Patent Description:
Wire arc additive manufacturing refers to manufacture three-dimensional solid parts by taking wire arc as a heat source and depositing the materials layer by layer, based on the fusion-deposition principle.

For the traditional plane-based wire arc additive manufacturing, the rolling processes can be combined to achieve the excellent mechanical properties of parts. Most of the existing rolling mechanisms are cylindrical rolls, and the layout of the welding gun and rolling mechanism is not flexible enough, thus only simple weld beads (linear or circular arc weld beads) can be rolled. For the curved-surface wire arc additive manufacturing, the weld bead is no longer a simple weld bead, and the machined surface where the weld bead is located is a curved surface and is difficult to combine with existing rolling process, thus a new rolling mechanism and a method need to be provided.

Spinning process is a machining process for achieving metal plastic molding through a spinning mechanism. The bottom end surface of the spinning mechanism may be a curved surface, and thus the spinning machining of the curved surface can be achieved. Therefore, the spinning process has the potential of being applied to the wire arc additive manufacturing, and a wire arc additive-spinning combined process is achieved. However, the existing spinning mechanism is still hard to combine with the existing wire arc additive manufacturing process. Therefore, there is an urgent need of a spinning mechanism and a method for a curved-surface wire arc additive manufacturing.

For example, patent application No. <CIT> (forming the basis for the preamble of the independent claims) discloses a wire arc additive manufacture (WAAM) synchronous ultrasonic hot rolling and quick cooling combined processing device and method and belongs to the technical field of 3D printing. The combined processing device mainly comprises an additive manufacturing device, an ultrasonic vibration hot rolling device and a liquid nitrogen cooling device. During the WAAM process, an ultrasonic vibration profile roller is added; according to the forming characteristics of WAAM, the roller is designed into three different forms of profile rollers, namely, the dot-matrix profile roller,the screw type profile roller and the bevel gear type profile roller. The combined processing device adopts ultrasonic impact to impact the profile roller and the liquid nitrogen cooling device. Through the processing method of the combined processing device, the internal porosity of a WAAM formed part is reduced, the influence of heat accumulation is reduced, grains are refined, and accordingly, the mechanical performance is improved.

Patent application No. <CIT> discloses a method and a system for the combined additive and forming production of a metallic shaped body (<NUM>). The shaped body (<NUM>) is built up in layers in accordance with geometry description data, in particular by melting a wire or powdered metallic material (<NUM>) and applying the molten material (<NUM>) to an already finished layer (<NUM>) or a construction platform (<NUM>). , wherein a pressure-forming processing of the already completed layers (<NUM>, <NUM>) takes place during production. A smoothing of the surface roughness determined by the additive manufacturing is thus made possible in an advantageous manner.

Patent application No. <CIT> discloses a 3D printing system and method for improving the surface quality of a model. The 3D printing system comprises a rack, a Y-direction displacement device, a Z-direction displacement device, a feeding device and a control device are installed on the rack, the Y-direction displacement device is connected with a printing platform, the Z-direction displacement device is connected with an X-direction displacement device, the X-direction displacement device is connected with a spray head device, and the spray head device is connected with the feeding device to realize feeding; and the spray head device comprises a spray head, the spray head is installed on the X-direction displacement device, the side face of the spray head is connected with a Z-direction driving device, and the Z-direction driving device is connected with a contour modification device. According to the method of the invention, an equal-material forming process is utilized, a modification ball head is controlled to move along the outline of the model, so that the part, extruded by the modification ball head, on a laminated striation is plastically deformed, the material at the wave crest flows towards the wave trough, the corrugation becomes shallow, and the size precision and the surface quality of the model are effectively improved.

Patent application No. <CIT> discloses a multi-head rolling surface polishing cutter, and belongs to the technical field of machining cutters. The multi-head rolling surface polishing cutter comprises a cutter rest and five cutter bits, wherein the cutter bits are rolling bits, and mainly consist of balls, support frames, wear resistant plates, lower pressing plates, compression springs, upper pressing plates, pressing screws and the like. The cutter rest can be connected with a machine tool spindle through a Morse taper handle and the like; the balls are put into the support frames, and are pressed with the wear resistant plates having circular grooves; the wear resistant plates are pressed with the lower pressing plates and the upper pressing plates; and the compression springs are mounted between the upper and lower pressing plates. The multi-head rolling surface polishing cutter has the following advantages: through the cutter bit mechanical rolling effect, the material surface smoothness and levelness are improved, the surface pressure stress is improved, the material surface grain size is reduced, and the material surface performance is enhanced; and through the cutter multi-head design, the cutter machining efficiency and using performance are improved.

Patent application No. <CIT> discloses a reinforcing assembly, an additive machining device with an on-line reinforcing effect and a machining method. In order to solve the technical problem that when additive reinforcing is performed by an existing additive machining device, a part of areas can not be reinforced, the additive machining device comprises a machine tool and a printing head, wherein the machine tool comprises a spindle box and a workbench, the workbench is located below the spindle box, and a spindle connecting port is arranged at the lower end of the spindle box; the printing head comprises a laser cladding head and the reinforcing assembly, the laser cladding head is installed on the spindle box, is located on the outer side of the spindle box and can move up and down relative to the spindle box, and the reinforcing assembly is installed at the spindle connecting port of the spindle box; and during machining, the cladding head moves downwards to a designated position for single-layerlaser cladding, and then the reinforcing assembly installed in the spindle and tool handle connecting port performs reinforcing according to the cladding track. According to the reinforcing assembly, the additive machining device with the on-line reinforcing effect and the machining method, defects such as voids, looseness and micro-cracks in the structure of a cladding layer can be eliminated, and the density of a workpiece can be improved.

In view of the above defects or improvement demands in the prior art, the present invention provides a wire arc additive manufacturing-spinning combined machining device and a method using the same, the purpose of which is to achieve the combination of the wire arc additive manufacturing and the spinning process, and can perform spinning machining on a weld bead with an irregular shape, thus obtaining curved surface parts with excellent surface appearance and mechanical property.

To achieve the above mentioned purpose, in accordance with one aspect of the present invention, a wire arc additive manufacturing-spinning combined machining device according to claim <NUM> is provided, which includes c spinning mechanism and a fused deposition modeling mechanism.

The spinning mechanism includes a machine tool and a spinning head. The spinning head is installed on the machine tool by a main shaft, and the main shaft is configured to drive the spinning head to rotate so as to achieve movements in three vertical directions. The spinning head includes a spinning base and balls, and each of the balls is installed in a corresponding one of first arc grooves at a bottom of the spinning base.

The fused deposition modeling mechanism may include a moving track, a robot, and a heat source generator. The moving track may be arranged around the machine tool. The robot is movably installed on the moving track, and the heat source generator may be installed at a tail end of the robot.

The spinning base may have a cross-sectional radius R satisfying L>2R. L may be determined in such a way that: according to a predetermined curved surface layer of a part, finding out all recessed areas in the predetermined curved surface layer; for each of the all recessed areas, determining a lowest point P of the recessed area, and making a horizontal plane intersecting the recessed area at a height H above the lowest P point so as to obtain a closed contour C which may have a plurality of intersection points with a predetermined machining path; and calculating the diameter of an inscribed circle passing through each intersection point in the closed contour C, respectively. The minimum value may be L.

The height H may be equal to a height of each of the balls exposed at a lower end of the spinning base plus a height of a weld bead.

In some embodiments, the balls may include three balls, and the three balls may be circumferentially and uniformly installed at the bottom of the spinning base.

In some embodiments, a half of each of the balls may be installed in the corresponding one of the first arc grooves at the bottom of the spinning base. An axis of the ball may be flush with a bottom surface of the spinning base. A supporting piece may be installed on the bottom surface of the spinning base. Second arc grooves are formed in the supporting piece, and each of the second arc grooves is configured to support a corresponding one of the balls.

A dimension of each portion of the spinning head may be denoted by: <MAT>.

Where θ may be a maximum curvature angle of a to-be-machined curved surface, D may be the diameter of each of the balls, d may be a thickness of the supporting piece, m is a distance between the ball and an edge of the spinning base, and h may be a distance between a lower end of the supporting piece and an edge of the spinning base.

In some embodiments, the moving track nay be annular or semi-annular.

In accordance with another aspect of the present invention, a wire arc additive manufacturing-spinning combined machining method using the machining device above is provided according to claim <NUM>.

In some embodiments, the heat source generator may be a welding gun. The welding gun may be inclined during machining, and an inclination direction of the welding gun is a traveling direction of a weld bead.

In conclusion, compared with the prior art, the above technical solution conceived through the embodiments have the following main technical effects.

Throughout the drawings, like reference numerals are used to refer to like elements or structures. List of the reference characters: <NUM> heat source generator; <NUM> spinning head; <NUM> main shaft; <NUM> base; <NUM> spinning base; <NUM> ball; <NUM> machine tool; <NUM> worktable; <NUM> robot; <NUM> first limit position; <NUM> second limit position; and <NUM> moving track.

To make the objective, the technical solution and advantages of the present invention more clearly, the following further describes the present invention in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention rather than limiting the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

In accordance with a wire arc additive manufacturing-spinning combined machining device provided by an embodiment of the present invention, the wire arc additive manufacturing forming is achieved while a weld bead with an irregular shape is subjected to spinning machining, such that the parts can obtain better surface appearance and mechanical property. The weld bead with the irregular shape includes a linear weld bead or a curved welded bead, a machining surface where the weld bead is located may be a plane or a curved surface with a certain curvature (the plane is a particular curved surface, hereinafter collectively referred to as the curved surface).

As shown in <FIG> and <FIG>, the wire arc additive manufacturing-spinning combined machining device includes a spinning mechanism and a fused deposition modeling mechanism.

The spinning mechanism includes a machine tool <NUM> and a spinning head <NUM>. The spinning head <NUM> is installed on the machine tool <NUM> by a main shaft <NUM>. The main shaft <NUM> is configured to drive the spinning head <NUM> to rotate so as to achieve movements in X, Y, and Z directions. The spinning head <NUM> includes a spinning base <NUM> and balls <NUM>. Each of the balls <NUM> is installed in a corresponding one of circular arc grooves at a bottom of the spinning base <NUM>.

The fused deposition modeling mechanism includes a moving track <NUM>, a robot <NUM>, and a heat source generator <NUM>. The moving rack <NUM> is annular or semi-annular, and is arranged around the machine tool <NUM>. A specific arrangement method of the moving rack <NUM> needs to be determined according to the dimension and a machining area of the machine tool. The robot <NUM> is movably installed on the moving track <NUM>. One end of the moving track is a first limit position <NUM>, and the other end of the moving track is a second limit position <NUM>. The robot may move between the first limit position <NUM> and the second limit position <NUM>. The heat source generator <NUM> is installed at a tail end of the robot <NUM>, and the heat source generator <NUM> is specifically a welding gun.

Preferably, the balls <NUM> includes three balls, and the three balls <NUM> are circumferentially and uniformly installed at the bottom of the spinning base <NUM>. A half of each of the balls <NUM> is installed in the corresponding one of the circular arc grooves at the bottom of the spinning base <NUM>, that is, an axis of the ball <NUM> is flush with a bottom surface of the spinning base <NUM>. A supporting piece is installed at the bottom of the spinning base <NUM>, and the three balls <NUM> are respectively supported by three arc grooves on the supporting piece and are placed in the circular arc grooves of the spinning base <NUM>.

Further, before the wire arc additive manufacturing, a three-dimensional model of a part should be layered, and the height of each layer is the height of one layer produced by the wire arc additive manufacturing (namely the height of a weld bead). and then, the planning of the path (i.e., the traveling path of the welding gun) is carried out layer by layer. When the planar layer is adopted, the welding gun and the spinning head move along a plane path without generating interference. However, when the curved surface layer is adopted, the welding gun and the spinning head move along a curved path, and the welding gun and the spinning head may collide with a forming surface. The collision problem of the welding gun may be prevented by changing a posture. But for the spinning head, it is necessary to determine collision points of the spinning head and curved surface layer in advance, and design the dimension of the spinning base accordingly.

Based on the shape characteristics of the spinning head, the recessed portions of the curved surface layer is most likely to interfere with the spinning head. As shown in <FIG>, firstly, all recessed areas of the curved surface layer are found out, for a certain recessed area Ω through which a Path passes, the lowest point of the recessed area is P, a horizontal plane is made at a certain height H above the lowest point P to intersect with the recessed area Ω, and thus a closed contour C is obtained. The Path has multiple intersection points with the closed contour C. At an intersection point Q, if the diameter L of the smallest inscribed circle padding through the intersection point Q in the closed contour C is smaller than the diameter of the supporting piece, the spinning head is bound to collide with the forming surface. Therefore, for the diameter L of the minimum inscribed circle, the cross-sectional radius R of the spinning base <NUM> should satisfy L>2R. The height H is a height of an exposed portion of the ball below the supporting piece plus a height of a layer of the weld bead, that is, the height H is equal to a sum of D/<NUM>-d and the height of the weld bead, wherein D is the diameter of the ball, d is the thickness of the supporting piece.

Furthermore, in order to guarantee that the designed spinning head <NUM> can be configured to perform curved surface machining in a large curvature range, as shown in <FIG>, a dimension of each portion of the spinning head <NUM> is denoted by, such that the curved surface is tangent to the balls <NUM> and the curved surface is prevented from colliding with the edge of the supporting piece: <MAT>.

Where θ is the maximum curvature angle of a to-be-machined curved surface, D is the diameter of the ball, d is the thickness of the supporting piece, m is a distance between the ball and the edge of the spinning base, and h is a distance between the lower end of the supporting piece and the edge of the spinning base.

A method for performing shape machining of the part by using the wire arc additive manufacturing-spinning combined machining device, as shown in <FIG>, includes the following steps.

The robot <NUM> moves along the moving track <NUM> and drives the welding gun to perform metal fused deposition layer by layer on a worktable <NUM> in a predetermined machining path. The spinning head <NUM> follows the heat source generator <NUM> at a suitable distance behind and moves along a trajectory of the heat source generator <NUM>, and is driven by the main shaft <NUM> to rotate rapidly. When the metal material deposited by the welding gun is not completely solidified, the spinning head <NUM> rotates rapidly and rolls the metal fused deposition position to refine crystal grains, and make the surface of the part smoother. The part obtained by the additive manufacturing is printed on a base <NUM>, and after the machining is finished, the printed part is separated from the base <NUM> by using techniques such as wire cutting.

Specifically, if the spinning head is far away from the welding gun, the temperature of the weld bead is low when being rolled, the strength of the weld bead is high, and the rolling effect is not obvious. If the spinning head is close to the welding gun, the interference is prone to occur. To guarantee the rolling effect and avoid interference, the welding gun needs to be properly inclined, and an inclination direction of the welding gun is a traveling direction of the weld bead. For the linear weld bead, it is only necessary to keep the posture of the welding gun during printing. For the curved weld bead, the welding direction needs to be changed continuously. In order to keep an included angle between the inclination direction and the welding direction, the posture of the welding gun can be changed from time to time by changing the posture of a six-axis machine. If the curvature of the curve is large, it may exceed the travel range of the robot arm. By using the arc moving track around the machine tool, the robot is installed on the moving track to move in a wide range, thus solving the over-travel problem.

Claim 1:
A wire arc additive manufacturing-spinning combined machining device comprising a spinning mechanism and a fused deposition modeling mechanism, wherein
the spinning mechanism comprises a machine tool (<NUM>) and a spinning head (<NUM>), wherein the spinning head (<NUM>) is installed on the machine tool (<NUM>) by a main shaft (<NUM>), the main shaft (<NUM>) is configured to drive the spinning head (<NUM>) to rotate so as to achieve movements in three vertical directions; the spinning head (<NUM>) comprises a spinning base (<NUM>) and balls (<NUM>), and each of the balls (<NUM>) is installed in a corresponding one of first arc grooves at a bottom of the spinning base (<NUM>);
the fused deposition modeling mechanism comprises a moving track (<NUM>), a robot (<NUM>), and a heat source generator (<NUM>), wherein the moving track (<NUM>) is arranged around the machine tool (<NUM>), the robot (<NUM>) is movably installed on the moving track (<NUM>), and the heat source generator (<NUM>) is installed at a tail end of the robot (<NUM>).