Real-time detection system and method for molten pool in selective laser melting 3D printing process

Abstract

The invention provides a real-time detection system for a molten pool in the selective laser melting 3D printing process. The real-time detection system comprises a forming substrate, a coaxial optical system, a molten pool radiation detection device, an optical fiber laser and an industrial personal computer. The molten pool radiation detection device comprises a photoelectric detection circuit module, a data preprocessing module and a power management module; the industrial personal computer is connected with the molten pool radiation detection module and is in telecommunication connection with the fiber laser and the coaxial optical system; the photoelectric detection circuit module is configured to be used for collecting radiation light signals of a molten pool and amplifying the radiation light signals through a two-stage amplifier. Therefore, rapid detection of weak molten pool radiation light signals is met.

Description

Technical Field

[0001] The present application relates to the field of real-time monitoring of laser selective melting, and specifically to a system and method for real-time detection of a molten pool in a laser selective melting 3D printing process. Background Art

[0002] Selective Laser Melting (SLM) is considered one of the most advanced and promising technologies. This technology uses laser to move and irradiate the powder layer to melt and deposit the powder. It integrates laser, precision transmission, new materials and CAD / CAM technologies. The powder materials used include titanium alloy, stainless steel, high-temperature alloy, tungsten alloy, etc. The printed workpiece has the advantages of high precision, good surface quality and nearly 100% density, and can achieve mechanical properties close to those of traditional forging process materials.

[0003] Under the action of highly directional heat input and rapid heat source, the powder bed undergoes a rapid melting and solidification process locally, generating a large temperature gradient and transient thermal stress in the spot area. As the thermal cycle proceeds, some thermal stress is released, but most of it is left behind, forming residual stress. If the heat input cannot be effectively controlled during the forming process, the accumulation of local thermal stress and the formation of residual stress cannot be guided and controlled, the microstructure performance of the part will eventually decrease, causing the part to warp, deform, crack, and form metallurgical defects such as micropores and microcracks.

[0004] Currently, there is no accurate method to measure the molten pool temperature during the selective laser melting printing process. Most of the monitoring of the molten pool thermal process uses infrared thermal imagers. This method is limited by the response speed of the thermal imager. The required level of molten pool monitoring is at the us level, and thermal imagers are far from reaching this speed. Summary of the invention

[0005] In order to solve the above technical problems, in the first aspect of the present application, a real-time detection system for a molten pool in a laser selective melting 3D printing process is proposed, comprising: a molding substrate, a coaxial optical system, a molten pool radiation detection device, an optical fiber laser and an industrial computer; the molten pool radiation detection device comprises a photoelectric detection circuit module, a data preprocessing module and a power management module; the industrial computer is connected to the molten pool radiation detection module, and is electrically connected to the optical fiber laser and the coaxial optical system; the photoelectric detection circuit module is configured to collect the radiation light signal of the molten pool, and amplify the radiation light signal through a two-stage amplifier.

[0006] Through the above-mentioned technical means, the applicant built an eye tracking interaction system to collect the gaze points of open eyes in real time, obtain the user's gaze points on the real scene through the eye tracking deep learning model, and determine whether the user is looking at a specific real target, thereby realizing the control of real objects through eye movements.

[0007] Preferably, the coaxial optical system includes: a beam expander, a galvanometer system, a coaxial beam splitter, a narrowband filter and a field lens; the optical fiber laser, the beam expander, the galvanometer system and the field lens are optically connected in sequence; the field lens, the galvanometer system, the coaxial beam splitter and the narrowband filter are optically connected in sequence.

[0008] Preferably, the galvanometer system comprises: a first reflector and a second reflector; the first reflector and the second reflector change their rotation angles in response to a control signal from an industrial computer.

[0009] Preferably, the coaxial beam splitter comprises: a beam splitter, a total reflection mirror, a first lens and a second lens.

[0010] Preferably, the total reflection mirror can change the reflection angle in response to the instruction of the industrial computer.

[0011] Preferably, the narrowband filter includes: a first narrowband filter and a second narrowband filter; the field mirror, the second reflector, the first reflector, the beam splitter, the beam splitter, the first lens and the first narrowband filter are optically connected in sequence; the field mirror, the second reflector, the first reflector, the beam splitter, the beam splitter, the second lens and the second narrowband filter are optically connected in sequence; and radiation light signals of different wavelengths are respectively transmitted to the photoelectric detection circuit module through the first narrowband filter and the second narrowband filter.

[0012] Preferably, the field mirror is an f-θ field mirror after achromatization processing is performed on the laser wavelength and the radiation wavelength.

[0013] Preferably, the photoelectric detection circuit module includes: a first comparator, a second comparator, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor and a photosensitive diode; the reverse input terminal of the first comparator is simultaneously connected to the second resistor, the third capacitor and the photosensitive diode; the non-inverting input terminal of the first comparator is simultaneously connected to the first capacitor and the third resistor, and is connected to the second comparator through the third resistor; the output terminal of the first comparator is connected to the inverting input terminal of the second comparator through the first resistor and the fifth resistor; the second capacitor is connected in parallel across the first resistor; the fourth capacitor is connected in parallel to the output terminal and the inverting input terminal of the second comparator.

[0014] In a second aspect of the present application, a method for real-time detection of a molten pool in a laser selective melting 3D printing process is provided, which specifically comprises the following steps:

[0015] S1, the laser is emitted by the fiber laser, passes through the beam expander in one direction, and then is deflected by the galvanometer system and focused by the field lens, and then transmitted to the surface of the molding substrate to melt the metal powder to form a molten pool;

[0016] S2, the radiant light of the molten pool passes through the field mirror, the galvanometer system and the beam splitter in the reverse direction, and returns to the beam splitter, and the beam splitter transmits the radiant light to the first lens and the total reflection mirror respectively, the radiant light passing through the first lens passes through the first narrow-band filter and transmits the radiant light signal with a wavelength of λ1 to the photoelectric detection circuit module, and the radiant light passing through the total reflection mirror passes through the second lens and the second narrow-band filter and transmits the radiant light signal with a wavelength of λ2 to the photoelectric detection circuit module;

[0017] S3, the radiated light signal with a wavelength of λ1 and the radiated light signal with a wavelength of λ2 are amplified by the photoelectric detection circuit module, converted into analog signals and transmitted to the data preprocessing and communication module, and then transmitted to the industrial computer after being processed by the data preprocessing and communication module;

[0018] S4. The industrial computer uses a two-color temperature measurement method to calculate the measured temperature of the molten pool in real time and generate a real-time temperature field of the molten pool.

[0019] Preferably, S3 further includes: a photoelectric detection circuit module simultaneously collecting laser power data of laser emitted by the optical fiber laser.

[0020] Compared with the prior art, the beneficial results of this application are:

[0021] 1. Amplification circuit to meet the rapid detection of weak molten pool radiation light signals;

[0022] 2. The molten pool temperature control system reduces the influence of many practical factors on the emissivity by comparing the molten pool radiation intensity at dual wavelengths;

[0023] 3. The light radiation and laser power data collected by the light spot detection circuit are transmitted to the industrial computer in real time and completely, and the industrial computer is used to integrate and analyze data such as the location of the molten pool and its radiation signal intensity, thereby realizing functions such as three-dimensional display of the molten pool detection temperature, query of the current oxygen content of the powder, defect identification and real-time query of the optimal processing temperature of the powder. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are included to provide a further understanding of the embodiments and are incorporated into and constitute a part of this specification. The accompanying drawings illustrate the embodiments and are used together with the description to explain the principles of the present application. It will be easy to recognize other embodiments and many expected advantages of the embodiments because they become better understood by reference to the following detailed description. The elements of the drawings are not necessarily to scale with each other. The same reference numerals refer to corresponding similar parts.

[0025] Figure 1 It is an overall block diagram of a real-time detection system for a molten pool in a laser selective melting 3D printing process according to an embodiment of the present application;

[0026] Figure 2This is a system schematic diagram of a real-time detection system for a molten pool in a laser selective melting 3D printing process according to an embodiment of the present application;

[0027] Figure 3 This is a schematic diagram of a coaxial optical system of a real-time detection system for a molten pool in a laser selective melting 3D printing process according to an embodiment of the present application;

[0028] Figure 4 It is a circuit structure diagram of a photoelectric detection circuit module of a real-time detection system for a molten pool in a laser selective melting 3D printing process according to an embodiment of the present application.

[0029] Description of reference numerals:

[0030] R1, first resistor; R2, second resistor; R3, third resistor; R4, fourth resistor; R5, fifth resistor; C1, first capacitor; C2, second capacitor; C3, third capacitor; C4, fourth capacitor; D1, first comparator; D2, second comparator; VD, photodiode; E, beam expander; P, beam splitter; S1, first reflector; S2, second reflector; F, field mirror; A, beam splitter; B, total reflector; C, lens; L1, first narrow-band filter; L2, second narrow-band filter. DETAILED DESCRIPTION

[0031] In the following detailed description, reference is made to the accompanying drawings, which form a part of the detailed description and are shown by illustrative specific embodiments in which the present application can be practiced. To this end, directional terms, such as "top", "bottom", "left", "right", "up", "down", etc., are used with reference to the orientation of the figures described. Because the components of the embodiments can be positioned in several different orientations, directional terms are used for the purpose of illustration and are by no means limiting. It should be understood that other embodiments may be utilized or logical changes may be made without departing from the scope of the present application. Therefore, the following detailed description should not be adopted in a limiting sense, and the scope of the present application is defined by the appended claims.

[0032] like Figures 1 to 3 As shown, it includes: a forming substrate, a coaxial optical system, a molten pool radiation detection device, an optical fiber laser and an industrial computer; the molten pool radiation detection device includes a photoelectric detection circuit module, a data preprocessing module and a power management module; the industrial computer is connected to the molten pool radiation detection module, and is electrically connected to the optical fiber laser and the coaxial optical system; the photoelectric detection circuit module is configured to collect the radiation light signal of the molten pool, and amplify the radiation light signal through a two-stage amplifier.

[0033] Specifically, the coaxial optical system includes: a beam expander E, a galvanometer system, a coaxial beam splitter P, a narrow-band filter and a field lens F; the optical fiber laser, the beam expander E, the galvanometer system and the field lens F are optically connected in sequence; the field lens F, the galvanometer system, the coaxial beam splitter P and the narrow-band filter are optically connected in sequence.

[0034] The galvanometer system includes: a first reflector S1 and a second reflector S2; the first reflector S1 and the second reflector S2 change the rotation angle in response to the control signal of the industrial computer.

[0035] The coaxial beam splitter P comprises a beam splitter A, a total reflection mirror B, a first lens C and a second lens C.

[0036] The total reflection mirror B can change the reflection angle in response to the instructions of the industrial computer.

[0037] The narrowband filter includes: a first narrowband filter L1 and a second narrowband filter L2; a field lens F, a second reflector S2, a first reflector S1, a beam splitter P, a beam splitter A, a first lens C and the first narrowband filter L1 are optically connected in sequence; the field lens F, the second reflector S2, the first reflector S1, the beam splitter P, the beam splitter A, the second lens C and the second narrowband filter L2 are optically connected in sequence; and radiation light signals of different wavelengths are respectively transmitted to the photoelectric detection circuit module through the first narrowband filter L1 and the second narrowband filter L2.

[0038] The field lens F is an f-θ field lens F after achromatization processing is performed on the laser wavelength and the radiation wavelength.

[0039] Figure 4 is a circuit structure diagram of a photoelectric detection circuit module of a real-time detection system for a molten pool in a laser selective melting 3D printing process according to an embodiment of the present application, such as Figure 4 The photoelectric detection circuit module includes: a first comparator D1, a second comparator D2, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4 and a photosensitive diode VD; the inverting input end of the first comparator D1 is simultaneously connected to the second resistor R2, the third capacitor C3 and the photosensitive diode VD; the in-phase input end of the first comparator D1 is simultaneously connected to the first capacitor C1 and the third resistor R3, and is connected to the second comparator D2 through the third resistor R3; the output end of the first comparator D1 is connected to the inverting input end of the second comparator D2 through the first resistor R1 and the fifth resistor R5; the second capacitor C2 is connected in parallel at both ends of the first resistor R1; the fourth capacitor C4 is connected in parallel to the output end and the inverting input end of the second comparator D2. The collected radiation light signal is amplified by a two-stage comparator, so that the detection circuit has the performance of high magnification, wide bandwidth, low drift, and a certain anti-interference ability, thereby meeting the demand for rapid detection of weak molten pool radiation light signals.

[0040] At the same time, in order to better understand the technical solution of the present application, in a specific embodiment, the working process of the system is as follows:

[0041] S1, the laser is emitted by the fiber laser, passes through the beam expander in one direction, and then is deflected by the galvanometer system and focused by the field lens, and then transmitted to the surface of the molding substrate to melt the metal powder to form a molten pool;

[0042] S2, the radiant light of the molten pool passes through the field mirror, the galvanometer system and the beam splitter in the reverse direction, and returns to the beam splitter, and the beam splitter transmits the radiant light to the first lens and the total reflection mirror respectively, the radiant light passing through the first lens passes through the first narrow-band filter and transmits the radiant light signal with a wavelength of λ1 to the photoelectric detection circuit module, and the radiant light passing through the total reflection mirror passes through the second lens and the second narrow-band filter and transmits the radiant light signal with a wavelength of λ2 to the photoelectric detection circuit module;

[0043] S3, the radiated light signal with a wavelength of λ1 and the radiated light signal with a wavelength of λ2 are amplified by the photoelectric detection circuit module, converted into analog signals and transmitted to the data preprocessing and communication module, and then transmitted to the industrial computer after being processed by the data preprocessing and communication module;

[0044] S4. The industrial computer uses a two-color temperature measurement method to calculate the measured temperature of the molten pool in real time and generate a real-time temperature field of the molten pool.

[0045] More specifically, S3 also includes: a photoelectric detection circuit module simultaneously collects laser power data of the laser emitted by the optical fiber laser.

[0046] The technical solution of the present application solves the following problems well: 1. Since the working wavelength is outside the red zone, the interference caused by the background environment is very large; 2. The radiation light from the molten pool itself is very weak and contains certain noise.

[0047] By designing an amplifier circuit with a composite structure, the photoelectric detection circuit module has the performance of high magnification, wide bandwidth, low drift, and a certain anti-interference ability, thus meeting the demand for rapid detection of weak molten pool radiation light signals.

[0048] And through the two-color temperature measurement method, the influence of many practical factors on emissivity can be weakened.

[0049] Obviously, those skilled in the art can make various modifications and changes to the embodiments of the present application without departing from the spirit and scope of the present application. In this way, if these modifications and changes are within the scope of the claims of the present application and their equivalents, the present application is also intended to cover these modifications and changes. The word "comprising" does not exclude the presence of other elements or steps not listed in the claims. The simple fact that certain measures are recorded in mutually different dependent claims does not indicate that the combination of these measures cannot be used to profit. Any figure mark in the claims should not be considered to limit the scope.

Claims

1. A real-time detection system for the molten pool in a laser selective melting 3D printing process, characterized in that: include: Forming substrate, coaxial optical system, molten pool radiation detection device, fiber laser and industrial computer; The molten pool radiation detection device includes a photoelectric detection circuit module, a data preprocessing module and a power management module; the industrial computer is connected to the molten pool radiation detection module, and is electrically connected to the optical fiber laser and the coaxial optical system; the photoelectric detection circuit module is configured to collect the radiation light signal of the molten pool, and amplify the radiation light signal through a two-stage amplifier.

2. A real-time detection system for molten pool in laser selective melting 3D printing process according to claim 1, characterized in that: The coaxial optical system comprises: a beam expander, a galvanometer system, a coaxial beam splitter, a narrowband filter and a field lens; the optical fiber laser, the beam expander, the galvanometer system and the field lens are optically connected in sequence; the field lens, the galvanometer system, the coaxial beam splitter and the narrowband filter are optically connected in sequence.

3. A real-time detection system for molten pool in laser selective melting 3D printing process according to claim 2, characterized in that: The galvanometer system includes: a first reflector and a second reflector; the first reflector and the second reflector change their rotation angles in response to the control signal of the industrial computer.

4. A real-time detection system for molten pool in laser selective melting 3D printing process according to claim 3, characterized in that: The coaxial beam splitter comprises a beam splitter, a total reflection mirror, a first lens and a second lens.

5. A real-time detection system for molten pool in laser selective melting 3D printing process according to claim 4, characterized in that: The total reflection mirror can change the reflection angle in response to the instruction of the industrial computer.

6. A real-time detection system for molten pool in laser selective melting 3D printing process according to claim 5, characterized in that: The narrowband filter includes: a first narrowband filter and a second narrowband filter; the field mirror, the second reflector, the first reflector, the beam splitter, the beam splitter, the first lens and the first narrowband filter are optically connected in sequence; the field mirror, the second reflector, the first reflector, the beam splitter, the beam splitter, the second lens and the second narrowband filter are optically connected in sequence; and radiation light signals of different wavelengths are respectively transmitted to the photoelectric detection circuit module through the first narrowband filter and the second narrowband filter.

7. A real-time detection system for molten pool in laser selective melting 3D printing process according to claim 6, characterized in that: The field mirror is an f-θ field mirror after achromatization processing is performed on the laser wavelength and the radiation wavelength.

8. A real-time detection system for molten pool in laser selective melting 3D printing process according to claim 7, characterized in that: The photoelectric detection circuit module includes: a first comparator, a second comparator, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor and a photosensitive diode; the inverting input terminal of the first comparator is simultaneously connected to the second resistor, the third capacitor and the photosensitive diode; the in-phase input terminal of the first comparator is simultaneously connected to the first capacitor and the third resistor, and is connected to the second comparator through the third resistor; the output terminal of the first comparator is connected to the inverting input terminal of the second comparator through the first resistor and the fifth resistor; the second capacitor is connected in parallel at both ends of the first resistor; the fourth capacitor is connected in parallel to the output terminal and the inverting input terminal of the second comparator.

9. A method for real-time detection of molten pool in laser selective melting 3D printing process, characterized in that: The method is implemented by using a real-time detection system for a molten pool in a laser selective melting 3D printing process as described in claim 8, and specifically comprises the following steps: S1, the fiber laser emits laser light, the laser light passes through the beam expander in one direction, and then is deflected by the galvanometer system and focused by the field lens, and then transmitted to the surface of the molding substrate to melt the metal powder to form a molten pool; S2, the radiant light of the molten pool passes through the field mirror, the galvanometer system and the beam splitter in reverse, and returns to the beam splitter, and the beam splitter transmits the radiant light to the first lens and the total reflection mirror respectively, the radiant light passing through the first lens passes through the first narrow-band filter and transmits the radiant light signal with a wavelength of λ1 to the photoelectric detection circuit module, and the radiant light passing through the total reflection mirror passes through the second lens and the second narrow-band filter and transmits the radiant light signal with a wavelength of λ2 to the photoelectric detection circuit module; S3, the radiated light signal with a wavelength of λ1 and the radiated light signal with a wavelength of λ2 are amplified by the photoelectric detection circuit module, converted into analog signals and transmitted to the data preprocessing and communication module, and then transmitted to the industrial computer after being processed by the data preprocessing and communication module; S4. The industrial computer uses a two-color temperature measurement method to calculate the measured temperature of the molten pool in real time and generate a real-time temperature field of the molten pool.

10. A method for real-time detection of molten pool in laser selective melting 3D printing process according to claim 9, characterized in that: The S3 also includes: the photoelectric detection circuit module simultaneously collects laser power data of the laser emitted by the optical fiber laser.

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