ES2362999T3 - PROCEDURE AND DEVICE FOR THE MANUFACTURE OF THREE-DIMENSIONAL OBJECTS BY RADIATION OF MICROWAVES AND MOLDED BODIES SO OBTAINED. - Google Patents

Abstract

The present invention relates to a process for bonding material to produce three-dimensional objects by means of selective heating via microwave radiation. Unlike selective laser sintering, the present process for producing three-dimensional objects uses the type of simple microwave radiation available in any household. The selectivity of heating is achieved by applying a susceptor to certain subregions of a layer composed of a pulverulent substrate, and then heating the susceptor by means of microwave radiation. The heated susceptor transfers the energy present therein to a pulverulent substrate surrounding the susceptor, and the substrate is thereby melted, giving firm bonding within the substrate after cooling.

Description

The invention relates to a process for the manufacture of three-dimensional objects from a substrate in powder form by means of union p. ex. by fusion or sintering of parts of the substrate, where the heat energy necessary for the substrate binding is generated by microwave radiation through a susceptor and is delivered to the partial areas of the substrate through it.

The fluid provision of prototypes is a mission often established in recent times. In the known state of the art, the method of stereolithography is described, on the one hand, having the disadvantage that complex support structures and prototypes are necessary during the manufacture of prototypes from a liquid (resin). obtained have relatively bad mechanical properties, which must be attributed to the limited number of raw materials.

The other procedure often mentioned in the known state of the art, which is well suited for the purpose of rapid prototyping, is selective laser sintering (SSL) that has already found widespread diffusion. In the case of this procedure, synthetic material powders are briefly illuminated in a chamber selectively with a laser beam, thereby melting the dust particles that are reached by the laser beam. The molten particles mix together and consolidate relatively quickly again to form a solid mass. By repeated illumination of layers applied each time again, complex three-dimensional bodies can be manufactured with this procedure, simply and quickly.

The process of laser sintering (rapid prototyping) for the manufacture of molded bodies from powder polymers is described extensively in US 6,136,948 and WO 96/06881 (both of DTM Corporation). The SSL procedures described in the known state of the art have the disadvantage that an expensive laser technique is required for this procedure. Both the laser that acts as a source of energy and the optical devices necessary for the preparation and guidance of the laser beam, such as lenses, wideners and reflector mirrors, are extremely expensive and sensitive. Other procedures for rapid prototyping have been developed, which, however, have not yet acquired commercialization. In WO 01/38061 a process for the manufacture of prototypes is described, which is based on the use of sintering inhibitors that prevent sintering, triggered by the supply of energy, of substrate in powder form in the selected areas. . In the case of this procedure you can give up a complex laser technique. However, a specific heat input is not possible with this procedure. The disadvantage of this procedure is, e.g. For example, that the surrounding powder that was not melted contains the inhibitor and therefore cannot be recycled. In addition, for this procedure a new software has been developed, since it is precisely not printed as usual the cross section of the piece, but the environment. In the case of plugs and cross-sectional variations, a large-scale application of inhibitors is necessary. In addition, there is a risk of heat retention formation.

US 5 338 611 describes the use of microwave radiation for polymer fusion, using polymers in the form of powder and carbon black on a nanometric scale. Prototype manufacturing is not described. In DE 197 27 677 prototypes are generated by the action of a microwave beam focused on selected areas of layers in powder form. Through the action of the predetermined microwave beam, the powder-shaped substrates are bonded by bonding, sintering or melting in the layer as well as with the powder-shaped substrates in the layer below. Also, in the case of this procedure a complex technique is required in order to allow microwave radiation to access only the selected areas.

EP 888868 discloses the characteristics of the pre-characterizing clauses of claims 1 and 20.

The procedures for the manufacture of prototypes, known by the state of the art, are all relatively complex in relation to the technique used. In particular, the use of lasers or microwave focused radiation requires high precision and, therefore, expensive and prone to damage equipment. Known procedures are certainly suitable for prototyping, but these procedures are unsuitable for application in rapid manufacturing or as a home application.

Therefore, it was the mission of the present invention to provide a process for the manufacture of three-dimensional objects that could be carried out with simple equipment, thereby economical and not prone to breakdowns. The construction pieces should preferably be carried out in a robust way, being able to resort to construction pieces of equipment of the daily necessities.

Surprisingly, it was found that it is relatively simple to manufacture three-dimensional objects from substrates in powder form by microwave radiation, e.g. ex. also by microwave cooking appliances, when applied on a layer based on a substrate in the form of dust, which does not absorb microwave radiation or only defectively, a susceptor on the areas to join the layer, which can absorb microwave radiation and emitting the energy absorbed in the form of heat to the substrate that surrounds it, whereby the substrate of the layer or possibly a layer located below or above can be joined in the aforementioned areas by fusion or sintering . The application of the susceptor can take place with a printhead, similar to that of an inkjet printer.

Therefore, a process for the manufacture of a three-dimensional object, the object of the present invention, is

which is characterized in that it comprises the steps of a) providing a layer of a substrate in powder form, b) selectively applying at least one microwave absorbing susceptor on areas to be treated in the

layer of a), choosing the areas on which the susceptor is arranged in accordance with the cross section of the three-dimensional object, namely so that only the susceptor is disposed on the zones that constitute the cross-section of the three-dimensional object,

c) treating, at least once, the layer with microwave radiation so that the areas of the layer provided with the susceptor as well as possibly with areas of the layer below provided with the susceptor are joined together by fusion,

 as well as molded bodies produced according to this procedure.

The object of the present invention is also a device for the production of three-dimensional objects in layers, which is characterized in that the device has

-a mobile device for the application in the form of layers of a substrate in the form of powder on a work platform or of a layer possibly already present on the work platform of a substrate (2) in the form of treated or untreated powder,

-a device (3), mobile in the x plane, and, for the application of a susceptor (4) on selected areas of the substrate-based layer in powder form and -a microwave generator (5) suitable for creating microwave radiation in the range of 300 MHz to 300 GHz.

The process according to the invention has the advantage that it does not employ any complex directed radiation such as, for example, laser radiation or closely focused microwave radiation. The deliberate incidence of energy in certain areas of the layer or of a matrix consisting of several layers is achieved by the microwave-excited susceptor, which is applied to the desired areas of the layer

or of the layers of the matrix.

By means of the process according to the invention, an automated layered constitution of a three-dimensional object is simply possible by the use of microwave radiation in combination with a suitable susceptor. Dust not treated with the susceptor can simply be used again, which is not possible in the case of procedures using inhibitors.

The device is easily manipulable in a manner similar to a usual inkjet printer and, therefore, can be connected e.g. eg, to a personal computer, particularly when microwave irradiation is then carried out in the microwave usually existing in most homes. This makes 3D printing affordable and manageable, also for a normal budget. The process according to the invention also has the advantage that the surrounding material can be used again without further ado. In addition, special properties such as electrical conductivity or colors can be "printed together" directly. This part can be provided in this way selectively selected properties.

The functional principle of the present process for the manufacture of three-dimensional objects according to the invention is based, in principle, on the principle used in all other procedures for rapid prototyping. The three-dimensional object is constituted in layers. The constitution takes place because parts of layers of liquid (sterolithography) or layers of dust (laser sintering) consolidate either join together or with parts of layers located below, providing energy to these parts of the layers. The parts of the layers that were not given any energy continue to be presented as a liquid or powder. By repeating the application and joining or consolidating the powder or liquid, a three-dimensional object is obtained in layers. After removing the unreacted powder or the unreacted liquid, a three-dimensional object is obtained whose dissolution (in relation to the contours) depends on the thickness of the layer and the particle size of the substrate in the form of powder used.

Unlike the previously known procedures, energy is not contributed directly to the substrates to be joined, but through a susceptor that absorbs the energy and delivers it to the surrounding substrate in the form of heat energy. Energy is provided to the subscribers in the process according to the invention in the form of microwave radiation which is absorbed by the subscribers, transformed into heat energy and delivered to their direct neighbors in the form of substrate dust that are not in conditions or that they are not enough to absorb microwave radiation. To a limited extent it does not mean in the present case that by absorbing microwave radiation, the substrate in powder form cannot be heated to such an extent that it can participate in a joint by fusion or sintering with adjacent substrate particles, or the Time required for this is too long. However, the heat delivered by the susceptor is sufficient to bind by melting or sintering the substrate in powder form adjacent to the susceptor with itself and also with the susceptor. In this way, three-dimensional objects are manufactured with the process according to the invention by melting or sintering a powder-shaped substrate.

The bonding of the substrate in certain areas within the layer as well as of the layers with each other takes place, as in laser sintering and the other procedures for rapid prototyping, again by joining, in particular fusion or sintering of the substrate in powder form The functional principle of rapid prototyping can be deduced, e.g. eg, of US 6,136,948 and WO 96/06881.

The application of the subscribers in step b), which usually takes place in a computer-controlled manner with the use of CAD applications for the calculation of cross-sectional surfaces, has the consequence that only the powdered substrates treated are joined in a subsequent treatment stage c). Therefore, the susceptor only applies to selected areas of the a) layer that belong to the cross section of the three-dimensional object to be produced. The application itself can take place, e.g. eg, by means of a printhead equipped with nozzles. After the subsequent treatment step c) of the last layer, with the process according to the invention a matrix with a partially bonded powder material is obtained that releases the solid three-dimensional object after removing the unbound powder.

The process according to the invention is described in the following by way of example, without the invention being limited thereto.

The process according to the invention for the manufacture of a three-dimensional object is distinguished in that

understand the stages of

a) provide a layer of a substrate in powder form,

b) selectively apply at least one microwave absorbing susceptor on areas to be treated

layer of a), choosing the zones on which the susceptor is applied according to the cross section of the three-dimensional object, namely so that only the susceptor is arranged

on the areas that constitute the cross section of the three-dimensional object,

c) at least once treat the layer with microwave radiation, so that the areas of the layer

provided with the susceptor as well as eventually the areas of the layer below

provided with the susceptor are joined together by fusion or sintering,

Step c) can be carried out in each case when steps a) and b) have been performed x times, with x being equal to 1 up to a number of stages a) and b) carried out. Depending on the powder material used, the depth of penetration dependent on the microwave radiation material can be taken into account. Thus, depending on the powder material and the number of stages a) it may happen that a single microwave radiation treatment is not sufficient to join all the areas treated with susceptor of the layers of powder material present in the construction space. In this case, it may be advantageous to carry out step c), p. For example, in each case after having carried out stages a) and b) during 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 30, 40 or 50 times. Furthermore, it may be advantageous to carry out stage c) only when stages a) and b) have already been carried out at least twice, since in this way a firmer association of the layers with each other is achieved. In a particular embodiment of the process according to the invention, steps a) and b) are repeated until all the cross-sectional surfaces, of which the three-dimensional object is constituted, are present in a matrix and the shapes have been formed. external delimitations of the object by the boundary between the powder material with the susceptor applied and the untreated powder material and then step c) is carried out. Thus, only a single microwave radiation treatment is necessary, which means significantly lower energy consumption.

In another variant of carrying out the process according to the invention, at the beginning of the manufacturing of the three-dimensional object, stage c) is carried out once, after having carried out stage a) once, then stage b ) and then again stage a) and then the other stages in sequence b), a), c) are carried out. In this variant embodiment, a layer of powder treated with susceptor is covered in each case with a layer of untreated powder. Therefore, in the case of step c), the particles of the uppermost layer are not joined, e.g. for example, by fusion or sintering, but the particles of the layer below, where at the boundary between the layers, the particles of the two layers are already joined. In this way, a particularly durable bond between the layers can be achieved. In addition, transitions from one layer to the next layer in the finished object are smoother. Step c) can then be carried out again in each case when stages b) have already been carried out x times, with x being equal to 1 up to a number of stages b) and a) carried out, the advantages being achieved above mentioned.

Stage c) can be carried out directly in the construction space, when it takes place in each case after performing stages a) and b) or b) and a) once or several times. If only one treatment according to step c) takes place, it can take place in the lower construction space or in another suitable place of the device. It is also possible that stage c) is carried out on a device other than the equipment to carry out stages a) and b). So, p. ex. the matrix based on treated powder layers, produced by means of steps a) and b), can be transformed, e.g. ex. in a usual commercial microwave for food preparation, in which stage c) is carried out. By these possibilities, the process according to the invention is particularly suitable for domestic applications.

The provision of the powder layer may take place, e.g. for example, by applying a powder material as a substrate on a bottom plate or, if it is already present, on a layer treated according to step b) or c) already present. The application can take place by scraper, roller, pouring and subsequent removal, or similar procedures. The only premise that the provision of the layer must fulfill is that it has a uniform height. Preferably, the layer provided in step a) has a height of less than 1 mm, preferably 50 to 500 μm and, particularly preferably, 100 to 200 μm. The height of the layers determines in this case the dissolution and, thus, the smoothness of the external structure of the manufactured three-dimensional object. The bottom plate or the equipment for the provision of the layer can be made mobile in height, so that after carrying out a step b) or c) the obtained layer can be lowered to the height of the layer a apply next, or the equipment can be raised to the height of the next layer with respect to the previous layer.

The height of the layer provided according to step a) also depends, among others, on the average particle size or the maximum particle size. It is understood that with particles with a particle size of 150 μm solid and compact layers of the same height cannot be produced, since the volume between the particles should undergo a very large contraction in step c).

The powder material used particularly preferably as a substrate in powder form has an average grain size (d50) of 10 to 150 μm, particularly preferably 20 to 100 μm and, very particularly preferably, of 40 to 70 μm. Depending on the purpose of use, it may, however, also be advantageous to use a powder material having particularly small particles, but also particularly large particles. In order to achieve three-dimensional articles with a solution as high as possible and a surface as smooth as possible, it may be advantageous to use particles having an average particle size of 10 to 45 μm, preferably 10 to 35 μm and, very particularly preferably, from 20 to 30 μm.

A thin material less than 20 μm, in particular less than 10 μm, can hardly be worked, since it does not drip and the apparent density drops drastically, with which more hollow spaces can be formed. For easier handling, it may be advantageous to use particles having an average particle size of 60 to 150 µm, preferably 70 to 120 µm and, very particularly preferably, 75 to 100 µm.

As a powder substrate, a powder material is preferably used which has been prepared by grinding, precipitation and / or anionic polymerization, or by combinations thereof, especially precipitation of a somewhat too coarse powder and subsequent subsequent grinding, or precipitation and subsequent classification.

The particle size can be chosen arbitrarily in the case of the indicated average grain sizes of the powder materials. Preferably, powder materials are used which have a wide or narrow granulometry, preferably a narrow granulometry. Particularly preferred powder materials for use in the process according to the invention have a particle size in which a maximum of 20%, preferably 15% and, very particularly preferably, a maximum of 5% of the particles has a deviation in particle size in relation to the average grain size of more than 50%. The granulometry can be adjusted by usual classification procedures such as, e.g. eg, winged, etc. By means of a granulometry as narrow as possible, three-dimensional objects having a very uniform surface and which, if present, have very uniform pores are obtained in the process according to the invention.

At least a part of the substrate in powder form used may be amorphous, crystalline or partially crystalline. Preferred powder material has a linear or branched structure. Particularly preferred powder material, which is used in the process according to the invention, has, at least in part, a melting temperature of 50 to 350 ° C, preferably 70 to 200 ° C.

As substrates, materials according to the invention which, in comparison with the chosen susceptors, are heated with greater difficulty by microwave radiation are adapted in the process according to the invention. The powder-used substrate should also have sufficient fluidity in a heated state. As powdered substrates, polymers or copolymers, preferably chosen from polyesters, polyvinyl chloride, polyacetal, polypropylene, polyethylene, polystyrene, polycarbonate, poly (N-methylmethacrylamides) (PMMI), may be used in particular. methyl polymethacrylate (PMMA), ionomer, polyamides, copolyesters, copolyamides, terpolymers, acrylonitrile-butadiene-styrene copolymers (ABS) or mixtures thereof.

Particularly preferably, in the process according to the invention a powder material is used as a powder substrate which has a polyamide, preferably at least one polyamide 6, polyamide 11 and / or polyamide 12 or a copolyester or a copolyamide Through the use of polyamides, particularly non-deformable three-dimensional molded bodies can be manufactured. Particularly preferred is the use of polyamide powder 12, preferably prepared as described in DE 197 08 946 or also DE 44 21 454 and, particularly preferably, having a melting temperature and a enthalpy of fusion as described. indicated in EP 0 911 142. As preferred copolyamides or copolyesters, those commercially acquired under the trade name VESTAMELT of Degussa AG are preferably used. Particularly preferred copolyamides have a melting temperature, determined by differential scanning calorimetry (DSC) of 76 to 159 ° C, preferably 98 to 139 ° C and, very particularly preferably, 110 to 123 ° C. Copolyamides can be prepared, e.g. eg, by polymerization of mixtures of suitable monomers, e.g. ex. chosen from laurinlactam and / or caprolactam as bifunctional components, subteric acid, azelaic acid, dodecanedioic acid, adipic acid and / or sebacic acid as an acid-bearing component, and 1,6-hexanediamine, isophorondiamine and / or methylpenta -methylene diamine as diamine.

In order to achieve a better processing capacity of the substrates in powder form, it may be advantageous to use a powder material having additives. Additives of this type may be, e.g. eg anti-caking agents. Particularly preferably, the substrate in powder form used has from 0.05 to 5% by weight, preferably from 0.1 to 1% by weight of additives. Anti-caking agents may be, e.g. eg, pyrogenic silicic acids, stearates or other anti-caking agents known in the literature such as, e.g. eg, calcium triphosphate, calcium silicates, Al2O3, MgO, MgCO3 or ZnO. Pyrogenic silicic acid is offered, for example under the trade name Aerosil®, by Degussa AG. In addition, it may be advantageous if the substrate in powder form used has laser activatable additives. By means of this type of additives it is possible, for example, the inscription or subsequent provision of three-dimensional objects with electrical conductive bands. Usable additives are described, e.g. eg, in DE 4402329. Together with or instead of partly inorganic anti-caking agents of this type or other additives, a powder-shaped substrate used in accordance with the invention may also have inorganic fillers. The use of filling bodies of this type has the advantage that they essentially retain their shape by treatment at the joint and, consequently, reduce the contraction of the three-dimensional object. In addition, by using filler bodies it is possible, e.g. eg, modify the plastic and physical properties of objects. Thus, by using powder material that has metallic powder, both transparency and color can be adjusted as well as the magnetic or electrical properties of the object. As materials or filler bodies, the powder material may have p. eg, glass particles, ceramic particles or metal particles. Typical loading materials are p. eg, fine metallic grains, aluminum powder, steel or glass spheres. Particularly preferably, powder materials are used which, as filler bodies, have glass spheres. In a preferred embodiment variant, the powder material according to the invention has from 1 to 70% by weight, preferably from 5 to 50% by weight and, most particularly preferably, from 10 to 40% by weight of materials. of filling. Together with or instead of anti-caking agents or inorganic fillers, a powder-shaped substrate used in accordance with the invention may also have inorganic or organic pigments. These pigments can be, together with colored pigments that determine the color aspect of the three-dimensional body to be produced, also pigments that affect other physical properties of the three-dimensional objects to be manufactured such as, e.g. eg, magnetic pigments or conductive pigments such as, e.g. eg, titanium dioxide or modified tin oxide so that it is conductive, that modify the magnetism or conductivity of the object. Particularly preferred, the powder material to be used has, however, pigments of inorganic or organic colors, selected from clay, ocher, shade earth, green earth, calcined Siena earth, graphite, titanium white (titanium dioxide) , lead white, zinc white, lithophone, antimony white, carbon black, iron oxide black, manganese black, cobalt black, antimony black, lead chromate, minium, zinc yellow, zinc green , cadmium red, cobalt blue, Berlin blue, ultramarine blue, manganese violet, cadmium yellow, Schweinfurt green, molybdate orange, molybdate red, chrome orange, chrome red, iron oxide red, chrome oxide green, strontium yellow, metallic effect pigments, pearl pigments, luminous pigments with fluorescence and / or phosphorescence pigments, shade earth, gutta percha, bone charcoal, Kasseler brown, indigo, chlorophyll, colora With azo, indigoids, dioxazine pigments, quinacridone pigments, phthalocyanine pigments, isoindolinone pigments, perylene pigments, perinone pigments, metal complex pigments, alkaline blue pigments and ditopyrrolopyrrole. Additional information on employable pigments can be taken, e.g. eg, from Römpp Lexikon Chemie -version 2.0, Stuttgart / New York: Georg Thieme 1999 editorial, as well as the bibliography cited there.

The pigments used may have grain sizes such as those described for the powder material. Often, the pigments have, however, grain sizes that are clearly smaller than the average grain sizes of the polymers used. The pigments can be applied, e.g. ex. in a manner similar to the subscribers, through nozzles as used in printheads, or they may be present in the powdered substrates used, in particular in the polymer particles. Particularly preferably, the powder material according to the invention has polymer particles having one or more of the mentioned pigments - preferably with the exception of single white pigments -. The proportion of the pigments in the powder material is preferably 0.01 to 25% by weight, preferably 0.1 to 10% by weight and, particularly preferably, 1 to 3% by weight. The possibility of being able to use pigmented substances is another advantage of the process according to the invention with respect to laser sintering procedures, in which the colored pigments or the metallic pigments hinder or weaken the laser beam and, therefore, make it impossible an elaboration of materials of this type. As a powdered material, substances that can be considered as a particular form of the filler bodies or pigments mentioned above can also be used. In this type of powder material, the powder has grains of a first material with a size that is smaller than the above-mentioned dimensions for the powder material. The grains are coated with a layer of a second material, the thickness of the layer being chosen so that the powder material based on a combination of grain of the first material and coating with the second material has a size as indicated above. The grains of the first material preferably have a size that has a deviation in the size of the powder material less than 25%, preferably less than 10% and, particularly preferably, less than 5%. The second material, which represents the coating of the grains, is a material that, in comparison to the chosen susceptors, can be heated worse by microwave radiation. The second material should also have sufficient fluidity in a heated state and should be able to be sintered or melted by the action of heat, the heat being provided by the susceptor. As a coating material, the substrates in powder form (the powdered materials) may, in particular, have the aforementioned polymers or copolymers, preferably chosen from polyesters, polyvinyl chloride, polyacetal, polypropylene, polyethylene, polystyrene, polycarbonate, poly (N-methylmethacrylamides) (PMMI), poly (methyl methacrylate) (PMMA), ionomer, polyamides, copolyesters, copolyamides, terpolymers, acrylonitrile-butadiene-styrene copolymers (ABS) or mixtures thereof, or phenolic resins. The first material of this particular form of the powder material may comprise grains, e.g. ex. of sand, ceramic material, metal and / or alloys. A particularly preferred powder material of this type is sand coated with phenolic resin or thermoplastic synthetic material, the so-called molding sand.

When the susceptor is able to transfer a sufficient amount of heat, it is also possible to use as a powder material, metal powder, in particular low melting metal powder such as, e.g. e.g., lead or tin or alloys they present, e.g. eg, tin or lead. Also, this powder material preferably has the dimensions mentioned above. (In the case of using metallic powder, it must first be verified if the metal is suitable for microwave treatment or if the formation of sparks occurs

or a destruction of the microwave generator. A verification of this type is possible through simple previous tests).

Therefore, with the process according to the invention, three-dimensional objects can be manufactured that can be provided with one or more functionalized layers. For example, a functionalization such as, e.g. For example, the provision with conductive properties of the entire molded part or of only certain areas determined by the application of corresponding pigments or substances can take place analogously to the susceptor or by providing a layer based on a powder-like substance that presents these pigments.

The application of the susceptor can take place analogously to the application of the inhibitor described in WO 01/38061. Preferably, the application of the susceptor takes place with a mobile device in the x, y plane. The device presents the possibility of delivering to the layer provided according to stage a) liquid and / or powder-shaped susceptors in defined areas. The device can be, e.g. eg, a printhead as used in an inkjet printer. The control of the device for positioning the print head can also take place in the same manner as the control of the print head of an inkjet printer. With this device the susceptor is applied in the areas of the layer provided according to step a) to which the substrate must be attached by sintering or fusion.

In the process according to the invention all the susceptors that are heated by microwave radiation can be used. To them belong powdered materials such as, e.g. eg, metal powders, metal compounds, powders of ceramic material, graphite, carbon black or activated carbon, or protic liquids, chosen from the group of saturated aliphatic, monovalent or polyvalent, linear, branched or cyclic alcohols, alone or mixed with water or water alone. As protic liquids, glycerol, trimethylolpropane, ethylene glycol, diethylene glycol or butanediol, or mixtures thereof alone or in admixture with water are preferably used. It is also possible to use mixtures of solid, liquid or solid and liquid susceptors. Likewise, it may be advantageous to suspend in susceptor liquids present in the form of solids, which are not susceptors, in order to achieve a better distribution of the susceptors present in solid form over the entire surface of the provided layer. Another advantage can be achieved if, for better wetting of the substrate, the susceptor, in particular the liquid susceptor, is provided with surfactants.

In this process according to the invention, in addition, many combinations of susceptor / substrate are imaginable, a sufficiently large difference of susceptor and substrate in their capacity being heated by microwave radiation being important for the process so that at the end of the procedure a matrix is obtained that reaches a clear boundary between bound substrate (ie, treated with susceptor) and unbound substrate. Only in this way is it ensured that the three-dimensional object produced has a sufficiently smooth contour and can be easily detached from the unbound substrate.

In order to make a sufficiently large and prolonged heat transfer from the susceptor to the substrate possible, the boiling point of the susceptor or, in the case of a mixture of susceptors, of at least one susceptor, should be greater than the point of fusion of the substrate used. The dosage of the susceptor, as well as the properties of the powder and the susceptor must be adjusted to each other, so that the susceptor, in particular in the case of using a liquid susceptor, does not run through the layers, but is absorbed exclusively by the dust to be wetted. The determination can take place, e.g. eg, by adjusting the viscosity and the amount of the susceptor used. In this case, the amount of the liquid susceptor used depends particularly on the thickness of the powder layer, the porosity of the powder and the size of the particles. For the different combinations of materials the optimum quantity and viscosity can be determined in simple previous tests. For viscosity adjustment known viscosity inductors such as pyrogenic silicic acids or also organic agents can be used. The susceptor can remain in the molten mass or in the molded part. This may even be an advantage in the case of reinforcement or in the case of adjustment of other properties by the susceptor (magnetic electrical conductivity).

The energy necessary for heating the susceptor is provided in the form of microwave radiation. It may be advantageous to bring the layers to be sintered, by means of heat input, at an elevated temperature or to keep them at an elevated temperature that is below the melting or sintering temperature of the polymer employed. In this way, the energy or the power to be incorporated by the microwave energy can be reduced. The disadvantage of such an execution is, however, that special devices must be used that are not often present in the home such as, e.g. eg, baking ovens combined with a built-in microwave. However, if such devices find a wide diffusion, it is also possible in the case of a domestic application of the process according to the invention not to provide a part of the sintering energy required by microwave energy.

Microwave radiation treatment according to stage c) can take place as described above according to any stage b), or only after all layers have been treated with the susceptor. In particular, in the case of using a liquid susceptor it has proved advantageous to carry out the microwave treatment in each case directly after the treatment of a layer according to step b), preferably directly in the construction space, since if it does not exist the risk that the liquid susceptor is also distributed in unwanted parts of the layer or of the matrix consisting of several layers.

The microwave radiation necessary for the process according to the invention is generated by a microwave generator, preferably external, which can be in a frequency range of 300 MHz to 300 GHz. The frequencies used in industrial processes and subject to authorization As a general rule, the state amounts to 430 to 6800 MHz (Encyclopedia of Chemical Processing and Design, vol. 30, p. 202 ff, Marcel Dekker, NY - Basel, 1989). Therefore, microwave radiation in the frequency range of 430 to 6800 MHz is preferably used in the process according to the invention. The radiation generated by the microwave generator can eventually be polarized and / or filtered.

Three-dimensional molded bodies can be manufactured by means of the process according to the invention. These three-dimensional objects manufactured in layers are at the end, after the conclusion of the process according to the invention, in a matrix that is formed by several layers. From this matrix, which is composed of a substrate in the form of bound and unbound powder, as well as a susceptor, the object can be removed, while the unbound substrate, possibly after a treatment, e.g. eg, by sieving, it can be used again. The molded bodies according to the invention may have filler bodies, selected from glass spheres, silicic acids or metal particles.

The process according to the invention is preferably carried out in a device according to the invention for layered manufacturing of three-dimensional objects, which is characterized in that it has

-a mobile device for the application in layers of a substrate in powder form on a

work platform or a layer possibly already present on the work platform of a

substrate in powder form, treated or untreated, such as, e.g. eg a scraper,

-a mobile device in the x-plane, and for the application of a susceptor over selected areas of the

substrate layer in powder form such as, for example, a printhead, and

-a microwave generator, suitable for generating microwave radiation in the interval

from 300 MHz to 300 GHz, preferably from 430 to 6800 MHz, with which you can heat the

susceptor until the substrate is joined by fusion or sintering in the areas where it was already

applied the susceptor on the substrate.

The device is preferably equipped with several reservoir reservoirs, from which the substrate in powder form to be made to the device for the production of the layers can be provided, and the subscriber (s) used can be contributed to the mobile device in the x plane, and for the application of a susceptor on selected areas of the powder-based substrate layer. By using printheads with several nozzles and the provision of a mixer, it can be achieved that in certain areas of the layer, e.g. ex. in areas particularly with watermarks or, e.g. For example, at the edge of the object to be produced, other mixtures of susceptors are used than in the core area of the object to be produced. In this way a different energy contribution can be created in different positions of the layer.

Likewise object of the present invention is the powder material as described above, which is suitable for use in the process according to the invention and which is particularly characterized in that it has an average grain size of 10 to 150 μm. and at least one polyester or copolyester, chosen from polyvinyl chloride, polyesters, polyacetal. polypropylene, polyethylene, polystyrene, polycarbonate, PMMA, PMMI, ionomer, polyamides, copolyesters, copolyamides, terpolymers or ABS, or mixtures thereof. Particularly preferably, the powder has polyamide 11, polyamide 12, copolyamide or copolyester, or mixtures thereof. Particularly preferably, the powder has polymer particles that are colored and have a color other than white.

The process according to the invention and the device according to the invention are explained in more detail with the aid of Fig. 1, without the invention being limited to this embodiment. Fig. 1 schematically reproduces the device according to the invention. On a movable bottom (6), a substrate in the form of untreated powder (2), which is arranged in a reserve container (1), is formed to form a matrix (8). The substrate is distributed by means of a scraper (2) in thin layers on the movable bottom or on previously applied layers. Through a mobile device (3) in the x, y plane, the susceptor (4) is applied on selected areas of the powder-based substrate layer. After each treatment with a susceptor a new layer of the substrate in powder form is applied. By means of a microwave generator, suitable for generating microwave radiation in the range of 300 MHz to 300 GHz (5), the areas of the applied substrate that were treated with the susceptor are joined to form a three-dimensional object such as, e.g. eg, a cup (7).

The process according to the invention is explained in more detail with the aid of the following Examples, without the invention having to be limited thereto.

Example 1: Manufacture of a cup from a copolyamide

In the device described in Fig. 1 a model of a cup with an external diameter of 80 mm, a height of 60 mm and a wall thickness of 1.5 mm is manufactured from a copolyamide powder (VESTAMELT 840, Degussa AG, Marl). As a susceptor a graphite-based suspension is used that has 40% by mass of water, 40% by mass of graphite and 20% by mass of isopropanol. The device has an operating temperature of approx. 40 ° C The frequency of the microwave generator is 2450 MHz. The layer thickness is 0.15 mm. For each layer a power of 700 watts is introduced for 30 seconds in each case. The d50 value of the powder amounts to 60 μm.

Example 2: Manufacture of a polyamide-based tie 12

In the device already described, a strap with a length of 160 mm, a width of 10 mm and a height of 4 mm is manufactured from a polyamide powder 12 (EOSINT P PA 2200, EOS GmbH Electro Optical Systems, Krailling, Germany ). As a susceptor, ethylene glycol is used. The device has an operating temperature of approx. 160 ° C. The frequency of the microwave generator is 2450 MHz. The thickness at which the powder layers were applied was 0.15 mm. For each layer a power of 750 watts is introduced for 45 seconds. The powder used had a d50 value of 55 μm.

Claims (22)

1.- Procedure for the manufacture of a three-dimensional object, which comprises a provision of a) provide a layer of a powder-shaped substrate, characterized by the steps b) selectively apply at least one microwave absorbing susceptor on areas to be treated layer of a), choosing the areas on which the susceptor is arranged in accordance with the cross section of the three-dimensional object, namely so that only the susceptor on the zones that constitute the cross section of the three-dimensional object, c) at least once treat the layer with microwave radiation, so that the areas of the layer provided with the susceptor as well as eventually with areas of the layer below provided with the susceptor are joined together by fusion or sintering. 2. Method according to claim 1, characterized in that step c) is carried out after executing in each case x times stage a) and stage b), with x equal to 1 up to a number of stages a) and b) performed. 3. Method according to claim 1, characterized in that at the beginning stage c) is carried out once, after having carried out stage a) once, then stage b) and then stage a ), and then the other steps in sequence b), a) and c) are carried out. 4. Method according to one of claims 1 to 3, characterized in that steps a) and b) are repeated so many times until in a matrix all the cross-sectional surfaces of which the three-dimensional object is constituted, and the delimitations are present External objects are formed by the boundary between the powdered material with the applied susceptor and the untreated powdered material and then step c) is carried out. 5. Method according to claim 4, characterized in that step c) is carried out in the lower construction space of the device. 6. Method according to one of claims 1 to 5, characterized in that step c) is carried out on other equipment than the equipment for carrying out steps a) and b). 7. Method according to one of claims 1 to 6, characterized in that step c) is carried out in a microwave commercially available for food preparation. 8. Method according to one of claims 1 to 7, characterized in that the substrate in powder form used has an average grain size of 10 to 150μm. 9. Method according to at least one of claims 1 to 8, characterized in that the microwave radiation is used in the frequency range of 430 to 6800 MHz. 10. Method according to at least one of claims 1 to 9, characterized in that as a susceptor metal powder or metal compounds, ceramic material powder, graphite or activated carbon, or protic liquids, chosen from the group of aliphatic alcohols are used saturated, monovalent or polyvalent, linear, branched or cyclic alone or in admixture with water or water alone. 11. Method according to claim 10, characterized in that as a protic liquid glycerol, trimethylolpropane, ethylene glycol, diethylene glycol or butanediol, or mixtures thereof are used alone or in admixture with water. 12. Method according to one of claims 1 to 11, characterized in that polymers are used as a powder substrate. 13. Method according to claim 12, characterized in that as a substrate in powder form polymers or copolymers are used, preferably chosen from polyesters, polyvinyl chloride, polyacetal, polypropylene, polyethylene, polystyrene, polycarbonate, PMMI, PMMA , ionomer, polyamides, copolyesters, copolyamides, terpolymers, ABS or mixtures thereof. 14. Method according to one of claims 1 to 13, characterized in that a substrate in the form of a powder is used which has from 0.05 to 5% by weight of an anti-caking agent. 15. Method according to one of claims 1 to 14, characterized in that a substrate in the form of a powder having inorganic fillers is used. 16. Method according to claim 15, characterized in that glass spheres are used as filler bodies. 17. Method according to one of claims 1 to 16, characterized in that a substrate in the form of a powder having inorganic or organic pigments is used. 18. Method according to one of claims 1 to 17, characterized in that a substrate is used in powder form that has laser-activatable additives. 19. Method according to one of claims 1 to 11, characterized in that as a substrate in powder form, which can be sintered or melted by the action of heat, grains coated with sand, ceramic material, metal and metal are used. / or alloys or metal dust. 20.- Device for the production in layers of three-dimensional objects, in which the device presents -a mobile device for the application in layers of a substrate in powder form on a work platform or a layer possibly already present on the work platform of a substrate in the form of treated or untreated powder, and -a microwave generator, suitable for generating microwave radiation in the interval 300 MHz to 300 GHz, characterized by a mobile device in the x-plane, and for the application of a susceptor over selected areas of the powder-based substrate layer.  21. Molded body, manufactured according to a method according to one of claims 1 to 19. 22. Molded body according to claim 21, characterized in that the molded body has filler bodies chosen from glass spheres, silicic acids, metal particles or aluminum particles.