Additive manufacturing device with removable and replaceable frame-like spacer foils

Abstract

The present invention relates to an additive manufacturing apparatus (1) for additively manufacturing a part (2), comprising a resin vat unit (3) with a reservoir (4) for storing a UV light curable resin (5) and a frame assembly (6) holding a UV transparent window (6-4) at the bottom of the reservoir (4), wherein the UV transparent window (6-4) comprises a UV transparent plate (6-4a) and a UV transparent adhesive prevention flexible foil (6-4b), a projection unit (7) for projecting UV light (8) through the UV transparent window (6-4) into the reservoir (4), and a surface on which the part (2) can be formed by layer-by-layer curing of the resin (5). and a movable build platform (9) having a UV-transparent window (6-4) and a UV-transparent adhesive-free flexible foil (6-4b) for forming a plate-foil gap (6-4d), the UV-transparent window (6-4) further comprising a removable frame-like spacer foil (6-4c) having a predetermined thickness and capable of being removably mounted by the frame assembly (6) between the UV-transparent plate (6-4a) and the UV-transparent adhesive-free flexible foil (6-4b) to create a plate-foil gap (6-4d), and at least one air hole (6-2a) for communicating the plate-foil gap (6-4d) with the atmosphere.

Description

[Technical field]

[0001] The present invention relates to additive manufacturing devices, and more particularly to removable frame-like spacer foils for use in UV-transmitting windows of additive manufacturing devices. [Background technology]

[0002] In additive manufacturing techniques such as stereolithography (SLA) or digital light processing (DLP), three-dimensional parts are printed layer by layer by light-based curing of a liquid printing medium, i.e. a photocurable resin, which is selectively cured under the influence of UV radiation. In a commonly known variant of additive manufacturing, the 3D part is preferably pulled upside down from a photocurable resin in a vat of resin by a build platform. Other variants of additive manufacturing are also known to those skilled in the art.

[0003] According to the state of the art, the resin vat has a UV-transparent window consisting of a UV-transparent anti-adhesive flexible foil (typically made of fluoropolymers, e.g., FEP, PMP, Teflon AF, or similar) and a mechanically rigid UV-transparent plate, such as glass or plexiglass, on which the flexible foil rests under the weight of the photocurable resin.

[0004] Upon exposure of the photocurable resin through a UV-transmitting window in the bottom of the resin vat, the polymerized layer adheres to the flexible foil and to the build platform. This adhesion to the flexible foil is typically released by a peeling movement in the Z direction, i.e. perpendicular to the bottom of the resin vat. A prerequisite for this peeling is that the anti-adhesive flexible foil can be separated from the polymerized layer as it is pulled away by the build platform. The separation of the flexible foil can be described as a peeling process, essentially the same as a foil or film is peeled from a rigid surface.

[0005] In the state of the art, the flexible foil is generally disposed on the UV-transmitting plate such that the interface between the foil and the UV-transmitting plate is kept open to the atmosphere, thereby creating an air gap, and the foil can assume a convex shape during the peeling process. Usually, the anti-adhesive flexible foil and the UV-transmitting plate are separated via a rim, collar, or seating flange that is integrally manufactured with the resin bat to maintain the air gap.

[0006] US2018 / 0207867A1 discloses a method and apparatus for photocuring a photosensitive material to form a three-dimensional object in a tank having a flexible, self-lubricating substrate.

[0007] A problem with the prior art is that the force to peel off the polymerized layer also depends on the size of the area of ​​the polymerized layer, which is also limited by the size of the polymerizable layer within the optical / mechanical limitations of the additive manufacturing equipment. Summary of the Invention

[0008] The inventors are not aware of any additive manufacturing techniques in which removable and replaceable frame-like spacer foils are used on the UV-transparent windows of an additive manufacturing apparatus to create and maintain an air gap having a size specifically desired according to the characteristics of the apparatus and the printing application.

[0009] It is an object of the present invention to overcome the above-mentioned problems of the prior art and to provide an additive manufacturing device that provides an application-dependent user-adjustable gap to reduce the force required to peel a UV-transparent anti-adhesive flexible foil from a UV-transparent plate and to increase the utilization area for additive manufacturing.

[0010] This object is achieved by an additive manufacturing device according to claim 1 and by a removable frame-like spacer foil according to claim 5. The dependent claims relate to further embodiments and developments.

[0011] The present invention provides an additive manufacturing apparatus for additively manufacturing 3D parts. The additive manufacturing apparatus comprises a resin vat unit having a reservoir for storing UV light curable resin and a frame assembly holding a UV transparent window at the bottom of the reservoir, the UV transparent window including a UV transparent plate and a UV transparent adhesive-resistant flexible foil. The additive manufacturing apparatus further comprises a projection unit for projecting UV light through the UV transparent window into the reservoir, and a movable build platform having a surface on which the 3D part can be formed by layer-by-layer curing of the resin. The UV transparent window further comprises a removable frame-like spacer foil having a predetermined thickness and capable of being removably mounted in the frame assembly between the UV transparent plate and the UV transparent adhesive-resistant flexible foil to create an air gap between the plate and the foil, and at least one air hole for communicating the air gap between the plate and the foil with the atmosphere.

[0012] For comparison with the present invention, prior art resin batts are manufactured with an integral collar, which generally entails stringent requirements since the collar height must be uniform in the circumferential direction and must have an accurate value within a range of a few micrometers to a few millimeters depending on the device characteristics. The manufacturing process of the prior art is generally achieved by a milling process or an injection molding process of the resin batt with an integral collar. Unlike the present invention, in the prior art, the collar height of the resin batt cannot be changed or adjusted according to the device characteristics and printing application after the bat is manufactured.

[0013] The present invention allows users to set different intervals between the UV-transmitting anti-adhesive flexible foil and the UV-transmitting plate inside the UV-transmitting window. Basically, this is achieved by a removable frame-like spacer foil provided with a desired interval thickness. The thickness of the removable frame-like spacer foil can be appropriately selected depending on the printing requirements. Users can retrofit the removable frame-like spacer foil with a desired thickness to the resin vat unit.

[0014] According to the present invention, the resin vat unit may be provided as a unit that can be completely removed from the additive manufacturing apparatus. Thus, in a preferred embodiment, the reservoir and the frame assembly including the UV-transmitting window are configured to define a separable resin vat unit that can be separated, e.g., pulled out, by a user from the additive manufacturing apparatus by a separation mechanism. This allows the user to take the resin vat unit out, e.g., for refilling with new resin. The user can also retrofit the resin vat unit with a frame-like spacer foil having a desired thickness according to printing requirements after removing the resin vat unit from the additive manufacturing apparatus. Alternatively, the resin vat unit may be provided as a unit that is partially or completely integrated with the additive manufacturing apparatus.

[0015] The main advantageous effect of the present invention is that it enables the adaptation of various spacings between the flexible foil and the rigid plate for different printing applications, thus eliminating the need for additive manufacturing, in particular a complete replacement of the resin vat unit, but simply retrofitting a frame-like spacer foil with the desired thickness.

[0016] Another major advantageous effect of the present invention is that the peel force can be reduced by increasing the gap thickness, thereby accelerating the peel process and therefore the duration of the overall printing process can also be reduced.

[0017] Another major advantage of the present invention is that the use of relatively thick spacer foils allows for a relatively increased area utilization of the projection area within the mechanical limitations of the additive manufacturing equipment.

[0018] In the following description, further aspects and advantages of the invention are detailed using exemplary embodiments and by reference to the drawings. [Brief description of the drawings]

[0019] [Figure 1] 1 is a schematic vertical cross-sectional view of a portion of a stereolithography apparatus according to an embodiment; [Diagram 2] FIG. 2 is a schematic perspective view of a completely separable resin vat unit of a stereolithography apparatus according to an embodiment. [Diagram 3] 3 is a schematic perspective exploded view of the resin vat unit of FIG. 2. [Figure 4A] 4 is a schematic perspective top view of an inner frame of a frame assembly of the resin bat unit of FIG. 3. [Figure 4B] FIG. 4B is a schematic perspective bottom view of the inner frame of FIG. 4A. [Figure 5A] FIG. 4C is a schematic cross-sectional view of the inner frame of FIG. 4B taken along line II. [Figure 5B] FIG. 5B is a schematic enlarged view of detail II of FIG. 5A. [Figure 6] FIG. 2 is a schematic top view of a removable frame-like spacer foil. [Figure 7] FIG. 2 is a schematic top view of a UV-transmitting anti-adhesive flexible foil. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] 1…Stereolithography device 2. Parts 3…Resin bat unit 4…Reservoir 4a...Opening 4b…Grip 5...UV photocurable resin 6…Frame assembly 6-1…Inner frame 6-1a…Inner frame element 6-1b…Inner frame element 6-1c…Screw 6-1d…Screw hole 6-2…Outer frame 6-2a…Air hole 6-2b…Air channel 6-2c…Hose 6-2d…Screw 6-2d'...Screw 6-2e…Screw hole 6-2e'...Screw hole 6-3…Ceiling 6-4…UV transmission window 6-4a…UV transmission plate 6-4b…UV transparent adhesion prevention flexible foil 6-4c…Removable frame-shaped spacer foil 6-4d…Gap between plate and foil 7…Projection unit 8...UV light 9. Mobile building platform 9a…Surface

[0021] FIG. 1 shows an embodiment of an additive manufacturing apparatus (1) for additively manufacturing a 3D part (2). As shown in FIG. 2, the additive manufacturing apparatus (1) has a resin vat unit (3) including a reservoir (4) for storing a UV light curable resin (5) and a frame assembly (6) that holds a UV transparent window (6-4) at the bottom of the reservoir (4). As shown in FIG. 1, the UV transparent window (6-4) includes a UV transparent plate (6-4a) and a UV transparent adhesive-preventive flexible foil (6-4b). As shown in FIG. 1, the additive manufacturing apparatus (1) has a projection unit (7) for projecting UV light (8) through the UV transparent window (6-4) into the reservoir (4). The additive manufacturing apparatus (1) includes a transport unit with a movable build platform (9), the build platform (9) having a surface (9a) facing the bottom of the resin vat unit (3) on which the 3D part (2) can be formed by layer-by-layer curing of the resin (5) by the projection unit (7). The build platform (9) can be moved in and out of the reservoir (4) by the transport unit. The build platform (9) can also be moved laterally within the reservoir (4) by the transport unit. The additive manufacturing apparatus (1) has a computer implemented control device for controlling the projection unit (7) and the transport unit and for the overall functioning of the additive manufacturing apparatus (1).

[0022] As shown in FIG. 1, the UV-transmitting window (6-4) further includes a removable frame-like spacer foil (6-4c) having a predetermined thickness. As shown in more detail in FIG. 5B, the removable frame-like spacer foil (6-4c) can be mounted by a frame assembly (6) between the UV-transmitting plate (6-4a) and the UV-transmitting anti-adhesive flexible foil (6-4b) to create a plate-foil gap (6-4d). The details of the frame assembly (6) will be described later. As shown in FIG. 3, the UV-transmitting window (6-4) has an air hole (6-2a) for communicating the plate-foil gap (6-4d) with the atmosphere.

[0023] The frame assembly (6) will be described in detail below. As shown in FIG. 3, the frame assembly (6) comprises an inner frame (6-1) and an outer frame (6-2) mounted on the inside and outside of the opening (4a) of the resin vat unit (3), respectively. A seal (6-3) is preferably disposed at the interface between the inner frame (6-1) and the resin vat unit (3). Another seal (6-3) is preferably disposed at the interface between the inner frame (6-1) and the outer frame (6-2). As shown in FIG. 5B, the inner frame (6-1) has two inner frame elements (6-1a; 6-1b) attached to each other via screws (6-1c). The screws (6-1c) can be easily removed by the user to replace the removable frame-like spacer foil (6-4c). The UV-transmitting adhesive-free flexible foil (6-4b) and the removable frame-like spacer foil (6-4c) are sandwiched / clamped between the two inner frame elements (6-1a; 6-1b). When they are assembled, as shown in FIG. 5B, a plate-foil gap (6-4d) is created by the frame-like spacer foil (6-4c) on top of the UV-transmitting plate (6-4a). As shown in FIG. 3, the UV-transmitting plate (6-4a) is fixed on the outer frame (6-2), for example with glue. The outer frame (6-2) has air holes (6-2a) at each corner, which are preferably connected to each other via air channels (6-2b) that run around the periphery. The frame-like spacer foil (6-4c) has a width such that it does not completely cover the air holes (6-2a) and the air channels (6-2b). The air holes (6-2a) are preferably connected to the atmosphere by a hose (6-2c). The outer frame (6-2) has a screw hole (6-2e) for receiving a screw (6-2d) screwed into the screw hole (6-1d) (see FIG. 4B). The outer frame (6-2) also has a screw hole (6-2e') for receiving a screw (6-2d') screwed into a screw hole (not shown) on the outside of the resin vat unit (3). In the assembled state, the frame-like spacer foil (6-4c) is sandwiched between the UV-transmitting adhesive-preventive flexible foil (6-4b) and the UV-transmitting plate (6-4a), thereby together defining the UV-transmitting window (6-4).The weight of the photocurable resin (5) in the resin vat unit (3) causes a deflection of the UV-transmitting anti-adhesive flexible foil (6-4b) up to the thickness of the frame-like spacer foil (6-4c). The plate-foil gap (6-4d) may therefore have a non-uniform shape depending on the tension of the flexible foil (6-4b) and the weight of the photocurable resin (5). The flexible foil (6-4b) may have a partially concave deflection or a purely concave deflection at the periphery in combination with a parallel contact with the UV-transmitting plate (6-4a) around the center depending on the tension of the flexible foil (6-4b) and the weight of the photocurable resin (5). The screw (6-2d) may also be used to adjust the tension on the flexible foil (6-4b) when the inner frame (6-1) is clamped to the outer frame (6-2) with the elastic sealing (6-3) located between them. The tighter the screw (6-2d) is fixed, the higher the tension on the flexible foil (6-4b). When the screw (6-2d) is tightened, the edges of the UV-transmitting anti-adhesive flexible foil (6-4b) and the frame-like spacer foil (6-4c) are pulled relatively down while riding on the rounded edges of the plate (6-4a), and are therefore stretched across the UV-transmitting plate (6-4a) and accordingly pressed against the UV-transmitting plate (6-4a) due to the relative movement of the inner frame (6-1) towards the outer frame (6-2). The inner frame (6-1), the outer frame (6-2), the screw (6-2d) and the elastic sealing (6-3) thus define a means for tensioning the UV-transmitting anti-adhesive flexible foil (6-4b). The tension is adjustable.

[0024] In one embodiment, the reservoir (4) and the frame assembly (6) including the UV transparent window (6-4) are configured to define a separable resin vat unit (3) that can be completely separated by a user and manually removed from the additive manufacturing device using a separation mechanism. In this embodiment, the resin vat unit (3) preferably has a hand grip (4b).

[0025] In one embodiment, the anti-adhesive flexible foil (6-4b) preferably has a rectangular area of ​​about 107.7×166.5 mm and a thickness of preferably 0.127 mm. However, foils (6-4b) with different dimensions, larger or smaller, may be used. The removable frame-like spacer foil (6-4c) is preferably provided with a thickness of at least 100 micrometers. This allows the specific pull-out force to be reduced to less than 30 N with an area utilization of 60% of the available projection foil area of ​​about 134.4 mm×75.6 mm, which is suitable for dental applications such as aligners, bite splints, models, drill templates, and dentures. Different area utilizations may be used. For an even smaller utilization of the available projection foil area, the removable frame-like spacer foil (6-4c) may be provided with a smaller thickness, preferably at least 50 micrometers. A smaller height would not be sufficient to meet the peeling requirements. Therefore, the thickness is preferably in the range of 50-150 μm, more preferably in the range of 150-200 μm, or even more preferably at least 200 μm. As shown in FIG. 6, the removable frame-like spacer foil (6-4c) preferably has a rectangular shaped opening in its center to ensure a plate-foil gap (6-4d) in the assembled state. FIG. 7 shows a UV-transmitting anti-adhesive flexible foil (6-4b) which preferably has the same outer contour as the removable frame-like spacer foil (6-4c) of FIG. 6. The peripheral frame width of the removable frame-like spacer foil (6-4c) is preferably about 13 mm, and preferably also has rounded corners. Different widths, larger or smaller, may be used. The removable frame-like spacer foil (6-4c) may be made of the same material as the UV-transmitting anti-adhesive flexible foil (6-4b). Alternatively, the removable frame-like spacer foil (6-4c) may be produced from different materials, preferably plastic, metal, ceramic or paper in the form of a thin sheet.

[0026] The UV-transmitting anti-adhesive flexible foil (6-4b) can be made from any of the plastic materials such as fluorinated ethylene propylene (FEP), polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), perfluoroalkoxy polymers (PFA), Teflon AF™, fluoropolymers such as polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), etc.

[0027] The removable frame-like spacer foil (6-4c) can be made from any plastic material, for example plastic polymers such as polyethylene (PE), polypropylene (PP), polymethylmethacrylate (PMMA), polyvinyl chloride (PVC), polycarbonate (PC), etc.

[0028] The above-mentioned metallic material may be metals such as aluminum, aluminum-based alloys, copper-based alloys, stainless steel, etc.

[0029] The ceramic material mentioned above can be a ceramic such as alumina, zirconia, silicon carbide, silicon nitride, and the like.

[0030] Furthermore, in one embodiment, the removable frame-like spacer foils (6-4c) may be provided in different colors or with color code markings visible from the outside, allowing the user to distinguish between the different sizes, thicknesses and materials thereof. Here, the user may refer to a look-up table in the display of the user interface of the additive manufacturing device (1) or in the user manual for the color code. The additive manufacturing device (1) may have a memory for storing such information or may retrieve them from an external memory, preferably located in the cloud or in a local area network. The additive manufacturing device (1) may be connectable to a local area network or the internet in order to receive / send data regarding the print job and / or other information as will be described in more detail later.

[0031] Before starting the printing process, the user can manually input information about the type of attached resin vat unit (3) and / or about the properties of the spacer foil (6-4c) attached to the resin vat unit (3), such as size, thickness, material and / or color, in particular, via a user interface or by an optical reader unit, such as a scanner (camera / barcode reader, etc.) of the additive manufacturing device (1). In this regard, default or user generated barcode labels or QR Code labels or the like can be used on the resin vat unit (3) that store such information. Alternatively or additionally, a mobile phone camera or an intraoral scanner connectable to a system comprising the additive manufacturing device (1) may be used as an optical reader unit.

[0032] Furthermore, in one embodiment, the separable resin vat unit (3) is preferably provided with an RFID tag (not shown) that alternatively or additionally contains information on the type of such resin vat unit (3) and on the presence or absence of a removable frame-like spacer foil (6-4c) in the UV-transparent window (6-4). Furthermore, any combination of information on the thickness, size, material and / or color of the removable frame-like spacer foil (6-4c) may also be stored in the RFID tag. Furthermore, the additive manufacturing device (1) is preferably provided with an RFID reader / writer, by which the additive manufacturing device (1) can recognize the type of the attached resin vat unit (3) and whether it comprises a spacer foil (6-4c), retrieve said information on the spacer foil (6-4c), and optionally display said information to the user via the user interface of the additive manufacturing device (1) and apply the required printing mode.

[0033] The control device is adapted to perform control according to information entered by a user and / or read from an RFID tag or label. This control is implemented by software. The control device can prompt the user via a user interface to load a spacer foil (6-4c) with a required / sufficient minimum thickness appropriate for the print job, in particular the area utilization, resin type, and further adapt the peeling force applied by the transport unit accordingly.

[0034] The user can also edit the RFID tag via the user interface according to any changes made to the resin batt unit (3), for example after retrofitting a removable frame-shaped spacer foil (6-4c) or replacing the frame-shaped spacer foil (6-4c) with a different one.

[0035] The resin vat unit (3) may be provided with a separable refill cartridge (not shown) containing a specific UV light curable resin (5) for refilling the reservoir (4). One or more RFID tags and / or labels may be provided on the wall of the reservoir (4) and / or directly on the separable refill cartridge. The RFID tag and / or label may also contain information about the type of the specific UV light curable resin (5). Thereby, different UV light curable resins (5) can be recognized by the additive manufacturing apparatus (1) and used for different dental applications. The control device is adapted to perform control according to the recognized type of UV light curable resin (5).

[0036] The present invention also provides a method for additively manufacturing a part (2) by using the additive manufacturing apparatus (1) of the present invention, in particular by using a removable frame-like spacer foil (6-4c) of the separable resin batt unit (3) to adjust the peel force and determine the optimal utilization area, and the control device accordingly adapts the peel force applied by the conveying unit according to the thickness of the removable frame-like spacer foil (6-4c).

Claims

1. An additive manufacturing apparatus (1) for additively manufacturing a part (2), comprising: A resin vat unit (3) comprising a reservoir (4) for storing a UV light curable resin (5) and a frame assembly (6) for holding a UV transparent window (6-4) at the bottom of the reservoir (4), wherein the UV transparent window (6-4) includes a UV transparent plate (6-4a) and a UV transparent anti-adhesive flexible foil (6-4b); a projection unit (7) for projecting UV light (8) through said UV-transmitting window (6-4) into said reservoir (4); a movable build platform (9) having a surface (9a) on which the part (2) can be formed by layer-by-layer curing of the UV light curable resin (5); An additive manufacturing apparatus (1) comprising: the UV-transmitting window (6-4) is replaced by a removable frame-like spacer foil (6-4c), which has a predetermined thickness and can be removably mounted by the frame assembly (6) between the UV-transmitting plate (6-4a) and the UV-transmitting anti-adhesive flexible foil (6-4b) to create a plate-foil gap (6-4d); At least one air hole (6-2a) for connecting the plate-foil gap (6-4d) to the atmosphere; An additive manufacturing apparatus (1), further comprising:

2. The additive manufacturing device (1) of claim 1, characterized in that the reservoir (4) and the frame assembly (6) including the UV transparent window (6-4) are configured to define a separable resin vat unit (3) that can be separated by a user from the additive manufacturing device (1).

3. 3. The additive manufacturing apparatus (1) of claim 2, further comprising an RFID tag reader / writer, characterized in that the resin vat unit (3) comprises one or more RFID tags that store information regarding the type of the resin vat unit (3) and information regarding the removable frame-like spacer foil (6-4c).

4. 3. An additive manufacturing apparatus (1) according to claim 2, further comprising an optical reader unit, characterized in that the resin vat unit (3) comprises one or more optically readable labels that store information regarding the type of the resin vat unit (3) and information regarding the removable frame-like spacer foil (6-4c).

5. A removable frame-like spacer foil (6-4c) suitable for use in an additive manufacturing apparatus (1) according to any one of claims 1 to 4.

6. A removable frame-like spacer foil (6-4c) according to claim 5, characterized in that the removable frame-like spacer foil (6-4c) is provided with one or more colour codes indicating its thickness, material and / or size.

7. A removable frame-like spacer foil (6-4c) according to claim 5 or 6, characterized in that said removable frame-like spacer foil (6-4c) has a thickness of at least 100 micrometers.

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