CN111702175A - Additive manufacturing method applying OCT technology - Google Patents
Additive manufacturing method applying OCT technology Download PDFInfo
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- CN111702175A CN111702175A CN202010574630.5A CN202010574630A CN111702175A CN 111702175 A CN111702175 A CN 111702175A CN 202010574630 A CN202010574630 A CN 202010574630A CN 111702175 A CN111702175 A CN 111702175A
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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
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
- G01B11/0608—Height gauges
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01B11/00—Measuring arrangements characterised by the use of optical techniques
- G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
- G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
- G01B11/0616—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating
- G01B11/0675—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material of coating using interferometry
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- 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
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- 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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Abstract
The invention provides an additive manufacturing method applying an OCT technology. The method provided by the invention can be used for accurately measuring the initially laid powder height and the part height in the printing process by applying the OCT technology in the SLM printing process, thereby realizing the functions of accurately measuring and controlling the thickness difference, finding out problems in time, putting an end to the accumulated error formed by the fine thickness difference along with the increase of the number of the melting layers in the additive manufacturing process, being widely applied to the additive manufacturing of materials taking laser as a heat source such as engineering plastics, ceramics, metals and the like, reducing the product rejection rate, improving the production efficiency, reducing the cost and having obvious effect on the stability of the control process.
Description
Technical Field
The invention designs a 3D printing (additive manufacturing) method, in particular to a method for realizing additive manufacturing by applying an OCT (optical coherence tomography) technology.
Background
Selective Laser Melting (SLM) is a major technical approach in additive manufacturing of engineering plastics, ceramics, metal materials, etc. using laser as a heat source. The technology selects laser as an energy source, scans layer by layer on a powder bed layer according to a planned path in a three-dimensional slice model, and the scanned powder achieves the effect of metallurgical bonding through melting and solidification, so that the part designed by the model is finally obtained. The SLM technique overcomes the difficulties associated with the conventional techniques for manufacturing parts having complex shapes. It can directly form the parts which are nearly full-compact and have good mechanical properties. The powder spreading height and thickness in the SLM printing process often determine the material strength and quality in the material increase process, however, fine thickness differences are inevitably generated in the process due to the long SLM process period and the high cost, and the fine thickness differences form accumulated errors along with the increase of the number of the melting layers, so that the strength and quality of the finished product material are influenced, and therefore, the control of the thickness differences in the printing process is very important for the material strength and quality of the material increase obtained by SLM printing.
However, there is still no mature effective method for controlling the difference in powder thickness during printing in the prior art. In the prior art, a new layer of powder is paved on the surface by a brush scraper or a hard alloy scraper mainly depending on the set powder paving thickness of each descending of a powder bin. Whole process relies on mechanical structure's precision completely, but brush scraper and carbide scraper can appear wearing and tearing or even the condition of hitting the sword takes place in the use repeatedly to at the shop powder in-process, there is the regional powder thickness of shop that appears to be unusual, this can't be detected by prior art, and powder thickness is unusual can direct influence the mechanics and the metallographic property of material, causes product defect, even scrap.
Disclosure of Invention
The invention provides an additive manufacturing method capable of accurately controlling the powder spreading thickness difference by applying an Optical Coherence Tomography (OCT) technology in the SLM printing process, and aims to solve the problems, reduce the product rejection rate, improve the production efficiency and reduce the cost. The invention accurately measures the thickness of the initially laid powder and the thickness of the layer in the printing process by applying the OCT technology, thereby realizing the additive manufacturing method for accurately controlling the thickness difference. The OCT technique can be used for detecting the height of powder and the height of parts in the printing process, so that problems can be found in time, the rejection rate of products can be reduced, the production efficiency can be improved, and the cost can be reduced. The detection of these two heights using OCT techniques is of great help in controlling process stability.
The invention is realized by the following technical scheme:
an additive manufacturing method applying an OCT technique, comprising the steps of:
step 1: the powder to be printed is arranged on the position to be printed of the substrate. The layer thickness to be applied at the location of the substrate to be printed is selected according to the material of the powder and the particle size of the particles. The additive manufacturing industry has the existing and mature empirical parameters for commonly used materials and particle diameters of different particles, the empirical parameters are stored in an equipment database in the prior art, when the additive manufacturing industry is applied to a specific printing task, only corresponding process parameters need to be selected from the equipment database, and the general layer thickness is two to three times of the diameter of the powder particles. The powder spreading method commonly used in the prior art comprises the following steps: the brush scraper or the hard alloy scraper is used for realizing that the powder is fully discharged on the surface of the base material and is dense;
step 2: performing single-point or continuous measurement on the height of the powder in the step 1 of the position to be printed by using the OCT beam to obtain powder height data, and comparing the obtained powder height data with a preset threshold value: when the powder height data exceeds a preset threshold value, if the powder height data exceeds the threshold value, returning to the step 1 to adjust the powder spreading thickness; entering step 3 until the powder height is within a preset threshold value; the preset threshold value is usually determined according to the existing experimental results, namely, the change of the powder thickness is not more than the specific percentage of the powder spreading thickness under the condition of meeting the requirements of specific product mechanics, metallographic phase and the like.
And step 3: carrying out selective laser melting on the powder, and stacking layer by layer to realize part printing; the specific implementation and process are as follows: a laser process technology is designated according to the size of a position to be printed, the part property and the like, the laser process technology refers to that a system automatically generates a light beam movement track route, and selects proper movement speed and laser power by combining parameters in an existing database, wherein the laser process parameters generally comprise power, scanning speed, focus position and the like. According to the process parameters in the step 1 and the laser process obtained in the step 3, selective laser melting is carried out on the powder, namely, the powder is subjected to laser action in a preset track area, and part printing is realized by stacking layer by layer;
and 4, step 4: in the process of layer-by-layer stacking and printing, after the layer number stacked layer by layer reaches a certain specific number of layers, single-point or continuous measurement is carried out on the surface of the part by using an OCT (optical coherence tomography) measuring beam to obtain the height data of the surface of the part, and the height data of the surface of the part is compared with a preset threshold value: if the printing speed exceeds a preset threshold value, stopping printing; and if the preset threshold value is not exceeded, continuing printing until printing is finished. And (4) when the layer number piled layer by layer in the step (4) reaches a certain number of layers, the certain number is formulated based on the requirements on the control of the mechanical and metallographic characteristics of the product according to the previous experimental results or actual production requirements.
Further, according to the specific print job setting, the steps 1 to 4 may be repeated until all print jobs are completed.
Further, the method for obtaining powder height data by single-point or continuous measurement of the height of the powder by using the OCT beam in step 2 includes the following steps:
step 2.1: generating a laser beam by using a low-coherence interference light source, dividing the laser beam into a first light beam and a second light beam by a spectroscope, and respectively passing through a first optical path and a second optical path; wherein, the first optical path is a reference optical path with fixed distance, and the light beam is reflected back to the spectroscope after passing through the first optical path; and the second light path is a light path to be detected, and the second light beam reaches the surface of the material through the light path to be detected, is reflected by the surface of the material and then returns to the spectroscope. The method specifically comprises the following steps: the second light beam passes through the vibrating mirror interface, is coupled into a laser light path in the vibrating mirror by using a reflecting mirror or a light splitting mirror, reaches the surface of the material after the coupling position is a collimation light path and before a focusing light path, is reflected by the surface of the material, and returns to the spectroscope through the vibrating mirror and the coupling light path;
step 2.2: measuring the interference phenomenon of the first light beam and the second light beam returning to the spectroscope to obtain the optical path difference of the first light beam and the second light beam;
step 2.3: and converting the optical path difference of the first light beam and the second light beam into the height change value of the measured powder surface to obtain powder height data. The principle is as follows: ideally, the optical paths of the first light beam and the second light beam should be consistent, no interference phenomenon occurs at this time, when the height of the powder surface changes, the distance of the second light path changes, and the optical path difference obtained by the interference phenomenon is the height difference generated by the height change of the powder surface at this time.
Further, the method for obtaining the height data of the surface of the part by performing single-point or continuous measurement on the surface of the part by using the OCT measuring beam in the step 4 includes the following steps:
step 3.1: generating a laser beam by using a low-coherence interference light source, dividing the laser beam into a first light beam and a second light beam by a spectroscope, and respectively passing through a first optical path and a second optical path; wherein, the first optical path is a reference optical path with fixed distance, and the light beam is reflected back to the spectroscope after passing through the first optical path; and the second light path is a light path to be detected, and the second light beam reaches the surface of the material through the light path to be detected, is reflected by the surface of the material and then returns to the spectroscope. The method specifically comprises the following steps: the second light beam passes through the vibrating mirror interface, is coupled into a laser light path in the vibrating mirror by using a reflecting mirror or a light splitting mirror, reaches the surface of the material after the coupling position is a collimation light path and before a focusing light path, is reflected by the surface of the material, and returns to the spectroscope through the vibrating mirror and the coupling light path;
step 3.2: measuring the interference phenomenon of the first light beam and the second light beam returning to the spectroscope to obtain the optical path difference of the first light beam and the second light beam;
step 3.3: and converting the optical path difference of the first light beam and the second light beam into the height change value of the measured powder surface to obtain powder height data.
The principle of using OCT beam to measure the height of powder or parts is as follows: under an ideal state, the optical path is equal to the optical path two, at the moment, two beams of light meet again, optical path difference does not exist, and interference phenomenon does not occur, but if the powder surface or the part surface is protruded or sunken due to the failure of powder spreading equipment or the damage of a scraper or other reasons, the optical path of the OCT light beam is increased or reduced when the OCT light beam reaches the position, the optical path difference exists when the two beams of light meet again, interference phenomenon occurs, the specific optical path difference of the two beams of light can be obtained by measuring the interference phenomenon, and the optical path difference can be indirectly converted into the height change of the powder or the part surface because the optical path one is a reference optical path and the distance is fixed.
The interference phenomenon can be measured by reflecting the light beam splitter to a sensor arranged on the other side of the light beam splitter.
Further, the selective laser melting in step 3 may be performed by using a continuous laser or a pulsed laser according to the characteristics of different materials to the laser action.
Further, the continuous laser is continuous laser with average power of 100W-7000W.
Furthermore, the pulse laser is pulse laser with the peak power of 1000W-40000W.
Furthermore, the OCT measuring beam is a measuring beam with the average power of 1W-50W, the wavelength of 800nm-1600nm and optical coherence property.
By using the additive manufacturing method provided by the invention, the OCT technology is utilized to realize the detection of the powder height and the part height in the printing process, so that the problems can be found in time, the product rejection rate is reduced, the production efficiency is improved, and the cost is reduced. The detection of these two heights using OCT techniques is of great help in controlling process stability.
Drawings
FIG. 1 is a flow chart of one embodiment of an additive manufacturing method using OCT techniques
Detailed Description
In this section, the technical solutions in the embodiments of the present invention will be clearly and completely described with reference to the accompanying drawings, and it is obvious that the described embodiments are some, not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
An additive manufacturing method applying an OCT technique, comprising the steps of:
step 1: the powder to be printed is arranged on the position to be printed of the substrate. In the prior art, the commonly used process and manner of arranging the powder to be printed is: the layer thickness to be applied at the location of the substrate to be printed is selected according to the material of the powder and the particle size of the particles. The additive manufacturing industry has the existing and mature empirical parameters for commonly used materials and particle diameters of different particles, the empirical parameters are stored in an equipment database in the prior art, when the additive manufacturing industry is applied to a specific printing task, only corresponding process parameters need to be selected from the equipment database, and the general layer thickness is two to three times of the diameter of the powder particles. The powder spreading method commonly used in the prior art comprises the following steps: the brush scraper or the hard alloy scraper is used for realizing that the powder is fully discharged on the surface of the base material and is dense;
the method of arranging and laying the powder to be printed in this step may also be any other method in the art that can achieve this effect.
Step 2: performing single-point or continuous measurement on the height of the powder in the step 1 of the position to be printed by using the OCT beam to obtain powder height data, and comparing the obtained powder height data with a preset threshold value: when the powder height data exceeds a preset threshold value, if the powder height data exceeds the threshold value, returning to the step 1 to adjust the powder spreading thickness; entering step 3 until the powder height is within a preset threshold value; the determination of the preset threshold value can be realized in any mode in the prior art, and usually, according to the existing experimental result, the change of the powder thickness cannot exceed the specific percentage of the powder spreading thickness under the condition of meeting the requirements of specific product mechanics, metallographic phase and the like.
And step 3: carrying out selective laser melting on the powder, and stacking layer by layer to realize part printing; the specific process of the common method in the prior art is as follows: and selecting a laser process technology according to the size of the position to be printed and the property of the part, wherein the laser process technology refers to the technology that a system automatically generates a light beam movement track route according to the slice shape of the layer of the part, and selects proper movement speed and laser power by combining parameters in an existing database, and the laser process parameters generally comprise power, scanning speed and focus position. According to the process parameters in the step 1 and the laser process obtained in the step 3, selective laser melting is carried out on the powder, namely, the powder is subjected to laser action in a preset track area, and part printing is realized by stacking layer by layer;
and 4, step 4: when the number of layers stacked layer by layer in the step 3 is a certain number of layers, performing single-point or continuous measurement on the surface of the part by using an OCT (optical coherence tomography) measuring beam to obtain the height data of the surface of the part, and comparing the height data of the surface of the part with a preset threshold value: if the printing speed exceeds a preset threshold value, stopping printing; and if the preset threshold value is not exceeded, continuing printing until printing is finished. The principle is as follows: the preset threshold is determined according to the process parameters or the geometric shape requirement characteristics of the printing material, and/or the specific requirements for the additive product in the specific printing task are set, for example, the height of the current printing material is h, the height of the powder bin descending at the next moment is d, the powder laying thickness at the next moment should be d-h theoretically, and the thickness of d-h is also the preset threshold in step 2. The following are three corresponding cases, respectively: if h is greater than d, the material height at the measurement exceeds this threshold, a collision with the blade may occur. If the d-h is greatly changed due to the change of h, or the powder thickness at the position cannot meet the preset layer thickness threshold value in the step 2 in the next powder laying process due to the change of the height. If the change of h is not enough to cause the change of d-h exceeding the preset threshold, but h itself exceeds a certain range due to the dimensional control of the product or the reason that the requirement of the product on the surface flatness of the part is high, and the like, the preset threshold can be set as the height difference of the surface of the part. If the height difference of each measuring point exceeds the preset threshold value, indicating that the surface height or the flatness of the part cannot meet the requirement, stopping printing; when the number of layers stacked layer by layer in the step 4 is a certain number of layers, the specific number is formulated based on the requirements on the control of the mechanical and metallographic characteristics of the product according to the previous experimental results or actual production requirements, and the method is a mature technology in the prior art.
Example 2
The present embodiment is different from embodiment 1 in that:
the method for obtaining the powder height data by single-point or continuous measurement of the height of the powder by using the OCT beam in the step 2 comprises the following steps:
step 2.1: generating a laser beam by using a low-coherence interference light source, dividing the laser beam into a first light beam and a second light beam by a spectroscope, and respectively passing through a first optical path and a second optical path; wherein, the first optical path is a reference optical path with fixed distance, and the light beam is reflected back to the spectroscope after passing through the first optical path; and the second light path is a light path to be detected, and the second light beam reaches the surface of the material through the light path to be detected, is reflected by the surface of the material and then returns to the spectroscope. The specific implementation mode is as follows: the second light beam passes through the vibrating mirror interface, is coupled into a laser light path in the vibrating mirror by using a reflecting mirror or a light splitting mirror, reaches the surface of the material after the coupling position is a collimation light path and before a focusing light path, is reflected by the surface of the material, and returns to the spectroscope through the vibrating mirror and the coupling light path;
the OCT measuring beam is a measuring beam with average power of 1W-50W, wavelength of 800nm-1600nm and optical coherence.
Step 2.2: measuring the interference phenomenon of the first light beam and the second light beam returning to the spectroscope to obtain the optical path difference of the first light beam and the second light beam;
step 2.3: and converting the optical path difference of the first light beam and the second light beam into the height change value of the measured powder surface to obtain powder height data.
The conversion can adopt all the realizable modes in the prior art, and the method adopted in the embodiment is as follows: two beams of light with optical path difference meet to generate light and shade alternative stripes, and the brightness distribution of the stripes meets the requirement
k is an optical wave number, Z is an optical path difference value, the larger the visible light path difference is, the shorter the period of the trigonometric function is, namely the more the number of the sensitive stripes is, the denser the sensitive stripes are, after the stripes are captured by the sensor, the period analysis is carried out on the stripes, and the period Z, namely the optical path difference value and the height difference can be obtained.
The principle of using OCT beam to measure the height of powder or parts is as follows: under an ideal state, the optical path should be equal to the optical path two, at the moment, two beams of light meet again, optical path difference does not exist, and interference phenomenon does not occur, but if the powder surface is protruded or sunken due to failure of powder laying equipment or damage of a scraper or other reasons, the optical path of the OCT light beam is increased or reduced when the OCT light beam reaches the position, the optical path difference exists when the two beams of light meet again, interference phenomenon occurs, specific optical path difference of the two beams of light can be obtained by measuring the interference phenomenon, and the optical path difference can be indirectly converted into height change of the powder surface because the optical path I is a reference optical path and the distance is fixed.
The interference phenomenon measuring mode is that the interference phenomenon is reflected to a sensor arranged on the other side of the spectroscope through the spectroscope to be measured.
Example 3
The present embodiment is different from embodiment 2 in that:
in the step 4, the method for obtaining the height data of the surface of the part by performing single-point or continuous measurement on the surface of the part by using the OCT measuring beam comprises the following steps:
step 3.1: generating a laser beam by using a low-coherence interference light source, dividing the laser beam into a first light beam and a second light beam by a spectroscope, and respectively passing through a first optical path and a second optical path; wherein, the first optical path is a reference optical path with fixed distance, and the light beam is reflected back to the spectroscope after passing through the first optical path; and the second light path is a light path to be detected, and the second light beam reaches the surface of the material through the light path to be detected, is reflected by the surface of the material and then returns to the spectroscope. The specific implementation mode is as follows: the second light beam passes through the vibrating mirror interface, is coupled into a laser light path in the vibrating mirror by using a reflecting mirror or a light splitting mirror, reaches the surface of the material after the coupling position is a collimation light path and before a focusing light path, is reflected by the surface of the material, and returns to the spectroscope through the vibrating mirror and the coupling light path;
the OCT measuring beam is a measuring beam with average power of 1W-50W, wavelength of 800nm-1600nm and optical coherence.
Step 3.2: measuring the interference phenomenon of the first light beam and the second light beam returning to the spectroscope to obtain the optical path difference of the first light beam and the second light beam;
step 3.3: and converting the optical path difference of the first light beam and the second light beam into the height change value of the measured powder surface to obtain powder height data.
Example 4
The present embodiment is different from embodiment 3 in that: and 3, performing selective laser melting, and adopting a continuous laser mode according to the characteristics of different materials on the laser action, wherein the continuous laser is continuous laser with the average power of 100-7000W.
Example 5
The present embodiment is different from embodiment 3 in that: and 3, performing selective laser melting, and adopting a pulse laser mode according to the characteristics of different materials on the laser action, wherein the pulse laser is the pulse laser with the peak power of 1000W-40000W.
Example 6
An additive manufacturing method applying an OCT technique, as shown in fig. 1, in this embodiment, an aluminum-based alloy material is used as a SLM as a printing powder raw material, and includes the following steps:
step 1: the metal powder AlSi10Mg to be printed is arranged on the position to be printed of the substrate, and the average particle size of the AlSi10Mg powder raw material is 27 μm. Selecting the process parameters from the empirical parameter database as follows: the layer thickness was 50 μm and the layer thickness threshold was set to the standard powder layer thickness plus the average particle size, 77 μm.
Step 2: the height of the metal powder in step 1 of the position to be printed is measured in a single point or continuous manner by means of an OCT beam, obtaining powder height data, and comparing said obtained powder height data with a preset threshold value of 77 μm: when the powder height data exceeds a preset threshold value, if the powder height data exceeds the threshold value, returning to the step 1 to adjust the powder spreading thickness; entering step 3 until the powder height is within a preset threshold value;
and step 3: the laser process selected in this example is: the laser power is 180W, the scanning speed is 900mm/s, the laser scanning interval is 0.05mm, the metal powder is selectively melted by laser, and the metal powder is stacked layer by layer to realize part printing;
and 4, step 4: after the number of layers stacked layer by layer in step 3 is a certain number of layers, the certain number is set based on the requirements on the control of the mechanical and metallographic properties of the product according to the previous experimental results or actual production requirements, and is 5 layers in this embodiment, the problem of consistency of the surface height of the part is mainly concerned, so that the surface of the part is continuously measured by using the OCT measurement beam, and the preset threshold is set to be 27 μm, where the height difference of the surface to be measured does not exceed the average particle diameter. After obtaining the height data of the surface of the part, comparing the height data of the surface of the part with a preset threshold value: if the printing speed exceeds a preset threshold value, stopping printing; and if the preset threshold value is not exceeded, continuing printing until printing is finished.
And 5: and (4) repeating the steps 1-4 until all printing tasks are completed.
The aluminum alloy has the advantages of good conductivity, high specific strength, low density and the like, is subjected to additive manufacturing by taking the aluminum alloy as a printing powder raw material, and is widely applied to the fields of aerospace, buildings, automobiles and the like. By adopting the method provided by the invention to perform additive manufacturing by taking the aluminum alloy powder as the raw material, the process stability can be obviously improved, the production efficiency is improved, and the production cost is reduced.
Example 7
An additive manufacturing method applying OCT technology, in the embodiment, using titanium-based alloy material as SLM as printing powder raw material, includes the following steps:
step 1: the metal powder to be printed, Ti-6Al-4V, with an average particle size of 35 μm was disposed on the substrate at the position to be printed. Selecting the process parameters from the empirical parameter database as follows: the layer thickness was 40 μm and the layer thickness threshold was set to the standard powder layer thickness plus the average particle size, 75 μm.
Step 2: performing single-point or continuous measurement on the height of the metal powder in the step 1 of the position to be printed by using the OCT beam to obtain powder height data, and comparing the obtained powder height data with a preset threshold value of 75 μm: when the powder height data exceeds a preset threshold value, if the powder height data exceeds the threshold value, returning to the step 1 to adjust the powder spreading thickness; entering step 3 until the powder height is within a preset threshold value;
and step 3: the laser process selected in this example is: the laser power is 160W, the scanning speed is 600mm/s, the laser scanning interval is 0.02mm, the metal powder is selectively melted by laser, and the metal powder is stacked layer by layer to realize part printing;
and 4, step 4: after the number of layers stacked layer by layer in step 3 is a certain number of layers, the certain number is set based on the requirements on the control of the mechanical and metallographic properties of the product according to the previous experimental results or actual production requirements, and is 5 layers in this embodiment, the problem of consistency of the surface height of the part is mainly concerned, so that the surface of the part is continuously measured by using the OCT measurement beam, and the preset threshold is set to be 35 μm, i.e., the height difference of the surface to be measured does not exceed the average particle size. Obtaining part surface height data, and comparing the part surface height data with a preset threshold value: if the printing speed exceeds a preset threshold value, stopping printing; and if the preset threshold value is not exceeded, continuing printing until printing is finished.
And 5: and (4) repeating the steps 1-4 until all printing tasks are completed.
Titanium and titanium alloy have density low, specific strength high, high mechanical property of high temperature, advantage such as being strong of corrosion resistance, are used in fields such as the car, aerospace, etc. extensively, but because the processing difficulty is greater, lead to the price of the titanium alloy product to be higher, adopt the method that the invention provides to carry on the additive manufacturing taking titanium alloy powder as raw materials, can improve the technological stability more apparently, raise the production efficiency, lower production cost, reduce the price of the 3D printed products of titanium alloy greatly.
The additive manufacturing method applying the OCT technology can be widely applied to printing of metal, engineering plastics, ceramics and the like by using laser as an acting heat source. The OCT technique is used for detecting the powder height and the part height in the printing process, so that problems can be found in time, the product rejection rate is reduced, the production efficiency is improved, and the cost is reduced. The detection of these two heights using OCT techniques is of great help in controlling process stability.
Claims (7)
1. An additive manufacturing method applying an OCT technique is characterized in that: the method comprises the following steps:
step 1: arranging powder to be printed on a position to be printed of the base material;
step 2: performing single-point or continuous measurement on the height of the powder in the step 1 of the position to be printed by using the OCT light beam to obtain powder height data, and comparing the obtained powder height data with a preset threshold: if the powder height data exceeds the preset threshold value, returning to the step 1, and entering the step 3 until the powder height is within the preset threshold value;
and step 3: carrying out laser melting on the powder, and stacking layer by layer to realize printing;
and 4, step 4: in the process of layer-by-layer accumulation printing, single-point or continuous measurement is carried out on the surface of the part by using an OCT (optical coherence tomography) measuring beam to obtain the height data of the surface of the part, and the height data of the surface of the part is compared with a preset threshold value: if the printing speed exceeds a preset threshold value, stopping printing; if the printing speed is within the preset threshold value, the printing is continued until the printing is finished.
2. The additive manufacturing method using OCT as claimed in claim 1, wherein: the method for measuring the height of the powder by using the OCT beam in the step 2 to obtain the powder height data comprises the following steps:
step 2.1: generating a laser beam by using a low-coherence interference light source, dividing the laser beam into a first light beam and a second light beam by a spectroscope, and respectively passing through a first optical path and a second optical path; wherein, the first optical path is a reference optical path with fixed distance, and the light beam is reflected back to the spectroscope after passing through the first optical path; the second optical path is an optical path to be detected, and the second light beam reaches the surface of the material through the optical path to be detected, is reflected by the surface of the material and then returns to the spectroscope;
step 2.2: measuring the interference phenomenon of the first light beam and the second light beam returning to the spectroscope to obtain the optical path difference of the first light beam and the second light beam;
step 2.3: and converting the optical path difference of the first light beam and the second light beam into the height change value of the measured powder surface to obtain powder height data.
3. An additive manufacturing method applying OCT technology as claimed in claim 1 or 2, characterized in that: in the step 4, the method for obtaining the height data of the surface of the part by performing single-point or continuous measurement on the surface of the part by using the OCT measuring beam comprises the following steps:
step 3.1: generating a laser beam by using a low-coherence interference light source, dividing the laser beam into a first light beam and a second light beam by a spectroscope, and respectively passing through a first optical path and a second optical path; wherein, the first optical path is a reference optical path with fixed distance, and the light beam is reflected back to the spectroscope after passing through the first optical path; the second optical path is an optical path to be detected, and the second light beam reaches the surface of the material through the optical path to be detected, is reflected by the surface of the material and then returns to the spectroscope;
step 3.2: measuring the interference phenomenon of the first light beam and the second light beam returning to the spectroscope to obtain the optical path difference of the first light beam and the second light beam;
step 3.3: and converting the optical path difference of the first light beam and the second light beam into the height change value of the measured powder surface to obtain powder height data.
4. The additive manufacturing method using OCT as claimed in claim 3, wherein: the laser melting in step 3 may be performed by using a continuous laser or a pulsed laser.
5. The additive manufacturing method using OCT as claimed in claim 4, wherein: the continuous laser is continuous laser with the average power of 100W-7000W; the pulse laser is pulse laser with peak power of 1000W-40000W.
6. The additive manufacturing method using OCT as claimed in claim 3, wherein: the OCT measuring beam is a measuring beam with the average power of 1W-50W, the wavelength of 800nm-1600nm and optical coherence property.
7. An additive manufacturing method using OCT as claimed in any one of claims 1-2,4-6, wherein: the OCT measuring beam is a measuring beam with the average power of 1W-50W, the wavelength of 800nm-1600nm and optical coherence property.
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| US20170120337A1 (en) * | 2010-09-25 | 2017-05-04 | Queen's University At Kingston | Methods and Systems for Coherent Imaging and Feedback Control for Modification of Materials |
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