DE102015212193A1 - 3D printing with improved form reproduction and strength - Google Patents

3D printing with improved form reproduction and strength

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Publication number
DE102015212193A1
DE102015212193A1 DE102015212193.3A DE102015212193A DE102015212193A1 DE 102015212193 A1 DE102015212193 A1 DE 102015212193A1 DE 102015212193 A DE102015212193 A DE 102015212193A DE 102015212193 A1 DE102015212193 A1 DE 102015212193A1
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Germany
Prior art keywords
melt
drops
characterized
drop generator
starting material
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
DE102015212193.3A
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German (de)
Inventor
Udo Riegler
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Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
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Filing date
Publication date
Application filed by Robert Bosch GmbH filed Critical Robert Bosch GmbH
Priority to DE102015212193.3A priority Critical patent/DE102015212193A1/en
Publication of DE102015212193A1 publication Critical patent/DE102015212193A1/en
Application status is Withdrawn legal-status Critical

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    • BPERFORMING OPERATIONS; TRANSPORTING
    • B33ADDITIVE MANUFACTURING TECHNOLOGY
    • B33YADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00Processes of additive manufacturing
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/10Processes of additive manufacturing
    • B29C64/106Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material
    • B29C64/112Processes of additive manufacturing using only liquids or viscous materials, e.g. depositing a continuous bead of viscous material using individual droplets, e.g. from jetting heads
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/10Processes of additive manufacturing
    • B29C64/165Processes of additive manufacturing using a combination of solid and fluid materials, e.g. a powder selectively bound by a liquid binder, catalyst, inhibitor or energy absorber
    • BPERFORMING OPERATIONS; TRANSPORTING
    • B29WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29CSHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/30Auxiliary operations or equipment
    • B29C64/386Data acquisition or data processing for additive manufacturing

Abstract

A printhead unit (2) for a 3D printer (1) for producing a three-dimensional object (6), comprising at least one first drop generator (21) for dividing a first melt (72) of a first starting material (71) into individual drops (73 ) of a first type, wherein these drops (73) of the first kind are connectable to the object (6) by addition in the liquid state at the locations associated with the shape of the object (6) and subsequent solidification, at least one second drop generator ( 22, 222, 322, 422, 522) which is provided for dividing a second melt (82, 282, 382, 482, 582) of a second starting material (81, 281, 381, 481, 581) into individual drops (83, 283, 383, 483, 583) of a second type, the second drop generator (22, 222, 322, 422, 522) being controllable independently of the first drop generator (21). A 3D printer (1) for producing a three-dimensional object (6) from a first starting material (71) and a second starting material (81, 281, 381, 481, 581), the 3D printer (1) comprising at least one print head unit (2 ) according to one of claims 1 to 6, at least one positioning unit (3) for generating a relative movement between the print head unit (2) and the object (6) and at least one control unit (5) comprising the print head unit (2) and / or the positioning unit (3). Each method of operation.

Description

  • The invention relates to 3D printing from metallic starting materials and provides for this purpose a printhead unit, a 3D printer and methods of operation.
  • State of the art
  • In 3D printers for plastics, the solid starting material in the print head is melted and added at the locations associated with the shape of the object to be formed in the form of a liquid stream. A three-dimensional object is assembled layer by layer in this way.
  • Instead, metallic starting materials are divided with a drop generator into individual drops, which are subsequently brought in liquid form to the locations associated with the shape of the object. As the drops solidify, they bind firmly to the object to be made. Such a 3D printer is for example made of ( Song Yi Zhong et al., Journal of Materials Processing Technology 214, 3089-3097 (2014) ) known. The printhead assembly of this 3D printer contains a source reservoir and an induction heater that allows this source material to be melted. By applying a gas pressure to the surface of the melt, individual metal drops are expelled from a nozzle-shaped opening at the bottom of the reservoir and thrown to their destination.
  • The accuracy with which the desired shape of the object is reproduced and the mechanical strength of the resulting object depend on the tight process windows for the temperature of the melt in the printhead assembly and for the temperature of the substrate on which the object is being built become. Accuracy and strength can be opposing goals. Studies on this topic are for example in ( M. Orme, EP Muntz, "New Techique for Producing Highly Uniform Droplet Streams to Extended Range of Disturbance Wave Numbers", Review of Scientific Instruments 58 (2), 279-284 (1987). ) M. Orme, RF Smith, "Enhanced Aluminum Properties by Precision Droplet Deposition", Journal of Manufacturing Science and Engineering - Transactions of the ASME 122 (3), 484-493 (2000) ) such as ( Yan-pu Chao, Le-hua Qia et al., International Journal of Machine Tools and Manufacture 69, 38-47 (2013), "Remelting and bonding of deposited aluminum alloy droplets and substrate droplets in metal droplet deposition manufacture". ) released.
  • Drop generators for metallic materials are still from the US 5,171,360 A , from the US 5,226,948 A , from the WO 2001 091 524 A1 as well as from the WO 2001 091 525 A1 known.
  • Disclosure of the invention
  • In the context of the invention, a print head unit for a 3D printer for the production of a three-dimensional object has been designed. This print head unit comprises at least one first drop generator, which is designed to divide a first melt of a first starting material into individual drops of a first kind. These drops of the first variety can be fixed to the object by addition in the liquid state of aggregation at the locations associated with the shape of the object and subsequent solidification.
  • According to the invention, at least one second drop generator is provided, which is designed to divide a second melt of a second starting material into individual drops of a second kind. In this case, this second drop generator can be controlled independently of the first drop generator.
  • The inventor has recognized that it is fundamentally difficult to produce a filled volume of defined contours from approximately spherical drops of a single variety. The spherical shape of the drops can not be preserved in the finished object, because even with the densest sphere packing the volume would be filled only to 74%, and the balls would be connected only via very small contact points. The strength of the resulting object would be insufficient. Therefore, the drops will be remelted on arrival at their destination further, which improves both the cohesion of the drops and better fill the volume. However, there is a limit to this further melting since the final shape of the finished object is becoming increasingly difficult to control. Therefore, the inventor pursues the approach of filling the gaps remaining in the composition of the drops of the first variety with drops of the second variety. In this case, both starting materials can be materially identical, so that the drops of the two varieties can differ, for example, only in their shape and / or in their size. However, it is also possible to use different starting materials for the drops of both types, so that the object is built up as a very defined alloy of both starting materials. The starting materials may in particular be metals.
  • In a particularly advantageous embodiment of the invention, the second drop generator for the production of drops of a second variety are formed, which are smaller than the drops of the first variety. The drops of the second variety are then particularly well suited to gaps in a grid To fill out drops of the first kind. The better the gaps are filled and the more compact the object produced is, the greater the mechanical strength of the object. Ideally, the object may have a greater strength than the starting materials in the respective raw state.
  • Particularly advantageously, the second drop generator is designed for the production of drops of a second variety, which have a diameter of 25% to 45%, preferably from 30% to 45%, of the diameter of the drops of the first variety. A drop of the second variety then has approximately the volume remaining free in a regular lattice of drops of the first variety between adjacent drops of the first variety.
  • Advantageously, the first drop generator has a first reservoir for the first melt with a first outlet formed as a nozzle for the first melt. The second drop generator has a second reservoir for the second melt with a second outlet formed as a nozzle for the second melt. The size of the resulting drops can then be adjusted in particular via the nozzle diameter. A drop generator emits drops whose diameter is about 1.89 times the nozzle diameter. In order to make both droplet generators controllable independently of one another, the first reservoir, and / or the second reservoir, on the side of the first melt or the second melt facing away from the first outlet or the second outlet can have means for applying a gas pressure p. The gas pressure p can be controlled in particular with a valve, for example with a solenoid valve or with a piezoelectric actuator in the reservoir. The injected gas may in particular be an inert gas, for example argon.
  • Each drop generator can be periodically driven, for example with a function generator that outputs a sine or cosine wave. It can then be emitted in the order of 24,000 drops per second, so that the throughput of starting material is very large. For example, a monodisperse chain of single drops may be emitted. Alternatively or in combination, the printhead unit and the substrate, or the object resulting therefrom, can always be relatively repositioned relative to one another and subsequently a single drop can be triggered ("drop on demand"). The positioning is then not tied to the clock of the drop generator, but the drop generation is inversely dependent on how fast the positioning can be done. The speed for the positioning can then be selected advantageously so that no excessive acceleration forces occur.
  • Advantageously, the ejection directions of the first outlet and the second outlet are aligned so that straight lines along these ejection directions intersect or pass at a distance equal to the sum of the radius of a first grade drop and the radius of a second grade drop. After the application of a drop of the first grade, a drop of the second type can then be applied directly to the correct location, without the printhead unit having to be repositioned relative to the substrate or relative to the object formed thereon.
  • In a further particularly advantageous embodiment of the invention, the first drop generator has a regular grid of outlets for the first melt, and the second drop generator has a regular grid of outlets for the second melt. The grids are offset from each other and have the same lattice constants d 7 , d 8 .
  • In this case, in each drop generator several or all outlets may have a common reservoir for the respective melt. However, each outlet can also have an independent reservoir.
  • The arrangement of a plurality of outlets each in a regular, one- or two-dimensional grid makes it possible, analogously to a shower head, to occupy a line or a surface particularly quickly with a layer containing both starting materials. If, for example, the object to be produced is composed of discrete cuboidal or cuboidal elementary bodies (voxels), then such a layer can cover the base surface of this elementary body. By stacking several layers, the volume of the elementary body can be filled successively.
  • The invention also relates to a method for operating the printhead unit according to the invention. The method is characterized in that the second melt is kept at a higher temperature than the first melt. In particular, both starting materials may be metallic, and the second melt may be maintained at a temperature at least 100 ° C higher than the first melt. A second grade drop is then softer to such an extent than the already existing first grade drop grid that this grid remains substantially untouched and only the second grade drop is deformed to completely fill the gap left in the grid.
  • In a particularly advantageous embodiment of the invention is aluminum or a Aluminum alloy as the first starting material, and / or as a second starting material selected. Aluminum has a melting point of 660 ° C. The temperature of the first melt in the first reservoir can then be maintained between 750 ° C and 800 ° C, for example. From this melt, large drops of the first variety can be formed, which after the impact on the substrate, or on the resulting object, immediately cool and do not change their shape further. The second melt in the second reservoir may then be maintained at a temperature of 900 ° C or more. From this small drops of the second variety can be formed, which flow into the gap between the already existing drops of the first variety when hitting the resulting object without damaging the lattice formed from these drops of the first variety.
  • Another method for operating a printhead unit according to the invention is characterized in that the first drop generator and the second drop generator are controlled alternately. Then a drop of the second variety fuses particularly well with the drops of the first variety, which were emitted immediately before or after this drop of the second variety. This embodiment of the method is particularly advantageous in combination with the design of the print head unit, in which both drop generators each have a regular grid of outlets. If, for example, first of all outlets simultaneously emit drops from all the outlets of the first drop generator, then out of all the outlets of the second drop generator and then again out of all outlets of the first drop generator, while the print head unit remains laterally in the same position, then layers of the starting materials grow on one another, which are particularly well merged with each other.
  • In the context of the invention, a 3D printer for producing a three-dimensional object from a first starting material and a second starting material was also designed, wherein these starting materials can also be materially identical. This 3D printer comprises at least one print head unit according to the invention, at least one positioning unit for generating a relative movement between the print head unit and the object, and at least one control unit which controls the print head unit and / or the positioning unit. With this 3D printer, metallic objects can be used to produce high-strength objects with good accuracy.
  • Particularly advantageously, at least one modeling unit is provided for converting the shape of the object into a model composed of discrete elementary bodies, and the control unit is designed to control the print head unit and / or the positioning unit for producing the discrete elementary bodies of the model. The discretization into elementary bodies creates an additional level of abstraction. It is immediately obvious, particularly with regard to possible compromises between the production speed and the accuracy of the final shape obtained. On the other hand, the user does not have to worry about the way in which the elementary bodies are ultimately formed from drops of the first kind and drops of the second kind. This is the sole task of the control unit. New elementary bodies can be subsequently implemented and made available to the user.
  • The elementary bodies may in particular be cube-shaped or cuboidal. However, other geometric structures, such as honeycomb structures, may be useful and further increase, for example, the strength of the object. The model can in particular be composed of elementary bodies which differ in their dimensions and / or in their volumes. For example, areas inside the object can be formed from large cube-shaped or cuboid elementary bodies, which can be produced particularly quickly. Near the surface of the object, where the accuracy of the shape is important, smaller elementary bodies and / or elementary bodies, with which the desired shape of the surface can be reproduced more precisely, can be chosen.
  • Further measures improving the invention will be described in more detail below together with the description of the preferred embodiments of the invention with reference to figures.
  • embodiments
  • It shows:
  • 1 Embodiment of the 3D printer according to the invention 1 with aligned ejection directions 24a . 26a the outlets 24 . 26 ,
  • 2 Embodiment of the 3D printer according to the invention 1 with increased material throughput.
  • 3 Filling gaps in a grid of drops 73 a first kind and drops 83 a second kind.
  • 4 Example of a discrete elementary body 41 . 41a - 41c composite model of an object 6 ,
  • 5 Embodiment of a printhead unit 2 for producing cube-shaped elementary bodies 41 . 41a ,
  • To 1 includes the printhead unit 2 of the 3D printer 1 a first drop generator 21 and a second drop generator 22 , The first drop generator 21 has a first reservoir 23 for the melt 72 of the first starting material 71 on. This reservoir 23 is from a heater 21a surround. The reservoir 23 has an outlet 24 for the melt 72 on. By the reservoir 23 above the level of the melt 72 via a first solenoid valve 27 is applied with a pressure pulse of the pressure p, one of the first starting material 71 formed single drop 73 along the ejection direction 24a from the outlet 24 in the direction of the object 6 shot. The object 6 arises on a substrate surface provided for this purpose 31 leading to the positioning unit 3 belongs. Through the positioning unit 3 can the substrate surface 31 , and thus the resulting object 6 , against the printhead unit 2 to be moved.
  • The printhead unit 2 also contains a second drop generator 22 , This includes a second reservoir 25 for the melt 82 of the second starting material 81 , The reservoir 25 is from a heater 22a surround. It has an outlet 26 on. If over the second solenoid valve 28 a pressure pulse with the pressure p in the reservoir 25 is one of the second starting material 81 formed single drop 83 a second variety along the ejection direction 26a out of the opening 26 shot out.
  • Here are the ejection directions 24a and 26a aligned so that straight lines along these ejection directions 24a and 26a in the area of the object 6 to cut. The second drop generator 22 is mechanically strong with the first drop generator 21 coupled, allowing any relative movement between the object 6 and the first drop generator 21 also as an analogous relative movement between the object 6 and the second drop generator 22 acts.
  • The first solenoid valve 27 is via a control line 51 with the control unit 5 connected. The second solenoid valve 28 is via the control line 52 with the control unit 5 connected. The control unit 5 controls via a third control line 50 also the movement of the positioning unit 3 , As input receives the control unit 5 that from the modeling unit 4 created model 42 in which the shape of the object 6 in discrete, in 1 not drawn, elementary bodies 41 is divided.
  • The embodiment according to 2 differs from the embodiment according to 1 only with regard to the printhead unit 2 , In contrast to 1 are next to the first drop generator 21 that with the first starting material 71 is filled, a second drop generator 222 , a third drop generator 322 , a fourth drop generator 422 and a fifth drop generator 522 intended.
  • The second drop generator 222 contains a reservoir 225 for the melt 282 of the second starting material 281 , The reservoir 225 is from a heater 222a surround. The reservoir 225 contains an outlet 226 , from along an ejection direction 226a one from the second starting material 281 formed drop 283 a second variety can be shot. To a drop 283 can generate via a solenoid valve 228 that over a control line 252 with the control unit 5 is connected, a pressure p in the reservoir 225 be controlled.
  • The third drop generator 322 contains a reservoir 325 for the melt 382 of the third starting material 381 , The reservoir 325 is from a heater 322a surround. The reservoir 325 contains an outlet 326 , from along an ejection direction 326a one from the third starting material 381 formed drop 383 a third variety can be shot. To a drop 383 can generate via a solenoid valve 328 that over a control line 352 with the control unit 5 is connected, a pressure p in the reservoir 325 be controlled.
  • The fourth drop generator 422 contains a reservoir 425 for the melt 482 of the fourth starting material 481 , The reservoir 425 is from a heater 422a surround. The reservoir 425 contains an outlet 426 , from along an ejection direction 426a one from the fourth starting material 481 formed drop 483 a fourth variety can be shot. To a drop 483 can generate via a solenoid valve 428 that over a control line 452 with the control unit 5 is connected, a pressure p in the reservoir 425 be controlled.
  • The fifth drop generator 522 contains a reservoir 525 for the melt 582 of the fifth starting material 581 , The reservoir 525 is from a heater 522a surround. The reservoir 525 contains an outlet 526 , from along an ejection direction 526a one from the fifth starting material 581 formed drop 583 a fifth variety can be shot. To a drop 583 can generate via a solenoid valve 528 that over a control line 552 with the control unit 5 is connected, a pressure p in the reservoir 525 be controlled.
  • All drop generators 21 . 22 . 322 . 422 and 522 are fixed with a mounting plate 200 connected. This also ensures that all ejection directions 24a . 226a . 326a . 426a and 526a parallel to each other. To a drop 283 the second kind, a drop 383 the third kind, a drop 483 the fourth variety or a drop 583 the fifth variety to one immediately before the object 6 accumulated drops 73 To store the first grade, the positioning unit 3 be controlled so that the destination for the drop 283 . 383 . 483 respectively. 483 in the extension of the corresponding ejection direction 226a . 326a . 426a or 526a lies. In return, offers the variety of drop generators 21 . 222 . 322 . 422 . 522 the advantage that per unit time a whole lot more starting material 71 . 281 . 381 . 481 . 581 can be processed. Two or more of the starting materials 71 . 281 . 381 . 481 and 581 may advantageously be complete or in certain properties, such as material, identical.
  • 3 illustrates the filling of a volume with starting material 71 . 81 . 281 . 381 . 481 . 581 in that it is applied in drop form. 3a shows the filling of the volume with only one sort of drops 73 , each having a diameter d 1 and are set by spatial offset in such a way that the resulting regular grid has a lattice constant d 2 <d 1 . The drops 73 advantageously overlap by amounts up to 10% of the diameter d 1 . The drops 73 touch each other only on small contact surfaces a to g. Between the drops 73 there are gaps 74 showing the structure of the drop 73 formed object 6 weaknesses.
  • 3b illustrates how this problem according to the invention by the drops 83 the second variety is remedied. To go to that in 3b First, the four drops were coming 73 the first kind applied. Subsequently, the three drops 83 of the second kind applied.
  • 3c shows the final state of the object 6 , Compared to 3b were two more drops 73 the first kind applied. The volume is now inside the object 6 completely filled out without gaps 74 , In this way, all the individual drops 73 and 83 maximally fused together, so that the microstructure of the object 6 is homogeneous and its strength is advantageously increased.
  • The drops 73 the first variety come from a nozzle 24 with a diameter of 0.3 mm. Thus, the drops have 73 a diameter d 1 of 0.571 mm. The drops 73 are so close together that the lattice constant d 2 of the resulting regular grid only 90% of the diameter d 1 of the drops 73 is. A cube-shaped unit cell with an edge length corresponding to the lattice constant d 2 has a volume of 0.136 mm 3 . Of this, a proportion of 0.038 mm 3 is still unfilled. With it a drop 83 the second species fills in this residual volume becomes a drop 83 needed with a diameter of 0.21 mm. To such a drop 83 produce, becomes a nozzle 26 needed with a diameter of 0.11 mm.
  • Because the contact between the drops 73 The first variety is no longer mediated only by the small contact surfaces A to G, but also by the drops 83 of the second variety, depends on the strength of the manufactured object 6 no longer so critical of the exact relative positioning of all drops 73 and 83 to each other. This is more advantageous, the more drops 73 and 83 should be applied per second. According to the prior art, it was already very demanding, for a repetition rate of 300 drops per second, the positioning unit 3 to set with the same frequency in the required accuracy.
  • By the temperature of the melt 82 that the drops 83 come from the second variety, was selected to be 100 ° C higher than the temperature of the melt 72 from which the drops of the first kind 73 were produced, were the drops 83 much softer than the drops 73 , When applying the drops 83 The second variety was therefore the already completed part of the drop 73 the first sort of compound grid did not change. The one for the drops 83 Alloy used in the second grade can be used as a further degree of freedom to optimally fuse all drops 73 and 83 to achieve.
  • 4 shows by way of example the discretization of the shape of an object 6 in a model 42 from discrete elementary bodies 41a and 41b , The elementary bodies 41a that account for the largest share of the volume of the model 42 are cubes with an edge length d 3 . The elementary bodies 41b are triangular discs with a base d 5 , a height d 4 and an angle α in their tip. Its thickness is d 6 .
  • With the cube-shaped elementary bodies 41a can that portion 62 of the object 6 be modeled having only rectangular edges. The amount 63 with non-rectangular edges, on the other hand, with the elementary bodies 41b modeled in the form of triangular discs. It is each task of the control unit 5 , by suitably driving the print head unit 2 and the positioning unit 3 all elementary bodies 41a and 41b one after the other and thus the complete object 6 to realize. The speed can be further increased by, as in 4 indicated, each 18 cube-shaped elementary body 41a to a cuboid elementary body 41c be summarized. For producing such elementary body 41c can bigger drops 73 . 83 and therefore also nozzles 24 . 26 be used with a larger diameter, which is synonymous with a larger material throughput per unit time.
  • The transformation of the shape of the object 6 in a discrete elementary bodies 41 . 41a . 41b . 41c composite model 42 allows, in particular, an abstraction of 3D metal printing over different orders of magnitude of the objects 6 time. The orders of magnitude can range, for example, from 10 mm 3 to 100 mm 3 in dental technology, but from 0.1 dm 3 to 5 dm 3 in mechanical engineering. The user of the 3D printer 1 Regardless of the size class, it must always be elementary bodies 41 . 41a . 41b . 41c put together. It's all up to the control unit 5 like the elementary body 41 . 41a . 41b . 41c depending on the size class and required accuracy in detail by controlling the positioning unit 3 and the printhead unit 2 will be produced. For example, in the control unit 5 a statement, such as a cube with edge length 0.5 mm, 1 mm or 2 mm by layering matching drops 73 a first variety with interspersed drops 83 a second variety can best be realized. The 3D printer 1 can also have several differently sized printhead units 2 have, depending on the size classes of the object to be produced 6 be used.
  • Furthermore, several printhead units can also be used 2 be controlled simultaneously to further increase the material throughput per unit time.
  • 5a shows an embodiment of the printhead unit according to the invention 2 , especially for the production of cube-shaped elementary bodies 41 . 41a suitable is. The first drop generator 21 includes a regular grid 240 of 5 × 5 outlets 24 for the first melt 72 , The second drop generator 22 includes a regular grid 260 from 4 × 4 outlets 26 for the second melt 82 , The outlets 24 have a diameter of 100 microns, the outlets 26 have a diameter of 30 microns. Both grids 240 and 260 have a lattice constant d 7 of 200 μm in the horizontal direction and a lattice constant d 8 of likewise 200 μm in the vertical direction.
  • If initially all the outlets 24 of the grid 240 be controlled at the same time, so that they each have a drop 73 of the first starting material 71 emit, and then all outlets of the grid 260 be controlled at the same time, so that they each have a drop 83 of the second starting material 81 then an area of 1 μm 2 is substantially complete with the starting materials 71 and 81 busy. This condition is in 5b outlined. Because the second melt 82 has a higher temperature than the first melt 81 , becomes the second starting material 81 in the overlap area 91 between a drop 83 of the second starting material 81 and a previously applied drop 73 of the first starting material 71 in gaps 92 between these drops 83 and 73 pressed, leaving a closed layer without holes from the starting materials 71 and 81 arises. The production of such a layer takes, for example, with the "drop on demand" technique, in which each emission of a drop is individually excited, about 10 ms.
  • Be by alternately controlling the two drop generators 21 and 22 a total of five such layers stacked on top of each other is an elementary body (voxel) 41 . 41a essentially completely filled with a volume of 1 mm 3 .
  • QUOTES INCLUDE IN THE DESCRIPTION
  • This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.
  • Cited patent literature
    • US 5171360 A [0005]
    • US 5226948 A [0005]
    • WO 2001091524 A1 [0005]
    • WO 2001091525 A1 [0005]
  • Cited non-patent literature
    • Song Yi Zhong et al., Journal of Materials Processing Technology 214, 3089-3097 (2014) [0003]
    • M. Orme, EP Muntz, "New Techique for Producing Highly Uniform Droplet Streams to Extended Range of Disturbance Wave Numbers", Review of Scientific Instruments 58 (2), 279-284 (1987) [0004]
    • M. Orme, RF Smith, "Enhanced aluminum properties by precipitate droplet deposition", Journal of Manufacturing Science and Engineering - Transactions of the ASME 122 (3), 484-493 (2000) [0004]
    • Yan-pu Chao, Le-hua Qia et al., International Journal of Machine Tools and Manufacture 69, 38-47 (2013), "Remelting and bonding of deposited aluminum alloy droplets and substrate droplets in metal droplet deposition manufacture". [0004]

Claims (15)

  1. Printhead unit ( 2 ) for a 3D printer ( 1 ) for producing a three-dimensional object ( 6 ) comprising at least one first drop generator ( 21 ), which is used to split a first melt ( 72 ) of a first starting material ( 71 ) into individual drops ( 73 ) of a first type, these drops ( 73 ) of the first variety by addition in the liquid state of aggregation to the shape of the object ( 6 ) and then solidifying to the object ( 6 ), characterized in that at least one second drop generator ( 22 . 222 . 322 . 422 . 522 ) is provided, which for the division of a second melt ( 82 . 282 . 382 . 482 . 582 ) of a second starting material ( 81 . 281 . 381 . 481 . 581 ) into individual drops ( 83 . 283 . 383 . 483 . 583 ) of a second type, wherein the second drop generator ( 22 . 222 . 322 . 422 . 522 ) independent of the first drop generator ( 21 ) is controllable.
  2. Printhead unit ( 2 ) according to claim 1, characterized in that the second drop generator ( 22 . 222 . 322 . 422 . 522 ) for the production of drops ( 83 . 283 . 383 . 483 . 583 ) of a second kind, which are smaller than the drops ( 73 ) of the first kind.
  3. Printhead unit ( 2 ) according to claim 2, characterized in that the second drop generator ( 22 . 222 . 322 . 422 . 522 ) for the production of drops ( 83 , 283 . 383 . 483 . 583 ) of a second type which has a diameter of 25% to 45%, preferably of 30% to 45%, of the diameter d 1 of the drops ( 73 ) of the first variety.
  4. Printhead unit ( 2 ) according to one of claims 1 to 3, characterized in that the first drop generator ( 21 ) a first reservoir ( 23 ) for the first melt ( 72 ) with a nozzle designed as the first outlet ( 24 ) for the first melt ( 72 ) and that the second drop generator ( 22 . 222 . 322 . 422 . 522 ) a second reservoir ( 25 . 225 . 325 . 425 . 525 ) for the second melt ( 82 . 282 . 382 . 482 . 582 ) with a nozzle formed as a second outlet ( 26 . 226 . 326 . 426 . 526 ) for the second melt ( 82 . 282 . 382 . 482 . 582 ) having.
  5. Printhead unit ( 2 ) according to claim 4, characterized in that the first reservoir ( 23 ), and / or the second reservoir ( 25 . 225 . 325 . 425 . 525 ), on the first outlet ( 24 ) or the second outlet ( 26 . 226 . 326 . 426 . 526 ) facing away from the first melt ( 72 ) or the second melt ( 82 . 282 . 382 . 482 . 582 ) Medium ( 27 . 28 . 228 . 328 . 428 . 528 ) to be exposed to a gas pressure p.
  6. Printhead unit ( 2 ) according to one of claims 4 to 5, characterized in that the ejection directions ( 24a ) of the first outlet ( 24 ) and ( 26a ) of the second outlet ( 26 ) are aligned so that lines along these ejection directions ( 24a . 26a ) either intersect or pass at a distance equal to or less than the sum of the radius of a drop ( 73 ) of the first grade and the radius of a drop ( 83 ) of the second variety.
  7. Printhead unit ( 2 ) according to one of claims 1 to 6, characterized in that the first drop generator ( 21 ) a regular grid ( 240 ) of outlets ( 24 ) for the first melt ( 72 ) and that the second drop generator ( 22 ) a regular grid ( 260 ) of outlets ( 26 ) for the second melt ( 82 ), wherein the grids ( 240 . 260 ) are offset from each other and have the same lattice constants d 7 , d 8 .
  8. Method for operating a printhead unit ( 2 ) according to one of claims 1 to 7, characterized in that the second melt ( 82 . 282 . 382 . 482 . 582 ) is maintained at a higher temperature than the first melt ( 72 ).
  9. Method according to claim 8, characterized in that a metallic first starting material ( 71 ) and a metallic second starting material ( 81 ) and that the second melt ( 82 . 282 . 382 . 482 . 582 ) is maintained at a temperature at least 100 ° C higher than the first melt ( 72 ).
  10. Method according to one of claims 8 to 9, characterized in that aluminum or an aluminum alloy as the first starting material ( 71 ), and / or as a second starting material ( 81 . 281 . 381 . 481 . 581 ), is selected.
  11. Method for operating a printhead unit ( 2 ) according to one of claims 1 to 7, characterized in that the first drop generator ( 21 ) and the second drop generator ( 22 ) are controlled alternately.
  12. 3D printer ( 1 ) for producing a three-dimensional object ( 6 ) from a first starting material ( 71 ) and a second starting material ( 81 . 281 . 381 . 481 . 581 ), characterized in that the 3D printer ( 1 ) at least one printhead unit ( 2 ) according to one of claims 1 to 7, at least one positioning unit ( 3 ) for generating a relative movement between the printhead unit ( 2 ) and the object ( 6 ) and at least one control unit ( 5 ), which is the printhead unit ( 2 ) and / or the positioning unit ( 3 ).
  13. 3D printer according to claim 12, characterized in that at least one modeling unit ( 4 ) for transforming the shape of the object ( 6 ) into discrete elementary bodies ( 41 . 41a . 41b . 41c ) composite model ( 42 ) and that the control unit ( 5 ) is adapted to the printhead unit ( 2 ) and / or the positioning unit ( 3 ) for the production of discrete elementary bodies ( 41 . 41a . 41b . 41c ) of the model ( 42 ) head for.
  14. Method for operating a 3D printer ( 1 ) according to any one of claims 12 to 13, characterized in that cube-shaped or cuboid elementary bodies ( 41 . 41a . 41c ) to get voted.
  15. Method according to claim 14, characterized in that the model ( 42 ) from elementary bodies ( 41 . 41a . 41b . 41c ), which differ in their dimensions, and / or in their volumes.
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PCT/EP2016/060683 WO2017001100A2 (en) 2015-06-30 2016-05-12 3d printing with improved dimensional resolution and strength

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