Surface grinding machine

A surface grinding machine, comprising:

• at least one wheel head supported movably in the vertical direction;
• at least one cup-shaped diamond wheel supported by a rotatable wheel shaft at one end of said wheel head, said diamond wheel having an abrasive grain layer at the lower end of said diamond wheel;
• at least one wheel shaft driving motor for rotating said cup-shaped wheel, said motor being supported at the other end of said wheel head;
• at least one servomotor for vertically moving said wheel head;
• at least one chuck table for fixing a surface of a II-IV group compound semiconductor wafer, predetermined elements being fabricated on said surface;
• an index table for revolvably supporting said chuck table;
• a chuck driving table driving motor for turning said chuck table;
• said surface grinding machine further comprising:
• a main shaft motor current analysis circuit for detecting the current value of said wheel shaft driving motor
• a main shaft rotation number analysis circuit for detecting the number of revolutions of said wheel shaft driving motor;
• and
• a feed control circuit for controlling said servomotor in such a manner as to decrease, by obtaining grinding resistance from the number of revolutions the feed speed corresponding to a speed at which said wheel head moves down when the grinding resistance is greater than a predetermined resistance value, and increase the feed speed when the grinding resistance is smaller than the predetermined resistance value.