There are various devices, such as for example gear milling machines or gear grinding machines, which are configured specifically for the machining of gear wheels. As the very names of these machines suggest, the first type of machine operates with milling tools and the second type of machine with grinding tools.
One basically draws a distinction between machines which operate in an indexing method and machines which operate continuously. In the indexing method, there is machined a tooth gap, then there is carried out a movement of relative displacement to extract the tool from a tooth gap and what is known as an indexing movement (indexing rotation), in which the gear wheel rotates relative to the tool before the subsequent tooth gap is then machined. A gear wheel is thus manufactured step by step or gap by gap. A gear cutting machine 10, as indicated in FIG. 1, which operates in an indexing method, is typically provided with an indexing apparatus which rotates the workpiece 15 with teeth 16 by one or more pitches about the workpiece axis 12 at the moment at which the tool 13 is disengaged. In order to ensure that the tool 13 (in the present case, a grinding wheel indicated schematically in FIG. 1) is disengaged, there is carried out a relative movement in which the tool 13 is moved out of the tooth gap parallel to the tool axis 14 (parallel to the x-axis). If the 14 (parallel to the x-axis). If the tooth 16 has a tooth depth H, the tool 13 has to be moved by a distance HA to ensure that the tool 13 and one of the teeth 15 do not collide when the indexing rotation is carried out.
The individual movement sequences in machines 10 of this type are mechanically coordinated with one another and use is made of drives which transmit motor rotations, using worm gears and other means, to the workpiece 15 to be machined and the tool 13.
In more modern machines, a CNC control is employed instead of the indexing apparatus, which is configured to allow all the indexing movement to be carried out at the appropriate moment. Modern CNC machines typically use what are known as direct drives.
The continuous method, also sometimes referred to as the continuous indexing method, is based on relatively complex movement sequences in which the tool and the workpiece to be machined carry out a continuous indexing movement relative to each other. The indexing movement results from the coordinated driving of a plurality of axle drives.
The indexing method has the drawback that it is slower that the continuous method. Nowadays, in the industrial manufacture of larger batches, particular importance is attached to the time required for carrying out the indexing movement. In the manufacture of a gear wheel with n=20 teeth, n=20 tooth gaps have to be machined individually and n−1=19 indexing movements are required. If each indexing movement is reckoned to take 1 second, the indexing process alone takes approx. 19 seconds.
The object of the invention is therefore to provide an approach allowing the indexing method to be sped up.
The object is achieved by a device according to the present invention.
According to the invention, this object is achieved in that use is made of a device which is equipped with a workpiece spindle for receiving a gear wheel, a tool spindle for receiving a tool and with a plurality of drives for machining the gear wheel in an indexing process. In this indexing process, a tooth gap in the gear wheel is machined, then the tool is moved relative to the gear wheel to remove the tool from the tooth gap, then the gear wheel carries out an indexing rotation and the tool is advanced to machine a further tooth gap. According to the invention, one of the drives is activated via a control means in such a way that the relative movement includes a tilting movement by means of which a relative change of angle between the tool and the gear wheel is achieved, the tilting movement being coordinated with the indexing rotation.
According to the invention, this object was achieved in that for machining a gear wheel, use is made of a specific device comprising a workpiece spindle for receiving the gear wheel, a tool spindle for receiving a tool and a plurality of drives for machining the gear wheel using the tool. The device carries out the following steps:                machining a tooth gap in the gear wheel using the tool by carrying out a machining movement,        carrying out a relative movement between the tool and the workpiece to remove the tool from the tooth gap,        carrying out an indexing rotation to transfer the gear wheel into a different angular position,        machining a further tooth gap in the gear wheel using the tool by repeated carrying out of a machining movement.According to the invention, the relative movement includes in this case a tilting movement which changes the relative angle between the tool and the gear wheel.        
Further advantageous embodiments may be inferred from the dependent claims.