Systems and methods for lithography-based additive manufacturing of three-dimensional (3D) structures - Patents.com

Abstract

An apparatus for additive manufacturing of three-dimensional structures based on lithography comprises a build platform defining a build surface, a light engine designed for dynamically patterning light in an exposure field of said light engine, first drive means for transporting a material layer across the exposure field, second drive means for causing relative movement of the light engine and the build platform along a displacement path extending parallel to the build surface, a linear encoder for sensing the position and / or velocity of the light engine relative to the build platform, and control means configured to adjust the supply rate of the pattern data supply means based on the position or velocity sensed by the linear encoder.

Description

[Technical field]

[0001] The present invention relates to systems and methods for lithography-based additive manufacturing of three-dimensional (3D) structures. [Background technology]

[0002] Many additive manufacturing (AM) processes of polymers address the challenge of combining high surface quality as well as small feature resolution with good thermo-mechanical material properties. Stereolithography (SLA) is a promising candidate for producing articles with features where high precision is desired. Some SLA processes use a large photopolymer resin vat into which the build platform and layers of structures already printed on the build platform are immersed during the printing process. In these systems, new layers are added to the surface of the liquid resin, one on top of the other. Different light sources are typically used to trigger the photopolymerization of the liquid photopolymer resin layers. As an example, Digital Light Processing (DLP), other active mask projection systems, and / or laser scanner-based systems may be used to selectively project light information onto the surface of the photopolymer resin. These printing concepts advantageously allow the use of large resin vats, often resulting in large build areas.

[0003] However, the creation of a thin resin layer between the immersed structure and the free surface of the liquid resin bath is limited in accuracy (e.g., in terms of the thickness of the liquid layer) due to various factors including the viscosity of the resin formulation used and / or surface tension phenomena. Furthermore, when using large build areas, the accuracy of the features is typically limited, even when using laser / scanner systems. The optical limitations of the scanner lens structure, the timing limitations of the conventionally used pulsed laser sources, as well as the large deviation angles of the scanning range limit the accuracy of the entire printing process, resulting in deviations in accuracy at the center and the edges of the scan. Another very important issue is that a significant amount of photopolymer material is required before the printing job (e.g., the bath filling procedure) can start. Photopolymer resins can be chemically unstable, so that the storage and degradation of the resin, as well as the cleaning of large resin baths, can become economical issues, limiting the stability of the process over time.

[0004] Some stereolithography techniques use a bath-based concept, where liquid resin is filled into a transparent material bath. According to these approaches, a layer of liquid resin is irradiated by selective light information from below, for example through the bottom of the material bath, so that a printed component is generated upside down, attached to a so-called build platform. These systems present several advantages, such as the possibility of mechanically adjusting the height of the resin layer by lowering the build platform into the resin bath. This allows for a layer of resin with a desired thickness (for example a thin layer of resin) and / or a product with the desired resolution characteristics. However, many such systems are limited in their maximum printing area. When lowering the build platform into the resin bath and generating the desired layer thickness, residual resin needs to be extruded from a narrowing gap. This process is characterized by a two-dimensional interplate pressing phenomenon, so that the pressure in the gap often increases with respect to the printing area (for example with the square of the printing area). Moreover, often such a layer may have to be separated from the bottom of the material bath after photopolymerization. This process may also generate strong forces depending on the size of the printing area. The concept itself may be limited in the physical dimensions of the printed components.

[0005] Various solutions have been proposed to at least partially overcome the problems associated with the interplate SLA concept. European Patent Application Publication No. 3418033A1, entitled "Method and Device for Lithography-Based Generative Production of Three-Dimensional Forms" to Gmeiner et al., describes a process in which a transparent material support element is coated with a thin layer of photopolymer resin so that less material is extruded from the gaps between the layers into the liquid material layer when the build platform is lowered. By precisely heating such a material support element, even photopolymer formulations of different viscosities (e.g., highly viscous photopolymer formulations) can be processed. By using an optimized surface material or lining for such a material support element, the separation force between the freshly printed layer and the support element can be further reduced.

[0006] Some concepts (e.g., those described in U.S. Patent Application Publication No. 2017 / 0066185A1, entitled "Method and apparatus for three-dimensional fabrication" to Ermoshkin et al.) include an oxygen-permeable membrane to create a so-called "dead zone" between the material support element and the resin, where photopolymerization is chemically prevented by molecular oxygen. However, the chemical stability of such dead zones can be difficult to control, making this technique unsuitable for many industrial production processes where it may be desirable for the composition to be stable in its quality over time.

[0007] According to US 2017 / 0066185 A1, a carrier film is used to transport the layer of liquid resin to the process zone, the carrier film being transparent to the radiation used to polymerize the resin layer. As the layer of liquid material carried by the carrier film gradually comes into contact with the build platform, the radiation source used to irradiate the resin layer moves along the length of the build platform. In this way, large areas can be printed by a relatively small movable print head, since the contact zone moves along the length of the build platform together with the exposure zone of the radiation source. The system disclosed in US 2017 / 0066185 A1 involves the risk of positioning errors along the displacement path of the print head, since the print head moves relative to the build platform, resulting in respective structuring errors as well as the risk of misalignment between the superimposed layers. Moreover, in such dynamic systems, it becomes complicated to control the exposure time to provide a sufficient exposure to obtain solidification of the photopolymer resin material.

[0008] This may be the case when further considering the specific requirements imposed by various photopolymers. A further challenge in printing photopolymers with enhanced thermomechanical properties is related to the relatively low reactivity of such resins. Most SLA resin formulations contain a large proportion of di- or polyfunctional monomers or oligomers. A high content of reactive groups (e.g. double bonds in acrylate or methacrylate groups) may lead to an earlier gel point of the formulation. This means that even with a relatively low double bond conversion (sometimes 15-30%), the liquid resin gels and becomes sufficiently hard and strong to be recoated with a new layer without compromising the structural integrity of the previous layer (e.g. without destroying and / or deforming the previous layer). In such cases, only a very short light pulse (e.g. by scanning a laser beam over the surface) is needed to provide exposure (e.g. sufficient exposure for solidification) until the material has hardened beyond a certain amount. The remaining uncured double bonds can be converted by a post-cure step to finally result in a highly crosslinked polymer. Such highly crosslinked polymers may exhibit high glass transition temperatures (Tg), but suffer from low toughness due to the covalent bond network and therefore may be of limited use in industrial and / or mass production applications.

[0009] In contrast, resins with lower amounts of multifunctional monomers result in less crosslinked polymer networks, improving the toughness of the polymer but lowering the glass transition temperature. To obtain high toughness as well as high glass transition temperatures, photopolymer formulations with small amounts of multifunctional monomers in combination with monomers or oligomers with strong secondary bonds (e.g. hydrogen bonds, van der Waals bonds) and large molecular weights can be used. Strong secondary bonds increase the glass transition temperature and stiffness of the final polymer network, while oligomers with high molecular weights (long chains) increase the elongation at break and further result in improved toughness of the material. Such photopolymer networks thus offer similar thermomechanical properties to thermoplastic materials currently processed by injection molding and used in a wide variety of engineering applications.

[0010] The challenges for processing such low cross-linked photopolymer networks with strong secondary bonds are two-fold: the low content of reactive groups can delay the gel point, and the strong secondary bonds in combination with high molecular weight oligomers can significantly increase the viscosity of the formulation, resulting in a formulation that cannot be processed by state-of-the-art systems for lithography-based AM. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] European Patent Application Publication No. 3418033A1 [Patent Document 2] US Patent Application Publication No. 2017 / 0066185A1 [Patent Document 3] International Publication No. 2019 / 213585A1 [Patent Document 4] International Publication No. 2019 / 213588A1 [Patent Document 5] European Patent No. 3319543A1 Summary of the Invention [Problem to be solved by the invention]

[0012] It is therefore an object of the present invention to provide improved apparatus and methods for lithography-based additive manufacturing of three-dimensional (3D) structures suitable for processing low-crosslinked photopolymer networks with strong secondary bonds. In particular, the apparatus and / or methods described herein allow for precise manufacturing of 3D structures on large build platforms, whose printing area is a multiple of the exposure field of the light engine. Furthermore, the apparatus and / or methods described herein allow for precise control of the exposure time to provide sufficient exposure to obtain solidification of the photopolymer resin material. For example, the exposure time provides exposure until the material hardens beyond a certain amount (e.g., exposure for sufficient amount of solidification). This may be exposure to bring the material to a solid state, exposure to harden the material completely and / or partially beyond a threshold, etc.

[0013] A further objective of the present invention is to provide a stable and continuous additive manufacturing process for photopolymer materials (unfilled and filled photopolymer resins) while providing high printing accuracy, great process flexibility regarding the chemical composition of the photopolymer resin, high production stability, high autonomy, and an overall process concept that is physically scalable without significant changes in printing parameters. The targeted photopolymers should provide excellent thermo-mechanical properties and support a printing process that is able to handle resins with low reactivity, low crosslink density, delayed gel point and high viscosity. [Means for solving the problem]

[0014] To achieve these and other objectives, the present invention provides an apparatus for lithography-based additive manufacturing of three-dimensional structures, the apparatus comprising: - a build platform defining a build surface; - a light engine designed for dynamically patterning light in an exposure field of said light engine; a material transport unit comprising first drive means for transporting a material layer across an exposure field; - second drive means for causing relative movement of the light engine and the build platform along a displacement path extending parallel to the build surface; - first control means configured to control the first and / or second drive means to minimize a relative movement between the material layer in the exposure field and the build platform during the relative movement of the light engine with respect to the build platform; - pattern data supplying means for supplying a sequence of pattern section data to the light engine at an adjustable supply rate, causing the light engine to emit the sequence of pattern sections at said supply rate during said relative movement of the light engine and the build platform along the displacement path; - a linear encoder for sensing the position and / or velocity of the light engine relative to the build platform; - second control means for adjusting a supply speed of the pattern data supply means based on the position or speed sensed by the linear encoder; Equipped with.

[0015] As used herein, "pattern data" may include data that is provided to a light source (e.g., a light engine) to cause the light engine to selectively harden material on the build platform according to a particular pattern.

[0016] The apparatus features a relative movement between the light engine and the build platform to enable the production of 3D structures on a large build platform, the printing area of ​​which is a multiple of the exposure field of the light engine, in particular at least three times the exposure field of the light engine. According to the present disclosure, the "relative movement" of the two apparatuses may mean that either one or both of the two apparatuses move relative to the other. For example, the "relative movement" of the light engine and the build platform may mean that the light engine and the build platform move relative to each other. For example, if the build platform is stationary, the second drive means can move the light engine along a displacement path. Alternatively, the light engine may be stationary and the build platform may be driven to move relative to the build platform along a displacement path.

[0017] As used herein, "light" can include any electromagnetic radiation capable of inducing polymerization of a photopolymer resin. The term "light" need not be limited to visible light, e.g., that portion of the spectrum that can be perceived by the human eye.

[0018] The light engine is designed to pattern light in the exposure field of the light engine to selectively harden the photopolymer resin according to the pattern. In particular, this may involve dynamic patterning of light in the exposure field of the light engine. The patterning of light may be achieved by a digital light processor (DLP) or other active mask projection system as well as a laser scanner based system to selectively project light information onto the surface of the photopolymer resin. The dynamic light engine may generate dynamic light information such as dynamic projected images, laser scanning, or other zero-, one-, or two-dimensional dynamic light information. In particular, the invention provides a pattern data supply means for supplying a series of pattern section data to the light engine at an adjustable supply speed. The exposure field of the light engine extends over only a portion of the length of the build platform, so that the light engine is provided with a series of sections of the entire pattern. The individual pattern sections received by the light engine from the pattern data supply means are projected without delay to preserve precise control of the pattern to be printed. By controlling the rate at which the pattern sections are fed to the light engine, the rate at which the series of light pattern sections are projected onto the material layer is controlled.

[0019] Providing the set of pattern section data to the light engine includes providing control data or pattern data to the light engine, the control or pattern data adapted to cause the light engine to emit a respective light pattern represented by said control or pattern data.

[0020] According to the invention, the light engine is caused to emit a series of light pattern sections onto the material during the relative movement of the light engine and the build platform along a displacement path, thus achieving a continuous process of continuously moving the light engine relative to the build platform and vice versa while a series of pattern sections are projected at a particular speed.

[0021] In such continuous processes, it is often desirable to synchronize the dynamic patterning of light by the light engine with the relative movement of the light engine and the build platform. Such synchronization ensures that each pattern section is precisely positioned in time and position relative to the build platform and that the material layers are precisely built up in registration and overlapping one another. According to the invention, said synchronization is achieved by providing a linear encoder for sensing the position and / or velocity of the light engine relative to the build platform, and a second control means is provided for adjusting the supply rate of the pattern data supply means based on the position or velocity sensed by the linear encoder. In this way, dynamic light information is projected onto the photopolymer resin such that the dynamic speed of this light information (i.e. the speed at which successive pattern sections are projected, e.g. the "scroll speed" of the pattern) matches as closely as possible the physical speed of the relative movement between the light engine and the build platform.

[0022] For proper synchronization over the entire displacement path, the linear encoder is configured to sense the position and / or velocity of the light engine relative to the build platform over the entire displacement path of the light engine relative to the build platform. Furthermore, the linear encoder is preferably configured to sense the position and / or velocity continuously or at defined intervals. Accordingly, the second control means is preferably configured to adjust the feed speed continuously or at said defined intervals.

[0023] To ensure high accuracy, the linear encoder can accurately detect the actual relative position or velocity between the optical engine and the build platform, preferably with an accuracy of 0.1 nanometers (nm) to 1.000 micrometers (μm). In various embodiments, the accuracy may be 1 nm to 10 μm, and the linear encoder may be capable of simultaneously measuring this position or velocity information at a high repetition rate and supplying it to the second control means. The linear encoder is preferably configured to detect the relative position or velocity at a frequency of 10 Hz to 100 MHz. In a preferred embodiment, such a linear encoder comprises an active encoder unit (logic unit) capable of interpreting discrete positioning signals, preferably attached to the moving unit, and a physical measurement bar or encoder bar, preferably attached to the non-moving unit, that physically characterizes the position signal information (e.g. optical marks, electromagnetic marks, magnetic marks, etc.). The linear encoder preferably senses the position and / or velocity data in a non-contact manner, such as optical, electromagnetic or magnetic.

[0024] In order to provide real time position or velocity data, the linear encoder is configured to supply its position and / or velocity data to the second control means with a latency of 50 μs, preferably with a latency of 30 μs.

[0025] The second drive means may be controlled to ensure that the relative speed between the light engine and the build platform is as constant as possible to provide stable and uniform printing conditions. The ability to physically scale additive manufacturing processes benefits from this requirement of speed consistency. Adding mass to the moving parts helps to facilitate the selection of control algorithms and drive engines to achieve constant speeds. However, achieving a constant speed does not have to be a prerequisite for accurate additive manufacturing, since the feed speed of the pattern data supply means can be adjusted to changes in the light engine's movement speed. Thus, sufficient dynamic light accuracy over the build area is fully achieved in the movement between the light engine and the build platform, even during acceleration and deceleration phases, for example towards the edge of the build platform.

[0026] According to a preferred embodiment of the invention, the light engine is designed to intermittently emit light into said exposure field with an adjustable light pulse rate, the light engine being preferably configured to synchronize the light pulse rate to the feed rate of the pattern data supply means. By intermittently turning on and off the light engine to generate light pulses, the material layer is illuminated only over a portion of the available time slot, i.e. a time slot defined by the feed rate of the pattern data supply means. In particular, the light pulses are synchronized with the feed rate of the pattern data supply means such that a light pulse is generated each time the light engine switches (e.g. "scrolls") to a new pattern section. Since the light pulses are emitted while the second driving means moves the light engine and the build platform relative to each other, the position of the patterned light emitted on the material layer changes during the time slot, which has a blurring effect. By emitting light only over a portion of the available time slot, such effects can be minimized.

[0027] At the same time, it may be desirable for various photopolymers and / or advanced photopolymer resins to be subjected to a threshold amount of radiant energy (e.g., above a minimum radiant energy) to induce polymerization. Non-limiting examples of photopolymer formulations to which this may be applied include those described in International Publication Nos. WO 2019 / 213585 A1, WO 2019 / 213588 A1, and EP 3319543 A1, the contents of which are incorporated herein by reference as if fully set forth herein.

[0028] According to a preferred embodiment, the light engine is configured to adjust the pulse duty factor of the light pulses. The pulse duty factor is the ratio of the pulse duration to the pulse period. For example, a higher pulse duty factor may be selected for photopolymer materials requiring a higher amount of radiant energy, and a lower pulse duty factor may be selected for photopolymer materials requiring a lower amount of radiant energy.

[0029] A good compromise between these conflicting considerations can be achieved if the pulse duty factor is set to a value between 0.1 and 0.8, preferably between 0.2 and 0.7.

[0030] In relation to the pattern data providing means, a preferred embodiment provides that the pattern data providing means comprises a data storage configured to store pattern data representative of a pattern of a material layer to be built on the build platform, said pattern data being associated with a length dimension of said pattern measured along a displacement path of the second actuation means, and said pattern data comprising pattern section data representative of a plurality of pattern sections of said pattern along the length of said pattern.

[0031] The pattern data is preferably arranged as a rectangular pixel grid comprising a plurality of rows of pixels, with each pattern section comprising at least one row of pixels.

[0032] If each pattern section contains exactly one row of pixels, then each row of pixels is projected one after the other onto the material layer with a frequency corresponding to the feed rate of the pattern data supply means.

[0033] Where each pattern section includes multiple rows of pixels, a preferred embodiment of the invention provides that the series of pattern section data provided to the light engine represents pattern sections that are offset from one another by one row of pixels. Sequentially arranged pattern sections in the series thus overlap one another, and as the light engine moves relative to the build platform a distance corresponding to the dimension of one row of pixels, the transition from one pattern section to the next is made by adding a new row of pixels at the leading edge of the exposure field and removing a row of pixels at the trailing edge of the exposure field. In this way, the light engine scrolls the pattern at a speed corresponding to the speed of movement of the light engine relative to the build platform.

[0034] As mentioned above, a material transport unit is provided for transporting the material layer across the exposure field. According to a preferred embodiment, the material transport unit comprises a flexible carrier film that is at least partially transparent to the light emitted by the light engine, and the coating means (e.g. coating blade) are arranged to coat the front side of the flexible carrier film with the material layer, the front side of the carrier film facing the build platform as it moves across the exposure field. The carrier film is preferably designed as an endless carrier film, a continuous carrier film, a carrier film that is coated in a position upstream of the exposure field, rotating using a belt or other drive mechanism. A coating removal system may preferably be provided downstream of the exposure field, which makes it possible to remove final residues of photopolymer material from the carrier film before a new layer is applied. The coating removal system preferably comprises a scraper blade, which is pressed against a support plate with the moving carrier film sandwiched therebetween. In some embodiments, such a system collects the scraped-off material and sends it back towards a storage area or storage tank.

[0035] In some embodiments, if the carrier film is not an endless film, its length is matched to the length of the build platform, or the carrier film is significantly longer than the build platform.

[0036] The light engine, the (endless) flexible carrier film and the coating means are preferably arranged in or on a print head, which is movable by a second drive means for causing a relative movement of the print head with respect to the build platform. In this way, the print head incorporates all parts that move with respect to the build platform. Here, the build platform can be designed as a platform that remains stationary in the length direction while the print head is moved by the second drive means.

[0037] The print head may include a carrier film tensioning mechanism (e.g., a mechanism for adding, removing, modifying, etc. tension in the carrier film) capable of providing an appropriate tension in the film. Sufficient tension in the carrier film is advantageous for obtaining good resin coating and exposure results. In a preferred embodiment, the tensioning mechanism is directly attached to the roller that guides the carrier film.

[0038] Furthermore, one or more rollers (e.g. an array of rollers) may be provided to guide the carrier film during its operation in the process. Such rollers are preferably arranged only on one side of the carrier film, e.g. on the inside of an endless carrier film, to avoid direct contact with the material layer. However, the invention also encompasses embodiments in which rollers are attached to the coated side of the carrier film, if necessary in alternative embodiments of the device. In this case, the roller surface may be adapted to contact the material layer, for example by selecting a particular roller surface or texture. Optionally, such rollers may be individually heated in a controlled manner.

[0039] According to the invention, first control means are provided for controlling the first and / or second drive means so as to minimize relative movement between the layer of material in the exposure field and the build platform during said relative movement of the light engine with respect to the build platform, preferably the first control means being configured to control the first and / or second drive means so that there is essentially no relative movement between the layer of material and the build platform.

[0040] The first drive means for transporting the material layer preferably comprises a drive engine, e.g. controlled by said first control means, for moving the carrier film in a controlled manner so as to synchronize the speed of the carrier film with the relative movement caused by the second drive means, such that there is no relative movement in the contact zone between the material layer and the build platform during the relative movement of the light engine with respect to the build platform.

[0041] In some embodiments, the first drive means may be coupled and / or directly attached to one of the rollers of the carrier film system, for example, two or more rollers may be connected to the drive engine, for example, one driven roller may be near the coating zone and another driven roller may be a guide roller.

[0042] In view of the drift problem, a guide mechanism for guiding the carrier film is preferably provided, such as a steerable guide roller system that can steer the carrier film. Such rollers are preferably directly connected to the carrier film motor drive. Optionally, such a mechanism can be heated in a controlled manner.

[0043] A guide plate is preferably disposed within the exposure field between the light engine and the carrier film to define a gap between the carrier film and the build surface, the guide plate being at least partially transparent to the light emitted by the light engine. The guide plate is disposed such that the carrier film is in contacting relationship with the guide plate as it moves across the exposure field, thereby guiding the carrier film. The guide plate is thus in contact with a backside of the flexible carrier film, the backside of the carrier film facing away from the build platform as it moves across the exposure field. The guide plate may include a planar surface on the side facing the build platform such that a gap is formed between two parallel planes, the planar surface of the guide plate and the build surface of the build platform. The width of the gap defines the thickness of the material layer exposed to the radiation of the light engine in the exposure field.

[0044] Optionally, the guide plate is adjustable in a direction perpendicular to the build surface to adjust the width of the gap as needed.

[0045] Considering the high viscosity of advanced photopolymer resins, the device of the invention may preferably comprise heating means for controlling the temperature of the material layer. In particular, since the chemical reactivity of the photopolymer is directly influenced by its temperature, the temperature of the material layer may be controlled in the exposure field. The control of the temperature in the exposure field can be achieved by heating a guide plate which guides the carrier film in the exposure field. A preferred embodiment therefore provides for providing first heating means for heating the guide plate. In particular, the heating means is configured to heat the guide plate in the exposure field.

[0046] Indirect heating means are preferred since the guide plate is optically transparent to the wavelength or range of wavelengths used for curing the resin. Preferred heating means include hot air heating, such as heating means configured to heat the surrounding air or process gas, heating means configured to heat a transparent liquid pumped through the guide plate or surrounding the guide plate on one side, and heating means comprising a heating element for conductively heating the guide plate in the area adjacent to the exposure field. According to a preferred embodiment, the heating means comprises an infrared heating element, such as an infrared radiator, for heating the guide plate from the side facing away from the build platform. In this way, the infrared radiation first hits the guide plate before hitting the photosensitive material. In this context, a preferred embodiment provides that the guide plate is made of a material that is opaque or only partially transparent to infrared radiation and transparent or at least partially transparent to the radiation wavelengths used for curing the photopolymer resin.

[0047] Another process zone to consider for temperature control is the coating zone where the carrier film is coated with photopolymer resin. Heating the coating zone to a certain temperature may be advantageous to reduce the viscosity of the photopolymer resin, which is determined by its temperature. To coat the carrier film with a thin layer of photopolymer resin, the coating means comprises a rakel mechanism, such as a doctor blade, disposed on the front side of the carrier film, and the carrier film is supported in the coating zone by a support plate disposed on the back side of the carrier film opposite the rakel mechanism. A heating element is preferably provided for heating the rakel mechanism, such as a doctor blade. Furthermore, a heating element may also preferably be provided for heating the support plate. When heated, the support plate transfers heat to the carrier film, which heats the photopolymer resin coated on the carrier film in the coating zone.

[0048] Furthermore, pre-heating and post-heating zones can be implemented around the exposure field to support heating of the resin before it is transferred to the exposure field by the carrier film and consequently reduce the viscosity of the resin. The post-heating zones can help to regulate a smooth temperature gradient and add further process stability. In this context, a preferred embodiment of the invention provides that a second heating means for heating the material layer is arranged between the coating means and the exposure field.

[0049] Since the resin temperature drops significantly when applied to a cold build platform, additional heating means are preferably provided to control the temperature of the build platform. This is important for the first layer printed on the build platform, since such layer is in direct contact with the surface of the build platform. It is also preferable to heat the build platform later in the printing process, since the thermal expansion phenomenon of the build plate will negatively affect the printing accuracy over time if the temperature of the build platform is not properly controlled. Heating of the build platform may be achieved by heating the build platform or a carrier element for carrying the build platform, by using a heating pad or other heating element.

[0050] In this connection, according to a preferred embodiment of the invention, the building platform is exchangeably arranged. For example, the building platform may be exchangeably arranged on or connected to a carrier element. This allows the building platform to be easily removed after the printing process is finished and a new building platform to be installed for the next printing process. The process of removing and installing the building platform can preferably be performed automatically, such as by a coupling unit configured to couple the building platform and the carrier element to each other and / or by a means for fixing the building platform on the carrier element that can be activated and released by an electric signal. In a preferred embodiment, the building platform is exchangeably fixed to the carrier element by a vacuum device or an electromagnetic device. In particular, the surface of the carrier element is provided with at least one channel, which is connected to a vacuum source that can generate a negative pressure between the building platform carrier and the exchangeable building platform. In such an embodiment, the exchangeable building platform may be a simple sheet metal plate. Furthermore, such a carrier element may also be equipped with an automatic building platform exchange means. In a preferred embodiment, the exchange means comprises holes or gaps in the carrier element that are aligned with protrusions arranged under the carrier element. When the carrier element moves downwards, the protrusions penetrate the holes or gaps from below and lift the build platform from the carrier element. In a preferred embodiment, such protrusion elements comprise wheels or a carrier-belt mechanism that can not only lift the build platform from the carrier element but also move or transport the build platform out of the print zone. Such a mechanism can preferably be part of an automated build platform exchange mechanism, which is beneficial for an autonomous printing procedure.

[0051] In a preferred embodiment, the carrier element consists of a metal plate with heating elements mounted thereon (eg, on the bottom and / or sides).

[0052] According to a preferred embodiment of the invention, the build platform and the transport unit are configured for a relative movement in a direction perpendicular to the build plane. For this purpose, drive means are preferably provided for the relative movement of the transport unit and the build platform along a displacement path extending perpendicular to the build plane. By means of this height adjustment, the width of the gap between the build platform and the resin side of the carrier film can be adjusted to define the layer thickness of the material layer.

[0053] Furthermore, the relative mobility of the build platform and the transport unit allows the system to be adjusted to print additional layers on top of the first one on the build platform, with each additional layer increasing the distance between the build platform and the carrier film by a dimension corresponding to the layer thickness.

[0054] The build platform and the print head are therefore movable relative to each other in two directions, along a displacement path extending parallel to the build surface and along a displacement path extending perpendicular to the build surface. In this regard, a preferred embodiment provides that the build platform is movable in a direction extending perpendicular to the build surface, but the print head is fixed in said direction, and that the print head is movable in a direction extending parallel to the build surface, but the build platform is fixed in said direction. An alternative embodiment provides that the print head is movable in a direction extending perpendicular to the build surface, and that the build platform is movable in a direction extending parallel to the build surface.

[0055] The inventive device may show great potential for combining the printing process with other manufacturing systems, in particular with non-lithographic and / or non-additive manufacturing systems. This may be due to the fact that during the lithographic additive manufacturing of a part, every volume point in the interior of such part is easily addressable for other mechanical, chemical or physical manufacturing steps. According to a preferred embodiment, at least one secondary material structuring and / or material placement and / or material removal unit is arranged adjacent to the print head, said material structuring and / or material placement and / or material removal unit being guided in a relative movement with respect to the build platform along a displacement path preferably extending parallel to the build surface.

[0056] Examples of material structuring and / or material placement and / or material removal units include inkjet printing units, fused deposition modeling units, fiber placement or fiber coating units, hole punching and boring units, soldering units, dye coating units, die bonding units, low and high temperature plasma processing units such as plasma coating units, wire bonding units, spray coating or micro-droplet units, casting units such as shell filling mechanisms that can fill the printed shells with the same or different materials, cutting units, and multi-purpose pick and place units such as robotic arms or other physical object manipulators. Such process intensification units may interact with the actual lithographic printing process in that they are physically connected to the print head and therefore use the same or additional positioning control systems such as linear encoders, or may move individually along the build platform area by the same or different physical guidance systems as the print head or build platform. Some of the manufacturing and manipulation systems mentioned above may also be attached to robotic arms or other object manipulation systems that can move laterally or in three dimensions or in a compound manner using mechanical joints and / or fixed or moving attachment points or joints.

[0057] According to another aspect, the present invention refers to a three-dimensional (3D) printer system. The 3D printer system can include a build platform that defines a build surface. The material transport unit of the 3D printer system can include a carrier film. The carrier film can have one or more surfaces that receive and / or transport photopolymer resin as described herein. As described herein, the carrier film can include a continuous / endless carrier system. The 3D printing system can include a nozzle or other device for dispensing photopolymer resin onto the carrier film. The nozzle / other device can generate one or more material layers of the photopolymer resin. In some embodiments, the nozzle / other device is configured to dispense enough resin to generate a single material layer of the photopolymer resin onto the carrier film.

[0058] The 3D printing system can include a device for maintaining a layer of photopolymer resin material at a particular thickness. In one example, the 3D printing system can include a coating blade configured to maintain a layer of material dispensed from a nozzle onto a carrier film at a particular thickness. The coating blade can be adjustable in a direction perpendicular to the carrier film such that the thickness of the layer of material deposited on the carrier film can be adjusted. In some embodiments, the 3D printing system includes a device for mixing the layer of photopolymer resin material within the coating zone on the carrier film. Examples of such devices include scrapers, mixers, and the like.

[0059] The 3D printing system can include a material management unit configured to structure, place, remove, or any combination thereof on one or more layers of material. The material management unit can include, for example, a robotic arm, a sensor configured to sense the one or more layers of material, etc.

[0060] The 3D printing system can include a light engine configured to provide light for curing the photopolymer resin. The light engine can include a light source and can include / be coupled to a power source to power the light source. An exposure field associated with the light engine can enable the light engine to expose light from the light engine to at least a portion (possibly all) of the build platform. In some embodiments, the exposure field is associated with a window or other area that is substantially transparent to the light from the light source. One or more sensors can sense attributes of the light engine relative to the build platform, such as position, velocity, acceleration, angular motion, etc. The sensors can include linear encoders, calibrators, and / or other devices that sense attributes of the light engine relative to the build platform. In some embodiments, the sensors perform optical measurements of the light engine.

[0061] In some embodiments, the 3D printing system includes a pattern data provider configured to provide pattern section data to a light engine at a feed rate (e.g., an adjustable feed rate) to cure a portion of the material layer according to the pattern section data at a feed rate (e.g., an adjustable feed rate). The light engine may be configured to emit a series of pattern sections at a feed rate (e.g., an adjustable feed rate) as one or more of the light engine and the build platform move relative to one another along a displacement path. The pattern data provider may receive instructions from one or more control units as described herein.

[0062] The 3D printing system may include one or more drive mechanisms configured to move components of the 3D printing system relative to one another. As used herein, a "drive mechanism" may include a device configured to move an item and may include an actuator, a transducer, an electrical component, and the like. The drive mechanism of the 3D printing system may be configured to transport a layer of material toward a build platform, an exposure field, and / or other areas of the 3D printing system. In some examples, the drive mechanism includes a first drive mechanism that moves the material transport unit, the light engine, and / or the build platform relative to one another. The first drive mechanism may be configured to transport one or more layers of material (e.g., formed from photopolymer resin ejected from a nozzle) toward a portion of the light engine's exposure field and / or the build platform. In some examples, the first drive mechanism may be configured to rotate a conveyor or other structure on the carrier film toward the exposure field and / or the build platform. The first drive mechanism may include rollers, such as tension rollers, adjustable rollers, and / or other devices configured to manage tension in the carrier film.

[0063] The drive mechanism of the 3D printing system may be configured to move the light engine and / or the build platform relative to one another. In some embodiments, the drive mechanism includes a second drive mechanism configured to move the light engine and / or the build platform such that the light engine moves relative to the build platform. Such relative movement may (but need not) be achieved along a build plane defined by the build platform.

[0064] The 3D printing system may include one or more control units. Any of the control units may include memory and one or more processors, volatile and / or non-volatile storage, data input and / or output, etc. Any of the control units may receive sensor data from sensors that sense attributes of other components, such as the light engine. The one or more processors may execute computer program instructions stored in the memory and / or storage. In some embodiments, the control units include a first control unit configured to instruct the drive mechanism to optimize (e.g., reduce, minimize, etc.) the movement of the material transport unit and the light engine relative to the build platform. The instructions may include instructions to the first drive mechanism to change the position and / or speed of the carrier film of the material transport unit. This may include slowing down or speeding up the material transport unit. The instructions from the first control unit may also include instructions to the second drive mechanism to move the light engine and / or the build platform such that the material transport unit and the light engine are synchronized with each other (e.g., in time and / or space). The control unit can provide instructions to only one or to more than one of the material transport unit, the light engine, and the build platform. One or more of the control units can adjust a feed rate of the pattern data feed device in response to the sensor signal.

[0065] The 3D printing system can include a heating system configured to heat the material layer while the material layer is on at least a portion of the build surface within an exposure field associated with the light engine. The heating system can be configured to reduce a viscosity of the photopolymer resin such that the material layer can be 3D printed while on the build surface. Exposure to a light source can allow the material layer to at least partially harden during the 3D printing process. Examples of heating systems include non-contact heat lamps, infrared lamps, and the like.

[0066] In some embodiments, the 3D printing system includes a pre-heat plate configured to maintain at least a portion of the material layer at a particular temperature, e.g., before heating by the heating system. The pre-heat plate may, but need not, be coupled to a portion of the carrier film, e.g., a portion of the carrier film over which the material transport unit moves toward the build surface. The 3D printing system can include a post-heat plate configured to maintain the material layer at a particular temperature after the material layer is heated and / or printed.

[0067] The 3D printing system can include a guide plate that is at least partially transparent to the wavelengths of light from the light source. The guide plate can allow light from the light source to pass through the guide plate, through the exposure field, and onto the build surface. In some embodiments, the guide plate guides the carrier film to a specific position relative to the build platform. Such a configuration can create a gap of a specific width between the carrier film and the build platform to allow for 3D printing and / or curing of a material layer between the guide plate and the build platform.

[0068] According to another aspect, the present invention provides a method according to claim 16 for the additive manufacturing of lithography-based three-dimensional structures, the method comprising the steps of: - dispensing the photopolymer resin onto a carrier film of a material transport unit to generate at least one material layer of the photopolymer resin on the carrier film; - driving a material transport unit to transport a material layer of photopolymer resin toward an exposure field configured to expose light from a light engine toward at least a portion of a build surface of a build platform; - causing a relative movement of the exposure field with respect to the build platform along a displacement path extending parallel to the build surface; - controlling the movement of the material transport unit, the exposure field and / or the build platform so as to minimize a relative movement between the material layer in the exposure field and the build platform during said relative movement of the exposure field with respect to the build platform; - providing a set of pattern section data to a light engine; - emitting a series of pattern sections with an adjustable feed rate by a light engine during said relative movement between the exposure field and the build platform along a displacement path, thereby selectively hardening a material layer of portions of the build surface in accordance with said series of pattern sections; - sensing a position or velocity of the exposure field and / or the light engine relative to the build platform and providing a sensor signal in response to the sensing of the position or velocity; - adjusting the feed rate in response to the sensor signal; Includes.

[0069] Preferred embodiments of the method are defined in the dependent claims.

[0070] The present invention will now be described in more detail by reference to certain preferred embodiments thereof. [Brief description of the drawings]

[0071] [Figure 1] 1 is a first exemplary embodiment of a printing device of the present invention; [Diagram 2] 2 is a print head for use in the apparatus of FIG. 1; [Diagram 3] 2 is a second exemplary embodiment of a printing device of the present invention; [Figure 4] The pattern data arranged as a grid of pixels is fed to the apparatus of the present invention. [Diagram 5] 1 is a flow diagram of an exemplary method for 3D printing an object using a 3D printing system. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0072] In FIG. 1, the build platform 1 is exchangeably arranged on a plate-like carrier element 2. The print head is indicated by the reference number 3 and comprises a flexible carrier film 4, which is designed as a continuous belt (e.g. an endless belt). In a coating zone 6, the carrier film 4 can be coated with a layer of photopolymer resin. The carrier film 4 is driven to move according to the arrows 5 or 9 by a first drive mechanism in order to transport the material layer continuously across an exposure field 7 of a light engine (shown in FIG. 2). The light engine is designed for dynamic patterning of light in the exposure field 7, which induces polymerization of the photopolymer resin layer arranged on the carrier film 4 between the carrier film 4 and the build platform 1.

[0073] A second drive mechanism is provided for moving the print head 3 relative to the build platform 1 along a displacement path 8 extending parallel to the build surface of the build platform 1. A first control unit is provided for controlling the circulation speed of the carrier film 4 to be identical to the speed of the print head 3 relative to the build platform 1, so that there is no relative movement of the material layer and the build platform 1 in the exposure field 7 during the relative movement of the print head 3 relative to the build platform 1. In other words, the carrier film 4 supplies the material layer to the exposure field 7 with the same speed as the print head moves along the build platform 1 in the direction of the arrow 8. For this purpose, the carrier film 4 circulates according to the arrow 5 if the print head 4 moves from right to left and the carrier film 4 circulates according to the arrow 9 if the print head 4 moves from left to right. Each time the print head 3 passes over the build platform 1 (either from right to left or in the opposite direction), a layer of solidified material is generated on the build platform 1 or the semi-finished workpiece, and after each pass the build platform 1 is lowered in the direction of arrow 10 so that solidified layers can be generated one after the other. However, in some embodiments, the print head 3 may only move in one direction along arrow 8 to print a new layer and only use the reverse movement to return to its initial position. In such a configuration, the build platform 1 is temporarily lowered by more than two layer thicknesses to allow the print head 3 to return to its initial position, and then the build platform 1 is lifted back up to the next layer printing position after the print head 3 has reached its initial position. In such a configuration, the carrier film 4 circulates only according to one of the arrows 5 or 9 to perform the printing process.

[0074] Each layer may be structured according to a defined pattern determined by pattern data supplied to the light engine. For example, to enable a continuous process of moving the print head 3 continuously along the build platform 1 without interrupting the linear movement of the print head 3 over the entire length of the component to be printed, a pattern data supply device is provided for supplying a data sequence of pattern section data to the light engine, which causes the light engine to emit a sequence of pattern sections during the movement of the print head 3 relative to the build platform 1.

[0075] In order to achieve the desired accuracy of the printing process, the feeding speed of the pattern data supply device is synchronized with the movement speed of the print head 3. For this purpose, the print head 3 is provided with a linear encoder 11 moving along a stationary linear encoder bar 12 to sense the position and / or the speed of the print head 3 relative to the build platform 1. The feeding speed of the pattern data supply device is controlled based on the position and / or speed signals obtained by the linear encoder 11. Said control process is performed continuously or at a high frequency in order to achieve synchronization over the entire movement path of the print head 3.

[0076] The apparatus may be equipped with a calibrator 13 to allow optical measurements of the light engine. Such measurements may be achieved manually or automatically. The calibrator 13 may comprise various optical elements such as a camera system (e.g. in the visible or UV range), light sensors (e.g. for signal timing or positioning control systems or for light or radiation intensity measurements). Such a system may also be used to investigate focal plane measurements and potential stitching phenomena, e.g. stitch zone phenomena when combining multiple dynamic light engines to physically enlarge the build area of ​​the process or increase the process throughput by providing more light energy in the exposure field.

[0077] Additionally, resin overflow collectors 40 may be positioned on both ends or all sides of the build platform 1 to collect excess resin.

[0078] Furthermore, a vacuum device may be provided for releasably fixing the build platform 1 to the carrier element 2. For this purpose a vacuum line 14 may be connected to the carrier element 2. Alternatively, magnetic means, such as electromagnetic elements, may be provided for fixing the build platform 1 on the carrier element 2.

[0079] A heating pad 15 is arranged underneath the carrier element 2 in order to heat the carrier element 2 and therefore the build platform 1 .

[0080] The exchange mechanism for exchanging the build platform 1 comprises wheels 41 or other transport elements, which are supported for rotation about a rotation axis 42. When the exchange mechanism is raised towards the build plate, the wheels 41 protrude through slots (not shown) in the carrier element 2 and, upon contact with the underside of the build platform 1, lift the build platform from the carrier element. The rotation of the wheels 41 then transports the build platform out of the print zone.

[0081] The print head 3 is shown in more detail in FIG. 2. The print head 3 comprises an endless carrier film 4 guided to circulate along a closed path. The carrier film 4 is guided by a number of rollers, including a deflection roller 16, a tension roller 17, and an adjustable roller 18. The coating zone 6 is provided with a nozzle 19 connected to a resin supply hose 20. The nozzle 19 dispenses photopolymer resin onto the carrier film 4. In one embodiment, the resin is dispensed as a result of an overpressure (e.g., a pressure above an acceptable threshold) in the hose 20 and the nozzle 19 compared to the environment, which overpressure can be generated by a mechanical or pneumatic system to pump the viscous photopolymer resin from a storage tank towards the coating zone 6. In some embodiments, such a coating mechanism, including the storage tank, the hose 20 and the nozzle 19, can be heated in a controlled manner.

[0082] The coating blade 21 serves to define a material layer of a defined thickness on the carrier film 4. The coating blade 21 is height adjustable to adjust the desired layer thickness. Furthermore, a scraper 22 is provided to refresh or mix the material in the coating zone 6. In various embodiments, the scraper 22 may be heated in a controlled manner. A support plate 27 is arranged behind the carrier film 4 in the coating zone 6. The support plate 27 may function as a heating element if required.

[0083] An optional coating removal system, indicated by reference numeral 23, can be operated to decoat (e.g. remove material from) the carrier film 4 for various purposes during process cleaning or material change procedures. The coating removal system 23 may comprise a scraper blade pressed against a support plate 26 with the moving carrier film 4 sandwiched therebetween.

[0084] To maintain or heat the material layer at an elevated temperature, heating elements may be provided, including a front heater 24 and a rear heater 25. Depending on the direction of movement of the carrier film 4, said heaters may switch between functioning as a front or rear heater. As an example, if the carrier film 4 is rotating in a counterclockwise direction, element 24 may act as a front heater and element 25 may act as a rear heater, and conversely, if the carrier film 4 is rotating in a clockwise motion, element 25 may act as a front heater and element 24 may act as a rear heater.

[0085] A light engine 28 of the print head 3 is indicated with the reference number 28 and emits light into the exposure field 7. A guide plate 29 is arranged in the exposure field 7, which is at least partially transparent to the wavelengths of light emitted by the light engine 28. The guide plate is arranged behind the carrier film 4 and serves to guide the carrier film 4 so as to define a precise position of the carrier film 4 relative to the build platform 1 by means of a precisely defined gap arranged between the carrier film 4 and the build platform 1. The transparent guide plate 29 is heated by a non-contact heating system including infrared lamps 30.

[0086] In a supplementary embodiment according to Figure 3, one or more material management units (e.g. material structuring and / or material placement and / or material removal units) are arranged adjacent to the print head 3, and the material structuring and / or material placement and / or material removal units are guided to move relative to the build platform 1 along a displacement path 8 extending parallel to the build surface of the build platform 1.

[0087] In some embodiments, the material management units can include a spray coating system 31, an inkjet system 32, a soldering system, a plasma coating system or a wiring system 33, and a multipurpose robotic arm 34. Each of these units can have its own linear encoder 11.

[0088] FIG. 4 shows diagrammatically the structuring of the pattern data in the form of a virtual grid 35 of pixels 36 representing the pattern to be printed on a particular layer during the printing process. The length of the pattern along the direction 8 corresponds to the length of the component to be printed. The pattern may be divided into a number of pattern sections which may contain one or more rows 37 of patterns. For example, a first pattern section is indicated at 38 and comprises five rows 37. A second pattern section is indicated at 39 and is offset by one row 37 with respect to the first pattern section 38. The same applies to further pattern sections which are each offset by one row of pixels. As the print head 3 moves successively relative to the build platform 1, a succession of pattern sections 38, 39 etc. is fed to the light engine 28 in order to adapt the pattern to the current position of the print head 3. According to the invention, the feeding speed of the succession of pattern sections is adapted to the speed of the print head 3 sensed by the linear encoder 11 in order to safeguard a precise printing process.

[0089] The printing process can be physically scaled in terms of the maximum build platform length extending along the displacement path 8. Furthermore, it can be scaled in terms of the build platform width by choosing an appropriate width of the exposure field, e.g. the width of the light engine (such as the length of the laser scan line or the length of the LED or micro LED array) or by using several light engines side by side. The process can also be scaled in terms of throughput or exposure speed, since the accuracy of the printing process does not depend on the relative speed of the print head and the build platform due to the position and / or speed measurement systems that control the feed speed of the pattern data feeder. There are photochemical constraints on the maximum printing speed, but these limits are strongly material dependent and can therefore also vary significantly with different photosensitive materials and different printing conditions such as printing temperature and atmospheric conditions (e.g. process gases).

[0090] 5 illustrates a flowchart 500 of an exemplary method for 3D printing an object using a 3D printing system. Flowchart 500 is described with reference to the exemplary structures described in the context of FIGS. 1-4. However, it should be noted that the operations of flowchart 500 may be performed by structures and / or apparatuses other than those illustrated in FIGS. 1-4. It should be noted that the operations of flowchart 500 are merely examples, and various implementations may employ more or less operations than those illustrated in FIG. 5.

[0091] In operation 52, photopolymer resin may be dispensed onto a carrier film of the material transport unit to produce one or more material layers of photopolymer resin on the carrier film. In some embodiments, nozzle 19 may dispense photopolymer resin onto coating zone 6 on carrier film 4. As described herein, this may occur on a surface of carrier film 4 adjacent support plate 27 and / or other convenient surfaces of the carrier film.

[0092] In operation 54, the thickness of one or more layers of material may be maintained at a particular thickness. In some embodiments, maintaining the thickness of one or more layers of material may involve removing at least a portion of the layers of material to planarize the layers of material. With reference to FIG. 2, the coating blade 21 may be operated to maintain the layers of material at a desired thickness, for example, by removing and / or planarizing the layers of material.

[0093] In operation 56, one or more layers of material may be mixed in the coating zone on the carrier film. Referring to Figure 2, the scraper 22 may be operable, for example, to mix layers of material on the carrier film 4 in the coating zone 6.

[0094] In operation 58, the material transport unit may be driven to transport one or more layers of material towards an exposure field configured to expose light from the light source towards at least a portion of the build surface of the build platform. Referring again to FIG. 2, the carrier film 4 may be driven along arrow 5 or arrow 9 by a first drive mechanism, depending on the embodiment, to transport one or more layers of material deposited on the coating zone 6 towards the build surface on the build platform 1 and / or towards an exposure field 7 associated with the light engine 28. As described herein, other drive mechanisms may be used to similarly drive the material layers towards the exposure field and / or the build surface.

[0095] In operation 60, a position or velocity of the light engine relative to the build platform may be sensed. In response to sensing the position or velocity of the light engine, a sensor signal may be provided. With reference to FIGS. 1 and 2, the linear encoder 11 may operate to sense a position / velocity of the light engine 28 relative to the build platform 1. As described herein, the linear encoder 11 may provide a sensor signal to a control unit that may be internal to the linear encoder 11 and / or may be coupled to the linear encoder 11. In some embodiments, the linear encoder 11 may perform optical measurements of the light engine 28 to derive position / velocity measurements. The linear encoder 11 may also be configured to sense optical, electromagnetic, and / or magnetic marks. As described herein, the control unit may adjust a feed speed of the pattern data feed device in response to the sensor signal.

[0096] In operation 62, instructions may be provided to optimize movement of the material transport unit or light engine relative to the build platform while one or more layers of material are on the build surface within the exposure field. A control unit (possibly external or internal to the linear encoder 11) may be configured to provide instructions to optimize movement of the carrier film 4, the light engine 28, the build platform 1, or some combination thereof, to optimize their movement relative to one another. In some embodiments, this may involve minimizing relative movement and / or synchronizing the movements of the carrier film 4, the light engine 28, and / or the build surface 1 such that they are synchronized in position and / or velocity.

[0097] In operation 64, the movement of the material transport unit, the light engine, and / or the build platform may be optimized in response to the command. For example, the movement of the carrier film 4, the light engine 28, and / or the build platform 1 may be optimized (e.g., minimized, etc.) such that the carrier film 4, the light engine 28, and / or the build surface 1 are synchronized in position and / or velocity. As described herein, the tension roller 17 and / or the adjustable roller 18 may be operative to modify the position / velocity of the carrier film in response to the command. The print head 3 may similarly be operative to modify the position / velocity of the light engine 28 in response to the command. In some embodiments, the movement of the tension roller 17 and / or the adjustable roller 18 is synchronized with the movement of the print head 3 to optimize the movement between the carrier film 4 and the light engine 28 relative to the build platform 1.

[0098] In operation 66, the carrier film may be guided to a particular position relative to the build platform to create a gap having a particular width between the carrier film and the build platform. For example, the carrier film 4 may be guided to a particular position relative to the build platform to create a gap having a particular width between the carrier film 4 and the build platform 1. This gap may enable 3D printing and / or selective curing (as described in more detail herein) between the carrier film 4 and the build platform 1.

[0099] In operation 68, one or more layers of material may be maintained at a particular temperature, for example by being heated within the exposure field. As an example, if carrier film 4 is moving along arrow 5, pre-heater plate 24 (or alternatively, if carrier film is moving along arrow 9, element 25) may be operable to heat the layer of material before it is heated by non-contact heating system 30 within exposure field 7.

[0100] In operation 70, at least a portion of the layer of material may be heated while it is on the build surface in the exposure field 7. In some embodiments, the non-contact heating system 30 may heat the layer of material while it is on the build plate 1 in the exposure field 7.

[0101] In operation 72, the pattern section data may be provided to the light engine at a feed rate. A series of pattern sections may be emitted at this feed rate during relative movement of the light engine and the build platform along the displacement path. In some embodiments, the pattern data provider may provide the pattern section data to the light engine 28 at a feed rate. As described herein, the feed rate may be controlled by a control unit coupled to or internal to the linear encoder 11. This may occur along the displacement path (e.g., displacement path 8) or other paths.

[0102] At least a portion of the build surface of the build platform may be exposed to light from the light engine in operation 74. In some embodiments, the light engine 28 may be operable to expose light (e.g., through guide plate 29) toward the build platform 1. Advantageously, such light from the light engine 7 may be operable to 3D print materials, even those having formulations with viscosities that have traditionally been difficult to 3D print, for positioning and / or heating of the material layer.

[0103] In operation 76, at least some of the material layers may be maintained at a particular temperature (in some cases, but not necessarily the same as the particular temperature at which they were maintained prior to photocuring) after they have been heated and / or cured. Depending on the orientation, post-heat plate 25 or element 24 may perform this operation, as described herein.

Claims

1. a build platform defining a build surface; a light engine designed for dynamically patterning light in an exposure field of said light engine; a material transport unit comprising first drive means for transporting a layer of material across said exposure field; - second drive means for causing a relative movement of said light engine with respect to said build platform along a displacement path extending parallel to said build surface; first control means configured to control the first and / or second drive means so as to minimize a relative movement between the material layer in the exposure field and the build platform during the relative movement of the light engine with respect to the build platform; - pattern data supplying means for supplying a sequence of pattern section data to said light engine at an adjustable supply rate, causing said light engine to emit a sequence of pattern sections at said supply rate during said relative movement of said light engine and said build platform along said displacement path; a linear encoder for sensing the position and / or velocity of the light engine relative to the build platform; second control means for adjusting the supply speed of the pattern data supply means on the basis of the position or the speed sensed by the linear encoder; 1. An apparatus for lithography-based additive manufacturing of three-dimensional structures, comprising:

2. 10. The apparatus of claim 1, wherein the light engine is designed to intermittently emit light into the exposure field at an adjustable light pulse rate.

3. 3. The apparatus of claim 2, wherein the light engine is configured to synchronize the light pulse rate to the supply speed of the pattern data supply means.

4. 4. The apparatus of claim 2 or 3, wherein the light engine is configured to adjust a pulse duty factor of the light pulses.

5. The device of claim 4, wherein the pulse duty coefficient is set to 0.1 to 0.

8.

6. 6. The apparatus of claim 1, wherein the pattern data providing means comprises a data storage device configured to store pattern data representative of a pattern of a material layer to be built on the build platform, the pattern data being associated with a length dimension of the pattern measured along the displacement path of the second actuation means, and the pattern data including pattern section data representative of a plurality of pattern sections of the pattern along the length of the pattern.

7. 7. The apparatus of claim 6, wherein the pattern data is organized as a rectangular grid of pixels comprising multiple rows of pixels, each pattern section comprising at least one row of pixels.

8. 8. The apparatus of claim 7, wherein the set of pattern section data provided to the light engine represents pattern sections offset from one another by a column of pixels.

9. 9. The apparatus of claim 1, wherein the material transport unit comprises a flexible carrier film that is at least partially transparent to the light emitted by the light engine, and wherein a coating means is configured to coat a front surface of the flexible carrier film with the material layer, the front surface of the carrier film facing the build platform as it moves across the exposure field.

10. 10. The apparatus of claim 9, wherein the light engine, the flexible carrier film, and the coating means are disposed in or on a print head, the print head being movable by the second drive means for causing relative movement of the print head with respect to the build platform.

11. 11. The apparatus of claim 9 or 10, wherein a guide plate is positioned within the exposure field between the light engine and the carrier film to define a gap between the carrier film and the build surface, the guide plate being at least partially transparent to the light emitted by the light engine.

12. The apparatus of claim 11 , wherein the guide plate is adjustable in a direction perpendicular to the build surface.

13. 13. Apparatus according to claim 11 or 12, wherein first heating means are provided for heating the guide plate.

14. 14. Apparatus according to any one of claims 9 to 13, wherein second heating means are arranged between the coating means and the exposure field for heating the material layer.

15. 15. The apparatus according to claim 1, further comprising a third drive means for causing relative movement between the transport unit and the build platform along a displacement path extending perpendicular to the build surface.

16. 16. An apparatus according to claim 10 and any one of claims 11 to 15 depending on claim 10, wherein at least one secondary material structuring and / or material placement and / or material removal unit is arranged adjacent to the print head.

17. An apparatus as described in claim 16, wherein the secondary material structuring and / or material placement and / or material removal unit is guided to move relative to the build platform along a displacement path extending parallel to the build surface.

18. - dispensing a photopolymer resin onto a carrier film of a material transport unit to generate at least one material layer of said photopolymer resin on said carrier film; - driving the material transport unit to transport the layer of photopolymer resin towards an exposure field configured to expose light from a light engine towards at least a portion of a build surface of a build platform; - causing a relative movement of the exposure field with respect to the build platform along a displacement path extending parallel to the build surface; - controlling the movement of the material transport unit, the exposure field and / or the build platform so as to minimize the relative movement of the material layer in the exposure field and the build platform during the relative movement of the exposure field with respect to the build platform; - providing a set of pattern section data to said light engine; - emitting a sequence of pattern sections with an adjustable feed rate by the light engine during said relative movement between the exposure field and the build platform along said displacement path, thereby selectively hardening said layer of material of said portion of said build surface in accordance with said sequence of pattern sections; - sensing a position or velocity of the exposure field and / or the light engine relative to the build platform and providing a sensor signal in response to sensing said position or velocity; - adjusting said feed rate in response to said sensor signal; 1. A method for lithography-based additive manufacturing of three-dimensional structures, comprising:

19. The method of claim 18 , further comprising exposing light from the light engine towards the portion of the build surface of the build platform.

20. The method of claim 19, further comprising intermittently exposing the light at an adjustable light pulse rate.

21. 21. The method of claim 20, further comprising synchronizing the light pulse rate to the feed speed of the series of pattern sections.

22. 22. The method according to claim 20 or 21, further comprising the step of adjusting the pulse duty factor of the light pulses.

23. The method of claim 22, wherein the pulse duty factor is set to between 0.1 and 0.

8.

24. 24. The method according to claim 18, wherein the step of driving the material transport unit to transport the material layer of the photopolymer resin towards the exposure field includes a step of rotating the carrier film towards the exposure field.

25. 25. The method of any one of claims 18 to 24, further comprising heating the portion of the layer of material while the portion is on the build surface within the exposure field.

26. 26. The method of any one of claims 18 to 25, further comprising the step of maintaining said portion of said layer of material at a particular temperature before transporting said portion of said layer of material towards said exposure field.

27. ​​A method described in any one of claims 18 to 25, further comprising the step of maintaining the portion of the material layer at a specific temperature using a pre-heat plate (24) before transporting the portion of the material layer towards the exposure field.

28. 28. The method of any one of claims 18 to 27, further comprising the step of maintaining the portion of the layer of material at a particular temperature after transporting the portion of the layer of material away from the exposure field.

29. A method described in any one of claims 18 to 27, further comprising the step of maintaining the portion of the material layer at a particular temperature using a post-heat plate (24) after transporting the portion of the material layer away from the exposure field.

30. 30. The method of claim 18, further comprising guiding the carrier film to a specific position relative to the build platform to create a gap having a specific width between the carrier film and the build platform.

31. 31. The method of any one of claims 18 to 30, further comprising the step of maintaining the layer of photopolymer resin material at a particular thickness.

32. 32. The method according to any one of claims 18 to 31, further comprising the step of mixing the at least one material layer of the photopolymer resin in a coating zone on the carrier film.

33. 33. The method of any one of claims 18 to 32, further comprising the step of structuring, depositing, removing, or any combination thereof, on the one or more layers of material.

34. 34. The method of any one of claims 18 to 33, further comprising heating the portion of the material layer while the portion is on the build surface within the exposure field using one or more of a non-contact heating lamp (30) and an infrared lamp (30).

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