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To create a wind-turbine tower, the manufacturer rolls a flat metal plate into a cylindrical shape called a can. The can is then rotated while a machine welds the plate along its circumference. Longitudinal welds are also required.
During a weld, most of the welding equipment remains stationary while the weld head constantly moves small distances along and across the seam. A linear actuator mounted at the end of a horizontal arm moves the weld head.
AMET Inc. has been creating custom welding systems for wind-turbine builders since the 1990s. Recently, AMET developed a new submerged arc welding system in conjunction with Northwest Motion, a distributor of Bosch-Rexroth Corp. linear motion products.
The key component of the welding system is the CKK 20-145 linear actuator made by Bosch-Rexroth. AMET chose the actuator for several reasons. First, it provides smooth and precise control of the weld head. The actuator is accurate to within 0.01 inch. The actuator’s rigid aluminum frame has a dynamic load capacity of 61,000 newtons, and can support weld head acceleration of up to 3 meters per second squared and travel speeds of 1.5 meters per minute.
The actuator comes in standard lengths of 490 millimeters and 590 millimeters and features a dual-rail system with a sealed rolling strip. This strip protects the actuator from pitting corrosion caused by the particulates generated during welding. This increases uptime and reduces maintenance.
“These particulates, especially flux dust, can really cause problems for the machine’s finer controls,” says Craig Dees, AMET engineering manager. “We needed to be sure that the linear motion components would withstand this harsh welding environment.”
The actuator also features an integrated ballscrew drive, which simplifies design, saves space, and removes the costs and effort of machining, assembly, bearing alignment and other application engineering tasks. The screw drive also has enabled AMET to build its wind-turbine welding system quicker—in 12 weeks, rather than 14.
“The CKK actuators are ready to run as soon we get them,” says Dees. “We just add them to the system.”
Wind-turbine manufacturers also like the AMET welding system because it can be used with small and large tower sections, including those needed to create towers more than 300 feet high.
For more information on linear motion components, call 269-695-0151 or visit www.boschrexroth-us.com.