DE9018138U1 - Selective radiation sintering device - Google Patents

Description

Dipl.-Chem. Dr. Steffen ANDRAE
Dipl.-Phys. Dieter FLACH
Dipl.-Ing. Dietmar HAUG
Dipl.-Chem. Dr. Richard KNEISSL
Balanstrasse 55
81541 Munich

Our file: 2218

Applicant: BOARD OF REGENTS THE UNIVERSITY OF TEXAS SYSTEM Office of General Council, 201 West 7th Street Austin, Texas 78701, US

Device for selective radiation sintering

This invention relates to an apparatus that applies a directed energy beam to selectively sinter a powder to produce a part. More particularly, this invention relates to a computer-aided laser apparatus that sequentially sinters multiple layers of the powder to build the desired part layer by layer. The present application is particularly directed to a powder comprising multiple powders in combination, each powder consisting of a material having a bonding temperature that may be the same or different from that of the other material, and one powder being dissociated and consisting of a material having a dissociation temperature that may be the same or different from that of the other, and to an apparatus and method for dispersing a layer of powder to achieve a high mass density of the powder in each layer during sintering.

The economic efficiency associated with conventional manufacturing processes for parts is demonstrated in

generally have a direct relationship to the quantity of parts to be produced and the desired material properties of the finished parts. For example, the large-scale manufacturing processes of casting and extrusion are often cost-effective, but these manufacturing processes are generally not acceptable for small quantities - i.e., spare parts or prototype production. Many such conventional processes for manufacturing parts require expensive part-specific tooling. Even powder metallurgy requires a mold for shaping the powder, making powder metallurgy unattractive as a process for manufacturing small numbers of parts.

Where only a small number of parts are desired, conventional manufacturing processes, which include the subtractive machining process, are most often used to produce the desired part. In such subtractive processes, material is cut out of a starting block of material to produce a more complicated shape. Examples of subtractive processes using machine tools include: milling, drilling, grinding, turning, flame cutting, the electric discharge machine, etc. While such conventional subtractive processes using machine tools are most often effective in producing the desired part, they are deficient in many respects.

First, such conventional subtractive processes using machine tools produce a large amount of waste material that must be disposed of. In addition, such processes using machine tools usually involve a great deal of initial effort in setting up the correct machining sequence and tooling arrangement. As such, the preparation time is not only costly, but also relies heavily on human judgment.

and experience. These problems are of course exacerbated when only a small number of parts are to be produced.

Another difficulty associated with such conventional machining methods includes tool wear - which not only involves the cost of replacement, but also reduces the accuracy of the machining when the tool wears. Another limitation on the accuracy and tolerance of a part produced by conventional machining methods is the tolerance limits inherent in the machine tool in question. For example, in a conventional milling machine or lathe, the lead screws and guides are manufactured to a certain tolerance which limits the tolerances achievable when producing a part on the machine tool. Of course, the achievable tolerances are reduced as the machine tool ages.

The final difficulty associated with such conventional subtractive processes using machine tools is the difficulty or impossibility of producing many shapes of parts. That is, the conventional machining processes are best suited to the production of symmetrical parts and those parts where only the external part is machined. However, where a desired part has an unusual shape or internal features, machining becomes more difficult and quite often the part must be divided into segments for manufacture. In many cases a special shape of part is not possible because of the restrictions imposed on the location of the tool on the part. Thus the size and design of the cutting tool do not allow access

of the tool to produce the desired shape.

There are other machining processes that are additive, such as electroplating, plating, and some welding processes are additive in that the material is added to the starting substrate. In recent years, other additive machining processes have been developed that use a laser beam to deposit the material onto a starting article. Examples include U.S. Patent Nos. 4,117,302; 4,474,861; 4,300,474 and 4,323,756. These recent applications of lasers have been primarily limited to applying a coating to a previously machined article. Often, such coating processes using lasers have been used to achieve certain metallurgical properties that can only be obtained by such coating processes. Typically, in such laser coating processes, the starting article is rotated and the laser is aimed at a fixed location and the coating material is sprayed onto the article so that the laser will melt the coating material onto the article.

Additionally, a method is proposed for compacting a material in powder form into a coherent mass prior to sintering. An example includes U.S. Patent No. 4,752,352.

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The problems identified above are largely solved by the apparatus of the present invention. The present invention involves a directed energy beam - such as a laser - and is so adaptable that almost any three-dimensional part can be made. The process of the present invention is an additive process in which the powder is dispersed in a target area, the laser selectively sintering a portion of the powder to produce a sintered layer. Sintering is carried out at a temperature which causes viscous flow, e.g. at the adjacent boundaries of the particles of the powder, with at least some portion of each particle remaining solid. Such sintering causes the density of the sintered part to increase when compared to the bulk density of that portion of the powder before it was sintered, and a part formed by the layer-by-layer bonding of multiple layers will therefore be autogenously densified. The method of the present invention is not limited to a specific type of powder, but rather is applicable to plastic, metal, polymer, ceramic, wax, semiconductor or amorphous or composite powders.

Generally, the apparatus includes a laser or other directed energy source selectable for emitting a beam into a target area where the part is to be manufactured. A powder distribution system applies the powder to the target area. A control mechanism of the laser functions to move the target of the laser beam and modulates the laser to selectively sinter a layer of the powder distributed in the target area. The control mechanism functions to selectively sinter only the powder located within the specified boundaries to produce the desired layer of the part. The control mechanism actuates the

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Laser so as to selectively sinter sequential layers of the powder, thereby producing a finished part having a plurality of sequentially sintered layers. The specified boundaries of each layer correspond to the respective cross-sectional areas of the part. Preferably, the control mechanism includes a computer - such as a CAD/CAM system - to determine the specified boundaries for each layer. That is, given the overall dimensions and shape of the part, the computer determines the specified boundaries for each layer and operates the control mechanism of the laser in accordance with the specified boundaries. Alternatively, the computer may be initially programmed with the specified boundaries of each layer.

In a preferred embodiment, the laser control mechanism includes a mechanism for directing the laser beam into the target area and a mechanism for modulating the on and off switching of the laser beam to selectively sinter the powder in the target area. In one embodiment, the directing mechanism functions to move the target of the laser beam in a continuous raster scan of the target area. The modulation mechanism turns the laser beam on and off so that the powder is sintered only when the target of the laser beam is found within the specified limits for the particular layer. Alternatively, the directing mechanism directs the laser beam only within the specified limits for the particular layer so that the laser beam can remain continuously on to sinter the powder within the specified limits for the particular layer.

In a preferred embodiment, the alignment mechanism moves the laser beam in a repetitive raster scan of the target surface using a pair of mirrors driven by galvanometers. The

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first mirror reflects the laser beam to the second mirror, which reflects the beam into the target area. The translational movement of the first mirror through its galvanometer translates the laser beam generally in one direction into the target area. Likewise, the translational movement of the second mirror through its galvanometer translates the laser beam into the target area in a second direction. Preferably, the mirrors are oriented relative to each other so that the first and second directions are generally perpendicular to each other. Such an arrangement allows for many different types of scanning patterns of the laser beam in the target area, including the raster scanning pattern of the preferred embodiment of the present invention.

The method of the present invention for manufacturing parts includes the steps of applying a first portion of the powder to a target surface, scanning the target of a directed energy beam (preferably a laser) over the target surface, and sintering a first layer of the first portion of the powder to the target surface. The first layer corresponds to a first cross-sectional area of the part. The powder is sintered by actuating the directed energy source when the target of the beam is within the boundaries defining the first layer. A second portion of the powder is applied to the first sintered layer and the target of the laser beam scans over the first sintered layer. A second layer of the second portion of the powder is sintered by actuating the directed energy source when the target of the beam is within the boundaries defining the second layer. Sintering the second layer also bonds the first and second layers into a cohesive mass. The successive portions of the powder are applied to the previously sintered layers, with each layer being sintered in turn. In one embodiment, the powder is continuously

Target area applied.

In a preferred embodiment, the laser beam is modulated to turn on and off during the raster scan so that the powder is sintered when the aim of the beam is aligned within the boundaries of the particular layer. Preferably, the laser is controlled by a computer; the computer may comprise a CAD/CAM system, the overall dimensions and shape of the part to be manufactured being presented to the computer and the computer determining the boundaries of each cross-sectional area of the part. Using the specified boundaries, the computer controls the sintering of each layer according to the cross-sectional areas of the part. In an alternative embodiment, the computer is simply programmed with the boundaries of each cross-sectional area of the part.

In addition, another embodiment of the present invention includes a powder comprising a plurality of materials, wherein the plurality of materials exhibit more than one dissociation temperature. By dissociation temperature is meant the temperature at which a molecule splits into its constituents. In yet another embodiment of the present invention, the powder comprises a plurality of materials, wherein the plurality of materials exhibit more than one binding temperature. By binding temperature is meant the temperature at which the powder is sintered, wherein such temperature causes viscous flow only at the adjacent boundaries of the particles, and where at least a certain portion of each particle remains solid.

In some of the preferred embodiments of the present invention, a powder comprising a plurality of materials in combination, one material with another, comprises (i) a mixture of a first material mixed with a second

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material, and optionally mixed with a third and additional materials; and (ii) a first material coated with a second material, and optionally coated with a third and additional materials. Once mixed, a first powder may be applied to a target surface and sintered, followed by the application and sintering of a second powder, thereby bonding one layer to the next subsequent layer. If desired, additional materials may be added sequentially and sintered, each layer individually.

Furthermore, a further embodiment of the present invention includes an apparatus for manufacturing a part, comprising: an irradiation device for selectively emitting a directed energy beam; a structure for providing a target surface for manufacturing the part; a device for depositing the powder in the target surface; and a control device for moving the target of the beam and for modulating the beam to selectively sinter, within predetermined limits, a layer of the powder deposited in the target surface. The control device can selectively sinter the sequential layers of the powder within the respective predetermined limits.

to produce a part having a plurality of layers sintered one after the other. Preferably, the powder attains a high mass density during sintering.
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In a further embodiment, the device for applying the powder comprises a device for electrostatically charging and distributing the powder. Preferably, an electromagnetic field is generated near the target surface, the field causing a high mass density in the powder in the target surface during sintering.

As used in this document, the electromagnetic field includes, but is not limited to, electrostatic and magnetostatic fields.

In yet another embodiment of the present invention, the device for applying the powder comprises a device for dispensing a polarizable powder. Preferably, an electromagnetic field is generated near the target area, the field causing a high mass density in the powder in the target area during sintering due to the polarization forces.

In a further embodiment of the present invention, the device for applying comprises a device for dispersing the powder, wherein the powder has a first electrical charge and the target surface has a second electrical charge. The first electrical charge is opposite to the second electrical charge, and the first charge may have a different magnitude than the second charge.

In a further embodiment of the present invention, the device for applying comprises a device for dispersing a first portion of the powder having a first electrical charge thereon. The first portion of the powder flows past a shaping device which is close enough to the powder to remove its charge before the powder is applied to the target area. Preferably, the device for applying also comprises a device for dispersing a second portion of the powder.

with a second electrical charge on it. The second electrical charge is opposite to the first electrical charge; the first charge can have a different magnitude than the second charge. 35

In yet another embodiment of the present invention, the device for applying comprises a

Device that directs a liquid flow to the powder deposited in the target area to increase the mass density of the deposited powder during sintering.
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In a further embodiment of the present invention, the device for applying comprises a device that enables the application of centrifugal force to the applied powder in order to induce a high mass density in the powder.

The electromagnetic fields generated in embodiments of the present invention may have varying field strengths across the target area.

In a still further embodiment of the present invention, the apparatus for applying the powder further comprises: an electrically charged drum; means for moving the drum from one end of an area having a powder bed to another end of the area at a desired distance between the area and the drum; means for rotating the drum in the opposite direction to the direction of movement of the drum from one end of the area to the other, the drum means being operable when rotated in the opposite direction and moved from one end of the area to the other to contact the powder bed and to eject the powder in the direction of movement to leave a layer of powder between the drum and one end of the area. The layer of powder has a thickness approximately equal to the desired distance.

In yet another embodiment of the present invention, the powder is magnetic and the device for 5 applying the powder preferably comprises a device for generating an electromagnetic field in the vicinity of the target area where the electromagnetic

field causes a high mass density in the powder in the target area during sintering.

An embodiment of a method for manufacturing a part according to the present invention comprises the steps of: depositing a first portion of the powder on a target surface; scanning the target of a directed energy beam over the target surface; sintering a first layer of the first portion of the powder corresponding to a first cross-sectional area of the part by actuating the beam when the target of the beam is within the boundaries delimited by the first cross-sectional area; depositing a second portion of the powder on the first sintered layer; scanning the target of a directed energy beam over the first sintered layer; sintering a second layer of a second portion of the powder corresponding to a second cross-sectional area of the part by actuating the beam when the target of the beam is within the boundaries delimited by the second cross-sectional area; and bonding the first and second layers together during sintering of the second layer. The successive layers of powder are applied to the previously sintered layers and sintering of each successive part is carried out to produce a part having a plurality of sintered layers. Preferably, the steps of applying the powder each further comprise the substep of achieving a high mass density in the first and second parts of the powder during sintering.

In a further embodiment of the method of the present invention, each stage of application further comprises the sub-stages of electrostatically charging and dispersing the powder. Preferably, an electromagnetic field is generated in the vicinity of the target area, and the electromagnetic field induces a high mass density in the

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applied powder during sintering.

In a further embodiment of the method of the present invention, a polarizable powder is dispensed. Preferably, an electromagnetic field is generated near the target area, where the electromagnetic field induces a high mass density through the polarization forces in the applied powder during sintering.

In yet another embodiment of the method of the present invention, each step of applying further comprises the substeps of dispersing the powder, the powder having a first electrical charge, and applying a second electrical charge to the target surface. The first electrical charge exhibits an opposite charge to the second electrical charge, and the first charge may exhibit a different GrO ₁ Se than the second charge.

In yet another embodiment of the method of the present invention, each step of applying further comprises the substep of directing a liquid flow to the applied powder to induce a high mass density in the applied powder during sintering.

In yet another embodiment of the method of the present invention, each step of applying further comprises the substep of applying a centrifugal force to the applied powder to induce a high mass density in the applied powder so as to pre-densify the powder before it is sintered.

In yet another embodiment of the method of the present invention, each step of applying further comprises the substeps of applying a first electrical charge to a first portion of the powder, dispensing the first portion, and passing a molding device proximate the dispensed first portion. In addition, a second

electrical charge is preferably applied to the second part of the powder and the second part is distributed. The first electrical charge preferably exhibits a charge opposite to the second electrical charge and the first charge may have a different magnitude than the second charge.

In a further embodiment of the method of the present invention, the powder is magnetic, for example a ferromagnetic or otherwise magnetizable material, and the steps of applying each further comprise the substep of generating an electromagnetic field proximate the target area where the electromagnetic field induces a high mass density in the applied powder during sintering.

A further embodiment of the present invention proposes a method of applying a layer of powder in an area comprising the steps of: applying a bed of powder near one end of the area; moving an electrically charged drum in one direction from one end of the area to another end of the area; rotating the drum in the opposite direction of movement from one end of the area to the other end; contacting the bed of powder with the counter-rotating drum as it moves to the other end; and dispersing the powder from beneath the drum in the direction of movement of the drum so that a layer of powder is left behind the drum.

As can be seen from the foregoing general description, the apparatus of the present invention solves many of the problems associated with the known methods for manufacturing parts. First, the present invention is well suited for the manufacture of prototype parts or replacement parts in limited quantities.

Furthermore, the method and apparatus herein are capable of producing parts with complicated shapes that cannot be obtained using conventional manufacturing processes. Furthermore, the present invention eliminates tool wear and machine design as limiting factors on the tolerances that can be obtained in the manufacture of the part. Finally, with the apparatus of the present invention, which is integrated with CAD/CAM systems, a large number of spare parts can be programmed in the computer and can be easily manufactured with little set-up or human intervention.

The invention is explained in more detail below with reference to the drawings. It shows

Fig. 1 is a schematic representation of the device of the present invention,

Fig. 2 is a schematic diagram showing a portion of the layered structure of a part made in accordance with the present invention and illustrating the raster scan pattern of the laser beam in the target area.

Fig. 3 is a block diagram illustrating the interface hardware between the computer, the laser and the galvanometers of the present invention,

Fig. 4 is a perspective view of a sample part made according to the present invention,

0 Fig. 5 is a sectional view with sections broken away and in phantom of the part shown in Fig. 4,

Fig. 6 is a flow chart of the data measurement program according to the present invention,

Fig. 7 is a sectional view taken along line 7-7 in Fig. 4,

0 Fig. 8 is a diagrammatic representation of the interrelationship between a single scan of the laser over the layer of Fig. 7 and the control signals of the present invention,

5 Fig. 9 a mixture of the materials in a powder,

Fig. 10 the materials in a powder, one by

the other is coated.

Fig. 11 shows a portion of the sintering cycle for a mixture of materials as currently understood,

Fig. 12 two materials mixed as sequentially applied layers before sintering,

Fig. 13 is a schematic vertical sectional view of the device for distributing the powder according to the present invention, in which the powder is spread in a layer on the part to be produced,

Fig. 14 is a schematic perspective view of the device for distributing the powder according to the present invention,

Fig. 15 electric and magnetic fields interacting with a 0 powder according to the present invention,

Fig. 16 shows a charged platen and an oppositely charged layer of powder according to the present invention,

Fig. 17 and 18 a pressurized liquid interacting with the applied powder of the present invention,
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Fig. 19 shows a magnetic field interacting with the applied powder of the present invention, and

Fig. 20 an electric field interacting with the powder of the present invention.

In the drawings, Fig. 1 generally shows the advantages

device 10 according to the present invention. In general, the device 10 includes a laser 12, the powder dispensing device 14 and the laser control device 16. In more detail, the powder dispensing device 14 includes a hopper 20 for receiving the powder 22 and has an exit opening 24. The exit opening 24 is directed for dispensing a combination of materials in powder form onto a target area 26, which is generally defined by the boundary 28 in Fig. 1. Of course, there are many alternatives in dispensing the powder 22.

The components of laser 12 are shown somewhat schematically in Fig. 1 and include a laser head 30, a safety shutter 32 and a front mirror assembly 34. The type of laser used depends on many factors and in particular on the type of powder 22 to be sintered. In the embodiment of Fig. 1, a Nd:YAG laser (Lasermetrics 9500Q) was used which can be operated in a continuous or pulsed mode with a maximum output power of 100 watts in the continuous mode. The laser beam output of laser 12 has a wavelength of about 1060 nm which is near infrared. Laser 12 shown in Fig. 1 includes an internal pulse frequency generator with a selectable range of about 1 kHz to 40 kHz and exhibits a pulse duration of about 6 nanoseconds. In both the pulsed and continuous modes of operation, the laser 12 can be modulated to be turned on or off to selectively produce a laser beam that moves generally along the path shown by the arrows in Fig. 1.

In order to focus the laser beam, a diverging lens 3 6 and a converging lens 3 8 are arranged along the path of movement of the laser beam, as shown in Fig. 1.

by using the converging lens 38, the location of the actual focus is not controlled simply by changing the distance between the converging lens 38 and the laser 12. The diverging lens 36, which is placed between the laser 12 and the converging lens 38, creates a virtual focus between the diverging lens 36 and the laser 12. Changing the distance between the converging lens 38 and the virtual focus allows the actual focus to be controlled along the path of travel of the laser beam on the side of the converging lens 38 remote from the laser 12. In recent years, there have been many advances in the field of optics, and it is recognized that many alternatives exist for effectively concentrating the laser beam at a known location.

In more detail, the laser controller 16 includes the computer 40 and the scanning system 42. In a preferred embodiment, the computer 40 includes a microprocessor for controlling the laser 12 and a CAD/CAM system for generating the data. In the embodiment shown in Figure 1, a personal computer (Commodore 64) is used whose primary features include an accessible interface port and a flag line that generates a non-maskable interrupt.

As shown in Fig. 1, the scanning system 42 includes a prism 44 for redirecting the path of travel of the laser beam. Of course, the physical design of the device 10 is the primary consideration in determining whether one prism 44 or a plurality of prisms are needed to manipulate the path of travel of the laser beam. The scanning system 42 also includes a pair of mirrors 46, 47 driven by the respective galvanometers 48, 49. The galvanometers 48, 49 are connected to their respective mirrors 46, 47 to selectively align the mirrors 46, 47. The galvanometers 48, 49

are mounted perpendicular to each other such that the mirrors 46, 47 are nominally mounted at right angles to each other. A driver 50 for the function generator controls the movement of the galvanometer 48 (the galvanometer 49 is coupled to the movement of the galvanometer 48) so that the aim of the laser beam (shown by the arrows in Fig. 1) in the target area 26 can be controlled. The driver 50 is operatively connected to the computer 40 as shown in Fig. 1. It will be appreciated that alternative scanning methods are available for use as a scanning system, including acoustic-optical scanners, rotating polygon mirrors and resonant mirror scanners.

In Fig. 2 of the drawings, a portion of a part 52 is shown schematically and four layers 54-57 are shown. The target of the laser beam, designated 64 in Fig. 2, is directed into a raster scan pattern as at 66. As used herein, "target" is used in the usual sense of "indicating the direction" but does not mean the modulation state of the laser 12. For convenience, axis 68 is considered the fast scan axis while axis 70 is referred to as the slow scan axis. Axis 72 is the direction of build of the part.

Figures 9 and 10 schematically show a powder comprising first and second materials from which a part can be made using the present invention.

Fig. 9 shows a mixture of the first material 901 and the second material 902. The materials are combined in a mixture using conventional mixing techniques. Fig. 10 shows the material 1002 coated with the material 1001. The material 1002 is coated using conventional coating techniques.

As will be further appreciated by those skilled in the art, the coated materials as shown in Figure 10 may be mixed to produce a desired blend of materials.
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In Fig. 11, a portion of a sintering cycle is illustrated, as currently understood. Fig. 11a shows a mixture of materials prior to the application of energy capable of causing sintering. Preferably, the materials comprising the powder mass 1100 exhibit more than one bonding or dissociation temperature. Fig. 11b shows the powder 1100 during the application of energy sufficient to promote sintering. Fig. 11b shows the material 1101 having a lower bonding or dissociation temperature than the material 1102. In a preferred embodiment, the material 1101 having the low temperature phase infiltrates into the powder mass 1100 in the area surrounding each particle of the material 1101. In a powder mixture of polymers of different materials, such infiltration is demonstrated by chain diffusion and entanglement of the chains of one polymer with those of the other. In a mixture of first and second metals present as a mass of porous powder of given porosity, such infiltration is evidenced by mutual diffusion of one metal into the surface of the other. Additional powder components could also be added to the mixture to promote infiltration. Similarly, a gas phase can be used to promote infiltration and sintering. The gas phase can be either inert or active, preferably to either displace an undesirable gas or to introduce a desired gas. Fig. 1c shows a potential mechanism by whose action, including but not limited to capillary effects, the material 1101 can infiltrate the powder mass 1100. Fig. 11d shows the part following sintering at the pre-

underlying invention.

Because a material having a higher bonding or dissociation temperature than the temperature obtained during sintering can be selected, the material with the higher bonding or dissociation temperature does not sinter but can maintain its original structure. Particularly in the case of crystalline material, this enables control of epitaxial growth in the selective beam sintering process according to the present invention. _For example, when a material with a higher bonding or dissociation temperature is arranged in a special structure, which can preferentially lead to epitaxial growth from the previous layer, only the material with the lower bonding or dissociation temperature allows bonding or dissociation since the material with the higher temperature maintains its structure.

The choice of materials for the powder allows for a wide range of resulting sintered materials. For example, a conductive material is preferably coated with an insulating polymeric material to produce a powder. The powder is then dispersed in the target area. The material is preferably sintered and the insulating material can later be removed by a conventional process including, but not limited to, a chemical process, resulting in a conductive sintered product.

It is further shown that extremely hard materials can be made using the present invention. For example, tungsten carbide/cobalt tools, which are difficult to shape or grind because of their extreme hardness, can be made by coating the tungsten carbide with cobalt to produce a powder, or

by mixing tungsten carbide and cobalt to produce a powder. During sintering, the cobalt preferably melts under the applied energy beam, causing local infiltration of the tungsten carbide. The part being manufactured is preferably ready for use after a second process, which includes, but is not limited to, annealing.

It is further demonstrated that copper and tin can be combined in a powder. The tin, which has a lower melting temperature than the copper, will melt and infiltrate the copper during sintering.

Secondary treatment may also be applied to parts made according to the present invention. For example, where the tin may melt and infiltrate the copper during sintering, annealing as a post-treatment will dissolve the tin in the copper in the solid state, producing a bronze with minimal volume change or distortion.

It is further shown that a metal, including but not limited to iron or steel, can be coated with the polyethyl methacrylate polymer (PMMA) to form a powder. Sintering allows the PMMA to flow and bond the metal. Annealing as a post-treatment will dissociate the PMMA and sinter the metal, producing the finished part.

Ceramic materials can also be processed in this way. For example, a mixture of fluorophosphate glass powders with alumina powders will result in softening of the glass and infiltration of the alumina during sintering. In another example, aluminum silicate, silicon dioxide or another ceramic powder can be coated with a polymer using a variety of methods that

spray drying and solvent coating. A surfactant may be used to pretreat the ceramic powder prior to coating. This agent may be based on organic silane chemistry or other chemistry known to promote wettability of the ceramic material by the polymer and adhesion of the ceramic material to the polymer. A polymer, either thermoplastic or thermosetting, that can be coated onto the ceramic material may be used as a binder. Typical materials include PMMA, polystyrene, various epoxies and phenolic resins.

Any combination of materials including, but not limited to, metals, ceramics, and polymers enables the manufacture of parts according to the present invention, wherein at least one material in the powder has a low bonding or 0 dissociation temperature relative to the other materials in the powder.

In a further preferred embodiment of the present invention, the temperature of the powder mass can be increased by using conventional heating devices which allow the energy beam to provide only a small increase in energy to cause the binding or dissociation of one of the elemental materials of the powder.

0 The materials making up the powder can be selected for the selective absorption of the energy from a laser beam (represented by the arrows in Figs. 11a and 11b) for each material. In a preferred embodiment, shown in Fig. 11, the material 1101 5 can be selected to absorb the wavelength of the applied beam energy represented by the arrows, while the elemental material 1102 has less

Energy is absorbed, allowing the elemental material 1101 to be bound or dissociated before the elemental material 1102 is bound or dissociated. This absorption of energy can be achieved by either the selection of the material or the wavelength of the laser beam, or both in a variety of combinations.

In Fig. 12, in yet another preferred embodiment, a material 1201 is preferably deposited on the surface 1200, and then a second material 1203 is deposited on the material 1201 prior to sintering. The materials 1201 and 1203 preferably have different bonding or dissociation temperatures.

In Figs. 13 and 14, an alternative form of powder distribution device 20 is shown. Generally, a support defines a target area 102, which is preferably electrically charged, and to which the aim of the jet 64 is directed (see Fig. 1). A hopper 104 distributes the powder 106 through the opening 108 into the target area 102. A metering roller (not shown) is disposed in the opening 108 so that when the metering roller is rotated, a metered deposit of the powder is applied in a line at the end of the target area 102.

A balancing mechanism 114 distributes the load of powder 106 from one end 110 to the other end 112 of the target surface. The balancing mechanism 114 includes a cylindrical drum 116 having an electrical charge of opposite polarity to the target surface 102. It is believed that the attractive forces between the charged layer of powder 164 and the oppositely charged target surface 102 create a pressure in the powder layer 164, thereby causing a high mass density of the powder 106 that encloses the powder in the layer 164. A motor 118 mounted on a rod 120 is connected to the

Drum 116 via pulley 122 and belt 124 to rotate the drum.

The balancing mechanism 114 also includes a mechanism 126 for moving the drum 116 between the end 110 and the end 112 of the target surface. The mechanism 126 includes an X/Y table for horizontally and vertically moving the rod 120. That is, the table 128 is fixed while the plate 130 is selectively movable relative to the table.

In the preferred embodiments of the present invention, the high mass density of the applied powder is preferably achieved by applying a force to the applied powder during sintering.

A high mass density in a powder can be obtained simply by applying a mechanical press to the powder during sintering, whereby the press is preferably both transparent to the laser beam and has a high thermal conductivity.

Fig. 15 shows a preferred embodiment for achieving a high mass density in the powder 1207 deposited on the platen 1201 in the target area. The powder 1207 is preferably electrically conductive. A positively charged plate 1209 and a negatively charged plate 1211 are preferably disposed substantially perpendicular to the platen 1201 and in a parallel and spaced relationship to each other. The powder 1207 is disposed between the plates 1209 and 1211 on the platen 1201. An electric field 1203 is generated through the powder 1207 between the positively charged plate 1209 and the negatively charged plate 1211. The magnetic field 1205 is also generated. The current flow due to field 1203 in conjunction with field 1205 creates a downward pressure 1213 on the

Powder 1207, whereby the powder 1207 can achieve a higher mass density than would have been the case in the absence of the fields. The fields 1203 and 1205 can be maintained during sintering, whereby a force is maintained on the powder 1207 and whereby a high mass density is achieved in the powder 1207 during sintering.

Fig. 16 shows the powder 13 03, which is preferably insulating, disposed on the charged platen 13 01. A charged layer of powder 1305 is preferably disposed as the upper layer of powder 13 03, and is preferably charged opposite to the charge on the platen 13 01. In a preferred embodiment, a charged, counter-rotating drum (as shown in Fig. 13) can be used to charge the layer 13 05. The attraction between the opposite charges in the platen 1301 and the layer of powder 13 05 causes a high mass density in the powder 13 03.

In Fig. 17 and 18 two preferred embodiments are shown in which a pressurized liquid stream is used. In Fig. 17 the powder 1401 is placed on a sieve support 1405 which also serves as a support plate for the distributed powder in the target area. The liquid stream 1403 is applied from above the sieve support 1405 as shown in Fig. 17, whereby the powder 1401 can achieve a high mass density. The sieve support 1405 preferably comprises a material which causes the liquid stream 1403 to pass through but the powder 1401 is retained. Fig. 18 shows another preferred embodiment in which a liquid stream is used to achieve a high mass density in the powder. In Fig. 18, the powder 1501 is placed on the support plate 1507 and a pressurized liquid stream 1503 is supplied from above the support plate

1507 and the powder 1501 as shown in Fig. 18. The screen pads 1505 are positioned substantially perpendicular to the platen 1507 in a spaced relationship to the powder 1501 deposited between the screen pads 1505. The design shown in Fig. 18 enables a reduction in the buildup of excessive pressure on the powder 1501 near the platen 1507 by allowing the liquid stream 1503 to exit the powder 1501 through the screen pads 1505.

In Figure 19, a magnetic powder 1603, which is preferably either a magnetizable or hard ferromagnetic material, is placed on the platen 1601. A magnetic field 1605 is preferably applied, causing the powder 1603 to achieve a high mass density.

In Figure 20, the powder 1703 includes polarizable elements 1705. For clarity, the polarizable elements 1705 are shown only in a distal relationship to the platen 1701. However, the elements 1705 may appear throughout the powder 1703. The electric field 1707 is preferably generated by a charge appearing on the platen 1701. The field 1707 generates a downward force on the elements 1705, causing a high mass density in the powder 1703.

Figures 15 to 20 show preferred embodiments in which a plurality of layers of the sintered powder are arranged close to a support plate, with a single layer of the unsintered powder arranged distal to the support plate. An external force is therefore only required to achieve a high mass density in the upper layer.

A fundamental concept of the present invention is the

Building a part layer by layer. That is, a part is viewed as a multitude of individual cross-sectional regions that cumulatively have the three-dimensional shape of the part. Each individual cross-sectional region has defined two-dimensional boundaries - of course, each region can have unique boundaries.

In the process, a first portion of the powder 22 is deposited in the target area 26 and selectively sintered by the laser beam 64 to produce a first sintered layer 54 (Fig. 2). The first sintered layer 54 corresponds to a first cross-sectional area of the desired part. The laser beam selectively sinters only the deposited powder 22 within the specified boundaries.
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There are of course alternative methods of selectively sintering the powder 22. One method is to direct the target of the beam in a "vector" manner - i.e., the beam would actually scan the outline and interior of each cross-sectional area of the desired part. Alternatively, the target of the beam 64 is scanned in a repeating pattern and the laser 12 is modulated. In Fig. 2, a raster scan pattern 46 is used and it is advantageous over the vector method mainly because of the simplicity of its implementation. Another possibility is to combine the vector and raster scan methods so that the desired boundaries of the layer are scanned in a vector manner and the interior is irradiated in a raster scan manner. There are of course trade-offs associated with the methods selected. For example, the raster method has a disadvantage when compared to the vector method in that the arcs and lines that are not parallel to the axes 68, 70 of the raster pattern 66 of the laser beam 64 are only approximated. Therefore, in certain cases, the resolution of the part can be deteriorated if, after the raster pattern processing,

However, the raster method has an advantage over the vector method because of the simplicity of its implementation.

In Fig. 1, the target of the laser beam 64 is scanned in the target area 26 in a continuous raster pattern. Generally, the driver 50 controls the galvanometers 48, 49 to execute a raster pattern 66 (see Fig. 2). The translating movement of the mirror 46 controls the movement of the target of the laser beam 64 in the fast scan axis 68 (Fig. 2), while the movement of the mirror 47 controls the movement of the target of the laser beam 64 in the slow scan axis.

The instantaneous position of the target of the beam 64 is fed back to the computer 40 by the driver 50 (see Fig. 3). As will be described in more detail below, the computer 40 has information relating to the desired cross-sectional area of the part then to be produced. That is, a portion of the loose powder is dispersed in the target area 26 and the target of the laser beam 64 is moved in its continuous raster pattern. The computer 40 modulates the laser 12 to selectively produce a laser beam at desired intervals in the raster pattern 66. In this manner, the directed beam of the laser 12 selectively sinters the powder 22 in the target area 26 to produce the desired sintered layer having the specified boundaries of the desired cross-sectional area. This process is repeated layer by layer, with each layer being sintered one after the other to produce a cohesive part, such as part 52 in Fig. 2.

During operation, the wavelength of the laser 12 can be changed 5 to achieve a higher absorption capacity of energy by the selected materials in the powder relative to the other materials in the powder 22. During operation

mixed, coated or other combinations of the powders are preferably selected to produce a sintered product with properties including, but not limited to, tight dimensional tolerances, structural integrity and the required mechanical behavior.

In Figs. 13 and 14, the distribution mechanism 114 provides a controlled, uniform layer of powder in the target area 102 without disturbing the part being manufactured. A metered amount of powder 106 is applied to the end 110 of the target area 102. The electrically charged drum 116 is spaced from the end 110 as the powder 106 is distributed. In the system shown in Fig. 14, the plate 130 and rod 120 (and the mechanisms attached thereto) are raised vertically after the powder is distributed in the fill. Movement of the plate 130 toward the hopper 104 brings the drum 116 into a position adjacent the fill of powder aligned along the end 110. The drum 116 is lowered to contact the bed of powder and is brought horizontally over the target surface 102 to spread the bed of powder in a uniform, flat layer. Of course, the exact location of the plate 130 relative to the table can be controlled so that the distance between the drum 116 and the target surface 102 can be precisely controlled to provide the desired thickness of the layer of powder. Preferably, the distance between the drum 116 and the target surface 102 is constant to obtain parallel motion, but other spacing options are applicable.

As the drum 116 is moved horizontally across the target surface 102 from end 110 to end 112, the motor 118 5 is activated to counter-rotate the drum 116. As shown in Fig. 13, "counter-rotation" means that the drum 116 is rotated in the direction R opposite to the direction of movement

M of the drum 116 is rotated horizontally over the target surface 102.

In more detail (Fig. 13), the drum 116 is rotated at a high speed in a counterclockwise direction while it contacts the pile of powder 106 along the rear edge 160. The mechanical action of the drum on the powder causes the powder to be ejected in the direction of movement M so that the ejected particles fall in front of the drum. As shown in Fig. 13, a uniform, flat layer of powder is left behind the drum 116 (between the drum 116 and the end 110) as shown at 164.

Figure 13 also schematically shows that the powder 106 can be distributed over the target area without disturbing the previously sintered powder 166 or the unsintered powder 168. That is, the drum 116 is moved over the target area 102 without imparting shear stress to the previously built-up layers and without disturbing the article during its manufacture. The absence of such shear stress allows a uniform layer of the powder 106 to be distributed over the frangible substrate in the target area, comprising both the sintered particles 166 and the unsintered particles 168.

As shown in Figs. 15 to 20, pressure in the form of either liquid flows or electromagnetic fields can be applied to both the layers of sintered powder and preferably to an upper layer of the applied, non-sintered powder in order to achieve a high mass density of the applied powder during sintering.

The interface hardware functionally connects the computer 40 with the laser 12 and the galvanometers 48, 49. The output

gate of the computer 40 (see Figs. 1 and 3) is connected directly to the laser 12 to selectively modulate the laser 12. When operating in the pulsed mode, the laser 12 is easily controlled by digital inputs to the pulsed gate input of the laser. The galvanometer 48 is driven by the function generator driver 50 to steer the beam in the fast scan axis 68 independent of any control signals from the computer 40. However, a position feedback signal from the galvanometer 48 is fed to a voltage comparator 74 as shown in Fig. 3. The other input to the comparator is connected to the digital-to-analog converter 76, which points to the lowest valid six bits (bits 0-5) of the user port of the computer 40. As shown in Fig. 3, the output of the voltage comparator 74 is connected to the flag line on the user port of the computer 40. When the voltage comparator detects that the feedback signal from the galvanometer 48 crosses the signal from the digital-to-analog converter 76, the flag line goes low, causing a non-maskable interrupt. As discussed below, the non-maskable interrupt causes the next byte of data to be brought out on the user port of the computer 40.

Finally, as shown in Fig. 3, the galvanometer 49 which drives the target of the laser beam 64 in the slow scan axis 70 is controlled by a second digital-to-analog converter 78. The digital-to-analog converter 78 is driven by a counter 79 which increments with each scan of the target of the beam 64 in the fast scan axis 68. The 8-byte counter is designed to overflow after 256 scans in the fast scan axis 68 to begin a new cycle or raster scan pattern 66.

Preferably, the control information data (i.e., the defined boundaries of the cross-sectional areas) for each

Raster pattern 66 is determined by means of a CAD system which is given the overall dimensions and shape of the part to be manufactured. Whether programmed or derived, the control information data for each raster pattern 66 is stored in the computer's memory as a series of 8-bit words. The data format represents a pattern of the "on" and "off" regions of the laser 12 versus the distance along the raster pattern 66 traveled by the target of the beam 64. The data is stored in a "tilt point" format where the data represents the distance along each raster scan pattern 66 where the laser is modulated (i.e., switched from on to off or from off to on). Although a "bit map" format could be used, the "tilt point" format has been found to be more effective for manufacturing high resolution parts.

For each 8-bit word, the lowest valid six bits (bits 0-5) represent the location of the next flip-flop point - that is, the next location for modulation of the laser 12. The next bit (bit 6) represents whether the laser is on or off, immediately before the flip point identified in the lowest valid six bits. The highest valid bit (MSB or bit 7) is used for loop operation and for controlling the slow scan axis 70 of the aim of the beam 64. Because the Commodore 64 had limited memory, loop operation was necessary, it being understood that a computer 40 with a larger memory would not require loop operation.

Fig. 6 shows the flow chart for the data measurement program. The data measurement program is in operation whenever the flag line goes low, causing a non-maskable interrupt (see Fig. 3). The interrupt causes the microprocessor of the computer 40 to

2-byte interrupt vector which indicates the location in memory where program control is transferred at the interrupt. As shown in Fig. 6, the data program first pushes the registers onto the stack and then loads the next byte of data into the accumulator. The data word is also output to the user port, with the sixth bit being used to modulate the laser 12 (Fig. 3).

As shown in Fig. 6, the highest valid bit (MSB or bit 7) of the data word in the accumulator is checked. If the value of the highest valid bit is one, it means that the end of the loop has not been reached; therefore, the data pointer is incremented, the registers are popped from the stack, and the data measurement program is exited, returning control to the microprocessor at the point of interruption. If the highest valid bit in the accumulator is zero, the data word is the last word in the loop. If the data word is the last word in the loop, the next bit in memory is a loop counter, and the following two bytes are a vector pointing to the top of the loop. As can be seen from Fig. 6, if the highest valid bit is zero (end of loop), the loop counter (next bit) is decremented and analyzed. If the loop counter is still greater than zero, the data pointer takes the value of the next two bytes of memory after the loop counter, the registers are popped from the stack, and program control returns to the point of interruption.

On the other hand, if the loop counter is zero, the data pointer is incremented by three and the loop counter is reset to ten before stopping the program. It can be seen that the need for such looping operation is eliminated if the memory size of the computer 40 is adequate.

4 and 5, a pattern part 52 is shown. As can be seen in the drawing, the pattern part 52 takes on an unusual shape in that it is not symmetrical and would therefore be difficult to manufacture using conventional machining techniques. For reference purposes, the part 52 includes an outer base structure 80 having an inner cavity 82 and a column 84 disposed within the cavity 82 (see Fig. 4). Fig. 5 shows the part within the boundary 28 which defines the target surface 26 as shown in Fig. 1. As shown in Fig. 5, a portion of the powder 22 is loose while the remainder of the powder is selectively sintered to have the structure of the part 52. Fig. 5 is shown in vertical section with portions broken away and in phantom to illustrate the sintered cohesive portions of part 52.

Fig. 7 shows a horizontal cross-sectional area taken along line 7-7 in Fig. 4. Fig. 7 shows a single layer 86 bonded to the cross-sectional area of the part to be manufactured. As such, the sintered layer 86 of Fig. 7 is a product of a single grid pattern 66 as shown in Fig. 2.

5 For reference purposes, a scan line through the sintered layer 8 6 has been labeled "L". Fig. 8 shows the software and hardware interface operation during scan L. The upper graphical representation shows the position of the feedback signal from the fast axis galvanometer 48 and 0 the output signal of the first digital-to-analog converter 76

(see Fig. 3). The voltage comparator 74 generates an output signal to the flag line of the computer each time the feedback signal and the output signal of the first digital-to-analog converter cross. 35

In the upper illustration of Fig. 8, these points are marked with T to represent the tipping points. As can be seen from

As can be seen in the lower graph, the flag line generates a non-maskable interrupt corresponding to each tipping point T. The sixth bit of each data word is analyzed and the current state of the laser 12 will reflect the value. The second to last graph of Fig. 8 shows a laser modulation signal for the scan line L of Fig. 7. The second graph of Fig. 8 shows that an up-going edge in the highest valid bit will be encountered at the end of each scan of the target of the laser beam 64 in the fast scan axis 68. As shown in Figs. 3 and 6, the counter 79 increments on an up-going edge and outputs a signal to the second digital-to-analog converter 78 to drive the slow axis galvanometer 49.

As can be seen from the example shown in the drawing, parts of complex shape can be manufactured with relative ease. Those skilled in the art will recognize that the part 52 shown in Fig. 4 would be difficult to manufacture using conventional machining techniques. In particular, machine tool access would make the manufacture of the cavity and column 84 difficult, if not impossible, if the part 52 is of a relatively small size.

In addition to avoiding the problem of access, it is recognized that the accuracy of manufacture is not dependent on the wear of the machine tool and the accuracy of the mechanical parts experienced by conventional machine tools. That is, the accuracy and tolerances of the parts manufactured by the method and apparatus of the present invention are primarily a function of the quality of the electronics, optics and application software. Of course, heat transfer and material considerations affect the tolerances obtained.

38
can.

Those skilled in the art will recognize that conventional machining processes require considerable human intervention and judgment. For example, a conventional machining process such as milling would require creativity to make such decisions as tool selection, part segmentation, sequence of cuts, etc. Such decisions would be even more important when producing a control strip for a punched tape controlled milling machine. On the other hand, the apparatus of the present invention requires only the data associated with each cross-sectional area of the part to be manufactured. Although such data can be easily programmed into the computer 40, the computer 40 includes a CAD/CAM system. That is, the CAD/CAM portion of the computer 40 is presented with the overall dimensions and shapes of the desired part to be manufactured, and the computer 40 determines the boundaries for each individual cross-sectional area of the part. In this way, a very large amount of information about the part can be stored and fed to the computer 40 on a selectable basis. The apparatus 10 produces a selected part without any setup time, part-specific tooling, or human intervention. Even the complicated and costly molds associated with powder metallurgy and conventional casting processes are eliminated.

Although the use of conventional manufacturing processes enables large volume production and allows certain material properties of the part to be achieved most advantageously, the method and apparatus 10 of the present invention are useful in many contexts. In particular, prototypes are

type models and casting patterns are easily and inexpensively produced. For example, casting patterns are easily produced for use in sand casting, lost wax casting or other manufacturing processes. In addition, where the quantities desired are very small, such as for obsolete spare parts, the production of such spare parts using the apparatus 10 of the present invention has many advantages. Finally, the use of the apparatus 10 may be useful where the size of the production equipment is a major obstacle, such as on a ship or in space. Similarly, the use of the methods and apparatus shown in Figs. 16-20 may also be useful for manufacturing where the size of the equipment or the lack of gravity is a major obstacle.

Further modification and alternative embodiments of the apparatus of this invention will be apparent to those skilled in the art in light of this description.
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Claims (32)

&bull; · » &diams; PROTECTION CLAIMS 1. Device for the manufacture of a part, which comprises: an irradiation device (30) for selectively emitting a directed energy beam (64); a structure (28) for providing a target surface (26, 102) for the manufacture of the part; a powder (22) comprising a plurality of materials (901, 902; 1001, 1002), wherein the plurality of materials have more than one bonding temperature; a device (116) for distributing the powder; and a control device (40) for moving the target of the beam and for modulating the irradiation device to selectively sinter, within the specified limits, a layer (54, 55, 56, 57) of the powder distributed in the target area, the control device being operable to effect the selective sintering of the sequential layers of the powder within the respective specified limits to produce a part having a plurality of layers (54, 55, 56, 57) sintered sequentially. 2. Device according to claim 1, characterized in that/? the plurality of materials comprises at least a first material (901) mixed with at least one second material (902). 3. Device according to claim 1, characterized in that the plurality of materials comprises at least a first material 0 1002) coated with at least a second material (1001). 4. Device according to claim 1, characterized by a structure for providing a gaseous environment to promote sintering. 5. Device according to claim 1, characterized by a A plurality of powders, the plurality of powders having more than one binding temperature; and a device for dispensing each powder of the plurality of powders. 6. Apparatus for manufacturing a part, comprising: an irradiation device (30) for selectively emitting a directed energy beam (64); a structure (28) for providing a target surface (26, 102) for manufacturing the part; a device (20) for depositing a powder in the target area (26, 102); control means (40) for moving the target of the beam and for modulating the irradiation device to selectively sinter, within the specified limits, a layer of the powder distributed in the target area (26, 102), the control means being operable to effect selective sintering of the sequential layers (54, 55, 56, 57) of powder within the respective specified limits to produce a part having a plurality of layers (54, 55, 56, 57) sintered sequentially; and means for achieving a high mass density in the powder in the target area. 7. Device according to claim 6, characterized in that the device for achieving a high mass density enables the achievement of this high mass density during sintering. 0 8. Device according to claim 6, characterized in that the device (20) for application has a device for electrostatically charging and distributing the powder. 5 9. Device according to claim 8, characterized in that/3 the device for achieving a high mass density comprises a device for generating an electro- magnetic field near the target surface (26, 102), wherein the electromagnetic field causes a high mass density in the powder in the target surface during sintering. 10. Device according to claim 6, characterized in that the powder comprises polarizable elements, and in that the device (20) for application comprises a device for distributing the powder. 11. Device according to claim 10, characterized in that the device for bringing about a high mass density comprises a device for generating an electromagnetic field near the target surface (26, 102), the electromagnetic field causing a high mass density in the powder in the target surface (26, 102) during sintering. 12. Device according to claim 11, characterized in that the device for generating an electromagnetic field enables the generation of a field that has varying field strengths across the target area (26, 102). 13. Device according to claim 6, characterized in that/3 5 the device (20) for application comprises a device for distributing the powder with a first electrical charge, and wherein the target surface (26, 102) has a second electrical charge, the first electrical charge having a charge opposite to the second electrical charge. 14. Device according to claim 6, characterized in that the device (20) for application comprises: a device for distributing a first part of the powder (5) with a first electrical charge on the first part; and a shaping device which can be passed near the distributed first part. 15. Device according to claim 14, characterized in that the device (20) for applying further comprises a device for distributing a second part of the powder having a second electrical charge on the second part, the first electrical charge having a charge opposite to the second electrical charge. 16. Apparatus according to claim 6, characterized in that the device (20) for applying further comprises means for distributing a bed (106) of powder at one end of an area as a layer of the powder in the area, comprising: an electrically charged drum device (116); means for moving the drum from one end of the area to another end of the area with a desired distance between the area and the drum (116); means for rotating the drum (116) opposite to the direction (M) of movement of the drum from one end to the other end, the drum device being operable when rotated in the opposite direction (R) and moved from one end to the other end to contact the bed (106) and eject the powder in the direction of movement (M) to leave a layer of powder between the drum device and the one end having a thickness approximately corresponding to the desired distance. 17. Apparatus according to claim 6, characterized in that the powder is magnetic, and in that the means for achieving a high mass density comprises means for generating an electromagnetic field in the vicinity of the target surface (26, 102), the electromagnetic field causing a high mass density in the powder in the target surface (26, 102) during sintering. 18. Device according to claim 6, characterized in that the means for producing a high mass density comprises means for directing a jet of liquid towards the powder deposited in the target area (26, 102) to produce a high mass density in the powder in the target area (26, 102) during sintering. 19. Apparatus according to claim 6, characterized in that the device for producing a high mass density comprises a device for enabling the application of centrifugal force to the applied powder in order to produce a high mass density in the powder in the target area (26, 102). 20. Device according to one of the preceding claims, characterized by a device for removing unbound portions of the powder in order to produce the part (52). 21. Device according to one of the preceding claims, characterized in that the second material (1001) has a lower softening temperature than the first material (1002), wherein the irradiation in the second material (1001) in the selected portion of the powder causes parts of the first material (1002) to bind at the irradiated locations. 22. Device according to one of the preceding claims, characterized by a device for heating the 0 produced part (52). 23. Device according to one of the preceding claims, characterized in that the directed energy beam (64) has a specific wavelength, wherein the second material (1001) has a higher absorption coefficient for the specific wavelength than the first material (1002). 24. Device according to one of the preceding claims, characterized in that the heat of the heating device removes the second material (1001) and parts of the first material (1002) fuse together. 25. Device according to one of claims 1 to 23, characterized in that the heat of the heating device forms a bond of the first and second materials (1001, 1002). 26. Device according to one of the preceding claims, characterized in that the first material (1002) is electrically conductive. 27. Device according to one of the preceding claims, characterized in that the second material (1001) is an electrically insulating polymer. 28. Device according to one of claims 1 to 26, characterized in that the second material (1001) contains a polymer. 29. Device according to one of the preceding claims, characterized in that the second material (1001) is selected from the group of methacrylic acid derivatives, polystyrenes, epoxy resins or phenols. 30. Device according to one of the preceding claims, characterized in that the first and the second material (1001, 1002) react with each other due to the heat of the heating device. 31. Device according to one of the preceding claims, characterized in that the thermal conductivity of the first material (1002) is substantially greater than that of the second material (1001). 32. Device according to one of the preceding claims, characterized in that by irradiating the selected areas, the second material (1001) binds parts of the first (1002) in the selected sections of the powder.