RU2717761C1 - Apparatus for selective laser sintering and method of producing large-size articles on said apparatus - Google Patents

Abstract

FIELD: metallurgy.SUBSTANCE: group of inventions relates to production of metal articles by selective laser sintering. Plant comprises a sealed chamber, a vacuum system, an inert gas feed unit, an inert gas cleaning system, an inert gas circulation system, water cooling system of inert gas, loading hopper for powder material, support for formed product support, leveler, laser system for sintering powder material, cooling system of laser system, control system, powder material dispenser and a vacuum sluice device connecting the loading hopper and dispenser to each other. Loading hopper, vacuum sluice device, dispenser and laser system are located inside sealed chamber in its upper part, support for formed product support is located in lower part of sealed chamber and consists of heated base and substrate. Sealed chamber is equipped with overpressure valve and at least two ventilation holes, which are connected to inert gas supply unit, inert gas circulation system, and vacuum system.EFFECT: improved operational characteristics of manufactured articles, reduced probability of defects in manufacturing process.16 cl, 2 dwg

Description

A selective laser sintering apparatus for manufacturing large-sized metal products and a method for manufacturing large-sized metal products in this installation.

The invention relates to means for the manufacture of parts and structures by 3D printing, in particular, to the manufacture of metal products by the method of layer-by-layer selective laser fusion (sintering).

The prior art methods and devices for volumetric (three-dimensional, 3D) printing, based on the principle of layer-by-layer creation (growing) of a solid geometric figure, namely: (RU 2481191 C2, B29C 67/04 publ. 05/10/2013, / 1 / ) a device for generatively creating a three-dimensional object using polymer powder as a building material, which includes: a frame, which defines the construction area with its upper section; a panel that connects the frame to the device body; the substrate, which is located in the frame and can be vertically moved using a lifting mechanism at least below the area of construction. The device for the generative creation of a three-dimensional body also has an irradiation device that generates an energy beam that, using a deflecting device, focuses at any points in the construction region to selectively sinter or melt the powder material located in the construction region, and a coating device for coating powder material on a substrate or previously applied layer of powder material. Thermal insulation is located between the frame and the panel with the possibility of detachment and is made in the form of a removable insert.

The disadvantage of the above analogue / 1 / is that this method and devices are designed to create products from polymers and copolymers, and they cannot be used for the manufacture of metal parts.

From the prior art, a device and method are known (patent US 4863538 A dated 08/05/1989, / 2 /) for layer-by-layer formation of a three-dimensional object using powder material, which can be cured by irradiating it with an energy beam. In particular, the present invention relates to a device equipped with an electron gun for generating an energy beam and a work area in which the powder material is distributed and along which the energy beam slides during irradiation. The manufacturing process of a part is carried out by selective fusion of a metal powder with a powerful electron beam, the trajectory of which corresponds to the cross section of the product generated from a digital CAD model using software. The energy beam is controlled by an electromagnetic field and serves to focus and move the electron beam according to the boundaries of the sintering of the powder layer.

The disadvantages of this method / 3 / include the complexity of the equipment and auxiliary systems used, as well as the possibility of contamination of the installation when working with volatile materials due to the lack of gas exchange.

The closest analogue, according to the applicant, is (US 5908569 A, B22F 3/10, 06/01/1999, / 3 /) apparatus for the production of a three-dimensional object by laser sintering by sequentially solidifying metal layers in places corresponding to the cross section of the object, by radiation, provided that the device contains a support to support the formed object, a device for coating, for applying layers of hardened material on a carrier or pre-hardened layer, an irradiator for strengthening the layers of material in places corresponding to the cross-section of the object, and the heating device located above the support in the working position for heating the hardened material, a heating device containing at least one direct radiating heater with a variable heating power along its length.

The disadvantage of the above analogue / 3 / is that the device has the ability to create only small and very limited dimensions of the parts, as well as a high probability of formation of defects in the product.

The objective is to create a device and method by which it is possible to produce large-sized products from high-strength alloys with enhanced performance characteristics by the method of layer-by-layer selective laser fusion.

The technical result to which this invention is directed is to increase the mechanical properties, increase the size and reduce the likelihood of defects in the product.

The technical result is achieved due to the fact that the installation of selective laser sintering for the manufacture of metal products, containing a sealed chamber configured to create an inert medium in it, a vacuum system, an inert gas supply unit, an inert gas purification system, an inert gas circulation system, a water cooling system inert gas, hopper for powder material, support for supporting the molded product, made with the possibility of vertical movement, leveling device, tries extending above the support and made with the possibility of horizontal and / or vertical movement, the laser system for sintering powder material, the cooling system of the laser system and the control system, characterized in that it contains a powder material dispenser and a vacuum lock device connecting the hopper and the dispenser with each other while the loading hopper, the vacuum lock device, the dispenser and the laser system are located inside the sealed chamber in its upper part, a support to support the formed and the unit is located in the lower part of the sealed chamber and consists of a heated base and a substrate for the formed product, the sealed chamber configured to extract the formed product from it, equipped with an overpressure valve and at least two ventilation holes that are connected to the inert gas supply unit, an inert gas circulation system and a vacuum system, while the equalizer and support are connected through the drive to at least one engine to ensure they are moved lia, and a laser system, a dispenser and said at least one engine are connected to the control system.

In a possible embodiment of the installation, it contains a frame.

In a possible development option, the loading hopper, dispenser and airlock are mounted on the frame.

In a possible embodiment of the installation, the laser system consists of a laser emitter, a scanning device, a collimator and an optical fiber.

In a possible embodiment of the installation, the sealed chamber may have a viewing window.

In a possible embodiment of the installation, the inert gas circulation system is made in the form of a turbine with pipelines connected by ventilation openings to a sealed chamber.

In a possible embodiment of the installation, the water cooling system is located on the pipelines of the inert gas circulation system.

In a possible embodiment of the installation inside the sealed chamber contains a video recording device.

In a possible development variant of the installation, the support has a flat surface.

In a possible development of the installation, sensors are located inside the sealed chamber for taking readings and transmitting them to the control system.

In a possible embodiment of the installation, the equalizer is made in the form of a carriage, which on top has a cavity for loading powder material.

In a possible embodiment of the installation, the sealed chamber, below the plane of construction of the formed product, contains a receiving hopper.

The method of manufacturing metal products by selective laser sintering at the installation described above, characterized in that the first stage is carried out, in which the powder material is poured into the loading hopper, the sealed chamber is closed, air is pumped out of the sealed chamber using a vacuum system, and then the internal volume of the sealed chamber is filled with inert gas from the inert gas supply unit until the specified pressure is reached, the inert gas circulation system is switched on, and the alloy zone is continuously blown powder material and optical equipment of the laser system through the ventilation holes and produce heating of the base with the substrate for the molded product, after which the second stage is carried out, which feeds the powder material from the loading hopper in an inert gas through a gateway device into the dispenser, unloading and leveling volume of powder material using an equalizer from the dispenser to the substrate, the resulting layer is irradiated with focused laser radiation at the points of the layer, respectively After the irradiation is completed, lower the support to support the molded product by the thickness of the obtained layer, the equalizer is moved in the opposite direction, then the operations of the second stage are repeated until the product is completely formed, after which the third stage is carried out , which removes the protective gas from the sealed chamber, equalizes the pressure in the sealed chamber with atmospheric, opens the sealed chamber and removes cabins product obtained from the camera.

In a possible variant of the development of the method, the internal volume of the sealed chamber is filled with inert gas until an overpressure of 0.01-0.05 atm is reached.

In a possible embodiment of the method, argon is used as an inert gas.

In a possible variant of the development of the method, the steps of the second stage are automated, regulated and controlled by the program.

In FIG. 1 and 2, an installation diagram is shown.

1 - Dispenser;

2 - Gas purification system;

3 - Vacuum system;

4 - Water cooling system;

5 - Inert gas circulation system;

6 - loading hopper;

7 - Laser system;

8 - The cooling system of the laser system;

9 - Management System;

10 - Inert gas supply unit;

11 - Leveling device;

12 - Support;

13 - Gateway device;

14 - Sealed chamber;

15 - Ventilation openings;

16 - Receiving hopper.

The sealed chamber 14 is a power structure welded from sheets reinforced with stiffeners. It is designed to create a controlled inert gas environment.

The gas purification system 2 is a cylindrical chamber with a conical lower part. The system is designed to clean the gas circulating through the installation from metal particles formed during the evaporation of the fused powder material by laser radiation. The gas flow enters the pipe, which is installed tangentially in the upper part of the apparatus, under the action of centrifugal force, the particles are deposited on the walls and poured into the lower part of the chamber. For additional filtration of gas passing through the system, a fine filter element is installed in it.

The vacuum system 3 consists of a Roots pump of the brand ZJ-150 and a mechanical rotary vane vacuum pump MS-301, connected through nozzles and vents to a sealed chamber 14. In the installation, this system is used to remove gas from the internal volume of the installation.

The water cooling system 4 is closed, independent of the laser cooling system 8, filled with distilled water, and is a TAEevo M10 chiller connected through a pressure-discharge manifold to cooling jackets for pipes that discharge gas from the chamber. Gas cooling is necessary to prevent violation of the temperature regime of the installation.

The inert gas circulation system 5 is a turbine that is connected through nozzles and vents to a sealed chamber. The system also includes pipelines equipped with a water cooling system 4, used for supplying and circulating shielding gas according to the commands of the control system 9. The presence of this system is necessary to maintain a given temperature in the sealed chamber 14, as well as to remove suspended particles of condensed material from the area above the zone fusion. The presence of foreign bodies in the area of passage of the laser beam emitted by the laser system 7 may lead to a decrease in the power supplied to the fused material, which will cause a deterioration in the operational properties of the manufactured part. A continuous flow of gas in the chamber is also necessary for blowing the protective glass of the laser system 7 in order to prevent its contamination with metal vaporization products.

To provide shielding gas circulation, a turbine driven by a three-phase electric motor was used. The gas flow through the circulation system is regulated by the control system 9.

The loading hopper 6 is a sealed container with powder attached to the chamber 14 through the lock device 13 and serves to supply powder in the vacuum medium into the dispenser 1 through the lock device 13.

The laser system 7 is a collimator, a laser source, a scanning system. Laser radiation is transmitted from the source to the collimator through a flexible optical cable. The scanning system focuses the parallel beam emitted by the collimator to a point with coordinates specified by the control system and is a set of lenses and mirrors moved by high-precision servos.

The laser cooling system 8 is closed, filled with distilled water. The system includes a chiller with inlet and outlet pipes. Chilled water is supplied to the laser system 7 - the source of laser radiation, the collimator and the scanning system.

The control system 9 consists of two electrical cabinets - racks with servo motors controllers installed inside, receivers and analyzers of sensor signals located on the installation, actuator controllers: relays, damper drives, etc. The system is necessary to maintain a given state of the atmosphere in the chamber, control and adjust the temperature of the substrate, perform operations to prepare the unit for operation (opening the cover, switching overflow valves, controlling the turbine), as well as to perform cyclic operations during sintering (moving the carriage, table, powder control)

The inert gas supply unit 10 is a system of high pressure cylinders filled with inert gas, and serves to store and supply inert gas.

The equalizer 11 is a carriage, which is made in the form of a box-shaped structure, on the sides of which two knives are installed, perpendicular to the direction of movement of the carriage. The knives are designed to level the layer of applied powder and have bevels to prevent jamming of the carriage when it touches the manufactured part.

The support 12 is a heated base and a substrate that is attached to the base.

The lock device 13 is a sealed shutter with a reciprocal flange and serves to supply powder to their hopper 6 in the dispenser 1.

The ventilation openings 15 serve to connect the sealed chamber 14 with various installation systems, for example, systems 3, 5, 10, and are equipped with diffusers with guide devices installed inside, designed to equalize the gas flow rates.

The receiving hopper 16 is a container for pouring unused powder and cakes.

An internal view of the camera with the cover removed is shown in FIG. 2.

In the interior of the sealed chamber 14, a table with rails and a loading hopper 6, which is mounted on the frame, are mounted. The table is a metal frame with a horizontal thick-walled plate mounted on top. Inside the table, a square shaft was mounted, drives, actuators, electrical connectors and cables were installed. There are also guides on the table for installing receiving hoppers 16 for spent powder.

A support 12 is installed in the mine, consisting of a base heated by a heater, which is made in the form of a plate with channels for installing a nichrome heater and a substrate on which the building (formation) process takes place. A spring-loaded felt seal is located along the contour of the support to prevent powder from spilling out of the construction area. The need for heating the powder granules on the support is due to the maximum permissible cooling rate of the molten metal. At a high cooling rate during fusion, deformation of a metal in a solid-liquid state is possible due to the shrinkage of the already hardened part of the manufactured product. Therefore, heating the base of the support 12 reduces the likelihood of the formation of hot cracks in the resulting part.

The substrate is removable, attached to the base of the support 12 with four bolts and serves to freely remove the formed product along with the substrate from the sealed chamber 14.

To control the temperature in the upper part of the base are thermocouples in contact with the substrate. The temperature data is supplied to the control system 9, which adjusts the heater power necessary to maintain it. The support 12 is mounted on two guides, ensuring its horizontal movement. To achieve the necessary positioning accuracy in the design, the screw-nut transmission MA25V RL isp. 1U-RH С560 with XML servo motor SE-15AEK, bevel gear BG86-R1-R-M2-conf. 10-Е-Н0 and jack MA25BRL. The system of equipping programmatic compensation of the backlash of actuators. Skew when raising and lowering is eliminated due to the use of double symmetrical guides and linear gears. Between the substrate and the shaft structurally laid a gap to compensate for thermal expansion. Sealing the joint to prevent spilling of the powder is ensured by spring-loaded felt pads.

On the upper part of the table there are horizontal guides on which the carriage is fixed. The range of movement is set using limit switches located on the frame. The carriage is driven by a belt drive with a servo motor.

In the upper part of the table there are longitudinal cuts made so that the carriage in extreme positions with its edge stops close to them. Thus, the excess powder is poured into the receiving hopper 16. In one of the extreme positions, the carriage stops in the area of the dispenser 1. The dispenser 1 is mounted on the wall of the airtight chamber 14 and is a reservoir for storing powder with a clip fixed at the bottom with two grooves - loading and unloading . The loading groove is located at the top of the cage and is connected to the powder reservoir. The unloading groove is located on the opposite side of the cage, inside which a gear shaft is installed. When the shaft is rotated, the powder through the loading groove is poured into the cavity between the recess in it and the holder and moves in the direction of the discharge opening. Thus, a metered supply of powder material into the inner cavity of the carriage is ensured.

On the ceiling of the sealed chamber 14 there are installed: a laser system 7, a video fixation unit, lighting, a lock device 13 for filling material from the loading hopper 6 into the dispenser 1. A viewing window is provided on the side of the camera 14 from the side of the operator.

The device operates as follows.

Before starting the fusion process, air is evacuated from the sealed chamber 14 using a vacuum system 3. Then, the internal volume of the chamber 14 is filled with inert gas — an agronomist from block 10 until an overpressure of ~ 0.01 - 0.05 atm is reached. Upon reaching the set pressure, the turbine 5 is turned on, providing continuous blowing of the zone of fusion of the powder and optical equipment through the ventilation holes 15.

Before starting the process, the initial three-dimensional model is adapted - division into flat sections of a relatively small height corresponding to the future layer thickness.

Next, the base and substrate are heated for the molded product to 200 C.

Next, the equalizer 11, made in the form of a carriage, is fed to the dispenser 1, filled with powder from the loading hopper 6 earlier, and the calculated volume of powder is unloaded from it into the carriage. Between the carriage and the substrate of the base of the support 12, a gap equal to the thickness of the layer (40-80 μm) is established. The carriage, using the XML-SBP04AEK engine and the NMRV050-FL worm gearbox, is retracted in the opposite direction, pouring out and leveling the powder in the direction of travel.

The resulting layer is irradiated by focused laser radiation directed by a three-axis scanning device of the laser system 7. The beam path is set according to a given cross section of the model loaded into the control system 9.

After irradiation is completed, the support is lowered by the value of the layer thickness, the carriage moves in the opposite direction and the scanning process of the next section is performed.

Thus, thin layers of powder are deposited on a substrate and irradiated with an LS-1000 ytterbium fiber laser according to the program.

The specs and excess powder material are displaced from the support 12 during horizontal reverse movement of the equalizer 11 and poured through the holes into the receiving hoppers 16. The operations are repeated step by step until the part is completely manufactured.

All processes take place in an environment filled with an inert gas - argon, including the process of pouring granules into dispenser 1. The absence of direct contact of the powder with air reduces the possibility of the formation of metal oxides, as well as the ingress of water vapor from the environment, which positively affects the quality of the finished product.

After the complete formation of the part, the sealed chamber 14 is degassed, followed by air inlet until atmospheric pressure inside the chamber is reached.

The fabricated part is removed from the sealed chamber assembly with the substrate and sent for further processing.

Thus, the claimed invention provides improved operational characteristics manufactured with its use of products, and also reduces the likelihood of defects in the manufacturing process.

Claims (16)

1. Installation for the manufacture of metal products by selective laser sintering, comprising a sealed chamber configured to create an inert medium, a vacuum system, an inert gas supply unit, an inert gas purification system, an inert gas circulation system, an inert gas water cooling system, a loading hopper for powder material, a support for supporting the molded product, made with the possibility of vertical movement, an equalizer located above the support and made with the possibility of th vertical and / or vertical movement, a laser system for sintering powder material, a cooling system of the laser system and a control system, characterized in that it contains a powder material dispenser and a vacuum lock device connecting the feed hopper and the dispenser to each other, while the feed hopper, vacuum a lock device, a dispenser and a laser system are located inside the sealed chamber in its upper part, a support for supporting the formed product is located in the lower part of the sealed chamber erya and consists of a heated base and substrate for the molded product, and the sealed chamber is made with the possibility of extracting the molded product from it, equipped with an overpressure valve and at least two ventilation holes that are connected to the inert gas supply unit, the inert gas circulation system, vacuum system, while the equalizer and support are connected through the drive to at least one engine to ensure their movement, and the laser system, dispenser and the aforementioned necks least one motor connected to the control system. 2. Installation according to claim 1, characterized in that it comprises a frame. 3. Installation according to claim 2, characterized in that the loading hopper, dispenser and airlock are mounted on the frame. 4. Installation according to claim 1, characterized in that the laser system consists of a laser emitter, a collimator connected to the laser emitter through an optical fiber, and a scanning device for focusing the beam at a point specified by the control system. 5. Installation according to claim 1, characterized in that the sealed chamber is made with a viewing window. 6. Installation according to claim 1, characterized in that the inert gas circulation system is made in the form of a turbine with pipelines connected by ventilation openings to a sealed chamber. 7. Installation according to claim 6, characterized in that the water cooling system is located on the pipelines of the inert gas circulation system. 8. Installation according to claim 1, characterized in that it comprises a video recording device located inside a sealed chamber. 9. Installation according to claim 1, characterized in that the support has a flat surface. 10. Installation according to claim 1, characterized in that it comprises a temperature sensor located inside the sealed chamber and configured to transmit readings to the control system. 11. Installation according to claim 1, characterized in that the equalizer is made in the form of a carriage, which on top has a cavity for loading powder material. 12. Installation under item 1, characterized in that it contains a receiving hopper located in a sealed chamber below the plane of construction of the formed product. 13. A method of manufacturing metal products by selective laser sintering using the apparatus of claim 1, characterized in that the first stage is carried out, in which the powder material is poured into the loading hopper, the sealed chamber is closed, air is pumped out of the sealed chamber using a vacuum system, then filled the internal volume of the sealed chamber with inert gas from the inert gas supply unit until the specified pressure is reached, the inert gas circulation system is switched on, and the zone is continuously blown melting the powder material and the optical equipment of the laser system through the ventilation holes and produce heating of the base with the substrate for the formed product, after which the second stage is carried out, which feeds the powder material from the loading hopper in an inert gas medium through the gateway device to the dispenser, unloading and leveling volume of powder material using an equalizer from the dispenser to the substrate, the resulting layer is irradiated with focused laser radiation at the points of the layer, with corresponding to the cross section of the molded product according to a given program in the control system of the said installation, after the irradiation is completed, lower the support to support the molded product by the thickness of the obtained layer, the equalizer is moved in the opposite direction, then the operations of the second stage are repeated until the product is completely formed, after which the third stage is carried out on which the protective gas is removed from the sealed chamber, equalize the pressure in the sealed chamber with atmospheric, open the sealed chamber the resulting product is removed from the chamber. 14. The method according to p. 13, characterized in that the internal volume of the sealed chamber is filled with inert gas until an overpressure of 0.01-0.05 atm is reached. 15. The method according to p. 13, characterized in that argon is used as an inert gas. 16. The method according to p. 13, characterized in that the operations of the second stage are automated.

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