EP3538350A1

EP3538350A1 - Device and method for additive manufacturing of components with a plurality of spatially separated beam guides

Info

Publication number: EP3538350A1
Application number: EP17803829.5A
Authority: EP
Inventors: Reinhart Poprawe; Florian EIBL; Wilhelm Meiners; Lucas JAUER
Original assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Current assignee: Fraunhofer Gesellschaft zur Forderung der Angewandten Forschung eV
Priority date: 2016-11-10
Filing date: 2017-11-09
Publication date: 2019-09-18
Also published as: DE102016222068A1; WO2018087218A1; JP2020501008A; CN109937131A; US20200055144A1

Abstract

The present invention relates to a device and a method for the additive manufacturing of components, in particular for selective laser melting or laser sintering. The device comprises a processing head (7) having a plurality of spatially separated beam guides, via which one or more laser beams can be directed onto a processing plane (8) along spatially separated beam paths, and one or more optical switching devices (4) by means of which the beam path of each laser beam can be switched between the spatially separated beam paths. The device allows one laser beam source (1) to be used for different beam paths or target positions using such a processing head (7), resulting in better utilization of the beam sources and making it possible to irradiate the processing plane (8) corresponding to a desired component geometry using a smaller number of laser beam sources (1).

Description

Device and method for generative

Component production with several spatially separated

radiates tours of the farm

Technical application

The present invention relates to a device for additive component manufacturing, in particular for

selective laser melting or laser sintering, comprising a machining head with several spatially separated

Beam guides, over which one or more laser beams can be directed on spatially separated beam paths on a working plane. The invention also relates to a corresponding method for the generative component production, in which the

proposed device can be used.

In powder bed-based beam melting, such. B. selective laser melting (SLM: Selective Laser Melting) are three-dimensional components

generatively manufactured directly from 3D-CAD models. In a repetitive process becomes a thin one

Powder layer of typically less than 100 μιη thickness applied with a slider on a substrate plate and selectively melted in a next step according to the geometry information from the 3D-CAD model using one or more energetic beams, in particular laser beams. This recirculation process allows the production of three-dimensional components with little restrictions in terms of design complexity. The compaction of the component is based on a complete melting of the SLM Powder and the previous layer. This achieves component densities of up to 100% and comparable mechanical properties with conventional production methods.

The process chain runs with such

Method within the manufacturing plant based on a construction platform sequentially, as shown schematically in Figure 1. The value-adding

Exposure process, in which the corresponding portions of the layer are selectively melted with the energetic radiation is interrupted by non-value-added processes such as the layer order, the Prozessvor ^¬ preparation and the process follow. Depending on the equipment used, for example. When using galvanometer scanners for beam deflection, it comes within the value-adding exposure process in addition to technically induced exposure dead times, although those required for beam deflection

Scanner levels are moved, but no exposure takes place. This is the case, for example

geometrically not directly adjoin each other scan vectors to be exposed sequentially. Additional non ^¬ productive times occur in the acceleration and deceleration of the scanning mirror. The beam source is thus not used 100% for the exposure.

State of the art

In addition to the previously mainly used beam deflection systems based on galvanometer scanners with upstream or downstream focusing optics, alternative exposure concepts are also known. It acts It is mostly about less complex optical systems, which are guided by means of a movement device over the surface to be exposed. This offers the advantage of a possible scaling of installation space size and / or melting performance, without the basic

To change the system structure.

For example, WO 2015/003804 A1 shows a

Device in which an exposure or processing head is moved over a powder bed with the aid of an axis system. The processing head forms by means of an optical device several individual laser beams in a fixed arrangement as laser spots next to each other or partially overlapping on the processing level from, for. B. in a line arrangement perpendicular to the direction of movement of the machining head. The laser ^¬ rays are each of a separate

Beam source generated by means of optical fibers for

Machined head and simultaneously to the movement of the machining head according to the produced

Component geometry modulated or switched on and off. WO 2014/199149 A1 shows a similar device in which the respective beam sources direct the radiation without optical fibers directly to the working plane. However, these devices require a separate beam source for each individual laser spot in the processing plane. In this way, although the spot arrangement on an increase in the number of

Beam sources are widened almost arbitrarily. However, this is associated with a linear increase in costs. In addition, the necessary design effort is increased accordingly. The US 2014/0198365 AI describes a

An exposure apparatus wherein the radiation of a single beam source is via one or more

Beam splitter is divided into several sub-beams. The partial beams are then each with its own deflection independent of each other on the

Directed processing level. In this arrangement, however, due to the constant distribution of the laser power to the individual partial beams, care must be taken to ensure that the area to be exposed by the respective beam deflecting devices is identical.

WO 00/21735 Al proposes an exposure apparatus in which the radiation of a light source is directed onto the working plane via a multiplicity of individual optical fibers which are arranged in a stationary array. Behind each fiber end, a light valve is provided which is capable of either transmitting or absorbing the radiation exiting the fiber in response to a control signal. In this way, by the movement of the fiber array and dependent on the geometry of the component control of the light valves belonging to the component areas in the working plane can be selectively exposed. When operating this device, the radiation must

certain irradiated areas not intended for

Component structure needed to be absorbed in the associated light valves. This leads in

Practical use, however, to a very low ratio of used and actually used Laser power. This also applies to some of the devices already mentioned.

The above-described disadvantages of the known devices make an economical use of powder-bed-based jet melting processes, for example in the mass production of metallic components, difficult.

The object of the present invention is to provide a device and a method for

Generative component production by layer by layer

Melting a powdery material with

To specify laser radiation that improved

Utilization of the beam sources used allows, without being limited to certain surfaces to be exposed.

Presentation of the invention

The task is with the device and the

Process according to claims 1 and 10 solved. Advantageous embodiments of the device and the method are the subject of the dependent patent claims ^¬ or can be the following

Description and the exemplary embodiments.

The proposed device has a

Processing head with several spatially separated

Beam guides with corresponding Strahlführungs- and / or Strahlablenkelementen on the one or more laser beams on spatially separated

Beam paths can be directed to a working plane, a laser beam source arrangement, with which the laser beam (s) are producible, and means for providing a material in the working plane. The device further comprises a movement device with which a relative movement between the machining head and the machining plane

preferably in mutually parallel planes can be generated and a control device with which the

Movement device for generating the relative movement can be controlled. The device is characterized in particular by the fact that one or more optical switching devices are provided with which the

Beam path of the one or more laser beams between the spatially separated beam paths can be switched. The optical switching devices are preferably formed as a beam switch. These can, for example, by optoelectronic elements or by one or more tiltable mirror elements

be formed. By this embodiment of the proposed

Device is the possibility of better utilization of the generation of the respective

Laser beam used laser beam source. Thus, in a powder bed-based beam melting method, the laser beam can be switched from a first beam path to a second beam path if it is no longer needed at the target position of the first beam path for exposure at least temporarily, while at a target position of the second beam path still an exposure is required. While previously two laser beam sources were required for such a situation, one of which temporarily switched off had to be, can be used by the proposed Vor ^¬ direction only one laser beam ^source , which is better utilized temporally by the switchover. Of course, the number of spatially separated beam paths per laser beam source is not limited to two.

Another way of one possible

uninterrupted operation of the laser beam source is pulsed to the laser beam source

operate and the switching between the

If possible, carry out beam paths in pulse pauses.

By suitable control of the relative speed between the processing head and the machining ^¬ tung flat can with a corresponding line-shaped arrangement of the target positions of the individual beam paths, a laser line on the working plane exposed by the pulsed or CW laser beam (CW: Continuous Wave) in sequence over all beam paths

is switched.

Basically there is also the possibility not the full power of a laser beam on one

single beam path to switch, but to divide this power on multiple beam paths simultaneously. The total number of possible target positions, that is, the end positions of the individual beam paths in the

Working level, is at the proposed

Device greater than the maximum possible number of positions to be exposed simultaneously, hereinafter also referred to as processing positions. In the preferred embodiment of the proposed device, the laser beam source assembly includes a plurality of laser beam sources that produce a plurality of separate laser beams. Each of these

Laser beams is then assigned its own optical switching ^¬ element, which can switch the laser beams each on a plurality of spatially separated beam paths. There is the possibility of the optical

To design switchgear so that everyone

Laser beam can use all available beam guides or beam paths. Another possibility is to assign each laser beam other beam paths over which the laser beam can be directed to the working plane. Preferably, in this case, adjacent beam paths under ^¬ schiedlicher laser beams common goal positions. Also a combination of the ones described above

Possibilities can be realized. The above-explained embodiments, in which a plurality of laser beam sources are used with the respective associated optical switching elements, allow better use of the. By switching between the individual beam paths

Laser beam sources and also - depending on the geometry to be exposed - a reduction in the number of crossings with the machining head on the processing ^¬ level. This is achieved in that the radiation is not needed during a single passage for a given area may be directed through the optical switching elements ^¬ in other device areas, which might otherwise be achieved through a further crossing. In the proposed method is

according to a powdered material for the component layer by layer by irradiation with laser ^¬ radiation melted in a working plane. The laser beams for the irradiation of the material are guided over the working plane and switched so between the beam paths, that in each case one layer of the material according to the

desired component geometry is melted and the laser power generated by the laser beam sources is maximally utilized by the switching.

The generation of the relative movement can take place in the same way as described in the already cited document WO 2015/003804 AI.

The proposed device on the one hand on the simple scalability of build rate and space size achieved by using a larger number of laser beam sources, a higher productivity. On the other hand, the proposed device provides the possibility of achieving these advantages with the smallest possible number of individual beam sources. In addition, these beam sources are operated virtually uninterrupted in the proposed device. This results in the operation of

Device maximum efficiency - defined by the ratio of used to melting to total installed laser power. The

The device and the method can be used for any powder bed-based laser beam melting process deploy. Especially the use of such

Device within industrial manufacturing environments has great potential. The

Device enables the generative production of components with maximized added value. This results in a significant increase in the productivity of the corresponding manufacturing facility and thus also significant economic benefits, the use of powder bed-based laser beam melting in the context of industrial mass production strong

favor.

Brief description of the drawings

The proposed apparatus and methods are provided ^¬ troubled below with reference to

Embodiments in conjunction with the drawings explained in more detail. 1 is a schematic representation of the

Process chain during selective laser melting;

FIG. 2 shows a comparison of the exposure unit of a device according to FIG

State of the art and the exposure ^¬ unit of an embodiment of

proposed device in a highly schematic representation;

Fig. 3 is a schematic representation of a

Design of the proposed

Contraption; 4 shows a comparison of the exposure sequence in a device according to the prior art and in an embodiment of the proposed device; and

Fig. 5 is a schematic representation of a

further embodiment of the proposed device.

Ways to carry out the invention

In the case of powder bed-based beam melting processes such as selective laser melting, the value-adding exposure process is interrupted by non-value adding processes such as coating, process preparation and postprocessing. This process chain is shown schematically in FIG. 1, which shows the processes of the process preparation 12, the coating application 13, the exposure 14 and the process ^after- treatment 15 in the specified sequence. The processes of the layer application 13 and the exposure 14 repeat themselves layer by layer until the three-dimensional component is finished. The proposed method and the associated device thereby enable an optimization of the exposure ^¬ process.

With the proposed device, the

Utilization of the laser beam sources with respect to one

Increase apparatus according to the prior art, as described for example in WO 2015/003804 AI. In this device of the prior Technique several laser beam sources 1 are used, which are connected via optical fibers 6 with a machining head. The machining head has a beam guide for each laser beam source 1

Focusing optics 2 on which the respective

Laser beam strikes a target position in the processing plane 8 on a fixed beam path. This can be generated in the processing plane 8, an array of laser spots 3, whose spot number of

Number of installed laser sources corresponds. This is schematic in the left part of FIG

shown.

In comparison, the right part of Figure 2 shows in the upper portion of a device according to the present invention, in which in this example, only one laser beam source 1 is used, which via an optical fiber 6 or another

Light-guiding device is connected to an optical switching element 4, by which the laser radiation can be directed in each case to one of a plurality of beam paths and thus to one of a plurality of target positions 5 in the processing plane 8. These too

required separate beam guides with

Focusing optics are not shown in the figure.

In the lower part of the figure is a plan view of this arrangement can be seen. For the schematically illustrated five beam paths, therefore, only one laser beam source 1 is required, the laser beam via the optical switching element 4 as needed on the

different beam paths can be switched. For a simultaneous exposure of several

Target positions are proposed at the

Device multiple laser beam sources 1 and a plurality of optical switching elements 4 used, as shown in Figure 3 by way of example. Each laser beam source 1 or each laser beam is then associated with one of the optical switching elements 4, which can switch the laser beam corresponding to several beam paths or target positions. The optical switching elements 4 are in each case integrated in the machining head 7. The laser beam sources 1 can also in the

Processing head 7 integrated or arranged outside the machining head 7 and be connected for example via optical fibers to the machining head 7.

In the example of Figure 3 are

within the processing head 7 four optical

Switching elements 4, which are each connected to a beam source 1. The processing head 7 is at a

Fixed linear axis 10, which in turn is mounted on two perpendicular to linear axes 9.

Of course, only one drive axle in conjunction with an additional guide could be provided for this purpose. Thus, the machining head 7 can be moved over the entire machining plane 8. The beam sources 1 are in this example at the

Linear axis 10 arranged. They can also be arranged in other places.

The optical elements 4 are arranged such that at least one, but preferably a plurality of target positions of the respectively adjacent optical elements 4 can be exposed with an optical element. These Target positions are shown in FIG. 3 as laser spots 3 in the working plane. Preferably, the individual target positions lie in a row, as is indicated schematically in the figure. Thus, for example, a laser line can be realized in the working plane. To build a component of the machining head 7 is moved, for example, meandering over the working plane and the optical

Switching elements 4 are controlled so that in each case the target positions are exposed, which belong within the current exposure field of the machining head 7 to the component geometry to be generated.

A further exemplary realization is based on the figure 4 compared to the use of a

Apparatus of the prior art as shown in WO 2015/003804 AI. In the upper part of the figure here is the exposure process with the device of the prior art, in the lower part of the

Exposure process illustrated with the proposed device. In this comparison, it is assumed that both devices have the same number of laser beam sources 1, but in the case of the proposed device, due to the switching possibilities, a higher number of adjacent ones

Target positions or laser spots and thus a larger exposure width is achieved. From the figure 4 it can be seen that with the proposed device, the illustrated component geometry 11 of a layer can be exposed with less crossings of the machining head than with the device of the prior art. This is achieved in the present example in that during a single crossing not required radiation can be directed by the optical switching elements in other component areas, which can be achieved in the device of the prior art only by a second crossing. The solid arrows represent thereby distances with exposure, the dashed arrows distances without exposure. From the comparison of Figure 4 is also seen that the laser beam sources used are better exploited in the proposed device, as it in this example nearly at ^¬ imperforate for melting the component layer to be operated. Of course that is

Increased effectiveness of the proposed device over the prior art device in each case of the component geometry to be generated

dependent .

The proposed device can also be designed so that the target positions not in one but in several consecutive

Rows lie. This extension of the field of

Target positions also in a second dimension can be seen by way of example in the schematic representation of FIG. Here is a second row

Target positions generated by further optical switching elements 4 and associated laser beam sources 1. The

Beam sources 1 are also arranged on the linear axis 10 in this example. They can also be arranged in other places. Of course, the proposed device is not on the illustrated arrangements of the target positions

limited. These can rather be distributed in other ways. The number of target positions per optical

Switching element and the number of optical switching ^¬ elements per machining head depend in addition to the technological limits, especially in terms of dimensions and resilience of the components of the optical switching element, in particular from the spot size, the space dimensions and the desired system productivity. An essential design criterion is that the beam sources used can be operated virtually uninterrupted in the average application, so that the highest possible proportion of installed laser power in the exposure process can be converted into remelted component volume.

The device can be used particularly advantageously if a pulsed or modulated process control is used instead of a continuous wave (cw) operation. The optical switching element requires a certain switching time to switch the laser radiation to another beam path and thus to redirect from one target position to the next. Is this switching time in a favorable relationship to the duty cycle used, i. Pulse duration and pulse pause, it can be exposed at a relative to the component geometry relative speed between machining head and working plane an entire spot line with significantly fewer beam sources as spot or target positions

available. The target positions may also be arranged so that the laser spot in the working plane over ^¬ overlap. Preferably, the processing head is formed with the optical switching elements so that each target position can be irradiated by a plurality of laser beam sources. The exposure of a component layer takes place in such a way that during the crossing of the

Processing head the individual optical switching ^¬ elements are controlled so that all lying within the field of the available target positions component areas are exposed, while the associated beam sources emit radiation as possible interruption-free to melt the component layer. The emitted power can be varied in the proposed device preferably via a control ^¬ device depending on the component geometry and the switching position of the associated optical switching element in their amount.

Reference sign list

1 laser beam source

2 focusing optics

3 laser spot

4 Optical switching element

5 target position

6 optical fiber

7 machining head

8 processing level

9 linear axes

10 linear axis

11 Component geometry

12 process preparation

13 shift order

14 exposure

15 process follow-up

Claims

claims

Device for additive component production, in particular for selective laser melting or laser sintering, with

- A processing head (7) having a plurality of spatially separated beam guides over which one or more laser beams can be directed on spatially separated beam paths on a working plane (8),

a laser beam source arrangement for generating the one or more laser beams,

a device for providing a material in the working plane (8),

- A movement device (9, 10) with which a relative movement between the machining head (7) and machining plane (8) can be generated, and

a control device with which the movement device (9, 10) can be activated to generate the relative movement,

wherein one or more optical Schaltein ^¬ directions (4) are present, with which the beam path of the one or more laser beams between the spatially separated

Beam paths can be switched.

Device according to claim 1,

characterized,

the laser beam source arrangement has several

Laser beam sources (1) for generating a plurality of laser beams, wherein for each Laser beam own optical switching device (4) is present.

Device according to claim 2,

characterized,

that each beam path terminates in a target position (5) in the processing plane (8), wherein at least some of the target positions (5) of the beam paths of different laser beams

distinguish.

Device according to claim 3,

characterized,

in that adjacent beam paths of different laser beams have common target positions (5).

Device according to one of claims 1 to 4, characterized

that the control device is designed such that it has the one or more optical

Switching devices (4) controls so that in each case for a component geometry to be exposed by the laser beam sources (1) generated

Maximum laser power is utilized.

Device according to one of claims 1 to 5, characterized

that the number of spatially separated beam paths the number of laser beam sources (1) to

exceeds at least the factor 2. Device according to one of claims 1 to 6, characterized

the processing head (7) has a plurality of focusing optics (2) through which the laser beams can be focused in the direction of the working plane (8).

Device according to one of claims 1 to 7, characterized

in that the optical switching devices (4) are formed by electro-optical elements.

Device according to one of claims 1 to 8, characterized

in that the movement device (9, 10) has a

Translationsachse or two mutually perpendicular translation axes over which the

Processing head (7) in a plane parallel to the working plane (8) is movable.

A method for generating generative components using a device according to one of the preceding claims, in which a powdery material for the component is melted in layers by irradiation with laser radiation of one or more laser beam sources (1) in a working plane (8),

wherein for the irradiation of the material, the laser beams are guided over the working plane (8) and so switched between the beam paths, that in each case one layer of the material according to the desired

Part geometry melted and that of the Laser beam sources (1) generated laser power is utilized to the maximum.