3D printing device, 3D printing method, and 3D tubular object obtained by the method

Abstract

To provide a 3D printing device or a 3D printing method.SOLUTION: A 3D printing device or a 3D printing method, the device including: a build platform having an outer surface; means for providing a polymerizable fluid resin on the outer surface; an electromagnetic radiation source that emits a beam of electromagnetic radiation onto the outer surface; beam positioning means for variably positioning an impingement point of the beam; and means for controlling the electromagnetic radiation source and the beam positioning means to produce a 3D tubular object according to a model, wherein the build platform comprises a stem forming a tubular surface about a longitudinal axis such that the outer surface of the build platform is included in the tubular surface, and the beam positioning means is configured to variably position the impingement point of the beam at different points of the fluid resin provided on the tubular surface.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention refers to the field of manufacturing objects by additive manufacturing processes, commonly known as 3D printing.

[0002] More particularly, the present invention relates to a 3D printing apparatus for manufacturing at least one 3D tubular object according to a printing model, said 3D printing apparatus comprising: a build platform having an exterior surface; a resin supply means configured to provide a fluid resin polymerizable by electromagnetic radiation to the exterior surface of the build platform; an electromagnetic radiation source configured to emit a beam of electromagnetic radiation from an output onto the exterior surface of the build platform that is suitable for polymerizing the fluid resin; beam positioning means configured to variably position the impact point of the beam on the fluid resin provided on the outer surface; and control means configured to control the beam positioning means and the electromagnetic radiation source according to the printing model to produce the 3D tubular object.

[0003] The invention also refers to a corresponding 3D printing method, as well as to a 3D tubular object obtained by said method. [Background technology]

[0004] Solutions that enable the production of high-resolution objects are known in the field of 3D printing. In particular, stereolithography (SL) is a technique known to allow for the printing of 3D objects with such high resolution. It is based on the successive creation of micrometer-sized layers of resin, typically 10 microns thick or more, which are polymerized by the incidence of a beam of electromagnetic radiation, typically ultraviolet light. The incident light is usually emitted from a laser device or a homogeneous light source that is masked according to the point to be polymerized in each layer of resin. In both cases, high precision can be achieved in the polymerization points, and therefore this technique is capable of printing 3D objects with high resolution. Stereolithography requires the use of a tray filled with the resin to be polymerized, where successive horizontal layers of material are created from a flat substrate that serves as a build platform. During the creation of each layer, the device remains stationary without moving the build platform. Typically, after each layer, the 3D object under construction must be moved or new resin added to create the next layer. This results in a slow printing method based on layer-by-layer manufacturing. Generally, the time required to create a 3D object increases with resolution. That is, the smaller the details to be created, the finer the successive layers must be, and therefore the greater the number of layers required. Furthermore, stereolithography can involve expensive resins, since, on the one hand, the object to be printed must be immersed in a printing tray and covered with sufficient resin, and, on the other hand, support structures for the cantilevered parts of the object must be created, which must then be removed to achieve the finished object.

[0005] Other techniques do not achieve the same precision as stereolithography, but offer higher manufacturing speeds and economy. This is the case, for example, with FDM (fused deposition modeling), a technique based on the point-to-point deposition of molten thermoplastic material. Known FDM techniques cannot achieve high-resolution details below 200 microns. This is primarily because the nozzle delivering the molten material cannot be too small, since the material will not flow through it. Another drawback of FDM is that, due to point-to-point deposition, the produced object has irregularities. Furthermore, the speed at which the molten material flows from the nozzle usually cannot be controlled with high precision. Therefore, FDM is not suitable for producing high-resolution objects with very small details.

[0006] A special case of 3D printing refers to the creation of tubular objects. In this document, the term "tubular object" generally refers to any object having an empty interior region bounded by a tubular surface and having polymerized material extending across all or a portion of said tubular surface. Unless otherwise indicated, the term "tubular surface" generally refers to a surface extending around a longitudinal axis and is not necessarily limited to a regular shape, such as, for example, a cylindrical shape.

[0007] FDM technology can be used for 3D printing tubular objects. However, these techniques have the drawback that the tubular surface of the printed tubular object's hollow regions typically has significant irregularities between the points where the molten material is deposited by the nozzle. To address this issue, a specific FDM 3D printing method has been proposed by Antonio Guerra-Sanchez in "Contribution to the Manufacturing of Bioabsorbable Stents by Additive Manufacturing (Ph.D.)" (2019, University of Girona, Proceedings: http: / / hdl.handle.net / 10803 / 667867). In this particular method, material is deposited onto the surface of a cylindrical core by a nozzle. Because the molten material is deposited onto the smooth cylindrical surface of the core by the nozzle, a much more regular tubular surface can be obtained in the hollow regions of the printed tubular object. However, in addition to the inherent drawbacks of FDM technology mentioned above, a problem that arises with this particular method is that the combination of point-to-point deposition and relative rotation between the nozzle and the cylindrical core limits the printing speed.

[0008] JP 2000-043150A discloses a 3D printer intended to manufacture a composite product comprising a metal shaft and a gear wheel. Only the gear wheel is made of polymerized resin by 3D printing. The shaft is rotatably mounted inside a liquid resin tank, and a radiation beam polymerizes the resin on the shaft to form the gear wheel. The final product is a composite product in which the 3D-printed gear wheel is integrated with the metal shaft.

[0009] US2019311822A1 discloses a similar method, in which the composite product is a conductor rod with a capacitor. The rod is partially submerged in a liquid resin tank and rotated at a controlled speed to adjust the thickness of the resin layer formed on the rod. A radiation beam polymerizes the resin layer on the rod, forming a capacitor. The final product is a composite product with a 3D-printed light concentrator integrated into the rod.

[0010] Therefore, a 3D printing solution is needed to print high-resolution tubular objects, which solves the aforementioned problems of slowness, cost, and additional steps. Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the present invention is to provide a 3D printing device of the type described above, which is able to avoid the problems identified above. [Means for solving the problem]

[0012] This object is achieved by a 3D printing apparatus of the first mentioned type, characterized in that the build platform comprises a stem having a longitudinal axis, said stem forming a tubular surface around said longitudinal axis, whereby an outer surface of the build platform is included in the tubular surface, and the beam positioning means is configured to variably position the impact point of the beam at different points on at least a portion of the fluid resin provided on the tubular surface.

[0013] The tubular surface is formed along at least a portion of the stem, but not necessarily along the entire stem, and the stem itself is not necessarily formed as a single piece.

[0014] In this way, the flat support of traditional stereolithography techniques is not used; instead, a stem with a tubular surface is used as the build platform. Resin is applied over the tubular surface of the stem and polymerized directly onto it. The thickness of the fluid resin on the support corresponds to the thickness of the polymerized resin layer, excluding possible shrinkage or expansion effects during polymerization. In this way, successive layers are formed concentrically around the stem. In this way, the number of layers is significantly reduced compared to the production of horizontal layers aligned with each other. In some cases, a single layer is sufficient to create a 3D tubular object.

[0015] This reduction in the number of layers and their arrangement has several advantages. First, manufacturing time is significantly reduced. Furthermore, the strength of the resulting object is improved due to fewer layer joints and the concentric arrangement of the layers. On the other hand, compared to stereolithography methods known in the art, it is easier to manufacture objects with cantilevered components, since the aforementioned support structures, which must then be removed, are not required. Furthermore, the concentric arrangement of these layers allows for the encapsulation of therapeutic agents between the layers. Finally, it is possible to manufacture 3D tubular objects with concentric layers made of different resins, which can be particularly advantageous, for example, in the manufacture of tubular objects requiring different mechanical properties between the inner and outer layers. All of this contributes to the fact that the proposed solution is particularly advantageous for the manufacture of 3D tubular objects requiring tubular hollow regions.

[0016] Preferably, the beam positioning means is configured to variably position the impact point of the beam on the fluid resin by at least: Circumferential positioning about said major axis. Longitudinal positioning along a longitudinal direction defined by said major axis.

[0017] Thus, it is possible to use a 3D printing model in which the points of each layer are defined using only two coordinates: one corresponding to the relative circumferential position between the beam and the stem, and the other corresponding to the relative longitudinal position. This type of coordinate differs from the Cartesian coordinates used in traditional stereolithography. In this invention, it is not necessary to create layers in the XY plane and then deposit each layer along the Z axis. Instead, in this invention, each layer is defined according to the tubular geometry, albeit using only two coordinates, already resulting in a three-dimensional body. This type of positioning simplifies 3D modeling and reduces the computational costs required in the printing device, since it does not require a decomposition of Cartesian coordinates into the relative position between the support and the corresponding beam. Notably, the type of positioning described relates to cylindrical coordinates, which is particularly advantageous when the support being printed is tubular, and especially when it is cylindrical.

[0018] Preferably, the beam positioning means is further configured to variably position the impact point of the beam on the fluid resin by positioning the distance between the output and the tubular surface of the stem, thereby defining the beam length. This distance positioning has two main advantages. First, it allows determining the appropriate beam length so that the focal point coincides with the point of incidence on the resin. Second, it allows the beam length to be adapted to the geometry of the stem, so that the stem does not need to be cylindrical, and other less regular shapes can be envisioned.

[0019] Preferably, the electromagnetic radiation includes at least one of the following: infrared, visible, and ultraviolet radiation. While ultraviolet (UV) radiation has been commonly used in the field of stereolithography, the apparatus of the present invention is not limited to specific UV-polymerizable resins. Specific applications, such as biocompatible resins with photoinitiators sensitive to visible or infrared wavelengths (IR), and different fluid resins, may also be envisioned.

[0020] Preferably, the tubular surface of the stem has rotational symmetry about the long axis. If the stem is a body of revolution, the distance from the long axis of the stem to the tubular surface for each longitudinal point is the same for any angle, which facilitates beam positioning and reduces the computational cost required to determine this positioning according to a printing model.

[0021] The tubular surface of the stem preferably has a conical, frusto-conical or cylindrical shape, thus enhancing the above-mentioned advantages, especially in the case of a cylindrical shape: in fact, in the latter case, the distance between the longitudinal axis and the tubular surface of the stem is the same at any angle and along the entire length of the tubular surface of the stem.

[0022] In the art, the term diffuse surface refers to a surface in which incident electromagnetic radiation is reflected at multiple angles, rather than at a single angle. This phenomenon is usually caused by the presence of surface irregularities, said irregularities being of the same order of magnitude as the wavelength of the incident electromagnetic radiation. In contrast, specular surfaces exhibit a more pronounced phenomenon of specular reflection, which occurs when the reflectivity is close to zero at all angles except one. These are generally smooth, polished materials. As a result, diffuse surfaces are substantially free of specular reflection.

[0023] Preferably, the tubular surface of the stem is a diffusive surface with respect to the wavelength of the electromagnetic radiation. Thus, the portion of the energy of the reflected electromagnetic radiation is distributed at various angles and not concentrated in a single direction as in specular reflection, which may otherwise cause polymerization of the fluid resin in the path of the specular reflection. This results in less parasitic polymerization at adjacent points affected by the reflected beam, thereby increasing the precision of the object produced.

[0024] Preferably, the tubular surface of the stem does not reflect the electromagnetic radiation, i.e. the incident beam is not substantially reflected by the tubular surface and energy is absorbed by it, at least for wavelengths corresponding to the electromagnetic radiation, thus minimizing the effects of parasitic polymerization mentioned above.

[0025] Preferably, the tubular surface of the stem is opaque to the electromagnetic radiation, so that the incident beam does not transmit through the stem and / or is not subject to other internal reflections that could result in undesired polymerization if there is fluid resin at the exit point.

[0026] Preferably, the stem comprises a hard core surrounded by an outer layer of elastomeric material, which forms the tubular surface of the stem. The hard core provides the stem with high mechanical resistance and makes it less prone to twisting. Furthermore, the elastomeric layer, due to its elasticity, facilitates removal of the object after printing. Furthermore, the elastomer also has a diffusive surface with respect to the electromagnetic radiation of the beam. The hard core is preferably made of metal, particularly steel, which maximizes the aforementioned effects while maintaining a reasonable manufacturing cost for the device. The elastomeric material is preferably latex or nylon, whose physical and chemical properties are particularly advantageous for achieving the aforementioned effects of anti-mold and diffuse reflection.

[0027] Preferably, the resin supply means is arranged to include a resin tank and a stem extending through the resin tank, such that fluid resin is supplied directly from the resin tank to the tubular surface of the stem. This configuration simplifies the device by avoiding the use of more complex means for supplying resin to the tubular surface of the stem, such as via irrigation, brushing, transfer rollers, etc. In this way, the manufacturing costs of the device can be minimized and the control methods required to manage the fluid resin supply can be simplified. As the fluid resin polymerizes, the resin tank is filled with more fluid resin as needed.

[0028] In a preferred embodiment, the stem is positioned horizontally so that all of its tubular surfaces are located below the resin fill level of the resin tank. Therefore, the long axis is horizontal and thus longitudinal. Preferably, the apparatus includes a means for rotating the stem around its longitudinal axis so that the beam strikes the point on the stem's tubular surface that is highest relative to the predetermined longitudinal position to print a point at that position. The thickness of the polymerized resin at that point corresponds to the distance between the height of that point and the resin fill level. Therefore, the thickness of each layer can be controlled by the resin fill level, taking into account the shape of the stem as well as allowing for the contraction or expansion of the fluid resin as it is polymerized. Preferably, the tank is filled with additional fluid resin as the fluid resin is used up during printing. Those skilled in the art will understand that the fill level may vary, e.g., it may be necessary to increase the level between successive printing layers or, alternatively, to lower the stem. This embodiment is particularly advantageous when the stem is cylindrical, as it makes it easier to control the thickness of the resin layer, since the distance between the fill level and the highest point of the stem is the same over the entire length of the stem.

[0029] In an alternative embodiment, the stem is positioned horizontally so that one part of its tubular surface is located above the resin fill level of the resin tank and another part of its tubular surface is located below said resin fill level. Thus, as the stem rotates around its longitudinal axis, the fluid resin is drawn by the tubular surface of the stem from the bottom of the tank to the top of the fill level where it can be emitted by the beam and polymerized. In this way, a thin layer can be obtained that can be polymerized precisely. Experts will understand that the layer thickness depends on the properties of the fluid resin, in particular its viscosity, as well as on the tubular surface of the stem, in particular its porosity or contours. Consequently, the desired layer thickness can be obtained by controlling these properties.

[0030] In another preferred embodiment, the resin tank comprises a container arranged around the stem, defining a resin chamber between the container and the tubular surface of the stem, the container being made of a material transparent to electromagnetic radiation. In this way, fluid resin can be emitted from the outside of the container, through the transparent wall, and into the resin chamber. This has several advantages. First, the thickness of the resin layer is very precisely determined by the thickness of the resin chamber. Furthermore, because the stem is enclosed by the container, the stem can be positioned at the most convenient angle, even vertically. A further advantage is that resin waste is minimized, since it is only necessary to provide a precise amount of fluid resin to the resin chamber.

[0031] Preferably, the 3D printing apparatus further comprises a temperature control means configured to control the temperature of the fluid resin provided on the tubular surface of the stem by the resin supply means, thus enabling control of the viscosity of the fluid resin. Preferably, the temperature control means includes a thermoelectric cell, also known as a Peltier cell, and in this way can warm up and cool down the temperature of the fluid resin.

[0032] In a preferred embodiment, the electromagnetic radiation source comprises an electromagnetic radiation generator and a fiber optic guidance module configured to guide the electromagnetic radiation to an optical fiber output, the optical fiber output being configured such that the light source output is the optical fiber output, the optical fiber output preferably including one or more lenses to focus the output radiation into a narrow beam.

[0033] In an alternative embodiment, the electromagnetic radiation source includes a laser device having a laser output, such that the light source output is the laser output, thus utilizing the narrow and focused laser beam characteristics to impinge with high precision on the desired point. Those skilled in the art will understand that laser beam guidance can include known elements, among other non-limiting examples, mirrors, prisms, lenses, or combinations of the foregoing. In the context of the present invention, the laser output refers to the point at which the beam exits the guidance system, if any, and is directed toward the impingement point on the tubular surface of the stem.

[0034] Preferably the stem is mounted rotatably about its longitudinal axis and the beam positioning means comprises: a rotational control element for controlling rotation of the stem about the longitudinal axis, thereby controlling circumferential positioning of the impingement point of the beam in a circumferential direction about the longitudinal axis; a longitudinal position control element that controls the longitudinal position of the impingement point of the beam along a longitudinal direction defined by the major axis; a distance control element that controls the distance between the output portion and the tubular surface of the stem to define a beam length.

[0035] Thus, the beam can be positioned by controlling the relative position of the stem and the beam. In particular, the stem is rotated around its long axis, while the beam is arranged longitudinally and at a distance. Alternatively, it is also possible to envisage an embodiment in which the beam is arranged in rotation around the stem, while the latter remains stationary. However, stem rotation is the preferred option, as it simplifies the design of the device and its energy consumption during its operation. Distance control allows for adaptation to the shape of the stem as well as positioning the impact point of the beam according to its focus.

[0036] Preferably, the rotation control element comprises a servo motor operably connected to the stem and rotating the stem about the longitudinal axis, whereby the support can be rotated by a technical element that can be easily integrated into a printing device.

[0037] Preferably, the longitudinal position control element comprises at least a straight longitudinal guide configured to longitudinally position the output portion in a direction parallel to the longitudinal axis. As a non-limiting example, the position control element comprises one straight longitudinal guide such that the laser device is shiftable along said straight longitudinal guide.

[0038] Preferably, the distance control element includes at least a straight vertical guide configured to vertically position the output in a direction perpendicular to the longitudinal axis. As a non-limiting example, the distance control element may comprise two parallel guides along which the aforementioned longitudinal guide is shiftable, each end of the longitudinal guide being attached to one of the parallel guides.

[0039] Preferably, the stem is positioned horizontally, the output is positioned to emit the beam vertically downward, and the distance control element is configured to position the output vertically. This configuration is particularly advantageous when the stem is placed over a resin tank with an opening at the top, allowing the beam to impinge on the tubular surface of the stem through the opening. Furthermore, this configuration allows for partial reuse of Cartesian 3D printing devices in which the electromagnetic radiation source (e.g., a laser device) can be shifted vertically and horizontally. This further facilitates the design of the 3D printing device of the present invention based on existing know-how for current stereolithography devices.

[0040] In an alternative embodiment, the stem is arranged vertically, the output is arranged to emit the beam horizontally, and the distance control element is configured to arrange the output horizontally. As an alternative to the previous embodiment, it also allows the reuse of known devices for moving an electromagnetic radiation source. With regard to these two exemplary embodiments, the choice of one or the other alternative embodiment depends on the characteristics, in particular the dimensions of the stem, the substrate, and the space required to accommodate the printing device.

[0041] Preferably, the 3D printing apparatus further comprises a layer measuring means configured to determine a measure of the thickness of the layer of the fluid resin provided on the tubular surface. The thickness of the layer of polymerized resin corresponds to the layer of polymerized fluid resin, excluding any eventual shrinkage or expansion during polymerization. Thus, measuring the thickness of the layer of fluid resin on the tubular molding surface allows for the thickness of the layer of polymerized resin to be determined.

[0042] Preferably, the layer measurement means includes a laser profiler, such that a thickness measurement is determined from the difference between a laser profiler measurement when the tubular surface is not provided with fluid resin and a measurement when the tubular surface is provided with the fluid resin. Laser profilers are known in the art and provide good accuracy. In this case, measuring the thickness of the fluid resin layer involves two steps: first, the laser profiler is directed at the tubular surface where no fluid resin is present, so the measured distance is from the profiler to the surface; second, the fluid resin is provided, and the laser profiler takes another measurement. In this case, the measured distance is from the profiler to the fluid resin. Therefore, the difference between the two measures can be used to determine the thickness of the resin layer. Those skilled in the art will understand that the specific calculation depends on the positioning of the laser profiler and the stem. If the 3D tubular object being created includes more than one layer, an equivalent thickness determination can be obtained for the second and subsequent layers by comparison with layers already polymerized, rather than with the tubular surface itself.

[0043] Preferably, the 3D printing device further comprises a layer thickness control means configured to receive the thickness measurements and, if necessary, vary the thickness of the resin layer provided on the tubular surface. Thus, the thickness of the resin layer is not only known, but can also be varied according to the requirements of the 3D tubular object to be printed using the model; in particular, if the measured thickness differs from that specified in the model, the layer thickness control means increases or decreases the thickness accordingly. The means for varying the thickness depend on the type of 3D printing device, the fluid resin used, how the resin is provided on the tubular surface, etc. Although different options can be envisaged, preferably, the thickness variation is achieved by at least one of the following means: Means for varying the amount of resin provided by said resin supply means. A means for varying the temperature of said fluid resin. Means for varying the rotational speed of said stem.

[0044] As a non-limiting example, if the stem is placed horizontally inside a tank, varying the amount of resin provided in the tank will affect the level of fluid resin inside the tank and, consequently, the thickness of the layer of resin if the tubular surface is below the level of fluid resin. In other cases where the tubular surface is only partially submerged below the level of fluid resin, the resin fluidity can be varied by varying the temperature of the fluid resin, and therefore the thickness of the layer drawn to the polymerization point as the stem rotates. Similarly, varying the rotation speed will affect how the fluid resin is drawn.

[0045] The present invention also refers to a 3D printing method for manufacturing a 3D tubular object from a printed model, starting from a build platform having an outer surface, the method comprising generating one or more successive layers of polymerized resin, each layer of polymerized resin being generated by: Providing a fluid resin polymerizable by electromagnetic radiation on the exterior surface of the build platform. Positioning a beam of electromagnetic radiation suitable for polymerizing the fluid resin onto the exterior surface of the build platform according to the printing model, thereby producing a layer of the polymerized resin. The build platform comprises a stem having a longitudinal axis, the stem forming a tubular surface around the longitudinal axis, whereby the outer surface is included in the tubular surface, and the beam is variably positioned according to a printing model so as to impinge on different points of fluid resin on at least a portion of the tubular surface of the stem.

[0046] The technical elements and effects are equivalent to those of the above-mentioned device, and therefore will not be repeated below for the sake of brevity.

[0047] Preferably, positioning the beam towards the tubular surface of the stem according to the printed model comprises positioning said beam by at least: Circumferential positioning in a circumferential direction about said longitudinal axis. Longitudinal positioning along a longitudinal direction defined by said major axis. Preferably, the beam length is defined by positioning the distance between the source output and the tubular surface of the stem.

[0048] Preferably, the method includes the additional step of producing one or more successive additional layers of polymerized resin, wherein each additional layer is produced by the following steps: A further fluid resin is provided on the tubular surface of the stem, the further fluid resin being polymerizable by electromagnetic radiation. According to a printing model, a beam of electromagnetic radiation suitable for polymerizing an additional beam of fluid resin towards the tubular surface of the stem is variably positioned to impinge the fluid resin at different points on at least a portion of the tubular surface of the stem having a tubular shape, thereby generating the layer of polymerized resin.

[0049] Thus, unlike known methods that can use only one resin and in which each successive layer is arranged, for example, in successive planes perpendicular to the longitudinal axis, the present method allows for the production of 3D tubular objects in which each concentric layer can be made from a different polymerized resin. Preferably, the present method includes repeating the process with the fluid resin, additional fluid resins, or even other fluid resins or resins. Furthermore, the application of multiple resins that can be arranged in substantially concentric layers allows for the production of objects intended for applications not currently possible in the field of 3D printing. Therefore, it is expected that this method will be the subject of future research and development efforts.

[0050] Preferably, the fluid resin, or, if appropriate, the additional fluid resin, independently of the polymerizable compound, is prolycaprolactone, PCL, in particular PCL-diacrylate, which is particularly advantageous in the case of the present invention, since it is a material that can be polymerized by ultraviolet radiation and whose viscosity can be controlled by controlling its temperature.

[0051] Preferably, the fluid resin, or, if appropriate, the additional fluid resins, are biocompatible, which allows for use in medical applications, for example, for the manufacture of stents. A therapeutic product may optionally be added to at least one of such resins, so that the 3D tubular object itself has a therapeutic effect.

[0052] The present invention also refers to a 3D tubular object manufactured by the aforementioned 3D printing method.

[0053] The present invention also relates to tubular objects produced by 3D printing, comprising at least one layer of resin polymerized by electromagnetic radiation, each of which has a tubular shape around a longitudinal axis, with each successive layer being arranged concentrically with respect to said longitudinal axis, in contrast to objects currently obtainable by stereolithography, particularly for the creation of high-resolution details with dimensions less than 200 microns. Objects of this type have the additional advantage of improved structural strength compared to those made by overlapping flat layers. Objects of this type are not known in the art and can also be printed using one of the preferred manufacturing methods described above.

[0054] Preferably, said layer of polymerized resin is formed by one or more biocompatible resins, preferably at least one of these resins having a therapeutic product with the technical effect described above.

[0055] The present invention also refers to a printing model defining a 3D tubular object printable by a method according to any of the preferred embodiments described above, comprising at least a model of the layer to be printed, wherein each point of the layer to be printed comprises coordinates relative to at least the following: The angle of rotation of the stem about the major axis. A longitudinal position along the major axis. The radial distance from the major axis is preferred.

[0056] The present invention also relates to the use of a method according to any of the above preferred embodiments for the manufacture of a stent.

[0057] The present invention also encompasses other features that are illustrated in the detailed description of embodiments of the invention and the accompanying drawings.

[0058] Further advantages and features of the present invention will become apparent from the following description, in which preferred embodiments of the invention are disclosed, without being limited in any way, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0059] [Figure 1] FIG. 1 is a perspective view of one embodiment of a 3D printing device according to the present invention. [Figure 2] FIG. 2 is a front view of the same embodiment of the 3D printing device shown in FIG. [Figure 3] 3 is a detailed front view of a 3D printing apparatus according to one embodiment of the present invention, showing the electromagnetic radiation source, beam, stem, and corresponding portions of the resin tank. The resin tank is shown in cross section to reveal the stem. The cross section is indicated by parallel diagonal lines in the figure. [Figure 4A] FIG. 4A is a detailed perspective view of a stem of a 3D printing apparatus according to one embodiment of the present invention, being used to fabricate a 3D tubular object, specifically a stent, still attached to the stem. [Figure 4B] FIG. 4B is a view corresponding to FIG. 4A, but in a different embodiment, the stem is made from a solid block instead of a hard core and outer layer. [Figure 5] FIG. 5 is a perspective view of the stent of FIG. 8 after it has been removed from the stem of the 3D printing device. [Figure 6] FIG. 6 is a detailed front view of a 3D printing apparatus according to another embodiment of the present invention. [Figure 7] FIG. 7 is a detailed front view of the tank and stem of a 3D printing apparatus according to another embodiment of the present invention. [Figure 8] FIG. 8 is a detailed front view of a 3D printing apparatus according to one embodiment of the present invention having a laser profiler measuring the thickness of the layer of fluid resin on the tubular surface of the stem. [Figure 9] FIG. 9 is a front view of a 3D printing apparatus according to another embodiment of the present invention. [Figure 10] FIG. 10 is a front view of a 3D printing apparatus according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0060] Some of the embodiments shown in the drawings were carried out using known stereolithography 3D printers, in particular the PRUSA MK2S, as a basis and have been adapted solely for experimental evaluation in the laboratory, which has given very positive results. Those skilled in the art will clearly identify any modifications required for the invention. Future versions aimed at the market will likely use different structures, which a skilled person will have no problems designing using the teachings herein.

[0061] 1, 2, 3, and 4 illustrate a first exemplary embodiment of a 3D printing apparatus 1 of the present invention. The 3D printing apparatus 1 is intended to produce at least one 3D tubular object 100 according to a printing model and includes a build platform having a surface 2. In this first embodiment, the build platform is a stem 3 having a longitudinal axis 9, as shown in FIG. 3. The stem 3 forms a tubular surface 2 about the longitudinal axis 9. The outer surface of the build platform is therefore the tubular surface 2 of the stem 3, which has a tubular shape about the longitudinal axis 9. As shown in the figures, the tubular surface 2 of the stem 3 has rotational symmetry about the longitudinal axis 9. In particular, the stem 3 is tubular, and the surface 2 has a tubular shape.

[0062] The 3D printing device 1 also comprises a resin supply means configured to provide a fluid resin 4 polymerizable by electromagnetic radiation on the tubular surface 2 of the stem 3. In particular, the resin supply means comprises a resin tank 12, through which the stem 3 passes. As shown in Figure 3, the stem 3 is horizontally positioned such that all of the tubular surfaces 2 are located below a resin fill level 13 of the resin tank 12.

[0063] The 3D printing apparatus 1 comprises an electromagnetic radiation source 5 configured to emit from an output 6 a beam 7 of electromagnetic radiation suitable for polymerizing a fluid resin 4 onto the tubular surface 2 of the stem. In a first embodiment, the electromagnetic radiation source 5 is a laser device 19 having a laser output, and consequently the output 6 is the laser output. The laser beam 7 is represented in the figure by a dashed line.

[0064] To position the beam 7, the 3D printing apparatus also includes a beam positioning means 8 arranged to variably position the impact point of the beam 7 so that the beam 7 impacts different points on at least a portion of the fluid resin 4 provided on the tubular surface 2. The 3D printing apparatus 1 also includes a control means used to control the beam positioning means 8 and the electromagnetic radiation source 5 according to a printing model to produce the 3D tubular object 100. For clarity, the control means is not shown in the figures. FIGS. 1 and 2 show that the beam positioning means 8 is configured to variably position the impact point of the beam 7 on the fluid resin 4 using three types of positioning elements corresponding to three coordinates. First, circumferential positioning is performed around the longitudinal axis 9. The circumferential positioning is performed by a rotational control element 20, in particular a servo motor operatively connected to the stem 3, which drives the rotation of the stem 3 around the longitudinal axis 9. Second, longitudinal positioning is performed along the longitudinal direction defined by the longitudinal axis 9. Longitudinal positioning is achieved by a longitudinal position control element 21 having two parallel straight longitudinal guides 211 configured to longitudinally position the laser device 19 slidably mounted thereon and, accordingly, position the output section 6. A longitudinal traction belt 212 is used to slide the laser device 19 longitudinally along the longitudinal guides 211. The longitudinal guides 211 are parallel to the stem 3 and the longitudinal axis 9, and the output section 6 is positioned to emit the beam 7 in a downward vertical direction perpendicular to the longitudinal axis 9. Third, positioning the distance between the output section 6 and the tubular surface 2 of the stem 3 allows the length of the beam 7 to be determined by a distance control element 22. The distance control element 22 has four straight vertical guides 221 configured to vertically position the output section 6 in a direction perpendicular to the longitudinal axis 9. In the first embodiment, the vertical guides 221 are vertically oriented to position the output section 6 vertically. In particular, two vertical guides 221 are arranged at each longitudinal end of the longitudinal guide 211 slidably mounted thereon, so that the longitudinal guide 211 can slide up and down along the vertical guide 221 to position the output section 6 in the vertical direction.

[0065] The 3D printing apparatus 1 of the first embodiment further includes a temperature control means. For ease of understanding, the temperature control means includes a Peltier cell disposed in the tank (not shown), so that the temperature of the fluid resin 4 can be controlled.

[0066] In the first embodiment, the laser device 19 emits a beam 7 of ultraviolet radiation, UV. The 3D printing device 1 can therefore be used with UV-polymerizable resins. In particular, it is possible to use prolycaprolactone-derived resins, such as PCL-diacrylate. Nevertheless, other types of electromagnetic radiation and fluid resins 4 are also conceivable within the scope of the present invention, for example, if the laser device 19 emits a beam 7 of infrared radiation or visible light. Also, biocompatible fluid resins 4, possibly with therapeutic additives, can be used with the 3D printing device of the present invention.

[0067] A 3D printing method for printing a 3D tubular object using the 3D printing apparatus 1 of the embodiments described herein can include several steps for producing successive layers of polymerized resin. Since each layer is created by providing a fluid resin 4, it can be envisioned that different fluid resins 4 are used for different layers.

[0068] FIG. 4A is a detailed view of a stem 3 according to a first embodiment. In this case, the stem 3 has a rigid core 10 made of steel surrounded by an outer layer 11 made of nylon, which forms the tubular surface 2 of the stem 3. Other metals, such as titanium, can be envisioned for the rigid core 10. Furthermore, other elastomeric materials, such as latex, can also be envisioned for the outer layer 11. FIG. 4A shows a 3D tubular object produced in a 3D printing apparatus 1 following the 3D printing method of the present invention, still attached to the tubular surface 2. FIG. 5 shows the same 3D tubular object once removed from the stem 3. In the case of FIGS. 4A and 5, the present invention is used to produce a 3D-printed stent. FIG. 4B shows a different embodiment of the stem 3, in which, instead of a rigid core and outer layer, the tubular surface 2 is made of a solid block, and the tubular surface 2 is not made of a different material from the rest of the stem 3.

[0069] Also, in the first embodiment, the tubular surface 2 of the stem 3 is a diffuse surface that does not reflect said wavelengths of electromagnetic radiation: the tubular surface 2 of the stem 3 is opaque to said wavelengths.

[0070] Other embodiments of a 3D printing apparatus according to the present invention are disclosed below. These embodiments share most of the features disclosed in the first embodiment above. Therefore, only the differentiating features will be described in detail. For the sake of brevity, common features shared with the first embodiment disclosed above will not be described again here.

[0071] Figure 6 shows a second embodiment of a 3D printing apparatus 1 according to the invention, in which the electromagnetic radiation source 5 comprises an electromagnetic radiation generator 16 and an optical fiber guidance module 17 that guides the electromagnetic radiation to an optical fiber output, such that the output 6 becomes the optical fiber output.

[0072] 7 shows a third embodiment of the 3D printing device 1 in which the stem 3 is arranged horizontally, with one part of the tubular surface 2 located above the resin fill level 13 of the resin tank 12 and another part of the tubular surface 2 located below said resin fill level 13.

[0073] FIG. 8 shows a fourth embodiment of the 3D printing apparatus 1, in which the stem 3 is positioned horizontally and the tubular surface 2 is located below the resin fill level 13 of the resin tank 12. In this embodiment, the 3D printing apparatus 1 further comprises a layer measurement means 40 configured to determine a measurement of the thickness of the layer of the fluid resin 4 provided on the tubular surface 2. The layer measurement means 40 comprises a laser profiler, whereby the thickness measurement is determined by the difference between the measurement of the laser profiler when the tubular surface 2 is not provided with fluid resin 4 and the measurement when the tubular surface 2 is provided with fluid resin 4. Furthermore, the apparatus further comprises a layer thickness control means for receiving the thickness measurement and, if necessary, varying the thickness of the resin layer provided on the tubular surface 2, in this case by varying the amount of fluid resin 4 provided by the resin supply means, i.e., the amount of fluid resin 4 provided to the resin tank 12. For example, starting from the third embodiment of FIG. 7, other embodiments can be envisaged in which the layer thickness control means is configured to vary the thickness by varying the temperature of the fluid resin 4 and / or by varying the rotation speed of the stem 3.

[0074] 9 shows a fifth embodiment of the 3D printing apparatus 1, in which the stem 3 is arranged vertically, the output unit 6 is arranged to emit the beam 7 horizontally, and a distance control element 22 is configured to position the output unit 6 horizontally. In this fifth embodiment, the resin tank 12 has a container 14 arranged around the stem 3, such that a resin chamber 15 is defined between the container 14 and the tubular surface 2 of the stem 3. In this fifth embodiment, the container 14 is made of a material that is transparent to the electromagnetic radiation emitted by the laser device 19.

[0075] FIG. 10 shows a sixth embodiment of the 3D printing apparatus 1, in which the stem 3 is vertically arranged and the output unit 6 is arranged to emit the beam 7 horizontally. In this sixth embodiment, the resin tank 12 has a container 14 arranged around the stem 3, such that a resin chamber 15 is defined between the container 14 and the tubular surface 2 of the stem 3. The container 14 is made of a material that is transparent to the electromagnetic radiation emitted by the laser device 19. In contrast to the previous example, this sixth embodiment does not include a distance control element 22. Furthermore, there is no rotation control element 20 affecting the stem 3, but there is an output source rotation element 30 affecting the laser device 19, so that the output unit 6 is moved around the stem 3, particularly around the longitudinal axis 9. As shown in FIG. 9, the output source rotation element 30 comprises a rotating structure, rotatably mounted around the longitudinal axis 9, in this case, vertically arranged. A longitudinal position control element 21 is fixed to the rotating structure and is configured to position the beam 7 circumferentially as the rotating structure rotates.

[0076] In other possible embodiments not shown in the figures, the tubular surface 2 of the stem 3 has orbital symmetry about said longitudinal axis 9, so that the tubular surface 2 has a shape that is conical or frusto-conical.

Claims

1. 1. A 3D printing method for manufacturing a 3D tubular object (100) from a printed model, starting with a build platform having an outer surface, the 3D printing method comprising producing one or more successive layers of polymerized resin, each layer of polymerized resin comprising: providing a fluid resin (4) polymerizable by electromagnetic radiation on the outer surface of the build platform; generating a layer of polymerized resin by positioning a beam of electromagnetic radiation (7) to polymerize the fluid resin (4) onto the outer surface of the build platform according to the printing model; is generated by the build platform comprises a stem (3) having a longitudinal axis (9), the stem (3) forming a tubular surface (2) around the longitudinal axis (9) such that the outer surface of the build platform is configured to the tubular surface (2); the beam (7) is variably positioned according to the printing model to impinge on different points of the fluid resin (4) on at least a portion of the tubular surface (2); 3D printing method, characterized in that the 3D tubular object (100) is obtained by removing from the stem (3) a 3D object formed on the tubular surface (2) by one or more successive layers of the polymerized resin.

2. Positioning the beam (7) on the tubular surface (2) of the stem (3) according to the printed model includes at least circumferential positioning about said longitudinal axis (9); longitudinal positioning along the longitudinal direction defined by said major axis (9); defining a beam length by positioning the distance between the output (6) and the tubular surface (2) of the stem (3); 2. The 3D printing method of claim 1, further comprising positioning the beam (7) by

3. and forming one or more successive additional layers of polymerized resin in addition to the successive layer, each of the additional layers comprising: providing, on said tubular surface (2) of said stem (3), in addition to said fluid resin (4), an additional fluid resin that is polymerizable by electromagnetic radiation; forming a layer of polymerized resin by impinging different points of the fluid resin (4) on at least a portion of the tubular surface (2) of the stem (3) having a tubular shape by variably positioning a beam (7) of electromagnetic radiation for polymerizing the additional fluid resin onto the tubular surface (2) of the stem (3) according to the printing model; 2. The 3D printing method of claim 1, wherein the 3D printing method is generated by:

4. 4. The 3D printing method according to any one of claims 1 to 3, characterized in that the fluid resin (4) is biocompatible and the 3D tubular object (100) produced by the 3D printing method is a stent.

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