阅读说明：本技术 一种光固化三维打印预览方法 (Photocuring three-dimensional printing preview method ) 是由 管清宝 游正伟 高奕 赵阳 徐磊 严旎娜 于 2019-10-23 设计创作，主要内容包括：本发明涉及一种光固化三维打印预览方法,包括以下步骤：通过测量不同固化条件下的光敏树脂体系的吸光度与时间的关系,得到不同固化条件下,光敏树脂体系转化率与时间的关系曲线；基于光固化动力学方程,使用迭代求解法对实验曲线进行拟合,得到光敏树脂体系的光固化动力学常数；使用定步长欧拉方法解所述光固化反应动力学微分方程组,得到光敏树脂体系在光固化反应过程中各组分含量的空间分布与时间关系曲线；进行模拟打印,并结合所述各组分含量的空间分布与时间关系曲线得到打印完成后三维打印产品中每层结构内各组分含量的空间分布,完成光固化三维打印预览。本发明弥补了三维打印控制软件在预览功能方面的空白。(The invention relates to a photocuring three-dimensional printing preview method, which comprises the following steps: obtaining a relation curve of the conversion rate of the photosensitive resin system and the time under different curing conditions by measuring the relation between the absorbance of the photosensitive resin system and the time under different curing conditions; fitting the experimental curve by using an iterative solution method based on a photocuring kinetic equation to obtain a photocuring kinetic constant of the photosensitive resin system; solving the photocuring reaction kinetic differential equation set by using a fixed-step Euler method to obtain a spatial distribution and time relation curve of each component content of the photosensitive resin system in the photocuring reaction process; and performing simulated printing, and combining the spatial distribution of the content of each component with the time relation curve to obtain the spatial distribution of the content of each component in each layer of structure in the three-dimensional printed product after printing is finished, so as to finish the photocuring three-dimensional printing preview. The invention makes up the blank of the three-dimensional printing control software in the aspect of the preview function.)

1. A photocuring three-dimensional printing preview method is characterized by comprising the following steps:

(1) obtaining a relation curve of the conversion rate of the photosensitive resin system and the time under different curing conditions by measuring the relation between the absorbance of the photosensitive resin system and the time under different curing conditions;

(2) fitting an experimental curve by using an iterative solution method based on a photocuring kinetic equation to obtain a photocuring kinetic constant of a photosensitive resin system, and establishing a photocuring reaction kinetic differential equation set;

(3) solving the photocuring reaction kinetic differential equation set by using a fixed-step Euler method to obtain a spatial distribution and time relation curve of each component content of the photosensitive resin system in the photocuring reaction process;

(4) measuring a relation curve of incident light transmittance and cured product thickness before and after the photocuring reaction of the photosensitive resin system by using an ultraviolet spectrum;

(5) and performing simulated printing according to the structure, the light source intensity, the layer thickness and the single-layer printing time of the three-dimensional printing product, and combining a spatial distribution and time relation curve of the content of each component in the photocuring reaction process of the photosensitive resin system to obtain the spatial distribution of the content of each component in each layer of the structure of the three-dimensional printing product after printing is completed, so as to complete photocuring three-dimensional printing preview.

2. The photo-curing three-dimensional printing preview method according to claim 1, wherein the step (1) is specifically: measuring the change condition of the absorbance of functional groups of 3-7 groups of photosensitive resin with time under different curing conditions by using an in-situ Fourier transform infrared spectrometer, and converting the change condition into a change curve of the conversion rate with time by an internal standard method, wherein the different curing conditions comprise different ultraviolet light source intensities and different photoinitiator contents.

3. The method for previewing on three-dimensional photo-cured print according to claim 1, wherein the photo-curing kinetic constants obtained in the step (2) comprise a chain initiation constant, a chain growth constant and a termination constant.

4. The method for previewing on three-dimensional photo-cured print according to claim 1, wherein said system of photo-curing reaction kinetics differential equations of step (2) is obtained by simultaneous reaction rate equations including initiator decomposition, chain initiation, chain growth, and chain termination.

Technical Field

The invention relates to the technical field of photocuring three-dimensional printing simulation, in particular to a photocuring three-dimensional printing preview method.

Background

The Three-Dimensional Printing (3 DP) is a novel rapid prototyping technology developed by relying on a plurality of fields such as electronic information, machining, sensor and new material development, has the advantages of incomparable design and manufacture integration, short production period, low cost and the like of the traditional forced prototyping technology such as lathing, planning and milling, and is called as a manufacturing technology with industrial revolution significance, and is widely applied to the fields such as tissue engineering, industrial manufacturing, energy materials, aerospace and the like at present. Compared with other 3DP technologies, the photocuring three-dimensional printing forming technology has the advantages of high precision, low cost, diversified design of functional photosensitive resin and the like, so that the photocuring three-dimensional printing forming technology becomes one of the hottest 3DP technologies at present.

Photocuring three-dimensional printing uses ultraviolet light to shine the pile up the shaping to thin-layer liquid photosensitive resin, contains the thermosetting liquid resin of photoinitiation and takes place the cross-linking reaction between the interlaminar under the ultraviolet irradiation, consequently, influences the printing setting of reaction kinetics, like slice layer thickness, every layer printing time and ultraviolet lamp source light intensity all will influence finished product printing effect and quality, and the debugging process is more time-consuming and energy-consuming than two-dimensional printing, easily causes the waste of material. Compared with two-dimensional printing editing software with a built-in printing preview function, such as OFFICE series and the like, 3DP particularly relates to photocuring three-dimensional printing control software of a crosslinking reaction, and besides the slicing function, the printing preview function is required to be introduced to help a user to perform printing setting guidance and even to perform automatic design and comparison of a printing setting scheme according to an imported graph.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a photocuring three-dimensional printing preview method, which simulates the resin layer conversion rate of a printed part under the printing setting by combining a 3DP layer-by-layer stacking mechanism and a photocuring crosslinking dynamics principle to represent the preview effect.

The technical scheme adopted by the invention for solving the technical problems is as follows: the photo-curing three-dimensional printing preview method comprises the following steps:

(1) obtaining a relation curve of the conversion rate of the photosensitive resin system and the time under different curing conditions by measuring the relation between the absorbance of the photosensitive resin system and the time under different curing conditions;

(2) fitting an experimental curve by using an iterative solution method based on a photocuring kinetic equation to obtain a photocuring kinetic constant of a photosensitive resin system, and establishing a photocuring reaction kinetic differential equation set;

(3) solving the photocuring reaction kinetic differential equation set by using a fixed-step Euler method to obtain a spatial distribution and time relation curve of each component content of the photosensitive resin system in the photocuring reaction process;

(4) measuring a relation curve of incident light transmittance and cured product thickness before and after the photocuring reaction of the photosensitive resin system by using an ultraviolet spectrum;

(5) and performing simulated printing according to the structure, the light source intensity, the layer thickness and the single-layer printing time of the three-dimensional printing product, and combining a spatial distribution and time relation curve of the content of each component in the photocuring reaction process of the photosensitive resin system to obtain the spatial distribution of the content of each component in each layer of the structure of the three-dimensional printing product after printing is completed, so as to complete photocuring three-dimensional printing preview.

The step (1) is specifically as follows: measuring the change condition of the absorbance of functional groups of 3-7 groups of photosensitive resin with time under different curing conditions by using an in-situ Fourier transform infrared spectrometer, and converting the change condition into a change curve of the conversion rate with time by an internal standard method, wherein the different curing conditions comprise different ultraviolet light source intensities and different photoinitiator contents.

The photocuring kinetic constants obtained in the step (2) comprise a chain initiation constant, a chain growth constant and a termination constant.

The photocuring reaction kinetic differential equation system in the step (2) is obtained by simultaneously obtaining reaction rate equations including initiator decomposition, chain initiation, chain growth and chain termination.

Advantageous effects

Due to the adoption of the technical scheme, compared with the prior art, the invention has the following advantages and positive effects: according to the invention, by combining the infrared spectrum and the ultraviolet spectrum to represent the laminated curing characteristics of the photosensitive resin, the kinetic parameter input value of the photosensitive resin system with unknown or arbitrary formula can be obtained, so that the simulation result is more in line with the reality. The invention provides a method for realizing simulation of a photocuring three-dimensional printing preview effect by combining a classical free radical polymerization kinetic model introducing oxygen inhibition and a light attenuation principle, and fills the blank of three-dimensional printing control software in the aspect of a preview function.

Drawings

FIG. 1 is a diagram of an in-situ light-cured Fourier transform infrared spectrometer optical path system and a liquid resin sample installation provided by an embodiment of the invention;

FIG. 2 is a graph of absorption characteristic peak-monomer concentration of infrared spectrum of monomer provided by an example of the present invention;

FIG. 3 is a graph of monomer conversion curves for different curing parameters from IR spectroscopy data and simulated calculations provided by an embodiment of the present invention;

FIG. 4 is a graph showing the kinetic constants of the photosensitive resin according to the embodiment of the present invention;

FIG. 5 is a graph illustrating a thickness calculation result of a photo-cured three-dimensional printed simulated cured layer provided by an embodiment of the present invention;

fig. 6 is a graph of curing effects of photo-curing three-dimensional printing simulation with different exposure times according to an embodiment of the present invention.

Detailed Description

The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. Further, it should be understood that various changes or modifications of the present invention may be made by those skilled in the art after reading the teaching of the present invention, and such equivalents may fall within the scope of the present invention as defined in the appended claims.

The embodiment of the invention relates to a photocuring three-dimensional printing preview method, which is based on a free radical crosslinking reaction model, wherein the three-dimensional printing process is usually carried out in an air atmosphere, and active free radicals generated in the oxygen capture reaction process are introduced into an oxygen inhibition model in the classical chain initiation, chain growth and chain termination mechanisms; the method is characterized in that a fixed-step Eulerian method is used for solving a dynamic differential equation set and deriving a time-varying numerical value of each variable, so that a three-dimensional printing preview effect is simulated, and the method specifically comprises the following steps:

(1) obtaining a relation curve of the conversion rate of the photosensitive resin system and the time under different curing conditions by measuring the relation between the absorbance of the photosensitive resin system and the time under different curing conditions; the method specifically comprises the following steps: measuring the change of the absorbance of functional groups of 3-7 groups of photosensitive resin with time under different curing conditions (different ultraviolet light source intensities, different photoinitiator contents and the like) by using an in-situ Fourier transform infrared spectrometer, and converting the change into a change curve of the conversion rate with time by an internal standard method.

(2) Fitting the experimental curve by using an iterative solution method based on a photocuring kinetic equation according to a relation curve of the conversion rate of the photosensitive resin system and time under different curing conditions, and calculating to obtain the photocuring kinetic constant of the photosensitive resin system. For the same curing system, kinetic constants (chain initiation constant, chain growth constant, termination constant) which conform to each experimental curve can be calculated according to input curves of conversion rate with time under different sets of settings. Various parameters of the photosensitive resin free radical photopolymerization reaction involved in the calculation can be set according to experimental measurement results and actual requirements of photocuring printing, and specifically include calculation parameters such as calculation step length, grid size and area size; light intensity of a light source, layer thickness, single-layer exposure time and other curing parameters; resin monomer and initiator density, molar absorption coefficient, temperature, initial molar concentration, etc.

(3) Solving a photocuring reaction kinetic differential equation set by using a fixed-step Euler method to obtain a spatial distribution and time relation curve of the content of each component of the photosensitive resin system in the photocuring reaction process;

(4) measuring a relation curve of incident light transmittance and cured product thickness before and after the photocuring reaction of the photosensitive resin system by using an ultraviolet spectrum;

(5) simulating printing according to the structure, light source intensity, layer thickness and single-layer printing time of the three-dimensional printing product; and combining the spatial distribution of the content of each component in the photocuring reaction process of the photosensitive resin system with a time relation curve to obtain the spatial distribution of the content of each component in each layer structure in the three-dimensional printed product after printing is finished, thereby finishing the photocuring three-dimensional printing preview.

In the process of simulating layer-by-layer curing and stacking, the change of the absorbance of the functional group along with time is collected through infrared spectroscopy, the change is converted into a change curve of the conversion rate along with time through an internal standard method, and then a kinetic constant is obtained, so that the spatial distribution of the content of each component in the reaction process is obtained, and the spatial distribution can be embodied in a mode that the data or the numerical value represented by the gradient color displays the spatial content graph of any component according to the selected section.

The invention is further illustrated by the following specific example.

Step one, collecting a photosensitive resin curing infrared spectrum

Preparing epoxy acrylic resin containing 1%, 2% and 3% of 2,4, 6-trimethylbenzoyl-diphenyl phosphine oxide respectively, dividing the epoxy acrylic resin into three groups for experiment, adopting an in-situ photocuring Fourier transform infrared spectrometer for each group of resin, and realizing ultraviolet photocuring in-situ infrared spectrum detection through an optical path system: ultraviolet light is projected to the surface of the sample through an optical fiber, and the energy density of the light source is measured by an ultraviolet light power meter to realize closed-loop control. The liquid resin was placed between two pieces of potassium bromide salt windows, 1mm thick, and surrounded by an annular member, fixing the thickness and preventing the liquid monomer from leaking out. The infrared light source enters the detector after penetrating the sample to be detected, and the infrared spectrum of the sample is measured by the computer at intervals. The in-situ photocuring Fourier transform infrared spectrometer optical path system and the liquid resin sample are installed as shown in FIG. 1. As can be seen in fig. 1, the fiber is mounted in a position to project light from the curing light source and cover the potassium bromide window surface and the uv detector area. At the same time, the infrared beam passes through the sample wafer and into the infrared detector via the mounted mirror.

Step two, calculating the kinetic parameters of the photosensitive resin

And (3) selecting a characteristic peak according to the infrared spectrum data of the monomer, calculating a monomer conversion curve according to the reduction of the absorption peak relative to the initial state, and obtaining monomer conversion curves with different curing parameters according to the experimental results of different initiator concentrations. Setting calculation parameters including calculation step length, grid size, area size and other calculation parameters; light intensity of a light source, layer thickness, single-layer exposure time and other curing parameters; resin monomer and initiator density, molar absorption coefficient, temperature, initial molar concentration and other physical properties, and chain initiation constant, chain propagation constant, termination constant and other estimated values of reaction kinetic constants. And the calculation program automatically calculates the experimental value of the reaction kinetic constant according to the input parameters. The characteristic peak-monomer concentration curve of the infrared spectrum of the monomer is shown in FIG. 2, and it can be seen from FIG. 2 that the intensity of the characteristic peak of the infrared spectrum absorption is linearly related to the monomer concentration. The monomer conversion curves of different curing parameters obtained from the infrared spectrum data and the simulation calculation data are shown in fig. 3, and it can be seen from fig. 3 that the infrared spectrum data and the simulation calculation data have higher matching degree. The result of the calculation of the kinetic constant of the photosensitive resin is shown in fig. 4, and it can be seen from fig. 4 that the change of the kinetic constant causes the change of the conversion rate curve of the simulation calculation, the conversion rate curve is gradually close to the experimental curve through a plurality of iterations of the kinetic constant, and the kinetic constant finally matched with the experimental result is the kinetic constant of the experimental data. The values of the photocuring calculation parameters are shown in table 1.

Step three, calculating the photocuring three-dimensional printing curing process

Inputting a three-dimensional model file, setting calculation parameters and curing parameters, performing simulation calculation on a curing process by a program according to the setting, finally outputting various parameter time and space distribution data including monomer conversion rate, light intensity and initiator concentration, and generating a three-dimensional printing forming effect preview according to the calculation data. Comparison of curing thicknesses of three-dimensional printing layers under different additive concentrations referring to fig. 5, fig. 5 shows the spatial distribution of the conversion rate of the photocuring three-dimensional printing simulation curing monomer at the last moment, from which it can be seen that the higher the absorbance of the photocuring three-dimensional printing resin is, the smaller the curing depth is, and the smaller the layer thickness is. The comparison of the three-dimensional printing forming effects of different single-layer exposure times is shown in fig. 6, and it can be seen that the exposure time has a great influence on the photocuring forming quality, and the photocuring forming quality is greatly improved after the three-dimensional printing preview optimization.