Post-treatment procedure and post-treatment system

Description

[0001] The invention relates to a method for post-treatment of a three-dimensional object produced by selective layer-by-layer solidification of a powdered build-up material and / or of unsolidified build-up material in which the three-dimensional object is embedded, as well as to a corresponding post-treatment system.

[0002] Methods and devices for manufacturing a three-dimensional object by selectively solidifying a powdered build material layer by layer are used, for example, in rapid prototyping or additive manufacturing. One example of such a method is known as "selective laser sintering" or "selective laser melting." Another example is known as "multi-jet fusion." In this process, a thin layer of powdered build material is repeatedly applied, and the material is selectively solidified in each layer by selectively irradiating areas corresponding to a cross-section of the object to be manufactured with a laser.

[0003] Document WO 2009 / 141047 A1 describes a method for producing a three-dimensional object by selectively solidifying a powdered material at the points corresponding to the object's cross-section in the respective layer using electromagnetic radiation. The powder is a plastic powder. Unsolidified powder is treated with water or steam after the object has been produced and then reused to build a new object.

[0004] After the three-dimensional object has been manufactured, the three-dimensional object and the unsolidified build material in which the three-dimensional object is embedded are post-treated to cool the three-dimensional object and the unsolidified build material.

[0005] US patent 2010 / 0155985 A1 proposes passing a cooling fluid, for example nitrogen, through the powder cake containing the manufactured object in order to cool it.

[0006] US Patent 2014 / 283936 A1 describes a device for ejecting or retaining a liquid, comprising a liquid ejection or retention zone and a one-piece three-dimensional structure, referred to as a sponge, which includes a set of substantially wire-like elements or wire elements spaced apart from one another and extending between the circumferential zone and the liquid ejection or retention zone. The wire elements are substantially oriented in a flow direction of the liquid within the device. The liquid is retained by capillary action between the wire elements.

[0007] DE 10 2009 047 237 A1 describes a rinsing fluid for removing support material from a three-dimensional print, which includes support material and build material. The rinsing fluid consists of an aqueous solution of industrial cleaner.

[0008] US 2007 / 0241482 A1 describes the fabrication of three-dimensional objects by melting and solidifying portions of a powdered material. The removal of support material using a solvent is also described.

[0009] DE 693 33 169 T2 describes the removal of loose powder from the internal channels of a body produced using a layer-by-layer manufacturing technique. The body is placed in a liquid bath. Energy is applied to bring the liquid to a boil. The resulting fluid movement causes the powder to be expelled from the channels.

[0010] An object of the present invention is to provide an alternative and / or improved method or an alternative and / or improved system for post-treating a three-dimensional object produced by selective layer-by-layer solidification of a powdered building material and / or unsolidified building material in which the three-dimensional object is embedded.

[0011] This object is achieved by a method according to claim 1 and an aftertreatment system according to claim 14. The aftertreatment system according to the invention can also be further developed by features directed to the method according to the invention, which are listed further below in the description or in the subclaims. Conversely, the method according to the invention can also be further developed by features directed to the aftertreatment system according to the invention, which are listed further below in the description.

[0012] The inventiveThe method serves for post-treatment of an unsolidified build-up material in which a three-dimensional object produced by selective layer-by-layer solidification of a powdered build-up material is embedded, or of the three-dimensional object and the unsolidified build-up material in which the produced three-dimensional object is embedded, and comprises the steps of: treating the unsolidified build-up material or the produced three-dimensional object and the unsolidified build-up material with a liquid, and drying at least a part of the unsolidified build-up material treated with the liquid or of the three-dimensional object treated with the liquid and the unsolidified build-up material treated with the liquid, wherein the liquid (33) contains a liquid carrier substance and at least one further substance that reduces the surface tension of the carrier substance.

[0013] By using such a liquid, the liquid can migrate into the unsolidified build material; in other words, the liquid can penetrate the unsolidified build material more effectively and thus cool a larger surface area. This can, for example, accelerate the cooling of the three-dimensional object and / or the unsolidified build material.

[0014] The invention makes it possible, for example, to reduce or stop the degradation (aging) of the material of the manufactured three-dimensional object and / or the unsolidified building material, thereby improving the quality of the manufactured three-dimensional object and / or the reusability of the unsolidified building material.

[0015] Furthermore, the invention also makes it possible, for example, to improve the quality of the manufactured three-dimensional object, such as its dimensional accuracy and shape retention. In particular, uneven shrinkage and / or deformations that occur during slow cooling, e.g., due to an inhomogeneous temperature distribution in the cooling object, can be partially or completely avoided.

[0016] Furthermore, the invention also makes it possible, for example, to at least partially freeze the state of the three-dimensional object and / or the unsolidified build-up material prior to post-treatment, i.e., to subject the three-dimensional object and / or the unsolidified build-up material to quenching. Quenching is understood to mean a rapid or sudden cooling or quenching of an object or component and / or material.

[0017] Preferably, the additional substance is volatile, in particular more volatile than the carrier substance. This can, for example, simplify the evaporation of the liquid after treatment of the manufactured three-dimensional object and / or the unsolidified build-up material.

[0018] For example, the further substance contains a substance selected from the group consisting of acyclic aliphatic hydrocarbons and cyclic aliphatic hydrocarbons, which can be alkanes, alkenes and alkynes, aromatic hydrocarbons, halogenated hydrocarbons, alcohols, ketones, aldehydes, carboxylic acids, ethers and esters.

[0019] Preferably, the further substance is an alcohol, preferably an acyclic alcohol, more preferably an acyclic alcohol with a molecular formula CnH2n+2O with n = 1, 2, 3 or 4, and even more preferably ethanol. According to the inventors' experiments, this can, for example, have a particularly favorable effect on the cooling rate, the reusability of the unsolidified build material and / or the quality of the produced three-dimensional object.

[0020] Preferably, the concentration of the further substance in the liquid is at least 0.1% by weight, more preferably at least 0.5% by weight, more preferably at least 1% by weight, even more preferably at least 2.5% by weight, most preferably at least 5% by weight, and / or at most 45% by weight, more preferably at most 35% by weight, more preferably at most 25% by weight, even more preferably at most 15% by weight, most preferably at most 10% by weight. With such concentrations, the reaction can be carried out, for example, without further safety measures such as special explosion-proof devices. According to the inventors' experiments, the advantageous effects of the process according to the invention described above can be achieved in a particularly pronounced manner with such concentrations.

[0021] Preferably, the carrier substance contains water, wherein the concentration of water in the liquid is preferably at least 65% by weight, more preferably at least 75% by weight, even more preferably at least 85% by weight, and most preferably at least 90% by weight, and / or wherein the concentration of water in the liquid is preferably at most 99.5% by weight, more preferably at most 99% by weight, even more preferably at most 97.5% by weight, and most preferably at most 95% by weight. This choice of carrier substance and its concentration allows, for example, the cost of the liquid to be kept low and the positive effects of the process according to the invention described above to be realized in a particularly pronounced manner.

[0022] Preferably, the powdered building material contains at least one of the polymers from the group consisting of polyetherimides, polycarbonates, polyphenylsulfones, polyphenyl oxides, polyethersulfones, acrylonitrile butadiene styrene copolymers, polyacrylates, polyesters, polyamides, polyaryletherketones, polyethers, polyurethanes, polyimides, polyamideimides, polyolefins and copolymers which contain at least two different monomer units of the aforementioned polymers, and / or contains at least one polyblend based on at least two of the aforementioned polymers and copolymers, wherein the powdered building material preferably contains a polyamide, and more preferably contains a polyamide 12 (PA12).When using such a build-up material, the advantageous effects of the inventive method, in particular the stopping of the degradation of the material of the three-dimensional object and / or the unsolidified build-up material, can be particularly pronounced.

[0023] Preferably, the additional substance is a substance that has been used in the production of the powdered build-up material. This can, for example, prevent the unsolidified build-up material from being contaminated by the process according to the invention.

[0024] Preferably, the liquid has a temperature lower than the temperature of the manufactured three-dimensional object before post-treatment. This allows the three-dimensional object to be cooled by treatment with the liquid.

[0025] Preferably, the process is carried out such that at least a portion of the unsolidified build-up material has a temperature below the glass transition temperature of a polymer contained in the build-up material after post-treatment. This can, for example, minimize the aging effect of the powder.

[0026] Preferably, the process is carried out such that the manufactured three-dimensional object and / or the unsolidified build-up material has a temperature after post-treatment that is essentially at room temperature. For example, this makes it possible to subject the three-dimensional object or the unsolidified build-up material directly to further processing and / or treatment.

[0027] Preferably, the entire manufactured three-dimensional object, including its interior, is cooled to a temperature below the glass transition temperature of a polymer contained in the build material. This minimizes or completely prevents deformations of the three-dimensional object ("warping") that occur during cooling.

[0028] Preferably, treatment with the liquid is carried out by at least partially immersing the three-dimensional object and / or the unsolidified build-up material in the liquid. In this way, for example, close contact between the liquid and the three-dimensional object or the unsolidified build-up material can be quickly established, including penetration of the object or the unsolidified build-up material by the liquid. Treatment with the liquid can also be carried out by pouring the liquid over the three-dimensional object and / or the unsolidified build-up material. Preferably, the three-dimensional object and / or the unsolidified build-up material is placed in or above a container, for example, a tub. In this way, the liquid can be collected and, for example, stored for later processing and / or reuse.

[0029] When immersing the three-dimensional object and / or the unconsolidated building material, a force is particularly preferably exerted on the three-dimensional object and / or the unconsolidated building material that opposes the buoyancy force acting on the three-dimensional object and / or the unconsolidated building material. For example, it is possible to immerse a three-dimensional object and / or unconsolidated building material with a specific gravity that is less than the specific gravity of the liquid into the liquid.

[0030] Preferably, the unsolidified build-up material, particularly unsolidified build-up material located in channels and / or cavities of the three-dimensional object, is detached from the three-dimensional object, wherein the three-dimensional object and / or the unsolidified build-up material are treated with ultrasound and / or infrasound and / or with at least one jet, in particular with at least one jet of the liquid, and / or wherein at least the liquid is set in motion, in particular shaken and / or stirred and / or agitated. This allows, for example, the manufactured three-dimensional object and the unsolidified build-up material to be completely and particularly effectively separated from one another.

[0031] According to the invention, at least a portion of the unsolidified building material and / or the three-dimensional object is dried, preferably by evaporation or volatilization of the liquid and / or preferably by means of a centrifuge and / or by means of a gas stream and / or by means of a heater. The drying process can also be accelerated by other aids such as the use of drying agents like silica gel, zeolites, and / or sodium sulfate. Other suitable drying agents are known to those skilled in the art. A dried three-dimensional object or dried unsolidified building material can, for example, be directly subjected to further processing or machining.

[0032] Preferably, the post-treatment is carried out in at least two consecutive post-treatment steps, with at least one post-treatment step being carried out using another liquid. By treating the three-dimensional object and / or the unconsolidated building material with different liquids, the advantageous effects of the method according to the invention described above can be enhanced, for example, and / or several of these effects can be combined.

[0033] The additional liquid can, for example, be a mixture of several substances, in particular a solution, for example a solution of water and ethanol, or a pure substance, for example water.

[0034] Preferably, the post-treatment is carried out in at least two successive steps, with at least one step including waiting for a predetermined pause. By waiting for a pause, preferably as the first post-treatment step after layer-by-layer selective hardening, the manufactured three-dimensional object can, for example, be cooled to a temperature from which it can be cooled further during subsequent treatment with a liquid in such a way that no cracks and / or deformations form in the three-dimensional object.

[0035] Preferably, the post-treatment is carried out in at least two consecutive post-treatment steps, so that at least a portion of the unconsolidated build material after the first of the post-treatment steps has a temperature below the glass transition temperature of a polymer contained in the build material. In this way, for example, aging effects of the unconsolidated build material can be minimized or completely avoided. A liquid used in a subsequent treatment step can differ, for example, in terms of its composition and / or temperature from the liquid used in the first post-treatment step.

[0036] Preferably, the build-up material used to manufacture the three-dimensional object contains at least a proportion of recycled powder that was previously left over as unsolidified build-up material during the manufacture of a three-dimensional object. The proportion of recycled powder is preferably at least 20% by weight, more preferably at least 40% by weight, even more preferably at least 60% by weight, and particularly preferably at least 80% by weight. The use of recycled powder allows, for example, the consumption of build-up material to be reduced in an economically and ecologically sound manner.

[0037] Preferably, the liquid is at least partially regenerated after post-treatment, in particular by sedimentation and / or filtration to remove unsolidified build-up material. This can, for example, reduce the consumption of carrier liquid and / or the consumption of at least one other substance in an economically and ecologically advantageous manner.

[0038] The inventiveA post-treatment system for post-treating an unsolidified build-up material into which a three-dimensional object produced by selective layer-by-layer solidification of a powdered build-up material is embedded, or of the three-dimensional object and the unsolidified build-up material into which the produced three-dimensional object is embedded, comprises a post-treatment device in which the unsolidified build-up material or the produced three-dimensional object and the unsolidified build-up material are treated with a liquid during operation, a supply arrangement for supplying the liquid in such a way that it contains a liquid carrier substance and at least one further substance that reduces the surface tension of the carrier substance, and a drying device for drying at least a part of the unsolidified build-up material treated with the liquid.of the three-dimensional object treated with the liquid and of the unsolidified building material treated with the liquid.

[0039] The corresponding post-treatment device preferably comprises a post-treatment container for receiving the three-dimensional object and / or the unsolidified build-up material and for supplying liquid, wherein the post-treatment container is preferably at least temporarily permeable to the liquid, and more preferably has areas in its base that are at least temporarily permeable to the liquid. Such a device, for example, provides a device with which the method according to the invention can be carried out.

[0040] The corresponding supply arrangement for supplying the liquid can comprise a mixing device (for example a mixer tap in which the liquid carrier substance and the at least one further substance are led from two separate lines into a common forwarding line and mix in the forwarding line and / or an intermediate mixing container in which the liquid carrier substance and the at least one further substance are introduced for the purpose of mixing and mixed there) or can comprise a single container (such as a tank) in which the liquid carrier substance and the at least one further substance are already present in a mixed state and can thus be provided directly at any time. Furthermore, the supply arrangement preferably comprises a feed line for the liquid into the aftertreatment device.

[0041] With the aid of the post-treatment system according to the invention, the process according to the invention can be carried out in a straightforward and controlled manner, whereby in principle both a ready-made liquid mixture (i.e. the liquid in the sense of the invention - also in the following) and a liquid mixture produced by the post-treatment system itself can be provided.

[0042] The surface tension of a liquid is measured according to DIN 55660. Typical values ​​for the surface tension of various liquids at a temperature of 20°C are given in Table 1. Table 1 Material Surface tension (N / m) Water 0,0728 benzene 0,0289 Glycerin 0,0634 Glycol 0,0477 Methanol 0,0226 Ethanol 0,02255 acetone 0,02330 benzene 0,0289 Ethylene glycol 0,0484 n-pentane 0,0160 n-hexane 0,0184 H 2 SO 4 (98.5%) 0,0551

[0043] In the context of the invention, a volatile, i.e., rapidly evaporating, substance is understood to be a substance with a low evaporation number VD, in particular with a VD < 80. The evaporation number is measured according to DIN 53170.

[0044] A first substance is more volatile than a second substance if the first substance has a lower evaporation rate than the second substance.

[0045] The terms "substance" and "carrier substance" can each refer to a pure substance, for example a chemical compound, as well as a mixture of substances, for example a solution.

[0046] Features and advantages of the invention will become apparent from the description of exemplary embodiments with reference to the accompanying drawings. Fig. 1 is a schematic, partially sectioned view of an apparatus for producing a three-dimensional object by selectively solidifying a powdered building material layer by layer. Fig. 2 is a schematic, sectioned view of a post-treatment apparatus for a post-treatment system according to an embodiment of the present invention. Fig. 3 is a schematic flow block diagram of an embodiment of the method according to the invention within the overall framework of producing a three-dimensional object.

[0047] Several embodiments of the present invention are described below with reference to the drawings.

[0048] The Fig. 1 The device shown according to an exemplary embodiment is a laser sintering or laser melting device 1. For the production of an object 2, it contains a process chamber 3 with a chamber wall 4.

[0049] In the process chamber 3, an upwardly open construction container 5 with a construction container wall 6 is arranged. A working plane 7 is defined by the upper opening of the construction container 5, wherein the area of ​​the working plane 7 lying within the opening, which can be used for the construction of the object 2, is referred to as the construction area 8.

[0050] Inside the construction container 5, a support 10, movable in a vertical direction V, is arranged. A base plate 11 is attached to the support plate, forming the bottom of the construction container 5. The base plate 11 can be a separate plate attached to the support 10, or it can be integral with the support 10. Depending on the construction material and process used, a construction platform 12 can be attached to the base plate 11 as a base on which the object 2 is built. Alternatively, the object 2 can be built directly on the base plate 11, which then serves as the base. Fig. 1 The object 2 to be formed in the construction container 5 on the construction platform 12 is shown below the working level 7 in an intermediate state with several solidified layers surrounded by the unsolidified building material 13.

[0051] The construction container 5 can be designed as an interchangeable container, which can be removed from the device 1 for producing a three-dimensional object and can be used as a post-treatment container in a post-treatment device to be described in more detail below.

[0052] The laser sintering device 1 further comprises a storage container 14 for a powdered build material 15 that can be solidified by electromagnetic radiation and a coater 16 movable in a horizontal direction H for applying the build material 15 within the build area 8. Preferably, the coater 16 extends transversely to its direction of movement over the entire area to be coated.

[0053] Optionally, a radiant heater 17 is arranged in the process chamber 3, which serves to heat the applied build-up material 15. For example, an infrared radiator can be provided as the radiant heater 17.

[0054] The laser sintering device 1 further includes an exposure device 20 with a laser 21 which generates a laser beam 22 which is deflected via a deflecting device 23 and focused by a focusing device 24 via a coupling window 25 which is attached to the top of the process chamber 3 in the chamber wall 4 onto the working plane 7.

[0055] Furthermore, the laser sintering device 1 includes a control unit 29, which coordinates the operation of the individual components of the device 1 to carry out the process for producing a three-dimensional object 2. Alternatively, the control unit 29 can also be located partially or completely outside the device 1. The control unit 29 can contain a CPU, the operation of which is controlled by a computer program (software). The computer program can be stored separately from the device 1 on a storage medium, from which it can be loaded into the device 1, in particular into the control unit 29.

[0056] In operation, to apply a layer of the powdered build-up material (powder layer), the carrier 10 is first lowered to a height corresponding to the desired layer thickness. The coater 16 moves to the storage container 14 and takes from it a quantity of the build-up material 15 sufficient to apply at least one layer. It then moves over the build area 8 and applies a thin layer of the powdered build-up material 15 to the build substrate or to a previously existing powder layer. The application takes place at least over the entire cross-section of the object 2 to be produced, preferably over the entire build area 8, i.e., the area of ​​the working plane 7 bounded by the build container wall 6. Optionally, the powdered build-up material 15 is heated to a working temperature by means of a radiant heater 17.

[0057] Subsequently, the cross-section of the object 2 to be produced is scanned by the laser beam 22, so that the powdered building material 15 is solidified at the locations corresponding to the cross-section of the object 2 to be produced. Powder particles at these locations are partially or completely melted by the energy introduced by the radiation, so that after cooling, they are bonded together as a solid.

[0058] These steps are repeated until object 2 is completed.

[0059] Subsequently, the manufactured three-dimensional object 2 and / or the unconsolidated build material 13 in which the three-dimensional object is embedded are post-treated. The post-treatment preferably takes place outside the process chamber 3. This allows the process chamber to be available for the production of another three-dimensional object during the post-treatment.

[0060] In Fig. 2 A post-treatment device 30 is schematically shown as a component of a post-treatment system according to an embodiment of the present invention. Other components of the post-treatment system according to the invention are shown in the Fig. 2 Not shown for clarity – reference is made to the preceding description with corresponding examples. The post-treatment device 30 comprises a post-treatment container 31, which is designed to hold the three-dimensional object 2 and the unsolidified build-up material 13 in which the three-dimensional object 2 is embedded.

[0061] The post-treatment device 30 further comprises an upwardly open liquid container 32 which can be filled with a liquid 33 and which is designed in such a way that it can at least partially accommodate the post-treatment container 31 inside it, so that the post-treatment container 31 can be at least partially immersed in the liquid 33 with which the liquid container 32 is filled.

[0062] In one embodiment, the post-treatment container 31 is the build container 5, which can be removed as an interchangeable container from the laser sintering device 1 and immersed in the liquid container 32. Optionally, the build container 5 can be provided with a liquid-permeable lid.

[0063] Alternatively, the aftertreatment tank 31 can have an at least partially fluid-permeable (i.e., permeable to a fluid, i.e., a gas and / or a liquid) bottom and / or an at least partially fluid-permeable lid. Alternatively or additionally, the aftertreatment tank 31 can be designed to be at least partially fluid-permeable in the region of its side wall.

[0064] In the Fig. 2 In the operating state shown, the aftertreatment tank 31 is located inside the liquid tank 32. The aftertreatment tank 31 is immersed in the liquid 33. A portion of the liquid 33 is located inside the aftertreatment tank 31.

[0065] In one embodiment of the method for post-treatment, the three-dimensional object 2 and the unconsolidated building material 13 surrounding the three-dimensional object 2 are treated in the post-treatment device 30 according to the method described in Fig. 2The aftertreatment is carried out in accordance with the schematically illustrated and described embodiment. For this purpose, the aftertreatment container 31 is immersed in the liquid 33 located in the liquid container 32.

[0066] When the post-treatment container 31 is immersed in the liquid 33, the liquid 33 penetrates into the interior of the post-treatment container 31 and comes into contact with the three-dimensional object 2 and / or the unsolidified building material 13, i.e., the three-dimensional object 2 and / or the unsolidified building material 13 are treated with the liquid 33. It is preferred that the liquid 33 completely penetrates the powder bed formed by the unsolidified building material 13, so that all areas of the powder bed come into contact with the liquid 33 and no dry areas remain. It is further preferred that the liquid 33 essentially completely wets the unsolidified building material.

[0067] When the aftertreatment tank 31 is immersed in the liquid 33, a force can be exerted on the aftertreatment tank 31 that is opposite to the buoyancy force of the liquid 33.

[0068] The liquid used to treat the three-dimensional object 2 and / or unsolidified building material 13 contains a liquid carrier substance and at least one further substance that reduces the surface tension of the carrier substance.

[0069] The carrier substance and the at least one further substance are selected, among other things, with regard to the compatibility of these substances with one another and with the powdered building material. Preferably, the carrier substance and the further substance are coordinated with one another in such a way that, after drying of the three-dimensional object 2 and / or the unsolidified building material 13, no residues remain on the three-dimensional object 2 and / or the unsolidified building material that could lead to a material combination that is incompatible with further use and / or contamination. As the further substance, in particular, a substance that has been used in the production of the powdered building material is used. For example, powdered PA12 is produced using ethanol.For example, in the case of a powdered construction material containing PA12, the choice of ethanol as an additional substance has proven to be suitable, especially when water is used as a carrier substance.

[0070] The concentration of the additional substance in the liquid is selected, among other things, with a view to reducing the surface tension of the carrier substance to improve wetting of the unconsolidated and / or solidified building material. A concentration of at least 0.1 weight percent, preferably at least 0.5 weight percent, more preferably at least 1 weight percent, even more preferably at least 2.5 weight percent, and most preferably at least 5 weight percent, has proven suitable. A concentration of at most 45 weight percent, preferably at most 35 weight percent, more preferably at most 25 weight percent, even more preferably at most 15 weight percent, and most preferably at most 10 weight percent, has also proven suitable.

[0071] A suitable concentration of the carrier substance in the liquid has proven to be, for example, a concentration of at least 65 weight percent, preferably at least 75 weight percent, more preferably at least 85 weight percent, and particularly preferably at least 90 weight percent. A suitable concentration of the carrier substance in the liquid has also proven to be, for example, a concentration of at most 99.5 weight percent, preferably at most 99 weight percent, more preferably at most 97.5 weight percent, and particularly preferably at most 95 weight percent.

[0072] The liquid with which the three-dimensional object 2 and / or the unsolidified building material 13 are treated may contain several other substances in addition to the carrier substance.

[0073] In one embodiment of the post-treatment method, water is used as the carrier substance. To avoid contamination of the three-dimensional object 2 and / or the unconsolidated building material 13 by substances (e.g., lime) contained in spring or tap water in addition to H2O, purified water can be used. Purified water can be, for example, distilled, deionized, demineralized, or ultrapure water.

[0074] In this embodiment, the liquid with which the manufactured three-dimensional object 2 and / or the unconsolidated building material 13 are treated contains ethanol as an additional substance. The addition of ethanol reduces the surface tension of the carrier substance, water. This improves the wetting of the unconsolidated and / or solidified building material with the carrier substance.

[0075] In a specific example, the ethanol concentration of the aqueous ethanol solution used as liquid 33 for post-treating a three-dimensional object 2 and unconsolidated building material 13 is 5 weight percent. A powdered building material 15 containing PA12 was used to produce the dimensional object 2, with ethanol being used in particular in the production of the PA12. The liquid 33 penetrates the unconsolidated building material 13 even when it forms a highly compressed powder bed.

[0076] Alternatively or in addition to ethanol, the liquid can also contain at least one substance other than ethanol that reduces the surface tension of the carrier substance as a further substance. The at least one substance other than ethanol can, for example, be an organic compound, for example a compound selected from the group consisting of the following compounds: acyclic and cyclic aliphatic hydrocarbons, which can each be alkanes, alkenes and alkynes, aromatic hydrocarbons, halogenated hydrocarbons, alcohols (in particular acyclic alcohols such as methanol, n-propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol), ketones, aldehydes, carboxylic acids, ethers and esters. The substance other than ethanol can also be a surfactant, for example sodium dodecyl sulfate.The use of volatile compounds, in particular volatile organic compounds, has proven advantageous since they can be removed from the three-dimensional object 2 or the unsolidified building material 13 by evaporation in a simple manner and without leaving residues.

[0077] In one embodiment of the method for post-treatment, the liquid 33 has a temperature before post-treatment that is lower than the temperature of the produced three-dimensional object 2, so that the three-dimensional object 2 is cooled during post-treatment. For example, the three-dimensional object 2 and / or the unsolidified building material are cooled to a temperature that essentially corresponds to room temperature. To reduce the occurrence of aging effects in the unsolidified building material 13, at least a portion of the unsolidified building material 13 can be cooled during post-treatment to a temperature that is below the glass transition temperature of a polymer contained in the building material.In order to minimize or prevent deformations of the three-dimensional object 2 occurring during cooling, the entire three-dimensional object, including its interior, can be cooled to a temperature below the glass transition temperature of a polymer contained in the building material.

[0078] In one embodiment of the method for post-treatment, the treatment of the three-dimensional object 2 and / or the unsolidified building material 13 with a liquid 33 is carried out in that the three-dimensional object 2 and / or the unsolidified building material 13 are introduced together with the liquid 33 into a post-treatment container designed, for example, as a drum and the post-treatment container executes a rotational movement in order to establish intimate contact between the liquid and the three-dimensional object 2 or the unsolidified building material.

[0079] In a further embodiment, the liquid is brought into contact with the three-dimensional object 2 and / or the unsolidified building material 13 in the form of one or more jets directed onto the three-dimensional object 2 and / or the unsolidified building material 13 in order to treat the three-dimensional object or the unsolidified building material 13.

[0080] In a further embodiment, a container, in the interior of which the three-dimensional object 2 and / or the unsolidified building material 13 are located, is at least partially filled with the liquid by introducing the liquid in order to treat the three-dimensional object 2 or the unsolidified building material 13.

[0081] In a further embodiment, the liquid is transported through a container containing the three-dimensional object and / or the unconsolidated building material 13. The liquid can be circulated, for example, by means of a pump, and it is possible for a station for processing and / or cleaning the liquid to be arranged in the circuit.

[0082] In a further exemplary embodiment, the post-treatment takes place in at least two consecutive post-treatment steps, wherein at least one post-treatment step is carried out using a further liquid. The further liquid can be, for example, a mixture of several substances, in particular a solution, or a pure substance, for example water. The liquids used in different post-treatment steps can differ from one another, for example, in terms of their composition and / or their temperature. It is thus possible for the three-dimensional object 2 and / or the unsolidified building material 13 to be treated in one of the post-treatment steps with a liquid which has a different concentration of the further substance than the liquid used in a previous post-treatment step.For example, to accelerate drying by evaporation, the three-dimensional object and / or the unsolidified building material can be treated in a second post-treatment step with a liquid that is more volatile and / or has a higher content of the more volatile component than the liquid used in the first post-treatment step.

[0083] In a further embodiment, the post-treatment is carried out in at least two consecutive post-treatment steps, with at least one post-treatment step comprising waiting for a predetermined pause. This makes it possible, for example, for the manufactured three-dimensional object to be cooled to a temperature in a first post-treatment step, from which it is cooled with a liquid in a subsequent post-treatment step in such a way that cracks and / or deformations do not form in the three-dimensional object.

[0084] In a further embodiment, the post-treatment is carried out in at least two consecutive post-treatment steps, so that at least a portion of the unconsolidated build material after the first of the post-treatment steps has a temperature below the glass transition temperature of a polymer contained in the build material. In this way, for example, aging effects of the unconsolidated build material can be minimized or completely avoided.

[0085] Mechanical forces can be used to separate the manufactured three-dimensional object 2 and the unsolidified building material 13, which has been slurried by the treatment with the liquid. In particular, the separation takes place after and / or in combination with the treatment with the liquid 33.

[0086] In a further embodiment of the post-treatment method, one or more jets of the liquid are used to remove unsolidified building material 13 from the three-dimensional object 2, in particular to flush unsolidified building material 13 out of channels and / or cavities of the three-dimensional object 2.

[0087] Alternatively or additionally, the three-dimensional object and / or the unsolidified build-up material and / or the liquid 33 can be set in motion to facilitate separation. The movement can be, for example, a shaking movement and / or a rocking movement and / or a pivoting movement and / or a stirring movement.

[0088] The aftertreatment device 30 may, for example, include a vibrating plate on which the aftertreatment container is arranged for generating a vibrating movement.

[0089] Alternatively or additionally, the post-treatment device 30 may contain a gripper that grips the post-treatment container and / or the three-dimensional object 2 and sets it in motion, for example pivots it back and forth.

[0090] Alternatively or additionally, the post-treatment device 30 may contain a stirring device for generating a stirring motion. A magnetic stirrer, for example, may be used as the stirring device.

[0091] In a further embodiment of the post-treatment method, the three-dimensional object 2 and / or the unconsolidated building material 13 are treated with pressure waves, preferably with acoustic waves or sound waves, in particular with ultrasound and / or infrasound, in order to facilitate the separation of the unconsolidated building material 13 from the three-dimensional object 2.

[0092] The post-treatment device can, for example, contain one or more ultrasonic transducers for generating ultrasound. The ultrasonic transducer can, for example, be attached to the wall of the post-treatment tank. Alternatively or additionally, it is also possible to at least partially immerse the post-treatment tank in an ultrasonic bath equipped with an ultrasonic transducer.

[0093] Alternatively or additionally, the aftertreatment device may contain one or more infrasound generators for generating infrasound.

[0094] After treating the three-dimensional object 2 and / or the unconsolidated building material 13, the three-dimensional object 2 and / or the unconsolidated building material 13 is dried.

[0095] Drying can be achieved, for example, by evaporating the liquid. To accelerate drying, drying can be carried out at elevated temperature and / or reduced pressure. For example, evaporation can be carried out in a condenser dryer, a vacuum or low-pressure dryer, or a rotary evaporator. To accelerate drying of the unsolidified build material, it can also be distributed or spread out so that a larger accessible surface is available, allowing the liquid to evaporate more quickly. The three-dimensional objects can be dried packed or stacked. To accelerate drying of the components, they can be stored individually or separately, i.e., they can be stored as unobstructed as possible with air or gas flowing around them, so that the smallest possible surface area is in contact with other surfaces, e.g. support surfaces or holding surfaces of a holding device.

[0096] Drying can also be carried out with the aid of a gas stream that flows against or through the three-dimensional object 2 and / or the unsolidified building material 13. The gas stream is preferably formed from a protective or inert gas, in particular nitrogen, or air, in particular dry air. The gas stream is preferably formed from a heated gas, the temperature of which is in particular selected to be higher than the current temperature of the object 2 or the unsolidified building material 13 and / or lower than the temperature that would lead to aging phenomena in the object 2 or the unsolidified building material 13. Aging phenomena are understood here to be heat-induced effects of the building material inside or outside the object, which essentially only occur beyond a material-dependent limit temperature. In other words, the temperature of the heated gas should preferably be below this material-dependent limit temperature.

[0097] For heating the three-dimensional object 2 and / or the unsolidified building material, for example, convection heaters (such as a circulating air oven), radiant heaters (such as an IR radiator), contact heaters (such as a heat plate) or other heaters can be used.

[0098] If drying takes place at elevated temperature, the temperature is selected in particular such that essentially no degradation effects occur in the three-dimensional object 2 and / or the unconsolidated building material 13 as a result of the elevated temperature. When using a building material 15 containing PA12, a temperature higher than room temperature, not exceeding 80°C, has proven suitable.

[0099] Drying, in particular drying the unconsolidated building material 13, using a centrifuge is also possible. Centrifugation is therefore also considered drying within the scope of the invention.

[0100] The drying methods mentioned can be combined with each other as far as possible.

[0101] In order to at least partially recover the liquid or the carrier substance and / or the at least one further substance, the liquid separated from the three-dimensional object 2 or the unsolidified building material 13 can be collected, possibly after condensation of vapors produced by evaporation of the liquid.

[0102] Before reuse, the recovered liquid or the recovered carrier substance and / or the recovered at least one other substance can be regenerated and / or purified. Purification of the recovered liquid can be achieved, for example, by sieving, centrifuging, filtering, evaporating the more volatile component, distilling, or using a hydrocyclone.

[0103] The features of the embodiments described above can, as far as possible, be combined and modified with one another.

[0104] Although the production of a three-dimensional object by laser sintering or laser melting was described above, the invention is not limited to the post-treatment of a three-dimensional object produced by laser sintering or laser melting and the unconsolidated build material in which such a three-dimensional object is embedded after its production. The invention can be applied to the post-treatment of three-dimensional objects produced by any generative manufacturing method or to corresponding build materials.

[0105] The exposure device can, for example, comprise one or more gas or solid-state lasers or any other type of laser, such as laser diodes, in particular VCSELs (Vertical Cavity Surface Emitting Lasers) or VECSELs (Vertical External Cavity Surface Emitting Lasers), or a line of these lasers. In general, any device with which energy can be applied selectively to a layer of the build material as wave or particle radiation can be used as the exposure device. Instead of a laser, for example, another light source, an electron beam, or any other energy or radiation source suitable for solidifying the build material can be used. Instead of deflecting a beam, exposure with a movable line exposure device can also be used.The invention can also be applied to selective mask sintering, in which an extended light source and a mask are used, or to high-speed sintering (HSS), in which a material is selectively applied to the build-up material that increases (absorption sintering) or reduces (inhibition sintering) the radiation absorption at the corresponding locations, and is then exposed non-selectively over a large area or with a movable line exposure unit.

[0106] Various materials can be used as the powdered building material, preferably plastic powder, metal powder, ceramic powder, sand, filled, or mixed powders. The powdered building material can, for example, contain at least one of the polymers selected from the group consisting of the following polymers: polyetherimides, polycarbonates, polyphenylsulfones, polyphenyl oxides, polyethersulfones, acrylonitrile-butadiene-styrene copolymers, polyacrylates, polyesters, polyamides, polyaryletherketones, polyethers, polyurethanes, polyimides, polyamideimides, polyolefins, and copolymers containing at least two different monomer units of the aforementioned polymers. The powdered building material can additionally or alternatively contain at least one polyblend based on at least two of the aforementioned polymers and copolymers.

[0107] Fig. 3shows a schematic of the sequence of a method according to the invention. In a first step A (a preliminary step to the actual method according to the invention), a three-dimensional object 2 is produced by selectively solidifying a powdered building material 15 layer by layer. In a second step B, a liquid 33 is provided which contains a liquid carrier substance and at least one further substance which reduces the surface tension of the carrier substance. In a step C (of the method according to the invention), the three-dimensional object 2 or the unsolidified building material 13 is post-treated with this liquid. In an optional step D, the three-dimensional object 2 or the unsolidified building material 13 is dried.

Claims

1. A method of post-treating an unsolidified building material (13), in which a three-dimensional object (2) produced by selectively layer-wise solidifying a pulverulent building material (15) is embedded, or of the three-dimensional object (2) and the unsolidified building material (13), in which the manufactured three-dimensional object (2) is embedded, comprising the steps of: - treating the unsolidified building material or the manufactured three-dimensional object (2) and the unsolidified building material (13) with a liquid (33), and - drying at least a part of the unsolidified building material treated with the liquid, or of the three-dimensional object treated with the liquid and of the unsolidified building material treated with the liquid, wherein the liquid (33) comprises a liquid carrier substance and at least one further substance which reduces the surface tension of the carrier substance.

2. The method according to claim 1, wherein the further substance is volatile, in particular more volatile than the carrier substance.

3. The method according to one of the preceding claims, wherein the further substance is an alcohol, preferably an acyclic alcohol, more preferably an acyclic alcohol having a molecular formula CnH2n+2O with n = 1, 2, 3 or 4, even more preferably ethanol.

4. The method according to one of the preceding claims, wherein the concentration of the further substance in the liquid is at least 0.1 percent by weight, preferably at least 0.5 percent by weight, more preferably at least 1 percent by weight, still more preferably at least 2.5 percent by weight, most preferably at least 5 percent by weight, and / or wherein the concentration of the further substance in the liquid is at most 45 percent by weight, preferably at most 35 percent by weight, more preferably at most 25 percent by weight, still more preferably at most 15 percent by weight, most preferably at most 10 percent by weight.

5. The method according to one of the preceding claims, wherein the carrier substance comprises water, wherein preferably the concentration of water in the liquid is at least 65 percent by weight, more preferably at least 75 percent by weight, still more preferably at least 85 percent by weight, most preferably at least 90 percent by weight, and / or wherein preferably the concentration of water in the liquid is at most 99.5 percent by weight, more preferably at most 99 percent by weight, still more preferably at most 97.5 percent by weight, most preferably at most 95 percent by weight.

6. The method according to one of the preceding claims, wherein the pulverulent building material (15) comprises at least one of the polymers selected from the group consisting of polyetherimides, polycarbonates, polyphenylene sulfones, polyphenylene oxides, polyether sulfones, acrylonitrile-butadiene-styrene copolymers, polyacrylates, polyesters, polyamides, polyaryl ether ketones, polyethers, polyurethanes, polyimides, polyamide-imides, polyolefins and copolymers which contain at least two different monomer units of the aforementioned polymers, and / or at least one polyblend based on at least two of the aforementioned polymers and copolymers, wherein the pulverulent building material preferably contains a polyamide, wherein the pulverulent building material more preferably contains a PA12.

7. The method according to claim 6, wherein the further substance is a substance that was used in the production of the pulverulent building material (15).

8. The method according to one of the preceding claims, wherein the treatment with the liquid (33) is carried out by at least partially immersing the unsolidified building material (13) in the liquid (33) or by at least partially immersing the three-dimensional object (2) and the unsolidified building material (13) in the liquid (33), wherein, in particular, a force is exerted on the unsolidified building material (13) or on the three-dimensional object (2) and the unsolidified building material (13), which force is directed opposite to the buoyancy force acting on the unsolidified building material (13) or on the three-dimensional object (2) and the unsolidified building material (13).

9. The method according to one of the preceding claims, wherein the unsolidified building material (13), in particular unsolidified building material (13) located in channels and / or cavities of the three-dimensional object, is detached from the three-dimensional object (2), wherein the unsolidified building material (13) is treated with ultrasound and / or infrasound and / or with a jet, in particular with a jet of the liquid (33), or the three-dimensional object (2) and the unsolidified building material (13) are treated with ultrasound and / or infrasound and / or with a jet, in particular with a jet of the liquid (33), and / or wherein at least the liquid (33) is set in motion, in particular shaken and / or stirred and / or swiveled.

10. The method according to one of the preceding claims, wherein the drying is implemented by means of a centrifuge and / or by means of a gas flow and / or by means of a heater.

11. The method according to one of the preceding claims, wherein the post-treatment is carried out in at least two post-treatment steps carried out in succession, and wherein at least one post-treatment step is carried out with the aid of a further liquid.

12. The method according to one of the preceding claims, wherein the post-treatment is carried out in at least two post-treatment steps carried out in succession, and wherein at least one post-treatment step comprises waiting for a predetermined resting time.

13. The method according to one of the preceding claims, wherein the liquid (33) is at least partially regenerated after the post-treatment, in particular is cleared by sedimentation and / or filtration of unsolidified building material (13).

14. A post-treatment system for post-treating an unsolidified building material (13) in which a three-dimensional object (2) is embedded that is produced by selectively layer-wise solidifying a pulverulent building material (15), or of the three-dimensional object (2) and the unsolidified building material (13) in which the manufactured three-dimensional object (2) is embedded, comprising a post-treatment device (30) in which the unsolidified building material (13) or the manufactured three-dimensional object (2) and the unsolidified building material (13) are treated with a liquid (33) during operation, a provisioning assembly for providing the liquid (33) in such a way that it contains a liquid carrier substance and at least one further substance which reduces the surface tension of the carrier substance, and a drying device for drying at least a part of the unsolidified building material treated with the liquid or of the three-dimensional object treated with the liquid and the unsolidified building material treated with the liquid.