Oct 11 2005
How can metal parts with wave-shaped or oval surfaces be produced without casting? The answer is a highly dynamic lathe which engineers are presenting at the EMO machine tool trade fair in Hanover.
If you wanted to produce a simple egg shape from a cylindrical metal bar, there would be no great problem along its longitudinal axis. It is a different matter, however, when the shape is clamped into the lathe in the direction of its lateral axis. In this case, the metal-cutting tool has to move quickly up and down on each revolution. In the metalworking industry, far more complex geometries than that of an egg have to be produced with high accuracy. Engineers at the Fraunhofer Institute for Production Technology IPT in Aachen have specialized in this task. They have developed and built a machine that enables components such as pistons for internal combustion engines with an elliptical cross-section to be produced quickly and cost-effectively. "New machine concepts" will be the focus of their trade fair presentation at the World of Machine Tools EMO in Hanover from September 14 to 21, where they are sharing Stand B63 in Hall 12 with colleagues from five other Fraunhofer institutes.
The HDM highly dynamic lathe makes it possible to produce an extremely wide range of non-round geometries in the millimeter range. The shape can be freely programmed; there is no longer any need for manual procedures to reset non-round grinding machines for other tasks. "All you have to do is insert a new NC data record in the machine's computer control system," emphasizes Ralf Schug from the Precision Machinery Department at the IPT. He also mentions another feature: "Compared with conventional precision lathes, this machine can complete particularly long strokes to form the recesses and protrusions on the workpiece."
Such a machining process is very often highly dynamic, requiring extremely rapid acceleration of the machining head and tool carriage. This is counteracted by the mass of the machine parts. The research scientists have therefore replaced metals with lighter fiber-reinforced plastics whose low thermal expansion also increases the precision that can be achieved. Particularly fast linear motors deliver high feed forces and rates of acceleration up to ten times the earth's gravitational pull. The workpiece carriage that supports the turning spindle accelerates at double the earth's gravitation. The maximum travel speeds for the tool carriage amount to more than half a meter per second, and the workpiece carriage achieves twice that amount.
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