Damped boring bar

A tool for a boring machine includes an elongated elongated body extending longitudinally from a proximal end to a distal end, the distal end being shaped to receive a cutting tip, and a cavity inside the body. The tool includes a lattice provided within the cavity and a powder provided in the cavity with the lattice.

TECHNICAL FIELD

The present disclosure relates generally to cutting tools, and more particularly, to boring bars that may be used in turning or boring processes.

BACKGROUND

In one process of machining a workpiece, a securing device, such as a lathe, fixes the workpiece and brings the workpiece into rotation. A cutting tool is brought into a desired position adjacent to the workpiece and drawn into contact with the rotating workpiece. A hard edge of the cutting tool may remove material as the workpiece rotates. The cutting tool can be used to remove material from an outer surface of the workpiece in a process termed “turning.” The cutting tool may also be used to remove material from within a pre-drilled hole in the workpiece, thereby enlarging the hole, in a process termed “boring.”

In a boring procedure, the cutting tool, known as a boring bar, is elongated to provide sufficient depth to the machined bore in the workpiece. The elongated shape of the boring bar may promote vibration of the boring bar during machining. This vibration, also known as chatter, may increase during the boring process due to resonance between the workpiece and the boring bar. Thus, even relatively minor initial vibrations can result in significant chatter and workpieces with uneven and roughened machined surfaces. Prior attempts to reduce chatter require modifying the turning or boring process, for example by altering the speed of rotation of the workpiece, or incorporating damping mechanisms in the boring bar. However, prior attempts may introduce additional complexity to the machining process and/or require the use of boring bars that are difficult to manufacture, yet still fail to fully reduce chatter.

U.S. Patent Application Publication No. 2016/0377140 to Frota de Souze Filho (“the '140 publication”), describes damping systems for boring bars. In the '140 publication, a dynamic vibration absorber is disposed in a cavity of the boring bar. An elastomeric buffer is arranged in a spacing between one or more surfaces of the absorber and a cavity wall. The elastomeric material is injected into the spacing between the absorber and the cavity walls via one or more conduits in the boring bar. While the boring bar damping system of the '140 publication may be useful, one or more of the manufacture, strength, and damping characteristics may be improved. The systems and methods of the present disclosure may solve one or more of the problems set forth above and/or other problems in the art. The scope of the current disclosure, however, is defined by the attached claims, and not by the ability to solve any specific problem.

SUMMARY

In one aspect, a tool for a boring machine may include an elongated body extending longitudinally from a proximal end to a distal end, the distal end being shaped to receive a cutting tip, and a cavity inside the body. The tool may include a lattice provided within the cavity and a powder provided in the cavity with the lattice.

In another aspect, a boring bar may include a monolithic body formed by additive manufacturing and extending longitudinally from a proximal end to a distal end, the distal end shaped to receive a cutting tip, and a cavity inside the body. The boring bar may also include a lattice provided within the cavity, the lattice formed by additive manufacturing, and an inner surface of the body completely enclosing the lattice.

In yet another aspect, a boring bar may include, a monolithic body extending longitudinally from a proximal end to a distal end, the proximal end shaped to be secured by a tool holder, the distal end shaped to secure a cutting tool, and a bore extending from the proximal end of the body. The boring bar may include a completely enclosed cavity within the body at the distal end of the body, a wall that separates the bore from the cavity, and a lattice disposed within the cavity. The boring bar may include a powder enclosed within the cavity, wherein the body, wall, lattice, and powder are all formed by additive manufacturing.

DETAILED DESCRIPTION

Both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the features, as claimed. As used herein, the terms “comprises,” “comprising,” “having,” “including,” or other variations thereof, are intended to cover a non-exclusive inclusion such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements, but may include other elements not expressly listed or inherent to such a process, method, article, or apparatus. As used herein, the term “elongated” is used to describe a feature that extends farther in a length direction as compared to a width direction.

In this disclosure, relative terms, such as, for example, “about,” “substantially,” “generally,” and “approximately” are used to indicate a possible variation of ±10% in a stated value. Although the current disclosure is described with reference to a boring bar, this is only exemplary. While the present disclosure will be discussed in connection with a boring machine or lathe, it is understood that the current disclosure can be applied as to any machine that employs an elongated arm or body that may experience chatter.

FIG. 1illustrates a perspective view of a cutting tool such as a boring bar10, according to aspects of the present disclosure. Boring bar10may have a monolithic structure that includes an elongated body12extending along a longitudinal axis A-A. Body12is elongated in the sense that a length of boring bar10(as measured in a direction along or parallel to longitudinal axis A-A) is greater than a width of boring bar10. Body12includes a proximal end14and an opposing distal end16. A flange18may be positioned closer to proximal end14than distal end16. Body12may further include a proximal portion36that extends from flange18to proximal end14. Proximal portion36may be shaped so as to be received by a chuck of a CNC (computer numeric control) machine such a lathe. A distal portion38may extend from flange18to distal end16of body12.

Distal end16of boring bare10may include a head20, which may be monolithically formed with, and part of, elongated body12. Alternatively, head20may be formed as a separate component that is permanently fixed to or removable from body12. If head20is removable from body12, distal end16may include a fixation mechanism (e.g. threading) that receives a complementary feature (e.g. threading) of a removable head. Head20may include a cutting tip mounting surface22shaped to receive a complementary cutting tip76. The shape of cutting tip mounting surface22may be of any shape that provides support to cutting tip76. As can be seen inFIG. 1, cutting tip76may have a circular or cylindrical shape. However, cutting tip76may also have a triangular, rectangular, square, diamond, or any other shape. An adjacent cutting tip clamp mounting surface24may be formed within head20(see alsoFIG. 2) so as to receive a clamp78that secures the cutting tip76to head20.

FIG. 2is a cross-sectional view of the boring bar10shown inFIG. 1with cutting tip76and clamp78removed. As can be seen inFIG. 2, elongated body12may be formed with a first cavity40and a second cavity60. First cavity40and second cavity60may be separated from one another by a dividing wall or divider26.

First cavity40may be provided within a distal portion38of body12and extend to the distal end16of body12. First cavity40may include a proximal end46and a distal end48, and include a taper from the distal end48to the proximal end46. For example, with reference toFIGS. 2, 5, and 6, first cavity40may include a distal endwall34, a proximal endwall32opposite distal endwall34, an inclined wall42forming a flat boundary from distal endwall34to proximal endwall32, and a circumferentially-extending wall44extending from opposite sides of inclined wall42and from distal endwall34to proximal endwall32. Proximal endwall32may form a point of convergence between inclined wall42and the circumferential wall44. Distal endwall34may extend approximately orthogonal to axis A-A. Thus, first cavity40includes a distal end48having a larger size (e.g. a larger cross-sectional area as measured in a plane orthogonal to axis A-A) than a size of proximal end46of first cavity40. As best shown inFIGS. 5 and 6, first cavity40may be have a shape corresponding to a cylinder having a angled planar portion removed. When referencing cutting tip mounting surface22and cutting tip clamp mounting surface24as located at a top of boring bar10, inclined wall42forms a top portion of first cavity40, and circumferentially-extending wall44forms a bottom portion of first cavity40. Walls42and44together provide an inner surface of body12that completely encloses first cavity40. First cavity40may be entirely sealed, or enclosed, by body12so that cavity does not include any conduits or pathways allowing access to first cavity40. As used herein, a cavity that is completely enclosed does not include any conduits or passageways leading out of the cavity, including conduits or passageways that are filled with a material provided in the cavity. It is understood that first cavity40can have a different shape and relative size than that depicted in theFIGS. 2, 5, and 6. For example, proximal endwall32could be formed orthogonal to axis A-A, rather than as the point of convergence shown inFIG. 2. Further, while proximal endwall32may be disposed between flange18and head20, endwall32may be provided at other locations to increase or decrease the length of first cavity40along axis A-A. In one aspect, proximal endwall32may extend farther in a direction toward proximal end14of boring bar10and be provided at or near flange18. In such a configuration, an angle of inclination of divider26may be reduced.

As can be seen inFIG. 2, a lattice50may be formed within first cavity40. Lattice50may be formed from the same material as body12, and may, for example, be formed monolithically with body12by an additive manufacturing process. In one aspect, lattice50may substantially fill first cavity40and extend to inclined wall42, circumferential wall44, proximal endwall32, and distal endwall34. In such a configuration, lattice50may be substantially the same size as first cavity40. Lattice50may engage walls of first cavity40, for example by engaging only inclined wall42and circumferential wall44, or by engaging all of inclined wall42, circumferential wall44, proximal endwall32, and distal endwall34. In one aspect, lattice50may be formed by a regularly (or irregularly) repeating series of strut members52that are connected to each other at joints54(seeFIGS. 5 and 6). Lattice50may form a repeating pattern of spaces56between the strut members52and joints54.

A powder58may substantially fill the entirety of first cavity40—including the spaces56of lattice50. Powder58may be formed of the same material as body12, and/or the same material as lattice50. In one aspect, body12, lattice50, and powder58may be formed of the same material. Specifically, body12and lattice50may be formed of a sintered metal, while powder58is formed of the same metal material in an unsintered form. Thus, powder58may be disconnected from body12and move relative to body12to form a vibration-absorbing sub stance.

With continued reference toFIG. 2, and as noted above, a second cavity60may also extend within body12. Second cavity60may be defined by an inclined wall62located within distal portion38of body12. According to one aspect, inclined wall62may be the same wall as inclined wall42of the first cavity40, and the divider26. Referring toFIGS. 4-6, the remainder of the second cavity60may be defined by a circumferential wall64of body12. Circumferential wall64may extend from opposite sides of inclined wall62within a distal portion74of second cavity60(seeFIGS. 5 and 6). Circumferential wall64may extend 360 degrees so as to surround second cavity60at a proximal portion72of second cavity60.

Second cavity60may extend within proximal portion36and distal portion38of body12. Also, as shown inFIG. 2, second cavity60may extend from a proximal opening28to a distal endwall68. Thus, second cavity60may have a shape that is not fully enclosed by body12. Distal endwall68of second cavity60may instead be approximately aligned with the distal endwall34of first cavity40. However, distal endwalls34and68may be offset from each other along longitudinal axis A-A. The portion of circumferential wall64extending from proximal opening28of second cavity60may be formed with threading70.

With continued reference toFIG. 2, second cavity60may receive a tapered insert80that has a complementary shape to second cavity60. Insert80may be formed of a material such as a carbide (e.g. one or more of tungsten carbide, titanium carbide, and tantalum carbide) and may have a stiffness that is sufficient to reduce or eliminate deflection of boring bar10. Insert80may overlap lattice50in a longitudinal direction of body12(e.g. along axis A-A). As shown, the overlap may extend substantially the entire longitudinal distance of the lattice50, however, it is understood that the overlap may extend less or more than the longitudinal distance of lattice50.

A set screw30may be provided within second cavity60. Specifically, as can be seen inFIG. 2, set screw30may include threads that engage the internal threading70of second cavity60. Set screw30may apply a compressive force against a proximal endwall82of insert80so as to press a distal endwall84of insert80against distal endwall68of second cavity60with a predetermined compressive force. Thus, set screw30may close proximal opening28.

Thus, as shown inFIG. 2, first cavity40and second cavity60may each have mirroring tapered portions that taper along longitudinal axis A-A. As noted above, first cavity40may be provided so as to have an increasing cross-sectional area (as measured in a plane orthogonal to longitudinal axis A-A) from proximal end14toward distal end16. Whereas, second cavity60may have a decreasing cross-sectional area (as measured in a plane orthogonal to longitudinal axis A-A) in a distal portion74that extends from a proximal portion72. Second cavity60may also extend more proximally than first cavity40, and, as best shown inFIGS. 3 and 4, may include a region in which the cross-sectional area is approximately constant, such as within proximal portion72. In the area in which first cavity40and second cavity60overlap, the cross-sectional areas of first cavity40and second cavity60(as measured in a plane orthogonal to longitudinal axis A-A) may be inversely proportional to each other when considered at two or more locations along longitudinal axis A-A. Thus, cross-sectional areas of first cavity40and second cavity60may respectively increase and decrease in a direction toward distal end16. The rate at which the cross-sectional area of first cavity40increases (when considered at different positions toward distal end16), and the rate at which the cross-sectional area of second cavity60decreases (when considered at different positions toward distal end16), in an area at which the cavities40and60overlap with each other, may be approximately the same. Thus, an inclination of the tapered regions of the first cavity40and second cavity60may be approximately equal.

FIG. 3is a perspective view illustrating an exemplary insert80of boring bar10. As can be seen inFIG. 3, insert80may be substantially cylindrically-shaped so as to extend between a proximal endwall82and a distal endwall84. Proximal endwall82may have an approximately circular shape. This circular shape may extend through an entirety of proximal portion72of second cavity60. A substantially cylindrical proximal portion86may have a circular cross-sectional shape along an entirety thereof. Additionally, proximal portion86may have a shape that corresponds to the shape of proximal portion72of second cavity60. Distal end84of insert80may have a flat surface facing longitudinal axis A-A and forming an approximately semicircular shape or the shape of a circular segment when viewed from axis A-A. A tapered portion88may extend from proximal portion86and form a transitional area in which the cross-sectional area of insert80gradually decreases or tapers from proximal end portion86to distal endwall84. Tapered portion88may include an approximately flat, inclined surface90. In one aspect, inclined surface90may form an angle of approximately 5-15 degrees with respect to longitudinal axis A-A. However, other angles may be formed between inclined surface90and longitudinal axis A-A. A circumferential surface92of insert80extends from opposite sides of inclined surface90.

As shown inFIG. 2, inclined surface90may be formed so as to face and contact a portion of divider26that defines inclined wall62. As can be seen inFIG. 2, the angle of inclination of divider26may be substantially the same as the angle of inclination of inclined surface90. Thus, the portions86and88of insert80may be formed with shapes that closely match the corresponding interior surfaces of second cavity60. Additionally, proximal end82may have a shape that is substantially flat and shaped to receive a pressing surface of set screw30, while distal end84may have a shape that closely matches distal wall68of the second cavity60.

FIGS. 4-6illustrate a series of sectional views taken along lines4-4,5-5, and6-6, respectively, ofFIG. 2. Turning first toFIG. 4, a relationship between body12and insert80within second cavity60is illustrated. As can be seen inFIG. 4, proximal portion86may have a substantially circular cross-sectional shape that corresponds to the cross-sectional shape of second cavity60. However, other cross-sectional shapes (e.g. rectangular, circular, triangular, etc.) may also be employed for the shape of proximal portion86and the corresponding shape of second cavity60. Regardless of the shape of insert80, proximal portion86of insert80may be surrounded by wall64of body12. When proximal portion86of insert80has a circumferentially-shaped surface, wall64may have a circular (circumferential) shape, as shown inFIGS. 4-6.

FIG. 5illustrates a cross-sectional view along line5-5ofFIG. 2. As can be seen inFIG. 5, at a position approximately halfway along first cavity40, the cross-sectional areas of first cavity40and second cavity60may be approximately equal to each other. Additionally, the first cavity40and second cavity60may have semicircular shapes that substantially correspond with each other.

FIG. 6illustrates a sectional view along line6-6ofFIG. 2. Thus,FIG. 6shows boring bar10at a position that is closer to distal end16as compared to the positions ofFIGS. 4 and 5. As can be seen inFIG. 6, first cavity40and second cavity60may each have cross-sectional shapes that form circular segments. First cavity40may have a cross-sectional shape that forms a circular segment smaller than a semicircle. Second cavity60may have a cross-sectional shape that forms a segment that is larger than a semicircle.

As shown inFIGS. 5 and 6, and as mentioned above, lattice50may extend to interior walls of the cavity40. Thus, lattice50may be a rigid structure that provides support to divider26via inclined wall42. This support may allow divider26to be formed with a relatively small thickness to provide for a relative large first cavity40. Additionally, the rigid structure of lattice50may provide support to divider26, allowing an increased cross-sectional area in distal portion48and corresponding increase in an amount of powder58provided at distal portion48.

As can also be seen inFIGS. 5 and 6, powder58may be substantially uniformly distributed within first cavity40and within spaces56of lattice50. Powder58may substantially fill the entirety of first cavity40—including spaces56. Powder58may be made of fine particulate material. For example, powder58may have particles that are approximately as fine as particles of sand, or finer. Thus, even when powder58fills substantially all of the first cavity40, individual particles of powder58may be able to move relative to each other when body12experiences movement, particularly vibration. This movement of particles of powder58may result in the absorption of vibration and produce a damping effect.

In one aspect, the body12, lattice50, and powder58may each be made of a material that is compatible with an additive manufacturing process and which provides sufficient strength for use as a cutting tool. In one aspect, one or more of body12, lattice50, and powder58may be a metal material, such as a stainless steel. In another aspect, one or more of body12, lattice50, and powder58may be formed of 17-4 stainless steel or 316 L stainless steel. However, other materials may also be employed for one or more of body12, lattice50, and powder58.

INDUSTRIAL APPLICABILITY

The disclosed aspects of boring bar10may be used in any machining device. For example, boring bar10may be employed in machining devices that removes material from an exterior or an interior of a rotating workpiece.

As noted above, the disclosed boring bar10and/or lattice50may be manufactured using techniques generally referred to as additive manufacturing, additive fabrication, or 3D printing. Such a process deposits material in successive layers under the control of a computer until the device is fully formed. The layers may be deposited in a melted (flowable) or partially-melted form. The computer may control additive fabrication equipment to deposit the successive layers according to a three-dimensional model (e.g. a digital file such as an AMF or STL file). The model is converted into a plurality of slices, for example substantially two-dimensional slices, that each define a cross-sectional layer of the part. In one case, the boring bar10may be an original component and the 3D printing process would be utilized to manufacture the boring bar10.

Additive manufacturing/fabrication or 3D printing processes may include techniques such as, for example, powder bed fusion, which may produce boring bar10. In powder bed fusion, which may also be referred to as selective laser melting, a powder such as a metal powder of one or more of the materials discussed above, is deposited in a layer-by-layer manner. After a layer of powder is deposited, a laser controlled by a computer, for example, may selectively melt or sinter portions of the deposited layer of powder, permanently fusing predetermined regions of the powder bed while allowing surrounding regions to remain in powdered form. Additional layers may be added sequentially, for example by a roller controller by the computer, each layer being selectively fused to adjacent layers by the operation of the laser. The computer may control the laser and roller, along with assisting equipment, to deposit and sinter successive layers according to the three-dimensional model. Thus, boring bar10may be formed in a layer-by-layer manner such that body12and lattice50may be monolithically formed with respect to each other. Powder58may be formed of portions of each layer of powder that were not sintered by the computer-controlled laser.

The additive manufacturing process utilized to construct the boring bar10may include additional processes performed to create a finished product. Such additional processes may include, for example, one or more of cleaning, hardening, heat treatment, material removal, and polishing. Other processes necessary to complete a finished product may be performed in addition to or in lieu of these processes.

As described above, an additive manufacturing process may provide body12and lattice50as an integral and/or monolithic body. Powder58may be enclosed within first cavity40by employing an additive manufacturing process. Once the additive manufacturing process has completed, including any additional processes, if necessary, tapered insert80may be passed through opening28and positioned such that inclined surface90is slid into contact with inclined wall62. Set screw30may then be rotated to engage internal threading70until an end of set screw30engages proximal endwall82of tapered insert80, applying a predetermined compressive force that presses distal endwall84against distal wall68of second cavity60. Cutting tip76may then be mounted to mounting surface22and secured in place by clamp78. Boring bar10may then be used in a machining operation.

During a machining operation (e.g. turning or boring) such as boring in which boring bar10is used to machine a workpiece, cutting tip76may be used to remove material from a workpiece. Cutting tip76protrudes beyond head20at by a predetermined amount. A chuck of a CNC machining device may secure proximal portion36of boring bar10therein. If desired, proximal portion36may be provided with a series of grooves, may be provided in a polygonal shape, and/or may be provided with one or more flat surfaces to improve the retention of boring bar10in the chuck of the machining device. Boring bar10may then be translated, by the machining device, until cutting tip76contacts a rotating workpiece so as to remove material therefrom. Cutting tip76may be made of a carbide material having a hardness sufficient to perform a machining operation.

During a boring operation, boring bar10may be progressively extended into a pre-drilled bore so as to remove material from a side wall that defines the bore. Thus, as boring bar10removes material so as to enlarge a bore, vibration may tend to occur, particularly if boring bar10is elongated with an extended length. However, powder58enclosed within first cavity40may absorb some or all of the force of vibration. Thus, a level of vibration may be prevented from reaching a magnitude that is capable of affecting a machining operation. The first cavity40is located at the distal end16of the boring bar10to facilitate the dampening of vibration forces that originate and may be larger at the free end of the boring bar10. At the distal end16of the boring bar10, the overlap between the tapered insert80and the lattice50help to provide additional structural support or stiffness to the boring bar10. Thus, an increased amount of powder58may be provided in the area where vibration originates while maintaining resistance to deflection.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed boring bar without departing from the scope of the disclosure. Other embodiments of the machine will be apparent to those skilled in the art from consideration of the specification and practice of the tool for a boring machine and boring bar disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.