The goal of this project, funded by the German Research Foundation (DFG), is to demonstrate that the prototype of a magnetically preloaded air cushion is suitable for use in machine tools. The basic requirements for this are the precise stabilization of the levitation height and the compensation of disruptive forces acting on the prototype.
The function of a guide is to restrict the movement of an element in specific directions. Guides are used in machine tools to precisely guide the tool and workpiece. In addition to conventional rolling guides, there are also frictionless, non-contact guides. These include magnetic, aerostatic, and hydrostatic guides. Magnetic guides, in particular, offer advantages in terms of wear behavior and maintenance requirements due to their lack of friction and the absence of lubricants.
However, due to the underlying principle of reluctance, magnetic guides can only generate tensile forces, making a precisely aligned mechanical clamping mechanism necessary. Aerostatic bearings and combined magneto-aerostatic bearings, on the other hand, are characterized by low load capacities and high tolerance requirements for the guide surfaces.
In the approach pursued, a controlled electromagnet was incorporated into the sliding cushion to stiffen it. The elastic properties of the sliding cushion bellows proved advantageous, as they were able to compensate for unevenness in the substrate and maintained a nearly constant and small air gap at various flight heights, thereby enabling high load-bearing capacities.
Through active control with a feedforward loop to linearize the magnet’s nonlinear force response, the suspension height could be precisely maintained within an operating range of 250–280 µm to within 1 µm. Furthermore, the controller was able to stably compensate for external disturbances of up to 250 N. The fundamental suitability of air cushions in guidance systems for machine tools was thus confirmed.
This fundamental study therefore constitutes the first step toward the development of a multi-actuator system capable of moving large components in the aerospace industry precisely and friction-free along low-tolerance guide surfaces.
Contact:
For further information, please contact Adrian Bergmann on +49 511 762 18294 or by email at adrian.bergmann@ifw.uni-hannover.de.
