CN-122007449-A - System and method for manufacturing unsupported additive of laser energy field auxiliary overhang structure

CN122007449ACN 122007449 ACN122007449 ACN 122007449ACN-122007449-A

Abstract

The invention discloses a system and a method for manufacturing a laser energy field auxiliary overhang structure unsupported additive, wherein the system comprises a forming processing unit, an energy field auxiliary unit and an online monitoring unit, the energy field auxiliary unit comprises a second laser and a laser collimator, the second laser is an energy field auxiliary preheating laser, the energy field auxiliary preheating laser is arranged outside a powder bed fusion forming cabin in a paraxial mode, emergent light beams of the energy field auxiliary preheating laser are used for carrying out local preheating on a powder bed in a printing process after being processed by the laser collimator, the online monitoring unit comprises an industrial camera, an optical tomography camera and a control and analysis unit, the industrial camera and the optical tomography camera are respectively used for collecting a deposition layer image and a molten pool light intensity signal in the printing process, and the control and analysis unit is used for receiving online monitoring data from the industrial camera and the optical tomography camera and analyzing the image and the signal. The paraxial energy field auxiliary preheating laser provided by the invention obviously improves the controllability and the forming quality of unsupported forming.

Inventors

WEI HUILIANG
DU CHUANPENG
LIAO WENHE
LIU TINGTING
LI ZHIYONG
CHEN RONG

Assignees

南京理工大学

Dates

Publication Date: 20260512
Application Date: 20260203

Claims (10)

1. The laser energy field auxiliary suspension structure unsupported additive manufacturing system is characterized by comprising a forming processing unit, an energy field auxiliary unit and an online monitoring unit, wherein the forming processing unit comprises a powder bed fusion forming cabin, a first laser, a vibrating mirror system, a scraper powder spreading system, a protective gas system and a substrate, the energy field auxiliary unit comprises a second laser and a laser collimator, the second laser is an energy field auxiliary preheating laser, the energy field auxiliary preheating laser is arranged outside the powder bed fusion forming cabin by a paraxial way, and an emergent beam of the energy field auxiliary preheating laser is used for carrying out local preheating on the powder bed in a printing process after being processed by the laser collimator; The on-line monitoring unit comprises an industrial camera, an optical tomography camera and a control and analysis unit, wherein the industrial camera and the optical tomography camera are both arranged outside the powder bed fusion forming cabin in a paraxial manner and are respectively used for collecting a sediment layer image and a molten pool light intensity signal in a printing process, the control and analysis unit consists of a computer and is arranged outside the powder bed fusion forming cabin, and the computer receives on-line monitoring data from the industrial camera and the optical tomography camera and analyzes and processes the image and the signal.
2. The laser energy field assisted overhang structure unsupported additive manufacturing system of claim 1 wherein the first laser is a 1064nm Yb fiber laser and the second laser is a 808nm semiconductor laser.
3. The method for manufacturing the unsupported additive material of the laser energy field auxiliary overhang structure is characterized by comprising the following steps of: s1, collecting surface images of a deposited layer after powder is paved by a scraper and after powder is melted by a first laser layer by an industrial camera, performing perspective transformation correction on the images, monitoring a forming apparent state and obtaining an apparent state image; s2, collecting light intensity time sequence signals of a molten pool layer by layer through an optical tomography camera, and performing splicing processing on the signals based on a time domain integration method to obtain dynamic information of the molten pool; s3, acquiring point cloud data of the formed part by using an optical scanner after forming is finished, reconstructing a three-dimensional solid model of the formed part, registering and comparing the three-dimensional solid model with an original design three-dimensional model, analyzing geometric deviation between the three-dimensional solid model and the original design three-dimensional model, and further quantitatively evaluating forming precision of the part; s4, combining an original design three-dimensional model, a reconstructed three-dimensional solid model and apparent state images and molten pool dynamic information in the forming process of the formed part to obtain a space-time evolution rule of fracture and buckling deformation defects of the part in forming; s5, based on analysis of space-time evolution rules of defects, providing a laser energy field auxiliary overhang structure unsupported additive manufacturing strategy; S6, performing three-dimensional model geometric analysis and slicing layering treatment on an original design three-dimensional model of the part to be formed, identifying an overhanging region and the corresponding layer number of the part to be formed, and further determining a preheating region, a starting layer and a stopping layer and corresponding preheating temperature requirements for performing laser energy field auxiliary preheating by a second laser; s7, carrying out collaborative design and system configuration on the spot size, output power, action position and action time sequence of the second laser according to the preheating area, the start-stop layer and corresponding preheating temperature requirements; and S8, carrying out unsupported additive manufacturing in the forming process of the overhang structure, and synchronously executing powder fusion forming of the first laser and energy field auxiliary preheating of the second laser in the overhang region, wherein the second laser provides continuous and controllable auxiliary heat input for the overhang region.
4. A method of unsupported additive manufacturing a laser energy field assisted overhang structure according to claim 3, wherein S1 comprises the steps of: S11, setting up an industrial camera on a side shaft outside a fusion forming cabin of a powder bed, synchronously collecting surface images of each layer after powder spreading is completed by a powder spreading scraper, and synchronously collecting the surface images again after fusion powder is completed by a first laser of the layer; And S12, performing perspective transformation correction on the surface image after powder laying and the surface image after melting by using preset calibration parameters so as to eliminate visual angle distortion caused by oblique installation of a camera, thereby obtaining an apparent state image for real-time monitoring and subsequent analysis.
5. The laser energy field of claim 4 an unsupported additive manufacturing method for an auxiliary suspension structure, the method is characterized in that the step S2 comprises the following steps: S21, an optical tomography camera is arranged on a paraxial frame outside a powder bed fusion forming cabin, and light intensity time sequence signals radiated by a molten pool are collected in real time in the process of fusing powder by each layer of first laser; S22, processing the time sequence signals by adopting a time domain integration method, and reconstructing molten pool dynamic information reflecting the light intensity distribution of the molten pool through an image stitching algorithm.
6. The laser energy field of claim 5 an unsupported additive manufacturing method for an auxiliary suspension structure, the method is characterized in that the step S3 comprises the following steps: S31, after forming is completed, performing three-dimensional scanning on all surfaces of the formed part by using an optical scanner, and collecting point cloud data of the formed part; S32, processing the point cloud data through reverse engineering software to reconstruct a three-dimensional solid model of the formed part; And S33, carrying out space registration and comparison on the three-dimensional solid model of the formed part and the original design three-dimensional model by adopting analysis software, analyzing geometric deviation distribution between the three-dimensional solid model and the original design three-dimensional model, and calculating critical dimension deviation of an overhang area so as to quantitatively evaluate the final forming precision of the part.
7. The method for manufacturing the unsupported additive material of the laser energy field assisted overhang structure of claim 6, wherein S4 comprises the steps of comparing and analyzing an original design three-dimensional model, a reconstructed three-dimensional solid model and apparent state images and molten pool dynamic information in a forming process of a formed part, identifying and positioning an initial layer and a space position of a fracture and buckling deformation defect, and further carrying out visual presentation and rule extraction on a time-space evolution process of the defect according to the occurrence time sequence and the form evolution of the defect between layers to obtain a time-space evolution rule of the fracture and buckling deformation defect.
8. The method for manufacturing the unsupported additive of the suspension structure assisted by the laser energy field according to claim 7, wherein the step S5 specifically comprises the step of proposing a method for manufacturing the unsupported additive of the suspension structure assisted by the laser energy field based on a fracture and buckling deformation defect space-time evolution rule, and realizing active regulation and control of local thermal stress by carrying out in-situ, directional and adjustable preheating on a suspension area through a second laser, so as to effectively inhibit fracture and buckling deformation tendency.
9. The laser energy field of claim 8 an unsupported additive manufacturing method for an auxiliary suspension structure, the method is characterized in that the step S6 comprises the following steps: S61, importing an original design three-dimensional model into three-dimensional modeling software, and identifying all overhanging regions and local geometric shapes thereof in which the included angles with the horizontal direction are smaller than a preset threshold value through geometric analysis; s62, slicing and layering processing is carried out on the original design three-dimensional model, contour information of each printing layer is obtained, and a printing layer serial number containing the overhanging region and space coordinates in the layer are determined according to the space position relation between the overhanging region and each layering; S63, judging the space-time position of the easily-broken and warped suspension area by combining the local geometric shape of the suspension area, the space-time evolution rule of the broken and warped defect and the determined space coordinates of the suspension area, and further determining a key preheating area and a starting layer and a finishing layer thereof, wherein the key preheating area needs to be preheated by a second laser in an auxiliary way; S64, integrating the local geometric shapes of the overhang regions, and determining the preheating temperature process requirements of the corresponding preheating regions according to the critical dimension deviation of the overhang regions under the condition of no preheating, which is obtained in the step S3.
10. The laser energy field of claim 9 an unsupported additive manufacturing method for an auxiliary suspension structure, the method is characterized in that the step S7 comprises the following steps: S71, matching and designing the spot size of the second laser according to the overhang area and the local geometric shape thereof determined in the step S6, and planning the accurate action position of the spot of the second laser on the powder bed; S72, setting output power, action time sequence and start-stop control logic of the second laser according to the preheating temperature process requirement of the preheating area determined in the step S6, forming a preheating process parameter set cooperated with the first laser, and completing the overall system configuration of the second laser energy field.

Description

System and method for manufacturing unsupported additive of laser energy field auxiliary overhang structure Technical Field The invention belongs to the technical field of laser powder bed melting, and particularly relates to a system and a method for manufacturing a laser energy field auxiliary suspension structure unsupported additive. Background The severe reliance of laser powder bed fusion techniques on support structures has limited their wide application in the manufacture of complex components. The support structure not only increases additional material consumption, post-processing costs and manufacturing cycle, but also significantly constrains the geometric freedom of design. For components with internal cavities, flow channels or lattice-skin integration, the traditional support is often not configured or difficult to remove. Thus, the development of unsupported forming techniques is a key challenge in driving the technology toward high performance, high complexity manufacturing. The problem of the quality of the formation of the overhanging region is a major difficulty in unsupported conditions. Taking a lattice-skin structure as an example, a horizontal or near-horizontal overhanging region of the lower surface of the skin is extremely prone to macrocrack and severe warpage under conventional process parameters. The root cause of this is the extremely high temperature gradients, rapid cooling and complex thermal cycling associated with laser powder bed fusion processes, resulting in significant residual stresses built up inside the part. In the overhanging region, heat is more likely to accumulate due to the much lower heat conducting capacity of the unmelted powder below than the dense solid, creating a localized high temperature zone, thereby exacerbating thermal stress concentrations. If the process parameters are improperly matched, the accumulated tensile stress induces buckling deformation and even cracking in the overhanging region, and meanwhile, the molten pool is easy to flow unstably due to lack of physical support, so that the surface is collapsed or spheroidized, and the forming precision and the component performance are seriously affected. To address the above challenges, on-line monitoring and active thermal management are key technology approaches. The industrial camera is used as a non-contact monitoring means to image and visually analyze the surface state after powder spreading and melting in real time, and the optical tomography system can collect the light intensity signal of the molten pool in real time for analyzing the dynamic behavior of the molten pool. The online monitoring method based on the two is gradually applied to forming quality tracking, molten pool behavior analysis and defect early warning. Laser powder bed fusion is essentially a dynamic thermal process whose shaping quality is highly dependent on the thermal equilibrium state of the system. Conventional methods typically manage the overall temperature field by regulating the interlayer cooling time or by employing substrate preheating to reduce the temperature gradient and relieve residual stress. However, the interlayer cooling time is limited by the geometry of the parts, and is difficult to flexibly regulate and control, the influence range of the preheating of the substrate is limited, the effect on the high-depth structure or the local characteristic is gradually attenuated, and the accurate requirement of the local heat management of the complex structure cannot be met. Disclosure of Invention The invention aims to provide a system and a method for manufacturing an unsupported additive of a laser energy field auxiliary suspension structure, which solve the problem of breakage and buckling deformation of the unsupported printing suspension structure. The technical scheme adopted by the invention is as follows: The laser energy field auxiliary suspension structure unsupported additive manufacturing system comprises a forming processing unit, an energy field auxiliary unit and an online monitoring unit, wherein the forming processing unit comprises a powder bed fusion forming cabin, a first laser, a vibrating mirror system, a scraper powder paving system, a protective gas system and a substrate, the energy field auxiliary unit comprises a second laser and a laser collimator, the second laser is an energy field auxiliary preheating laser, the energy field auxiliary preheating laser is paraxial arranged outside the powder bed fusion forming cabin, and an emergent beam of the energy field auxiliary preheating laser is used for carrying out local preheating on the powder bed in the printing process after being processed by the laser collimator; The on-line monitoring unit comprises an industrial camera, an optical tomography camera and a control and analysis unit, wherein the industrial camera and the optical tomography camera are both arranged outside the powder bed fusion forming cabin in a paraxial ma