A more efficient method for producing three-dimensional objects using rapid prototyping

Description

[0001] The invention relates to a device according to claim 1 and a method according to claim 7 for producing three-dimensional objects, in particular at least parts of dental prosthetic restorations, in that a wiping device wipes plastic protruding above a container into a collection container, forming a projection surface. According to the invention, a wiping device and a light source are guided simultaneously over the liquid, light-curing plastic at a defined distance, the wiping device being guided at a defined distance directly in front of the light source and / or the exposure field and forming the projection surface for the exposure field of the light source. The invention also relates to a method for producing a homogenized light distribution using a surface light modulator and to a rapid prototyping method in which such a method is used.

[0002] A level control system for the resin tank during the build process is known from the prior art. For example, a surface sensor and a controller adjust the preset height of the tank (resin level) to maintain the level. The resin level is checked for each layer and, if necessary, adjusted to a preset level. The build process then continues.

[0003] There are also processes in which no regulation of the fill level is required. These processes expose the resin-filled vat from below through a transparent layer. The component is then built up layer by layer. The fill level is only used for carrying out the build process and is not adjusted during the build phase. Such a process is known from EP 2337668 B1.

[0004] Furthermore, there is a technology in which the resin floats on a layer of salt water. This process therefore requires very little resin, thus saving material and a mechanical axis. This is known, for example, from the Peachy Printer.

[0005] US6051179A discloses a device according to the preamble of claim 1.

[0006] WO 95 / 31325 discloses a device in which the container has an overflow for adjusting the level of the curable resin. The overflow can be V-shaped. A device located above the surface, which may include a smoothing element, is used to apply a layer. This device applies a new, uniform layer of the curable resin. A disadvantage of this method is the complex metering and control of the device required for the uniform application of the layer to be polymerized.

[0007] DE4414775 A1 discloses a device for producing three-dimensional objects with a scraper and an inlet and outlet provided in the container, through which material is transported from the bath to the surface when the carrier is lowered. The container has an outlet whose upper edge is lower than the upper edge of the container. A disadvantage of the device is, again, a further positioning device that must be lowered by the amount of the layer thickness in order to set the layer thickness above the carrier (column 3, lines 4 to 40). The material is conveyed directly in front of the scraper, which then distributes it. A further disadvantage arises from the fact that the scraper must first distribute the material over the carrier.

[0008] Another focus of rapid prototyping processes is on the light sources. In addition to ultraviolet (UV) lasers, UV LED projectors are increasingly being used in rapid prototyping. Methods for this are known, for example, from EP 1 880 830 A1 and EP 1 894 705 A2. A disadvantage of lasers is their point-like illumination field. The UV light from the light source is projected onto a light-curing plastic as an illumination field. Optics and an area light modulator are used for this projection. Due to the optics, an inhomogeneous light distribution, or intensity distribution, occurs. The outer regions of the illumination field typically have a lower intensity than the areas in the center. This effect, also known as barrel distortion, means that the light-curing plastic does not receive the same intensity everywhere and therefore cures differently and thus inhomogeneously.

[0009] EP 1 982 824 A2 proposes to homogenize the intensity distribution by reducing the intensity level of the brighter pixels of the UV projector to that of the pixels at the edge by means of a gray distribution.

[0010] A disadvantage of this method is that the desired gray distribution can only be achieved through precise control of the intensity. Therefore, it is also an objective of the invention to provide a less complex method with which a similar effect can be achieved.

[0011] The object of the invention was to provide a constant level of polymerizable material, such as a monomer-based composition, along the z-axis using minimal design elements and without requiring additional positioning or measuring devices. Furthermore, the object was to enable constant fill level control. Additionally, a device was to be developed that allows for a faster build process of three-dimensional objects. In particular, a less complex method was to be provided in which the process steps could be carried out more quickly and, especially, a satisfactory homogenization of the light intensity of the exposure field was to be achieved. The method was to be as cost-effective as possible.

[0012] The objects of the invention are solved by a device according to claim 1 and a method according to claim 7, in which the light-curing plastic is removed planarly from the upper edge of the walls of the container by means of a scraping device along the projection surface. The plastic is preferably a light-curing plastic, such as a composition comprising monomers polymerizable by electromagnetic radiation, preferably dental UV-polymerizable monomers.

[0013] The invention relates to a device comprising, in particular, a component unit with a light source, especially for producing a homogenized light distribution, for producing a three-dimensional object by exposing a liquid, light-curing plastic, with a container for receiving a bath of the light-curing liquid plastic, a build platform for positioning the object relative to the surface (z-axis) of the bath, wherein the container is associated with a feed device for supplying the liquid, light-curing plastic, in particular the feed device is associated with the container below the surface of the bath, wherein the feed device comprises an outlet opening in the container and a line, wherein the line is connected to a pump, furthermore, the container is associated with at least one collection container, in particular two opposing collection containers are associated with the container on either side of the container.The liquid, light-curing plastic, preferably the excess plastic with a convex surface, is transferred into the at least one receiving container by means of a scraper device movable along an axis of the container, preferably into a planar surface. The movable scraper device preferably comprises a squeegee having a planar underside. The squeegee may have a rubber lip.

[0014] The device according to the invention is designed such that it utilizes, for the first time, the surface tension of the light-curing plastic or a polymerizable composition to provide the curable plastic in excess above the last cured layer or above the build platform. Only then is a scraping device, which is fixedly aligned at a defined distance from the top edge of the container, e.g., a height difference of 0.1 mm, used to adjust the planar plastic surface.

[0015] It is particularly preferred if, in the device, the liquid, light-curing plastic, in particular the plastic protruding above the walls of the container, which has a curved surface due to the surface tension of the plastic, can be transferred into at least one receiving container by means of a scraping device movable along an axis, in particular a longitudinal or transverse axis, such as the longitudinal center axis, of the container, wherein in particular a surface, preferably a planar surface, is formed as a projection surface.

[0016] According to the invention, the planar radiating light source, together with the imaged field of the imaged light source (imaged via optics), is guided over a projection surface, wherein the light source is guided along an axis of the container simultaneously by means of a wiping device movable along an axis, in particular a longitudinal or transverse axis, of the container. A device according to the invention thus preferably comprises a complete assembly comprising a wiping device movable along an axis of the container and assembly unit 0, wherein the wiping device is located in front of the light source and / or the imaged field, in particular the assembly unit, and wherein the light source is guided simultaneously along the axis of the container by means of the wiping device movable along an axis of the container.

[0017] Furthermore, the invention relates to a device comprising a component (0) that includes an arrangement, wherein the arrangement comprises a planar radiating light source, a planar light modulator, and optics. A lens system preferably forms the optics. The light source can be a UV laser or a projector, such as a UV LED projector.

[0018] According to a further embodiment, the invention relates to a device with a feed mechanism located below the surface of the bath and associated with the container. In particular, the feed mechanism has an outlet opening in the container and comprises a line connecting the outlet opening and a pump. The outlet opening is preferably located below the surface of the bath.

[0019] The invention also relates to a device with which the liquid, light-curing plastic is fed from the collection container back into the bath via a suction line, in particular through a filter, using a pump, preferably a peristaltic pump or diaphragm pump, and via the feed device. Particular attention must be paid to ensuring a bubble-free feed.

[0020] According to a particularly preferred embodiment of the invention, the device comprises a component 0# – the entire component – ​​comprising a scraper device movable along an axis (x, y-plane) of the container and a smaller component, wherein the scraper device is located in front of the light source of component 0. The scraper device is positioned at a defined distance in front of the light source, in particular 20 to 150 mm, preferably 20 to 80 mm. Preferably, the movable scraper device and the light source of component 0 form a connectable, movable entire component / combined component 0#. According to a preferred embodiment, the scraper device has a coupling device and is moved in front of the light source and / or the illumination field of the light source by means of a blade associated with the light source or component 0.The blade can preferably be guided through a coupling device at the front and rear ends of the container, in the region of the reversal points of the assembly, in order to reposition the scraper device in front of the light source when the entire assembly 0# is moved back along the container. By assigning a blade to the light source or assembly 0 and guiding it through the scraper's coupling device at the endpoints (reversal points of the entire assembly 0# in the container), the blade can, when the assembly changes direction, push the coupling device and thus the scraper device in front of the light source and / or the exposure field. Preferably, the coupling device comprises two elements, in particular trapezoidal elements, preferably symmetrical elements containing at least one trapezoid, which can be pressed together by springs.The elements are preferably designed and aligned such that a notch forms between them in the horizontal plane. This notch allows the blade to widen into a gap by pushing the two spring-mounted elements apart. Through this gap, the blade can be pivoted at the reversal point to guide the coupling device in front of the blade across the plastic surface again when the entire assembly 0# is returned to its starting position. A damper is positioned at the reversal points to stop the squeegee (wiper, slider) and build up pressure until the blade pushes through the aforementioned notch in the coupling device and the resulting gap. Once the blade is positioned on the opposite side of the coupling device, assembly 0 can push the squeegee across the container again in the opposite direction.

[0021] The lower edge(s) of the scraper are set at a defined distance from the planar upper edges of the side walls of the container; preferably, for example, a distance of 0.1 mm can be preset. Alternatively, the scraper can be guided over the planar upper edges of the side walls of the container.

[0022] The component unit 0 – small component unit – comprises an arrangement including a planar light source, a planar light modulator, and the optics, which are preferably a lens system. The light source can be a UV laser or a projector. The projector can, for example, be a projector with DLP (Digital Light Processor) technology from Vitech AS. A micromirror reactor is preferably used in the DLP technology. The optical power of the UV light source is preferably in the range of 0.5 to 100 W. Preferred emission wavelengths of the light source are 340 nm to 500 nm.

[0023] According to a particularly preferred embodiment of the invention, the wiping device is guided simultaneously with the light source in front of the light source's exposure field along an axis of the container (x, y plane) in order to form the layer (x1, y1) of the plastic to be polymerized as a projection surface on which the exposure field is projected and the plastic polymerizes through exposure within the exposure field. "Simultaneous" in the sense of the invention means the simultaneous guidance of the wiping device and the light source along an axis of the container. According to the invention, step a), the level control of the bath and the creation of the curved surface, preferably takes place at the reversal point of the exposure process or in the process step in which the assembly has its reversal point.

[0024] The invention also relates to a method according to claim 7 for producing a three-dimensional object, in particular at least a part of a dental prosthetic component, as well as prosthetic components obtainable according to this method, in which the three-dimensional object, such as a dental prosthetic component, is produced layer by layer by producing a layer (x1, y1) as a projection surface of a liquid, light-curing plastic, and polymerizing it at least partially in an exposure field by means of light from a planar radiating light source, wherein a) a layer (x, y) of the liquid, light-curing resin is produced on a build platform or support, or on a polymerized layer, by adjusting the amount of resin in a bath of the liquid, light-curing resin such that i) at the top edge of the side walls of the container, the resin protrudes in height (z-axis) due to the surface tension of the resin and flows into the at least one collection container arranged laterally to the container, forming a convex surface of the protruding resin, or ii) the resin protrudes at the top edge of the walls of the container in height (z-axis) due to the surface tension of the resin, forming a convex surface, and optionally the resin flows into the at least one collection container arranged laterally to the container, subsequently b) the protruding liquid,The light-curing plastic is removed from the curved surface by means of a scraper device movable along an axis, in particular the longitudinal or transverse central axis (x-, y-plane), of the container, and a layer (x1, y1) to be polymerized is obtained, in particular a planar surface, and optionally, c) the layer to be polymerized (x1, y1) produced in b) is polymerized as a projection surface of the liquid, light-curing plastic with an exposure field using light from a planar radiating light source, and optionally, d) the build platform is lowered by one layer thickness (z1), and optionally, furthermore, steps a) to d) are repeated at least once or several times in e).

[0025] The building platform is used to adjust the z-axis for the layer-by-layer construction of the objects.

[0026] The process can be carried out statically. In a static process, the movable scraper is moved along an axis of the container. Exposure is achieved using a static light source. According to a particularly preferred embodiment of the invention, however, the light source is movable along an axis of the container and is also preferably coupled to the scraper or the wiping device. According to a particularly preferred embodiment, steps b) and c) are carried out simultaneously. The simultaneous execution of forming the planar surface as a projection surface and the immediately subsequent exposure can be achieved by having a movable wiping device and the light source form a coupleable, movable assembly 0# according to the invention.The wiping device and the light source or the component unit 0 - small component unit - are connectable and decoupleable, in particular mechanically, magnetically and / or electrically, and form the overall component unit 0#.

[0027] Furthermore, the invention relates to a method in which the assembly 0# - overall assembly - comprises a movable scraping device and an assembly 0 - small assembly - wherein the assembly 0 comprises an arrangement comprising a planar radiating light source, a planar light modulator and the optics, in particular a lens system forms the optics.

[0028] A further advantage of the method according to the invention is that the liquid, light-curing plastic from the collection container can be returned to the bath. According to the invention, it is preferred if the device is protected from electromagnetic radiation or is located in a dark room.

[0029] It is further preferred if the method is carried out by performing step a), i) after step d) has been carried out, or ii) after steps c) and preferably d) have been carried out, or iii) after the movable scraper, the light source, or the entire assembly 0# has been moved over the exposure field and is located outside the exposure field, or iv) after the movable scraper, the light source, or the entire assembly 0# is located at a front or rear end of the container, particularly in the region of the reversal point. The front and rear are defined as the areas of the side walls of the container where the scraper and the light source have their reversal points. According to the invention, it is preferred that the level control of the fill level, as in step a), takes place at the reversal points of the exposure process.

[0030] According to a preferred embodiment, the upper edges of the container walls and the lower edge of the scraper device can lie in the plane of the projection surface.

[0031] Furthermore, it is preferred if the assembly for homogenizing the light quantity distribution comprises an area light modulator which has a plurality of controllable tiltable micromirrors arranged in rows and columns, in which the light of an area emitting light source is imaged via an optic and an exposure field of the imaged light source is guided over a projection surface, the projection surface preferably representing the layer (x1, y1), wherein an increasing number of pixels towards the center of the exposure field are not exposed, so that in the time integral a homogenization of the light intensity of all pixels exposed on the projection surface is achieved.

[0032] The invention also relates to a method in which the building units 0# or 0 and thus the exposure field and the wiper device are simultaneously and periodically guided over the projection surface, wherein preferably the surface of a liquid light-curing plastic is used as the projection surface, in particular the layer (x1, y1).

[0033] According to a further object of the invention, a rapid prototyping method is claimed in which a liquid light-curing plastic is exposed according to a method described above, preferably with UV light, wherein the wiping device is guided simultaneously with the exposure field in front of the exposure field of an axis (x, y-plane) of the container, in particular over the container, in order to form the layer (x1, y1) of the plastic to be polymerized as a projection surface on which the exposure field is imaged and the plastic polymerizes by exposure in the exposure field.

[0034] The invention also relates to the use of a device according to the invention for the production of at least parts of dental prosthetic restorations.

[0035] The method can also be modified by using an area light modulator to produce a homogenized light quantity distribution. This modulator has a multitude of controllable tiltable micromirrors arranged in rows and columns, in which the light from a planar radiating light source is imaged via optics and an exposure field of the imaged light source is guided over a projection surface with the area light modulator, whereby an increasing number of pixels towards the center of the exposure field are not exposed, so that a homogenization of the light intensity of all pixels exposed on the projection surface is achieved in the time integral.

[0036] Within the scope of the present invention, a pixel is understood to be the smallest controllable light source from which the image of the projector is composed.

[0037] Suitable area light modulators include, for example, the particularly well-suited DLP® chips from Texas Instruments or Visitech.

[0038] According to the invention, a projector, preferably an LED projector, and particularly preferably a UV LED projector, can be used as the planar emitting light source. Alternatively, a laser system can be used.

[0039] Both the projector and the laser system preferably emit light with a wavelength selected from 180 to 600 nm, preferably from 230 to 500 nm, and particularly preferably from 340 to 500 nm. Generally, polychromatic light sources can be used as projectors, although monochromatic or essentially monochromatic light sources are particularly preferred. Using monochromatic light sources allows for a more uniform light intensity or radiation intensity, resulting in more homogeneous polymerization. LED-UV projectors with a wavelength around 385 nm or laser systems with a laser having a wavelength around 285 nm are particularly preferred. Projectors with a resolution of 1024x800 pixels or higher are preferred, preferably 1920x1080 pixels or higher, and especially high-resolution projectors with up to 100,000 or more pixels. Planar-emitting light sources with coherent light beams are particularly preferred.Spatial coherence is also achieved by a very small distance between the light source 1 and / or the assembly unit 0 and the exposure field 5.

[0040] A short distance between the planar light source, arrangement, and / or the assembly and the exposure field is considered to be 3 mm to 500 mm, in particular 3 mm to 250 mm, particularly preferably 3 mm to 150 mm, preferably 3 mm to 50 mm; alternatively, the distance can also be 1 mm to 50 mm. According to the invention, the planar radiating light source, the planar light modulator, and the optics, in particular a lens system, form an arrangement. Furthermore, the planar radiating light source, the planar light modulator, and the optics, in particular a lens system, are arranged as a single unit.

[0041] It can be provided that the unexposed pixels are defined by a mask stored for controlling the projector, in particular a programmable mask, by keeping certain light points of the projector permanently switched off. A mask according to the invention corresponds to a motif of the switched-off light points of the light source, wherein the motif is represented in the exposure field as unexposed pixels, in particular as a static motif of unexposed pixels.

[0042] The mask used allows for the simple reduction of light intensity in specific areas of the exposure field. This mask can then be used to homogenize the exposure field, particularly the light intensity within the exposure field, and most preferably, the time integral of the light intensity within the exposure field.

[0043] As an alternative to using a stored mask, it can also be provided that the unexposed pixels are defined by blackening the micromirrors, by using an area light modulator with gaps in the micromirror arrangement, or by deflecting the luminous points through the micromirrors.

[0044] By omitting individual micromirrors, the costs for the area light modulator and / or the number of necessary connections can be reduced. When using a blackened surface, commercially available, fully populated area light modulators can be used.

[0045] In a further development of the inventive method, it can also be provided that the number of unexposed pixels increases towards the center according to a function, preferably linearly or according to a parabola, particularly preferably according to a function that takes into account the interferences occurring, preferably according to a function that improves the coherence at the exposure field, preferably of the motif to be exposed or printed.

[0046] This allows for particularly good compensation of the variations in intensity of the exposure field that typically occur due to the optics. Such a function compensates especially well for the increase in intensity in the center of the exposure field.

[0047] It may be provided that the function is determined, preferably calculated, depending on the inhomogeneity of the exposure field caused by the optics, in particular a lens system.

[0048] Preferably, the function is determined, preferably calculated, as a function of the inhomogeneity of the illumination field caused by the planar light source, the arrangement comprising the planar light source, the area light modulator, and / or the optics. Alternatively, the function is calculated as a function of the inhomogeneity caused by the assembly comprising the light source.

[0049] The function according to which the number of unexposed pixels increases towards the center of the exposure field is determined as a function of a reference 1, which specifies the original light intensity of the light source in the exposure field on the projection surface (plane), and correlated with a reference 2, which specifies the homogeneous, planar light intensity (energy density in the plane, averaged over x pixels) of the projection surface, particularly over 12x13 to 1920x1080 pixels. The projection surface can also have a higher pixel resolution.

[0050] This measure also serves to compensate as accurately as possible for construction-related errors in the intensity distribution and thus to create the most homogeneous lighting field possible.

[0051] According to a particularly preferred embodiment of the method according to the invention, it can also be provided that the intensity distribution of the exposure field at maximum exposure by the light source and the area light modulator is measured or calculated and the number of unexposed pixels in each row and / or column is determined from this.

[0052] This provides a particularly suitable method for easily compensating for specific intensity deviations of certain light sources, such as projector types or individual projectors.

[0053] According to the invention, the planar radiating light source, preferably the arrangement comprising the planar radiating light source and / or the assembly comprising a planar radiating light source, can be guided over the projection surface in order to guide the illumination field of the imaged light source over the projection surface, wherein the illumination field can be guided back and forth over the projection surface. This can be done continuously or discontinuously. Preferably, the assembly is guided periodically over the projection surface.

[0054] This provides a particularly easy-to-implement method for implementing the process in rapid prototyping. This method is less error-prone than other methods, especially those in which only the exposure field is moved across the projection surface.

[0055] In a further development of the method according to the invention, it is proposed that the exposure field is periodically moved across the projection surface. By periodically sweeping across the projection surface, a more uniform intensity is achieved along the direction of movement of the exposure field.

[0056] The individual images used to expose the motif are obtained by superimposing a) the extracted motif images, i.e., derived from the motif to be printed, displayed as individual motifs during the scrolling process or by guiding the arrangement, encompassing the light source across the projection surface, with b) the motif of the switched-off light points or the motif of the mask. The light intensity of the individual motif images used to expose the motif is homogenized compared to exposure without a surface light modulator or mask.

[0057] According to a particularly preferred embodiment, the method generates individual motif images exposed in the exposure field by superimposing a) extracted motif images with b) the motif of the deactivated luminous points. The extracted motif images correspond to the motif to be printed, which has been broken down into motif images for the scrolling process. Figure 7b ).

[0058] The motif of the switched-off light points ( Figure 7c ) shows the unexposed pixels, the static motif of unexposed pixels. The exposed motif individual images ( Figure 7d ) are obtained by superimposing the respective individual motif images (extracted motif images, Figure 7b ) with the static motif of switched-off light points, represented as a static motif with unexposed pixels.

[0059] The image to be printed is obtained by moving the exposure field with the exposed individual images of the image across the projection surface.

[0060] It can also be provided that the surface of a liquid light-curing resin is used as the projection surface. In particular, a light-curing dental material is used as the light-curing resin. According to the invention, the initiator system of the light-curing resin and the wavelength of the light source are optimally matched.

[0061] A light-curing resin is defined as a resin or, preferably, a mixture of light-curing monomers, optionally comprising photoinitiators or a photoinitiator system. Dental light-curing resins are particularly preferred in the process according to the invention. These dental light-curing resins may further comprise fillers and generally include alkyl(meth)acrylates. When a liquid light-curing resin is used as the projection surface, the process is suitable for producing three-dimensional molded bodies (synonymous with objects) (as a so-called rapid prototyping process).The problems underlying the invention are also solved by a rapid prototyping process in which a liquid light-curing plastic is exposed using such a process, preferably with UV light, wherein the exposure field is mapped onto the surface of the plastic and the plastic cures through exposure in the exposure field.

[0062] The inventive method for homogenizing the light intensity of the exposure field is particularly effective in rapid prototyping processes, as it allows the produced objects or plastic bodies to be built up homogeneously.

[0063] The invention is based on the surprising finding that by using dead or always-black pixels, i.e., non-illuminating pixels, it is possible to achieve a homogenization of the UV light intensity without having to adjust gray values ​​with the area light source. A predefined mask, stored in a projector, preferably a UV projector, can be used for this purpose. The number of pixels defined as black in the rows or columns, i.e., non-illuminating pixels, increases towards the center of the exposure field to compensate for the attenuation of the exposure field towards the edges due to the optics. This is necessary because the middle rows (or columns) are, by design (due to the optics), more brightly illuminated.

[0064] The method according to the invention achieves the following effect. By moving the projector or the radiation emitted by the projector, the entire line of the exposure field is activated during an exposure. This generates a maximum amount of light (UV light) when the beam passes over it. For an exposure field with, for example, 1920 x 1080 pixels, the maximum amount of light would be generated with 1080 pixels. If fewer pixels are activated, the power or the time-integrated light intensity is reduced. In this way, the uneven illumination of the optics is compensated for according to the invention.

[0065] Exemplary embodiments of the invention are explained below with reference to schematically represented figures. These show: Figure 1: Device of the invention with a curved surface 21a of the polymerizable plastic. Figure 2: Device of the invention with a planar surface 21b of the polymerizable plastic. Figures 3a, 3b and 4: Coupling device and coupling element. Figure 5: A schematic cross-sectional view of a method according to the invention; and Figure 6: A schematic comparison of a fully exposed UV projector chip according to the prior art ( Figure 6A ) compared to a UV projector chip operated according to the invention ( Figure 6BFigure 7a: a motif (13) to be printed, wherein the light points are represented as black pixels; Figure 7b: the images individually displayed by the light source (1) of the projector (extracted motif images (13a, 13b, 13c, 13d, 13e, 13f) for generating the motif (13) to be printed during the movement of the light source over the projection surface (without a mask), wherein the light points are represented as black pixels; Figure 7c: a motif of the switched-off light points (14) generated via a mask or switched-off light points generated by the area light modulator for adjusting exposure differences, wherein the switched-off light points are represented as gray pixels; Figure 7d: an addition orThe motif of the deactivated luminous points (14), generated by the area light modulator and / or the mask, is superimposed on the extracted motif images 13a to 13f, wherein the mask with the deactivated luminous points (14) is represented as gray pixels and the luminous points are represented as black pixels. The motif of the deactivated luminous points (14, negative motif), represented by gray pixels, is statically represented in all motif images as a superimposition or subtraction, i.e., the motif of the permanently switched-off or switched luminous points (14) is subtracted from the motif images (13a to 13f) of the motif 13 to be printed and is represented as a superimposition in the motif images (14a, 14b, 14c, 14d, 14e, 14f) to be exposed. Figure 8: Complete assembly (0#) comprising a stripping device (20) that can be attached to and detached from the assembly (0). .

[0066] In the inventive "exposure and processing process in the stereolithography process", the level of the fill is controlled at the reversal points of the exposure process. During the period in which the exposure unit (component 0, 0#) is decelerated and restarted, the peristaltic pump 19 pumps ( Figure 1, 2 ) a sufficient quantity of resin (polymerizable plastic, composition comprising monomers) into container 8. This quantity must be chosen such that a sufficient amount of resin builds up above the wall 8a of container 8. The domed surface 21a is formed ( Fig. 1 Due to the surface tension of the resin or plastic, this increased amount of material remains until the doctor blade (wiping device 20) removes it and smooths the surface. The layer (x1, y1) with the projection surface has been formed ( Figure 2), this layer also corresponds to surface 21b. Thus, the exposure unit (unit 0, 0#) moves along an axis of the container and pushes the doctor blade across the surface, smoothing surface 21b by removing the excess material. Surface 21b also forms the planar projection surface. The material that ran over wall 8a ( Figure 2 ) is collected in the collection container ( Figure 2 ) and through a suction opening with suction line 17a back into the pump circuit ( Figures 1 and 2 ) This ensures a consistently high level throughout the construction process and / or exposure phase.

[0067] Construction platform 12 ( Figures 1 and 2 ) is lowered by one layer thickness and the process starts again.

[0068] The horizontal positions of container 8 and doctor blade 20 do not change during the build phase or process. These positions are set once and remain unchanged. The vertical distance between them is set and aligned to a defined value (0.1 mm in the first test). This distance primarily serves to maintain a mechanical and vibration-free separation of the two systems (coating system (build unit, wiper device) = moving / container system = static). The distance should not exceed the height that the liquid can achieve through surface tension. Preferably, the distance is equal to or slightly less than the height of the liquid.

[0069] The stripped, light-curing plastic is drawn into the circuit via a suction line 17a and a peristaltic pump 19 (Fig.) and preferably filtered (filter 18) and returned to the container 8 (tub). The system is sealed to prevent air from entering the circuit. Air inclusions disrupt the polymerization or build process and reduce the quality of the molded part / object.

[0070] The Figure 3a (not in perspective, schematic) and 4 schematically represent the coupling device 22 between the assembly unit 0 or the light source 1 and the wiping device (squeegee) 20. According to Figures 3a, 3b and 4A blade 11 is assigned to the light source 1 or the assembly 0, which it uses to push the scraper 20 forward by means of the coupling device 22. The scraper is arranged in front of the exposure field 5 of the light source 1 and is pushed forward in front of the exposure field 5, preferably horizontally, in the process. The coupling device 22 is provided on top of the scraper and comprises at least one element 20a, which is connected to the upper end of the scraper, which can also be an element 20a, by means of an elastic element, such as a spring 20c and a fixing 20b. A damper 23 can now be assigned to the blade 11 in the region of the reversal point of the container, which decelerates the scraper 20. The blade of the assembly 0 or the light source 1 is then pushed into the notch A between the two elements 20a.At a certain pressure, the blade pushes the two elements 20a apart and slides between them. The elastic elements 20c then press the elements 20a back together. At the subsequent change of direction (reversal point), the blade again pushes the scraper device ahead of it over the container. At the subsequent change of direction (reversal point), the blade 11 again pushes the scraper device ahead of it over the container. In the inventive method, if the exposure unit 0, 0# with UV projector 1 (UV LED projector; in assembly unit 0, 0#) is moved symmetrically to the container 8 and at a defined distance over the surface 21a, 21b, and the exposure field 5 is guided, preferably horizontally, over the resulting projection surface, the squeegee 20 (scraper device) is automatically carried along in front of the light source 1 or in front of the exposure field 5 to smooth the surface (trailing method or dragging method). The . Fig. 3b The exposure field 5 is shown on top of the plastic in the container 8. The exposure field 5 can be projected onto the projection surface or surface 21b by means of a lens 2.

[0071] Figure 5 Figure 1 shows a schematic cross-sectional view of a setup for implementing a method according to the invention. A UV LED projector 1, which emits ultraviolet light (UV light), is projected onto a surface light modulator 4. The UV LED projector 1 has a resolution of 1920 x 1080 pixels, which are projected as a rectangular area onto the surface of a chip of the UV LED projector 1. The surface light modulator 4 comprises a plurality of controllable micromirrors with which the light from the UV LED projector 1 is reflected and focused onto the surface of a liquid light-curing plastic 6 by means of a lens system 2. The micromirrors are arranged in Figure 1The liquid plastic 6 is represented as differently oriented small rectangles on a surface of the area light modulator 4. The liquid plastic is arranged in a container 8, which is open at the top towards the area light modulator 4 or the lens system 2.

[0072] The lens system 2, which is in Figure 5 The surface of the pixels of the UV-LED projector 1, shown schematically only as a simple lens, projects onto the surface of the light-curing plastic 6. With the aid of a suitable motor (not shown), the UV-LED projector 1 is moved over the container 8, thereby sweeping the exposure field over the surface of the light-curing plastic 6, so that each line of the chip of the UV-LED projector 1 completely passes over, or can pass over, every point to be exposed.

[0073] The resulting exposure field on the surface of the light-curing plastic 6 hardens the liquid components, forming a solid plastic body 10. The solid plastic body 10 is mounted on a support 12, which is slowly lowered so that the upper surface of the plastic body 10 is wetted by the liquid light-curing plastic 6, and a new solid layer can be formed on the plastic body 10 by means of the exposure field. For details of the implementation, refer to EP 1 880 830 A1 or EP 1 894 705 A2.

[0074] Homogenization of the light field and thus of the produced plastic body 10 is achieved by not using the pixels located in the center of the chip of the UV LED projector 1, i.e., by leaving them black.

[0075] For better understanding, an inventive use or control of such a chip is shown in Figure 6B shown and explained below.

[0076] Figure 6 Figure 2A shows a schematic comparison of a fully exposed UV projector chip according to the prior art compared to a UV projector chip operated according to the invention. Figure 6B The UV LED chip shown as an example has only 12x13 pixels, so that the basic principle of the present invention can be easily illustrated. In a real-world implementation, UV LED projectors with a significantly higher resolution are used, such as 1920x1080 pixels.

[0077] Each of the UV LED chips has 12 columns and 13 rows. In the fully exposed UV LED chip, according to the state of the art ( Figure 6AThe inner areas of the projection field are irradiated with a higher UV intensity than the outer areas. This results in the highest intensity in the central column, which decreases towards the outside. Due to scattering effects and other properties of the optics, the individual pixels of the UV LED projector cannot be imaged with arbitrary sharpness. Each pixel therefore also illuminates areas of the projection field that should actually be illuminated by its neighboring pixels. As a result, the areas of the projection field illuminated by the inner pixels receive a higher intensity than the areas illuminated by the outer pixels.

[0078] This will be done with respect to the columns (In Figure 6(from top to bottom) is compensated for by moving the UV LED projector across the exposure field along a direction of movement X. The direction of movement X of the UV LED projector, or of the exposure field, is defined in both Figures 6A and 6B indicated by the arrow. The image emitted by the UV LED chips is therefore projected in the direction of the lines (In Figure 6 from left to right (i.e., along arrow X) across the exposure field. A DLP® chip from Texas Instruments can be used for the imaging.

[0079] Through the in Figure 6B The light intensity in the various slits of the UV-LED projector operated according to the invention is reduced more and more towards the center by the black pixels shown, which remain switched off or which are not reflected by the area light modulator onto the surface of the liquid light-curing plastic.

[0080] This ensures that the central areas of the exposure field swept along the direction of movement X receive the same intensity of ultraviolet radiation as the outer areas (rows).

[0081] The simplest implementation of a method according to the invention can be achieved by storing a mask on the projector that defines which pixels are not switched on or used and therefore remain black. Alternatively, a surface light modulator can be used which has fewer or blackened mirrors in the central region.

[0082] In Figure 6BOnly the two outermost rows are illuminated with all twelve pixels, while for each row closer to the middle row, one fewer pixel is illuminated or projected. In the middle row, only six pixels are then active, or rather, only six pixels are projected. As the projector sweeps across the exposure area along the direction of movement X, an average exposure intensity is generated at the illuminated points of the field, which is directly proportional to the number of pixels used or projected by the UV LED projector. Suitable projectors can have a resolution of up to 100,000 or up to 1.5 million pixels. Projectors with XGA and Super-XGA (SXGA) resolutions of 1280 x 1024 pixels can also be used.

[0083] To achieve a uniformly homogeneous light distribution on the surface of the light-curing resin or the projection surface, especially a planar projection surface, the exposure field is moved across a build platform at a constant speed. The build platform here has a size of 1,920 x 20,000 pixels (pixel size here 50 x 50 µm). During the movement, image sections are continuously displayed across the exposure field.

[0084] The mask, once defined and stored in the UV projector, creates dead (always black) pixels in each row. In this case, the number of pixels defined as black in the rows increases towards the center, because the middle rows are brighter due to the projector's design (optics).

[0085] The effect is as follows: When the UV projector is moved, the entire line of the exposure field is activated during a single exposure. This ensures that a maximum amount of UV light is generated at 1080p when the projector moves across the field. If fewer pixels are activated, the power is reduced, thus compensating for uneven illumination of the optics.

[0086] Figure 7a Figure 13 shows a motif to be printed, in which the luminous points are represented as black pixels. Figure 7b Figure 1 shows the sequence of images individually displayed by the light source (extracted motif images 13a, 13b, 13c, 13d, 13e, 13f) for generating the motif 13 to be printed during the movement of the light source or its arrangement over the projection surface (without the motif of the switched-off light points and / or without a mask). The light points are represented as black pixels. Figure 7cThe pattern of the switched-off light points 14 is shown. The pattern of the switched-off light points is generated by the area light modulator and / or the mask. The switched-off light points are represented as gray pixels. In this way, light points can be switched off or redirected by the area light modulator to equalize exposure differences.

[0087] In Figure 7d The superimposition of the motif of the switched-off luminous points 14, in particular the static motif, generated by the area light modulator and / or the mask, and the extracted motif images 13a to 13f is shown. The motif of the switched-off luminous points 14 or the mask are represented as gray pixels. The exposed pixels in the exposure field are represented as black pixels and form the motif images to be exposed (14a, 14b, 14c, 14d, 14e, 14f).

[0088] Figure 8The complete assembly (0#) comprises a stripping device 20, which can be attached to and detached from the assembly 0. The light source 1, or at least the exposure field 5 of the light source 1, is guided in front of the complete assembly 0# or the assembly 0 behind the stripping device 20 for the polymerization of the plastic 6. The stripping device 20 can be coupled to the light source 1 or the exposure field 5 of the light source 5, in particular via the coupling device 22, and is guided in front of the light source 1 or the exposure field 5. Reference symbol list

[0089] 0 Assembly unit comprising light source (1) or (A), such as UV LED projector (1) or laser system, optics, in particular lens system (2), area light modulator (4), 0# Entire assembly unit or complete assembly unit comprising: wiper device (20) and assembly unit (0) comprising light source (1), such as UV LED projector (1) or laser system, optics, in particular lens system (2), area light modulator (4), wherein the wiper device is coupling or decoupling to the assembly unit (0) 1 UV LED projector 2 Lens system 3 Arrangement of the area light source (1), the area light modulator (4) and / or the lens system / optics (2) 4 Area light modulator 5 Exposure field 6 Light-curing liquid plastic, in particular mixture comprising monomers, composition comprising dental monomers 7 Bath 8 Container 10 Cured light-curing plastic / plastic body 11 Blade, the blade preferably has a coupling device orNotch A adapted geometry 12 Holder, build platform 13 Motif to be printed 13a to 13f individually displayed images for generating the motif to be printed 14 Motif of the switched-off luminous points / motif unexposed pixels 14a to 14f motif individual images to be exposed with homogenized light quantity distribution.Individually displayed images (14a, 14b, 14c, 14d, 14e, 14f) for generating the motif to be printed 13, shown as individually displayed images (13a, 13b, 13c, 13d, 13e, 13f) for generating the motif to be printed when scrolling with a static superimposition of the motif of the switched-off luminous points (14) 15 Feeding device 16 Collection container 17 Line, 17a Suction line, 17b Feed line 18 Filter 19 Pump, in particular peristaltic pump 20 Scraper device, squeegee (C) 20a Element, in particular plate 20b Fixation, in particular screw (E) 20c Elastic element, in particular spring 21a Surface of bath during overflow of plastic into collection container, 21b Surface (planar surface) of bath according to exposure or after adjustment of the surface by means of a scraper device, squeegee. Surface 21b corresponds at least partially to the projection surface or is the surface of the layer to be polymerized (x1, y1).22 Coupling device, A' notch, in particular comprising 20a, 20b, 20c and 20 or upper part on a doctor blade 20 23 Damper A' notch; A# direction of movement; D dragging method, E compression springs held by means of stud bolts, z1: ​​layer thickness; x,y; x1,y1: layer as plane.

Claims

1. Device comprising an assembly (0) with a light source (1), for production of a three-dimensional object (10) by means of illuminating a liquid light-curing plastic material (6), having a container (8) for accommodation of a bath (7) of the light-curing liquid plastic material (6), having a building platform (12) for positioning the object (10) relative to the surface (21a, 21b) of the bath (7), wherein the container (8) has assigned to it a feeding device (15) for feeding the liquid light-curing plastic material (6), wherein at least one collecting container (16) is assigned to the container (8) into which the liquid light-curing plastic material (6) is transferable by means of a stripping device (20) that is drivable along an axis of the container, wherein in that the assembly (0) serves for producing a homogenised distribution of light intensity and exhibits an arrangement (3) that comprises a spatially emitting light source (1), a spatial light modulator (4), and an optical system (2), characterised in that, the stripping device (20) that is drivable along the axis of the container (16) and the spatially emitting light source (1) are simultaneously guidable, at a defined distance, across the liquid light-curing plastic material, whereby the stripping device is guidable at a defined distance right ahead of the light source (1) and forms the projection surface for the illuminated field of the light source (1), wherein the spatially emitting light source (1) is guidable across a projection surface together with the illuminated field of the projected light source (1).

2. Device according to claim 1, characterised in that, the optical system (2) being a lens system.

3. Device according to claim 1, characterised in that the feeding device (15) at a level below the surface (21) of the bath (7) is assigned to the container.

4. Device according to any one of the claims 1 or 3, characterised in that the liquid light-curing plastic material (6), in particular the protruding plastic material of the arched surface (21a) is transferable into the at least one collecting container (16) by means of a stripping device (20) that is drivable along an axis of the container, whereby, a surface (21b) is formed as projection surface.

5. Device according to any one of the claims 1 to 4, characterised in that the liquid light-curing plastic material (6) is fed again from the collecting container (16) via the feeding device (15) to the bath (7) by means of a suction line (17a), in particular through a filter (18), by means of a pump (19).

6. Device according to any one of the claims 1 to 5, characterised in that an entire assembly (0#) comprises a stripping device (20) that is drivable along an axis of the container, and the assembly (0), whereby the stripping device (20) is situated in front of the light source (1) and / or of the illuminated field (5), in particular of the assembly (0).

7. Method for producing a three-dimensional object (10) with a device according to any of claims 1 to 6, in which the three-dimensional object is generated layer-by-layer, by one layer (x1, y1) each being produced as a projection surface of a liquid light-curing plastic material (6) and being polymerised in an illuminated field (5), at least in part, by light of a light source (1), characterised in that a) a layer (x, y) of the liquid light-curing plastic material (6) is generated on a building platform (12) or on a polymerised layer by the amount of the plastic material being appropriately adjusted in a bath (7) of the liquid light-curing plastic material (6) such that the plastic material protrudes vertically at the upper edge of the walls (8a) of the container (8) due to the surface tension of the plastic material, and an arched surface (21a) of the protruding plastic material is formed, and, optionally, the plastic material flows into the at least one collecting container (16) arranged on the side of the container (8), followed by b) the protruding liquid light-curing plastic material (6) of the arched surface (21a) being removed by a stripping device (20) that is drivable along an axis of the container and a layer to be polymerised (x1, y1) being obtained as projection surface (21b), and, optionally, c) the layer to be polymerised (x1, y1) generated in b) is polymerised as projection surface of the liquid light-curing plastic material (6) by an illuminated field by light of the light source (1), and, optionally, d) lowering the building platform (12) by one layer thickness (x1, y1) and, optionally, e) steps a) to d) are being repeated at least one to multiple times.

8. Method according to claim 7, characterised in that steps b) and c) take place simultaneously.

9. Method according to claim 7 or 8, characterised in that the drivable stripping device (20) and the light source (1), in particular the light source of the assembly (0), form a drivable entire assembly (0#) that can be coupled and uncoupled.

10. Method according to any one of the claims 7 to 9, characterised in that the entire assembly (0#) comprises a drivable stripping device (20) and an assembly (0), whereby the assembly (0) comprises an arrangement (3) comprising a spatially emitting light source (1), a spatial light modulator (4), and the optical system (2), in particular with the optical system (2) being a lens system.

11. Method according to any one of the claims 7 to 10, characterised in that step a) is performed i) after performing step d), or i) after performing step c) and, preferably, d), or iii) after the drivable stripping device (20), the light source (1) or the entire assembly (0#) have been guided across the illuminated field and are situated outside of the illuminated field or iv) after the drivable stripping device (20), the light source (1) or the entire assembly (0#) have become situated at a front or rear end of the container (8), in particular in the region of the reversal point.

12. Method according to any one of the claims 7 to 11, characterised in that the entire assembly (0#) or the assembly (0) for homogenising the distribution of light intensity comprises a spatial light modulator (4) that comprises a multitude of controllable and tiltable micro-mirrors that are arranged in rows and columns, in which the light of a spatially emitting light source (1) is projected by means of an optical system (2) and an illuminated field of the projected light source (1) is guided across a projection surface, whereby, towards the middle of the illuminated field, an increasing number of pixels is not being illuminated such that a homogenisation of the light intensity of all pixels that are illuminated on the projection surface is attained in the time integral.

13. Method according to any one of the claims 7 to 12, characterised in that the entire assembly (0#) or the assembly (0) and thus the illuminated field and the stripping device (20) are simultaneously periodically guided across the projection surface, whereby, preferably, the surface (21b) of a liquid light-curing plastic material (6) is used as projection surface.

14. Method according to any of claims 7 to 13, characterised in that it is used for the production of at least parts of dental prosthetic restorations.

15. Rapid prototyping method, in which a liquid light-curing plastic material (6) is illuminated by means of a method according to any one of the preceding claims 7 to 14, is illuminated with UV light, whereby the stripping device (20) is guided simultaneously and together with the illuminated field (5) ahead of the illuminated field along an axis of the container in order to form the layer to be polymerised (x1, y1) of the plastic material (10) as projection surface (21b) onto which the illuminated field is projected and on which the plastic material (10) polymerises due to the illumination in the illuminated field.