RU2674588C2 - Method for additive welding and melting manufacture of three-dimensional products and installation for its implementation - Google Patents

Abstract

FIELD: manufacturing technology.SUBSTANCE: invention relates to the method of additive manufacturing of three-dimensional products and installation for its implementation. Three-dimensional model of this product is created, divided in layers into calculated sections for the subsequent control of the process of layer-by-layer melting by a laser beam of the base material in the form of two wires of different refractoriness and diameters. First, the boundary layers of the product are formed by layer-by-layer welding with a laser beam of a more refractory wire and then fill the space between the boundary layers with a layer-by-layer melting with a laser beam of less refractory wire. Installation contains a structural support for maintaining the product during construction, the node supplying the base material to the construction zone and the laser node. Mentioned structural support is made in the form of a platform of refractory non-metal, placed in a sealed chamber with the possibility of rotation around its vertical axis and movement along it with the help of a positioner. Base material feed unit consists of a feeder for a more refractory wire, which can move along two mutually perpendicular horizontal axes, rotate around its vertical axis and rotate around the longitudinal axis of this device, as well as the feeder of a less refractory wire, which can move along two mutually perpendicular horizontal axes and rotate around its vertical axis. Laser unit consists of two laser optical heads mounted, respectively, on a feeder for a more refractory wire and on a feeder for a less refractory wire.EFFECT: technical result consists in increasing the accuracy and purity of the surface of products of complex configuration, made by means of additive technology.9 cl, 5 dwg, 1 tbl

Description

The invention relates to the technology of additive manufacturing of products using laser radiation.

Additive production includes processes aimed at the formation of objects by the sequential addition of materials, in contrast to the traditional "subtractive" methods used in machine processing and involving the removal of excess mass (cutting, milling, drilling, etc.).

It is known that a 3D printer for manufacturing products is a special device that makes it possible to create, including metal products, by successively applying thin layers of base material to a workpiece or a special substrate. The basic sequence of operations is as follows:

- using a computer, scanner and special software creates a virtual model in three planes, divided into digital layers.

- physical formation of the product by layer-by-layer deposition of molten or sintered metal (or non-metal).

Below are briefly described the most widely used methods of additive manufacturing of products using radiation energy and the possibility of application for the manufacture of really functioning products.

Selective Laser sintering (SLS) - (http://3dtoday.ru/wiki/SLS_print/) - involves the use of one or more high-power lasers for sintering (partial melting) of material particles to form a three-dimensional object. As materials, powder is used from plastic, metal, ceramic or glass. Sintering of the powder is carried out by drawing laser contours embedded in a digital model. Powder is poured onto a work platform that can move in the vertical direction. Upon completion of the sintering of one layer, the working platform is lowered, a new layer of material is applied and leveled by the moving carriage. The process is repeated until a complete model is formed. SLS devices use either a uniform powder, or (in most cases) composite granules with a refractory core and a shell of a material with a lower melting point are used. SLS is used for small-scale production of finished products.

Strength characteristics are not sufficient for use as functional prototypes of machine parts.

Selective Laser Melting (SLM) The Selective Laser Melting is an additive manufacturing method that uses high-power lasers to create three-dimensional physical objects by melting metal powders. Consumables are not sintered, but completely melted until a homogeneous mass is formed. The printing process takes place in a working chamber filled with inert gases. Each layer of the model is fused, repeating the contours of the layers of the digital model. The build cycle is similar to SLS. The most popular materials are powder metals and alloys, including stainless steel, tool steel, cobalt-chromium alloys, titanium, aluminum, gold, etc.

Strength characteristics are sufficient for use as functional prototypes of machine parts.

Electron beam melting (EBM) Electron beam melting was developed and applied by the Swedish company Arcam AB. EBM is similar to SLM. A significant difference is the use of electronic emitters (so-called electron guns) instead of lasers as energy sources for melting. Therefore, melting is carried out in vacuum working chambers, which allows working with materials sensitive to oxidation.

Strength characteristics are sufficient for use as functional prototypes of machine parts.

Direct Metal Laser Sintering (DMLS) Direct Metal Laser Sintering was developed by EOS in Munich. The build cycle is similar to SLM. Strength characteristics are sufficient for use as functional prototypes of machine parts.

It is known that in the SLM, SLS, and EBM methods, a powder material is used as the base material. A component or product is generated directly from the powder layer. Other additive manufacturing methods, such as laser metal forming (LMF), bulk laser cladding (LENS), or direct metal deposition (DMD), locally deposit material onto an existing part.

Arbitrary electron beam melting (EBF3) Electron beam free form fabrication. The method uses high-power electron beams for sequential deposition of materials in the form of a metal wire. The technology uses high-power electronic emitters in a vacuum chamber to melt metal. The electron beam moves along the working surface, repeating the contours of the digital model, while the metal wire is gradually fed to the beam focusing point. The molten material solidifies, forming durable layers of a given model. The process is repeated until a complete model is built. Used wire with a thickness of more than 2 mm.

The EBF3 process takes place in a special vacuum chamber in which an electron beam is focused on a metal source, which is continuously supplied to the beam. This beam melts the metal over a rotating surface, it stacks it in layers, in accordance with a certain 3D-model of the object.

Strength characteristics are sufficient for use as functional prototypes of machine parts.

The following is a list of shortcomings that should be addressed by our technical solution:

Selective Laser Sintering (SLS):

very high porosity of the product and, therefore, low strength;

poor surface quality;

low precision manufacturing parts;

Selective Laser Melting (SLM):

high energy consumption;

poor surface quality;

relatively low manufacturing speed;

low precision manufacturing parts;

Electron beam melting (EBM) Electron beam melting:

requires evacuation of the chamber;

poor surface quality;

high energy consumption;

low precision manufacturing parts;

In addition, all the “powder” technologies for the additive manufacturing of metal products have inherent disadvantages associated with the high price of powders (there are no cheap methods for producing metal powders of fine fractions (∅≤200 μm)), the need to introduce extremely laborious powder operations into the technological process: sifting , removal from the chamber, pouring, etc., as well as the inability to create products with a mesh, tubular, cellular or cellular internal structure.

In our opinion, the problem is that a promising 3D printer should have at least the following characteristics:

- precision manufacturing details - not higher than 8 qualifications;

- surface roughness of the part - not higher than Ra25;

- production speed of the part - not less than 100 cubic cm / hour;

- low power consumption - not more than 50 W * hour / cc.

Of all the additive technologies listed above, none of them meets all the specified requirements for a promising 3D printer.

In addition, all powder technologies have a negative aspect - it is impossible to obtain hollow (for example, honeycomb) structures on their basis, since excess powder is removed only after the complete construction of the product as a whole and, therefore, the powder inside each individual cell will be sealed (remains inside the cell).

A non-powder version of the technology of electron beam melting of metal wire ("EBF3"), which seems promising, has the following significant disadvantages:

- high-power electron beams can only be used in vacuum, since they are strongly scattered by gas molecules, and the creation and maintenance of a deep vacuum will entail an increase in the cost and weight of the structure;

- the platform with the product rotates, therefore, there will be problems with the manufacture of products that do not have axial symmetry;

- at the moment, electron beam melting is limited to an accuracy of 0.2 mm, due to the size of the electron beam, which is 0.2-1.0 mm - this leads to a high quality of precision parts and a large roughness of the finished product;

- the wire feed device is stationary (or has few degrees of freedom), which greatly complicates the manufacture of products of complex configuration.

From the patent literature as a prototype we consider it possible to accept the patent RU (11) 2574536, IPC B22F 3/105, B22F 5/04, B23K 26/34, C23C 26/00, F01D 9/02, publication: 05/27/2015. The invention relates to a method for manufacturing a three-dimensional metal part, comprising the steps of sequentially increasing the specified part from the metal base material using the additive manufacturing process by scanning the energy beam, while creating a controlled orientation of the grains in the Z direction, perpendicular to the XY plane of the part, and the direction in the XY plane of the part, and the orientation of the grains in the XY plane of the part is created by scanning the energy beam in accordance with the profile e cross sections or local load conditions on the part, while controlling the grain orientation in the X-Y plane of the part is achieved by conducting scanner motion paths in successive layers alternately, parallel and perpendicular to the direction corresponding to the smallest Young's modulus in the part. A three-dimensional model of the specified part is created, followed by a layer-by-layer separation process for calculating cross sections; after that, the indicated calculated sections are sent to the control device; provide a powder of the specified base material, which is necessary for the process; a powder layer is obtained with a constant and uniform thickness on a plate substrate or on a previously treated powder layer; perform melting by scanning the energy beam in the area corresponding to the cross section of the specified part according to the three-dimensional model stored in the control device; lowering the upper surface of the preformed section by the thickness of one layer; repeat the indicated steps) until the last section according to the three-dimensional model is reached.

Since multidirectional scanning (melting) of the powder layers does not affect the porosity of the product, the roughness and quality of its surface, as well as the energy and time parameters of the technology, all the previously mentioned disadvantages of the above technologies and products made using these technologies remain valid.

Thus, the task is to offer a method and equipment for the additive manufacturing of high-quality products with a complex surface, including a mesh, mesh or cellular internal structure.

The technical result consists in increasing the accuracy and cleanliness of the surface of products of complex configuration made by means of additive technology.

The specified technical result is achieved in the method of additive welding - smelting manufacturing of three-dimensional products, including sequential layer-by-layer construction of the specified product from the base material in accordance with a previously created three-dimensional model of the specified product, divided by layers into design sections for subsequent control of the process of layer-by-layer construction by melting the base material with a laser beam , the fact that they use the base material in the form of two wires of different refractoriness, and in percent sse first construction form the boundary layers of the stratified product with a laser beam welding wire more refractory and then fill the space between the boundary layers of stratified melting laser beam less refractory wire.

In addition, use a wire of greater refractoriness of a smaller diameter than the diameter of the wire of lower refractoriness.

In addition, they use a wire of higher refractoriness from metal, and a wire of lower refractoriness from non-metal.

In addition, the base material is metal or non-metal.

In addition, the product construction process is carried out in a sealed chamber with normal or reduced pressure in an atmosphere of inert gas, nitrogen or air.

The same technical result is achieved in the installation for additive welding and smelting manufacturing of three-dimensional products, containing a structural support for supporting the product during the construction of the base material, a base material supply unit to the construction zone and a laser unit, in that the structural support is made in the form placed in a sealed chamber of the platform of refractory non-metal, mounted to rotate around its vertical axis and move along it using a positioner, the base feed unit about the material in the construction zone consists of a device for feeding a more refractory wire having the ability to move along two mutually perpendicular horizontal axes, rotating around its vertical axis and rotating around the longitudinal axis of this device, as well as a device for feeding a less refractory wire, having the ability to move along two mutually perpendicular horizontal axes and rotation around its vertical axis, while the laser unit consists of two laser optical heads, mounted, corresponding continuously on a refractory feeder wire feeder and less refractory wire.

In addition, the installation is equipped with a power frame having two horizontal levels mutually perpendicular, interconnected by clutches of guides and drive screw pins, on which the carriages for the respective wire feed devices are placed, each drive screw pin equipped with a positioner in the form of a stepper or other motor, a feeder for a more refractory wire is mounted on the corresponding carriage by means of a rotary tower with a rotary tower bar, and a feeder is less refractory Coy wire mounted on the respective carriage by means of pivoting of the tower.

In addition, the sealed chamber is equipped with a vacuum pump and / or an inert gas supply device.

In addition, the feeder for a less refractory wire is equipped with an induction or other wire feed heater.

In addition, a feeder for a more refractory wire and a feeder for a less refractory wire are mounted on the same carriage.

The proposed invention is illustrated by drawings.

In FIG. 1 - an example of a product obtained by the proposed method of additive welding and smelting manufacturing.

In FIG. 2 - shows a diagram of the construction of the boundary layer.

In FIG. 3 - shows a diagram of fill metal - filling the space between the boundary layers (view B shows slice, wherein the removed outer boundary layer).

In FIG. 4 - presents the installation diagram - front view.

In FIG. 5 - shows the installation diagram - top view (feeder less refractory wire is not shown).

The method of additive welding and smelting manufacturing of three-dimensional products, includes sequential layer-by-layer construction of the specified product 1 from the base material in accordance with a previously created three-dimensional model of the specified product, divided by layers into design sections for subsequent control of the process of layer-by-layer construction by melting the base material with a laser beam 2, base material in the form of two wires 3 and 4 of different refractoriness, and in the process of construction, boundary layers are formed first Their products by layer-by-layer laser beam welding 2 of a more refractory wire 3 and then melt 7 fill the space between the boundary layers 5 and 6 by layer-by-layer laser beam melting of a less refractory wire 4. Mostly, a wire of higher refractoriness 3 of smaller diameter is used than the diameter of a wire of lower refractory 4. Base material is metal or non-metal.

The process of constructing the product is carried out in a sealed chamber 8 with normal or reduced pressure in an atmosphere of inert gas, nitrogen or air.

Installation for additive welding and smelting manufacturing of three-dimensional products, contains a structural support 9 for supporting the product 1 during the construction of the base material, the node 10 for supplying the base material to the construction zone 32 and the laser unit 11. The structural support 9 is made in the form of a sealed chamber 8 platforms 12 made of refractory non-metal, mounted to rotate around its vertical axis and move along it using a positioner 25, the node 10 for supplying the base material to the construction zone consists of a feed device 13 of a more refractory wire having the ability to move along two mutually perpendicular horizontal axes, rotate around its vertical axis and rotate around the longitudinal axis 14 of this device, and also a feed device 15 of a less refractory wire having the ability to move along two mutually perpendicular horizontal axes and rotation around its vertical axis, while the laser unit 11 consists of two laser optical heads 16 and 17, mounted, respectively, on the feeder 13 more it infusible and wire feeder 15 less refractory wire. The installation is equipped with a power frame 18, which has two horizontal levels mutually perpendicular, interconnected by clutches 19 and 20 of the guides 21 and the drive screw pins 22, on which the carriages 23 and 24 are placed for the respective wire feed devices, with each drive screw 22 equipped with a positioner 25 in the form of a stepper or other motor, a feed device 13 with a more refractory wire is mounted on the corresponding carriage 23 by means of a rotary tower 26 with a rotary tower rod 27, and the feed device m less refractory wire is mounted on the corresponding carriage 24 by means of a rotary tower 28. The sealed chamber 8 is equipped with a vacuum pump 29 and / or an inert gas supply device. The less-refractory wire feeder is equipped with an induction or other heater 30 of the feed wire.

A causal relationship between the operations of the method and the features of the device with the solution of the technical problem and the achievement of the technical result is shown by the example of manufacturing a metal product.

The surface of the product (boundary layers) is made layer-by-layer from a metal wire of refractory and durable metal (for example, titanium or copper-nickel alloys), which is layer-by-layer laid on the previous layer and welded to it with a laser beam. The movement of the wire feed device and the laser optical head follows the external and internal contours of the layers of the digital model ( see Fig. 2 ).

The internal volume between the boundary layers forming the surface of the product is filled with a filler metal having a melting point lower than the melting temperature of the boundary layer metal and melted by a second laser optical head ( see Fig. 3 ). Such a sequence of actions gives a big gain in the speed of manufacturing the product, in comparison with the “powder” technologies and, at the same time, allows with high accuracy (not higher than 10 quality) and low roughness (not more than Ra25.0) to produce the surface of the part (specified accuracy the parameters are typical for wires) by welding the wire layers with a laser beam, and the bulk of the metal of the part is actually filled by melting the supplied thick wire from the filler metal. While the technologies listed in the first section can guarantee, at best, 11 Ra25.0 quality and roughness

The boundary layer wire used can have different sizes (from tens of microns to several millimeters), but the resulting surface will, in any case, be much better (in terms of roughness), and the manufacturing accuracy of the part will be more accurate than that obtained by fusion or sintering of metal powder with particle sizes, for example, 50 microns, since the wire has a flat, smooth surface, and the "balls" of powder lie randomly. As for the comparison with EBF3 technology, in which the wire is fused, this technology uses a wire of ∅ 2 mm and an electron beam of very high energy with a “spot” (focusing) of 2 mm, which automatically leads to a surface accuracy of ~ 1 mm (11- 13 qualifications) and roughness Ra100 (or worse). And because of the high power of the melting beam, there are numerous bursts and sprays.

The product construction zone 32 is located in a chamber with normal or reduced pressure in an atmosphere of inert gas, nitrogen or air, depending on the material of the product and manufacturing conditions. By blackening the walls of the chamber, the system of additional cooling of the chamber body, by blowing inert gas, nitrogen or air and other methods (depending on the thermal regime of the process), the most even thermal field in the chamber is achieved to ensure the safety of stepper motors and other high-precision equipment operating inside the chamber 8.

The feed device 13 of the refractory wire is mounted on a tower rod 27 ( see Fig. 2 and Fig. 5 ) and has four degrees of freedom: movement (together with the carriage 23) along the X and Y axes ( see Fig. 5 ), rotation around a vertical axis 360 ° (with turret 26) and rotation around the longitudinal axis 180 ° (with turret 27). The wire feed device 13 coupled to the laser optical head 16 is positioned with respect to the boundary layer of the article under construction using a positioner 25 having a positioning accuracy of about 20 μm. The wire feeder stacks each layer of wire on top of the previous wire layer (taking into account the geometry data of the 3d model embedded in the control program), feeding the wire to the focus point of the 32 laser beams. The laser beam 2, passing through the optical head 16, mounted together with the feed device 13 of the refractory wire on the tower rod 27, welds a new layer of wire to the underlying layer ( see Fig. 2 ). Rotations around the vertical axis and around the longitudinal axis allow you to form the contour of any surface of the product 1.

The metal filler is supplied in the form of a thick (0.5-2 mm) wire from a vertically located nozzle of the wire feed device 15 ( see FIG. 3 and FIG. 4 ) heated with a heater 30 (below the melting temperature of the filler metal). The filler wire 15 of the metal-filler metal can be attached both to the carriage 23, on which the feed device 13 of the refractory wire is located, and have an independent positioner 25 and a separate carriage 24. In FIG. 4 shows a second embodiment of fastening a wire feed device 15 of a metal filler wire.

The wire feed device 15 of the filler metal has three degrees of freedom: movement (together with the carriage 24) along the X and Y axes, 360 ° rotation around the vertical axis (with the turret 28). The wire feed device 15 coupled to the laser optical head 17 is positioned relative to the wall 31 of the product under construction by the second positioner 25, by means of which the nozzle of the wire feed device 15 is set so that the metal-filler molten by laser 2 is poured onto the underlying metal-filler layer between the formed boundary layers of a more refractory metal. The supply of metal wire 4 filler is carried out after completion of several cycles of construction of the boundary layers 5,6 of refractory wire 3 or at the same time with the formation of the boundary layers 5.6 (when necessary). The wire is fed to the focusing point 32 of the laser beam 2, the optical head 17 of which is fixed together with the filler 15 of the metal filler wire on the turret 28 ( see Fig. 4, Fig. 3 ).

The platform 12 on which the product 1 is formed is made of refractory non-metal (for example, graphite) and has two degrees of freedom: up and down movement along the vertical Z axis (in which after the formation of each boundary layer 5, 6 of refractory metal is completed, the platform is lowered to start the formation of a new layer) and rotation around the vertical axis by 360 ° ( see Fig. 4 and Fig. 5 ).

The following is a table comparing the parameters achieved by the present invention parameters with the parameters of known technologies.

Comparative table

Thus, the proposed invention provides a technical result, which consists in increasing the accuracy and cleanliness of the surface of products of complex configuration made by means of additive technology.

Claims (9)

1. The method of additive manufacturing of a three-dimensional product, including sequential layer-by-layer construction of the specified product from the base material in accordance with the created three-dimensional model of the specified product, divided by layers into design sections for subsequent control of the process of layer-by-layer construction by melting the base material with a laser beam, characterized in that the base material in the form of two wires from materials with different melting points and different diameters, and during construction Boundary layers form a first product stratified welding laser beam more refractory smaller diameter wire and then fill the space between the boundary layers of stratified melting laser beam less refractory wire of larger diameter. 2. The method according to p. 1, characterized in that they use a wire of higher refractoriness from metal, and a wire of lower refractoriness from non-metal. 3. The method according to p. 1, characterized in that as the base material using metal or non-metal. 4. The method according to p. 1, characterized in that the construction of the product is carried out in a sealed chamber with normal or reduced pressure in an atmosphere of inert gas, nitrogen or air. 5. Installation for additive manufacturing of a three-dimensional product, comprising a sealed chamber, a support for supporting the product during construction from the base material, a base material supply unit to the construction zone, and a laser unit, characterized in that the support is made in the form of a platform of refractory non-metal installed in sealed chamber with the ability to rotate around its vertical axis and move along it with the help of a positioner, the feed unit of the base material in the construction zone consists of a device for feeding more refractory a wire made with the ability to move along two mutually perpendicular horizontal axes, rotate around its vertical axis and rotate around the longitudinal axis of the device, and a device for feeding less refractory wire made to move along two mutually perpendicular horizontal axes and rotate around its vertical axis, wherein the laser unit consists of two laser optical heads mounted, respectively, on the refractory wire feeder and on the device odachi less refractory wire. 6. Installation according to claim 1, characterized in that it is equipped with a power frame made with two horizontal mutually perpendicular levels interconnected by means of guide couplings and drive screw pins, on which the carriages of two corresponding wire feed devices are placed, each drive the screw pin is equipped with a positioner in the form of a stepper motor, while a feeder for supplying a more refractory wire is mounted on the corresponding carriage by means of a rotary tower with a rotary tower minutes post and less refractory feeder wire mounted on the respective carriage by means of pivoting of the tower. 7. Installation according to claim 1, characterized in that the sealed chamber is equipped with a vacuum pump and / or an inert gas supply device. 8. Installation according to claim 1, characterized in that the feeder of a less refractory wire is equipped with an induction heater of the feed wire. 9. Installation according to claim 1, characterized in that the feeder for a more refractory wire and the feeder for a less refractory wire are mounted on the same carriage.

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