Unique hardening solutions for unique hardening demands
Karl Hirsch, General Manager of Heat Treatment Services at EFD Induction Germany, is no stranger to tough challenges. But two particular demands—and the special solutions devised by EFD Induction—stand out.
“Well, our work team here in Freiburg was presented with a tough problem: how to lessen distortion when hardening complete steering racks, shafts and gear parts. And, of course, how to lessen it in a way that was cost-effective and met stringent quality levels. ”
The problem is that when hardening by scanning, the coupling needs to be adjusted because of distortion in the workpiece. Moreover, non-uniform hardening patterns create a risk of cracking. Traditional remedies such as forced fixing or empirical methods are unsuitable, as they reduce process reliability. They also result in non-uniform hardening. To solve the problem, Hirsch and his team began intensive lab testing. Says Hirsch: “Coming up with a purely technical solution is only one part of the job. The really hard part is to devise a cost-effective solution that fits the customer’s existing line con-figuration.” The team’s solution was a standard HGL-type machine with a double spindle augmented with lateral axes and a specially developed sensing device. “The solution,” comments Hirsch, “gave excellent results. The combination of the sensing device and our control concept lets us measure distortion during the heating cycle, and, by controlling the axis in real time, we ensure a constant coupling distance. Distortion is significantly reduced because the induction coil follows the workpiece.”
The second development was a drum-hardening machine. “Here,” says Hirsch, “we had to achieve a constant tension force on the work piece via the centers with simultaneous adjustment of the coupling distance between workpiece and coil.” Using standard components, Hirsch’s team came up with a concept that features automatic length compensation provided by an electronic measurement system and CNC-axis. The machine is also easy to maintain, and boasts short setting times. Changing and aligning of the coil is performed outside the working area. The solution also eliminated all mechanical moving components from the quench tank, while a fast portal loading unit and chain-linking assured flexibility. Precise process control was made possible by an advanced CNCcontrol system.
Although developed as one-off customized solutions, both developments have since been adopted by several customers. Says Hirsch. “We modify the machines for each customer. To date, the feedback has been excellent. Both developments work without a hitch, and the customers are more than happy.”