Friction stir processing tip, apparatus, and method

In one aspect of the present disclosure, a friction stir processing tip is provided for a friction stir processing device. The friction stir processing tip includes a body having a central longitudinal axis, a friction stir processing portion of the body, and a connecting portion of the body configured to connect to a tip holder of the friction stir processing device. The connecting portion includes splines configured to receive a torque from the tip holder for rotating the body about the central longitudinal axis.

TECHNICAL FIELD

This disclosure relates generally to a tip for a friction stir processing device.

BACKGROUND

Friction stir processing of metals may include, for example, friction stirring of a workpiece to refine grain structure in a workpiece. As other examples, friction stir processing may include friction stir welding of two or more workpieces and friction stir riveting.

In one approach, a friction stir processing tool is coupled to a rotatable spindle of a machine. The friction stir processing tool includes a friction stir processing tip and a body. In one type of friction stir processing device, the friction stir processing tip is intended to be removed from the body and replaced at the end of the lifespan of the friction stir processing tip.

To connect a friction stir processing tip to the body, the body has a socket that receives the friction stir processing tip and the friction stir processing tip has a recess that receives a set screw of the body. The friction stir processing tip also has threads that engage threads of the body to center and secure the friction stir processing tip within the body. The threads of the friction stir processing tip and the body are configured to have a rotational removal direction for the friction stir processing tip that is opposite the direction of rotation of the spindle to inhibit the threaded connection from loosening during a friction stir processing operation. Once the friction stir processing tip has worn out, the set screw of the body is disengaged from the friction stir processing tip and the friction stir processing tip is unthreaded from the body. A new friction stir processing tip may then be loaded into the body.

In one embodiment, the friction stir processing tip may include a pin and a shoulder having surface features and/or material that provide a superabrasive surface for frictionally engaging workpieces to be friction stir welded. As the rotating friction stir processing tip is moved along the workpieces, the pin and shoulder frictionally engage the two workpieces, plasticize the metallic material of the workpieces, and stir the plasticized material to form a weld between the workpieces.

There are a number of factors that may cause the friction stir processing tip to bind in the body, requiring replacement of both the friction stir processing tip and the body. For example, the machine spindle may press the friction stir processing tool against the workpieces in the Z-axis direction with high force, such as 8,000 lbs. The machine spindle may also impart a large torque on the body and the friction stir processing tip held therein in order to rotate the friction stir processing tip at high speeds, such as in excess of 10,000 rotations per minute. The workpieces being friction stir welded may also impart a lateral load on the friction stir processing tip that resists movement of the rotating friction stir processing tip across the workpieces. This lateral load may be around 2,000 lbs in some applications. Further, the friction stir processing tip may reach or exceed 500 degrees Celsius during the friction stir welding operation which causes the friction stir processing tip to expand. The body of the friction stir processing tool may experience lower temperatures than the friction stir processing tip and expands less during the friction stir processing operation.

The axial loading, torque, lateral load, and high temperatures experienced by the friction stir processing tip have been found to bind the engaged threads of the friction stir processing tip and the body. Binding between the friction stir processing tip and the holder may compromise the holder and require replacement of both the holder and the friction stir processing tip.

DETAILED DESCRIPTION

In one aspect of the present disclosure, a friction stir processing tip is provided for a friction stir processing device. The friction stir processing tip includes a body having a central longitudinal axis, a friction stir processing portion of the body, and a non-threaded connecting portion of the body configured to connect to a tip holder of the friction stir processing device. The non-threaded connecting portion permits the body to be connected to the tip holder without engaging threads of the friction stir processing tip and the tip holder that could bind during a friction stir processing operation. The non-threaded connecting portion including splines configured to receive a torque from the tip holder for rotating the body about the central longitudinal axis.

In another aspect of the present disclosure, a friction stir processing tip is provided for a friction stir processing device. The friction stir processing tip has a body with a central longitudinal axis and a friction stir processing portion. The friction stir processing portion may include, for example, a pin and a shoulder. The body has a connecting portion configured to connect to a tip holder of the friction stir processing device. The connecting portion has splines configured to receive a torque from the body for rotating the tip holder about the central longitudinal axis. The body may have a lateral locating surface axially offset from the splines that extends along the central longitudinal axis. The lateral locating surface may include, for example, a pair of annular locating surfaces on opposite sides of the splines. The lateral locating surface is configured to form a sliding fit connection with the tip holder and keep the central longitudinal axis of the body concentric with an axis of rotation of the tip holder. By keeping the central longitudinal axis of the body concentric with the axis of rotation of the tip holder, the friction stir processing tip inhibits axial run out and vibrations during friction stir processing operations.

The present disclosure also provides a friction stir processing apparatus having a friction stir processing tip and a tip holder. The friction stir processing tip has a central longitudinal axis, a torque receiving structure, and a lateral locating surface axially offset from the torque receiving structure. The torque receiving structure may include at least one of splines, a thread, and a keying structure, as some examples. The tip holder is rotatable about an axis and has a torque transmitting structure configured to engage the torque receiving structure of the friction stir processing tip and cause rotation of the friction stir processing tip with rotation of the tip holder. The torque transmitting structure may include at least one of splines, a thread, and a key as some examples of structures that may cooperate with the torque receiving structure of the friction stir processing tip.

The tip holder has a support surface that forms a sliding fit connection with the lateral locating surface of the friction stir processing tip. The contact between the lateral locating surface of the friction stir processing tip and the support surface of the tool holder keeps laterally directed loads away from the torque receiving structure of the friction stir processing tip during a friction stir processing operation. The separation of torque-receiving and lateral load-receiving portions of the friction stir processing tip permits high speed friction stir processing without the friction stir processing tip binding to the tip holder.

In one aspect of the present disclosure, a method is provided for connecting a friction stir processing to a tip holder of a friction stir processing device. The method includes shifting the friction stir processing tip and the tip holder relative to one another along an axis of rotation of the tip holder to bring together splines of the friction stir processing tip and the tip holder. The method further includes forming a sliding fit connection between the friction stir processing tip and the tip holder. The method further includes securing the friction stir processing tip to the tip holder, such as by engaging a set screw of the tip holder with a recess of the friction stir processing tip.

RegardingFIG.1, a friction stir processing device100is provided that includes a friction stir processing tip125and a tool holder152. The friction stir processing tip125has a pin102and a shoulder104suitable to friction stir metallic workpieces. The friction stir processing device100may be connected to a spindle of a machine and used to friction stir process at rotational speeds faster than 10,000 rotations per minute, such as approximately 15,000 rotations per minute. The tool holder152includes a tip holder150having a socket101that receives the friction stir processing tip125. The tip holder150forms a releasable connection103with the friction stir processing tip125. The releasable connection103permits the tip holder150to apply high axial loads in the Z-axis direction to the friction stir processing tip125, permits the tip holder150to apply high torque loads to the friction stir processing tip125, and permits the friction stir processing tip125to reach temperatures of 500° C. or higher without the friction stir processing tip125binding to the tip holder150. Further, the releasable connection103permits the friction stir processing tip125to be readily replaced at the end of the lifespan of the friction stir processing tip125without having to replace the tip holder150and/or tool holder152.

RegardingFIG.2, the friction stir processing tip125includes a body107having a connecting portion109configured to couple to the tip holder150, which in one form includes a replaceable torque insert175. The tool holder152includes a tool holder body111that supports the replaceable torque insert175. The tool holder152also includes an electronics package160carried on the tool holder body111that receives electrical power from a battery165. The electronics package160may include a processor160A that is operably coupled to the components of the electronic package160.

The tool holder body111has an internal compartment113that houses a load transfer and thermal insulation insert155, a load cell170, and a battery165. The friction stir processing device100is rotatable about a longitudinal axis115and may be urged in direction117, which is along a Z-axis of the associated machine, against one or more workpieces by a spindle of the machine. The urging of the friction stir processing device100in direction117against a workpiece causes the friction stir processing tip125to apply a reactionary force in direction119against the load transfer and thermal insulation insert155, which in turn transfers the force in direction119to the load cell170. The processor160A may receive data from the load cell170to facilitate a determination of the force with which the friction stir processing tip125presses against a workpiece.

The electronics package160has a thermocouple121with a probe, such as a wire, that extends into a blind bore127of the friction stir processing tip125to measure the temperature of the friction stir processing tip125. The electronics package160may include communication circuitry129configured to communicate with an associated machine via wireless approaches such as Bluetooth, near field communication, and inductive approaches. In another embodiment, the communication circuitry129may utilize wired communication approaches. The electronics package160further includes a torque sensor123configured to detect the torque applied to the replaceable torque insert175and friction stir processing tip125held therein.

As shown inFIG.2, the friction stir processing tip125, load transfer and thermal insulation insert155, load cell170, battery165, and electronics package160are all centered on the longitudinal axis115. The coaxial alignment of these components reduces the torque the components impart on the friction stir processing device100as the friction stir processing device100rotates during a friction stir processing operation. The load cell170and battery165are also positioned proximally along the longitudinal axis115to provide a center of gravity of the friction stir processing device100close to the spindle, and bearings thereof, holding the friction stir processing device100. In this manner, the friction stir processing device100may be rotated at speeds in excess of 10,000 rotations per minute with minimal wobbling and vibration.

With reference toFIG.3, the friction stir processing tip125has splines130and one or more lateral locating surfaces, such as lateral locating surfaces135,140, arranged about a central longitudinal axis141of the friction stir processing tip125. The splines130may include, for example, 10 or more splines, 15 or more splines, or 20 or more splines.

The friction stir processing tip125has a recess, such as an annular channel114, that receives a retaining member of the friction stir processing device100, such as a set screw. The engagement between the retaining member and the annular channel114keeps the friction stir processing tip125from falling out of the replaceable torque insert175. In one embodiment, the splines130are involute splines and the lateral locating surfaces135,140are smooth, annular surfaces. The lateral locating surfaces135,140of the friction stir processing tip125form a sliding fit connection between the lateral locating surfaces135,140and one or more support surfaces, such as support surfaces143,147(seeFIG.2) of the replaceable torque insert175. The sliding fit is sized to provide enough clearance to permit the friction stir processing tip125to be loaded into the replaceable torque insert175without significant frictional resistance, while being tight enough to inhibit tilting of the friction stir processing tip125within the replaceable torque insert175. In one embodiment, the sliding fit is defined according to the ANSI B4.1-1967 standard.

RegardingFIG.2, to connect the friction stir processing tip125to the replaceable torque insert175, the connecting portion109is advanced in direction119into an opening175A of the replaceable torque insert175. The splines130of the friction stir processing tip125are rotationally aligned with recesses149(seeFIG.4) of the replaceable torque insert175and the longitudinal movement in direction119slides the splines130into the recesses149. The machine spindle moves the friction stir processing device100in lateral direction151across a workpiece during a friction stir processing operation, which imparts a force in lateral direction153against the friction stir processing tip125. The support surfaces143,147provide reactionary forces, in radially inward directions against the friction stir processing tip125, to counteract the loading in lateral direction153against the friction stir processing tip125and resist tilting of the friction stir processing tip125within the replaceable torque insert175. The support surfaces143,147thereby keep the central longitudinal axis141of the friction stir processing tip125coaxial with the longitudinal axis115and inhibit axial lead-out of the friction stir processing tip125. Further, the lateral support surfaces135,140absorb the lateral loads so that the splines130may only be subjected to torque loads, which reduces binding between the friction stir processing tip125and the replaceable torque insert175.

With reference toFIG.3, the lateral locating surfaces135,140of the friction stir processing tip125are offset from the splines130along the central longitudinal axis141of the friction stir processing tip125. In this manner, the lateral supporting surfaces135,140are separate from the torque-receiving structure130A including the splines130. Because the lateral support surfaces135,140center the friction stir processing tip125in the replaceable torque insert175, the splines130and recesses149may have small gaps157(seeFIG.5) therebetween that facilitate insertion and removal of the splines130into the recesses149. The small gaps157also provide clearance for thermal expansion of the friction stir processing tip125during a friction stir processing operation.

RegardingFIG.5, the replaceable torque insert175may rotate in direction161which circumferentially shifts the replaceable torque insert175in direction161relative to the friction stir processing tip125. Rotation of the replaceable torque insert175in direction161presses surfaces of the splines130and recesses149together, such as torque transferring surfaces163,167of the splines130and recesses149and closes the gap157therebetween. The splines130may be involute splines and have a pressure angle158between the torque-transferring surface163and a radius159of the friction stir processing tip125. As shown inFIG.5, the recesses149are defined by splines169and lands171of the replaceable torque insert175. The splines169of the replaceable torque insert175extend into recesses169A of the friction stir processing tip125.

RegardingFIG.3, the friction stir processing tip125may have a unitary, one-piece construction. In other embodiments, the friction stir processing tip125is made of two or more assembled components. The body107may be made of a single material, be made of a first material coated with a second material, or be made of a base material with a plurality of layers as some examples. The body107of the friction stir processing tip125may include one or more ultrahard materials and/or one or more super abrasive materials. Suitable ultrahard materials include tungsten carbide, tungsten lanthanum, tungsten alloys, and steel. Examples of suitable steels include H13 steel and MP159 steel. Suitable super abrasive materials include polycrystalline cubic boron nitride (PCBN) and polycrystalline diamond. As an example, the friction stir processing tip125may be made of an ultrahard material such as H13 steel with a coating, the coating being one or more of a carbide coating, PCBN, tungsten lanthanum, or diamond particulates in a metal matrix.

RegardingFIG.6, a friction stir processing tip325is provided that is similar in many respects to the friction stir processing tip125discussed above. The friction stir processing tip325has a friction stir processing portion327including a pin302and a shoulder303. The friction stir processing portion327may include surface features on the pin302and shoulder303to create material flow and generate heat. The friction stir processing tip325also has a connecting portion329that includes lateral locating surfaces310,340, splines320, and a channel330. The channel330is configured to receive a retaining member, such as a set screw, to keep the friction stir processing tip325within a tip holder. The lateral locating surface340has a smaller outer diameter that the outer diameter of the lateral locating surface310and the splines320to permit the friction stir processing tip325to be advanced in direction331into the socket of a tool holder.

The friction stir processing tip325has a distal end portion333and a proximal end portion337. The lateral locating surfaces310,340are configured to form sliding fit connections with support surfaces of tip holder150. The sliding fit connections between the lateral locating surfaces310,340of the friction stir processing tip325and the tip holder permit the lateral locating surfaces310,340to absorb lateral loading rather than the splines320. Because the lateral locating surfaces310,340absorb lateral loading, an appropriate amount of play may be provided between the splines320of the friction stir processing tip325and recesses of the associated tip holder to permit the splines320of the friction stir processing tip325to be advanced into the recesses of the tip holder.

The sliding fit connections formed between the lateral locating surfaces310,340and the support surfaces of the tip holder also keep the friction stir processing tip325centered in the tool holder which prevents planetary gear-type movement of the friction stir processing tip325in the tip holder. In this manner, the locating surfaces310,340inhibit galling between the friction stir processing tip325and the tip holder. Further, because the splines320may be subjected to only a torque load, the friction stir processing tip325inhibits binding between the splines320of the friction stir processing tip325and the recesses of the tip holder.

RegardingFIG.6, the friction stir processing tip325may further include a blind bore345. The blind bore345may receive a thermocouple probe for measuring the temperature of the friction stir processing tip325.

The friction stir processing tip325also includes an annular channel330for receiving a retaining member. The channel330includes radially extending side walls330A,330B and a cylindrical surface330C extending axially therebetween. For example, the retaining member may be a set screw that extends from a tip holder such as tip holder150. The set screw may contact the side walls330A,330B of the channel330and inhibit the friction stir processing tip325from falling out of the tip holder.

The pin302, shoulder303, locating surfaces310,340, splines320, channel330, and blind bore345may be formed concentrically about a central longitudinal axis351of the friction stir processing tip325. The concentric arrangement of the structures of the friction stir processing tip325helps limit radial lead-out of the friction stir processing tip325during a friction stir processing operation.

The splines320may be, for example, involute splines. The splines320may be arranged in a contiguous circular pattern about the central longitudinal axis351of the friction stir processing tip325. The splines320may each be straight and extend parallel to the central longitudinal axis351of the friction stir processing tip325. In another embodiment, the splines320may each be curved and extend helically about the central longitudinal axis351.

RegardingFIG.7, the friction stir processing tip125may be utilized in a friction stir processing device400. The friction stir processing device400includes a tip holder402having a body404with a socket406that receives the friction stir processing tip125. The tip holder402includes support surfaces408,410that form sliding fit connections with the lateral locating surfaces135,140of the friction stir processing tip125. The tip holder402includes recesses412that receive the splines130of the friction stir processing tip125and splines414that intermesh with the splines130. To retain the friction stir processing tip125in the socket406, the friction stir processing device400includes a retaining member, such as a set screw416, shiftable in a radially inward direction418until a leading end portion419extends into the channel114of the friction stir processing tip125. To remove the friction stir processing tip125, the set screw416is shifted radially outward in direction420and the friction stir processing tip125is removed in direction430out of the socket406. The tip holder402may also include a through bore432to permit a probe of a thermocouple of the associated machine to extend into the blind bore127of the friction stir processing tip125. Further, the tip holder402may include a notch434to receive a set screw that keys the body404within a spindle.

RegardingFIG.8, a friction stir processing tip450is provided that is similar in many respects to the friction stir processing tip125and friction stir processing tip325discussed above. The friction stir processing tip450includes a body451that has a distal end portion453and a proximal end portion455. The friction stir processing tip450has a friction stir processing portion452including a pin454and a shoulder456. The friction stir processing portion452may include surface features on the pin454and/or the shoulder456to create material flow and generate heat. For example, the pin454may have helical features such as threads457and may also include flats459of the threads456.

The friction stir processing tip450also has a connecting portion460that includes splines462and a channel464. The splines462may be, for example, involute splines. The splines462may be arranged in a contiguous circular pattern about a central longitudinal axis472of the friction stir processing tip450. The splines462may be evenly spaced about the central longitudinal axis472of the friction stir processing tip450. The splines462may each be straight and extend parallel to the central longitudinal axis472. In another embodiment, the splines462may each be curved and extend helically about the central longitudinal axis472.

The splines462may be configured to form a sliding fit connection with a corresponding tip holder such as tip holder152. The splines462may be sized to provide enough clearance to permit the friction stir processing tip450to be loaded into the tool holder without significant frictional resistance, while being tight enough to inhibit tilting of the friction stir processing tip450within the tool holder.

The channel464includes an annular rim464A and a cylindrical surface464B that extends axially between the annular rim464A and the splines462. The channel464is configured to receive a retaining member to keep the friction stir processing tip450within a tip holder. For example, the retaining member may be a set screw that extends from a tip holder such as tip holder150. The set screw may contact one or both of the annular rim464A and the cylindrical surface464B and inhibit the friction stir processing tip450from falling out of the tip holder.

The friction stir processing tip450may further include a blind bore470. The blind bore470may receive a thermocouple probe for measuring the temperature of the friction stir processing tip450.

The pin454, shoulder456, splines462, channel464, and blind bore470may be formed concentrically about a central longitudinal axis472of the friction stir processing tip450. The concentric arrangement of the structures of the friction stir processing tip450helps limit radial lead-out of the friction stir processing tip450during a friction stir processing operation.

While there have been illustrated and described particular embodiments of the present invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is intended for the present invention to cover all those changes and modifications which fall within the scope of the appended claims. It is intended that the phrase “at least one of” as used herein be interpreted in the disjunctive sense. For example, the phrase “at least one of A and B” is intended to encompass A, B, or both A and B.