Fritz Studer Integrated EDM dressing system increases grinding power
Switzerland – With Studer-Wiredress, Swiss grinding specialist Fritz Studer brings a dressing device to the market that uses the wire erosion principle and is completely integrated into the grinding machine and its control system.
The integrated electro-discharge dressing technology Wiredress opens up brand-new possibilities for grinding with metal-bonded grinding wheels and drastically cuts auxiliary times. According to Studer, it has been possible to increase grinding power in the grinding process by 30% and reduce grinding wheel wear by 70% in comparison with ceramic and resin bonds. Grinding wheels with very intricate contours can also be dressed.
Electro-discharge dressing for metal-bonded wheels
Metal-bonded grinding wheels offer particular benefits when working on difficult-to-machine materials such as high-alloy, hardened steels, tungsten carbides and ceramics, Studer explained. Such wheels are said to offer superior dimensional and thermal stability and dissipate the heat produced by grinding more quickly. However, in addition to the advantages of metal bonds, there are also disadvantages, as dressing these wheels involves greater expense and effort. Dressing with silicon carbide wheels, for example, often does not achieve satisfactory results, and intricate profiles are not possible. The integrated Wiredress system solves these problems.
The dressing device is in principle a small wire erosion machine. The electrode is a wire, which is drawn with a small gap tangentially past the machining point at a constant speed of 100 mm/s. The opposite pole is the grinding wheel, which moves at peripheral speeds of 50 to 140 m/s during dressing.
It does not need any dielectric, as the grinding oil used during grinding fulfills this function. The dressing wire is guided in a groove on the circumference of a thin, circular ceramic disk. The ceramic disk has a notch where the sparks jump between the wire and the wheel.
Electrical discharge dressing processes use the basic principle of EDM machines, which have been used for precision machining for many years. As with these machines, the material is removed without contact by extremely short direct current pulses following each other in quick succession, which generate a discharge in the gap between electrode and workpiece in the dielectric, Studer said. During the discharge, tiny areas of the metal bond of the grinding wheel are melted and flushed out of the gap.
According to the company, the grinding wheel never has to be removed for dressing. Thanks to the high proportion of grain space, the wheel is very free-cutting. The dressing intervals can be longer. However, as the dressing process requires so little expense and effort, very complex contours can also be dressed at shorter intervals, Studer added.
Dressing unit contains ten kilometres of wire
Feeds of 15 to 25 mm/min can be achieved when dressing a typical metal bond. In this way, largely free geometries and intricate contours with internal radii of 0.2 mm and external radii of 0.05 mm are generated on the grinding wheel. Removal rates of up to 80 mm3/min are achieved, Studer said. The grain retains its original shape during this contactless dressing process.
The wire reel in the dressing unit contains ten kilometres of wire; this supply would allow dressing to be continued for approx. 16 hours without interruption. The used wire is cut into short pieces immediately after the dressing process and collected in a container.