears have to be mounted on shafts, heat-shrink assembly brings about a considerable reduction in component weight while ensuring the required functionality. Moreover, the process is suitable for workpieces that are subject to high torque and high dynamic loads.
Power-train production often requires a high degree of flexibility, with a diversity of camshafts or gear shafts featuring complex geometries being produced in the same production facility and in different batch sizes.
Demands on the components themselves are also increasing: high-tensile materials are being used, geometries are getting more complex, and components are required to be ever more compact and to weigh less.
Moreover, composite camshafts are of increasing importance in the automotive industry, where individual components are made in large quantities and then joined according to engine type. The result is a significant reduction in production costs while maintaining the necessary precision and performance.
One of the companies developing heat-shrink technology is Emag Automation (
www.emag.com), which has its headquarters in Heubach, southern Germany. Emag’s patented heat-shrink assembly process is used to make a variety of precision components, although composite camshafts are the main focus of this development, which is characterised by its force-free assembly sequence.
Tight control
The Emag system sees the relevant components brought to precisely the required temperature using an inductive or contact heating process, and the workpiece joined with the shaft without any force being applied.
As the workpiece cools, it clamps down firmly on the shaft. A combination of robots, NC axes and gripper technology guarantees a reliable process based on joining clearances of less than 15µm.
The whole process for camshafts — from picking up the relevant component to completion of the individual assembly action — takes just 7sec; a complete camshaft for a four-cylinder engine can be assembled in about 40sec (the processing speed is further increased by the fact that while one component is being heat-shrunk, the next one is already being pre-heated within the Emag system).
The user benefits not only from short cycle times but also from the fact that a multitude of materials can be heat-shrunk — including forged or sintered cams that do not require further grinding once they have been shrunk onto the shaft.
This process also benefits thedesign/development process. For example, gears can be fitted snuggly against shoulders, allowing many new design variants to be implemented within the smallest possible space.
In the emerging Asian markets, which have rapidly growing automotive production, many suppliers will have to increase their manufacturing capacity considerably over the next few years.
Heat-shrinking technology supports the development of engines for utility vehicles — engines that feature camshafts with integrated bearing elements and require no downstream grinding processes.