Technical Field

[0001] The invention relates to a 3D printer, a platform for a 3D printer, and a method of using said platform in a 3D printer.

Background Art

[0002] A platform, sometimes called a substrate, made from a material that has the same or similar chemical composition as the powder material used to make metal models is inserted into 3D printers with the Powder Bed Fusion technology based on selective laser melting. Metal models, also called prototypes, which are created by laser sintering a powdered metal alloy layer by layer, are printed on this platform. The platform is essentially a solid plate attached by four screws to the 3D printer’s conveyor, which moves layer by layer in the Z-axis. A disadvantage of a solid platform is that all models are part of the platform after the print job is completed. This leads to the issue of removing the printed models from the solid platform. The removal can be done by bandsaw, electroerosive wire cutting, or other machining technology, and the removal of the models from the solid platform is limited by the working space of the machine tool. The platform is reusable, but before the next print job, it is essential to machine and grind down the entire surface on which the models were printed. Reuse is possible as long as the height of the solid platform is not so low that the screw heads protrude from the platform holes and could cause a collision with the powder material applicator. This reduces the overall life of the platform, which is disadvantageous when printing precious metal alloys. Another disadvantage of the solid platform is the unevenly distributed residual stress and unevenly distributed heat resulting from the thermal process of laser sintering of the powder material. These effects result in deformation of the solid platform, which manifests itself in the form of deformations on the printed models. There have also been cases where the screws fixing the solid platform to the 3D printer’s conveyor have pulled out of the threaded inserts, causing the solid platform to collide with the powder material applicator. [0003] In the state of the art, for example, a solid metal plate made of a material having the same or similar chemical composition as the printing material is used as a platform. The dimensions of the platform are 250 x 250 x 15 mm. The platform has four holes for cylinder head screws with an internal hexagon. This platform is fixed by means of screws to the conveyor in the space of the 3D printer, which moves in the Z-axis, i.e., in the vertical axis. This solution has the shortcomings described above.

[0004] The platforms can have different surface area dimensions, e.g., 250 x 250 mm or 400 x 400 mm, depending on the type of the 3D printer. The width of the platform varies depending on the printing material, and there are usually four side grooves and screw openings in the corners.

[0005] A solution which consists of a solid platform bolted to a conveyor that moves in the Z-axis is described, for example, in the patent US 9597730B2 or in the patent application WO 2013/140146. These solutions exhibit the above- mentioned problems and shortcomings associated with unevenly distributed heat, heat conduction, and residual stress that accumulates in large models. A similar solution for a different additive manufacturing technology, the so-called Material Extrusion, is described in the patent application EP1279480A1 .

[0006] The patent application US 2018/0117854A1 describes a structural plate having at least one recess therein and at least one block configured such that it can be connected to the structural plate. The working surface of the block is raised. In the patent, the method of accommodating the blocks is described in two variants. In the first variant, the blocks are embedded in the structural plate on the upper surface. The second solution consists in blocks that have a groove on the left side and a recess on the right side. The structural plate is open on the side and contains a groove and a recess. The block is fitted into the groove of the structural plate by means of a recess. Other blocks are gradually mounted on the block, which are connected to each other by grooves and recesses and are connected to the structural plate. This solution differs in its design and subsequent problems, for example, it does not address the issue of heat transfer and creation of a residual stress that leads to problematic distribution of the whole assembly in case of thermal expansion. The blocks have the same dimensions, and it is therefore problematic to print models having greater dimensions than the block surface.

Summary of Invention

[0007] The object of the invention is to eliminate the effects of residual stress, thermal expansion, and deformation caused by insufficient heat conduction. Another goal is to design a modular platform solution.

[0008] These objects are addressed and the above mentioned shortcomings of the state of the art are eliminated to a significant extent by a platform for 3D print, i.e. for accommodating a printing material irradiated by a laser during the 3D printing of the invention, comprising a base plate and a plurality of individually removable segment plates 2 attached thereto at the same height level suitable for accommodating the printing material, comprising a layer of material suitable for contact with the printing material, where the essence of the invention is that the adjacent segment plates 2 are placed at a predefined minimum or greater spacing distance from each other.

[0009] The connection of the segment plates must ensure the necessary cohesion of the segments with their surface layer at the required level for the print job, which is realised by placing the segments on the base plate.

[0010] The minimum spacing distance provides a gap between the segment plates and it is the smallest distance that two adjacent segment plates can be brought together, which is, for example, not less than 10 mm. The dimensions are given at normal room temperatures, i.e., around 20 °C.

[0011 ] By sufficient spacing distance of the segment plates and the resulting gap, the effect of even residual stress distribution and even heat distribution is achieved. The problems with the thermal expansion of the platform are thus significantly reduced.

[0012] The new segment plate is preferably composed of a material suitable for contact with the printing material to a depth of at least 15 mm in its surface layer, or is made entirely of a suitable printing material and has an exemplary minimum thickness of 15 mm. Such a layer ensures that the plate can be reused, wherein reuse grinds down the surface and thins this surface layer. It is therefore preferable to manufacture the segment plates in larger thicknesses, for example 17 mm, 20 mm, 25 mm, 50 mm.

[0013] In a preferred embodiment, the platform is attachable to a 3D printer conveyor, preferably it is suitable for a 3D printer with the Power Bed Fusion technology for printing 3D models from a metal powder material, wherein the segment plates comprise a layer of material suitable for platforms in contact with the printing metal powder material. For example, the material may be a material with the same chemical composition as the metal printing powder material or a different chemical composition suitable for the powder material in question. A 3D printer expert knows what chemical composition can be used for the platform layer that comes into contact with a particular printing material, so the chemical composition can be similar or the same as in the case of the printing material, for example. The powder printing material can be, for example, a metal powder alloy that is sintered by the effects of laser radiation. On each segment plate, a model or multiple models are created separately by 3D printing.

[0014] The advantage is that the shape and thus the size of the platform surface can be easily and quickly changed, the platform can be disassembled and reassembled to the same or different shape according to the user’s requirements and the current print job.

[0015] The removable attachment can be realised by means of fastening screws insertable into the base plate from below through the through openings made therein, and furthermore attachable to the threaded inserts corresponding in shape thereto with one part placed in the base plate and with the other part screwed into the segment insert in the segment plate. The advantage of such a connection is that the threaded insert can be easily replaced if the screw is deformed or has to be drilled out. In this case, it is sufficient to replace only the threaded insert, and it will not be necessary to replace the entire segment plate for further use.

[0016] A number of these through openings may be regularly spaced in the base plate to form a matrix, or the through openings for the screws may be in other regular or irregular arrangements. [0017] The individual segment plates may have a square, rectangular, or other shape, may have the same or different size of their upper surface area, and the segment plates may cover the entire base plate with the exception of the spacing distances and the resulting plate gaps, or they may cover a smaller part of the base plate. The segment plates can be combined in various ways on the base plate. The covering of the base plate with the segment plates can be planned completely arbitrarily, which is advantageous compared to, for example, the solution described in US 2018/0117854A1 , where the plates are essentially stacked in a row and at the very least a whole row of segments has to be stacked, which is additionally held by a marginal raised frame.

[0018] An advantage of the invention compared to the state of the art is the modularity of the platform, i.e., the division of the platform into several smaller segments that can be combined as required and according to the shape and size of the models. Different designs of the segment plates can therefore be placed on the base plate, which can be rotated in different ways. A further advantage is that, for example, only a part of the usable platform surface can be used, and differently sized and shaped segment plates can be freely stacked.

[0019] Generally, the platforms need to be evened out, i.e., their surface needs to be ground down, usually on machine tools, before each print job in 3D printers. The platform with the segment plates preferably reduces the size of the surface that needs to be ground down on machine tools, because if not all the segment plates were used during the previous print job, only the used ones need to be machined and ground down to the prescribed height.

[0020] The solution of the invention evenly distributes heat and residual stress to multiple segment plates, thus avoiding deformation of all models in the current print job.

[0021] Another object of the invention is a 3D printer with the above-described platform of the invention.

[0022] Another object of the invention is a method of using the platform disclosed above for 3D printing in a Power Bed Fusion type 3D printer, where in step A) at least two segment plates are attached to the platform base plate and the platform is attached to a conveyor of the 3D printer; in step B) 3D printing is performed by laser irradiation based on a programmed print job to create a 3D model, and the model and platform are removed from the 3D printer and separated from each other; in step C) the used segment plates are ground down and the procedure is repeated, or those not required for the next print job are separated from the base plate, and/or those required are repositioned, then the procedure is repeated according to the next print job.

[0023] Thanks to the structure and modularity of the platform and easy handling, the 3D printer allows easy removal of printed models from the segment plates without the need to machine the base plate. Machining and grinding down are carried out only on segment plates before the next print job. This simplifies and streamlines the work of removing the printed models from the segment plates after the print job is complete. Overall, the handling of the printed products or models that do not cover the entire base plate is made easier.

[0024] A print job means an additive technology process during which models are manufactured using the 3D printing technology. For example, it is the Powder Bed Fusion technology.

[0025] The output product of the 3D printer is a 3D model, for example a product, a component, after 3D printing according to the pre-programmed print job.

[0026] Preferably, in steps A and C, the segment plates are attached to and removed from the base plate by means of fastening screws, through openings in the base plate and threaded inserts corresponding in shape that can be at least partially fixed in the segment plates.

Brief Description of Drawings

[0027] The summary of the invention is explained in more detail by means of the following drawings:

Fig. 1

[0028] Fig. 1 shows the platform of the invention with a base plate and segment plates attached thereto.

Fig. 2

[0029] Fig. 2 shows a disassembled platform assembly, which consists of the base plate, segment plates, threaded inserts, screws for fixing the segment plates to the base plate, and screws for fixing the platform through the through openings to the 3D printer conveyor.

Fig. 3

[0030] Fig. 3 shows another possible arrangement of differently shaped segment plates on the base plate.

Fig. 4

[0031] Fig. 4 shows the arrangement of identically shaped segment plates on the base plate.

Description of Embodiments

[0032] In the simplest exemplary embodiment, the platform of the invention comprises two side-by-side segment plates, placed at the same height level, removably separately attached to the base plate. The segment plates are made of a suitable metal powder alloy for 3D printing, in this exemplary embodiment specifically of a corrosion resistant steel. The segment plates are placed with a minimum spacing distance between the nearest segment plate walls of 10 mm. This platform is suitable for accommodating the above-mentioned printing material on a segment plate also made of corrosion resistant steel. In a 3D printer with the Powder Bed Fusion technology, this material is irradiated with a laser during 3D printing and, according to the print job, with a step-by-step lifting of the platform using a 3D conveyor attached, for example, via a through opening directly to the base plate.

[0033] A more sophisticated exemplary embodiment of the modular platform of the invention for 3D printers with the Powder Bed Fusion technology is shown in Figs. 1 and 2, in which a base plate 1 with a plurality of through openings 3 arranged in fours regularly spaced in a matrix is fitted with five segment plates 2 of different sizes, wherein a threaded insert is inserted into the through openings, which partially fits into the through opening 3 and which is expanded at the upper part so as not to fall through the base plate. The smallest segment plate is approximately a 50 mm x 50 mm square, its corners are rounded, the minimum spacing distance is 10 mm. The base plate is 240 mm x 240 mm. From the bottom part of the base plate 1 , at the point of the through opening 3, the fastening screw 4 is screwed into the thread in the threaded insert 5. The expanded part of the threaded insert 5 is further screwed into the segment insert in the segment plate 2 also by means of a thread. Near the corners of the platform there are through holes 6 made in the segment plates 2, further connected to some of the through openings 3 in the base plate 1 , and through these openings from above are inserted fixing screws 8, which are used to attach the whole platform to the not shown conveyor of the 3D printer.

[0034] The segment plate 2 is formed in its surface layer to a depth of 15 mm by a corrosion resistant material, in this exemplary embodiment chromium corrosion resistant steel, in which chromium oxides comprise 16.5 to 18.5 % by weight, nickel oxides 10 to 13 % by weight. Alternatively, the entire segment plate 2 is made of this material and has a thickness of 15 mm. Said material of the segment plate 2 is suitable for contact with a corrosion resistant printing material of chromium steel, in which chromium oxides comprise 16.5 to 18.5 % by weight and nickel oxides 10 to 13 % by weight.

[0035] Alternatively, the platform is attached to the 3D printer conveyor only through the through opening 3.

[0036] Alternatively, some through openings 3 may be formed in the segment plates 2 to also allow the segment plates 2 to be attached to the base plate 1 from above.

[0037] Alternatively, it may be a different arrangement of, for example, the through openings 3, for example, a simple matrix, other regular or irregular spacing.

[0038] The segment plates 2 are preferably, for example, in the shape of a square rectangle with sharp or rounded corners, but other arrangements of different shapes and sizes are also possible, for example L-shaped, etc., see Figs. 1 to 4, which show the coverage of the entire base plate 1 except for the spacing distances forming the gaps between the segment plates 2, but it is also possible to leave free space on the base plate 1 in some parts without placing one or more segment plates 2.

[0039] The 3D printer has a platform installed therein such that the base plate 1 is screwed onto the 3D printer conveyor by means of screws 8 which are inserted into the respective openings as described above. For the correct placement, the front side of the base plate 1 and the segment plates 2 is marked with a mark, for example, an indentation 7.

[0040] The platform is used in such a way that segment plates 2, the size, shape, and arrangement of which can be freely changed according to the user’s needs and the current print job, are attached to the main base plate 1 of the platform by means of the fastening screws 4 and threaded inserts 5. Said assembly is inserted into the 3D printer space and attached by means of screws 8 to the 3D printer conveyor ensuring that the platform moves up and down along the vertical axis, thus adjusting it to the desired height level. Next, the 3D printing is performed by laser irradiation based on the programmed print job to create a 3D model and the model and platform are removed from the 3D printer, the model and platform are separated from each other, which can be done in the 3D printer or after removing both outside the 3D printer. The used segment plates 2 are ground down, the segment plates 2 not required for the next print job are removed, the required ones are moved to the desired place and supplemented with additional segment plates 2, if needed, according to the new print job, and the platform modified in this way is again placed in the 3D printer for further printing.

[0041 ] In another exemplary embodiment, for example, pairs of a powder material for the printing of metal alloys and a material of the surface layer of the segment plate 2, or the entire segment plate, were used of two materials of the same or close composition, for example aluminium based. In alternative exemplary embodiments, the materials were titanium-based or copper-based alloys or nickel-cobalt-based alloys.

Reference Signs List

[0042] 1 - base plate

[0043] 2 - segment plate

[0044] 3 - through opening

[0045] 4 - fastening screw

[0046] 5 - threaded insert

[0047] 6 - through hole [0048] 7 - indentation

[0049] 8 - fixing screw