A production type CNC hobbing machnie (a maximum module to be cut of 4 mm and a maximum workpiece diameter of 150 mm) has been newly designed and manufactured based on the concept that a special attention is paied to a rigidity and a thermal deformation of the machine structure as well as a rotational transmission mechanism to enable high speed drive. A maximum speed of hob shaft is 1200 rpm and a table speed is possible up to 160 rpm due to a full spur gear drive. A CNC controller used is a common type for a hobbing machine which has a 32 bit CPU and five axes are numerically controlled.

By paying a special attention to a torsional rigidity and a dynamic synchronous error between a hob and table, some tests are carried out. The results are compared with those of a full mechanical drive (FMD) hobbing machine.

It is ascertained that by high accuracy gear cutting tests spur gears are generated with a sufficiently high accuracy although a correction of synchronous error between a hob and table is not applied at all by NC software. Also, in a production shop, it is demonstrated that a lot of helical gears for automobile can be manufactured with high-productivity and high-accuracy, that is : a machining cycle time per one gear is shortened by shortening a loading and unloading time of gear blank; a lead error is maintained within a small deviation in spite of high feed rate; and a measured value by over roll method is maintained within a permitted limit during a continuously long machining operation, for example, all day-long.

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