Method and apparatus for determining the angular position of a workpiece and positioning the same

A method of automatically and accurately determining an angular position of a workpiece, and positioning said workpiece, relative to at least one tool, said workpiece having at least one set of teeth;

• said method in sequence comprising the steps of:
• first determining the angular position of a reference workpiece manually centered, having the same set of teeth as the workpiece to be machined, using a measuring device;
• then providing a reference shaft which has a known gear ratio with said reference workpiece and consequently rotates when said reference workpiece rotates;
• deriving pulses from said reference workpiece and said reference shaft as the reference workpiece and said reference shaft rotate;
• undertaking a first phase measurement between said pulses as a reference result;
• thereafter storing the reference result of said first phase measurement as a reference value;
• exchanging said reference workpiece by completely removing said reference workpiece that was taken for determining the reference value and replacing said reference workpiece with a further workpiece which is still to be finish machined subsequently thereto;
• undertaking a second phase measurement between further said pulses derived from said reference shaft and said further workpiece as the further workpiece and said reference shaft rotate relative to each other;
• comparing said stored reference value of said first phase measurement with the result of said second phase measurement to determine the difference between the first phase measurement and second phase measurement;
• and
• adjusting accurately the centering and angular positioning on said further workpiece quickly prior to machining said further workpiece by turning said further workpiece relative to said reference shaft in conformity to the difference between said reference value and said result of said second phase measurement so that subsequently the further workpiece is machined with the tool in a desired manner.