A method of contour scanning of a three-dimensional object, a device and an additive manufacturing apparatus

Abstract

A kind of profile scanning method, device and additive manufacturing equipment of three-dimensional object, wherein scanning method includes: selecting the at least one closed loop profile that current layer in the printed part to be contained simultaneously lower surface profile line and non-lower surface profile line, as closed loop profile A to be handled;Get all the junction points of lower surface profile line and non-lower surface profile line in closed loop profile A to be handled;According to the position of each junction point, judge whether it needs to be moved on closed loop profile A to be handled to obtain closed loop profile B to be handled containing new lower surface profile line and new non-lower surface profile line;Get all the closed loop profiles of current layer in the printed part to be, which contains the closed loop profile B to be handled obtained by the above processing;According to the way that every N layer scanning sequence is reversed, all closed loop profiles are scanned.The present application improves the surface quality of the printed part to be and improves printing efficiency.

Description

Technical Field

[0001] This application relates to the field of additive manufacturing technology, and in particular to a method, apparatus and additive manufacturing equipment for contour scanning of three-dimensional objects. Background Technology

[0002] Additive manufacturing is a rapid manufacturing technology that uses a laser to scan and stack layers to form a three-dimensional object. The process is as follows: First, the 3D model of the workpiece (usually in STL format) is sliced ​​to obtain the contour information of each layer. Powdered material is then evenly spread onto the surface of the work platform, and the laser selectively melts the powder according to system instructions. After one section is completed, a new layer of material is laid on top, and scanning continues selectively based on the cross-sectional information corresponding to the 3D object. This process is repeated for the next cross-section, ultimately resulting in the 3D object.

[0003] In existing technologies, one or more contour lines are typically scanned along the outline before or after scanning the infill area of ​​the workpiece to be printed in order to improve its surface quality.

[0004] A 3D model in STL format is composed of several triangular facets. Each facet is considered a bottom surface by the angle between its normal vector (with its positive direction pointing outwards from the 3D model) and the printing direction. For example, if this angle threshold is set to 120°, then the facets in the 3D model composed of facets whose normal vectors have an angle greater than 120° with the printing direction are considered bottom surfaces, and the other facets are considered non-bottom surfaces. The intersection line between the bottom surface and the sliced ​​facet is the bottom surface contour line, and the intersection line between the non-bottom surface and the sliced ​​facet is the non-bottom surface contour line. A complete closed-loop contour can consist of the following scenarios: ① only a bottom surface contour line, ② only a non-bottom surface contour line, ③ both a bottom surface contour line and a non-bottom surface contour line. This invention optimizes the printing strategy for the connection point between the bottom surface contour region and the non-bottom surface contour region in the third scenario to improve the forming effect of this area.

[0005] Currently, lower line energy density is generally used for scanning the lower surface contour lines to avoid excessive scanning energy, which could lead to powder adhesion or even warping and printing failure. However, this area has a matte finish. Higher laser line energy density is generally used for scanning non-lower surface contour lines to achieve a brighter surface quality. However, when the closed-loop contour falls under case ③ above, a clear boundary exists between the lower surface contour lines on the matte surface and the non-lower surface contour lines on the glossy surface. Microscopically, this boundary has a height difference, affecting the local surface quality and dimensional accuracy of the workpiece, and increasing the difficulty and workload of removing the boundary line in post-processing. Furthermore, the molten pool morphology and energy conditions at the start and end points of the contour vector lines are different. The start point has higher energy and is more convex than the end point. If the start points of each contour layer are stacked at the same position in the forming direction, it can easily cause localized powder bed protrusions at that position, resulting in warping. Summary of the Invention

[0006] To address the aforementioned technical problems in the existing technology, the present invention provides a method, apparatus, and additive manufacturing equipment for contour scanning of three-dimensional objects. This method for contour scanning of three-dimensional objects achieves both improved surface quality of the part to be printed and improved printing efficiency.

[0007] To achieve the above objectives, the present invention provides a contour scanning method for a three-dimensional object, comprising the following steps: Step S1: Select at least one closed-loop contour in the current layer of the part to be printed that simultaneously contains the lower surface contour line and the non-lower surface contour line, and denote it as the closed-loop contour A to be processed. Step S2: Obtain all connection points between the lower surface contour line and the non-lower surface contour line in the closed loop contour A to be processed; Step S3: Determine whether it is necessary to move the closed loop profile A to be processed based on the position of each connection point to obtain the closed loop profile B to be processed, which includes the new lower surface profile and the new non-lower surface profile. Step S4: Obtain all closed-loop contours of the current layer in the part to be printed. All closed-loop contours include the closed-loop contours B to be processed obtained through steps S1-S3 above. Scan all closed-loop contours in reverse order every N layers, and scan all lower surface contours included in all closed-loop contours using the first printing parameter. Scan all non-lower surface contours included in all closed-loop contours using the second printing parameter.

[0008] As a further preferred embodiment of the present invention, step S3 specifically includes: Step S31: For all connection points between the lower surface contour line and the non-lower surface contour line in the closed-loop contour to be processed, process them as follows: When the connection point is located at the inflection point of the broken line, the connection point is the original connection point and does not need to be moved. It is denoted as connection point A. When the connection point is located on the arc, the connection point moves randomly within a preset interval to obtain a new connection point, denoted as connection point B; wherein, the preset interval is obtained by moving the connection point as the starting point and moving a first preset distance to both sides along the closed contour A to be processed where it is located. Step S32: Obtain the closed-loop contour B to be processed by the above step S31. The closed-loop contour B to be processed includes a new lower surface contour line with connection point A and connection point B and a new non-lower surface contour line.

[0009] As a further preferred embodiment of the present invention, the preset interval is centered at the connection point, and the first preset distance is 1mm.

[0010] As a further preferred embodiment of the present invention, after step S4 is performed, the contour scanning method for a three-dimensional object further includes: Select all lower surface contour lines, and for each lower surface contour line, move it parallel to its vertical direction in its slice plane and outwards a second preset distance away from the physical object to be printed to form an offset contour line. The offset contour line is scanned according to the first printing parameters.

[0011] As a further preferred embodiment of the present invention, the second preset distance is half the difference between the width of the lower surface contour line melt channel and the width of the non-lower surface contour line melt channel.

[0012] As a further preferred embodiment of the present invention, the value of N is in the range of 1-5.

[0013] As a further preferred embodiment of the present invention, both the first printing parameter and the second printing parameter include laser line energy density.

[0014] As a further preferred embodiment of the present invention, the laser line energy density of the first printing parameter is less than the laser line energy density of the second printing parameter.

[0015] The present invention also provides a contour scanning device for a three-dimensional object, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the contour scanning method for a three-dimensional object as described in any one of the present invention.

[0016] The present invention also provides an additive manufacturing apparatus, including the contour scanning device for three-dimensional objects described above.

[0017] The three-dimensional object contour scanning method, apparatus, and additive manufacturing equipment of the present invention, on the one hand, scan all closed-loop contours in a reverse manner according to the scanning sequence every N layers, so that the starting point and ending point of the contour scanning vector change every N layers (reverse), thereby causing the starting point and ending point of the scanning vector to appear alternately and interlaced locally. During the scanning and forming process, it can effectively repair the molten pool protrusion at the starting point of the scanning vector and the molten pool pit at the ending point of the scanning vector, avoid repeated stacking of the contour starting points of adjacent layers in the construction direction, thereby suppressing the local protrusion of the contour from the powder bed and causing warping, improving surface quality and printing success rate; On the other hand, corresponding strategies are adopted according to the shape of the part to be printed. When the connection point is located at the inflection point of the broken line, the requirements for surface quality and precision at this position are not very high. It can be achieved by simply using the above-mentioned reverse scanning every N layers. Therefore, it is not necessary to move the connection point, which simplifies the processing procedure and improves work efficiency. However, when the connection point is located on the arc, the requirements for surface quality and precision at this position are very high. Since the starting point or ending point of the lower surface contour line and the ending point or starting point of the non-lower surface contour line are different in terms of molten pool morphology and energy, the starting point has higher energy and is more convex than the ending point. If each connection point is stacked at the same position in the forming direction, it is easy to cause local bulging of the powder bed at this position and form warping. Therefore, this application addresses this situation by controlling the connection point to move randomly within a preset interval to obtain a new connection point. This allows the connection points to be staggered from each other within the preset interval. The staggered position is random, thereby preventing the formation of regular boundary lines between the lower surface contour line and the non-lower surface contour line to the greatest extent, which improves the sintering quality of the part to be printed.

[0018] Therefore, the three-dimensional object contour scanning method, apparatus, and additive manufacturing equipment of the present invention achieve both improved surface quality of the part to be printed and improved printing efficiency. Attached Figure Description

[0019] Figure 1 A three-dimensional display of the part to be printed provided in Embodiment 1 of the present invention. Figure 1 ; Figure 2 A three-dimensional display of the part to be printed provided in Embodiment 1 of the present invention. Figure 2 ; Figure 3 This is a front view of the part to be printed provided in Embodiment 1 of the present invention; Figure 4 The right view of the part to be printed provided in Embodiment 1 of the present invention Figure 1 ; Figure 5 The right view of the part to be printed provided in Embodiment 1 of the present invention Figure 2 ; Figure 6 This is a vector diagram of the cross-sectional contour of the (N-1)th layer of the part to be printed provided in Embodiment 1 of the present invention; Figure 7 This is a schematic diagram of the Nth layer cross-sectional contour line of the part to be printed provided in Embodiment 1 of the present invention; Figure 8 This is a vector diagram of the cross-sectional contour of the (N+1)th layer of the part to be printed provided in Embodiment 1 of the present invention; Figure 9 The front view of the part to be printed provided in Embodiment 2 of the present invention Figure 1 ; Figure 10 The front view of the part to be printed provided in Embodiment 2 of the present invention Figure 2 ; Figure 11 This is a schematic diagram of the Nth layer cross-sectional contour line of the part to be printed provided in Embodiment 3 of the present invention; Marked in the image: 1. Lower surface contour area; 2. N-1th layer section; 3. Nth layer section; 4. N+1th layer section; 5. Non-lower surface contour area; 6. Connection position between lower surface contour area and non-lower surface contour area; Z, construction direction; 7. Lower surface contour line; 8. Non-lower surface contour line; 9. Preset interval segment; 10. Offset contour line. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application. Example

[0021] like Figures 1-5 As shown, the contour scanning method for a three-dimensional object in this embodiment includes the following steps: Step 11: Select at least one closed-loop contour in the current layer of the part to be printed that simultaneously contains the lower surface contour line 7 and the non-lower surface contour line 8, and denote it as the closed-loop contour A to be processed; for example, in a specific implementation, the closed-loop contour A to be processed can be one or more, and each closed-loop contour A to be processed is processed in accordance with the following steps 11 and 12. Step 12: Obtain all connection points of the lower surface contour line 7 and the non-lower surface contour line 8 in the closed-loop contour A to be processed; In specific implementation, the number of connection points can be one or more, and each connection point is processed in accordance with step 13 below; Step 13: Determine whether it is necessary to move the closed loop profile A to be processed based on the position of each connection point to obtain a closed loop profile B to be processed containing a new lower surface profile line 7 and a new non-lower surface profile line 8. Step 13 specifically includes: Step 131: For all connection points of the lower surface contour line 7 and the non-lower surface contour line 8 in the closed-loop contour to be processed, process them as follows: When the connection point is located at the inflection point of the broken line, the connection point is the original connection point and does not need to be moved. It is denoted as connection point A (this situation does not exist in this embodiment). When the connection point is located on an arc (such as...) Figures 3-5 As shown), the connection point moves randomly within the preset interval segment 9 to obtain a new connection point, denoted as connection point B; wherein, the preset interval segment 9 is obtained by moving a first preset distance to both sides along the closed contour A to be processed, with the connection point as the starting point; it should be noted that, due to the different shapes of the parts to be printed (e.g., irregularly shaped parts, which may be on the same layer or different layers, there may be connection points located at the inflection point and connection points located on the arc); Figures 6-8 The following diagrams show the vector outlines of the N-1th layer section 2, the Nth layer section 3, and the N+1th layer section 4 after they have been moved.

[0022] Preferably, in order to make the random movement more accurate and to improve the sintering quality as much as possible, the preset interval segment 9 is centered at the connection point, and the first preset distance is 1mm.

[0023] Step 132: Obtain the closed-loop contour B to be processed by the above step 131. The closed-loop contour B to be processed includes a new lower surface contour line 7 with connection point A and connection point B and a new non-lower surface contour line 8.

[0024] Step 14: Obtain all closed-loop contours of the current layer in the part to be printed. All closed-loop contours include the closed-loop contours B to be processed obtained through steps 11-13 above. Scan all closed-loop contours in reverse order every N layers, and scan all lower surface contours 7 included in all closed-loop contours using the first printing parameter. Scan all non-lower surface contours 8 included in all closed-loop contours using the second printing parameter.

[0025] Step 14, which involves scanning all closed-loop contours in reverse order every N layers, means that starting from the first layer of the workpiece to be printed, the scanning order of all closed-loop contours from the first layer to the Nth layer is A, while the scanning order of all closed-loop contours from the (N+1)th layer to the 2Nth layer is B (B is the reverse of A; for example, when A is clockwise, B is counterclockwise; when A is counterclockwise, B is clockwise), and so on. In practice, the value of N ranges from 1 to 5, preferably 1. Figure 6-8As shown, the scanning order of adjacent layers is reversed.

[0026] In specific implementation, both the first and second printing parameters include laser line energy density. The laser line energy density of the first printing parameter is lower than that of the second printing parameter. More preferably, to better ensure the sintering accuracy of the part, the ratio of the laser line energy density of the first printing parameter to that of the second printing parameter is 1:5-1:2. The laser line energy density is determined by the laser power, scanning speed, and layer thickness parameters. Specifically, laser line energy density = (laser power / scanning speed) / layer thickness. Of course, in specific implementation, the first and second printing parameters may also include other printing parameters depending on the printing needs, which will not be described in detail here.

[0027] The lower surface contour region 1 of this application is composed of several lower surface contour lines 7; the non-lower surface contour region 5 is composed of several non-lower surface contour lines 8; several preset interval segments 9 form the connection position 6 between the lower surface contour region and the non-lower surface contour region; Z is the construction direction Z of the additive manufacturing process. Example

[0028] The contour scanning method for a three-dimensional object in this embodiment includes the following steps: Step 21: Select at least one closed-loop contour in the current layer of the part to be printed that simultaneously contains the lower surface contour line 7 and the non-lower surface contour line 8, and denote it as the closed-loop contour A to be processed; for example, in a specific implementation, the closed-loop contour A to be processed can be one or more. Step 22: Obtain all connection points of the lower surface contour line 7 and the non-lower surface contour line 8 in the closed-loop contour A to be processed; in specific implementations, the number of connection points can be one or more. Step 23: Determine whether it is necessary to move the closed loop profile A to be processed based on the position of each connection point to obtain a closed loop profile B to be processed containing a new lower surface profile line 7 and a new non-lower surface profile line 8. Step 23 specifically includes: Step 231: For all connection points of the lower surface contour line 7 and the non-lower surface contour line 8 in the closed-loop contour to be processed, process them as follows: When the connection point is located at the inflection point of the broken line (such as...) Figures 9-10 As shown in the figure, this connection point is the original connection point and does not need to be moved. It is denoted as connection point A. When the connection point is located on the arc, the connection point moves randomly within the preset interval segment 9 to obtain a new connection point, denoted as connection point B; wherein, the preset interval segment 9 is obtained by moving the connection point as the starting point and moving it to both sides by a first preset distance along the closed contour A to be processed (this situation does not exist in this embodiment); it should be noted that due to the different shapes of the parts to be printed (e.g., irregularly shaped parts, which may be on the same layer or different layers, there may be connection points located at the inflection point and connection points located on the arc); Step 232: Obtain the closed-loop contour B to be processed by the above step 231. The closed-loop contour B to be processed includes a new lower surface contour line 7 with connection point A and connection point B and a new non-lower surface contour line 8.

[0029] Step 24: Obtain all closed-loop contours of the current layer in the part to be printed. All closed-loop contours include the closed-loop contours B to be processed obtained through steps 21-23 above. Scan all closed-loop contours in reverse order every N layers, and scan all lower surface contours 7 included in all closed-loop contours using the first printing parameter. Scan all non-lower surface contours 8 included in all closed-loop contours using the second printing parameter. Example

[0030] The technical solution of this embodiment is basically the same as that of embodiment one, except that this embodiment is further optimized based on embodiment one, that is, it further includes the following steps: Select all lower surface contour lines 7, and for each lower surface contour line 7, move it in its vertical direction within its slice plane and outwards a second preset distance away from the entity to be printed to form an offset contour line 10; in specific implementation, the second preset distance is half of the difference between the width of the melt channel of the lower surface contour line and the width of the melt channel of the non-lower surface contour line. The offset contour line 10 is scanned according to the first printing parameters (e.g., Figure 11 (As shown).

[0031] This embodiment can better avoid the problem of obvious steps at the joint position that may occur due to the lower laser line energy density and narrower melt pool width of the lower surface contour line 7 compared to the non-lower surface contour line 8, thus further improving the sintering quality of the part to be printed.

[0032] It should be noted that this application only describes the contour scanning of a single part to be printed. In specific implementations, multiple parts to be printed can be printed simultaneously. That is, the current layer may contain multiple work packages of parts to be printed. Each part to be printed is executed in accordance with the above scheme of this application (for example, Embodiment 1 to Embodiment 3), and will not be repeated here. Example

[0033] This embodiment provides a contour scanning device for a three-dimensional object, including a memory and a processor. The memory stores a computer program, and the processor executes the computer program to implement the steps of the contour scanning method for a three-dimensional object as described in any embodiment of the fir tree. Example

[0034] This embodiment provides an additive manufacturing apparatus, including the contour scanning device for three-dimensional objects described in Embodiment 4 above.

[0035] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0036] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for contour scanning of a three-dimensional object, characterized in that, Includes the following steps: Step S1: Select at least one closed-loop contour in the current layer of the part to be printed that simultaneously contains the lower surface contour line and the non-lower surface contour line, and denote it as the closed-loop contour A to be processed. Step S2: Obtain all connection points between the lower surface contour line and the non-lower surface contour line in the closed loop contour A to be processed; Step S3: Determine whether it is necessary to move the closed loop profile A to be processed based on the position of each connection point to obtain the closed loop profile B to be processed, which includes the new lower surface profile and the new non-lower surface profile. Step S4: Obtain all closed-loop contours of the current layer in the part to be printed. All closed-loop contours include the closed-loop contours B to be processed obtained by the above steps S1-S3. Scan all closed-loop contours in reverse order every N layers, and scan all lower surface contours included in all closed-loop contours using the first printing parameters. The second printing parameter is used to scan all non-lower surface contours contained in all closed-loop contours; the value of N ranges from 1 to 5. Specifically, step S3 includes: Step S31: For all connection points between the lower surface contour line and the non-lower surface contour line in the closed-loop contour to be processed, process them as follows: When the connection point is located at the inflection point of the broken line, the connection point is the original connection point and does not need to be moved. It is denoted as connection point A. When the connection point is located on the arc, the connection point moves randomly within a preset interval to obtain a new connection point, denoted as connection point B; wherein, the preset interval is obtained by moving a first preset distance to both sides along the closed loop contour A to be processed, with the connection point as the starting point. Step S32: Obtain the closed-loop contour B to be processed by the above step S31. The closed-loop contour B to be processed includes a new lower surface contour line with connection point A and connection point B and a new non-lower surface contour line.

2. The contour scanning method for a three-dimensional object according to claim 1, characterized in that, The preset interval is centered at the connection point, and the first preset distance is 1mm.

3. The contour scanning method for a three-dimensional object according to claim 1, characterized in that, After step S4 is performed, the contour scanning method for the three-dimensional object further includes: Select all lower surface contour lines, and for each lower surface contour line, move it parallel to its vertical direction in its slice plane and outwards a second preset distance away from the physical object to be printed to form an offset contour line. The offset contour line is scanned according to the first printing parameters.

4. The contour scanning method for a three-dimensional object according to claim 3, characterized in that, The second preset distance is half the difference between the width of the weld channel on the lower surface contour line and the width of the weld channel on the non-lower surface contour line.

5. The contour scanning method for a three-dimensional object according to claim 1, characterized in that, Both the first and second printing parameters include laser line energy density.

6. The contour scanning method for a three-dimensional object according to claim 5, characterized in that, The laser line energy density of the first printing parameter is less than that of the laser line energy density of the second printing parameter.

7. A contour scanning device for a three-dimensional object, characterized in that, The device includes a memory and a processor, the memory storing a computer program, characterized in that the processor executes the computer program to implement the steps of the contour scanning method for a three-dimensional object according to any one of claims 1 to 6.

8. An additive manufacturing apparatus, characterized in that, Includes the contour scanning device for a three-dimensional object as described in claim 7.

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