CN114851549B - Method for manufacturing product formed by selective laser sintering - Google Patents
Method for manufacturing product formed by selective laser sintering Download PDFInfo
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- CN114851549B CN114851549B CN202210524490.XA CN202210524490A CN114851549B CN 114851549 B CN114851549 B CN 114851549B CN 202210524490 A CN202210524490 A CN 202210524490A CN 114851549 B CN114851549 B CN 114851549B
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- 238000000034 method Methods 0.000 title claims abstract description 48
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 22
- 238000000110 selective laser sintering Methods 0.000 title claims abstract description 14
- 238000007639 printing Methods 0.000 claims abstract description 75
- 238000012937 correction Methods 0.000 claims abstract description 38
- 239000000463 material Substances 0.000 claims abstract description 24
- 239000000843 powder Substances 0.000 claims abstract description 16
- 238000002844 melting Methods 0.000 claims abstract description 8
- 230000008018 melting Effects 0.000 claims abstract description 8
- 238000000149 argon plasma sintering Methods 0.000 claims abstract description 4
- 238000012360 testing method Methods 0.000 claims description 75
- 238000005259 measurement Methods 0.000 claims description 40
- 238000013461 design Methods 0.000 claims description 22
- 238000010586 diagram Methods 0.000 claims description 12
- 238000009826 distribution Methods 0.000 claims description 11
- 230000010354 integration Effects 0.000 claims description 8
- 230000008602 contraction Effects 0.000 claims description 6
- 230000000694 effects Effects 0.000 claims description 6
- 238000004140 cleaning Methods 0.000 claims description 3
- 230000001105 regulatory effect Effects 0.000 claims description 3
- 238000005488 sandblasting Methods 0.000 claims description 3
- 238000003892 spreading Methods 0.000 claims description 3
- 239000000047 product Substances 0.000 description 44
- 238000010146 3D printing Methods 0.000 description 4
- 238000004364 calculation method Methods 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 238000001514 detection method Methods 0.000 description 4
- 239000000654 additive Substances 0.000 description 3
- 230000000996 additive effect Effects 0.000 description 3
- 238000013459 approach Methods 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 3
- 238000005245 sintering Methods 0.000 description 3
- 238000012795 verification Methods 0.000 description 3
- 229920000299 Nylon 12 Polymers 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 239000012467 final product Substances 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 229920003023 plastic Polymers 0.000 description 2
- 239000004033 plastic Substances 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 238000010200 validation analysis Methods 0.000 description 2
- JHWNWJKBPDFINM-UHFFFAOYSA-N Laurolactam Chemical compound O=C1CCCCCCCCCCCN1 JHWNWJKBPDFINM-UHFFFAOYSA-N 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000004927 fusion Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 238000003475 lamination Methods 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/10—Processes of additive manufacturing
- B29C64/106—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
- B29C64/124—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified
- B29C64/129—Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using layers of liquid which are selectively solidified characterised by the energy source therefor, e.g. by global irradiation combined with a mask
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/20—Apparatus for additive manufacturing; Details thereof or accessories therefor
- B29C64/205—Means for applying layers
- B29C64/209—Heads; Nozzles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/20—Apparatus for additive manufacturing; Details thereof or accessories therefor
- B29C64/227—Driving means
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
- B29C64/30—Auxiliary operations or equipment
- B29C64/386—Data acquisition or data processing for additive manufacturing
-
- 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B33—ADDITIVE MANUFACTURING TECHNOLOGY
- B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
- B33Y50/00—Data acquisition or data processing for additive manufacturing
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
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Abstract
The invention discloses a method for manufacturing a product formed by selective laser sintering, which comprises the steps of dividing the product into a plurality of layers along the height direction by a computer, paving material powder layer by layer from bottom to top, and then adopting a laser sintering melting mode to print layer by layer according to the product contour of each layer until the product is formed; and correcting the printing program by adopting the printing correction coefficients in the x direction and the y direction and the laser spot compensation coefficient, and printing the product. The invention can better solve the errors caused by materials and printing equipment, thereby improving the dimensional accuracy of products, and has the advantages of simple operation, convenient implementation and practicality.
Description
Technical Field
The invention relates to the technical field of additive manufacturing and 3D printing, in particular to a method for manufacturing a product formed by selective laser sintering.
Background
3D Printing (3D Printing) belongs to one of the rapid prototyping technologies, and is also called additive manufacturing; the technology is based on a digital model, and materials such as plastics, metals, ceramic powder and the like are stacked layer by utilizing a laser mode, a hot melting nozzle mode and the like to bond and mold to construct an object. In recent years, 3D printing technology is widely applied to various fields such as industrial design, jewelry, automobiles, aerospace, dental and medical industries, education and the like. The 3D printer commonly used at present has a plurality of types such as Selective Laser Melting (SLM), selective Laser Sintering (SLS), three-dimensional powder bonding, fusion lamination Forming (FDM) and the like.
Among them, selective Laser Sintering (SLS) is a 3D printed product manufacturing method that sinters a powder material (which may be plastic, metal, ceramic or glass frit) using a laser as a power source and prints layer by layer to finally obtain the product profile, as an Additive Manufacturing (AM) technique.
In the process of selectively sintering and forming a printed product by laser, printing errors can be generated due to different shrinkage rates of materials and different printing equipment caused by different selected printing materials. When the product to be manufactured is mass manufactured with a simple structure, a product sample can be printed by directly adopting printing equipment, and then the printing program is corrected after the dimensional error is measured to print the product. However, for some complex structures, especially products with complex internal cavity structures, this approach suffers from the disadvantages of difficult structural dimension measurement and excessive printing costs. Therefore, a product manufacturing mode which can better improve the printing and manufacturing precision of the product, is simple and feasible and is convenient to operate is needed to be designed, so that the precision and quality of the product are improved.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to solve the technical problems that: the method for manufacturing the selective laser sintering formed product can better solve the errors caused by materials and printing equipment, so that the dimensional accuracy of the product is improved, and the method has the characteristics of simplicity in operation, convenience in implementation and practicability.
In order to solve the technical problems, the invention adopts the following technical scheme:
a method for manufacturing a product formed by selective laser sintering includes dividing the product into a plurality of layers along the height direction by a computer, spreading material powder layer by layer from bottom to top, and then printing layer by layer according to the product contour of each layer by adopting a laser sintering melting mode until the product is formed; and then correcting and compensating the printing program by adopting the printing correction coefficients in the x direction and the y direction and the laser spot compensation coefficient, and printing the product.
In this way, there is an error in printing accuracy due to the difference in shrinkage of the material itself between different printing materials. In the height direction, because 3d printing is layered printing, the influence of errors in the height direction can be overcome by means of layering, only the dimension correction in the horizontal direction is considered, and the correction result can be obtained more quickly. Meanwhile, the quality of laser spots can be caused to distinguish and influence the sintering and melting speed, efficiency and the like of materials due to different printing equipment. Therefore, the compensation coefficient of the laser light spot is calculated and corrected according to different printing devices, and the influence of different laser light spots of different printing devices on printing precision can be overcome. Therefore, the method can better improve the product precision.
Further, a series of test samples with different sizes are printed by adopting the same printing material and printing equipment, the size data of the series of test samples in the x direction and the y direction are measured, the measured size data are subjected to scatter diagram distribution, the data are subjected to linear fitting by adopting a least square method according to the linear rule of each data point, and the printing correction coefficients and the laser spot compensation coefficients of the product in the x direction and the y direction are obtained according to the linear fitting result.
Therefore, the test sample can adopt a sample with a simple structure, can be printed and measured very conveniently and rapidly, and then obtains the corresponding printing correction coefficient and the laser spot compensation coefficient according to the calculation result for correcting the actual printing program of the product, so that the printing precision of the product can be improved, and the method is more convenient and feasible compared with the method of obtaining the correction parameters through measurement after the actual printing of the product. In specific implementation, a specific manner of performing scatter diagram distribution and linear fitting of the data by the least square method is the prior art, and is not described in detail herein.
Further, the test specimen is a rectangular frame member having a rectangular hollow cavity in the horizontal direction and a rectangular hollow cavity in the vertical direction.
Therefore, the test sample is simple in structure, quick to print and convenient to measure, the inner contour dimension and the outer contour dimension can be obtained simultaneously, after the inner contour dimension and the outer contour dimension are respectively linearly fitted, when the coefficient difference obtained by the respective linear fitting of the inner contour dimension and the outer contour dimension is larger than a preset threshold, the difference exists between the correction coefficients of the inner contour and the outer contour. At the moment, the data of the inner contour size and the outer contour size can be integrated, so that a more scientific and reliable correction coefficient is obtained, and the printing precision is better improved.
Further, the series of test specimens had contour length and width dimensions in the horizontal direction of 150 mm ×30 mm,120 mm×30 mm,100 mm×30 mm,80 mm×30 mm,40 mm×20 mm, respectively, and a contour width of 5mm (i.e., inner contour dimensions of 140 mm ×20 mm,110 mm×20 mm,90 mm×20 mm,70 mm×20 mm,30 mm×10 mm, respectively).
The test samples with the series of sizes are adopted, so that the production, the preparation and the measurement are easier.
Further, the same 8 groups of test samples are adopted, and two groups are respectively arranged in parallel in the four directions of front, back, left and right during printing, and each group is symmetrically arranged in a discontinuous reverse shape in the four directions according to the mode of small inside and large outside.
Like this, each place two sets of (transversely put around in the jar body, left and right vertical put) in the region around in, can reduce the difference that different regional errors lead to better after taking the mean value during the measurement. In the different directions of x and y, the different sizes of the length directions of the four groups of test pieces are used as measurement data samples in the different directions, so that the sizes of the data samples in the x and y directions are kept consistent, more detection samples are obtained by adopting samples with fewer specifications, and the four samples are used for the samples in the corresponding sizes in each direction, and the average value can be taken during measurement to better avoid accidental factors, so that the accuracy of the detection result is ensured. The arrangement structure can save the plane space of the cylinder body and enable the sample to be swung to the plane of the cylinder body as much as possible.
Further, the outline dimensions of the series of test samples in the height direction are unified, so that the test sample pieces are taken out after being cooled to room temperature after being printed, and the warpage is not generated as the lowest standard, and the height dimension is larger than the lowest standard and smaller than or equal to the height dimension of an actual product.
When the method is implemented, if the measurement efficiency is required to be improved and the time is shortened, the method can be selected according to the approach to the minimum standard, and if the accuracy and the reliability are required to be improved to the maximum extent, the method can be selected according to the actual height of the product. However, since the error in the height direction is small, the effect of the selection of the product according to the actual height is limited, and the product can be usually implemented according to the size of 5mm as the height direction.
Further, the outline dimensions of the series of test specimens in the height direction were unified to a size of 5mm.
Further, after the printing of the series of test samples is finished, the printing material powder of about 5mm is continuously paved above the test samples until the test samples are taken down after cooling.
Therefore, the surface warping of the surface of the test sample piece in the cooling process can be avoided to the greatest extent, and the influence of the warping of the test piece on the accuracy of the measurement dimension is avoided.
Further, after the test sample is printed and taken out, sand blasting and powder cleaning treatment is carried out on the test sample, after the residual powder on the surface is cleaned up, measurement data is carried out on the test sample by using an electronic vernier caliper, and the sizes of the two end positions of the opposite sides are measured and the average value is measured for a plurality of times during measurement.
Therefore, the cuboid sample piece is empty in the middle of the length direction, so that the sample piece is deformed in the middle of measurement, and data are inaccurate, so that the two ends of the cuboid sample piece are measured as much as possible during measurement, and the measurement is performed for multiple times to obtain an average value, thereby better improving the measurement accuracy and improving the final calculation reliability.
Further, during measurement, the inner contour dimension and the outer contour dimension of the test sample are measured respectively, scatter diagram distribution and linear fitting are conducted on the inner contour dimension and the outer contour dimension of each series of test samples in the X direction and the Y direction respectively, a linear relation coefficient k (between a design dimension and a printing dimension) of each of the inner contour dimension and the outer contour dimension is obtained, and when the linear relation coefficient k of each of the inner contour dimension and the outer contour dimension is different, a new linear relation coefficient k value is obtained in a secondary integration mode to serve as a linear fitting result of each of the inner contour dimension and the outer contour dimension.
This is because there is usually a difference in the k values to which the inner and outer dimensions of the test specimen are fitted, which is also the meaning of designing the test specimen to be hollow and detecting the inner and outer dimensions, respectively. However, the correction coefficient required by the final printing program is not divided into inner and outer contours, so that the linear fitting results of the inner contour dimension and the outer contour dimension are integrated first to obtain the integrated linear relation coefficient k value and linear fitting formula, and the correction coefficient required by the final printing program can be finally obtained, so that the correction can be performed more accurately, and the dimensional accuracy of the final product is improved.
Further, the specific step of performing secondary integration on the inner contour dimension and the outer contour dimension of the series of test samples in the X direction comprises the following steps:
1 firstly separating the measured inner contour dimension data and outer contour dimension data in the x direction, respectively carrying out scatter diagram distribution, and then carrying out linear fitting by using a least square method, wherein the fitting is y Outer part =k Outer part x Outer part +b Outer part And y Inner part =k Inner part x Inner part +b Inner part Obtaining k by linear fitting Outer part 、b Outer part 、k Inner part And b Inner part Wherein; y is Outer part Representing the actual print measurement size, x of the outer contour Outer part Represents the design size, k of the outer contour Outer part Represents the number of outer profile contractions, b Outer part The outer contour facula influence number is represented; y is Inner part Indicating the actual printed measurement size, x of the inner contour Inner part Representing the design dimensions, k, of the inner contour Inner part Indicating the number of inner contour contractions, b Inner part Indicating the influence number of the inner contour light spots; theoretically k Outer part And k Inner part The two steps are carried out in step 2, wherein the inner and outer profile shrinkage numbers are uniform because the inner and outer profile shrinkage numbers are the same as the inner profile shrinkage number;
2 k outer part And k Inner part Different, due to b Outer part And b Inner part Is two constant terms, the absolute value of the two constant terms is taken and then averaged, and the [ (|b) 1 |+|b 2 |）/2]=c, c represents the quadratic fit decompartment term impact number; will y Outer part -c，y Inner part +c as a new set of actual measured data, the constant term effects can be eliminated to obtain a set (x Outer part ，y Outer part -c) and (x) Inner part ，y Inner part +c) data, a second linear fit is performed on the set of data using a least squares method to obtain y Heald =k Heald x Heald +b, where y Heald Representing the actual printed measured dimensions, k Heald Representing the inner and outer profile shrinkage factor, x Heald Representing the design size of the inner and outer contours, b is the straight line intercept obtained by data fitting; this step is to obtain k Heald B is dropped;
3. then c is moved up and down to obtain the final fitting relation, namely y Heald =k Heald x Heald C (outer and inner contours can be characterized simultaneously);
4. in the printing program, the design size of the printed piece is regulated, and the light spot compensation coefficient B, namely y, is added after the design size is multiplied by the correction coefficient K Heald =k Heald （Kx Heald +b) ±c, yielding k=1/K, B Outer 1 =-c/k，B Inner 1 C/k, since both sides of the part are affected by the laser spot, the final B Outer part =-c/2k，B Inner part =c/2 k; wherein K represents shrinkage correctionCoefficient B Outer 1 Representing the total compensation coefficient of the outer contour facula, B Inner 1 Representing the total compensation coefficient of the inner contour facula, B Outer part Representing the compensation coefficient of the flare of the outer contour, B Inner part Indicating the inner profile spot compensation coefficient.
Therefore, by adopting the secondary integration mode, the influence of the inner contour dimension data and the outer contour dimension on the printing coefficient is considered, and the correction coefficient and the laser spot compensation coefficient required by the printing program are obtained by means of the integrated linear relation coefficient and constant value, so that the accuracy and the reliability of final correction can be improved better.
In implementation, the Y direction is integrated twice in the same manner, and the specific process is not repeated.
In summary, the invention can better solve the errors caused by materials and printing equipment, thereby improving the dimensional accuracy of products, and has the advantages of simple operation, convenient implementation and practicality.
Drawings
FIG. 1 is a schematic diagram of a series of test specimens and their arrangement in the practice of the present invention. The reference numbers in the figures are sample numbers, for a total of 1-40 samples.
FIG. 2 is a table of print data measurements and design values versus data for a series of test samples without correction and compensation at the time of test validation.
FIG. 3 is a table of print data measurements and design value versus data for a series of test samples after correction and compensation using the present method at the time of test validation.
Detailed Description
The present invention will be described in further detail with reference to the following embodiments.
The specific embodiment is as follows: a method for manufacturing a product formed by selective laser sintering includes dividing the product into a plurality of layers along the height direction by a computer, spreading material powder layer by layer from bottom to top, and then printing layer by layer according to the product contour of each layer by adopting a laser sintering melting mode until the product is formed; and then correcting and compensating the printing program by adopting the printing correction coefficients in the x direction and the y direction and the laser spot compensation coefficient, and printing the product.
In this way, there is an error in printing accuracy due to the difference in shrinkage of the material itself between different printing materials. In the height direction, because 3d printing is layered printing, the influence of errors in the height direction can be overcome by means of layering, only the dimension correction in the horizontal direction is considered, and the correction result can be obtained more quickly. Meanwhile, the quality of laser spots can be caused to distinguish and influence the sintering and melting speed, efficiency and the like of materials due to different printing equipment. Therefore, the compensation coefficient of the laser light spot is calculated and corrected according to different printing devices, and the influence of different laser light spots of different printing devices on printing precision can be overcome. Therefore, the method can better improve the product precision.
The method comprises the steps of printing a series of test samples with different sizes by adopting the same printing material and printing equipment, measuring respective size data of the series of test samples in the x direction and the y direction, performing scatter diagram distribution on the measured size data, performing linear fitting on the data by adopting a least square method according to the linear rule of each data point, and obtaining printing correction coefficients and laser spot compensation coefficients of the product in the x direction and the y direction according to the linear fitting result.
Therefore, the test sample can adopt a sample with a simple structure, can be printed and measured very conveniently and rapidly, and then obtains the corresponding printing correction coefficient and the laser spot compensation coefficient according to the calculation result for correcting the actual printing program of the product, so that the printing precision of the product can be improved, and the method is more convenient and feasible compared with the method of obtaining the correction parameters through measurement after the actual printing of the product. In specific implementation, a specific manner of performing scatter diagram distribution and linear fitting of the data by the least square method is the prior art, and is not described in detail herein.
The test sample is a rectangular frame member with a rectangular hollow cavity in the horizontal direction and a rectangular hollow cavity in the vertical direction.
Therefore, the test sample is simple in structure, quick to print and convenient to measure, the inner contour dimension and the outer contour dimension can be obtained simultaneously, after the inner contour dimension and the outer contour dimension are respectively linearly fitted, when the coefficient difference obtained by the respective linear fitting of the inner contour dimension and the outer contour dimension is larger than a preset threshold, the difference exists between the correction coefficients of the inner contour and the outer contour. At the moment, the data of the inner contour size and the outer contour size can be integrated, so that a more scientific and reliable correction coefficient is obtained, and the printing precision is better improved.
The horizontal profile length and width dimensions of the test specimens of the series were 150 mm ×30 mm,120 mm×30 mm,100 mm×30 mm,80 mm×30 mm,40 mm×20 mm, and 5mm in profile width (i.e., 140 mm ×20 mm,110 mm×20 mm,90 mm×20 mm,70 mm×20 mm,30 mm×10 mm, respectively).
The test samples with the series of sizes are adopted, so that the production, the preparation and the measurement are easier.
The serial test samples adopt the same 8 groups, and are respectively arranged in parallel in the front, back, left and right directions during printing, and each group is symmetrically distributed in a discontinuous shape in the four directions according to the mode of small inside and large outside. With particular reference to fig. 1.
Like this, each place two sets of (transversely put around in the jar body, left and right vertical put) in the region around in, can reduce the difference that different regional errors lead to better after taking the mean value during the measurement. In the different directions of x and y, the different sizes of the length directions of the four groups of test pieces are used as measurement data samples in the different directions, so that the sizes of the data samples in the x and y directions are kept consistent, more detection samples are obtained by adopting samples with fewer specifications, and the four samples are used for the samples in the corresponding sizes in each direction, and the average value can be taken during measurement to better avoid accidental factors, so that the accuracy of the detection result is ensured. The arrangement structure can save the plane space of the cylinder body and enable the sample to be swung to the plane of the cylinder body as much as possible.
The outline dimension of the series of test samples in the height direction is unified, the test sample pieces are taken out after being cooled to room temperature after being printed, the warpage is not generated as the lowest standard, and the height dimension is larger than the lowest standard and smaller than or equal to the height dimension of an actual product.
When the method is implemented, if the measurement efficiency is required to be improved and the time is shortened, the method can be selected according to the approach to the minimum standard, and if the accuracy and the reliability are required to be improved to the maximum extent, the method can be selected according to the actual height of the product. However, since the error in the height direction is small, the effect of the selection of the product according to the actual height is limited, and the product can be usually implemented according to the size of 5mm as the height direction.
Wherein, the outline dimension of the series of test specimens in the height direction is unified to be 5mm in size.
After the series of test samples are printed, continuously paving printing material powder with the thickness of about 5mm above the test samples until the test samples are taken down after cooling.
Therefore, the surface warping of the surface of the test sample piece in the cooling process can be avoided to the greatest extent, and the influence of the warping of the test piece on the accuracy of the measurement dimension is avoided.
After the test sample is printed and taken out, sand blasting and powder cleaning treatment is carried out on the test sample, after the residual powder on the surface is cleaned up, measurement data are carried out on the test sample by using an electronic vernier caliper, and the sizes of the two end positions of the opposite sides are measured and the average value is measured for a plurality of times during measurement.
Therefore, the cuboid sample piece is empty in the middle of the length direction, so that the sample piece is deformed in the middle of measurement, and data are inaccurate, so that the two ends of the cuboid sample piece are measured as much as possible during measurement, and the measurement is performed for multiple times to obtain an average value, thereby better improving the measurement accuracy and improving the final calculation reliability.
During measurement, the inner contour dimension and the outer contour dimension of the test sample are measured respectively, scatter diagram distribution and linear fitting are carried out on the inner contour dimension and the outer contour dimension of each series of test samples in the X direction and the Y direction respectively, a linear relation coefficient k (between a design dimension and a printing dimension) of each of the inner contour dimension and the outer contour dimension is obtained, and when the linear relation coefficient k of each of the inner contour dimension and the outer contour dimension is different, a new linear relation coefficient k value is obtained in a secondary integration mode to be used as a linear fitting result of each of the inner contour dimension and the outer contour dimension.
This is because there is usually a difference in the k values to which the inner and outer dimensions of the test specimen are fitted, which is also the meaning of designing the test specimen to be hollow and detecting the inner and outer dimensions, respectively. However, the correction coefficient required by the final printing program is not divided into inner and outer contours, so that the linear fitting results of the inner contour dimension and the outer contour dimension are integrated first to obtain the integrated linear relation coefficient k value and linear fitting formula, and the correction coefficient required by the final printing program can be finally obtained, so that the correction can be performed more accurately, and the dimensional accuracy of the final product is improved.
The specific step of performing secondary integration on the inner contour dimension and the outer contour dimension of the X-direction series test samples comprises the following steps:
1 firstly separating the measured inner contour dimension data and outer contour dimension data in the x direction, respectively carrying out scatter diagram distribution, and then carrying out linear fitting by using a least square method, wherein the fitting is y Outer part =k Outer part x Outer part +b Outer part And y Inner part =k Inner part x Inner part +b Inner part Obtaining k by linear fitting Outer part 、b Outer part 、k Inner part And b Inner part Wherein; y is Outer part Representing the actual print measurement size, x of the outer contour Outer part Represents the design size, k of the outer contour Outer part Represents the number of outer profile contractions, b Outer part The outer contour facula influence number is represented; y is Inner part Indicating the actual printed measurement size, x of the inner contour Inner part Representing the design dimensions, k, of the inner contour Inner part Indicating the number of inner contour contractions, b Inner part Indicating the influence number of the inner contour light spots; theoretically k Outer part And k Inner part The two steps are carried out in step 2, wherein the inner and outer profile shrinkage numbers are uniform because the inner and outer profile shrinkage numbers are the same as the inner profile shrinkage number;
2 k outer part And k Inner part Different, due to b Outer part And b Inner part Is two constant items, and the two constant items are takenThe absolute values are re-averaged, and let [ (|b) 1 |+|b 2 |）/2]=c, c represents the quadratic fit decompartment term impact number; will y Outer part -c，y Inner part +c as a new set of actual measured data, the constant term effects can be eliminated to obtain a set (x Outer part ，y Outer part -c) and (x) Inner part ，y Inner part +c) data, a second linear fit is performed on the set of data using a least squares method to obtain y Heald =k Heald x Heald +b, where y Heald Representing the actual printed measured dimensions, k Heald Representing the inner and outer profile shrinkage factor, x Heald Representing the design size of the inner and outer contours, b is the straight line intercept obtained by data fitting; this step is to obtain k Heald B is dropped;
3. then c is moved up and down to obtain the final fitting relation, namely y Heald =k Heald x Heald C (outer and inner contours can be characterized simultaneously);
4. in the printing program, the design size of the printed piece is regulated, and the light spot compensation coefficient B, namely y, is added after the design size is multiplied by the correction coefficient K Heald =k Heald （Kx Heald +b) ±c, yielding k=1/K, B Outer 1 =-c/k，B Inner 1 C/k, since both sides of the part are affected by the laser spot, the final B Outer part =-c/2k，B Inner part =c/2 k; wherein K represents a shrinkage correction coefficient, B Outer 1 Representing the total compensation coefficient of the outer contour facula, B Inner 1 Representing the total compensation coefficient of the inner contour facula, B Outer part Representing the compensation coefficient of the flare of the outer contour, B Inner part Indicating the inner profile spot compensation coefficient.
Therefore, by adopting the secondary integration mode, the influence of the inner contour dimension data and the outer contour dimension on the printing coefficient is considered, and the correction coefficient and the laser spot compensation coefficient required by the printing program are obtained by means of the integrated linear relation coefficient and constant value, so that the accuracy and the reliability of final correction can be improved better.
In implementation, the Y direction is integrated twice in the same manner, and the specific process is not repeated.
To better verify the principles and effects described above, the applicant has verified the process of the above method using actual printing. The printing material adopted for verification is nylon 12 (PA 12), the printing equipment adopted for verification is implemented in the model SLS400, the printing method adopted for verification is used for correcting and compensating the printing program according to the steps in the embodiment, and then the test sample is repeatedly printed again. FIG. 2 is a comparison of the measured values of the print data and the design values for the series of test samples without correction and compensation, and it can be seen that the error is generally in the range of about 5mm. FIG. 3 shows that the measured value of the printing data after correction and compensation of the printing program is compared with the design value by the method, and the error is basically within 0.1mm and the small part is within the range of 0.1-0.2mm, so that the method can greatly improve the printing precision. The printing device is particularly suitable for printing and manufacturing products with complex inner cavity structures.
Claims (6)
1. A method for manufacturing a product formed by selective laser sintering includes dividing the product into a plurality of layers along the height direction by a computer, spreading material powder layer by layer from bottom to top, and then printing layer by layer according to the product contour of each layer by adopting a laser sintering melting mode until the product is formed; then adopting the printing correction coefficients in the x direction and the y direction and the laser spot compensation coefficient to correct and compensate the printing program, and printing the product;
printing a series of test samples with different sizes by adopting the same printing material and printing equipment, measuring respective size data of the series of test samples in the x direction and the y direction, performing scatter diagram distribution on the measured size data, performing linear fitting on the data by adopting a least square method according to the linear rule of each data point, and obtaining printing correction coefficients and laser spot compensation coefficients of the product in the x direction and the y direction according to the linear fitting result;
the test sample is a rectangular frame member with a rectangular hollow cavity in the horizontal direction and a rectangular hollow cavity in the vertical direction;
during measurement, the inner contour dimension and the outer contour dimension of the test sample are measured respectively, scatter diagram distribution and linear fitting are carried out on the inner contour dimension and the outer contour dimension of each series of test samples in the X direction and the Y direction respectively, the respective linear relation coefficient k of the inner contour dimension and the outer contour dimension is obtained, and when the respective linear relation coefficient k of the inner contour dimension and the outer contour dimension is different, a secondary integration mode is adopted to obtain a new linear relation coefficient k value as the respective linear fitting result of the inner contour dimension and the outer contour dimension;
the specific steps of carrying out secondary integration on the inner outline size and the outer outline size of the X-direction series test samples comprise the following steps:
1 firstly separating the measured inner contour dimension data and outer contour dimension data in the x direction, respectively carrying out scatter diagram distribution, and then carrying out linear fitting by using a least square method, wherein the fitting is y Outer part =k Outer part x Outer part +b Outer part And y Inner part =k Inner part x Inner part +b Inner part Obtaining k by linear fitting Outer part 、b Outer part 、k Inner part And b Inner part Wherein; y is Outer part Representing the actual print measurement size, x of the outer contour Outer part Represents the design size, k of the outer contour Outer part Represents the number of outer profile contractions, b Outer part The outer contour facula influence number is represented; y is Inner part Indicating the actual printed measurement size, x of the inner contour Inner part Representing the design dimensions, k, of the inner contour Inner part Indicating the number of inner contour contractions, b Inner part Indicating the influence number of the inner contour light spots;
2 k outer part And k Inner part Different, due to b Outer part And b Inner part Is two constant terms, the absolute value of the two constant terms is taken and then averaged, and the [ (|b) 1 |+|b 2 |）/2]=c, c represents the quadratic fit decompartment term impact number; will y Outer part -c，y Inner part +c as a new set of actual measured data, the constant term effects can be eliminated to obtain a set (x Outer part ，y Outer part -c) and (x) Inner part ，y Inner part +c) data, a second linear fit is performed on the set of data using a least squares method to obtain y Heald =k Heald x Heald +b, where y Heald Representing the actual printed measured dimensions, k Heald Representing the inner and outer profile shrinkage factor, x Heald Representing the design size of the inner and outer contours, b is the straight line intercept obtained by data fitting; this step is to obtain k Heald B is dropped;
3. then c is moved up and down to obtain the final fitting relation, namely y Heald =k Heald x Heald ±c；
4. In the printing program, the design size of the printed piece is regulated, and the light spot compensation coefficient B, namely y, is added after the design size is multiplied by the correction coefficient K Heald =k Heald （Kx Heald +b) ±c, yielding k=1/K Heald ，B Outer 1 =-c/k Heald ，B Inner 1 =c/k Heald Because both sides of the workpiece are affected by the laser spot, the final B Outer part =-c/2k Heald ，B Inner part =c/2 k Heald The method comprises the steps of carrying out a first treatment on the surface of the Wherein K represents a shrinkage correction coefficient, B Outer 1 Representing the total compensation coefficient of the outer contour facula, B Inner 1 Representing the total compensation coefficient of the inner contour facula, B Outer part Representing the compensation coefficient of the flare of the outer contour, B Inner part Indicating the inner profile spot compensation coefficient.
2. The method of manufacturing a selectively laser sintered molded product as claimed in claim 1, wherein the series of test specimens have contour length and width dimensions in the horizontal direction of 150 mm ×30 mm,120 mm×30 mm,100 mm×30 mm,80 mm×30 mm,40 mm×20 mm, and contour widths of 5mm, respectively.
3. The method for manufacturing a product by selective laser sintering according to claim 1, wherein the same 8 sets of test samples are used, and two sets of test samples are arranged in parallel in four directions, namely front, back, left and right, during printing, and each set is symmetrically arranged in a discontinuous zigzag shape from four directions in a mode of small inside and large outside.
4. The method of manufacturing a selectively laser sintered molded product according to claim 1, wherein the serial test specimens are unified in the contour dimension in the height direction so that the test specimens are not warped to the lowest standard after being taken out after being cooled to room temperature after printing, and the height dimension is greater than the lowest standard and less than or equal to the actual product height dimension.
5. The method for producing a selectively laser sintered molded product as claimed in claim 4, wherein the contour dimensions of the series of test specimens in the height direction are unified to a size of 5mm.
6. The method for manufacturing a product by selective laser sintering according to claim 1, wherein after the series of test samples are printed, the printing material powder of about 5mm is continuously paved above the test samples until the test samples are removed after being cooled;
and (3) performing sand blasting and powder cleaning treatment on the test sample after the test sample is printed and taken out, and measuring the measurement data of the test sample by using an electronic vernier caliper after the residual powder on the surface is cleaned, and measuring the sizes of the two end positions of the opposite sides and measuring the average value for a plurality of times during measurement.
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