CN117681438A - Method and system for 3D printing appliance based on gray scale regulation and control - Google Patents
Method and system for 3D printing appliance based on gray scale regulation and control Download PDFInfo
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Abstract
The invention discloses a method and a system for 3D printing of an appliance based on gray level regulation. The method comprises the following steps: preparing a photosensitive resin, wherein a UV light absorber is added into the photosensitive resin; dividing a region corresponding to the appointed teeth from a 3D printing model of the appliance, and modifying the gray scale of the region corresponding to the appointed teeth; slicing the 3D printing model of the appliance to obtain a plurality of slice patterns; completing the first curing of each layer of the appliance based on each slice pattern, wherein the wavelength of the light of the first curing is the first wavelength; and (3) performing secondary curing on the appliance by adopting light with a second wavelength, thereby completing 3D printing of the appliance. The gray scale is regulated and controlled, so that larger correction amount can be realized during correction without causing discomfort of a patient; the phenomenon of stress relaxation of the bracket-free invisible orthodontic appliance can be relieved, and excessive errors are not introduced compared with a 4D printing appliance.
Description
Technical Field
The invention relates to the technical field of 3D printing, in particular to a method and a system for 3D printing correction appliances based on gray level regulation.
Background
At present, a hot-pressed film forming technology is adopted for manufacturing a transparent appliance on the market, a doctor obtains an intraoral model of a patient through a digital scanner, 3D printing of the dental model of the patient is performed in a factory after three-dimensional software design, then a film is heated to cover the printed dental model, and the corresponding transparent appliance can be obtained after the film is cooled. However, the hot-pressed film forming process reduces the thickness of the appliance compared to the original size of the film sheet, which affects the mechanical properties and clinical treatment effects thereof, the uniformity of the thickness of the appliance plays an important role in the magnitude of the orthodontic force, and the difference in thickness affects the accuracy and the adaptability to teeth, which makes it difficult to realize the controllability of the orthodontic force by the existing bracket-free invisible orthodontic appliance. And because each group of transparent appliances are pressed and a corresponding physical three-dimensional model is needed, the pressed appliances are trimmed, and the processes are time-consuming and labor-consuming, and the problem of resource waste is caused.
Therefore, direct 3D printing of transparent appliances (bracket-free invisible orthodontic appliances) is an object of interest. The use of 3D printed bracket-less invisible orthodontic appliances can reduce the cumulative errors introduced by the printing of dental casts and subsequent thermoforming workflow and can provide a more uniform thickness.
In order to realize the correction force regulation of the bracket-free invisible orthodontic appliance, three technical routes are currently known to be developed.
The first is to design a multi-layer material appliance, by combining a rigid material surface with an inner layer of an elastic material, gentle and continuous stable orthodontic forces can be applied to the teeth, and the ratio of soft to hard surfaces can be designed to better control orthodontic treatment. The method can realize the regulation and control of the correction force to a certain extent, but can also cause the thickness increase of the correction device, thereby improving the uncomfortable feeling of wearing.
The second is to modify the thickness of the appliance model in digital model software using the digital characteristics of the 3D printing. By detecting movement of the teeth, the operator adds additional thickness to the appliance model for that area of teeth, thereby adjusting the amount of appliance force experienced by the teeth. Such a direct 3D printed transparent appliance can provide a more uniform thickness and enable customization of the thickness, but it relies on the functionality of the modeling software, the mechanisms of different software tooth motion detection are not the same, which may have an impact on customization of the thickness, and modification of the thickness may result in reduced transparency of the appliance.
The third is 4D printing based on shape memory materials that change shape over time under given environmental conditions. By utilizing the shape memory characteristic, the geometric shapes of different teeth correction positions in the orthodontic treatment process are recorded, so that a single appliance can realize multi-step tooth movement through continuous recovery of the shapes. The 4D printing bracket-free invisible orthodontic appliance can solve the problems of excessive use of accessories and the like, but because a single orthodontic appliance can affect a plurality of steps, if an error occurs in one step, the error can affect the subsequent orthodontic links and is accumulated continuously.
The appliance is formed layer by layer in the 3D printing process, so that layering exists on the surface of the appliance after printing, the roughness of the surface is affected, and the transparency of the appliance is reduced. In order to achieve high transparency of 3D printed appliance surfaces, two technical routes are currently known to be developed.
The first is a method for producing fine droplets: the method comprises the steps of depositing droplets of printing material one by one or one on top of the other, and solidifying the deposited droplets by light irradiation to build up a three-dimensional pre-model; the second step is to make at least one plane of the three-dimensional pre-model in a smooth state by using supplementary droplets at the boundary region of adjacent deposited droplets and/or the edge of the surface, thus printing a three-dimensional structure having a smooth surface. The proposal can well form a smooth surface, but has high control precision on equipment and high manufacturing cost.
The second is a light scattering scheme, which allows for the 3D printing projector to achieve pattern variation by pixels, but the light intensity of individual pixels is not evenly distributed due to hardware limitations. This results in a step effect also in the single layer of the printed object. According to the scheme, the phenomenon that the light intensities of all pixels are crossed is caused by reducing the definition degree of pattern light projected to a focal plane (the bottom of a trough and the initial curing surface of resin), so that the effect that the light intensity of one plane is uniform is achieved, the bulges and the hollows on the surface of a printing body are reduced, and the transparency of a printing object is improved. However, this solution does not improve the layering problem, and the transparency problem still exists. In addition, as the sharpness of the pattern light decreases, the minimum feature accuracy that can be printed in a plane also decreases.
Disclosure of Invention
The present invention has been made in view of the above problems, and an object thereof is to provide a method and system for gray scale based 3D printing appliances that overcomes or at least partially solves the above problems.
One embodiment of the present invention provides a method of gray scale control based 3D printing appliances, the method comprising:
preparing a photosensitive resin, wherein a certain proportion of UV light absorbent is added into the photosensitive resin;
dividing a region corresponding to a specified tooth from a 3D printing model of the appliance, and modifying the gray level of the region corresponding to the specified tooth;
slicing the 3D printing model of the appliance to obtain a plurality of slice patterns;
completing first curing of each layer of the appliance based on each slice pattern, the wavelength of light of the first curing being a first wavelength;
performing secondary curing on the appliance by adopting light with a second wavelength, thereby completing 3D printing of the appliance;
wherein the absorbance of the light of the first wavelength is smaller than the absorbance of the light of the second wavelength by the photosensitive resin added with the UV light absorber.
Optionally, the preparing a photosensitive resin includes:
adding the UV light absorbent and the photosensitive resin into a light-resistant container, placing the light-resistant container into a stirrer for stirring for a certain period of time to obtain a stirred mixture, and then placing the mixture into an ultrasonic machine for ultrasonic dispersion for a certain period of time to obtain the photosensitive resin for printing.
Optionally, the proportion of the UV light absorber is 0.3% -1%.
Optionally, the UV light absorber is a UV-327 light absorber.
Optionally, the first wavelength is 405nm and the second wavelength is 365nm.
Optionally, the modifying the gray scale of the area corresponding to the designated tooth includes:
the gray level of the area corresponding to the designated tooth is turned up or down.
Optionally, the step of lowering the gray level of the area corresponding to the designated tooth includes:
the gray level of the area corresponding to the designated tooth is reduced by 40% -60%.
Optionally, in the case of turning down the gray scale of the area corresponding to the designated tooth, the method further includes:
and acquiring the surface pixels of the appointed teeth, and recovering the gray values of the surface pixels of the appointed teeth to be original values.
Optionally, the acquiring the surface pixel of the specified tooth includes:
acquiring edges of the corresponding slice patterns of the designated teeth, wherein the edges of the corresponding slice patterns of the designated teeth are surface pixels in the horizontal direction of the designated teeth;
and acquiring surface pixels in the vertical direction of the appointed teeth according to the difference value of gray values of the pixels of the adjacent slice patterns.
Optionally, before the second curing of the appliance with light of the second wavelength, the method further comprises:
and driving the appliance to rotate at a specified speed by using a centrifugal rotating device for a plurality of times, wherein residual resin on the surface of the appliance after centrifugal rotation cannot be completely thrown out, and a thin layer is left to be attached to the surface of the appliance.
Alternatively, the specified speed is 1000-5000rpm and the number of times is 20-60s.
Another embodiment of the present invention provides a system for gray scale based 3D printing appliances employing a method of gray scale based 3D printing appliances as described above.
The invention has the beneficial effects that the gray scale of the area corresponding to the designated teeth in the bracket-free invisible orthodontic appliance model is modified, and the crosslinking degree of the area is controlled by utilizing the change of the light intensity, so that the Young modulus of the area is changed, and the areas with different hardness are created, which means that the customized design can be provided for the orthodontic force of the teeth, thereby achieving the effect of regulating and controlling the orthodontic force. The thickness of the appliance model is not modified, which means uniform thickness; by regulating and controlling the gray scale, larger correction amount can be realized during correction without causing discomfort of a patient; and as the appliance can continuously increase the internal crosslinking degree along with the time, the rigidity of the appliance continuously increases, the phenomenon of stress relaxation of the bracket-free invisible orthodontic appliance can be relieved, the correction efficiency of a single appliance is improved, and in addition, compared with a 4D printing appliance, the appliance cannot introduce excessive errors.
The secondary curing process enables the modulus inside the appliance to change more uniformly, and can provide more stable correction force. Since the non-cured areas within the appliance will gradually cure over time under visible light illumination, a higher amount of movement can be provided for the appliance to maintain an acceptable level of force for the patient. Meanwhile, as the inside is continuously solidified, the modulus of the area is continuously increased, the stress relaxation phenomenon of the appliance can be resisted, and the clinical efficiency is improved.
In addition, the invention also considers the problem of cytotoxicity caused by low crosslinking degree, and the UV light absorber is added into the resin for printing the bracket-free invisible orthodontic appliance, so that the printed orthodontic appliance can be completely solidified on the surface during secondary solidification, and the internal mechanical property is not obviously influenced.
The invention also utilizes the centrifugal rotating device to spin-dry the residual resin on the surface of the appliance, eliminates the surface lines of the appliance, and realizes higher transparency and smoother surface. The smoother surface of the appliance makes it difficult for bacteria to adhere to the surface of the appliance, thereby reducing the risk of the patient suffering from periodontitis.
Drawings
FIG. 1 is a flow chart of a method of gray scale control based 3D printing appliance according to one embodiment of the present invention;
FIG. 2 is a schematic diagram of a system of gray scale control based 3D printing appliances according to one embodiment of the present invention;
FIG. 3 is a schematic diagram showing the absorbance of light of different wavelengths after adding UV-327 light absorber to photosensitive resin according to one embodiment of the present invention;
FIG. 4A is a schematic view of the penetration depth of a light-sensitive resin according to one embodiment of the present invention irradiated with 405nm light after adding a UV-327 light absorber;
FIG. 4B is a schematic view of the penetration depth of a photosensitive resin according to one embodiment of the present invention irradiated with 365nm light after adding a UV-327 light absorber;
FIG. 5 is a schematic representation of a slice pattern of an appliance after gray scale modification of a given tooth in accordance with one embodiment of the present invention;
FIG. 6 is a schematic representation of a slice pattern with the gray scale of a surface pixel of a tooth designated for gray scale modification adjusted in accordance with one embodiment of the present invention;
FIG. 7 is a schematic representation of a three-dimensional model of an appliance after internal gray scale modification to a designated tooth of the appliance according to one embodiment of the present invention;
FIG. 8 is a schematic illustration of a bioactivity test of an appliance after secondary curing in accordance with an embodiment of the present invention; FIG. 9 is a schematic view of a centrifugal rotating apparatus according to an embodiment of the invention;
FIG. 10A is a schematic view of an appliance subjected to centrifugation in accordance with one embodiment of the present invention;
FIG. 10B is a schematic illustration of an appliance without centrifugation according to one embodiment of the present invention;
FIG. 11 is a schematic diagram of an appliance after centrifugation for a second light cure according to one embodiment of the present invention;
FIG. 12A is an enlarged view of the centrifuged appliance surface according to one embodiment of the present invention;
FIG. 12B is an enlarged view of an appliance surface without centrifugation according to one embodiment of the present invention;
FIG. 13A is a schematic view of a centrifuged appliance surface under a microscope according to one embodiment of the present invention;
FIG. 13B is a schematic view of an appliance surface without centrifugation under a microscope according to one embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the present invention more apparent, the embodiments of the present invention will be described in further detail with reference to the accompanying drawings.
Fig. 1 is a flow chart of a method of gray scale control based 3D printing appliance according to one embodiment of the present invention. As shown in fig. 1, the method of the embodiment of the present invention includes:
s11: preparing a photosensitive resin, wherein a certain proportion of UV light absorbent is added into the photosensitive resin;
it will be appreciated that the purpose of the UV light absorber is to absorb excess UV light and inhibit polymerization.
S12: dividing a region corresponding to a specified tooth from a 3D printing model of the appliance, and modifying the gray level of the region corresponding to the specified tooth;
it will be appreciated that the basic principle of embodiments of the present invention is to modify the local modulus of the appliance model with gray scale to adjust the impact on the appliance force. In the pretreatment process of the model, the correction force of the partial area of the appliance model needs to be adjusted according to the requirement, and the gray level of the area is modified.
S13: slicing the 3D printing model of the appliance to obtain a plurality of slice patterns;
in practical application, the model is sliced by using 3D printing software to obtain a plurality of slice patterns.
The gray value in the slice pattern is positively correlated with the light intensity value of the projection pattern light, and when the gray value is high, the light intensity is high, and the more energy the resin receives, the higher the solidification degree.
S14: completing first curing of each layer of the appliance based on each slice pattern, the wavelength of light of the first curing being a first wavelength;
s15: performing secondary curing on the appliance by adopting light with a second wavelength, thereby completing 3D printing of the appliance;
wherein the absorbance of the light of the first wavelength is smaller than the absorbance of the light of the second wavelength by the photosensitive resin added with the UV light absorber.
In the embodiment of the invention, a certain proportion of UV light absorbent should be added into the photosensitive resin, and two light sources with different wavelengths are needed to be used for carrying out the first curing and the second curing, and the absorbance of the photosensitive resin added with the UV light absorbent to the light with the first wavelength is smaller than that to the light with the second wavelength.
According to the embodiment of the invention, the gray scale of the area corresponding to the designated teeth in the bracket-free invisible orthodontic appliance model is modified, and the crosslinking degree of the area is controlled by utilizing the change of the light intensity, so that the Young modulus of the area is changed, and the areas with different hardness are created, which means that the customized design can be provided for the orthodontic force of the teeth, and the effect of regulating and controlling the orthodontic force is achieved. The thickness of the appliance model is not modified, which means uniform thickness; by regulating and controlling the gray scale, larger correction amount can be realized during correction without causing discomfort of a patient; and as the appliance can continuously increase the internal crosslinking degree along with the time, the rigidity of the appliance continuously increases, the phenomenon of stress relaxation of the bracket-free invisible orthodontic appliance can be relieved, the correction efficiency of a single appliance is improved, and in addition, compared with a 4D printing appliance, the appliance cannot introduce excessive errors.
The secondary curing process enables the modulus inside the appliance to change more uniformly, and can provide more stable correction force. Since the non-cured areas within the appliance will gradually cure over time under visible light illumination, a higher amount of movement can be provided for the appliance to maintain an acceptable level of force for the patient. Meanwhile, as the inside is continuously solidified, the modulus of the area is continuously increased, the stress relaxation phenomenon of the appliance can be resisted, and the clinical efficiency is improved.
In addition, the invention also considers the problem of cytotoxicity caused by low crosslinking degree, and the UV light absorber is added into the resin for printing the bracket-free invisible orthodontic appliance, so that the printed orthodontic appliance can be completely solidified on the surface during secondary solidification, and the internal mechanical property is not obviously influenced.
In an alternative implementation of the embodiment of the present invention, the preparing a photosensitive resin includes:
adding the UV light absorbent and the photosensitive resin into a light-resistant container, placing the light-resistant container into a stirrer for stirring for a certain period of time to obtain a stirred mixture, and then placing the mixture into an ultrasonic machine for ultrasonic dispersion for a certain period of time to obtain the photosensitive resin for printing.
In practical application, the stirring time period may be 10 minutes, and the ultrasonic dispersion time may be 15 minutes.
Specifically, the proportion of the UV light absorber is 0.3% -1%. Preferably, the proportion of UV light absorber is 0.5%
Preferably, the UV light absorber is a UV-327 light absorber.
Preferably, the first wavelength is 405nm and the second wavelength is 365nm.
It can be understood that by adding a certain amount of UV light absorber, 405nm light used for curing is not absorbed by the absorber in the first curing to realize printing with different gray scales, and 365nm light is used for curing in the second curing, and the light is limited to the shallow layer area of the appliance due to strong absorption of the absorber, so that the surface of the appliance has high crosslinking degree, the inside of the appliance still has low crosslinking degree, and the biotoxicity of the printed appliance is reduced on the basis of keeping the regulation of mechanical properties.
Another embodiment of the present invention provides a system for gray scale based 3D printing appliances employing a method of gray scale based 3D printing appliances as described above. In practice, the hardware composition of the system of 3D printing appliances may utilize existing techniques.
Fig. 2 is a schematic diagram of a system of gray scale control based 3D printing appliances according to one embodiment of the present invention. In order to better understand the technical solution of the embodiment of the present invention, the following description is given with reference to fig. 2.
As shown in fig. 2, the system for 3D printing an appliance according to an embodiment of the present invention includes a stepper motor 1, a guide rail 2, a printing platform 3, a trough 5 filled with photosensitive resin 4, a mirror 6, a motor driver 7, a display 8, a DLP light engine 9, and a control motherboard 10. Wherein the stepper motor 1 is used for controlling the movement of the printing platform 3; the guide rail 2 is used to limit the moving direction of the printing platform 3 so that the printing platform 3 can move in the vertical direction; the printing platform 3 is connected with the guide rail 2 through a cross beam, and a printing body is formed on the printing platform 3; the reflecting mirror 6 is used for reflecting the projection light to the bottom of the trough 5; the motor driver 7 is used for driving the stepping motor 1 to move; the display 8 is used for providing an operation interface; a DLP optical machine 9 for projecting pattern light; the control main board 10 is responsible for control of the overall 3D printing flow. The operator can operate via the display 8 to set the printing parameters. The printing parameters comprise the moving speed and the moving distance of the printing platform, the set printing layer thickness and the exposure time of the DLP optical machine. The moving speed and moving distance of the printing platform can influence the printing success rate of the printing body, the thickness of the printing layer can influence the printing precision of the printing body in the vertical direction, the exposure time can influence the success rate and precision of printing, if the exposure is small, the adhesion failure between the layers can be caused due to insufficient resin curing, and the excessive exposure can cause over-curing to influence the precision of the printing body. The control main board 10 transmits the slice pattern into the DLP optical machine 9 and projects the slice pattern, after a certain time of exposure, the photosensitive resin of the corresponding pattern in the trough 5 is solidified, and the DLP optical machine 9 is closed. Subsequently, the stepper motor 1 starts to move upwards after receiving the control command, so that the solidified resin is separated from the bottom surface of the trough 5, and the printing process of one layer is completed. And then the DLP optical machine projects the next slice pattern, and the slice pattern undergoes the same process, so that the appliance with gray scale is finally manufactured.
Specifically, the modifying the gray scale of the area corresponding to the designated tooth includes:
the gray level of the area corresponding to the designated tooth is turned up or down.
The gray value in the slice pattern is positively correlated with the light intensity value of the projection pattern light, and when the gray value is high, the light intensity is high, and the more energy the resin receives, the higher the solidification degree. When the gray scale of the region corresponding to the designated tooth is turned down, the light intensity of the region is reduced, so that the curing degree of the photosensitive resin of the region is reduced, thereby reducing the modulus of the region. Conversely, when the gray level of the region corresponding to the designated tooth is increased, the light intensity of the region is increased, so that the curing degree of the photosensitive resin of the region is increased, thereby increasing the modulus of the region.
The modulus is in a proportional relation with the correction force, and the correction force is regulated and controlled after the modulus of the appointed tooth area is regulated based on gray modification.
Further, the step of lowering the gray level of the region corresponding to the designated tooth includes:
the gray level of the area corresponding to the designated tooth is reduced by 40% -60%.
FIG. 3 is a schematic diagram showing the absorbance of light of different wavelengths after adding UV-327 light absorber to photosensitive resin according to one embodiment of the present invention.
FIG. 4A is a schematic representation of the penetration depth of a light irradiation with 405nm light after adding UV-327 light absorber to a photosensitive resin according to one embodiment of the present invention. FIG. 4B is a schematic representation of the penetration depth of a photosensitive resin according to one embodiment of the present invention irradiated with 365nm light after the addition of UV-327 light absorber.
As shown in fig. 3, 4A and 4B, in the embodiment of the present invention, the first curing is performed using a DLP light engine with a light source wavelength of 405nm, and the added UV light absorber hardly absorbs light with a wavelength of 405nm, so that the resin curing is not affected, and the modulus of a local area is reduced due to the graying treatment of the area in the slice pattern. In the second curing, the light source used is 365nm, and at the wavelength, the resin is continuously cured after being irradiated by light, but the light absorbent added has strong absorptivity to 365nm light, so that the penetration of the light is limited, the shallow curing degree of the printing appliance is improved, the deep curing degree is hardly changed, and the function of adjusting the correcting force is reserved on the basis of reducing the biotoxicity of the printing appliance.
Preferably, the gray scale of the area corresponding to the designated tooth is reduced by 50%. As shown in fig. 5, the designated tooth position is the incisor, and the gray scale of the region corresponding to the incisor is reduced by 50%, and the effect after the reduction is as shown in fig. 5.
Further, in the case of turning down the gradation of the region corresponding to the specified tooth, it further includes:
and acquiring the surface pixels of the appointed teeth, and recovering the gray values of the surface pixels of the appointed teeth to be original values.
It is appreciated that in view of the biotoxicity of the photosensitive resin and its higher degree of cure, the lower the toxicity, and therefore the need to increase the surface cure of the appliance. In the graying treatment of the model, since the gray value of the region of the designated tooth is reduced, the degree of curing of the region is reduced to increase the biotoxicity thereof, and the region of which the gray value is modified is subjected to the treatment of enhancing the degree of curing of the surface. The thinking of the processing operation is that firstly, the surface pixels of the appointed teeth are obtained, and the gray values of the surface pixels of the appointed teeth are restored to the original values, so that the exposure is improved, and the surface solidification degree of the modified area is enhanced.
Specifically, the acquiring the surface pixel of the specified tooth includes:
acquiring edges of the corresponding slice patterns of the designated teeth, wherein the edges of the corresponding slice patterns of the designated teeth are surface pixels in the horizontal direction of the designated teeth;
and acquiring surface pixels in the vertical direction of the appointed teeth according to the difference value of gray values of the pixels of the adjacent slice patterns.
It will be appreciated that acquisition of surface pixels in the vertical direction requires calculation of differences in gray values of individual pixels of adjacent two-layer slice patterns. For example, if a pixel a is a model surface pixel, the gray value of the corresponding pixel B of the slice pattern adjacent to it is 0, which means that the B pixel position has no pattern, and also indicates that the a pixel position is a model surface. Then by differencing the two slices of the model, if the model surface, the difference for the corresponding pixel is the absolute value of the a pixel. And then, according to the set gray value of 50%, screening out pixels with the difference value matched with 50% gray, wherein the pixels are the surface area of the model in the vertical direction.
After the surface pixels of the model are obtained, the gray values are modified back to 100%, the purpose of this operation is to increase the surface light flux of the printed appliance, increase the surface solidification degree, and fig. 6 is a slice image after the gray values of the surface pixels are modified. After the gray level is modified, the three-dimensional schematic of the model is shown in fig. 7, the interior of the tooth corresponding to the modified gray level of the appliance has a 50% gray level value, and the surface has a 100% gray level value.
And (3) importing the modified model slice pattern into a control main board, and starting the first curing treatment after setting the printing parameters. The process uses DLP light machine as curing light source, the wavelength of projection light is 405nm, and the light intensity is 11.6mW/cm 2 . As can be seen from fig. 3, the light absorber does not have strong absorption to 405nm light, the first curing can print out the appliance, and gray scale control is realized.
After printing, the surface of the printing model was washed with ethanol and then subjected to a second curing treatment using a 365nm light source with a light intensity of 73.6mW/cm 2 . As can be seen from fig. 4B, the absorber has strong absorption to 365nm light, so the light intensity can be rapidly attenuated with the increase of the penetration depth curedepth, so that the effective light intensity is limited to the shallow region of the appliance, and the internal mechanical property regulation can be maintained on the basis of improving the surface solidification degree of the appliance. The second curing method is to put the printed appliance on a turntable rotating at a constant speed, and then add a 365nm secondary curing light source for irradiation for 20 minutes.
In practical application, the modulus of a local tooth is reduced by a gray level regulating method, and when the movement of a certain tooth needs to be accurately controlled, the modulus of two teeth around the tooth can be reduced, so that the influence of the moving tooth on the non-moving tooth is reduced.
FIG. 8 is a schematic illustration of a bioactivity test of an appliance after a secondary cure in accordance with an embodiment of the present invention. As shown in FIG. 8, the ordinate is cell activity and the abscissa is the concentration of added UV light absorber. And (3) printing a wafer with the thickness of 0.8mm and the diameter of 7mm, and performing secondary curing by using 365nm light after primary curing. The samples were soaked with ethanol. The sample is immersed in the cell culture solution to prepare an extract. After 48h of culture, extracting the extracting solutions with the concentration of 100% and the extracting solutions with the concentration of 50% respectively, and calculating the cell activity of the extracting solutions, the result shows that the whole cell activity is more than 70%. The 3D printing appliance of the embodiment of the invention can meet the requirement of biological activity.
Further, before the second curing of the appliance with light of the second wavelength, the method further comprises:
and driving the appliance to rotate at a specified speed by using a centrifugal rotating device for a plurality of times, wherein residual resin on the surface of the appliance after centrifugal rotation cannot be completely thrown out, and a thin layer is left to be attached to the surface of the appliance.
Specifically, the specified speed is 1000-5000rpm, and the times are 20-60s.
The invention also utilizes the centrifugal rotating device to spin-dry the residual resin on the surface of the appliance, eliminates the surface lines of the appliance, and realizes higher transparency and smoother surface. The smoother surface of the appliance makes it difficult for bacteria to adhere to the surface of the appliance, thus reducing the risk of periodontitis.
According to the invention, the once solidified appliance is connected with the high-speed rotating motor, and the appliance is driven to rotate at a high speed by the rotation of the motor. Under the action of rotation, surplus residual resin on the surface of the appliance can be thrown away from an object, and a layer of film can be remained on the surface of the printing body after the printing body rotates at a high speed due to the capillary action of the resin, so that the printing body can be well covered with the layer patterns, and then secondary solidification treatment is carried out, so that the manufacturing of a smooth surface is realized.
Fig. 9 is a schematic view of a centrifugal rotating apparatus according to an embodiment of the invention. As shown in fig. 9, a first motor 9001 is used for providing torque to drive a printing object 9007 to rotate, a first rigid coupler 9002 is used for switching a motor joint, a screw rod 9005 is used for connecting the first rigid coupler 9002 and a printing platform 9006, the first motor 9001 is connected with the printing platform 9006 through the first rigid coupler 9002 and is responsible for driving the printing platform 9006 to rotate, and therefore the printing object 9007 on the printing platform 9006 is driven to rotate.
The second motor 9011 is connected to the moving rail 9003 through a second rigid coupling 9012, and is configured to drive the support 9004 to move up and down through the moving rail 9003.
The UV light source 9008 is used for secondary curing after the centrifugal processing of the print object 9007. The guard 9009 is fixed for preventing the printing platform 9006 or the printing object 9007 from accidentally flying off when rotated at a high speed. The operation flow of the specific centrifugal treatment is as follows: the printing platform after printing is taken down from the 3D printer, the printing object is not taken down, then the printing platform is arranged on the centrifugal rotating device, after the printing platform is fixed, the rotating speed of the first motor 9001 and the rotating time are set, the rotating speed is set at 1000-5000rpm, the rotating time is set at 20-60s, the printing object 9007 starts to rotate, and the surface resin can be thrown off the surface of the printing object 9007 under the action of centrifugal force. After the waiting time is over, the first motor 9001 is turned down, the UV light source 9008 is turned on, and the surface of the print object 9007 is cured by irradiation of UV light. Subsequently, the UV light source 9008 is turned off, and the moving guide 9003 moves the print object 9007 away from the region where the protective shutter 9009 can provide protection. The print object 9007 is removed, and the surface of the print object 9007 is cleaned with alcohol, thereby completing the production of the transparent member.
Considering that the performance of the printed object is related to the resin used, the rotation speed of the first motor 9001 needs to be controlled, if the viscosity of the resin used is high, the rotation speed and rotation time of the motor need to be increased, the centrifugal force is increased, and the bottom heater 9010 is turned on to reduce the viscosity of the resin. If the resin viscosity is low, it is not necessary to provide an excessive motor speed.
FIG. 10A is a schematic view of an appliance subjected to centrifugation in accordance with one embodiment of the present invention; FIG. 10B is a schematic of an appliance without centrifugation according to one embodiment of the present invention. By comparison, it can be seen that the surface of the centrifuged appliance is smoother and more transparent.
FIG. 11 is a schematic diagram of an appliance after centrifugation for a second light cure according to one embodiment of the present invention. After the whole primary solidified appliance is subjected to centrifugal treatment, the half side part is subjected to shading treatment, then, only the left side is subjected to secondary solidification, a resin film is reserved, then, the left side is washed by alcohol, and after the uncured film on the right side is washed cleanly, the surface is not transparent any more.
FIG. 12A is an enlarged view of the centrifuged appliance surface according to one embodiment of the present invention; FIG. 12B is an enlarged view of an appliance surface without centrifugation, according to one embodiment of the present invention. By comparison, it can be seen that the layering of the centrifuged appliance surface is significantly improved.
FIG. 13A is a schematic view of a centrifuged appliance surface under a microscope according to one embodiment of the present invention; FIG. 13B is a schematic view of an appliance surface without centrifugation under a microscope according to one embodiment of the present invention. By comparison, it can be seen that the layering of the centrifuged appliance surface is filled. According to the invention, layering of the 3D printing appliance can be reduced in a centrifugal rotation mode, the smoothness of the printing appliance is improved, the high transparency of the 3D printing appliance is realized, and the printing appliance can be applied to high-viscosity resin.
It should be noted that:
in the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In some instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description.
Similarly, it should be appreciated that in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. However, the disclosed method should not be construed as reflecting the intention that: i.e., the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.
Furthermore, those skilled in the art will appreciate that while some embodiments described herein include some features but not others included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments.
The foregoing is merely a specific embodiment of the invention and other modifications and variations can be made by those skilled in the art in light of the above teachings. It is to be understood by persons skilled in the art that the foregoing detailed description is provided for the purpose of illustrating the invention more fully, and that the scope of the invention is defined by the appended claims.
Claims (12)
1. A method of gray scale control based 3D printing appliance comprising:
preparing a photosensitive resin, wherein a certain proportion of UV light absorbent is added into the photosensitive resin;
dividing a region corresponding to a specified tooth from a 3D printing model of the appliance, and modifying the gray level of the region corresponding to the specified tooth;
slicing the 3D printing model of the appliance to obtain a plurality of slice patterns;
completing first curing of each layer of the appliance based on each slice pattern, the wavelength of light of the first curing being a first wavelength;
performing secondary curing on the appliance by adopting light with a second wavelength, thereby completing 3D printing of the appliance;
wherein the absorbance of the light of the first wavelength is smaller than the absorbance of the light of the second wavelength by the photosensitive resin added with the UV light absorber.
2. The gray scale control based 3D printing appliance method of claim 1, wherein the preparing a photosensitive resin comprises:
adding the UV light absorbent and the photosensitive resin into a light-resistant container, placing the light-resistant container into a stirrer for stirring for a certain period of time to obtain a stirred mixture, and then placing the mixture into an ultrasonic machine for ultrasonic dispersion for a certain period of time to obtain the photosensitive resin for printing.
3. The gray scale control based 3D printing appliance method of claim 1, wherein the proportion of UV light absorber is 0.3% -1%.
4. The gray scale control based 3D printing appliance method of claim 1, wherein the UV light absorber is UV-327 light absorber.
5. The gray scale control based 3D printing appliance method of claim 1, wherein the first wavelength is 405nm and the second wavelength is 365nm.
6. The gray scale control based 3D printing appliance method of claim 1, wherein modifying the gray scale of the area corresponding to the designated tooth comprises:
the gray level of the area corresponding to the designated tooth is turned up or down.
7. The gray scale control based 3D printing appliance method of claim 6, wherein the gray scale lowering of the area corresponding to the designated tooth comprises:
the gray level of the area corresponding to the designated tooth is reduced by 40% -60%.
8. The gray scale control based 3D printing appliance method of claim 6, further comprising, in the event that the gray scale of the area corresponding to the designated tooth is turned down:
and acquiring the surface pixels of the appointed teeth, and recovering the gray values of the surface pixels of the appointed teeth to be original values.
9. The gray scale control based 3D printing appliance method of claim 8, wherein the acquiring the surface pixels of the designated teeth comprises:
acquiring edges of the corresponding slice patterns of the designated teeth, wherein the edges of the corresponding slice patterns of the designated teeth are surface pixels in the horizontal direction of the designated teeth;
and acquiring surface pixels in the vertical direction of the appointed teeth according to the difference value of gray values of the pixels of the adjacent slice patterns.
10. The gray scale based 3D printing appliance method of claim 1, wherein prior to the second curing of the appliance with light of the second wavelength, the method further comprises:
and driving the appliance to rotate at a specified speed by using a centrifugal rotating device for a plurality of times, wherein residual resin on the surface of the appliance after centrifugal rotation cannot be completely thrown out, and a thin layer is left to be attached to the surface of the appliance.
11. The gray scale control based 3D printing appliance method of claim 10, wherein the specified speed is 1000-5000rpm and the number of times is 20-60s.
12. A gray scale based 3D printing appliance system, wherein the gray scale based 3D printing appliance method of any of claims 1-11 is employed.
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