A line scanning laser infrared detection system for on-line detection of electric arc additive defects

Abstract

The application discloses a kind of line scanning laser infrared detection systems of arc additive defect on-line detection, including host computer, synchronous controller, infrared detection mechanical arm, continuous wave laser driver, continuous wave laser, line laser shaping lens group and infrared thermal imager, and the application relates to the technical field of defect detection.The line scanning laser infrared detection system of arc additive defect on-line detection can realize non-contact, visualization and automatic defect on-line detection of components during arc additive manufacturing, thereby ensuring the quality and reliability of parts during production.

Description

Technical Field

[0001] This invention relates to the field of defect detection technology, specifically to a line-scanning laser infrared detection system for online detection of defects in electric arc additive manufacturing. Background Technology

[0002] With the advent of the industrial age, additive manufacturing technology will play a significant role in future industrial manufacturing. Unlike traditional subtractive manufacturing methods, additive manufacturing constructs parts by stacking raw materials layer by layer. It uses pre-established digital models and employs multi-layer, multi-pass cladding processes with powder or wire materials to easily construct large and complex structural components. Additive manufacturing technologies can be categorized by energy beam, primarily into electric arc, laser, and electron beam technologies. Among these, electric arc additive manufacturing offers higher manufacturing efficiency and lower material costs compared to other types. Its application goal is the rapid near-net-shape forming of large and complex components. Compared to conventional machining or forging techniques, electric arc additive manufacturing significantly reduces manufacturing costs and shortens the manufacturing cycle, demonstrating enormous application potential in the manufacturing of large components in critical fields such as aerospace, nuclear power, petrochemicals, and shipbuilding.

[0003] Arc additive manufacturing technology still faces several challenges. During component forming, temperature fluctuations, complex workpiece structures, and external factors can lead to various defects in the molten pool during solidification, such as porosity, delamination, cracks, surface voids, and inclusions. These defects can affect the service life and structural strength of components, and even cause major safety accidents. Therefore, introducing online defect detection technology in arc additive manufacturing to promptly identify and repair defects is essential to ensuring component quality and reliability.

[0004] The main idea of ​​online inspection in arc additive manufacturing is based on the layer-by-layer stacking characteristic of additive manufacturing, inspecting the component after each layer of material is deposited. Due to the high temperature and high roughness of the component surface during manufacturing, non-contact non-destructive testing methods suitable for these harsh conditions are required. Currently, commonly used non-contact non-destructive testing methods mainly include laser ultrasonic testing, eddy current testing, visual inspection, and infrared thermal imaging. Each of these methods has its advantages, but also significant limitations. Laser ultrasonic testing and eddy current testing are easily affected by the surface roughness of the component, making signal acquisition and analysis difficult, hindering effective defect identification. Furthermore, they require point-by-point scanning for signal acquisition, resulting in a slow inspection speed, which is unsuitable for the high-efficiency manufacturing requirements of arc additive manufacturing. Visual inspection relies on optical image interpretation, and this method can only detect open defects on the component surface. Infrared inspection identifies defects by analyzing the surface temperature field of the object. When defects exist on the surface or inside the tested object, abnormal temperature rises or falls can be observed in the surface temperature field of the specimen in an infrared thermal imager. Infrared detection methods can be divided into passive and active types. Active infrared detection technology uses a heat source to heat the surface of the specimen, which can detect defects directly and efficiently. Laser infrared detection technology is a new type of active infrared detection technology. It uses a laser as a thermal excitation source and has the advantages of concentrated energy, strong directivity, and non-contact operation, making it very suitable for online defect detection in additive manufacturing processes.

[0005] Currently, research on online infrared thermal imaging nondestructive testing methods for additive manufacturing processes is in its early stages both domestically and internationally. Most studies employ passive infrared detection methods, visually detecting surface or internal defects in components by observing global temperature changes in the molten pool. This paper proposes directly analyzing full-field infrared data and establishing an in-situ infrared thermal imaging process monitoring system. The feasibility of infrared thermal imaging detection for minute defects in additive manufacturing processes has been verified, indicating a 100% detection success rate for defects larger than 500 micrometers. A non-contact off-axis thermal detection device using a high-frame-rate mid-wave infrared thermal imager is constructed to monitor the laser-melted powder bed manufacturing process online. The paper proposes using threshold time (TOT) as a characteristic quantity to evaluate internal defects generated during material construction, yielding conclusions highly consistent with CT tomography detection. Early studies proposed using active infrared thermal imaging (IREM) for defect detection in additive manufacturing specimens, employing scanning line laser thermal excitation to monitor subsurface defects in the laser powder bed additive manufacturing process. This research validated the feasibility of using laser IREM nondestructive monitoring technology for detecting minute subsurface defects. While these studies demonstrate the significant potential of IREM for defect detection in additive manufacturing, they primarily focus on laser-based additive manufacturing technologies, lacking research on arc-based additive manufacturing. Compared to IREM, arc-based additive manufacturing components are typically much larger and have rougher surface conditions, posing new challenges to IREM.

[0006] Therefore, existing arc additive manufacturing equipment lacks online non-destructive testing technology for components during operation. Due to the high temperature and high roughness of the component surface during arc additive manufacturing, traditional non-destructive testing methods are unable to achieve online defect detection. Existing offline non-destructive testing methods cannot perform efficient and comprehensive post-production inspection of complex-shaped finished products, and even if defects are detected, repairing the finished product is extremely difficult.

[0007] Therefore, this invention provides a line-scanning laser infrared detection system for online defect detection in arc additive manufacturing, which can realize non-contact, visual, and automated online defect detection of components during the arc additive manufacturing process, thereby ensuring the quality and reliability of parts in the production process. Summary of the Invention

[0008] To address the shortcomings of existing technologies, this invention provides a line-scanning laser infrared detection system for online defect detection in arc additive manufacturing, which solves the problem that existing arc additive manufacturing equipment lacks online non-destructive testing technology for components during operation.

[0009] To achieve the above objectives, the present invention is implemented through the following technical solution: a line-scanning laser infrared detection system for online detection of defects in electric arc additive manufacturing, comprising a host computer and a synchronous controller, and further comprising an infrared detection robotic arm, a continuous wave laser driver, a continuous wave laser, a line laser shaping lens group and an infrared thermal imager.

[0010] The line laser shaping lens group comprises, from left to right, a first plano-concave lens, a biconvex lens, a concave cylindrical lens, and a second plano-convex lens, which are assembled together.

[0011] Preferably, the infrared detection robotic arm is used to control a continuous wave laser driver and an infrared thermal imager to actively thermally excite the top molten pool of the building layer and collect the surface temperature field, so as to realize the infrared online detection of defects in the arc additive manufacturing process.

[0012] Preferably, the synchronization controller is used to control the continuous wave laser driver and the infrared detection robotic arm to achieve coupling between the thermal excitation state of the continuous wave laser and the motion of the infrared detection robotic arm.

[0013] Preferably, the infrared thermal imager is used to record an infrared thermal imaging sequence of the surface temperature field.

[0014] Preferably, the host computer is used to perform post-processing on the infrared thermal imaging sequence.

[0015] Preferably, the continuous wave laser is used to excite a Gaussian spot.

[0016] Preferably, the first plano-concave lens and the biconvex lens are used to expand the Gaussian spot.

[0017] Preferably, the concave cylindrical mirror is used to shape the light spot into a linear shape.

[0018] Preferably, the second plano-convex lens focuses the linear back spot of light and forms a thin, elongated line laser for thermal excitation of the infrared detection system.

[0019] This invention provides a line-scanning laser-infrared detection system for online detection of defects in electric arc additive manufacturing. Compared with existing technologies, it has the following advantages: 1. The proposed online detection system for arc additive manufacturing defects, using a line-scanning laser infrared detection method, is an online detection mode that can monitor the defects formed during the printing of each layer in the arc additive manufacturing process in real time, enabling timely detection and repair of defects. Compared with conventional offline detection methods (radio detection, ultrasonic detection, eddy current detection, etc.), it can better handle the forming quality control of complex components.

[0020] 2. The proposed online detection system for defects in arc additive manufacturing uses a line-scanning laser as the thermal excitation source and acquires data through an infrared thermal imager, enabling non-contact detection. Due to the harsh working conditions in the arc additive manufacturing process, the high temperature and high roughness of the specimen surface make it impossible to implement some traditional contact non-destructive testing methods. This system solves this problem.

[0021] 3. This online arc additive manufacturing defect detection line scanning laser infrared detection system can perform online detection of large-sized components using arc additive manufacturing technology. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the system of the present invention; Figure 2 This is a schematic diagram of the line laser shaping lens assembly of the present invention; Figure 3 This is a schematic diagram of the defect detection system of the present invention.

[0023] In the diagram: 1. Host computer; 2. Synchronization controller; 3. Infrared detection robotic arm; 4. Continuous wave laser driver; 5. Continuous wave laser; 6. Line laser shaping lens group; 7. Infrared thermal imager; 11. First plano-concave lens; 12. Biconvex lens; 13. Concave cylindrical mirror; 14. Second plano-convex lens. Detailed Implementation

[0024] The technical solutions in the embodiments of the present invention have been clearly and completely described. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Please see Figure 1-3 The present invention provides a technical solution: a line scanning laser infrared detection system for online detection of defects in electric arc additive manufacturing, the main components of which are a host computer 1, a synchronous controller 2, an infrared detection robotic arm 3, a continuous wave laser driver 4, a continuous wave laser 5, a line laser shaping lens group 6, and an infrared thermal imager 7.

[0026] The system uses an infrared detection robotic arm 3 to control a continuous wave laser 4 and an infrared thermal imager 7 to actively excite the top molten pool of the newly constructed layer and collect the surface temperature field, thereby realizing online infrared detection of defects in the arc additive manufacturing process.

[0027] The synchronous controller 2 simultaneously controls the continuous wave laser driver 4 and the infrared detection robotic arm 3, thereby achieving coupling between the thermal excitation state of the continuous wave laser 5 and the movement of the infrared detection robotic arm 3.

[0028] The host computer 1 controls the infrared thermal imager 7 to work and processes the infrared thermal imaging temperature sequence collected by the infrared thermal imager 7 in real time, which facilitates subsequent defect identification.

[0029] The internal structure of the line laser shaping lens group 6 is as follows: Figure 2 As shown, its function is to shape a Gaussian spot 10 into a thin line laser 15. The Gaussian spot excited by the continuous wave laser 5 first passes through a first plano-concave lens 11 and a biconvex lens 12 to expand the beam. Then, the spot is shaped into a line shape by a concave cylindrical mirror 13 and further focused by a second plano-convex lens 14 to form a thin line laser, which is used for thermal excitation of the infrared detection system.

[0030] The principle of line scanning laser infrared detection is as follows: Figure 3 As shown, after the line laser prints the latest layer, it performs scanning thermal excitation on the top molten pool. At the same time, the infrared thermal imager 7 records the infrared thermal imaging sequence of the surface temperature field, and the host computer 1 performs post-processing on the infrared thermal imaging sequence. When the surface of the top molten pool is subjected to scanning thermal excitation by the line laser, the heat wave will continuously spread within the specimen. Since the thermal conductivity, density, and specific heat at the defect are significantly different from those of the material itself, the defect will hinder the normal propagation of the heat wave, forming a large thermal resistance, which manifests as an abnormal temperature rise in the infrared thermal imaging sequence. Based on the above principle, the defect can be identified and located.

[0031] The following is in conjunction with the appendix Figure 1-3 The specific embodiments of the present invention are described below: Step 1: Plan the scanning path of the infrared detection robotic arm 3. Since defects on the surface and inside of the component are usually formed during the cooling and solidification stage of the molten pool in the arc additive manufacturing process, the current molten pool needs to be fully cooled before the detection can begin. That is, after a certain layer is printed, the infrared detection robotic arm 3 starts to run, driving the continuous wave laser 5 to be excited synchronously, and the infrared thermal imager 7 collects the surface temperature field of the current printed layer to perform the detection of the layer. After the detection is completed, the arc additive manufacturing equipment continues to print the next layer.

[0032] Step 2: Adjust the line laser shaping lens group 6 so that it is perpendicular to the scanning path, such as... Figure 3 As shown, this allows the line laser to be focused on the top molten pool, meaning the line laser spot is at its finest point. The line laser shaping lens group 6 is as follows... Figure 2 As shown, the optical lens system mainly consists of three parts. The first part is a beam expander group formed by a concave lens and a double convex lens, which is used to further expand the initial light spot emitted by the continuous wave laser 5. The second part is a concave cylindrical mirror 13, which is used to shape the large light spot after beam expansion into a linear shape; The third part is the second plano-convex lens 14, which is used to further focus the diverging linear laser into a concentrated, elongated linear laser.

[0033] Step 3: Start the infrared thermal imager 7 to collect the surface temperature field of the top molten pool in real time. The infrared thermal imager 7 is controlled by the host computer 1 and processes the infrared thermal imaging temperature sequence collected by the infrared thermal imager 7 in real time to facilitate subsequent defect identification.

[0034] Step 4: Start the infrared detection robotic arm 3 and the continuous wave laser driver 4 to begin detection. The start and stop of the infrared detection robotic arm 3 and the continuous wave laser driver 4 are controlled by the synchronization controller 2. When the robotic arm starts running, the continuous wave laser 5 starts thermal excitation synchronously. The synchronization controller 2 will adjust the output power of the continuous wave laser driver 4 according to the current speed of the robotic arm movement, so that the thermal excitation energy of the line laser 15 is within a suitable range, avoiding excessive energy and burning of components.

[0035] Step 5: After the current printing layer is inspected, the infrared inspection robotic arm 3 returns to its original position to avoid obstructing the construction of the next layer of the arc additive manufacturing equipment, and performs the inspection of the next layer according to the scanning path preset in Step 1. This process is repeated until the component is printed.

[0036] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0037] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0038] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A line-scanning laser infrared detection system for online detection of defects in electric arc additive manufacturing, comprising a host computer (1) and a synchronous controller (2), characterized in that: It also includes an infrared detection robotic arm (3), a continuous wave laser driver (4), a continuous wave laser (5), a line laser shaping lens group (6), and an infrared thermal imager (7); The line laser shaping lens group (6) includes, from left to right, a first plano-concave lens (11), a biconvex lens (12), a concave cylindrical mirror (13), and a second plano-convex lens (14), which are assembled together.

2. The line-scanning laser infrared detection system for online detection of defects in electric arc additive manufacturing according to claim 1, characterized in that: The infrared detection robotic arm (3) is used to control the continuous wave laser driver (4) and the infrared thermal imager (7) to perform active thermal excitation and surface temperature field acquisition on the top molten pool of the building layer, so as to realize the infrared online detection of defects in the process of arc additive manufacturing.

3. The line-scanning laser infrared detection system for online detection of defects in electric arc additive manufacturing according to claim 1, characterized in that: The synchronous controller (2) is used to control the continuous wave laser driver (4) and the infrared detection robotic arm (3) to achieve coupling between the thermal excitation state of the continuous wave laser (5) and the motion of the infrared detection robotic arm (3).

4. The line-scanning laser infrared detection system for online detection of defects in electric arc additive manufacturing according to claim 1, characterized in that: The infrared thermal imager (7) is used to record infrared thermal imaging sequences of the surface temperature field.

5. The line-scanning laser infrared detection system for online detection of defects in electric arc additive manufacturing according to claim 1, characterized in that: The host computer (1) is used to perform post-processing on the infrared thermal imaging sequence.

6. The line-scanning laser infrared detection system for online detection of defects in electric arc additive manufacturing according to claim 1, characterized in that: The continuous wave laser (5) is used to excite a Gaussian spot.

7. The line-scanning laser infrared detection system for online detection of defects in electric arc additive manufacturing according to claim 1, characterized in that: The first plano-concave lens (11) and biconvex lens (12) are used to expand the Gaussian spot.

8. The line-scanning laser infrared detection system for online detection of defects in electric arc additive manufacturing according to claim 1, characterized in that: The concave cylindrical mirror (13) is used to shape the light spot into a line.

9. The line-scanning laser infrared detection system for online detection of defects in electric arc additive manufacturing according to claim 1, characterized in that: The second plano-convex lens (14) focuses the light spot behind the line and forms a thin line laser for thermal excitation of the infrared detection system.

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