技术领域：
[0002]The present invention belongs to the field of additive manufacturing of three-dimensional objects (3D printing) using powdered materials. More particularly, the present invention belongs to the field of 3D printing in which powdered materials are melted using kinetic energy of particles with mass.
BACKGROUND OF THE INVENTION
[0003]In the book 3D-Tisk by authors Tadeja Muck and Igor Kriz̆anovskij (Zaloz̆ba Pasadena, Nov. 2015, ISBN: 9789616661690) the 3D printing technologies are described in detail and are divided into four groups: (i) technologies in which objects are fabricated by material extrusion (ASTM—material extrusion); (ii) technologies in which objects are fabricated by selective solidifying of fluid photopolymers using a light source (ASTM: vat photopolymerization, material jetting); (iii) technologies in which powder materials are used and bound together with either binder material or by melting the powdered material using various thermal sources (ASTM—binder jetting, powder bed fusion, direct energy deposition); (iv) technologies in which objects are fabricated by stacking and binding or laminating the basic material in the shape of sheets (ASTM—sheet lamination).
[0004]In all the technologies described above the additive manufacturing of an object is performed by fabrication of individual, two-dimensional (2D) layers in a specific sequence by progressively stacking one layer on top of another in one defined direction, which is usually the height (z coordinate). Individual 2D and flat layers, which have a defined minimal thickness, are therefore stacked and either melted or illuminated or bonded in a specific sequence in one direction of height z. In the technologies of 3D printing in which objects are fabricated by extruding material from extruder heads, the individual object layer is fabricated in a point-by-point manner, each point having its own coordinate. The printing sequence of coordinates of such individual points is executed relative to the number of extruder heads for the given layer. This method of 3D printing is therefore extremely time-consuming, but it enables fabrication of wide range of materials, due to the melting of material in the print heads before the material exits from the printing head to the dedicated printing point.
[0005]The technologies of 3D printing in which objects are fabricated by solidifying liquid polymers with the use of light are also based on sequential fabrication of two-dimensional layers of photosensitive polymers. In these technologies each consecutive layer is added onto the previous, already solidified layer, and the surface of the following, added, liquid photopolymer layer is illuminated thereafter and solidified in this way. This method of 3D printing is extremely limited by the choice of material because the printed object needs to be fabricated using photosensitive polymers.
[0006]The technologies of 3D printing in which objects are fabricated by binding or stacking of powdered material are also based on fabrication of sequential 2D layers and fabricate objects by progressive stacking of individual, flat, two-dimensional layers on top of each other, in a layer-by-layer manner in the direction of height z.
THE TECHNICAL PROBLEM
[0007]The existing technologies for 3D printing, which use additive stacking of thin two-dimensional layers of material, represent a limitation in regards to printing resolution or outer object appearance, respectively. If a very precisely fabricated object with high printing resolution on its outer surface is desired, then stacking of appropriately thin layers of material would be necessary. The desired printing resolution of the object in the direction of print, or the thickness of an individual layer in height z, respectively, therefore determines the thickness of the added material layer. Known technologies for additive manufacturing of three-dimensional objects therefore do not enable the application of thicker layers, even though there would be enough binder material or melting or solidifying energy available to do so; if an object with a smooth outer surface is to be fabricated, the fabrication of layers which are all as thin as possible is necessary.
[0008]The main problem solved by invention according to the present disclosure is the problem of additive manufacturing of three-dimensional objects by sequential stacking of two-dimensional layers of material, where said layers are stacked in one main printing direction (third dimension, usually height z) and where the thickness of said layers, which are being stacked, also determines the outer edge of the object or its surface, respectfully and in this way the thickness of said layers effects the appearance of the fabricated object.
STATE OF THE ART
[0009]The technical problem of additive manufacturing of objects from powder materials with the use of localized melting is described in large numbers of records in literature. Hereinafter the focus will be given on a technique for melting powdered material using energy an electron beam which is described in some patents and patent applications. In patent application EP 2 918 396 A1 a machine and a method for additive manufacturing of 3D objects are described, which are based on localized melting of the powdered material using kinetic energy of an electron beam. The machine comprises a beam generator, a lens, a controller for the beam generator and a support stage on which the powder material is spread tightly. Beam generator produces a beam in the direction towards an individual, thin layer of powder material, and lenses are used for appropriating the focus of the beam onto the surface of said layer of powder material and directing the electron beam onto various positions on the thin layer of powdered material placed on the support element. The controller manages the beam generator in a way in which selectively a pulsating or continuous electron beam can be produced. Continuous electron beam locally melts the material due to the collision of electrons with the powdered material. A two-dimensional layer is formed by moving the beam over the layer of the object, which is being fabricated, and the process of material addition and fabrication of the next layer in the printing sequence in the direction of height z is repeated. The object is therefore fabricated in a sequence by progressively stacking two-dimensional layers on top of each other in height z; and within an individual layer by sequentially melting smaller two-dimensional regions of said layer.
[0010]Method for additive manufacturing described in patent number EP2937163 B1 is based on the use of two individual electron guns wherein the first electron gun is used to melt a given region of powdered material and the second electron gun is being used for eliminating static electricity of powdered material. The machine comprises of two electron guns, a vacuum chamber, a support stage on top of which thin layers of powdered material are being stacked gradually, and a control unit for controlling the electron guns. In the mentioned patent the powdered material is spread tightly on the support stage in a form of a thin, two-dimensional layer. The first electron gun is set to melt the material and is placed perpendicular to the powdered bed. The first electron gun produces an electron beam which selectively melts the powdered material. The second electron gun produces a second electron beam which is used to eliminate static electricity, is set at a lower energy and is tilted at a tilt angle set to either 45 degrees or less relative to the sample surface. The second electron gun is being used to eliminate secondary electrons that gathered in the material due to the melting performed using first electron beam. The mentioned patent describes a three-dimensional object being fabricated by gradual stacking and melting of thin two-dimensional layers of powdered material on top of each other, in a layer-by-layer manner. Only the first electron gun is being used for the purpose of melting powdered material.
[0011]Patent application WO2015/120168 A1 describes an energy gun of an additive manufacturing system comprising a plurality of energy beams composed of either photons or electrons or any other particles capable of melting the powdered material. Lenses are used for focusing two energy beams onto a layer of powdered material. The hot spots of energy beams are set at a distance and energy beams are constructed and arranged to move in unison at a controlled velocity and to follow one-another in desired direction over the substrate. The first energy beam produces a melt pool from the substrate, and the second energy beam is used for post heating the melted pool to a temperature lower than the melting threshold. This enables the use of the second energy beam to control the solidification rate of the melt pool. In the case where the travel direction of the electron gun is reversed, the second energy beam is used for producing a melt pool and the first energy beam is used for post heating to control the solidification rate of the melt pool. This additive manufacturing system enables the fabrication of a three-dimensional object in a layer-by-layer. The powdered material is applied onto the build table using a particle spreader.
[0012]Patent application US 2016/0031156 A1 describes a machine comprising a plurality of print heads located at different positions across space for extruding material into space. The machine uses magnetic levitation or sound levitation for manipulation of features of a part, which is being fabricated in space. Magnetic levitation is performed so that the object (part) is cooled down below the temperature of phase transition of matter being printed into a superconductive state in which matter behaves as an ideal diamagnetic and the magnetic force on the matter in magnetic field is high. Sound levitation of parts of the object is performed with multiple sound sources and appropriate acoustic reflectors creating a standing wave or a 3D standing wave pattern in space. The machine uses a plurality of print heads placed across space. Material is applied to the final printing point with the use of standard print heads, the positions of which determine the application of material. Object is fabricated with a combination of plurality of print heads and changing of said print heads' spatial orientation relative to the printed object or rotating and manipulating said object using magnetic or acoustic levitation. Printing of the object is based on addition of extruded material from the print heads, whilst the object is levitated using magnetic or acoustic force. Machine according to the mentioned patent application is the only one that enables the fabrication of an object from multiple printing directions simultaneously, but is limited by the application of the material through print heads. This machine enables fabrication of objects in a point-by-point manner. The invention according to the present disclosure differs from the patent application US 2016/0031156 A1 in a way that it comprises either two or more electron beams or beams of other particles with mass which are used for melting the powdered material in a predefined, curved, melting volume; whilst the machine described in patent application US 2016/0031156 A1 comprises a plurality of print heads. Invention described in the patent application US 2016/0031156 A1 uses magnetic and acoustic levitation to support the printed object or its assembly parts; whilst the invention according to the present disclosure describes a machine and a method where the already printed object part is mechanically supported, and the magnetic levitation is used for transport and application of the powdered material into a predefined melting volume.
SOLUTION TO TECHNICAL PROBLEM
[0013]Described machines and methods which enable additive manufacturing of objects using particle beams fabricate an object in a point-by-point, region-by-region and layer-by-layer manner. Overview of the current patents, patent applications or other documents on the subject of material melting with the use of particle sources shows that none of the above mentioned technical solutions uses a sum of either two or more clusters of particles with mass being emitted from either two or more particle sources and where the sum occurs at a predefined time and in a predefined three-dimensional space (hereinafter volume) for the purpose of melting material in a predefined curved three-dimensional volume (hereinafter melting volume) as it is claimed by the invention according to the present disclosure. All of the above mentioned technologies (using particle beams) enable the fabrication of three-dimensional objects by stacking and melting one thin, practically flat, two-dimensional layer on top of another; and within an individual layer, the melting is performed either in a point-by-point manner, or by melting of sequential regions of the surface of the individual layer.
[0014]Invention according to the present disclosure differs from all of the above mentioned technologies in that powdered material is melted using a sum of energies of either two or more particle clusters individually emitted from plurality of sources of particles with mass, in a predefined, curved, three-dimensional melting volume. This means that the material will only melt in those volumetric parts of a three-dimensional space where either two or more particle clusters overlap in space and time or where beams comprising said particle clusters, intersects, respectfully.
[0015]In the melting volumes the energy exerted by either two or more particle sources adds up and is higher than the energy required for melting of the powdered material. Disclosed are some example embodiments using electrons (electron guns), but the disclosed invention is not limited by the use of electrons because any particles with mass can be used which are capable of heating material by transferring the particles kinetic energy onto the powdered material during collision. Each particle source emits a beam comprising a cluster series comprising a plurality of particle clusters. Either two or more particle sources are spatially positioned in a way that the beams emitted from said particle sources spatially intersect in one or plurality of volumes. The intersections of particle beams form one or plurality of curved intersection volumes at a predefined moment in time. Using magnetic levitation or electric force or electrostatic pull, respectively the powdered material is transferred to the spatial intersection volumes of particle clusters. Powdered material melts only in those parts of a three-dimensional space noted as melting volume which is inside the intersection volume and in which the clusters of particles overlap spatially and in a timely manner so that the density and therefore available kinetic energy is higher than the energy threshold required for melting the powdered material. By predefining the time delays between arrivals of clusters of particles emitted from at least two particle sources located at different spatial positions and if necessary by controlling other parameters of particle sources, the shape and the position of the melting volume can be changed and in this way the shape and the amount of the melted powdered material.
[0016]Described machines and methods which enable additive manufacturing of objects using particle beams fabricate an object according to the principle of a point-by-point or region-by-region and layer-by layer fabrication. Invention according to the present disclosure enables additive manufacturing of 3D objects in an arbitrary volume-by-volume manner with the use of two or more particle sources emitting individual clusters of particles with mass which overlap in space and time in a controlled and predefined manner. The fabrication of three-dimensional objects according to the disclosed invention is not bound by progressive stacking of thin, two-dimensional layers or by the thickness of such layers which defines the external appearance of the object at the same time, respectfully. Invention described herein is also not limited by the number of printing volumes which can be printed simultaneously because either two or more particle beams can create a plurality of intersection volumes and can therefore melt material in plurality of melting volumes located at different positions in space simultaneously. Invention according to the present disclosure enables spatially independent printing meaning that larger print volumes can be fabricated inside of the object and therefore the printing process is made faster in this way, whilst smaller print volumes can be fabricated at the surface of the printed object. In this way, the desired higher print resolution on the objects surface is achieved and therefore an improved external appearance of the object, whilst printing the parts inside of the object can be made faster by fabricating larger print volumes which is achieved by enlarging the melting volume. Machine and method according to the present invention also differ from all other above described machines and methods in a way that for the purpose of material application, a magnetic force or an electrostatic pull onto powdered material is used. This enables the transport or the application of powdered material into predefined volumetric parts of a three-dimensional space where fabrication of print volumes of the object occurs, therefore the method and the machine according to the present invention is not limited by progressive stacking of flat two-dimensional layers in the third direction z.
[0017]Hereinafter the phrase ‘particles with mass’ will be shortened as ‘particles’. Because the invention described herein differs from the other known inventions and therefore the terms used herein are new, hereinafter the definitions of terms used in this text are noted. The terminology used for description of the present invention is explained specifically for the purpose of clear definition of the following terms:
[0018]volume: is understood to be a specific three-dimensional space with limits or outer surface, respectfully;
[0019]curved volume: is a three-dimensional volume of which the outer surface is curved, and the size of which is not limited (meaning that the curved volume is limited itself but it can be of various sizes during fabrication). Curved volume is therefore not a two-dimensional layer with a specific height, and it is also not a small point with a permanently fixed size. Curved volume is therefore a term used to describe an arbitrary large plurality of points describing the interior parts of an enclosed curved surface of arbitrary size in a three-dimensional space;
[0020]print volume: is a curved volume in which all the steps of the printing process are being or shall be performed, from the outlet of powdered material 102 through the stopper 103 on the container 101, up to electrically discharging an already printed object part 1000 and by necessity the movement of said object part 1000 using multi-directional support system mechanization 110 or mechanization 114. The term ‘print volume’ is used for the purpose of marking a)a virtual print volume created in simulator 8 or b) a real print volume inside a real object which is being fabricated, such as object 3 (FIG. 14);
[0021]melting volume: is a curved volume in which the density of momentum of particles emitted from at least two particle sources 11, 12 exceeds the melting threshold of the powdered material 102 which is used for fabrication of object, such as an object 3, using the machine 1 and the method according to the disclosed invention;
[0022]intersection volume: is a curved volume in which at least two beams E1, E2 of particles emitted from at least two particle sources 11, 12 intersect and in which the melting volume 280 is formed;
[0023]The term “or” is used herein both in alternative in conjunctive sense unless otherwise indicated. Terms such as ‘a’, ‘an’, and ‘the’ are not intended to refer to only a singular entity but include the general class of which specific example may be used for illustration. The terminology herein used to describe specific embodiments of the invention, but their usage does not delimit the invention, except as outlined in the claims.
具体实施方式：
[0041]Various embodiments of the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which some, but not all embodiments of the invention are shown. Indeed, the embodiments of the invention may be embodied in many different forms and should not be considered as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements.
[0042]FIG. 1 depicts the basic principle of method and machine operation according to the present invention in an example embodiment wherein particles used for melting material for the purpose of fabricating a three-dimensional object are electrons. FIG. 1 shows a part of the machine according to the present invention and comprising a first particle source 11 and a second particle source 12 which are both emitting electrons therefore said particle sources 11, 12 are electron beamforming guns in this example. Particle source 11 emits a particle beam E1 in the direction of a geometrical axis 13 of said particle source 11. Particle source 12 emits a particle beam E2 in the direction of a geometrical axis 14 of said particle source 12. Particle source 11 is equipped with a system of magnetic lenses 18 used for shaping a radius r1, a divergence a, and a deflection of the beam E1 with respect to the direction of the geometrical axis 13. Particle source 12 is equipped with a system of magnetic lenses 19 used for shaping a radius r2, a divergence 13, and a deflection of the beam E2 with respect to the direction of the geometrical axis 14. Geometrical axis 13 of particle source 11 and geometrical axis 14 of particle source 12 are spatially arranged at an angle Ω1 with respect to each other and intersect in the intersection point 15. Particle source 11 is controlled with a control unit CT 1 to where the machine sends a control signal CTRL 1, and particle source 12 is controlled with a control unit CT 2 to where the machine sends a control signal CTRL 2.
[0043]The control signals CTRL 1, CTRL 2 controlling particle sources 11, 12 are synchronised in a timely manner and in this example embodiment exhibit no time delay between clusters emitted from the first particle source 11 and clusters emitted from the second particle source 12. Particle source 11 emits a cluster series 16 produced by pulsating of the particle sources 11 in time. Particle source 12 emits a cluster series 17 created by pulsating of the particle sources 12 in time. The intensity of cluster series 16 or the number of particles going through an imaginary surface S in a unit of time (i.e. the flux), respectfully is either constant in time or changing in time. FIG. 1 depicts an example embodiment where the flux of particles is changing in time from the value zero j=0 to a certain arbitrary value j determined by the density of particles g1 and their travel speed v1. Changing of the flux of particles can be either periodical in time or it can have any other predefined time dependency. In this way the emission of pulses or (better said) cluster series 16, 17, respectfully is achieved from particle sources 11, 12 wherein said cluster series 16, 17 comprise a plurality of individual particle clusters following one another at a predefined time intervals. Individual particle clusters in cluster series 16 have travel speeds v1, lengths L1, and follow one another at distances D1 which are lengths of the volumetric parts with no particles. Individual particle clusters in cluster series 17 have travel speeds v2, lengths L2, and follow one another at distances D2 which are lengths of volumetric parts with no particles. The length L1 of an individual particle cluster in cluster series 16 is defined by the duration of emission of particles from the particle source and by particle's travel speed v1. The length L2 of individual cluster in cluster series 17 is defined by the duration of emission of particles from the particle source 12 and by particle's travel speed v2. All assembly parts and parameters for operating the particle sources 11, 12 include but are not limited to: pulsating, therefore creation of lengths L1, L2 and distances D1, D2; defining the particle travel speeds v1, v2 by manipulation of particle acceleration voltages U1, U2 in particle sources 11, 12; defining particle flux j1, j2; controlling the divergences α, β and the deflections of beams E1, E2 using systems of magnetic lenses 18, 19.
[0044]Furthermore FIG. 1 shows instantaneous depiction of two particle sources 11, 12 emitting cluster series 16, 17 in the direction of geometrical axes 13, 14 of said sources 11, 12 in which said cluster series 16, 17 are mutually arranged spatially and in a timely manner so that two predefined particle clusters, which are emitted from different particle sources 11, 12, arrive and overlap in a volumetric part surrounding the intersection point 15 of said geometrical axes 13, 14 at the same time. It is evident that traveling clusters in the cluster series 16 and 17 enable the creation of a sum g of particle densities in an intersection volume 28 of beams E1, E2 at a specifically predefined time interval during which the densities g1, g2 of particle clusters assembling beams E1, E2 overlap. FIG. 1 illustrates an example embodiment of basic principle of method and machine operation at the moment in which the sum g of particle densities g1, g2 in the intersection volume 28 is at maximum value. The addition of particle densities in the intersection volume 28 will continue in time and will be repeating by overlapping of sequential two particle clusters having lengths L1, L2 and distances D1, D2 in between them. A spatially localised sum of particle flux j=j1-j2 which is pulsating in time is created in such a way. Individual clusters in cluster series 16 exhibit a velocity vector {right arrow over (v)}1, and individual clusters in cluster series 17 exhibit a velocity vector {right arrow over (v)}2 ; consequently the intersection volume 28 exhibits a velocity vector {right arrow over (v)}1, which is equal to the vector sum of velocity vectors {right arrow over (v)}1, and {right arrow over (v)}2 . In the case where said velocity vectors {right arrow over (v)}1, and {right arrow over (v)}2 are equal in speed and individual clusters from both cluster series 16, 17 have the same particle flux (j1=j2), the direction of the intersection volume 28 creation is in the direction of the line of symmetry between beam E1 and beam E2.
[0045]Hereinafter describing FIG. 1 it is explained that during the printing process 100 (FIG. 13) using a machine 1 a powdered material 102 (FIG. 7), which is intended to melt, is added and particle sources 11, 12 start emitting particles causing the spatially localised sum g (FIG. 1, indicated region) of particle densities g1, g2 in the intersection volume 28. Due to the sum g of densities (g1+g2) of both beams E1, E2 emitted from particle sources 11, 12, the kinetic energy density in a part of the intersection volume 28 is high enough to overcome the energy threshold required to melt the powdered material being located in the melting volume 280 during the time interval during which the clusters of electrons overlap. During the collision of particles emitted from sources 11, 12 with powdered material 102 the particles transfer their kinetic energy into heat and therefore cause the powdered material to melt in a part the intersection volume 28 which is noted as melting volume 280.
[0046]An example embodiment of the basic principle of operation of the machine and the method as shown in FIG. 2 depicts the influence of a time delay tf between a cluster series 16 emitted from particle source 11 and a cluster series 17 emitted from a particle source 12. FIG. 2 shows two spatially positioned particle sources 11, 12 which are both equipped with its own system of magnetic lenses 18, 19 and which are both emitting appropriately shaped and pulsating particle beams E1, E2 in the direction of geometrical axes 13, 14 of said particle sources 11, 12. Geometrical axes 13, 14 of particle sources 11, 12 intersect at the intersection point 15. Particle source 11 is pulsating in time and produces the particle beam E1 comprising cluster series 16 comprising individual clusters 160, 161, 162, 163, 164 with distances D1 in between them. Particle source 12 is pulsating in time, and produces the particle beam E2 comprising cluster series 17 comprising individual clusters 170, 171, 172, 173, 174 with distances D2 in between them. In this example length L1 is equal to length L2, and particle travel speed v1 is equal to v2. Cluster series 16 emitted from particle source 11 is time delayed with respect to the cluster series 17 emitted from particle source 12, so that individual clusters 160, 161, 162, 163, 164 are arriving at the intersection point 15 with a time delay tf (phase shift) with respect to the arrival of particle clusters 170, 171, 172, 173, 174 emitted from particle source 12. The time delay tf consequently causes a spatial offset AD. Delaying cluster series 16 against cluster series 17 with a time delay tf significantly influences the sum g of particle densities in the intersection volume 28 of particle beams E1, E2. Shown in FIG. 2 is the instantaneous picture of the cluster series 16, 17 overlapping at a specific moment, and the current intersection volume is marked.
[0047]A spatial offset of cluster series 17 with respect to cluster series 16 is achieved using the time delay tf and results in a travel path difference which influences the position and the shape of the intersection volume 28 of beams E1, E2 and which causes said intersection volume 28 to be spatially offset in a direction outwards from the intersection point 15.
[0048]Furthermore it is claimed that with the use of time delays tf between individual clusters such as 160, 170 in series 16, 17 and with the use of controlled divergence α, β of beams E1, E2, a travel direction of the intersection volume 28 can be manipulated. As shown in FIG. 1, the travel speed and direction of the local particle density g maximum in the intersection volume 28 is equal to the vector sum of velocity vectors {right arrow over (v)}1+{right arrow over (v)}2 of the travelling individual clusters 160, 170 in series 16, 17.
[0049]The position and the shape of the intersection volume 28 can be additionally manipulated with systems of magnetic lenses 18, 19 of particle sources 11, 12. Systems of magnetic lenses 18, 19 are therefore used for controlling the divergences α, β and the deflections of the beams E1, E2. Although the deflection represents a constituent part of the machine and method operation according to the disclosed invention, the deflection of beams E1, E2 is not separately depicted in any of the FIG. due to the complexity of this application.
[0050]FIG. 3 depicts an example embodiment of the basic principle of operation of the machine and the method wherein the individual particle clusters assembling series 16, 17 emitted from particle sources 11, 12 are longer and wider than those shown in FIG. 1 and FIG. 2. In this example embodiment it is therefore considered that: a length L3 of an individual clusters in series 16 is longer than the length L1 depicted in FIG. 1, the divergence α1 is wider that the divergence α depicted in FIG. 1, a diameter r3 (FIG. 3) of beam E1 is wider than the radius r1 depicted in FIG. 1, a length L4 (FIG. 4) of clusters in series 17 is longer than the length L2 depicted in FIG. 1, the divergence β1 is wider that the divergence β in FIG. 1, and a diameter r4 (FIG. 3) of beam E2 is wider than the radius r2 depicted in FIG. 1 (L3>L1, L4>L1, α1>α, β1>β, r3>r1 and r4>r2.)
[0051]Parts of control signals CTRL 1 and CTRL 2 which control the accelerating voltage U1, U2 (FIG. 3) and result in the emission of individual clusters with specific lengths L in cluster series 16,17 emitted from particle sources 11,12 are pulsating. In FIG. 3 said pulsating parts of control signals CTRL 1, CTRL 2 are implemented with the use of longer pulses than in the example embodiment shown in FIG. 1. The divergences α1, β1 are controlled by another dedicated parts of control signals CTRL 1, CTRL 2 for determining divergence α, β, and are larger in the example depicted in FIG. 3 than divergences α, β depicted in FIG. 1. In this way, the intersection volume 28 of particle clusters is spatially enlarged but it remains located in the centre (meaning its central point is coinciding with the intersection point 15) because there is no time delay tf between the cluster series 16 and 17 in this example embodiment.
[0052]The length of the intersection volume 28 in the direction of geometrical axes 13, 14 can be increased with the use of prolongation of the duration of individual pulses (lowering the frequency of pulsation) within dedicated parts of control signals CTRL 1, CTRL 2 which control the accelerating voltage U1, U2, and with which the emission of series 16, 17 comprising clusters of lengths L1, L2 is achieved. With the use of gradual increase of divergences α, β a wider melting volume 280 can be achieved in the direction perpendicular to geometrical axes 13, 14. The melting volume 280 is a three-dimensional part of the intersection volume 28 defined as the volumetric part in which the applied kinetic energy is above the energy threshold required for melting of the material and where said energy therefore causes the melting of the powdered material 102 (FIG. 7). Melting volume 280 and intersection volume 28 are separately noted because it is possible that not all of the volumetric parts of the intersection volume 28 will suffice the energy conditions necessary to melt the powdered material 102 (FIG. 7), but for the purpose of description of the present invention, the term intersection volume 28 is generally used with an intention to describe the melting volume 280. Shown in FIG. 3 is a melting volume 280 which is of the same size as the intersection volume 28. When lengths L are increased, said lengths L being those of individual clusters in cluster series 16, 17 emitted from plurality of particle sources 11, 12, the total applied energy in the intersection volume 28 is increased at the same time. The size of the melting volume 280 (indicated region 280) can be precisely set in a controlled manner by way of appropriating the lengths L of individual clusters in cluster series 16, 17 or by appropriating the divergences α, β of the particle beams E1, E2. The divergences α, β of particle beams E1, E2 are controlled using systems of magnetic lenses 18, 19 which are controlled by dedicated parts of control signals CTRL 1, CTRL 2 via control units CT 1, CT 2. Control signals CTRL 1, CTRL 2 are therefore assembled from said different parts of control signals, which individually contain synchronized controls expressed as time functions and are used for managing all constituent parts of particle sources 11, 12 at a desired time during the printing process, said parts of control signals CTRL 1, CTRL 2 therefore contain time-adjusted controls for managing the divergence α, β, the deflection, particle vector velocities {right arrow over (v)}1, {right arrow over (v)}2, particle densities g1, g2 and particle acceleration voltages U1, U2 used for creation of particle clusters.
[0053]Hereinafter it is explained how the angle Ω1 between the geometrical axes 13,14 of two particle sources 11,12 influences a shape, a development of the shape and a travel direction of the intersection volume 28 in time. For reasons of clarity, FIG. 4 depicts an example embodiment of the basic principle of operation of the machine and the method comprising two pulsating particle sources 11, 12 placed on a common plane (plane of the FIG.) and in which the angle Ω1 between the geometrical axis 13,14 of particle source 11,12 is in this case Ω1<90 degrees.
[0054]FIG. 4 shows two particle sources 11, 12 emitting cluster series 16, 17 which are synchronized and without any time delay tf amongst them. Both beams E1, E2 are made divergent by a certain amount using the systems of magnetic lenses 18, 19 so that they are widened in the volumetric parts surrounding the intersection point 15. It is evident from FIG. 4 that the intersection volume 28 of particle beams E1, E2 is divided into a plurality of smaller intersection volumes consecutively numbered with 45, 46, 47, 48, 49, and 410 in this case. Because cluster series 16 and 17 travel with vector velocities {right arrow over (v)}1 and {right arrow over (v)}2 and the angle Z between their geometrical axes 13, 14 is present as is, it is evident from FIG. 4 that the intersection volume 28 and its smaller constituent intersection volumes 45, 46, 47, 48, 49 and 410 will travel with a vector velocity {right arrow over (v)} in the direction of the line of symmetry between the geometrical axes 13, 14. At any given moment a plurality of smaller constituent intersection volumes 45, 46, 47, 48, 49, 410 which travel in the direction of the vector sum {right arrow over (v)} being a sum of individual vector velocities {right arrow over (v)}1, {right arrow over (v)}2 can be achieved.
[0055]In the case of applying a time delay tf between at least two appropriately pulsating particle beams E1, E2, which have the same pulsating frequency (meaning that the length L1 is equal to length L2 and the distance D1 is equal to distance D2), the vector velocity {right arrow over (v)} of smaller constituent intersection volumes 45, 46, 47, 48, 49, 410 can be modified in an arbitrary direction outward from the line of symmetry between geometrical axes 13 and 14. Furthermore it is claimed that the direction of velocity vector {right arrow over (v)} of smaller constituent intersection volumes 45, 46, 47, 48, 49, 410 can be manipulated by modifying the particle flux j1 and j2 emitted from particle sources 1112.
[0056]Individual smaller constituent intersection volumes 45, 46, 47, 48, 49, 410 as depicted in FIG. 4, can exhibit the shape of elongated, flattened, three-axial ellipsoids. A maximum length A of a smaller constituent intersection volume 48 is determined by lengths L1, L2 of individual particle clusters 160, 170, which overlap at an angle Ω1 in this example. A Maximum width B is the width of a smaller constituent intersection volume 48 and is determined with transverse overlapping of the beams E1, E2 emitted from two particle sources 11, 12 at an angle Ω1. The maximum of width B depends on the amount of divergence α, β which defines the maximum radii r1, r2 of particle clusters 160, 170 overlapping under the angle Ω1 at a specific moment t and in this way create said smaller constituent intersection volume 48 in this case. The height or the third axis of such an ellipsoid 48, respectfully is not visible herein, is directed into depth of the image, and is also determined by the angle Ω1, divergence α, β, and lengths L1, L2.
[0057]The shape of such individual smaller constituent intersection volumes 45, 46, 47, 48, 49, 410, which altogether constitute the total intersection volume 28, is depicted in FIG. 4 as being similar to ellipsoids, and is uniquely determined with divergences α, β of particle beams E1, E2, the angle Ω1 between geometrical axes 13, 14 of particle sources 11, 12, and the shape of controls in the parts of control signals CTRL 1, CTRL 2 which determine the pulsating of beams E1, E2 via acceleration voltage U1, U2 on the particle sources 11, 12 during time t and consequently create the individual clusters 160, 170 in cluster series 16, 17 and which have predetermined lengths L1, L2.. The mentioned parts of control signals CTRL 1, CTRL 2 can exhibit the shape of different time functions (sinusoidal, square wave or any other shape). FIGS. 1, 2 and 3 depict example embodiments wherein said parts of control signals CTRL 1, CTRL 2 which determine the pulsating of particle sources 11, 12, exhibit the shape of square wave functions of time, whilst in the FIG. 4 this shape is a sinusoid.
[0058]Hereinafter described is an example embodiment as depicted in FIG. 5. FIG. 5 is showing an instantaneous image of two cluster series 16, 17 emitted from two particle sources 11, 12 which are positioned so that they emit individual clusters 160, 170 of equal lengths (L1=L2) in the direction one towards the other, so that the angle Ω is 180 degrees and wherein said angle Ω is the angle between the geometrical axes 13, 14 of said sources 11, 12. Cluster series 16, 17 are synchronised amongst themselves and have no time delay tf applied between them, meaning that an individual particle cluster 160 in cluster series 16 emitted from particle source 11 and an individual particle cluster 170 in cluster series 17 emitted from particle source 12 both arrive to the volumetric part surrounding the intersection point 15 at the same time. A distance 20 marks the distance from particle source 11 to the intersection point 15 and a distance 21 marks the distance from particle source 12 to the intersection point 15. If the distance 20 is not the same as distance 21, the synchronous arrival of individual clusters 160, 170 can be achieved with appropriate time delay tf which can be used to compensate for the difference between the distances 20 and 12 or a difference between the travel speeds v1 and v2. In such an example embodiment as evident from FIG. 5, the the shape of the intersection volume 28 can be similar to a cylinder during the entire time in which clusters overlap, if the individual clusters 160, 170 which overlap are of cylindrical shape. The length of such a cylindrically shaped intersection volume 28 will change during the time in which clusters overlap, with the maximum length of such an intersection volume 28 being the same as lengths L1, L2 of individual clusters 160, 170 which create such an intersection volume 28. The cross section of individual particle clusters 160, 170 is round in this example embodiment; therefore the depicted intersection volume 28 is a cylinder with a radius r1.
[0059]Using appropriate modulation of intensities of fluxes j1, j2 or divergences α, β it can be achieved so that the individual clusters 160, 170 are of any other shape; instead of cylindrical volume of clusters 160, 170, the individual clusters 160, 170 can be shaped for example as a half of a sinusoid wave as shown in FIG. 4, or in any other predefined way. For reasons of clarity in depicting the intersection volume 28, shown in FIG. 1-3 and FIG. 5 is the use of parts of control signals for pulsating which are shaped as a square wave function whilst the divergences α, β are not changed during pulsating, because in this way it is easier to depict the limits between high and low densities of particles. But in a case where parts of control signals for pulsating shaped as a sinusoid function are used, the intersection volume 28 of two clusters shaped as a sinusoid and travelling toward each other will be shaped as a rotationally symmetrical object in the shape of a tactoid. A cross-section of such a tactoid is a circle. If a sinusoid function is used at the same time also for the modulation of divergences α, β than individual clusters 160,170 can be of a spherical shape and therefore the intersection volume 28 of such a plurality of clusters can also be shaped as a sphere.
[0060]From FIG. 5 it is also easier to imagine the location of the intersection volume 28 (FIG. 1-3) in the case where individual clusters 160, 170 emitted from particle sources 11, 12 and which overlap in the intersection volume 28, are time delayed. If cluster series 16 emitted from particle source 11 will be travelling ahead of the cluster series 17 emitted from particle source 12 and the distance 20 of particle source 11 to the intersection point 15 is the same as the distance 21 of particle source 12, then particle series 16, 17 will be overlapping in a volumetric part which is closer to the particle source 12. An individual cluster 160 in cluster series 16 will travel ahead and already pass by the intersection point 15 whilst at the same an individual cluster 170 in cluster series 17 will not arrive at the intersection point 15 yet. Location of an intersection volume 28 can therefore be determined with the use of predefined time delays tf applied amongst individual clusters 160, 170 in cluster series 16, 17 emitted from two separate particle sources 11, 12.
[0061]FIG. 6 depicts an example embodiment comprising six particle sources 11, 12, 61, 62, 63, 64 which are spatially arranged so that they create 3 pairs of particle sources. In each pair the individual constituent particle sources are directed towards each other (facing each other), and the said pairs being: the first pair comprising particle sources 11 and 12, the second pair comprising particle sources 61 and 62, and the third pair comprising particle sources 63 and 64. Said particle sources are managed by control signals CTRL 1, CTRL 2, CTRL 3, CTRL 4, CTRL 5, CTRL 6 via control units CT 1, CT 2, CT 3, CT 4, CT 5, CT 6. The control units CT 1, CT 2, CT 3, CT 4, CT 5, CT 6 manage the particle sources 11, 12, 61, 62, 63, 64 according to the control signals and therefore control parameters such as the lengths L1, L2, L3, L4, L5, L6 of individual clusters of particles, the time delay tf, divergences α1-α6, energy determined by means of acceleration voltage U1, U2, U3, U4, U5, U6, vector velocities v1, v2, v3, v4, v5, v6, and densities g.
[0062]Shown in FIG. 6 are 3 pairs of particle sources which are mutually arranged so that all of the geometrical axes of said sources intersect in a single intersection point 15 and that geometrical axes of pairs of particle sources intersect at angles Ω1, Ω2, and Ω3. All particle sources 11, 12, 61, 62, 63, 64 are individually equipped with systems of magnetic lenses 18, 19, 69, 70, 71, 72, are synchronized amongst themselves, and are emitting cluster series 16, 17, 65, 66, 67, 68 simultaneously in the direction of velocity vectors {right arrow over (v)}1, {right arrow over (v)}2 , {right arrow over (v)}3 , {right arrow over (v)}4 , {right arrow over (v)}5 , {right arrow over (v)}6, so that each particle source is emitting cluster series towards the other particle source in each pair of particle sources. Therefore, in the first pair of particle sources the particle source 11 is emitting cluster series 16 in the direction towards the opposite particle source 12 and said particle source 12 is emitting cluster series 17 towards the particle source 11, which is causing said cluster series 16 and 17 to travel towards each other. Similarly, in the second pair of particle sources the particle source 61 is emitting cluster series 65 towards the particle source 62 and said particle source 62 is emitting cluster series 66 towards the particle source 61, which is causing said cluster series 65 and 66 to travel towards each other. Similarly, in the third pair of particle sources the particle source 63 is emitting cluster series 68 towards the particle source 64, and the particle source 64 emitting cluster series 67 towards the particle source 63, which is causing said cluster series 67 and 68 to travel towards each other. Predefined particle clusters in cluster series 16, 17, 65, 66, 67, 68 arrive simultaneously into volumetric parts surrounding the intersection point 15, which is equally separated from all six particle sources 11, 12, 61, 62, 63, 64. In the example embodiment pictured in FIG. 6 the divergences of beams emitted from particle sources 11, 12, 61, 62, 63, 64 are the same, furthermore it is claimed that said divergences can be different. Furthermore it is claimed that the deflections can be different wherein said deflections are the one of different beams emitted from particle sources 11, 12, 61, 62, 63, 64 and are caused by systems of magnetic lenses 18, 19, 69, 70, 71, 72.
[0063]It is clear that in an example embodiment where appropriately shaped control signals are used, the intersection volume 28 of all cluster series 16, 17, 65, 66, 67, 68 can be a sphere with the diameter 2R and the centre in the intersection point 15. It is claimed that the diameter 2R of the intersection volume 28 can be changed by manipulation of those parts of control signals CTRL 1-6 which determine divergences α1-α6 and the shape of pulsating of the individual beams emitted from particle sources 11, 12, 61, 62, 63, 64. In the example embodiment as shown in FIG. 6 pulses in the shape a square wave are used for pulsating of said beams and the intersection volume 28 is shaped somewhere in-between a sphere and a cube, similar to a sphere. Furthermore, in an example embodiment shown in FIG. 6, the spatial symmetry of the intersection volume 28 in all the directions of vector velocities {right arrow over (v)}1, {right arrow over (v)}2, {right arrow over (v)}3, {right arrow over (v)}4, {right arrow over (v)}5, {right arrow over (v)}6 outwards from the intersection point 15 is clearly depicted. Furthermore, it is claimed that example embodiments of the basic principle of machine and method of operation are possible wherein geometrical axes of plurality of particle sources, for example particle sources 11, 12, 61, 62, 63, 64, intersect in a plurality of intersection points in space. Furthermore, it is claimed that example embodiments of the machine and the method are possible in which geometrical axes of plurality of particle sources such as 11, 12, 61, 62, 63, 64 intersect at different angles Ω which can also change during the printing process.
DESCRIPTION OF EMBODIMENTS
[0064]Hereinafter based on the FIG. 7, 8, 9, 10, 11, 12 some example embodiments of the machine for additive manufacturing of three-dimensional objects will be described in detail.
[0065]FIG. 7 depicts an example embodiment of the machine for additive manufacturing of three-dimensional objects comprising two particle sources 11, 12 which are spatially arranged so that their geometrical axes 13, 14 intersect at the intersection point 15. The machine is equipped with two windings 105, 106 individually carrying an electric current I used for creation of a magnetic field B. Windings 105 and 106 have a common geometrical axis 107. Windings 105, 106 are each individually connected to control units CT B1, CT B2 controlled by control signals CTRL B1, CTRL B2. In a machine printing space 2 the time-varying and spatially non-homogenous magnetic field B can be achieved using the windings 105, 106 so that magnetic levitation and transport of powdered material 102 is achieved using the magnetic force into a pre-determined position in the intersection volume 28 where powdered material 102 melts during the printing process 100 (FIG. 13) used for fabricating a predefined, three-dimensional object, such as an object 3. Printing space 2 of the machine 1 is the largest area inside machine 1 where it is possible to transport and melt the powdered material 102 and therefore marks the entire space inside a vacuum chamber 116 where fabrication is possible.
[0066]Control units CT 1, CT 2 are controlled by control signals CTRL 1, CTRL 2 and are used to manage the parameters of beams E1, E2 emitted from particle sources 11, 12. A control signal CTRL B1 via a control unit CT B1 and a control signal CTRL B2 via a control unit CT B2 determine amplitudes and directions of electrical currents I running through windings 105, 106 during the printing process 100 (FIG. 13) for the purpose of transporting the powdered material 102 into the melting volume 280 (FIG. 3). An appropriate magnetic field B, which assures the transport of powdered material 102 into the desired part within the intersection volume 28, is achieved by alternating the direction or modulating amplitudes or phases of the electrical currents I running through windings 105, 106.
[0067]Powdered material 102, which is used for fabrication of a three-dimensional object such as object 3 (FIG. 14) during the printing process 100 (FIG. 100), is kept in a container 101 (FIG. 7) before the printing process 100. Dosing of the powdered material 102 (FIG. 7) is managed by the stopper 103 positioned on the exit of the container 101. The opening and closing of the stopper 103 is controlled with a control signal CTRL C1 via control unit CT C1 during the printing process 100 (FIG. 13) thus enabling a predetermined amount of the powdered material 102 to be added in this way. The windings 105, 106 creating the magnetic field B can be located either inside or outside of a vacuum chamber 116. The support of an already printed obj