CN114632945A - Morphology error compensation method for laser metal direct forming process - Google Patents
Morphology error compensation method for laser metal direct forming process Download PDFInfo
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/20—Direct sintering or melting
- B22F10/25—Direct deposition of metal particles, e.g. direct metal deposition [DMD] or laser engineered net shaping [LENS]
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
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- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/30—Process control
- B22F10/31—Calibration of process steps or apparatus settings, e.g. before or during manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/30—Process control
- B22F10/36—Process control of energy beam parameters
- B22F10/366—Scanning parameters, e.g. hatch distance or scanning strategy
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
- B22F10/80—Data acquisition or data processing
- B22F10/85—Data acquisition or data processing for controlling or regulating additive manufacturing processes
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- 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
- B33Y10/00—Processes of additive manufacturing
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y50/00—Data acquisition or data processing for additive manufacturing
- B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
Abstract
A morphology error compensation method of a laser metal direct forming process is applied to a laser material increase system; the laser additive system comprises a powder feeding device, a laser and a working platform; the powder feeding device comprises a powder feeder and a powder feeding nozzle, the central point of the powder convergence surface is defined as a powder convergence point, and the powder convergence point is marked as Fp(ii) a The laser comprises a laser generator, a laser controller and a power supply, the central point of the laser deposition area is defined as a laser deposition point, and the laser deposition point is markedIs Fs(ii) a In the laser metal direct forming process, the following specific parameters are adopted: fpAt FsThe lower part is 0.05-0.25mm in height. The invention is applied to the laser metal direct forming process, and only an operator needs to converge the powder at a point FpArranged at a laser deposition point FsThe height of the lower part is within the range of 0.05-0.25mm, so that the problem that the surface of the additive layer is more uneven along with the increase of the number of stacked layers of the deposition layers in the direct forming process of the laser metal is solved.
Description
Technical Field
The invention relates to the technical field of laser metal direct forming, in particular to a morphology error compensation method of a laser metal direct forming process.
Background
The laser metal direct forming technology uses a laser beam with high energy density as a processing heat source, melts into a molten pool on the metal surface, is matched with a synchronous powder feeding technology, instantly melts and deposits metal powder on the surface of a substrate to form a deposition layer, and then controls the scanning motion of a processing head through a numerical control processing platform to stack the deposition layer on the metal surface layer by layer, thereby forming a metal piece with excellent mechanical property.
In the laser metal direct forming process, factors influencing the surface flatness of a formed part mainly include: errors caused by a clamping process of a workpiece, errors caused by uneven surface appearance of a base material and errors caused by non-optimized technological parameters of direct laser metal forming, wherein the errors caused by the non-optimized technological parameters of the direct laser metal forming are the most main factors influencing the surface flatness of the workpiece.
In the laser metal direct forming process, the mode that adopts multichannel deposit covers the target area of work piece in order to form the increase material layer, because the single track deposit presents the arched strip form of cross section, thereby the increase material layer surface that makes multichannel deposit formation presents the form of wave fluctuation (unevenness), stack along with the number of piles on increase material layer, the form of this kind of wave fluctuation (unevenness) is obvious more, and then cause the formed part surface smoothness to descend, seriously influence the size precision of formed part, reduce the material increase efficiency, increase the machining allowance, promote manufacturing cost.
Therefore, it is necessary to compensate/regulate the wave fluctuation (unevenness) of the additive layer in the laser metal direct forming process, but unfortunately, no relevant compensation/regulation method is available in the industry at present.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a morphology error compensation method for a laser metal direct forming process, which solves the problem that the surface flatness and the dimensional accuracy of a formed part are reduced because the surface of an additive layer is in a wavy (uneven) form in the laser metal direct forming process.
The technical scheme of the invention is as follows: a topography error compensation method of a laser metal direct forming process is applied to a laser material increase system; the laser additive system comprises a powder feeding device, a laser and a working platform; the powder feeding device comprises a powder feeder and a powder feeding nozzle, the powder feeder and the powder feeding nozzle are communicated through a gas path pipeline, the powder feeding nozzle is used for spraying and covering laser additive powder on the surface of a workpiece, one end of the powder feeding nozzle is provided with a powder outlet plane, a plurality of powder feeding pipelines are arranged inside the powder feeding nozzle, the end part of each powder feeding pipeline penetrates through the powder outlet plane to form a powder outlet, all the powder outlets are annularly and uniformly distributed on the powder outlet plane, all the powder outlet paths of the powder outlets face obliquely below and finally intersect in one plane, the intersecting plane is defined as a powder converging plane, the central point of the powder converging plane is defined as a powder converging point, and the powder converging point is marked as Fp(ii) a The laser comprises a laser generator, a laser controller and a power supply, wherein the laser generator is used for emitting laser to the surface of the workpiece to form a molten pool, the area where the laser is irradiated on the surface of the workpiece is defined as a laser deposition area, the central point of the laser deposition area is defined as a laser deposition point, and the laser deposition point is marked as Fs(ii) a The working platform is arranged below the laser；
Performing a laser metal direct forming process based on specific parameters; the specific parameters are as follows: fpIs located at FsThe lower part is 0.05-0.25mm in height.
The further technical scheme of the invention is as follows: fsAnd FpThe solution of relative position of (a) is as follows:
s01, pretreating the metal base material and the metal powder: selecting a metal base material and metal powder for a laser additive experiment, polishing and flattening the surface to be processed of the metal base material, cleaning the surface, and finally drying in a drying oven; sending the metal powder into a drying oven for drying treatment to remove moisture and improve the fluidity of the powder;
s02, determining the scanning speed: because the scanning speed is lower than 300mm/min or higher than 500mm/min, the material increasing quantity of the laser is unstable, and the selection range of the scanning speed is preliminarily defined to be between 300 and 500 mm/min; preselecting three scanning speeds within the selection range, wherein the three scanning speeds are respectively 300mm/min, 400mm/min and 500mm/min, and respectively carrying out single-pass deposition experiments aiming at the three scanning speeds; then measuring the deposition height values at the three scanning speeds, and selecting the scanning speed with the maximum deposition height value of 300mm/min to perform subsequent laser metal direct forming experiments;
s03, preparing an evaluation sample: due to powder convergence point FpAnd laser deposition point FsIs a key factor influencing the flatness of the deposited surface after multi-layer scanning, and a plurality of F are firstly setpAnd FsRespectively, is FpAt FsLower 0.6mm or FpAt FsLower 0.4mm or FpAt FsLower 0.2mm or FpAnd FsCoincidence or FpAt Fs0.2mm above or FpAt Fs0.4mm above or FpAt Fs0.6mm above; respectively carrying out laser metal direct forming experiments according to various set relative position values to obtain 7 formed parts corresponding to different relative position values, wherein the No. 1 formed part corresponds to FpAt FsThe lower part is 0.6 mm; no. 2 formed part corresponds to FpAt FsThe lower part is 0.4 mm; number 3 molded part correspondence FpAt FsThe lower part is 0.2 mm; no. 4 molded article correspondence FpAnd FsOverlapping; no. 5 formed part corresponds to FpIs located at Fs0.4mm above; no. 6 molded article correspondence FpAt Fs0.6mm above;
s04, determine FpAnd FsRelative position of (a): evaluating the degree of unevenness of the deposition surface of each molded part by calculating a standard deviation σ of the deposition height of the surface of each molded part;
on the one hand, it is found by calculation that the standard deviation σ is smaller for part No. 3 and part No. 4 compared to the other parts, so that F is preselected firstpIs located at FsThe parameter range of 0-0.2mm below;
on the other hand, only when FpAt FsThe negative feedback effect of the profile error compensation of the molding layer is generated below the mold, so that an error of 0.05mm is introduced to ensure FpAt FsBelow, F is finally selectedpAt FsThe parameter range of 0.05-0.25mm below.
The invention further adopts the technical scheme that: in step S02, the single deposition experiment was performed as follows: clamping a workpiece for a single-pass deposition experiment on a workpiece platform, and setting various processing parameters as follows: the defocusing amount is 25 mm; laser power 500W; the powder feeding speed is 5.3 g/min; the protective gas flow is 5L/min; the scanning speed is 300mm/min or 400mm/min or 500 mm/min; starting a laser material increase system, wherein on one hand, laser irradiates on a surface to be processed of a workpiece to form a molten pool, and on the other hand, metal powder is continuously conveyed into the molten pool through a powder feeding nozzle; finally, three single-channel deposition layers corresponding to the three scanning speeds are formed on the surface to be processed of the workpiece.
The further technical scheme of the invention is as follows: in step S03, on the one hand, the powder feeding nozzle and the powder convergence point F can be calculated according to the inherent structural size of the powder feeding nozzlepIs marked as h1On the other hand, the relative position of the powder feeding nozzle and the laser generator is fixed, and on the other hand, the laser generator and the laser deposition point FsCan be straightMeasuring; by combining the three conditions, F can be obtained in real time in the process of the laser metal direct forming experimentpAnd FsThe relative position of (a).
The further technical scheme of the invention is as follows: in step S03, verification h is performed through a powder feeding test1Whether the numerical value is accurately calculated or not; the powder feeding test procedure was as follows: clamping a workpiece for powder feeding test on a workpiece platform, and setting various processing parameters as follows: the defocusing amount is 25 mm; laser power 500W; the powder feeding speed is 5.3 g/min; the protective gas flow is 5L/min; starting a laser material increasing system, wherein on one hand, laser irradiates on a surface to be processed of a workpiece to form a molten pool, and on the other hand, metal powder is continuously conveyed into the molten pool through a powder conveying nozzle; thereby forming a single deposition layer on the surface to be processed of the workpiece; in the testing process, the vertical height difference between the powder feeding nozzle and the surface to be processed of the workpiece is continuously adjusted, other processing parameters are kept unchanged, the change of the height of the bump of the deposition layer is observed by naked eyes, when the height of the bump of the deposition layer reaches the highest height, the utilization rate of the metal powder is indicated to be the highest, the vertical height difference between the corresponding powder feeding nozzle and the surface to be processed of the workpiece at the moment is recorded and recorded as h2(ii) a H is to be2Value of h is equal to1And comparing the values, and if the error is within 10%, judging that the calculation result is accurate.
The further technical scheme of the invention is as follows: in the step S03, the laser metal direct structuring experiment steps are as follows: clamping a workpiece for a laser metal direct forming experiment on a workpiece platform, and setting various processing parameters as follows: the defocusing amount is 25 mm; laser power 500W; the powder feeding speed is 5.3 g/min; the protective gas flow is 5L/min; the scanning speed is 300 mm/min; depositing 10 layers; fpAt FsLower 0.6mm or FpAt FsLower 0.4mm or FpIs located at FsLower 0.2mm or FpAnd FsCoincidence or FpAt Fs0.2mm above or FpAt FsUpper 0.4mm or FpIs located at Fs0.6mm above; starting the laser material increasing system, on one hand, irradiating laser on the surface to be processed of the workpiece to form a molten pool, and on the other hand, continuously conveying metal into the molten pool through the powder feeding nozzleA powder; processing a deposition layer which completely covers the surface to be processed of the workpiece in a multi-deposition mode, and then repeating the multi-deposition operation to stack 10 deposition layers on the surface to be processed of the workpiece; the final results correspond to different FpAnd Fs7 shaped parts in relative position.
The further technical scheme of the invention is as follows: in step S04, a micrometer-scale digital display height measuring instrument is used to uniformly measure the deposition height of 25 points distributed in a rectangular array on the surface of each formed part, and the deposition height is recorded as h1、h2、h3......h25(ii) a Then, measuring the unevenness degree of the deposition surface by using the standard deviation sigma of the deposition height h, wherein the larger the standard deviation sigma is, the larger the unevenness degree of the deposition surface is, and specifically using a formula 1 and a formula 2;
equation 1:
equation 2:
the further technical scheme of the invention is as follows: the specific parameters further include: the defocusing amount is 24.75-25.25 mm; laser power 495-; the powder feeding speed is 5.247-5.353 g/min; the protective gas flow is 4.95-5.05L/min.
The further technical scheme of the invention is as follows: the specific parameters further include: the defocusing amount is 25 mm; the laser power is 500W; the powder feeding speed is 5.3 g/min; the protective gas flow is 5L/min.
Compared with the prior art, the invention has the following advantages:
1. the method is applied to a laser metal direct forming process, and only an operator needs to deposit a laser deposition point FsArranged at the powder convergence point FpThe height range of 0.05-0.25mm directly above the surface of the additive layer is within the range, so that the problem that the surface of the additive layer is more uneven along with the increase of the number of stacked layers of the deposition layers in the direct forming process of the laser metal is solved.
2. Based on FsAnd FpIn laser additiveIn the process, the concave part of the forming layer is positioned at the position closest to the powder convergence point, relatively more metal powder falls into a molten pool, the coupling of laser and the metal powder is higher, and the deposition height of the concave part is relatively higher; the convex part of the molding layer is positioned at a position slightly higher than the powder convergence point, relatively less metal powder falls into a molten pool, the coupling of laser and the metal powder is lower, and the deposition height of the convex part is relatively lower; thereby generating the negative feedback effect of the surface morphology error compensation of the molding layer and achieving the effect of reducing the unevenness degree of the surface of the additive layer.
The invention is further described below with reference to the figures and examples.
Drawings
Fig. 1 is a surface height measurement of No. 1 molded part;
FIG. 2 is a surface height measurement of part No. 2;
FIG. 3 is a surface height measurement of part No. 3;
fig. 4 is a surface height measurement of part No. 4;
FIG. 5 is a surface height measurement of No. 5 molded part;
FIG. 6 is a surface height measurement chart of No. 6 molded part
Fig. 7 is a surface height measurement of part No. 7;
FIG. 8 is a schematic diagram of the topography error compensation of the laser metal direct structuring process;
fig. 9 is a standard deviation σ chart of 7 molded parts;
FIG. 10 is a surface topography of part No. 4;
fig. 11 is a surface topography of part No. 6.
Detailed Description
Example 1:
a morphology error compensation method of a laser metal direct forming process is applied to a laser material increase system. The laser additive system comprises a powder feeding device, a laser and a working platform. The powder feeding device comprises a powder feeder and a powder feeding nozzle, the powder feeder is communicated with the powder feeding nozzle through a gas path pipeline, the powder feeding nozzle is used for spraying laser additive powder on the surface of a workpiece, and one end of the powder feeding nozzle is provided with a powder outletThe powder feeding nozzle is internally provided with a plurality of powder feeding pipelines, the end parts of the powder feeding pipelines penetrate through the powder outlet plane to form powder outlets, all the powder outlets are annularly and uniformly distributed on the powder outlet plane, powder outlet paths of all the powder outlets face obliquely below and finally intersect in one plane, the intersecting plane is defined as a powder converging plane, the central point of the powder converging plane is defined as a powder converging point, and the powder converging point is marked as Fp. The laser comprises a laser generator, a laser controller and a power supply, wherein the laser generator is used for emitting laser to the surface of the workpiece to form a molten pool, the area where the laser is irradiated on the surface of the workpiece is defined as a laser deposition area, the central point of the laser deposition area is defined as a laser deposition point, and the laser deposition point is marked as Fs. The working platform is positioned below the laser.
In the laser metal direct forming process, the following specific parameters are adopted: fpAt FsThe lower part is 0.05-0.25 mm. Referring to fig. 8, in the laser additive process, only when F ispAt FsWhen the laser powder is positioned below the forming layer, the concave part of the forming layer is positioned at the position closest to the powder convergence point, relatively more metal powder falls into a molten pool, the coupling performance of the laser and the metal powder is higher, and the deposition height of the concave part is relatively higher; the convex part of the forming layer is positioned at a position slightly higher than the powder convergence point, relatively less metal powder falls into a molten pool, the coupling property of laser and the metal powder is lower, and the deposition height of the convex part is relatively lower; thereby generating the negative feedback effect of the surface morphology error compensation of the molding layer and achieving the effect of reducing the unevenness degree of the surface of the additive layer.
FsAnd FpThe solution of relative position of (a) is as follows:
s01, pretreating the metal base material and the metal powder: selecting a metal base material and metal powder for a laser additive experiment, polishing and flattening the surface to be processed of the metal base material, cleaning the surface, and finally drying in a drying oven; and (3) sending the metal powder into a drying box for drying treatment to remove moisture and improve the fluidity of the powder.
In this step, the selected metal substrate is Q235, and the selected metal powder is AH 09506515-B.
S02, determining the scanning speed: because the scanning speed is lower than 300mm/min or higher than 500mm/min, the material increasing quantity of the laser is unstable, and the selection range of the scanning speed is preliminarily defined to be between 300 and 500 mm/min; preselecting three scanning speeds within the selection range, wherein the three scanning speeds are respectively 300mm/min, 400mm/min and 500mm/min, and respectively carrying out single-pass deposition experiments aiming at the three scanning speeds; then measuring the deposition height values at the three scanning speeds, and selecting the scanning speed 300mm/min with the maximum deposition height value to perform subsequent laser metal direct forming experiments.
In this step, the single deposition experiment steps are as follows: clamping a workpiece for a single-pass deposition experiment on a workpiece platform, and setting various processing parameters as follows: the defocusing amount is 25 mm; laser power 500W; the powder feeding speed is 5.3 g/min; the protective gas flow is 5L/min; the scanning speed is 300mm/min or 400mm/min or 500 mm/min; starting a laser material increase system, wherein on one hand, laser irradiates on a surface to be processed of a workpiece to form a molten pool, and on the other hand, metal powder is continuously conveyed into the molten pool through a powder feeding nozzle; finally, three single-pass deposition layers corresponding to three scanning speeds are formed on the surface to be processed of the workpiece, wherein the three single-pass deposition layers are respectively 0.471mm (corresponding to the single-pass deposition layer with the scanning speed of 300 mm/min), 0.382mm (corresponding to the single-pass deposition layer with the scanning speed of 400 mm/min) and 0.249mm (corresponding to the single-pass deposition layer with the scanning speed of 500 mm/min).
S03, preparing an evaluation sample: preparation of evaluation samples: due to powder convergence point FpAnd laser deposition point FsIs a key factor influencing the flatness of the deposited surface after multi-layer scanning, and a plurality of F are firstly setpAnd FsRespectively, is FpAt FsLower 0.6mm or FpAt FsLower 0.4mm or FpAt FsLower 0.2mm or FpAnd FsCoincidence or FpAt Fs0.2mm above or FpAt Fs0.4mm above or FpAt Fs0.6mm above; and respectively carrying out laser metal direct forming experiments according to various set relative position values to obtain 7 formed parts corresponding to different relative position values, wherein the No. 1 formed part corresponds to the formed partFpIs located at FsThe lower part is 0.6 mm; no. 2 formed part corresponds to FpAt FsThe lower part is 0.4 mm; no. 3 formed part correspondence FpIs located at FsThe lower part is 0.2 mm; no. 4 molded article correspondence FpAnd FsOverlapping; no. 5 formed part corresponds to FpAt Fs0.4mm above; number 6 molded part correspondence FpAt Fs0.6mm above.
In this step, on the one hand, the powder feeding nozzle and the powder convergence point F can be calculated according to the inherent structural size of the powder feeding nozzlepIs marked as h1On the other hand, the relative position of the powder feeding nozzle and the laser generator is fixed, and on the other hand, the laser generator and the laser deposition point FsThe vertical height difference can be directly measured; by combining the three conditions, F can be obtained in real time in the process of the laser metal direct forming experimentpAnd FsRelative position of (a).
In this step, verification h is carried out by a powder feeding test1Whether the numerical value is accurately calculated or not; the powder feeding test procedure was as follows: clamping a workpiece for powder feeding test on a workpiece platform, and setting various processing parameters as follows: the defocusing amount is 25 mm; laser power 500W; the powder feeding speed is 5.3 g/min; the protective gas flow is 5L/min; starting a laser material increasing system, wherein on one hand, laser irradiates on a surface to be processed of a workpiece to form a molten pool, and on the other hand, metal powder is continuously conveyed into the molten pool through a powder conveying nozzle; thereby forming a single deposition layer on the surface to be processed of the workpiece; in the testing process, the vertical height difference between the powder feeding nozzle and the surface to be processed of the workpiece is continuously adjusted, other processing parameters are kept unchanged, the change of the height of the bump of the deposition layer is observed by naked eyes, when the height of the bump of the deposition layer reaches the highest height, the utilization rate of the metal powder is indicated to be the highest, the vertical height difference between the corresponding powder feeding nozzle and the surface to be processed of the workpiece at the moment is recorded and recorded as h2(ii) a H is to be2Value of h is the same as above1And comparing the values, and if the error is within 10%, judging that the calculation result is accurate.
In the step, the laser metal direct forming experiment comprises the following steps: clamping a workpiece for a laser metal direct forming experiment on a workpiece platform,the processing parameters are set as follows: the defocusing amount is 25 mm; the laser power is 500W; the powder feeding speed is 5.3 g/min; the protective gas flow is 5L/min; the scanning speed is 300 mm/min; depositing 10 layers; fpAt FsLower 0.6mm or FpAt FsLower 0.4mm or FpAt FsLower 0.2mm or FpAnd FsCoincidence or FpAt Fs0.2mm above or FpAt Fs0.4mm above or FpAt Fs0.6mm above; starting a laser material increase system, wherein on one hand, laser irradiates on a surface to be processed of a workpiece to form a molten pool, and on the other hand, metal powder is continuously conveyed into the molten pool through a powder feeding nozzle; processing a deposition layer which completely covers the surface to be processed of the workpiece by adopting a multi-deposition mode, and then repeating the multi-deposition operation to stack 10 deposition layers on the surface to be processed of the workpiece; the final results correspond to different FpAnd Fs7 shaped parts in relative position.
S04, determining FpAnd FsRelative position of (a): evaluating the degree of unevenness of the deposition surface of each molded part by calculating a standard deviation σ of the deposition height of the surface of each molded part;
on the one hand, it is found by calculation that the standard deviation σ is smaller for part No. 3 and part No. 4 compared to the other parts, so that F is preselected firstpAt FsThe parameter range of 0-0.2mm below;
on the other hand, only when FpAt FsThe negative feedback effect of the profile error compensation of the molding layer is generated below the mold, so that an error of 0.05mm is introduced to ensure FpAt FsBelow, F is finally selectedpAt FsThe parameter range of 0.05-0.25mm below.
In the step, the deposition heights of 25 points distributed in a rectangular array are respectively and uniformly measured on the surface of each formed part by using a micron-sized digital display height measuring instrument and are respectively recorded as h1、h2、h3......h25(ii) a Then, the degree of the unevenness of the deposition surface is measured by the standard deviation sigma of the deposition height h, and the larger the standard deviation sigma is, the unevenness distance of the deposition surface is representedThe greater the degree is; the calculation formula of the standard deviation σ is as follows:
equation 1:
equation 2:
referring to fig. 9, it is calculated that:
Fpat FsThe standard deviation σ of the molded part 0.6mm below was 0.26258;
Fpat FsThe standard deviation σ of the molded part 0.4mm below was 0.41615;
Fpis located at FsThe standard deviation σ of the molded part 0.2mm below was 0.18675;
Fpand FsThe standard deviation σ of the coincident shaped parts was 0.18269;
Fpat FsThe standard deviation σ of the molded part 0.2mm above was 0.27096;
Fpat FsThe standard deviation σ of the molded part 0.4mm above was 0.59887;
Fpat FsThe standard deviation σ of the molded part 0.6mm above was 0.35301.
In this step, after the relevant data is input into the function drawing tool software Origin, surface height measurement maps of 7 formed parts are derived, and referring to fig. 1 to 7 in particular, it can be seen visually in combination with fig. 1 to 7 that the surface flatness of the No. 3 formed part corresponding to fig. 3 and the No. 4 formed part corresponding to fig. 4 is better.
In this step, the surface appearances of the molded part nos. 4 and 6 are respectively shown in fig. 10 and 11, and it can be seen visually by combining fig. 10 and 11 that the molded part No. 4 has good powder coupling (coupling of laser and metal powder) and good surface flatness, and the molded part No. 6 has poor powder coupling and poor surface flatness.
Preferably, the specific parameters further include: the defocusing amount is 25 mm; laser power 500W; the powder feeding speed is 5.3 g/min; the protective gas flow is 5L/min.
Claims (9)
1. A topography error compensation method of a laser metal direct forming process is applied to a laser material increase system; the laser material increase system comprises a powder feeding device, a laser and a working platform; the powder feeding device comprises a powder feeder and a powder feeding nozzle, the powder feeder and the powder feeding nozzle are communicated through a gas path pipeline, the powder feeding nozzle is used for spraying and covering laser additive powder on the surface of a workpiece, one end of the powder feeding nozzle is provided with a powder outlet plane, a plurality of powder feeding pipelines are arranged inside the powder feeding nozzle, the end part of each powder feeding pipeline penetrates through the powder outlet plane to form a powder outlet, all the powder outlets are annularly and uniformly distributed on the powder outlet plane, all the powder outlet paths of the powder outlets face obliquely below and finally intersect in one plane, the intersecting plane is defined as a powder converging plane, the central point of the powder converging plane is defined as a powder converging point, and the powder converging point is marked as Fp(ii) a The laser comprises a laser generator, a laser controller and a power supply, wherein the laser generator is used for emitting laser to the surface of the workpiece to form a molten pool, the area where the laser is irradiated on the surface of the workpiece is defined as a laser deposition area, the central point of the laser deposition area is defined as a laser deposition point, and the laser deposition point is marked as Fs(ii) a The working platform is positioned below the laser; the method is characterized in that: performing a laser metal direct forming process based on specific parameters; the specific parameters are as follows: fpAt FsThe lower part is 0.05-0.25mm in height.
2. The method of claim 1, wherein the method further comprises: fsAnd FpThe solution of relative position of (a) is as follows:
s01, pretreating the metal base material and the metal powder: selecting a metal base material and metal powder for a laser additive experiment, polishing and flattening the surface to be processed of the metal base material, cleaning the surface, and finally drying in a drying oven; sending the metal powder into a drying oven for drying treatment to remove moisture and improve the fluidity of the powder;
s02, determining the scanning speed: because the scanning speed is lower than 300mm/min or higher than 500mm/min, the material increasing quantity of the laser is unstable, and the selection range of the scanning speed is preliminarily defined to be between 300 and 500 mm/min; preselecting three scanning speeds within the selection range, wherein the three scanning speeds are respectively 300mm/min, 400mm/min and 500mm/min, and respectively carrying out single-pass deposition experiments aiming at the three scanning speeds; then measuring the deposition height values at the three scanning speeds, and selecting the scanning speed with the maximum deposition height value of 300mm/min to perform subsequent laser metal direct forming experiments;
s03, preparing an evaluation sample: due to powder convergence point FpAnd laser deposition point FsIs a key factor influencing the flatness of the deposited surface after multi-layer scanning, and a plurality of F are firstly setpAnd FsRespectively, is FpAt FsLower 0.6mm or FpAt FsLower 0.4mm or FpAt FsLower 0.2mm or FpAnd FsCoincidence or FpAt Fs0.2mm above or FpAt Fs0.4mm above or FpAt Fs0.6mm above; respectively carrying out laser metal direct forming experiments according to various set relative position values to obtain 7 formed parts corresponding to different relative position values, wherein the No. 1 formed part corresponds to FpAt FsThe lower part is 0.6 mm; no. 2 formed part corresponds to FpAt FsThe lower part is 0.4 mm; no. 3 formed part correspondence FpIs located at FsThe lower part is 0.2 mm; no. 4 molded article correspondence FpAnd FsOverlapping; no. 5 formed part corresponds to FpIs located at Fs0.4mm above; no. 6 molded article correspondence FpAt Fs0.6mm above;
s04, determining FpAnd FsRelative position of (a): evaluating the degree of unevenness of the deposition surface of each molded part by calculating a standard deviation σ of the deposition height of the surface of each molded part;
on the one hand, it is found by calculation that the standard deviation σ is smaller for part No. 3 and part No. 4 compared to the other parts, so that F is preselected firstpAt FsThe parameter range of 0-0.2mm below;
on the other hand, only when FpAt FsThe negative feedback effect of the profile error compensation of the molding layer is generated below the mold, so that an error of 0.05mm is introduced to ensure FpAt FsBelow, F is finally selectedpAt FsThe parameter range of 0.05-0.25mm below.
3. The method of claim 2, wherein the step of compensating for the profile error comprises: in step S02, the single deposition experiment was performed as follows: clamping a workpiece for a single-pass deposition experiment on a workpiece platform, and setting various processing parameters as follows: the defocusing amount is 25 mm; laser power 500W; the powder feeding speed is 5.3 g/min; the protective gas flow is 5L/min; the scanning speed is 300mm/min or 400mm/min or 500 mm/min; starting a laser material increase system, wherein on one hand, laser irradiates on a surface to be processed of a workpiece to form a molten pool, and on the other hand, metal powder is continuously conveyed into the molten pool through a powder feeding nozzle; finally, three single-channel deposition layers corresponding to the three scanning speeds are formed on the surface to be processed of the workpiece.
4. The method of claim 3, wherein the method further comprises: in step S03, on the one hand, the powder feeding nozzle and the powder convergence point F can be calculated according to the inherent structural size of the powder feeding nozzlepIs marked as h1On the other hand, the relative position of the powder feeding nozzle and the laser generator is fixed, and on the other hand, the laser generator and the laser deposition point FsThe vertical height difference can be directly measured; by combining the three conditions, F can be obtained in real time in the process of the laser metal direct forming experimentpAnd FsThe relative position of (a).
5. The method of claim 4, wherein the step of compensating for the shape error comprises: in step S03, verification h is performed by powder feeding test1Whether the numerical value is accurately calculated or not; the powder feeding test procedure was as follows: clamping a workpiece for powder feeding test on a workpiece platform, and setting various processing parameters as follows: the defocusing amount is 25 mm; laser power 500W; powder feeding speed 5.3gMin; the protective gas flow is 5L/min; starting a laser material increase system, wherein on one hand, laser irradiates on a surface to be processed of a workpiece to form a molten pool, and on the other hand, metal powder is continuously conveyed into the molten pool through a powder feeding nozzle; thereby forming a single deposition layer on the surface to be processed of the workpiece; in the testing process, the vertical height difference between the powder feeding nozzle and the surface to be processed of the workpiece is continuously adjusted, other processing parameters are kept unchanged, the change of the height of the bump of the deposition layer is observed by naked eyes, when the height of the bump of the deposition layer reaches the highest height, the utilization rate of the metal powder is indicated to be the highest, the vertical height difference between the corresponding powder feeding nozzle and the surface to be processed of the workpiece at the moment is recorded and recorded as h2(ii) a H is to be2Value of h is the same as above1And comparing the values, and if the error is within 10%, judging that the calculation result is accurate.
6. The method of claim 5, wherein the step of compensating for the shape error comprises: in the step S03, the laser metal direct structuring experiment steps are as follows: clamping a workpiece for a laser metal direct forming experiment on a workpiece platform, and setting various processing parameters as follows: the defocusing amount is 25 mm; laser power 500W; the powder feeding speed is 5.3 g/min; the protective gas flow is 5L/min; the scanning speed is 300 mm/min; depositing 10 layers; fpAt FsLower 0.6mm or FpAt FsLower 0.4mm or FpAt FsLower 0.2mm or FpAnd FsCoincidence or FpAt Fs0.2mm above or FpAt FsUpper 0.4mm or FpAt Fs0.6mm above; starting a laser material increase system, wherein on one hand, laser irradiates on a surface to be processed of a workpiece to form a molten pool, and on the other hand, metal powder is continuously conveyed into the molten pool through a powder feeding nozzle; processing a deposition layer which completely covers the surface to be processed of the workpiece by adopting a multi-deposition mode, and then repeating the multi-deposition operation to stack 10 deposition layers on the surface to be processed of the workpiece; the final results correspond to different FpAnd Fs7 shaped parts in relative position.
7. As claimed inSolving 6 the shape error compensation method of the laser metal direct forming process, which is characterized in that: in step S04, a micrometer-scale digital display height measuring instrument is used to uniformly measure the deposition height of 25 points distributed in a rectangular array on the surface of each formed part, and the deposition height is recorded as h1、h2、h3......h25(ii) a Then, measuring the unevenness degree of the deposition surface by using the standard deviation sigma of the deposition height h, wherein the larger the standard deviation sigma is, the larger the unevenness degree of the deposition surface is, and specifically using a formula 1 and a formula 2;
equation 1:
equation 2:
8. the method of compensating for profile errors in a laser metal direct structuring process as claimed in any one of claims 1 to 7, wherein: the specific parameters further include: the defocusing amount is 24.75-25.25 mm; laser power 495-; the powder feeding speed is 5.247-5.353 g/min; the protective gas flow is 4.95-5.05L/min.
9. The method of claim 8, wherein the step of compensating for topography errors comprises: the specific parameters further include: the defocusing amount is 25 mm; laser power 500W; the powder feeding speed is 5.3 g/min; the protective gas flow is 5L/min.
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