Multi-Laser-Head Position Mosaic Method and Device

Abstract

The present invention discloses a multi-laser head position splicing method and device, belonging to the technical field of 3D printing. The method includes the steps of: S1, calibrating the coordinate position of the field center position of the fine-tuning camera in the global camera coordinate system, denoted as P j ; S2, using the global camera to detect the spot position of the reference red laser generated by the galvanometer print head on the laser printing working surface, denoted as P i ; S3, controlling the movement of the galvanometer to move the spot at position P i to position P j ; S4, the galvanometer forms a printing spot on the laser printing working surface, and then controls the movement of the galvanometer to move the center point of the spot to position P j , and records the current position of the galvanometer motor driving the movement of the galvanometer, denoted as P i‑j ; S5, according to the position P i‑j , complete the coordinate transformation of each galvanometer according to the preset coordinate transformation equation. The splicing method provided by the present invention does not require manual intervention, has a high degree of automation, the provided splicing device has a simple structure and high splicing accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and particularly to a method and device for splicing the positions of multiple laser heads. Background Art

[0002] Laser 3D printing is a method of using a laser beam, which is reflected by a galvanometer mirror and then scans and prints patterns layer by layer on the printing working surface. With the increasing maturity of laser 3D printing technology, the printing demand has transitioned from being able to print to achieving high-efficiency printing. High-efficiency printing usually adopts a multi-galvanometer mirror scheme, that is, using more than 2 galvanometer mirrors for simultaneous printing. Currently, the highest number of galvanometer mirrors used in the industry for simultaneous printing is 12. When multiple galvanometer mirrors jointly print a part, it is necessary to accurately splice the areas jointly printed by multiple galvanometer mirrors. Currently, it is usually done by splicing each printing head (laser head) of each galvanometer mirror one by one. The splicing method is usually as follows: print a test pattern, measure the difference at the splicing point between the patterns through a third-party measuring device, calculate the correction amount based on the difference, and then adjust the position of the galvanometer mirror and continue printing. When the number of laser heads is large, this pairwise position splicing method requires printing test images multiple times and calculating the correction amount pairwise respectively, which is time-consuming and has low splicing accuracy. At the same time, it requires the aid of a third-party measuring device, making the correction inconvenient and inefficient. Summary of the Invention

[0003] The present invention aims to improve the splicing accuracy and efficiency of multiple laser heads, and provides a method for splicing the positions of multiple laser heads.

[0004] To achieve this purpose, the present invention adopts the following technical solutions:

[0005] Provide a method for splicing the positions of multiple laser heads, including the steps of:

[0006] S1, calibrate the coordinate position of the center of the field of view of the fine-tuning camera in the global camera coordinate system, denoted as P j ;

[0007] S2, use the global camera to detect the position of the light spot of the reference red laser generated by the galvanometer printing head on the laser printing working surface, denoted as P i ;

[0008] S3, control the movement of the galvanometer mirror to move the light spot at position P i to position P j ;

[0009] S4, the galvanometer mirror forms a printing light spot on the laser printing working surface, and then control the movement of the galvanometer mirror to move the center point of the light spot to the position P j , and record the current position of the galvanometer motor that drives the movement of the galvanometer mirror, denoted as P i-j, where i represents the i-th galvanometer disposed inside the multi-laser head position splicing device, and j represents the j-th fine-tuning camera disposed inside the multi-laser head position splicing device;

[0010] S5. According to the position P i-j , perform coordinate transformation on each of the galvanometers according to the preset coordinate transformation equation.

[0011] Preferably, when the printing area of the laser printing working surface is 500 mm × 500 mm, the number m of the fine-tuning cameras disposed inside the multi-laser head position splicing device is 4, and the 4 fine-tuning cameras are respectively disposed above each of the 4 corners of the laser printing working surface with the global camera as the central point.

[0012] Preferably, when the number m of the fine-tuning cameras disposed inside the multi-laser head position splicing device is 1, in step S4, the coordinates of the galvanometer are transformed by the first coordinate transformation equation expressed by the following formula (1):

[0013]

[0014] In formula (1), x and y respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer before coordinate transformation at the position P i-j ;

[0015] a, a′, b, b′ respectively represent the coordinate conversion coefficients of x and y;

[0016] x′ and y′ respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer predicted by coordinate transformation.

[0017] Preferably, when the number m of the fine-tuning cameras disposed inside the multi-laser head position splicing device is 4, in step S4, the coordinates of the galvanometer are transformed by the second coordinate transformation equation expressed by the following formula (2):

[0018]

[0019] In formula (2), x and y respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer before coordinate transformation at the position P i-j ;

[0020] x′ and y′ respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer predicted by coordinate transformation.

[0021] a1, a2, a3, a4, b1, b2, b3, b4 are coordinate conversion coefficients.

[0022] The present invention also provides a multi-laser head position splicing device, which has a laser printing working surface and at least one galvanometer inside. It includes a global camera fixed above the central point of the laser printing working surface, and at least one fine-tuning camera fixed above each corner of the laser printing working surface. The position calibration device calibrates the center position of the field of view of each fine-tuning camera as the coordinate position in the global camera coordinate system, denoted as P j , and then uses the global camera to detect the position of the light spot of the reference red laser generated by the galvanometer printing head on the laser printing working surface, denoted as P i , and then the galvanometer driving device drives the galvanometer i to move according to the instruction, so as to move the light spot at the position P i to the position P j , and then controls the galvanometer to form a printing light spot on the laser printing working surface. Subsequently, the galvanometer driving device drives the galvanometer i to move, so as to move the center point of the light spot to the position P j , and records the current position of the galvanometer driving device that drives the galvanometer to move, denoted as P i-j , and finally, performs coordinate transformation on each galvanometer i according to the position P i-j and according to the preset coordinate transformation equation.

[0023] Preferably, the multi-laser head position splicing device further includes the galvanometer driving device, and the galvanometer driving device is a galvanometer motor.

[0024] Preferably, when the printing format of the laser printing working surface is 500mm×500mm, the number m of the fine-tuning cameras arranged inside the multi-laser head position splicing device is 4, and the 4 fine-tuning cameras are respectively arranged above each of the 4 corners of the laser printing working surface with the global camera as the center point.

[0025] Preferably, the preset coordinate transformation equation is expressed by the following formula (3):

[0026]

[0027] In formula (3), x and y respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer at the position P i-j before coordinate transformation;

[0028] x' and y' respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer predicted by coordinate transformation.

[0029] a1, a2, a3, a4, b1, b2, b3, b4 are coordinate conversion coefficients.

[0030] The multi-laser head position splicing method provided by the present invention can be automatically completed by software throughout the process without manual intervention. The multi-laser head position splicing device has a simple structure and high splicing accuracy. Moreover, the present invention is not limited to the splicing position correction in the initial installation situation, but is also suitable for the splicing position correction during the powder spreading gap in the printing process. The correction process is automatically carried out by software and can be completed in only a few seconds throughout the process. The application threshold is low and it is very convenient to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0032] Figure 1 is a flowchart showing the implementation steps of the multi-laser head position splicing method provided by an embodiment of the present invention;

[0033] Figure 2 is an exemplary diagram showing the installation positions of the global camera and the fine-tuning camera in the 3D printing device;

[0034] Figure 3 is an exemplary diagram showing the installation positions of the global camera, the fine-tuning camera, and the galvanometer printing head in the 3D printing device;

[0035] Figure 4 is an exemplary diagram showing the coordinate position of the calibrated center position of the field of view of the fine-tuning camera in the global camera coordinate system;

[0036] Figure 5 is an exemplary diagram showing the global camera and the fine-tuning camera installed above the laser printing working surface;

[0037] Figure 6 is an exemplary diagram showing the field of view range of the global camera;

[0038] Figure 7 is an exemplary diagram showing the field of view range of the fine-tuning camera. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0039] The technical solutions of the present invention will be further described below with reference to the drawings and through specific embodiments.

[0040] Among them, the drawings are only for illustrative purposes, showing only schematic diagrams, not physical diagrams, and should not be construed as a limitation to this patent; in order to better illustrate the embodiments of the present invention, some components in the drawings will be omitted, enlarged or reduced, and do not represent the dimensions of the actual product; for those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0041] In the drawings of the embodiments of the present invention, the same or similar reference numerals correspond to the same or similar components; in the description of the present invention, it should be understood that if terms such as "upper", "lower", "left", "right", "inner", "outer", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, the terms describing the positional relationship in the drawings are only for illustrative purposes and cannot be construed as a limitation of this patent. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0042] In the description of the present invention, unless otherwise clearly specified and limited, if terms such as "connection" are used to indicate the connection relationship between components, this term should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two components or the interaction relationship between two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0043] Multi-laser head splicing is mainly used in the following two usage scenarios:

[0044] 1. After multiple sets of galvanometers are installed on the same device, the initial positions of the laser heads are adjusted for splicing. As Figure 4 shown, the initial positions of each galvanometer (reference numerals 100-107 in the drawings) are different, and due to installation errors, especially the zero position errors of each galvanometer motor (used to drive the galvanometer to perform 3D printing actions) of each set of galvanometers, the difference between its initial position and the theoretically assumed position is very large. In this case, the amount of position adjustment required for multi-head splicing is relatively large.

[0045] 2. After multiple sets of galvanometers have been used for a long time, due to reasons such as long-term cumulative position drift, changes in working temperature, and changes in mechanical stress, the splicing state between multiple galvanometers will also change. Therefore, it is also necessary to perform regular adjustments during use.

[0046] In the above two scenarios, the following requirements need to be met for the position splicing of multiple galvanometer laser heads:

[0047] (1) The observable and adjustable deviation range should be large enough. The initial zero position of the galvanometer depends on the angle sensor of the galvanometer motor used. Even if the installation error of the angle sensor can be controlled within 1°, the spot error presented on the printing work surface is usually about 20 mm. Therefore, to calibrate the position of the galvanometer in its initial state, it is best to be able to identify the initial spot position throughout the range of the printing work surface.

[0048] (2) The splicing accuracy should be high enough. According to the current printing accuracy requirements, the upper limit of the printing error at the splicing position shall not exceed 50 μm, and for high-precision printing, the error shall be kept below 30 μm. The printing error includes not only the splicing error, but also the shaft runout error of the galvanometer motor and the repeat positioning error of the motor driver. Therefore, to achieve a printing error of no more than 30 - 50 μm at the splicing position, excluding the shaft runout error of the motor and the repeat positioning error of the motor driver, the splicing error of multiple laser heads needs to be controlled below 10 μm, and the requirement for splicing accuracy is very high.

[0049] (3) The splicing detection device should be built-in and automated. For the splicing detection device, if only external third-party detection equipment can be used, the detection process will be very cumbersome. If frequent detection is required, the actual operability will be even worse. Therefore, it is hoped that the splicing detection device can be built into the 3D printing device and can achieve automated error detection and splicing.

[0050] To meet the above three splicing requirements, the multi-laser head position splicing method provided by the embodiments of the present invention is as Figure 1 shown, including the steps:

[0051] S1, calibrate the coordinate position of the field center of the fine-tuning camera in the global camera coordinate system, denoted as P j , where j is the j-th fine-tuning camera installed inside the 3D printing device;

[0052] The calibration method is:

[0053] Taking the fine-tuning camera 21 in the debugging Figure 4 as an example ( Figure 4 The reference numerals "20, 21, 22, 23" in the Figure 6 are all fine-tuning cameras), print the laser spot on the printing work surface 200 shown in Figure 6 . Drive the galvanometer motor to drive the galvanometer to move through the galvanometer motor control software, and then move the spot so that the center point of the spot coincides exactly with the center point of the CMOS of the fine-tuning camera 21. At this time, read the position of the spot in the global camera 10 and record its coordinate center point in the global camera 10. This spot center coordinate point is the position of the fine-tuning camera 21 in the global camera 10, and calibrate it as the center coordinate position P 21 ;

[0054] S2, Use the global camera to detect the position of the light spot of the reference red laser emitted by the galvanometer print head (laser head) on the printing work surface, denoted as P i ;

[0055] For example, use Figure 4 the global camera 10 shown in Figure 6 to detect the position of the light spot of the reference red laser on the printing work surface 200 shown in 103 ;

[0056] S3, Control the movement of the galvanometer to move the light spot at position P i to position P j ;

[0057] For example, control Figure 4 the movement of the galvanometer 103 shown in 103 to move the light spot at position P 21 . After this step, the light spot of the reference red laser of the galvanometer 103 has entered the field of view of the fine-tuning camera 21.

[0058] S4, The galvanometer forms a printing light spot on the printing work surface, and then controls the movement of the galvanometer to move the center point of the light spot to P j , and record the current position of the galvanometer motor that drives the movement of the galvanometer, denoted as P i-j , where i represents the i-th galvanometer installed inside the multi-laser head position splicing device, and j represents the j-th fine-tuning camera installed inside the multi-laser head position splicing device;

[0059] For example, move the center point of the printing light spot formed by the galvanometer 103 in Figure 4 to position P 21 , and record the position of the galvanometer motor that drives the movement of the galvanometer after moving the center point of the light spot to position P 21 , denoted as P 103-21 ;

[0060] S5, According to the position P i-j , complete the coordinate transformation of each galvanometer according to the preset coordinate transformation equation.

[0061] The following takes an example of an identical 3D printing device with Figure 4 8 galvanometers (denoted by the reference numerals "100-107" respectively), a global camera (denoted by the reference numeral "10"), and 4 fine-tuning cameras (denoted by the reference numerals "20-23" respectively) shown in

[0062] to specifically illustrate the method of transforming the coordinates of the galvanometer: i-jWith 4 sets of data, such as association Figure 4 P of the galvanometer 103 i-j The four sets of data are P 103-20 , P 103-21 , P 103-22 , P 103-23 , 8 galvanometers have a total of 32 groups of P i-j Coordinate data. This application uses the following coordinate transformation equation (2) to transform the galvanometer coordinates:

[0063]

[0064] In formula (2), x and y represent the position P of the galvanometer before coordinate transformation. i-j The horizontal and vertical coordinates of

[0065] x′ and y′ respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer predicted by coordinate transformation.

[0066] a1, a2, a3, a4, b1, b2, b3, b4 are coordinate transformation coefficients, which can be solved by substituting multiple sets of coordinate data before and after the coordinate transformation. i-j After that, we only need to change P i-j The horizontal axis coordinate value in is the variable value of the x variable in formula (2), and the vertical axis coordinate value is the variable value of the y variable in formula (2). Solving x' and y' gives the transformed coordinates. After the transformation, the coordinates of the eight galvanometers will be unified, and the coordinate correction of the eight galvanometer print heads is completed.

[0067] It should be noted that the method for detecting the position of the reference red laser spot by the global camera is an existing mature technology, so the method for detecting the position of the light spot by the global camera is not described. i The light spot moves to position P j , move the center of the light spot to position P j , get the P of the galvanometer motor driving the galvanometer from the light spot i Move to position P j The current position after position P i-j And according to P i-j The control process of automatically calculating the galvanometer coordinate transformation and driving the galvanometer to adjust the splicing position after completing the coordinate transformation can be realized through software program and automated execution. Therefore, the multi-laser head position splicing method provided in the embodiment of the present invention solves the technical problem recorded in the above requirement (3).

[0068] In addition, when calculating the stitching position adjustment amount with a conventional square printing format of 300 - 500 mm, taking an example where a single camera is used and the camera sensor resolution is 20 million pixels, that is, the resolution is 4000 * 5000, in the case where the 500 - mm side length can be fully covered, the single - pixel resolution is 0.125 mm. Considering the statistical error of image recognition, the effective resolution is about 0.4 mm. Therefore, when using a single camera for position recognition, the accuracy cannot meet the usage requirements. To solve this problem, the embodiments of the present invention use 5 cameras (1 global camera and 4 fine - tuning cameras) to complete the multi - laser - head stitching process. The imaging coverage ranges of the 5 cameras are as Figure 2 shown. The imaging coverage range of the global camera 30 is the entire printing format. Taking a 500 - mm * 500 - mm printing format as an example, the global camera can cover the entire printing area, and its resolution is approximately 0.4 mm; while each fine - tuning camera uses a telephoto lens with a magnification ratio of about 1:1. The observation area 40 of the camera is equivalent to the CMOS size, about a 5 - mm side - length range, and its detection accuracy is about 4 μm, which can meet requirements (1) and (2) described above.

[0069] The present invention also provides a multi - laser - head position stitching device, as Figure 2-3 、 Figure 5-7 shown. It has a laser printing working surface 200 and at least one galvanometer 100 inside. The multi - laser - head position stitching device includes a global camera 10 fixed above the central point on the laser printing working surface, and at least one fine - tuning camera (represented by the reference numerals "20, 21, 22, 23") fixed above each corner of the laser printing working surface. The position calibration device calibrates the center position of the field of view of each fine - tuning camera as the coordinate position in the global camera coordinate system, denoted as P j , and then uses the global camera to detect the position of the light spot of the reference red laser generated by the galvanometer printing head on the laser printing working surface, denoted as P i . Then, the galvanometer driving device drives the galvanometer i to move according to the instruction to move the light spot at position P i to position P j . Then, control the galvanometer to form a printing spot on the laser printing working surface. Subsequently, the galvanometer driving device drives the galvanometer i to move to move the center point of the spot to position P j , and record the current position of the galvanometer driving device (preferably a galvanometer motor) that drives the galvanometer to move, denoted as P i-j . Finally, perform coordinate transformation on each galvanometer i according to position P i-j and in accordance with the preset coordinate transformation equation.

[0070] In summary, the multi-laser head position splicing method provided by the embodiments of the present invention can be automatically completed by software throughout the process without manual intervention. The multi-laser head position splicing device has a simple structure and high splicing accuracy. Moreover, the present invention is not limited to the splicing position correction in the initial installation situation, but is also suitable for the splicing position correction during the powder spreading gap in the printing process. The correction process is automatically performed by software and can be completed in only a few seconds throughout the process. The application threshold is low and it is very convenient to use.

[0071] It should be noted that the above specific embodiments are only the preferred embodiments of the present invention and the applied technical principles. Those skilled in the art should understand that various modifications, equivalent replacements, changes, etc. can be made to the present invention. However, as long as these transformations do not deviate from the spirit of the present invention, they should be within the protection scope of the present invention. In addition, some terms used in the description and claims of this application are not restrictive, but are only for the convenience of description.

Claims

1. A method for splicing the positions of multiple laser heads, characterized in that, Including the steps: S1, calibrate and finely adjust the coordinate position of the center of the field of view of the camera in the global camera coordinate system, denoted as P j ; S2, use the global camera to detect the position of the light spot of the reference red laser generated by the galvanometer print head on the laser printing work surface, denoted as P i ; S3, control the galvanometer mirror to move so as to move the light spot at position P i to position P j ; At S4, the galvanometer forms a printing light spot on the laser printing working surface, and then controls the movement of the galvanometer to move the central position point of the light spot to the position P j , and record the current position of the galvanometer motor that drives the movement of the galvanometer, denoted as P i-j , where i represents the ith galvanometer arranged inside the multi-laser head position splicing device, and j represents the jth fine-tuning camera arranged inside the multi-laser head position splicing device; S5, according to the position P i-j , perform coordinate transformation on each of the galvanometers according to a preset coordinate transformation equation; When the printing format of the laser printing working surface is 500mm×500mm, the number m of the fine-tuning cameras arranged inside the multi-laser head position splicing device is 4, and the 4 fine-tuning cameras are respectively arranged above each of the 4 corners of the laser printing working surface with the global camera as the central point; In step S5, the coordinates of the galvanometer are transformed by the second coordinate transformation equation expressed by the following formula (2): In formula (2), x and y respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer at the position P before coordinate transformation. i-j ; x ′ , y ′ respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer predicted through coordinate transformation; a1, a2, a3, a4, b1, b2, b3, b4 are coordinate transformation coefficients.

2. The multi-laser head position splicing method according to claim 1, wherein When the number m of the fine-tuning cameras arranged inside the multi-laser head position splicing device is 1, in step S5, the coordinates of the galvanometer are transformed by the first coordinate transformation equation expressed by the following formula (1): In formula (1), x and y respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer mirror before coordinate transformation at the position P i-j ; a, a′, b, and b′ respectively represent the coordinate transformation coefficients of x and y; x ′ , y ′ respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer mirror predicted through coordinate transformation.

3. A multi-laser head position splicing device, which has a laser printing working surface and at least one galvanometer inside, is characterized in that, including a global camera fixed at a position above the central point of the laser printing working surface, and at least one fine-tuning camera fixed at a position above each corner of the laser printing working surface, wherein a position calibration device calibrates the center position of the field of view of each of the fine-tuning cameras as a coordinate position in the global camera coordinate system, denoted as P j , then use the global camera to detect the position of the light spot of the reference red laser generated by the galvanometer printing head on the laser printing working surface, denoted as P i , then the galvanometer driving device drives the galvanometer i to move according to the instruction to move the light spot at position P i to position P j , then control the galvanometer to form a printing light spot on the laser printing working surface, and then the galvanometer driving device drives the galvanometer i to move to move the central point of the light spot to the position P j , and record the current position of the galvanometer driving device that drives the galvanometer to move, denoted as P i-j , finally, perform coordinate transformation on each galvanometer i according to the position P i-j and in accordance with a preset coordinate transformation equation; When the printing format of the laser printing working surface is 500mm×500mm, the number m of the fine-tuning cameras arranged inside the multi-laser head position splicing device is 4, and the 4 fine-tuning cameras are respectively arranged above each of the 4 corners of the laser printing working surface with the global camera as the central point; The preset coordinate transformation equation is expressed by the following formula (3): In formula (3), x and y respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer before coordinate transformation at the position P i-j ; x ′ , y ′ respectively represent the horizontal axis coordinate and the vertical axis coordinate of the galvanometer predicted by coordinate transformation; a1, a2, a3, a4, b1, b2, b3, b4 are coordinate transformation coefficients.

4. The multi-laser head position splicing device according to claim 3, characterized in that It further includes the galvanometer driving device, and the galvanometer driving device is a galvanometer motor.

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