3D printing dual galvanometer detection device, surface defect detection method and spot magnification measurement method

Abstract

The present invention discloses a 3D printing dual-galvanometer detection device, a surface defect detection method and a spot magnification determination method, which belong to the field of 3D printing technology. The device includes a first laser beam, a scanning galvanometer unit, a printing work surface and a detection galvanometer unit; the scanning galvanometer unit includes a first medium reflector, a first galvanometer and a first focusing mirror arranged on the optical path of the first laser beam, and is used to obliquely inject the first laser beam into the printing work surface; the detection galvanometer unit is located on the optical path of the first laser beam after being reflected by the printing work surface, and includes a second galvanometer, a second focusing mirror and a position sensor arranged on the optical path of the first laser beam. The device can be used for surface defect detection and spot magnification determination, can identify defects of 1mm level or even smaller, and can accurately determine whether there is an error in the magnification of the current optical path system, so as to compensate for the error or shut down for maintenance.

Description

Technical Field

[0001] The present invention belongs to the technical field of 3D printing, and in particular relates to a 3D printing dual-galvanometer detection device, a surface defect detection method and a spot magnification measurement method. Background Art

[0002] Additive manufacturing, or 3D printing technology, is a technology that uses digital model files as the basis to form objects by printing metal, plastic, ceramic, sand and other bondable materials layer by layer. It breaks through the processing limitations of traditional processes and can quickly form parts with complex structures. Depending on the type of consumables and the feeding method, the types of technologies used in 3D printing devices are also different, including: Stereolithography SLA, Selective Laser Melting SLM, and Selective Laser Sintering SLS. Among them, the SLS and SLM processes are based on sintering or cladding the powder with a heat source such as a laser after layering the powder.

[0003] The powder spreading device of existing 3D printing equipment is mainly composed of a scraper, a powder feeding bin and a recovery bin. The specific printing process is: the scraper spreads a layer of powder material on the upper surface of the formed part, the laser beam scans the cross-sectional contour of the part, sinters the current layer of powder, and the sintered layer automatically bonds with the formed part below. When the sintering of a layer of cross section is completed, the workbench drops a layer of thickness, and the scraper continues to spread a layer of powder material on it, sintering a new layer of cross section until the entire model is completed. During the printing process, scanning abnormalities may occur. Abnormal conditions accumulate layer by layer, which can easily cause damage to parts. During the printing process, real-time detection and identification of the printed surface of each layer of the part can timely understand the printing quality of the part. When abnormal conditions occur, it is also convenient to promptly know the location of the abnormal area, which is conducive to remediation. At present, the existing real-time recognition of surface defects in the printing process adopts the method of taking pictures with a camera and making judgments based on the photographed images. For example, the application publication number is CN114372958A. For a conventional 500*500mm frame device, the camera uses 2000W (4000*5000) pixels, and a single pixel needs to cover at least 0.125mm. For clear imaging and image analysis, the recognizable defects are close to the 10mm level, and defects of 1mm level or even smaller cannot be recognized. However, these defects are more numerous in terms of probability and have a huge impact on printed parts. Therefore, the use of cameras to identify printed surface defects will have the problem of low detection accuracy.

[0004] In addition, as 3D printing technology becomes more mature, 3D printing begins to develop in the direction of higher efficiency and higher precision. In order to improve scanning efficiency, the utility model patent with the authorization announcement number CN 215867306U proposes a scheme to change the magnification of the optical system. This scheme uses a small spot when printing the stroke content to maintain the printing accuracy. When printing the filling part of the part, a large spot is used to improve the efficiency. In order to improve the printing efficiency, it is a scheme of changing the spot size; in order to improve the printing accuracy, the invention patent application with the application publication number CN113459678A proposes an invention patent for compensating the edge spot. The use of this scheme requires the entire optical path to be magnified and the spot size to be adjusted dynamically in real time, so that the spot size can be kept consistent throughout the printing format and the printing quality can be improved. Based on this, it can be seen that in order to achieve high-efficiency and high-precision 3D printing, it is necessary to make real-time dynamic changes to the magnification of the optical path system. In addition, the consistency of 3D printed parts must be good, and the scanning spot energy density needs to be kept constant. If the spot size changes slightly, the printing power needs to be adjusted accordingly. Therefore, when the magnification of the optical path system needs to be changed in real time, a detection feedback system is needed to determine whether there is an error in the magnification of the optical path execution system. However, the current 3D printing system lacks a spot magnification measurement module. Summary of the invention

[0005] The present invention provides a 3D printing dual-galvanometer detection device, a surface defect detection method and a spot magnification measurement method to solve the defects of the existing 3D printing system such as low recognition accuracy of surface accuracy and inability to measure the spot magnification.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0007] The present invention relates to a 3D printing dual-galvanometer detection device, which comprises a first laser beam, a scanning galvanometer unit, a printing work surface and a detection galvanometer unit; the scanning galvanometer unit comprises a first medium reflector, a first galvanometer and a first focusing mirror arranged on the optical path of the first laser beam, and is used for obliquely irradiating the first laser beam onto the printing work surface; the detection galvanometer unit is located on the optical path of the first laser beam after being reflected by the printing work surface, and comprises a second galvanometer, a second focusing mirror and a position sensor arranged on the optical path of the first laser beam.

[0008] Preferably, it also includes a second laser beam, and the detection galvanometer unit also includes a second dielectric reflector, which is located between the position sensor and the combined structure formed by the second galvanometer and the second focusing mirror, and is used to reflect the second laser beam, so that the optical path of the reflected second laser beam coincides with the optical path of the first laser beam and the direction is opposite. During the scanning process, the scanning galvanometer unit or the detection galvanometer unit can be selected for 3D printing.

[0009] Preferably, the first focusing lens is an imaging lens or a field lens; the second focusing lens is an imaging lens or a field lens.

[0010] The present invention also relates to a surface defect detection method based on the above-mentioned 3D printing dual-galvanometer detection device, which comprises the following steps:

[0011] Step 1. After being reflected by the first medium reflector and the first galvanometer and focused by the first focusing mirror, the first laser beam is tilted and incident on the printing work surface to form a light spot, which is captured by the position sensor through the second galvanometer and the second focusing mirror to obtain the position of the light spot on the position sensor;

[0012] Step 2. Rotate the first galvanometer and the second galvanometer simultaneously, so that the first laser beam scans the printing work surface line by line, while keeping the paths of the first galvanometer and the second galvanometer the same, and the position sensor always receives the first laser beam;

[0013] Step 3. When the position of the light spot detected by the position sensor changes, it indicates that there is a defect on the printed surface.

[0014] Preferably, in step 3, when the position of the light spot detected by the position sensor changes, the degree of unevenness of the printed surface is calculated according to the change value, and the degree of unevenness of the printed surface is expressed by the displacement of the printed surface, and the calculation formula is:

[0015]

[0016] In the formula, h is the displacement of the printing surface, L is the equivalent focal length of the second galvanometer, a is the angle between the first laser beam and the horizontal plane before and after reflection from the printing work surface, b is the angle between the first laser beam and the horizontal plane, D is the distance of the optical path between the position sensor and the second focusing mirror, and r is the displacement of the light spot detected on the position sensor.

[0017] The present invention also relates to a method for measuring the spot magnification based on the above-mentioned 3D printed dual-galvanometer detection device, which comprises the following steps:

[0018] Step 1. After being reflected by the first medium reflector and the first galvanometer and focused by the first focusing mirror, the first laser beam is tilted and incident on the printing work surface to form a light spot, which is captured by the position sensor through the second galvanometer and the second focusing mirror to obtain the position of the light spot on the position sensor;

[0019] Step 2. Control the first galvanometer to rotate an angle so that the light spot moves on the printing work surface, and the position of the light spot on the position sensor also changes accordingly. Calculate the magnification of the optical path system during the rotation of the first galvanometer, and determine whether the magnification of the optical path system is normal based on the magnification change rate.

[0020] Preferably, the calculation formula for calculating the magnification of the optical path system during the rotation of the first galvanometer in step 2 is:

[0021]

[0022] In the formula, k is the magnification of the optical path system, m is the moving distance of the light spot on the printing work surface at a certain moment, β is the angle between the reflected light and the vertical direction at that moment, and r is the offset of the light spot captured by the position sensor at that moment relative to the position before the first galvanometer rotates.

[0023] Preferably, in step 2, when the magnification change rate is greater than the allowable line width change ratio required by the printing work, it indicates that the magnification of the optical path system is abnormal, and the commonly used standard in the industry is 1% to 3%.

[0024] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0025] 1. The 3D printing dual galvanometer detection device involved in the present invention includes a scanning galvanometer unit and a detection galvanometer unit. The scanning galvanometer unit is used to obliquely inject a laser beam into the printing work surface. The detection galvanometer unit is located on the optical path of the laser beam after it is reflected by the printing work surface, and includes a second galvanometer, a second focusing mirror and a position sensor arranged on the optical path of the first laser beam; when detecting surface defects of the printed part, the paths of the first galvanometer and the second galvanometer are always kept the same. When the position of the light spot detected by the position sensor changes, it indicates that there are defects on the printed surface. The degree of unevenness of the printed surface can be calculated based on the change value, and defects of 1mm level or even smaller can be identified.

[0026] 2. The 3D printing dual-galvanometer detection device involved in the present invention includes a scanning galvanometer unit and a detection galvanometer unit. The scanning galvanometer unit is used to obliquely inject the laser beam into the printing work surface. The detection galvanometer unit is located on the optical path of the laser beam after it is reflected by the printing work surface, and includes a second galvanometer, a second focusing mirror and a position sensor arranged on the optical path of the first laser beam; when measuring the light spot magnification, the scanning galvanometer unit controls the laser beam to move on the printing work surface, and the angle between the reflected light and the vertical direction and the position of the light spot on the position sensor also change accordingly. The magnification of the light spot in the optical path system can be measured in real time through the movement of the light spot on the printing work surface, the angle between the reflected light and the vertical direction, and the movement of the light spot on the position sensor, and it is possible to determine whether there is an error in the current light path system magnification, so as to compensate for the difference in time or shut down the machine for maintenance of the zoom module in the scanning galvanometer unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a structural schematic diagram of a 3D printed dual-galvanometer detection device using an imaging lens as a first focusing mirror and a second focusing mirror in Example 1;

[0028] Figure 2 It is a structural schematic diagram of a 3D printed dual-galvanometer detection device using a field mirror as a first focusing mirror and a second focusing mirror in Example 1;

[0029] Figure 3 This is a schematic diagram of the use of a 3D printing dual-galvanometer detection device to detect printed surface defects;

[0030] Figure 4 This is a schematic diagram of the spot magnification measurement using a 3D printed dual-galvanometer detection device;

[0031] Figure 5 is a schematic structural diagram of a 3D printed dual-galvanometer detection device using an imaging lens as a first focusing mirror and a second focusing mirror in Example 2;

[0032] Figure 6 It is a structural schematic diagram of a 3D printed dual-galvanometer detection device in Example 2 using a field mirror as a first focusing mirror and a second focusing mirror.

[0033] Figure numerals: 1 - first laser beam, 21 - first dielectric reflector, 22 - first galvanometer, 23 - first focusing mirror, 3 - printing work surface, 41 - second dielectric reflector, 42 - second galvanometer, 43 - second focusing mirror, 44 - position sensor, 5 - second laser beam. DETAILED DESCRIPTION

[0034] In order to further understand the content of the present invention, the present invention is described in detail in conjunction with examples. The following examples are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0035] Example 1

[0036] See attached Figure 1 and 2 As shown, the present invention relates to a 3D printing dual-galvanometer detection device including a first laser beam 1, a scanning galvanometer unit, a printing work surface 3 and a detection galvanometer unit. The scanning galvanometer unit includes a first medium reflector 21, a first galvanometer 22 and a first focusing mirror 23 arranged on the optical path of the first laser beam 1, and is used to obliquely inject the first laser beam 1 onto the printing work surface 3; the detection galvanometer unit is located on the optical path of the first laser beam 1 after being reflected by the printing work surface 3, and includes a second galvanometer 42, a second focusing mirror 43 and a position sensor 44 arranged on the optical path of the first laser beam 1. The first focusing mirror 23 and the second focusing mirror 43 are both imaging lenses, such as Figure 1 As shown; or the first focusing mirror 23 and the second focusing mirror 43 are both field mirrors, such as Figure 2As shown; of course, the first focusing mirror 23 can also be an imaging lens, and the second focusing mirror 43 can be a field lens; or the first focusing mirror 23 can be a field lens, and the second focusing mirror 43 can be an imaging lens; when an imaging lens is used, the imaging lens is an equivalent lens group formed by a combination of multiple concave lenses or / and convex lenses. The first dielectric reflector 21 is a total reflector; the position sensor 44 uses a CMOS sensor or a photoelectric sensor PSD, and its position detection resolution accuracy is higher than 0.1um.

[0037] See attached Figure 3 As shown, the surface defect detection method based on the above 3D printed dual galvanometer detection device includes the following steps:

[0038] Step 1. The first laser beam 1 is reflected by the first dielectric reflector 21 and the first galvanometer 22 and focused by the first focusing mirror 23, then incident on the printing work surface 3 at an angle and forms a light spot, which is captured by the position sensor 44 after passing through the second galvanometer 42 and the second focusing mirror 43, and the position of the light spot on the position sensor 44 is obtained;

[0039] Step 2. Rotate the first galvanometer 22 and the second galvanometer 42 simultaneously, so that the first laser beam 1 scans the printing work surface 3 line by line, while keeping the paths of the first galvanometer 22 and the second galvanometer 42 the same, and the position sensor 44 always receives the first laser beam 1;

[0040] Step 3. When the position of the light spot detected by the position sensor 44 changes, it indicates that there is a defect on the printing surface. Since the response time of the position sensor 44 used is at the ns level, the three-dimensional position of the current printing work surface 3 can be obtained in real time and dynamically. When a printing defect occurs on the printing work surface 3, the abnormal result can be obtained immediately. Furthermore, when the detection result is abnormal, the degree of unevenness of the printing surface is calculated based on the change value. The degree of unevenness of the printing surface is expressed by the displacement of the printing surface. The calculation formula is:

[0041]

[0042] In the formula, h is the displacement of the printing surface, L is the equivalent focal length of the second galvanometer 42, a is the angle between the first laser beam 1 before and after being reflected by the printing work surface 3, b is the angle between the first laser beam 1 and the horizontal plane, D is the distance of the optical path between the position sensor 44 and the second focusing mirror 43, and r is the displacement of the light spot detected on the position sensor 44.

[0043] See attached Figure 4 As shown, the present invention also relates to a method for measuring the spot magnification based on the above-mentioned 3D printed dual-galvanometer detection device, which comprises the following steps:

[0044] Step 1. The first laser beam 1 is reflected by the first dielectric reflector 21 and the first galvanometer 22 and focused by the first focusing mirror 23, and then is incident on the printing work surface 3 at an angle to form a light spot, which is captured by the position sensor 44 through the second galvanometer 42 and the second focusing mirror 43, and the position of the light spot on the position sensor 44 is obtained;

[0045] Step 2. Control the first galvanometer 22 to rotate an angle so that the light spot moves on the printing work surface 3, and the position of the light spot on the position sensor 44 also changes accordingly. Calculate the magnification of the optical path system during the rotation of the first galvanometer 22. The calculation formula is:

[0046]

[0047] In the formula, k is the magnification of the optical path system, m is the moving distance of the light spot on the printing work surface 3 at a certain moment, β is the angle between the reflected light and the vertical direction at that moment, and r is the offset of the light spot captured by the position sensor 44 at that moment relative to the position before the first galvanometer 22 rotates.

[0048] Whether the magnification of the optical system is normal is judged based on the magnification change rate. That is, when the magnification change rate is greater than the allowable line width change ratio required by the printing work, it means that the magnification of the optical system is abnormal. The commonly used standard in the industry is 1% to 3%.

[0049] According to the measured magnification result, the first focusing lens 23 of the scanning galvanometer unit can be controlled to compensate for the difference. How to control the first focusing lens of the scanning galvanometer unit belongs to the conventional technology in this field, such as the method disclosed in the authorization announcement number CN215867306U, and it is not the content to be protected by the present invention, and is not described in detail here. After adjustment, the current spot position is read from the position Chang'an area to determine whether the magnification has returned to the normal value. If it has not returned to the normal value, the above process is cycled again. After two cycles, the magnification has not returned to the normal value, then the magnification system has a fault, and the system can be shut down to manually check the fault of the magnification module.

[0050] Example 2

[0051] See attached Figure 5 and 6As shown, the present invention relates to a 3D printing dual-galvanometer detection device including a first laser beam 1, a scanning galvanometer unit, a printing work surface 3, a detection galvanometer unit and a second laser beam 5. The scanning galvanometer unit includes a first dielectric reflector 21, a first galvanometer 22 and a first focusing mirror 23 arranged on the optical path of the first laser beam 1. The first dielectric reflector 21 is a total reflection mirror, which is used to obliquely inject the first laser beam 1 onto the printing work surface 3; the detection galvanometer unit is located on the optical path of the first laser beam 1 after it is reflected by the printing work surface 3, and includes a second galvanometer 42, a second focusing mirror 43, a second dielectric reflector 41 and a position sensor 44 arranged on the optical path of the first laser beam 1. The second dielectric lens is a beam splitter. The second dielectric reflector 41 is located between the position sensor 44 and the combined structure formed by the second galvanometer 42 and the second focusing mirror 43, and is used to reflect the second laser beam 5, so that the optical path of the reflected second laser beam 5 coincides with the optical path of the first laser beam 1 and is in the opposite direction. The first focusing mirror 23 and the second focusing mirror 43 are both imaging lenses, such as Figure 5 As shown; or the first focusing mirror 23 and the second focusing mirror 43 are both field mirrors, such as Figure 6 As shown; of course, the first focusing lens 23 can also be an imaging lens, and the second focusing lens 43 can be a field lens; or the first focusing lens 23 can be a field lens, and the second focusing lens 43 can be an imaging lens; when an imaging lens is used, the imaging lens is an equivalent lens group formed by a combination of multiple concave lenses or / and convex lenses. The position sensor 44 uses a CMOS sensor or a photoelectric sensor PSD, and its position detection resolution accuracy is higher than 0.1um.

[0052] When the 3D printing dual galvanometer detection device involved in this embodiment is used for surface defect detection and spot magnification measurement, the second laser beam 5 is turned off, and the surface defect detection and spot magnification measurement method is the same as in Example 1, and this embodiment will not be described in detail. During the scanning process, the detection galvanometer unit can be used as another scanning galvanometer unit to reflect and focus the second laser beam 5 onto the printing work surface 3 for scanning and printing. Therefore, the scanning galvanometer unit or the detection galvanometer unit can be selected for 3D printing.

[0053] The present invention is described in detail above in conjunction with the embodiments, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of application of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for measuring a spot magnification, which is implemented based on a 3D printing dual-galvanometer detection device, wherein the 3D printing dual-galvanometer detection device comprises a first laser beam, a scanning galvanometer unit, a printing work surface and a detection galvanometer unit; the scanning galvanometer unit comprises a first medium reflector, a first galvanometer and a first focusing mirror arranged on the optical path of the first laser beam, and is used to obliquely inject the first laser beam into the printing work surface; the detection galvanometer unit is located on the optical path of the first laser beam after being reflected by the printing work surface, and comprises a second galvanometer, a second focusing mirror and a position sensor arranged on the optical path of the first laser beam; characterized in that: It includes the following steps: Step 1. After being reflected by the first medium reflector and the first galvanometer and focused by the first focusing mirror, the first laser beam is tilted and incident on the printing work surface to form a light spot, which is captured by the position sensor through the second galvanometer and the second focusing mirror to obtain the position of the light spot on the position sensor; Step 2. Control the first galvanometer to rotate an angle so that the light spot moves on the printing work surface, and the position of the light spot on the position sensor also changes accordingly. Calculate the magnification of the optical path system during the rotation of the first galvanometer, and determine whether the magnification of the optical path system is normal according to the magnification change rate; The formula for calculating the magnification of the optical path system during the rotation of the first galvanometer is: （2）， In the formula, k is the magnification of the optical system, m is the moving distance of the light spot on the printing work surface at a certain moment, β is the angle between the reflected light and the vertical direction at that moment, r It is the offset of the light spot captured by the position sensor at that moment relative to the position of the first galvanometer before rotation.

2. The method for measuring the spot magnification according to claim 1, characterized in that: The 3D printing dual galvanometer detection device also includes a second laser beam, and the detection galvanometer unit also includes a second dielectric reflector, which is located between the position sensor and the combined structure formed by the second galvanometer and the second focusing mirror, and is used to reflect the second laser beam so that the optical path of the reflected second laser beam coincides with the optical path of the first laser beam and is in opposite directions.

3. The method for measuring the spot magnification according to claim 1, characterized in that: The first focusing lens is an imaging lens or a field lens; the second focusing lens is an imaging lens or a field lens.

4. The method for measuring the spot magnification according to claim 1, characterized in that: When the magnification change rate in the step 2 is greater than the allowable change ratio of the line width required by the printing work, it indicates that the magnification of the optical path system is abnormal.

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