The scientific implementation and coordination is the responsibility of the Institute of Production Engineering and Machine Tools at the Leibniz Universität Hannover's Centre for Production Technology (PZH), and the goal is clear: by the end of 2018, a cutting robot will be able to prototype the good results of previous simulation-based research and put them into practice. With its stiffness, which will be about 10 times higher than the stiffness of conventional industrial robots, it will actually be a low-cost alternative for many applications in machining.
The project is funded by the Federal Ministry of Education and Research; in addition to the consortium leader Deckel Maho Pfronten GmbH, a large machine tool manufacturer, five other companies belong to it. Thomas Lepper, an engineering scientist at the Institute of Production Engineering and Machine Tools (IFW), coordinates the scientific part of the project. He outlines the challenge: "Lower structural, drive and bearing stiffness of conventional industrial robots lead to vibrations during machining and thus to process instabilities, which results in much lower productivity compared to machine tools. With our approach, however, we are now creating a robot with a stiffness of 5 N/µm - in other words, a force of five Newtons generates a displacement of at most one micrometer." This means that the developers have not achieved the stiffness of a machine tool, but a stiffness that is ten times better than that of conventional industrial robots. They have succeeded in achieving this through stiffer bearings and drives and through machine tool technology, which has been further developed and adapted for robots. In addition, online compensation, with the aid of process forces measured in real time, is to largely compensate for the displacement that occurs.
Such a machining robot would be an ideal solution because it would be cost-effective for machining steps that do not require high precision, or for newer materials such as CFRP. "We have a special focus on processing CFRP", explains Lepper, "and therefore also integrate an energy-efficient extraction system, which is indispensable due to the very abrasive and harmful CFRP dust produced. In addition to CFRP, we are also interested in aluminium-CFRP composites and aluminium. We will sound out the limits there. And in the distance, of course, there is the question: What about steel?"
In the development of the current 5-axis machining robot, all those involved in the project can benefit from the experience of IFW, which has contributed in several projects since 2006 to further optimising the performance of industrial robots for machining. "IFW has meanwhile acquired a pioneering role here," says head of the institute Professor Berend Denkena, "and we want to continue to push the limits of what is feasible in this area together with our project partners."
