Improved stereolithography machine and operation method thereof

Abstract

A stereolithography machine (1) comprising: a tank (4); a source (5) of electromagnetic radiation adapted to selectively irradiate the tank (4); a modelling platform (6), which is carried in a mobile manner along a first reference axis (A) orthogonal to the bottom (8) of the tank (4); a multifunction assembly (23) provided at least with levelling means (22), which are adapted to level the fluid substance in said tank (4), equipped with an oblong paddle (27), which extends along a second reference axis (B) orthogonal to the first reference axis (A) and is carried in a movable manner along a direction (di) orthogonal to the first reference axis (A) and the second reference axis (B), and wherein the paddle (27) is pivotally carried about a rotation axis (C) parallel to the second reference axis (B).

Description

[0001] " IMPROVED STEREOLITHOGRAPHY MACHINE AND OPERATION METHOD

[0002] THEREOF"

[0003] CROSS-REFERENCE TO RELATED APPLICATIONS

[0004] This Patent Appl ication claims priority from Italian Patent Application No . 102024000001521 filed on January 26 , 2024 , the entire disclosure of which is incorporated herein by reference .

[0005] TECHNICAL SECTOR

[0006] This invention relates to a stereolithography machine and operation method thereof . This is the use to which this invention will explicitly refer , without any loss of generality thereby .

[0007] STATE OF THE ART

[0008] As is well known, stereolithography, also known as tank photopolymeri zation, is an additive manufacturing process that essentially involves making three-dimensional obj ects by selectively and repeatedly solidifying, layer by layer, a photosensitive resin in a tank by means of electromagnetic radiation, until the three-dimensional obj ect to be made is obtained .

[0009] Stereolithography machines currently on the market generally comprise : a tank, which is adapted to contain the photosensitive resin and is equipped with an at least partially transparent bottom; an electromagnetic radiation source , which is generally placed underneath the tank and is adapted to irradiate a portion of the bottom of the tank to selectively solidi fy a layer of the photosensitive resin; and a modelling platform, which is supported vertically above the tank and is adapted to support the three-dimensional obj ect to be produced during the printing process . The operation of such stereolithography machines involves lowering the modelling platform until the latter, or possibly a solid layer previously formed on the same platform, is brought to a distance from the bottom of the tank equal to the thickness of the layer to be made ; solidi fying this layer by selective exposure to electromagnetic radiation; and, finally, raising the modelling platform to separate the newly solidi fied layer from the bottom of the tank .

[0010] Unfortunately, raising the solidi fied layer from the bottom of the tank results in the formation of depressions and voids in the photosensitive resin, which are then slowly filled by the spontaneous flow of the photosensitive resin .

[0011] Generally speaking, due to the high viscosity of the photosensitive resins usually used, the time required for their spontaneous flow into such depressions is very high and drastically af fects the overall production time of the three-dimensional obj ect , especially i f the production of the obj ect involves the solidi fication of a large number of consecutive layers .

[0012] To overcome these drawbacks , the use of paddles translating in a hori zontal direction was proposed to mechanically level the photosensitive resin in the tank .

[0013] For example , W02015120214 A2 and WO2022194769 Al describe stereolithography machines equipped with translating paddles .

[0014] The use of heat sources coupled to the tank and adapted to heat the bottom of the tank and, indirectly, the photosensitive resin contained therein, so as to reduce its viscosity, was also proposed .

[0015] Unfortunately, the above-mentioned techniques have not fully met the requirements of simpli fying and speeding up the stereolithography printing processes described above .

[0016] The purpose of this invention is , therefore , to provide a stereolithography machine and a related method of operation that can make stereolithography printing processes faster and more ef ficient .

[0017] SUMMARY OF THE INVENTION

[0018] In accordance with the above-mentioned obj ectives , according to this invention, a stereolithography machine and a related method of operation are provided as defined in the related independent claims and preferably, but not necessarily, in any of the claims dependent thereon .

[0019] The claims describe preferred embodiments of this invention forming an integral part of this description .

[0020] BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Below, some embodiments of the invention will be described to better understand the same by way of nonlimiting example and with reference to the attached figures in which :

[0022] - Figure 1 is a perspective view of a stereolithography machine made according to this invention, with parts removed for clarity,

[0023] - Figure 2 is a perspective view of a component of the stereolithography machine illustrated in Figure 1 according to one embodiment , with parts removed for clarity .

[0024] - Figures 3 to 6 are side views , in cross section along section I- I of Figure 2 , of the component shown in Figure 2 , with parts removed for clarity and in as many steps of its operation,

[0025] Figure 7 is a front view, in cross section along section I I- I I in Figure 2 , of the component shown in Figure 2, with parts removed for clarity; and

[0026] - Figure 8 is a perspective view of a component of the stereolithography machine illustrated in Figure 1 according to another embodiment, with parts removed for clarity,

[0027] - Figure 9 is a side view, in cross section along section IX-IX of Figure 8, of the component shown in Figure 8, with parts removed for clarity, and

[0028] - Figure 10 is a partially exploded view of the component shown in Figure 8, with parts removed for clarity.

[0029] EMBODIMENTS OF THE INVENTION

[0030] With reference to the example illustrated in Figure 1, the number 1 denotes a stereolithography machine or stereolithography printer (SLA - Stereolithography Apparatus) as a whole, which is adapted to produce / print three-dimensional objects from a photosensitive fluid substance by selectively and repeatedly solidifying, layer by layer, this fluid substance by means of electromagnetic radiation, until the three-dimensional object to be produced is obtained.

[0031] In this discussion, the term photosensitive fluid substance will refer generically to photopolymerizing fluid resins or other, similar, polymer-based fluid substances that can be solidified, i.e. polymerized, by electromagnetic radiation, e.g. ultraviolet radiation.

[0032] The machine 1 first comprises a load-bearing, ground support frame, which extends along a reference axis A and is preferably made of metal. In use, the reference axis A is advantageously orthogonal to the ground, i.e. it is vertical.

[0033] With reference to the example illustrated in Figure 1, the machine 1 also comprises: a tank or container 4, which is adapted to contain the photosensitive fluid substance; an electromagnetic radiation source 5 , which is adapted to selectively irradiate the tank 4 in such a way as to solidi fy portions of the fluid substance contained therein; and a modelling platform 6 , which is adapted to support the three- dimensional obj ect to be produced .

[0034] The tank 4 is preferably adapted to be placed on the frame 1 .

[0035] In addition, the tank 4 preferably comprises a container open at the top that can hold liquids or fluids , and preferably has an essentially rectangular shape .

[0036] More speci fically, the tank 4 is preferably provided with a flat bottom 8 , with an advantageously plate-like structure and pre ferably rectangular in shape , which in use is adapted to be placed orthogonal to the reference axis A, i . e . in a hori zontal position .

[0037] In addition, the bottom 8 is preferably at least partially transparent / permeable to electromagnetic radiation, so that the electromagnetic radiation emitted by the source 5 can pass through it and reach the fluid substance in the tank 4 .

[0038] The bottom 8 of the tank 4 is preferably also provided with an anti-stick surface coating, e . g . based on silicones and / or fluoropolymers , adapted to reduce the adhesion force exerted by the fluid substance on the bottom 8 itsel f .

[0039] In addition, the tank 4 preferably includes a perimeter wall 9 , which seamlessly surrounds the bottom 8 .

[0040] The frame 2 is also preferably provided with a seat 10 that is adapted to accommodate the tank 4 , advantageously placing the same tank 4 substantially orthogonal to the reference axis A.

[0041] In other words , the tank 4 is adapted to be rested / positioned on the seat 10 , advantageously in an easily removable manner .

[0042] According to the embodiment shown in Figure 1 , the modelling platform 6 is preferably arranged above the tank 4 , and the source 5 is preferably arranged below the tank 4 and is adapted to emit electromagnetic radiation towards the flat bottom 8 of the tank 4 .

[0043] In other words , the stereolithography machine 1 is a bottom-up machine .

[0044] With reference to the example illustrated in Figure 1 , in particular, the modelling platform 6 preferably comprises a plate 7 adapted to support the first solidi fied layer of the three-dimensional obj ect to be made .

[0045] The plate 7 is preferably essentially flat and, in use , is arranged orthogonal to the reference axis A.

[0046] More speci fically, the plate 7 is provided with a lower surface , i . e . facing the underlying tank 4 , which is substantially flat and / or with a structure with strong adherence , so as to favor the attachment / adhesion of the first layer j ust solidi fied to the modelling platform 6 .

[0047] According to one possible embodiment , the source 5 may instead comprise a laser radiation emitter and an optical assembly adapted to direct the laser radiation to a point on the bottom 8 of the tank 4 , so that a portion of the bottom 8 of the tank 4 can be progressively exposed, such portion corresponding to the layer to be solidi fied of the three- dimensional obj ect to be made .

[0048] Alternatively or additionally, the source 5 may comprise an electromagnetic radiation emitter and an optical assembly configured to instantaneously expose a predetermined area of the bottom 8 of the tank 4 , so as to simultaneously solidi fy a layer of the three-dimensional obj ect to be made .

[0049] In particular, the source 5 may include a DLP ( Digital Light Processing) optical assembly .

[0050] Alternatively or additionally, the source 5 could comprise an LCD ( Liquid Crystal Device ) optical assembly and / or could comprise a "Selecting Masking Device" , in a known manner not , therefore , further described .

[0051] With reference to the example illustrated in Figure 1 , the machine 1 preferably also includes an actuation mechanism 12 that is adapted to support the modelling platform 6 by placing it orthogonal to the reference axis A and to move , on command, the same modelling platform 6 along the reference axis A, preferably keeping it parallel to itself .

[0052] The actuation mechanism 12 preferably comprises a support bracket 13 , which is supported by the frame 2 so as to slide and is in turn adapted to support the modelling platform 6 .

[0053] With reference to the example illustrated in Figure 1 , in particular, the frame 2 comprises a column 15 that rises upwards , parallel to the reference axis A.

[0054] The support bracket 13 is preferably carried in a slidable by the column 15 and is able to translate along the same column 15 along the reference axis A.

[0055] In addition, the actuation mechanism 12 preferably comprises an actuator device 16 , advantageously electrically operated, adapted to translate the support bracket 13 along the frame 2 .

[0056] In particular, the actuator device 16 preferably comprises an electric motor 18 or other similar actuator and a transmission element 20 , for example a worm screw, mechanically coupled to the support bracket 13 . With reference to the example illustrated in Figures 1 and 2 , the machine 1 also includes levelling means 22 for the fluid substance that are adapted to level the fluid substance inside the tank 4 .

[0057] More speci fically, the levelling means 22 are adapted to level the fluid substance in the tank 4 in such a way as to fill any voids / depressions caused by the li fting of a layer of the three-dimensional obj ect previously made , and to form a layer of fluid substance of a uni form, predetermined thickness on the bottom 8 of the tank 4 .

[0058] In addition, in use , the levelling means 22 are also adapted to mix the fluid substance in the tank 4 , in such a way as to prevent the formation of clots / lumps and / or expel any air bubbles trapped in the fluid substance .

[0059] The levelling means 22 preferably contribute to forming a multi function assembly 23 , which, in use , at least has the function of level ling the fluid substance in the tank 4 and forming a layer of fluid substance , with a homogeneous and uni form / regular thickness , on the bottom 8 of the tank 4 .

[0060] With reference to the preferred embodiment illustrated in Figures 2 to 7 , the multi function assembly 23 preferably also comprises feeding means 24 for the fluid substance that are adapted to feed the fluid substance to be used for producing the three-dimensional obj ect inside the tank 4 .

[0061] In addition, the multi function assembly 23 preferably includes heating means 26 , which are adapted to heat the fluid substance in the tank 4 .

[0062] With reference to the example illustrated in Figures 2 to 7 , the levelling means 22 , in the first instance , comprise a paddle or squeegee or recoater 27 , advantageously oblong in shape . In particular, the paddle 27 preferably extends along a reference axis B, which, in use , is advantageously orthogonal to the reference axis A and parallel to the vertical midplane of the machine 1 . In other words , the reference axis B is preferably hori zontal .

[0063] In addition, in use , the reference axis B is preferably parallel to one side of the tank 4 , in particular the smaller side of the tank 4 .

[0064] Advantageously, the length of the paddle 27 along the reference axis B approximates , on the small side , the width of tank 4 . In particular, the length of the paddle 27 along the reference axi s B is preferably si zed in such a way that the axial ends of the same paddle 27 lie flush with the side walls of the tank 4 transverse to the reference axis B .

[0065] In use , the paddle 27 is preferably placed immediately above the tank 4 .

[0066] More speci fically, the paddle 27 engages the tank 4 so that it is in contact and / or flush with the bottom 8 of the tank 4 .

[0067] With reference to the preferred embodiment illustrated in Figures 2 to 7 , the paddle 27 i s movably supported by the machine 1 and is movable in a direction di transverse , in particular orthogonal , to the reference axis A and reference axis B .

[0068] In other words , the direction di is transverse , in particular orthogonal , to the vertical midplane of the machine 1 .

[0069] More speci fically, the paddle 27 is preferably able to translate along the direction di so that it can cross the entire bottom 8 of the tank 4 . More speci fically, the paddle 27 is preferably able to be positioned beyond the outline of the modelling platform 6 , so that the latter can reach the bottom 8 of the tank 4 without intercepting the paddle 27 .

[0070] In addition, with reference to the example illustrated in Figure 7 , the paddle 27 is also supported by the machine 1 so that it revolves about a rotation axis C, advantageously parallel to the reference axis B .

[0071] The paddle 27 is also preferably arranged eccentrically with respect to the rotation axis C, in particular below the same rotation axis C .

[0072] The technical ef fect related to the rotation of the paddle 27 around the rotation axis C is linked to the possibility of varying the distance between the lower end of the paddle 27 and the bottom 8 o f the tank 4 , so that the thickness of the layer of fluid substance formed by the paddle 27 on the bottom 8 o f the tank 4 can be varied in use .

[0073] In particular, the rotation of the paddle 27 around the axis C brings the lower end of the paddle to a distance from the bottom equal to the thickness of the single layer of fluid substance to be polymeri zed . This distance advantageously ranges between 0 . 01 and 1 mm, in particular it can be around 0 . 8 mm .

[0074] In addition, the rotation of the paddle 27 around the rotation axis C enables one of the lower ends of paddle 27 to be brought selectively into contact with the bottom 8 of the tank 4 to scrape the fluid substance on the bottom 8 .

[0075] More speci fically, the paddle 27 is preferably positioned at a distance from the bottom 8 of the tank 4 along said reference axis A so that , during its rotation around the axis C, one of the lower ends of the paddle 27 can selectively enter into contact with the bottom 8 of the tank 4 .

[0076] In particular, only one of the lower ends of the paddle 7 can temporarily come into contact with the bottom 8 of the tank 4 according to the angular rotation of the paddle 27 around the axis C .

[0077] With reference to Figure 2 , the levelling means 22 preferably comprise a support bracket or slide 29 that is adapted to carry the paddle 27 in a slidable manner along the direction di . The support bracket 29 is preferably carried by the frame 2 in a movable manner .

[0078] More speci fically, the support bracket 29 is positioned adj acent to the tank 4 , is coupled to the frame 2 in a movable manner and is slidable along the direction di .

[0079] In particular, the support bracket 29 is advantageously slidable aside the larger side of the tank 4 .

[0080] The paddle 27 , on the other hand, preferably extends cantilevered from the support bracket 29 along the reference axis B, above the tank .

[0081] The support bracket 29 is preferably also structured to carry the paddle 27 in a rotatable manner around its rotation axis C .

[0082] More speci fically, the support bracket 29 preferably comprises a first portion 29a carried by the frame 2 in a slidable manner, and a second portion 29b, which is carried by the first portion 29a in a rotatable manner about the axis C and, in turn, supports the paddle 27 .

[0083] With reference to the preferred embodiment illustrated in Figures 2 to 7 , the levelling means 22 preferably also comprise an actuation mechanism 30 that is adapted to move , on command, the paddle 27 relative to the tank 4 in the direction di, preferably by keeping the same paddle 27 essentially parallel to itsel f , so as to be able to level and / or scrape the fluid substance in the tank 4 .

[0084] The actuation mechanism 30 is preferably also adapted to rotate , on command, the paddle 27 about its axis C, so that its distance from the bottom 8 of the tank 4 can be varied .

[0085] More speci fically, the actuation mechanism 30 is preferably coupled to the support bracket 29 and is adapted to translate the same support bracket 29 along the direction di .

[0086] In addition, the actuation mechanism 30 is also adapted to rotate the second portion 29b of the support bracket 29 around the rotation axis C

[0087] With reference to the example illustrated in Figure 2 , the actuation mechanism 30 preferably comprises an actuator 32 , advantageously electrically operated, supported by the frame 2 and a transmission element 33 operatively coupled to the paddle 27 , in particular to the bracket 29 , to translate the paddle 27 along the direction di . For example , the actuator 32 may comprise an electric motor and the transmission element may comprise a worm screw coupled to the bracket 29 .

[0088] In addition, the actuation mechanism 30 preferably comprises an actuator 36 , advantageously electrically driven, carried by the bracket 29 and a transmission element 36 operatively coupled to the second portion 29b of the same bracket 29 , for rotating the bracket about the rotation axis C . For example , the actuator 36 may comprise an electric motor carried by the first portion 29a and the transmission element may comprise a gear coupled to the second portion

[0089] 29b of the bracket 29 .

[0090] With reference to the preferred embodiment illustrated in Figures 2 to 7 , in particular , the paddle 27 preferably comprises a cup-shaped or concave body 38 of oblong shape , extending along the reference axis B . The cross section of the cup-shaped body 38 is preferably shaped essentially like an inverted U or V . According to a possible embodiment , the paddle 27 can also be made of one piece , i . e . it can have a monolithic structure .

[0091] In use , the concavity of the cup-shaped body 38 preferably faces the bottom 8 of the tank 4 .

[0092] In other words , the cup-shaped body 38 is shaped so that it forms a chamber 39 adapted to be placed, in use , above the bottom 8 of the tank 4 .

[0093] The cup-shaped body 38 is preferably made of metal .

[0094] The cup-shaped body 38 may have a structure with an at least partially open cross section, i . e . it may comprise at least two side walls facing each other, which are preferably arranged transverse to each other and are advantageously, rigidly connected .

[0095] With reference to the example illustrated in Figures 2 to 7 , in particular, the paddle 27 , and more advantageously the cup-shaped body 38 , preferably comprises a pair of longitudinal walls 40 that preferably have a plate-like structure and extend parallel to the reference axis B . In addition, the longitudinal walls 40 preferably have an essentially rectangular shape .

[0096] The longitudinal walls 40 are pre ferably spaced opposite each other .

[0097] In addition, the longitudinal walls 40 , at their top edge / end, are connected / j oined to each other, preferably essentially seamlessly, by an upper wall 41 , so as to form the chamber 39 . The upper wall 41 extends essentially parallel to the reference axis B and has a profile preferably shaped in the form of an arch .

[0098] It is understood that the upper wall 41 may also not be included . For example , the two longitudinal walls 40 could be connected by connecting elements spaced apart .

[0099] The longitudinal walls 40 also preferably converge in the direction of their top edge / end .

[0100] In other words , the longitudinal walls 40 preferably lie on two planes that are transverse to each other .

[0101] The cup-shaped body 38 preferably also comprises a pair of axial walls 42 , which connect the axial ends / edges of the longitudinal walls 40 together, preferably essentially seamlessly .

[0102] With reference to the example illustrated in Figures 2 to 6 , the cup-shaped body 38 is preferably also provided with a pair of longitudinal flanges 45 , each extending cantilevered from the lower edge / end of a corresponding longitudinal wall 40 outwards , and preferably extending essentially seamlessly along the entire length of the same longitudinal wall 40 . According to one embodiment , the longitudinal flanges 45 can be made of a single piece with the corresponding longitudinal wall 40 .

[0103] Each longitudinal flange 45 is preferably flat and has a plate-like structure .

[0104] In addition, each longitudinal flange 45 lies on a plane transverse to the corresponding longitudinal wall 40 .

[0105] More speci fically, in use , one o f the two longitudinal flanges 45 is preferably alternately arranged so as to define an angle a with the bottom 8 of the tank 4 .

[0106] The value of the angle a in use may preferably vary depending on the rotation of the paddle 27 around the axis

[0107] C.

[0108] The angle a is preferably greater than 5° and, more advantageously, it is greater than 10°. In other words, in use, the angle a preferably has values greater than zero, i.e. the longitudinal flange 45 is arranged transverse (not parallel) to the bottom 8 of the tank 4.

[0109] For example, the angle a is preferably greater than 45° and, more conveniently, it is also greater than 60°.

[0110] In addition, during use, the angle a is also less than 90°, i.e. the longitudinal flange 45 does not lie orthogonal to the bottom 8 of the tank 4.

[0111] In other words, in use, one of the two longitudinal flanges 45 is preferably, alternatively arranged in a position converging towards the bottom 8 of the tank 4.

[0112] In addition, in use, the angle a of the flange 45 momentarily closest to the bottom 8 of the tank 4 and / or in contact with the fluid substance in the tank 4 preferably corresponds to the forward direction of the paddle 27. In other words, the flange 45 is preferably positioned so that its proximal edge connected to the corresponding longitudinal wall 40 is at a greater distance from the bottom 8 of the tank than the distance between the distal (free) edge of the same flange 45 and the bottom 8 of the tank 4.

[0113] As explained in more detail below, the technical effect related to the particular arrangement of the longitudinal flange 45 with respect to the bottom 8 is to be able to encourage the recirculation of the fluid substance and the formation of a homogeneous and uniform / regular layer of this fluid substance during the movement of the paddle 27.

[0114] With reference to Figure 7, the feeding means 24 preferably comprise a source of fluid substance adapted to supply at the outlet the fluid substance to be fed into the tank 4 on command .

[0115] For example , the source of the fluid substance may comprise a tank / reservoir (not shown) containing this substance and a pumping device , preferably electrically powered, to feed the fluid substance from the tank to the tank 4 .

[0116] The pumping device , for example , could include a peristaltic pump and / or other similar pumping device .

[0117] In addition, the feeding means 24 preferably comprise a tubular distribution duct 47 that is fluidly connected to the source of the fluid substance and is adapted to distribute / feed the fluid substance into the tank 4 .

[0118] With reference to the preferred embodiment illustrated in Figure 7 , the distribution duct 47 is preferably housed within the cup-shaped body 38 , is preferably straight and preferably extends parallel to the reference axis B .

[0119] In addition, the distribution duct 47 preferably engages , advantageously in a fluid-tight manner, a through opening made on an axial wall 42 o f the cup-shaped body 38 , to allow its connection to the fluid substance source .

[0120] More speci fically, the distribution duct 47 preferably extends flush with the upper wall 41 of the cup-shaped body 38 .

[0121] In addition, the distribution duct 47 preferably extends essentially along the entire length of the cup-shaped body 38 along the reference axis B .

[0122] With reference to the example illustrated in Figure 7 , the distribution duct 47 is preferably provided with multiple holes / noz zles 48 adapted to allow the outlet of the fluid substance that passes through the same distribution duct 47. The holes 48 are preferably positioned aligned with each other along the distribution duct 47, i.e. along the reference axis B, advantageously with a constant pitch.

[0123] According to a different embodiment not illustrated, the feeding means 24 could comprise a feeding duct that is arranged outside the paddle 27, is connected at the fluid level to the source of the fluid substance and the pumping device, and is adapted to feed the fluid substance into the tank 4. In other words, according to this variant, the feeding duct could be separate and distinct from the paddle 27.

[0124] With reference to the example illustrated in Figure 7, however, the heating means 26 preferably comprise an electrically powered heating device 49, in particular electric heaters, adapted to heat the fluid substance in the tank 4.

[0125] More specifically, the heating device 49 is preferably coupled to the cup-shaped body 38 and, in use, is adapted to heat the cup-shaped body 38 itself, so that the latter can in turn heat the fluid substance in the tank 4.

[0126] In other words, the heating device 49 is adapted to heat the chamber 39 and the fluid substance temporarily present at, i.e. within, the chamber 39.

[0127] With reference to the example illustrated in Figures 2 to 6, the machine 1 also includes sensor means 50 adapted to measure / detect the amount of fluid substance temporarily present in the tank 4, e.g. a level sensor.

[0128] The machine 1 also comprises an electronic control unit 52 that is operatively connected to at least the source 5, the modelling platform 6 and / or the multifunction assembly 23 and comprises electronic processing means configured to control the operation of the machine 1 as explained in detail below .

[0129] More speci fically, the electronic control unit 52 is preferably also connected to the sensor means 50 and is configured to control the operation of at least the multi function assembly 23 based on the signals / data provided by the sensor means 50 .

[0130] In accordance with another aspect of this invention, a computer program is provided comprising instructions that, when the program is executed by the electronic control unit 52 (by means of said processing means ) , cause the control unit 52 to perform the operation method described below .

[0131] First , the general operation of the machine 1 involves feeding the fluid substance into the tank 4 .

[0132] In addition, the general operation of the machine 1 essentially involves the following steps , in sequence : a ) lower the modelling platform 6 until the latter, or possibly a solid layer previously formed on the same modelling platform 6 , is brought to a distance from the bottom 8 of the tank 4 equal to the thickness of the layer to be made , so that a homogeneous layer of fluid substance of a predetermined thickness is f ormed / delimited between the modelling platform 6 and the bottom 8 of the tank 4 ; b ) solidi fy this layer through selective exposure to the electromagnetic radiation; and then c ) li ft the modelling platform 6 so as to separate the layer j ust solidi fied from the bottom 8 of the tank 4 . During the above-mentioned steps a ) , b ) and c ) , the operation of the machine 1 preferably includes controlling the multi function assembly 23 in such a way as to keep the paddle 27 positioned spaced along the modelling platform 6 , advantageously at one side of the tank 4 , so as not to obstruct the movement of the modelling platform 6 .

[0133] The operation of the multi function assembly 23 also includes the following steps : d) once li fted, the modelling platform 6 , rotating the paddle 27 in order to arrange the lower end of the paddle 27 at a predetermined distance from the bottom 8 of the tank 4 ; and then e ) translating the paddle 27 along the direction di , so as to fill the voids / depressions formed after li fting the modelling platform 6 , remixing the fluid substance and forming a new layer of the fluid substance of a uni form, predetermined thickness .

[0134] Step e ) preferably involves rotating the paddle 27 in such a way that the cavity of the paddle 27 , i . e . the chamber 39 , is arranged facing the forward direction of the paddle 27 .

[0135] Consequently, in use , the longitudinal flange 45 opposite the forward direction of the paddle 27 comes into contact with the fluid substance , while the other longitudinal flange 45 is raised by the same fluid substance .

[0136] During the movement of the paddle 27 , some of the fluid substance in the tank 4 accumulates inside the chamber 39 of the cup-shaped body 38 and is remixed .

[0137] During the movement of the paddle 27 , another part of the fluid substance, however, is trapped between the bottom 8 of the tank 4 and the longitudinal flange 45 and forms the fluid substance layer of homogeneous and uni form thickness , filling any voids or depressions caused by the previous li fting of the modelling platform 6 .

[0138] In particular, the convergent arrangement of the longitudinal flange 45 towards the bottom 8 of the tank 4 allows the pressure exerted on the fluid substance during the movement of the paddle 27 to be increased locally .

[0139] More speci fically, during the movement of the paddle 27 , the converging arrangement of the longitudinal flange 45 pushes the excess fluid substance forward, along the direction di, so it accumulates inside the chamber 39 and encouraging the creation of a circulatory / vortical motion in the fluid substance inside the chamber 39 , which facilitates the remixing of the same fluid substance .

[0140] Even more speci fically, the convergent arrangement of the longitudinal flange 45 towards the bottom 8 o f the tank 4 allows a force to be exerted on the fluid substance in the tank 4 inclined in a transverse direction with respect to the bottom 8 of the tank 4 . In particular, the force exerted by the longitudinal flange 45 on the fluid substance in the tank 4 has a component normal to the bottom 8 of the tank 4 and a component parallel to the same bottom 8 and the direction di . During the movement of the paddle 27 , this force pushes the fluid substance forward along the direction di and at the same time presses it against the bottom 8 , so as to create a homogeneous layer of a predetermined thickness on the bottom 8 and at the same time the excess fluid substance accumulates inside the chamber 39 .

[0141] In addition, the special arrangement of the flange 45 allows the pressure exerted by the paddle 27 on the fluid substance during the advancement of the paddle 27 to be locally increased as the distance between the flange 45 and the bottom 8 decreases , allowing the creation of a homogeneous layer of a predetermined thickness ( e . g . between 0 . 5 and 1 mm) and without discontinuities or voids . The increase in local i zed pressure exerted by the flange 45 and the generation of the above-mentioned turbulent motion during the advancement of the paddle 27 , in particular, allow the fluid substance to distribute itsel f homogeneously on the bottom 8 of the tank 4 and to fill any voids or depressions left by the li fting of the previously solidi fied layer of fluid substance .

[0142] According to the preferred embodiment of the invention, the operation of the multi function assembly 23 involves a translation of the paddle 27 for each printing step of the stereolithography machine 1 , i . e . after each li fting of the modelling platform 6 .

[0143] Alternatively, the operation of the multi function assembly 23 could involve two translations of the paddle 27 in opposite directions for each printing step of the stereolithography machine 1 , i . e . after each li fting of the modelling platform 6 .

[0144] The operation of the multi function assembly 23 may also involve rotating the paddle 27 in such a way as to bring the lower end of the paddle 27 into contact with the bottom 8 of the tank, and then translating the paddle 27 along the direction di so as to scrape the fluid substance from the bottom 8 of the tank 4 . This advantageously avoids the formation of lumps or clots of fluid substance on the bottom 8 of the tank 4 and allows all the fluid substance to be remixed .

[0145] The operation of the multi function assembly 23 also preferably involves : f ) determining the amount of fluid substance momentarily present inside the tank 4 ; and g) driving the feeding means 24 so as to feed the fluid substance into the tank 4 when its level falls below a predetermined threshold .

[0146] Step g) preferably involves determining the amount of fluid substance momentarily present in the tank 4 on the basis of signals provided by the sensor means 50 .

[0147] In addition, the operation of the multifunction assembly 23 preferably involves driving the feeding means 24 in such a way as to feed the fluid substance into the tank 4 when its level falls below a predetermined threshold, so that suf ficient fluid substance can be kept in the tank 4 to form a layer of predetermined thickness in that tank 4 .

[0148] In use , depending on the si ze of the layer ( s ) of newly solidi fied fluid substance ( s ) and, thus , the amount of the same fluid substance used, it may be necessary to drive the feeding means 24 to feed fluid substance into the tank 4 after each li fting of the modelling platform 6 or only after several successive steps of solidi fication of the fluid substance and li fting of the modelling platform 6 .

[0149] The feeding of the fluid substance into the tank 4 , i . e . step h) , is preferably performed during step c ) mentioned above , i . e . during the solidi fication of a layer of fluid substance by selective exposure to electromagnetic radiation .

[0150] This , in particular, decreases the overall duration of the printing process , because the feeding of the fluid substance required to form a subsequent layer of the same fluid substance at the bottom of the tank 4 is performed during the solidi fication of the previous layer, which is generally the longest machine 1 operation step . When the solidi fication of the previous layer is complete, therefore , the multi function assembly 23 can be controlled to rotate and translate the paddle 27 , without having to wait any longer to feed the fluid substance into the tank 4 .

[0151] The operation of the multi function assembly 23 preferably also involves driving the heating means 26 in such a way that the paddle 27 and the fluid substance on the paddle 27 are heated .

[0152] More speci fically, the operation of the multi function assembly 23 preferably also involves driving the heating means 26 so as to heat the cup-shaped body 38 and the chamber 39 , so as to heat the fluid substance that has accumulated in the chamber 38 .

[0153] From the above , the advantages of the machine 1 according to the invention and its method of operation are clear .

[0154] Firstly, the multi function assembly 23 allows the fluid substance to be quickly levelled out at the end of each printing step, signi ficantly speeding up the three- dimensional obj ect production time .

[0155] The special shape of the paddle 27 in particular, allows the fluid substance to be remixed with each pass , so as to avoid the formation of lumps or clots and, at the same time , expel any air bubbles trapped in the fluid substance .

[0156] The possibility of varying the distance between the paddle 27 and the bottom 8 of the tank 4 also makes it easy to change the thickness of the layer of fluid substance to be formed and / or to scrape the same fluid substance from the bottom 8 of the tank 4 .

[0157] In addition, the multi function assembly 23 can both remix the fluid substance in the tank 4 and heat it , with the obvious benefits that this entails .

[0158] In particular, heating the fluid substance allows its viscosity to be reduced to facilitate the formation of the new layer to be printed and, at the same time , reduce the tensile forces exerted on the newly solidi fied layer of fluid substance during the li fting of the modelling platform 6 .

[0159] In addition, the feeding means 24 of the multi function assembly 23 allow very precise control of the amount of fluid substance in the tank 4 , so that the amount of fluid substance can be limited to that required at each printing step, i . e . to that required to form a single layer of fluid substance at the bottom of the tank 4 .

[0160] This makes it possible to limit the amount of fluid substance exposed to air and light during the production of the three-dimensional obj ect and consequently reduces the amount of fluid substance to be di scarded once this process is complete .

[0161] In addition, this makes it possible to reduce the tensile forces exerted on the bottom 8 of the tank 4 by the layer of fluid substance that has j ust solidi fied during the li fting of the modelling platform 6 , with the obvious benef its that this entails .

[0162] In particular, by limiting the amount of fluid substance in the tank 4 , it is possible to reduce the thickness of the layer of fluid substance present alongside the modelling platform 6 that the air must pass through to fill the void created during the li fting of the modelling platform 6 . In other words , by limiting the amount of fluid substance in the tank 4 , it is possible to reduce the suction ef fect created when li fting the modelling platform 6 . Finally, it is clear that changes may be made to the machine 1 and its method of operation, and variations produced thereto , according to this invention that , in any case , do not depart from the scope of protection de fined by the claims .

[0163] For example , in the example illustrated in Figures 8 , 9 and 10 , the actuator 32 of the actuation mechani sm 30 may comprise an electric motor and the transmission element may comprise a belt , in particular a toothed belt . Similarly, the actuator 36 may comprise an electric motor supported by the first portion 29a and the transmission element may comprise a belt , in particular a toothed belt .

[0164] Figures 8 and 9 and 10 , on the other hand, illustrate an embodiment of the machine 1 that is similar to the embodiment illustrated in Figures 1 to 7 , and whose parts will be denoted, where possible , with the same reference numbers as the corresponding parts of the machine 1 .

[0165] The embodiment illustrated in Figures 8 , 9 and 10 di f fers from the previously illustrated embodiment in that the longitudinal flanges 45 could be made separate and distinct from the paddle 27 , i . e . the cup-shaped body 38 , and could be configured to be fixed to the same cup-shaped body 38 in a firm but removable manner .

[0166] In particular, the longitudinal flanges 45 could comprise an insert or thin plate or sheet 145 , advantageously flat in shape and / or with an essentially plate-like shape , which is adapted to be fixed to the corresponding longitudinal wall 40 in a firm but removable manner, so as to protrude cantilevered from the corresponding longitudinal wall and advantageously lie on a plane essentially coplanar to the same longitudinal wall 40 . In addition, in use, the insert 145 is intended to form an angle a of less than 90° with the bottom 8 of the tank 4, and more advantageously between about 70° and about 80°.

[0167] The insert 145 can comprise a straight plate, advantageously thin, i.e. between 0.1 mm and 3 mm thick, e.g. approximately 0.6 mm. In addition, the insert 145 may be made of metal, plastic, composite and / or similar materials .

[0168] The technical effect related to the use of the removable insert 145 is linked to the possibility of replacing, during use, only the insert 145, for example in order to be able to replace it with a new insert when the previous one is worn out and / or to replace it with an insert 145 of a different material in order to better adapt it to the fluid substance temporarily present in the tank 4, without the need to replace the entire paddle 27.

[0169] The use of composite fluid substances, e.g. containing ceramic particles, results in high wear of the part of the paddle 27 in contact with the same fluid substance.

[0170] With reference to the embodiment illustrated in Figure 10, in addition, the paddle 27 may not have a monolithic structure and may comprise an outer portion or cup-shaped body or cover 138a and an inner portion or cup-shaped body 138b, with a shape complementary to the outer cup-shaped body 138. The outer portion 138a preferably has an advantageously concave shape, is configured to fit over the inner portion 138b and is shaped to fit at least partially over the same inner portion 138b.

[0171] The inner portion 138b is advantageously arranged below the outer portion 138a, i.e., the inner portion 138b is preferably arranged close to the bottom 8 of the tank 4 below, while the outer portion 138 a is arranged close to the modelling platform 6 above .

[0172] Advantageously, the outer 138a and inner 138b portions are configured to be firmly but removably attached to each other, e . g . by means of threaded fasteners such as screws and / or the like .

[0173] In addition, the lateral ends , along the direction di, of the two outer 138a and inner 138b portions are preferably shaped in such a way as to define a thin seat / gap / pocket suitable for housing and mechanically retaining the relevant insert 145 .

[0174] More speci fically, the insert 145 is intended to be interposed between the relative lateral ends ( i . e . from the longitudinal walls 40 ) of the outer 138a and inner 138b portions , so as to proj ect , cantilevered, from them . In use , when the two outer 138a and inner 138b portions are fixed together, they hold / lock the inserts 145 in their respective seats .

[0175] In addition, the inserts 145 can be coupled to the outer portion 138a and / or the inner portion 138b via shape coupling . For example , the inserts 145 may be provided with protruding appendages 146 adapted to engage housing seats 147 with a complementary shape present on the outer 138a and / or the inner 138b portions .

Claims

CLAIMS1.- A stereolithography machine (1) for the production of three-dimensional objects starting from a photosensitive fluid substance; said stereolithography machine (1) comprising:• *a tank (4) adapted to contain said photosensitive fluid substance ;• *a source (5) of electromagnetic radiation adapted to selectively irradiate said tank (4) , in order to selectively solidify a layer of said photosensitive fluid substance arranged adjacent to the bottom (8) of said tank ( 4 ) ;• »a modelling platform (6) , which is carried in a mobile manner along a first reference axis (A) orthogonal to said bottom (8) and is adapted to support a solidified layer of said fluid substance; said stereolithography machine (1) being characterized in that it comprises a multifunction assembly (23) provided at least with levelling means (22) , which are adapted to level said fluid substance in said tank (4) , wherein said levelling means (22) include an oblong paddle (27) , which extends along a second reference axis (B) orthogonal to said first reference axis (A) and is carried in a movable manner along a direction (di) orthogonal to said first axis reference (A) and said second reference axis (B) , and wherein said paddle (27) is pivotally carried about a rotation axis (C) parallel to said second reference axis (B) .2.- The machine according to claim 1, wherein said paddle (27) is positioned at a distance from the bottom (8) of said tank (4) along said first reference axis (A) so that, during its rotation around the rotation axis (C) , one of thelower ends of the paddle (27) can selectively enter into contact with the bottom (8) of said tank (4) .3.- The machine according to claim 1 or 2, wherein said levelling means (22) comprise a support bracket (29) adapted to support said paddle in a sliding manner along said direction (di) and in a rotatable manner about said axis of rotation (C) , and an actuation mechanism (30) adapted to translate, on command, said paddle (27) along said direction (di) and to rotate, on command, said paddle (27) about said rotation axis (C) .4.- The machine according to claim 1, 2 or 3, wherein said paddle (27) comprises a cup-shaped body (38) , which extends along said second reference axis (B) .5.- The machine according to claim 4, wherein said cup-shaped body (38) has a transversal cross-section, with respect to said second reference axis (B) , substantially U- shaped or V-shaped, and is shaped so as to form a chamber(39) adapted to be arranged above the bottom (8) of said tank ( 4 ) .6.- The machine according to claim 4 or 5, wherein said cup-shaped body comprises a pair of longitudinal walls(40) , which extend facing each other and parallel to said second reference axis (B) .7.- The machine according to claim 6, wherein said cup-shaped body (38) further comprises a pair of longitudinal flanges (45, 145) , each of which extends cantilevered outwards from the lower edge of a corresponding longitudinal wall (40) and in use is adapted to form an angle (a) with said bottom (8) of predetermined amplitude.8.- The machine according to claim 7, wherein the longitudinal flange (45, 145) momentarily closest to thebottom (8) of the tank (4) and / or in contact with the fluid substance in the tank (4) is arranged in a position converging with the bottom (8) of the tank (4) with respect to the forward direction (di) .9.- The machine according to claim 7 or 8, wherein said longitudinal flanges (145) are made separate and distinct from said cup-shaped body (38) , and are configured to be firmly, but removably, fastened to said cup-shaped body ( 38 ) .10.- The machine according to claim 9, wherein said longitudinal flanges (145) each comprise an insert (145) with an essentially plate-shaped structure, which is adapted to be firmly, but removably, fastened to the corresponding longitudinal wall (40) , so that it can project, overhanging, from the corresponding longitudinal wall (40) .11.- The machine according to any one of claims 3 to 10, wherein said multifunction assembly (23) further comprises feeding means (24) adapted to feed said photosensitive fluid substance within said tank (4) .12.- The machine according to claim 11, wherein said feeding means (24) comprise a source of said photosensitive fluid substance and a distribution duct (47) , which is fluidly connected to said source and extends inside said cup-shaped body (38) .13.- The machine according to claim 12, wherein said distribution duct (47) is provided with a plurality of holes / nozzles (48) adapted to allow the outlet of the fluid substance that passes through said distribution duct (47) .14.- The machine according to any one of claims 3 to 13, wherein said multifunction assembly (23) comprises heating means (26) adapted to heat the photosensitive fluidsubstance contained in said tank (4) .15.- The machine according to claim 14, wherein said heating means (26) comprise a heating device (49) , which is coupled to said cup-shaped body (38) and in use is adapted to heat said cup-shaped body (38) and the photosensitive fluid substance present at said cup-shaped body (38) .16.- The machine according to any of the preceding claims, also comprising an electronic control unit (52) , which is operationally connected to at least said source (5) , to said modelling platform (6) , and / or to said multifunction assembly (23) and comprises electronic processing means configured to control its operation.17.- A method of operation of a stereolithography machine made according to any of the previous claims, said method of operation including, in sequence, the steps of : a) lowering said modelling platform (6) until bringing the latter, or eventually a solid layer previously formed on the same modelling platform (6) , at a distance from the bottom (8) of said tank (4) equal to the thickness of the layer to be created; b) solidifying said layer through selective exposure to said electromagnetic radiation; and then c) lifting said modelling platform (6) in order to separate the layer just solidified from the bottom (8) of said tank (4) ; wherein the operation of said multifunction assembly (23) includes the following steps: d) once lifted said modelling platform (6) , rotating said paddle (27) in order to arrange the lower end of said paddle (27) at a predetermined distancefrom the bottom (8) of said tank (4) ; and then e) translate said paddle (27) along said direction (di) in order to fill the voids / depressions formed after lifting said modelling platform (6) and the layer just solidified supported by the latter.18.- The method according to claim 17, also comprising the step of rotating said paddle (27) around said rotation axis (C) so as to bring the lower end of said paddle (27) in contact with the bottom (8) of the tank (4) , and then to translate the paddle (27) along said direction (di) .19.- A computer program comprising instructions that, when the program is executed by an electronic control unit (52) , in particular of the machine according to claim 15, bring the control unit (52) to perform the method according to claim 16 or 17.

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