Laser Additive Manufacturing Layer-by-Layer Optimization System and Method for Penetrating Cavity Inner Wall

Abstract

The present invention discloses a layer-by-layer optimization system for the inner wall of a through cavity in laser additive manufacturing, which includes a laser device with a downward-facing laser head capable of performing XYZ movement, a forming substrate, and a layer-by-layer optimization device for the inner contour of the through cavity; there is an enclosing wall around the substrate, and the forming groove is inside the enclosing wall; the laser device melts and then solidifies a preset area of the metal powder layer laid in the forming groove, so that a metal solidified layer with an inner contour is formed in the preset area, and the layer-by-layer optimization device for the inner contour of the through cavity optimizes a clear inner contour along the inner contour edge of the metal solidified layer; thus, the inner wall surface of the vertical through cavity of the finally formed target forming part is homogeneous, smooth and not prone to cracking.

Description

Technical Field

[0001] The invention belongs to the field of laser layer-by-layer additive manufacturing. Background Art

[0002] The working principle of laser additive manufacturing technology is to use a high-power laser beam to accurately melt metal powder. After the laser beam scans the surface of the metal powder layer, it melts the material locally by rapid heating, and quickly solidifies during the cooling process to form a metal solidification layer. The metal solidification layer is stacked layer by layer until the desired object is formed;

[0003] Since there are a large number of metal sintered particle bands on the contour edge of the solidified layer, which are formed by melting metal powder and gathering into droplets and then rapidly solidifying, the contour line of the contour edge is unclear. Therefore, the surface of the final molded product of laser additive manufacturing generally has a large number of small pits and burrs, and the surface stress is uneven; the existing treatment method is to use surface grinding and surface shot peening processes after molding to eliminate surface stress and burrs, and avoid the formation of a large number of burrs and later cracks on the surface of the final molded parts; when the final molded object has a through inner cavity, the inner wall of the cavity is not convenient for grinding and shot peening processes, especially not suitable for shot peening processes. Summary of the invention

[0004] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a layer-by-layer optimization system for the inner wall of a through-cavity in laser additive forming, so that the inner wall surface of the vertical through-cavity of the target molded part finally formed is homogeneous, smooth and not prone to cracking.

[0005] Technical solution: To achieve the above-mentioned purpose, the layer-by-layer optimization system of the inner wall of the through-cavity of the laser additive forming of the present invention comprises a laser device with a laser head facing downward and capable of XYZ movement, a molding substrate and a layer-by-layer optimization device for the inner contour of the through-cavity; the substrate has an enclosing wall on the outer periphery, and the inner part of the enclosing wall is a molding groove; the laser device melts a preset area of the metal powder layer laid in the molding groove and then solidifies it, so that the preset area forms a metal solidification layer with an inner contour, and the layer-by-layer optimization device for the inner contour of the through-cavity optimizes a clear inner contour along the inner contour edge of the metal solidification layer.

[0006] Furthermore, a downwardly extending sinking cylinder is integrally provided in the center of the forming substrate, and a metal powder pre-filling bin is contained in the sinking cylinder; the metal powder pre-filling bin is pre-filled with metal powder to form a pre-filling bin metal powder filling body.

[0007] Furthermore, the device for optimizing the inner contour of the through-cavity layer by layer includes a rotating disk coaxially arranged at the bottom end of the sinking cylinder.

[0008] Further, the through-type cavity inner contour layer-by-layer optimization device further includes a vertical rod fixedly connected coaxially at the upper end of the rotating disk and extending upward. The vertical rod coaxially passes through the metal powder pre-filling bin upward and extends out to the top higher than the forming groove. Lifting devices are fixedly installed on both sides of the vertical rod. The upper end of the lifting rod of the lifting device is fixedly connected to a servo base. A swing arm servo is installed on the servo base. A telescopic arm is vertically connected to the horizontal servo shaft of the swing arm servo. An a-motor is fixedly installed vertically at the end of the telescopic part of the telescopic arm. The output end of the a-motor is coaxially connected to an a-rotating cone head;

[0009] A b-motor is installed on the lower side of the edge of the rotating disk, and a b-rotating cone head with a pointed end upward is arranged on the upper side of the edge of the rotating disk. The b-motor can drive the b-rotating cone head to rotate;

[0010] A vertically extending alloy wire passing groove is hollowed out on the vertical rod, and a horizontal alloy wire restraining rod is fixedly arranged at the upper end of the alloy wire passing groove;

[0011] It further includes a hard alloy fine twisted rope, which obliquely passes through the alloy wire passing groove, and the upper and lower ends of the hard alloy fine twisted rope are respectively fixedly connected to the tip of the a-rotating cone head and the tip of the b-rotating cone head.

[0012] Further, the axis of the a-motor is perpendicular to the axis of the horizontal servo shaft.

[0013] Further, the outer diameter range of the cross-sectional contour of the hard alloy fine twisted rope is 1.5 mm to 2.5 mm.

[0014] Further, the hard alloy fine twisted rope is twisted by a number of hard alloy wires.

[0015] Further, the optimization process of the layer-by-layer optimization system for the inner wall of the through-type cavity formed by laser additive manufacturing:

[0016] Step 1, in the initial state, the telescopic arm is vertically upward, and the hard alloy fine twisted rope is in a taut state and straddles the lower side of the alloy wire restraining rod;

[0017] Step 2, a thin layer of metal powder with a preset thickness is laid in the forming groove;

[0018] Step 3, by controlling the laser device, a metal solidified layer with an inner contour formed by the solidification of molten metal is formed in the central area of the topmost thin layer of metal powder in the forming groove;

[0019] Step 4: Control the originally vertical telescopic arm to swing downward clockwise around the horizontal servo axis, and the telescopic part of the telescopic arm extends adaptively, so that while the hard alloy thin twist rope maintains tension, the hard alloy thin twist rope forms a local bend at the contact position with the inner contour edge of the topmost layer of metal solidification layer, and the local bend position of the hard alloy thin twist rope is recorded as the local bend part of the hard alloy thin twist rope; At this time, simultaneously control the tips of the a rotary cone head and the b rotary cone head to rotate at the same speed and in the same rotation direction, so that any cross-section of the tightened hard alloy thin twist rope rotates along its own center. While the hard alloy thin twist rope maintains stable tension, control the disc drive motor to drive the rotary disc to rotate at least one circle along the axis.

[0020] Beneficial effects: Each layer of metal solidification layer of the present invention is made denser and more uniform under the rolling of the inner contour edge at the local bend part of the hard alloy thin twist rope, the local surface stress is eliminated, and the metal sintered particles are peeled off. The contour line of the inner contour edge is clear and smooth; Therefore, the inner wall surface of the vertical through cavity of the finally formed target formed part is homogeneous, smooth, not easy to crack, and there are no a large number of irregular pits, protrusions and burrs. Description of the Drawings

[0021] Figure 1 Schematic diagrams of the "Step 1", "Step 2" and "Step 7" stages of this solution. In this figure, the pre-filled bin metal powder filling body, the peripheral powder filling body and the inner peripheral powder filling body are hidden.

[0022] Figure 2 It is a device for optimizing the inner contour of the through cavity layer by layer;

[0023] Figure 3 For " Figure 1 " The cross-sectional view in the state of the following figure;

[0024] Figure 4 For Figure 3 The front view of, including the pre-filled bin metal powder filling body, the peripheral powder filling body and the inner peripheral powder filling body;

[0025] Figure 5 It is the state when the target formed part is about to be taken out after the forming is completed;

[0026] Figure 6 It is a schematic diagram during the process that the contour edge of the solidification layer has a large number of metal sintered particle bands formed by the melting and aggregation of metal powder into drops and then quickly solidifying, and is rolled by the local bend part of the hard alloy thin twist rope. Detailed Embodiment

[0027] The present invention will be further described below with reference to the drawings.

[0028] There is a vertically penetrating cavity 18 running longitudinally through the center of the target formed part 22a of this solution, and the quality enhancement object of the core content of this solution is the inner wall surface of this vertically penetrating cavity 18.

[0029] As shown in the Figures 1 to 6 layer-by-layer optimization system for the inner wall of the laser additive manufacturing through cavity shown, which includes a laser device 3 with the laser head 2 facing down that can perform XYZ movement, a forming substrate 9, and a through cavity inner contour layer-by-layer optimization device 51; there is an enclosing wall 17 on the outer periphery of the substrate 9, and inside the enclosing wall 17 is a forming groove 7; the laser device 3 melts and solidifies a preset area of the metal powder layer laid in the forming groove 7, so that the preset area forms a metal solidified layer 22 with an inner contour, and the through cavity inner contour layer-by-layer optimization device 51 optimizes a clear inner contour along the inner contour edge 20 of the metal solidified layer 22.

[0030] As Figure 1 shown, a sinking cylinder 15 extending downward is integrally provided in the center of the forming substrate 9, and inside the sinking cylinder 15 is a metal powder preloading bin 10; after the metal powder preloading bin 10 is pre-filled with metal powder, a preloading bin metal powder filling body 10a is formed; the through cavity inner contour layer-by-layer optimization device 51 includes a rotating disk 11 coaxially arranged at the bottom end inside the sinking cylinder 15, and a disk driving motor 12 is arranged below the rotating disk 11, and the disk driving motor 12 can drive the rotating disk 11 to rotate along the axis.

[0031] A vertical rod 8 extending upward is coaxially and fixedly connected to the upper end of the rotating disk 11. The vertical rod 8 coaxially passes through the metal powder preloading bin 10 upward and extends upward to the top higher than the forming groove 7; lifting devices 1 are fixedly installed on both sides of the vertical rod 8. The upper end of the lifting rod 1a of the lifting device 1 is fixedly connected to a servo base 27, and a swing arm servo 4 is installed on the servo base 27. A telescopic arm 5 is vertically connected to the horizontal servo shaft 28 of the swing arm servo 4. The end of the telescopic part 5a of the telescopic arm 5 is vertically and fixedly installed with an a motor 23, and the axis of the a motor 23 is perpendicular to the axis of the horizontal servo shaft 28; the output end of the a motor 23 is coaxially connected to an a rotating cone head 6.

[0032] A b motor 13 is installed on the lower side of the edge of the rotating disk 11, and a b rotating cone head 14 with the tip facing upward is arranged on the upper side of the edge of the rotating disk 11. The b motor 13 can drive the b rotating cone head 14 to rotate; a wire passing groove 24 extending in the vertical direction is hollowed out on the vertical rod 8, and a horizontal wire restraining rod 16 is fixedly arranged at the upper end of the wire passing groove 24; it also includes a hard alloy fine twisted rope 19 made of a number of hard alloy wires twisted together. The hard alloy fine twisted rope 19 obliquely passes through the wire passing groove 24, and the upper and lower ends of the hard alloy fine twisted rope 19 are respectively fixedly connected to the tip of the a rotating cone head 6 and the tip of the b rotating cone head 14; the outer diameter range of the cross-sectional contour of the hard alloy fine twisted rope 19 is 1.5 mm to 2.5 mm.

[0033] Description of the specific process and process principle:

[0034] In the center of the target formed part 22a of this solution, there is a vertically penetrating vertical cavity 18. The object of quality strengthening of the core content of this solution is the inner wall surface of the vertical cavity 18.

[0035] Step 1: In the initial state, after the metal powder pre-filled bin 10 is pre-filled with metal powder, a pre-filled bin metal powder filling body 10a is formed. The upper surface of the pre-filled bin metal powder filling body 10a is flush with the surface of the substrate 9. And in the initial state, the telescopic arm 5 is vertically upward, and the hard alloy fine twist rope 19 is stretched across the lower side of the alloy wire restraint rod 16, and the upper section of the hard alloy fine twist rope 19 tends to be vertical; so that in the top view, the telescopic arm 5, the a rotary cone head 6 and the hard alloy fine twist rope 19 are all within the enclosure range of the vertical cavity 18 that needs to be finally formed, avoiding the necessary displacement path of the laser device 3 from interfering with the telescopic arm 5, the a rotary cone head 6 and the hard alloy fine twist rope 19 during the subsequent "Step 3".

[0036] Step 2: Uniformly spread a metal powder thin layer with a preset thickness on the common upper surface of the substrate 9 and the pre-filled bin metal powder filling body 10a.

[0037] Step 3: By controlling the XYZ displacement of the laser device 3, the laser device 3 accurately irradiates the laser beam on the topmost layer of the metal powder thin layer in the forming groove 7. By controlling the horizontal displacement of the laser device 3, the scanning range and path of the laser beam are controlled, and finally a metal solidified layer 22 with an inner contour formed by the solidification of molten metal is formed in the central area of the topmost layer of the metal powder thin layer in the forming groove 7; at this time, the inner contour edge 20 of the metal solidified layer 22 is within the enclosure range of the inner contour of the metal powder pre-filled bin 10 in the top view; there are a large number of metal sintered particles 35 formed by the melting and aggregation of metal powder into drops and then quickly solidified on the inner contour edge 20 of the metal solidified layer 22 and intersect with the metal powder, as Figure 6 shown, resulting in the boundary of the contour line of the inner contour edge 20 of the newly formed metal solidified layer 22 being blurred and unclear, and it is easy to have a large number of irregular pits, protrusions and burrs on the inner wall surface of the vertical cavity 18 of the finally formed target formed part 22a.

[0038] Step 4: Control the originally vertical telescopic arm 5 to swing downward clockwise around the transverse servo shaft 28, and the telescopic part 5a of the telescopic arm 5 extends adaptively, so that the hard alloy fine twist rope 19 swings downward around the tip of the b rotary cone head 14 while always being in a taut state, and disengages from the alloy wire restraint rod 16 downward. As the telescopic arm 5 continues to swing downward clockwise around the transverse servo shaft 28 until the hard alloy fine twist rope 19 vertically contacts the inner contour edge 20 of the uppermost layer of the metal solidification layer 22. At this time, the telescopic part 5a further applies a certain thrust to control the adaptive change of the transverse servo shaft 28, so that while the hard alloy fine twist rope 19 maintains tension, a local bend occurs at the contact position between the hard alloy fine twist rope 19 and the inner contour edge 20 of the uppermost layer of the metal solidification layer 22. Mark the local bend position of the hard alloy fine twist rope 19 as the local bend part 19a of the hard alloy fine twist rope. At this time, the local bend part 19a of the hard alloy fine twist rope forms a local pressing stress on the inner contour edge 20 of the uppermost layer of the metal solidification layer 22. At the same time, control the a motor 23 and the b motor 13 to make the tips of the a rotary cone head 6 and the b rotary cone head 14 rotate at the same speed and in the same rotation direction, so that any cross-section of the taut hard alloy fine twist rope 19 rotates along its own center at this time. At this time, the local bend part 19a of the hard alloy fine twist rope rolls and grinds a local area of the inner contour edge 20 of the uppermost layer of the metal solidification layer 22. Since the hard alloy fine twist rope 19 is made by twisting a number of hard alloy wires, a number of convex rib-like structures 64 are formed on the outer circumference of the cross-section of the local bend part 19a of the hard alloy fine twist rope. The metal sintered particles 35 adhered to the local position of the inner contour edge 20 of the uppermost layer of the metal solidification layer 22 are peeled off under the rolling and grinding of the local bend part 19a of the hard alloy fine twist rope, and the local position of the inner contour edge 20 of the uppermost layer of the metal solidification layer 22 becomes denser and more uniform under the rolling and grinding of the local bend part 19a of the hard alloy fine twist rope, thereby eliminating the local surface stress;

[0039] Subsequently, in the subsequent process of this step, the thrust of the telescopic part 5a of the telescopic arm 5 is always adaptively controlled to keep the tension of the cemented carbide fine twist rope 19 stable. At the same time, the disk drive motor 12 is controlled to drive the rotating disk 11 to rotate along the axis for at least one circle, so that the locally bent part 19a of the cemented carbide fine twist rope rolls along the contour path of the inner contour edge 20 of the topmost layer of the metal solidification layer 22, so that the locally bent part 19a of the rolling cemented carbide fine twist rope rolls and scans along the contour path of the inner contour edge 20 of the topmost layer of the metal solidification layer 22, so that all the bonded metal sintered particles 35 on the inner contour edge 20 of the topmost layer of the metal solidification layer 22 are peeled off under the rolling motion of the locally bent part 19a of the cemented carbide fine twist rope, and the inner contour edge 20 of the topmost layer of the metal solidification layer 22 becomes denser and more uniform under the rolling of the locally bent part 19a of the cemented carbide fine twist rope, thereby eliminating local surface stress and making the contour line of the inner contour edge 20 of the newly formed metal solidification layer 22 clear and smooth;

[0040] Step Five: The telescopic arm 5 swings counterclockwise upward around the transverse steering gear shaft 28 to restore the telescopic arm 5 to the vertically upward state in the initial state. The cemented carbide fine twist rope 19 is stretched and crosses under the alloy wire restraint rod 16, and the upper section of the cemented carbide fine twist rope 19 tends to be vertical; so that from the top view, the telescopic arm 5, the a rotating cone head 6 and the cemented carbide fine twist rope 19 are all within the enclosure range of the vertically penetrating cavity 18 that finally needs to be formed;

[0041] Step Six: Lay a new thin layer of metal powder in the forming groove 7;

[0042] Step Seven: Continuously cycle the process from "Step Three" to "Step Six" to stack several layers of metal solidification layers 22 layer by layer from bottom to top until the target formed part 22a is constructed; an outer powder filling body 7a is formed around the target formed part 22a, and an inner powder filling body 18a is formed in the vertically penetrating cavity 18 of the target formed part 22a;

[0043] Since each layer of the metal solidification layer 22 becomes denser and more uniform under the rolling of the inner contour edge 20 by the locally bent part 19a of the cemented carbide fine twist rope, the local surface stress is eliminated, and the metal sintered particles 35 are peeled off, and the contour line of the inner contour edge 20 is clear and smooth; therefore, the inner wall surface of the vertically penetrating cavity 18 of the finally formed target formed part 22a is homogeneous, smooth and not easy to crack, and there are no a large number of irregular pits, protrusions and burrs.

[0044] The above is only the preferred embodiment of the present invention. It should be pointed out that: for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and retouches can be made, and these improvements and retouches should also be regarded as the protection scope of the present invention.

Claims

1. A layer-by-layer optimization system for the inner wall of a through cavity formed by laser additive manufacturing, characterized in that: It includes a laser device (3) with a laser head (2) capable of performing XYZ movements facing downwards, a forming substrate (9), and a through-cavity inner contour layer-by-layer optimization device (51); there is an enclosing wall (17) on the outer periphery of the substrate (9), and a forming groove (7) is inside the enclosing wall (17); the laser device (3) melts and then solidifies a preset area of the metal powder layer laid in the forming groove (7), so that a metal solidified layer (22) with an inner contour is formed in the preset area, and the through-cavity inner contour layer-by-layer optimization device (51) optimizes a clear inner contour along the inner contour edge (20) of the metal solidified layer (22); A sinking cylinder (15) extending downwards is integrally provided at the center of the forming substrate (9), and a metal powder pre-filling bin (10) is inside the sinking cylinder (15); after the metal powder pre-filling bin (10) is pre-filled with metal powder, a pre-filled bin metal powder filling body (10a) is formed; The through-cavity inner contour layer-by-layer optimization device (51) includes a rotating disk (11) coaxially arranged at the bottom end inside the sinking cylinder (15); The through-cavity inner contour layer-by-layer optimization device (51) further includes a vertical rod (8) fixedly connected coaxially upwards at the upper end of the rotating disk (11), the vertical rod (8) coaxially passes upwards through the metal powder pre-filling bin (10) and extends upwards to the top higher than the forming groove (7); lifting devices (1) are fixedly installed on both sides of the vertical rod (8), the upper end of the lifting rod (1a) of the lifting device (1) is fixedly connected with a servo seat (27), a swing arm servo (4) is installed on the servo seat (27), a telescopic arm (5) is vertically connected to the lateral servo shaft (28) of the swing arm servo (4), the end of the telescopic part (5a) of the telescopic arm (5) is vertically and fixedly installed with an a-motor (23), and the output end of the a-motor (23) is coaxially connected with an a-rotating cone head (6); A b-motor (13) is installed on the lower side of the edge of the rotating disk (11), a b-rotating cone head (14) with a pointed head facing upwards is arranged on the upper side of the edge of the rotating disk (11), and the b-motor (13) can drive the b-rotating cone head (14) to rotate; A wire passing groove (24) extending in the vertical direction is hollowed out on the vertical rod (8), and a transverse wire restraining rod (16) is fixedly arranged at the upper end of the wire passing groove (24); It further includes a hard alloy thin twisted rope (19), the hard alloy thin twisted rope (19) obliquely passes through the wire passing groove (24), and the upper and lower ends of the hard alloy thin twisted rope (19) are respectively fixedly connected to the tip of the a-rotating cone head (6) and the tip of the b-rotating cone head (14); While the hard alloy thin twisted rope (19) maintains tension, a local bend occurs at the contact position of the hard alloy thin twisted rope (19) with the inner contour edge (20) of the topmost metal solidified layer (22), and the local bend position of the hard alloy thin twisted rope (19) is denoted as the hard alloy thin twisted rope local bend part (19a); the hard alloy thin twisted rope local bend part (19a) forms a local pressing stress on the inner contour edge (20) of the topmost metal solidified layer (22).

2. The layer-by-layer optimization system for laser additive manufacturing of a through cavity inner wall according to claim 1, characterized in that: The axis of the a-motor (23) is perpendicular to the axis of the lateral servo shaft (28).

3. The layer-by-layer optimization system for the inner wall of a through cavity formed by laser additive manufacturing according to claim 2, wherein: The outer diameter range of the cross-sectional profile of the cemented carbide fine twisted rope (19) is 1.5 mm to 2.5 mm.

4. The layer-by-layer optimization system for the inner wall of a laser additive manufacturing through cavity according to claim 3, wherein: The cemented carbide fine twisted rope (19) is made by twisting a number of cemented carbide wires.

5. The optimization process of the layer-by-layer optimization system for the inner wall of the laser additive manufacturing through cavity according to claim 4, characterized in that: Step 1, in the initial state, the telescopic arm (5) faces vertically upward, and the cemented carbide fine twisted rope (19) is stretched and passes over the lower side of the alloy wire restraining rod (16); Step 2, a metal powder thin layer with a preset thickness is laid in the forming groove (7); Step 3, by controlling the laser device (3), a metal solidification layer (22) with an inner contour formed by the solidification of molten metal is formed in the central area of the topmost metal powder thin layer in the forming groove (7); Step 4, control the originally vertical telescopic arm (5) to swing clockwise downward around the transverse servo axis (28), and the telescopic part (5a) of the telescopic arm (5) extends adaptively, so that while the cemented carbide fine twisted rope (19) maintains tension, the cemented carbide fine twisted rope (19) forms a local bend at the contact position with the inner contour edge (20) of the topmost metal solidification layer (22), and the local bend position of the cemented carbide fine twisted rope (19) is recorded as the local bend part (19a) of the cemented carbide fine twisted rope; at this time, simultaneously control the tips of the a rotary cone head (6) and the b rotary cone head (14) to rotate at the same rotational speed and in the same rotational direction, so that any cross-section of the tightened cemented carbide fine twisted rope (19) rotates along its own center. While the cemented carbide fine twisted rope (19) maintains tension and stability, control the disk drive motor (12) to drive the rotary disk (11) to rotate at least one circle along the axis.

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