METHOD AND DEVICE FOR MACHINING A MATERIAL LAYER USING ENERGETIC RADIATION

Abstract

The invention relates to a method and a device for machining a material layer using energetic radiation to produce three-dimensional components by melting a particulate material in layers. In the method, one or more energetic beams of one or more beam sources are directed onto a layer to be machined and guided over the layer by a dynamic beam guidance system. The method is characterized in that at least one of the energetic beams is divided into multiple individual beams by modulation over time, which are directed onto the layer to be machined in a spatially separated manner. The separation is carried out such that the sum of the power of the individual beams corresponds to the power of the respective energetic beam minus power losses caused by the separation process.

Claims

1. Method for machining a material layer using energetic radiation, in particular in order to produce three-dimensional components by melting a particulate material in layers, in which one or more energetic beams of one or more beam sources are directed onto a layer to be machined and guided over the layer by means of a dynamic beam guidance system in order to machine regions of the layer, characterized in that at least one of the energetic beams is separated into multiple individual beams by modulation over time, said individual beams being directed onto the layer to be machined in a spatially separated manner, wherein the separation is carried out in such manner that the sum of the power of the individual beams corresponds to the power of the respective energetic beam minus power losses caused by the separation process.

2. Method according to claim 1, characterized in that each individual beam is directed onto the layer to be machined by its own dynamic beam deflection device.

3. Method according to claim 1, characterized in that the energetic beam is separated into the individual beams in alternating manner by said modulation over time.

4. Method according to claim 2, characterized in that the energetic beam is separated into the individual beams in alternating manner by said modulation over time and is thus separated onto the beam deflection devices, wherein the beam deflection devices are operated in coordination with each other in such manner and the switch between the beam deflection devices is effected in such manner that times for which the beam does not reach the layer during the machining is minimised.

5. Method according to claim 4, characterized in that the switch between the beam deflection devices takes place for the energetic beam when changing between non-adjacent scan vectors and/or upon sudden changes of a direction in a machining path.

6. Method according to claim 1, characterized in that the energetic beam is separated into two individual beams by modulation over time, of which one individual beam has an amplitude modulation of <100%.

7. Method according to claim 1, characterized in that the separation into the individual beams is effected via one or more beam switches for the energetic beam.

8. Method according to claim 1, characterized in that the one or more beam sources is/are operated in continuous wave mode.

9. Device for machining a material layer using energetic radiation, in particular in order to produce three-dimensional components by melting a particulate material in layers, including at least: one or more beam sources which emit one or more energetic beams, at least one beam splitter device which can separate at least one of the energetic beams into multiple individual beams by modulation over time, and one or more dynamic beam guidance apparatuses, via which the individual beams can be directed onto a layer to be machined and guided over the layer in order to machine regions of the layer, wherein the beam splitter device is designed such that the sum of the power of the individual beams corresponds to the power of the respective energetic beam upon separation.

10. Device according to claim 9, characterized in that a dedicated dynamic beam deflection device is present for each individual beam, via which the individual beam is directed onto the layer to be machined.

11. Device according to claim 9, characterized in that the beam splitter device is designed in such manner that it separates the energetic beam into the individual beams in alternating manner by said modulation over time.

12. Device according to claim 10, characterized in that a control unit is present which actuates the beam splitter device and the beam deflection devices in such manner that the energetic beam is separated into the individual beams and thus also to the beam deflection devices in alternating manner by said modulation over time, the beam deflection devices are operated in coordination with each other in such manner and switching between the beam deflection devices is carried out in such manner that times in which the beam does not impinge on the layer during machining of the layer are minimised.

13. Device according to claim 9, characterized in that the beam splitter device is embodied such that it separates the energetic beam by the modulation over time into two individual beams, of which one individual beam has an amplitude modulation of <100%.

14. Device according to claim 9, characterized in that the beam splitter device includes one or more beam switches.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0020] In the following section, the suggested method and the suggested device will be explained again in greater detail with reference to an exemplary embodiment thereof in conjunction with the drawing. In the drawing:

[0021] FIG. 1 is a diagrammatic representation of the process chain in selective laser melting;

[0022] FIG. 2 is a diagrammatic representation of an example of the suggested method; and

[0023] FIG. 3 shows an example of a different separation of the output to the individual beams.

WAYS TO REALISE THE INVENTION

[0024] In powder-bed based beam fusion methods such as selective laser melting, the value-adding irradiation process is interrupted by processes that do not add value such as layer application, process preparation and follow-up processing. This process chain is represented diagrammatically in FIG. 1, which shows the process preparation 1, layer application 2, irradiation 3 and follow-up processing 4 processes in the defined sequence. The layer application 2 and irradiation 3 processes are repeated one layer at a time until the three-dimensional component is fully constructed. The suggested method and the associated device enable optimisation of the irradiation process in which dead times 5 typically occur, during which the energetic beam does not reach the layer and consequently no irradiation takes place. FIG. 1 indicates schematically the fraction of the irradiation process 2 taken up by the dead times 5. These may be necessitated by acceleration and deceleration phases of the scanner mirrors or due to non-adjacent scan vectors which must be irradiated consecutively. With the suggested method and the associated device, the fraction of these dead times 5 as part of the irradiation process is minimised.

[0025] FIG. 2 shows an example of an implementation of the suggested method for this purpose, in which the energetic beam 7 from a laser beam source 6 is separated alternatingly into two individual beams, which impinge on the layer for irradiation at spatially different points. The separation is effected by a beam splitter device 8, which is indicated schematically in the figure. As a result of the temporal modulation of the separation of the energetic beam 7 into two individual beams 9 performed in this example, the power distributions of the individual beams (minus any power losses due to the optical components used) correspond to the original temporal power distribution of the energetic beam 7. The power losses are therefore minimal and the laser power supplied by the laser beam source 6 is used without interruption or at least almost entirely without interruption for the irradiation of the layer for the entire duration of the layer irradiation process. In this regard, the power of the energetic beam 7 generated by the laserbeam source 6 over time is shown in the top part of FIG. 2. The laser beam source 6 is operated in continuous wave (CW) mode. In the lower part of the figure, the power distributions over time for the two individual beams 9 generated by the beam splitter device 8 are depicted on the left and right. The diagrams show the alternating separation of the energetic beam 7 into the two individual beams 9 over time. In this example, a periodic separation over time is evident.

[0026] However, this is not essential. The separation over time is selected as a function of the geometry to be irradiated depending on the irradiation task such that melting can be carried out continuously with minimal or no temporal interruption. Thus in one variant for example a separation over time of the continuous radiation may be effected into e.g. n temporally correspondingly offset pulse modulated individual beams with a duty cycle of 1/n, which individual beams are used for melting at different positions by the spatial separation or for repeated irradiation processes, for example pre-heating or post-heating.

[0027] In the example shown in FIG. 2, either of the two individual beams 9 may be directed onto the layer to be irradiated for example with a dedicated dynamic beam deflection device, in particular each with a galvanoscanner. A fast-switching beam switch may be used as the beam splitter device, for example. The dead times caused by repositioning, deceleration or acceleration processes may be avoided or reduced by appropriate switching between the two individual beams or galvanoscanners and suitable actuation of these scanners. Thus for example the energetic beam 7 may be guided over the surface to be irradiated via the first galvanoscanner while repositioning, deceleration or acceleration processes are being performed by the second scanner, and vice versa. The other scanner in each case is moved into the requisite position before switching or operated in such manner that it is already in the requisite position when switching is carried out, and can perform the subsequent beam deflection operations before the next switching process without additional acceleration or deceleration. In this way, the dead times represented in FIG. 1 may be reduced considerably. Ideally, corresponding dead times then occur only as a result of switching processes between the individual galvanoscanners or individual beams.

[0028] The energetic beam may also be separated in such manner that one of the individual beams continues to deliver an energetic permanent signal, whose power is modulated over time, however (power wobbling), and only the excess power is split to another individual beam. The individual beam with the excess power is thus not always present over time. This is represented schematically in FIG. 3, in which the diagram at the top shows the power over time of the energetic beam generated by the laser beam source, and the diagrams at bottom right and left in the figure show the temporal power distributions for the two individual beams generated by the beam splitter device.

LIST OF REFERENCE SIGNS

[0029] 1 Process preparation [0030] 2 Layer application [0031] 3 Irradiation [0032] 4 Follow-up processing [0033] 5 Dead times [0034] 6 Laser beam source [0035] 7 Energetic beam [0036] 8 Beam splitter device [0037] 9 Individual beams