RU2801360C1 - Installation for manufacturing parts by selective laser melting - Google Patents

Abstract

FIELD: selective laser melting.

SUBSTANCE: invention relates to a plant for manufacturing parts by selective laser melting. The installation contains a housing and a laser radiation system located in it, including a scanning device (2), a laser emitter (3) and a laser emitter fiber (4), a cooling system (5), and a construction module. The construction module includes a working table, a sealed working chamber (9), a construction well (6) and a feed well (7) with powder, a layer application system (8), a hopper (21) for collecting excess powder and a control unit (12). The laser radiation system is equipped with a movable telescope, made with the possibility of changing the diameter of the laser beam on the construction platform (32) of the part. Two guide rails (24) are fixed on the rear walls (23), carriages (25) are installed on the rails, on which the construction piston (26) and the feeder piston (27) are fixed respectively. The construction platform with its protruding part is attached to the side end of the plate with countersunk screws. Double rubber seals are mounted between the ends of the building platform and the wall of the building well to prevent powder from getting into the gap between the piston and the walls of said well. The construction well has a built-in system for heating the construction platform to a predetermined temperature.

EFFECT: design makes it possible to grow metal products by selective laser melting on the entire area of the build platform due to the system of lateral fixation on the piston, with high productivity due to the control of the spot diameter by a movable telescope, and high reliability due to double seals on the build and feeder pistons.

1 cl, 3 dwg

Description

The invention relates to the manufacture of parts by selective laser melting of high precision from powder materials and can be used in various branches of mechanical engineering and aircraft building.

A known installation for the production of products from powder materials, containing a welded box-shaped frame, a mechanism for metering the supply of powder material, made in the form of a vertical cylinder with a piston, the open end of which is installed in the plane of the desktop, and a leveling knife mounted cantilever on the rear wall of the protective chamber ( RU 154761 U1, В05С 19/04, 18.1 1.2014).

The disadvantage of the installation is the high complexity of adjustment when leveling the powder, the unevenness of the resulting layer due to the cantilever fastening of the leveling knife.

A known installation for the manufacture of parts by selective laser melting, which contains a housing and a laser radiation system located in it, including a scanning device, a laser emitter and a laser emitter fiber, a cooling system, a construction module, including a desktop, a sealed working chamber mounted on top of the desktop, construction well and feeder well with powder, layer application system, excess powder collection bin and control unit (RU 185513 U1, V23K 26/342, 12/07/2018).

A known installation for the manufacture of parts by layer-by-layer synthesis (RU 2487779 C1, V23K 26/00B 20.07.2013), which uses a pneumatic cylinder as a drive for powder application, requiring a compressor, a compressed air purification system. The system for collecting excess powder in a known installation is a welded structure. Extraction of the powder is possible only after the completion of the process and with the chamber door open through the same opening in the working table through which the excess powder enters the collection system. This increases the time of intermediate operations and leads to contact of the powder material with air, which can adversely affect its quality and make it unsuitable for subsequent use.

The positioning accuracy of the platform table is ±0.005 mm, which is insufficient for growing high-precision products with a layer of 20 microns.

The platform table has the ability to heat up to 100°C due to the electric heating element, which is insufficient temperature to reduce stresses and deformations in high-alloy steels, copper, aluminum and titanium alloys.

The technical task of the invention is to eliminate the above disadvantages of the known installation.

The essence of the invention is as follows.

SUBSTANCE: installation for production of parts by selective laser melting contains a housing and a laser radiation system located in it, including a scanning device, a laser emitter and a laser emitter fiber, a cooling system, a construction module, including a working table, a sealed working chamber mounted on top of the working table, a construction well and powder feed pit, layering system, excess powder collection bin and control unit. In addition, the installation contains a shielding gas supply system, a filtration system and a vacuum pump connected to the sealed working chamber, and the laser radiation system is equipped with a movable telescope configured to change the diameter of the laser beam on the part construction platform, while the construction well and the feed well have rear walls, on which two guide rails are fixed, carriages are installed on the rails, on which the construction piston and the feeder piston are fixed, respectively, and in each said piston an axial blind hole is made, in which a nut with a ball screw (ball screw) is placed and fixed , wherein a plate is mounted on the upper part of the construction piston, on which a construction platform is located with a part protruding beyond the plane of contact with the plate, made from the side of its side end, and the construction platform of the said protruding part is attached to the side end of the plate with countersunk screws, while between the ends of the platform double rubber seals are mounted on the wall of the construction well to prevent powder from getting into the gap between the piston and the walls of said well, and the system for heating the construction platform to a predetermined temperature is built into the construction well.

The SLM process consists in the sequential layer-by-layer melting of powder material by means of high-power laser radiation. It is used for single and small-scale production of complex products from special metal powders: stainless, tool, structural steels, nickel and cobalt alloys, aluminum and titanium alloys.

The SLS plant is a completely autonomous and functionally independent complex capable of operating independently, subject to the requirements for the premises and life support systems.

In FIG. 1 shows a general view of the SLP installation from the front in section; in fig. 2 - general view of the SLP installation on the left in the section; in fig. 3 - view A of Fig. 1.

The SLP installation includes the following main elements:

- building 1);

- scanning device (2)

- laser emitter (3) with fiber (4);

- cooling system (5);

Building module consisting of:

- construction well (6);

- well-feeder (7);

- layering system;

- sealed chamber (9);

- shielding gas supply system (10);

- shielding gas filtration system (11);

- control unit (12);

- vacuum pump (13).

The design of the SLM facility makes it possible to use it for technological operations (using laser radiation), such as: selective laser melting.

The housing (1) is designed to protect personnel and surrounding workers from harmful factors of technological processes, as well as to protect structural elements from environmental influences. Inside the cab are a scanning device (2), a laser emitter (3), a laser emitter fiber (4), a cooling system (5), a build well (6) and a feed well (7) with powder (8), a layer application system, sealed chamber (9), shielding gas supply system (10) and shielding gas filtration system (11), control unit (12), vacuum pump (13).

The scanning device (2) is a standard system of two rotating mirrors, the rotation of which ensures the scanning of the laser beam along two mutually perpendicular axes of the construction working area. The radiation from the emitter (3) is transported along the fiber (4) to the movable telescope (14). Unlike the standard scheme of the scanning system, which uses a fixed f-theta lens to focus laser radiation on the working plane, the proposed system with a movable telescope is able to change the diameter of the laser beam on the working plane. This allows processing thin sections and the surface of the part with high accuracy with a small diameter, and massive sections of the internal volume of the part with a spot of a larger diameter at higher power. This solution allows you to increase the performance of the construction process without reducing accuracy.

The case (1) is a closed frame made up of a set of cases, sheathed with panels to protect the working area from external influences of the working room: dust, possible falling of foreign objects (in industrial workshop conditions), etc. An optical fiber (4) from the laser emitter (3) to the telescope (14) of the scanning device (2) is provided through the holes in the cabin walls, the vacuum system is supplied through the hole with a valve (15) (hoses are not shown in the diagram) and protective gases are supplied through a slot (16) in the rear wall of the sealed chamber (9) (filtering system hoses are not shown in the diagram), cooling supply from the cooling system (5) to the laser emitter (3). The door of the hermetic chamber (9) is equipped with a viewing window (17) to control the progress of the processing.

Doors and removable panels are provided in the case for access of service personnel to the working area and technological elements.

In a sealed chamber (9) the part is grown. In order to avoid oxidation of the powder material during the construction process, the process takes place in an inert atmosphere (inertization) due to the protective gas supply system (10) through the slot (16). Before the start of the process, the atmosphere is pumped out of the sealed chamber to low vacuum values by the pump (13), then the chamber is filled with an inert gas. The inert gas circulates in a closed circuit through the intake port (18) and passes through the shielding gas filters (11) and then returns back to the building process in the chamber (9) through the slot (16).

The build module is the actual workspace of the PLS installation. It contains a working table (19) in the form of a plate with square holes, under which the product construction well (6) and the feeder well (7) are fixed and one rectangular hole (20) for collecting excess powder into the hopper (21). The hopper hose (21) is blocked by a valve (22), thus it is possible to direct the unused powder for screening and subsequent use without depressurization of the chamber (9). The construction well (6) and the feed well (7) have rear walls (23), on which two guide rails (24) are fixed, carriages (25) are installed on the rails, on which the construction piston (26) and the feed piston ( 27), and in each piston an axial non-through hole is made, in which a nut (28) with a screw (29) of a ball screw (ball screw) is placed and fixed, while the motors of the screws of the ball screw (30) are fixed on a fixed support (31) of the housing (1 ). The ball screw (29) is driven by the motor (30). When the screw is rotated, the corresponding piston moves in the vertical direction.

A plate is mounted on the upper part of the building piston, on which a building platform is located with a part protruding beyond the plane of contact with the plate, made from the side of its side end, and the building platform by said protruding part is attached to the side end of the plate with countersunk screws (34) (Fig. 3), from the ends to prevent powder from getting into the gap between the piston and the walls of the well. Usually one gasket is used. The SLP process can take several tens of hours. Under conditions of abrasive wear due to the presence of finely dispersed metal powder, as well as under conditions of heating to temperatures up to 300 degrees, one row of seals can become unusable, violating the construction process. The second row of compaction guarantees the successful completion of the growing process. On known installations for selective laser melting, the construction platform is fixed with screws that press the platform from above to the movable piston. The screw heads cover part of the build area, making it impossible to use the entire area of the platform. The proposed design allows you to fix the build platform (32) from the side with countersunk screws (34). This allows the entire area of the growing substrate to be used. For mounting, the piston is moved above the table (19) so that the holes for the mounting screws (34) are accessible. The build platform is mounted on the piston and secured with four screws (34).

The feed well (7) is filled with metal powder (8) before the start of the growing process and is designed for continuous supply of metal powder during the growing process. The height of the powder piston (27), and therefore the capacity of the powder well, can be adjusted using the control system (12).

Parts are grown in a sealed chamber (9). To do this, in the construction well (6), the construction platform (32) is placed on the base of the construction piston (26). The build platform is fixed in place in the manner described above. Also, a heating system (35) of the building platform (32) to the required temperature by the control system (12) is built into the construction well.

The application system ensures the transfer of powder from the feed well (7), after moving it a predetermined step up, to the build platform (32), evenly applying the powder over its surface, using a squeegee blade (36). The squeegee is fixed on a plate (37) which moves along rail guides (38) on carriages (39). The squeegee has a belt drive (not shown in the diagram), which provides a smooth and uniform application of the powder material.

The control unit (12) controls all mechanisms and systems of the plant. In accordance with the work program, the control system (12) sends commands to move the pistons (26) and (27), the layer formation system (8), the scanning system mirrors (2), the movable telescope (14), the laser on/off (3) , as well as pumping out the chamber (9) with a pump (13) and supplying inert gas (10) and filtering it (11) to the heating system (35).

The installation works as follows.

A control program is loaded into the control unit (12) (a three-dimensional computer model of the product divided into layers with growth parameters, such as laser radiation power, laser radiation movement speed, layer height and laser radiation movement trajectory). In the build well (6), the build platform (32) is placed on the base of the build piston (26) and fixed with countersunk screws (34) at the ends. Also, a heating system (35) of the build platform (32) to the required temperature is built into the construction well. The cultivation takes place in a sealed chamber (9) in an environment of inert or low-active gases. In order to avoid oxidation of the powder material and the part during the construction process, before the start of the process, the atmosphere is pumped out of the sealed chamber (9) to low vacuum values by the pump (13), then the chamber is filled with inert gas by the inert gas supply system (10). The inert gas is circulated in a closed circuit by the filtration system blower (11) through the intake port (18) and passes through the filters of the filtration system (11) and then returns to the building process in the chamber (9) through the slot (16).

During the SLM process, metal powder is deposited from the feed well (7) onto the build platform (32) using a squeegee blade (36) of the layer forming system (8). The squeegee is fixed on a plate (37) which moves along rail guides (38) on carriages (39). The squeegee has a belt drive (not shown in the diagram), which provides a smooth and uniform application of the powder material. Piston (27) rises by the amount of layer due to the screw (29), pushing out a portion of the powder from the well (7), piston (26) with a fixed platform (32) is lowered by the amount of layer due to the screw with an accuracy of ±0.001 mm, squeegee ( 36) transfers a portion of the powder and spreads it on the growing platform (32). The layer of metal powder deposited in this way is then fused by the laser beam emitted from the scanning system (2) in areas that are determined by the control system (12). This process is repeated until the product is completely grown.

This design allows you to grow metal products by selective laser melting on the entire area of the construction platform (32) due to the proposed system of lateral fixation on the piston (26), with high productivity due to the control of the spot diameter by a movable telescope (14), and high reliability, due to double seals (33) on the build (26) and feeder (27) pistons.

Claims (1)

Installation for the manufacture of parts by selective laser melting, containing a housing and a laser radiation system located in it, including a scanning device (2), a laser emitter (3) and a laser emitter fiber (4), a cooling system (5), a construction module, including a desktop , a sealed working chamber (9) installed on top of the working table (19), a construction well (6) and a feed well (7) with powder, a layer application system (8), a hopper (21) for collecting excess powder and a control unit ( 12), characterized in that it contains a protective gas supply system (10), a filtration system (11) and a vacuum pump (13) connected to the sealed working chamber, and the laser radiation system is equipped with a movable telescope, configured to change the diameter of the laser beam by construction platform (32) of the part, while the construction well (6) and the feed well (7) have rear walls (23), on which two guide rails (24) are fixed, carriages (25) are installed on the rails, on which construction piston (26) and feeder piston (27), respectively, and in each said piston there is an axial non-through hole, in which a nut (28) with a ball screw (29) screw (29) is placed and fixed, while on the upper part of the construction piston a plate is mounted on which a construction platform is placed with a part protruding beyond the plane of contact with the plate, made from the side of its side end, and the construction platform of the said protruding part is attached to the side end of the plate with countersunk screws (34), while between the ends of the construction platform and the wall of the construction well double rubber seals (33) are mounted to prevent powder from getting into the gap between the piston and the walls of said well, and the building well has a built-in heating system (35) of the build platform (32) to a predetermined temperature.

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