# US 5,910,719 A · Tool center point calibration for spot welding guns > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,910,719 A - Document ID: US5910719A - Status: Granted - Kind: A - Application number: 08/718,628 - Filed: 1996-09-17 - Granted: 1999-06-08 - Earliest claimed: 1996-09-17 - Assignees: Cycle Time Corporation - Inventors: Henry F. Thorne - Web page: https://patentgrep.com/patent/US5910719A ## CPC - G05B 19/401: characterised by control arrangements for measuring, e.g. calibration and initialisation, measuring workpiece for machining purposes (G05B19/19 takes precedence) - B25J 9/1692: {Calibration of manipulator} - G05B 2219/37405: Contact detection between workpiece and tool, probe, feeler - G05B 2219/39041: Calibrate only for end position - G05B: CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS (systems for controlling or regulating non-electric variables G05D; systems for regulating electric or magnetic variables G05F; control devices or systems insofar as characterised by mechanical features only G05G) - B25J: MANIPULATORS; CHAMBERS PROVIDED WITH MANIPULATION DEVICES ({manipulators specially adapted for use in surgery A61B34/70; manipulators used in cleaning hollow articles B08B9/04}; manipulators associated with rolling mills B21B39/20; manipulators associated with forging machines B21J13/10; {manipulators associated with picking-up and placing mechanisms B23P19/007}; means for holding wheels or parts thereof B60B30/00; {vehicles with ground-engaging propulsion means, e.g. walking members B62D57/02, B62D57/032; devices for picking-up and depositing articles or materials between conveyors B65G47/90, B65G47/91; manipulators with gripping or holding means for transferring packages B65H67/065}; cranes B66C; {manipulators used in the protection or supervision of pipe-line installations F17D5/00; walking equipment adapted for nuclear steam-generators F22B37/006}; manipulators specially adapted for, or associated with, nuclear reactors G21C; {apparatus used for handling wafers during manufacture or treatment of semiconductor H10P72/50}) ## Abstract A method for tool calibration for a robotic tool includes providing a calibration device within a robot envelope. The calibration device includes a calibrating member positioned along a calibrating plane. The tool tip of the robotic tool is positioned to an initial position within the calibrating plane and position values of the robot face plate are obtained. The tool tip is rotated about the estimated or prior tool center point, the tool tip is again positioned within the calibrating plane, and further position values of the robot face plate are obtained. The actual tool center point is calculated from the obtained position values. ## Claims ### Claim 1 A method for tool calibration for a robot with a face plate having a tool tip and tool tip axis, said tool tip movable by said robot within a robot envelope, said method comprising the steps of: a) providing a calibration means within the robot envelope, wherein said calibration means includes a calibrating member positioned along a calibrating plane; b) positioning said tool tip to an initial position within said calibrating plane; c) obtaining values of said robot face plate with said tool tip positioned within said calibrating plane; d) rotating said tool tip about an estimated tool center point in a first direction to at least a second position and positioning said tool tip within said calibrating plane; e) obtaining values of said robot face plate with said tool tip within said calibrating plane following said rotation to said second position; and f) calculating a tool center point based upon said obtained values. ### Claim 2 (depends on 1) The method of claim 1 wherein said robot is a spot welding robot. ### Claim 3 (depends on 2) The method of claim 2 wherein said calibrating member is formed by a workpiece to be worked on by said tool of said robot. ### Claim 4 (depends on 3) The method of claim 3 wherein said workpiece is sheet metal. ### Claim 5 (depends on 1) The method of claim 1 wherein said calibrating member is formed by a workpiece to be worked on by said tool of said robot. ### Claim 6 (depends on 5) The method of claim 5 wherein said workpiece is sheet metal. ### Claim 7 (depends on 1) The method of claim 1 wherein steps b) through e) are repeated and performed independently for each of two axes of said tool center point which are parallel to said calibrating plane. ### Claim 8 (depends on 7) The method of claim 7 wherein steps b) through f) are repeated with a greater angle of rotation. ### Claim 9 (depends on 1) The method of claim 1 further including the steps of rotating said tool tip about said estimated tool center point to a third position, positioning said tool tip within said calibrating plane and obtaining values of said face plate with said tool tip within said calibrating plane following said rotation to said third position. ### Claim 10 (depends on 9) The method of claim 9 wherein said rotation to said third position is in a second direction opposite to said first direction. ### Claim 11 (depends on 10) The method of claim 10 wherein said third position is rotationally offset from said first position an angle equal to an angle between said first position and said second position. ### Claim 12 (depends on 11) The method of claim 11 wherein steps b) through e) are repeated and performed independently for each of two axes of said tool center point which are parallel to said calibrating plane. ### Claim 13 (depends on 12) The method of claim 12 wherein steps b) through f) are repeated with a greater angle of rotation. ### Claim 14 (depends on 11) The method of claim 11 wherein said calibrating member is formed by a workpiece to be worked on by said tool of said robot. ### Claim 15 (depends on 14) The method of claim 14 wherein said robot is a spot welding robot.