DE102022111298A1 - System for the layered production of at least one object on a construction platform and associated production process, with a cooled aperture device - Google Patents

Abstract

A system (1) for the layer-by-layer production of at least one object (2) on a construction platform (13) by locally solidifying powdered material (6) in a respective layer (21) with a processing laser beam (18), comprising a laser source (15). Providing an output laser beam (16), the laser source (15) providing a multimode laser beam (16'), and a laser processing head (17) which provides the processing laser beam (18),
wherein the laser processing head (17).
- a collimation device (25) for collimating the output laser beam (16) provided by the laser source (15),
- a focusing device (27) for focusing a collimated laser beam (30) provided by the collimation device (25),
- a scanner device (28) for deflecting a laser beam (38) incident on the scanner device (28), and
- a cooled aperture device (26) for partially shading a laser beam (31) directed at the aperture device (26), with which a portion (31a) of the laser beam (31) directed at the aperture device (26) has a larger divergence angle (φ _A ) is shaded and a portion (31b) with a smaller divergence angle (φ _B ) is transmitted, the divergence angle (φ _A , φ _B ) being determined on the output laser beam (16) provided by the laser source (15).
The system can be used to quickly and precisely produce the at least one object in a simple manner.

Description

The invention relates to a system for the layer-by-layer production of at least one object on a construction platform by locally solidifying powdered material in a respective layer with a processing laser beam.

With the layer-by-layer production of objects through local solidification of powdery material using high-energy beams (usually laser beams or electron beams), three-dimensional objects can be manufactured comparatively easily and quickly. Geometric limitations of conventional manufacturing processes such as milling or injection molding can be overcome. Layered manufacturing is often used for prototypes or for objects that are only produced in small quantities.

Fundamental mode laser beams in a wavelength range of 1030-1080 nm are often used for the additive manufacturing of objects. For the processing of materials with a high reflectivity in the wavelength range of 1030-1080 nm, the use of laser beams with shorter wavelengths (for example a wavelength of 515 nm) is advantageous. Multimode laser beams can be used for these shorter wavelengths, which allow higher powers and correspondingly higher productivity during production.

However, the disadvantage of multimode laser beams is that they have a poorer beam quality (measured using the beam parameter product, SPP) than basic mode laser beams. The beam parameter product SPP is the product of half the divergence angle φ and the radius of a laser beam ω ₀ at its thinnest point (in focus), i.e. SPP=φ*ω ₀ . A high beam quality corresponds to a low beam parameter product and vice versa. The beam parameter product can also be expressed as SPP=M ² *λ/π, with M ² : diffraction index and λ : wavelength.

The high beam parameter product for multimode laser beams means that, given the usual sizes of the scanner optics, the multimode processing laser beam directed and focused on a process level has a comparatively large spot size. This makes precise layer-by-layer production of objects with a high level of detail resolution very difficult or impossible.

To reduce the spot size, a working distance between a laser processing head that provides the multimode laser beam and the process plane can be reduced. However, this reduces the area that the laser processing head can cover in a system for producing an object layer by layer on the construction platform. In addition, a major design change to the system is necessary. Furthermore, the reduced distance between the laser processing head and the process level increases the risk that the optical components of the laser processing head will be contaminated or damaged.

It would also be possible to enlarge the aperture of the scanner optics to reduce the spot size. However, larger scanner mirrors have greater inertia and therefore can only accelerate more slowly, reducing machine productivity.

The CN112605525A describes a laser cutting head. The laser cutting head is connected to an optical fiber via a laser cutting head connector. A water-cooled diaphragm is arranged in the laser cutting head connecting piece, between an exit opening of the optical fiber and a collimation device of the laser cutting head. Scattered light can be filtered using the aperture.

The CN107866639A discloses a laser processing device. The device comprises a source for a laser beam and an aperture device with a size-adjustable aperture which is arranged between a collimation lens and a focusing lens.

Task of the invention

It is the object of the invention to present a system for the layer-by-layer production of at least one object on a construction platform, with which the at least one object can be produced quickly and precisely in a simple manner.

Description of the invention

• - eine Kollimationseinrichtung zum Kollimieren des von der Laserquelle bereitgestellten Ausgangslaserstrahls, insbesondere wobei der bereitgestellte Ausgangslaserstrahl an einem Faserende eines Lichtleitkabels austritt,
• - eine Fokussiereinrichtung zum Fokussieren eines von der Kollimationseinrichtung bereitgestellten, kollimierten Laserstrahls,
• - eine Scannereinrichtung zur Ablenkung eines an der Scannereinrichtung einfallenden Laserstrahls, und
• - eine gekühlte Blendeneinrichtung zur teilweisen Abschattung eines auf die Blendeneinrichtung gerichteten Laserstrahls, mit welcher von dem auf die Blendeneinrichtung gerichteten Laserstrahl ein Anteil mit größerem Divergenzwinkel abgeschattet wird und ein Anteil mit kleinerem Divergenzwinkel durchgelassen wird, wobei der Divergenzwinkel am von der Laserquelle bereitgestellten Ausgangslaserstrahl bestimmt ist.

This object is achieved according to the invention by a system for the layer-by-layer production of at least one object on a construction platform by local solidification of powdery material in a respective layer with a processing laser beam
a laser source for providing an output laser beam, the laser source providing a multimode laser beam, and
a laser processing head which provides the processing laser beam, the laser processing head having

• - a collimation device for collimating the output laser beam provided by the laser source, in particular wherein the output laser beam provided exits at a fiber end of a light guide cable,
• - a focusing device for focusing a collimated laser beam provided by the collimation device,
• - a scanner device for deflecting a laser beam incident on the scanner device, and
• - a cooled aperture device for partially shading a laser beam directed at the aperture device, with which a portion with a larger divergence angle is shaded from the laser beam directed at the aperture device and a portion with a smaller divergence angle is let through, the divergence angle being determined on the output laser beam provided by the laser source .

The invention proposes to provide a multimode laser beam as the output laser beam and to shade a portion of the multimode laser beam with a larger divergence angle by means of a cooled aperture device arranged in a laser processing head and to allow a portion of the multimode laser beam with a smaller divergence angle to pass through.

The multimode laser beam provided as the output laser beam is guided to the laser processing head. There, the multimode laser beam is guided via a collimation device, a focusing device, a scanner device and through the aperture device and leaves the laser processing head as a processing laser beam for the layer-by-layer production of the at least one object on the construction platform. The processing laser beam is also a multimode laser beam. A higher laser power, particularly in the kW range, can be achieved using the multimode laser beam than with a basic mode laser beam (or single-mode laser beam). The increased laser power enables faster layer-by-layer production of the at least one object on the construction platform. This can increase the productivity of the system.

The beam parameter product SPP (which indicates a measure of the beam quality of a laser beam) is large for multimode laser beams compared to fundamental mode laser beams. In order to improve the beam quality of the multimode laser beam provided and to enable smaller focusing of the multimode laser beam, the cooled aperture device in the laser processing head is used.

In general, the beam parameter product SPP of a laser beam is proportional to the radius ω ₀ of the laser beam at its thinnest point and half the divergence angle φ of the laser beam. The beam parameter product SPP of the laser beam is influenced, among other things, by the divergence angle φ. The beam parameter product SPP of a laser beam is also proportional to the diffraction index M ² and the wavelength λ of the laser beam. Typically, multimode laser beams have diffraction coefficients M ² that deviate significantly from the smallest possible value for M ² of 1. The diffraction index M ² indicates how well a beam can be focused. A value close to 1 for M ² means that the beam can be focused particularly well. However, if M ² >>1, the beam can only be focused with difficulty.

mit φ_A: halber Divergenzwinkel (Austrittswinkel) des Ausgangslaserstrahls, ω_A: Radius des Ausgangslaserstrahls an seiner dünnsten Stelle, M_A ²: Beugungsmaßzahl des Ausgangslaserstrahls und λ_A: Wellenlänge des Ausgangslaserstrahls. Man beachte, dass SPP_A auch SPP_vor entspricht (siehe unten).The following applies to a beam parameter product SPP _A of the multimode laser beam provided as the output laser beam: $${\text{SPP}}_{\text{A}}={\mathrm{\phi }}_{\text{A}}*{\mathrm{\omega }}_{\text{A}}={\text{M}}_{\text{A}}{}^2*{\mathrm{\lambda }}_{\text{A}}/\mathrm{\pi }$$

with φ _A : half the divergence angle (emergence angle) of the output laser beam, ω _A : radius of the output laser beam at its thinnest point, M _A ² : diffraction index of the output laser beam and λ _A : wavelength of the output laser beam. Note that SPP _A also corresponds to SPP _before (see below).

mit φ_B: halber Divergenzwinkel des Bearbeitungslaserstrahls, ω_B: Radius des Bearbeitungslaserstrahls an seiner dünnsten Stelle, M_B ²: Beugungsmaßzahl des Bearbeitungslaserstrahls und λ_B: Wellenlänge des Bearbeitungslaserstrahls. Man beachte, dass SPP_B auch SPP_nach entspricht (siehe unten). Man beachte weiterhin, dass die Wellenlänge λ_A für den Ausgangslaserstrahl gleich groß zur Wellenlänge λ_B des Bearbeitungslaserstrahls ist, also λ_A=λ_B=λ.The following applies to a beam parameter product SPP _B of the multimode laser beam provided as a processing laser beam: $${\text{SPP}}_{\text{b}}={\mathrm{\phi }}_{\text{b}}*{\mathrm{\omega }}_{\text{b}}={\text{<figure-callout id="2" label="M b" filenames="DE102022111298A1\_0003.png" state="{{state}}">M</figure-callout>}}_{\text{b}}{}^2*{\mathrm{\lambda }}_{\text{b}}/\mathrm{\pi }$$

with φ _B : half the divergence angle of the processing laser beam, ω _B : radius of the processing laser beam at its thinnest point, M _B ² : diffraction index of the processing laser beam and λ _B : wavelength of the processing laser beam. Note that SPP _B also corresponds to SPP _after (see below). Note further that the wavelength λ _A for the output laser beam is equal to the wavelength λ _B of the processing laser beam, i.e. λ _A =λ _B =λ.

Without the cooled aperture device, the beam parameter product SPP _A of the output laser beam would be equal to the beam parameter product SPP _B of the processing laser beam, i.e. SPP _A =SPP _B. The beam quality would be the same. With the help of the cooled aperture device, a portion of the output laser beam with a larger divergence angle can be shaded. The processing laser beam that leaves the laser processing head then has a smaller divergence angle than the output laser beam, i.e. φ _B <φ _A. The diffraction coefficient for the processing laser beam also becomes smaller, i.e. M _B ² <M _A ² . The processing laser beam can be focused better and precise production of the at least one object is possible. The beam parameter product SPP _B of the processing tung laser beam is smaller than the beam parameter product SPP _A of the output laser beam, i.e. SPP _B <SPP _A.

Note that the aperture device also increases the beam parameter product SPP _B or increases M _B ² due to diffraction effects. In fundamental mode laser beams (with originally low M _A ² ), this diffraction effect dominates, and limiting the divergence angle does not lead to any noticeable improvement (lowering) of the SPP _B. In the case of multimode laser beams (with originally high M _A ² , usually approx. 4 or more, often 10 or more), the effect of diffraction is relatively small, and the SPP _B can be significantly improved (lowered) by limiting the divergence angle φ _B according to the invention ) become.

By cooling the cooled aperture device, the heat generated by the shaded portion of the multimode laser beam in the aperture device can be efficiently dissipated. Damage or deformation of the aperture device or surrounding components of the aperture device can thereby be avoided.

Furthermore, the cooled aperture device can be installed in the laser processing head in a simple and uncomplicated manner. A major structural change to the system is not necessary.

The diaphragm device can be designed, for example, as a perforated disk or as an iris diaphragm. The collimation device can be designed, for example, as a single collimation lens, a combination of lenses or as a collimating concave mirror. The focusing device can be designed, for example, as a single focusing lens, a combination of lenses or as a focusing concave mirror. The scanner device can, for example, be designed with one or two movable scanner mirrors.

Preferred embodiments of the system according to the invention

Particularly preferred is an embodiment of the system according to the invention in which the aperture device is selected such that a beam parameter product SPP _after a laser beam transmitted through the aperture device is smaller than a beam parameter product SPP _{in front of} the laser beam directed at the aperture device, with SPP _after ≤ SPP _before *0 ,90,
preferably with SPP _after ≤0.80*SPP _before ,
particularly preferably with SPP _after ≤0.70*SPP _before .

Such an improvement (reduction) of the beam parameter product SPP _after compared to SPP _before (and thus the quality of the transmitted laser beam) already brings about a significant increase in the manufacturing precision of the at least one object. In most cases SPP _after ≥0.40*SPP _before , preferably SPP _after ≥0.50*SPP _before , particularly preferably SPP _after ≥0.60*SPP _before ; then not too much power of the laser beam directed at the aperture device is absorbed, so that the at least one object can be manufactured with high productivity.

A further particularly preferred embodiment provides that the diaphragm device is selected such that an absorbed power component AB is absorbed by an incident laser power EL of the laser beam directed onto the diaphragm device, with AB/EL ≥ 0.10,
preferably with AB/EL ≥ 0.20, particularly preferably AB/EL ≥ 0.25.

The aperture device designed in this way has proven itself in practice. AB/EL ≤ 0.60 also applies in most cases, preferably AB/EL ≤ 0.50, particularly preferably AB/EL ≤ 0.40; then not too much power of the laser beam directed at the aperture device is absorbed, so that the at least one object can be manufactured with high productivity.

In a likewise preferred embodiment, the diaphragm device is fluid-cooled, wherein the diaphragm device or a heat sink thermally connected to the diaphragm device has one or more cooling channels for a cooling fluid.

In this way, the aperture device can be cooled efficiently. Heat generated by absorbed laser power at the aperture device can be dissipated quickly and in large quantities. Deformation or damage to the aperture device or other components arranged in the vicinity of the aperture device can be prevented. The cooling is structurally simple to implement and minimally increases the space required for the processing head.

The fluid cooling can take place via an external cooler which is connected to the aperture device or the heat sink via fluid lines. For example, a liquid, in particular water or a silicone oil, or a gas, in particular compressed air, can be used as a fluid for cooling. Alternatively, the diaphragm device can also be cooled via cooling fins that are formed on the diaphragm device or are thermally connected to the diaphragm device, in particular where the cooling fins are exposed to an external air flow are exposed, which is generated, for example, by a fan of a fan.

Also advantageous is an embodiment in which the diaphragm device is arranged between the collimation device and the focusing device in the collimated laser beam provided by the collimation device.

This is structurally particularly easy to set up and implement. Portions of the collimated laser beam can be shaded particularly easily and precisely by the aperture device. The shading is independent of the position of the aperture device along the beam propagation direction, which simplifies its adjustment.

Alternatively, the diaphragm device can also be arranged in front of the collimation lens in the output laser beam provided by the laser source, in particular between the fiber end of a light guide cable of the laser source and the collimation device in the output laser beam emerging at the fiber end of the light guide cable.

Equally advantageous is an embodiment in which the scanner device is arranged after the focusing device in a focused laser beam provided by the focusing device.

This is particularly easy to implement structurally; the focusing device can always remain central and coaxial with the collimated laser beam.

Alternatively, the scanner device can be arranged between the collimation device and the focusing device in the collimated laser beam provided by the collimation device.

Also preferred is an embodiment which is characterized in that the following applies to a laser power P of the output laser beam provided by the laser source: P≥200W,
preferably P≥500W, particularly preferably P≥1000W, very particularly preferably P≥2000W.

These values for the laser power P have proven particularly useful in practice. With such values for the laser power P, a high production speed can be achieved.

Also preferred is an embodiment in which the following applies to a mean laser wavelength λ of the output laser beam provided by the laser source: λ ≤ 540nm, preferably 500nm ≤ λ ≤ 540nm or preferably 330nm ≤ λ ≤ 360nm, particularly preferably λ = 515nm.

The values for the average laser wavelength λ have proven particularly useful in practice. In particular, materials with a high reflectivity outside the average laser wavelengths λ or laser wavelength ranges specified here can be processed particularly well. In addition, the inventors do not know of any single-mode fiber lasers for these medium laser wavelengths (in the green, blue or UV spectral range), nor any multi-mode fiber lasers with the above-mentioned performances desired for 3D printing. Within the scope of the invention, a green disk laser with a multimode laser beam can be used well, in particular with high laser power or productivity and high manufacturing accuracy.

In a further preferred embodiment, the laser source is designed as a disk laser or diode laser, in particular a blue diode laser.

Disk lasers can be used to provide high laser powers. Furthermore, the modular design of disk lasers can offer a high degree of flexibility in the design of the system. Furthermore, the aforementioned laser wavelength ranges are easily accessible by doubling or tripling the frequency of the disk lasers.

Diode lasers enable a compact design. Furthermore, diode lasers can provide high laser power. Likewise, diode lasers typically have a long service life (e.g. up to 30,000 hours).

Method according to the invention

• - der bereitgestellte Ausgangslaserstrahl mit einer Kollimationseinrichtung kollimiert wird, insbesondere wobei der bereitgestellte Ausgangslaserstrahl an einem Faserende eines Lichtleitkabels austritt,
• - ein von der Kollimationseinrichtung bereitgestellter, kollimierter Laserstrahl mit einer Fokussiereinrichtung fokussiert wird,
• - ein an einer Scannereinrichtung einfallender Laserstrahl mit der Scannereinrichtung abgelenkt wird, und
• - ein auf eine gekühlte Blendeneinrichtung gerichteter Laserstrahl mit der Blendeneinrichtung teilweise abgeschattet wird, wobei von dem auf die Blendeneinrichtung gerichteten Laserstrahl ein Anteil mit größerem Divergenzwinkel abgeschattet wird und ein Anteil mit kleinerem Divergenzwinkel durchgelassen wird, wobei der Divergenzwinkel am von der Laserquelle bereitgestellten Ausgangslaserstrahl bestimmt ist.

The scope of the present invention also includes a method for the layer-by-layer production of at least one object on a construction platform by local solidification of powdered material in a respective layer with a processing laser beam, in particular using a system according to the invention as described above,
wherein an output laser beam is provided with a laser source, the output laser beam being a multimode laser beam,
wherein the output laser beam is fed to a laser processing head,
and wherein the processing laser beam is provided with the laser processing head, wherein with the laser processing head

• - the output laser beam provided is collimated with a collimation device, in particular the output laser beam provided exits at a fiber end of a light guide cable,
• - a collimated laser beam provided by the collimation device is focused with a focusing device,
• - a laser beam incident on a scanner device is deflected by the scanner device, and
• - a laser beam directed at a cooled aperture device is partially shaded with the aperture device, a portion with a larger divergence angle being shaded by the laser beam directed at the aperture device and a portion with a smaller divergence angle being transmitted, the divergence angle being determined on the output laser beam provided by the laser source .

This method allows the at least one object to be produced quickly and precisely on the construction platform in a simple manner.

Preferred variants of the method according to the invention

Particularly preferred is a variant of the method according to the invention in which the aperture device is selected such that a beam parameter product SPP _after a laser beam transmitted through the aperture device is smaller than a beam parameter product SPP _{in front of} the laser beam directed at the aperture device, with SPP _after ≤ SPP _before *0 ,90,
preferably with SPP _after ≤0.80*SPP _before ,
particularly preferably with SPP _after ≤0.70*SPP _before .

Such an improvement (reduction) of the beam parameter product SPP _after compared to SPP _before (and thus the quality of the transmitted laser beam) already brings about a significant increase in the manufacturing precision of the at least one object. In most cases SPP _after ≥0.40*SPP _before , preferably SPP _after ≥0.50*SPP _before , particularly preferably SPP _after ≥0.60*SPP _before ; then not too much power of the laser beam directed at the aperture device is absorbed, so that the at least one object can be manufactured with high productivity.

A further particularly preferred variant provides that the diaphragm device is selected such that an absorbed power component AB is absorbed by an incident laser power EL of the laser beam directed onto the diaphragm device, with AB/EL ≥ 0.10,
preferably with AB/EL ≥ 0.20, particularly preferably AB/EL ≥ 0.25.

The aperture device designed in this way has proven itself in practice. AB/EL ≤ 0.60 also applies in most cases, preferably AB/EL ≤ 0.50, particularly preferably AB/EL ≤ 0.40; then not too much power of the laser beam directed at the aperture device is absorbed, so that the at least one object can be manufactured with high productivity.

In a likewise preferred variant, the diaphragm device is fluid-cooled, wherein the diaphragm device or a heat sink thermally connected to the diaphragm device has one or more cooling channels for a cooling fluid, and the cooling fluid flows through the cooling channels.

In this way, the aperture device can be cooled efficiently. Heat generated by absorbed laser power at the aperture device can be dissipated quickly and in large quantities. Deformation or damage to the aperture device or other components arranged in the vicinity of the aperture device can be prevented. The cooling is structurally simple to implement and minimally increases the space required for the processing head.

The fluid cooling can take place via an external cooler which is connected to the aperture device or the heat sink via fluid lines. For example, a liquid, in particular water or a silicone oil, or a gas, in particular compressed air, can be used as a fluid for cooling. Alternatively, the aperture device can also be cooled via cooling fins that are formed on the aperture device or are thermally connected to the aperture device, in particular wherein the cooling fins are exposed to an external air flow, which is generated, for example, by a fan of a fan.

A variant is also advantageous in which the diaphragm device is arranged between the collimation device and the focusing device in the laser beam collimated by the collimation device.

This is structurally particularly easy to set up and implement. Portions of the collimated laser beam can be shaded particularly easily and precisely by the aperture device. The shading is independent of the position of the aperture device along the beam propagation direction, which simplifies its adjustment.

Alternatively, the diaphragm device can also be arranged in front of the collimation lens in the output laser beam provided by the laser source, in particular between the fiber end Light guide cable of the laser source and the collimation device in the output laser beam emerging at the fiber end of the light guide cable.

Equally advantageous is a variant in which the scanner device is arranged after the focusing device in a focused laser beam provided by the focusing device
This is particularly easy to implement structurally; the focusing device can always remain central and coaxial with the collimated laser beam.

Alternatively, the scanner device can be arranged between the collimation device and the focusing device in the collimated laser beam provided by the collimation device.

Also preferred is a variant which is characterized in that the following applies to a laser power P of the output laser beam: P≥200W, preferably P≥500W, particularly preferably P≥1000W, very particularly preferably P≥2000W.

These values for the laser power P have proven particularly useful in practice. With such values for the laser power P, a high production speed can be achieved.

Also preferred is a variant in which the following applies to a mean laser wavelength λ of the output laser beam: λ ≤ 540nm, preferably 500nm ≤ λ ≤ 540nm or preferably 330nm ≤ λ ≤ 360nm, particularly preferably λ = 515nm.
The values for the average laser wavelength λ have proven particularly useful in practice. In particular, materials with a high reflectivity outside the average laser wavelengths λ or laser wavelength ranges specified here can be processed particularly well. In addition, the inventors do not know of any single-mode fiber lasers for these medium laser wavelengths (in the green, blue or UV spectral range), nor any multi-mode fiber lasers with the above-mentioned performances desired for 3D printing. Within the scope of the invention, a green disk laser with a multimode laser beam can be used well, in particular with high laser power or productivity and high manufacturing accuracy.

In a further preferred variant, the laser source is selected as a disk laser or diode laser, in particular a blue diode laser.

Disk lasers can be used to provide high laser powers. Furthermore, the modular design of disk lasers can offer a high degree of flexibility in the design of the system. Furthermore, the aforementioned wavelength ranges are easily accessible by doubling or tripling the frequency of the disk lasers.

Diode lasers enable a compact design. Furthermore, diode lasers can provide high laser power. Likewise, diode lasers typically have a long service life (e.g. up to 30,000 hours).

Also within the scope of the present invention is the use of a system according to the invention as described above in a method according to the invention as described above.

The system has a simple structure and, in particular, does not require any major design changes compared to conventional systems. With the system and the method, the layer-by-layer production of the at least one object can be carried out quickly and the object can be manufactured precisely.

Further advantages of the invention result from the description and the drawing. Likewise, according to the invention, the features mentioned above and those further detailed can be used individually or in groups in any combination. The embodiments shown and described are not to be understood as an exhaustive list, but rather have an exemplary character for describing the invention.

Detailed description of the invention and drawing

• 1 zeigt eine schematische Ansicht einer erfindungsgemäßen Anlage zur schichtweisen Fertigung eines Objekts, zur Durchführung des erfindungsgemäßen Verfahrens;
• 2 zeigt eine schematische Ansicht einer Laserquelle, einer Kühleinrichtung und eines Laserbearbeitungskopfs einer erfindungsgemäßen Anlage in einer ersten Ausführungsform, wobei im Laserbearbeitungskopf eine gekühlte Blendeneinrichtung zwischen einer Kollimationseinrichtung und einer Fokussiereinrichtung angeordnet ist;
• 3 zeigt eine schematische Ansicht einer Laserquelle, einer Kühleinrichtung und eines Laserbearbeitungskopfs einer erfindungsgemäßen Anlage in einer zweiten Ausführungsform, wobei im Laserbearbeitungskopf eine gekühlte Blendeneinrichtung vor einer Kollimationseinrichtung angeordnet ist;
• 4 zeigt ein schematisches Diagramm, in dem das Strahlparameterprodukt sowie der relative Leistungsverlust eines Bearbeitungslaserstrahls für vier unterschiedliche, durch die Blendeneinrichtung eingestellte Divergenzwinkel aufgetragen ist.

The invention is shown in the drawing and is explained in more detail using exemplary embodiments.

• 1 shows a schematic view of a system according to the invention for the layer-by-layer production of an object for carrying out the method according to the invention;
• 2 shows a schematic view of a laser source, a cooling device and a laser processing head of a system according to the invention in a first embodiment, wherein a cooled aperture device is arranged in the laser processing head between a collimation device and a focusing device;
• 3 shows a schematic view of a laser source, a cooling device and a laser processing head of a system according to the invention in a second embodiment, wherein a cooled diaphragm device is arranged in front of a collimation device in the laser processing head;
• 4 shows a schematic diagram in which the beam parameter product and the relative power loss of a processing laser beam are plotted for four different divergence angles set by the aperture device.

1 shows a schematic, partially sectioned view from the side of an exemplary system 1 according to the invention for the layered production of an object 2, the system 1 being suitable for carrying out the method according to the invention.

The system 1 includes a construction chamber 3. Typically, the construction chamber 3 is designed to be gas-tight, so that a protective gas atmosphere can be set up in the construction chamber 3.

A powder cylinder arrangement 4 is connected to the construction chamber 3. The powder cylinder arrangement 4 has a powder cylinder 5 for a powdery material 6 (area shown in dotted lines). The object 2 is made from the powdery material 6, for example by sintering or melting. By gradually raising a powder piston 7, a small amount of the powdery material 6 is raised above the level of a floor 8 of the construction chamber 3. This small amount of powdery material 6 can be transferred to a construction cylinder arrangement 10 using a slide 9. Excess powdery material 6 can be spread using the slider 9 into a collecting container 11 connected to the construction chamber 3.

The construction cylinder arrangement 10 is also connected to the construction chamber 3. The construction cylinder arrangement 10 has a movable piston plate 12, on which a construction platform 13 (area shown hatched) is arranged on the top side. Object 2 is built on the construction platform 13. The construction platform 13 can be moved with the piston plate 12 in a base body 14. In the embodiment shown here, the piston plate 12 has already been lowered several times and the object 2 has already been partially manufactured.

An output laser beam 16 is provided via a laser source 15. The output laser beam 16 is a multimode laser beam 16'. The output laser beam 16 is guided to a laser processing head 17 (for the structure of the laser processing head 17 see 2 and 3 ). The laser processing head 17 then provides a processing laser beam 18. The processing laser beam 18 is a multimode processing laser beam 18'.

The processing laser beam 18 is guided into the construction chamber 3 via a window 19. The processing laser beam 18 is focused on a process plane 20, which typically corresponds to a top side of a top layer 21 of the powdery material 6. For local solidification of the top layer 21 (area framed by dashed lines) of powdery material 6 for layer-by-layer production of the object 2, the processing laser beam 16 is directed to predetermined positions on the process level 20. The processing laser beam 16 is absorbed by the powdery material 6. The powdery material 6 melts and solidifies again when it is no longer irradiated. The solidified material then forms a further part of the object 2. The construction platform 13 can then be lowered by a further layer thickness, a further layer of powdery material 6 can be applied and locally solidified, and so on.

2 shows a schematic, partially sectioned view from the side of the laser source 15, the laser processing head 17 (indicated by the dotted box) and a cooling device 22 of an exemplary system according to the invention in a first embodiment, which is suitable for carrying out the method according to the invention.

In the embodiment shown here, the laser source 15 is designed as a disk laser 15a. The laser source 15 provides the output laser beam 16, which is a multimode laser beam 16'. The output laser beam 16 here has a laser power P of 2000W and an average laser wavelength λ of 515nm (so it is a laser beam in the green wavelength range).

A light guide cable 23 is connected to the laser source 15 here. The output laser beam 16 emerges from a fiber end 24 of the light guide cable 23. The output laser beam 16 is guided to the laser processing head 17 via the light guide cable 23. Note that at the fiber end 24, the fiber radius corresponds to the radius (ω _A ) of the output laser beam 16.

The laser processing head 17 has a collimation device 25, a cooled aperture device 26, a focusing device 27 and a scanner device 28. In the embodiment shown here, the collimation device 25 is designed as a collimation lens 25a, the cooled aperture device 26 as a cooled pinhole 26a and the focusing device 27 as a focusing lens 27a. The scanner device 28 here comprises a movable scanner mirror 29. The scanner mirror 29 can be pivoted about two axes here, for example with piezo actuators (not shown in detail).

The output laser beam 16 provided is guided (directed) from the fiber end 24 onto the collimation device 25 in the laser processing head 17. The collimation device 25 collimates the output laser beam 16 and thus provides a collimated laser beam 30. The collimated laser beam 30 is guided to the focusing device 27. In the embodiment shown here, the aperture device 26 is arranged between the collimation device 25 and the focusing device 27.

A laser beam 31 (here the collimated laser beam 30) directed onto the aperture device 26 is partially shaded by the aperture device 26. In this case, a portion 31a (marked by its edge beam) of the laser beam 31 directed at the aperture device 26 is shaded and a portion 31b (marked by its edge beam) of the laser beam 31 directed at the aperture device 26 is let through.

A divergence angle φ _A of portion 31a is greater than a divergence angle φ _B of portion 31b. The divergence angle φ _A is determined at an associated output laser beam portion 16a on the output laser beam 16 provided by the laser source 15 (or on the output laser beam 16 as a whole), where φ _A is approximately 130 mrad. The divergence angle φ _B is determined at an associated output laser beam portion 16b on the output laser beam 16 provided by the laser source 15, where φ _B is approximately 78 mrad. It is therefore true that φ _B <φ _A .

The laser beam 31 directed at the aperture device 26 _has a beam parameter product SPP (corresponding to the larger divergence angle φ _A of portion 31a), which is larger than a beam parameter product SPP _after a laser beam 32 transmitted at the aperture device 26 (corresponding to the smaller divergence angle φ _B of portion 31b). The transmitted laser beam 32 here corresponds to the proportion 31b of the laser beam 31 directed onto the aperture device 26 after passing through the aperture device 26. In the embodiment shown here, SPP is _after =0.6*SPP _before .

The laser beam 31 directed onto the aperture device 26 has incident laser power EL, which here essentially corresponds to the laser power P of 2000W of the output laser beam 16 provided at the laser source 15. An absorbed power component AB of the incident laser power EL of the laser beam 31 is absorbed at the aperture device 26. The absorbed power component AB here corresponds to approximately 500W; So approximately a quarter of the incident laser power EL is absorbed. A passed power component DL then corresponds to approximately 1500W. Due to the absorption of the power component AB in the diaphragm device 26, the diaphragm device 26 heats up.

In order to dissipate the heat effectively, the diaphragm device 26 in the embodiment shown here is thermally connected to a heat sink 33. The heat sink 33 is connected to an external cooler 36 via fluid lines 35 filled with cooling fluid 34. A coolant circuit is set up between the heat sink 33 and the external cooler 36. A cooling channel 33a for the cooling fluid 34 is set up in the heat sink 33.

The collimated laser beam 30, more precisely the transmitted laser beam 32 in the embodiment shown here, is guided to the focusing device 27. The focusing device 27 focuses the collimated laser beam 30 and thus provides a focused laser beam 37.

The focused laser beam 37 then hits the scanner device 28 as an incident laser beam 38. The incident laser beam 38 is deflected via the movable scanner mirror 29, led out of the scanner device 28 and the laser processing head 17 and made available as a processing laser beam 18.

According to the invention, the laser source 15 provides the multimode laser beam 16'. This multimode laser beam 16 'is collimated in the laser processing head 17, partially shaded, focused and deflected with the scanner device 28. The processing laser beam 18 provided by the laser processing head 17 is still a multimode laser beam, namely the multimode processing laser beam 18 '. Due to the high laser power P of the multimode laser beam 16 '(compared to a laser power of a basic mode laser beam) that is made available, and the beam parameter product of the processing laser beam 18, which is reduced by means of the aperture device 26, the object can be manufactured particularly quickly and precisely high productivity of the system can be achieved.

Furthermore, the aperture device 26 ensures that a beam quality of the processing laser beam 18 is better than a beam quality of the output laser beam 16. The processing laser beam 18 can be better focused and precise production of the object with a multimode laser beam, here the multimode processing laser beam 18 ', is possible.

3 shows a schematic view from the side of the laser source 15, the laser processing unit device head 17 and the cooling device 22 of an exemplary system according to the invention in a second embodiment, which is suitable for carrying out the method according to the invention. Since the procedure in 2 analogous to 3 runs and a variety of components in 3 right away 2 are, only the main differences are presented here 3 to 2 explained.

In the embodiment shown here, the laser source 15 is designed as a diode laser 15b, more precisely a blue diode laser 15b '. The output laser beam 16 here has a laser power P of 2000W and an average laser wavelength λ of 345nm (so it is a laser beam in the ultraviolet wavelength range).

In the embodiment shown here, the diaphragm device 26 is arranged in front of the collimation device 25. The scanner device 28 is arranged between the collimation device 25 and the focusing device 27.

The output laser beam 16 provided by the laser source 15 emerges from the fiber end 24 of the light guide cable 23 and is guided to the collimation device 27.

The diaphragm device 26 is arranged between the fiber end 24 and the collimation device 27. The laser beam 31 directed onto the aperture device 26 (here the output laser beam 16) is partially shaded by the aperture device 26. The portion 31a of the laser beam 31 directed at the aperture device 26 is shaded and the portion 31b of the laser beam 31 directed at the aperture device 26 is allowed to pass through. The transmitted laser beam 32 here corresponds to the proportion 31b of the laser beam 31 directed onto the aperture device 26 after passing through the aperture device 26.

The divergence angle φ _A of portion 31a is larger than a divergence angle φ _B of portion 31b. The divergence angle φ _A is determined by the output laser beam portion 16a (which here corresponds to portion 31a) on the output laser beam 16 provided by the laser source 15 (i.e. by the entire output laser beam 16). The divergence angle φ _B is determined at the output laser beam portion 16b (which here corresponds to portion 31b) on the output laser beam 16 provided by the laser source 15. It is again true that φ _B <φ _A . Note that in the embodiment shown, the size of the divergence angle φ _B can be changed by moving the aperture device 26 in the direction of beam propagation. The divergence angle φ _B becomes smaller here the closer the diaphragm device 26 is moved to the collimation device 25.

In order to effectively dissipate the heat associated with the absorbed portion AB, the diaphragm device 26 in the embodiment shown here is in turn thermally connected to the heat sink 33. Cooling fins 39 are attached to the heat sink 33. An external air flow 42 is generated via a fan 40 of a fan 41. The cooling fins 39 are exposed to the external air flow 42 and are cooled in this way.

The output laser beam 16, more precisely the transmitted laser beam 32 in the embodiment shown here, is guided to the collimation device 25. The collimation device 25 collimates the output laser beam 16 and thus provides the collimated laser beam 30.

The collimated laser beam 30 then hits the scanner device 28 as the incident laser beam 38. The incident laser beam 38 is deflected via the movable scanner mirror 29 and guided out of the scanner device 28 as a collimated laser beam 30 to the focusing device 27. The focusing device 27 focuses the collimated laser beam 30 and thus provides the focused laser beam 37. The focused laser beam 37 is led out of the laser processing head 17 and made available as a processing laser beam 18.

4 shows a schematic, exemplary diagram in which for the processing laser beam provided the beam parameter product SPP (also referred to as SPP _B ) and the relative power loss (compared to the output laser beam) for four different divergence angles φ _B set by the aperture device (according to the system according to the invention or of the method according to the invention, cf. in particular 2 ) are applied. Four aperture devices of different sizes were used here, which shade different portions of a laser beam directed at the aperture device. The output laser beam is always the same, and here has an SPP _A of approximately 3.3mm*mrad and a divergence angle φ _A of approximately 130mrad. The output laser beam is provided here via an optical fiber cable with a fiber diameter of 50µm.

The four different values (70 mrad, 78 mrad, 102 mrad, 114 mrad) for the divergence angle φ _B (in mrad) are entered on the abscissa (note that the distances on the abscissa are not evenly distributed). The left ordinate shows (with ruling) the beam parameter product SPP (in mm*mrad) or SPP _B of the processing laser beam and the right ordinate shows (without ruling) the relative power loss (in%) of the processing laser beam due to the partial shadowing of the output laser beam by the aperture device tung. A first curve 43 shows the relative power loss through the aperture device at the different divergence angles. A second curve 44 shows the obtained beam parameter product SPP of the processing laser beam at the different, set divergence angles.

With a divergence angle φ _B of 114 mrad set by the aperture device, a processing laser beam with a beam parameter product SPP of approximately 3.2 mm*mrad can be obtained. The relative power loss of the laser beam is approximately 9%. In this case, the remaining power of the processing laser beam is still very high and suitable for a very high production speed, but the beam parameter product is also still relatively high, although significantly lower than without using the aperture device.

With a divergence angle φ _B of 102 mrad set by the aperture device (i.e. a reduction of 12 mrad from the previous divergence angle of 114 mrad), the processing laser beam has a beam parameter product SPP of approximately 2.6 mm*mrad. The beam parameter product therefore improves by approximately 0.6 mm*rad. The relative power loss of the laser beam is approximately 18%. In this case, the remaining power of the processing laser beam is slightly lower, but still good for high manufacturing speed. The processing laser beam can also be focused better, enabling more precise processing of the object during production.

With a divergence angle φ _B of 78 mrad set by the aperture device (i.e. a reduction of 24 mrad from the previous divergence angle of 102 mrad), the processing laser beam has a beam parameter product SPP of approximately 2.05 mm*mrad. The beam parameter product therefore improves by approximately 0.6 mm*rad. The relative power loss of the laser beam is approximately 27%. In this case, the remaining power of the processing laser beam is still slightly lower than before, but still good for high production speed. The laser beam can be focused even better, enabling even more precise processing of the object during production.

With a divergence angle φ _B of 70 mrad set by the aperture device (i.e. a reduction of 8 mrad from the previous divergence angle of 78 mrad), the processing laser beam has a beam parameter product SPP of approximately 1.85 mm*mrad. The beam parameter product therefore improves by approximately 0.2 mm*rad. The relative power loss of the laser beam is approximately 37%. In this case, the remaining power of the processing laser beam is even lower than before, so that the achievable production speed is somewhat reduced. However, the laser beam can be focused even better, enabling even more precise processing of the object during production.

Reference symbol list

1

Attachment

2

object

3

Construction chamber

4

Powder cylinder arrangement

5

Powder cylinder

6

powdery material

7

powder flask

8th

Floor (of the building chamber)

9

Slider

10

Construction cylinder arrangement

11

collection container

12

Piston plate

13

construction platform

14

Basic body

15

Laser source

15a

Disk laser

15b

diode laser

15b'

blue diode laser

16

Output laser beam

16'

Multimode laser beam

16a, b

Output laser beam proportion

17

Laser processing head

18

Processing laser beam

18'

Multimode processing laser beam

19

Window

20

Process level

21

(top layer

22

Cooling device

23

Light guide cable

24

fiber end

25

Collimation device

25a

collimating lens

26

Aperture setup

26a

Pinhole

27

Focusing device

27a

Focusing lens

28

Scanner facility

29

(movable) scanner mirror

30

collimated laser beam

31

Laser beam directed at the aperture device

31a

shaded portion of the laser beam directed at the aperture device

31b

transmitted portion of the laser beam directed at the aperture device

32

transmitted laser beam

33

Heat sink

33a

Cooling channel

34

Cooling fluid

35

Fluid line

36

external cooler

37

focused laser beam

38

incident laser beam (at the scanner device)

39

cooling fins

40

fan

41

Fan

42

Airflow

43

first curve (power losses)

44

second curve (SPP _B values)

φa

Divergence angle (output laser beam)

φb

Divergence angle (processing laser beam)

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• CN 112605525 A [0008]
• CN 107866639 A [0009]

Claims (19)

System (1) for the layer-by-layer production of at least one object (2) on a construction platform (13) by local solidification of powdery material (6) in a respective layer (21) with a processing laser beam (18), comprising a laser source (15) for provision an output laser beam (16), the laser source (15) providing a multimode laser beam (16'), and a laser processing head (17) which provides the processing laser beam (18), the laser processing head (17) having - a collimation device (25) for collimating the output laser beam (16) provided by the laser source (15), in particular wherein the provided output laser beam (16) emerges at a fiber end (24) of a light guide cable (23), - a focusing device (27) for focusing one of the collimation device (25 ) provided, collimated laser beam (30), - a scanner device (28) for deflecting a laser beam (38) incident on the scanner device (28), and - a cooled aperture device (26) for partially shading a laser beam directed onto the aperture device (26). (31), with which a portion (31a) with a larger divergence angle (φ _A ) is shaded by the laser beam (31) directed onto the aperture device (26) and a portion (31b) with a smaller divergence angle (φ _B ) is allowed to pass through, whereby the divergence angle (φ _A , φ _B ) is determined on the output laser beam (16) provided by the laser source (15). Appendix (1). Claim 1 , characterized in that the aperture device (26) is selected such that a beam parameter product SPP _after a laser beam (32) transmitted through the aperture device (26) is smaller than a beam parameter product SPP _{in front of} the laser beam (X) directed at the aperture device (31). , with SPP _after ≤ SPP _before *0.90, preferably with SPP _after ≤0.80*SPP _before , particularly preferably with SPP _after ≤0.70*SPP _before . Appendix (1). Claim 1 or 2 , characterized in that the diaphragm device (26) is selected such that an absorbed power component AB is absorbed by an incident laser power EL of the laser beam (31) directed onto the diaphragm device (26), with AB/EL ≥ 0.10, preferably with AB/EL ≥ 0.20, particularly preferably AB/EL ≥ 0.25. System (1) according to one of the preceding claims, characterized in that the diaphragm device (26) is fluid-cooled, wherein the diaphragm device (26) or a heat sink (33) thermally connected to the diaphragm device (26) has one or more cooling channels (33a) for has a cooling fluid (34). System (1) according to one of the preceding claims, characterized in that the diaphragm device (26) is arranged between the collimation device (25) and the focusing device (27) in the collimated laser beam (30) provided by the collimation device (25). System (1) according to one of the preceding claims, characterized in that the scanner device (28) is arranged after the focusing device (27) in a focused laser beam (37) provided by the focusing device (27). System (1) according to one of the preceding claims, characterized in that the following applies to a laser power P of the output laser beam (16) provided by the laser source (15): P≥200W, preferably P≥500W, particularly preferably P≥1000W, very particularly preferred P≥2000W. System (1) according to one of the preceding claims, characterized in that the following applies to a mean laser wavelength λ of the output laser beam (16) provided by the laser source (15): λ ≤ 540nm, preferably 500nm ≤ λ ≤ 540nm or preferably 330nm ≤ λ ≤ 360nm , particularly preferably λ=515nm. System (1) according to one of the preceding claims, characterized in that the laser source (15) is designed as a disk laser (15a) or diode laser (15b), in particular a blue diode laser (15b'). Method for producing at least one object (2) in layers on a construction platform (13) by locally solidifying powdered material (6) in a respective layer (21) with a processing laser beam (18), in particular using a system (1) according to one of Claims 1 until 8th , wherein an output laser beam (16) is provided with a laser source (15), wherein the output laser beam (16) is a multimode laser beam (16 '), wherein the output laser beam (16) is fed to a laser processing head (17), and with which Laser processing head (17) the processing laser beam (18) is provided, with the laser processing head (17) - the provided output laser beam (16) being collimated with a collimation device (25), in particular wherein the provided output laser beam (16) at a fiber end (24). Light guide cable (23) emerges, - a collimated laser beam (30) with a focus provided by the collimation device (25). sizing device (27) is focused, - a laser beam (38) incident on a scanner device (28) is deflected with the scanner device (28), and - a laser beam (31) directed onto a cooled aperture device (26) is deflected with the aperture device (26) is partially shaded, a portion (31a) with a larger divergence angle (φ _A ) being shaded by the laser beam (31) directed onto the aperture device (26) and a portion (31b) with a smaller divergence angle (φ _B ) being transmitted, the Divergence angle (φ _A , φ _B ) is determined on the output laser beam (16) provided by the laser source (15). Procedure according to Claim 10 , characterized in that the aperture device (26) is selected such that a beam parameter product SPP _after a laser beam (32) transmitted to the aperture device (26) is smaller than a beam parameter product SPP _{in front of} the laser beam (31) directed at the aperture device (26) , with SPP _after ≤ SPP _before *0.90, preferably with SPP _after ≤0.80*SPP _before , particularly preferably with SPP _after ≤0.70*SPP _before . Procedure according to one of the Claims 10 or 11 , characterized in that the diaphragm device (26) is selected such that an absorbed power component AB is absorbed by an incident laser power EL of the laser beam (31) directed onto the diaphragm device (26), with AB/EL ≥ 0.10, preferably with AB/EL ≥ 0.20, particularly preferably AB/EL ≥ 0.25. Procedure according to one of the Claims 10 until 12 , characterized in that the aperture device (26) is fluid-cooled, wherein the aperture device (26) or a heat sink (33) thermally connected to the aperture device (26) has one or more cooling channels (33a) for a cooling fluid (34), and the or the cooling fluid (34) flows through the cooling channels (33a). Procedure according to one of the Claims 10 until 13 , characterized in that the diaphragm device (26) is arranged between the collimation device (25) and the focusing device (27) in the laser beam (30) collimated by the collimation device (25). Procedure according to one of the Claims 10 until 14 , characterized in that the scanner device (28) is arranged after the focusing device (27) in a focused laser beam (37) provided by the focusing device (27). Procedure according to one of the Claims 10 until 15 , characterized in that the following applies to a laser power P of the output laser beam (16): P≥200W, preferably P≥500W, particularly preferably P≥1000W, very particularly preferably P≥2000W. Procedure according to one of the Claims 10 until 16 , characterized in that for a mean laser wavelength λ of the output laser beam (16): λ ≤ 540nm, preferably 500nm ≤ λ ≤ 540nm or preferably 330nm ≤ λ ≤ 360nm, particularly preferably λ = 515nm. Procedure according to one of the Claims 10 until 17 , characterized in that the laser source (15) is selected as a disk laser (15a) or diode laser (15b), in particular blue diode laser (15b '). Use of a system (1) according to one of the Claims 1 until 9 in proceedings according to one of the Claims 10 until 18 .

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