Rexroth CKK Ball Screw Actuators Raise Performance for Wind Turbine Builders

Wind turbine technology is an established sustainable, green technology. Many consider it a technology that will help define the energy future. But wind energy also depends, to a great extent, on more traditional manufacturing techniques, such as welding – vitally important for creating the massive towers.

One of the leaders in creating welding solutions for the energy industry – as well as many other applications – is Rexburg, ID-based machine builder AMET Inc. (www.ametinc.com). Recently, AMET called upon the Linear Motion and Assembly Technology specialists of Bosch Rexroth to help them create a new generation of custom welding systems for the increasingly important wind energy industry.

The design of AMET welding equipment – and the role of linear motion technologies – is largely dictated by the techniques required to create massive wind turbine towers that can be around 90 meters high (close to 300 feet). During a weld, while the bulk of the equipment remains stationary, the weld head constantly moves small distances along at least 2 axes, both along and across the seam. A linear control actuator mounted at the end of a horizontal arm determines the motion of the weld head.

AMET’s goal was to create a cost-effective, dependable welding system that could perform accurate longitudinal and circumferential submerged arc welding. One of the most important challenges, however, was to assure smooth and precise (within 1/100th of an inch) control of the weld head, to avoid improper welds that would need to be redone and ultimately result in wasted time and materials. And this precise control had to be maintained within a very demanding environment. “The tremendous amount of particulates, especially flux dust, generated by this form of welding can really cause problems for this machine’s finer controls, particularly with systems such as linear actuators,” said Craig Dees, AMET Engineering Manager.

AMET also wanted linear motion elements that offered good strength (dynamic loads in excess of 20,000 Newton) with light weight and compact size. Yet another challenge was to support smooth weld head acceleration of up to 3 meters per second squared (3m/s2), for a travel speed of 1.5 meters per minute.

To meet these needs, AMET turned to a familiar source for linear motion: Northwest Motion, Inc. (www.nwmotion.com), a distributor of Rexroth linear motion products. Rexroth precision-ground, hardened steel guide rails were to be specified for the guide rail that carries the suspended weld head for outside welding. With the CKK Compact Modules, however, AMET put Rexroth linear motion systems in a particularly crucial role.

The compact CKK design, light in weight but durable and strong, makes machine assembly smoother and easier. “We knew that other linear motion solutions couldn’t give us the reliability and protection against contamination and pitting that the CKK modules could,” Dees says.

Another important feature leading to better and faster machine production is the fact that CKK 20-145 modules are complete, prepackaged systems, with dual ball rails and a ball screw drive integrated into the module. This simplifies design, saves space, and removes the costs and effort of machining, assembly, bearing alignment and other application engineering tasks.

Download the complete case study from the Bosch Rexroth Case Studies & Technical Papers web page.

Bosch Rexroth
www.boschrexroth-us.com