WO2019062143A1 - 一种三维打印方法 - Google Patents

一种三维打印方法 Download PDF

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Publication number
WO2019062143A1
WO2019062143A1 PCT/CN2018/087057 CN2018087057W WO2019062143A1 WO 2019062143 A1 WO2019062143 A1 WO 2019062143A1 CN 2018087057 W CN2018087057 W CN 2018087057W WO 2019062143 A1 WO2019062143 A1 WO 2019062143A1
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WO
WIPO (PCT)
Prior art keywords
model
support
area
supporting
printer
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Application number
PCT/CN2018/087057
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English (en)
French (fr)
Inventor
沈洪垚
叶潇翔
黎清雨
傅建中
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浙江大学
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Publication date
Application filed by 浙江大学 filed Critical 浙江大学
Priority to US16/309,248 priority Critical patent/US11104078B2/en
Publication of WO2019062143A1 publication Critical patent/WO2019062143A1/zh

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/40—Structures for supporting 3D objects during manufacture and intended to be sacrificed after completion thereof
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y50/00—Data acquisition or data processing for additive manufacturing
    • B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/30—Auxiliary operations or equipment
    • B29C64/386—Data acquisition or data processing for additive manufacturing
    • B29C64/393—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y50/00—Data acquisition or data processing for additive manufacturing

Definitions

  • the present invention relates to the field of three-dimensional printing technology, and in particular to a three-dimensional printing method.
  • 3D printing is a technique for manufacturing solid parts by layer-by-layer material stacking by 3D printing equipment according to the designed three-dimensional CAD model. Because 3D printing has the advantages of low cost in the production and customization of complex parts, it has great advantages in prototype and mold manufacturing. 3D printing is widely used in areas including government, aerospace and defense, medical equipment, high technology, education, and manufacturing. Specifically, the 3D printing operation is divided into five steps: 1) acquisition of the 3D model, 2) data format conversion, 3) slice calculation, 4) print path planning, and 5) output to the 3D printer.
  • FDM Fused Deposition Manufacturing Technology
  • the research content of FDM support technology mainly focuses on supporting algorithms and supporting materials, and the development of new printing equipment to remove or reduce the support structure is also the current research direction.
  • the support algorithm initially solves the problem of the support structure generation area, and the latter is the optimization of the support structure, and it is desirable to obtain a support structure with less usage and high strength.
  • the purpose of the research of the support material is to make the support structure easy to remove, and it is divided into two types according to the post-treatment method: a peelable material and a water-soluble material.
  • the release material is peeled off by hand or tweezers after printing is completed; and the water soluble material is removed by post treatment with the corresponding solution.
  • the support material makes the post-processing of the FDM production more convenient.
  • the five-axis printer has two more rotating axes than the traditional 3-axis printing device, which makes the printing direction more free.
  • the working surface can be adjusted to an angle without adding support to avoid the support structure. generate.
  • the support algorithm can not currently generate the ideal support structure with less usage and high strength. It is difficult to ensure the stability of the support structure itself while reducing the support. It is also necessary to study a more intelligent method; the support material does not solve the time consumption of the print support structure. And the problem of material waste, and the need for multi-nozzle printing, also has strict requirements on the accuracy of the printer; the control of the five-axis printer is more complicated than the traditional printing equipment, and requires a lot of previous process research as the basis, and it is currently impossible to print the planning of any model.
  • the patent document of the application publication No. CN 104647753 A discloses a three-dimensional printing method, which provides a database for storing a support member, which is taken from a database and placed at a predetermined position on the printer substrate for printing when printing is required.
  • Such methods currently solve the problem of three-dimensional printing support for photocuring, and are not well suited for other types of 3D printing methods.
  • the printer nozzle collides with the previously placed support member when the manufacturing model is printed layer by layer due to the production mode of the FDM layer stacking.
  • the invention provides a three-dimensional printing method, which has the advantages of saving materials and reducing printing time.
  • a three-dimensional printing method comprising the following steps:
  • a support unit arranged in an array is arranged below the printing area, and the printing area where the model is located is divided into corresponding number of supporting areas according to the arrangement of the supporting unit;
  • a support device for three-dimensional printing is provided.
  • the device is composed of a plurality of supporting units arranged in a row, and the device is located below the molding area of the three-dimensional printer instead of the printer substrate of the three-dimensional printer; the supporting unit can be driven by the motor to the target position.
  • the support unit combines different support structures according to the shape of the model to be printed and the relative position of the printing model and the supporting device to replace the original printed support, thereby achieving the function of reducing support; the upper computer according to the printer motion parameters and targets Height, combined with the previously set support unit speed curve, calculate the rise time of the support unit to avoid collision between the printer and the support device in the coordination work.
  • the supporting device replaces the printer substrate of the three-dimensional printer, and the model is printed on the upper surface composed of the supporting unit; the specifications of the supporting unit are consistent; when the supporting unit is at the starting position, the upper surface of the unit can be spliced into a complete The plane; the support unit should avoid sharp or protruding shapes to prevent the support unit from colliding with the printer nozzle; the support unit should have sufficient rigidity to ensure the stability of the support structure.
  • the support structure combined by the support unit replaces most of the support structures automatically generated by the three-dimensional printing software to reduce the support.
  • the three-dimensional printer continues to print a small amount of support based on the support structure formed by the support unit, thereby forming the support structure required for the solid model.
  • the method of the present invention subdivides the printing space area into individual supporting areas according to the arrangement of the supporting units, and calculates the rising height of the supporting unit of each supporting area according to the shape of the model and the position of the supporting device.
  • the support unit in the area where the model is located rises during the printing process, and the external support structure is combined instead of the printed support.
  • the rising height of the supporting unit that is, the target height
  • the target height value is not greater than the lowest point height value, and the operator can set the height margin according to actual needs.
  • the target height value is the lowest point height value minus the height margin.
  • the supporting structure for continuing printing on the upper surface of the supporting unit should have a horizontal margin at the boundary of the supporting area to prevent the printed supporting structure from colliding with the supporting unit.
  • the shape of the printed model in the method of the present invention refers to the shape of the model near the side of the support device.
  • the fineness of the shape can be changed according to actual needs.
  • the relative position of the print model to the support device refers to the position of the print model relative to the origin of the work, and the origin of the support device should coincide with the origin of the printer.
  • the avoidance of collision between the printer and the support unit proposed by the method of the invention essentially ensures that the support unit is lower than the working height of the printer during the movement, that is, the support unit is kept no higher than the height of the printer nozzle.
  • the printer nozzle and the support unit move to the target height at the same time, that is, the support unit can provide support in time when the print nozzle is about to reach the target height.
  • the method of the invention sets the speed curve of the supporting unit in advance, and as long as the moving speed of the supporting unit is always greater than the rising speed set by the printer in the Z direction before reaching the target height, collision can be avoided.
  • the printer motion parameter when the printer reaches the target height, the support unit speed curve and the target height value can be reversed to obtain the time when the support unit rises.
  • the printer motion parameters required by the method of the present invention include the printing speed of each portion of the printer, the material length of the printing layer, the printer Z-direction rising speed, and the like.
  • the invention applies the discretization idea to the field of three-dimensional printing.
  • the upper machine divides the printing area where the model is located into discrete support areas according to the position and angle of the supporting device, and each support The area corresponds to a support unit.
  • the upper computer calculates the target height of the support unit on each area, and processes the support structure, minus the volume replaced by the support unit.
  • the support unit of each area rises to the target height, and then the printer continues to print on this basis to form a complete support and solid model.
  • the required support is greatly reduced compared to the original support structure, achieving the purpose of reducing material consumption and improving printing efficiency.
  • the upper computer calculates the rising time of the supporting unit according to the movement parameter and the target height of the printer, and combines the preset support unit speed curve.
  • the supporting unit is driven to the target height, thereby avoiding the printer and the support.
  • the device collides in coordination work.
  • the upper computer analyzes the stress state when the model is separated, and by planning the movement of the supporting unit, the model is automatically separated from the supporting device when the printing is completed without causing damage to the printing model.
  • step (6) according to the time when the printer nozzle reaches the target height value position of the support unit, the specific steps of determining the running time of the supporting unit and the running speed to reach the target height are as follows:
  • the printer motion parameter including the printing speed of each part set by the printer, the material length of the printing layer, and the rising speed, the speed of the printer in the vertical direction is obtained by these parameters;
  • the printer nozzle reaches the target height, the speed curve of the support unit, and the target height value, the time when the support unit rises is obtained, so that the support unit and the printer nozzle reach the target height position at the same time.
  • the printer leaves a margin in the horizontal direction at the boundary of each support region during printing.
  • the upper computer analyzes the force state when the model is separated, and by planning the movement of the supporting unit, the model is automatically separated from the supporting device when the printing is completed without causing damage to the printing model.
  • the method further comprises the step (8), wherein according to the characteristics of the model, a plurality of separation zones and push zone combinations are defined for the region where the model is located.
  • a combination of the separation zone and the push zone is selected to divide the model area, the support unit of the push zone moves upward, and the separation zone is misaligned to realize demolding of the model in the separation zone, and then the zone support unit is pushed back. To the position before the rise. Then, the area where the combination of the next separation zone and the push zone is divided is selected, and the above process is repeated until all the separation zone and the push zone combination are traversed, so that the model is completely demolded.
  • step (8) according to the characteristics of the model, the specific steps of dividing the region where the model is located into a plurality of separation zones and push zones are as follows:
  • the sub-region is the push zone, and the remaining part of the model is the separation zone.
  • the sub-area is a combination of support areas in which more than one support unit is located.
  • the order of the combination of the separation zone and the push zone is arranged in accordance with the interface stress from large to small.
  • the support unit speed and stroke of the push zone are divided into three categories according to the maximum value of the model deformation stress generated by the calculation of step 8-2, if the maximum deformation stress is compared If you choose a low speed and a short stroke, if the deformation stress is moderate, select a low speed and a long stroke. If the maximum deformation stress is small, select the maximum speed and long stroke.
  • the supporting unit combines different external supporting structures according to the shape of the model to be printed and the relative position of the printing model and the supporting device, instead of the supporting structure which requires a large amount of printing, thereby reducing the material. Waste and shorten processing time and increase production efficiency, but also enable the completion of 3D printed physical objects can reduce the complexity of subsequent processing, but also reduce environmental pollution.
  • FIG. 1 is a schematic flow chart of a three-dimensional printing method of the present invention.
  • FIG. 2 is a schematic perspective view showing the result of printing on the supporting device using the arch bridge model printed by the three-dimensional printing method of the present invention.
  • FIG. 3 is a support area in which the area of the arch bridge model in FIG. 2 is divided by the support unit in the vertical projection direction.
  • FIG. 4 is a front elevational view showing the result of printing on the support device using the arch bridge model printed by the three-dimensional printing method of the present invention.
  • Figure 5 is a schematic diagram of a print control process for a cantilever model during use of the three-dimensional printing method of the present invention and for avoiding collision (holding) of the printer nozzle with the support unit.
  • FIG. 6 is a schematic diagram of a print control process for using a cantilever model and avoiding collision (supporting) of a printer nozzle with a support unit during use of the three-dimensional printing method of the present invention.
  • Fig. 7 is a schematic view showing a model separation method (before pushing) using the three-dimensional printing method of the present invention.
  • Fig. 8 is a schematic view showing a model separation method (after pushing) using the three-dimensional printing method of the present invention.
  • the three-dimensional printing method of this embodiment includes the following contents:
  • FIG. 2 is a isometric view of a print result of an arch bridge model 200 made in accordance with the method of FIG. 1.
  • the arch bridge model 200 is printed on the printer substrate according to the conventional method, since there is a wide range of suspended portions at the bridge hole, it is necessary to provide a sufficient support structure here to avoid collapse of the suspended portion due to gravity during printing.
  • the printed support structure is peeled off after printing to obtain a printed arch bridge model 200.
  • a large number of support structures result in waste of raw materials, while printing time is extended and production efficiency is not high.
  • the external support structure of FIG. 2 can be formed, the printed support is greatly reduced, material waste is reduced, and printing efficiency is improved.
  • FIGS. 5 and 6 are the avoidance printer nozzle and the supporting unit provided in the embodiment. Collision print control process.
  • the control mode of the embodiment is to generate an instruction for control, and the steps S1 to S8 are implemented in the three-dimensional printing control software.
  • the operator imports the model at step S1, at which point the model exists in a common three-dimensional print file format.
  • the software needs to confirm the relative position of the printing model and the supporting device 100, that is, the position of the printing model with respect to the working origin, and the origin of the supporting device 100 should coincide with the working origin of the printer.
  • the step S2 divides the printing area in which the model is located into a plurality of supporting areas 300 according to the supporting unit 110, and each supporting area 300 corresponds to one supporting unit 110.
  • the printing area in which the arch bridge model 200 is used is divided into a plurality of supporting areas 300 in the vertical projection direction, and the subsequent operations are performed in units of the supporting area 300.
  • each support area 300 is traversed to obtain the lowest point of the model on the area, the height of the point is the maximum height that the corresponding support unit 110 can rise, and the target height value 220 is not greater than the lowest point height value.
  • the operator can set the height margin according to actual needs, and the target height value 220 is the model lowest point height minus the height margin.
  • Step S4 layering the model and constructing the inter-layer relationship, intersecting the model according to the layer height water plane, and obtaining a series of two-dimensional contour lines, and then classifying and marking based on the obtained contour lines to identify each characteristic area, such as a support structure area. And the solid model area.
  • the subsequent print path will be planned according to the characteristics of the area and the previously set regional characteristic parameters.
  • Step S5 is a process of performing calculation processing on the support structure identified in S4. Since the external support formed by the rise of the support unit 110 replaces the original support structure at that place, there is no need to print the support at that place.
  • the initial generation position of the support structure in S4 is the printer substrate, so step S5 is to shift the initial generation position on each support area 300 and move it to the target height 220 of the area. Referring to FIG. 4, after the support unit 110 of the printing area where the arch bridge model 200 is raised to the target height 220, the printer continues to print the support structure and the solid model on the support unit 110, at which time the support structure in each support area 300 starts to generate a position. Both were offset and moved to the target height of 220, which ultimately achieved the goal of reduced support.
  • step S5 it is necessary to leave a margin in the horizontal direction at the boundary of the support region 300, because the actual position and the theoretical position of the model are deviated during the actual manufacturing process, and if there is no margin, the printing continues at the boundary of the support region 300.
  • the support structure crosses the boundary, causing the support unit 110 of the adjacent area to collide with the over-bound support structure when it rises.
  • step S5 the model three-dimensional file conversion processing process is finished.
  • step S6 is to perform path planning of the printer for each feature area and supporting structure according to its characteristics and parameter settings, including printing speed, discharging speed, etc., and then generate a working instruction of the printer.
  • Step S7 is based on the parameters of the print model and the support unit thrust value to analyze the force state of the model at the time of separation and seek an optimal disengagement strategy: the parameters of the print model include the shape, size, material, and support area of the model, such information. It is obtained by the software in steps S2, S4, and the thrust of the support unit is measured in advance.
  • the model separation herein refers to the separation of the model from the support device 100 by the lifting dislocation of the support unit 110 after the printing is completed.
  • the stress state analysis includes the stress condition of the model at the time of separation and the interface stress condition of the model in contact with the supporting device 100. The two cases are analyzed to avoid damage to the fragile portion of the part caused by the separation and to find the most easily separated support unit 110.
  • the embodiment employs a stepwise separation method.
  • each operation divides the separation area S and the push area P on the area where the model 600 is located, and the support unit 110 on the push area P pushes the model 600 to rise, and the stress destruction model 600 generated by the model deformation is used.
  • the joint surface of the supporting device 100 on the separation zone S realizes the separation of the partial model.
  • an operation is completed. Thereafter, each operation is to re-divide the separation zone S and the push zone P, and the push zone P rises so that the model on the separation zone S is separated and then returns to the original position.
  • the separation of the separation zone S and the push zone P at each separation is obtained by the force analysis of the upper computer: the software first transforms the model structure and converts the complex structure into a conventional structure; secondly, one or more supports are selected.
  • the support area 300 corresponding to the unit 110 constitutes a sub-area, calculates the maximum interface stress between the model 600 and the supporting device 100 when the supporting unit 110 on the sub-area rises, and calculates the maximum value of the deformation stress of the model 600 at this time;
  • the sub-region is a suitable selection of the pushing zone P, and the remaining part is the separation zone S; finally, a series of feasible
  • the combination of the separation zone S and the push zone P, the order of selection of the separation zone S and the push zone P at each operation is arranged in accordance with the calculated interface stress from large to small.
  • the maximum deformation region 700 is the most vulnerable region of the model during the separation, and the maximum deformation stress is generated here. According to the maximum value of the deformation stress, the model can be prevented from being damaged by the motion planning of the support unit of the push zone P.
  • the above critical values can be measured in advance.
  • step S8 will plan the motion of the support unit.
  • the solution nozzle rise time T is used to ensure that the printer nozzle 500 and the support unit 110 do not collide during operation.
  • the specific method is as follows: the printer motion parameters have been obtained in step S6, including the printing speed of each part of the printer, and the printing layer. The length of the material, the rising speed of the printer in the Z direction, etc., from these parameters, the displacement of the printer in the Z direction with time is obtained. Therefore, the displacement amount of the supporting unit 110 during movement is always not larger than the Z-direction displacement of the printer, and the target height 220 is not reached until the time T', so that collision can be avoided.
  • the above conditions are the basis for planning the movement path of the support unit.
  • the support unit 110 continuously rises, as long as the movement speed of the support unit 110 is always greater than the rising speed set by the printer in the Z direction, the support unit 110 can be prevented from catching up with the printer when the target height is not reached.
  • This condition is a mathematical reinforcement of the basic conditions mentioned in the previous paragraph.
  • the speed curve of the supporting unit is set in the software according to the strengthening condition. It can be calculated from the printer motion parameter that the printer reaches the target height at time T', and the time T at which the support unit rises can be reversed according to the support unit speed curve and the target height value.
  • the supporting unit 110 performs the corresponding operation according to the model disengagement strategy to realize the separation of the model from the supporting device 100: the supporting unit 110 of the pushing zone P rises each time, completes the separation of the model part on the separation zone S, and then returns. The position at the end of printing is performed, and the next operation is performed; the speed and the stroke of the support unit 110 are classified into three categories according to the maximum value of the deformation stress generated by the operation recorded in the step S7. If the stress value is large, select a low speed short stroke. If the stress value is moderate, select a low speed long stroke. If the stress value is negligible, select the maximum speed and long stroke.
  • step S9 the printer command and the support unit command are combined and output according to a certain rule, and the layer-by-layer printing of the solid model is started to enter the actual printing stage.
  • the rules are determined according to the hardware connection conditions of the printer and the supporting device 100: if the serial connection mode is adopted, the supporting device instructions are directly inserted into the printer command, because the printer commands are arranged according to the height, so as long as the code at the target height If the printer and the support device 100 are independent of each other, a prompt instruction is added to the printer command to indicate that the support unit 110 starts to move at the time T, and when the host computer processes the prompt command, the support device command is issued. .
  • Step S10 is a specific printing control process for avoiding collision of the printer nozzle 500 with the supporting unit 110, and essentially ensures that the supporting unit 110 is lower than the working height of the printer during the movement, that is, the holding unit 110 is not higher than the height of the printer nozzle 500.
  • the printer nozzle 500 and the supporting unit 110 move to the target height 220 at the same time.
  • the printer will print to the cantilever structure of the cantilever model 410, and the supporting unit 110 of the area starts to rise, and the T' moment The printer has been printing the cantilever structure of the cantilever model 410', and the support unit 110' has risen to the target height 220 to provide support.
  • step S11 on the basis that the support unit 110 forms a support structure, the printer continues to print a small number of support structures to form a complete support and solid model of the model.
  • step S12 the solid model is separated from the supporting device 100 according to the above-mentioned stepwise separated model separation strategy, and a complete model is obtained through simple post-processing.
  • step S13 the support unit 110 returns to its initial position at the support device 100, and the motor is stopped.
  • the final step S14 ends the printing process.
  • the supporting device 100 is assembled by a plurality of supporting units 110, and the model is printed on the upper surface composed of the supporting unit 110.
  • the support unit 110 has the same specifications, the top surface can be spliced out of the complete plane, and there should be no excessive gaps; the shape of the support unit 110 should avoid sharp or protruding shapes to avoid the printer nozzle and the external support when constructing the external support
  • the protruding support structure collides; the support unit 110 should have sufficient rigidity to ensure the stability of the support structure; the support unit 110 needs to be controllable at the same time, and has sufficient motion precision to ensure that the motion error does not affect the print quality.
  • the support unit 110 combines different shapes of the externally supported structure according to the shape of the model to be printed and the relative position of the printing model and the supporting device 100, instead of requiring a large amount of printing.
  • the support structure can reduce the waste of materials and shorten the processing time and increase the production efficiency.
  • the physical objects after 3D printing can reduce the complexity of subsequent processing and reduce the pollution to the environment.
  • the host computer can calculate the time T of the rise of the support unit 110 according to the printer motion parameter and the target height in advance, in combination with the preset support unit speed curve, thereby ensuring that the height of the support unit 110 during the movement is not higher than the height of the printer nozzle 500.
  • the printer and the support unit 110 are prevented from colliding in coordinated work. Furthermore, the upper computer analyzes the state of stress when the model is separated, and adopts a stepwise separation manner by planning the movement of the supporting unit 110, and automatically realizes the model from the supporting device 100 when the printing is completed without causing damage to the printing model. Separation.

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Abstract

本发明公开了一种三维打印方法，包括以下步骤：(1)打印区域导入待打印模型；(2)打印区域的下方设有阵列排布的支撑单元，根据支撑单元排布将模型所在的打印区域划分成对应数量的支撑区域；(3)每个支撑区域进行遍历，获取该支撑区域上的模型最低点，设定每个支撑单元的目标高度值，目标高度值不大于最低点高度值；(4)对模型进行分层切片并构建层间关系，得到一系列二维轮廓线；(5)根据支撑单元的目标高度值，对支撑结构进行处理，减去支撑结构中支撑单元替代的部分；(6)确定支撑单元的运行时刻和到达目标高度的运行速度从而使打印机喷嘴和支撑单元的顶面同时到达目标高度；(7)根据计算结果控制打印机和支撑单元工作完成实体模型的打印。

Description

一种三维打印方法 技术领域
本发明涉及三维打印技术领域，特别涉及一种三维打印方法。
背景技术
3D打印，是根据所设计的三维CAD模型，通过3D打印设备逐层堆积材料来制造实体零件的技术。因为3D打印在复杂零件的制作和个性化定制上具有成本低廉等优势，其在原型和模具制造方面具有巨大的优势。在包括政府、航天和国防、医疗设备、高科技、教育业以及制造业等领域3D打印获得广泛应用。具体来说，3D打印操作分为5步：1)3D模型的获取，2)数据格式转换，3)切片计算，4)打印路径规划，5)输出到3D打印机。
熔融沉积制造技术(FDM)是目前市场份额最多的3D打印技术，具有操作简单、环境友好、技术开源等优点。其工作原理是加工成丝状的热熔融材料(ABS、PLA、蜡等)经送丝机构送进热熔喷嘴，在喷嘴内丝状材料被加热熔融，同时喷头沿零件层片轮廓和填充轨迹运动，并将熔融材料挤出，使其沉积在工作台上指定的位置后凝固成型，与前一层已成型的材料粘结层层堆积最终形成产品模型。
由于FDM型三维打印机打印原理类似于简单的“堆积木”，在打印物体模型中的悬空部位时，被挤出的塑料丝悬在空中而无法融合。用户需要在切片前对物体模型悬空部位下方添加支撑结构。这些支撑结构作为物体模型的一部分被打印机打印。支撑结构会对FDM的成型时间和质量有很大影响，阻碍了FDM技术发展。
目前FDM的支撑技术的研究内容主要集中在支撑算法和支撑材料上，同时开发新型打印设备以去除或者减少支撑结构为目的也是当前研究方向。支撑算法最初解决的是支撑结构生成区域的问题，后期则是对支撑结构进行优化，希望获得用量少且强度高的支撑结构。支撑材料的研究目的是使得支撑结构易于去除，按后处理方式分为两种：剥离性材料和水溶 性材料。剥离性材料是在打印完成后用手或者镊子剥离；而水溶性材料则是用相应的溶液进行后处理去除。支撑材料使得FDM生产的模型后处理更加方便。五轴打印机作为一种新型打印设备，相比于传统的3轴打印设备多出两个旋转轴使得打印方向更加自由，理论上可以将工作面调整到无需添加支撑的角度上从而避免支撑结构的生成。
支撑算法目前不能生成理想中的用量少且强度高的支撑结构，在减少支撑的同时难以保证支撑结构本身的稳定，还需要研究更加智能的方法；支撑材料则没有解决打印支撑结构的时间消耗和材料浪费问题，且需要多喷头打印，对打印机精度也有苛刻的要求；五轴打印机的控制比传统打印设备复杂，需要前期大量工艺研究作为基础，目前无法对任意模型进行打印规划。
除了上述研究内容，有行业内人员提出了用外部支撑结构代替原有打印结构的想法。如果事先有支撑件与待打印模型的支撑结构相同或者近似，那么打印中用支撑件来取代支撑结构将能节省时间和材料。例如申请公布号CN 104647753 A的专利文献公开了一种立体打印方法，提供了一种存放支撑件的数据库，在需要打印时从数据库中取支撑件置于打印机基板的预定位置上进行打印。此类方法目前能解决光固化成型的三维打印支撑问题，对于其他类型的3D打印方法并不能很好的适用。比如在FDM生产过程中，如果事先在打印机基板上放置支撑件，则由于FDM层层堆积的生产方式，打印机喷头在逐层打印制造模型时就会与事先放置的支撑件碰撞。
发明内容
本发明提供了一种三维打印方法，具有节省材料、减少打印时间的优点。
一种三维打印方法，包括以下步骤：
(1)打印区域导入待打印模型；
(2)打印区域的下方设有阵列排布的支撑单元，根据支撑单元排布将模型所在的打印区域划分成对应数量的支撑区域；
(3)每个支撑区域进行遍历，获取该支撑区域上的模型最低点，该点的高度就是对应的支撑单元能上升的最大高度，设定每个支撑单元的目 标高度值，目标高度值不大于最低点高度值；
(4)对模型进行分层切片并构建层间关系，按层高用水平面与模型相交，得到一系列二维轮廓线，然后就是基于得到的轮廓线进行分类标记，识别各个特征区域，包括支撑结构区域和实体模型区域；之后的打印路径会依照区域特点和事先设置的区域特征参数进行规划；
(5)根据支撑单元的目标高度值，对支撑结构进行处理，减去支撑结构中支撑单元替代的部分；
(6)根据打印机喷嘴到达支撑单元的目标高度值位置的时间，确定支撑单元的运行时刻和到达目标高度的运行速度从而使打印机喷嘴和支撑单元的顶面同时到达目标高度，并且保持所有的支撑单元的顶面时时低于打印机喷嘴；
(7)根据步骤(5)和(6)的计算结果控制打印机和支撑单元工作完成实体模型的打印。
本发明中设有三维打印用的支撑装置，装置由多个支撑单元排列组合而成，装置位于三维打印机的成型区域下方，取代了三维打印机的打印机基板；支撑单元可由电机驱动到目标位置。
对于任意模型，支撑单元根据待打印模型的形状和打印模型与支撑装置的相对位置组合出不同的支撑结构替代原有打印出的支撑，从而实现支撑减少的功能；上位机根据打印机运动参数和目标高度，结合事先设置好的支撑单元速度曲线，计算支撑单元的上升时刻，避免打印机和支撑装置在协调工作中发生碰撞。
所述的支撑装置取代三维打印机的打印机基板，模型在由支撑单元组成的上表面被打印制造出来；支撑单元的规格要求一致；当支撑单元位于起始位置时，单元的上表面可以拼接成完整的平面；支撑单元应避免尖锐或者突起的形状，防止支撑单元与打印机喷嘴碰撞；支撑单元应有足够的刚度，保证支撑结构的稳定。
本发明方法由支撑单元组合出的支撑结构将三维打印软件自动生成的大部分的支撑结构进行替代，达到减少支撑的目的。三维打印机在由支撑单元形成的支撑结构基础上继续打印少量的支撑，从而构成实体模型所需的支撑结构。
本发明方法按照支撑单元排列方式将打印空间区域细分成各个支撑 区域，根据模型的形状和相对支撑装置位置计算每个支撑区域的支撑单元上升高度。模型所在区域中的支撑单元在打印过程中上升，组合出外部支撑结构代替打印出的支撑。
本发明方法中支撑单元上升高度即目标高度，是由每个支撑区域上模型最低点的高度决定的，目标高度值不大于最低点高度值，操作人员可以视实际需要设置高度余量。目标高度值为最低点高度值减去高度余量。
本发明方法中在支撑单元上表面继续打印的支撑结构应在支撑区域边界留有水平方向的余量，避免打印出的支撑结构与支撑单元碰撞。
本发明方法中的打印模型形状指的是模型靠近支撑装置一侧的形状。可以根据实际需要改变形状的精细程度。打印模型与支撑装置的相对位置指的是打印模型相对于工作原点的位置，而支撑装置的原点应与打印机工作原点重合。
本发明方法提出的避免打印机和支撑单元碰撞实质上是保证支撑单元在运动过程中低于打印机工作高度，即保持支撑单元不高于打印机喷嘴所在高度。最理想的情况是打印机喷嘴和支撑单元同时运动到目标高度，即打印喷嘴将要到达目标高度时支撑单元能及时提供支撑。
本发明方法事先设置好了支撑单元的速度曲线，只要保证在达到目标高度前支撑单元运动速度始终大于打印机在Z方向所设定的上升速度，就能避免碰撞。根据打印机运动参数得到打印机到达目标高度的时刻，则由支撑单元速度曲线和目标高度值可以反推得到支撑单元上升的时刻。
本发明方法所需的打印机运动参数包括打印机所设置各个部分打印速度、打印层的材料长度、打印机Z方向上升速度等。
本发明将离散化思想应用到三维打印领域中，在待打印模型导入上位机后，由上位机将模型所在打印区域按照其相对于支撑装置的位置和角度划分成离散的支撑区域，每个支撑区域对应一个支撑单元。上位机计算每个区域上支撑单元的目标高度，对支撑结构进行处理，减去支撑单元代替掉的体积。在打印机工作过程中，每个区域的支撑单元上升到达目标高度，然后打印机在此基础上继续打印形成完整的支撑和实体模型。所需支撑相比原有支撑结构大幅度减少，达到减少材料消耗和提高打印效率的目的。
上位机根据打印机运动参数和目标高度，结合事先设置好的支撑单元速度曲线，计算支撑单元的上升时刻，当将要打印需要添加支撑结构的几 何特征时支撑单元驱动到目标高度，从而避免打印机和支撑装置在协调工作中发生碰撞。另外，上位机对模型分离时的受力状态进行分析，通过规划支撑单元运动，在不造成打印模型受损的情况下，实现打印完成时模型从支撑装置上自动分离。
为了实现快速和有效的地计算，优选的，步骤(6)，根据打印机喷嘴到达支撑单元的目标高度值位置的时间，确定支撑单元的运行时刻和到达目标高度的运行速度的具体步骤如下：
6-1、根据步骤(5)中，打印机运动参数，包括打印机所设置各个部分打印速度、打印层的材料长度和上升速度，由这些参数得到打印机在垂直方向的速度；
6-2、设定出支撑单元的速度曲线，使支撑单元开始上升时支撑单元的运动速度始终大于打印机在垂直方向所设定的上升速度；
6-3、根据打印机喷嘴到达目标高度的时间、支撑单元的速度曲线和目标高度值，得到支撑单元上升的时刻使支撑单元与打印机喷嘴同时到达目标高度位置。
为了避免支撑单元上升时与已打印部分碰撞挤压，优选的，步骤(4)和(5)中，打印机在打印过程中留出各支撑区域边界处水平方向的余量。
上位机对模型分离时的受力状态进行分析，通过规划支撑单元运动，在不造成打印模型受损的情况下，实现打印完成时模型从支撑装置上自动分离。优选的，还包括步骤(8)，根据模型的特点，对模型所在区域划分出多种分离区和推动区组合。待模型打印完成后，选择一种分离区和推动区的组合划分模型所在区域，推动区的支撑单元向上运动，与分离区产生错位以实现分离区中的模型脱模，随后推动区支撑单元回到上升前的位置。之后选择下一种分离区和推动区的组合划分模型所在区域，重复上述过程，直至遍历所有的分离区和推动区组合，使得模型完全脱模。
优选的，步骤(8)中，根据模型的特点，将模型所在区域划分出多种分离区和推动区组合的具体步骤如下：
8-1、计算每个子区域的支撑单元推动时，模型与支撑装置间的界面应力；
8-2、计算每个子区域的支撑单元推动时，模型在分离时产生的形变应力最大值；
8-3、当任一子区域的界面应力超过界面应力临界值，同时形变应力最大值不超过模型变形临界值时，则该子区域为推动区，模型所在区域剩下部分即为分离区，子区域为一个以上支撑单元所在的支撑区域组合。
为了提高分离效果，优选的，步骤(8)中，分离区和推动区组合选择的顺序按照界面应力从大到小排列。
为了保证模型的完整性，优选的，步骤(8)中，所述推动区的支撑单元速度和行程依据步骤8-2的计算产生的模型形变应力最大值分成三类，若形变应力最大值较大则选择低速短行程，若形变应力最大值适中，则选择低速长行程，若形变应力最大值较小则选择最大速度长行程。
本发明的有益效果：
本发明的三维打印方法对于任意模型，支撑单元根据待打印模型的形状和打印模型与支撑装置的相对位置组合出不同的外部支撑结构，代替了原有需要大量打印的支撑结构，因而得以减少材料的浪费并缩短处理时间与提高生产效率，同时也让完成三维打印后的实体物件能降低后续处理的复杂度，也减少对于环境的污染。
附图说明
图1为本发明的三维打印方法的流程示意图。
图2为使用本发明的三维打印方法打印的拱桥模型在支撑装置上打印结果的立体结构示意图。
图3为图2中拱桥模型的所在区域在垂直投影方向上按支撑单元排布所划分的支撑区域。
图4为使用本发明的三维打印方法打印的拱桥模型在支撑装置上打印结果的主视示意图。
图5为使用本发明的三维打印方法过程中悬臂模型以及避免打印机喷嘴与支撑单元碰撞(支撑前)的打印控制过程示意图。
图6为使用本发明的三维打印方法过程中悬臂模型以及避免打印机喷嘴与支撑单元碰撞(支撑中)的打印控制过程示意图。
图7为使用本发明的三维打印方法的模型分离方式(推动前)的示意图。
图8为使用本发明的三维打印方法的模型分离方式(推动后)的示意 图。
图中的标记：100：支撑装置；110：支撑单元；200：拱桥模型；210：继续打印的支撑结构；220：所在支撑区域的支撑单元的目标高度；300：支撑区域；400：悬臂模型；410：打印过程中的悬臂模型；500：打印机喷嘴；600：打印完成后待分离模型；700：分离时产生最大形变应力区域；T：打印时刻T(此时将要打印到悬臂结构，支撑单元上升时刻)；T’：打印时刻T’(此时已在打印悬臂结构)；110’：T’时刻的支撑单元；410’：T’时刻的打印中的悬臂模型；500’：T’时刻的打印机喷嘴；S:分离区；P:推动区。
具体实施方式
如图1～8所示，本实施例的三维打印方法包括以下内容：
图2是依据图1的方法制造的拱桥模型200的打印结果的正轴测图。若按照传统方法，在打印机基板上打印制造拱桥模型200时，由于其桥洞处有大范围的悬空部分，所以需要在此处提供足够的支撑结构，以避免打印过程中悬空部分因重力影响坍塌。打印出的支撑结构在打印完成后会被剥离舍弃从而得到打印的拱桥模型200。大量的支撑结构造成了原材料的浪费，同时打印时间延长，生产效率不高。在使用本实施例需要的支撑装置100辅助打印后，能形成图2的外部支撑结构，大量减少打印出的支撑，减少材料浪费，提高打印效率。但是如果提前让支撑单元110到达目标高度220，则打印机喷嘴500在逐层打印制造过程中会与支撑单元110碰撞导致打印失败，图5和图6是本实施例提供的避免打印机喷嘴与支撑单元碰撞的打印控制过程。
在使用本实施例提供的方法实际打印制造实体模型时，请参考图1所述流程，本实施例的控制方式是生成指令进行控制，步骤S1～S8是在三维打印控制软件中实现的。
操作人员在步骤S1时导入模型，此时模型以常见的三维打印文件格式存在。此时软件需要确认打印模型与支撑装置100的相对位置，即打印模型相对于工作原点的位置，支撑装置100的原点应与打印机工作原点重合。
此后，步骤S2会根据支撑单元110排布将模型所在的打印区域划分 成一个个支撑区域300，每个支撑区域300对应一个支撑单元110。请参考图3，所用的拱桥模型200所在的打印区域在垂直投影方向被划分成一个个支撑区域300，之后的操作是以支撑区域300为单位进行的。
步骤S3中会对于每个支撑区域300进行遍历，获取该区域上的模型最低点，该点的高度就是对应的支撑单元110能上升的最大高度，而目标高度值220不大于最低点高度值。操作人员可以视实际需要设置高度余量，则目标高度值220为模型最低点高度减去高度余量。
步骤S4对模型分层切片并构建层间关系，按层高用水平面与模型相交，得到一系列二维轮廓线，然后就是基于得到的轮廓线进行分类标记，识别各个特征区域，比如支撑结构区域和实体模型区域。之后的打印路径会依照区域特点和事先设置的区域特征参数进行规划。
步骤S5是对S4中识别的支撑结构进行计算处理的过程。因为支撑单元110上升构成的外部支撑取代了该处原有的支撑结构，所以该处就不用再打印支撑。而S4中支撑结构的起始生成位置为打印机基板，所以步骤S5就是将各个支撑区域300上的起始生成位置进行偏移，将其移至该区域的目标高度220处。请参考图4，拱桥模型200所在打印区域的支撑单元110上升到目标高度220之后，打印机继续在支撑单元110上打印支撑结构和实体模型，此时各个支撑区域300中的支撑结构起始生成位置都进行了偏移，移动到了目标高度220处，最终实现了支撑减少的目的。在此步中需要留出支撑区域300边界处水平方向的余量，这是因为实际制造过程中模型实际位置和理论位置存在偏差，如果没有余量，就使得在支撑区域300边界处继续打印出的支撑结构过界，从而造成相邻区域的支撑单元110上升时与过界的支撑结构碰撞。在完成步骤S5后，模型三维文件转化处理过程就结束了。
此后步骤S6就是对各个特征区域和支撑结构按其特征和参数设置进行打印机的路径规划，包括打印速度、出料速度等，然后生成打印机的工作指令。
步骤S7是基于打印模型的参数和支撑单元推力数值分析模型在分离时的受力状态并寻求最佳脱离策略：打印模型的参数包括模型的形状、尺寸、材料、所在支撑区域等信息，这些信息由软件在步骤S2、S4中获得，而支撑单元的推力是事先测量所得。这里的模型分离指的是在打印完成后 利用支撑单元110的升降错位将模型从支撑装置100上分离。受力状态分析包括分离时模型的应力情况和模型与支撑装置100接触的界面应力情况，两种情况分析是为了避免分离导致的零件脆弱部分受损以及寻找最易分离的支撑单元110运动方式。
实施例采用的是逐步分离方法。请参考图7和图8，每次操作在模型600所在区域上划分出分离区S和推动区P，推动区P上的支撑单元110推动模型600上升，利用模型形变产生的应力破坏模型600与支撑装置100在分离区S上的结合面，实现局部模型的分离，此后推动区的支撑单元110回到原来位置，则算完成一次操作。此后每次操作都是重新划分分离区S和推动区P，推动区P上升使得分离区S上模型分离，然后回到原来的位置。
每次分离时的分离区S与推动区P的划分则是由上位机进行受力分析得到的：软件首先会对模型结构进行转化处理，将复杂结构转化成常规结构；其次任选一个以上支撑单元110对应的支撑区域300组成子区域，计算子区域上的支撑单元110在上升时模型600与支撑装置100间的界面应力最大值，并计算模型600在此时具有的形变应力最大值；然后当界面应力最大值超过界面应力临界值且形变应力最大值低于形变临界值时，该子区域为一种合适的推动区P的选择，剩余部分即为分离区S；最后得到一系列可行的分离区S和推动区P的组合，则每次操作时的分离区S和推动区P选择的顺序按照计算得到的界面应力从大到小排列。
同时形变最大区域700是该模型在此次分离时最易受损的区域，形变应力最大值会在此处产生。根据形变应力最大值，通过之后推动区P的支撑单元运动规划可以避免模型受损。上述的临界值都可以事先测得。
在得到打印机运动路径和模型脱离策略后，步骤S8将规划支撑单元的运动。首先会通过求解单元上升时刻T来保证打印机喷嘴500和支撑单元110在工作中不发生碰撞，具体方法如下：步骤S6中已经获得了打印机运动参数，包括打印机所设置各个部分打印速度、打印层的材料长度、打印机Z方向上升速度等，由这些参数得到打印机在Z方向的位移随时间变化关系。因此支撑单元110运动时的位移量始终不大于打印机的Z方向位移，直到T’时刻才同时达到目标高度220，这样才能避免碰撞的发生。上述条件是规划支撑单元运动路径的基础。当支撑单元110连续上升时， 只要保证支撑单元110运动速度始终大于打印机在Z方向所设定的上升速度，就能避免支撑单元110在未到达目标高度时就追上打印机。该条件是上一段所说的基本条件数学上的强化。本实施例在软件中依据所述强化条件设置好了支撑单元的速度曲线。由打印机运动参数可以计算得到打印机是在T’时刻到达目标高度，则根据支撑单元速度曲线和目标高度值可以反推得到支撑单元上升的时刻T。
其次支撑单元110依照模型脱离策略，分步执行相应操作实现模型从支撑装置100上的分离：每次操作时推动区P的支撑单元110上升，完成分离区S上模型部分的分离，然后回到打印结束时的位置，再执行下一次操作；支撑单元110速度和行程依据步骤S7记录的该次操作产生的形变应力最大值分成三类。若应力值较大则选择低速短行程，若应力值适中，则选择低速长行程，若应力值可以忽略，则选择最大速度和长行程。
此后步骤S9将打印机指令和支撑单元指令按一定规则进行合并输出，开始逐层打印实体模型进入实际打印阶段。这里的规则是根据打印机和支撑装置100的硬件连接条件决定的：若采用串联式连接方式，则支撑装置指令直接插入打印机指令中，因为打印机指令按高度划分排布，所以只要在目标高度的代码前插入支撑装置指令；若打印机和支撑装置100是各自独立的，则需要在打印机指令中增加提示指令，用于指示支撑单元110开始运动时刻T，当上位机处理提示指令时就发出支撑装置指令。
步骤S10是避免打印机喷嘴500与支撑单元110碰撞的具体打印控制过程，本质上要保证支撑单元110在运动过程中低于打印机工作高度，即保持支撑单元110不高于打印机喷嘴500所在高度。请参考图6，最理想的情况是打印机喷嘴500和支撑单元110同时运动到目标高度220，T时刻打印机将要打印到悬臂模型410的悬臂结构，所在区域的支撑单元110开始上升，而T’时刻打印机已经在打印悬臂模型410’的悬臂结构，支撑单元110’已经上升到目标高度220提供支撑。
在步骤S11中，在支撑单元110形成支撑结构的基础上打印机继续打印少量的支撑结构来构成模型完整的支撑和实体模型。
随后步骤S12按照上述逐步分离的模型分离策略将实体模型从支撑装置100上分离下来，经过简单的后处理得到完整模型。
然后步骤S13时支撑单元110回到其在支撑装置100初始位置，电机 停止。
最后步骤S14打印过程结束。
在使用本实施例提供的方法进行打印时，需要提供支撑装置100取代原有的打印机基板，支撑装置100由多个支撑单元110排列组合而成，模型在由支撑单元110组成的上表面被打印制造出来；支撑单元110的规格要求一致，其顶面能拼接出完整的平面，不能存在过大的空隙；支撑单元110外形上应避免尖锐或者突起的形状，以避免构建外部支撑时打印机喷头与突出的支撑结构碰撞；支撑单元110应有足够的刚度，保证支撑结构的稳定；支撑单元110同时需要可控，有足够的运动精度，能保证运动误差不影响打印质量。
综上所述，在本实施例中，对于任意模型，支撑单元110根据待打印模型的形状和打印模型与支撑装置100的相对位置组合出不同的外部支撑结构，代替了原有需要大量打印的支撑结构，因而得以减少材料的浪费并缩短处理时间与提高生产效率，同时也让完成三维打印后的实体物件能降低后续处理的复杂度，也减少对于环境的污染。其次，上位机可以事先根据打印机运动参数、目标高度，结合事先设置好的支撑单元速度曲线，计算支撑单元110上升的时刻T，从而保证支撑单元110运动过程中高度不高于打印机喷嘴500高度，避免打印机和支撑单元110在协调工作中发生碰撞。再者，上位机对模型分离时的受力状态进行分析，通过规划支撑单元110运动采用逐步分离的方式，在不造成打印模型受损的情况下，实现打印完成时模型从支撑装置100上自动分离。
最后应说明的是:以上实施例仅用以说明本发明的技术方案，而非对其限制；尽管参照前述实施例对本发明进行了详细的说明，本领域的普通技术人员应当理解:其依然可以对前述实施例所记载的技术方案进行修改，或者对其中部分或者全部技术特征进行等同替换；而这些修改或者替换，并不使相应技术方案的本质脱离本发明实施例技术方案的范围。

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  1. 一种三维打印方法，其特征在于，包括以下步骤：
    (1)打印区域导入待打印模型；
    (2)打印区域的下方设有阵列排布的支撑单元，根据支撑单元排布将模型所在的打印区域划分成对应数量的支撑区域；
    (3)每个支撑区域进行遍历，获取该支撑区域上的模型最低点，设定每个支撑单元的目标高度值，目标高度值不大于最低点高度值；
    (4)对模型进行分层切片并构建层间关系，按层高用水平面与模型相交，得到一系列二维轮廓线，然后就是基于得到的轮廓线进行分类标记，识别各个特征区域，包括支撑结构区域和实体模型区域；
    (5)根据支撑单元的目标高度值，对支撑结构进行处理，减去支撑结构中支撑单元替代的部分；
    (6)根据打印机喷嘴到达支撑单元的目标高度值位置的时间，确定支撑单元的运行时刻和到达目标高度的运行速度从而使打印机喷嘴和支撑单元的顶面同时到达目标高度，并且保持所有的支撑单元的顶面时时低于打印机喷嘴；
    (7)根据步骤(5)和(6)的计算结果控制打印机和支撑单元工作完成实体模型的打印。
  2. 如权利要求1所述的三维打印方法，其特征在于，步骤(6)，根据打印机喷嘴到达支撑单元的目标高度值位置的时间，确定支撑单元的运行时刻和到达目标高度的运行速度的具体步骤如下：
    6-1、根据步骤(5)中，打印机运动参数，包括打印机所设置各个部分打印速度、打印层的材料长度和上升速度，由这些参数得到打印机在垂直方向的速度；
    6-2、设定出支撑单元的速度曲线，使支撑单元开始上升时支撑单元的运动速度始终大于打印机在垂直方向所设定的上升速度；
    6-3、根据打印机喷嘴到达目标高度的时间、支撑单元的速度曲线和目标高度值，得到支撑单元上升的时刻使支撑单元与打印机喷嘴同时到达目标高度位置。
  3. 如权利要求1所述的三维打印方法，其特征在于，步骤(4)和(5) 中，打印机在打印过程中留出各支撑区域边界处水平方向的余量。
  4. 如权利要求1所述的三维打印方法，其特征在于，还包括步骤(8)，根据模型的特点，对模型所在区域划分出多种分离区和推动区组合，待模型打印完成后，选择一种分离区和推动区的组合划分模型所在区域，推动区的支撑单元向上运动，与分离区产生错位以实现分离区中的模型脱模，随后推动区的支撑单元回到上升前的位置，之后选择下一种分离区和推动区的组合划分模型所在区域，重复上述过程，直至遍历所有的分离区和推动区组合，使得模型完全脱模。
  5. 如权利要求4所述的三维打印方法，其特征在于，步骤(8)中，根据模型的特点，将模型所在区域划分出多种分离区和推动区组合的具体步骤如下：
    8-1、计算每个子区域的支撑单元推动时，模型与支撑装置间的界面应力；
    8-2、计算每个子区域的支撑单元推动时，模型在分离时产生的形变应力最大值；
    8-3、当任一子区域的界面应力超过界面应力临界值，同时形变应力最大值不超过模型变形临界值时，则该子区域为推动区，模型所在区域剩下部分即为分离区，子区域为一个以上支撑单元所在的支撑区域组合。
  6. 如权利要求5所述的三维打印方法，其特征在于，步骤(8)中，分离区和推动区组合选择的顺序按照界面应力从大到小排列。
  7. 如权利要求5所述的三维打印方法，其特征在于，步骤(8)中，所述推动区的支撑单元速度和行程依据步骤8-2的计算产生的模型形变应力最大值分成三类，若形变应力最大值较大则选择低速短行程，若形变应力最大值适中，则选择低速长行程，若形变应力最大值较小则选择最大速度长行程。
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