Mounting for surface-sensing stylus and a method of using said mounting
AssigneeRenishaw PLC
InventorDavid R. McMurtry
Life of this patent
Estimating the term…
Abstract
A mounting comprises a base supporting a first rotary motor whose shaft has secured thereto a housing supporting a second rotary motor whose shaft has the stylus secured thereto. Each motor is operable optionally in a constant torque mode and a positioning mode and each motor has an angular position transducer. In use, the base is secured to the operating member of a coordinate measuring machine and the machine is driven through a path such that the free end of the stylus can maintain engagement with the surface of a workpiece under the force generated by one of the motors while that motor is in the constant torque mode. The profile of said surface is then determined as a function of the coordinate position of the operating member, the angular position and the length of the stylus.
Claims9
Apparatus for use on a coordinate positioning machine in measuring a surface, the machine having a head movable relative to a table on which said surface is supported, the apparatus comprising:
- a base connectable to the head;
- a first rotor supporting a surface-sensing device, the first rotor being mounted to, and for rotation relative to the base about a first axis;
- a first motor for rotating the first rotor about said first axis in response to an input signal;
- first transducing means for measuring, relative to a reference orientation, an angle of rotation of the first rotor about the first axis;
- and
- first controlling means for providing:
- (a) a torque input signal or operating said first motor to apply a constant torque to said first rotor;
- and
- b) a positioning input signal for operating said first motor to position said first rotor at a given angle of rotating relative to said reference orientation,
- wherein said first controlling means is selectively operable for passing on of said torque input signal and said positioning input signal to the motor as said input signal.
A method of operating an apparatus comprising a surface-sensing stylus for mounting on a head of a coordinate positioning machine, the surface-sensing stylus being rotatable about first and second axes by means of first and second motors respectively, to contact a surface, the method comprising the steps of:
- driving the head of the machine along a path adjacent a plane of the local surface;
- applying a torque input signal to one of the first and second motors, thereby to urge the surface-sensing stylus into contact with the surface;
- and
- applying to the other of the first and second motors positioning input signals such that said surface-sensing stylus has an oscillatory motion transverse to the path of the head of the machine.
A method of scanning a surface of a workpiece with a surface sensing device, the device being supported on a head of a coordinate positioning machine by amounting device providing movement of said surface sensing device with 2 degrees of freedom relative to said head, the workpiece being supported on a table of the machine relative to which said head is movable, the method comprising the steps of:
- operating the machine to drive the head in a first direction along a path adjacent the workpiece surface;
- simultaneously operating the mounting device to move the surface sensing device into a sensing relationship with the surface, along a second direction, the second direction being transverse to said first direction and the plane of the local surface;
- simultaneously operating the mounting device to move the surface sensing device with an oscillatory motion substantially parallel to the plane of the local surface;
- and
- measuring, at predetermined intervals of time:
- a) the position of the surface sensing device relative to the head;
- and
- b) the position of th head relative to the table.
Dependencies are inferred from the claim text.