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

Description

[0001] The invention relates to a device and a method for producing three-dimensional objects, in particular at least parts of dental prosthetic restorations, in which a stripping device, which protrudes at a height above a container, strips plastic into a collecting container and forms a projection surface. According to the invention, a stripping device and a light source are coupled and guided simultaneously at a defined distance over the liquid, light-curing plastic, wherein the stripping device is guided at a defined distance directly in front of the light source and forms the projection surface for the exposure field of the light source. The invention also relates to a method for producing a homogenized light quantity distribution using a surface light modulator and to a rapid prototyping method in which such a method is used.

[0002] Stereolithography is a rapid prototyping technique. Rapid prototyping is a three-dimensional printing process. Light-curable monomers or compositions comprising a mixture of monomers are polymerized, preferably with UV light. Starting with a 3D model in STL format, this model may be provided with a support structure to increase stability in the bath on the build platform. The resulting model is then digitally divided into individual layers; a process known as slicing. The individual layers are imported into a machine control system and adjusted accordingly. The machine control system regulates the sequence of movements and the exposure process.

[0003] A process is also known in the art in which a movable mirror projects the laser (laser exposure process) onto the projection surface of the polymerizable resin. Typically, the contours of the three-dimensional object are exposed first, followed by the surfaces of the layered object. This process is static, using point-by-point exposure. The process is therefore very time-consuming.

[0004] In a DLP process, a surface is illuminated via a DLP chip (Digital Light Processing, a micromirror reactor) with LED technology and an optical power of 0.5 to 100 watts. The DLP process is also known as a static process. The light source remains stationary during the exposure phase (static) and exposes new resin layers to be polymerized in still images.

[0005] In the conventional processes, the surface is removed with a squeegee. After a waiting period, the exposure process begins. After exposure, the surface is squeegeed again. This is due to the current designs of RP printers.

[0006] In addition to ultraviolet (UV) lasers, UV LED projectors are also increasingly being used in known rapid prototyping processes. Methods for this are known, for example, from EP 1880830 A1 and EP 1894705 A2. The disadvantage of lasers is their point-shaped exposure field. The UV light from the light source is projected onto a light-curing plastic as the exposure field. An optics and a surface light modulator are used for the imaging. Due to the optics, an inhomogeneous light distribution or intensity distribution occurs. The edge areas of the exposure field typically have a lower intensity than the areas in the center of the exposure field. This effect, also known as a barrel image, means that the light-curing plastic does not receive the same intensity at every point and therefore cures differently, i.e. inhomogeneously.

[0007] EP 1 982 824 A2 proposes to homogenize the intensity distribution by reducing the brighter pixels of the UV projector to the intensity level of the pixels at the edge by means of a gray distribution.

[0008] The disadvantage of this is that the gray distribution can only be achieved through precise control of the intensity. Therefore, the object of the invention is to provide a less complex method with which a similar effect can be achieved.

[0009] US2014 / 052288A1 discloses an apparatus and method for producing three-dimensional objects using a vacuum knife. DE 44 14 775 A1 discloses an apparatus and method for producing a three-dimensional object, wherein the apparatus comprises a laser with a deflection mirror for deflecting and positioning a light beam. US2007 / 284547A1 discloses a method for adjusting light with substantially uniform energy.

[0010] The object of the invention was to drastically shorten construction times with minimal design resources in order to make the process more economical. The object was therefore to develop a device and a method with which three-dimensional molded bodies can be printed in shorter construction times than with known static methods. Likewise, the object was to be able to provide a constant level of polymerizable material, such as a composition comprising monomers, with respect to the z-axis using simple means, without the need for additional positioning devices or measuring equipment. Furthermore, the object was to enable constant fill level regulation. In particular, a less complex method should be provided which, in particular, achieves satisfactory homogenization of the light intensity of the exposure field. The method should be implementable as cost-effectively as possible.

[0011] The objects of the invention are achieved by a device according to claim 1 and a method according to claim 9. In the device, light-curing plastic is polymerized by means of a light source, wherein a stripping device is guided in front of the light source at a fixed distance and allows simultaneous generation of the planar projection surface and guidance of the exposure field of the light source in one method step or in one pass. A pass is defined as a distance traveled by the light source from a turning point on one side of the container of the device to the turning point on the opposite side of the container. Compositions comprising monomers polymerizable with electromagnetic radiation, preferably dental, UV-polymerizable monomers, are preferably considered light-curing plastic.

[0012] According to the invention, smoothing with the doctor blade and exposure take place simultaneously in a single process step, as explained below. According to the invention, the wiping device and the exposure field are only a few millimeters apart. This measure has made it possible to significantly reduce the construction time.

[0013] The subject of the invention is a device comprising a structural unit with a light source for producing a three-dimensional object by irradiating a liquid, light-curing plastic, with a container for holding a bath of the light-curing, liquid plastic, with a construction platform for positioning the object relative to the surface of the bath, wherein the light source and a stripping device are coupleable and the stripping device is arranged in front of the light source and / or in front of the exposure field, wherein the stripping device has a coupling device and a coupling element is assigned to the light source or the structural unit, with which the stripping device is pushed in front of the light source and / or the exposure field, wherein the coupling element releasably engages the coupling device and the coupling element is designed to be form-fitting with the coupling device, wherein the coupling element is non-positively,can be coupled electrically or magnetically detachably to the coupling device, wherein the coupling device has at least one element and the upper end of the stripping device is designed in the form of an element, wherein these elements are fixed to one another by at least one elastic element and by at least one fixing element, and wherein the coupling element engages laterally with the elements in a form-fitting manner and can be passed through in a form-fitting manner between the two elements fixed by an elastic element and a fixing element with a defined force between the two elements, wherein the device has a damper which triggers a passing through or slipping through of the coupling element between the two elements of the coupling device.

[0014] Preferably, the light source or a structural unit comprising the light source is associated with a motor that drives the structural unit or the light source. The stripping device is preferably indirectly driven via this drive and moved along an axis of the container. The light source or the exposure field and the stripping device are spaced apart from each other by approximately 20 to 150 mm, preferably 20 to 80 mm, in relation to the x,y plane.

[0015] According to a particularly preferred embodiment, this structural unit 0 comprises the light source and can be coupled to the stripping device, forming an overall structural unit 0# or the entire structural unit. It is further preferred if the stripping device has a coupling device and a coupling element, in particular a type of blade, is assigned to the light source or the structural unit. Alternatively, a coupling element can be assigned to the stripping device, and a coupling device can be assigned to the light source or the structural unit. It can also be preferred if the coupling element is provided with a motor for the drive. According to the invention, the movable light source, structural unit, or overall structural unit is driven by a motor.According to a particularly preferred embodiment of the invention, the stripping device can be guided simultaneously together with the movable light source in front of the exposure field of the light source, along an axis of the container (x, y plane), wherein a drive is assigned to the light source, the structural unit or the overall structural unit.

[0016] According to the invention, the coupling element releasably engages the coupling device, wherein the coupling element is configured to form a positive fit with the coupling device. Preferably, the coupling element can interact with the coupling device by means of a positive fit. In this case, the coupling element can take on the shape of a polygon, such as a hexagon, or form a flat element with two pointed lateral regions, which can be passed through or slipped through between the elements of the coupling device. Other releasable connections known to those skilled in the art can be configured according to the invention, such as a slip clutch, preferably a locking body clutch, connecting fitting, or tongue and groove. In general, the coupling element can be coupled to the coupling device; this can be done mechanically, such as by form-fitting, force-fitting, or electrically or magnetically.Likewise, the coupling element can be pivoted by means of an axis in such a way that it can be pivoted at the reversal point in such a way that the stripping device is always moved in front of the exposure field.

[0017] The invention also relates to a device comprising a coupling device with at least one element which is assigned to the stripping device and wherein the upper end of the stripping device is designed in the form of an element, wherein these elements are fastened to one another with at least one elastic element and with at least one fixing element, and the coupling element engages laterally with the elements in a form-fitting manner and can be passed through in a form-fitting manner between the two elements fastened with an elastic element and a fixing element with a defined force between the two elements. The coupling mechanism acts like a slip clutch. Preferably, the coupling element is designed to be form-fitting with the elements of the coupling device. Thus, the coupling element can have the shape of a sword, the geometry of which is preferably adapted to the coupling device or notch A.

[0018] Furthermore, the invention relates to a device with a damper that triggers the coupling element to pass or slip between the two elements of the coupling device. The damper is preferably provided in the region of the two lateral reversal points of the light source's path.

[0019] It is further preferred if the movable stripping device and the light source, in particular the light source of the structural unit 0, form a movable structural unit 0# with a slip clutch, in particular a locking body clutch.

[0020] According to further preferred alternatives, a feed device for feeding the liquid, light-curing plastic is assigned to the container of the device. In particular, the feed device is assigned to 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, at least one collecting container is assigned to the container. In particular, two opposing collecting containers are assigned to the side of the container, in particular laterally along the longitudinal or transverse axis of the container. The liquid, light-curing plastic, preferably the protruding plastic with a curved surface, can be transferred into the at least one collecting container by means of a stripping device movable along an axis of the container, preferably into a planar surface.The movable wiping device preferably comprises a squeegee with a planar underside. The squeegee may have a rubber lip.

[0021] The device according to the invention is designed in such a way that, for the first time, it utilizes the surface tension of the light-curing plastic or a polymerizable composition to provide an excess of curable plastic above the last cured layer or above the build platform. Only then is a stripping device, which is fixedly aligned at a defined distance from the top edge of the container, for example, with a height difference of 0.1 mm, used to adjust the planar plastic surface.

[0022] In this case, it is particularly preferred if, in the device, the liquid, light-curing plastic, in particular the plastic which protrudes above the walls of the container and which has a curved surface due to the surface tension of the plastic, can be transferred into at least one collecting container by means of a stripping device which is movable along an axis of the container, in particular a longitudinal or transverse axis, such as the longitudinal central axis, wherein in particular one surface, preferably a planar surface, is formed as a projection surface. The stripping device extends essentially transversely across the open area of the container. According to the invention, the stripping device is guided indirectly via the drive, propulsion and / or advance of the light source, the structural unit or the entire structural unit along an axis of the container, in particular in a horizontal plane.Thus, the stripping device according to the invention does not require its own electronic drive or motor. According to the invention, an electronic motor is assigned to the light source, assembly, and / or overall assembly for driving, propulsion, or feeding, in order to be moved across the container. With the device according to the invention, it is possible to move the stripping device simultaneously with the exposure field, but in front of the exposure field, along an axis of the container by means of a coupling device and a coupling element.

[0023] The inventive combination of the coupling mechanism and the level control made it possible to provide a particularly economical scrolling rapid prototyping method and a device for carrying out the method.

[0024] The invention further relates to a device comprising a structural unit (0) that includes an arrangement, wherein the arrangement comprises a light source, in particular a planar light source, a planar light modulator, and an optical system. A lens system preferably forms the optical system. The light source can be a UV laser or a projector, such as a UV-LED projector.

[0025] According to a further embodiment, the invention provides a device with a feed device that is assigned to the container below the surface of the bath. In particular, the feed device has an outlet opening in the container and comprises a line that connects the outlet opening and a pump. The outlet opening is preferably located below the surface of the bath.

[0026] In a preferred embodiment, the liquid, light-curing plastic can be fed back into the bath from the collecting container via a suction line, in particular through a filter, or by means of a pump, preferably a peristaltic pump or diaphragm pump, via the feed device. Particular attention must be paid to ensuring bubble-free feeding.

[0027] According to a particularly preferred embodiment of the invention, the device comprises a structural unit 0# - entire structural unit - comprising a stripping device movable along an axis (x, y plane) of the container and a smaller structural unit, wherein the stripping device is located in front of the exposure field or in front of the light source of the structural unit 0. The stripping device is mounted at a defined distance in front of the exposure field or in front of the light source, in particular 20 to 150 mm, preferably 20 to 80 mm. Preferably, the movable stripping device and the light source of the structural unit 0 form a coupleable, movable overall structural unit 0#. According to a preferred embodiment, the stripping device has a coupling device and is pushed in front of the light source or in front of the exposure field by means of a sword assigned to the light source or the structural unit 0.The blade can preferably be guided through a coupling device in the region of the reversal points of the assembly on the container at the front and rear ends of the container, in order to position the stripping device again in front of the light source or in front of the exposure field when the assembly 0# is moved again along the return path over the container. By assigning a blade to the light source or the assembly 0 and guiding it through the coupling device of the stripper at the end points (reversal points of the assembly 0# in the container), the coupling element, in particular the blade, can push the coupling device and thus the stripping device in front of the light source and / or the exposure field when the assembly changes direction.

[0028] The coupling device is preferably a device comprising two elements, in particular approximately trapezoidal elements, preferably symmetrical elements containing at least one trapezoid, which can be pressed together with springs. The elements are preferably formed and aligned with one another in such a way that a notch forms between them in the horizontal plane. By pressing the two spring-mounted elements apart, the blade can widen the plane to form a gap. The blade can be pivoted through this gap in the region of the reversal point in order to be able to guide the coupling device in front of the coupling element, such as the blade, over the surface of the plastic again when the assembly 0# is returned. A damper is positioned at the reversal points, which stops the squeegee (wiper, slider) and builds up pressure until the blade slides through the aforementioned notch of the coupling device and the resulting gap.Once the blade is positioned on the opposite side of the coupling device, the assembly 0 can again push the squeegee over the container in the opposite direction.

[0029] The lower edge(s) of the stripping device are set at a defined distance from the planar upper edges of the container's side walls; preferably, a distance of 0.1 mm can be preset, for example. Alternatively, the stripping device can be guided over the planar upper edges of the container's side walls.

[0030] Unit 0 – small unit – comprises an arrangement including a planar light source, a planar light modulator, and the optics, which is preferably a lens system. The light source can be a UV laser or a projector. The projector can be, for example, a projector with DLP (Digital Light Processor) technology from Visitech AS. A micromirror reactor is preferred for DLP technology. The optical power of the UV light source is preferably in the range of 0.5 to 100 watts. Preferred wavelengths are 340 nm to 500 nm.

[0031] According to a particularly preferred embodiment of the invention, the stripping device is guided simultaneously together with the light source in front of the exposure field of the light source, along an axis of the container (x, y plane) in order to form the layer of plastic to be polymerized (x1, y1) as a projection surface, on which the exposure field is imaged and the plastic polymerizes by exposure in the exposure field. Simultaneously in the sense of the invention is understood to mean simultaneous guidance of the stripping device and the light source along an axis of the container. Step a), the level regulation of the bath and creation of the curved surface, preferably takes place according to the invention at the reversal point of the exposure process or in the process step in which the structural unit has its reversal point. It may be preferred if the light source is driven by a motor, in particular an electric motor.

[0032] The invention also relates to a method for producing a three-dimensional object with the device according to the invention, in particular of at least a part of a dental prosthetic part, as well as prosthetic parts obtainable by this method, in which the three-dimensional object, such as a dental prosthetic part, is produced layer by layer by producing a layer (x1, y1) as a projection surface of a liquid, light-curing plastic, and is polymerized in an exposure field at least partially by means of light from a light source, preferably a planar radiating light source, wherein a) a layer (x1, y1) of the liquid, light-curing plastic is produced on a build platform or a polymerized layer by moving a stripping device, which can be coupled to a light source, in front of the exposure field and / or in front of the light source in a bath of the liquid, light-curing plastic, and i) a layer (x1, y1) to be polymerized is obtained as a projection surface, and ii) the layer (x1, y1) to be polymerized produced in i) is polymerized as a projection surface of the liquid, light-curing plastic with an exposure field using light from the light source in step a) (in particular, i) and ii) are carried out simultaneously, and b) i) in the region of a reversal point of the path of the stripping device or the light source, in particular a planar light source, the stripping device is coupled to the light source in such a way that the light source again moves the stripping device in front of it,and optionally ii) in step b) the construction platform is lowered by a layer thickness (z1) and optionally a layer (x,y) of the liquid, light-curing plastic is produced over the previously polymerized layer (x1,y1), and optionally c) at least one to several repetitions of steps a) and b), wherein the stripping device has a coupling device and the light source or the assembly is assigned a coupling element with which the stripping device is pushed in front of the light source and / or the exposure field.

[0033] According to an alternative, the layer (x1,y1) can be produced as follows: a) a layer (x,y) of the liquid, light-curing plastic is produced on a building platform or a polymerized layer by adjusting the amount of plastic in a bath of the liquid, light-curing plastic such that the plastic protrudes at the upper edge of the walls of the container due to the surface tension of the plastic and a curved surface is formed, and optionally the plastic flows into the at least one collecting container arranged laterally of the container, subsequently the protruding liquid, light-curing plastic of the curved surface is removed by means of a stripping device movable along an axis of the container, in particular with a coupling device, and a layer (x1,y1) to be polymerized is obtained as a projection surface and optionally the produced layer (x1,y1) as a projection surface, the liquid, light-curing plastic is polymerized with an exposure field using light from a light source, and optionally b) the build platform is lowered by a layer thickness (z1) and optionally c) steps a) to b are repeated at least one to several times. The build platform serves to adjust the z-axis for the layer-by-layer construction of the objects.

[0034] The method can be carried out statically. In a static method, the movable stripper is moved along an axis of the container. The exposure takes place by means of a static light source. According to a particularly preferred alternative of the invention, however, the light source is movable along an axis of the container and can also preferably be coupled to the stripper, in particular mechanically or magnetically. According to a particularly preferred embodiment, steps b) and c) are carried out simultaneously. The simultaneous implementation of the formation of the planar surface as a projection surface and the immediately subsequent exposure can take place in that, according to the invention, a movable stripper device and the light source form a coupleable, in particular mechanically or magnetically coupleable, movable entire structural unit 0#, ieThe stripping device and the light source or the assembly 0 - small assembly - can be coupled and decoupled from each other and form the entire assembly or complete assembly 0#.

[0035] Furthermore, the subject matter of the invention is a method in which the structural unit 0# - overall structural unit - has a movable stripping device and a structural unit 0 - small structural unit -, wherein the structural unit 0 has an arrangement comprising a planar radiating light source, a surface light modulator and the optics, in particular a lens system forms the optics.

[0036] A further advantage of the method according to the invention is that the liquid, light-curing plastic can be returned to the bath from the collecting container. According to the invention, it is preferred if the device is protected from electromagnetic radiation or is located in a dark room.

[0037] It is further preferred if the method is carried out with the steps in that step b) ii) is carried out simultaneously with step b) i). It is further preferred if the method is carried out with the steps in that step b) ii) is carried out after step b) i) has been carried out, or step b) ii) is carried out after the movable stripping device, the light source or the structural unit 0# have been moved over the exposure field and are located outside the exposure field, in particular after carrying out steps a) i) and ii), or after the movable stripping device, the light source or the structural unit 0# are located at a front or rear end of the container, in particular in the region of the reversal point. The regions of the lateral walls of the container in which the stripper and the light source have their reversal points are considered to be front and rear.According to the invention, it is preferred that the control of the level of the fill level, as in step a), takes place at the reversal points of the exposure process.

[0038] According to a preferred embodiment, the upper edges of the walls of the container and the lower edge(s) of the scraper device can lie in the plane of the projection surface.

[0039] It is further preferred if the structural unit for homogenizing the light quantity distribution comprises a surface light modulator comprising a plurality of controllable, tiltable micromirrors arranged in rows and columns, in which the light from a planar light source is imaged via an optical system, and an exposure field of the imaged light source is guided over a projection surface. The projection surface preferably represents the layer (x1, y1), with an increasing number of pixels remaining unexposed toward the center of the exposure field, so that, in the temporal integral, a homogenization of the light intensity of all exposed pixels on the projection surface is achieved.

[0040] Likewise, the subject of the invention is a method in which the entire structural unit 0# or the structural unit 0 and thus the exposure field and the stripping device are simultaneously 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).

[0041] According to a further subject matter 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 exposed with UV light, wherein the stripping device is guided simultaneously together with the exposure field, in particular with the light source, the structural unit or the entire structural unit, and in front of the exposure field along an axis (x, y plane) of the container, in particular is guided 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 is polymerized by the exposure in the exposure field.

[0042] After the exposure process, the resulting 3D object is cleaned in an alcoholic bath, preferably isopropanol, and unpolymerized monomer is removed in an ultrasonic bath at temperatures between 30 and 60 °C. The object is then post-annealed in a light oven. In the light oven, it is exposed to light at a wavelength between 300 and 500 nm and optionally thermally treated at temperatures between 20 and 90 °C. The invention also relates to the use of a device according to the invention for producing at least parts of dental prosthetic restorations.

[0043] The method can also be modified by using a surface light modulator to produce a homogenized light quantity distribution, which has a plurality of controllable, tiltable micromirrors arranged in rows and columns, in which the light of a surface-emitting light source is imaged via an optics and an exposure field of the imaged light source is guided over a projection surface with the surface light modulator, 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.

[0044] In the context of the present invention, a pixel is understood to be the smallest controlled light source from which the image of the projector is composed.

[0045] The particularly suitable DLP ®< chips from Texas Instruments or Visitech can be used as area light modulators.

[0046] According to the invention, a projector, preferably an LED projector, particularly preferably a UV-LED projector, can be used as the planar light source. Alternatively, a laser system can be used.

[0047] 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, with 340 to 500 nm being particularly preferred. In general, polychromatic light sources can be used as projectors, although monochromatic light sources or even essentially monochromatic light sources are particularly preferred. By using monochromatic light sources, the light intensity or radiation intensity can be standardized and thus a more homogeneous polymerization can be achieved. LED UV projectors with a wavelength of around 385 nm or laser systems with a laser with a wavelength of around 285 nm are particularly preferred. Projectors with a resolution of greater than or equal to 1024x800, preferably greater than or equal to 1920x1080 pixels are preferred, in particular high-resolution ones with up to 100,000 or more pixels. Light sources with coherent light beams that emit light over a large area are particularly preferred.Spatial coherence is also achieved by a very small distance of the light source 1 and / or the structural unit 0 from the exposure field 5.

[0048] A minimum distance of the planar light source, arrangement, and / or structural unit from 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 light source, the planar light modulator, and the optics, in particular a lens system, form an arrangement. The planar light source, the planar light modulator, and the optics, in particular a lens system, are also present as an arrangement in a structural unit.

[0049] In this case, it can be provided that the unexposed pixels are defined by a mask stored for controlling the projector, in particular a programmable mask, in which certain light points of the projector remain always switched off. A mask according to the invention corresponds to a motif of the switched-off light points of the light source, whereby the motif is displayed in the exposure field as unexposed pixels, in particular as a static motif of unexposed pixels.

[0050] The masked layer provides a simple way to reduce the light intensity in specific areas of the exposure field. This mask can then be used to homogenize the exposure field, in particular to homogenize the light intensity of the exposure field, and particularly preferably to homogenize the time integral of the light intensity of the exposure field.

[0051] As an alternative to using a deposited mask, it can also be provided that the unexposed pixels are defined by blackening the micromirrors or by a surface light modulator with gaps in the micromirrors or by deflecting the luminous points by the micromirrors.

[0052] By omitting individual micromirrors, the cost of the surface light modulator and the number of required connections can be reduced. When using a blackened coating, commercially available full-surface surface light modulators can be used.

[0053] With a further development of the method according to the invention, 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 interference that occurs, preferably according to a function that improves the coherence at the exposure field, preferably of the motif to be exposed or printed.

[0054] This allows for particularly effective compensation of the variations in the intensity of the exposure field that typically occur due to the optics. This function compensates for the increase in intensity in the center of the exposure field particularly well.

[0055] It can be provided that the function is determined, preferably calculated, as a function of the inhomogeneity of the exposure field caused by the optics, in particular a lens system.

[0056] Preferably, the function is determined, preferably calculated, as a function of the inhomogeneity of the exposure field caused by the planar light source, the arrangement comprising the planar light source, the planar light modulator, and / or the optics. Alternatively, the function is calculated as a function of the inhomogeneity caused by the structural unit comprising the light source.

[0057] The function according to which the number of unexposed pixels increases toward 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 is correlated with 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 include a higher pixel resolution.

[0058] This measure also serves to compensate for the construction-related errors in the intensity distribution as accurately as possible and thus to create an exposure field that is as homogeneous as possible.

[0059] 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 from this the number of unexposed pixels in each row and / or column is determined.

[0060] This provides a particularly suitable method with which specific intensity deviations of certain light sources, such as projector types or individual projectors, can be easily compensated.

[0061] According to a preferred embodiment of the invention, the planar light source, preferably the arrangement comprising the planar light source, and / or the assembly comprising a planar light source, can be guided across the projection surface in order to guide the exposure field of the imaged light source across the projection surface, wherein the exposure field can be guided back and forth across the projection surface. This can occur continuously or discontinuously. Preferably, the assembly is guided periodically across the projection surface.

[0062] This provides a particularly easy-to-implement method for rapid prototyping. This method is less error-prone than other methods, especially those that only require the exposure field to be moved across the projection surface.

[0063] A further development of the method according to the invention proposes that the exposure field be periodically moved across the projection surface. By periodically sweeping the projection surface, a more uniform intensity is achieved along the direction of movement of the exposure field.

[0064] The exposed motif images are obtained by overlaying a) the extracted motif images, i.e., derived from the motif to be printed, displayed as individual motifs in a scrolling process or by moving the arrangement comprising 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 exposed motif images is homogenized compared to exposure without an area light modulator or mask.

[0065] According to a particularly preferred embodiment, exposed motif images are generated in the exposure field by superimposing a) extracted motif images with b) the motif of the switched-off luminous dots. 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 ).

[0066] The motif of the switched off luminous dots ( Figure 7c ) shows the unexposed pixels, the static motif of unexposed pixels. The exposing motif frames ( Figure 7d ) are obtained by superimposing the respective individual motif images (extracted individual motif images, Figure 7b ) with the static motif of the switched off luminous dots, displayed as a static motif with unexposed pixels.

[0067] The motif to be printed is obtained by moving the exposure field with the exposed individual motif images over the projection surface.

[0068] 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.

[0069] A light-curing plastic is considered to be a resin or, preferably, a mixture of light-curing monomers, optionally comprising photoinitiators or a photoinitiator system. Dental light-curing plastics are particularly preferably used in the method according to the invention. The dental light-curing plastics may further comprise fillers and generally comprise alkyl (meth)acrylates. When using a liquid light-curing plastic as a projection surface, the method is suitable for producing three-dimensional molded bodies (synonymously, objects) (as a so-called rapid prototyping method).The objects underlying the invention are also achieved by a rapid prototyping method in which a liquid light-curing plastic is exposed using such a method, preferably exposed to UV light, wherein the exposure field is imaged onto the surface of the plastic and the plastic is cured by the exposure in the exposure field.

[0070] An embodiment of the method according to the invention for homogenizing the light intensity of the exposure field is particularly effective in rapid prototyping processes, since it allows the produced objects or plastic bodies to be constructed homogeneously.

[0071] One embodiment of the invention is based on the surprising discovery that by using dead or always black pixels, i.e. non-luminous pixels, it is possible to achieve homogenization of the UV light intensity without having to adjust gray values with the area light source. A mask can be used once and stored in a projector, preferably a UV projector. The number of pixels defined as black in the rows or columns, here non-luminous pixels, increases towards the center of the exposure field in order to compensate for the intensity attenuation of the exposure field towards the edge due to the optics. This is necessary because the middle rows (or columns) are brighter exposed due to the design (due to the optics).

[0072] One embodiment of 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 controlled during an exposure. This generates a maximum amount of light (UV light) when moving across it. For an exposure field with, for example, 1920x1080 pixels, the maximum amount of light would be generated with 1080 pixels. If fewer pixels are controlled, 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.

[0073] The invention also relates to a computer-readable medium on which a computer program for using a device according to the invention is stored, which, when executed by a microprocessor, is adapted to carry out the method according to the invention explained above for controlling the device.

[0074] The invention also relates to a program element for controlling the device according to the invention, which, when executed by a microprocessor, is adapted to carry out the above-mentioned method according to the invention. Exemplary embodiments of the invention are explained below with reference to schematically illustrated figures, without, however, limiting the invention. In the following, the following figures 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 the structure for implementing a method according to the invention. 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 6B). Figure 7a: a motif to be printed (13), wherein the luminous dots are shown as black pixels, Figure 7b: the images individually displayed by the light source (1) of the projector (extracted individual motif images (13a, 13b, 13c, 13d, 13e, 13f)) for generating the motif to be printed (13) during the movement of the light source across the projection surface (without a mask), wherein the luminous dots are shown as black pixels. Figure 7c: a motif of the switched-off luminous dots (14) that are generated via a mask or switched-off luminous dots generated by the area light modulator for equalizing exposure differences, wherein the switched-off luminous dots are shown as grey pixels, Figure 7d: an addition orOverlay of the motif of the switched-off luminous dots (14), generated by the area light modulator and / or the mask and the extracted individual motif images 13a to 13f, wherein the mask with the switched-off luminous dots (14) is represented as gray pixels and the luminous dots are represented as black pixels. The motif of the switched-off luminous dots (14, negative motif), represented by gray pixels, is statically in all individual motif images as an overlay or subtraction, ie the motif of the permanently switched-off or switched luminous dots (14) is subtracted from the individual motif images (13a to 13f) of the motif 13 to be printed and represented as an overlay in the individual motif images (14a, 14b, 14c, 14d, 14e, 14f) to be exposed. Figure 8: Overall module (0#) comprising a stripping device (20) which can be coupled to and detached from the module (0). .

[0075] In one embodiment of the inventive "exposure and processing process in the stereolithography process," the control of the fill level takes place at the reversal points of the exposure process. During the period in which the exposure unit (assembly unit 0, total assembly unit 0#, Fig. 8 ) is braked and started again, the hose pump 19 ( Fig. 1, 2 ) a sufficient amount of resin (polymerizable plastic, composition comprising monomers) into the container 8. This amount must be selected so that a sufficient amount of resin is built up over the wall 8a of the container 8. The curved surface 21a ( Fig. 1 ). Due to the surface tension of the resin or plastic, this increased amount of material is retained until the squeegee (scraping device 20) scrapes it off and smoothes the surface. The layer (x1,y1) with the projection surface has been formed ( Fig. 2 ).

[0076] The exposure unit (assembly unit 0, 0#) then moves and pushes the squeegee over the surface and smoothes the surface 21b by removing the excess material. The material that has run over the wall 8a ( Fig. 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 consistent level throughout the construction process and the exposure phase.

[0077] The construction platform 12 ( Fig. 1 and 2 ) is reduced by one layer thickness (z1) and the process starts again.

[0078] The horizontal positions of the container 8 and the doctor blade 20 do not change during the construction phase or process. These positions are set once and remain unchanged. The vertical distance between them is set and aligned to a defined value (this is 0.1 mm in the first test). The distance primarily serves to maintain a mechanical and vibration-free separation of the two systems (coating system (assembly unit, wiping device) = in motion / container system = static). The distance should not be greater than the height that the liquid can achieve through surface tension. Preferably, the distance is the same or slightly smaller.

[0079] The stripped light-curing plastic is removed by means of a suction line 17a and a peristaltic pump 19 ( Fig. 1 or 2) is sucked into the circuit and preferably filtered (filter 18) and returned to container 8 (tank). The system is sealed to prevent air from entering the circuit. Air inclusions disrupt the polymerization or construction process and reduce the quality of the molded body / object.

[0080] The Fig. 3a (not perspective, schematic) and 4 schematically represent the coupling device 22 between the assembly 0 or the light source 1 and the wiping device (doctor blade) 20. According to Fig. 3a, 3b and 4A coupling element 11, such as a sword, is assigned to the light source 1 or the assembly 0, with which they can push the stripping device 20 in front of them by means of the coupling device 22. The stripping device is arranged in front of the exposure field 5 of the light source 1 and is pushed in front of the exposure field 5 during the process. The coupling element 11 can be assigned to the side of the container or the bath of the assembly, for example, the coupling element 11 is connected to the assembly 0 via an arm (not shown). Therefore, the coupling element 11 of the Figures 3a and barranged laterally, behind the container and not above the bath 7, so that the light source 1 (not shown) in the assembly can project an exposure field 5 onto the plastic 6. The coupling device 22 is provided on top of the stripping device and comprises at least one element 20a, which is connected to the upper end of the stripping device, which can also be present as element 20a, by means of an elastic element, such as a spring 20c and a fixation 20b. The sword 11 can now be provided with a damper 23 ( Figure 3b), which decelerates the stripping device 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 elements 20a are pressed against each other again by the elastic elements 20c. During the subsequent change of direction (reversal point), the blade now pushes the stripping device in front of it over the container again.If, in the method according to the invention, the exposure unit / assembly 0, 0# with UV projector 1 (UV-LED projector; in assembly 0, 0#), in particular with an electric motor, 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 formed projection surface, the squeegee 20 (stripping device) for smoothing the surface is automatically moved in front of the light source 1 and / or in front of the exposure field 5 (towing method or dragging method). The squeegee is neither mechanically nor electrically connected in this embodiment, but merely touches the exposure unit. The squeegee is pushed in front of the exposure unit (assembly 0) or the exposure field 5 at a distance of 20 to 150 mm. At the start of the exposure process, the exposure unit slowly moves towards the stripping device (squeegee) until it makes contact with the device.The exposure unit then accelerates to process speed and pushes the squeegee in front of it. The exposure step follows. At the opposite end of the container, the squeegee is stopped by a damper, while the exposure unit continues to move. The damper builds up pressure until the blade of the exposure unit slips through the squeegee coupling device. The springs 20c, which hold the plates 20a via stud screws 20b, give way, and the blade slides between the plates 20a. After the exposure unit has passed this reversal point, the squeegee is once again on the opposite side of the exposure unit in front of the exposure field 5 and now pushes it back to the starting point. In this way, two layers can be polymerized at the same time. By repeating these cycles, the three-dimensional objects are built.The process time could be significantly reduced by coupling the stripping device with the light source or assembly 0 and thus with the exposure field. Fig. 3b shows the exposure field 5 on top of the plastic in the container 8. The exposure field 5 can be projected onto the projection surface by means of a lens 2.

[0081] Fig. 5shows 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 radiated onto a surface light modulator 4. The UV-LED projector 1 has a resolution of 1920x1080 pixels, which radiate as a rectangular area on 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 imaged onto the surface of a liquid light-curing plastic 6 with the aid of a lens system 2. The micromirrors are arranged in Figure 1 as differently oriented small rectangles on a surface of the area light modulator 4. The liquid plastic 6 is arranged in a container 8, which is open at the top towards the area light modulator 4 or the lens system 2. The lens system 2, which is Figure 5is only schematically shown as a simple lens, projects the area of the pixels of the UV-LED projector 1 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 and the surface of the light-curing plastic 6 is thereby covered with the exposure field, so that each line of the chip of the UV-LED projector 1 completely travels over or can travel over each point to be exposed.

[0082] The resulting exposure field on the surface of the light-curing plastic 6 hardens the liquid components, creating a solid plastic body 10. The solid plastic body 10 is mounted on a holder 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 created on the plastic body 10 with the aid of the exposure field. For details on the implementation, see EP 1 880 830 A1 or EP 1 894 705 A2.

[0083] Homogenization of the light field and thus of the resulting 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. For better understanding, an inventive use or control of such a chip is shown in Figure 2B and is explained below.

[0084] Fig. 6 shows a schematic comparison of a fully exposed UV projector chip (Figure 2A) according to the prior art compared to a UV projector chip operated according to the invention ( Fig. 6B The UV LED chip shown as an example has only 12x13 pixels to easily illustrate the basic principle of the present invention. In a real implementation, UV LED projectors with a much higher resolution are used, such as 1920x1080 pixels.

[0085] Each of the UV LED chips has 12 columns and 13 rows. The fully exposed state-of-the-art UV LED chip ( Figure 6A ) the inner areas of the exposure field are irradiated with a higher UV intensity than the outer areas. This creates the highest intensity in the middle column, which decreases towards the outside. Due to scattering effects and other optical properties, the individual pixels of the UV LED projector cannot be imaged with arbitrary sharpness. Each pixel therefore also exposes those areas of the exposure field that should actually be exposed by its neighboring pixels. As a result, the areas of the exposure field irradiated by the inner pixels receive a higher intensity than the areas of the exposure field irradiated by the outer pixels.

[0086] This is done with regard to the columns (In Fig. 6from top to bottom) is compensated by moving the UV-LED projector along a direction of movement X over the exposure field. The direction of movement X of the UV-LED projector or the exposure field is in the two Fig. 6A and 6B indicated by the arrow. The image emitted by the UV LED chips is thus directed in the direction of the lines (In Figure 6 from left to right, i.e., along the arrow X) across the exposure field. A DLP ®< chip from Texas Instruments can be used for imaging.

[0087] Through the Fig. 6BFor the black pixels shown, which remain switched off or are not reflected by the area light modulator onto the surface of the liquid light-curing plastic, the light intensity in the various columns of the UV-LED projector operated according to the invention is reduced increasingly toward the center. This ensures that the central regions of the exposure field swept along the direction of movement X receive the same intensity of ultraviolet radiation as the outer regions (rows).

[0088] In one embodiment of a method according to the invention, a mask can be stored for the projector that defines which pixels are not switched on or used and therefore remain black. Alternatively, an area light modulator can be used, which has fewer or blackened mirrors in the center region.

[0089] In Figure 6Bonly the outermost two rows are irradiated with all twelve pixels, while for each row closer to the middle row, one fewer pixel is illuminated or imaged. In the middle row, only six pixels are then active or only six pixels are imaged. When the exposure area is swept along the direction of movement X, an average exposure intensity is created at the exposed points of the exposure field, which is directly proportional to the number of pixels used or imaged 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 displays in XGA and Super XGA (SXGA) with 1,280 x 1,024 pixels can also be used.

[0090] To achieve a uniform, homogeneous light distribution on the surface of the light-curing resin or the projection surface, the exposure field is moved at a constant speed across a build platform. The build platform in this case is 1,920 x 20,000 pixels in size (pixel size 50 x 50 µm). During the movement, image sections are continuously displayed across the exposure field.

[0091] Once the mask is defined and stored in the UV projector, it creates dead (always black) pixels in the individual rows. In this case, the number of black pixels in the rows increases toward the center, as the middle rows are brighter due to their design (optical characteristics).

[0092] The effect is as follows: By moving the UV projector, the entire line of the exposure field is addressed during an exposure. This generates a maximum amount of UV light at 1080 when moving across it. If fewer pixels are addressed, the power is reduced, thus compensating for the uneven illumination of the optics.

[0093] Fig. 7a shows a motif 13 to be printed, in which the luminous dots are represented as black pixels. In Fig. 3b3c shows the sequence of images individually displayed by the light source (extracted individual motif images 13a, 13b, 13c, 13d, 13e, 13f) to generate the motif 13 to be printed during the movement of the light source or the arrangement across the projection surface (without the motif of the switched-off luminous dots and / or without a mask). The luminous dots are shown as black pixels. Fig. 3c shows the motif of the switched-off luminous dots 14. The motif of the switched-off luminous dots is generated by the area light modulator and / or the mask. The switched-off luminous dots are shown as gray pixels. In this way, luminous dots can be switched off or redirected by the area light modulator in order to equalize exposure differences.

[0094] In Fig. 7dThe superposition of the motif of the deactivated luminous dots 14, in particular the static motif, generated by the area light modulator and / or the mask, and the extracted individual motif images 13a to 13f is shown. The motif of the deactivated luminous dots 14 or the mask are shown as gray pixels. The exposed pixels in the exposure field are shown as black pixels and form the individual motif images to be exposed (14a, 14b, 14c, 14d, 14e, 14f).

[0095] Figure 8represents the overall structural unit 0# comprising a stripping device 20, which can be coupled to and uncoupled from the structural unit 0. The light source 1, or at least the exposure field 5 of the light source 1, is guided in front of the overall structural unit 0# or the structural unit 0 behind the stripping device 20 for the polymerization of the plastic 6. The stripping device 20 can be mechanically 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.

[0096] The features of the invention disclosed in the foregoing description, as well as in the claims, figures and embodiments, may be essential both individually and in any combination for the realization of the invention in its various embodiments.

[0097] Reference symbol:0 Structural unit comprising light source (1) or (A), such as UV-LED projector (1) or laser system, optics, in particular lens system (2), surface light modulator (4); 0# Complete structural unit or complete structural unit comprising stripping device 20 and structural unit 0 comprising light source 1, such as UV-LED projector 1 or laser system, optics, in particular lens system 2, surface light modulator 4, wherein the stripping device can be coupled to or decoupled from the structural unit 0. 1 UV-LED projector, 2 lens system; 3 arrangement of the planar light source 1, the planar light modulator 4 and / or the lens system / optics 2; 4 planar light modulator; 5 exposure field; 6 light-curing liquid plastic, in particular a mixture comprising monomers, a composition comprising dental monomers; 7 bath; 8 container; 10 cured light-curing plastic / plastic body; 11 coupling element, such as a sword, the sword preferably has a geometry adapted to the coupling device or notch A'; 12 holder, construction platform; 13 motif to be printed, 13a to 13f individually displayed images (13a, 13b, 13c, 13d, 13e, 13f) for generating the motif to be printed;14 motif of the switched-off luminous dots / motif of unexposed pixels, 14a to 14f individual motif images to be exposed with homogenized light quantity distribution. Individually displayed images (14a, 14b, 14c, 14d, 14e, 14f) for generating the motif 13 to be printed, represented as individually displayed images (13a, 13b, 13c, 13d, 13e, 13f) for generating the motif to be printed when scrolling with a static overlay of the motif of the switched-off luminous dots (14); 15 feed device; 16 collecting container; 17 line, 17a suction line, 17b feed line; 18 filter; 19 pump, in particular peristaltic pump; 20 (C) stripping device, doctor blade; 20a element, in particular plate; 20b fixing device, in particular screw; 20c elastic element, in particular spring (E); 21a surface of bath during overflow of plastic into collecting container;21b Bath surface corresponding to the exposure or after adjustment of the surface by means of a wiping device, in particular a planar surface, doctor blade, 22 coupling device, A' notch; 23 damper; A# direction of movement; D dragging method, E compression springs held by stud screws, z1: layer thickness; x,y; x1,y1: layer as a 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 light source (1) and a stripping device (20) are couplable and in that the stripping device (20) is arranged in front of the light source (1) and / or in front of the illuminated field (5), wherein the stripping device (20) exhibits a coupling device (22) and a coupling element (11) is assigned to the light sources (1) or the assembly (0), with which the stripping device (20) is guided in front of the light source (1) and / or in front of the illuminated field (5), characterized in that the coupling element (11) engages the coupling device (22) in detachable manner and in that the coupling element (11) is formed to be form-fitting with the coupling device (22), in that the coupling element (11) is couplable to the coupling device in detachable manner in force-locking, electrical or magnetic manner, wherein the coupling device (22) comprises at least one element (20a) and in that the upper end of the stripping device (20) is formed to take the shape of an element (20a), whereby said elements (20a) are attached against each other by at least one elastic element (20c) and at least one fixation (20b), and wherein the coupling element (11) engages the elements (20a) laterally in form-fitting manner and is guided through, with a defined force, between the two elements (20a) that are attached by an elastic element (20c) and a fixation element (20b) in force-locking manner, wherein in that the device has an attenuator (23) that triggers a guiding-through or sliding-through of the coupling element (11) between the two elements (20a) of the coupling device (22).

2. Device according to claim 1, characterised in that the assembly (0) serves for producing a homogenised distribution of light intensity and comprises an arrangement (3) that comprises a spatially emitting light source (1), a spatial light modulator (4), and an optical system (2), with a lens system, in particular, being the optical system (2).

3. Device according to claims 1 or 2, characterised in that the liquid light-curing plastic material (6), in particular the protruding plastic material of the arched surface (21a), can be transferred into the at least one collecting container (16) by means of a stripping device (20) that can be driven along an axis of the container, whereby, in particular, a surface (21b) is formed as projection surface.

4. Device according to any one of the claims 1 to 3, characterised in that the drivable stripping device (20) is guided directly along an axis of the container by means of the drive or propulsion of the light source, assembly or entire assembly.

5. Method for producing a three-dimensional object (10) with a device according to any of claims 1 to 4, that 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 (x1, y1) of the liquid light-curing plastic material (6) is generated on a building platform (12) or on a polymerised layer by guiding a stripping device (20), which is couplable to a light source (1), in a bath (7) of the liquid light-curing plastic material (6) ahead of the illuminated field (5) and / or ahead of the light source (1), and i) a layer (x1, y1) to be polymerised is obtained as projection surface; and ii) the layer (x1, y1) to be polymerised generated in i) is polymerised as projection surface of the liquid light-curing plastic material (6) using an illuminated field (5) by means of light of the light source (1) in step a); and, b) i) in the region of a reversal point of the pathway of the stripping device (20) or of the light source (1), the stripping device (20) is appropriately coupled to the light source (1) such that the light source (1) again guides the stripping device (20) ahead of itself; and, optionally, ii) in step b), the building platform (12) is lowered by one layer thickness (z1) and, optionally, a layer (x, y) of the liquid light-curing plastic material is generated above the previously polymerised layer (x1, y1); and, optionally, c) steps a) and b) are repeated at least one to multiple times, wherein the stripping device (20) exhibits a coupling device (22) and a coupling element (11) is assigned to the light sources (1) or the assembly (0), with which the stripping device (20) is guided in front of the light source (1) and / or in front of the illuminated field (5).

6. Method according to claim 5, characterised in that steps a) i) a layer (x1, y1) to be polymerised is obtained as projection surface; and ii) the layer (x1, y1) to be polymerised generated in i) is polymerised as projection surface of the liquid light-curing plastic material (6) using an illuminated field (5) by means of light of the light source (1) take place simultaneously in step a).

7. Method according to claim 5 or 6, 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 assembly (0#) with a slip clutch, in particular with barrier body clutch.

8. Method according to any one of the claims 5 to 7, 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 tiltable micro-mirrors that are arranged in rows and columns and can be triggered, 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 when integrating over time.

9. Method according to any one of the claims 5 to 8, characterised in that the assembly (0# or 0) and thus the illuminated field and the stripping device (20) are simultaneously periodically guided across the projection surface, whereby, preferably, the surface of a liquid light-curing plastic material (10) is used as projection surface.

10. Use of a device according to any one of the claims 1 to 9 for the production of at least parts of dental prosthetic restorations.

11. Computer-readable medium on which a computer program for use of a device according to any one of the claims 1 to 4 is stored, which, when executed by a microprocessor, is made operable in order to be able to implement the method according to any one of the claims 5 to 9, for controlling a device according to any one of the claims 1 to 4.

12. A program element for controlling the device according to any one of the claims 1 to 4, which, when executed by a microprocessor, is made operable in order to be able to implement the method according to any one of the claims 5 to 9.