CN116618823A - Closed-loop regulation and control system and method for wire-guide ultrasonic-assisted laser additive manufacturing - Google Patents
Closed-loop regulation and control system and method for wire-guide ultrasonic-assisted laser additive manufacturing Download PDFInfo
- Publication number
- CN116618823A CN116618823A CN202310525093.9A CN202310525093A CN116618823A CN 116618823 A CN116618823 A CN 116618823A CN 202310525093 A CN202310525093 A CN 202310525093A CN 116618823 A CN116618823 A CN 116618823A
- Authority
- CN
- China
- Prior art keywords
- wire
- molten pool
- laser
- ultrasonic
- state
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 238000000034 method Methods 0.000 title claims abstract description 48
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 45
- 239000000654 additive Substances 0.000 title claims abstract description 44
- 230000000996 additive effect Effects 0.000 title claims abstract description 44
- 230000033228 biological regulation Effects 0.000 title claims abstract description 38
- 230000007704 transition Effects 0.000 claims abstract description 93
- 238000012545 processing Methods 0.000 claims abstract description 70
- 238000012544 monitoring process Methods 0.000 claims abstract description 66
- 238000011065 in-situ storage Methods 0.000 claims abstract description 26
- 230000009123 feedback regulation Effects 0.000 claims abstract description 19
- 239000007788 liquid Substances 0.000 claims description 50
- 230000000694 effects Effects 0.000 claims description 34
- 238000002844 melting Methods 0.000 claims description 27
- 230000008569 process Effects 0.000 claims description 20
- 230000001105 regulatory effect Effects 0.000 claims description 18
- 238000001914 filtration Methods 0.000 claims description 16
- 238000007781 pre-processing Methods 0.000 claims description 16
- 230000009467 reduction Effects 0.000 claims description 16
- 238000000605 extraction Methods 0.000 claims description 14
- 230000010355 oscillation Effects 0.000 claims description 14
- 238000012360 testing method Methods 0.000 claims description 14
- 238000002604 ultrasonography Methods 0.000 claims description 14
- 239000007787 solid Substances 0.000 claims description 13
- 239000000758 substrate Substances 0.000 claims description 13
- 230000000007 visual effect Effects 0.000 claims description 12
- 238000007711 solidification Methods 0.000 claims description 10
- 230000008023 solidification Effects 0.000 claims description 10
- 230000003287 optical effect Effects 0.000 claims description 9
- 229910000838 Al alloy Inorganic materials 0.000 claims description 8
- 239000000463 material Substances 0.000 claims description 8
- 230000008018 melting Effects 0.000 claims description 7
- 239000013307 optical fiber Substances 0.000 claims description 7
- 238000004364 calculation method Methods 0.000 claims description 6
- 230000005669 field effect Effects 0.000 claims description 6
- 238000006243 chemical reaction Methods 0.000 claims description 4
- 230000008021 deposition Effects 0.000 claims description 4
- 238000002474 experimental method Methods 0.000 claims description 4
- 229910001338 liquidmetal Inorganic materials 0.000 claims description 4
- 230000002093 peripheral effect Effects 0.000 claims description 4
- 230000015572 biosynthetic process Effects 0.000 claims description 3
- 238000011217 control strategy Methods 0.000 claims description 3
- 230000002596 correlated effect Effects 0.000 claims description 3
- 230000003631 expected effect Effects 0.000 claims description 3
- 239000000155 melt Substances 0.000 claims description 3
- 239000004065 semiconductor Substances 0.000 claims description 3
- 230000000087 stabilizing effect Effects 0.000 claims description 3
- 230000001960 triggered effect Effects 0.000 claims description 3
- 230000001276 controlling effect Effects 0.000 claims 1
- 239000000835 fiber Substances 0.000 claims 1
- 230000007547 defect Effects 0.000 description 4
- 238000006073 displacement reaction Methods 0.000 description 4
- 239000011159 matrix material Substances 0.000 description 4
- 238000005253 cladding Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- QYEXBYZXHDUPRC-UHFFFAOYSA-N B#[Ti]#B Chemical compound B#[Ti]#B QYEXBYZXHDUPRC-UHFFFAOYSA-N 0.000 description 2
- 229910033181 TiB2 Inorganic materials 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000005764 inhibitory process Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 238000003908 quality control method Methods 0.000 description 2
- 238000010146 3D printing Methods 0.000 description 1
- 241001270131 Agaricus moelleri Species 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 210000001787 dendrite Anatomy 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K26/00—Working by laser beam, e.g. welding, cutting or boring
-
- 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
- B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
-
- 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
Landscapes
- Engineering & Computer Science (AREA)
- Physics & Mathematics (AREA)
- Optics & Photonics (AREA)
- Plasma & Fusion (AREA)
- Mechanical Engineering (AREA)
- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Materials Engineering (AREA)
- Laser Beam Processing (AREA)
Abstract
The application provides a closed-loop regulation and control system and a method for wire-guide ultrasonic-assisted laser additive manufacturing, wherein a wire front end centering unit, a wire transition monitoring unit, a molten pool flow monitoring unit and an in-situ feedback regulation and control unit are added on the basis of an original wire-guide ultrasonic-assisted laser additive manufacturing system, and the rapid centering of a laser beam center and the wire front end, the identification of a molten drop transition state, the judgment of a molten pool flow state under wire-guide ultrasonic and the in-situ regulation and control of wire transition and molten pool flow can be realized by combining with the wire-guide ultrasonic-assisted laser additive manufacturing closed-loop regulation and control method, so that the laser additive manufacturing quality is finally ensured. The application can utilize the existing laser head image coaxial acquisition unit, does not need to add more sensors, has less signal interference, high processing speed and wide adaptability, and has important help for improving the laser additive manufacturing quality and industrialized application.
Description
Technical Field
The application relates to the technical fields of laser additive manufacturing, remanufacturing and laser processing, in particular to a closed-loop regulation and control system and method for wire-guide ultrasonic-assisted laser additive manufacturing.
Background
The laser additive manufacturing technology can adopt a wire feeding or powder feeding mode to feed materials, and then synchronously utilizes laser beams to melt and solidify the powder or the wire, so as to realize 3D printing forming, remanufacturing repair and surface coating cladding. The method is widely applied to the fields of aeroengine blade forming, rolling mill roll remanufacturing, high temperature resistant barrier coating cladding and the like, and is widely paid attention to the academia and the industry. In the development process of laser additive manufacturing, high performance and quality are always important points of development. However, limited by the complex physical metallurgical phenomenon and the strong heat accumulation process in the laser manufacturing process, how to suppress coarse grains and metallurgical defects has been the focus of laser additive manufacturing.
The ultrasonic energy field assisted laser additive manufacturing can induce cavitation phenomenon or interrupt dendrite growth process by introducing high-frequency ultrasonic vibration, so as to realize the purposes of grain refinement and defect inhibition. The introduction of the ultrasonic energy field can be done on the one hand by means of applying ultrasonic vibrations to the object itself, and on the other hand also by means of wire-guided ultrasonic vibrations, i.e. wire-guided ultrasound. However, ultrasonic vibration of the processing object itself is generally difficult to be used for large complex members, and wire ultrasound can avoid the above problems to some extent, only by ultrasonic vibration of the wire, and then introduced into the molten pool via the wire. However, the above solution still has a problem in that, because the wires are formed into drops or liquid bridges and then subjected to ultrasonic conduction, a higher requirement is put on the stability of the wire transition in the processing process, and the unstable wire transition state will seriously interfere with the action effect of the ultrasonic energy field.
Therefore, aiming at the demands of tissue refinement and defect inhibition in laser additive manufacturing and the problems of difficult control of molten drop transition and molten pool flow during wire guide ultrasonic, it is necessary to provide a closed-loop regulation and control system and method for wire guide ultrasonic-assisted laser additive manufacturing, which assist in forming, repairing and cladding high-quality laser additive manufacturing.
Patent document CN111748815a (application number: CN202010630442. X) discloses a laser additive manufacturing system based on closed-loop control and a method thereof, which includes an optical measurement system, an image processing system, a feedforward controller, a first comparison module, a PID control unit, a second comparison module, an LPD process module, and a measurement transmitting module. However, the patent does not monitor the solid wire-liquid molten pool-paste state metal transition process, can not realize the identification of the transition state of the wire and the flow state of the molten pool, and can not solve the quality control difficulty in the wire-guide ultrasonic-assisted laser additive manufacturing process.
Disclosure of Invention
Aiming at the defects in the prior art, the application aims to provide a closed-loop regulation and control system and method for wire-guide ultrasonic-assisted laser additive manufacturing.
The application provides a closed-loop regulation and control system for wire-guide ultrasonic-assisted laser additive manufacturing, which comprises the following components: the device comprises a laser, a laser head, an image coaxial acquisition unit, an industrial camera unit, a wire front end centering unit, a wire transition monitoring unit, a molten pool flow monitoring unit and an in-situ feedback regulation and control unit;
the laser emits laser beams to be transmitted to the laser head through the optical fibers, and then the laser beams irradiate the aluminum alloy substrate or the deposition layer through the light outlet, and wire feeding is performed synchronously, so that a liquid aluminum alloy molten pool is generated;
in the processing process, the image coaxial acquisition unit is used for acquiring two-dimensional optical signals of a visible light wave band, the two-dimensional optical signals are transmitted to the industrial camera unit, and finally, the data are transmitted to the computer for processing through photoelectric signal conversion;
the wire front end centering unit aligns the center of a laser spot with the center of the wire front end, so that the laser beam accurately melts the wire;
the wire transition monitoring unit is used for obtaining a process of converting solid wire melting into liquid droplets or liquid bridges after the wire front end centering unit is used for accurately centering and emitting light, and then monitoring the wire transition state in real time;
the molten pool flow monitoring unit is used for observing the flow condition of the liquid molten pool and the solidification process of the liquid molten pool while the wire transition monitoring unit is operated, and then identifying the flow and solidification state of the molten pool;
the in-situ feedback regulation and control unit generates a feedback regulation and control strategy by utilizing the results of the wire transition monitoring unit and the molten pool flow monitoring unit, and realizes closed-loop regulation.
Preferably, the wire front end centering unit comprises a laser beam center positioning module, a wire end position identification module and a wire end position control module;
the laser beam center positioning module is used for determining the coordinate (x) of the laser spot center in the laser head image coaxial acquisition unit 1 ,y 1 )；
The wire end position identification module is used for determining the coordinate (x 2 ,y 2 )；
The wire end position control module performs position comparison by using the coordinate data obtained by the laser beam center positioning module and the wire end position recognition module, and then performs position comparison by moving (x 1 -x 2 ,y 1 -y 2 ) The front end centering of the wire is realized.
Preferably, the wire transition monitoring unit comprises a wire image processing module and a transition state identification module;
the wire image processing module is used for obtaining wire melting time characteristics of shape outline, oscillation frequency, oscillation amplitude and gray level through gray level processing, filtering noise reduction and visual characteristic extraction;
and the transition state identification module is used for identifying and judging the transition state of the wire according to the data obtained by the wire image processing module.
Preferably, the molten pool flow monitoring unit comprises a molten pool image processing module and a flow state identification module;
the molten pool image processing module is used for extracting molten pool characteristics of molten pool length, molten pool width, oscillation frequency and oscillation amplitude through gray level processing, filtering noise reduction and visual characteristic extraction;
the flow state identification module is used for identifying and judging the flow state of the molten pool according to the data obtained by the molten pool image processing module.
Preferably, the in-situ feedback regulation and control unit integrally judges the manufacturing state of the wire guide ultrasonic auxiliary laser additive according to the data obtained by the wire transition monitoring unit and the molten pool flow monitoring unit and generates a decision scheme, and the purpose of closed loop feedback is achieved by in-situ regulation and control of technological parameters;
the technological parameters include laser power, scanning speed, wire feeding speed, ultrasonic frequency, ultrasonic amplitude, lifting amount and overlap amount.
Preferably, the laser comprises a semiconductor laser or an Nd-YAG laser, and the laser head are connected in an optical fiber mode; the industrial camera unit includes a general industrial camera, a high dynamic industrial camera, an infrared industrial camera, and a hyperspectral industrial camera.
The application provides a closed-loop regulation and control method for wire-guide ultrasonic-assisted laser additive manufacturing, which comprises the following steps:
step 1: adjusting the height h of the laser head and the substrate 1 The processing requirements of an initial layer are met, and the industrial camera unit is matched with the image coaxial acquisition unit to accurately focus;
step 2: opening test point laser, adjusting exposure of an industrial camera unit, calculating the pixel size m= (C+D)/2 of the laser spot diameter according to the average value of the pixel length C and the width D of the maximum peripheral rectangular outline, and combining the laser head and the substrate height h 1 The actual size n of the spot diameter of the test point laser is determined to be m to n;
step 3: binarization of the test point laser spot image is carried out by adopting an Otsu algorithm or a fixed threshold algorithm to obtain a center of the laser spot, namely a centroid position (x) 1 ,y 1 )；
Step 4: adjusting the height h of the front end of the wire from the base plate 2 Moving the wire end into the visual field range of the image coaxial acquisition unit, and extracting the wire material by adopting a binarization methodIn a rectangular region in the acquired image, a coordinates (x 2 ,y 2 ) Namely the front end position of the wire;
step 5: the height from the front end of the wire to the base plate is fixed at h 2 In the case of (a), the wire distance (x 1 -x 2 ,y 1 -y 2 ) Centering of the front end of the wire and the center of the laser spot is realized;
step 6: laser processing light, adjusting exposure and frame rate of an industrial camera unit, setting a mask according to the wire profile and the molten pool profile, wherein the mask takes the center of a laser spot as a circle center, R as a radius and R 1 <R<R 2 Wherein R is 1 Is the radius of the wire material, R 2 The inner area of the mask is an image required by the wire transition monitoring unit and the outer area of the mask is an image required by the molten pool flow monitoring unit;
step 7: preprocessing an image in the mask and extracting features, wherein the preprocessing comprises gray processing and image filtering noise reduction, and the extracting features comprise a shape contour a when a wire material transits from solid state to liquid state 1 Vibration frequency a of wire transition stage 2 Vibration amplitude a of wire transition stage 3 And gray level a of the wire transition stage 4 ；
Step 8: based on the wire transition characteristics, identifying the wire transition state, wherein specific state types comprise under-melting, drop-shaped, liquid bridge and over-melting;
step 9: preprocessing the image outside the mask plate, wherein the preprocessing comprises gray processing and image filtering noise reduction, and the feature extraction comprises liquid metal bath length l, bath width w and vibration frequency b of the bath 1 And vibration amplitude b of molten pool 2 ；
Step 10: based on the flow characteristics of the molten pool, carrying out the flow state identification of the molten pool, wherein specific state types comprise unstable molten pool, stable molten pool and unexpected ultrasonic effect;
step 11: the in-situ mode is adopted to regulate and control by an in-situ feedback regulation and control unit, the transition state of the wire is regulated and controlled to be a liquid bridge, the flow state of a molten pool is regulated and controlled to be stable, and finally whether the ultrasonic effect accords with the expectation is judged.
Preferably, the identifying the transition state of the wire in the step 8 includes:
under-melting: no obvious molten drop and liquid bridge are formed, a 1 In rectangular form with a sharp contour, vibration frequency a 2 ≤α 1 And amplitude a 3 ≤β 1 Low gray level a 4 ≤γ 1 ；
Drop-shaped: has obvious droplet formation, a 1 In a nearly circular state and with a sharp contour, the vibration frequency alpha 1 <a 2 ≤α 2 And amplitude beta 1 <a 3 ≤β 2 Low gamma gray scale 1 <a 4 ≤γ 2 ；
Liquid bridge: no rectangular outline and near circular droplet presence, a 1 In a fan shape with unobvious contour characteristics, the vibration frequency alpha 1 <a 2 ≤α 2 And amplitude beta 1 <a 3 ≤β 2 Moderate gamma of gray level 1 <a 4 ≤γ 2 ；
And (3) oversmelting: no rectangular outline and near circular droplet presence, a 1 In a fan shape with unobvious contour characteristics, the vibration frequency alpha 2 <a 2 And amplitude beta 2 <a 3 Gray level high gamma 2 <a 4 ；
α 1 、α 2 、β 1 、β 2 、γ 1 、γ 2 All are wire transition state identification thresholds.
Preferably, the identifying of the flow state of the molten pool in the step 10 includes:
the molten pool is unstable: extracting the length l and the width w of the molten pool image through the maximum circumscribed rectangle of the molten pool image or the maximum length of the molten pool along the scanning direction and the maximum width algorithm of the molten pool along the vertical scanning direction, and further calculating the relative standard deviation l 'and the relative standard deviation w' of the length and the width:
when l'>l 1 Or w'>w 1 When the molten pool is unstable; wherein l 1 And w 1 Identifying a threshold for the molten bath flow condition;
and (3) stabilizing a molten pool: when l' is less than or equal to l 1 Or w' is less than or equal to w 1 When the molten pool is judged to be stable;
the ultrasonic effect meets the expectations: after the molten pool is judged to be stable, the ultrasonic effect is identified and judged, and the mass center (x 3 ,y 3 ) Then calculate the centroid vibration frequency b 1 And amplitude b 2 ，b 1 The calculation formula of (2) is as follows:
b 2 the calculation formula of (2) is as follows:
wherein B is 1 、B 2 T is vibration time, S is the area of the extracted liquid-solid solidification interface, and b is calibrated according to a pre-experiment when the expected effect is met 1 And b 2 The threshold ranges of (a) are [ delta ] 1 ,δ 2 ]And [ delta ] 3 ,δ 4 ]If b 1 And b 2 Within the range, judging that the ultrasonic effect meets the expected requirement;
the ultrasound effect does not meet the expectations: if b 1 And b 2 Any value not within a pre-calibrated range [ delta ] 1 ,δ 2 ]And [ delta ] 3 ,δ 4 ]In that case, the ultrasound effect is not as expected.
Preferably, the step 11 includes:
undermelting and overmelting: when the undermelting and the overmelting occur, the energy input density is regulated through the laser power or the scanning speed, the energy input density is improved when the undermelting occurs, and the energy input density is reduced when the overmelting occurs;
drop and liquid bridge: when the control is carried out until the problems of under-melting and over-melting do not exist, the drop-shaped and liquid bridge state control is carried out, and if the drop-shaped state is the drop-shaped state, the liquid bridge state is triggered by reducing the height of the laser head;
whether the flow state is stable: in the liquid bridge state, if the flow state of the molten pool is unstable, the energy input is improved; if interference with the over-melting regulation occurs, the wire feeding quantity is reduced; if the flow state of the molten pool is stable, entering into ultrasonic effect adjustment;
whether the ultrasound effect meets the expectations: after the molten pool is stable, judging the ultrasonic energy field effect, and regulating the ultrasonic effect of the molten pool by regulating the frequency and the amplitude of the ultrasonic energy field, wherein the ultrasonic energy field effect and the ultrasonic energy field are positively correlated.
Compared with the prior art, the application has the following beneficial effects:
(1) The application can carry out real-time monitoring and closed-loop feedback adjustment on the wire-guide ultrasonic-assisted laser additive manufacturing processing process, realizes the identification of the transition state and the molten pool flow state of the wire through the monitoring of the solid wire-liquid molten pool-paste state metal transition process, simultaneously provides a closed-loop regulation and control method, and solves the quality control problem in the wire-guide ultrasonic-assisted laser additive manufacturing process;
(2) The application has high integration degree and strong adaptability, can utilize the coaxial monitoring capability of the laser head, does not need to newly add any hardware equipment, has lower cost, can be realized by utilizing a single industrial camera, and can carry out closed-loop regulation and control by means of the coaxial image acquisition unit, the wire front end centering unit, the wire transition monitoring unit, the molten pool flow monitoring unit and the in-situ feedback regulation and control unit.
Drawings
Other features, objects and advantages of the present application will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:
FIG. 1 is a schematic diagram of a wire front end centering unit coordinate, wherein 1 is a wire and 2 is a test point laser spot;
FIG. 2 is a schematic diagram of a droplet transition monitoring unit and a molten pool flow state monitoring unit, wherein 1 is a wire, 3 is a wire transition region, 4 is a molten pool region, and 5 is a liquid-solid solidification interface extraction position;
FIG. 3 is a schematic diagram of a closed loop feedback system for wire guided ultrasound assisted laser additive manufacturing;
fig. 4 is a flow chart of a closed loop feedback method of wire guided ultrasonic assisted laser additive manufacturing.
Detailed Description
The present application will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present application, but are not intended to limit the application in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present application.
Example 1:
the application provides a closed-loop regulation and control system for wire-guide ultrasonic-assisted laser additive manufacturing, which comprises the following components: the device comprises a laser, a laser head, an image coaxial acquisition unit, an industrial camera unit, a wire front end centering unit, a wire transition monitoring unit, a molten pool flow monitoring unit and an in-situ feedback regulation and control unit; the laser emits laser beams to be transmitted to the laser head through the optical fibers, and then the laser beams irradiate the aluminum alloy substrate or the deposition layer through the light outlet, and wire feeding is performed synchronously, so that a liquid aluminum alloy molten pool is generated; in the processing process, the image coaxial acquisition unit is used for acquiring two-dimensional optical signals of a visible light wave band, the two-dimensional optical signals are transmitted to the industrial camera unit, and finally, the data are transmitted to the computer for processing through photoelectric signal conversion; the wire front end centering unit aligns the center of the laser spot with the center of the wire front end, so that the laser beam accurately melts the wire, as shown in fig. 1; the wire transition monitoring unit is used for obtaining a process of converting solid wire melting into liquid droplets or liquid bridges after the wire front end centering unit is used for accurately centering and emitting light, and then monitoring the wire transition state in real time; the molten pool flow monitoring unit is used for observing the flow condition of the liquid molten pool and the solidification process of the liquid molten pool while the wire transition monitoring unit is operated, and then identifying the flow and solidification state of the molten pool, as shown in fig. 2; the in-situ feedback regulation and control unit generates a feedback regulation and control strategy by using the results of the wire transition monitoring unit and the molten pool flow monitoring unit, and realizes closed-loop regulation as shown in fig. 3.
The wire front end centering unit comprises a laser beam center positioning module, a wire end position identification module and a wire end position control module; the laser beam center positioning module is used for determining the coordinate (x) of the laser spot center in the laser head image coaxial acquisition unit 1 ,y 1 ) The method comprises the steps of carrying out a first treatment on the surface of the The wire end position identification module is used for determining the coordinate (x 2 ,y 2 ) The method comprises the steps of carrying out a first treatment on the surface of the The wire end position control module performs position comparison by using the coordinate data obtained by the laser beam center positioning module and the wire end position recognition module, and then performs position comparison by moving (x 1 -x 2 ,y 1 -y 2 ) The front end centering of the wire is realized.
The wire transition monitoring unit comprises a wire image processing module and a transition state identification module; the wire image processing module is used for obtaining wire melting time characteristics of shape outline, oscillation frequency, oscillation amplitude and gray level through gray level processing, filtering noise reduction and visual characteristic extraction; and the transition state identification module is used for identifying and judging the transition state of the wire according to the data obtained by the wire image processing module.
The molten pool flow monitoring unit comprises a molten pool image processing module and a flow state identification module; the molten pool image processing module is used for extracting molten pool characteristics of molten pool length, molten pool width, oscillation frequency and oscillation amplitude through gray level processing, filtering noise reduction and visual characteristic extraction; the flow state identification module is used for identifying and judging the flow state of the molten pool according to the data obtained by the molten pool image processing module.
The in-situ feedback regulation and control unit integrally judges the manufacturing state of the wire guide ultrasonic auxiliary laser additive according to the data obtained by the wire transition monitoring unit and the molten pool flow monitoring unit and generates a decision scheme, and the purpose of closed loop feedback is achieved through in-situ regulation and control of technological parameters; the technological parameters include laser power, scanning speed, wire feeding speed, ultrasonic frequency, ultrasonic amplitude, lifting amount and overlap amount. The laser comprises a semiconductor laser or an Nd-YAG laser, and the laser head are connected in an optical fiber mode; the industrial camera unit includes a general industrial camera, a high dynamic industrial camera, an infrared industrial camera, and a hyperspectral industrial camera.
As shown in fig. 4, the application provides a closed-loop regulation and control method for wire-guide ultrasonic-assisted laser additive manufacturing, which comprises the following steps:
step 1: adjusting the height h of the laser head and the substrate 1 The processing requirements of an initial layer are met, and the industrial camera unit is matched with the image coaxial acquisition unit to accurately focus;
step 2: opening test point laser, adjusting exposure of an industrial camera unit, calculating the pixel size m= (C+D)/2 of the laser spot diameter according to the average value of the pixel length C and the width D of the maximum peripheral rectangular outline, and combining the laser head and the substrate height h 1 The actual size n of the spot diameter of the test point laser is determined to be m to n;
step 3: binarization of the test point laser spot image is carried out by adopting an Otsu algorithm or a fixed threshold algorithm to obtain a center of the laser spot, namely a centroid position (x) 1 ,y 1 )；
Step 4: adjusting the height h of the front end of the wire from the base plate 2 Moving the wire end into the visual field range of the image coaxial acquisition unit, extracting a rectangular area of the wire in the acquired image by adopting a binarization method, and calculating the central position coordinate (x 2 ,y 2 ) Namely the front end position of the wire;
step 5: the height from the front end of the wire to the base plate is fixed at h 2 In the case of (a), the wire distance (x 1 -x 2 ,y 1 -y 2 ) Centering of the front end of the wire and the center of the laser spot is realized;
step 6: laser processing light, adjusting exposure and acquisition frame rate of industrial camera unit, and according to wire profileSetting a mask with the contour of the molten pool, wherein the mask takes the center of a laser spot as a circle center, R is a radius 1 <R<R 2 Wherein R is 1 Is the radius of the wire material, R 2 The inner area of the mask is an image required by the wire transition monitoring unit and the outer area of the mask is an image required by the molten pool flow monitoring unit;
step 7: preprocessing an image in the mask and extracting features, wherein the preprocessing comprises gray processing and image filtering noise reduction, and the extracting features comprise a shape contour a when a wire material transits from solid state to liquid state 1 Vibration frequency a of wire transition stage 2 Vibration amplitude a of wire transition stage 3 And gray level a of the wire transition stage 4 ；
Step 8: based on the wire transition characteristics, identifying the wire transition state, wherein specific state types comprise under-melting, drop-shaped, liquid bridge and over-melting;
step 9: preprocessing the image outside the mask plate, wherein the preprocessing comprises gray processing and image filtering noise reduction, and the feature extraction comprises liquid metal bath length l, bath width w and vibration frequency b of the bath 1 And vibration amplitude b of molten pool 2 ；
Step 10: based on the flow characteristics of the molten pool, carrying out the flow state identification of the molten pool, wherein specific state types comprise unstable molten pool, stable molten pool and unexpected ultrasonic effect;
step 11: the in-situ mode is adopted to regulate and control by an in-situ feedback regulation and control unit, the transition state of the wire is regulated and controlled to be a liquid bridge, the flow state of a molten pool is regulated and controlled to be stable, and finally whether the ultrasonic effect accords with the expectation is judged.
The identifying the transition state of the wire in the step 8 comprises the following steps:
under-melting: no obvious molten drop and liquid bridge are formed, a 1 In rectangular form with a sharp contour, vibration frequency a 2 ≤α 1 And amplitude a 3 ≤β 1 Low gray level a 4 ≤γ 1 ；
Drop-shaped: has obvious droplet formation, a 1 In a nearly circular state and with a sharp contourVibration frequency alpha 1 <a 2 ≤α 2 And amplitude beta 1 <a 3 ≤β 2 Low gamma gray scale 1 <a 4 ≤γ 2 ；
Liquid bridge: no rectangular outline and near circular droplet presence, a 1 In a fan shape with unobvious contour characteristics, the vibration frequency alpha 1 <a 2 ≤α 2 And amplitude beta 1 <a 3 ≤β 2 Moderate gamma of gray level 1 <a 4 ≤γ 2 ；
And (3) oversmelting: no rectangular outline and near circular droplet presence, a 1 In a fan shape with unobvious contour characteristics, the vibration frequency alpha 2 <a 2 And amplitude beta 2 <a 3 Gray level high gamma 2 <a 4 ；
α 1 、α 2 、β 1 、β 2 、γ 1 、γ 2 All are wire transition state identification thresholds.
The bath flow state identification in step 10 includes:
the molten pool is unstable: extracting the length l and the width w of the molten pool image through the maximum circumscribed rectangle of the molten pool image or the maximum length of the molten pool along the scanning direction and the maximum width algorithm of the molten pool along the vertical scanning direction, and further calculating the relative standard deviation l 'and the relative standard deviation w' of the length and the width:
when l'>l 1 Or w'>w 1 When the molten pool is unstable; wherein l 1 And w 1 Identifying a threshold for the molten bath flow condition;
and (3) stabilizing a molten pool: when l' is less than or equal to l 1 Or w' is less than or equal to w 1 When the molten pool is judged to be stable;
the ultrasonic effect meets the expectations: after the molten pool is judged to be stable, the ultrasonic effect is identified and judged, and the mass center (x 3 ,y 3 ) Then calculate the centroid vibration frequency b 1 And amplitude b 2 ，b 1 The calculation formula of (2) is as follows:
b 2 the calculation formula of (2) is as follows:
wherein B is 1 、B 2 T is vibration time, S is the area of the extracted liquid-solid solidification interface, and b is calibrated according to a pre-experiment when the expected effect is met 1 And b 2 The threshold ranges of (a) are [ delta ] 1 ,δ 2 ]And [ delta ] 3 ,δ 4 ]If b 1 And b 2 Within the range, judging that the ultrasonic effect meets the expected requirement;
the ultrasound effect does not meet the expectations: if b 1 And b 2 Any value not within a pre-calibrated range [ delta ] 1 ,δ 2 ]And [ delta ] 3 ,δ 4 ]In that case, the ultrasound effect is not as expected.
The step 11 includes:
undermelting and overmelting: when the undermelting and the overmelting occur, the energy input density is regulated through the laser power or the scanning speed, the energy input density is improved when the undermelting occurs, and the energy input density is reduced when the overmelting occurs;
drop and liquid bridge: when the control is carried out until the problems of under-melting and over-melting do not exist, the drop-shaped and liquid bridge state control is carried out, and if the drop-shaped state is the drop-shaped state, the liquid bridge state is triggered by reducing the height of the laser head;
whether the flow state is stable: in the liquid bridge state, if the flow state of the molten pool is unstable, the energy input is improved; if interference with the over-melting regulation occurs, the wire feeding quantity is reduced; if the flow state of the molten pool is stable, entering into ultrasonic effect adjustment;
whether the ultrasound effect meets the expectations: after the molten pool is stable, judging the ultrasonic energy field effect, and regulating the ultrasonic effect of the molten pool by regulating the frequency and the amplitude of the ultrasonic energy field, wherein the ultrasonic energy field effect and the ultrasonic energy field are positively correlated.
Example 2:
example 2 is a preferred example of example 1.
The matrix material adopted in the embodiment is AlSi7Mg, the matrix size is 145mm multiplied by 15mm, the wire is AlSi7Mg, the in-situ autogenous TiB2 is contained, the diameter of the wire is 1mm, the laser is a 450nm blue laser, the displacement device is a 3-axis displacement table, the diameter of the optical fiber is 1mm, and the industrial camera is a common industrial camera. The closed-loop regulation and control system for the wire-guide ultrasonic-assisted laser additive manufacturing comprises a laser, a laser head, a displacement device, a wire feeding device, an ultrasonic-assisted device, an image coaxial acquisition unit, an industrial camera unit, a wire front end centering unit, a wire transition monitoring unit, a molten pool flow monitoring unit and an in-situ feedback regulation and control unit.
The laser beam emitted by the laser transmits to the laser head through the optical fiber, and irradiates to the aluminum alloy substrate or the deposition layer through the light outlet, the diameter of the laser spot is 2mm, and the laser spot is synchronously fed to generate a liquid aluminum alloy molten pool. In the processing process, the image coaxial acquisition unit is utilized to acquire two-dimensional optical signals of a visible light wave band, the two-dimensional optical signals are transmitted to a common industrial camera in the industrial camera unit, and finally data are transmitted to the image on-line processing unit of the computer through photoelectric signal conversion, wherein the image is 400×400pixels, each pixel point is 8 bits, and the gray level is 256.
The specific implementation process parameters are that the laser power is 1000W, the scanning speed is 5mm/s, the wire feeding amount is 3mm/s, the scanning length is 50mm, the lifting amount of each layer is 0.4mm, the stay time at the two ends is 0s, the ultrasonic frequency is 20kHz, and the ultrasonic amplitude is 5 mu m.
The wire front end centering unit, the wire transition monitoring unit, the molten pool flow monitoring unit and the in-situ feedback regulation and control unit are integrated into one workstation. The wire front end centering unit can align the laser beam center with the wire front end, so that subsequent processing is ensured. After centering is completed, the wire transition monitoring unit can judge whether the wire transition state is under-melting, over-melting, drop-shaped or liquid bridge; the molten pool flow monitoring unit can judge the stability degree of the molten pool and the effect of the ultrasonic energy field. The closed-loop feedback adjusting unit can make comprehensive decisions according to the data of the wire transition monitoring unit, the molten pool flow monitoring unit and the current processing state, and then execute regulation and control.
The wire transition monitoring unit comprises a wire image processing module and a transition state identification module. The wire image processing module is used for obtaining wire melting time characteristics such as shape contour, oscillation frequency, gray level and the like through gray level processing, filtering noise reduction and visual characteristic extraction; and the transition state identification module is used for identifying and judging the transition state of the wire according to the data of the wire image processing module.
The molten pool flow monitoring unit comprises a molten pool image processing module and a flow state identification module. The molten pool image processing module is used for extracting molten pool characteristics such as shape contours, oscillation frequencies, gray scales and the like through gray scale processing, filtering noise reduction and visual characteristic extraction; the flow state identification module is used for identifying and judging the flow state of the molten pool according to the data of the molten pool image processing module.
In this embodiment, the process parameters that can be adjusted in the in-situ feedback control unit mainly include laser power, scan speed, wire feed speed, ultrasonic frequency, ultrasonic amplitude, and lift amount.
The embodiment provides a closed-loop regulation and control method for manufacturing a wire-guide ultrasonic-assisted laser additive, which adopts the wire-guide ultrasonic-assisted laser additive manufacturing closed-loop regulation and control system and comprises the following steps:
(1) And (5) initial position adjustment. According to the characteristics of the equipment, the height of the laser head and the height of the base plate are adjusted to be 11mm, the processing requirement of an initial layer is met, and on the other hand, the industrial camera based on the image coaxial acquisition unit can be accurately focused.
(2) And (5) light emission and size calibration of the test point laser. The laser beam center positioning module is used for assisting in completing, the test point laser is turned on, the exposure of an industrial camera unit is regulated, the pixel size m= (154+150)/2=152 pixel of the laser spot diameter is calculated according to the average value of the pixel length C and the width D of the maximum peripheral rectangular outline, the actual size of the test point laser spot diameter is 2mm when the height of the laser head and the substrate is 11mm, and the ratio of the pixel size to the actual size is 152:2, namely 76:1.
(3) And (5) identifying the center position of the laser spot. The method is completed by a laser beam center positioning module, binarization of the test point laser spot image is carried out by adopting an Otsu algorithm, and the center of the laser spot, namely the centroid position is 212.14,230.56.
(4) And (5) identifying coordinates of the wire ends. The method is completed by a wire end position recognition module, the height of the front end of the wire from the substrate is adjusted to be 4mm, the parameter is predetermined by a process optimization result, then the wire end is moved to be within the visual field range of an image coaxial acquisition unit, a binarization method is adopted to extract a rectangular area of the wire in an acquired image, and the center position coordinate of the suspended end of the rectangular area is calculated to be 180.22,225.79, so that the front end position of the wire is obtained.
(5) And (5) adjusting the position of the wire end. And the wire end position control module of the wire front end centering unit executes centering adjustment of the wire end position, and the wire electric displacement device automatically adjusts (31.92,4.77) the distance under the condition that the height of the wire front end from the substrate is fixed at 4mm, so that the centering of the wire front end and the laser spot center is realized.
(6) And (5) image acquisition during laser processing. And (3) laser processing is carried out, the exposure and acquisition frame rate of an industrial camera unit is regulated, a mask is set according to the wire profile and the molten pool profile, and the mask takes the center of a laser spot as the center of a circle and takes 1.5mm as the radius. The mask is internally provided with images required by the wire transition monitoring unit, and the mask is externally provided with images required by the molten pool flow monitoring unit.
(7) And (5) performing transition image processing on the wire. And preprocessing and extracting features of the image in the mask by using a wire image processing module of the wire transition monitoring unit. The preprocessing comprises gray processing and image filtering noise reduction. Feature extraction includes shape profile a when wire transitions from solid to liquid 1 Vibration frequency a of wire transition stage 2 Vibration amplitude a of wire transition stage 3 And wire transitionGray scale of stage a 4 。
(8) And (5) identifying the transition state of the wire. The threshold ranges for each parameter are listed according to pre-experiments, see table 1.
TABLE 1 threshold table for identifying transition states of wires
| Parameters (parameters) | Numerical value | Parameters (parameters) | Numerical value |
| α 1 | 5Hz | β 2 | 0.015 |
| α 2 | 25Hz | γ 1 | 20 |
| β 1 | 0.005 | γ 2 | 100 |
Accordingly, 1 to 5 layers of average monitoring data and recognition results can be listed. See table 2.
TABLE 2 identification results of transition states for 1 st to 5 th layer wires
| Layer number | a 1 | a 2 | a 3 | a 4 |
| 1 | Sector shape | 8Hz | 0.11 | 33 |
| 2 | Sector shape | 12Hz | 0.12 | 40 |
| 3 | Sector shape | 15Hz | 0.10 | 47 |
| 4 | Sector shape | 16Hz | 0.09 | 60 |
| 5 | Nearly circular | 20Hz | 0.12 | 65 |
Thus, it can be seen that layers 1 to 4 in this example are liquid bridge transitions and layer 5 is a drop transition.
(9) And (5) processing a molten pool flow image. And preprocessing and extracting features of the image outside the mask by using a molten pool image processing module of the molten pool flow monitoring unit. The preprocessing comprises gray processing and image filtering noise reduction. The feature extraction includes the length l and width w of the liquid metal bath, the vibration frequency b of the bath 1 Vibration amplitude b of molten pool 2 。
(10) And (5) recognizing the flow state of the molten pool. The threshold values are shown in Table 3.
TABLE 3 bath flow State identification threshold Table
| Parameters (parameters) | Numerical value | Parameters (parameters) | Numerical value |
| l 1 | 0.020 | δ 2 | 80 |
| w 1 | 0.050 | δ 3 | 0.006 |
| δ 1 | 60 | δ 4 | 0.012 |
The results of layers 1 to 4 are shown in Table 4.
TABLE 4 results of identification of molten pool flow conditions at layers 1 to 4
| Layer number | l’ | w’ | b 1 | b 2 |
| 1 | 0.005 | 0.022 | 71 | 0.008 |
| 2 | 0.012 | 0.039 | 62 | 0.009 |
| 3 | 0.011 | 0.045 | 65 | 0.009 |
| 4 | 0.015 | 0.040 | 70 | 0.010 |
The transition of the wire at layer 5 is drop-shaped, and is therefore not considered. It can be judged that the ultrasonic effects of layers 1 to 4 meet the expectations.
(11) And (5) in-situ regulation decision and execution. Aiming at the drop-shaped transition problem in the layer 5, the lifting quantity is reduced by 0.1mm in real time, so that the lifting quantity is converted into liquid bridge transition. L ', w', b of adjusted layer 5 1 、b 2 0.17, 0.45, 78, 0.09, respectively. At this time, the flow state is stable, the ultrasonic effect is in line with expectations, so no other regulation is performed.
The embodiment is applicable to processing AlSi7Mg matrix and AlSi7Mg-2% TiB2 wire by blue laser, and the matrix is a horizontal plane and vertical to the laser head. The embodiment obtains a closed-loop regulation and control system and a method for manufacturing the wire-guide ultrasonic-assisted laser additive according to different images, and the recognition characteristic threshold range under the working condition is defined.
In the description of the present application, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, are merely for convenience in describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application.
Those skilled in the art will appreciate that the systems, apparatus, and their respective modules provided herein may be implemented entirely by logic programming of method steps such that the systems, apparatus, and their respective modules are implemented as logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers, etc., in addition to the systems, apparatus, and their respective modules being implemented as pure computer readable program code. Therefore, the system, the apparatus, and the respective modules thereof provided by the present application may be regarded as one hardware component, and the modules included therein for implementing various programs may also be regarded as structures within the hardware component; modules for implementing various functions may also be regarded as being either software programs for implementing the methods or structures within hardware components.
The foregoing describes specific embodiments of the present application. It is to be understood that the application is not limited to the particular embodiments described above, and that various changes or modifications may be made by those skilled in the art within the scope of the appended claims without affecting the spirit of the application. The embodiments of the application and the features of the embodiments may be combined with each other arbitrarily without conflict.
Claims (10)
1. A closed-loop regulation and control system for wire-guided ultrasonic-assisted laser additive manufacturing, which is characterized by comprising: the device comprises a laser, a laser head, an image coaxial acquisition unit, an industrial camera unit, a wire front end centering unit, a wire transition monitoring unit, a molten pool flow monitoring unit and an in-situ feedback regulation and control unit;
the laser emits laser beams to be transmitted to the laser head through the optical fibers, and then the laser beams irradiate the aluminum alloy substrate or the deposition layer through the light outlet, and wire feeding is performed synchronously, so that a liquid aluminum alloy molten pool is generated;
in the processing process, the image coaxial acquisition unit is used for acquiring two-dimensional optical signals of a visible light wave band, the two-dimensional optical signals are transmitted to the industrial camera unit, and finally, the data are transmitted to the computer for processing through photoelectric signal conversion;
the wire front end centering unit aligns the center of a laser spot with the center of the wire front end, so that the laser beam accurately melts the wire;
the wire transition monitoring unit is used for obtaining a process of converting solid wire melting into liquid droplets or liquid bridges after the wire front end centering unit is used for accurately centering and emitting light, and then monitoring the wire transition state in real time;
the molten pool flow monitoring unit is used for observing the flow condition of the liquid molten pool and the solidification process of the liquid molten pool while the wire transition monitoring unit is operated, and then identifying the flow and solidification state of the molten pool;
the in-situ feedback regulation and control unit generates a feedback regulation and control strategy by utilizing the results of the wire transition monitoring unit and the molten pool flow monitoring unit, and realizes closed-loop regulation.
2. The wire-guide ultrasonic-assisted laser additive manufacturing closed-loop regulation and control system according to claim 1, wherein the wire front end centering unit comprises a laser beam center positioning module, a wire end position identification module and a wire end position control module;
the laser beam center positioning module is used for determining the coordinate (x) of the laser spot center in the laser head image coaxial acquisition unit 1 ,y 1 )；
The wire end position identification module is used for determining the coordinate (x 2 ,y 2 )；
The wire end position control module performs position comparison by using the coordinate data obtained by the laser beam center positioning module and the wire end position recognition module, and then performs position comparison by moving (x 1 -x 2 ,y 1 -y 2 ) The front end centering of the wire is realized.
3. The wire-guided ultrasonic-assisted laser additive manufacturing closed-loop regulation and control system according to claim 1, wherein the wire transition monitoring unit comprises a wire image processing module and a transition state identification module;
the wire image processing module is used for obtaining wire melting time characteristics of shape outline, oscillation frequency, oscillation amplitude and gray level through gray level processing, filtering noise reduction and visual characteristic extraction;
and the transition state identification module is used for identifying and judging the transition state of the wire according to the data obtained by the wire image processing module.
4. The wire-guide ultrasonic-assisted laser additive manufacturing closed-loop regulation and control system according to claim 1, wherein the molten pool flow monitoring unit comprises a molten pool image processing module and a flow state identification module;
the molten pool image processing module is used for extracting molten pool characteristics of molten pool length, molten pool width, oscillation frequency and oscillation amplitude through gray level processing, filtering noise reduction and visual characteristic extraction;
the flow state identification module is used for identifying and judging the flow state of the molten pool according to the data obtained by the molten pool image processing module.
5. The closed-loop regulation and control system for wire-guide ultrasonic-assisted laser additive manufacturing according to claim 1, wherein the in-situ feedback regulation and control unit is used for integrally judging the wire-guide ultrasonic-assisted laser additive manufacturing state according to data obtained by the wire transition monitoring unit and the molten pool flow monitoring unit and generating a decision scheme, and achieving the purpose of closed-loop feedback by regulating and controlling process parameters in situ;
the technological parameters include laser power, scanning speed, wire feeding speed, ultrasonic frequency, ultrasonic amplitude, lifting amount and overlap amount.
6. The closed-loop regulation and control system for wire-guide ultrasonic-assisted laser additive manufacturing according to claim 1, wherein the laser comprises a semiconductor laser or an Nd-YAG laser, and the laser head are connected in a fiber mode; the industrial camera unit includes a general industrial camera, a high dynamic industrial camera, an infrared industrial camera, and a hyperspectral industrial camera.
7. A closed-loop regulation and control method for wire-guided ultrasonic-assisted laser additive manufacturing, characterized in that the closed-loop regulation and control system for wire-guided ultrasonic-assisted laser additive manufacturing is adopted, and comprises the following steps:
step 1: adjusting the height h of the laser head and the substrate 1 The processing requirements of an initial layer are met, and the industrial camera unit is matched with the image coaxial acquisition unit to accurately focus;
step 2: opening test point laser, adjusting exposure of an industrial camera unit, calculating the pixel size m= (C+D)/2 of the laser spot diameter according to the average value of the pixel length C and the width D of the maximum peripheral rectangular outline, and combining the laser head and the substrate height h 1 The actual size n of the spot diameter of the test point laser is determined to be m to n;
step 3: binarization of the test point laser spot image is carried out by adopting an Otsu algorithm or a fixed threshold algorithm to obtain a center of the laser spot, namely a centroid position (x) 1 ,y 1 )；
Step 4: adjusting the height h of the front end of the wire from the base plate 2 Moving the wire end into the visual field range of the image coaxial acquisition unit, extracting a rectangular area of the wire in the acquired image by adopting a binarization method, and calculating the central position coordinate (x 2 ,y 2 ) Namely the front end position of the wire;
step 5: the height from the front end of the wire to the base plate is fixed at h 2 In the case of (a), the wire distance (x 1 -x 2 ,y 1 -y 2 ) Centering of the front end of the wire and the center of the laser spot is realized;
step 6: laser processing light, adjusting exposure and frame rate of an industrial camera unit, setting a mask according to the wire profile and the molten pool profile, wherein the mask takes the center of a laser spot as a circle center, R as a radius and R 1 <R<R 2 Wherein R is 1 Is the radius of the wire material, R 2 The inner area of the mask is an image required by the wire transition monitoring unit and the outer area of the mask is an image required by the molten pool flow monitoring unit;
step 7: preprocessing an image in the mask and extracting features, wherein the preprocessing comprises gray processing and image filtering noise reduction, and the extracting features comprise a shape contour a when a wire material transits from solid state to liquid state 1 Vibration frequency a of wire transition stage 2 Vibration amplitude a of wire transition stage 3 And gray level a of the wire transition stage 4 ；
Step 8: based on the wire transition characteristics, identifying the wire transition state, wherein specific state types comprise under-melting, drop-shaped, liquid bridge and over-melting;
step 9: preprocessing the image outside the mask plate, wherein the preprocessing comprises gray processing and image filtering noise reduction, and the feature extraction comprises liquid metal bath length l, bath width w and vibration frequency b of the bath 1 And vibration amplitude b of molten pool 2 ；
Step 10: based on the flow characteristics of the molten pool, carrying out the flow state identification of the molten pool, wherein specific state types comprise unstable molten pool, stable molten pool and unexpected ultrasonic effect;
step 11: the in-situ mode is adopted to regulate and control by an in-situ feedback regulation and control unit, the transition state of the wire is regulated and controlled to be a liquid bridge, the flow state of a molten pool is regulated and controlled to be stable, and finally whether the ultrasonic effect accords with the expectation is judged.
8. The method of claim 7, wherein the identifying the transition state of the wire in step 8 comprises:
under-melting: no obvious molten drop and liquid bridge are formed, a 1 In rectangular form with a sharp contour, vibration frequency a 2 ≤α 1 And amplitude a 3 ≤β 1 Low gray level a 4 ≤γ 1 ；
Drop-shaped: has obvious droplet formation, a 1 In a nearly circular state and with a sharp contour, the vibration frequency alpha 1 <a 2 ≤α 2 And amplitude beta 1 <a 3 ≤β 2 Low gamma gray scale 1 <a 4 ≤γ 2 ；
Liquid bridge: no rectangular outline and near circular droplet presence, a 1 In a fan shape with unobvious contour characteristics, the vibration frequency alpha 1 <a 2 ≤α 2 And amplitude beta 1 <a 3 ≤β 2 Moderate gamma of gray level 1 <a 4 ≤γ 2 ；
And (3) oversmelting: no rectangular outline and near circular droplet presence, a 1 In a fan shape with unobvious contour characteristics, the vibration frequency alpha 2 <a 2 And amplitude beta 2 <a 3 Gray level high gamma 2 <a 4 ；
α 1 、α 2 、β 1 、β 2 、γ 1 、γ 2 All are wire transition state identification thresholds.
9. The method of closed loop regulation of ultrasound-assisted laser additive manufacturing by wire guidance according to claim 7, wherein the step 10 of recognizing the flow state of the molten pool comprises:
the molten pool is unstable: extracting the length l and the width w of the molten pool image through the maximum circumscribed rectangle of the molten pool image or the maximum length of the molten pool along the scanning direction and the maximum width algorithm of the molten pool along the vertical scanning direction, and further calculating the relative standard deviation l 'and the relative standard deviation w' of the length and the width:
when l'>l 1 Or w'>w 1 When the molten pool is unstable; wherein l 1 And w 1 Identifying a threshold for the molten bath flow condition;
and (3) stabilizing a molten pool: when l' is less than or equal to l 1 Or w' is less than or equal to w 1 When the molten pool is judged to be stable;
the ultrasonic effect meets the expectations: after the molten pool is judged to be stable, the ultrasonic effect is identified and judged, and the mass center (x 3 ,y 3 ) Then calculate the centroid vibration frequency b 1 And amplitude b 2 ，b 1 The calculation formula of (2) is as follows:
b 2 the calculation formula of (2) is as follows:
wherein B is 1 、B 2 T is vibration time, S is the area of the extracted liquid-solid solidification interface, and b is calibrated according to a pre-experiment when the expected effect is met 1 And b 2 The threshold ranges of (a) are [ delta ] 1 ,δ 2 ]And [ delta ] 3 ,δ 4 ]If b 1 And b 2 Within the range, judging that the ultrasonic effect meets the expected requirement;
the ultrasound effect does not meet the expectations: if b 1 And b 2 Any value not within a pre-calibrated range [ delta ] 1 ,δ 2 ]And [ delta ] 3 ,δ 4 ]In that case, the ultrasound effect is not as expected.
10. The method of closed-loop control for wire-guided ultrasound-assisted laser additive manufacturing according to claim 7, wherein the step 11 comprises:
undermelting and overmelting: when the undermelting and the overmelting occur, the energy input density is regulated through the laser power or the scanning speed, the energy input density is improved when the undermelting occurs, and the energy input density is reduced when the overmelting occurs;
drop and liquid bridge: when the control is carried out until the problems of under-melting and over-melting do not exist, the drop-shaped and liquid bridge state control is carried out, and if the drop-shaped state is the drop-shaped state, the liquid bridge state is triggered by reducing the height of the laser head;
whether the flow state is stable: in the liquid bridge state, if the flow state of the molten pool is unstable, the energy input is improved; if interference with the over-melting regulation occurs, the wire feeding quantity is reduced; if the flow state of the molten pool is stable, entering into ultrasonic effect adjustment;
whether the ultrasound effect meets the expectations: after the molten pool is stable, judging the ultrasonic energy field effect, and regulating the ultrasonic effect of the molten pool by regulating the frequency and the amplitude of the ultrasonic energy field, wherein the ultrasonic energy field effect and the ultrasonic energy field are positively correlated.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310525093.9A CN116618823A (en) | 2023-05-10 | 2023-05-10 | Closed-loop regulation and control system and method for wire-guide ultrasonic-assisted laser additive manufacturing |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202310525093.9A CN116618823A (en) | 2023-05-10 | 2023-05-10 | Closed-loop regulation and control system and method for wire-guide ultrasonic-assisted laser additive manufacturing |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116618823A true CN116618823A (en) | 2023-08-22 |
Family
ID=87609155
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202310525093.9A Pending CN116618823A (en) | 2023-05-10 | 2023-05-10 | Closed-loop regulation and control system and method for wire-guide ultrasonic-assisted laser additive manufacturing |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116618823A (en) |
-
2023
- 2023-05-10 CN CN202310525093.9A patent/CN116618823A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN106881462B (en) | A kind of on-line checking and optimization system for selective laser fusing forming defects | |
| CN109778182B (en) | Laser cladding additive forming height online monitoring device and closed-loop control method | |
| US6605795B1 (en) | Control system for depositing powder to a molten puddle | |
| US7423236B2 (en) | Method and system for real-time monitoring and controlling height of deposit by using image photographing and image processing technology in laser cladding and laser-aided direct metal manufacturing process | |
| US20170326867A1 (en) | Hybrid micro-manufacturing | |
| CN106404795A (en) | Infrared information-based metal additive manufacturing process control apparatus and method | |
| CN107688028B (en) | Laser additive manufacturing lap joint rate online monitoring method | |
| CN108489986A (en) | A kind of increasing material manufacturing on-line checking and restorative procedure | |
| JP2020075504A (en) | Melt pool monitoring system and method for detecting errors in additive manufacturing process | |
| CN114012210B (en) | Deposition quality judgment system and method in electric arc additive process | |
| Shao et al. | Monitoring of liquid droplets in laser-enhanced GMAW | |
| CN109518180B (en) | Self-adaptive laser deposition repair device and method | |
| CN115415549B (en) | Laser cladding flattening control system and method based on nonlinear autoregressive neural network | |
| CN112828311A (en) | Metal additive manufacturing online track adjusting method based on real-time three-dimensional detection | |
| CN116618823A (en) | Closed-loop regulation and control system and method for wire-guide ultrasonic-assisted laser additive manufacturing | |
| Jardon et al. | Offline powder-gas nozzle jet characterization for coaxial laser-based directed energy deposition | |
| Colodrón et al. | Performance improvement of a laser cladding system through FPGA-based control | |
| CN117283133A (en) | Earphone production line electrode laser welding method and laser welding equipment | |
| CN115338517B (en) | Ultrasonic vibration auxiliary arc additive manufacturing device and method based on machine vision control | |
| CN113560574B (en) | 3D printing defect repairing method | |
| CN115283694A (en) | Short-process multi-laser-beam composite additive manufacturing method | |
| Wang et al. | High-speed synchrotron X-ray imaging of directed energy deposition of titanium: effects of processing parameters on the formation of entrapped-gas pores | |
| CN115326811A (en) | System and method for monitoring morphology defects of laser melting deposition aluminum alloy thin-wall structure | |
| CN112605402A (en) | Device and method for controlling relative height of wire piece in electron beam fuse deposition process | |
| CN117816981A (en) | Silk powder composite laser additive manufacturing system and quality feedback regulation and control method |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |