Assembly in Action: Welding Cell Three Times Faster Than Operators
September 29, 2009
Located about an hour outside Prague, Czechoslovakia, STROS is one of the world’s leading suppliers of hoist machinery for building sites. Its product line includes cranes that carry loads of more than 7,000 pounds at speeds of nearly 300 fpm to heights of about 1,000 feet.
Critical to the success of its products are what STROS calls its tetrahedral vertical mast sections, each of which requires 222 separate welds in what has traditionally been a labor-intensive process. Although the company has been using robotics for years, the complex arc welds required for this particular job made it impossible to automate. As a result, the company found itself employing three welders per shift at three separate workstations to keep up with demand.
Recently, however, the company was able to cut costs and improve product quality by implementing a fully automated workstation from ABB Robotics.
“ABB was the only company that could supply the entire workstation,” says STROS project manager Milan Skorpa. “We didn’t want to buy just a robot. We wanted a completely robotized workplace, which would include a workpiece positioner and would also handle the transfer of components. ABB also did all the programming for us, which means it effectively delivered a complete solution.”
Key to the new system is an IRB 1600ID industrial robot equipped with what ABB calls its “process arm.” The arm is slim and rotates 360 degrees, making it ideal for entering the narrow spaces in the mast sections and carrying out the complex arc welds required by the application. An integrated welding cable follows the arm’s movements, ensuring that it doesn’t get caught in either the surrounding fixture or workpiece.
In addition to the robot, the workstation employs a rotating IRBP 500D workpiece positioner, equipped with two separate fixtures. Having two fixtures allows the robot to be in constant use, because an operator can prepare pieces for welding on one side of the positioner while another part is being welded.
After the robot has finished its work on one section, the positioner rotates so that the robot can begin welding a second section while the operator removes the completed part. The cycle time for a single mast section is now 54 minutes, about three times faster than the time required by a human welder to make the same piece.
“The robot effectively does the work of three welders using just one workstation,” Skorpa says, noting that the resulting savings have meant the system will pay for itself in two to three years.
In addition to this increased productivity, Skorpa says the system has provided his company with a number of other intangible benefits that are proving to be equally beneficial in terms of the company’s overall competitiveness.
“There are important returns on the investment that can’t be quantified,” he says. “For instance, we now don’t have to worry about trying to hire properly trained welders, who are in short supply these days. It also pays off in terms of the quality of the welding. Even if you have a good welder, you are never going to get the same consistency that a robot gives you. Robots don’t forget any welds.”
For more on robotic welding, call 248-391-9000 or visit www.abb.us.