Laser powder bed additive-subtractive composite manufacturing process and equipment

Abstract

A kind of laser powder bed additive-subtractive composite manufacturing process and equipment, including machine tool bed and the sealing cover connected above it, additive powder feeding mechanism, powder recycling mechanism are connected in machine tool bed, sealing cover interior is connected with powder spreading mechanism, screw motor module and parallel manipulator on it, tool magazine and hydraulic locking mechanism, laser light source is connected above sealing cover, additive part consisting of additive powder feeding mechanism, powder recycling mechanism, laser light source and powder spreading mechanism realizes L-PBF process, subtractive part consisting of screw motor module, parallel manipulator, tool magazine and hydraulic locking mechanism realizes subtractive machining;The laser powder bed and parallel manipulator of the present application are combined, improve overall processing efficiency and reduce the manufacturing defects caused by the heat dissipation of additive process, reduce the influence brought by vibration when subtractive machining, and set preheating slow cooling mechanism and elastic sealing mechanism, realize the adjustment of thermal history in ASHM process and the protection of normal operation of motor.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology, specifically to a laser powder bed additive and subtractive composite manufacturing process and equipment. Background Technology

[0002] Additive manufacturing (AM) is a near-net-shape forming technology that uses digital control to "stack" materials layer by layer, converting digital models into solid objects. It is not constrained by the complex conditions of tools, molds, fixtures, and processes inherent in traditional machining, thus overcoming the bottlenecks of traditional machining. It liberates designers from the constraints of part assembly and structural limitations that are present in traditional machining. Taking Laser Powder Bed Fusion (L-PBF) technology as an example, it uses a laser as an energy source to heat and melt powder layers at designated locations based on the model, fusing powder particles together and accumulating layer by layer to ultimately form the desired shape. Its advantages include: easy one-piece molding of complex components, facilitating prototyping; freeing up space for innovative design, enabling the design of new structures; and high material utilization, responding to the call for green manufacturing. Therefore, it has broad application prospects in aerospace, vehicle engineering, nuclear power, and other fields.

[0003] However, with in-depth research into the technology, its limitations have gradually emerged. The geometric accuracy and surface quality of additive manufacturing cannot be compared with traditional machining, especially when manufacturing some suspended or internal flow channel components. The model needs to be equipped with supporting structures, which further affects the internal surface quality of the formed part and even its basic function. Currently, some researchers have combined the advantages of additive manufacturing in easily forming complex components with the advantages of subtractive manufacturing in terms of dimensional accuracy and surface quality, proposing the concept of Additive and Subtractive Hybrid Manufacturing (ASHM). Some devices have been developed, but most solutions are based on traditional CNC machine tools to integrate additive manufacturing functions. The movement of each axis of the subtractive tool in the equipment is mainly achieved by moving the slide table through linear motors or ball screw modules. This results in large inertia of the tool's degrees of freedom, affecting positioning accuracy and repeatability. Furthermore, it is necessary to limit the movement speed of each axis of the tool, which affects the efficiency of subtractive machining.

[0004] In traditional additive manufacturing (AM) processes, although materials repeatedly undergo laser heating and natural cooling, the natural cooling time is short (only the supply time of the next layer of powder material needs to be considered) and regular, making it easy to control the machining quality of the target part. However, in the ASHM process, the addition of subtractive processing results in a significantly longer cooling time for the corresponding processed layer compared to other AM processes (heat generated in the previous additive process undergoes prolonged dissipation during subtractive processing). This causes significant and irregular variations in the thermal history of the material, making it more likely to affect the final quality of the target part (easily leading to seams, voids, and incomplete fusion defects at the alternating additive and subtractive processing points). Therefore, in the ASHM process, the efficiency of subtractive processing should be maximized to minimize the subtractive processing time interspersed within the AM process. This not only improves the overall efficiency of the ASHM process but also helps reduce defects in the part caused by different thermal histories.

[0005] At the same time, it is also necessary to consider that the L-PBF process in AM technology requires layer-by-layer processing on a substrate with vertical degrees of freedom. This means that the development of the corresponding ASHM device must not only consider the processing range of the subtractive cutting tool on the substrate, but also the vibration problem generated by the parts on the substrate with motion degrees of freedom during subtractive processing. This will not only affect the current powder layer laying (the L-PBF process has high requirements for the quality of each powder layer laying), but also affect the accuracy and quality of subtractive processing (it itself requires the processing table to have high rigidity), and ultimately affect the quality of the parts.

[0006] To address the two types of drawbacks mentioned above, existing ASHM devices and processes have not yet disclosed corresponding technical solutions. Summary of the Invention

[0007] To overcome the shortcomings of the prior art, the present invention aims to provide a laser powder bed additive-subtractive composite manufacturing process and equipment, which combines a laser powder bed with a parallel robotic arm to reduce the subtractive processing time in the ASHM process, effectively improve the overall processing efficiency, and reduce manufacturing defects caused by heat dissipation generated during the additive process. The additive substrate has a constrained design on the vertical motion mechanism to reduce the impact of vibration during subtractive processing, and a preheating and slow cooling function mechanism and an elastic sealing mechanism are set to adjust the thermal history during the ASHM process and protect the normal operation of the motor, respectively.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A laser powder bed additive-subtractive composite manufacturing equipment includes a machine bed 2 and a sealed cover 1 connected above it. The machine bed 2 is connected to an additive powder feeding mechanism 3 and a powder recovery mechanism 4. The sealed cover 1 is connected to a powder spreading mechanism 7, a lead screw motor module 8 and a parallel robotic arm 9, a tool magazine 10 and a hydraulic locking mechanism 12. A laser light source 6 is connected above the sealed cover 1. The additive part, composed of the additive powder feeding mechanism 3, the powder recovery mechanism 4, the laser light source 6 and the powder spreading mechanism 7, realizes the L-PBF process. The subtractive part, composed of the lead screw motor module 8, the parallel robotic arm 9, the tool magazine 10 and the hydraulic locking mechanism 12, realizes the subtractive machining. The machine bed 2 and the sealed cover 1 are connected to a control cabinet 5.

[0010] The sealing cover 1 is made of multiple aluminum alloy plates spliced ​​together, and gas sealing is achieved at the connection between the plates; a gas pressure sensor 101 and an oxygen content sensor 102 are arranged on the top of the sealing cover 1 to ensure that the set gas protective atmosphere is maintained during the processing; an airtight door 103 is provided in front of the sealing cover 1, and a glove opening is provided; a first detachable plate 104 is provided on both sides of the sealing cover 1.

[0011] The additive manufacturing powder feeding mechanism 3 includes a vertical transmission structure for the forming cylinder and the inner plate of the powder feeding cylinder; the vertical transmission structure for the inner plate of the forming cylinder includes a forming cylinder motor 310, which is connected to a forming cylinder lead screw 307. A first connecting guide block 308 on the forming cylinder lead screw 307 is connected to a forming cylinder top column 304. The forming cylinder top column 304 is connected to a forming substrate 301 inside the forming cylinder 303. The forming cylinder top column 304 pushes the forming substrate 301 to move in the vertical direction.

[0012] The vertical transmission structure of the inner plate of the powder feeding cylinder includes a powder feeding cylinder motor 311, which is connected to a powder feeding cylinder lead screw 313. The second connecting guide block 316 on the powder feeding cylinder lead screw 313 is connected to a powder feeding cylinder top column 317. The powder feeding cylinder top column 317 is connected to a powder feeding plate 302 inside the powder feeding cylinder 318. The powder feeding cylinder top column 317 pushes the powder feeding plate 302 to move in the vertical direction.

[0013] In addition to the slider and guide rail required for the basic movement of the lead screw and connecting guide block, forming cylinder constraint sliders 305 and forming cylinder constraint guide rails 306 are arranged on the left and right sides of the forming cylinder top column 304; powder feeding cylinder constraint sliders 314 and powder feeding cylinder constraint guide rails 315 are arranged on the left and right sides of the powder feeding cylinder top column 317.

[0014] Maintenance windows 319 are provided on both sides of the additive manufacturing powder feeding mechanism 3. A forming area sealing plate 320 and a powder feeding area sealing plate 324 are installed on the front of the additive manufacturing powder feeding mechanism 3. A second detachable plate 321 is provided on the forming area sealing plate 320 and the powder feeding area sealing plate 324. The motor wiring and oil circuit within the sealing area are connected out through the plate module 322 and the aviation connector 323.

[0015] A preheating and slow cooling mechanism is provided under the forming substrate 301 inside the forming cylinder 303. The preheating and slow cooling mechanism includes a heating plate 325, which is connected to the bottom of the forming substrate 301. The heating plate 325 is connected to a thermocouple to monitor its temperature in real time. A heat insulation plate 326 is connected below the heating plate 325. The upper half of the water cooling plate 327 and the lower half of the water cooling plate 328 are connected below the heat insulation plate 326. The upper half of the water cooling plate 327 and the lower half of the water cooling plate 328 are spliced ​​to form a water-cooled inner flow channel. A forming area support plate 329 is connected below the lower half of the water cooling plate 328. The forming area support plate 329 is fixed on the top column 304 of the forming cylinder.

[0016] Elastic sealing structures are provided on the upper half of the water-cooled plate 327 and the forming area support plate 329. The elastic sealing structure adopts a felt ring 334. A series of springs 330 are used to press the felt ring 334 against the inner wall of the forming cylinder 303 through corner clamping blocks 333, parallelogram side clamping blocks 331 and trapezoidal side clamping blocks 332. The inclined sides between the corner clamping blocks and the side clamping blocks can also form mutual limit.

[0017] The powder feeding plate 302 inside the powder feeding cylinder 318 is connected to the powder feeding area support plate 335. The powder feeding area support plate 335 is fixed on the top column 317 of the powder feeding cylinder. The powder feeding area support plate 335 also achieves a flexible powder sealing function through the felt ring 334, corner clamping block 333, parallelogram side clamping block 331 and trapezoidal side clamping block 332.

[0018] The powder spreading mechanism 7 is a cantilever powder spreading structure, including a powder spreading scraper 701, which is connected to a powder spreading bar 704. The powder spreading bar 704 is fixed on a guide rail platform 702 and connected to a stepper motor 703. A protective curtain 705 is provided on the transmission mechanism between the powder spreading scraper 701 and the powder spreading bar 704. An air blowing port 706 is provided on one side of the forming substrate 301 and below the guide rail platform 702. An exhaust port 708 is provided on the opposite side of the air blowing port 706. The air blowing port 706 blows out a horizontal airflow that can effectively cover the surface of the forming substrate 301, and the air wall 11 on the machine tool bed 2 blows out an airflow with a downward pressure effect. The two work together to stably blow the smoke and dust generated during the L-PBF process into the exhaust port 708.

[0019] The lead screw motor module 8 includes a module fixing frame 801, on which a parallel robotic arm lifting motor 802 is connected. The parallel robotic arm lifting motor 802 is connected to a lifting lead screw 804. A parallel robotic arm 9 is connected to a lifting block 805 on the lifting lead screw 804. The lifting block 805 is connected to a lifting guide rail 807 via a lifting slider 806.

[0020] The parallel robotic arm 9 includes two sets of high-torque motors 901 connected to the motion platform 903. Two lead screw motor modules 8 above the machine tool bed 2 realize the stable movement of the motion platform 903 in the vertical direction. A swing arm 904 is connected below the high-torque motors 901. The swing arm 904 is hinged to the electric spindle platform 907 through the connecting rod 905. The mechanism formed by the motion platform 903, the two swing arms 904 and the two connecting rods 905 ultimately realizes the large-range movement of the electric spindle platform 907 in the two-dimensional plane. An electric spindle 908 is connected to the electric spindle platform 907, and the electric spindle 908 performs milling processes with micro-feed.

[0021] The process utilizing the equipment includes the following steps:

[0022] The L-PBF process uses a bottom-feeding method, that is, during each powder spreading process, the powder feeding plate 302 will be raised to a specified height, the forming substrate 301 will be lowered by one powder layer height, the powder spreading mechanism 7 will evenly spread the powder onto the forming substrate 301, and then the laser galvanometer 6 will scan the powder along a specified path.

[0023] Each time the additive material reaches the set layer height, the laser galvanometer 6 stops working, the powder spreading mechanism 7 returns to its position, and the lead screw motor module 8 and the parallel robotic arm 9 cooperate to realize the three-dimensional movement of the electric spindle platform 907 in space. The subtractive processing of the added material is a milling process with micro-feed. After setting the specified vertical processing depth, the parallel robotic arm 9 selects the appropriate tool in the tool magazine 10 according to the processing needs and relies on the hydraulic locking mechanism 12 to ensure rigidity. The forming substrate 301 serves as the platform for subtractive processing, and the forming cylinder top column 304 below it has an over-constraint structure to improve its rigidity in the horizontal plane.

[0024] After the subtractive processing is completed, the parallel robotic arm 9 returns to its position, and space is left between the swing arm 904 and the connecting rod 905 to allow the laser galvanometer 6 to scan. The additive powder feeding mechanism 3 and the powder spreading mechanism 7 continue to work, and so on, until the manufacturing of the part is finally completed.

[0025] Compared with existing technologies, the beneficial effects of the present invention are as follows:

[0026] 1. This invention achieves high-precision, high-efficiency, and low-inertia movement of subtractive cutting tools on a horizontal plane by using parallel robotic arms. This can improve the accuracy of the tool machining path, reduce the subtractive machining time in the ASHM process, reduce micro-defects caused by significant changes in the thermal history of the L-PBF process, improve overall machining efficiency, and ensure the final machining quality and comprehensive performance of the parts.

[0027] 2. This invention addresses the potential issue of insufficient rigidity in parallel robotic arms during milling. First, it ensures that in the ASHM process, for the already additively formed parts, the subtractive cutting tool does not need to perform roughing and blanking; only a milling process with a small feed rate (finishing) is required, resulting in low cutting forces. Second, a high-torque motor and coupling are installed at the pivot of the swing arm of the parallel robot to increase torque. Finally, a hydraulic locking mechanism is installed at the pivot between the swing arm and the connecting rod, which can restrict the corresponding axis degrees of freedom at any time during the specified subtractive path, ultimately ensuring the rigidity of the robotic arm during the subtractive machining process.

[0028] 3. The motion mechanism of the forming substrate in this invention has been designed to improve rigidity. Traditional L-PBF equipment only needs to consider the motion mode of the forming substrate when designing the corresponding functional structure. However, when the subtractive process is added, the horizontal vibration generated by the cutting tool may affect the surface processing quality of the part. By adding an over-constrained structure to the top cylinder under the forming substrate, the rigidity of the upper substrate platform during the subtractive processing is fully improved, ensuring the final processing quality of the part.

[0029] 4. In order to prevent powder leakage in the cylinder from vibrating during the movement of the forming substrate and the powder feeding substrate or during the subtractive processing, thereby affecting the normal operation of the moving mechanism below, the present invention is equipped with a self-limiting elastic sealing structure (two layers in the forming cylinder and one layer in the powder feeding cylinder). Through the design of springs and top clamping blocks, the sealing felt ring can be kept in close contact with the inner wall of the powder cylinder at all times, and the inclined sides between each top clamping block can restrict the movement direction of each other, so that the felt ring being pushed can always be subjected to a relatively uniform top clamping force.

[0030] 5. The present invention provides a preheating and slow cooling function for the forming substrate area, which can heat the substrate area to a certain extent, slow down the dissipation rate of residual heat in the parts after the end of the previous L-PBF process and the subtractive processing, increase the initial temperature before the start of the next L-PBF process, help adjust the overall thermal history of the ASHM process, and set up heat insulation and water cooling mechanisms to protect the moving mechanism of the forming substrate from damage. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the overall invention.

[0032] Figure 2This is a front view of the present invention.

[0033] Figure 3 This is a schematic diagram of the processing area of ​​the present invention.

[0034] Figure 4 This is a top view of the processing area of ​​the present invention.

[0035] Figure 5 This is a schematic diagram of the high-rigidity scheme of the additive powder feeding mechanism of the present invention.

[0036] Figure 6 This is a schematic diagram illustrating the vertical transmission method of the forming substrate of the present invention.

[0037] Figure 7 This is a schematic diagram illustrating the vertical transmission principle of the powder feeding plate in this invention.

[0038] Figure 8 This is a front view of the additive manufacturing powder feeding mechanism of the present invention.

[0039] Figure 9 This is a schematic diagram of the functional mechanism inside the forming cylinder of the present invention.

[0040] Figure 10 This is a schematic diagram of the functional mechanism inside the powder feeding cylinder of the present invention.

[0041] Figure 11 This is a schematic diagram of the self-limiting elastic sealing method of the present invention.

[0042] Figure 12 This is a schematic diagram of the powder spreading mechanism of the present invention.

[0043] Figure 13 This is a schematic diagram of the vertical transmission method of the parallel robotic arm of the present invention.

[0044] Figure 14 This is a schematic diagram of the parallel robotic arm mechanism of the present invention.

[0045] Figure 15 This is a schematic diagram of the hydraulic self-locking mechanism of the parallel robotic arm of the present invention. Detailed Implementation

[0046] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0047] Reference Figure 1 , Figure 2 , Figure 3A laser powder bed additive-subtractive composite manufacturing equipment includes a machine bed 2 and a sealed cover 1 connected above it. The machine bed 2 is connected to an additive powder feeding mechanism 3 and a powder recovery mechanism 4. The sealed cover 1 is connected to a powder spreading mechanism 7, a lead screw motor module 8 and a parallel robotic arm 9, a tool magazine 10 and a hydraulic locking mechanism 12. A laser light source 6 is connected above the sealed cover 1. The additive part, composed of the additive powder feeding mechanism 3, the powder recovery mechanism 4, the laser light source 6 and the powder spreading mechanism 7, realizes the L-PBF process. The subtractive part, composed of the lead screw motor module 8, the parallel robotic arm 9, the tool magazine 10 and the hydraulic locking mechanism 12, realizes the subtractive processing function. A control cabinet 5 is connected to the back of the machine bed 2 and the sealed cover 1. The equipment's electrical control devices and dust circulation filtration system are fixed in the control cabinet 5.

[0048] Reference Figure 2 The sealing cover 1 is composed of multiple aluminum alloy plates. Sealing grooves and sealing strips are set at the joints between the plates to achieve gas sealing. This ensures that during actual operation, after the air inside the sealing cover 1 is discharged using an inert gas (such as argon) through a specific pipeline, the processing area inside the sealing cover 1 remains in a low-oxygen environment for an extended period. A gas pressure sensor 101 and an oxygen content sensor 102 are arranged above the sealing cover 1 to monitor the internal gas pressure and oxygen content in real time. If the internal gas pressure or oxygen content exceeds the set value, the corresponding pipeline can be controlled to achieve pressure relief and oxygen discharge functions, ensuring that the set gas protective atmosphere is maintained throughout the processing. An airtight door 103 is provided at the front of the sealing cover 1 to observe the processing process, and it is equipped with a glove opening to facilitate the operator's entry into the processing area when necessary. First detachable plates 104 are provided on both sides of the sealing cover 1 to facilitate the installation and daily maintenance of the equipment.

[0049] Reference Figure 4 , Figure 5 , Figure 6 and Figure 7 The additive manufacturing powder feeding mechanism 3 includes a vertical transmission structure for the forming cylinder and the inner plate of the powder feeding cylinder; the vertical transmission structure for the inner plate of the forming cylinder includes a forming cylinder motor 310, which is connected to the forming cylinder screw 307 via a forming cylinder motor coupling 309. The forming cylinder motor 310 drives the forming cylinder screw 307 to rotate. The first connecting guide block 308 on the forming cylinder screw 307 is connected to the forming cylinder top column 304. The forming cylinder top column 304 is connected to the forming substrate 301 inside the forming cylinder 303. The forming cylinder top column 304 pushes the forming substrate 301 to move in the vertical direction.

[0050] The vertical transmission structure of the inner plate of the powder feeding cylinder includes a powder feeding cylinder motor 311, which is connected to a powder feeding cylinder lead screw 313 via a powder feeding cylinder motor coupling 312. The powder feeding cylinder motor 311 drives the powder feeding cylinder lead screw 313 to rotate. The second connecting guide block 316 on the powder feeding cylinder lead screw 313 is connected to a powder feeding cylinder top column 317, which is connected to a powder feeding plate 302 inside the powder feeding cylinder 318. The powder feeding cylinder top column 317 pushes the powder feeding plate 302 to move in the vertical direction.

[0051] To improve the rigidity of the forming substrate 301 during the subtractive processing and reduce the impact of processing vibration on processing quality, its vertical motion structure is designed with constraints. In addition to the sliders and guide rails required for the basic movement of the forming cylinder lead screw 307 and the first connecting guide block 308, eight additional forming cylinder constraint sliders 305 and four forming cylinder constraint guide rails 306 are arranged on the left and right sides of the forming cylinder top column 304 to further limit its horizontal swaying during the subtractive process and improve the stability of the forming substrate 301 as a subtractive platform.

[0052] Four additional powder feeding cylinder constraint sliders 314 and two powder feeding cylinder constraint guide rails 315 are arranged on the left and right sides of the top column 317 of the powder feeding cylinder to reduce the impact of the vibration of the powder feeding mechanism 3 as a whole during the additive manufacturing process on the powder storage effect of the powder feeding cylinder 318.

[0053] Reference Figure 8 The additive manufacturing powder feeding mechanism 3 is provided with maintenance windows 319 on both sides for easy installation and regular maintenance by the operator. Since the additive manufacturing powder feeding mechanism 3 is directly connected to the inner space of the sealing cover 1, airtightness requirements also need to be considered. In addition to the cast structural components, a forming area sealing plate 320 and a powder feeding area sealing plate 324 need to be installed on the front of the additive manufacturing powder feeding mechanism 3. Sealing grooves and sealing strips are provided to achieve gas sealing at the joint with the cast parts. A second detachable plate 321 is provided on the forming area sealing plate 320 and the powder feeding area sealing plate 324 for easy operation and regular maintenance. The motor wiring and oil circuit within the sealing area are connected out through the over-plate module 322 and the aviation connector 323 to ensure normal functioning while ensuring airtightness.

[0054] Reference Figure 9 and Figure 11To prevent some parts produced by the L-PBF process from cooling too quickly during the sublimation process, which would cause a significant change in the thermal history of the L-PBF process, a preheating and slow cooling mechanism is provided below the forming substrate 301 in the forming cylinder 303. The preheating and slow cooling mechanism includes a heating plate 325, which is connected below the forming substrate 301. The heating plate 325 can heat the forming substrate 301 (a thermal resistor is installed inside the heating plate 325), and a thermocouple can be connected to monitor its temperature in real time. Meanwhile, to prevent the heating plate 325 from affecting the normal operation of the forming cylinder motor 310 below, a heat insulation plate 326 is connected below the heating plate 325. This first isolates the heat, causing the heat to dissipate at different rates on the upper and lower sides of the heating plate 325. Below the heat insulation plate 326 are the upper half 327 and the lower half 328 of the water-cooling plate. The upper half 327 and the lower half 328 of the water-cooling plate are joined together to form a water-cooling inner flow channel, which can remove the heat generated by the heating plate 325 below, protecting the forming cylinder motor 310 from damage. Below the lower half 328 of the water-cooling plate is a forming area support plate 329, which is fixed to the forming cylinder top column 304.

[0055] To prevent a large amount of metal powder in the forming cylinder 303 from falling onto the forming cylinder motor 310 below during the ASHM process, which could pose a safety hazard, elastic sealing structures are provided on the upper half of the water-cooled plate 327 and the forming area support plate 329. The elastic sealing structure uses felt rings 334. To accommodate the movement of the forming substrate 301 itself and the vibration caused by the subtractive cutting tool, a series of springs 330 are used to press the felt rings 334 against the inner wall of the forming cylinder 303 around the perimeter through corner clamping blocks 333, parallelogram side clamping blocks 331, and trapezoidal side clamping blocks 332. Furthermore, the inclined sides between the corner clamping blocks and the side clamping blocks can also mutually limit each other. When the springs 330 lift the clamping blocks, the corresponding inclined sides can mutually limit the movement direction of the corresponding clamping blocks, avoiding incorrect clamping direction.

[0056] Reference Figure 10 and Figure 11 The powder feeding plate 302 inside the powder feeding cylinder 318 is connected to the powder feeding area support plate 335. The powder feeding area support plate 335 is fixed on the top column 317 of the powder feeding cylinder. The powder feeding area support plate 335 also achieves a flexible powder sealing function through the felt ring 334, corner clamping block 333, parallelogram side clamping block 331 and trapezoidal side clamping block 332.

[0057] Reference Figure 3 and Figure 12The powder spreading mechanism 7 is a cantilevered powder spreading structure, including a powder spreading scraper 701 connected to a powder spreading bar 704, which is fixed to a guide rail platform 702. The powder spreading bar 704 is connected to a stepper motor 703. The horizontal movement of the powder spreading scraper 701 is driven by the stepper motor 703 to rotate the powder spreading bar 704, thus realizing the movement of the powder spreading scraper 701. A protective curtain 705 is provided on the transmission mechanism between the powder spreading scraper 701 and the powder spreading bar 704 to prevent dust from affecting the movement of the mechanism. The powder spreading scraper 701 can stably spread the powder fed in during the lifting of the powder feeding plate 302 onto the forming substrate 301 to form a new powder layer. Excess powder will be spread out. The powder scraper 701 is pushed into the powder collection tank 707 and sent to the powder recovery mechanism 4 through the pipeline. In order to effectively remove the dust generated during the L-PBF process and avoid affecting the quality of the parts, an air blowing port 706 is set on one side of the forming substrate 301 and below the guide rail platform 702, and an exhaust port 708 is set on the opposite side of the air blowing port 706. In the actual L-PBF process, the air blowing port 706 blows out a horizontal airflow that can effectively cover the surface of the forming substrate 301, and the air wall 11 on the machine tool bed 2 blows out an airflow with a downward pressure effect. The two work together to stably blow the dust generated during the L-PBF process into the exhaust port 708 and avoid the normal powder layer on the forming substrate 301 being greatly affected.

[0058] Reference Figure 13 The lead screw motor module 8 includes a module mounting frame 801, on which a parallel robotic arm lifting motor 802 is connected. The parallel robotic arm lifting motor 802 is connected to a lifting lead screw 804 via a high-torque coupling 803. A parallel robotic arm 9 is connected to a lifting block 805 on the lifting lead screw 804. The parallel robotic arm lifting motor 802 drives the lifting lead screw 804 to rotate, thereby realizing the vertical movement of the lifting block 805. The lifting block 805 is connected to a lifting guide rail 807 via two lifting sliders 806. The two lifting sliders 806 guide the lifting block 805 to move on the lifting guide rail 807, thereby improving the stability of the lifting block 805 during its movement.

[0059] Reference Figure 3 and Figure 14The parallel robotic arm 9 includes two sets of high-torque motors 901 fixed on the motion platform 903 and corresponding couplings 902. Two lead screw motor modules 8 above the machine tool bed 2 enable stable vertical movement of the motion platform 903. A swing arm 904 is connected below the coupling 902. The two sets of high-torque motors 901 on the motion platform 903 control the independent rotation of the corresponding swing arm 904 via the coupling 902. The swing arm 904 is connected to the electric... The spindle platform 907 is hinged, and the mechanism formed by the motion platform 903, two swing arms 904, and two connecting rods 905 ultimately enables the electric spindle platform 907 to move a wide range in the two-dimensional plane. An electric spindle 908 is connected to the electric spindle platform 907, which can perform milling processes with micro-feed. In the two-dimensional plane, the structure has one frame, four moving parts (n=4), five revolute joints (P2=5), and zero prismatic joints (P1=0). According to the degree of freedom calculation formula:

[0060] F=3n-2P2-P1=3×4-2×5-1×0=2

[0061] It can be seen that this structure has two degrees of freedom. At this time, the swing arm structure can move rapidly on the two-dimensional plane. Through the cooperation between the two high-torque motors 901, the electric spindle 908 can be accurately and quickly positioned. The relevant circuits of the electric spindle 908 are constrained by the cable bundler 906 to ensure that they will not cause any impact during normal operation. The milling tools on the electric spindle 908 can be replaced as needed in the tool magazine 10 on one side of the machine tool bed 2. The structural rigidity of the electric spindle 908 during the subtractive machining process is achieved by the hydraulic locking mechanism 12.

[0062] Reference Figure 15The hydraulic locking mechanism 12 is located at the pivot connecting the swing arm 904 and the connecting rod 905, and is fixed by the swing arm 904. The hydraulic locking mechanism 12 includes a caliper 1202. The roughness soft pad 1201 on the caliper 1202 can clamp the pivot according to the processing requirements, restricting the movement of the corresponding connecting rod 905. The rear of the caliper 1202 is connected to the connecting block 1203 and the bracket 1204. The connecting block 1203 is connected to the hydraulic slider 1205. The hydraulic slider 1205 is connected to the front end of the connecting rod 1207. The rear end of the connecting rod 1207 is connected to the piston 1208 located in the oil cylinder 1210. The front end of the oil cylinder 1210 is connected to the bracket 1204. The oil cylinder 1210 has a front oil port 1206 and a rear oil port 1209. The clamping action is achieved by: the front oil port 1206 injecting oil into the oil cylinder 1210, and the rear oil port 1209 injecting oil into the cylinder 1210. 09. The oil is discharged, and the oil pressure causes the piston 1208 to move away from the rotating shaft. This movement is transmitted through the connecting rod 1207 to the hydraulic slider 1205. Since the two connecting points of the caliper 1202 are connected to the connecting block 1203 and the bracket 1204 respectively, the movement of the hydraulic slider 1205 will cause the two connecting blocks 1203 to move in the same direction, which in turn will cause the two calipers 1202 to rotate around the corresponding rotating shaft on the bracket 1204, ultimately achieving the clamping action. When one of the hydraulic locking mechanisms 12 clamps the rotating shaft, the relative movement between a set of swing arms 904 and connecting rods 905 on the two-dimensional plane is restricted. The two can be regarded as a single component, and the number of revolute joints will also be reduced. At this time, the structure has 1 frame, 3 moving components (n=3), 4 revolute joints (P2=4), and 0 prismatic joints (P1=0). According to the formula for calculating the degree of freedom:

[0063] F=3n-2P2-P1=3×3-2×4-1×0=1

[0064] It can be seen that this structure has only one degree of freedom at this time. At this time, the swing arm structure can perform stable motion with a precise material reduction path. If the caliper 1202 is to be released, oil is introduced into the rear oil port 1209 and the oil is discharged from the front oil port 1206, thereby realizing the reverse motion of the corresponding mechanism.

[0065] Furthermore, if both hydraulic locking mechanisms 12 clamp their respective rotating shafts, the structure has one frame, two moving parts (n=2), three revolute joints (P2=3), and zero prismatic joints (P1=0). The formula for calculating the degrees of freedom is:

[0066] F=3n-2P2-P1=3×2-2×3-1×0=0

[0067] At this point, the movement of the parallel robotic arm structure can be completely restricted in the two-dimensional plane, retaining only the degree of freedom of the electric spindle 908 in the vertical direction. This situation is suitable for simple and stable drilling processes for some internal hole features. Through the cooperation of the two motors 901 and the two sets of hydraulic locking mechanisms 12, three-dimensional subtractive machining processes for various feature surfaces of the target part can be realized.

[0068] The process using the aforementioned equipment is as follows:

[0069] Before starting work, in the initial state, space is left between the swing arm 904 and the connecting rod 905 of the parallel robotic arm 9 for scanning by the laser galvanometer 6. The equipment first prepares for the L-PBF process. Argon gas is filled into the sealed cover 1 to expel the oxygen in the equipment processing area. The gas pressure sensor 101 and oxygen content sensor 102 on the sealed cover 1 monitor the gas pressure and oxygen content inside the equipment in real time. When the oxygen content inside the equipment does not drop to the specified value, argon gas will be continuously introduced into the equipment, and the equipment will also be pressurized. When the gas pressure exceeds the set value, the pressure reducing valve opens. The pressure reducing valve is closed again after the gas pressure inside the equipment drops to a reasonable value. After the oxygen content inside the equipment reaches the required level, it enters the standby state.

[0070] Users import the process data package of the parts to be processed (including the 3D model of the parts, the machining path for adding and subtracting materials, the electric spindle speed and the laser power, etc.) on the equipment operation interface, and start the formal processing after confirming that everything is correct.

[0071] The equipment first begins the L-PBF process. During each powder spreading process, the powder feeding plate 302 will be raised to a specified height, and the forming substrate 301 will be lowered by one powder layer height. The powder spreading mechanism 7 will evenly spread the powder onto the forming substrate 301, and then the laser galvanometer 6 will scan the powder along a specified path. At this time, the air blowing port 706 and the air wall 11 blow out a stable airflow to discharge the smoke and dust generated during the laser additive manufacturing process into the exhaust port 708.

[0072] Each time the additive material reaches a certain layer height, the laser galvanometer 6 stops working, the powder spreading mechanism 7 returns to its position, and the lead screw motor module 8 and the parallel robotic arm 9 cooperate to realize the three-dimensional movement of the electric spindle platform 907 in space. The subtractive processing of the added material is usually a micro-feed finishing process, which only requires a few vertical feed processes. The parallel robotic arm 9 completes the milling in the horizontal plane. The electric spindle 908 can select the appropriate tool from the tool magazine 10 according to the processing needs. The parallel robotic arm 9 can rely on the hydraulic locking mechanism 12 to ensure that the rigidity of the mechanism meets the requirements during the processing. The forming substrate 301 serves as the platform for subtractive processing. The forming cylinder top column 304 in the motion mechanism below it has an over-constraint structure, which improves its rigidity in the horizontal plane and ensures the stability of subtractive processing.

[0073] After the subtractive processing of this part is completed, the parallel robotic arm 9 returns to its position, and space is re-established between the swing arm 904 and the connecting rod 905 to allow the laser galvanometer 6 to scan. The additive powder feeding mechanism 3 and the powder spreading mechanism 7 continue to work, and the equipment's smoke and dust removal system is restarted. This cycle repeats until the manufacturing of the part is finally completed.

[0074] This invention utilizes a parallel robotic arm, characterized by low dynamic inertia, high speed, good dynamic response, and high motion precision, to achieve three-dimensional motion of the subtractive cutting tool. The addition of a preheating and slow cooling mechanism effectively improves overall processing efficiency and reduces defects such as seams, holes, and incomplete powder fusion caused by thermal history variations during the additive manufacturing process. An over-constraint structure is designed to enhance the rigidity of the formed substrate, ultimately serving the integrated additive-subtractive composite manufacturing of complex components with high surface quality and comprehensive performance.

[0075] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the protection scope of the present invention.

Claims

1. A laser powder bed additive / subtractive composite manufacturing equipment, characterized in that: The machine tool includes a machine bed (2) and a sealing cover (1). The sealing cover (1) is connected above the machine bed (2). The machine bed (2) is connected to an additive manufacturing powder feeding mechanism (3) and a powder recovery mechanism (4). The sealing cover (1) is connected to a powder spreading mechanism (7), a lead screw motor module (8), a parallel robotic arm (9), a tool magazine (10), and a hydraulic locking mechanism (12). The parallel robotic arm (9) is mounted on the lead screw motor module (8). A laser light source (6) is connected above the sealing cover (1). The additive manufacturing part, composed of the additive manufacturing powder feeding mechanism (3), the powder recovery mechanism (4), the laser light source (6), and the powder spreading mechanism (7), realizes the L-PBF process. The subtractive manufacturing part, composed of the lead screw motor module (8), the parallel robotic arm (9), the tool magazine (10), and the hydraulic locking mechanism (12), realizes the subtractive manufacturing process. The machine bed (2) and the sealing cover (1) are connected to a control cabinet (5). The lead screw motor module (8) includes a module mounting frame (801), a parallel robotic arm lifting motor (802) is connected to the module mounting frame (801), the parallel robotic arm lifting motor (802) is connected to the lifting lead screw (804), a parallel robotic arm (9) is connected to the lifting block (805) on the lifting lead screw (804), and the lifting block (805) is connected to the lifting guide rail (807) through the lifting slider (806); The parallel robotic arm (9) includes two sets of high-torque motors (901) connected to the motion platform (903). Two lead screw motor modules (8) above the machine tool bed (2) realize the stable vertical movement of the motion platform (903). A swing arm (904) is connected below the high-torque motor (901). The swing arm (904) is hinged to the electric spindle platform (907) through the connecting rod (905). The mechanism formed by the motion platform (903), the two swing arms (904) and the two connecting rods (905) finally realizes the large-range movement of the electric spindle platform (907) on the two-dimensional plane. An electric spindle (908) is connected to the electric spindle platform (907). The electric spindle (908) performs a milling process with micro-feed. The hydraulic locking mechanism (12) is located at the pivot connecting the swing arm (904) and the connecting rod (905), and is fixed by the swing arm (904). The hydraulic locking mechanism (12) includes a caliper (1202). The roughness soft pad (1201) on the caliper (1202) can clamp the pivot according to the processing requirements, restricting the movement of the corresponding connecting rod (905). The rear of the caliper (1202) is connected to the connecting block (1203) and the bracket (1204). The connecting block (1203) is connected to the hydraulic slider (1205). The hydraulic slider (1205) is connected to the front end of the connecting rod (1207). The rear end of the connecting rod (1207) is connected to the piston (1208) located in the oil cylinder (1210). The front end of the oil cylinder (1210) is connected to the bracket (1208). 1204) connection, the oil cylinder (1210) is provided with a front oil port (1206) and a rear oil port (1209); the clamping action is realized as follows: the front oil port (1206) rushes oil into the oil cylinder (1210), the rear oil port (1209) discharges oil, the oil pressure causes the piston (1208) to move away from the rotating shaft, and drives the hydraulic slider (1205) to move through the connecting rod (1207). Since the two connection points of the caliper (1202) are connected to the connecting block (1203) and the bracket (1204) respectively, the movement of the hydraulic slider (1205) will drive the two connecting blocks (1203) to move in the same direction, and then drive the two calipers (1202) to rotate around the corresponding rotating shaft on the bracket (1204), and finally realize the clamping action.

2. The equipment according to claim 1, characterized in that: The additive manufacturing powder feeding mechanism (3) includes a transmission structure for the inner plate of the forming cylinder in the vertical direction and a transmission structure for the inner plate of the powder feeding cylinder in the vertical direction; the transmission structure for the inner plate of the forming cylinder in the vertical direction includes a forming cylinder motor (310), the forming cylinder motor (310) is connected to the forming cylinder screw (307), the first connecting guide block (308) on the forming cylinder screw (307) is connected to the forming cylinder top column (304), the forming cylinder top column (304) is connected to the forming substrate (301) in the forming cylinder (303), and the forming cylinder top column (304) pushes the forming substrate (301) to move in the vertical direction; The vertical transmission structure of the inner plate of the powder feeding cylinder includes a powder feeding cylinder motor (311), which is connected to a powder feeding cylinder lead screw (313). The second connecting guide block (316) on the powder feeding cylinder lead screw (313) is connected to a powder feeding cylinder top column (317). The powder feeding cylinder top column (317) is connected to a powder feeding plate (302) inside the powder feeding cylinder (318). The powder feeding cylinder top column (317) pushes the powder feeding plate (302) to move in the vertical direction.

3. The equipment according to claim 2, characterized in that: In addition to the lead screw and the slider and guide rail required for the movement of the connecting guide block, the forming cylinder constraint slider (305) and the forming cylinder constraint guide rail (306) are arranged on the left and right sides of the forming cylinder top column (304); the powder feeding cylinder constraint slider (314) and the powder feeding cylinder constraint guide rail (315) are arranged on the left and right sides of the powder feeding cylinder top column (317).

4. The equipment according to claim 2, characterized in that: Maintenance windows (319) are provided on both sides of the additive lower powder feeding mechanism (3). A forming area sealing plate (320) and a powder feeding area sealing plate (324) are installed on the front of the additive lower powder feeding mechanism (3). A second detachable plate (321) is provided on the forming area sealing plate (320) and the powder feeding area sealing plate (324).

5. The equipment according to claim 2, characterized in that: A preheating and slow cooling mechanism is provided under the forming substrate (301) inside the forming cylinder (303). The preheating and slow cooling mechanism includes a heating plate (325), which is connected to the bottom of the forming substrate (301). The heating plate (325) is connected to a thermocouple to monitor its temperature in real time. A heat insulation plate (326) is connected below the heating plate (325). The upper half (327) and the lower half (328) of the water cooling plate are connected below the heat insulation plate (326). The upper half (327) and the lower half (328) of the water cooling plate are spliced ​​together to form a water cooling inner flow channel. The lower half (328) of the water cooling plate is connected to a forming area support plate (329), which is fixed on the top column (304) of the forming cylinder.

6. The equipment according to claim 5, characterized in that: Elastic sealing structures are provided on the upper half of the water-cooled plate (327) and the forming area support plate (329). The elastic sealing structure adopts a felt ring (334). A series of springs (330) are used to press the felt ring (334) against the inner wall of the forming cylinder (303) through corner clamping blocks (333), parallelogram side clamping blocks (331) and trapezoidal side clamping blocks (332). The inclined sides between the corner clamping blocks, parallelogram side clamping blocks and trapezoidal side clamping blocks can also form mutual limit. The powder feeding plate (302) inside the powder feeding cylinder (318) is connected to the powder feeding area support plate (335). The powder feeding area support plate (335) is fixed on the top column (317) of the powder feeding cylinder. The powder feeding area support plate (335) also achieves a flexible powder sealing function through the felt ring (334), corner clamping block (333), parallelogram side clamping block (331) and trapezoidal side clamping block (332).

7. The equipment according to claim 2, characterized in that: The powder spreading mechanism (7) is a cantilever powder spreading structure, including a powder spreading scraper (701), which is connected to a powder spreading bar (704). The powder spreading bar (704) is fixed on a guide rail platform (702), and the powder spreading bar (704) is connected to a stepper motor (703). A protective curtain (705) is provided on the transmission mechanism between the powder spreading scraper (701) and the powder spreading bar (704). An air blowing port (706) is provided on one side of the forming substrate (301) and below the guide rail platform (702). An exhaust port (708) is provided on the opposite side of the air blowing port (706). The air blowing port (706) blows out a horizontal airflow covering the surface of the forming substrate (301), and the airflow with a downward pressure effect is blown out by the air wall (11) on the machine tool bed (2). The two work together to stably blow the smoke and dust generated during the L-PBF process into the exhaust port (708).

8. The process using the equipment according to any one of claims 2-7, characterized in that, Includes the following steps: The L-PBF process uses a bottom-feeding method, that is, during each powder spreading process, the powder feeding plate (302) will be raised to a specified height, the forming substrate (301) will be lowered by one powder layer height, the powder spreading mechanism (7) will spread the powder evenly on the forming substrate (301), and then the laser light source (6) will scan the powder on the specified path. Each time the additive material reaches the set layer height, the laser light source (6) stops working, the powder spreading mechanism (7) returns to its position, and the lead screw motor module (8) and the parallel robotic arm (9) cooperate to realize the three-dimensional movement of the electric spindle platform (907) in space. The subtractive processing of the added material is a milling process with micro-feed. After setting the specified vertical processing depth, the parallel robotic arm (9) selects the appropriate tool in the tool magazine (10) according to the processing needs and relies on the hydraulic locking mechanism (12) to ensure rigidity. The forming substrate (301) serves as the platform for subtractive processing. The forming cylinder top column (304) below it has an over-constraint structure, which improves its rigidity in the horizontal plane. After the subtractive processing is completed, the parallel robotic arm (9) returns to its position, and a space is left between the swing arm (904) and the connecting rod (905) structure for the laser light source (6) to scan. The additive powder feeding mechanism (3) and the powder spreading mechanism (7) continue to work, and so on, until the manufacturing of the part is finally completed.

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