High performance ballscrew and linear motion products developed and manufactured by THK are ideal for playing an important role in manufacturing cells used by automotive producers for the manufacture of a range of drive shafts used in front wheel drive cars, vans and trucks.  The THK ballscrews and linear guides are suitable for use where, traditionally, hydraulic components were installed, and are providing both cost savings and a far higher degree of machine control than would otherwise have been the case.

Constant velocity joints and jointed side-shafts are used by all major vehicle manufacturers and typically comprise two joints and a shaft that transfer steering, suspension and variable torque to the driven wheels of a vehicle, while minimising noise, vibration and harshness.

The drive shaft manufacturing cell can be based around a series of four purpose built machines, each of which carries out a specific part of the assembly operation.  For example, a first stage journal press assembles the drive shaft and universal drive joint that connects the shaft to the driven wheel and suspension components. 

The second stage is to add a rubber boot, secured with a crimped band, to protect the joint in use; this is then followed by two further operations to add a double offset joint on the inboard end of the shaft, with the joint effectively allowing the shaft to move inward and outward as the suspension unit oscillates.

Throughout, it is critical that the splined joints and shaft are located precisely to ensure consistent long term operation, with minimal wear and guaranteed vehicle safety.  The new manufacturing cell replaces a largely manual operation by developing production systems that allow automation of an essentially complex process, at realistic cost and with a high degree of positional accuracy and repeatability.

A combination of THK HBN ballscrews, driven by servo motors, and THK SHS Caged Ball linear guides are therefore used to precisely control the vertical positioning and alignment of each tool head and workpiece.

A high degree of control is especially important on the system that locates and then locks the splined shafts and joints together and then, while the two components are still clamped, exerts a retraction force to check that they are fully engaged.  The pull force is always greater than that required to engage the parts, while the first stage in the process requires a gentle oscillating motion to ensure that the splines locate correctly.

The THK ballscrews and linear guides have enabled the machine to achieve a level of positional accuracy, together with high speed acceleration and deceleration and precise positive and negative pressure, that is far more controllable than would have been possible using traditional hydraulic systems.  Perhaps as importantly, machine build costs are minimised as the THK products are considerably less expensive than comparable hydraulic parts.

The HBN and SHS products are also extremely robust and rigid, factors that further improve positional accuracy.  In addition, all THK products are virtually maintenance free, thereby reducing long term operating costs still further.