A powder collection device and method for laser melting deposition process

Abstract

The present invention relates to a powder collection system and method for a laser melting deposition process. The system mainly includes a fixture that can realize the integrated functions of clamping and powder collection, a powder collection device, and a control system based on the device. The fixture is hollowed out, a filter is installed, and the pipeline and fan are combined to finally realize the design of the powder collection device. The simulation method is used to design the number and position of clamping and the fan speed, and a corresponding database is established. Finally, the fan speed of the laser melting deposition process is controlled in real time by a computer to realize the filtering and collection of powder in the laser melting deposition process, effectively improve the powder utilization rate in the laser melting deposition process, and significantly reduce the cost of laser melting deposition.

Description

Technical Field

[0001] The invention relates to the technical field of laser forming of powder materials, and in particular to a powder collecting device and method in a laser melting deposition process. Background Art

[0002] As a new type of rapid prototyping technology, laser melting deposition technology has the characteristics of low cost and excellent performance of molded parts. Laser melting deposition can realize processes such as repair and remanufacturing of parts.

[0003] In the process of laser melting deposition, since the powder is blown to the laser molten pool by inert gas, a considerable proportion of metal powder cannot form a cladding layer or a deposition layer and is wasted due to the collision between powders, the accuracy of the powder feeding channel and the laser spot diameter. The powder utilization rate is only about 50% to 80%. Therefore, in order to save costs, the powder needs to be recycled and reused. Since the laser melting deposition process is a cyclic process, the powder accumulated on the substrate in the previous layer will be affected by the airflow of the next layer of powder feeding, so that a considerable amount of powder will rush out of the substrate under the action of the airflow. The powder that rushes out of the substrate is very easy to be contaminated due to the influence of oil stains such as the workbench, resulting in serious waste. Therefore, if the flying powder is collected and processed during the laser melting deposition process, the utilization rate of the powder can be effectively improved and the cost of laser melting deposition can be reduced. Summary of the invention

[0004] In order to solve the above problems existing in the above background technology, the present invention proposes a device and method for improving the powder collection process of the melting deposition process. By setting up a pneumatic powder collection device regularly on the laser melting deposition substrate, a circulating flow field is formed around the additive part, and the airborne powder is brought to the powder collection device for screening and collection through the airflow, which greatly improves the powder utilization rate of the laser melting deposition process and saves the cost of laser melting deposition.

[0005] The present invention is achieved through the following technical solutions:

[0006] A device for improving the utilization rate of laser melting deposition powder was built, which includes a cladding head, a fixture, a powder feeding head, a workpiece, a substrate, a workbench, a hose, a powder collecting device, a computer, a protective cavity, and a control cabinet. The cladding head, fixture, powder feeding head, workpiece, substrate, workbench, hose, and powder collecting device are all located in the protective cavity. The device adopts a coaxial powder feeding method. The workpiece is fixed on the workbench by a fixture, the front end of the hose is fixed at the fixture, and the tail end is connected to the powder collecting device, which is located at the bottom of the workbench.

[0007] The fixture consists of a hollow stud, a connecting rod and a long rod. The long rod and the hollow stud are connected by the connecting rod. The long rod is fixed with the workbench. The fixture can be clamped at any position on the workbench. The front end of the connecting rod is equipped with an internal thread. The hollow stud is fastened and clamped to the substrate by cooperating with the internal thread at the front end of the connecting rod. Square notches are opened on both sides of the front end of the hollow stud. A filter is placed at the notch to filter large-particle powder.

[0008] Furthermore, the filter supports a disassembly function and can be replaced according to the powder particle size.

[0009] Furthermore, the powder collecting device consists of two parts: an exhaust device and a powder collection box. The exhaust device is powered by a fan and collects powder that is not fully utilized in the additive process through a hose. There are three hose interfaces on both sides of the powder collecting device, and the air pressure on both sides can be achieved by adjusting the fan speed.

[0010] Furthermore, the powder collecting device is connected to the control cabinet, the control cabinet is connected to the computer, and the wind speed of the fan in the exhaust device can be adjusted in real time by the computer.

[0011] Furthermore, the fixture clamping position is designed by means of computer simulation optimization, and a database of the correlation between the cladding head position and the fan speed is established with the powder collection stability as the goal.

[0012] Furthermore, by regularly placing the fixtures and controlling the speed of the fan, a circulating airflow is achieved near the cladding head during the cladding process, and the powder can be blown to the filter screen by the airflow to complete the collection of the powder.

[0013] In addition, in the above-mentioned laser repair system based on preheating of light alloy powder, the present invention also proposes a method for increasing the utilization rate of laser melting deposition powder, which is characterized by:

[0014] 1) Preparation

[0015] Finite element simulation software is used to calculate the residual stress distribution of the workpiece after the additive manufacturing process, find the optimal clamping position, perform finite element and discrete element calculations on the workpiece flow field, and select the optimal fixture clamping position and the required speed of the fan motor at different positions of the cladding head to establish a database. According to the calculation and simulation results, the fixture is assembled and connected to the hose to clamp the workpiece on the workbench.

[0016] 2) Working stage

[0017] The cladding head moves according to the pre-set laser process parameters and additive path, and the computer obtains the position information of the cladding head in real time. According to the position information of the cladding head, the computer adjusts the fan speed in real time based on the database knowledge to ensure the stability of the flow field around the cladding head, and finally achieve stable collection of powder.

[0018] Advantages of the present invention:

[0019] (1) The present invention proposes a powder collection device and method for the laser melting deposition process, which can significantly reduce the powder waste rate in the laser melting deposition process, thereby reducing the laser melting deposition cost.

[0020] (2) The present invention integrates the fixture and the pipeline into an integrated design, which reduces the space loss near the substrate and provides a larger movable space for the cladding head to move. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is the front view of the device of the present invention

[0022] Figure 2 This is a schematic diagram of the fixture

[0023] Figure 3 Isometric diagram of workpiece clamping

[0024] Figure 4 Schematic diagram of the flow field during the additive process

[0025] Figure 5 It is a workflow diagram

[0026] Figure 1 The cladding head 1, the fixture 2, the powder feeding device 3, the workpiece 4, the substrate 5, the workbench 6, the hose 7, the powder collecting device 8, the protection chamber 9, the computer 10, and the control cabinet 11.

[0027] Figure 2 Middle-long rod 2-1, connecting rod 2-2, rotating handle 2-3, stud 2-4, filter screen 2-5. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention.

[0029] Reference Figure 1A powder collection device for a laser melting deposition process is composed of a cladding head 1, a fixture 2, a powder feeding head 3, a workpiece 4, a substrate 5, a workbench 6, a hose 7, a powder collecting device 8, a protective cavity 9, a computer 10, and a control cabinet 11. Except for the computer 10 and the control cabinet 11, all other components are located in the protective cavity 9. The cladding head 1 is coaxially connected to the powder feeding head 3, the workpiece 4 is fixed on the workbench by the fixture 2, the front end of the hose 7 is fixed at the front notch of the fixture, and the rear end is connected to the powder collecting device 8, and the powder collecting device 8 is located under the workbench.

[0030] The powder collecting device 8 consists of two parts: exhaust devices on both sides and a powder collecting box at the rear end. The exhaust port is located at the rear of the powder collecting device 8. The powder collecting device 8 is connected to the control cabinet 11. The fan speed can be controlled in real time by the computer 10. During the melting and deposition process, the computer will compare the cladding head position information with the existing database to adjust the fan speed. The database is established and improved by simulation and experiment.

[0031] Reference Figure 2 , the front end of the connecting rod 2-2 in the clamp 2 is built with an internal thread, and the hollow stud 2-4 cooperates with the internal thread at the front end of the connecting rod 2-2 to achieve the fastening and clamping of the substrate. Square notches are opened on both sides of the front end of the hollow stud 2-4, and a small section of adapter is provided on the upper end of the notch, which is tightly fitted with the hollow stud. The tail end of the hose is connected to an adapter, and a filter 2-5 is placed at the notch to filter larger particle size powder. The filter is detachable, and a suitable filter can be selected according to the particle size of the powder. The hollow stud 2-4, the connecting rod 2-2, and the long rod 2-1 can all accommodate hoses of different lengths. In the working state, the hose is connected from the tail end of the long rod, through the connecting rod, and finally connected to the adapter in the hollow stud.

[0032] A method for collecting powder in a laser melting deposition process, referring to Figure 5 , including the following steps:

[0033] 1) Preparation

[0034] Through the finite element simulation software, the residual stress distribution of the workpiece after the additive manufacturing process is calculated to find the optimal clamping position. The finite element and discrete element calculations of the flow field of the workpiece are performed. Figure 4 , with the goal of achieving stable collection of particles under the circulating flow field, the optimal fixture clamping position is selected and the required motor speed of the cladding head at different positions is obtained, and a database is established. According to the calculation and simulation results, the fixture is assembled and connected to the hose to clamp the workpiece on the workbench.

[0035] 2) Working stage

[0036] The cladding head moves according to the pre-set laser process parameters and additive path, and the computer obtains the position information of the cladding head in real time. Based on the cladding head position information, the computer compares the current cladding head position with the known database, thereby adjusting the speed of the exhaust device fan in real time to ensure stable collection of powder.

[0037] Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the implementation methods of the present invention. It is not necessary and impossible to list all implementation methods exhaustively. The content of this specification should not be understood as limiting the present invention. For those of ordinary skill in the art, based on the idea of ​​the present invention, other different forms of changes or modifications can be made on the basis of the above description. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the claims of the present invention.

Claims

1. A powder collection device for a laser melting deposition process, comprising a cladding head (1), a fixture (2), a powder feeding head (3), a workpiece (4), a substrate (5), a workbench (6), a hose (7), a powder collecting device (8), a protective chamber (9), a computer (10), and a control cabinet (11), wherein all parts except the computer (10) and the control cabinet (11) are located in the protective chamber (9); the cladding head (1) is coaxially connected to the powder feeding head (3), and the workpiece (4) is held by the fixture (2). The hose (7) is fixed on the workbench (6), the front end of the hose (7) is fixed on the front notch of the fixture (2), and the rear end is connected to the powder collecting device (8), and the powder collecting device (8) is located below the workbench (6); the powder collecting device (8) is composed of two parts: exhaust devices on both sides and a powder collecting box at the rear end, and the exhaust port is located at the rear of the powder collecting device (8). The powder collecting device (8) is connected to the control cabinet (11), and the fan speed can be controlled in real time by the computer (10). During the melting and deposition process, the computer (10) The fan speed is adjusted by comparing the position information of the cladding head (1) with the existing database, and the database is established and improved by simulation and experiment; the front end of the connecting rod (2-2) in the fixture (2) is built with an internal thread, and the hollow stud (2-4) and the front end internal thread of the connecting rod (2-2) cooperate with each other to achieve the fastening and clamping of the substrate (5); square notches are opened on both sides of the front end of the hollow stud (2-4), and a small section of ∅8 adapter is provided on the upper end of the notch, and is connected to the hollow stud ( 2-4) are tightly closed, the tail end of the hose (7) is connected to a ∅6 adapter, and a filter (2-5) is placed at the notch to filter powder with larger particle size; the filter (2-5) is detachable; the hollow stud (2-4), the connecting rod (2-2), and the long rod (2-1) can accommodate hoses (7) of different lengths; when in working state, the hose (7) is connected from the tail end of the long rod (2-1), through the connecting rod (2-2), and finally connected to the ∅8 adapter in the hollow stud (2-4).

2. The powder collecting device for laser melting deposition process according to claim 1, characterized in that: Finite element simulation software is used to calculate the residual stress distribution of the workpiece after the additive manufacturing process, find the optimal clamping position, and perform flow field finite element and discrete element calculations on the workpiece, with the goal of achieving stable collection of particles under a circulating flow field, selecting the optimal fixture clamping position and obtaining the required motor speed of the cladding head at different positions, and establishing a database; based on the calculation and simulation results, the fixture is assembled and connected to the hose to clamp the workpiece on the workbench.

3. The fan speed control according to claim 2, characterized in that: The computer controls the speed of the fan in the exhaust device in real time based on the cladding head position information and the database; The database is composed of fan speed parameters that can keep the powder stably collected when the cladding head is in different positions. The parameters are obtained through simulation and experimental methods.

Images