Deep rolling tool and method

Abstract

An embodiment of a tool assembly includes a robotic assembly, a tool mount, and a non-axisymmetric deep rolling tool. The robotic assembly includes a plurality of linear arms connected in series between a base end and a working end. Adjacent ones of the plurality of arms are connected via a corresponding plurality of multi-axis joints such that the working end is articulated by movement of one or more of the plurality of arms relative to one or more of the plurality of multi-axis joints. The tool mount is connected to one of the linear arms or one of the multi-axis joints at the working end of the robotic assembly. The non-axisymmetric deep rolling tool is connected to the tool mount, and includes a spring-loaded shaft assembly disposed along a first axis. A hub has an upper hub portion adjacent to the distal end of the spring-loaded shaft assembly aligned with the first axis, and a lower hub portion extending along a second axis, forming a nonzero angle relative to the first axis. A roller disk is joined to the lower portion of the hub and is rotatable about the second axis parallel to the second portion of the hub.

1 . A tool assembly comprising:
 a robotic assembly including a plurality of linear arms connected in series between a base end and a working end, adjacent ones of the plurality of arms connected via a corresponding plurality of multi-axis joints such that the working end is articulated by movement of one or more of the plurality of arms relative to one or more of the plurality of multi-axis joints;   a tool mount connected to an arm or a multi-axis joint at the working end of the robotic assembly; and   a non-axisymmetric deep rolling tool connected to the tool mount, the non-axisymmetric deep rolling tool comprising:
 a spring-loaded shaft assembly disposed along a first axis; 
 a hub connected to a distal end of the spring-loaded shaft assembly, the hub having an upper hub portion adjacent to the distal end of the spring-loaded shaft assembly aligned with the first axis, and a lower hub portion extending along a second axis, the second axis forming a nonzero angle relative to the first axis; and 
 a roller disk joined to the lower portion of the hub, the roller disk having a working surface about its perimeter and being rotatable about the second axis parallel to the second portion of the hub. 
   
     
     
         2 . The assembly of  claim 1 , wherein the spring-loaded shaft assembly comprises a flexible shaft. 
     
     
         3 . The assembly of  claim 1 , wherein the spring-loaded shaft assembly comprises:
 a rigid shaft; and   a resilient element disposed at a distal end of the spring-loaded shaft assembly proximate to the hub.   
     
     
         4 . The assembly of  claim 3 , wherein the rigid shaft is supported by a linear bearing arranged along the first axis. 
     
     
         5 . The assembly of  claim 3 , wherein the resilient element comprises a plurality of stacked Belleville washers. 
     
     
         6 . The assembly of  claim 1  and further comprising:
 a load cell disposed along the first axis, the load cell adapted to measure a force applied along the shaft between a proximal end of the shaft assembly and the roller disk. 
 
     
     
         7 . The assembly of  claim 3 , wherein the load cell is contiguous with the resilient element. 
     
     
         8 . The assembly of  claim 7 , wherein the load cell is in communication with a monitor adapted to receive signals corresponding to an instantaneous load on the resilient element. 
     
     
         9 . The assembly of  claim 8 , wherein the monitor is part of a controller for the robotic arm with closed-loop feedback logic, the controller adapted to vary a downward force applied by the robotic arm to the tool along the first axis based on one or more of the received signals. 
     
     
         10 . The assembly of  claim 1 , wherein the working surface of the roller disk includes a profile along its width such that an effective radius of the roller disk varies along a width thereof. 
     
     
         11 . A method comprising:
 supporting a workpiece in a fixture, the workpiece having a first nonplanar surface: and   performing a first rolling operation on the first nonplanar surface, the first rolling operation comprising:   operating a robotic assembly to apply a downward force over a rolling path of a non-axisymmetric deep rolling tool, the downward force is applied to a proximal end of a spring-loaded tool shaft aligned with a first axis, such that the downward force is transferred through the shaft to a hub disposed at a distal end of the shaft assembly; and   transmitting the transferred downward force from an upper portion of the hub aligned with the first axis to a lower portion of the hub parallel to a second axis, the second axis forming a nonzero angle relative to the first axis, about which a roller disk is supported by one or more bearings, such that a resulting compressive force is applied to the first nonplanar surface of the workpiece via a working surface of the roller disk;   wherein the robotic assembly comprises a plurality of linear arms connected in series between a base end and a working end, adjacent ones of the plurality of arms connected via a corresponding plurality of multi-axis joints such that the working end is articulated by movement of one or more of the plurality of arms relative to one or more of the plurality of multi-axis joints.   
     
     
         12 . The method of  claim 11 , wherein the working surface includes a profile along its width such that an effective radius of the roller disk varies along a width thereof, such that the resulting compressive force applied to the first nonplanar surface varies along the width of the working surface. 
     
     
         13 . The method of  claim 12 , wherein the working surface of the roller disk is crowned from a center to opposing first and second edges. 
     
     
         14 . The method of  claim 11 , wherein the deep rolling tool shaft comprises:
 a rigid shaft extending along the first axis; and   a resilient element disposed at a distal end of the rigid shaft adjacent to the hub.   
     
     
         15 . The method of  claim 11 , and further comprising:
 operating a load cell disposed along the first axis to generate signals corresponding to an instantaneous load on the spring-loaded tool shaft.   
     
     
         16 . The method of  claim 15 , and further comprising:
 transmitting the signals to a controller for monitoring the applied compressive forces during the first rolling operation   
     
     
         17 . The method of  claim 11 , and further comprising:
 varying the downward force of the robotic arm based on the signals generated by the load cell such that the resulting compressive force is within a predetermined range along a tool rolling path.   
     
     
         18 . The method of  claim 11 , and further comprising using the tool to perform a second rolling operation on a second nonplanar surface of the workpiece. 
     
     
         19 . The method of  claim 18 , wherein the workpiece comprises a fan blade for a gas turbine engine. 
     
     
         20 . The method of  claim 19 , wherein the first nonplanar surface includes a junction between an airfoil and a dovetail root.