RU2850236C1 - Device for producing articles from powder materials - Google Patents

Abstract

FIELD: powder metallurgy.

SUBSTANCE: invention relates to powder metallurgy, particularly to devices for layer-by-layer synthesis of parts of complex spatial configuration from fine powder and can be used in mechanical engineering, for example, for the manufacture of corrosion-resistant, wear-resistant, heat-resistant articles, parts and assemblies. Device for producing articles from powder materials comprises a bearing frame, a sealed chamber mounted thereon, arranged therein powder material application means in form of double knife installed with possibility of horizontal reciprocating movement and article layer forming, heating elements arranged on double knife, pyrometer, a production hopper with heaters built into its walls, powder collection and supply hoppers and a movable laser head. Laser head is in the form of a housing at the input of which there is a laser optical fibre with an optically welded collimator and coaxially mounted laser beam expander and focusing lens. Laser head protective nozzle is secured at the end of lens output link. Device is equipped with an additional laser head made identical to the main one and arranged mirror-like opposite the latter. Pyrometer is installed through a bracket with its protective nozzle.

EFFECT: reliability of the product formation process due to the use of two independent laser beams and increased accuracy of the applied powder layers.

1 cl, 8 dwg

Description

The invention relates to powder metallurgy, in particular to the technology of layer-by-layer synthesis of parts of complex spatial configuration from fine powder by selective laser melting and/or sintering (SLM) using a computer 3D model, and can find application in various branches of mechanical engineering, for example, for the manufacture of corrosion-resistant, wear-resistant, heat-resistant products, parts and assemblies.

A device for the layer-by-layer production of a three-dimensional object from a powdered material is known from the prior art, comprising a process platform for layer-by-layer placement of the powdered material, a module for applying and compacting layers of powdered material onto the platform or onto a previously hardened layer containing a knife, with the possibility of its reciprocating movement along the platform, a laser unit installed with the possibility of selective processing of the powder material of each layer on the platform until the formation of the finished object (Russian Federation Patent for Invention No. 2370367, B29C 67/00, 2006).

A device for manufacturing parts using the layer-by-layer synthesis method is known (RU Patent for Invention No. 2487779, B22F 3/105, B23K 26/00, 2012). According to the patent, an installation for manufacturing parts by the layer-by-layer synthesis method comprises: a sealed chamber, a work table, a sintering table, a mechanism for feeding powder to the work table, a device for collecting excess powder and a device for leveling layers of powders, including a carriage with a knife, moved above the surface of the work table by means of a drive, characterized in that the carriage is made in the form of a rectangular body part and is equipped with L-shaped brackets mounted on its ends, located in two parallel grooves made in the work table on the sides of its working area, and a leveling knife body mounted on its front edge, while at the ends of the L-shaped brackets are located sliders mounted on guides fixed to the lower surface of the work table, and the work table is equipped with groove protection devices. The installation also differs in that the groove protection devices are made in the form of endless belts mounted on rotating drums, secured to the lower surface of the work table, passed over the slots and secured to the ends of the carriage, while the rotating drums are equipped with devices for moving them to adjust the tension of the belts.

A device for the layer-by-layer production of products from powdered material is known from the company Phenix Systems (US patent 7789037, published 09/07/2010).

The disadvantages of the known (above mentioned) technical solutions are:

- lack of reliable and precise control of the thermal process of local remelting of powder material by a laser beam;

- low productivity of the product formation process, since the remelting of the powder material is carried out by a single laser beam;

- the lack of a system for monitoring the actual movement of the product construction platform under conditions of exposure to high temperatures.

All these shortcomings lead to a loss of precision in the applied powder layers and unstable heating (high temperature gradients) in various local remelting zones throughout the volume of the manufactured product and the formation of molten protrusions along the boundaries of local zones at the junctions of the melt and unmelted powder, which ultimately leads to a deterioration in the physical and mechanical properties of the formed product, and also the possibility of direct destruction of the product at the moment of applying the next layer of powder material when the means for feeding and compacting the powder material in the form of a knife catches on the formed protrusions on the surface of the previous layer.

The closest in technical essence and the achieved result is a device for obtaining articles from powder materials, comprising a load-bearing frame, a sealed chamber mounted on it with a means for applying powdered material placed in it in the form of a double knife mounted with the possibility of horizontal reciprocating movement and forming a layer of the article, a pyrometer, a production bin with heaters built into its walls, collection bins and powder feed bins with metering shafts in each, quartz halogen heating elements placed on the double knife and a movable laser head installed in the sealed chamber (Patent of the Russian Federation No. 159233, published on 10.02.2016).

The disadvantages of the known technical solution are:

- low productivity of the product (part) formation process, since the remelting of the powder material is carried out by a single laser beam;

- the lack of a system for monitoring the actual movement of the product construction platform under conditions of exposure to high temperatures.

All these shortcomings lead to the following:

- high cost of manufacturing the product;

- loss of precision of the applied powder layers, as well as unstable heating (high temperature gradients) in various local remelting zones throughout the volume of the manufactured product and the formation of molten protrusions along the boundaries of local zones at the junctions of the melt and unmelted powder, which ultimately leads to deterioration of the physical and mechanical properties of the formed product and the possibility of direct destruction of the product at the moment of applying the next layer of powder material when the means for feeding and compacting the powder material in the form of a knife catches on the formed protrusions on the surface of the previous layer.

The claimed invention is based on the technical result of a multiple increase in the productivity and reliability of the product formation process due to the improved design of the present invention, which allows the use of two independent laser beams during the remelting of powder material, as well as an increase in the accuracy of the applied powder layers.

The technical result is achieved in that a device for producing articles from powder materials, comprising a load-bearing frame, a sealed chamber mounted thereon with a means for applying powdered material placed therein in the form of a double knife mounted with the possibility of horizontal reciprocating movement and forming a layer of the article, a pyrometer, a production hopper with heaters built into its walls, collection hoppers and powder feed hoppers with metering shafts in each, quartz halogen heating elements placed on the double knife and a movable laser head installed in the sealed chamber, made in the form of a housing, at the entrance to which a laser optical fiber is located with an optically welded collimator and a coaxially mounted laser beam expander and a focusing lens located in the output link of the laser head, at the end of which a protective nozzle of the laser head is fixed, wherein the device is provided with an additional laser head, made identical to the main one and located mirror-like opposite the latter, and the pyrometer is installed through a bracket with its protective nozzle, the optical axis of the pyrometer is directed orthogonally to the specified powder layer and passes through the focus of the reflected focused laser beam, while the housings of the main and additional laser heads and pyrometers are mounted on dynamic rear direct, front direct, transverse direct electric drives and a vertical movement electric drive.

The invention is explained with graphic images.

Fig. 1 is an axonometric view of a device for producing products from powder materials.

Fig. 2 is an orthogonal view from above of a device for producing products from powder materials.

Fig. 3 is a section A-A from Fig. 2.

Fig. 4 is a section B-B from Fig. 3.

Fig. 5 is a local enlarged view B from Fig. 3.

Fig. 6 is a local enlarged view G from Fig. 3.

In Fig. 7 - auxiliary view D from Fig. 3 (for clarity, the following positions are not shown: sealed chamber 2, feed hoppers 11, 12, metering shafts 13, powder feed funnels 45; dynamic rear direct electric drive (coordinate X1 and coordinate X2) 30, dynamic front direct electric drive (coordinate X1 and coordinate X2) 31, dynamic transverse direct electric drive (coordinate Y) 32, electric drive for vertical movement of the laser head (coordinate Z1) 33, dynamic transverse direct electric drive (coordinate Y1) 72, electric drive for vertical movement of the laser head (coordinate Z2) 71, powder receiving funnel 47).

In fig. 8 - section E-E from Fig. 7.

A device for producing articles from powder materials comprises a load frame 1, a sealed chamber 2 mounted on it with a means 3 for applying powdered material placed in it in the form of a double knife 4 mounted with the possibility of horizontal reciprocating movement and forming a layer of the article, a pyrometer 5, a hopper 6 for producing with heaters 8 built into its walls 7, hoppers 9, 10 for collecting and hoppers 11, 12 for feeding powder with metering shafts 13 in each, quartz halogen heating elements 14 placed on the double knife 4 and a movable laser head 15 installed in the sealed chamber 2. In this case, the laser head 15 is made in the form of a housing 16, at the input 17 of which a laser optical fiber 18 is located with an optically welded collimator 19 and a coaxially installed expander 20 of the laser beam and a focusing lens 21 located in output link 22 of laser head 15, on the end 23 of which a protective nozzle 24 of laser head 15 is fixed. In addition, the device is provided with an additional laser head 25, made identically to the main one (15) and located mirror-like opposite the latter (15), and the pyrometer 5 is installed through a bracket 26 with its protective nozzle 27, the optical axis 28 of the pyrometer 5 is directed orthogonally to a given layer of powder and passes through the focus 29 of the reflected focused laser beam, while the housings 16 of the main (15) and additional (25) laser heads and the pyrometer 5 are installed on dynamic rear direct, front direct, transverse direct electric drives 30, 31, 32 and an electric drive 33 for vertical movement.

The manufacturing hopper 6, which is installed to the lower plane 34 of the plate 35 for applying powder layers, contains a working table 36, located on the piston 37, and a table heater 39 is installed on its upper plane 38. A removable substrate 41 is fixed to the upper plane 40 of the table heater 39, forming a working area 42 for manufacturing parts and products. The means 3 for applying powdery material is moved by means of an electric drive 43 of the means 3 for applying layers of powdery material, leveling the applied powder with the help of compacting rollers 44. Funnels 45 for feeding powder are installed on the lower wall 46 of the sealed chamber 2 coaxially with the hoppers 11, 12 for feeding, and funnels 47 for receiving powder are installed on the upper plane 48 of the means 3 for applying powdery material. On the upper wall 49 of the sealed chamber 2, a wide-angle infrared camera 50, four optical video cameras 51, four pyrometers 52 and four triangulation laser sensors 53 are mounted. On the upper plane 54 of the plate 35 for applying powder layers between the production bin 6 and the electric drive 43, the means 3 for applying layers of powdery material, as well as on the lower plane 55 of the upper wall 49 of the sealed chamber 2, are located along the block 56 for supplying protective gas, which supplies the lower (57) and upper (58) flows of protective gas to the corresponding blocks 59 for removing protective gas. A door 60 is mounted outside the sealed chamber 2.

When the device is in operation, the laser beam 61 enters the laser beam expander 20 and transforms it into an expanded laser beam 62, which passes through the focusing lens 21 and transforms into a focused laser beam 63. Next, the focused laser beam 63 enters the deflecting fixed mirror 64 and transforms into a reflected focused laser beam 29.

For ease of designating displacements, we introduce a coordinate system with the Z-axis directed from the work zone, where the powder layers are spread, to the wide-angle infrared camera 50 (Fig. 3, Fig. 4, Fig. 7). Additional linear displacements along each coordinate axis will be designated according to the coordinate axis along which the displacement occurs, assigning a serial number. Rotational displacements around the Y-axis will be designated as coordinate B.

The power frame 1 (Fig. 3, Fig. 4) is a supporting unit for basing all the main elements of the device.

Sealed chamber 2 is designed to create a closed space (along with the other components and parts described below) within which a protective atmosphere of nitrogen or argon gas is created and maintained. Creating a protective atmosphere in sealed chamber 2 is necessary to protect the manufactured part from oxidation. Sealed chamber 2 is hermetically mounted on the upper surface 54 of powder application plate 35.

Collection bins 9 and 10, as well as a production bin 6, are hermetically sealed against the lower plane 34 of the powder application plate 35. Collection bins 9 and 10 are designed to collect excess powder.

The manufacturing bin 6 forms a closed space for the part being manufactured layer by layer (or several parts in a single cycle) along with powder unexposed to laser radiation. Heaters 8 are integrated into the side walls 7 of the manufacturing bin 6. These heaters are controlled by software from the device's central control system and can heat the space within the manufacturing bin 6 to a temperature of 600°C and maintain the required stable thermal conditions. After the part is completed, the manufacturing bin 6 is slowly cooled by software. After cooling to ambient temperature, the manufacturing bin 6 can be removed from the device for easy removal of the manufactured part and cleaning of unsintered powder. Creating stable, hot thermal conditions within the manufacturing bin 6 is necessary to minimize temperature gradients within the part being manufactured layer by layer, which prevents thermal deformation and warping.

During the manufacturing of a part, the working table 36 (Z coordinate) moves vertically within the manufacturing bin 6. Sealed gaskets (not shown in the figures) are located between the outer contour of the working table 36 and the inner walls 7 of the manufacturing bin 6. The working table 36 has the ability to precisely move vertically due to the piston 37, which in turn is moved by an electric drive (not shown in the figures). The lower plane 65 of the working table 36 has the ability to engage and disengage with the piston 37. Before manufacturing, when installing the clean manufacturing bin 6, the working table 36 is engaged with the piston 37, and when removing the manufacturing bin 6, the working table 36 is first disengaged from the piston 37. Thus, the manufacturing bin 6 is removed from the device together with the working table 36.

Before starting the production of a new part, a clean and empty production bin 6 is installed in the device and hermetically pressed against the lower plane 34 of the powder layer application plate 35.

Mounted on the top plane 38 of the worktable 36 is a table heater 39, which is controlled by software from the device's central control system and can heat the worktable to a temperature of 600°C and maintain the required stable thermal conditions. This is necessary to minimize temperature gradients within the layer-by-layer manufactured part, preventing thermal deformation and warping.

A removable backing plate 41 is securely attached to the top of the table heater 39. The first layer of powder is fused (welded) to the top surface 66 of the removable backing plate 41. Therefore, when selecting the material for the removable backing plate 41, it is necessary that it fuse (weld) well with the specific powder material used in the part's manufacture. After the part is manufactured, it is removed from the manufacturing bin 6 along with the removable backing plate 41. The removable backing plate 41 is then separated from the manufactured part.

Feed hoppers 11, 12 are hermetically sealed against the top wall 49 of the sealed chamber 2 from the outside. Feed hoppers 11, 12, using metering shafts 13, which can rotate around their axis (coordinates B1 and B2) thanks to an electric drive (not shown in the figures), feed powder portions through powder feed funnels 45 into the powder material application device 3.

The means 3 for applying powder material has the ability to move horizontally (coordinate X) thanks to the electric drive 43 of the means 3 for applying layers of powder material. The means 3 for applying powder material is intended for applying layers of powder and consists of a double knife 4 (Fig. 5), compacting rollers 44 and two quartz halogen heating elements 14. The quartz halogen heating element 14 can reach a temperature of 2600°C at peak heating and, using radiation according to a program, can heat the applied powder layer to a temperature of 600°C. The compacting rollers 44 are intended for applying and leveling layers of powder. For receiving powder from feed bins 11, 12, the means 3 for applying powder material has a powder receiving funnel 47.

The means 3 for applying powder material (Fig. 3) receives portions of powder from the feed bins 11, 12 through the powder feed funnel 45 at the moment when the means 3 for applying powder material is located under the feed bin 11 or the feed bin 12, respectively (the position of the means 3 for applying powder material is shown by the dotted line).

The means 3 for applying powder material (Fig. 7, Fig. 8) has a slit in the double knife 4 of such a length that it allows for the application of powder layers of width H in the first 25 layers (a smaller number of layers is permitted, but not less than 10 pieces), without allowing the powder to protrude beyond the conventional lines 67 limiting the width of the powder layers applied. The width of the applied powder layers H is selected in such a way that the edges of the removable substrate 41 are guaranteed to be free of powder in the first 25 layers of powder. The dimensions of the edges of the removable substrate 41, which are guaranteed to be free of powder over the first 25 layers, must be such as to ensure the reliable operation of four pyrometers 52 and four triangulation laser sensors 53. In other words, over the first 25 layers (a smaller number of layers is permitted, but not less than 10 pieces), four pyrometers 52 and four triangulation laser sensors 53 must record readings from the clean removable substrate 41. The ingress of powder particles into the measurement zones of the pyrometers 52 and triangulation laser sensors 53 will lead to a loss of the adequacy of the measurements and is therefore not permitted. The absence of powder particles in the measurement zones of the pyrometers 52 and triangulation laser sensors 53 is recorded by four optical video cameras 51.

General control of the preliminary heating of the applied layer of powder material (up to 600°C) is provided by a wide-angle infrared camera 50 (Fig. 2, Fig. 3, Fig. 4, Fig. 5), which is installed on the upper wall of the sealed chamber 2.

After heating each applied layer of powder to the temperature of gradient stress relief (the maximum possible heating temperature is up to 600°C), it is locally laser remelted using two independent primary (15) and secondary (25) laser heads, which greatly increases the productivity of the part manufacturing process.

The main (15) and additional (25) laser heads are located opposite each other in a mirror image, in such a way (Fig. 7) that the main laser head 15 has a zone 68 of possible laser processing of the main laser head 15, and the additional laser head 25 has a zone 69 of possible laser processing of the additional laser head 25. In addition, the main (15) and additional (25) laser heads have an area 70 of mutual intersection of the zone 68 of possible laser processing of the main laser head 15 and the zone 69 of possible laser processing of the additional laser head 25, the presence of which is necessary when manufacturing a large-sized part, the dimensions of which cover the zone 68 of possible laser processing of the main laser head 15 and the zone 69 of possible laser processing of the additional laser head 25.

The design and operating principles of the two independent main (15) and additional (25) laser heads are identical to each other.

The main laser head 15 (located on the opposite side) (Fig. 3, Fig. 4) is mounted on an electric drive 33 for vertical movement of the laser head (coordinate Z1). The electric drive 33 for vertical movement of the laser head is, in turn, mounted on a dynamic transverse direct electric drive 32 (coordinate Y), which in turn is fixed at its rear and front ends on a dynamic rear direct electric drive 30 beam and a dynamic front direct electric drive 31 beam, respectively (coordinate X1). The dynamic rear direct electric drive 30 and the dynamic front direct electric drive 31 operate synchronously, moving the dynamic transverse direct electric drive 32.

The operating principle of the dynamic rear direct electric drive 30, the dynamic front direct electric drive 31 and the dynamic transverse direct electric drive 32 is based on the use of linear electric motors, one of the elements of the magnetic system of which is open and has an unrolled winding that creates a magnetic field. The use of linear electric motors for implementing movements along the X1 coordinate and the Y coordinate is due to the high dynamics required for moving the main laser head 15 along these coordinates: the speed of working movements (with the laser on) up to 1 m/s; idle speed (with the laser off) 3 m/s or more; braking and acceleration times must be minimal. Only modern direct electric drives based on linear electric motors can ensure these high dynamic characteristics with a significant mass of the main laser head 15.

Electric drive 33 for vertical movement (coordinate Z1) is necessary for precise positioning and periodic adjustment of main laser head 15 relative to the plane in which the applied powder layer is processed by reflected focused laser beam 29. The focal length of reflected focused laser beam 29 emerging from main laser head 15 may periodically change due to errors introduced during operation of the device, namely: accumulation of optical errors due to contamination and thermal expansion of optical instruments in main laser head 15, thermal deformations of elements of the entire device, etc. To compensate for these errors, it is necessary to periodically perform optical adjustment of the operation of main laser head 15 so that its focal length precisely falls within the plane in which the applied powder layer is processed by reflected focused laser beam 29.

The additional laser head 25 is mounted on the electric drive 71 for vertical movement of the additional laser head 25 (coordinate Z2). The electric drive 71 for vertical movement of the additional laser head 25 is, in turn, mounted on the dynamic transverse direct electric drive 72 of the additional laser head 25 (coordinate Y1), which in turn is fixed at its rear and front ends on the dynamic rear direct electric drive beam 30 and the dynamic front direct electric drive beam 31, respectively (coordinate X2). The dynamic rear direct electric drive 30 and the dynamic front direct electric drive 31 operate synchronously, moving the dynamic transverse direct electric drive 72 of the additional laser head 25. The dynamic transverse direct electric drive 72 of the additional laser head 25 has the ability to move independently from the dynamic transverse direct electric drive 32.

The use of linear electric motors for movement along the X2 and Y1 coordinates is driven by the high dynamics required to move the additional laser head 25 along these coordinates: operating speeds (with the laser on) up to 1 m/s; idle speeds (with the laser off) of 3 m/s or more; and minimal braking and acceleration times. Only modern direct electric drives based on linear electric motors can ensure these high dynamic characteristics with the significant mass of the additional laser head 25.

The electric drive for vertical movement of the laser head 71 of the additional laser head 25 (coordinate Z2) is necessary for precise positioning and periodic adjustment of the additional laser head 25 relative to the plane in which the applied powder layer is processed by the reflected focused laser beam 29. The focal length of the reflected focused laser beam 29 emerging from the additional laser head 25 may periodically change due to errors introduced during the operation of the device, namely: the accumulation of optical errors due to contamination and thermal expansion of the optical instruments in the additional laser head 25, thermal deformations of the elements of the entire device, etc. To compensate for these errors, it is necessary to periodically perform optical adjustment of the operation of the additional laser head 25 so that its focal length precisely falls within the plane in which the applied powder layer is processed by the reflected focused laser beam 29.

The main laser head 15 (Fig. 6) consists of a laser head housing 16, at the input of which a laser optical fiber 18 is located with a collimator 19 optically welded to it. The collimator is an optical device that converts the laser radiation transported from the laser (not shown in the Fig.) through the optical fiber 18 into plane-parallel laser radiation with low divergence.

The laser beam 61 at the exit from the collimator 19 is plane-parallel, has a low divergence and a small diameter. The laser beam 61 then enters the laser beam expander 20, which expands it to the required larger diameter, converting it into an expanded laser beam 62. The expanded laser beam 62 then passes through the focusing lens 21 and is converted into a focused laser beam 63. After the focusing lens 21, the focused laser beam 63 enters the deflecting fixed mirror 64 and is converted into a reflected focused laser beam 29. The sum of the distances F1 and F2 is the focal length of the focusing lens 21. The focusing lens 21 is installed in the output link of the laser head 22. At the end 23 of the output link 22 of the laser head, a protective nozzle 24 of the laser head is installed, implementing a flow of protective gas (Nitrogen or Argon), which protects the main laser head 15 from dirt and dust getting into the optical channel, as well as from thermal heating coming from the working area of the powder processing reflected focused laser beam 29 and from all heaters in the device (heaters 8, table heater 39, quartz halogen heating elements 14). In addition, the main laser head 15 is protected from thermal heating by water cooling (not shown in the figure), located in the housing 16 of the laser head.

On the body 16 of the laser head, a pyrometer 5 is mounted through a bracket 26 in such a way that the optical axis 28 of the pyrometer is orthogonal to the applied powder layer and passes through the focus 29 of the reflected focused laser beam. An additional condition for the location of the pyrometer 5 is its location at a distance L from the focus of the reflected focused laser beam 29 to the front plane of the pyrometer 5. The distance L must correspond to the optimal distance of the optical system of the pyrometer 5, at which its operation is most accurate. For accurate and reliable control of the process of local remelting of the powder by the reflected focused laser beam 29, the pyrometer 5 must have the following characteristics: the diameter of the area from which heating data is obtained from 0.2 to 0.8 mm; the physical principle of calculating temperatures by the intensity ratio of two radiations (by the energy ratio); The reflected laser radiation from the remelted powder (usually with a wavelength of λ=1.06 μm) should not affect the pyrometer detector, i.e. should not introduce errors in the measurements; the pyrometer response time (measurement speed) should be no worse than 0.0001 s.

Due to the above-described installation principles of the pyrometer 5, the pyrometer 5 always moves in tandem with the main laser head 15 and is always optimally aimed at the local powder remelting zone. This allows for highly accurate and reliable real-time thermal monitoring of the local powder remelting process using the reflected focused laser beam 29 and, if necessary, adjustments to the remelting process modes (speed of movement along the X1, X2, Y, Y1 coordinates; laser power, etc.).

The pyrometer 5 is protected from thermal heating, contamination and dust by a special water cooling jacket placed on the outside of the housing (not shown in the figure), as well as by a protective nozzle 27 of the pyrometer, which implements a flow of protective gas (Nitrogen or Argon) in front of the optical system of the pyrometer 5.

For additional protection of the main (15) and additional (25) laser heads and pyrometers 5 from thermal heating, contamination and dust coming from the working area in which the powder is heated to 600°C and melted by two reflected focused laser beams 29, an additional flow 57 of protective gas (Fig. 4) is organized in the device from the supply block 56 of the protective gas to the outlet block 59 of the protective gas (located on the plate 35 for applying powder layers).

Before applying the first layer of powder onto the removable substrate 41, the working area of the device is heated up and reaches a stable heated state (in which temperature fluctuations in the working area are minimal) due to all heaters (table heater 39, heaters 8, quartz halogen heating elements 14). The working area of the device reaches a stable heated state is accompanied by thermal deformations, which can lead to a significant deviation in the required thickness of the first layer of powder, as well as during the application of subsequent layers of powder, i.e., to an incorrect movement of the removable substrate 41 downwards along the Z coordinate. To check the correct movement of the removable substrate 41 by the value of the first layer of powder, as well as during the application of subsequent layers of powder, four triangulation laser sensors 53 (Fig. 2, Fig. 3, Fig. 7, Fig. 8) are installed in the upper wall 49 of the sealed chamber 2, which record the distance T. To ensure high accuracy and reliability of the measurement of the distance T, the following measures are taken:

- four triangulation laser sensors 53 are used (the T value is calculated as the arithmetic mean);

- triangulation laser sensors 53 are pre-calibrated on the material from which the removable substrate 41 is made at a certain heating temperature (for example, 600°C);

- to accurately confirm the fact of heating the removable substrate 41 to a certain temperature of its calibration (for example, 600°C), four pyrometers 52 are installed in the upper part of the sealed chamber 2;

- the absence of powder particles in the measurement zones of pyrometers 52 and triangulation laser sensors 53 is guaranteed by the presence of four optical video cameras 51;

- an upper flow 58 of protective gas is organized (Fig. 4), which protects the pyrometers 52, triangulation laser sensors 53 and optical video cameras 51 from thermal heating, contamination and dust coming from the working area (the upper flow 58 of protective gas is realized due to the block 56 for supplying protective gas and the block 59 for removing protective gas (located in the upper wall 49 of the sealed chamber 2)).

For adequate and accurate measurement of the distance T (Fig. 7, Fig. 8), it must be measured from the clean upper plane 66 of the removable substrate 41. The entry of powder particles into the measurement zones of the pyrometers 52 and triangulation laser sensors 53 will lead to a loss of the adequacy of the measurements and is therefore not permitted.

The powder material application device 3 enables the application of the first powder layer 73 (or several subsequent layers) to a width H, without allowing the powder to extend beyond the conventional powder layer width limitation lines 67. The width of the applied powder layers H must be maintained for the first 25 layers (a smaller number of layers is permitted, but no less than 10) to accumulate statistical data on thermal deformations, which are then converted into compensation adjustments for the movements of the removable substrate 41 along the Z coordinate by the software of the general device control system. The width of the applied powder layers H is selected such that the edges of the removable substrate 41 are guaranteed to be free of powder during the first 25 powder layers. In other words, on the first 25 layers (a smaller number of layers is allowed, but not less than 10 pieces) four pyrometers 52 and four triangulation laser sensors 53 must record readings from a clean removable substrate 41.

The above-described measures and operating principles enable the calculation of the distance T for the first powder layer with acceptable accuracy. Furthermore, when applying subsequent powder layers, if the dimension T exceeds the permissible value, a command is sent through the control algorithms of the device's general control system to correct the movement of the removable substrate 41 along the Z coordinate using the Z coordinate electric drive (not shown in the figures). Thus, control of the actual movement of the removable substrate 41 along the Z coordinate is implemented under conditions of exposure to high temperatures for the first 25 layers (a smaller number of layers is permitted, but not less than 10 pieces). For the 26th layer (minimum for the 11th layer) and subsequent layers, the operation of the four pyrometers 52 and four triangulation laser sensors 53 is stopped, and powder particles are allowed to extend beyond the imaginary lines 67 limiting the width of powder layers applied. The size of the compensatory correction for the movement of the removable substrate 41 along the Z coordinate for all layers after the 25th layer (a smaller number of layers is allowed, but not less than 10 pieces) becomes constant and is calculated as the arithmetic mean among the sizes of the compensatory correction for the first 25 layers (a smaller number of layers is allowed, but not less than 10 pieces), which ultimately leads to an increase in the accuracy of the applied powder layers under conditions of exposure to high temperatures.

The device for producing products from powder materials operates as follows.

A computer-aided design (CAD) system creates a 3D computer model of a part/product and breaks it down into cross-sections, which serve as the basis for layer-by-layer fabrication. The CAD system selects the optimal remelting strategy for the required zones in each cross-section.

The device after preliminary preparation is presented in assembled form, namely (Fig. 3, Fig. 4):

- a clean and empty bin of production 6 is pressed hermetically from below to the plate 35 for applying powder layers;

- the working table 36 is coupled with the piston 37;

- a removable backing 41 is tightly installed on the table heater 39;

- feed bins 11, 12 are pressed hermetically from the outside to the upper wall 49 of the sealed chamber 2;

- bins 9, 10 for collecting excess are pressed hermetically from below to the plate 35 for applying powder layers;

- door 60 is hermetically closed (Fig. 1).

All cooling elements are started: pads 56 for supplying protective gas (Fig. 3, Fig. 4); pads 59 for removing protective gas; protective nozzles 24 of the main (15) and additional (25) laser heads; protective nozzle 27 of the pyrometer; water cooling built into the housings of the main (15) and additional (25) (water cooling is not shown in the Fig.).

Table heater 39 and heaters 8 in production bin 6 are heated to temperatures necessary to minimize thermal gradients within the layer-by-layer manufactured part (to prevent thermal deformation and warping). The maximum heating temperature of table heater 39 and heaters 8 is 600°C. The required purity of the shielding gas (nitrogen or argon) is achieved within sealed chamber 2.

The device is held for two hours to ensure uniform heating of all its components and the alignment of all thermal processes to prevent thermal distortion during operation. The device's working area is heated and reaches a stable, heated state. Removable substrate 41 is lowered to the thickness of the first powder layer being applied (typically ~40 µm).

The means 3 for applying powdered material without powder makes several imitation passes over the working area, including the quartz halogen heating elements 14, in such a way that the removable substrate 41 does not heat up more than 600°C and so that the stably heated state of the working area is not disturbed.

The powder material application device 3, together with the powder receiving funnel 47, moves to the extreme position under the feed hopper 11 (Fig. 3). The feed hopper 11 doses the required portion of powder with a reserve into the powder material application device 3 through the powder feeding funnel 45. The powder material application device 3 moves to the opposite position in the direction of movement, applying, leveling and compacting the first layer of powder using compacting rollers 44 on the removable substrate 41, and also dumping the excess powder into the collection hopper 10. When the powder material application device 3 moves from the extreme position to the opposite position, the quartz halogen heating element 14, due to its design, moves above the powder layer almost immediately after it is applied and precisely heats it to the temperature necessary to minimize thermal gradients inside the part being manufactured layer by layer (to prevent thermal deformations and warping). The maximum heating temperature of the applied powder layer is up to 600°C. The heating of the applied first powder layer is monitored by a wide-angle infrared camera 50. The width of the first applied powder layer does not exceed the size H (Fig. 7, Fig. 8), the powder particles do not extend beyond the conventional lines 67 limiting the width of the applied powder layers, which is confirmed by the operation of four optical video cameras 51.

Four triangulation laser sensors 53, working together with four pyrometers 52 (pyrometers 52 confirm that the measurement of distance T is carried out at the calibration temperature of triangulation laser sensors 53), measure the distance T and, if it goes beyond the permissible value, a command is sent through the control algorithms of the common control system of the device for compensatory corrective movement of the removable substrate 41 along the Z coordinate. If compensatory corrective movement is necessary, its value is stored by the common control system.

The means 3 for applying powder material together with the powder receiving funnel 47 moves to the opposite position exactly under the feed hopper 12 (Fig. 3 shown by the dotted line) and does not interfere with the movements of the main (15) and additional (25) laser heads.

The main (15) and additional (25) laser heads move to the positions for starting to process the applied powder layer with two reflected focused laser beams 29 (Fig. 6). Next, two independent identical laser beams with a wavelength of λ=1.06 μm are generated in two separate lasers (not shown in the figure) and these two laser beams are transported to the main (15) and additional (25) laser head via two separate and independent laser optical fibers 18 with a collimator 19 welded to each optical fiber 18. In each of the main (15) and additional (25) laser heads, the following occurs: the laser beam 61 obtained at the output of the collimator 19 enters the laser beam expander 20, which expands it to the required larger diameter, converting it into an expanded laser beam 62. The expanded laser beam 62 then passes through the focusing lens 21 and is converted into a focused laser beam 63. After the focusing lens 21, the focused laser beam 63 hits the deflecting fixed mirror 64 and a reflected focused laser beam is created beam 29.

The mutual mirror arrangement opposite each other of two main (15) and additional (25) laser heads, the presence of a synchronized dynamic rear direct electric drive 30 and a dynamic front direct electric drive 31 (movement X1 and X2), the presence of a dynamic transverse direct electric drive 32 (movement Y), the presence of a dynamic transverse direct electric drive 72 (movement Y1) make it possible to carry out remelting of powder with two independent reflected focused laser beams 29 in separate zones of the applied layer depending on the shape of the part being manufactured and melting (welding) of the powder in the first layer to the removable substrate 41.

The process of local remelting of powder material by two reflected focused laser beams 29 due to the movement of the main (15) and additional (25) laser heads is accurately and reliably controlled in real time by two pyrometers 5, each of which always moves together with the main (15) and additional (25) laser head and is always optimally directed into the local zone of powder remelting by the focused laser beam 29. If necessary, the technological modes of remelting are adjusted (speed of movement along coordinates X1, X2, Y, Y1; laser radiation power, etc.).

The removable substrate 41 is lowered to the thickness of the second powder layer to be applied (usually ~40 µm). Afterwards, the powder material application device 3, together with the powder receiving funnel 47, moves from the opposite position (Fig. 3) to the extreme position and, similar to the application of the first powder layer, applies the second powder layer, not exceeding the dimension H (Fig. 7), which is confirmed by the operation of four optical video cameras 51.

Four triangulation laser sensors 53, working in conjunction with four pyrometers 52, measure the distance T for the second powder layer, and if it exceeds the permissible value, a command is sent through the control algorithms of the general control system of the device for compensatory corrective movement of the removable substrate 41 along the Z coordinate. If compensatory corrective movement is necessary, its value is stored by the general control system.

The process of localized remelting of powder material is achieved by two reflected focused laser beams 29, driven by the movement of the primary (15) and secondary (25) laser heads. The second powder layer is fused (welded) to the localized remelted areas of the first layer's powder.

Next, a third layer of powder is applied and a similar process is repeated for 25 layers (a smaller number of layers is allowed, but not less than 10 pieces).

After applying the 26th layer (minimum after the 11th layer) and for all subsequent layers, the operation of the four pyrometers 52 and four triangulation laser sensors 53 ceases, and powder particles are allowed to extend beyond the conventional width limiting lines 67 of powder layer application. The size of the compensatory correction for the movement of the removable substrate 41 along the Z coordinate for all layers after the 25th layer (a smaller number of layers is allowed, but not less than 10 pieces) becomes constant and is calculated as the arithmetic mean of the compensatory correction sizes for the first 25 layers (a smaller number of layers is allowed, but not less than 10 pieces).

The process of applying new layers of powder and locally remelting them with two reflected focused laser beams 29, driven by the movement of the primary (15) and secondary (25) laser heads, continues until the part is fully fabricated. Once the entire part is complete, it, along with the volume of green powder in which it is immersed (cooling rate approximately 7°C per hour), cools very slowly in the device using software control of heaters 8 and table heater 39.

After the part and its unsintered powder have completely cooled, worktable 36 is disengaged from piston 37. Production hopper 6 is removed from the device and moved to a cleaning station, where the part is released along with removable substrate 41 and cleaned of unsintered powder. The part is then separated from removable substrate 41.

In this case, the entire sequence of technological processes is carried out automatically under technologically regulated conditions using special software and hardware thanks to the general control system of the device.

Thus, the claimed set of essential features, reflected in the independent claim of the invention, ensures the achievement of the claimed technical result - the creation of complex-shaped, high-strength, heat-resistant, biocompatible and other parts/products by the method of selective laser melting and/or sintering (SLM).

An analysis of the claimed technical solution for compliance with the conditions of patentability showed that the features specified in the formula are essential and interconnected with each other to form a stable set of necessary features, unknown at the priority date from the state of the art and sufficient to obtain the required synergistic (super-sum) technical result.

Thus, the above information indicates that the following set of conditions are met when using the declared technical solution:

- an object embodying the declared technical solution, when implemented, is intended for layer-by-layer sintering of parts of complex spatial configuration from fine powder using laser radiation based on data from a three-dimensional computer model;

- for the claimed object in the form in which it is characterized in the formula, the possibility of its implementation using the means and methods described above in the application or known from the state of the art on the priority date has been confirmed;

- an object that embodies the declared technical solution, when implemented, is capable of ensuring the achievement of the technical result envisaged by the applicant.

Consequently, the claimed object meets the patentability criteria of “novelty”, “inventive step” and “industrial applicability” under current legislation.

Claims (1)

A device for producing articles from powder materials, comprising a load-bearing frame, a sealed chamber mounted thereon with a means for applying powdered material placed therein in the form of a double knife mounted with the possibility of horizontal reciprocating movement and forming a layer of the article, a pyrometer, a production hopper with heaters built into its walls, collection hoppers and powder feed hoppers with metering shafts in each, quartz halogen heating elements placed on the double knife and a movable laser head installed in the sealed chamber, characterized in that the laser head is made in the form of a housing, at the input of which a laser optical fiber is located with an optically welded collimator and a coaxially mounted laser beam expander and a focusing lens located in the output link of the laser head, at the end of which a protective nozzle of the laser head is fixed, wherein the device is provided with an additional laser head, made identical to the main one and located mirror-like opposite the latter, and the pyrometer is installed through a bracket with its protective nozzle, the optical axis of the pyrometer is directed orthogonally to the specified powder layer and passes through the focus of the reflected focused laser beam, while the housings of the main and additional laser heads and pyrometers are mounted on dynamic rear direct, front direct, transverse direct electric drives and a vertical movement electric drive.