3D printing method capable of printing while spreading powder

Abstract

The invention discloses a 3D (three-dimensional) printing method capable of spreading powder while printing, which belongs to the technical field of 3D printing and comprises the following steps: S1, by taking a powder spreading scraper as a reference, arranging areas with a plurality of widths in the front and back of the moving direction of the powder spreading scraper as laser sintering closing areas, defining the printing working surface at the front part of the laser sintering closing area as an upper-layer pattern printing area, and defining the printing working surface at the rear part of the laser sintering closing area as a lower-layer pattern printing area; and S2, a powder spreading scraper moves at a constant speed to spread powder, the laser sintering closing area moves along with the powder spreading scraper, the width of the upper-layer pattern printing area and the width of the lower-layer pattern printing area change along with the powder spreading scraper, and meanwhile, laser is adopted for conducting laser sintering printing on the upper-layer pattern printing area and the lower-layer pattern printing area. The time of laser printing image interruption caused by powder laying can be shortened, and the printing speed is increased.

Description

Technical Field

[0001] The invention belongs to the technical field of 3D printing, and in particular relates to a 3D printing method for printing while spreading powder. 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 profile of the part, sintering the current layer of powder, and the sintered layer automatically bonds with the formed part below. When a layer of cross section is sintered, the workbench drops one 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.

[0004] The above printing method has the following problems: during the printing process, after each layer is printed, a scraper is required to spread powder. The printing action stops during the powder spreading period, and the next layer is printed after the powder spreading is completed. In traditional single-laser printing equipment, the printing time of each layer of pattern is much longer than the powder spreading time, so the time wasted for powder spreading has limited impact. As 3D printing equipment begins to enter the era of multi-laser printing, the number of lasers is as many as dozens or even hundreds. At this time, the time for laser printing a single-pass pattern is greatly shortened, and the proportion of powder spreading time in the entire working time suddenly increases. Therefore, how to reduce the powder spreading time becomes of great significance. At present, the conventional method of reducing the powder spreading time is to use two-way powder spreading, which allows the powder spreading scraper to spread powder once each single-pass movement, which can shorten the powder spreading time by nearly half. Even so, the time spent on powder spreading in printing a part is still as high as tens of hours, so a solution that can reduce the powder spreading time is of great significance to saving printing time. Summary of the invention

[0005] The purpose of the present invention is to provide a 3D printing method for printing while spreading powder, so as to solve the problems existing in the existing 3D printing method, such as the high proportion of powder spreading time in the whole working time and the long printing time.

[0006] In order to achieve the above object, the technical solution of the present invention is as follows: The present invention relates to a 3D printing method for printing while spreading powder, which comprises the following steps: S1. Taking the powder spreading scraper as a reference, set a certain width of area in front and behind the moving direction of the scraper as the laser sintering closing area, define the printing working surface in front of the laser sintering closing area as the upper pattern printing area, and define the printing working surface in the rear of the laser sintering closing area as the lower pattern printing area; S2. The powder spreading scraper moves at a constant speed to spread the powder, and the laser sintering closed area moves accordingly, and the width of the upper pattern printing area and the lower pattern printing area changes accordingly. At the same time, a laser is used to perform laser sintering printing on the upper pattern printing area and the lower pattern printing area respectively.

[0007] Preferably, during the S2 laser sintering printing, a wind field is used to take away the flying powder, and the wind field includes an air outlet module and an air suction module arranged in parallel and at intervals, and both the air outlet module and the air suction module adopt array-type multi-air outlets.

[0008] Preferably, the powder spreading scraper is a streamlined structure along the wind direction, with the windward side being an arc and the leeward side being a pointed cone, thereby reducing the turbulent wind field area caused by the powder spreading scraper.

[0009] Preferably, the distance between the windward surface of the powder spreading scraper and the air outlet of the air outlet module is less than 1 mm, so that the wind resistance of the air outlet is very large, and then the wind is no longer blown out from the air outlet, thereby no longer affecting the wind field of other air outlets.

[0010] Preferably, the S2 laser sintering printing adopts a multi-laser printing method, and the laser printing head is an M*N array. During the printing process, compensation is made for the printing width of the laser printing head of each row. The printing width calculation formula is: , Wherein, Di' is the width of the printing area allocated to the i-th row of print heads after compensation, D is the printing area width, N is the number of rows of laser print heads, Di is the width of the printing area allocated to the i-th row of print heads before compensation, V is the moving speed of the powder scraper, and s is the time required for the i-th row of print heads to print the printing area with a width of Di.

[0011] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects: 1. The 3D printing method of printing while spreading powder involved in the present invention divides the printing work surface into a laser sintering closed area, an upper pattern printing area and a lower pattern printing area based on a powder spreading scraper. When the powder spreading scraper moves at a uniform speed to spread powder, a laser is used to perform laser sintering printing on the upper pattern printing area and the lower pattern printing area respectively, thereby reducing the time of laser printing image interruption caused by powder spreading and increasing the printing speed.

[0012] 2. The powder-spreading scraper of the 3D printing method of the present invention for spreading powder and printing is a streamlined structure along the wind field direction. The windward side of the powder scraper is an arc shape, and the leeward side is a pointed cone shape, which reduces the turbulent wind field area and thus reduces the width of the laser sintering closed area. At the same time, the distance between the windward side of the powder scraper and the air outlet of the air outlet module is less than 1 mm, so that the wind resistance of the air outlet is very large, and the wind is no longer blown out from the air outlet, thereby no longer affecting the wind field of other air outlets, i.e., avoiding the wind field at other positions from changing from laminar flow to turbulent flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG1 is a schematic diagram of the printing process of the 3D printing method of printing while spreading powder according to the present invention; Figure 2 is a schematic diagram of the wind farm structure; Figure 3 It is a schematic diagram of the structure of the powder spreading scraper; Figure 4 Schematic diagram of wind direction in front of the fan to reduce the distance between the powder spreading scraper and the air outlet module; Figure 5 Schematic diagram of the wind field direction to reduce the distance between the powder spreading scraper and the air outlet module. DETAILED DESCRIPTION

[0014] 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.

[0015] Refer to the attached Figure 1 As shown, the 3D printing method for printing while spreading powder according to the present invention comprises the following steps: S1. Taking the powder spreading scraper as a reference, areas of several widths are set in front and behind its moving direction as laser sintering closing areas. The width of the laser sintering closing area is related to the shape structure and size of the powder spreading mechanism, the position of the powder spreading scraper and the wind field, etc. It can be set artificially according to different 3D printing equipment and experience. The printing working surface in front of the laser sintering closing area is defined as the upper pattern printing area, and the printing working surface in the rear of the laser sintering closing area is defined as the lower pattern printing area.

[0016] The principle of setting the laser sintering closed area is that during the laser printing process, the flying powder in the printing working chamber will seriously affect the printing quality. Therefore, the laser sintering printing process often requires the use of a wind field to take away the flying powder. The structure of the wind field is shown in the attached figure. Figure 2 As shown, it includes an air outlet module and an air suction module arranged in parallel and at intervals, and both the air outlet module and the air suction module adopt an array-type multi-air outlet; the powder spreading scraper will cause the wind field to change from laminar flow to turbulent flow, such as Figure 4As shown, therefore, it is necessary to leave a section of wind field turbulence zone in front and behind the powder spreading scraper to ensure that the laser sintering area is within the laminar flow range; and, when the powder spreading scraper is spreading powder, not only does it need to reserve a wind field turbulence zone in front of the movement direction, but it is also necessary to reserve a metal powder area according to the amount of powder spread each time. When in a one-way powder spreading mechanism, it is not necessary to reserve a metal powder area when the scraper returns.

[0017] Of course, the smaller the width of the laser sintering closed area, the better. The width of the laser sintering closed area can be reduced by the following two methods: (1) Changing the structural shape of the powder spreading scraper: The powder spreading scraper has a streamlined structure along the wind direction, and can adopt but is not limited to a symmetrical airfoil, such as Figure 3 As shown, under this structure, the windward side of the powder spreading scraper is arc-shaped, and the leeward side is pointed cone-shaped, thereby reducing the turbulent wind field area caused by the powder spreading scraper.

[0018] (2) Change the distance between the powder spreading scraper and the air outlet module: The distance between the windward surface of the powder spreading scraper and the air outlet of the air outlet module is less than 1 mm, so that when spreading powder, the end face of the powder spreading scraper will block the air outlet at the corresponding position, making the air outlet have a large wind resistance, and then the wind will no longer be blown out from the air outlet, and will no longer affect the wind field of other air outlets, thus avoiding the change of the wind field in the pattern printing area from laminar flow to turbulent flow, such as Figure 5 shown.

[0019] S2. The powder spreading scraper moves at a constant speed to spread the powder, and the laser sintering closed area moves accordingly, and the width of the upper pattern printing area and the lower pattern printing area changes accordingly. At the same time, the laser scanning systems corresponding to the upper pattern printing area and the lower pattern printing area are turned on, and the laser is used to perform laser sintering printing on the upper pattern printing area and the lower pattern printing area respectively.

[0020] Assuming that the width of the printing work surface along the powder spreading direction is D, the width of the laser printing closed area caused by the powder spreading component in the above figure is H, and the moving speed of the scraper during powder spreading is V, the expression of the laser printing interruption time t during the powder spreading process is: .

[0021] In contrast, the traditional solution of not printing during the powder spreading period is adopted. The expression of the laser interruption time t' during the powder spreading period is: .

[0022] Taking a device with a printing working area of ​​500*500mm as an example, when the width of the printing laser shutdown area caused by the scraper is 100mm, the time taken for laser printing interruption due to powder spreading in this solution is 1 / 6 of that in the traditional solution, which can greatly shorten the equivalent powder spreading time.

[0023] The above-mentioned laser sintering printing can adopt a multi-laser printing method. When the multi-laser printing method is adopted, since the laser needs to be turned off when the powder spreading scraper passes, the data allocation scheme of the multi-laser print head also needs to be optimized to ensure that the printing data volume or printing time of each laser head is basically the same, so as to achieve the best printing efficiency. For example, if the laser print head is an M*N array, and the number of laser print head rows along the powder spreading scanning direction is N, the print data segmentation has the following rules: (1) When the entire printing area is divided into equal parts according to the area, that is, N rows of laser print heads divide the printing area with a width of D, the width of the printing area responsible for each row of laser print heads is D / N. In this solution, there is no need to change the printing area range of the laser heads, and the width of the printing area of ​​each row of laser heads is still D / N. Here, the printing area width refers to the sum of the widths of the upper pattern printing area and the lower pattern printing area.

[0024] (2) When the entire format is divided into print formats according to the amount of print data, that is, the width of the printing area responsible for each row of laser print heads is different. In this solution, it is necessary to compensate for the printing width of each row of laser print heads. Under this solution, the calculation formula for the width of the area printed by the laser print head in the i-th row is:

[0025] , Wherein, Di' is the width of the printing area allocated to the i-th row of print heads after compensation, D is the printing area width, N is the number of rows of laser print heads, Di is the width of the printing area allocated to the i-th row of print heads before compensation, V is the moving speed of the powder scraper, and s is the time required for the i-th row of print heads to print the printing area with a width of Di.

[0026] 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 3D printing method for printing while spreading powder, characterized in that: It includes the following steps: S1. Taking the powder spreading scraper as a reference, set a certain width of area in front and behind the moving direction of the scraper as the laser sintering closing area, define the printing working surface in front of the laser sintering closing area as the upper pattern printing area, and define the printing working surface in the rear of the laser sintering closing area as the lower pattern printing area; S2. The powder spreading scraper moves at a constant speed to spread the powder, and the laser sintering closed area moves accordingly, and the width of the upper pattern printing area and the lower pattern printing area changes accordingly. At the same time, a laser is used to perform laser sintering printing on the upper pattern printing area and the lower pattern printing area respectively.

2. The 3D printing method of claim 1, wherein: During the S2 laser sintering printing, a wind field is used to take away the flying powder. The wind field includes an air outlet module and an air suction module arranged in parallel and at intervals. Both the air outlet module and the air suction module adopt array-type multi-air outlets.

3. The 3D printing method of claim 2, wherein: The powder spreading scraper is a streamlined structure along the wind direction, with a windward side in an arc shape and a leeward side in a pointed cone shape.

4. The 3D printing method of claim 2, wherein: The distance between the windward surface of the powder spreading scraper and the air outlet of the air outlet module is less than 1 mm.

5. The 3D printing method of claim 1, wherein: The S2 laser sintering printing adopts a multi-laser printing method, and the laser print head is an M*N array. During the printing process, the printing width of the laser print head of each row is compensated. The printing width calculation formula is: , Wherein, Di' is the width of the printing area allocated to the i-th row of print heads after compensation, D is the printing area width, N is the number of rows of laser print heads, Di is the width of the printing area allocated to the i-th row of print heads before compensation, V is the moving speed of the powder scraper, and s is the time required for the i-th row of print heads to print the printing area with a width of Di.

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