A powder laying type multi-laser additive and subtractive composite manufacturing method

Abstract

The application discloses a powder laying type multi-laser additive and subtractive composite manufacturing method, which comprises the following steps: forming a part shape contour on powder by using a forming laser; performing in-situ scanning on the part shape contour by using an ultrafast laser; according to a pre-tested subtractive thickness h, controlling the overall lifting of a substrate by h, and lifting the position where the part shape is not cut to the effective focal length range of the ultrafast laser; after one or more times of scanning on the current layer by using the ultrafast laser, the bottom lifting mechanism of the forming bin drives the substrate to be lifted by h again, and the part shape contour is subtracted by using the ultrafast laser again, and the above steps are repeated until the total height h of the substrate is greater than the additive height H t , and the subtractive process is ended; the bottom lifting mechanism of the forming bin drives the substrate to be lowered by h again n +H, the powder scraper lays the metal powder with the thickness of H on the substrate, and the additive process of the next layer is performed until the whole part printing process is ended. The application achieves the purpose of the multi-laser additive and subtractive composite manufacturing for compensating the height.

Description

TECHNICAL FIELD

[0001] The present application relates to a 3D printing method, in particular to a powder laying type multi-laser additive and subtractive composite manufacturing method. BACKGROUND

[0002] As a common process of metal additive manufacturing, selective laser melting (SLM) can realize near-net forming of complex structure parts by fusing metal powder layers with infrared laser (wavelength is usually 1064nm) layer by layer.

[0003] Compared with traditional mechanical processing, one of the shortcomings in the process of metal additive manufacturing is that the surface roughness of the part is high. Due to the characteristics of layer-by-layer printing in the additive process, the edges of layers will appear step effect, especially when printing inclined surface, the surface will inevitably appear the phenomenon of pyramid surface layer-by-layer step, which makes the part need to remove these steps by polishing after printing, and then the surface roughness of the part can meet the use requirements.

[0004] However, for parts with complex internal cavity structure, it is difficult to insert the grinding tool into the internal cavity from the outside after printing due to the large and complex internal cavity, so it is difficult to grind or polish the internal structure, and the method of abrasive flow is also not applicable. At present, the more common additive and subtractive method is to use the combination of laser energy deposition (DED) and machining center to realize additive and subtractive at the same time in the additive process, but this method has the disadvantages of complex control algorithm. In addition, in the multi-laser additive and subtractive method, the effective focal depth of the forming laser used for additive and the ultrafast laser used for subtractive is not consistent, so it is easy to appear the phenomenon that the single layer thickness of additive cannot be completely cut through by subtractive. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a multi-laser additive and subtractive composite manufacturing method for compensating the height, aiming at the problem of inconsistent effective focal depth of different types of lasers in the process of multi-laser additive and subtractive forming in the prior art.

[0006] To solve the above technical problems, the present application adopts the following technical solutions.

[0007] A powder laying type multi-laser additive and subtractive composite manufacturing method comprises the following steps: step S1, laying a metal powder with a thickness of H on a substrate by a powder scraper of a metal selective laser melting printing device; step S2, melting a part shape contour on the powder by a forming laser; step S3, in-situ scanning the part shape contour by a ultrafast laser; step S4, according to a pre-tested subtractive thickness h, controlling a forming bin bottom lifting mechanism of the metal selective laser melting printing device to drive the substrate to be lifted as a whole by h, so that the positions of the part shape contour which are not cut in the step S3 are lifted into the effective focal length range of the ultrafast laser; step S5, after one or more scans of the current layer by the ultrafast laser, the forming bin bottom lifting mechanism drives the substrate to be lifted as a whole again by h, and the part shape contour is subtracted by the ultrafast laser again, and the step S5 is repeatedly executed until the total height h t of the substrate is greater than the additive height H, and the subtractive process is ended, wherein h t =h n *n, n is the number of times of lifting; step S6, the forming bin bottom lifting mechanism drives the substrate to be lowered by a height of h n +H again, the powder scraper lays the metal powder with a thickness of H on the substrate, and the additive process of the next layer is performed; the steps S1 to S6 are repeatedly executed until the whole part printing process is ended.

[0008] Preferably, in the step S1, the metal selective laser melting printing device comprises an inert gas protection printing space, and the substrate is located in the inert gas protection printing space.

[0009] Preferably, in the step S1, the metal powder can be a non-metal powder or a multi-metal mixed powder.

[0010] Preferably, in the step S2, the part shape contour comprises an inner contour and an outer contour of the part.

[0011] Preferably, in the step S1, the powder laying thickness H is 20 microns to 180 microns.

[0012] Preferably, the ultrafast laser is a femtosecond or picosecond laser.

[0013] In the powder laying type multi-laser additive and subtractive composite manufacturing method disclosed in the present application, in the inert gas protection printing space, a powder laying device uniformly lays the powder on the substrate, after the metal powder forms a thin layer, one or more forming laser optical modules focus the light beams according to the preset track, instantaneously heat the powder to above the melting point, after completing the single-layer sintering, the substrate is lowered by a layer thickness, the cycle of powder laying, scanning and melting is repeated, and the layers are stacked until the printing of the entity is completed. When the above printing program is set, the printing layer thickness is H, the total height H t=H*n, the printing thickness H is the powder layer thickness during printing. In the above multi-laser-based additive and subtractive manufacturing process, the additive process is the same as the traditional SLM principle, the difference is that after completing a layer of printing each time, one or more ultrafast laser optical modules are enabled to scan the edge of the printed shape to realize subtractive machining, the purpose is to reduce the step effect between layers, thereby reducing the surface roughness of the part, and at the same time solving the problem of inconsistent effective focal length of different types of lasers in the prior art, achieving the purpose of multi-laser additive and subtractive composite manufacturing to compensate for the height. BRIEF DESCRIPTION OF DRAWINGS

[0014] Figure 1 Structure schematic diagram of metal selective laser melting printing equipment;

[0015] Figure 2 Structure schematic diagram of part layering in the forming laser printing process;

[0016] Figure 3 Schematic diagram of part scanning position after one-time scanning of ultrafast laser;

[0017] Figure 4 Schematic diagram of part scanning position after re-scanning of ultrafast laser;

[0018] Figure 5 Schematic diagram of part scanning position after n-time scanning of ultrafast laser;

[0019] Figure 6 Flow chart of multi-scanning process of ultrafast laser;

[0020] Figure 7 Flow chart of powder-based multi-laser additive and subtractive composite manufacturing method of the application. DETAILED DESCRIPTION

[0021] The application will be described in more detail below with reference to the drawings and examples.

[0022] Referring to Figure 3 , wherein H is the single-layer printing thickness of the forming laser, and h is the effective removal height of the ultrafast laser;

[0023] Referring to Figure 4 , h1 is the effective removal height of the ultrafast laser after completing each layer of additive;

[0024] Referring to Figure 5 , indicates that the lifting platform is finally moved up by h n , so that the ultrafast laser completes the subtraction of the layer;

[0025] Referring to Figure 6 , the scanning process is shown, and the states of the three stages are shown from left to right:

[0026] In the first figure, after each layer of additive is completed, the height h1 is effectively removed using the ultrafast laser;

[0027] In the second figure, the lifting platform is then moved up by h1 to enable the ultrafast laser to continue to effectively continue to remove the surface downward;

[0028] In the third figure, the lifting platform is finally moved up by h n to enable the ultrafast laser to complete the subtractive process of the printing layer, and then the lifting platform is lowered to h n +H to perform the next layer of additive printing.

[0029] A powder laying type multi-laser additive and subtractive composite manufacturing method is disclosed, which combines Figures 1 to 7 as shown, and includes the following steps:

[0030] Step S1, using the powder scraper of the metal selective laser melting printing device to lay a metal powder with a thickness of H on the substrate;

[0031] Step S2, using a forming laser to melt out a part shape contour on the powder;

[0032] Step S3, using an ultrafast laser to scan the part shape contour in situ;

[0033] Step S4, according to the pre-tested subtractive thickness h, controlling the forming bin bottom lifting mechanism of the metal selective laser melting printing device to drive the substrate to be raised by h, so that the positions of the part shape contour that are not cut in step S3 are raised to the effective focal length range of the ultrafast laser;

[0034] Step S5, after one or more scans of the current layer using the ultrafast laser, the forming bin bottom lifting mechanism drives the substrate to be raised by h again, and the ultrafast laser is used to perform subtractive on the part shape contour again, and step S5 is repeated until the total height h t of the substrate is greater than the additive height H, and the subtractive process ends, wherein h t =H n *n, n is the number of times of raising;

[0035] Step S6, the forming bin bottom lifting mechanism drives the substrate to be lowered by h n +H again, and the powder scraper lays a metal powder with a thickness of H on the substrate to perform the next layer of additive process;

[0036] Steps S1 to S6 are repeated until the entire part printing process is completed.

[0037] In the above method, within an inert gas-protected printing space, a powder-laying device evenly spreads powder onto the substrate. After the metal powder forms a thin layer, one or more forming laser optical modules focus the beam according to a preset trajectory, instantly heating the powder above its melting point. After single-layer sintering is completed, the substrate is lowered by one layer thickness, and the cycle of powder laying, scanning, and melting is repeated, layer by layer, until the solid is printed. In the above printing program setting, the printing layer thickness is H, and the total height of the part is H. t =H*n, where n = 1, 2, 3, 4…, and the printing thickness H is the powder layer thickness during printing. In the above multi-laser additive-subtractive manufacturing process, the additive process is the same as the traditional SLM principle. The difference is that after each layer is printed, one or more ultrafast laser optical modules are used to scan the edges of the printed shape to achieve subtractive processing. The purpose is to reduce the step effect between layers, thereby reducing the surface roughness of the part. It also solves the problem of inconsistent effective focal lengths of different types of lasers in the existing multi-laser additive-subtractive forming process, achieving the goal of multi-laser additive-subtractive composite manufacturing with height compensation.

[0038] Since the structure of parts made by additive or subtractive materials is generally quite complex, this invention uses a rectangle to represent the printing layer as an example for illustration in order to facilitate the explanation of the technical principles.

[0039] In this embodiment, when multiple lasers and supporting optical modules such as galvanometers and field lenses are installed on the additive and subtractive manufacturing equipment, the melting depth of the forming laser is sometimes greater than the subtractive thickness of the ultrafast laser. Therefore, direct in-situ subtraction cannot completely cut through the printed layer, which means it is difficult to effectively reduce the surface roughness of the parts.

[0040] In actual processing, it is generally necessary to test the parameters of the ultrafast laser and find the optimal subtractive thickness h, while here we assume that the powder spreading thickness set in the additive process is H.

[0041] As the core step of this embodiment, when the additive thickness H is greater than the subtractive thickness h, the printing contour can be subtracted layer by layer by printing one or more layers first, and then raising the bottom lifting mechanism of the forming chamber layer by layer according to the subtractive height h. After the subtractive is completed, the forming chamber substrate is lowered to the additive position.

[0042] In step S1 of this embodiment, the metal selective laser melting printing equipment includes an inert gas protected printing space, and the substrate is located within the inert gas protected printing space. Further, in step S1, the metal powder can be a non-metallic powder or a multi-metal mixed powder.

[0043] In a preferred embodiment, in step S2, the part shape profile includes the inner profile and the outer profile of the part.

[0044] The powder thickness H in the step S1 is 20 microns to 180 microns. The ultrafast laser is a femtosecond or picosecond laser.

[0045] In combination Figures 2 to 6 As shown, after the powder scraper spreads a layer of metal powder (or non-metal powder such as ceramic powder, polymer material powder, or multi-metal mixed powder, etc.) with a thickness of H, the forming laser melts out the shape of the part on the powder. Then the ultrafast laser is used to directly scan the inner contour or inner and outer contours on the layer in situ to achieve the subtractive effect, and the number of contour scans can be one or more times as needed;

[0046] Furthermore, according to the appropriate subtractive thickness h tested before, the part is raised by h by the lifting mechanism at the bottom of the forming bin, so that the position that cannot be cut by the previous part is raised to the effective focal length of the ultrafast laser, that is, the next layer is efficiently removed; the mechanism raises the part position by h again, and the ultrafast laser is used to subtract the contour again, until the total height h t =h n *n (n is the number of times of raising) is greater than the additive height H, the subtractive process ends or after multiple times, or after multiple times, the lifting mechanism raises the part position by h again, and the ultrafast laser is used to subtract the contour again, until the total height h t =h n *n (n is the number of times of raising) is greater than the additive height H, the subtractive process ends or after multiple times, or after multiple times, the lifting mechanism raises the part position by h again, and the ultrafast laser is used to subtract the contour again, until the total height h t =h n *n (n is the number of times of raising) is greater than the additive height H, the subtractive process ends or after multiple times, or after multiple times, the lifting mechanism raises the part position by h again, and the ultrafast laser is used to subtract the contour again, until the total height h

[0047] After the ultrafast laser scans the layer one or more times, the lifting mechanism raises the part position by h again, and the ultrafast laser is used to subtract the contour again, until the total height h t =h n *n (n is the number of times of raising) is greater than the additive height H, the subtractive process ends or after multiple times, or after multiple times, the lifting mechanism raises the part position by h again, and the ultrafast laser is used to subtract the contour again, until the total height h n +h is lowered by h, and the powder with a height of H is spread on the surface of the part by the powder spreading knife, preparing for the next layer of additive process, and the cycle continues until the entire part printing process is completed.

[0048] In the above additive and subtractive process, when H and h are not integer multiples, the total height h tShould be greater than H. That is, assuming the powder thickness is 50 microns, the effective subtractive depth is 20 microns, after printing a layer, the lifting mechanism will rise 3 times, that is, 20 microns*3 layers=60 microns>50 microns powder thickness, after which the subtractive step of the layer is ended, the lifting mechanism is lowered by 60+50=110 microns, and the powder of the next layer is waited.

[0049] After the component is printed based on the above method, it is taken out of the 3D printing device.

[0050] Compared with the prior art, the present application is realized based on the multi-laser additive and subtractive manufacturing process, the additive process is the same as the traditional SLM principle, the difference is that after finishing a layer of printing each time, one or more ultrafast laser optical modules are started to scan the edge of the printed shape to realize subtractive machining, the purpose is to reduce the step effect between layers, thereby reducing the surface roughness of the part.

[0051] The above is only the preferred embodiment of the present application and is not used to limit the present application, any modification, equivalent replacement or improvement within the technical scope of the present application should be included in the scope of protection of the present application.

Claims

1. A powder laying multi-laser additive and subtractive composite manufacturing method, characterized in that, The method comprises the following steps: S1, using a powder scraper of a metal selective laser melting printing device to lay a metal powder with a thickness of H on a substrate; S2, using a forming laser to melt a part shape profile on the powder; S3, using an ultrafast laser to scan the part shape profile in situ; S4, according to a pre-tested subtractive thickness h, controlling a forming bin bottom lifting mechanism of the metal selective laser melting printing device to drive the substrate to be raised by h, so that the positions of the part shape profile which are not cut in the step S3 are raised to the effective focal length range of the ultrafast laser; Step S5, after scanning one or more times on the current layer by using the ultrafast laser, the forming bin bottom lifting mechanism drives the substrate to be raised again as a whole by h, and the part shape profile is subtracted again by using the ultrafast laser, and the "after scanning one or more times on the current layer by using the ultrafast laser, the forming bin bottom lifting mechanism drives the substrate to be raised again as a whole by h, and the part shape profile is subtracted again by using the ultrafast laser" is repeatedly executed until the total height h of the substrate is raised n The subtractive machining is ended after the additive height H is greater than h, wherein h n =h*n, n is the number of times of rising; Step S6, the bottom of the forming bin is driven to lower the substrate by a height h n +H, the powder scraper spreads the metal powder on the substrate with a thickness of H, and the next layer of the additive process is performed; Steps S1 to S6 are repeatedly executed until the entire part printing process is completed; In the step S1, the metal selective laser melting printing device comprises an inert gas protection printing space, and the substrate is located in the inert gas protection printing space; In the step S1, the metal powder is a multi-metal mixed powder; In the step S2, the part shape profile comprises an inner profile and an outer profile of the part; In the step S1, the powder laying thickness H is 20 microns to 180 microns.

2. The powder-laying multi-laser additive-subtractive hybrid manufacturing method of claim 1, wherein, The ultrafast laser is a femtosecond or picosecond laser.

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