阅读说明：本技术 一种激光同轴熔融与检测反馈控制的增材制造系统 (Laser coaxial melting and detection feedback control additive manufacturing system ) 是由 王辉 黄卫东 叶盛 洪浩 郑建喜 张庆永 于 2020-12-21 设计创作，主要内容包括：本发明公开了一种激光同轴熔融与检测反馈控制的增材制造系统,包括激光成形系统、LIBS系统、双色高温计系统、控制系统。激光成形系统、LIBS系统、双色高温计系统,通过第一分束镜、第二分束镜、第三分束镜的串联,构成一个激光同轴熔融与检测反馈控制同时进行的系统。本发明利用激光诱导击穿光谱(LIBS)装置和双色高温计对功能梯度材料增材制造过程中的局部金属粉末混合比例及熔池温度进行实时在线检测,并根据局部的金属粉末混合比例及熔池温度对激光功率进行反馈控制,实现了功能梯度材料成形过程中的成形参数的实时调节,提高功能梯度材料的成形质量。(The invention discloses a laser coaxial melting and detection feedback control additive manufacturing system which comprises a laser forming system, an LIBS system, a two-color pyrometer system and a control system. The laser forming system, the LIBS system and the bicolor pyrometer system form a system for simultaneously carrying out laser coaxial melting and detection feedback control through the series connection of the first beam splitter, the second beam splitter and the third beam splitter. The invention utilizes a Laser Induced Breakdown Spectroscopy (LIBS) device and a bicolor pyrometer to carry out real-time online detection on the local metal powder mixing proportion and the molten pool temperature in the functional gradient material additive manufacturing process, and carries out feedback control on the laser power according to the local metal powder mixing proportion and the molten pool temperature, thereby realizing the real-time adjustment of the forming parameters in the functional gradient material forming process and improving the forming quality of the functional gradient material.)

1. A laser coaxial melting and detection feedback control additive manufacturing system comprises a forming chamber, and is characterized in that a fiber laser is arranged in the forming chamber and generates a forming laser beam; the forming laser beam sequentially passes through the beam isolator, the beam expander, the first beam splitter, the scanning galvanometer and the F-theta lens and is focused on the surface of the mixed powder in the forming cylinder at the bottom of the forming chamber to melt the mixed powder; after the shaping laser beam leaves the surface of the powder, the melted powder is solidified to form a shaped piece;

the bottom of the forming chamber is provided with a powder spreading roller, the powder to be treated is uniformly spread on the upper surface of the existing powder of the forming cylinder by the powder spreading roller, and the redundant powder enters the bottom of the forming cylinder of the powder recovery cylinder under the action of the powder spreading roller and is provided with a first lifting platform and a second lifting platform at the bottom of the recovery cylinder;

the additive manufacturing system comprises an LIBS laser, wherein the LIBS laser generates LIBS pulse laser, and the LIBS pulse laser forms plasma on the forming surface of the powder to be processed after being reflected by a second beam splitter, transmitted by a first beam splitter, reflected by a scanning vibrating mirror and converged by an F-theta mirror;

the additive manufacturing system further comprises a spectrometer and a dual-color pyrometer;

forming a laser beam to melt the powder to be processed and then emitting a composite spectrum; the composite spectrum is received by the bicolor pyrometer after passing through the F-theta mirror, the scanning galvanometer, the first beam splitter, the second beam splitter, the third beam splitter and the second lens group;

the plasma radiates a plasma composite spectrum, and the plasma composite spectrum is received by the spectrometer after passing through the F-theta lens, the scanning galvanometer, the first beam splitter, the second beam splitter, the third beam splitter and the first lens group;

the fiber laser, the LIBS laser, the spectrometer and the bicolor pyrometer are all connected with a computer, after laser beams are formed to melt powder to be processed, the computer controls the bicolor pyrometer to collect composite spectra emitted by the melted powder to be processed, after the bicolor pyrometer collects spectral information of the composite spectra, the computer controls the LIBS laser to generate LIBS pulse laser, and after a certain time delay, the computer control system controls the spectrometer to collect plasma radiation to form the plasma composite spectra;

the computer performs feedback adjustment on the laser power of the forming laser beam generated by the fiber laser according to the temperature information of the molten powder to be processed collected by the two-color pyrometer and the component information of the powder to be processed collected by the spectrometer;

the forming chamber is also internally provided with a powder mixing system for generating powder, the powder mixing system comprises at least 2 powder storage tanks, the bottom of each powder storage tank is provided with a powder outlet, and the powder outlet is provided with a valve controlled by a computer; the powder at each powder outlet falls into the powder premixing device; the powder mixing device mixes different material powders into functionally graded material powder, and the functionally graded material powder falls onto the bottom surface of the forming chamber.

2. A laser in-line melting and detection feedback controlled additive manufacturing system according to claim 1, wherein: the first lens group at least comprises a lens with positive diopter; the second lens group at least comprises a lens with positive diopter.

Technical Field

The invention belongs to the technical field of additive manufacturing, and relates to a laser coaxial melting and detection feedback control additive manufacturing system.

Background

The laser additive manufacturing technology is a forming mode for realizing part forming by layering a three-dimensional model of a part, planning a forming path according to the layering condition and finally melting materials by laser and utilizing a mode of accumulation from bottom to top, and is a novel manufacturing method for realizing rapid forming and manufacturing of three-dimensional parts. Through laser additive manufacturing, the aim of manufacturing the three-dimensional part by stacking and welding metal material powder layer by layer can be achieved.

The functionally graded material is a novel composite material which is formed by compounding two or more materials and has continuously graded components and structures, namely, the components of the material are continuously changed from one side to the other side along the thickness direction, so that the properties and functions of the material are continuously changed. Laser additive manufacturing techniques can be used to manufacture functionally graded materials, wherein the use of mixed powders of metallic materials to manufacture functionally graded materials is one of the important applications in the field of laser additive manufacturing.

In order to control the forming quality during the laser additive manufacturing process, the temperature of the molten pool of the forming material should be controlled within a reasonable range. During the forming process, the temperature of the molten pool changes dramatically, which may cause unpredictable cracks and bubbles in the formed parts. For the forming of the functionally graded material, the metal powder mixing ratio in different gradient regions is different, that is, the metal powder mixing ratio corresponds to the requirements of different forming temperatures, so that the feedback control of the forming laser power is further required to be realized through the real-time online monitoring of the metal powder mixing ratio and the forming temperature. Furthermore, the real-time online monitoring of the metal powder mixing ratio and the forming temperature can realize the real-time optimization of important forming parameters such as laser power, scanning distance, scanning speed, substrate powder thickness and the like.

The Laser Induced Breakdown Spectroscopy (LIBS) technique is a material composition detection technique that uses high-energy laser pulses focused on the surface of a sample, when the high-energy laser is focused on the surface of the material and reaches an optical breakdown threshold, a portion of the material at the focused portion of the sample is converted into a plasma state, then a signal collector is used to collect the spectrum from the plasma, and the collected spectral information is analyzed by a spectrometer, so that the composition and composition ratio of the sample to be detected can be accurately determined. A bicolor radiation pyrometer is also called as a colorimetric pyrometer, and is used for determining the temperature of an object by utilizing the single-value relation between the ratio of two paths of output signals of spectral radiance after photoelectric conversion and the temperature of two different wave bands emitted by the same object. The theory of the non-contact temperature measurement is derived from Planck's theorem of blackbody radiation energy distribution. The bicolor radiation pyrometer has small interference to temperature detection caused by smoke, impurities, protective gas and the like between the probe and a detection object, and can accurately detect the high-temperature molten pool temperature of materials in the laser additive manufacturing process. By utilizing the temperature monitoring of the bicolor radiation pyrometer and the component detection of the LIBS device, the laser additive manufacturing process of the functional gradient material can be monitored in real time and feedback controlled.

Disclosure of Invention

The invention aims to provide an additive manufacturing system for realizing laser coaxial melting and detection feedback control of a functional gradient material.

The technical scheme adopted by the invention is as follows:

a functional gradient material laser coaxial melting and detection feedback control additive manufacturing system comprises a forming chamber, wherein a fiber laser is arranged in the forming chamber and generates a forming laser beam; the forming laser beam sequentially passes through the beam isolator, the beam expander, the first beam splitter, the scanning galvanometer and the F-theta lens and is focused on the surface of the mixed powder in the forming cylinder at the bottom of the forming chamber to melt the mixed powder; after the shaping laser beam leaves the surface of the powder, the melted powder is solidified to form a shaped piece;

the bottom of the forming chamber is provided with a powder spreading roller, the powder to be treated is uniformly spread on the upper surface of the existing powder of the forming cylinder by the powder spreading roller, and the redundant powder enters the bottom of the forming cylinder of the powder recovery cylinder under the action of the powder spreading roller and is provided with a first lifting platform and a second lifting platform at the bottom of the recovery cylinder;

the additive manufacturing system comprises an LIBS laser, wherein the LIBS laser generates LIBS pulse laser, and the LIBS pulse laser forms plasma on the forming surface of the powder to be processed after being reflected by a second beam splitter, transmitted by a first beam splitter, reflected by a scanning vibrating mirror and converged by an F-theta mirror;

the additive manufacturing system further comprises a spectrometer and a dual-color pyrometer;

forming a laser beam to melt the powder to be processed and then emitting a composite spectrum; the composite spectrum is received by the bicolor pyrometer after passing through the F-theta mirror, the scanning galvanometer, the first beam splitter, the second beam splitter, the third beam splitter and the second lens group;

the plasma radiates a plasma composite spectrum, and the plasma composite spectrum is received by the spectrometer after passing through the F-theta lens, the scanning galvanometer, the first beam splitter, the second beam splitter, the third beam splitter and the first lens group;

the fiber laser, the LIBS laser, the spectrometer and the bicolor pyrometer are all connected with a computer, after laser beams are formed to melt powder to be processed, the computer controls the bicolor pyrometer to collect composite spectra emitted by the melted powder to be processed, after the bicolor pyrometer collects spectral information of the composite spectra, the computer controls the LIBS laser to generate LIBS pulse laser, and after a certain time delay, the computer control system controls the spectrometer to collect plasma radiation to form the plasma composite spectra;

the computer performs feedback adjustment on the laser power of the forming laser beam generated by the fiber laser according to the temperature information of the molten powder to be processed collected by the two-color pyrometer and the component information of the powder to be processed collected by the spectrometer;

the forming chamber is also internally provided with a powder mixing system for generating powder, the powder mixing system comprises at least 2 powder storage tanks, the bottom of each powder storage tank is provided with a powder outlet, and the powder outlet is provided with a valve controlled by a computer; the powder at each powder outlet falls into the powder premixing device; the powder mixing device mixes different material powders into functionally graded material powder, and the functionally graded material powder falls onto the bottom surface of the forming chamber.

Further, the first lens group at least comprises a lens with positive diopter; the second lens group at least comprises a lens with positive diopter. The invention has the beneficial effects that:

(1) the invention provides an additive manufacturing system for realizing laser coaxial melting and detection feedback control of a functional gradient material, which comprises the following steps: the laser melting forming system, the LIBS (laser induced breakdown spectroscopy) system and the bicolor pyrometer system share one set of optical system, belong to a coaxial optical path, can comprehensively acquire the component information and the temperature information of a laser melting point in situ, and have compact system structure.

(2) The bicolor pyrometer detects the temperature by utilizing the ratio of spectral radiant energy under two wavelengths of an object, can compensate the measurement error caused by protective atmosphere and local smoke dust in the additive manufacturing cavity, and effectively reduces the measurement error of the temperature of a molten pool caused by the protective atmosphere and the local smoke dust.

(3) The device is mainly used for the forming and manufacturing process of the functional gradient material, the powder proportion and the molten pool temperature of the functional gradient material in the forming process are monitored in real time, and the forming laser power and other forming parameters are regulated and controlled according to the powder proportion, so that the purpose of reducing the defects of cracks, bubbles and the like of a formed part is achieved.

Drawings

Fig. 1 is a schematic structural view of the present invention.

In the figure: 1. a forming chamber, 2, a protective gas chamber, 3, a fiber laser, 3a, a first fiber, 4, a forming laser beam, 5, a beam isolator, 6, a beam expander, 7, a first beam splitter, 8, a scanning galvanometer, 9, an F-theta lens, 10, powder to be processed, 11, a forming piece, 12, a LIBS laser, 12a, a second fiber, 13, LIBS pulse laser, 14, a second beam splitter, 15, a plasma composite spectrum, 16, a third beam splitter, 17, a first lens group, 18, a spectrometer, 18a, a third fiber, 19, a composite spectrum, 20, a second lens group, 21, a bicolor pyrometer, 21a fourth fiber, 22, a computer control system, 23, a first powder storage tank, 24, a second powder storage tank, 25, a powder mixing device, 26, a powder laying roller, 27, functional gradient material powder, 28, a forming cylinder, 29, a first lifting table, 30, a powder recovery cylinder, 31. a second lifting platform.

Detailed Description

The invention is further described below with reference to the accompanying drawings.

As shown in fig. 1, an additive manufacturing system for implementing laser coaxial melting and detection feedback control of a functionally graded material includes a laser forming system, a LIBS system, a two-color pyrometer system, and a control system.

The device can adopt 1064nm laser as a LIBS laser source.

The working process of the invention is as follows:

the first powder storage tank 23 and the second powder storage tank 24 store different material powders, respectively, and after the different material powders fall into the powder mixing device 25, the powder mixing device 25 mixes the different material powders to form functionally graded material powder 27, and the functionally graded material powder falls onto the bottom surface of the forming chamber 1. The powder spreading roller 26 uniformly spreads the functionally graded material powder 27 on the upper surface of the existing powder 10 to be treated in the forming cylinder 28, and the redundant powder 10 to be treated enters the powder recovery cylinder 30 under the action of the powder spreading roller 26. The computer control system 22 controls the fiber laser 3 to generate a shaped laser beam 4, and the shaped laser beam 4 is focused on the surface of the powder 10 to be processed through the beam isolator 5, the beam expander 6, the first beam splitter 7, the scanning galvanometer 8 and the F-theta lens 9, so that the powder 10 to be processed is melted. After the shaping laser beam 4 leaves the surface of the powder 10 to be treated, the already molten powder 10 to be treated solidifies to form the shaped part 11. The beam isolator 5 is used for blocking reflected laser, and the beam expander 6 is used for expanding the light beam and improving the collimation characteristic of the light beam. A first beam splitter 7 and a scanning galvanometer 8 are used to alter the path of the shaped laser beam 4. The F-theta mirror 9 is used to form the shaped laser beam 4 into a focused spot of uniform size on the shaped surface of the powder 10 to be treated.

After the shaping laser beam 4 has melted the powder 10 to be treated, the melted material will emit a composite spectrum 19. After the composite spectrum 19 is diffused by the F-theta mirror 9, reflected by the scanning galvanometer 8, transmitted by the first beam splitter 7, transmitted by the second beam splitter 14, transmitted by the third beam splitter 16 and converged by the second lens group 20, the computer control system 22 controls the bicolor pyrometer 21 to receive the composite spectrum 19, and the temperature of the molten powder 10 to be processed is further measured.

After the dual-color pyrometer 21 finishes collecting the spectrum information of the composite spectrum 19, the computer control system 22 controls the LIBS laser 12 to generate LIBS pulse laser 13, the LIBS pulse laser 13 is reflected by the second beam splitter 14, transmitted by the first beam splitter 7, reflected by the scanning galvanometer 8 and converged by the F-theta mirror 9, plasma is formed on the forming surface of the powder 10 to be processed, and the plasma radiates out of the plasma composite spectrum 15. The plasma composite spectrum 15 is received by the spectrometer 18 after being diffused by the F-theta mirror 9, reflected by the scanning galvanometer 8, transmitted by the first beam splitter 7, transmitted by the second beam splitter 14, reflected by the third beam splitter 16 and converged by the first lens group 17, and after a certain delay, the computer control system 22 controls the spectrometer 18 to collect plasma radiation to form the plasma composite spectrum 15. The collection of the composite spectrum 19 by the two-color pyrometer 21 is earlier than the collection of the plasma radiation by the spectrometer 18 out of the plasma composite spectrum 15, which effectively avoids the effect of the high temperature of the plasma caused by the LIBS pulsed laser 13 on the actual temperature measurement of the molten powder 10 to be treated.

The computer control system 22 can perform feedback adjustment on the laser power of the forming laser beam 4 generated by the fiber laser 3 according to the temperature information of the melted powder to be processed 10 collected by the two-color pyrometer 21 and the component information of the powder to be processed 10 collected by the spectrometer 18, so as to realize that the functional gradient material powders with different material ratios correspond to different laser powers, thereby improving the forming quality of the functional gradient material.

After a layer of powder 10 to be treated is melted and formed, the first lifting platform 29 is lowered by one layer, the powder laying roller 26 starts laying powder again, and a new layer of printing work is started. The second elevating platform 31 adjusts the height of the powder stored in the powder recovery cylinder 30 so that the height of the powder is not higher than the bottom surface of the molding chamber 1 by way of lowering.

In the present invention, the first lens group 17 includes at least one lens having a positive refractive power, and the second lens group 20 includes at least one lens having a positive refractive power.

The laser forming system, the LIBS system and the bicolor pyrometer system form a system for simultaneously carrying out laser coaxial melting and detection feedback control through the series connection of the first beam splitter 7, the second beam splitter 14 and the third beam splitter 16.

The number of the first powder storage tanks 23 or the second powder storage tanks 24 is not limited, and the number of the powder storage tanks may be increased according to the increase of the kinds of the powder materials.

The protective gas chamber 2 is connected with the forming chamber 1, the protective gas chamber 2 provides protective gas to prevent the powder from being oxidized, and the detection process and the forming process of the powder are protected.

The foregoing detailed description is intended to illustrate and not limit the invention, which is intended to be within the spirit and scope of the appended claims, and any changes and modifications that fall within the true spirit and scope of the invention are intended to be covered by the following claims.