WO2016206781A1

WO2016206781A1 - Device and method for the production of a three-dimensional object

Info

Publication number: WO2016206781A1
Application number: PCT/EP2016/000961
Authority: WO
Inventors: Florian Pfefferkorn
Original assignee: Eos Gmbh Electro Optical Systems
Priority date: 2015-06-22
Filing date: 2016-06-10
Publication date: 2016-12-29
Also published as: DE102015211494A1

Abstract

The invention relates to a device (1) for producing a three-dimensional object (2) by solidifying construction material layer by layer at points corresponding to the cross-section of the object (2) to be produced in the respective layer by applying electromagnetic radiation (22). Said device has a construction platform (9), on which the object (2) can be constructed, and an exposure unit (20) for emitting the electromagnetic radiation (22) in order to selectively solidify a layer of the construction material. The exposure unit (20) comprises a support (201, 21, 212), which can be rotated about an axis of rotation (R), and at least one exposure element (202), which is attached to the support (201, 21, 212). The invention further relates to a method for producing a three-dimensional object.

Description

Device and method for producing a three-dimensional object

The present invention relates to an apparatus and a method for producing a three-dimensional object by selective layer-by-layer solidification of building material by energy input.

A method of this kind is used, for example, for rapid prototyping, rapid tooling or rapid manufacturing. An example of such a process is known as "selective laser sintering or laser melting". In this case, powder is selectively solidified by selective irradiation with a laser beam.

European Patent EP 0 734 842 A1 discloses a device with a laser and an associated scanning device, by means of which solidification of powder takes place at points corresponding to the cross section of the object. Especially with large components, the scanning of the laser beam Be time-consuming over the surface to be consolidated in one layer.

A large-area exposure method that addresses this problem is the mask sintering method known, for example, from EP 1 015 214 B1. Here, a mask pattern corresponding to the cross-sectional area of a layer is placed on a mask apparatus, and the powder layer in the subregions not covered by the pattern is solidified by a radiation generator. By this method, the entire part surface to be solidified of a layer can be solidified simultaneously, whereby the construction time is shortened. However, a large part of the radiation energy is covered by the mask and can not be used to solidify the building material.

From US 2003/0214571 Al a linear exposure apparatus is known, which contains a multiplicity of exposure sources, which are arranged in the form of a matrix in rows and columns. The imagesetter extends over the entire width of the construction field, and by exposing the imagesetter in the longitudinal direction, all areas of the construction field are exposed. The exposure sources are switched on or off according to the cross section of a layer to be exposed by a DMD (Digital Micromirror Device). Around . covering the entire width of the construction area, however, a large number of exposure sources are required depending on the size of the component. In addition, a large part of the radiation energy is lost because the light of unused illumination sources is deflected by the micromirrors.

The object of the present invention is an alternative, preferably an improved, device and a corresponding method for producing a three-dimensional To provide object. In particular, it should be achieved here that the exposure speed can be increased without this being at the expense of energy efficiency or component accuracy.

The object is achieved by a device according to claim 1 and a method according to claim 13. Further developments of the invention are specified in the dependent claims. The developments or embodiments mentioned in the subclaims and the description below relating to the device can also be regarded as developments or embodiments of the method according to the invention or vice versa.

The inventive device for producing a three-dimensional object by sehichtweises solidification of structural material at the cross section of the object to be produced in the j eweiligen layer corresponding points by the action of electromagnetic radiation has a construction platform on which the ob ect is buildable, and an exposure unit for emitting the electromagnetic radiation for selectively solidifying a layer of the Aufaumaterials. In this case, the exposure unit comprises a support, which is rotatable about an axis of rotation, and at least one exposure element, which is mounted on the support. As a result of the rotation of the carrier, the energy input can take place on a circular path by means of the exposure unit, which can be carried out faster than by means of a translatory movement.

The hardening of the building material preferably takes place in at least one defined work plane. This allows the electromagnetic radiation to be focused to solidify a layer in a constant plane, which among other things the Construction of the device and the implementation of the manufacturing process simplified.

Preferably, the axis of rotation of the carrier is oriented substantially perpendicular to the working plane. It can thereby be achieved that the distance of the exposure element or of the exposure elements to the working plane in which the building material is solidified remains constant during the rotational movement of the support, which causes a constant surface energy input.

Preferably, the exposure unit comprises a plurality of exposure elements and the device is designed such that the radiation of each exposure element is imaged onto a pixel in the working plane at a point of illumination. As a result, a spatially exactly predetermined and delimited area of the working plane, namely the associated pixel, can be exposed by each exposure element.

The carrier may be designed as a single arm, which is rotatable about the axis of rotation. The support may be further embodied as two or more arms, which enclose an angle, preferably always the same angle, with each other and are rotatable about the axis of rotation. As a result, a circular surface to be exposed can be swept over in a simple manner.

Alternatively, the carrier may be formed as a disc which is rotatable about an axis of rotation. As a result, a circular area to be exposed can likewise be swept over in a simple manner. It is also possible to use the exposure elements over distribute the entire disc, which can further accelerate the exposure process.

Preferably, the exposure unit comprises a plurality of exposure elements arranged on the support such that, after one full rotation of the support, each pixel of a circular area in the work plane has been exposed at least at one exposure time when all of the exposure elements are on. As a result, by means of rotation of the carrier, a homogeneous, areal exposure of the building material within the swept circular area can be achieved.

Preferably, the at least one exposure element is arranged movably on the carrier such that its distance from the axis of rotation can be changed. Additionally or alternatively, the carrier is also translationally movable. This makes it possible to expose a wider area even by means of a single exposure element. In the case of a translatory movement of the carrier, the area which can be overrun by rotation of the carrier can also be smaller than the total area to be exposed.

Furthermore, it is preferred that a plurality of exposure elements are provided and the exposure elements are arranged on radius vectors from the rotational axis of a disc to a point on the outer periphery of the disc such that the distance between two adjacent exposure elements of such a radius vector is constant. Also, a plurality of exposure elements may be provided and the exposure elements are arranged on concentric circles about the axis of rotation, in particular such that the spacing of adjacent exposure elements on such a circle is constant. Preferably, a speed D of the carrier is constant when exposing a layer. The speed D is preferably greater than about 1 s ^-1, more preferably greater than about 5 s ^"1, even more preferably greater than about 10 s and ^_1. Preferably less than about 50 s." ^1, more preferably less than about 30 sec ^_1, still more preferably less than about 25 s, whereby any combinations of the upper and lower limits are possible.

This makes it possible to realize a uniform exposure.

The at least one exposure element is preferably in the form of a semiconductor laser, in particular as a semiconductor laser diode, more preferably as a vertical cavity surface emitting laser VCSEL or as a vertical external cavity surface

Emitting. Laser VECSEL. These exposure elements are suitable for fast on and off, and therefore the switching speed of the exposure elements and the speed D of the carrier can be well matched. In addition, the listed exposure elements have small spatial dimensions, so that many such exposure elements can be arranged close to each other on the support in order to achieve a good coverage of the surface to be exposed. Furthermore, it is easily possible to operate the listed exposure elements with variable power, so that, for example, not used for exposure exposure elements for preheating the surface of the building material can be used.

A method according to the invention for producing a three-dimensional object in a device for producing a three-dimensional object by layer-wise solidifying build-up material on the cross-section of the object to be produced in the respective layer corresponding locations by the action of electromagnetic radiation, the steps comprises building the object on a building platform and emitting the electromagnetic radiation to selectively solidify a layer of the building material. by means of an exposure unit. In this case, the exposure unit comprises a carrier which is rotated about an axis of rotation and at least one exposure element which is mounted on the carrier. Thus, a three-dimensional object can be produced by means of a device according to the invention.

Preferably, the switching speed of the exposure elements and the rotational speed of the carrier are adapted to one another and the at least one exposure element is switched on and off so that one of the object cross section in the respective

Layer corresponding surface is solidified. This is z. B. possible that the exposure elements deliver only as much energy as is required to solidify the cross-section of the object.

Preferably, the. Exposure unit multiple exposure elements and exposure elements which are not used for exposure at an exposure time are used at this exposure time for preheating the building material. As a result, the efficiency can be increased and a lower energy input can be used to solidify the material completely.

Further features and advantages of the invention will become apparent from the description of embodiments with reference to the accompanying drawings. FIG. 1 is a schematic view of an apparatus for layering a three-dimensional object according to an embodiment of the present invention.

FIGS. 2a and 2b each show a schematic side view of a carrier with two different arrangements of the exposure elements on the carrier. within the scope of embodiments of the present invention.

3a to 3d show schematic views of various embodiments of a carrier from above in the context of embodiments of the present invention.

In the following, an apparatus for layering a three-dimensional object according to an embodiment of the present invention will be described with reference to FIG. The device shown in FIG. 1 is a laser sintering device of the laser melting device 1 for constructing an object 2.

The laser sintering or laser melting device 1 has an upwardly open container 5 with a wall 6. In the container 5 a movable in a vertical direction V carrier device 7 is arranged, to which a base plate 8 is introduced, the. closes the container 5 down and thus forms its bottom. The base plate 8 may be a plate formed separately from the carrier device 7, which is fixed to the carrier device 7, or it may be formed integrally with the carrier device 7. Depending on the powder used (that is, generally building material) and process can be arranged on the base plate 8 is still a construction platform 9, on which the object 2 is constructed. The object 2 can also be on the Base plate 8 are built themselves, which then serves as a construction platform. In Fig. 1, the finished in the container 5 on the platform 9 finished Ob ekt 2 is shown. The object 2 is surrounded by unfixed building material 11.

The laser sintering or laser melting apparatus 1 further comprises a coater 14 movable in a horizontal direction H for applying a build-up material solidifiable by electromagnetic radiation from a reservoir not illustrated in detail in FIG. 1 to the working plane 10. Furthermore, an exposure unit 20 is arranged above the working plane. the electromagnetic radiation 22 emits and which will be described later with reference to Figs. 2a and 2b.

Furthermore, the laser sintering device 1 includes a control unit 29, via which the individual components of the device 1 are controlled in a coordinated manner for carrying out the building process. The control unit may include a CPU whose operation is controlled by a computer program (software). The computer program can be stored separately from the device on a storage medium, from which it can be loaded into the device, in particular into the control unit.

In operation, to apply a layer of the build-up material, first the support device 7 is lowered by a height which corresponds to the desired layer thickness. Using the coater 14, a layer of the building material is then applied. The application takes place at least over the entire cross-section of the object 2 to be produced, preferably over the entire construction field, ie the area of the working plane 10, the is within the upper opening of the container 5. Subsequently, the building material is solidified in the cross section of the herzustel sirloin object 2 corresponding points by the action of the electromagnetic radiation 22. These steps are repeated until the object 2 is completed and can be removed from the installation space.

FIG. 2a shows a schematic view of the exposure unit 20. The exposure unit 20 has a carrier 201 which is rotatable at a rotational speed D about an axis of rotation R. Preferably, the axis of rotation R of the carrier 201 is oriented substantially perpendicular to the working plane 10, and the carrier 201 is preferably aligned parallel to the working plane 10.

The rotational speed D is preferably constant during the exposure of a layer. The speed is given in revolutions per second (s ^"1 ) ^' , and preferably greater than 1 s" ¹ , more preferably greater than 5 s ^_1 , even more preferably greater than 10 s ^_1 and preferably less than 50 s " ¹ , more preferably less than 30 s " ¹ , even more preferably less than 25 s ^{" 1} , any combinations of the upper and lower limits are possible.

Furthermore, at least one exposure element 202 is provided on the underside of the carrier 201, ie on its side facing the working plane 10. Preferably, the exposure unit 20 comprises a plurality of exposure elements 202, wherein the radiation of each exposure element 202 at an exposure time is preferably imaged onto a limited area in the working plane, referred to as a pixel. Furthermore, the exposure unit 20 may also have a focusing device not shown in detail in FIG. 2a, which is arranged below the carrier 201 and focuses the electromagnetic radiation emitted by the exposure elements 202 onto the working plane 10. This focus allows the size of the pixels in the working plane to be adjusted.

As the exposure element 202, all electromagnetic radiation sources suitable for laser sintering or laser melting can be used. Preferably, at least one exposure element 202 is designed as a semiconductor laser, in particular as a semiconductor laser diode. The at least one exposure element can be designed, for example, as a VCSEL (Vertical Cavity Surface Emitting Laser) or as a VECSEL (Vertical External Cavity Surface Emitting Laser).

Furthermore, rows of exposure elements can also be mounted on the support 201, wherein the performance of one row of exposure elements depends on the number and power of the individual exposure elements. In this case, the radiation of a line of exposure elements at an exposure time point can be imaged onto a pixel in the working plane 10. This has the advantage, among other things, that the pixel can still be sufficiently exposed even if one exposure element of the line fails. Alternatively, the radiation of a

Line of exposure elements at an exposure time to several pixels in the working plane 10 are mapped. This has the advantage that several pixels can be exposed through a row of exposure elements.

The exposure elements 202 are preferably arranged on the carrier 201 such that after a full rotation of the carrier 201 each pixel within a circular area in the working plane 10 has been exposed at least once when all the exposure elements 202 are turned on. The switching speed of the exposure elements 202 and the rotational speed D of the carrier 201 are preferably adapted to one another such that the exposure elements

202 can be switched on and off during the rotation of the carrier 201 such that in the working plane 10, a surface corresponding to the object cross section in the respective layer is solidified. In this case, the cross-sectional area of the building material corresponding to the object does not have to be solidifiable by the energy input achieved by a full rotation of the support 201, but it is also possible to consolidate the building material by means of a multiple sweeping by the exposure elements 202 arranged on the support 201 to achieve.

Exposure elements 201 which do not contribute to the solidification of the building material at an exposure time may be switched off at this exposure time. Alternatively, exposure elements 201 that do not contribute to solidification of the build material at an exposure time may be operated at reduced power at this exposure time so that they preheat the deposited layer of build material in the work plane 10.

In FIG. 2 a, the exposure elements 202 on the underside of the carrier 201 are arranged symmetrically to the rotation axis R on a left and a right side of the carrier 201. The radiation of an imaging element 202 is imaged onto a pixel of the width in the working plane 10, and the exposure elements 202 of each arm are arranged so that the pixels exposed by them are a continuously exposed surface show that the pixels illuminated by adjacent exposure elements 202 are adjacent to one another.

If, in the example in FIG. 2a, n exposure elements each are arranged on the left and the right side of the carrier 201, then after a full rotation of the carrier 201, a circular area with a radius r has been exposed, where: r = n * p. Each pixel within this area was exposed once at two different exposure times.

Since both arranged on the left side of the support 201 exposing elements 202 and which are arranged on the right side of the support 201 exposing elements 202 expose completely the circular area of radius r at a full revolution of the ^'support 201, for example, on the right side can of the carrier 201 are operated with reduced power and can thus be used for preheating the applied layer of the building material, which is then solidified by the exposure elements 202 arranged on the left side of the carrier 201. The exposure elements 202 arranged on the left side of the carrier 201 are switched on and off in such a way that a surface corresponding to the object cross section in the respective layer is solidified.

Alternatively, the left and right side exposure elements 202 of the support 201 may each be operated at a reduced power such that the build material in a pixel in the work plane 10 is not energy input by each of the left and right side exposure elements 202 of the support 201 is fully solidified. The exposure elements 202 arranged on the left and right sides of the carrier 201 in FIG. 2a can also be switched such that they expose different partial areas of the circular area. For example, the left side exposure elements 202 may expose an inner circular area, and the right side exposure elements 202 may expose an outer circular ring adjacent the inner circular area. Exposure elements 202, which are not used for exposing a partial flat, can be used to preheat this partial surface.

In a modification shown in FIG. 2 b, the exposure elements 202 on the carrier 201 are arranged asymmetrically with respect to the axis of rotation R on a left and a right side of the carrier 201. The radiation of an exposure element

202 is imaged onto a pixel of width p in the working plane 10, and the exposure elements 202 are arranged on the carrier 201 so that the pixels exposed by them yield a continuously exposed area. If, in the example in FIG. 2b, each m exposure elements are arranged on the left and the right side of the carrier 201, a circular area with a radius r has been exposed after a full revolution of the carrier 201, where: r = m * p. Each pixel within that area was exposed exactly once, so no pixel within that area was exposed at two different exposure times. The exposure elements 202 are switched on and off in such a way that a surface corresponding to the object cross-section in the respective layer is solidified. In a further, ^'not represented in the figures modification of the exposure elements 202 are arranged on the substrate ^"201, that lying adjacent pixels have an overlap. As a result, an undesired offset of the exposure elements 202 are balanced, and thus possible exposure gaps can be avoided.

Various exemplary embodiments of the carrier 201 are shown schematically in FIGS. 3a-3d. As shown in FIG. 3a, the carrier may be implemented as a single arm 211 which is rotatable about an axis of rotation R. Further, as shown in Fig. 3b, the carrier may be embodied as two arms 211 which are rotatable about a common axis of rotation R, the arms forming an angle with each other. of preferably 180 °. The support may further be embodied, as illustrated in FIG. 3c, as three arms 211 which are rotatable about a common axis of rotation R, the arms enclosing an angle α of preferably 120 °. Generally, the carrier may be embodied as a number of arms which are rotatable about a common axis of rotation R, the arms preferably enclosing an angle of oc = 360 ° / a.

Furthermore, as shown in FIG. 3 d, the carrier may be designed as a disk 212 which is rotatable about an axis of rotation R, wherein the axis of rotation is preferably arranged in the center of the disk 212.

The exposure elements 202 are arranged on the carrier 201 such that, after one complete revolution of the carrier 201, each pixel of a circular area in the working plane 10 has been exposed at least once when all the exposure elements 202 of the carrier 201 are switched on. The exposure elements 202 become so On and Ausschal et that a the object cross section in the respective layer corresponding surface is solidified. Exposure elements 202, which are not used to solidify the build material at a time, may be used to preheat the build material.

The switching speed of the exposure elements 202 and the rotational speed D of the carrier 201 are adapted to one another such that the exposure element 202 can be switched on and off during the rotation of the carrier 201 in such a way that in the working plane 10 the object cross section in the respective one Layer corresponding surface is solidified. In this case, the cross-sectional area of the material corresponding to the object does not have to be solidifiable already by the energy input achieved by a full revolution of the carrier 201, but rather it is also possible to achieve solidification of the building material by repeatedly passing through the exposure elements 202 arranged on the carrier 201. Exposure elements 202 disposed close to the axis of rotation R on the carrier 201 become due to the rotational movement with a smaller line speed over the working plane _. 10 moved as exposure elements 202, which are arranged ■ further away from the ^' rotation axis on the carrier 201. In order to avoid uneven exposure of the building material in the working plane 10 by exposure times of radially different circular rings of different lengths, it is therefore advantageous to arrange fewer exposure elements on an inner circle of a disk 212 than on an outer circumferential circle. In particular, it is advantageous in an arrangement of exposure elements 202 on the disk 212 in m concentric circles, the number ni of the in the i- Depending on the radius ri of the ith circle to arrange th circle arranged exposure elements 202 so that approximately satisfies the condition η ^ Γχ = n ₂ / r _{2 ...} = ni / ri = ... n _m / r _m is. In a further modification, the exposure elements 202 are operated with different power depending on their radial distance from the axis of rotation R, so that the radial energy input per full revolution of the carrier 201, 211, 212 is constant when all the exposure elements 202 "are switched on.

In a further modification, the at least one adjustment element 202 is movable, preferably movable in the radial direction, arranged on the carrier 201. The traversing speed of the at least one exposure element 202 and the rotational speed (D) of the carrier are adapted to one another in such a way that all pixels of a circular area in the working plane 10 are exposed in the case of a number of revolutions of the carrier 201 when the exposure element 202 is switched on continuously. Furthermore, the switching speed and the travel speed of the at least one exposure element 202 and the rotational speed D of the carrier 201 are adapted to one another such that the at least one exposure element 202 is switched on and off during the rotation of the carrier 201 and moved on the carrier can ^' that in the working plane 10 a the Obj ktquerschnitt in the respective layer corresponding surface is solidified.

The shape of the carrier 201 is not limited to the forms shown by way of example in FIGS. 3a-3d;

201 take any suitable form. The cross-sectional area of the object 2 to be consolidated does not have to lie within the area of the support 201, 211, 212 over the surface. The surface swept over by the carrier 201, 211, 212 can also form only a part of the cross-sectional area of the object 2 to be consolidated and the entire cross-sectional area can be solidified by moving the carrier over the building field.

As construction material can be different materials. be used, in particular powdery materials such as metal powder, plastic powder, ceramic powder, sand, filled or mixed powder.

Claims

1. Device (1) for producing a three-dimensional object (2) by stratified solidification of building material at the cross section of the object to be produced (2) in the respective layer corresponding points by the action of electromagnetic radiation (22)

a building platform (8, 9) on which the object (2) can be built,

and

an exposure unit (20) for emitting the electromagnetic radiation (22) for selectively solidifying a layer of the building material, characterized in that

the exposure unit (2) comprises a support (201, 211, 212) which is rotatable about an axis of rotation (R), and the exposure unit (20) comprises at least one exposure element (202) which is mounted on the support (201, 211 , 212) is attached.

2. Device (1) according to claim 1, wherein the device (l) is formed so that the solidification takes place in at least one defined working plane (10).

3. Device (1) according to claim 2, wherein the axis of rotation (R) of the carrier (201, 211, 212) is oriented substantially perpendicular to the working plane (10).

4. Apparatus (1) according to any one of claims 1 to 3, wherein the exposure unit (20) comprises a plurality of exposure elements (202) and wherein the device (1) is formed so that the light of each exposure element (202) to a ^ Exposure time is mapped to a pixel in the working plane (10).

A device (1) according to any one of claims 1 to 4, wherein the carrier is a single arm (211) or two or more angled (a) enclosing arms. (211) is formed, which are rotatable about the rotation axis (R).

6. Device (1) according to one of claims 1 to 4, wherein the carrier is formed as a disc (212) which is rotatable about the rotation axis (R).

7. Device (1) according to any one of claims 1 bis 6 ^·, wherein a plurality of exposing elements (202) is provided, and

the exposure elements (202) on the support (201, 211,

212) are arranged such that, after a full rotation of the carrier (201, 211, 212), each pixel of a circular area in the working plane (10) has been exposed at least at one exposure time when all the exposure elements (202) are switched on.

8. Device according to one of claims 1 to 7, wherein

the at least one exposure element (202) is movably arranged on the support (201, 211, 212) in such a way that its distance from the rotation axis (R) can be changed, and / or the carrier (201, 211, 212) is also translationally movable.

9. Device (1) according to one of claims 1 to 8, wherein a speed (D) of the carrier (201, 211, 212) when exposing a layer is constant, preferably greater than about 1 s ^-1 , more preferably greater than about 5 s ^-1 , even more preferably greater than about 10 s ^_1, and preferably less than about 50 s ^-1 , more preferably less than about 30 s ^-1 , even more preferably less than about 25 s ^-1 , with any combination of the upper and lower limits are possible.

10. Device (1) according to one of claims 1 to 9, wherein the at least one exposure element (202) is designed as a semiconductor laser, in particular as a semiconductor laser diode.

The device (1) according to claim 10, wherein said at least one exposure element (202) is vertical _. Cavity Surface Emit- ing Laser VCSEL or is designed as a vertical external cavity surface erosion laser VECSEL.

The apparatus (1) according to any one of claims 1 to 11, wherein the exposure unit (20) comprises at least one line of exposure elements (202).

13. A method for producing a three-dimensional object (2) in a device (1) for producing a three-dimensional obj ect (2) by stratified solidification of building material at the cross section of the object to be produced (2) in the respective layer corresponding points by the action of electromagnetic radiation (22) with the. Steps:

Building the object (2) on a building platform (8, 9), and emitting the electromagnetic radiation (22) for selectively solidifying a layer of build material by means of ^■ · a. Exposure unit (20), characterized in that

the exposure unit (20) comprises a support (201, 211, 212) which is rotated about an axis of rotation (R) and the exposure unit (20) comprises at least one exposure element (202) which is mounted on the support (201, 211, 212 ) is attached.

14. The method of claim 13, wherein a switching speed of the at least one exposure element and a rotational speed of the carrier are adapted to one another and the at least one exposure element is so on and is turned off that a surface corresponding to the object cross section of the building material is solidified.

15. The method of claim 13 or 14, wherein

the exposure unit (20) has a plurality of exposure elements

(202) includes and

Exposure elements (202) which are not used for exposure at an exposure time are used at this exposure time for preheating the Aufaumaterials.