Continuous 3D Printing Method and 3D Printing Device Based on Morphological Deformation Algorithm

Abstract

The present application relates to a continuous 3D printing method and a 3D printing device based on a morphological deformation algorithm. By performing morphological deformation on the original model, the parts with insufficient exposure are found, and a deformed three-dimensional model is generated based on the supplemented parts. Then, a sliced image is generated based on the deformed three-dimensional model for printing, which can meet the exposure requirements of each point on the original model. Since the supplemented partial areas have insufficient exposure, they can be removed after printing, thereby obtaining a three-dimensional printed model with a complete shape and accurate dimensions.

Description

Technical Field

[0001] The present invention belongs to the technical field of photocuring 3D printing, and particularly relates to a continuous 3D printing method and 3D printing device based on a morphological deformation algorithm. Background Art

[0002] In the field of photocuring, according to the light source system of photocuring forming, the photocuring 3D printing technology is divided into laser point light source (SLA) and surface light source digital light projection (DLP). The process of photocuring is to use ultraviolet light to irradiate and cure the photosensitive resin layer by layer. The energy received by the irradiated photosensitive resin exceeds the critical value E c After that, a polymerization reaction will occur and it will be cured.

[0003] The continuous liquid surface printing technology is to make the irradiated and cured surface not adhere to the release film, for example, by establishing a non-curing area, so that the resin is always cured and formed above the non-curing area, thereby realizing continuous, smooth and rapid forming. Compared with the traditional layer-by-layer printing method (such as DLP), the continuous liquid surface 3D printing technology can realize the rapid printing of complex objects. In theory, when the material is irradiated by ultraviolet light, if the total energy is greater than the critical exposure amount within T seconds, curing will occur. Therefore, in continuous printing, due to the continuous upward movement of the printing platform, the light illumination of the current printing plane will spread upward along the already printed part. Therefore, as long as there is light below, the formed part above will continue to be exposed. The exposure energy of each formed surface is the result of integrating the light intensity over a period of time. Therefore, the continuous printing is faster than the traditional DLP technology with layer-by-layer exposure. However, when printing some models, due to the lack of a continuous formed surface below the current printing plane, as Figure 1 shown at the lower surface C2 in the middle and lower part, it will cause insufficient exposure of the lower surface of the three-dimensional model, resulting in the photosensitive resin material not being cured. The printed three-dimensional model will have uncured gaps at the positions where the lower surface is insufficiently exposed, affecting the forming effect. Summary of the Invention

[0004] The purpose of this application is to overcome the problem of insufficient exposure of some lower surfaces in the prior art, and provide a continuous 3D printing method and 3D printing device based on a morphological deformation algorithm.

[0005] In order to achieve the above-mentioned invention purpose, the present invention adopts the following technical solutions: A continuous 3D printing method based on a morphological deformation algorithm, comprising the following steps:

[0006] S1), obtaining the original model file M0 to be 3D printed;

[0007] S2), scan any point on the said model file along the optical axis direction, with a scanning depth of s. A number of points within the scanning depth generate a first model M1, where s is the attenuation distance of the projection beam in the photosensitive resin;

[0008] S3), translate any point on the said original model file along the direction opposite to the optical axis by a distance s, where s = vT. A number of points within the translation area generate a second model M2, v is the printing speed, and T is the exposure time for the photosensitive resin to reach the critical exposure amount when printing at the speed v;

[0009] S4), take the intersection of the first model M1 and the second model M2: M1 ∩ M2, and obtain the area that needs to be supplemented with exposure for the original model as: M2 - (M1 ∩ M2), and establish the deformed solid model M = M0 ∪ [M2 - (M2 ∩ M1)];

[0010] S5), generate a slice image based on the deformed solid model M and perform printing.

[0011] In an embodiment of the present application: 0.5 ≤ s ≤ 4 mm.

[0012] In an embodiment of the present application, T satisfies the formula:

[0013] Wherein,

[0014] E c represents the critical exposure amount of the photosensitive resin;

[0015] v represents the printing speed;

[0016] τ represents the transmittance of ultraviolet light in the photosensitive resin;

[0017] Δd represents the unit distance;

[0018] P represents the irradiation light intensity.

[0019] Another technical solution of the present application is to provide a continuous 3D printing device, including a material tank for containing photosensitive resin, a printing platform that is vertically movable above the said material tank along the Z-axis, a projection device, a memory, and a processor. The processor is configured to execute the foregoing printing method.

[0020] Compared with the prior art, the present invention has the following beneficial effects: By deforming the morphology of the original model file, generating a supplemented solid model, and then generating a slice image based on the deformed solid model for printing, the exposure requirements of each point on the original model can be met. Since some areas are insufficiently exposed, they can be removed after printing, thereby obtaining a three-dimensional printed model with a complete morphology and precise dimensions. Description of the Drawings

[0021] Attached Figure 1 shows a schematic structural view of a cylindrical three-dimensional model in a cross-section perpendicular to the printing platform;

[0022] Attached Figure 2 shows Figure 1 a schematic view of the printing process of the three-dimensional model in

[0023] Attached Figure 3 shows a schematic view of the original model M0 in an embodiment of the present application;

[0024] Attached Figure 4 shows Figure 3 a schematic view of the three-dimensional model shown in

[0025] Attached Figure 5 shows Figure 3 a schematic view of the three-dimensional model shown in

[0026] Attached Figure 6 shows Figure 3 the relationship among the original model M0, the first model M1, and the second model M2 of the three-dimensional model shown in

[0027] Attached Figure 7 shows a schematic view of the three-dimensional model M after deformation;

[0028] Attached Figure 8 shows the decay relationship of light intensity in the photosensitive resin;

[0029] Attached Figure 9 is a schematic structural view of a 3D printing device in an embodiment of the present application;

[0030] Attached Figure 10 is Figure 9 a schematic diagram of the 3D printing device in

[0031] Wherein: 101, optical machine; 102, material tank; 103, photosensitive resin; 104, Z-axis lifting mechanism; 105, printing platform; 106, three-dimensional model; 200, release film. Detailed implementation manners

[0032] To describe in detail the technical content, structural features, achieved objectives, and effects of the invention, the following will be described in detail in conjunction with embodiments and with reference to the accompanying drawings.

[0033] As mentioned in the background art above, during continuous 3D printing, when there is no longer an exposure surface below the exposure surface, there is a defect phenomenon caused by insufficient exposure time on the current exposure surface. The following takes Figure 1Taking the three-dimensional model 106 shown as an example, its defective parts and causes are introduced in detail. This three-dimensional model is a cylindrical thin-walled part. The upper surface C1 is represented by a solid line, and the lower surface C2 is represented by a dashed line. When forming this three-dimensional model on a continuous 3D printing device, the printing platform 105 moves slowly and continuously upward from below at a speed v. The photosensitive resin below the printing platform is cured under ultraviolet light irradiation, and the three-dimensional model is gradually formed as the printing platform rises. The optical axis direction described in this specification is Figure 1 the direction from bottom to top in Figure 1 , which is also the direction in which the printing platform rises, that is, the Z-axis direction.

[0034] Suppose a material will be cured when the exposure exceeds the critical exposure amount at a printing speed of v = 4 mm / min. This means that after any part leaves the exposure plane, there are at least some solid regions below it to ensure that ultraviolet light can continue to conduct to this region so that the cumulative exposure amount of this region meets the curing requirements. For example, Figure 1 the upper surface C1 of the three-dimensional model in Figure 1 and Figure 2 points A and B on Figure 2 have continuous solid parts for exposure below them. Therefore, in addition to being exposed in the photocuring window, they can also continue to receive ultraviolet light irradiation during the subsequent forming of the lower surface. When the ultraviolet light received by these points exceeds the critical exposure amount E c , this point can be cured. For the lower surface C2 of the three-dimensional model and Figure 2 points C and D in Figure 2 , at the next moment, the exposure will disappear immediately because there is no solid part below. In this way, the exposure time of this part will be much less than T, and the material cannot be cured.

[0035] Refer to Figure 2 . On the printing plane α, the projection beam irradiates points A, B, C, and D. Due to the light transmissivity of the material, the light will penetrate upward along the material and gradually weaken, forming a light column f. Therefore, the light of each exposure point on the printing plane α is perpendicular upward, so that the photosensitive material within a distance s above is continuously exposed. s is the attenuation distance of the projection beam in the photosensitive resin.

[0036] This application provides a continuous 3D printing method based on a morphological deformation algorithm, which can find the parts with insufficient light in the three-dimensional model and deform and supplement the original model file of the three-dimensional model so that the supplemented model can irradiate the area below the parts with insufficient light, thereby obtaining a three-dimensional model with a completely cured lower surface.

[0037] Specifically, the continuous 3D printing method based on the morphological deformation algorithm of the present invention includes the following steps:

[0038] S1), Obtain the original model file M0 to be printed. This original model file is a set containing a series of three-dimensional coordinate data. Refer toFigure 3 , for the sake of simplicity in this application, a cylindrical three-dimensional model is taken as an example, and a cross-section perpendicular to the printing plane of this three-dimensional model is used for explanation;

[0039] S2), scan any point on the original model file M0 along the optical axis direction, and the scanning depth is s, where s is the attenuation distance of the projection beam in the photosensitive resin; several points within this scanning depth generate the first model M1, as Figure 4 shown, where s is the attenuation distance of the projection beam in the photosensitive resin, and this first model M1 represents the model of the light attenuation region formed after any point on the original model is exposed and penetrates upward;

[0040] S3), as shown in Figure 5 , translate any point on the original model file M0 downward by a distance s, where s = vT, and several points within this translation region generate the second model M2, where v is the printing speed and T is the exposure time for the photosensitive resin to reach the critical exposure amount at the printing speed v. That is to say, for any point on the original model file to be fully cured, it should be irradiated for at least T seconds after being exposed by the printing plane. This requires continuous exposure within a range of vT below this point. Therefore, this second model M2 represents the model of the irradiation range required when any point on the original model satisfies the curing conditions;

[0041] S4), as shown in Figure 6 , take the intersection M1∩M2 of the above first model M1 and second model M2. The exposure amount received by any point within this intersection range can satisfy the full curing conditions of the photosensitive resin, while the points on the second model M2 outside this intersection cannot satisfy the full curing conditions. Therefore, additional exposure needs to be performed on M0, and the additional exposure area is the area that cannot be fully cured: M2-(M2∩M1). Based on the original model and the above additional exposure area, a deformed three-dimensional model M is established, M = M0∪[M2-(M2∩M1)];

[0042] S5), generate a slice image based on this deformed three-dimensional model M, configure corresponding projection parameters and printing data, etc., and perform printing.

[0043] In the deformed model, in addition to irradiating the original model, the additional exposure area also needs to be irradiated, which enables any point in the original model to satisfy the critical exposure amount for full curing. Only by adding this part of the additional exposure area can it be ensured that the original model above can be formed. For the points within the additional exposure area, their exposure amount is necessarily lower than the critical exposure amount. Therefore, when the three-dimensional model is printed and formed, the materials within these additional exposure areas will not be fully cured and can be removed in subsequent processes, ultimately obtaining a printed part with precise dimensions, intact appearance, and no distortion.

[0044] See Figure 8 As shown, the decay relationship of ultraviolet light in the photosensitive resin satisfies:

[0045] where d is the shortest straight-line distance from any point in the photosensitive resin to the projection image; τ is the light transmittance per unit thickness of the photosensitive resin (also written as tau), that is, for every Δd unit distance, the ratio of the transmitted light flux to the incident light flux is τ, and 0 < τ < 1. The more light dispersant added to the photosensitive resin, the smaller τ. Therefore, the diffused light intensity P received by the photosensitive resin at point d d is related to the light transmittance of the material and the distance, and decreases exponentially.

[0046] Figure 8 The Pτ in 0 represents the light intensity at the pixel point in the light curing window, and Pτ 1 represents the light intensity at the pixel point one unit thickness away from the light curing window, and so on, Pτ 4 represents the light intensity at the pixel point 4 unit thicknesses away from the light curing window. According to Formula 1, the distance s at which the light intensity above the light curing window decays to 0 can be calculated, and based on this, the first model M1 is established.

[0047] According to the above Formula 1, when the printing speed is v and the exposure time is t, the distance of a point on the printed part from the exposure plane is d = vt. Therefore, at any time t, the light intensity near the point with an initial distance of h from the exposure area:

[0048]

[0049] When the total exposure amount E of a certain point of the photosensitive resin material accumulates to a certain extent, curing will occur. If p th is integrated with respect to time t in the time period [0, T], then its total exposure amount E:

[0050]

[0051] where v is the printing speed; T is the time required to reach the critical exposure amount.

[0052] When T is large enough and satisfies E >= E c curing can be achieved, that is:

[0053]

[0054] It is derived that:

[0055] where the photosensitive resin material determines τ and E c, the 3D printing device determines the light intensity P and the printing speed v. Therefore, T can be calculated by Equation 4.

[0056] Through the exposure time T, the scanning distance s along the optical axis upward can be calculated:

[0057]

[0058] The printing speed v is related to the initial forming strength, light sensitivity (content of photoinitiator), light transmittance and viscosity of the photosensitive resin material. It can be a fixed value or a dynamically adjustable value set according to other parameters. For example, in this embodiment, v can be set to 10 mm / min for harder materials and v can be set to 5 mm / min for softer materials.

[0059] See Figure 9 - 10 As shown, the present application also discloses a continuous 3D printing device for implementing the above printing method, which includes a frame, a material tank 102 for containing photosensitive resin, a printing platform 105 arranged above the material tank and capable of lifting along the Z axis, a projection device, a memory and a processor. A horizontal workbench extending along the x-y plane is provided in the middle of the frame, and the material tank 102 is fixedly arranged on the horizontal workbench. The projection device in this embodiment is an optical engine 101. The optical engine 101 is fixedly installed below the horizontal workbench, the printing platform 105 is arranged above the horizontal workbench and can be lifted, and a Z-axis lifting mechanism 104 is arranged at the rear of the frame. The printing platform 105 realizes vertical upward or downward movement through the Z-axis lifting mechanism 104. A demolding element such as a demolding film is arranged at the bottom of the material tank 102.

[0060] When the continuous 3D printing device is working, the printing program is started, the printing platform descends above the non-curing area, the projection light emitted upward by the optical engine 101 passes through the demolding film 200, and cures the photosensitive resin 103 above the demolding film 200 to form a three-dimensional model 106. The upper part of the three-dimensional model 106 adheres to the printing platform 105 and moves upward with the printing platform 105. New photosensitive resin is continuously cured, making the three-dimensional model seem to be "pulled out" from the material tank. The lower part of the three-dimensional model 106 is always immersed in the photosensitive resin. There is an interface between the photosensitive resin 103 and the demolding film 200. The photosensitive resin stops the polymerization reaction at this interface, so that there is always liquid photosensitive resin between the three-dimensional model 106 and the demolding film 200, reducing the adhesion force between the three-dimensional model and the demolding film, and thus realizing continuous high-speed 3D printing.

[0061] The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements. The scope of protection required by the present invention is defined by the appended claims, the specification and their equivalents.

Claims

1. A continuous 3D printing method based on a morphological deformation algorithm, characterized in that, It includes the following steps: S1), obtaining the original model file M0 to be 3D printed; S2), scanning any point on the model file along the optical axis direction, with a scanning depth of s. A number of points within this scanning depth generate the first model M1, where s = vT, v is the printing speed, and T is the exposure time for the photosensitive resin to reach the critical exposure amount when printing at the speed v; S3), translating any point on the original model file by a distance s in the direction opposite to the optical axis. A number of points within this translation area generate the second model M2; S4), taking the intersection of the first model M1 and the second model M2: M1 ∩ M2, obtaining the area that needs to be supplemented with exposure for the original model as: M2 - (M1 ∩ M2), and establishing the deformed solid model M = M0 ∪ [M2 - (M2 ∩ M1)]; S5), generating a sliced image based on this deformed solid model M and performing printing.

2. The printing method according to claim 1, wherein: 0.5 ≤ s ≤ 4 mm.

3. The printing method according to claim 2, wherein T satisfies the formula: Among them, Ec represents the critical exposure amount of the photosensitive resin; v represents the printing speed; τ represents the transmittance of ultraviolet light in the photosensitive resin; Δd represents the unit distance; P represents the irradiation light intensity.

4. A continuous 3D printing device, including a material tank for containing the photosensitive resin, a printing platform that is vertically movable above the material tank along the Z axis, a projection device, a memory, and a processor, It is characterized in that The processor is configured to execute the printing method described in any one of claims 1 - 3.

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