Abstract: Techniques are described for calibrating an optical system in an additive fabrication device using an image of the build surface within the device. These techniques allow calibration to be performed by imaging one or more calibration features generated on (or at) the build surface, which may include illuminated regions of the build surface, regions of the build surface on which solid material has been formed, and/or regions of the build surface to which energy has otherwise been directed thereby making those regions distinguishable from their surroundings. The calibration features may be produced (at least in part) by the optical system to be calibrated. The location of the calibration features within the image may be compared with the intended location of these calibration features, and corrections to the optical system determined based on any differences between the actual and intended locations.

Abstract: A resin formulation that may be used for additive manufacturing, for example, to provide a water-breakable object is generally described.

Abstract: An improved additive fabrication device and a build platform are provided. The additive fabrication device is configured to form layers of material on a build surface. The additive fabrication device comprising: a build platform comprising: a rigid structure; an actuation structure attached to the rigid structure, wherein the actuation structure comprises one or more sheet handles and a flexible sheet, and wherein a first surface of the flexible sheet forms a build surface on which the additive fabrication device is configured to form layers of materials; and the one or more sheet handles are configured to be actuated to apply a force to the flexible sheet while at least a part of the actuation structure remains attached to the rigid structure, to deform at least a part of the flexible sheet away from the rigid structure.

Abstract: According to some aspects, a method is provided of casting an object from a mold, the method comprising obtaining a mold comprising a hollow shell of rigid material, the material comprising a thermoset polymer having a plurality of pores formed therein, providing a metal and/or ceramic slurry into an interior of the mold, exposing at least part of the mold to a low pressure environment so that a net flow of gas is produced from the interior of the mold into the low pressure environment. According to some aspects, a method of forming a porous mold is provided. According to some aspects, a photocurable liquid composition is provided, comprising a liquid photopolymer resin, particles of a solid material, in an amount between 30% and 60% by volume of the composition, and a water-soluble liquid.

Abstract: Washing apparatus and methods used to process additively fabricated (e.g., 3D printed) parts are described herein. The apparatus and methods may be used to wash uncured liquid resin from the parts. The washing apparatus may include two or more containers for storing respective solvents and may be fluidly connected to a vessel in which the additively fabricated parts are placed. One or more pumps and one or more valves may be controlled to introduce a first solvent from one of the containers into the vessel to wash the part in a first wash cycle and then the valve(s) may be re-configured to introduce a second solvent from another container into the vessel to wash the part in a second wash cycle. Advantageously, the parts may remain in the same vessel while being washed with both solvents in succession.

Abstract: Methods and compositions for additive manufacturing of silicone parts are provided. The methods can use SLA printing techniques to print silicone parts that exhibit excellent hardness, tear strength and elongation at break. The parts can be produced by using low dosages of radiation. In various embodiments, the silicone compositions include a mercapto-derivatized polysiloxane having two or more functional groups, an alkenyl-derivatized polysiloxane, and a photo-initiator.

Abstract: In additive fabrication, less stiff layers generally require a comparatively higher peel force during separation, and that therefore geometric structures that include less stiff layers will also require a comparatively higher peel force during separation. Techniques to lower or otherwise mitigate undesirably large peel forces are described. These techniques include modification to how layers susceptible to a large peel force are formed, modification to a model of a part prior to generating instructions for an additive fabrication device to fabricate the part, and/or improvements to an additive fabrication device hardware.

Abstract: According to some aspects, techniques are described for generating support structures that may be easily removed after fabrication yet provide sufficient structural support during fabrication. In some cases, the techniques may include tuning an extent to which pillars of a support structure are interconnected to one another in regions proximate to the part. In some cases, the techniques may include fabricating very small contact structures, referred to herein as “hair” supports, in regions of a support structure where it connects with the part. In some cases, the techniques may include generating support structures that comprise obliquely-angled tips, which allow forces during fabrication to be applied in a preferred direction even when the support structure does not make a connection to the part in the preferred direction.

Abstract: According to some aspects, an additive fabrication device and a build platform suitable for use within an additive fabrication device are provided. The build platform may include a build surface on which material may be formed by the additive fabrication device when the build platform is installed within the additive fabrication device. According to some embodiments, the build platform may include a flexible build layer and at least one removal mechanism configured to be actuated to apply a force to the flexible build layer. Such actuation may cause the flexible build layer to deform, thereby enabling separation of material adhered to the build surface from the build platform. According to some embodiments, the build platform may comprise a restorative mechanism that acts to return the flexible build layer to a flat state so that subsequent additive fabrication may form material on a flat build surface.

Abstract: According to some aspects, techniques are provided to mitigate challenges with additive fabrication devices that utilize a film. These techniques include: improvements to an additive fabrication device build platform to more evenly apply forces onto the film; techniques for inhibiting adhesion between a pair of films and for removing dirt or dust therein; techniques for detecting and/or mitigating the effects of scratches or dust on films; and techniques for detecting film punctures, detecting an imminent film puncture, and/or reducing the impact on the device when punctures occur.

Abstract: According to some aspects, techniques that address one or more drawbacks of laser-based optical systems in additive fabrication devices are described. In some aspects, an additive fabrication device may include one or more variable focus lenses that may be operated (e.g., actuated) during fabrication to adjust the focus, and thereby the spot size, of a laser beam. In some aspects, an additive fabrication device may comprise a laser array, such as a plurality of vertical-cavity surface-emitting lasers (VCSELs), that may be operated to direct light into a build region, rather than using a single laser beam, such as a single diode laser. In some aspects, an additive fabrication device may comprise a container that includes a flexible display film, such as a flexible LCD screen, which may be operated to direct light into the container to thereby cure a liquid photopolymer therein.

Abstract: According to some aspects, a method is provided of removing debris from a liquid photopolymer in an additive fabrication device. According to some embodiments, a mesh of solid material may be formed in an additive fabrication device from a liquid photopolymer, and particles of debris present in the liquid photopolymer may adhere to the mesh. The debris may thereby be removed from the liquid photopolymer by removing the mesh from the additive fabrication device. The mesh may then be discarded.

Abstract: Methods and compositions for additive manufacturing of silicone parts are provided. The methods can use SLA printing techniques to print silicone parts that exhibit excellent hardness, tear strength and elongation at break. The parts can be produced by using low dosages of radiation. In various embodiments, the silicone compositions include a mercapto-derivatized polysiloxane having two or more functional groups, an alkenyl-derivatized polysiloxane, and a photo-initiator.

Abstract: According to some aspects, degradation of material in a sintering additive fabrication process may be mitigated or avoided by fabricating parts within a chamber that includes one or more thermal breaks. The thermal break may be implemented using a variety of structures, but generally allows material in the chamber close to the surface to be maintained at different temperatures than the material further from the surface. For instance, as a result of the thermal break, parts located within the material of the chamber that were formed earlier during fabrication may be kept cooler to avoid damage to the parts yet the upper surface (sometimes called the “build surface”) of unconsolidated material may be heated enough so as to require minimal additional energy exposure to trigger consolidation.

Abstract: Techniques for producing a flat film surface in additive fabrication are provided. According to some aspects, a movable stage may be arranged beneath a container having a base that includes a flexible film. The movable stage may include a segmented member in which a number of segments are aligned along a common axis. The segmented member may maintain contact with the flexible film as the movable stage moves beneath the container, with the segmented member producing a flat surface of the flexible film, at least within a region above the movable stage. According to some embodiments, multiple segmented members may be provided within the movable stage, such as in parallel with one another.

Abstract: Techniques are described for consistently moving powder from a hopper into a trough for subsequent delivery into a build area of an additive fabrication system. A powder delivery apparatus may comprise a hopper, a trough, and a doser. The doser may be configured to rotate about an axis and may include a recess that, when the doser is rotated about the axis, travels into and out of the hopper and into and out of the trough. As a result, when powder is present in the hopper, the recess may carry powder from the hopper to the trough when the doser rotates. The trough and doser may be configured so that when the trough contains the desired amount of powder for recoating, the doser does not transfer additional material from the hopper into the trough. As a result, the amount of powder in the trough may be self-regulating.

Abstract: According to some aspects, techniques are provided for identifying contamination in additive fabrication devices by measuring light interacting with the contamination using one or more light sensors. Contamination located between a light source and a target of a light source can affect the uniformity and intensity of the light source when incident upon the target. For instance, in an inverse stereolithography device, contamination located between a light source and a liquid photopolymer resin that is to be cured can affect the quality of the fabricated object when the light is scattered or blocked by the contamination. Identifying the presence of contamination between the light source and the liquid photopolymer resin and alerting the user prior to initiating a fabrication process may increase the quality of the resulting fabricated object and improve the user experience by saving time and photocurable liquid.

Abstract: According to some aspects, a method of additive fabrication is provided wherein a plurality of layers are formed on a build platform, each layer contacting a container in addition to the build platform and/or a previously formed layer, the method comprising calculating, using at least one processor, one or more forces to be applied to a first layer of the plurality of layers subsequent to the first layer being formed, said calculating being based at least in part on a determined area of at least one portion of the first layer that overhangs a second layer of the plurality of layers, forming the first layer, the first layer being in contact with the container and in contact with a previously formed layer of the plurality of layers, and separating the first layer from the container by applying the calculated one or more forces to the first layer.

Abstract: An improved additive fabrication device and a build platform are provided. The additive fabrication device is configured to form layers of material on a build surface. The additive fabrication device comprising: a build platform comprising: a rigid structure; an actuation structure attached to the rigid structure, wherein the actuation structure comprises one or more sheet handles and a flexible sheet, and wherein a first surface of the flexible sheet forms a build surface on which the additive fabrication device is configured to form layers of materials; and the one or more sheet handles are configured to be actuated to apply a force to the flexible sheet while at least a part of the actuation structure remains attached to the rigid structure, to deform at least a part of the flexible sheet away from the rigid structure.

Abstract: A method for producing a three-dimensional (3D) object on an additive fabrication device includes receiving, by a computer, print instructions for the 3D object. The print instructions include a sequence of print maps, each print map corresponding to a sub-instruction for producing a respective cross-section of the 3D object. The method also includes exposing, by an energy source, resin stored in a resin container at a print plane according to a first print map of the sequence of print maps, and modifying a second print map of the sequence of print maps. The method further includes exposing, by the energy source, resin stored in the resin container at the print plane according to the modified second print map.