Method and system for 3D printing

Abstract

The disclosure regards a method for additive manufacturing an object, comprising the steps of providing a first radiation source emitting a first radiation; providing a container containing the photocurable resin curable by the first radiation, the container comprising a wall transparent or at least semi-transparent to at least a part of the first radiation; providing a second radiation source, wherein the photocurable resin is non-curable by said second radiation source; determining at least one property of the wall by measuring a second radiation from or reflected by the wall; providing a surface submerged on the container containing the resin; and controlling a set of processing parameters based on the at least one property of the wall for forming at least one layer of an object by curing a part of the photocurable resin on the submerged surface.

Description

[0001] Method and system for 3D printing

[0002] The disclosure relates to method and a system for printing objects with improved spatial resolution and reduced systematic errors and uncertainties during the printing.

[0003] Background

[0004] The performance of 3D printers is affected by the inverse correlation between throughput and the minimum size of printed features. As the features become smaller, the printing time increases significantly. Additionally, for micron / submicron resolutions, various errors and uncertainties arise. While these effects are typically insignificant, they become more pronounced when the resolution reaches a certain level, causing the errors to be comparable to the size of the printed features themselves. Consequently, this negatively impacts the printing outcome and leads to a suboptimal final product.

[0005] There are various methods for conducting polymer-based 3D printing, and when it comes to achieving high resolutions with a feature size below 10 pm, the predominant techniques fall into the categories of Stereolithography (SLA) and digital light processing (DLP), along with their respective variations, collectively called vat photopolymerization. In SLA, printed objects or structures are formed by a point-by- point approach where a polymerizing light source is guided over the printing area, creating a layer-by-layer object or structure. On the other hand, DLP utilizes lenses and a Direct Micromirror Device (DMD) to project an array of light points from a light source onto the printing area, allowing for the formation of an entire layer or large sections of a layer at once. While DLP is inherently faster, it often faces challenges in maintaining high resolution due to the light having to pass through multiple optical components. Typically, systems are designed with a focus on either speed or precision, as enhancing one aspect often comes at the expense of the other due to inherent limitations.

[0006] The most advanced systems employ a technique known as 2-photon polymerization (2PP). This process relies on the nonlinear optical phenomenon of two-photon absorption, where two photons are simultaneously absorbed by the photosensitive material. As the absorption is proportional to the square of the intensity, this phenomenon occurs only at the very center of the focus, enabling high spatial resolution of less than 100 nm. Another advantage of 2-photon polymerization is that many polymers exhibit minimal linear absorption in the near-infrared range, allowing the laser to penetrate deeply into the material. However, this method has drawbacks, including its extremely slow procedure, the need for precise stages, and a femtosecond laser pulse source to generate the photons driving the process.

[0007] When it comes to SLA, the resolution is primarily determined by the focal spot size of the light used, while the speed of printing is influenced by how quickly the beam can be scanned across the surface. However, practical limitations such as inertia, optical properties of the material, and optical aberrations can restrict these factors, resulting in an enlarged and varying spot size across different areas of the print volume due to the optical properties involved.

[0008] Current state-of-the-art systems have reportedly been able to achieve resolutions as fine as 1 pm within a printing volume of up to 50x50x100 mm. However, in practical applications, these numbers are often diminished by factors such as the mechanical stability of the system and the optical properties of both the printing material and the system itself. Moreover, the optics used tend to be bulky and expensive. Compensating for these challenges is often difficult due to limited control and oversight over critical aspects of the system, such as the build platform and the interaction of light with the printing medium. Additionally, printing parameters are typically fixed, which imposes limitations on material selection and the variability of system performance.

[0009] Therefore, advancements in spatial resolution on relatively big printing volumes and reduction in printing time are highly valuable in the field of SLA and vat- photopolymerization, as they can greatly enhance the quality and efficiency of the printed products.

[0010] In a typical setup for vat-photopolymerization, which involves 3D printing using a liquid and photo-curable resin, certain components are commonly found. These typically include a radiation source, a transparent membrane, a printing substrate, printing material, and a mechanism that enables the radiation source to scan over the printing medium to drive the process. Prior art, such as Pagac, Marek, et al. "A review of vat photopolymerization technology: materials, applications, challenges, and future trends of 3D printing." Polymers 13 (2021) 598 describe in detail the state of the art and the limitations of this 3D printing technique. A limiting factor in the vat-photopolymerization printing technique is the printing time scaling to the power of 3 with the printing resolution. This limitation poses the main drawback for printing high resolution objects or structures over volumes much larger than the printing resolution, like cm size objects.

[0011] Summary

[0012] Considering the prior art described above, it is an object of the present disclosure to provide a printing method and a printing system like a 3D printing method and a 3D printing system, respectively, to obtain and maintain high precision, repeatability, and resolution with limited errors and predictable behavior, and to manufacture an object with a high accuracy and repeatability. In particular, the present disclosure reduces the printing time limiting factor present in vat-photopolymerization by achieving and controlling in real time a variable printing resolution.

[0013] In a first aspect, the disclosure relates to a method for additive manufacturing of an object, comprising the steps of providing a first radiation source emitting a first radiation; providing a container or vat containing or comprising a photocurable resin or photopolymer curable by the first radiation, the container comprising a wall or a membrane transparent or at least semi-transparent to at least a part of the first radiation; providing a substrate submerged in the photocurable resin in the container; providing a second radiation source emitting a second radiation, wherein the photocurable resin is non-curable by said second radiation; determining at least one first property of the wall, the photocurable resin, the photocured resin and / or the substrate by measuring a scattered, transmitted, and / or reflected second radiation, comprising the second radiation reflected, transmitted, and / or scattered by the wall, the photocurable resin, the photocured resin and / or the substrate, respectively; and controlling a set of processing parameters based on the at least one first property for forming at least one layer of an object by curing a part of the photocurable resin on the submerged substrate. The first radiation source can be interchangeably called a curable radiation source or a photocurable radiation source. The second radiation source can be interchangeably called a non-curable radiation source or a non- photocurable radiation source. The terms vat and container may be understood to be interchangeable throughout the specification. That the wall is semi-transparent may mean that the wall is transparent or at least semi-transparent to the first radiation and / or to the second radiation or to at least a wavelength range of the first radiation and / or to the second radiation, or to at least a wavelength range of the first radiation that is at least partly overlapping the wavelength range, where the photocurable resin is curable. The photocurable resin may be transparent or at least semi-transparent to the second radiation or to at least a wavelength range of the second radiation. The wall may be a bottom wall and / or a side wall of the container or the vat. The object may be a 3D object. The first property and / or the processing parameter may be location of the membrane and / or the substrate and / or the photocured resin e.g. in relation to each other. The processing parameter may be temperature and / or humidity of the photocurable resin and / or of the environment around the photocurable resin. The processing parameter may be absorption / reflection, tilt, thickness, specifically position / flatness / roughness of the membrane during printing and optical properties as spot size and intensity of the first radiation and / or the second radiation. Throughout the present application, the terms photocurable polymer and photocurable resin may be understood to be interchangeable.

[0014] Photocurable resin can e.g. be photo sensitive in the UVA region from around 315 nm up to and halfway into the visible blue region, only covering the blue range, only covering the green range, stretching the range of yellow, orange, and red, or in the infrared, as provided by Spectra Photopolymers (Millbury, OH; USA).

[0015] Scattered and / or reflected radiation from the wall, the photocurable resin, the photocured resin and / or the substrate will provide information where the interfaces between the wall, the photocurable resin, the photocured resin, and / or the substrate are situated, and / or where the first radiation hits the photocurable resin, so that the wall, the photocurable resin, photocured resin and / or the substrate can be adjusted in relation to each other for an optimal subsequent print session, so that the volume of the photocurable resin that is transformed into photocured resin in the subsequent print session has the right depth, which is determined by the distance between the wall and the substrate / photocured resin, and width, which is determined by the width of the beam of the first radiation between the wall and the substrate / photocured resin.

[0016] The photocurable resin will need a certain amount of radiation energy of the first radiation to be cured. However, if the received radiation energy of first radiation is higher than the certain amount of radiation energy for curing the resin, the cured resin will be destroyed and the printed 3D object has to be reprinted. For that reason it is important to determine the absorption of first radiation by the photocurable resin. The absorption can be determined by determining the transmitted radiation using Beer- Lambert law.

[0017] The temperature of the photocurable resin is an important processing parameter, since the photocurable resin with a too low temperature will

[0018] An optimal temperature for the photocurable resin is between 30-70°C. For that reason the system may comprise a heater like a resistive heater for heating the photocurable resin to the desired temperature during the printing session.

[0019] Throughout the present application, the terms membrane and wall may be used interchangeably. Throughout the present application, the substrate may be called a substrate surface or just a surface.

[0020] In particular, the disclosure relates to a method to achieve these above-mentioned qualities when printing, especially in relation to vat-photopolymerization, but also other printing processes done with radiation sources consisting of light focused into a transparent or at least semi-transparent material to drive the process of fabrication. The method is designed such that the least amount of data acquired and actions are performed, in order to ensure the desired level of performance necessary to utilize our technology for the intended micro and nanoscale printing.

[0021] The method comprises the steps of measurements, data-acquisition, calibrations, and quality control. The combination and order of the steps enable the printing system to successfully print at high-resolution. The problems solved by this method lie within requirements to roughness, repeatability, quality, and material compatibility that exist within the fields using high-resolution printing for fabrication and manufacturing of delicate parts and components.

[0022] The disclosed method consists of multiple steps in which a non-curable radiation source is used to measure and characterize a semi- transparent or transparent wall (semi-transparent or transparent to at least a wavelength range of the non-curable radiation source), a printing material, and / or a substrate, on which to print the printing material, for characterizing physical properties (such as topography, roughness etc.) and / or optical properties (such as transmission and / or reflection). A detection sensor will measure radiation from the wall printing material, and / or a substrate, or scattered, or transmitted, or reflected by the wall printing material, and / or a substrate. All components of the wall, the printing material (the photocured resin), and / or the substrate irradiated by the radiation source can be characterized, calibrated, and controlled to a high level of precision.

[0023] The method utilizes a first radiation source, such as highly coherent radiation source, such as a laser, a second radiation source, such as highly coherent radiation source, such as a laser, and a detection sensor (such as a photodiode, spot-size analyser etc.). Said first radiation source or the laser may comprise a single frequency or emit within a narrow frequency range like e.g. less than 30 nm, or less than 20 nm or preferably less than 10 nm, wherein said single frequency or frequency range overlaps at least partly with the wavelength range within which the photopolymer or photocurable resin is curable. The first radiation source is selected based on the photocurable resin used, so that the range of the first radiation at least partly overlaps with the wavelength range within which the photopolymer or photocurable resin is curable. Generally, that means that first radiation is within the UV range such as in the UVA range (315-400 nm) and / or the UVB range (280-315 nm) and / or in the visible range.

[0024] The second radiation source enables the measurement of the topography and surface roughness / quality of the transparent or at least semi-transparent wall and / or of the printing substrate, and / or photocurable resin. The measured information and data may be stored as a topography map of each surface and saved in the processing unit of the system. The data is analyzed and used to automatically drive tilt motors to readjust the tilt and intermediate distance of the at least semi-transparent wall and the printing substrate. Said tilt motors are arranged along the at least semi-transparent wall and the printing substrate such that it is possible to tilt a range of independent angles 6 and < >. Said range of angles may be ± 10°. Lastly, the method may store the topography of the at least semi-transparent wall and the printing substrate to make a map to be used during the printing process to compensate for any surface abnormalities.

[0025] In a second aspect, the disclosure relates to a system for additive manufacturing of an object, the system comprising a first radiation source configured to emit a first radiation, a container configured to accommodate a photocurable resin and a substrate at least partly submerged in the photocurable resin, wherein the photocurable resin is curable to cured resin on the substrate by the first radiation, wherein the container comprises a wall transparent or at least semi-transparent to at least a wavelength range of the first radiation; a second radiation source configured to irradiate the wall, the photocurable resin, the photocured resin, and / or the substrate by a second radiation; a detection unit configured to measure a scattered, transmitted, and / or reflected second radiation comprising the second radiation scattered, transmitted, and / or reflected, respectively, by the wall, the photocurable resin, the photocured resin, and / or the substrate, respectively, and a Z stage movable towards and / or away from the first radiation source and configured to move the substrate, and / or the container; wherein the first radiation source, the second radiation source, and the detection unit are positioned on a common platform or a single platform, like a common rigid platform, wherein the system further comprises a first XY stage configured to move the first radiation source, the second radiation source and the detection unit by moving the common platform, or a second XY stage configured to move the substrate and / or the container; wherein the system is configured to determine a first property of the wall, the photocurable resin, the photocured resin, and / or the substrate based on the measured second radiation; and wherein the system is configured to control a set of processing parameters based on the first property for forming the object by curing a part of the photocurable resin on the substrate.

[0026] That the first radiation source, the second radiation source, and the detection unit are positioned on a common platform or a single platform means that relative distances between the first radiation source, the second radiation source, and the detection unit are kept constant, so that if the detection unit detects a movement in relation to the substrate and / or the container, there has been the same movement regarding distance and direction for the first radiation source in relation to the substrate and / or the container. Even a tine movement of the first radiation source in relation to the substrate and / or the container will be detected. When such a tiny movement is detected, the first XY stage or the second XY stage will be controlled to move the first radiation source and the substrate and / or the container, respectively, so that the correct part of the photocurable resin on the substrate is still cured despite the tiny movement.

[0027] The common platform or the single platform may comprise two or more platforms attached together such as by screws to function as one single platform. In a third aspect, the disclosure relates to a system for additive manufacturing of an object, the system comprising a first radiation source configured to emit a first radiation, a container configured to accommodate a photocurable resin and a substrate at least partly submerged in the photocurable resin, wherein the photocurable resin is curable to cured resin on the substrate by the first radiation, wherein the container comprises a wall transparent or at least semi-transparent to at least a wavelength range of the first radiation; a second radiation source configured to irradiate the wall, the photocurable resin, the photocured resin, and / or the substrate by a second radiation; a detection unit configured to measure a scattered, transmitted, and / or reflected second radiation comprising the second radiation scattered, transmitted, and / or reflected, respectively, by the wall, the photocurable resin, the photocured resin, and / or the substrate, respectively, and a Z stage movable towards and / or away from the first radiation source and configured to move the substrate, or the container; wherein the system further comprises a first XY stage configured to move the first radiation source, and optionally the second radiation source and / or the detection unit, or a second XY stage configured to move the substrate and / or the container; wherein the system is configured to determine a first property of the wall, the photocurable resin, the photocured resin, and / or the substrate based on the measured second radiation; and wherein the system is configured to control a set of processing parameters based on the first property for forming the object by curing a part of the photocurable resin on the substrate.

[0028] The Z stage may move the substrate away from the first radiation source, when a first layer of the object has been manufactured, so that a second layer of the object can be manufactured. The Z stage may move the container towards the first radiation source, when a first layer of the object has been manufactured, so that a second layer of the object can be manufactured.

[0029] The system can be used to perform the method of the first aspect of the disclosure.

[0030] The substrate configured to be movable within the photocurable resin allows to maintain a fixed or a predetermined distance between the printing substrate, the wall and the curable radiation source even during the printing. The predetermined distance may vary during the printing, e.g., if the design of the object to be printed allows one layer to be made thicker to save time and / or requires another layer to be made thinner to provide a higher resolution in the printed object. An effect of said configuration is that the curable radiation source is delivered to the substrate homogeneously, independently of local variation of distance induced by local increase in the width of the substrate or the membrane, local rugosity or other physical factors. The homogeneity of the delivered radiation improves the spatial resolution and allows to reduce the printing time due to the precise control of the position of the different elements comprising the system.

[0031] By the first radiation source, the second radiation source, and the detection unit being positioned on the same platform or preferably the same optical platform or the same rigid optical platform, the first radiation source, the second radiation source, and the detection unit will move together. One of the first radiation source, the second radiation source, and the detection unit cannot move alone without the other two. That means that any intentional or unintentional movement of the first radiation source relative the substrate and / or the container will always be detected by the second radiation source and the detection unit. The system will know, where the first radiation source hits the substrate and the photocurable resin, and where the additive manufacturing of the object is going on at the very moment. The additive manufacturing of the object can be made very precise in a very cost-effective way.

[0032] The first radiation source and / or the common platform can be moved relative the substrate and / or the container by the first XY stage moving the optical platform and / or by the second XY stage moving the substrate and / or the container.

[0033] If the system detects by the second radiation source and the detection unit an unintentional movement, the system may configured by a feedback loop to move the optical platform and the first radiation source back to the position, where the first radiation source is intended to be to continue the additive manufacturing of the object.

[0034] The object of the present disclosure can be achieved by means of a method for additive manufacturing of an object or structure on a part of a substrate submerged in a photocurable resin. Preferably, the manufactured object or structure is a 3D object or structure. Planar 2D objects may be manufactured by the disclosed method by curing one or more monolayers of the photocurable resin. With the herein disclosed method of the first aspect, the mentioned physical and optical properties and components that constitutes the printing process itself can be measured with the system of the second aspect or the third aspect. The method creates a closed- loop system (so-called “simulated environment”) in which a high level of control and reduction or removal of systematic errors and uncertainties created is / are achieved by using internal tools for these mentioned measurements. The use of the simulated environment is crucial to meet the requirements for the printing and results in high reproducibility regardless of environment, user, and material.

[0035] Description of the drawings

[0036] The disclosure will in the following be described in greater detail with reference to the accompanying drawings:

[0037] Fig. 1 is a schematic view of an embodiment of a system according to the present disclosure with first height and tilt adjustment motor(s) 101a and second height and tilt adjustment motor(s) 101b used to accommodate the distance between the wall 103 and the substrate 106, based on the inhomogeneities of a thickness 107 of the photocurable resin 102 or a distance 107 between the wall 103 and the substrate 106.

[0038] Fig. 2 is a schematic view of an embodiment of a system according to the present disclosure, with a detailed description of the optics 206 comprising the curable first 208 and non-curable second 207 radiation sources.

[0039] Fig. 3 shows an interface displacement vs the focus error signal graph 305. The plotted data is acquired by performing calibration steps, i.e. analyzing the focus error signal of the non-curable radiation source and measuring the distance between the focal point 304 of the non-curable radiation source and the intended plane 302 at which the curing process is performed.

[0040] Fig. 4A is a schematic view of the mechanical calibration step performed in an embodiment of a system according to the disclosure in real time to correct the changes in height A^ of the wall 404 along its length. Said changes in height may be caused by the rugosity of the wall, localized increases of the thickness or other physical deformations of the wall. Fig. 4B is a schematic view of the mechanical calibration step performed in an embodiment of a system according to the disclosure in real time to correct the changes in height A / I2of the wall 404 with respect to the printing substrate 403. Said changes in height may be caused by an undesired non-parallel position of the substrate 403 with respect to the wall 404 and / or the optics 402, by a local height variation of the substrate or other physical deformations affecting the surface of the substrate.

[0041] Fig. 4C is a schematic view of the mechanical calibration step performed in an embodiment of a system according to the disclosure in real time to correct a vertical displacement of the optics 402 with respect to the wall 404 and the substrate 403. This type of displacement allows, for example, to tune the printing resolution on the substrate, among other considerations related to the spot width of the radiation source.

[0042] Fig. 4D is a schematic view of a free displacement of the optics 402 with respect the wall 404 and the substrate 403 performed in an embodiment of a system according to the disclosure in real time to expose the substrate to the curing radiation source at a precise height along the exposure distance. This type of displacement allows, for example, to tune the printing resolution on the substrate and / or to improve the spatial resolution of the printed object or structure.

[0043] Fig. 5 shows an example of a flatness map or topography map extracted from the wall of a vat or a container, after collecting all the information from the mechanical calibration step described in the Fig. 4, wherein the height variations are in the order of 10 pm, implying that the wall is reasonably flat.

[0044] Detailed description

[0045] The transparent wall may be located at any position of the vat or the container. In particular, the transparent wall is located in a preferred embodiment at the bottom of the vat. Said wall is typically comprised of a membrane of a thickness in the order of pm up to 1 mm or a few mm or even more than 10 mm. The wall can be made of polymer, such as polydimethylsiloxane (PDMS), silicone, poly(methyl methacrylate), glass, such as an optical glass or quartz or silica, preferably fused silica, or a combination of said materials. The vat is preferably fluid tight regarding the photocurable resin. The wall made of polymer, such as polydimethylsiloxane (PDMS), silicone, poly(methyl methacrylate), is advantageous, since the polymer will not stick to the cured resin and the wall can easily be moved away from the substrate without the printed material being stuck to the wall by to the substrate. The wall made of glass, such as an optical glass or quartz or silica, preferably fused silica, is advantageous, since the glass will provide a strong, stiff, and rigid material that will not break.

[0046] In a preferred embodiment, the wall is comprised by a membrane located at the bottom of the polymerization vat. The location of the wall at the bottom of the polymerization vat has the advantage that only a small volume of photocurable resin may be necessary for covering the surface of the substrate, on which the printing should be performed. In addition, the location of the wall at the bottom of the polymerization vat allows to manufacture objects with no size limitation, due to the capability of vertically retracting the object from the vat while manufacturing, increasing the available space in the vat to continue the manufacturing. Alternatively, the wall may be located at a side of the polymerization vat to enable a side manufacturing of the object. Alternatively, the wall may be located at a side or a top of the polymerization vat to enable a top manufacturing of the object.

[0047] The tilt and distance of the at least semi-transparent membrane and / or the printing substrate are monitored and modified to ensure the substrate and membrane to be parallel over the entire printing surface or to have a known and well-defined tilt and distance in relation to each other. The tilt and / or the distance of the printing substrate in relation to the at least semi-transparent membrane can be controlled by tilt motors or adjustment motors, based on the measurement of the topography and surface roughness / quality of the at least semi-transparent membrane as well as the printing substrate made by a non-curable radiation source that is emitting outside the wavelength range, where the photocurable resin is cured. The voxel (3D pixel) size for the printing may be determined from the width of the first radiation or focused first radiation within the photocurable resin and the height of the photocurable polymer-resin between the surface of the substrate possibly with some printed material on the substrate and the membrane surface.

[0048] The disclosure may also relate to a system for additive manufacturing of an object, the system comprising: a first radiation source configured to emit a first radiation, a container configured to accommodate a photocurable resin and a substrate at least partly submerged in the photocurable resin, wherein the photocurable resin is curable to cured resin on the substrate by the first radiation, wherein the container comprises a wall transparent or at least semi-transparent to at least a wavelength range of the first radiation; a second radiation source configured to irradiate the wall, the photocurable resin, the photocured resin, and / or the substrate by a second radiation; a detection unit configured to measure a scattered, transmitted, and / or reflected second radiation comprising the second radiation scattered, transmitted, and / or reflected, respectively, by the wall, the photocurable resin, the photocured resin and / or the substrate, wherein the system is configured to determine a first property of the wall, the photocurable resin, the photocured resin, and / or the substrate based on the measured second radiation; and wherein the system is configured to control a set of processing parameters based on the first property for forming the object by curing a part of the photocurable resin on the substrate.

[0049] In an embodiment, the system may comprise a first XY stage configured to move the first radiation source, and optionally the second radiation source and / or the detection unit, or the common platform in relation to the substrate.

[0050] The first XY stage may be configured to move the first radiation source, and optionally the second radiation source and / or the detection unit, or the common platform, in relation to the substrate without substantially change the distance to the substrate. The first radiation source and the substrate may form a first axis between the first radiation source and the substrate, and the first XY stage may be configured to move the first radiation source, and optionally the second radiation source and / or the detection unit, or the common platform, in relation to the substrate in a plane substantially perpendicular to the first axis, so that one layer of photocurable resin can be cured on the substrate and / or the object. The first XY stage may be motorized.

[0051] In an embodiment, the system comprises a focusing lens and / or a focusing mirror for focusing collimated first radiation and / or the and / or the second radiation on the voxel of photocurable resin between the substrate / cured resin on the substrate and the wall, or on the part of the photocurable resin on the substrate. The focused first radiation will enable objects with even smaller details to be manufactured. The focused second radiation will allow the system to determine the position of the wall, the photocurable resin, the cured resin, the substrate, and / or where the first radiation hits the photocurable resin to an even higher degree of accuracy.

[0052] In an embodiment, the system may comprise a beam combiner for combining the first radiation from the first radiation source and the second radiation from the second radiation source. The beam combiner can be a semitransparent mirror or prism, where one of the first radiation source and the second radiation passes through the mirror or prism and the other one of the first radiation source and the second radiation is reflected by the mirror or prism, so that the first radiation source and the second radiation are guided to have a common optical path after the beam combiner. The first radiation source and the second radiation will then hit the wall, the photocurable resin, the cured resin, and the substrate at the same point and the system can determine the position of the voxel of the photocurable resin about to be cured to a high degree of accuracy.

[0053] In an embodiment, the second XY stage is configured to move the substrate and / or the container in relation to the common platform, preferably in a plane perpendicular to a line connecting the substrate and / or the container and the common platform. The second XY stage will move the substrate and / or the container in relation to the common platform, so that one layer of photocurable resin can be cured on the substrate and / or the object.

[0054] In an embodiment, the system may comprise a first Z stage configured to move the first radiation source, and optionally the second radiation source and / or the detection unit, or the common platform, towards and / or away from the substrate. Towards and / or away from means optically towards and / or away from - in the direction of the radiation beam from the first radiation source. That the first Z stage is moving the first radiation source may comprise the first Z stage moving the focusing lens and / or the focusing mirror for focusing collimated first radiation from the first radiation source on the voxel of photocurable resin between the substrate / cured resin on the substrate and the wall. In one embodiment, the first Z stage is only moving the focusing lens and / or the focusing mirror, while the first radiation source is stationary.

[0055] In one embodiment, the focusing lens and / or the focusing mirror may be positioned on the common platform, so that the focusing lens and / or the focusing mirror will not unintentionally move relative the first radiation source. By moving the common platform, the first radiation source, the second radiation source, the detection unit, and then also the focusing lens and / or the focusing mirror are moved together, and the system is able to always know, where the focusing point of the first radiation source is located.

[0056] The first XY stage may move in a plane that is perpendicular to movement of the first Z stage. The first Z stage may be motorized. The first XY stage and the first Z stage may form a first XYZ stage. The first XYZ stage may be motorized.

[0057] The first XY stage may be configured to move the first radiation source, and optionally the second radiation source and / or the detection unit, and / or the common platform, in relation to the substrate without substantially changing the distance to the substrate. The first radiation source and the substrate may form a first axis between the first radiation source and the substrate, and the first XY stage may be configured to move the first radiation source, and optionally the second radiation source and / or the detection unit, and / or the common platform, in relation to the substrate in a plane substantially perpendicular to the first axis. The second XY stage may be motorized.

[0058] In an embodiment, the system may comprise a second XY stage configured to move the substrate and / or the container in relation to the first radiation source and / or the common platform.

[0059] In an embodiment, the system may comprise a second Z stage configured to move the substrate and / or the container towards and / or away from the first radiation source, or to move the first radiation source towards and / or away from the substrate and / or the container. Towards and / or away from means optically towards and / or away from - in the direction of the radiation beam from the first radiation source. The second Z stage may be the Z stage.

[0060] The second XY stage may move in a plane that is perpendicular to movement of the second Z stage. The second XY stage and the second Z stage may form a second XYZ stage. The second ZY stage may be motorized. In an embodiment, the system may comprise a third Z stage configured to move a substrate at least partly within the photocurable resin, or the container towards and / or away from the first radiation source. Towards and / or away from means optically towards and / or away from - in the direction of the radiation beam from the first radiation source.

[0061] In an embodiment, the third Z stage may be configured to move the substrate in relation to the container or the container in relation to the substrate. The third Z stage may be motorized.

[0062] In an embodiment, the system may comprise a processor configured to determine the first property based on the measured scattered, transmitted, and / or reflected second radiation by the detection unit and / or configured to control

[0063] - the first XY stage,

[0064] - the first Z stage,

[0065] - the second XY stage,

[0066] - the second Z stage,

[0067] - the third Z stage,

[0068] - temperature of the photocurable resin, and / or

[0069] - the first radiation source, based on the determined first property.

[0070] The first XY stage, the first Z stage, the second XY stage, the second Z stage, and / or the third Z stage may be controlled by controlling motors of the first XY stage, the first Z stage, the second XY stage, the second Z stage, and / or the third Z stage, so that the first XY stage, the first Z stage, the second XY stage, the second Z stage, and / or the third Z stage can be moved in the desired direction.

[0071] The first radiation source may be controlled by controlling the emitting power of the first radiation source, and / or the direction of the first radiation, and / or the optics directing the first radiation from the first radiation source towards the substrate and / or cured resin.

[0072] Fig. 1 shows a schematic representation of a printing system, like a 3D printing system.

[0073] In one embodiment the first adjustment motor(s) (101a) and / or the second adjustment motor(s) (101b) can be used to position the printing substrate (106) in relation to the at least semi-transparent membrane (103) regarding tilt and distance, as shown in Fig. 1. The first adjustment motor(s) (101a) may act on the printing substrate (106) for controlling the tilt and / or distance of the printing substrate (106), and / or the second adjustment motor(s) (101b) may act on the vat (108) for controlling the tilt and / or distance of the vat. The vat (108) may comprise a photocurable resin (102), and the printing substrate (106) may be submerged in the photocurable resin. The first and / or second adjustment motor(s) may ensure the correct height for a printing voxel (104) coming from a radiation source (105), such as the first radiation source and / or the second radiation source. The information of a height compensation (107) and calibration of tilt and distance between membrane and substrate for controlling the printing voxel size is stored and used to constantly ensure the correct tilt and distance between the surface of the substrate possibly with some printed material on the substrate and the membrane surface for obtaining the desired height and shape of the printed object. In one embodiment of the first aspect and / or the second aspect and / or third aspect, only one of the first (101a) and the second (101b) adjustment motor(s) is / are provided, which will be a cost-effective solution. In one embodiment of the first aspect and / or the second aspect and / or third aspect, both the first (101a) and the second (101b) adjustment motors are provided, which will be a solution that can move the printing substrate in relation to the radiation source (105) and the vat or container (108) in relation to the radiation source (105). The first (101a) adjustment motors may act on the printing substrate (106) so that a corner of the printing substrate that is above the photocurable resin (102) can be submerged. The second (101b) adjustment motors may act on the vat (108) so that a side or a corner of the vat, where the photocurable resin (102) is too shallow, can be lowered.

[0074] The photocurable resin is curable by irradiation within a first curable radiation range. Each of a first radiation source and a second radiation source may be any coherent radiation source, preferably a laser. The first radiation source may provide first radiation that is coherent and has a narrow bandwidth, where the first radiation may be focused to a spot on the printing substrate forming a printing voxel that is narrow so that an object with tiny details can be manufactured. The first radiation source emits within a first frequency range, wherein said first frequency range overlaps at least partly with the first curable radiation range for curing the photocurable resin. The second radiation source emits within a second frequency range, which is not overlapping with the first curable frequency range, so the second radiation source cannot cure the photocurable resin.

[0075] Other radiations sources, such as non-coherent LEDs or other light emitters, may be used as the first and second radiation sources. A requirement for the wavelength range of the first radiation source is that the emitted wavelength range is at least partly within the range wherein the photocurable polymer-resin is cured. A requirement for the wavelength range of the second radiation source is that the emitted wavelength range is outside the range wherein the photocurable polymer-resin is cured.

[0076] In one embodiment, the method involves the step of controlling and / or varying the size or diameter of the printing voxel for printing details of the object to be manufactured having the right size. If the size of the printing voxel is smaller than a feature size of a particular part of the object, the additive manufacturing will take unnecessarily long time. If the size of the printing voxel is larger than the feature size of a particular part of the object, the additive manufacturing cannot correctly produce the particular part. To increase speed and still provide the object at the correct specification and / or resolution, the size or diameter of the printing voxel will preferably be varied during the additive manufacturing. The size or diameter of the printing voxel can be varied by varying a spot size or laser spot size coming out of the first radiation source, varying a nozzle size of a nozzle positioned between first radiation source and the object and / or printing substrate, varying a focal plane of focused first radiation in relation to the object and / or the printing substrate. In the focal plane, the spot size is the smallest and resolution the highest, while moving the focal plane up or down relative to the printing substrate or the semi-transparent membrane the size will be increased, and the deposited energy density of the radiation source will be reduced. By varying the spot size in the printing plane, variable printing resolution can be achieved and controlled and variable printing speed per surface area can be achieved and controlled. By measuring the disposed radiation energy and spot size of the first radiation, the printing size can be controlled at the correct size and the correct disposed radiation energy. By measuring the disposed radiation energy, the time for curing a voxel can be determined, and the voxel will not be irradiated longer than necessary.

[0077] This is a major advancement for making large volume 3D prints with microscale features, as the printing time scales to 3rdpower with printing resolution (for example, doubling the resolution will increase the time to print by 23= 8 times). By controlling the voxel size, it is possible to perform variable printing resolution. To be able to control the printing resolution, knowledge of the surface of the membrane, printing substrate, and the distance between these two must be known to achieve the correct and desired resolution.

[0078] Fig. 2 shows a focusing lens (200a) focusing first radiation (solid lines) from the first radiation source (208) on a voxel (201) below a surface of the printing substrate (202) and within the photocurable resin (204). The focused first radiation forms a conical shape (200) between the printing substrate (202) and the focusing lens (200a). By changing the position of the focal point of the focused first radiation in relation to the printing substrate (202) the printing resolution can be changed and controlled. By calibrating the radiation source optics (206) with the relevant surfaces (i.e. the surface of the printing substrate (202) and the surface of the semi-transparent membrane (205) in the printing setup, precise and variable printing resolution is achieved.

[0079] The data of where the focused light spot or laser spot or voxel (201) has a certain size and how strong the energy density at a given optical plane is, is measured with a sensor (209) and stored as a power-vs-height diagram, and calibrated to the measured surfaces (i.e. the surface of the printing substrate (202) and the surface of the at least semi-transparent membrane (205)) within the control software of the system.

[0080] In one embodiment, the radiation source optics (206) can be a stable and rigid optical platform (206), where the focusing lens (200a), the first (208) and second (207) radiation sources, the optical sensor (209) as well as further optics like mirrors (210) and semi-transparent mirrors (211) for guiding the radiation from the radiation sources to the focusing lens are mounted on the platform, so that moving the platform (206) means moving the focusing lens (200a), the first (208) and the second (207) radiation sources, the optical sensor (209), and the further optics all together. The advantage is that the relative position of the focusing lens, the first and second radiation sources, the optical sensor and the further optics will be constant, and moving the platform (206) a certain distance in a certain direction will move the voxel (201) the same certain distance in the same certain direction. A printing setup e.g. as the one shown in Fig. 2 may ensure correct and controllable printing and / or processing parameters with nano-scale precision and predictable behavior. This can be achieved using different materials, shapes, and mechanisms for all the components mentioned in the description above. By having first stages or motors like e.g. height adjustment motor(s), XY adjustment motor(s) and tilt adjustment motor(s) for XYZ movement of the container or vat (203), and / or of the printing substrate (202) and a second stage or motor for Z movement of the focusing lens (200a) and / or third stages or motors for XYZ movement of the radiation source optics (206) including the second stage or motor for independent Z movement of the focusing lens (200a), wherein the first stages or motors and the second stage or motor, and / or the third stages or motors and the second stage or motors are controlled by a computer or processor, wherein the computer / processor has electronic access to the electronic information regarding the shape and position of the printing substrate and / or the membrane (205), the container (203), and / or of the printing substrate (202) and / or the focusing lens (200a) can be positioned for each printing position on the printing substrate such that the desired resolution is achieved for each point and such that the printing time is minimized. The computer / processor will control the first stages or motors and the second stage or motor, and / or the third stages or motors and the second stage or motor so that the correct printing conditions are met. The printing substrate (202) and / or the membrane (205) will be moved in relation to the focusing lens (200a) and / or the focusing lens (200a) will be moved in relation the printing substrate (202) and / or the membrane (205) so that for each location on the printing substrate (202) the correct voxel regarding size is achieved for generating the object. Generally, such movements like the first stage and the second stage for moving the substrate can be called an XYZ stage, such an XYZ piezoelectric stage.

[0081] For achieving a high resolution during the printing process using the herein disclosed method nano-meter precise, high-speed stages to move the optics like the radiation source optics (206) and / or the substrate and / or the vat around to the correct position are preferable. The stages can be high precision stages, like e.g. nanopositioning stages, like nanopositioning stages manufactured by Smaract (Oldenburg, Germany), Standa (Vilnius, Lithuania) and Dover Motion (Boxborough, MA, USA). A computer numerical control (CNC) known as G-code can be used, which parses a CAD file into steps, lines and passages that constitutes a replica of the object that will be processed by the system. The micrometer-precise adjustments and calibrations are implemented by uploading a normal G-code of the desired object to the system software for the printing setup. The program then does all the measurements and calibrations, which is then added to the “path” of the G-code. Thus, the resulting printing passage is the uploaded 3D object plus the measurements of the different components, calculations of resolution etc. This overlap is calculated and made inside the software after uploading a print, but before printing.

[0082] An example of this is implemented into a printing setup shown in Fig. 2, which shows how the radiation source optics (206) are integrated in the vat-photopolymerization system (203). The radiation source optics (206) comprises the first (207) and the second (208) radiation sources, and a sensor, like an optical sensor, (209). The first radiation from the first radiation source (208) is capable of curing the photocurable resin (204), and the second radiation from the second radiation source (207) will pass through the photocurable resin (204) without curing the photocurable resin (204) and possibly with a minimal interaction with the uncured photocurable resin (204). The second radiation from the second radiation source (207) will preferably interact with the cured photocurable resin (204), so that printed layers can be detected and determined.

[0083] By detecting second radiation reflected, transmitted and / or scattered at a first interface between the substrate / cured resin and the uncured photocurable resin and by detecting second radiation reflected, transmitted, and / or scattered at a second interface between the wall and uncured photocurable resin using the optical sensor, the precise location of the first and second interfaces can be determined. That means that the topography of the interface between the substrate possibly including cured resin and the uncured photocurable resin can be determined to a high degree of precision, and that the topography of the interface between the uncured photocurable resin and the wall can be determined to a high degree of precision so that the border of the voxel at the substrate / cured resin and the border of the voxel at the wall can be determined at all times. By also knowing the width of the first radiation, i.e. the diameter of the cylinder beam or truncated cone beam of the first radiation, the size of the voxel can be determined at all times. The sensor measures a focus error signal (the optical sensor receives the reflected laser beam and generates a focus error signal to be precise) to predict a location of the focal plane on or in relation to a reflective surface. The first interface and / or the second interface can be the at least one first property.

[0084] The optical sensor may be a device capable of detecting the radiation or a part of the radiation generated by the radiation source and to quantify the amount of detected radiation. A commercial photodiode, an LCD camera or any other optical sensor capable of detecting and quantifying radiation, preferably laser beams, may be used.

[0085] The first radiation and / or the second radiation, like e.g. a laser, interacting with the bottom part of the wall (the at least semi-transparent membrane) or interacting with the printing substrate may be understood as a third or fourth radiation sources, respectively. The third and fourth radiation sources may not be radiation sources. The third and fourth radiation sources may be reflections of the first and second sources, respectively, detected by the optical sensor. Alternatively, the third and fourth radiation sources originate from scattering, transmission or emission from the different components of the system comprising the herein disclosed printing setup.

[0086] By knowledge of the cone-shape of the focused first radiation and the cone-shape of the focused second radiation, it is possible to calculate and determine at what height the laser will result in a certain printing resolution. Fig. 3 shows to the upper left a schematic example of the focal point (304) of the first or the second radiation being located in a lower area (303) below a printing plane (302), which can be the substrate or a somewhat finished object printed on the substrate. Fig. 3 shows to the upper center a schematic example of the focal point (304) of the first or the second radiation being located in the printing plane (301). Fig. 3 shows to the upper right a schematic example of the focal point (304) of the first or the second radiation being located in an upper area (301) above the printing plane (301). Furthermore, synchronous utilization of the focus error signal (305) allows for implementation of mechanical calibration, detection of residual material, and measurements of printing topography.

[0087] Some of the measured variables for the membrane and printing substrate are optical, like transmission, reflection, and absorption, which is directly used to calculate the power or intensity of the first radiation entering the voxel within the photocurable resin. This calculation is performed by a processor or a computer having the suitable software, as the returned signal can be subtracted from the initial radiation and give a difference in energy that corresponds to the disposed energy in the material. This calculation is stored within the program for a given membrane, substrate, and material. Thus, a database of properties for different consumables may be generated.

[0088] Example

[0089] A characterization of the membrane and / or the printing substrate can be performed prior to the printing process. Examples of this can be sorting out surfaces that are too rough, materials that exhibit incorrect properties (resin gone bad etc.) or damaged parts. From this, errors can be detected without having to run a printing process, and thus saving time and resources. These measurements can also be used to verify the preparation process of consumables are up to par with the required precision and make changes if, and when, necessary. This allows for management of any external processes performed to prepare and fabricate parts crucial for the printing process, enabling the necessary quality required to achieve the high resolution without the need for extra measurement equipment (as all relevant properties are measured by the system and stored in the database for future use).

[0090] Examples of measurements performed on the substrate 403 and the membrane 404 are shown in Fig. 4A, 4B, 4C and 4D. These are examples of measurements performed by the radiation source optics comprising the first and second radiation sources (not shown) and the optical sensor (not shown), where the first and second radiation is focused by the focusing lens 402. The measurements may be stored to an electronic print file and may be verified during the print by using a radiation source that does not cure the photocurable resin contained in the vat 401.

[0091] Fig. 4A shows a displacement of the focusing lens 402 parallel with respect to the vat 401 towards the right side of the vat, while measuring the changes of height of the membrane 404 for calibrating the system regarding the membrane and maybe the focusing lens. The measured changes in height may be caused by the rugosity of the membrane, localized increases of the thickness or other physical deformations of the membrane. By performing this scan of the membrane 404, preferably before any printing has been initiated, the position, like the height position, of the membrane for each voxel during the additive manufacturing of the object can be measured. In other words, for each XY coordinate over the surface of the membrane, a Z coordinate (Ahi) for the position of the membrane is determined. The measured coordinates for the membrane are stored electronically.

[0092] Fig. 4B shows a displacement of the focusing lens 402 parallel with respect to the vat 401 towards the right side of the vat, while measuring the changes of height A / I2of the printing substrate 403 for calibrating the system regarding the printing substrate and maybe the focusing lens. The measured changes in height may be caused by an undesired non-parallel position of the substrate 403 with respect to the membrane 404 and / or the focusing lens 402, by a local height variation of the substrate or other physical deformations affecting the surface of the substrate. By performing this scan of the printing substrate 403, preferably before any printing has been initiated, the position, like the height position, of the printing substrate 403 for each voxel during the additive manufacturing of the object can be measured. In other words, for each XY coordinate over the surface of the printing substrate, a Z coordinate (Ah2) for the position of the printing substrate is determined. The measured coordinates for the printing substrate are stored electronically. If e.g. the printing substrate 403 turns out to be tilted or the focusing lens 402 is not displaced parallel to the printing substrate, the printing substrate 403 and / or the focusing lens 402 can be corrected, so that the printing substrate 403 is not tilted and / or the focusing lens 402 is displaced parallel to the printing substrate. Generally, the stages for moving the printing substrate 403 and the focusing lens 402 are so precise that no further calibration of the substrate 403 is necessary. However, a second calibration measurement of the printing substrate could be contemplated, if e.g. the printing substrate was very much out place and have to be moved a long distance by the stages.

[0093] Fig. 4G shows a displacement of the focusing lens 402 perpendicular with respect to the membrane 404 and / or the substrate 403 and / or the photocured resin (not shown). The perpendicular displacement of the focusing lens allows to tune the width of the voxel or the spot size of the radiation sources on the membrane and / or the substrate and / or the photocured resin (not shown), wherein the minimum radiation spot is achieved at the focal plane of the focusing lens. The perpendicular displacement allows, for example, the printing resolution on the substrate to be calibrated for different positions of the focusing lens. Fig. 4D shows a free displacement of the focusing lens 402 with respect the membrane 404 and the substrate 403. The parallel and perpendicular displacements to the membrane and / or the substrate, and / or the photocured resin, are performed based on the measured height variations in Figs. 4A, 4B and 4C allowing to expose the photocurable resin to the curing first radiation source at each coordinate on the substrate at a precise distance between the substrate and the membrane and / or at a precise spot size of the focused first radiation, so that the voxel for each coordinate on the substrate will have the correct size in all three dimensions. Ultimately, this height and lateral displacement variations introduced to the focusing lens along its movement during the curing process allows to improve the spatial resolution of the printed object or structure.

[0094] In one embodiment, the focusing lens 402 can be mounted on a platform (not shown), where the first and second radiation sources (not shown) and the optical sensor (not shown) are also mounted on the platform, so that moving the platform moves the focusing lens 402, the first and second radiation sources and the optical sensor.

[0095] Extra features and parameters can be controlled and added to add functionality to the closed-loop system. For example, as some materials are temperature and humidity dependent, heating elements, humidifiers, and detectors for both can be integrated into the system and connected to the close-loop feedback system within the software. This allows for temperature and / or humidity dependent printing, modifying parameters over time. This can give different material properties in different parts of the printing substrate depending on the photocurable resin used. Measuring this data and integrating into the software along with information of material properties in given conditions can be used to vary printing properties. It will also be possible to measure and log the behavior of the printing materials and components under printing, and thus create a database of material functionalities under given parameters.

[0096] Lastly, notable data that can be recorded are residual photocurable resin in the vat, as well as surface topography of the substrate and of printed objects. While these are both “nice-to-haves”, inclusion of these saves resources on detectors and optical systems for post-print inspection. Using a non-curing radiation source, the residual photopolymer or photocurable resin in a vat can be detected. While moving the focal spot of the non-curing radiation source along the vertical direction to pass the interface of the material, the optical sensor receives the reflective beam. Then the height or distance difference between the interface of the membrane and of the photocurable resin, and the interface of the photocurable resin and of air or the substrate, can be calculated. The printing system can estimate the amount of residual photocurable resin in the vat by the height or distance difference. The function can be realized by two extra sensors (one for maximum, one for minimum).

[0097] In an embodiment, the photocurable resin in the vat might be refilled during the printing process or after the printing process is performed.

[0098] The disclosure allows the measurement of printed surface topography. While scanning the focal spot of the radiation source along the printed surface, the optical sensor can measure the surface height of each point by the feedback signal. After collecting all the height or coordinate information, the surface topography of the printed object can be constructed.

[0099] The collected measurements create an informative database of materials, membranes, substrates, preparation processes and optical properties. This information can be stored and used to do predictive analysis of new materials used for all components. With this information, tests and implementation of new methods and materials can be implemented much quicker. As many photocurable resin formulas share chemicals, it will help establish ideal printing parameters much quicker. It will also be a good way to screen useful materials for producing membranes and substrates, as well as keeping an overview of compatibility between different materials ().

[0100] For practical implementations, the disclosed embodiment features two radiation sources, namely e.g. a laser at 405 nm and another of 650 nm wavelength. One works to polymerize most photocurable resins, while the other transmits through without any effect. These two are used to realize all implemented features described above related to radiation sources. For the mentioned functions above, most of them are implemented, especially any physical measurements. Different types of photocurable resins may require different wavelengths depending on the chemical processes involved during the particular curation process.

[0101] Preferably, the manufactured object is a 3D object or structure. Alternatively, planar 2D objects may be manufactured by the disclosed method by curing one or more monolayers of the photocurable resin. Quasi-2D may also be manufactured by selectively curing a stack of monolayers to form a structure predominantly flat across its outermost surface in contact with the photocurable resin. Arrays of quasi-1 D objects or structures may be manufactured, wherein said arrays might comprise a periodic structure.

[0102] Print process method:

[0103] The optics are turned on, and the position of the vat membrane is determined using the focus error signal. This is possible due to the semi-transparent / reflective nature of the membrane. The membrane is calibrated in terms of position and tilt. This is possible due to stepper-motors attached to the vat, allowing for up / down movement of the corners of the vat.

[0104] Using geometrical calculations, the surface is measured. A program then calculates the tilt, determines the necessary movement to parallelize the vat membrane with the OPU, and activates the motors to move it. This is iterated until sufficient parallelism is achieved. Normally, parallelism around 1 pm can be achieved using this method, iterating 2-3 times. This is over a surface of several mm to cm in length / width.

[0105] When the membrane is adjusted so that the membrane is parallel to a plane in which the first and second radiation sources, the focusing lens, and the optical sensor together, e.g. on a platform, are movable by stages or motors, a measurement of the surface flatness of the membrane is made and stored into the software.

[0106] This measurement of the membrane may constitute the base-layer of the printing calibration. By knowing the exact position of all points of the membrane surface, the optics can be fixed at a known position relative to the surface of the photocurable resin. Then, the substrate / printing surface is brought in proximity to the vat membrane, approximately 10-1000 pm. When the substrate is adjusted so that the substrate is parallel to a plane in which the first and second radiation sources, the focusing lens, and the optical sensor together, e.g. on a platform, are movable by stages or motors, a measurement of the surface flatness of the substrate is made and stored into the software.

[0107] This measurement of the substrate may constitute the base-layer of the printing calibration. By knowing the exact position of all points of the substrate surface, the optics can be fixed at a known position relative to the surface of the photocurable resin. Then, the substrate / printing surface is brought in proximity to the vat membrane, approximately 10-1000 pm.

[0108] Using the focus error signal and the optics, the printing substrate surface is measured in terms of position and tilt. Applying the same method as for the membrane, the printing surface can be calibrated in terms of tilt related to the membrane.

[0109] When sufficient parallelism between the membrane and the printing substrate surface is achieved, the substrate printing surface may be measured once more to determine its flatness. This map is stored into the software. Fig. 5 shows an example of a flatness map extracted from the membrane of a vat. Note that the height variations are in the order of 10 pm, implying that the membrane is reasonably flat and that the method herein disclosed is capable of encompassing for the measured variation in height.

[0110] Using the two flatness maps, an optimal position for the substrate is determined. This corresponds to a desired distance between the two surfaces (i.e. the surface of the printing substrate and the surface of the semi-transparent membrane), taking into account the flatness of each surface (ensuring that the distance chosen maximizes the area at which the distance between the two surfaces is as desired). This is done by geometrical calculations in the software, determining the average distance of all measured points of the two surfaces being as close to the desired distance as possible.

[0111] All the above steps can be performed using a non-curable radiation source while the vat is filled with photocurable resin that is to the first radiation. When both surfaces (i.e. the surface of the printing substrate and the surface of the semi-transparent membrane facing the photocurable resin) are measured and the data are stored, the optics are adjusted. Here, based on experimental data for a given material and a certain laser output on the OPU / optics, an offset is calculated and processed into the stage of the OPU. Both the OPU / optics, vat and substrate can move on a separate Z-axis, allowing for continuous adaptation of all parameters revolving height and distance, focus point and penetration depth of the photocurable resin.

[0112] The G-code is initialized in the software. The G-code is generated from some CAD software, sliced in an external slicing tool, and uploaded to the software. The G-code only delivers geometrical information of the printed object (XYZ position coordinates). Upon uploading, parameters specific to the desired printing resolution and quality is added to the resulting G-code. These are parameters such as speed, laser intensity, printing offset, layer thickness, acceleration etc. These are specific and determined for each material. These settings are added as command-lines in the G-code. These parameters vary depending on the printing material and has been experimentally determined.

[0113] Depending on the prepared G-code, the program determines if some areas can be cured / cross-linked using lower resolution than initially drawn in the STL file (and later in the slicing software). For example, if the walls consist of 3 identical square layers with a size of 500x500 pm, then the software will change the trajectory, position, and printing parameters to generate conditions that would print the 3 layers in one, with much lower resolution (larger printing voxel) than normally. This feature can vary the resolution of the printing voxel diameter from 1-5 micron to 20-50 micron, depending on the material. In a different configuration, it is possible to achieve configurations that create a resolution of up to 500 pm or larger.

[0114] As layers can only be added to (it is not possible to move back down to the 2ndlayer if 5 layers are printed elsewhere, as the object would then crash into the membrane), the software must do the prediction based upon the entire object, layer-for-layer, and not just for a local area. If local areas have large, flat prints, then this can be cured with a lower resolution as well, but the distance between the membrane and the substrate printing surface would be the same to conform to the necessary layer thickness across the print. When the positions, trajectories, layers, and laser / optical settings are calculated, the printing may be initialized. Here, the software may read lines (typically a couple of lines of positions from the G-code) and calculate the corrected path that takes the surface calibration measurement of the membrane into account. This can be achieved by separating each line into smaller segments. The length of these segments can be determined and limited by technical limitations of the electronic control system (i.e., the “stream base rate” of the electronic controller used to do the calculations). Correction data of each intermediate point of trajectory can be made by interpolation of the membrane calibration surface data.

[0115] As the distance between the membrane surface and the focal point of the laser may be a crucial parameter to control the voxel width, the offset between the focal point and membrane may advantageously be kept the same at all times for enabling high and uniform printing resolution. As the cured photocurable resin between the membrane and the substrate is cross-linked (at least if the two surfaces (i.e. the surface of the printing substrate and the surface of the semi-transparent membrane) are within 50 pm of each other), a first printed layer will experience some variation at the substrate surface (typically in the 1-5 pm range depending on the flatness of the substrate relative to the membrane). This effect is cancelled out when the first printed layer has been printed. The overall quality and precision of the printed object is more dependent on the membrane surface. For that reason, it is especially important to characterize the membrane.

[0116] The printing process constitutes of layer-by-layer printing, the achieved resolution for each coordinate of the print is determined by the size of the voxel at that coordinate. Typically, the voxel is 2-20 pm in diameter and 5-25 pm in height (like a cylinder or more precisely a truncated cone since the first radiation is focused). The nature of the high resolution of this system causes feedback-control and inspection of the print extremely difficult. Some patents mention “visualization” of the printing, but only refers to having a camera or a window to look at the print. This would not allow for inspection of features at the range of our resolution. Instead, what is being proposed and used, is a non-curable radiation source to monitor the printed object. Currently the monitoring step can be performed between each printed layer, before the next is processed. Because all moving parts are calibrated and monitored in the same system software, all movements are being accounted for. Thus, very little active monitoring is necessary during the printing. Flatness, parallelization, and distance are constant.

[0117] Some distortions of the membrane and / or the substrate and / or the photocured resin can occur because of environmental changes such as temperature and humidity. This can be avoided by using a temperature sensor and / or a humidity sensor embedded into the system. Temperature and humidity can be actively controlled and monitored with a PID (proportional-integral-derivative) controller-like system. During the printing process, the system controls temperature dependent displacements of frame and internal components. This is done with reference to point-measurements relating displacements of the membrane and / or the substrate and / or the photocured resin to temperature changes. This way constant and precise position of most parts can be controlled.

[0118] For improving the printing result, dust in the environment around the photocurable resin should be avoided or at least be kept below a certain predefined level. In this connection, the system may comprise a dust particle measuring device for determining the number of particles in the vat, e.g. just above the photocurable resin. The system may be positioned in a dust proof chamber, where the chamber preferably is kept at an overpressure, e.g. by a pump, for preventing dust particles to enter the environment around the photocurable resin.

[0119] As the printing finishes, the substrate moves up, away from the vat, and the printing surface with the object can be taken off from the substrate for washing and post-print- processing.

[0120] The method may comprise the step of calculating a thickness of the wall or the membrane. In addition, the method may comprise the step of calculating a measurable distance between the substrate and the wall / membrane. The properties to be determined by any of the radiation sources are one or more of the following physical properties: roughness of e.g. the substrate and / or the wall, topography of e.g. the substrate and / or the wall, physical coordinates of e.g. the substrate and / or the wall, parallelism e.g. between the substrate and the wall, flatness of e.g. the substrate and / or the wall, deformation of e.g. the substrate and / or the wall, thickness of e.g. the wall and / or the photocurable resin such as between the wall and the substrate; optical properties: transmission characteristics of e.g. the photocurable resin and / or the wall, reflection characteristics of e.g. the substrate and / or the photocurable resin and / or the wall,; properties of the at least first radiation source, such as energy value, radiation source size, irradiation time; the distance between the first radiation source and the substrate; the distance between the substrate and the wall or between the substrate or the wall and the first radiation source, which will provide information about any unintentional mobility of the substrate, the wall and the first radiation source in relation to each other; or a height map for forming at least one layer.

[0121] The method may comprise the step of providing an analyzer unit configured such that the first property of the wall and / or the substrate and / or the photocured resin is measured and compared with a pre-defined property of the same kind as the first property; adjusting the position of the container, preferably the wall; adjusting the position of the substrate and / or the wall such that the substrate and the wall are parallel; adjusting the position of the substrate; or adjusting the position of the radiation source.

[0122] In addition, the method may comprise the step of controlling a spot size of the laser based on the first property of the wall; the step of measuring the first property of the wall and / or the substrate and / or the photocured resin before and / or during and / or after curing the part of the photocurable resin; the step of measuring the temperature and / or humidity of the photocurable resin; or the step of adjusting the set of processing parameters based on the measured temperature and / or humidity of the photocurable resin.

[0123] In an embodiment, the at least one layer has a thickness of between 0.1 pm to 1000 pm, preferably between 0.1 pm to 1000 pm, such as between 0.5 pm to 500 pm, between 1 pm to 50 pm; and the object has a height of between 0.1 pm to 10 cm, such as between 20 pm to 5 cm, between 1 mm to 2 cm.

[0124] In an embodiment the method comprises the step of providing a second photocurable resin curable into a second cured resin by the second radiation, wherein the second photocurable resin is contained in the container, and wherein the substrate and / or the object is submerged in the second photocurable resin. Using this second photocurable resin, the second radiation source can also be used for curing. The photocurable resin may be curable by UV radiation, while the second photocurable resin may be curable by IR radiation or heat, or vice versa. In addition or instead of UV radiation and IR radiation, one of the photocurable resin or the second photocurable resin is curable by visible light. The method can manufacture an object comprising two different materials having different properties, like a hard core and a soft outer part, two different colours, a hardwearing outer shell surrounding a cheaper material, etc. It may be advantageous that the photocurable resin is totally removed from the container before the second photocurable resin is added to the container, so that the first radiation will not cure any photocurable resin at this stage.

[0125] In an embodiment, the second photocurable resin is non-curable by the first radiation, and the method comprises the step of determining at least one second property of the wall, the second photocurable resin, the cured resin, the object and / or the substrate by measuring a scattered, transmitted, and / or reflected first radiation comprising the first radiation reflected, transmitted, and / or scattered by the wall, the photocurable resin, the cured resin, the substrate, and / or the object, respectively, and controlling a second set of processing parameters based on the at least one second property for forming at least one layer of a second object by curing a part of the second photocurable resin on the submerged substrate or the submerged object.

[0126] Since the second photocurable resin is non-curable by the first radiation, the first radiation can be used to determine the at least one second property, so that the second set of processing parameters based on the at least one second property can be used to control the position(s) of the wall, the second photocurable resin, the cured resin, the object, the substrate, the second radiation source, and / or where the second radiation hits the second photocurable resin, so that the second object can be manufactured to the same high degree of resolution as the object.

[0127] In an embodiment, the wavelength of the second radiation source is between 295 nm to 800 nm, like between 450 nm and 800 nm, or above 450 nm, preferably 650 nm; the wavelength of the first radiation source is between 295 nm to 800 nm, like between 295 nm and 600 nm, between 295 nm and 450 nm, preferably 405 nm; and the detection unit comprises an optical sensor, that is preferably sensitive within 295 nm to 800 nm, like between 450 nm and 800 nm, or above 450 nm, preferably 650 nm.

[0128] In an embodiment, the system may comprise a thermometer for measuring temperature of the photocurable resin and / or of the environment around the photocurable resin, and / or a hygrometer for measuring humidity of the photocurable resin and / or of the environment above the photocurable resin. The photocurable resin, the container and / or the substrate may expand and / or contract depending on the temperature and / or the humidity.

[0129] In an embodiment, the system may be configured to control the Z stage based on the set of processing parameters so that the substrate and the container have the right position relative to each other. The system may comprise a first feedback system that will control the position of the substrate and / or the container, so that the substrate and the container have the right position relative to each other.

[0130] In an embodiment, the system may be configured to control the Z stage based on the set of processing parameters so that a first unintentional move between the first radiation source, and the substrate and / or the container detected by the detection unit is corrected to at least partly eliminate the first unintentional move. The system may comprise a second feedback system that will at least partly eliminate any first unintentional move between the first radiation source, and the substrate and / or the container, so that the first unintentional move does not influence the additive manufacturing of the object.

[0131] In an embodiment, the system may be configured to control the second Z stage based on the set of processing parameters so that a second unintentional move between the first radiation source, and the substrate and / or the container detected by the detection unit is corrected to at least partly eliminate the second unintentional move. The system may comprise a third feedback system that will at least partly eliminate any second unintentional move between the first radiation source, and the substrate and the container, so that the second unintentional move does not influence the additive manufacturing of the object.

[0132] In an embodiment, the system may be configured control the first XY stage or the second XY stage based on the set of processing parameters so that a third unintentional move between the first radiation source, and the substrate and / or the container detected by the detection unit is corrected to at least partly eliminate the third unintentional move. The system may comprise a fourth feedback system that will at least partly eliminate any third unintentional move between the first radiation source, and the substrate and / or the container, so that the third unintentional move does not influence the additive manufacturing of the object.

[0133] In an embodiment, system may be configured to dynamically adjust the set of processing parameters such that a relative distance between the wall and the substrate is maintained. The wall and the substrate may create borders on two opposite sides of the voxel, where photocurable resin is cured into cured resin on the substrate or on the object. The first radiation passing through the wall may provide the other four borders of the voxel. To be able to manufacture the object with a high resolution, it is important to control the relative distance between the wall and the substrate.

[0134] Items

[0135] 1. A method for additive manufacturing of an object, comprising the steps of: providing a first radiation source emitting a first radiation; providing a container containing a photocurable resin curable into cured resin by the first radiation, the container comprising a wall transparent or at least semi-transparent to at least a part of the first radiation; providing a substrate submerged in the photocurable resin in the container; providing a second radiation source emitting a second radiation, wherein optionally the photocurable resin is non-curable by said second radiation; determining at least one first property of the wall, the photocurable resin, the cured resin, and / or the substrate by measuring a scattered, transmitted, and / or reflected second radiation comprising the second radiation reflected, transmitted, and / or scattered by the wall, the photocurable resin, the cured resin and / or the substrate, respectively; controlling a set of processing parameters based on the at least one first property for forming at least one layer of an object by curing a part of the photocurable resin on the submerged substrate.

[0136] 2. The method according to item 1, wherein the first property relates to or is a position of

[0137] - a first interface between the substrate / cured resin and the uncured photocurable resin and / or

[0138] - a second interface between the wall and uncured photocurable resin.

[0139] 3. The method according to item 1, wherein the first property relates to a first interface between the substrate / cured resin and the uncured photocurable resin and / or a second interface between the wall and uncured photocurable resin.

[0140] 4. The method for additive manufacturing according to any of the preceding items, wherein the step of determining the at least one first property of the substrate comprises a step of determining at least one first property of the object formed on the substrate.

[0141] 5. The method for additive manufacturing according to any of the preceding items, wherein the wall is made of polymer, such as polydimethylsiloxane (PDMS), silicone, poly(methyl methacrylate), glass, such as an optical glass or quartz or silica, preferably fused silica, or a combination thereof. The method for additive manufacturing according to any of the preceding items, wherein the substrate is provided above the wall and configured such that the substrate is movable upwards and / or downwards relative to the container. The method for additive manufacturing according to any of the preceding items, wherein the first radiation source is provided below the wall and configured such that the radiation source is movable upwards and / or downwards relative to the container. The method for additive manufacturing according to any of the preceding items, wherein the second radiation source is provided below the wall and configured such that the radiation source is movable upwards and / or downwards relative to the container. The method for additive manufacturing according to any of the preceding items, wherein the method comprises the step of moving the first and / or the second radiation source(s) towards the container, and / or away from the container, like upwards and / or downwards, respectively, if the first and / or the second radiation source(s) is / are provided below the wall. The method for additive manufacturing according to any of the preceding items, comprising the step of calculating a thickness of the wall. The method for additive manufacturing according to any of the preceding items, comprising the step of calculating a distance between the substrate at the location of the first and / or second radiation sources and the wall, or comprising the step of calculating a distance between the substrate and the wall. The method for additive manufacturing according to any of the preceding items, wherein the first property is one or more of the following physical properties:

[0142] - roughness of the substrate and / or the wall,

[0143] - topography of the substrate and / or the wall,

[0144] - physical coordinates of the substrate and / or the wall,

[0145] - parallelism between the substrate and the wall, - flatness of the substrate and / or the wall,

[0146] - deformation of the substrate and / or the wall,

[0147] - thickness of the photocurable resin and / or the wall,

[0148] - transmission characteristics of the photocurable resin and / or the wall,

[0149] - reflection characteristics of the substrate and / or the photocurable resin and / or the wall, and

[0150] - distance between the substrate or the wall and the first radiation source.

[0151] 13. The method for additive manufacturing according to any of the preceding items, wherein the first property is one or more of the following optical properties: transmission characteristics of the photocurable resin and / or the wall or reflection characteristics of the substrate and / or the photocurable resin and / or the wall.

[0152] 14. The method for additive manufacturing according to any of the preceding items, wherein the set of processing parameters comprises one or more of the following: properties of the at least first radiation source, such as energy value, radiation source size, irradiation time; the distance between the first radiation source and the substrate; the distance between the substrate and the wall; a height map for forming at least one layer.

[0153] 15. The method for additive manufacturing according to any of the preceding items, comprising the step of directing the first radiation based on the determined first property.

[0154] 16. The method for additive manufacturing according to any of the preceding items, comprising the step of controlling the set of processing parameters based on the property of the substrate.

[0155] 17. The method for additive manufacturing according to any of the preceding items, comprising the step of controlling the set of processing parameters based on the at least one layer of the object.

[0156] 18. The method for additive manufacturing according to any of the preceding items, comprising the steps of determining a second property of the first radiation source and controlling a set of processing parameters based on the second property. The method for additive manufacturing according to item 18, wherein the first radiation source is a laser, and wherein the second property is one or more of the following: laser intensity, laser uniformity, beam / laser spot shape, point spread function, laser focus point (z-shift of laser focus), depth of view of the first radiation source. The method for additive manufacturing according to any of the preceding items, comprising the step of providing an analyzer unit configured such that the first property of the wall and / or the substrate and / or the photocured resin is measured and compared with a pre-defined property. The method for additive manufacturing according to any of the preceding items, comprising the step of adjusting the position of the container, preferably the wall. The method for additive manufacturing according to any of the preceding items, comprising the step of adjusting the position of the substrate and / or the wall optionally such that the substrate and the wall are made parallel. The method for additive manufacturing according to any of the preceding items, comprising the step of adjusting the position of the substrate. The method for additive manufacturing according to any of the preceding items, comprising the step of adjusting the position of the first and / or the second radiation source. The method for additive manufacturing according to any of the preceding items, wherein the first and / or the second radiation source is / are (a) coherent radiation source(s), such as (a) laser(s). The method for additive manufacturing according to any of the preceding items 19 - 25, comprising the step of controlling a spot size of the laser based on the property of the wall. The method for additive manufacturing according to any of the preceding items, comprising the step of measuring the property of the wall and / or the substrate and / or the photocured resin before and / or during and / or after curing the part of the photocurable resin. The method for additive manufacturing according to any of the preceding items, comprising a step of measuring temperature of the photocurable resin and / or of the environment around the photocurable resin, such as the air above the photocurable resin and / or wall and / or the substrate and / or the photocured resin. The method for additive manufacturing according to any of the preceding items, comprising a step of measuring humidity of the photocurable resin and / or of the environment above the photocurable resin, such as the air above the photocurable resin. The method for additive manufacturing according to item 28 or 29, comprising the step of adjusting the set of processing parameters based on the measured temperature and / or humidity. The method for additive manufacturing according to any of the preceding items, wherein the container containing the photocurable resin is refilled with additional photocurable resin during the manufacturing of the object. The method for additive manufacturing according to any of the preceding items, wherein the at least one layer has a thickness of between 0.1 pm to 1000 pm, preferably between 0.1 pm to 1000 pm, such as between 0.5 pm to 500 pm, between 1 pm to 50 pm. The method for additive manufacturing according to any of the preceding items, wherein the object has a height of between 0.1 pm to 10 cm, such as between 20 pm to 5 cm, between 1 mm to 2 cm. The method for additive manufacturing according to any of the preceding items, wherein the method comprises the step of

[0157] - providing a second photocurable resin curable into a second cured resin by the second radiation, wherein the second photocurable resin is contained in the container, and wherein the substrate and / or the object is submerged in the second photocurable resin. 35. The method for additive manufacturing according to item 34, wherein the second photocurable resin is non-curable by the first radiation, and the method comprises the steps of determining at least one second property of the wall, the second photocurable resin, the cured resin, the object and / or the substrate by measuring a scattered, transmitted, and / or reflected first radiation comprising the first radiation reflected, transmitted, and / or scattered by the wall, the photocurable resin, the cured resin, the substrate, and / or the object, respectively, and controlling a second set of processing parameters based on the at least one second property for forming at least one layer of a second object by curing a part of the second photocurable resin on the submerged substrate or the submerged object.

[0158] 36. A computer program comprising instructions, which, when the program is executed by a computing device, cause the computing device to carry out the steps of the method of any of the items 1 - 35.

[0159] 37. A data processing system comprising a processor configured to perform the steps of the method of any of the items 1 - 36.

[0160] 38. A system for additive manufacturing of an object, the system comprising: a first radiation source configured to emit a first radiation, a container configured to accommodate a photocurable resin and a substrate at least partly submerged in the photocurable resin, wherein the photocurable resin is curable to cured resin on the substrate by the first radiation, wherein the container comprises a wall transparent or at least semi-transparent to at least a wavelength range of the first radiation; a second radiation source configured to irradiate the wall, the photocurable resin, the photocured resin, and / or the substrate by a second radiation; a detection unit configured to measure a scattered, transmitted, and / or reflected second radiation comprising the second radiation scattered, transmitted, and / or reflected, respectively, by the wall, the photocurable resin, the photocured resin and / or the substrate, wherein the system is configured to determine a first property of the wall, the photocurable resin, the photocured resin, and / or the substrate based on the measured second radiation; and wherein the system is configured to control a set of processing parameters based on the first property for forming the object by curing a part of the photocurable resin on the substrate.

[0161] 39. The system according to items 38, wherein the system comprises a first XY stage configured to move the first radiation source, and optionally the second radiation source and / or the detection unit, in relation to the substrate.

[0162] 40. The system according to item 38 or 39, wherein the system comprises a first Z stage configured to move the first radiation source, and optionally the second radiation source and / or the detection unit towards and / or away from the substrate.

[0163] 41. The system according to any of the items 38 - 40, wherein the system comprises a second XY stage configured to move the substrate and / or the container in relation to the first radiation source.

[0164] 42. The system according to any of the items 38 - 41 , wherein the system comprises a second Z stage configured to move

[0165] - the substrate and / or the container towards and / or away from the first radiation source, or

[0166] - the first radiation source towards and / or away from the substrate and / or the container.

[0167] 43. The system according to any of the items 38 - 42, wherein the system comprises a third Z stage configured to move

[0168] - a substrate at least partly within the photocurable resin, or

[0169] - the container towards and / or away from the first radiation source.

[0170] 44. The system according to item 43, wherein the third Z stage is configured to move the substrate in relation to the container or the container in relation to the substrate. The system according to any of the items 38-44, wherein the system comprises a processor configured to determine the first property based on the measured scattered, transmitted, and / or reflected second radiation by the detection unit and / or configured to control

[0171] - the first XY stage,

[0172] - the first Z stage,

[0173] - the second XY stage,

[0174] - the second Z stage,

[0175] - the third Z stage,

[0176] - temperature of the photocurable resin, and / or

[0177] - the first radiation source based on the determined first property. The system according to item any of the items 38 - 45, wherein said system is configured to dynamically adjust the set of processing parameters such that a relative distance between the wall and the substrate is maintained. The system according to any of the items 38 - 46, wherein the wall is made of polymer, such as polydimethylsiloxane (PDMS), silicone, poly(methyl methacrylate), glass, such as an optical glass or quartz or silica, preferably fused silica, or a combination thereof. The system according to any of the items 38 - 47, wherein the first radiation source and / or the second radiation source comprise(s) a coherent radiation source, such as a laser. The system according to any of the items 38 - 48, wherein the second radiation has a non-curing wavelength range outside or only emitting outside the curable wavelength range, where the photocurable resin is cured. The system according to any of the items 38 - 49, wherein the wavelength range of the second radiation source is between 295 nm to 800 nm, preferably 400 nm to 800 nm, like 650 nm. 51. The system according to any of the items 38 - 50, wherein the wavelength range of the first radiation source is between 295 nm to 800 nm, preferably 295 nm to 500 nm, like 405 nm.

[0178] 52. The system according to any of the items 38 - 51 , wherein the detection unit comprises an optical sensor.

[0179] 53. The system according to any of the items 38 - 52, wherein comprises a thermometer for measuring temperature of the photocurable resin and / or of the environment around the photocurable resin.

[0180] 54. The system according to any of the items 38 - 53, wherein the system comprises a hygrometer for measuring humidity of the photocurable resin and / or of the environment above the photocurable resin.

[0181] 55. The system according to any of the items 38 - 54, wherein the system comprises a common platform, wherein the first radiation source, the second radiation source, and the detection unit are positioned on the common platform.

[0182] 56. The system according to any of the items 39 - 55, wherein the first XY stage is configured to move the first radiation source, the second radiation source and the detection unit by moving the common platform.

[0183] 57. The system according to any of the items 38 - 56, wherein the system comprises a focusing lens and / or a focusing mirror configured to focus or collimate the first radiation and / or the second radiation on the part of the photocurable resin on the substrate, wherein optionally the focusing lens and / or the focusing mirror is / are positioned on the common platform.

[0184] 58. The system according to any of the items 38 - 57, wherein the system comprises a beam combiner for combining the first radiation from the first radiation source and the second radiation from the second radiation source.

[0185] 59. The system according to any of the items 38 - 58, wherein the second XY stage is configured to move the substrate and / or the container in relation to the common platform. 60. The system according to any of the items 38 - 59, configured to control the Z stage based on the set of processing parameters so that the substrate and the container have the right position relative to each other.

[0186] 61. The system according to any of the items 38 - 60, configured to control the Z stage based on the set of processing parameters so that a first unintentional move between

[0187] - the first radiation source, and

[0188] - the substrate and / or the container detected by the detection unit is corrected to at least partly eliminate the first unintentional move.

[0189] 62. The system according to any of the items 42 - 61 , configured to control the second Z stage based on the set of processing parameters so that a second unintentional move between

[0190] - the first radiation source, and

[0191] - the substrate and / or the container detected by the detection unit is corrected to at least partly eliminate the second unintentional move.

[0192] 63. The system according to any of the items 38 - 62, configured to control the first XY stage or the second XY stage based on the set of processing parameters so that a third unintentional move between

[0193] - the first radiation source, and

[0194] - the substrate and / or the container detected by the detection unit is corrected to at least partly eliminate the third unintentional move.

[0195] 64. The system according to any of the items 38 -63, wherein the system is configured to carry out any of the steps of a method according to any of the preceding items 1 - 37.

Claims

Claims1 . A method for additive manufacturing of an object, comprising the steps of: providing a first radiation source emitting a first radiation; providing a container containing a photocurable resin curable into cured resin by the first radiation, the container comprising a wall transparent or at least semi-transparent to at least a wavelength range of the first radiation; providing a substrate submerged in the photocurable resin in the container; providing a second radiation source emitting a second radiation, wherein the photocurable resin is non-curable by said second radiation; determining at least one first property of the wall, the photocurable resin, the cured resin, and / or the substrate by measuring a scattered, transmitted, and / or reflected second radiation comprising the second radiation reflected, transmitted, and / or scattered by the wall, the photocurable resin, the photocured resin, and / or the substrate, respectively; and controlling a set of processing parameters based on the at least one first property for forming at least one layer of an object by curing a part of the photocurable resin on the submerged substrate,- wherein the at least one first property is one or more of the following properties: roughness of the substrate and / or the wall,- topography of the substrate and / or the wall,- physical coordinates of the substrate and / or the wall,- parallelism between the substrate and the wall,- flatness of the substrate and / or the wall,- deformation of the substrate and / or the wall,- thickness of the photocurable resin and / or the wall,- transmission characteristics of the photocurable resin and / or the wall,- reflection characteristics of the substrate and / or the photocurable resin and / or the wall, and- distance between the substrate or the wall and the first radiation source.

2. The method according to claim 1 , wherein the first property relates to or is a position of- a first interface between the substrate / cured resin and the uncured photocurable resin, and / ora second interface between the wall and uncured photocurable resin.

3. The method according to any of the preceding claims, wherein the wall is located as a layer at the bottom of the container containing the photocurable resin.

4. The method according to any of the preceding claims, wherein the method comprises the step of moving the first and / or the second radiation source(s) towards the substrate, and / or away from the container, like e.g. upwards and / or downwards, respectively, if the first and / or the second radiation source(s) is / are provided below the wall.

5. The method according to any of the preceding claims, comprising the step of calculating a thickness of the wall and / or calculating a distance between the substrate and the wall.

6. The method for additive manufacturing according to any of the preceding claims, comprising the steps of determining a second property of the first radiation source and controlling a set of processing parameters based on the second property.

7. The method according to claim 6, wherein the second property is one or more of the following: laser intensity, laser uniformity, beam / laser spot shape, point spread function, laser focus point (z-shift of laser focus), depth of view.

8. The method according to any of the preceding claims, comprising the step of adjusting the position of the container, preferably the wall, and / or the step of adjusting the position of the substrate, such that the substrate and the wall are made parallel.

9. The method according to any of the preceding claims, comprising the step of- adjusting the position of the substrate, and / or- adjusting the position of the first and / or the second radiation source.

10. The method according to any of the preceding claims, comprising the step of measuring the first property of the wall and / or of the substrate before and / or during and / or after curing the part of the photocurable resin.

11. A system for additive manufacturing of an object, the system comprising: a first radiation source configured to emit a first radiation, a container configured to accommodate a photocurable resin and a substrate at least partly submerged in the photocurable resin, wherein the photocurable resin is curable to cured resin on the substrate by the first radiation, wherein the container comprises a wall transparent or at least semi-transparent to at least a wavelength range of the first radiation; a second radiation source configured to irradiate the wall, the photocurable resin, the cured resin, and / or the substrate by a second radiation; a detection unit configured to measure a scattered, transmitted, and / or reflected second radiation comprising the second radiation scattered, transmitted, and / or reflected, respectively, by the wall, the photocurable resin, the photocured resin, and / or the substrate, a common platform, wherein the first radiation source, the second radiation source, and the detection unit are positioned on the common platform, and a Z stage movable towards and / or away from the first radiation source and configured to move- the substrate, or- the container; wherein the system further comprises a first XY stage configured to move the first radiation source, the second radiation source and the detection unit by moving the common platform, or a second XY stage configured to move the substrate and / or the container; wherein the system is configured to determine a first property of the wall, the photocurable resin, the photocured resin, and / or the substrate based on the measured second radiation; and wherein the system is configured to control a set of processing parameters based on the first property for forming the object by curing a part of the photocurable resin on the substrate.

12. The system according to claim 11, wherein the system comprises a focusing lens and / or a focusing mirror configured to focus the first radiation and / or thesecond radiation on the part of the photocurable resin on the substrate, wherein the focusing lens and / or the focusing mirror is / are positioned on the common platform.

13. The system according to claim 11 or 12, wherein the system comprises a beam combiner for combining the first radiation from the first radiation source and the second radiation from the second radiation source.

14. The system according to any of the claims 11-13, wherein the second XY stage is configured to move the substrate and / or the container in relation to the common platform.

15. The system according to any of the claims 11-14, wherein the system comprises a processor configured to determine the first property based on the measured scattered, transmitted, and / or reflected second radiation by the detection unit.

16. The system according to claim 15, wherein the processor is configured to control the first radiation source, the Z stage, temperature of the photocurable resin, and / or one of the first XY stage or the second XY stage based on the determined first property.

17. The system according to any of the claims 11-16, configured to control the Z stage based on the set of processing parameters so that the substrate and the container have the right position relative to each other.

18. The system according to any of the claims 11-17, configured to control the Z stage based on the set of processing parameters so that a first unintentional move between- the first radiation source, and- the substrate and / or the containerdetected by the detection unit is corrected to at least partly eliminate the first unintentional move.

19. The system according to any of the claims 11-18, wherein the system comprises a second Z stage configured to move- the substrate and / or the container towards and / or away from the first radiation source, or- the first radiation source towards and / or away from the substrate and / or the container.

20. The system according to claim 19, configured to control the second Z stage based on the set of processing parameters so that a second unintentional move between- the first radiation source, and- the substrate and / or the container detected by the detection unit is corrected to at least partly eliminate the second unintentional move.

21. The system according to any of the claims 11-20, configured to control the first XY stage or the second XY stage based on the set of processing parameters so that a third unintentional move between- the first radiation source, and- the substrate and / or the container detected by the detection unit is corrected to at least partly eliminate the third unintentional move.

22. The system according to any of the claims 11-21, wherein said system is configured to dynamically adjust the set of processing parameters such that a relative distance between the wall and the substrate is maintained.

23. The system according to any of the claims 11 -22, wherein the system is configured to carry out any of the steps of a method according to any of the preceding claims 1 - 10.

24. A computer program comprising instructions, which, when the program is executed by a computing device, cause the computing device to carry out the steps of the method of any of the claims 1 - 10.

25. A data processing system comprising a processor configured to perform the steps of the method of any of the claims 1 - 10.

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