Method and apparatus for eliminating undulation errors on gear-tooth flanks in production gear-fabricating machines

A method for eliminating undulation errors on gear-tooth flanks when fabricating gears in a production gear-fabricating machine, wherein a generating motion corresponding to a desired involute profile is induced between a first gear-fabricating tool and a first gear-tooth flank as well as between a second gear-fabricating tool and a second gear-tooth flank of opposite orientation to said first gear-tooth flank by rotating a rotary table upon which a gear being fabricated is fixed at a predetermined angular velocity and by simultaneously translating the rotary table at a predetermined linear velocity, comprising the steps of:

• determining a reference drive ratio between a reference angular velocity and a reference linear velocity for said rotary table;
• measuring momentary angular velocities and momentary linear velocities of said rotary table during fabrication of each gear-tooth flank;
• determining momentary drive ratios between said momentary angular velocities and said momentary linear velocities;
• forming difference values between said reference drive ratio and said momentary drive ratios;
• storing said difference values in association with momentary generating motion positions of said gear being fabricated and in association with momentary stroke positions of said gear-fabricating tools at least until a further fabricating cycle;
• correcting feed motion values for said first gear-fabricating tool by the amount of said difference values during said further fabricating cycle for each gear-tooth flank at said associated generating motion and stroke motion positions;
• and
• simultaneously correcting feed motion values for said second gear-fabricating tool by the negative amount of said difference values during said further fabricating cycle for each gear-tooth flank at said associated generating motion and stroke motion positions.

An apparatus for eliminating undulation errors on gear-tooth flanks when fabricating gears in a production gear-fabricating machine having a rotary table for the gear to be fabricated, comprising:

• a first drive mechanism associated with said rotary table for rotating said rotary table at a predetermined angular velocity together with said gear to be fabricated and a second drive mechanism associated with said rotary table for simultaneously translating said rotary table at a predetermined linear velocity together with said gear to be fabricated for inducing a generating motion corresponding to a desired involute profile between at least one gear-fabricating tool and at least one gear-tooth flank;
• measurement devices associated with said rotary table for monitoring said angular and linear velocities;
• a computer for determining a reference drive ratio between a reference angular velocity and a reference linear velocity for said rotary table;
• a generating roll position transducer for determining a momentary generating roll position of said gear to be fabricated;
• a stroke position transducer for determining a momentary stroke position of said at least one gear-fabricating tool;
• a first measuring device for measuring momentary angular velocities of said rotary table;
• a second measuring device for measuring momentary linear velocities of said rotary table;
• a divider device for determining momentary drive ratios between said momentary angular velocities measured by said first measuring device and said momentary linear velocities measured by said second measuring device;
• a subtractor device for forming difference values between said reference drive ratio and said momentary drive ratios;
• said subtractor device having an output;
• said computer having a generating roll and stroke output;
• a storage device connected to said output of said subtractor device and to said generating roll and stroke output of said computer for storing said difference values in association with momentary generating roll positions of said gear to be fabricated and in association with momentary stroke positions of said at least one gear-fabricating tool;
• said storage device having an output;
• said gear-fabricating tool having a servo-valve;
• and
• a first correction device connected to said output of said storage device and to said servo-valve for correcting feed motion values for said at least one gear-fabricating tool by the amount of said difference values.