Chamfering of gearing
2Pages

Pressure deburring chamfering gear (top) measuring pins News from the Gear Technology Chamfering of gearing Gratomat detail burnishing gear fixing screw The special tools needed make pressure deburring less flexible with respect to workpiece geometry, but this is made up for with extremely short chamfering times. For this reason it is primarily employed simultaneously. So-called roll pressing tools are used for chamfering by way of pressure deburring (see Fig. 3). These roll off under pressure with the workpiece. The process consists of cold forming the sharp face edges. Displaced material is sheared off at the faces by deburring or filing discs. The pressing tool is a complex system of several gear wheels configured for a specific workpiece. Besides high component strength, the low level of flexibility restricts economy and use is limited primarily to large-scale production. The chamfering result is illustrated in Figure 4 by way of example. The chamfers in the area of the tooth flanks can be clearly seen. Furthermore, the sheared off deformations on the faces can also be seen. The tooth root can also be chamfered if the tool is configured accordingly, but this will lead to a shorter service life (less favourable rolling conditions). If the fine-machining procedure (shaving or hobbing) permit, it may be possible to skip the smoothing of the flanks; the deburring gears can mesh over the complete circumference. This will double the service life of the tool, reducing the price and improving versatility. Furthermore, if the Liebherr deburring gear is chamfered on both sides, it can be turned at the end of its service life. That also has a cost-reducing effect. When chamfering using the roller press process, sheared deformations are evident on the faces If the hard-fine machining process (e.g. gear honing) does not permit rejects or deformations in the flanks of the teeth for reasons of process reliability or tool life, rejects can also be eliminated with an additional finishing cut while hobbing. Owing to the kinematics, chamfers are formed that are greatest at the tooth crest and tooth base and spread evenly over all teeth with the Gratomat process With the Gratomat procedure, milling cutters are used to cut the chamfers on the contour of the teeth. The hard metal tools are pre-loaded and pressed onto the faces of the workpiece at a defined angle. The procedure is flexible with respect to workpiece geometry as the milling cutters are usually suitable for different components. Furthermore, it is rather insensitive with respect to component strength. With a sufficiently long cycle time for gearing, chamfering can be performed simultaneously. This is true in particular for spur gearing as here the top and bottom are chamfered at the same time. At helical angles > 10°, the faces are machined sequentially, which lengthens the time needed for chamfering. The main benefits of the procedure are: • Extremely versatile • Ideal for gear makers, but also for large-scale production • Different workpieces can be chamfered with standard milling cutters • No workpiece deformation • Root of tooth can be chamfered • Less sensitive to interference contours (e.g. a bulge close to the root circle of the gearing) Liebherr-Verzahntechnik GmbH Verzahntechnik und Automationssysteme Kaufbeurer Straße 141, D-87437 Kempten  +49 (0)831 786-0, Fax +49 (0)831 786-1279 www.liebherr.com, E-Mail: info.lvt@liebherr.com The kinematics of the procedure generate a characteristic, uniform chamfer form (see Fig. 2). Here, the chamfers are largest on the head of the tooth and around the root of the tooth, and smallest in the area of the root form circle. In contrast to the contour line, the width of the chamfer toward to the flank can be regulated with the circumferential speed and contact pressure of the tool. The Gratomat procedure produces rather flat chamfers relative to the face, i.e. rather large chamfer angles with respect to the helical angle. Integrating the procedure in the gear cutting machine allows Liebherr to offer a chamfering unit which is attached, for example, to the control side of the machine without requiring additional space. The workpieces are handled by a 4¬station ring loader. Roll pressing tools with an example of a press chamfering tool Printed in Germany by Roth BK Änderungen vorbehalten.

Different procedures can be selected for chamfering pre-geared spur wheels on gear cutting machines: Gratomat, pressure deburring and ChamferCut. Know the benefits and limitations of the different procedures and you will quickly find the optimum solution for your specific application. The ChamferCut procedure, in which the chamfer is produced with special chamfering bits, is on the rise. ChamferCut cutters classically enable the workpieces to be deburred and chamfered in the same clamping position directly after gearing. The tool, a workpiece-specific form cutter, works in the continuous...