RU2791739C1 - Multibeam raster selective laser melting machine - Google Patents

Abstract

FIELD: additive technologies.

SUBSTANCE: invention relates specifically to manufacture of parts by 3D printing from various materials, including plastics, metals, ceramics, etc. The machine tool contains semiconductor multimode laser modules, a portal system made in the form of two horizontal movement axes X and Y perpendicular to each other, a carriage mounted on the mentioned axes. The carriage contains a working head, which is configured with an optical system for focusing laser beams. Semiconductor laser modules are connected to the focusing system via fibre-optic bundles. The head also contains two scanning heads and a wire feed mechanism or a powder hopper with a squeegee installed between them. The machine also contains a construction chamber with a construction chamber platform, which is movable along the vertical Z axis and is located on the part construction chamber platform. The optical system for focusing laser beams is configured so that the laser beams are located at a distance from each other equal to or greater than the track width, forming tracks on the part with a distance between them equal to or greater than the track width. The focusing system is configured so that the laser beams fall on the part strictly perpendicular to it, and is made with the possibility of changing the overlap of the tracks melted by the laser beams.

EFFECT: increase in the speed of formation of the finished product and improvement of its quality.

11 cl, 10 dwg

Description

The field of technology to which the invention belongs

The invention relates to the field of additive technologies, namely to the manufacture of parts by 3D printing from various materials, including plastics, metals, ceramics, etc.

State of the art

The prior art system and method of additive manufacturing using high power diodes, Patent US9308583B2, USA, 2016, B. S. El-Dasher, A. Bayramian, J. A. Demuth, J. C: Farmer, S. G. Torres, SYSTEM AND METHOD FOR HIGH POWER DIODE BASED ADDITIVE MANUFACTURING, Patent Application Publication, Pub. No. US 2014/0252687 A1. In this case, a laser line (diode laser array) is used, consisting of several semiconductor laser emitters. The radiation of each emitter is focused by micro-optics, the distance between the emitters is small, i.e. focused beams in the working plane intersect, creating a single line. This can create great problems in the control of the molten bath. Another problem in metal processing is the low power of each emitter.

Laser diode area melting for high speed additive manufacturing of metallic components Miguel Zavala-Arredondo, Nicholas Boone, Jon Willmott, David T.D. Childs, Pavlo Ivanov, Kristian M. Groom, Kamran Mumtaz Materials and Design 117 (2017) 305-315. The multibeam system, which also uses a diode laser line, the radiation in the working plane is formed in the form of a line, i.e. a single melt pool is created, which, as noted above, is a disadvantage. Also a disadvantage is the low power of individual emitters.

The works of the Institute of Laser Technology of the Fraunhof Society are also known from the prior art (they are the closest analogue), Additive Manufacturing: Perspectives for Diode Lasers, Christian Hinke, Simon Merkt, Florian Eibl, Johannes Schrage, Sebastian Bremen, 2015 High Power Diode Lasers and Systems Conference ( HPD). Description of the principle in general terms. Describe the application of diode modules with a fiber optic bundle, but in fact in the source ([5] Hengesbach, S. et al., "Brightness and average power as a driver for advancements in diode lasers and their applications", Proc. SPIE 9348, High-Power Diode Laser Technology and Applications XIII, 93480B 2015 ) describes the use of a fixed array of multiple spots simultaneously in a “print head” moved by a gantry system).

Florian Eibl's dissertation, Laser Powder Bed Fusion of Stainless Steel with High Power Multi-Diode-Laser-Array, ISBN: 978-3-86359-587-6, describes exactly this prototype, but with five fiber-optic diode lasers. harnesses. The problem here is the location of the focusing lenses of each diode module. The first lens is located in the center in a strictly vertical position, the other four on the sides on four sides at an angle, this was done in order to have a single melt pool, which is a big drawback.

The essence of the invention

The problem solved by the claimed invention is to increase the speed of building parts by layer-by-layer laser melting. Additional positive effects are the absence of geometric deformation of laser spots in the working plane, which leads to a stable intensity of laser radiation at any point in the working field and, accordingly, leads to an improvement in the quality of manufactured parts. The design of the machine as a whole is also simplified, due to the absence of complex and expensive components.

The technical result of the claimed invention is to increase the speed of building parts by layer-by-layer laser melting and improve the quality of manufactured parts.

The technical result of the claimed invention is achieved due to the fact that a multi-beam raster machine for selective laser melting contains semiconductor laser modules, a portal system made in the form of two horizontal axes of movement X and Y perpendicular to each other, a carriage mounted on the said axes, a working head mounted on said carriage and containing an optical system for focusing laser beams, to which said semiconductor laser modules are connected by means of fiber-optic bundles, two scanning heads and a wire feed mechanism or a powder hopper with a squeegee installed between them, a build chamber with a build camera platform, made with the ability to move along the vertical Z axis and the part building camera located on the platform, while the laser beam focusing system is designed in such a way that the laser beams are located at a distance from each other equal to or greater than the width of the tr eka, forming tracks on the part with a distance between them equal to or greater than the width of the track, and the focusing system is designed in such a way that the laser beams fall on the part strictly perpendicular to it, and is made with the possibility of changing the overlap of the tracks melted by the laser beams.

In an embodiment of the claimed technical solution, the optical system for focusing laser beams consists of one collimator lens and one focusing lens.

In the embodiment of the claimed technical solution, the optical system for focusing laser beams is made with the possibility of focusing several laser beams with one lens, while the ends of the fiber-optic bundles are located at a distance from each other equal to or greater than the track width, while the laser beams are focused with the possibility of melting on parts of unconnected with each other tracks.

In an embodiment of the claimed technical solution, the optical system for focusing laser beams is configured to focus several laser beams by using a separate lens for each individual beam, while the ends of the fiber optic bundles are located at a minimum distance equal to the diameter of the lens, and the laser beams focused through separate lenses with the ability to formation of discrete tracks during melting of the part.

In the embodiment of the claimed technical solution, the optical system for focusing laser beams is made with the possibility of setting track overlap by turning the working head at an angle from 0° to 90° to the direction of movement, while the distance between the laser beams in the projection decreases with the formation of track overlap.

In the embodiment of the claimed technical solution, the optical system for focusing laser beams is made with the possibility of setting the overlap of tracks by moving the working head, while the working head is rigidly fixed on the carriage and is made with the possibility of floppy movement in the direction perpendicular to the direction of movement of the head.

In an embodiment of the claimed technical solution, the optical system for focusing laser beams is configured to set track overlap depending on the following parameters: the material from which the part is made, the laser radiation power, the speed of the working head, and the porosity of the finished part.

In an embodiment of the claimed technical solution, semiconductor multimode laser modules are made with a power of up to 300 watts.

In an embodiment of the claimed technical solution, optical fibers with a diameter of 50 to 700 microns are made.

In an embodiment of the claimed technical solution, semiconductor multimode laser modules are made with a power of up to 100 W, while optical fibers are made with a diameter of 50 - 100 μm.

In an embodiment of the claimed technical solution, the semiconductor multimode laser modules are configured to modulate the power of each individual module, regardless of the others.

Thanks to the use of a portal system, it is possible to move the working head with an optical system for focusing laser beams built into it in two planes X and Y. This allows you to reach any point in the working plane. To move the working head, stepper, linear, and servo motors can be used.

Semiconductor multimode laser modules with fiber optic bundles are made with sufficient power (up to 300 W) and optical fibers are made with a diameter of 50 to 700 microns. When using modules with a power of up to 100 W and a fiber diameter of 50 - 100 μm, an intensity sufficient for melting metals is achieved, i.e. the use of such modules in machines for selective laser melting is justified. One of the important advantages of these modules with a fiber optic bundle is a more uniform spot intensity distribution than that of fiber optic lasers, which leads to improved part quality.

The implementation of melting with the formation of discrete melt pools by diluting the laser beams from each other at such a minimum distance that the individual tracks do not intersect and a single melt pool does not form. This point is very important, as it allows achieving stable conditions for the existence of molten metal in each of the individual melt pools. This point distinguishes this technical solution from analogues in which they strive to obtain a single melt pool in the form of a line.

One of the ways to focus several laser beams is to use one optical system capable of transmitting these beams without critical distortion. In this case, the ends of the fiber optic bundles are located at the minimum possible distance from each other, which guarantees the discreteness of the tracks.

The second possibility is to focus each beam through a separate lens. In this embodiment of the claimed technical solution, simple optical systems are used, for example, telescopes with a diameter of 10 mm, consisting of two lenses, capable of transmitting one laser beam without distortion. Each laser diode module has its own focusing lens. The distance between tracks depends on the size of the optics.

A very important point is the location of the laser beams relative to the working plane. When using both focusing systems, all beams pass perpendicular to the working plane. In all machines using scanator laser deflection technology, the angle between the beam and the work plane is constantly changing, which leads to a change in the shape and size of the spot in the work plane. This also leads to a constantly changing reflectance of the laser radiation. For systems with semiconductor laser modules with fiber optic bundles, only the variant with peripheral beams at an angle has been implemented so far.

In the embodiment of the technical solution, the installation of track overlap is implemented by turning the optical system for focusing laser beams.

In this case, an optical system for focusing laser beams of any of the above forms is mounted on a rotary device. Laser beams are positioned in a line at a certain distance from each other. When this system is rotated, the distance between tracks in the work plane is reduced. Thus, by changing the angle of rotation of the system, it is possible to set the desired overlap.

In the embodiment of the technical solution, the installation of track overlap is implemented by moving the working head. In this case, the working head is mounted rigidly to the carriage. Laser beams are also arranged in a line at a certain distance from each other. The overlap is implemented by a settable shift/movement of the carriage along the corresponding axis.

In the embodiment of the technical solution, the possibility of digital photo-documentation of the melted layer and the layer of applied powder is implemented without loss of time. Since a machine with a portal system allows you to pass through the entire construction field along two axes (X, Y), you can mount the scanner head on the corresponding axis according to the principle of a flatbed scanner. When applying a layer of powder, the scanner head will move along with the squeegee and thereby transmit information about the state of the layer, revealing, for example, defects.

In the embodiment of the claimed technical solution, construction is provided by wire. In this version of the technology, not a powder chamber is used for building, but a wire made of the appropriate material is fed into the laser beam spot by a special conveyor. Also, as in the powder version, it is possible to implement multipath and, in addition, it is possible to implement a multimaterial version of the technology.

Brief description of the drawings

Details, features, and advantages of the present invention follow from the following description of the embodiments of the claimed technical solution using the drawings, which show:

Fig. 1 - general view of the machine;

Fig. 2 is a top view of the gantry machine;

Fig. 3 is a schematic diagram of the use of semiconductor laser modules with fiber optic bundles;

Fig. 4 - discrete melt baths;

Fig. 5 - focusing of several laser beams through one lens;

Fig. 6 - focusing of each laser beam through a separate lens;

Fig. 7 - installation of track overlap by turning the focusing system: a) the working head is perpendicular to the direction of movement; b) the working head is at an angle to the direction of movement;

Fig. 8 - setting the overlap of tracks by moving the working head;

Fig. 9 - the possibility of digital photo-documentation of the melted layer and the layer of applied powder without loss of time;

Fig. 10 - building with wire.

The figures indicate the following positions: 1 - axis of motion X; 2 - axis of movement Y; 3 - carriage with working head; 4 - building chamber; 5 - semiconductor laser modules; 6 - fiber optic bundles; 7 - optical system for focusing laser beams; 8 - detail; 9 - build chamber platform; 10 - axis of movement Z; 11 - powder hopper; 12 - squeegee; 13 - laser beams; 14 - distance between tracks; 15 - tracks; 16 - ends of fiber optic bundles; 17 - collimating optical element; 18 - focusing optical element; 19 - lenses; 20 - track overlap; 21 - direction of movement of the working head for building tracks/details; 22 - angle of rotation of the working head relative to the direction of movement; 23 - distance between laser beams; 24 - the direction of the discrete shift of the working head to set the overlap of the tracks; 25 - defect; 26 - new layer of powder; 27 - scanning heads; 28 - wire feed mechanism; 29 - wire.

Disclosure of invention

Multibeam raster selective laser melting machine (Fig. 1) is based on a portal system (Fig. 2) consisting of two axes of movement perpendicular to each other X (1) and Y (2). The carriage (3) mounted on these axes carries an optical system for focusing laser beams (7), to which semiconductor laser modules (5) are connected via fiber optic bundles (6). Focused laser beams (13) melt the powder in the build chamber (4) and thereby generate the part (8). The building chamber platform (9), moving along the Z axis (10), sets the specified layer thickness, a new layer of powder is applied from the powder hopper (11) using a squeegee (12), and the building process is repeated.

Unlike systems that use laser scanners to deflect the beam, in this case the laser beam passes through the working head (3) built into the carriage and thereby moves along the working plane along the X (1) and Y (2) axes.

The construction chamber (4) has a standard view, like that of scanner machines, its working platform moves along the Z axis perpendicular to the XY plane. Thus, the possibility of constructing parts with three degrees of freedom is realized. To move the working head, stepper, linear, and servo motors can be used. To melt the applied layer of powder in this technical solution, semiconductor laser modules (5) (Fig. 3) with fiber optic bundles (6) are used. Semiconductor multimode laser modules (5) have sufficient power (up to 300 W) and optical fibers with a diameter of 50 to 700 microns. When using modules with a power of up to 100 W and a fiber diameter of 50 - 100 μm, with focusing, for example, 1: 1, an radiation intensity sufficient for melting metals is achieved, i.e. the use of such modules in machines for selective laser melting is justified.

The short working distance (< 100 mm) implemented using the portal system allows focusing the beam of semiconductor laser modules in the working plane on the substrate or workpiece (8) into a spot with a diameter of 50 - 100 µm. One of the important advantages of these modules with a fiber optic bundle is a more uniform spot intensity distribution than that of fiber optic lasers. This leads to improved quality of parts.

The detail layer is built vectorially, i.e. the carriage with the working head (3) moves along one axis and linear melting of the powder occurs. At the places where the part is to be built, the laser modules are switched on independently of each other, where the part ends, the laser modules are switched off.

It is also possible to modulate the power of each individual module (5) independently of the others. As soon as this part of the part is built, the working head is shifted along the other axis by a predetermined distance and the process is repeated until the layer is completely built. A different number of laser modules (5) can be used to melt the powder (Fig. 3).

For the simplest machine options, this can be just one module, respectively, one laser beam will be used to build the part.

To further speed up the construction process, the number of laser modules and, accordingly, beams can be increased. Theoretically, the number of beams is limited only by the dimensions of the working chamber and the machine. For small desktop machines, a technically reasonable number of beams can vary from 1 to 20. For large industrial machines, the number of beams starting from 20 can reach several hundred or even thousands. Theoretically, the number of rays is not limited. An important feature of this technical solution are discrete, separate, not merging into one, melt baths (Fig. 4). That is, when several laser beams (13) pass through the focusing system (7), the laser beams (13) are at a distance from each other equal to or greater than the width of the track (15), which in turn leads to the formation of tracks on the part (8) ( 15) with a distance between them (10) equal to or greater than the width of the track (15), subject to focusing in a ratio of 1:1. Thus, conditions are achieved that do not allow the formation of one single elongated pool of melt.

This moment is very important for the high-quality construction of parts, as it allows achieving stable conditions for the existence of molten metal in each of the individual melt baths. This point distinguishes this technical solution from analogues in which they strive to obtain a single elongated melt pool in the form of a line. When using several laser beams, there are two options for focusing these beams, the first is focusing several beams with one lens. (Fig. 5). With this method, the ends of the fiber bundles (16) are located at a distance from each other equal to or greater than the width of the track (15), so that when passing through the optical system for focusing laser beams, in the simplest case consisting of one collimator lens (17) and one focusing lens (18) , the focused laser beams melted onto the parts (8) tracks that were not connected to each other (15). An important aspect of this system is the bandwidth of the optics, which makes it possible to focus several laser beams without deformation and other parasitic phenomena. In a ray tracing simulation program, it was verified that up to ten laser beams lying in a straight line can be focused with 50 mm diameter optics. As an additional option, the layout of fiber optic bundles in the form of a 10 x 10 matrix can be used, which will allow up to 100 laser beams to pass through and will make it possible to vary the geometry of the melting front in 2D mode.

The second method of focusing several laser beams is based on the use of simpler objectives. In this case, one lens is used for each individual beam (Fig. 6). When using such a focusing system, the ends of the fiber optic bundles are located at a minimum distance equal to the diameter of the lens, due to the fact that the dimensions of the lenses (19) do not allow them to be placed closer. Laser beams (13) passing through each lens (19) are focused on the part/substrate (8) forming discrete tracks (15).

It is important that both in the first and second versions, the laser beams fall on the part strictly perpendicular to it. This guarantees the absence of geometric deformations of the laser spot, as occurs when using scanners, and as a result leads to a stable intensity over the entire area of the laser spot. The constant angle of the laser beams to the substrate also leads to a more stable reflection coefficient, which also has a positive effect on the quality of the manufactured parts. To create a part, tracks melted by laser beams must have a certain overlap. For high-quality construction of parts, it should be possible to change the overlap depending on other parameters, such as the material from which the part is made, the power of laser radiation, the speed of the working head, and the porosity of the finished part. This technical solution provides two options for changing the overlap. It does not matter how the laser beams are focused, with one lens for all beams or each beam with a separate lens.

The first option is to set track overlap by turning the optical system for focusing laser beams (Fig. 7). when the beams are perpendicular (Fig. 7a) to the direction of movement of the working head (21), the laser beams (13) are located at a distance from each other (23) different from 0 mm so that the tracks (15) do not overlap. By turning the working head (Fig. 7b) at an angle from 0° to 90° (22) to the direction of movement (21), the distance between the laser beams (13) in the projection decreases, which in turn leads to overlap (20) of the tracks (15) .

Thus, depending on the angle of rotation of the working head, it is possible to set any overlap necessary for the construction process. The second option for installing an overlap does not imply any additional units or actuators. The required track overlap is set by moving the working head (Fig. 8). In this case, the working head for setting the overlap moves discretely in the direction perpendicular (24) to the direction of movement of the head (21). The discrete step of the laser beam shift (13) is set in the software depending on the required track overlap (20). Thus, a more technologically advanced than in the first variant possibility of installing an overlap appears. The use of the portal system makes it possible to implement the mode of digital photo-documentation of the melted layer and the layer of applied powder without wasting time for photographing the layers (Fig. 9). one possible implementation of this method is as follows.

The working head with an optical system for focusing laser beams (7) built into it, a powder hopper (11) with a squeegee (12) installed on it for applying powder layers and two scanning heads (27) after melting the next layer of powder, it starts moving to apply a new layer (26).

At this time, both scanning modules are simultaneously turned on and the first one in the direction of movement of the working head (21) transmits information about the quality of the construction of the previous layer and the part (8) as a whole, revealing possible defects (25), and the second scanning module mounted after the powder hopper transmits information on the state of the newly applied powder layer, also identifying possible defects (25) and areas with poor powder application.

If no defects are found, then the working head immediately starts building the part in the opposite direction, if defects are found, then it is possible to reapply the powder on the other side to improve the coverage of the part with powder. Thus, you do not need to spend time photographing the surface, as is done when using digital cameras. This method also guarantees minimum optical distortion and high image resolution.

The portal system also makes it possible to implement the additive construction of parts without layer-by-layer application of powders. Instead of powders, wire can be used (Fig. 10).

To do this, a wire (29) is fed into the laser beam (13) focused by the lens (19) using a special mechanism (28). The movement of the working head along one of the axes (21) creates a track (15) on the part (8). An overlap is established by a discrete shift in the direction perpendicular (24) to the movement of the head, and a two-dimensional construction of the layer is realized. This modification of the process can be implemented in both single-beam and multi-beam versions. In the multi-beam version, it is also possible to implement the multimaterial construction of parts. To do this, feeders must feed wires of various materials into the baths of the melt of laser beams. Thus, it becomes possible to change the material not only in layers, as can be done using powder, but also within each layer.

Claims (11)

1. A multi-beam raster machine for selective laser melting, containing semiconductor multi-mode laser modules, a portal system made in the form of two horizontal movement axes X and Y perpendicular to each other, a carriage mounted on them, a working head mounted on the said carriage and containing an optical focusing system laser beams, to which semiconductor multimode laser modules, two scanning heads and a wire feed mechanism or a powder hopper with a squeegee installed between them and a build chamber with a build camera platform movable along the vertical Z axis and located on the camera platform are connected by means of fiber optic bundles construction of a part, characterized in that the optical system for focusing laser beams is made with the possibility of ensuring a perpendicular incidence of laser beams on the part and with the possibility of changing the overlap of tracks melted by laser beams, when e In this case, the laser beams are located at a distance from each other equal to or greater than the track width, forming tracks on the part with a distance between them equal to or greater than the track width. 2. The machine according to claim 1, characterized in that the optical system for focusing laser beams consists of one collimator lens and one focusing lens. 3. The machine according to claim 1, characterized in that the optical system for focusing laser beams is made with the possibility of focusing laser beams from each of the laser modules with one lens to ensure melting on the details of tracks that are not connected to each other, while the ends of the fiber optic bundles are located at a minimum a distance equal to the lens diameter. 4. The machine according to claim 1, characterized in that the optical system for focusing laser beams is configured to focus laser beams from each of the laser modules with separate lenses for each beam, ensuring the formation of discrete tracks during melting of the part, while the ends of the fiber optic bundles are located at a minimum a distance equal to the lens diameter. 5. The machine according to claim 1, characterized in that the optical system for focusing laser beams is made with the possibility of setting the overlap of tracks by turning the working head at an angle from 0 ° to 90 ° to the direction of movement, while the distance between the laser beams in the projection decreases with the formation track overlap. 6. The machine according to claim 1, characterized in that the optical system for focusing laser beams is made with the possibility of setting the overlap of tracks by moving the working head, while the working head is rigidly fixed on the carriage and is made with the possibility of discrete movement in the direction perpendicular to the direction of movement of the head. 7. The machine according to claim 1, characterized in that the optical system for focusing laser beams is configured to set the overlap of tracks depending on the material from which the part is made, the power of laser radiation, the speed of movement of the working head and the porosity of the finished part. 8. The machine according to claim 1, characterized in that the semiconductor multimode laser modules are made with a power of up to 300 watts. 9. The machine according to claim 1, characterized in that the fiber optic bundles are made with a diameter of 50 to 700 microns. 10. The machine according to claim 1, characterized in that the semiconductor multimode laser modules are made with a power of up to 100 W, while the fiber optic bundles are made with a diameter of 50-100 microns. 11. The machine according to claim 1, characterized in that the semiconductor multimode laser modules are configured to modulate the power of each individual module, regardless of the others.

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