Patent Publication Number: US-2022234281-A1

Title: Multi-material photocuring 3d printer and 3d printing method

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims priority to Chinese Patent Application No. 202110099819.8, filed on Jan. 25, 2021, the content of all of which is incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The present disclosure relates to the technical field of 3D printing, more particularly, to a multi-material photocuring 3D printer and a 3D printing method. 
     BACKGROUND 
     Currently, in a field of photo-curing 3D printing, there are a plurality of graphic methods mainly including: Digital Light Procession (DLP), Liquid Crystal Display (LCD), Stereo Lithography Apparatus (SLA), and more. 
     A conventional photocuring 3D printing method is able to print with only one material in a single printing, and unable to achieve a switched printing between multiple materials, or a combination with a soft material and a hard material, as well as unable to achieve a multi-material photocuring 3D printing. 
     At present, although there have been a plurality of studies on a multi-material DLP 3D printing, most are achieved by adding an amount of resin slots to achieve a multi-material printing, however such a method may cause a serious pollution to a printed piece, thus still having a certain distance away from a target of a high precision and a multi-material. Therefore, a technical core of the multi-material photocuring 3D printing is cleaning a residual liquid when switching a material, so as to ensure that there is no pollution introduced. Therefore, a switching method of adding resin slots only, cannot really solve a problem. 
     In order to avoid from having a pollution induced during switching the resin slots, generally a cleaning slot and a drying slot will be added, wherein the cleaning slot has alcohol or other organic solvents contained, being able to clean and remove the resin on a surface of the printed piece, and the drying slot dries and removes a residual cleaning liquid on the surface of the printed piece, followed by printing with a second material. Although such a cleaning and drying method is able to remove most residual liquid, it still has a plurality of drawbacks: first, a plurality of repeated cleaning may cause damaging a printed structure, making a dimensional accuracy of the printed piece decrease. In addition, adding a cleaning process cannot be truly pollution-free, while there are still some residual organic solvent on the surface of the printed piece, causing inducing a new pollution repeatedly, thus resulting in a decrease in a resolution of the printed piece. 
     Therefore, the current technology needs to be improved and developed. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     According to the above described defects in the prior art, a purpose of the present disclosure is providing a multi-material photocuring 3D printer and a 3D printing method, to solve a problem in the prior art that the accuracy and the resolution of the printed piece decrease due to cleaning and removing the resin on the surfaces of the printed pieces in an existing multi-material photocuring 3D printer. 
     A technical solution of the present disclosure to solve the technical problems is as follows: 
     a multi-material photocuring 3D printer, comprising: 
     a frame; 
     a printing platform, arranged on the frame; 
     a lifting device, arranged on the printing platform; 
     a rotary motor, arranged on the lifting device; 
     a printing plate, arranged on the rotary motor; wherein a bottom surface of the printing plate is a printing plane; 
     a plurality of resin slots, arranged on the frame and located below the printing plate; 
     an optical engine, arranged on the frame and located below the printing plate. 
     A further configuration of the present disclosure, wherein the multi-material photocuring 3D printer comprises: 
     a locking device, arranged on the lifting device; 
     the rotary motor is arranged on the locking device; 
     wherein the printing plate restores to an initial absolute position through the locking device. 
     A further configuration of the present disclosure, wherein the locking device comprises: 
     a bracket; 
     a first cylinder, arranged on the bracket; 
     a clamping assembly, arranged on the first cylinder; 
     a clamped piece, arranged on the rotary motor and located at a middle position of the clamping assembly; 
     wherein, the rotary motor is a double axis high-speed DC motor, the printing plate connects to a bottom end of the rotary motor through a flange coupling, and the clamped piece is arranged on a top end of the rotary motor. 
     A further configuration of the present disclosure, wherein the clamping assembly further comprises: 
     two clamping blocks, the clamping blocks are arranged oppositely on the first cylinder; 
     a clamping permanent magnet, arranged in the clamping block; 
     the clamped piece comprising: 
     a clamped block, arranged above the rotary motor; 
     a rotary permanent magnet, arranged in the clamped block. 
     A further configuration of the present disclosure, wherein the multi-material photocuring 3D printer further comprises: 
     two resin collection devices, the resin collection devices are arranged oppositely on the frame; wherein, the resin collection device comprises: 
     a first connecting plate, arranged on the frame; 
     a second cylinder, arranged on the first connecting plate; 
     a second connecting plate, arranged on the second cylinder; 
     a third cylinder, arranged on the second connecting plate; 
     a first collection slot, arranged on the third cylinder; 
     wherein, an extension direction of the third cylinder is perpendicular to an extension direction of the second cylinder. 
     A further configuration of the present disclosure, wherein the multi-material photocuring 3D printer further comprises: 
     two post-curing devices, the post-curing devices are arranged oppositely and located on a side of the resin collection device; wherein, the post-curing device comprises: 
     a third connecting plate, arranged on the frame; 
     a fourth cylinder, arranged on the third connecting plate; 
     a fourth connecting plate, arranged on the fourth cylinder; 
     a fifth cylinder, arranged on the fourth connecting plate; 
     a post-curing slot, arranged on the fifth cylinder; 
     a UV curing light-emitting diode, arranged on the post-curing slot; 
     wherein, an extension direction of the fifth cylinder is perpendicular to an extension direction of the fourth cylinder. 
     A further configuration of the present disclosure, wherein the multi-material photocuring 3D printer further comprises: 
     a resin slot switching device, arranged on the frame; 
     the resin slots are arranged on the resin slot switching device; 
     wherein, the resin slot switching device comprises:
         a driving assembly, arranged on the frame;       

     a leveling plate, arranged on the driving assembly; 
     a base plate, arranged on the leveling plate; wherein the resin slots are arranged on the base plate at an interval; 
     a plurality of first leveling assemblies, arranged on the leveling plate and connected to the base plate; wherein, the first leveling assembly comprises: 
     a fifth connecting plate, connected to the base plate; 
     a first bolt, inserted through the fifth connecting plate; 
     a first spring, sleeved on the first bolt; 
     a first screw block, arranged on the leveling plate, and threadedly connected with the first bolt. 
     A further configuration of the present disclosure, wherein the printing platform comprises: 
     a plurality of second adjusting assemblies, the plurality of second adjusting assemblies are arranged on the bracket, and connected with the printing platform; wherein, the second adjusting assembly comprises: 
     a second bolt, penetrating through the printing platform; 
     a second spring, sleeved on the second bolt; 
     a second screw block, arranged on the frame and threadedly connected with the second bolt. 
     A further configuration of the present disclosure, wherein the lifting device comprises: 
     a first mounting dock, arranged on the printing platform; 
     a first driving motor, arranged on the first mounting dock and connected with the bracket; 
     the driving assembly comprises: 
     a second mounting dock, arranged on the frame; 
     a second driving motor, arranged on the second mounting dock and connected with the leveling plate. 
     According to a same inventive concept, the present disclosure further provides a printing method for the multi-material photocuring 3D printer, applied to the multi-material photocuring 3D printer stated above, wherein the method comprises: 
     adjusting a distance from the printing plane to the bottom surface of the resin slot, to make a focal point of the optical engine align with the bottom surface of the resin slot; wherein the resin slot has a resin material placed in, and the material in each of the resin slot is corresponding to a material set in a 3D model of the printed piece; 
     controlling the lifting device to move the printing plane to a distance having a thickness of one slice layer from the bottom surface of the resin slot; 
     controlling the optical engine project a projection pattern corresponding to the current layer, to complete printing the current layer; 
     wherein, if there is any other material existing in the current layer, or a material of a next layer is inconsistent with the material of the current layer, then controlling the rotary motor to spin, so as to remove any residual resin liquid on the printed piece and the printing plane by a method of spinning and centrifugation. 
     A further configuration of the present disclosure, the method further comprises: 
     collecting the residual resin liquid after removing the residual resin liquid on the printing plane, when it is needed to switch to another material for printing. 
     A further configuration of the present disclosure, the method further comprises: 
     performing a post-curing process on a designated layer. 
     The present disclosure provides a multi-material photocuring 3D printer and a 3D printing method, wherein the multi-material photocuring 3D printer comprises: a frame; a printing platform, arranged on the frame; a lifting device, arranged on the printing platform; a rotary motor, arranged on the lifting device; a printing plate, arranged on the rotary motor; wherein a bottom surface of the printing plate is a printing plane; a plurality of resin slots, arranged on the frame and located below the printing plate; an optical engine, arranged on the frame and located below the printing plate. The present disclosure connects the printing plate with the rotary motor, after finishing printing with one material, it is possible to remove the residual liquid resin on the printed piece and the printing plane by a method of high-speed centrifugation, to avoid any contaminations to the printed piece, thereby ensuring the printed piece in multi-material having a high precision and a high resolution. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order to describe the embodiments of the present disclosure or the technical solutions in the prior art more clearly, a plurality of drawings used in the description of the embodiments or the prior art will be briefly introduced hereafter. Obviously, the drawings in the following description are some embodiments of the present disclosure only, those of ordinary skills in the present art, without any creative work, may obtain other drawings based on the structure shown in these drawings. 
         FIG. 1  illustrates a schematic diagram on an overall structure of the multi-material photocuring 3D printer in the present disclosure. 
         FIG. 2  illustrates a schematic diagram on a structure of the printing platform and the second adjusting assembly in the present disclosure. 
         FIG. 3  illustrates a schematic diagram on a structure of the rotary motor and the locking device in the present disclosure. 
         FIG. 4  illustrates a schematic diagram on a structure of the clamping assembly in the present disclosure. 
         FIG. 5  illustrates a schematic diagram on a structure of the clamped piece in the present disclosure. 
         FIG. 6  illustrates a schematic diagram on a structure of the resin collection device and a structure of the post-curing device in the present disclosure. 
         FIG. 7  illustrates a schematic diagram on a structure of the resin slot and a structure of the resin slot switching device in the present disclosure. 
         FIG. 8  illustrates a schematic diagram on a structure of the optical engine and a structure of a third mounting dock in the present disclosure. 
         FIG. 9  illustrates a schematic flow chart on a printing method of the multi-material photocuring 3D printer in the present disclosure. 
     
    
    
     Numerals in the figures:  1 , frame;  2 , printing platform;  3 , lifting device;  31 , first mounting dock;  32 , first driving motor;  4 , rotary motor;  41 , flange coupling;  5 , printing plate;  6 , resin slot;  7 , optical engine;  71 , third mounting dock;  8 , locking device;  81 , bracket;  82 , first cylinder;  83 , clamping assembly;  831 , clamping block;  832 , clamping permanent magnet;  84 , clamped piece;  841 , clamped block;  842 , rotary permanent magnet;  9 , resin collection device;  91 , first connecting plate;  92 , second cylinder;  93 , second connecting plate;  94 , third cylinder;  95 , first collection slot;  10 , post-curing device;  101 , third connecting plate;  102 , fourth cylinder;  103 , fourth connecting plate;  104 , fifth cylinder;  105 , post-curing slot;  106 , ultraviolet curing light-emitting diode;  11 , resin slot switching device;  111 , driving assembly;  1111 , second mounting dock;  1112 , second driving motor;  112 , leveling plate;  113 , base plate;  114 , first leveling assembly;  1141 , fifth connecting plate;  1142 , first bolt;  1143 , first spring;  1144 , first screw block;  12 , second adjusting assembly;  121 , second bolt;  122 , second spring;  123 , second screw block. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The present disclosure provides a multi-material photocuring 3D printer and a 3D printing method, being able to print multi-material onto a same unit, in order to make the purpose, technical solution and the advantages of the present disclosure clearer and more explicit, further detailed descriptions of the present disclosure are stated here, referencing to the attached drawings and some embodiments of the present disclosure. It should be understood that the detailed embodiments of the disclosure described here are used to explain the present disclosure only, instead of limiting the present disclosure. 
     The implementations and the scope of the patent application, wherein unless specific limitations on articles are applied in the text, “a” and “the” may generally refer to a singular or a plural. 
     In addition, if there are descriptions related to “first”, “second”, and more in the embodiments of the present disclosure, the descriptions of “first”, “second”, and more are used for descriptive purposes only, instead of being understood as instructions or implications to its relative importance or as implicitly indications to a number of a technical feature indicated. Therefore, the features defined with “first” and “second” may explicitly or implicitly include at least one of the features. In addition, a plurality of technical solutions between various embodiments may be combined with each other, but they must be based on what can be achieved by an ordinary skilled in the art. When the combination of technical solutions is contradictory or impossible to achieve, it should be considered that such a combination of the technical solutions neither exists, nor falls within the scope of protection required by the present disclosure. 
     After a plurality of researches and studies, it has been found that, a technical core of a multi-material photocuring 3D printing technology lies in removing a residual liquid when switching a material. An existing method of removing the residual liquid is cleaning a cleaning slot with alcohol or a plurality of other organic solvents, performing a drying operation before printing with a second material. Such a method has a plurality of defects existing, first, a plurality of repeated cleaning may cause damaging a printed structure, and lowering a dimensional accuracy. Secondly, a material removal process thereof is complicated, time-costing and material-consuming, having a low efficiency. Finally, adding a cleaning process cannot be truly pollution-free, and there are still some residual organic solvents left on a surface of a printed piece, which, instead, causes a repeated introduction of a new pollution. In addition, there is another way to remove the residual liquids, which is removing the residual liquids on the surface of the printed piece directly by air blowing. Such a method cannot well remove the residual liquids on the surface of the printed piece either. Thus it can be seen that, the methods of removing the residual liquids when switching the materials, as mentioned above, will both reduce a printing accuracy and a resolution of the printed piece. 
     According to the technical problems mentioned above, the present disclosure provides a multi-material photocuring 3D printer and a printing method thereof. Wherein the 3D printer comprises: a frame; a printing platform, arranged on the frame; a lifting device, arranged on the printing platform; a rotary motor, arranged on the lifting device; a printing plate, arranged on the rotary motor; wherein a bottom surface of the printing plate is a printing plane; a plurality of resin slots, arranged on the frame and located below the printing plate; an optical engine, arranged on the frame and located below the printing plate. The present disclosure, wherein, by connecting the printing plate with the rotary motor, after finishing printing with one material, a residual liquid resin on the printed piece and the printing plane can be removed by a method of high-speed centrifugation, thereby prevents the printed piece from being contaminated and ensures a high precision and a high resolution of the printed piece with multi-material, having a great significance for an integrated molding of a flexible device and a multi-material soft driver. 
     Referencing to  FIGS. 1 to 8  together, the present disclosure provides a preferred embodiment of the multi-material photocuring 3D printer. 
     Shown as  FIG. 1 , the present disclosure provides a multi-material photocuring 3D printer, the multi-material photocuring 3D printer comprises: a frame  1 , a printing platform  2 , a lifting device  3 , a rotary motor  4 , a printing plate  5 , a plurality of resin slots  6 , and an optical engine  7 . Wherein the printing platform  2  is arranged on the frame  1 ; the lifting device  3  is arranged on the printing platform  2 ; the rotary motor  4  is arranged on the lifting device  3 ; the printing plate  5  is arranged on the rotary motor  4 ; wherein a bottom surface of the printing plate  5  is a printing plane; there are a plurality of resin slots  6  arranged, and arranged in intervals on the frame  1  while located below the printing plate  5 ; the optical engine  7  is arranged on the frame  1  and located below the printing plate  5 . 
     Specifically, the rotary motor  4  is a high-speed rotary motor, the printing plate  5  connects to the lifting device  3  through the rotary motor  4 , while the lifting device  3  is able to drive the printing plate  5  to move along a Z-axis direction, wherein the Z-axis direction refers to a direction of a Z-axis in a three-dimensional coordinate system. In addition, the resin slot  6  has a resin material stored inside, and a material in each of the resin slot  6  is corresponding to a material set by a 3D model of the printed piece. 
     When printing, first it is needed to adjust a position of each hardware and clarify each material parameter, specifically, adjusting the printing platform  2  and the resin slot  6  to a horizontal state, making a bottom surface of each resin slot  6  parallel to a printing plane of the printing plate  5 , before adjusting a distance from the printing plane to the bottom surface of the resin slot  6 , to ensure that a focal point of the optical engine  7  (an optical projection system) is aligned with the bottom surface of the resin slot  6 . 
     Secondly, performing a slicing process to the 3D model of the printed piece, and dividing each part of a different material into a picture corresponding to the material, wherein the pictures may be divided into two cases: one layer containing one material and one layer containing multiple materials. After confirming that the material in each resin slot  6  is corresponding to the material set by the 3D model, a plurality of printing parameters will be set. After the printing parameters are set, controlling the printing plane by the lifting device  3  move to a distance having a one-layer thickness from the bottom surface of the resin slot  6 , then the optical engine  7  projects a projection pattern corresponding to a current layer. In an embodiment, when printing a first layer, the printing plane is adjusted to a distance having a thickness of the first layer from the bottom surface of the resin slot  6 . When the printing plane rises, the resin in the resin slot  6  will fill in a gap between the resin slot  6  and the printing plane, while the optical engine  7  projects a pattern of the first layer in the 3D model and irradiates on a liquid resin, before performing a photocuring and molding, that completes printing the first layer. After finishing printing the first layer, the lifting device  3  lifts the printing plate  5  up for a certain distance (for example, lifting up a distance of 4 to 5 layers) before moving to a height of a next layer, to ensure that the resin can fill completely a thickness of the new layer. When the printing plate  5  is adjusted to a position of a second layer and the resin has filled a thickness of the second layer, the optical engine  7  projects a shape pattern of the second layer onto the resin, before finishing printing the second layer. By a plurality of repeated operations, it is able to print the model in a stacked form. 
     Wherein, if there is only one material in the current layer, and a material in a next layer is consistent with the material in the current layer, then controlling the lifting device  3  to raise the printing plane for a certain distance before moving to the position of the next layer. For example, if the materials of the first layer and the second layer are the same, then it is possible to print the next layer directly. 
     If the current layer has another material exist, or the material of the next layer is inconsistent with that of the current layer, then the rotary motor  4  is controlled to spin, in order to remove the residue resin liquid on the printed piece and the printing plane through a method of spinning and centrifugation. In an embodiment, the first layer has another material existing, or the material of the second layer to print is inconsistent with that of the first layer, then it is needed to clean the printed piece and the printing plane before performing printing. That is, when switching the material for printing is needed, it shall clean a previous liquid resin before printing with another resin material, specifically, after finishing printing with one resin material, the printing plate  5  is unplugged, since the printing plate  5  is connecting to the rotary motor  4 , thus under a high-speed spinning of the rotary motor  4 , it is possible to clean out the liquid resin on the printed piece and the printing plane in a method of spinning and centrifugation. 
     It can be seen that, the present disclosure connects the printing plate  5  with the rotary motor  4 , after finishing printing with one material, it is possible to remove the residual liquid resin on the printed piece and the printing plane by a method of a high-speed centrifugation, without using alcohol or any organic solvents. It is possible to avoid any residual organic solvents on the printed piece, thereby avoiding a repeated introduction of a new pollution, ensuring a resolution requirement of the printed piece, and also it is possible to avoid damages to a structure of the printed piece due to repeated cleaning, ensuring an accuracy requirement of the printed piece. In addition, the present disclosure removes the residual liquid resin in a method of spinning and centrifugation, having a simple process, also no organic solvent is required, which not only improves a cleaning efficiency, but also saves materials, thereby saving costs. 
     It should be noted that, when configuring a plurality of printing parameters, according to a viscosity of a printing liquid, a spinning speed of the printing platform  2  is configured to ensure that the material is able to be effectively removed. In addition, it is possible to summarize, by a plurality of experiments, the printing parameters required for each material, as well as the spinning speed and the time required to clean a residual liquid by spinning and centrifugation, and according to a property of the material, determining whether a post-curing is required. If necessary, a light intensity and a spacer layer shall be adjusted appropriately. 
     Referencing to  FIG. 1  and  FIG. 2 , in a further implementation of an embodiment, the multi-material photocuring 3D printer further comprises: a locking device  8 , the locking device  8  is arranged on the lifting device  3 ; the rotary motor  4  is arranged on the locking device  8 . Wherein, the printing plate  5  restores to an initial absolute position by the locking device  8 . 
     Specifically, a locking device  8  is further arranged between the rotary motor  4  and the lifting device  3 . After the rotary motor  4  drives the printing plate  5  and completes cleaning the residual liquid resin, the rotary motor  4  stops spinning. And the rotary motor  4  can be restored to the initial absolute position by the locking device  8 . Since the printing plate  5  connects to the rotary motor  4 , the printing plate  5  may also restore to an initial absolute position state, the initial absolute position of the rotary motor  4  is locked, and the printing plane is indirectly locked as well. Therefore, after the printing plane spins at a high speed to remove the residual resin, it is possible to always maintain the initial absolute position, thereby ensuring that the printed piece will not appear a misaligned state. 
     Referencing to  FIG. 2  and  FIG. 3 , in a further implementation of an embodiment, the locking device  8  comprises: a bracket  81 , a first cylinder  82 , a clamping assembly  83 , and a clamped piece  84 . Wherein, the first cylinder  82  is arranged on the bracket  81 ; the clamping assembly  83  is arranged on the first cylinder  82 ; the clamped piece  84  is arranged on the rotary motor  4  and located at a middle position of the clamping assembly  83 . Wherein, the rotary motor  4  is a double axis high-speed DC motor, the printing plate  5  connects to a bottom end of the rotary motor  4  through a flange coupling  41 , and the clamped piece  84  is arranged on a top end of the rotary motor  4 . 
     Specifically, the bracket  81  is arranged on the lifting device  3 , the clamping assembly  83  is arranged on the first cylinder  82 , and the clamped piece  84  is arranged on an upper end of the rotary motor  4  and located at a middle position of the clamping assembly  83 , while the printing plate  5  is arranged at a lower end of the rotary motor  4 . When the rotary motor  4  is in a spinning state, the clamping assembly  83  is also in an open state under an action of the first cylinder  82 , while the clamped piece  84  can spin freely. Similarly, the printing plane can also spin freely. Under a high-speed driving of the rotary motor  4 , the clamped piece  84  spins synchronously with the printing plane, to realize removing the residual resin. When the rotary motor  4  is in a locked state, the rotary motor  4  stops rotating, while the clamping assembly  83  is in a closed state under an action of the first cylinder  82 , the clamping assembly  83  clamps the clamped piece  84 , so as to restore the clamped piece  84  to an original absolute position thereof. At this time, since the clamped piece  84  and the printing plane both connect to the rotary motor  4 , thus the printing plane will also restore to an initial absolute position state. 
     Referencing to  FIG. 3  and  FIG. 4 , in a further implementation of an embodiment, the clamping assembly  83  comprises: a clamping block  831  and a clamping permanent magnet  832 , wherein two of the clamping block  831  are arranged, and arranged oppositely on the first cylinder  82 , and the clamping permanent magnet  832  is arranged in the clamping block  831 . In a plurality of embodiments, the first cylinder  82  is a double-slider cylinder, and the clamping blocks  831  are arranged on both sides of the first cylinder  82  respectively. 
     Furthermore, referencing to  FIG. 5 , the clamped piece  84  comprises: a clamped block  841  and a rotary permanent magnet  842 , wherein the clamped block  841  is arranged above the rotary motor  4 , and the rotary permanent magnet  842  is arranged in the clamped block  841 . 
     Specifically, the clamping assembly  83  is a magnetic clamping assembly  83 . The clamping permanent magnet  832  and the rotary permanent magnet  842  can attract each other, after the rotary motor  4  is powered off, under an action of a magnetic force, a relative balance will be maintained, and such a balance state is the initial absolute position of the clamped piece  84 . Thus, after the rotary motor  4  stops spinning, the clamping assembly  83  is clamped tightly by the first cylinder  82 , so as to clamp the clamped piece  84 , and a lock of the initial absolute position of the clamped piece  84  will be achieved. It can be understood that, after the initial position of the clamped piece  84  is locked, the printing plate  5  will be indirectly locked. Therefore, after the printing plane of the printing plate  5  spinning at a high speed and removing the residual resin, it is possible to always maintain the initial absolute position, thus ensuring that the printed piece will not appear a misaligned state between layers. 
     It should be noted that, in some embodiments, it is also possible to use a high-precision closed-loop servo motor to control the printing plane be able to restore to the initial absolute position. However, a cost of adopting a high-precision closed-loop servo motor is relatively high, which is much higher than the locking device  8  provided in the present disclosure. 
     Referencing to  FIG. 1  and  FIG. 6 , in a further implementation of an embodiment, the multi-material photocuring 3D printer further comprises: two resin collection devices  9 , the resin collection devices  9  are arranged oppositely on the frame  1 , when the rotary motor  4  removes the residual liquid on the printed piece and the printing plane, they are used to collect the residual liquid after cleaning. 
     In a plurality of embodiments, the resin collection device  9  comprises: a first connecting plate  91 , a second cylinder  92 , a second connecting plate  93 , a third cylinder  94 , and a first collection slot  95 . Wherein the first connecting plate  91  is arranged on the frame  1 , the second cylinder  92  is arranged on the first connecting plate  91 , the second connecting plate  93  is arranged on the second cylinder  92 , the third cylinder  94  is arranged on the second connecting plate  93 , the first collection slot  95  is arranged on the third cylinder  94 , wherein an extension direction of the third cylinder  94  is perpendicular to an extension direction of the second cylinder  92 . 
     Specifically, the second cylinder  92  and the third cylinder  94  are combined into a two-stage cylinder, wherein the second cylinder  92  is a rail cylinder, the third cylinder  94  is an ejection cylinder, the second cylinder  92  is mounted on the bracket  81  through the first connecting plate  91 , the third cylinder  94  connects to the second cylinder  92  through the second connecting plate  93 , and the first collection slot  95  is fixed on an end of the third cylinder  94 . When the rotary motor  4  needs to clear the residual liquid on the printed piece and the printing plane, the second cylinder  92  extends, and the third cylinder  94  moves a certain distance under an action of the second cylinder  92 , followed by the third cylinder  94  also extending, and that makes it possible to push the first collection slot  95  out for a certain distance, that is, the first collection slot  95  is in an ejected state at this time, when the printing plate  5  locates in the first collection slot  95 . Thus, under an action of the rotary motor  4 , the residual liquid removed from the printed piece and the printing plane due to the high-speed spinning and centrifugation will flow into the first collection slot  95 . 
     In some embodiments, a bottom surface of the first collection slot  95  has a plurality of first through holes arranged (not shown in the FIGs.), and the first through holes connect to a catheter (not shown in the FIGs.), the residual liquid collected in the first collection slot  95  may be drained through the catheter and collected in a collection box. 
     Continue referencing to  FIG. 1  and  FIG. 6 , in a further implementation of an embodiment, the multi-material photocuring 3D printer further comprises: two post-curing devices  10 , the post-curing devices  10  are arranged oppositely and located on a side of the resin collection device  9 . When a printing material is relatively soft, since a strength after curing is also relatively low, in order to prevent a printed piece from being thrown out after multiple high-speed centrifugation, thus a post-curing device  10  is required to perform a post-curing process on a designed layer of a cured material, before performing printing a next layer. 
     In a plurality of embodiments, the post-curing device  10  comprises: a third connecting plate  101 , a fourth cylinder  102 , a fourth connecting plate  103 , a fifth cylinder  104 , a post-curing slot  105 , and an ultraviolet curing light-emitting diode  106 . Wherein, the third connecting plate  101  is arranged on the frame  1 , the fourth cylinder  102  is arranged on the third connecting plate  101 , the fourth connecting plate  103  is arranged on the fourth cylinder  102 , the fifth cylinder  104  is arranged on the fourth connecting plate  103 , the post-curing slot  105  is arranged on the fifth cylinder  104 , the ultraviolet curing light-emitting diode  106  is arranged on the post-curing slot  105 , wherein, an extension direction of the fifth cylinder  104  is perpendicular to an extension direction of the fourth cylinder  102 . 
     Specifically, the fourth cylinder  102  and the fifth cylinder  104  are combined into a two-stage cylinder, the fourth cylinder  102  is mounted on the bracket  81  through the third connecting plate  101 , and the fifth cylinder  104  connects to the fourth cylinder  102  through the fourth connecting plate  103 , and the post-curing slot  105  is installed at an end of the fifth cylinder  104 . After finishing printing one layer, the fourth cylinder  102  pushes out and pushes the fifth cylinder  104  out for a certain distance. Now the fifth cylinder  104  pushes out and pushes the post-curing slot  105  out. Now the printing plate  5  locates in the post-curing slot  105 , and the current layer is post-cured by the ultraviolet curing light-emitting diode  106  on the post-curing slot  105 , before performing a next layer print or a same layer print. The present disclosure, by adding the post-curing device  10 , is possible to achieve curing while printing, thereby ensuring that an entire printed piece is completely cross-linked and has a higher strength, even after multiple centrifugal spinning, the printed piece will not appear a phenomenon of being thrown out or broken. 
     It should be noted that, a DLP3D printing is a photocuring 3D printing method. A curing mechanism in printing is that an ultraviolet light makes a material in the resin generate a polymer cross-linked network, while a cross-linking is still incomplete when molding. Although it is molded, from a microscopic respect of view, it is not very dense, and it requires a post-curing process to make the polymer material inside fully crosslink. In such a way, will a modulus and a performance of the printed piece be optimal. In addition, a post-curing process of a traditional DLP 3D printing is taking the printed piece out and placing into an ultraviolet curing box for post-curing, after finishing printing the printed piece and cleaning the surface residual liquid with alcohol. The reason that the present disclosure adds a post-curing device is, when printing with some materials having a low modulus or softer, since a not fully cross-linked state is easy to be thrown off or broken by the high-speed centrifugation when a printing height is increasing. Thus a post-curing device is added, so when the printing height of the printed piece reaches a certain height, a cross-linking degree can be higher. Of course, this has another advantage, that is, the printed piece can be used directly after the printing is completed, without requiring a cleaning and curing, because this part of work has been completed during the printing process. 
     Referencing to  FIG. 1  and  FIG. 7 , in a further implementation of an embodiment, the multi-material photocuring 3D printer further comprises: a resin slot switching device  11 , arranged on the frame  1 , the resin slot  6  is arranged on the resin slot switching device  11 , through the resin slot switching device  11 , it is achieved switching each resin slot  6 , so as to print with different materials. 
     In some embodiments, the resin slot switching device  11  comprises: a driving assembly  111 , a leveling plate  112 , a base plate  113  and a first leveling assembly  114 . Wherein, the driving assembly  111  is arranged on the frame  1 , the leveling plate  112  is arranged on the driving assembly  111 , the base plate  113  is arranged on the leveling plate  112 , and the resin slots  6  are arranged on the base plate  113  at an interval, a plurality of the first leveling assembly  114  are arranged, and arranged on the leveling plate  112  while connected with the base plate  113 . In one implementation, the first leveling assembly  114  is arranged on four corners of the leveling plate  112 . 
     Specifically, the base plate  113  is a quartz glass base plate, and the base plate  113  is mounted on the leveling plate  112  and arranged in parallel with the leveling plate  112 , while the resin slots  6  are arranged on the base plate  113  at an interval. The first leveling assembly  114  can be floated and leveled. Before printing, the leveling plate  112  may be adjusted to a horizontal state through the first leveling assembly  114 , to ensure that the bottom surfaces of the plurality of resin slots  6  are on a same level, to ensure that the bottom surface of the resin slot  6  is parallel to the printing plane of the printing plate  5 . 
     Referencing to  FIG. 7 , in some embodiments, the first leveling assembly  114  comprises: a fifth connecting plate  1141 , a first bolt  1142 , a first spring  1143 , and a first screw block  1144 . Wherein the fifth connecting plate  1141  is connected to the base plate  113 , the first bolt  1142  is inserted through the fifth connecting plate  1141 , and the first spring  1143  is inserted through the first bolt  1142 , the first screw block  1144  is arranged on the leveling plate  112  and is threadedly connected with the first bolt  1142 . 
     Specifically, the base plate  113  and the leveling plate  112  are connected together by the fifth connecting plate  1141 , the first bolt  1142 , and the first screw block  1144 , by adjusting the first bolt  1142 , it is possible to achieve a horizontal adjustment to the base plate  113 , to ensure that the bottom surface of the resin slot  6  is parallel to the printing plane. Wherein, the first bolt  1142  has a first spring  1143  sleeved on, which is beneficial to control and adjust a strength of the first bolt  1142 , to facilitate adjusting the base plate  113  to a horizontal state. 
     Referencing to  FIG. 2 , in a further implementation of an embodiment, the printing platform  2  comprises: a plurality of second adjusting assemblies  12 , the plurality of second adjusting assemblies  12  are arranged on the bracket  81 , and connected with the printing platform  2 ; wherein, the second adjusting assembly  12  connects to four corners of the printing platform  2 , the first leveling assembly  114  can be floated and leveled, adjusting the printing platform  2  to a horizontal state through the second adjusting assembly  12 , to adjust the printing plane to a horizontal state. 
     In some embodiments, the second adjusting assembly  12  comprises: a second bolt  121 , a second spring  122  and a second screw block  123 . Wherein the second bolt  121  is penetrating through the printing platform  2 , the second spring  122  is sleeved on the second bolt  121 , the second screw block  123  is arranged on the frame  1  and threadedly connected with the second bolt  121 . 
     Specifically, the printing platform  2  connects to the bracket  81  through the second bolt  121  and the second screw block  123 , by adjusting the second bolt  121 , it is possible to achieve a horizontal adjustment of the printing platform  2 , thus being able to adjust the printing plane to a horizontal state. Wherein, the second bolt  121  has the second spring  122  sleeved on, which is beneficial to control and adjust a strength of the second bolt  121 , so as to adjust the printing platform  2  to the horizontal state. 
     Referencing to  FIG. 1  and  FIG. 2 , in a further implementation of an embodiment, the lifting device  3  comprises: a first mounting dock  31  and a first driving motor  32 , wherein the first mounting dock  31  is arranged on the printing platform  2 , the first driving motor  32  is arranged on the first mounting dock  31  and connected with the bracket  81 . By the first driving motor  32  driving the bracket  81  to move up and down, it is possible to achieve that the printing plate  5  moves up and down. Wherein the first driving motor  32  drives the printing plate  5  to move along a direction of a z-axis. 
     Referencing to  FIG. 7 , in a further implementation of an embodiment, the driving assembly  111  comprises: a second mounting dock  1111  and a second driving motor  1112 , wherein the second mounting dock  1111  is arranged on the frame  1 , the second driving motor  1112  is arranged on the second mounting dock  1111  and connected with the leveling plate  112 . By the second driving motor  1112 . driving the leveling plate  112  to move, so as to drive the resin slot  6  to move, thus switching the resin slot  6  is achieved. Wherein the second driving motor  1112  drives the resin slot  6  to move along a direction of a y-axis. The direction of the y-axis is the direction of y-axis in a 3D coordinate system. 
     Referencing to  FIG. 1  and  FIG. 8 , in some embodiments, the multi-material photocuring 3D printer further comprises a third mounting dock  71 , the third mounting dock  71  is arranged on the frame  1 , and the optical engine  7  is arranged on the third mounting dock  71 . 
     Referencing to  FIG. 9 , in some embodiments, the present disclosure further provides a printing method for the multi-material photocuring 3D printer, applied to the multi-material photocuring 3D printer described above, wherein the method comprises 
     S 1 , adjusting a distance from the printing plane to the bottom surface of the resin slot, and making a focal point of the optical engine align with the bottom surface of the resin slot; wherein the resin slot has a resin material placed in, and the material in each of the resin slots is corresponding to a material set in a 3D model of the printed piece. Details are described as the embodiments of the multi-material photocuring 3D printer, and no more repeating herein. 
     S 2 , controlling the lifting device to move the printing plane to a distance having a thickness of one slice layer from the bottom surface of the resin slot. Details are described as the embodiments of the multi-material photocuring 3D printer, and no more repeating herein. 
     S 3 , controlling the optical engine project a projection pattern corresponding to a current layer, to complete printing the current layer. Wherein, if there is any other material in the current layer, or a material of a next layer is inconsistent with the material of the current layer, then controlling the rotary motor to spin, applied to remove any residual resin liquid on the printed piece and the printing plane by a method of spinning and centrifugation. If there is only one material in the current layer, and a material in a next layer is consistent with the material in the current layer, then controlling the lifting device to raise the printing plane for a certain distance before moving to the position of the next layer. Details are described as the embodiments of the multi-material photocuring 3D printer, and no more repeating herein. 
     In some embodiments, the method further comprises: 
     S 4 , collecting the residual resin liquid after removing the residual resin liquid on the printing plane, when it is needed to switch to another material for printing. 
     Specifically, when the materials are inconsistent, that is, the current layer has other materials exist, or the material of the next layer is inconsistent with that of the current layer, then controlling the lifting device move the printing plane to a position slightly higher than the bottom surface of the first collection slot, and ejecting the first collection slot by the first cylinder and the third cylinder on both sides, to make the first collection slot wrap the printing plane, while the clamping assembly is in an open state, and the rotary motor drives the printing plate to spin according to a speed of removing the current printing material after spinning and centrifugation. The first collection slot collects the residual liquid. After removing the residual liquid, the clamping assembly locks the printing plate at the initial absolute position, retracting the first collection slot, and controls the printing plane move into the resin slot, to print the same layer or the next layer with another material. 
     S 5 , performing a post-curing process on a designated layer. 
     Specifically, in addition, when a printing height is high, a printing material modulus is low, or the material has a soft property, a high-speed centrifugation will cause the printed piece to be thrown off, thus it is necessary to set a position of the designated layer and perform a post-curing process. Wherein, after removing the residual liquid by rotating and centrifugation, the first collection slot is retracted, and the fourth cylinder and the fifth cylinder eject the post-curing slot, so the post-curing slot wraps the printing plane, and at a same time, an ultraviolet curing light-emitting diode is lit up, to perform a post-curing process onto the designed layer, wherein a blinking parameter of the ultraviolet curing light-emitting diode may be preset. After the post-curing is completed, the post-curing slot is retracted, and the printing plane is controlled to move into the resin slot to print a same layer or the next layer with another material. By post-curing a printed object, it is possible to improve a degree of cross-linking in the printed piece, preventing from falling off or deforming a structure in a later printing process. 
     The present disclosure has a plurality of following benefits: 
     1, by connecting the printing plate with the rotary motor, after finishing printing with one material, it is possible to remove the residual liquid resin on the printed piece and the printing plane by a method of a high-speed centrifugation, without using alcohol or any organic solvents, being able to avoid any residual organic solvents on the printed piece, thereby avoiding a repeated introduction of a new pollution, ensuring a resolution requirement of the printed piece, and also it is possible to avoid damages to a structure of the printed piece due to repeated cleaning, ensuring an accuracy requirement of the printed piece. In addition, the present disclosure removes the residual liquid resin in a method of spinning and centrifugation, having a simple process, also no organic solvent is required, which not only improves a cleaning efficiency, but also saves materials, thereby saving costs. 
     2, after spinning, by a designed magnetic clamping assembly, it is possible to ensure that the printing plane returning to the original absolute position, in order to ensure that the printed pieces will not have a layer-to-layer misalignment; 
     3, adding the post-curing device, and improving a cross-linking degree of the printed piece, to ensure that the printed piece will not be thrown out or broken after a plurality of centrifugal rotations; 
     4, arranging leveling assemblies on both the printing platform and the resin slot switching device, which is able to make both the printing plane and the upper surface of the resin slot be level. 
     It should be understood that, the application of the present disclosure is not limited to the above examples listed. Ordinary technical personnel in this field can improve or change the applications according to the above descriptions, all of these improvements and transforms should belong to the scope of protection in the appended claims of the present disclosure.