CN107175329B - device and method for detecting reverse part model and positioning defects layer by layer in 3D printing - Google Patents

device and method for detecting reverse part model and positioning defects layer by layer in 3D printing Download PDF

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CN107175329B
CN107175329B CN201710245808.XA CN201710245808A CN107175329B CN 107175329 B CN107175329 B CN 107175329B CN 201710245808 A CN201710245808 A CN 201710245808A CN 107175329 B CN107175329 B CN 107175329B
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molten pool
layer
image
speed camera
model
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CN107175329A (en
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王迪
王艺锰
杨永强
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South China University of Technology SCUT
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South China University of Technology SCUT
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/20—Direct sintering or melting
    • B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/30—Process control
    • B22F10/31—Calibration of process steps or apparatus settings, e.g. before or during manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/30—Process control
    • B22F10/38—Process control to achieve specific product aspects, e.g. surface smoothness, density, porosity or hollow structures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/40—Radiation means
    • B22F12/49—Scanners
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/90—Means for process control, e.g. cameras or sensors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
    • B22F3/003—Apparatus, e.g. furnaces
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y50/00—Data acquisition or data processing for additive manufacturing
    • B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/40—Radiation means
    • B22F12/44—Radiation means characterised by the configuration of the radiation means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
    • G01N21/84—Systems specially adapted for particular applications
    • G01N21/88—Investigating the presence of flaws or contamination
    • G01N21/8851—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges
    • G01N2021/8887—Scan or image signal processing specially adapted therefor, e.g. for scan signal adjustment, for detecting different kinds of defects, for compensating for structures, markings, edges based on image processing techniques
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Abstract

The invention discloses a device and a method for detecting a reverse part model and positioning defects layer by layer in 3D printing; the device comprises a scanning galvanometer, a semi-transparent semi-reflecting mirror, an optical filter, a laser head, a high-speed camera, a controller and the like. The scanning galvanometer is used for controlling laser beams to selectively melt metal powder, and the semi-transparent semi-reflecting mirror reflects the molten pool radiation into the high-speed camera and converts the molten pool radiation into image information which is transmitted to the controller. The device monitors powder melting in the SLM processing process, feeds the powder melting back to a computer software interface, reflects molten pool characteristics at different positions in real time, accurately measures the profile of each melting layer, obtains a part model in a reverse solving mode, and compares and analyzes the model and an original three-dimensional model to obtain the error of the metal 3D printed part and the original model data in the aspect of precision and size. The position and the three-dimensional shape of the internal defect in the 3D printing process can be accurately acquired, and the destructive test of the printing part in the later stage on the part is avoided.

Description

Device and method for detecting reverse part model and positioning defects layer by layer in 3D printing
Technical Field
The invention relates to monitoring and quality accurate control of a metal 3D printing process, in particular to a device and a method for detecting a reverse part model and positioning defects layer by layer in 3D printing.
Background
selective Laser Melting (SLM) is a fast forming 3D printing technique that can directly form highly dense, high precision metal parts, but more than 50 different factors are in play during the Melting process, such as size and shape errors, voids in the molten layer, high residual stress of the final part, and the influence on the interrelation of various variables such as material properties, which makes the printing process difficult to control quantitatively.
advances in quality monitoring have resulted in significant improvements in surface roughness and performance of molded parts in additive manufacturing techniques, reducing deformation of internal structures. A number of critical parameters need to be monitored in a laser melting system, including oxygen content, laser output power, laydown and powder quality, among others. However, it is not sufficient to simply evaluate the quality of the parts comprehensively on the basis of the plant process, and the printing process itself must be monitored. The real-time monitoring system can make effective contribution to early and effective detection of printing defects and defect avoidance.
The QM puddle 3D system of Concept laser company monitors the entire printing process by a photodiode and a cmos camera, and monitors the puddle heat radiation using a coaxial sensor; the EOSTATE MeltPool system of EOS provides automated, intelligent process monitoring techniques-whether per point, per layer, or per component. In this way it allows for automated monitoring of the bath, while it also allows for internal inspection of the part during construction.
the difficulty of the quality monitoring at present lies in the accuracy of information collection and processing, whether the processing state can be accurately reflected or not; in addition, for the correction of the processing process, due to the printing defects or self-organization defects caused by a large number of influencing factors, and the whole process has high dynamic characteristics, the development of an automatic correction control loop is a big difficulty.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a device and a method for detecting and reversely solving a part model and positioning defects layer by layer in 3D printing. According to the invention, by monitoring the position and the characteristics of the molten pool and reversely solving the three-dimensional model through the profile data of each layer, such signals can be intuitively analyzed on the three-dimensional model immediately after the printing process is finished. The user can trace back the printing process of each part according to the position. The influence generated inside the part in the printing process can be better detected and analyzed. By analyzing the printing defects of the parts, the reasons are searched and the solution is proposed.
The invention is realized by the following technical scheme:
A3D prints the layer-by-layer and detects and reflects the part model and positions the defective device, including laser head 3, scanning galvanometer 9 and computer 1, semi-transparent semi-reflecting mirror 16, high-speed camera 20, controller 2; the high-speed camera 20 is in telecommunication connection with the computer 1 through the controller 2;
A laser light path 17 of the laser head 3 is reflected into the scanning galvanometer 9 through the semi-transparent semi-reflecting mirror 16, and the scanning galvanometer 9 controls a laser beam to selectively melt metal powder paved on the working platform 15; meanwhile, the scanning galvanometer 9 collects the molten pool radiation and transmits the molten pool radiation to the high-speed camera 20 through the semi-transparent semi-reflecting mirror 16, the high-speed camera 20 processes the molten pool radiation data and converts the molten pool radiation data into image information to be transmitted to the controller 2, and the controller 2 is used for processing the image data so as to determine the position of the molten pool and generate the outline of each melting layer.
the controller 2 includes: the image processing device comprises an image acquisition module, an image contour extraction module and an image triangularization module;
The image acquisition module is used for controlling the high-speed camera 20 to acquire real-time image data of a molten pool in the forming process of each layer of the workpiece and storing the real-time image data in a memory of the high-speed camera;
An image contour extraction module for displaying the color image fed back to the high-speed camera 20 as a gray image and establishing a coordinate system thereof; filtering the gray level image by using a median filter template to smooth the image and remove noise; selecting a threshold value of the histogram as a minimum value by utilizing the gray histogram, carrying out binarization processing on the image according to the threshold value, dividing the image into molten pool pixel points and non-molten pool pixel points, and extracting a molten pool contour;
The image triangularization module is used for approximating the fault outline obtained by image processing by using polygons, then connecting adjacent fault polygon vertexes into a triangle, triangularizing the upper end face and the lower end face of the object and outputting an STL file;
When the working period starts, the image acquisition module acquires image information, the image information is transmitted to the image contour extraction module to extract the contour information of the molten pool, a process file is established according to the information, the processing state is fed back on a computer interface, and after the layer is processed, the contour of the layer is extracted according to the process file; and the image triangularization module obtains a complete three-dimensional model of the workpiece according to the multilayer outline of the workpiece and outputs an STL file.
And an optical filter 19 is additionally arranged on a light path between the high-speed camera 20 and the semi-transparent semi-reflecting mirror 16 and is used for filtering out a molten pool acquisition waveband.
the optical filter 19 adopts a narrow-band optical filter with the central wavelength within the range of 600-650 nm to ensure the spectral sensitivity of the high-speed camera 20.
the high-speed camera 20 is a COMS high-speed camera, the pixel resolution is not lower than 1024 multiplied by 1024, and the frame number can reach 7000 frames/second; the shortest exposure time of the whole shutter is 1 us; the dynamic range is 120 dB; spectral range 400nm-950nm, 8 bit sampling resolution.
A3D printing layer-by-layer detection reverse part model and defect positioning method comprises the following steps:
The method comprises the following steps: the scanning galvanometer 9, the semi-transparent semi-reflecting mirror 16 and the optical filter 19 form a coaxial optical path, and the radiation light of the molten pool is reflected and filtered onto the high-speed camera 20 through the coaxial optical path;
step two: establishing a coordinate system by taking the center of a forming plane of a workpiece as an original point, capturing the position of a molten pool on the forming plane by a high-speed camera 20 according to a plane forming track, and simultaneously recording the molten pool form at the position;
Step three: the size of the molten pool is obtained through image processing of the controller 2, and when the size of the molten pool deviates from the deviation range of the standard value, the size of the molten pool is recorded as an abnormal position, otherwise, the size of the molten pool is recorded as a normal position; the controller 2 feeds the position information back to a real-time monitoring interface of the computer 1 in real time, the molten pool information is reflected at the corresponding position of the monitoring interface, if the position is a normal position, the molten pool information is displayed in green, and if the position is an abnormal position, the molten pool information is displayed in red;
Step four: after the layer of data is processed, the high-speed camera 20 collects the layer of forming plane data, and the controller 2 extracts and stores the layer of profile data of the workpiece; after the integral processing of the part is finished, generating a three-dimensional model according to each layer of profile data of the workpiece, and comparing and analyzing the currently generated three-dimensional model and an original three-dimensional model which is pre-built in a computer 1 to obtain the error of the metal 3D printed part and the original model data on the precision size; meanwhile, the abnormal position in the model is highlighted in red, and the number of layers is displayed for viewing.
And thirdly, taking the deviation range of the size of the molten pool deviating from the standard value as 5% -15%.
Compared with the prior art, the invention has the following advantages and effects:
The method monitors powder melting in the SLM processing process, feeds the powder melting back to a computer, reflects molten pool characteristics at different positions in real time, accurately measures the profile (including an internal closed profile) of each melting layer, obtains a part model in a reverse solving mode, and compares and analyzes the model and an original three-dimensional model to obtain the error of the metal 3D printed part and the original model data in the aspect of precision and size. Meanwhile, by combining data analysis of molten pool characteristics (width after molten pool solidification) at different positions, the positions and the three-dimensional shapes of internal defects in the 3D printing process can be accurately obtained, and destructive tests on parts at the later stage of printing the parts are avoided.
Drawings
FIG. 1 is a schematic structural diagram of a device for detecting a reverse part model and positioning defects layer by layer in 3D printing.
FIG. 2 is a schematic view of a computer interface; wherein A represents the molding layer of each layer of the part; b represents an abnormality.
Fig. 3 is a flow chart of the present invention.
In fig. 1: the device comprises a computer 1, a controller 2, a laser head 3, an auxiliary structure beam expander 4, a three-dimensional dynamic focusing system 5, a control board 6, a control board 7, a galvanometer control card 8, a scanning galvanometer 9, a Y scanning motor and a lens 10 thereof, an X scanning motor and a lens 11 thereof, control boards (12, 13 and 14), a working platform 15, a half-mirror 16, a laser light path 17, a molten pool radiation light path 18, a light filter 19 and a high-speed camera 20.
Detailed Description
The present invention will be described in further detail with reference to specific examples.
Examples
As shown in the figure. The invention discloses a device for detecting a reverse part model and positioning defects layer by layer in 3D printing, which comprises a laser head 3, a scanning galvanometer 9, a computer 1, a semi-transparent semi-reflecting mirror 16, a high-speed camera 20 and a controller 2; the high-speed camera 20 is in telecommunication connection with the computer 1 through the controller 2;
a laser light path 17 of the laser head 3 is reflected into the scanning galvanometer 9 through the semi-transparent semi-reflecting mirror 16, and the scanning galvanometer 9 controls a laser beam to selectively melt metal powder paved on the working platform 15; meanwhile, the scanning galvanometer 9 collects the molten pool radiation and transmits the molten pool radiation to the high-speed camera 20 through the semi-transparent semi-reflecting mirror 16, the high-speed camera 20 processes the molten pool radiation data and converts the molten pool radiation data into image information to be transmitted to the controller 2, and the controller 2 is used for processing the image data so as to determine the position of the molten pool and generate the outline of each melting layer.
and an optical filter 19 is additionally arranged on a light path between the high-speed camera 20 and the semi-transparent semi-reflecting mirror 16 and is used for filtering out a molten pool acquisition waveband.
The optical filter 19 adopts a narrow-band optical filter with the central wavelength within the range of 600-650 nm to ensure the spectral sensitivity of the high-speed camera 20.
The high-speed camera 20 is a COMS high-speed camera, the pixel resolution is not lower than 1024 multiplied by 1024, and the frame number can reach 7000 frames/second; the shortest exposure time of the whole shutter is 1 us; the dynamic range is 120 dB; spectral range 400nm-950nm, 8 bit sampling resolution.
the half mirror 16 is used to reflect 1064nm laser wavelength 100% and transmit visible and near infrared 100% to the high speed camera 20.
the controller 2 includes: the image processing device comprises an image acquisition module, an image contour extraction module and an image triangularization module.
the image acquisition module is used for controlling the high-speed camera 20 to acquire real-time image data of a molten pool in the forming process of each layer of the workpiece and storing the real-time image data in a memory of the high-speed camera;
an image contour extraction module for displaying the color image fed back to the high-speed camera 20 as a gray image and establishing a coordinate system thereof; filtering the gray level image by using a median filter template to smooth the image and remove noise; selecting a threshold value of the histogram as a minimum value by utilizing the gray histogram, carrying out binarization processing on the image according to the threshold value, dividing the image into molten pool pixel points and non-molten pool pixel points, and extracting a molten pool contour;
The image triangularization module is used for approximating the fault outline obtained by image processing by using polygons, then connecting adjacent fault polygon vertexes into a triangle, triangularizing the upper end face and the lower end face of the object and outputting an STL file;
When the working period starts, the image acquisition module acquires image information, the image information is transmitted to the image contour extraction module to extract the contour information of the molten pool, a process file is established according to the information, the processing state is fed back on a computer interface, and after the layer is processed, the contour of the layer is extracted according to the process file; and the image triangularization module obtains a complete three-dimensional model of the workpiece according to the multilayer outline of the workpiece and outputs an STL file.
The invention discloses a method for detecting a reverse part model and positioning defects layer by layer in 3D printing, which can be realized by the following steps:
the method comprises the following steps: the scanning galvanometer 9, the semi-transparent semi-reflecting mirror 16 and the optical filter 19 form a coaxial light path, and the radiation light of the molten pool is reflected and filtered onto the high-speed camera 20 through the coaxial light path;
Step two: establishing a coordinate system by taking the center of a forming plane of a workpiece as an original point, capturing the position of a molten pool on the forming plane by a high-speed camera 20 according to a plane forming track, and simultaneously recording the molten pool form at the position;
step three: the size of the molten pool is obtained through image processing of the controller 2, and when the size of the molten pool deviates from the deviation range of the standard value, the size of the molten pool is recorded as an abnormal position, otherwise, the size of the molten pool is recorded as a normal position; the controller 2 feeds the position information back to a real-time monitoring interface of the computer 1 in real time, the molten pool information is reflected at the corresponding position of the monitoring interface, if the position is a normal position, the molten pool information is displayed in green, and if the position is an abnormal position, the molten pool information is displayed in red;
step four: after the layer of data is processed, the high-speed camera 20 collects the layer of forming plane data, and the controller 2 extracts and stores the layer of profile data of the workpiece; after the integral processing of the part is finished, generating a three-dimensional model according to each layer of profile data of the workpiece, and comparing and analyzing the currently generated three-dimensional model and an original three-dimensional model which is pre-built in a computer 1 to obtain the error of the metal 3D printed part and the original model data on the precision size; meanwhile, the abnormal position in the model is highlighted in red, and the number of layers is displayed for viewing.
And thirdly, taking the deviation range of the size of the molten pool deviating from the standard value as 5% -15%.
The standard value of the size of the molten pool is determined according to the powder material, the laser energy density and the scanning speed.
As described above, the present invention can be preferably realized.
the embodiments of the present invention are not limited to the above-described embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and they are included in the scope of the present invention.

Claims (4)

1. A3D prints the layer-by-layer and detects and reverses model of the part and positions the defect method, including 3D prints the layer-by-layer and detects and reverses model of the part and positions the defect device, should reverse model of the part and position the defect device and include: the laser head (3), the scanning galvanometer (9) and the computer (1); it is characterized by also comprising: a half-transmitting and half-reflecting mirror (16), a high-speed camera (20) and a controller (2); the high-speed camera (20) is in telecommunication connection with the computer (1) through the controller (2);
A laser light path (17) of the laser head (3) is reflected into the scanning galvanometer (9) through the semi-transparent semi-reflective mirror (16), and the scanning galvanometer (9) controls a laser beam to selectively melt metal powder paved on the working platform (15); meanwhile, a scanning galvanometer (9) collects molten pool radiation and transmits the molten pool radiation to a high-speed camera (20) through a semi-transparent semi-reflecting mirror (16), the high-speed camera (20) processes the molten pool radiation data and converts the molten pool radiation data into image information to be transmitted to a controller (2), and the controller (2) is used for processing the image data to determine the position of a molten pool and generate the outline of each melting layer;
The controller (2) includes:
the image acquisition module is used for controlling the high-speed camera (20) to acquire real-time image data of a molten pool in the forming process of each layer of the workpiece and storing the real-time image data in a memory of the workpiece;
The image contour extraction module is used for displaying the color image fed back to the high-speed camera (20) into a gray image and establishing a coordinate system of the gray image; filtering the gray level image by using a median filter template to smooth the image and remove noise; selecting a threshold value of the histogram as a minimum value by utilizing the gray histogram, carrying out binarization processing on the image according to the threshold value, dividing the image into molten pool pixel points and non-molten pool pixel points, and extracting a molten pool contour;
The image triangularization module is used for approximating the fault outline obtained by image processing by using polygons, then connecting adjacent fault polygon vertexes into a triangle, triangularizing the upper end face and the lower end face of the object and outputting an STL file;
When the working period starts, the image acquisition module acquires image information, the image information is transmitted to the image contour extraction module to extract the contour information of the molten pool, a process file is established according to the information, the processing state is fed back on a computer interface, and after the layer is processed, the contour of the layer is extracted according to the process file; the image triangularization module obtains a complete three-dimensional model of the workpiece according to the multilayer outline of the workpiece and outputs an STL file;
An optical filter (19) is additionally arranged on a light path between the high-speed camera (20) and the semi-transparent semi-reflecting mirror (16) and is used for filtering out a molten pool acquisition waveband;
the method for detecting and reversely solving the part model and positioning the defects layer by layer in the 3D printing is realized by the following steps:
The method comprises the following steps: the scanning galvanometer (9), the semi-transparent semi-reflecting mirror (16) and the optical filter (19) form a coaxial optical path, and the radiation light of the molten pool is reflected and filtered onto the high-speed camera (20) through the coaxial optical path;
Step two: establishing a coordinate system by taking the center of a forming plane of a workpiece as an original point, capturing the position of a molten pool on the forming plane by a high-speed camera (20) according to a plane forming track, and simultaneously recording the form of the molten pool at the position;
Step three: the size of the molten pool is obtained through image processing of the controller (2), and the abnormal position is recorded when the size of the molten pool deviates from the deviation range of the standard value, otherwise the normal position is recorded; the controller (2) feeds the position information back to a real-time monitoring interface of the computer (1) in real time, the molten pool information is reflected at the corresponding position of the monitoring interface, if the molten pool information is a normal position, the molten pool information is displayed in green, and if the molten pool information is an abnormal position, the molten pool information is displayed in red;
step four: after the layer of data is processed, the high-speed camera (20) collects the layer of forming plane data, and the controller (2) extracts and stores the layer of profile data of the workpiece; after the integral processing of the part is finished, generating a three-dimensional model according to each layer of profile data of the workpiece, and comparing and analyzing the currently generated three-dimensional model and an original three-dimensional model which is pre-built in a computer (1) to obtain the error of the metal 3D printed part and the original model data on the precision size; meanwhile, the abnormal position in the model is highlighted in red, and the number of layers is displayed for viewing.
2. The 3D printing layer-by-layer detection inverse part model and defect positioning method according to claim 1, characterized in that: the optical filter (19) adopts a narrow-band optical filter with the central wavelength within the range of 600-650 nm so as to ensure the spectral sensitivity of the high-speed camera (20).
3. The 3D printing layer-by-layer detection inverse part model and defect positioning method according to claim 1, characterized in that: the high-speed camera (20) is a COMS high-speed camera, the pixel resolution is not lower than 1024 multiplied by 1024, and the frame number can reach 7000 frames/second; the shortest exposure time of the whole shutter is 1 mu s; the dynamic range is 120 dB; spectral range 400nm-950nm, 8 bit sampling resolution.
4. the 3D printing layer-by-layer detection reverse part model and defect positioning method according to claim 1, wherein the deviation range of the size of the molten pool deviating from the standard value in the third step is 5% -15%.
CN201710245808.XA 2017-04-14 2017-04-14 device and method for detecting reverse part model and positioning defects layer by layer in 3D printing Active CN107175329B (en)

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