Motorised measurement arm apparatus for a machine tool

A motorised measurement arm apparatus for a machine tool, the apparatus comprising

• a base for attachment to the machine tool tool;
• an arm member extending from the base for holding one or more sensors, the arm member being moveable relative to the base between a stowed position and an operative position, the operative position being defined by engagement of a mechanical stop arrangement:
• a motor for moving the arm member relative to the base;
• and
• a motor controller for energising the motor to move the arm member relative to the base,
• wherein the motor controller is configured to:
• energise the motor when the arm member is in the operative position to maintain engagement of the mechanical stop arrangement;
• supply a drive-in current to the motor for a first time period affer initial ngagement of the mechanical stop arrangement during movement of the arm member into the operative position:
• supply a holding current to the motor after the first time period to maintain engagement of the mechanical stop arrangement, the holding current being less than the drive-in current;
• and
• reduce the current supplied to the motor from the drive-in current to the holding current over a second time period.