CN114740048B - Active laser infrared thermal imaging-based online monitoring system and method for manufacturing quality of additive - Google Patents

Abstract

The invention discloses an active laser infrared thermal imaging-based online monitoring system and method for additive manufacturing quality. The monitoring method comprises the following steps: in the process of stacking material additive manufacturing layer by layer on a forming platform, laser beams emitted by a laser irradiate a certain area on the surface of a cured current printing layer through an optical fiber coupling laser homogenizing lens, the area is uniformly heated, the existence of internal defects of the printing layer can prevent downward diffusion of heat flow, so that local temperature rise is formed on the surface, and the temperature image of the surface of the area is acquired through a thermal infrared imager, so that the internal defects of the area are detected; the online monitoring system for the quality of the additive manufacturing by laser infrared thermal imaging can realize online monitoring of the structural quality of the additive manufacturing by keeping linkage with the printing nozzle through the motion scanning mechanism. The disposable qualification rate of the product is improved, and the product is prevented from being scrapped or reworked.

Description

Additive manufacturing quality online monitoring system and method based on active laser infrared thermal imaging

Technical Field

The present invention belongs to the field of additive manufacturing and laser infrared thermal imaging, and in particular relates to an additive manufacturing quality online monitoring system and method based on active laser infrared thermal imaging.

Background technique

Aerospace equipment is gradually developing towards lightweight, diversified functions, complex structures, long life, high reliability and low cost, and the traditional manufacturing methods of casting, forging and machining will be difficult to meet the above manufacturing needs. In terms of integrated forming of complex structures, additive manufacturing technology has advantages that other traditional manufacturing technologies cannot achieve. However, due to the fact that additive manufacturing is a layered printing forming method, the product is prone to poor density, anisotropy of organizational properties, local deformation and stress concentration, and is accompanied by many defects such as pores, cracks, and inclusions. Compared with destructive testing, non-destructive testing can achieve non-destructive testing of the entire product and can be performed in real time during the manufacturing process. At present, the quality inspection of additive manufacturing products is mostly carried out after the product is manufactured, also known as offline monitoring. If defects such as pores and delamination in the additive manufacturing process are not handled in time, it will lead to product quality problems, and more seriously, the product will be unqualified, causing huge losses. Therefore, there is a need for real-time monitoring of the additive manufacturing process, online detection of defects, and even possible process repair, which can greatly improve the quality of additive manufacturing parts, greatly reduce the scrap rate of products, and improve the one-time qualified rate of products.

At present, there are few research results on online monitoring of internal defects. Some researchers directly use infrared cameras to monitor the surface temperature of the molten pool online, and then feedback the morphology of the molten pool. However, passive infrared thermal imaging online monitoring that only relies on the waste heat of the printing process of additive manufacturing parts is susceptible to background interference, and its internal defects have little effect on the surface temperature distribution, and its internal defect detection sensitivity is low.

Summary of the invention

In view of the above defects or improvement needs of the prior art, the present invention provides an additive manufacturing quality online monitoring system and method based on active laser infrared thermal imaging, which aims to realize real-time quality monitoring of the entire additive manufacturing process. The laser infrared additive manufacturing quality online monitoring system is used to detect whether defects occur in the additive manufacturing area. When defects occur, measures can be taken in time to reduce the scrap rate of parts, improve the one-time qualified rate of products, and prevent products from being scrapped or returned for repair.

In order to achieve the above purpose, the present invention adopts the following technical scheme:

An additive manufacturing quality online monitoring system based on active laser infrared thermal imaging comprises a motion scanning mechanism 1, a laser 2, an optical fiber 4, an optical fiber coupled laser homogenizing lens 6, an infrared thermal imager 5 and a control computer 3 equipped with image acquisition and processing software; wherein the optical fiber coupled laser homogenizing lens 6 is connected to the laser 2 via the optical fiber 4, the infrared thermal imager 5 is connected to the control computer 3 equipped with the image acquisition and processing software, the motion scanning mechanism 1 is equipped with a high-resolution infrared thermal imager 5 and the laser homogenizing lens 6 for mobile scanning, and the control computer 3 equipped with the image acquisition and processing software is responsible for the synchronous control of the infrared thermal imager 5, the laser 2 and the motion scanning mechanism 1.

In the additive manufacturing process of stacking materials layer by layer on the forming platform, the Gaussian or quasi-Gaussian distribution collimated laser beam emitted by the laser 2 reaches the fiber-coupled laser homogenization lens 6 through the optical fiber 4, and is homogenized into a uniformly distributed laser to irradiate a certain area on the surface of the additive part 10 for uniform heating and forming a downwardly diffusing heat flow. The existence of internal defects in the printing layer and interlayer defects 11 will hinder the downward diffusion of the heat flow, thereby forming a local temperature increase on the surface. The surface temperature image of the area is collected by the infrared thermal imager 5 to detect defects in the area; the infrared thermal imager 5 and the laser homogenization lens 6 are linked with the print head 8 through the motion scanning mechanism 1, that is, the online monitoring of the overall quality of the additive manufacturing structure is realized.

The infrared thermal imager 5 is a high-resolution infrared thermal imager with a resolution of 640*512.

The monitoring method of the additive manufacturing quality online monitoring system based on active laser infrared thermal imaging comprises the following steps:

Step 1: Install the laser infrared thermal imaging additive manufacturing quality online monitoring system, set a preset delay time between the additive manufacturing system and the laser infrared thermal imaging additive manufacturing quality online monitoring system, set additive manufacturing parameters, and perform additive manufacturing of structural parts by controlling the motion system 7;

Step 2: Complete the settings on the control computer 3 equipped with image acquisition and processing software, and keep the laser infrared thermal imaging additive manufacturing quality online monitoring system linked with the printing nozzle 8 through the motion scanning mechanism 1 to control the high-power laser 2 to emit light;

Step 3: The collimated laser beam with Gaussian or quasi-Gaussian distribution generated by the laser 2 is incident on the fiber-coupled laser homogenization lens 6 through the optical fiber 4, and is shaped into a uniform laser heat source, which is irradiated onto the surface of the solidified print layer;

Step 4: As the additive manufacturing process begins, the additive manufacturing system works continuously, and the laser infrared thermal imaging additive manufacturing quality online monitoring system detects a certain area on the surface of the solidified printing layer step by step. After each layer and each area are printed, the laser infrared thermal imaging additive manufacturing quality online monitoring system promptly detects the corresponding area; first, the laser 2 does not emit light, and the infrared thermal imager 5 records the initial temperature F _ij ¹ in real time. Then, the laser 2 emits light, and the infrared thermal imager 5 records the temperature F _ij ² at the moment of heating in real time; the image temperature data is collected, and according to the formula F _ij =|F _ij ² -F _ij ¹ |, i, j = 1, 2, 3..., the background differential temperature of the jth area of the i-th layer is calculated, and the control computer 3 equipped with image acquisition and processing software is processed in real time; when all layers and all areas are printed, the additive manufacturing is completed, and the corresponding laser infrared thermal imaging additive manufacturing quality online monitoring system is detected, and the laser infrared thermal imaging additive manufacturing quality online monitoring system automatically generates a defect detection map.

The present invention uses a laser infrared thermal imaging additive manufacturing quality online monitoring system to perform real-time detection during the additive manufacturing process. During the detection process, a defect detection map with a high-precision display of parameters such as defect position and size is formed, thereby enabling real-time quality monitoring of the entire additive manufacturing process. When defects occur, timely measures can be taken to reduce the scrap rate of parts, improve the one-time qualified rate of products, and prevent product scrapping or rework.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of an additive manufacturing quality online monitoring system based on active laser infrared thermal imaging proposed by the present invention.

Figure 2 is a schematic diagram of the processing and inspection process of one layer of additive manufacturing.

Figure 3 shows the overall processing flow and defect detection diagram of additive manufacturing.

Detailed ways

The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

As shown in FIG1 , an additive manufacturing quality online monitoring system based on active laser infrared thermal imaging includes a motion scanning mechanism 1, a laser 2, an optical fiber 4, a fiber-coupled laser homogenization lens 6, an infrared thermal imager 5, and a control computer 3 equipped with image acquisition and processing software.

The present invention proposes an additive manufacturing quality online monitoring system and method based on active laser infrared thermal imaging. The system is composed of a high-power laser 2, an optical fiber 4, a fiber-coupled laser shaping lens 6, a high-resolution infrared thermal imager 5, a control computer 3 equipped with image acquisition and processing software, and a motion scanning mechanism 1. The detection method is as follows: when the materials are stacked layer by layer on the forming platform to form an additive manufacturing component, the laser beam emitted by the high-power laser 2 is irradiated to a certain area on the surface of the current printed layer that has been solidified through the fiber-coupled laser shaping lens 6 to perform uniform heating. The existence of internal defects in the printed layer will hinder the downward diffusion of the heat flow, thereby forming a local temperature rise on the surface. The surface temperature image of the area is collected by the infrared thermal imager 5 to detect its internal defects; the laser infrared thermal imaging additive manufacturing quality online monitoring system can realize the online monitoring of the quality of the additive manufacturing structure by keeping linkage with the print head 8 through the motion scanning mechanism 1.

The present invention will be further described in detail below in conjunction with FIG. 1 to FIG. 3 and specific embodiments.

The present invention is a monitoring method of an additive manufacturing quality online monitoring system based on active laser infrared thermal imaging, which specifically comprises the following steps:

Step 1: Install the additive manufacturing quality online monitoring system of laser infrared thermal imaging, set a suitable delay time between the additive manufacturing system and the additive manufacturing quality online monitoring system of laser infrared thermal imaging, set additive manufacturing parameters, and perform additive manufacturing of structural parts by controlling the motion system 7;

Step 2: Complete the settings on the control computer 3 equipped with image acquisition and processing software, and keep the laser infrared thermal imaging additive manufacturing quality online monitoring system linked with the printing nozzle 8 through the motion scanning mechanism 1 to control the high-power laser 2 to emit light;

Step 3: The collimated laser beam with Gaussian or quasi-Gaussian distribution generated by the high-power laser 2 is incident on the fiber-coupled laser homogenization lens 6 through the optical fiber 4, and is shaped into a uniform laser heat source, which is irradiated onto the surface of the solidified print layer;

Step 4: As the additive manufacturing process begins, powder is deposited onto the surface of the additive part 10 through the powder delivery nozzle 9, the additive manufacturing system works continuously, and the laser infrared additive manufacturing quality online detection system detects a certain area of the surface of the solidified printing layer step by step. After each layer and each area is printed, the laser infrared thermal imaging additive manufacturing quality online monitoring system performs corresponding detection in a timely manner. First, the laser 2 does not emit light, and the infrared thermal imager 5 records the initial temperature F _ij ¹ in real time. Then the laser 2 emits light, and the infrared thermal imager 5 records the temperature F _ij ² at the moment of heating in real time; the image temperature data is collected, and according to the formula F _ij =|F _ij ² -F _ij ¹ |, i, j = 1, 2, 3..., the background differential temperature of the jth area of the i-th layer is calculated, and it is processed in real time by the control computer 3 equipped with image acquisition and processing software. As shown in FIG2 , when the first area 12 of the first layer is printed and solidified, the laser infrared thermal imaging additive manufacturing quality online monitoring system detects the first area of the first layer. At this time, the additive manufacturing system continues to work and continues to print the second area 13 of the first layer; when the second area 13 of the first layer is printed and solidified, the laser infrared thermal imaging additive manufacturing quality online monitoring system detects the third area of the first layer. After the printing and detection of the first layer are completed, the second layer and the third layer are printed successively until the additive manufacturing of the object is completed, and the corresponding laser infrared thermal imaging additive manufacturing quality online monitoring system detection is completed. The laser infrared thermal imaging additive manufacturing quality online monitoring system automatically generates a defect detection map, as shown in FIG3 .

Claims (1)

1. A monitoring method for an additive manufacturing quality online monitoring system based on active laser infrared thermal imaging, the monitoring system comprising a motion scanning mechanism (1), a laser (2), an optical fiber (4), an optical fiber coupled laser homogenizing lens (6), an infrared thermal imager (5) and a control computer (3) equipped with image acquisition and processing software; wherein the optical fiber coupled laser homogenizing lens (6) is connected to the laser (2) via the optical fiber (4), the infrared thermal imager (5) is connected to the control computer (3) equipped with the image acquisition and processing software, the motion scanning mechanism (1) is equipped with a high-resolution infrared thermal imager (5) and the laser homogenizing lens (6) for mobile scanning, and the control computer (3) equipped with the image acquisition and processing software is responsible for the synchronous control of the infrared thermal imager (5), the laser (2) and the motion scanning mechanism (1); In the additive manufacturing process of depositing materials layer by layer on a molding platform, a Gaussian or quasi-Gaussian distribution collimated laser beam emitted by a laser (2) reaches a fiber-coupled laser homogenization lens (6) through an optical fiber (4), is homogenized into a uniformly distributed laser beam, and irradiates a certain area on the surface of an additive part (10) to uniformly heat the area and form a heat flow that diffuses downward. The presence of internal defects in the printed layer and interlayer defects (11) will hinder the downward diffusion of the heat flow, thereby forming a local temperature rise on the surface. The surface temperature image of the area is collected by an infrared thermal imager (5) to detect defects in the area. The infrared thermal imager (5) and the laser homogenization lens (6) are linked to the print head (8) through a motion scanning mechanism (1), thereby realizing online monitoring of the overall quality of the additive manufacturing structure. The infrared thermal imager (5) is a high-resolution infrared thermal imager with a resolution of 640*512; Characterized in that the monitoring method comprises the following steps: Step 1: Install the laser infrared thermal imaging additive manufacturing quality online monitoring system, set a preset delay time between the additive manufacturing system and the laser infrared thermal imaging additive manufacturing quality online monitoring system, set additive manufacturing parameters, and perform additive manufacturing of the structural parts by controlling the motion system (7); Step 2: Complete the settings on the control computer (3) equipped with image acquisition and processing software, and keep the laser infrared thermal imaging additive manufacturing quality online monitoring system linked with the printing nozzle (8) through the motion scanning mechanism (1) to control the high-power laser (2) to emit light; Step 3: The collimated laser beam with Gaussian or quasi-Gaussian distribution generated by the laser (2) is incident on the fiber-coupled laser homogenization lens (6) through the optical fiber (4), and is shaped into a uniform laser heat source, which is irradiated onto the surface of the solidified printed layer; Step 4: As the additive manufacturing process begins, the additive manufacturing system works continuously, and the laser infrared thermal imaging additive manufacturing quality online monitoring system detects a certain area on the surface of the solidified printing layer step by step. After each layer and each area are printed, the laser infrared thermal imaging additive manufacturing quality online monitoring system promptly detects the corresponding area; first, the laser (2) does not emit light, and the infrared thermal imager (5) records the initial temperature F _ij ¹ in real time. Then, the laser (2) emits light, and the infrared thermal imager (5) records the temperature F _ij ² at the moment of heating in real time; the image temperature data is collected, and according to the formula F _ij =|F _ij ² -F _ij ¹ |, i, j = 1, 2, 3 ..., the background differential temperature of the jth area of the i-th layer is calculated, and the control computer (3) equipped with image acquisition and processing software is processed in real time; when all layers and all areas are printed, the additive manufacturing is completed, and at the same time, the corresponding laser infrared thermal imaging additive manufacturing quality online monitoring system detection is completed, and the laser infrared thermal imaging additive manufacturing quality online monitoring system automatically generates a defect detection map.