CN109807328B

CN109807328B - Selective laser melting system, gas circulation device and printing method

Info

Publication number: CN109807328B
Application number: CN201711161535.7A
Authority: CN
Inventors: 王先礼; 喻鹏; 袁剑; 吕启涛; 高云峰
Original assignee: Han s Laser Technology Industry Group Co Ltd
Current assignee: Han s Laser Technology Industry Group Co Ltd
Priority date: 2017-11-20
Filing date: 2017-11-20
Publication date: 2021-06-22
Anticipated expiration: 2037-11-20
Also published as: CN109807328A

Abstract

The invention belongs to the technical field of additive manufacturing equipment, and relates to a selective laser melting system which comprises selective laser melting equipment, a protective gas output device and a gas circulating device, wherein the selective laser melting equipment comprises a forming cavity, a pressure gauge and an oxygen transmitter; the gas circulating device comprises a shell, a vacuumizing assembly and a gas circulating and filtering assembly; the forming cavity and the gas circulation filtering assembly form a first gas path, the protective gas output device, the forming cavity and the vacuumizing assembly form a second gas path, the protective gas output device and the gas circulation filtering assembly form a third gas path, each gas path comprises a plurality of connecting pieces, and the first gas path, the second gas path and the third gas path are interconnected through a shared part of the connecting pieces. According to the scheme provided by the invention, the internal oxygen removal efficiency of the forming material in the forming cavity can be improved, and the overall oxygen removal speed is increased; a gas circulation device and a printing method applied to the system are also provided.

Description

Selective laser melting system, gas circulation device and printing method

Technical Field

The embodiment of the invention belongs to the technical field of additive manufacturing equipment, and particularly relates to a selective laser melting system, a gas circulation device applied to the selective laser melting system and a printing method.

Background

The existing additive manufacturing equipment widely adopts Selective Laser Melting (SLM), SLM is an additive manufacturing technology for directly forming metal parts, the technology is an incremental manufacturing method for cladding and accumulating a forming material layer by using Laser focusing according to a CAD model, wherein the temperature, oxygen concentration and speed of protective gas flowing through the surface of the forming material (especially metal powder and plastic powder) in a forming cavity all affect the quality of a printed product, for example, when printing operation is performed without protective gas protection, elements such as Fe, C, Si, Mn, Ti, Ca and the like contained in the forming material are generally easy to chemically react with oxygen and nitrogen in the air, a layer of oxide is formed on the surface of liquid metal in a printing area, the wettability of the liquid metal is reduced, and the problems of spheroidization, cracking, slag inclusion and the like of the printed product are caused, sometimes even burning and explosion, so that it is necessary to inject a protective gas into the forming chamber to keep the oxygen content in the forming chamber below a certain value; in addition, when the forming material is melted at high temperature to generate splash during the printing operation under the protection of protective gas, so that a large amount of smoke and splash particles are accumulated in the forming cavity, the impurities are mixed with the forming material and are welded into the finished product by laser, the printed finished product has defects, smoke is deposited on the laser transmission glass to attenuate the input of laser energy, meanwhile, the smoke and the splash particles on the upper part of the forming area can absorb and reflect part of the energy of the laser, the energy of the laser on a focusing surface is greatly weakened, the forming material cannot absorb enough energy to be melted sufficiently, and therefore, the gas in the forming cavity needs to be purified during the processing process.

The inventor finds that the prior art has the following problems in the process of implementing the invention:

1. oxygen in the equipment is insufficiently removed, for example, when the selective laser melting equipment adds a forming material, high-purity protective gas is difficult to enter the processing material due to the possible contact of the material and air, so that the oxygen concentration is changed in the process of printing operation, and if the oxygen content in the processing material is too high, the problem of insufficient oxygen removal is generated, and the printing effect is influenced;

2. the oxygen removal time is too long, the existing scheme replaces the gas of equipment and a circulating gas circuit by using a normal-pressure convection mode before processing, long time is consumed to enable the oxygen concentration of a forming cavity to meet the processing requirement, and the working efficiency is low.

Disclosure of Invention

In order to solve the above problems, embodiments of the present invention provide a selective laser melting system to solve the problem in the prior art that oxygen is not sufficiently removed or oxygen is removed for a long time in the selective laser melting system.

In one aspect, embodiments of the present invention provide a selective laser melting system comprising a selective laser melting apparatus, a protective gas output device, and a gas circulation device, wherein the selective laser melting apparatus comprises a forming chamber, a pressure gauge disposed on a wall of the forming chamber, and an oxygen transducer; the gas circulation device comprises a shell, and a vacuumizing assembly and a gas circulation filtering assembly which are arranged in an inner cavity of the shell;

the forming cavity and the gas circulation filtering assembly form a first gas path, the protective gas output device, the forming cavity and the vacuumizing assembly form a second gas path, the protective gas output device and the gas circulation filtering assembly form a third gas path, each gas path comprises a plurality of connecting pieces, the first gas path, the second gas path and the third gas path are interconnected through a part of the connecting pieces in a shared mode, and each connecting piece comprises a connecting pipe and a gas path switch.

Further, the gas circuit switch on the first gas circuit comprises a first vacuum baffle valve and a second vacuum baffle valve, the gas circuit switch on the second gas circuit comprises a first electromagnetic valve and a third vacuum baffle valve, and the gas circuit switch on the third gas circuit comprises a second electromagnetic valve and a third electromagnetic valve;

the connecting pipe connected with the protective gas output device comprises a first gas pipe and a second gas pipe, the connecting pipe communicated with the forming cavity comprises a vacuumizing gas outlet pipe, a circulating gas outlet pipe and a circulating gas inlet pipe, the connecting pipe connected with the vacuumizing assembly comprises a vacuumizing gas inlet pipe, and the connecting pipe connected with the gas circulating and filtering assembly comprises a filtering gas inlet pipe and a filtering gas outlet pipe;

the circulating air outlet pipe is connected with the filtering air inlet pipe through a first vacuum baffle valve, and the filtering air outlet pipe is connected with the circulating air inlet pipe through a second vacuum baffle valve;

the first gas transmission pipe is connected with the circulating gas inlet pipe through a first electromagnetic valve, and the vacuumizing gas outlet pipe is connected with the vacuumizing gas inlet pipe through a third vacuum baffle valve;

the second air delivery pipe is connected with the filtering air inlet pipe through a second electromagnetic valve;

and the filtering air outlet pipe is also connected with a filtering air outlet branch pipe through a third electromagnetic valve.

Further, the gas circulation filter assembly comprises a first filter, a fourth vacuum flapper valve, a fifth vacuum flapper valve, a gas circulation power plant and a fourth solenoid valve;

the fourth vacuum baffle valve, the first filter, the fifth vacuum baffle valve and the gas circulation power device are sequentially connected through connecting pipes, the fourth vacuum baffle valve is also connected with the filtering gas inlet pipe, and the gas circulation power device is also connected with the filtering gas outlet pipe;

one end of the fourth electromagnetic valve is communicated with the filtering air inlet pipe through a connecting pipe, and the other end of the fourth electromagnetic valve is communicated with a connecting pipe between the fifth vacuum baffle valve and the gas circulation power device through a connecting pipe.

Furthermore, the vacuumizing assembly comprises a second filter, an electromagnetic vacuum belt inflation valve, a vacuum pump and a third filter, the second filter, the electromagnetic vacuum belt inflation valve, the vacuum pump and the third filter are sequentially connected through a connecting pipe, and the second filter is further connected with the vacuumizing air inlet pipe.

Furthermore, a silencer is arranged in the inner cavity of the shell, and the filtering air outlet branch pipe penetrates through the shell and is connected with the silencer.

Furthermore, a flowmeter is also arranged on the filtering air outlet pipe.

Further, the first air delivery pipe is also provided with an air flow speed regulating valve.

Further, a pressure relief valve is arranged on the wall of the forming cavity.

On the other hand, an embodiment of the present invention provides a gas circulation device, which is applied to a selective laser melting system, and the gas circulation device includes a housing, and a vacuum pumping assembly and a gas circulation filtering assembly that are arranged in an inner cavity of the housing, the vacuum pumping assembly is connected to a vacuum pumping air inlet pipe, and the gas circulation filtering assembly is connected to a filtering air inlet pipe and a filtering air outlet pipe, wherein:

the gas circulation filtering assembly comprises a first filter, a fourth vacuum baffle valve, a fifth vacuum baffle valve, a gas circulation power device and a fourth electromagnetic valve;

Further, the gas circulation power device is a vortex fan.

On the other hand, an embodiment of the present invention further provides a printing method applied to the above selective laser melting system, including:

closing a gas path switch in the first gas path, a gas path switch between the protective gas output device and the forming cavity in the second gas path, and opening a gas path switch between the vacuumizing assembly and the forming cavity in the second gas path and a gas path switch in the third gas path;

starting the protective gas output device, carrying out deoxidization operation on the third gas path, and simultaneously starting the vacuumizing assembly to carry out vacuumizing operation on the forming cavity;

when the pressure gauge detects that the air pressure in the forming cavity reaches a preset air pressure range, closing an air path switch between the vacuumizing assembly and the forming cavity in the second air path and an air path switch in the third air path;

stopping the operation of the vacuumizing assembly, starting a gas path switch between the protective gas output device and the forming cavity in the second gas path, and injecting protective gas into the forming cavity;

when the pressure gauge detects that the air pressure in the forming cavity reaches normal pressure, the protective gas output device in the second air path and an air path switch between the protective gas output device and the forming cavity are closed;

when the oxygen transmitter detects that the oxygen content in the forming cavity does not reach a preset range, repeating the previous steps until the oxygen content in the forming cavity reaches the preset range;

and opening a gas path switch in the first gas path, and starting the gas circulation filtering assembly and the selective laser melting equipment to perform printing operation and gas circulation filtering operation.

Further, the method comprises:

when printing operation is carried out, if the flowmeter on the first gas path detects that the gas flow of the first gas path is lower than a preset threshold value, the gas circulation filtering assembly and the selective laser melting equipment are stopped from operating, and a gas path switch in the first gas path is closed;

replacing the filter in the gas circulation filter assembly and the vacuum baffle valves at the two ends of the filter;

after the replacement is completed, the pipeline in the third gas path and the gas circulation filtering assembly are subjected to deoxidization operation, and after the deoxidization operation is completed, the gas circulation filtering assembly and the selective laser melting equipment are restarted to perform printing operation and gas circulation filtering operation.

Further, the operation of removing oxygen to the pipeline in the third gas path and the gas circulation filter assembly, after removing oxygen, restarting the gas circulation filter assembly and the selective laser melting equipment to perform printing operation and gas circulation filter operation includes:

if the interior of a filter in the gas circulation filtering assembly after replacement is protective gas, opening a gas circuit switch in the third gas circuit and gas circuit switches on a pipeline which is integrally connected in parallel with the filter and vacuum baffle valves at two ends of the filter, and carrying out deoxidization operation; after deoxygenation is completed, closing a gas path switch in the third gas path and gas path switches on the pipelines which are integrally connected in parallel with the filter and vacuum flapper valves at two ends of the filter, then opening the gas path switch in the first gas path and the vacuum flapper valves at two ends of the filter, and restarting the gas circulation filtering assembly and the selective laser melting equipment to perform printing operation and gas circulation filtering operation;

if the interior of the filter in the gas circulation filtering assembly after replacement is air, opening a gas circuit switch in the third gas circuit, a gas circuit switch on a pipeline which is integrally connected in parallel with the filter and vacuum baffle valves at two ends of the filter, and opening the vacuum baffle valves at two ends of the filter to perform oxygen removal operation; and after deoxygenation is completed, closing the gas path switch in the third gas path and the gas path switches on the pipelines which are integrally connected in parallel with the filter and the vacuum baffle valves at the two ends of the filter, then opening the gas path switch in the first gas path, and restarting the gas circulation filtering assembly and the selective laser melting equipment to perform printing operation and gas circulation filtering operation.

According to the scheme provided by the embodiment of the invention, the forming cavity in the selective laser melting system is deaerated in a mode of vacuumizing the forming cavity by the vacuumizing assembly and then injecting protective gas, so that the deaerating efficiency in the forming material in the forming cavity can be improved, meanwhile, oxygen in a pipeline in a third gas path and in the gas circulation filtering assembly is removed in a normal-pressure convection mode, and the oxygen is synchronous with the deaerating in the forming cavity in time, so that the deaerating time can be further reduced, the integral deaerating speed is accelerated, and the printing efficiency can be further improved; in addition, the oxygen concentration in the forming cavity can be monitored in real time by arranging the oxygen transmitter, and the automatic adjustment of the oxygen concentration in the circulating gas circuit can be realized; meanwhile, the smoke dust in the forming cavity is taken away in a mode of circulating protective gas, the smoke dust is filtered by the gas circulating filter assembly, and the filtered gas is refilled into the forming cavity, so that the protective gas can be reused.

Drawings

While the drawings needed to describe the invention or prior art arrangements in a more complete description of the embodiments or prior art are briefly described below, it should be apparent that the drawings described below are illustrative of some embodiments of the invention and that other drawings may be derived therefrom by those skilled in the art without the benefit of the inventive faculty.

FIG. 1 is a block diagram of a selective laser melting system according to an embodiment of the present invention;

FIG. 2 is a block diagram of another alternative embodiment of a selective laser melting system according to the present invention;

fig. 3 is a block diagram of a gas circulation device according to a second embodiment of the present invention;

fig. 4 is another block diagram of the gas circulation device according to the second embodiment of the present invention;

FIG. 5 is a flowchart of a printing method according to a third embodiment of the present invention;

fig. 6 is another flowchart of a printing method according to a third embodiment of the present invention.

Detailed Description

In order to make the technical solutions of the present invention better understood, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The terms "first," "second," and the like in the description and claims of the present invention and in the above-described drawings are used for distinguishing between different objects and not for describing a particular order. Furthermore, the terms "include" and "have," as well as any variations thereof, are intended to cover non-exclusive inclusions. For example, a process, method, system, article, or apparatus that comprises a list of steps or elements is not limited to only those steps or elements listed, but may alternatively include other steps or elements not listed, or inherent to such process, method, article, or apparatus.

Reference herein to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the invention. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are separate or alternative embodiments mutually exclusive of other embodiments. It is explicitly and implicitly understood by one skilled in the art that the embodiments described herein can be combined with other embodiments.

Example one

Referring to fig. 1, there is shown a block diagram illustrating an alternative configuration of a selective laser melting system provided by an embodiment of the present invention, the system including a selective laser melting apparatus 10, a protective gas output device 20, and a gas circulation device 30, wherein the selective laser melting apparatus 10 includes a forming chamber 11, a pressure gauge 12 provided on a wall of the forming chamber 11, and an oxygen transducer 13; the gas circulation device 30 comprises a shell 31, and an evacuation assembly 32 and a gas circulation filter assembly 33 which are arranged in the inner cavity of the shell 31, and the protective gas output device 20 is used for delivering protective gas to the selective laser melting device 10 and the gas circulation device 30, wherein the protective gas is helium or inert gas, such as argon;

the forming cavity 11 and the gas circulation filtering component 33 form a first gas path, the protective gas output device 20, the forming cavity 11 and the vacuumizing component 32 form a second gas path, the protective gas output device 20 and the gas circulation filtering component 33 form a third gas path, each gas path comprises a plurality of connecting pieces, the first gas path, the second gas path and the third gas path are interconnected through part of common connecting pieces, and each connecting piece comprises a connecting pipe and a gas path switch.

In this embodiment, the first gas path is a gas circulation filtering gas path, when a printing operation is performed, gas flows in the first gas path in a circulation manner, and the gas circulation filtering component 33 can filter waste gas smoke or dust waste slag generated in the forming cavity 11, so that defects of a printed finished product caused by welding of the waste gas smoke or the dust waste slag to the printed finished product by laser are avoided, and energy attenuation of laser on a processing surface caused by deposition of the waste gas smoke or the dust waste slag on laser projection glass is avoided;

the second gas path is a vacuumizing gas path, so that the vacuumizing assembly 32 can pump air out of the forming cavity 11 in the process of deoxidizing the selective laser melting system, the forming cavity 11 forms a vacuum environment, air among particle gaps in the forming material is pumped out quickly when the vacuumizing assembly 32 performs vacuumizing operation, a low-vacuum environment is formed among the particle gaps of the forming material, and favorable precondition is provided for that protective gas can quickly permeate into the particle gaps of the forming material when the protective gas is injected into the forming cavity 11;

the third gas path is used for removing oxygen from the pipelines of other parts except the forming cavity 11 in the first gas path before gas circulation filtering, specifically, protective gas in the protective gas output device 20 is injected into the third gas path, oxygen in the pipelines in the third gas path and the inside of the gas circulation filtering assembly 33 is removed in a normal-pressure convection mode, oxygen in the pipelines and the inside of the gas circulation filtering assembly 33 is prevented from entering the forming cavity 11 when gas circulation filtering is carried out in the printing operation process, oxygen concentration in the forming cavity 11 is prevented from being increased, and improvement of the quality of printed finished products is facilitated.

As an alternative to the embodiment of the present invention, the air path switch on the first air path includes a first vacuum flapper valve 41 and a second vacuum flapper valve 42, the air path switch on the second air path includes a first electromagnetic valve 51 and a third vacuum flapper valve 43, and the air path switch on the third air path includes a second electromagnetic valve 52 and a third electromagnetic valve 53;

further, in the present embodiment, the connection pipe connected to the protective gas output device 20 includes a first gas pipe 61 and a second gas pipe 62, the connection pipe connected to the forming cavity 11 includes a vacuuming gas outlet pipe 63, a circulating gas outlet pipe 64, and a circulating gas inlet pipe 65, the connection pipe connected to the vacuuming assembly 32 includes a vacuuming gas inlet pipe 66, and the connection pipe connected to the gas circulating and filtering assembly 33 includes a filtering gas inlet pipe 67 and a filtering gas outlet pipe 68;

specifically, the circulating air outlet pipe 64 is connected with the filtering air inlet pipe 67 through a first vacuum baffle valve 41, and the filtering air outlet pipe 68 is connected with the circulating air inlet pipe 65 through a second vacuum baffle valve 42; the circulating air outlet pipe 64 and the circulating air inlet pipe 65 are respectively communicated with the forming cavity 11, and the filtering air inlet pipe 67 and the filtering air outlet pipe 68 are respectively connected with two ends of the air circulating filtering component 33, so that a first air path is formed;

the first air delivery pipe 61 is connected with a circulating air inlet pipe 65 through a first electromagnetic valve 51, the vacuumizing air outlet pipe 63 is connected with a vacuumizing air inlet pipe 66 through a third vacuum baffle valve 43, the vacuumizing air inlet pipe 66 is connected with a vacuumizing assembly 32, and the circulating air inlet pipe 65 and the vacuumizing air outlet pipe 63 are respectively communicated with the forming cavity 11, so that a second air path is formed;

the second air pipe 62 is connected with a filtering air inlet pipe 67 through a second electromagnetic valve 52, the second electromagnetic valve 52 is close to the first vacuum baffle valve 41, and the filtering air outlet pipe 68 is also connected with a filtering air outlet branch pipe 69, so that a third air path is formed, wherein the filtering air outlet branch pipe 69 is provided with a third electromagnetic valve 53, and the inlet of the filtering air outlet branch pipe 69 and the third electromagnetic valve 53 are arranged close to the second vacuum baffle valve 42;

as an alternative to the embodiment of the present invention, the air circulation filtering assembly 33 is used for purifying the air in the first air path, and includes a first filter 331, a fourth vacuum flapper valve 332, a fifth vacuum flapper valve 333, an air circulation power device 334 and a fourth solenoid valve 335; the fourth vacuum flapper valve 332, the first filter 331, the fifth vacuum flapper valve 333 and the gas circulation power device 334 are connected in sequence through connecting pipes, the fourth vacuum flapper valve 332 is also connected with the filtering gas inlet pipe 67, and the gas circulation power device 334 is also connected with the filtering gas outlet pipe 68; one end of the fourth electromagnetic valve 335 is communicated with the filtering air inlet pipe 67 through a connecting pipe, and the other end is communicated with a connecting pipe between the fifth vacuum flapper valve 333 and the gas circulation power unit 334 through a connecting pipe, namely, a structure composed of the fourth vacuum flapper valve 332, the first filter 331 and the fifth vacuum flapper valve 333 is connected with the fourth electromagnetic valve 335 in parallel.

The gas circulation power device 334 is used for providing a power source for gas circulation in the first gas path, and in this embodiment, the gas circulation power device 334 is a vortex fan;

the first filter 331 is used to filter the smoke from the circulating gas in the first gas path, and maintain a clean printing environment for the forming chamber 11.

In this embodiment, the fourth solenoid valve 335 and the connecting pipe at both ends thereof are used to assist the oxygen removing operation of the third air path after the first filter 331 is replaced, wherein the fourth vacuum flapper valve 332 and the fifth vacuum flapper valve 333 are replaced together with the first filter 331 when the first filter 331 is replaced, and accordingly, the fourth vacuum flapper valve 332 and the fifth vacuum flapper valve 333 are manual vacuum flapper valves in this embodiment for installation and removal; the process of replacing the first filter 331 and the pipeline oxygen removal operation after the replacement will be described in detail later in this embodiment.

Further, in the present embodiment, the vacuum-pumping assembly 32 is used for performing vacuum-pumping treatment on the forming cavity 11 during the process of removing oxygen from the selective laser melting system, and includes a second filter 321, an electromagnetic vacuum belt inflation valve 322, a vacuum pump 323, and a third filter 324, wherein the second filter 321, the electromagnetic vacuum belt inflation valve 322, the vacuum pump 323, and the third filter 324 are sequentially connected by a connecting pipe, and the second filter 321 is further connected to the vacuum-pumping air inlet pipe 66.

The second filter 321 is used as a pre-filter of the vacuum pump 323 and is used for filtering smoke dust and particulate matters in the gas before the gas enters the vacuum pump 323 so as to reduce the abrasion of components in the vacuum pump 323;

the electromagnetic vacuum belt charging valve 322 is used for preventing liquid substances in the vacuum pump 323 from flowing back into the vacuumizing air inlet pipe 66 and the forming cavity 11 due to pipeline negative pressure after the vacuum pump 323 is powered off, for example, when the vacuum pump 323 is a vacuum oil pump, oil in the vacuum oil pump can be prevented from flowing into the vacuumizing air inlet pipe 66 and the forming cavity 11 due to pipeline negative pressure, so that pollution to the vacuumizing air inlet pipe 66 and the forming cavity 11 is avoided, and a clean printing operation environment is ensured;

the third filter 324 is used as a post-filter of the vacuum pump 323 for further filtering the exhaust gas of the vacuum pump 323, and in this embodiment, the third filter 324 is a soot filter for filtering soot in the exhaust gas of the vacuum pump 323.

In this embodiment, the vacuum pumping assembly 32 performs vacuum pumping on the forming cavity 11 through the vacuum pump 323, so as to form a vacuum environment in the forming cavity 11, and provide a precondition for removing oxygen in the forming cavity 11 and the forming material, optionally, in this embodiment, the air pressure in the forming cavity 11 after the vacuum pumping reaches a medium vacuum pressure, that is, the air pressure in the forming cavity 11 reaches 10²Pa～10^-1Pa。

Referring to fig. 2, which is another schematic structural diagram of the selective laser melting system according to an embodiment of the present invention, in this embodiment, the inner cavity of the gas circulation device 30 is further provided with a muffler 34, and the filtering gas outlet branch pipe 69 passes through the housing 31 and is connected to the muffler 34, so that during the oxygen removing operation of the third gas path, the redundant protective gas in the third gas path can be injected into the gas circulation device 31 and remain in the inner cavity of the gas circulation device 30, thereby reducing the oxygen concentration in the inner cavity of the gas circulation device 30, providing a protective atmosphere for the components in the vacuum pumping assembly 32 and the gas circulation filtering assembly 33, and facilitating to maintain the oxygen concentration in each gas path of the selective laser melting system stable for a longer time.

As an alternative of this embodiment, the first gas pipe 61 is further provided with an air flow rate adjusting valve 70, which is used for adjusting the air flow rate in the third gas path when the oxygen in the third gas path is removed, so that the oxygen removing process of the third gas path and the vacuum-pumping process of the forming cavity 11 are synchronized at a time node, the vacuum-pumping process of the forming cavity 11 is completed, the oxygen removing operation of the third gas path is completed at the same time, the time required by the oxygen removing operation is reduced, and the complexity of the overall operation is reduced.

As an alternative of this embodiment, a flow meter 80 is further installed on the pipeline of the first gas path, and is used for acquiring the gas flow rate in the first gas path in real time when performing the circulating filtration on the gas, and when the gas flow rate in the first gas path is lower than a preset threshold, the replacement of the first filter 331 in the gas circulating filtration component 33 is prompted, optionally, in this embodiment, the flow meter 80 is installed on the filtered gas pipe 68, so that the change of the gas flow rate in the first gas path can be detected more quickly, and the replacement of the first filter 331 is prompted more timely.

As an alternative to this embodiment, a pressure relief valve 14 is further provided on the wall of the forming chamber 11 to prevent the problem of excessive pressure inside the forming chamber 11 caused by failure of the industrial personal computer or the valves on the pipes in the selective laser melting system, and in this embodiment, the pressure relief valve 14 includes an overpressure relief valve 141 and a safety relief valve 142.

The operation of the selective laser melting system provided by the embodiment of the present invention is described in detail with reference to fig. 1 and 2, and after the selective laser melting system is installed, the operation includes an oxygen removal step and a circulating filtration step.

Before the oxygen removal step is performed, it is assumed that all of the pneumatic switches in the selective laser melting system are closed, including the first vacuum flapper valve 41 and the second vacuum flapper valve 42 in the first pneumatic circuit, the first solenoid valve 51 and the third vacuum flapper valve 43 in the second pneumatic circuit, the second solenoid valve 52 and the third solenoid valve 53 in the third pneumatic circuit, the fourth vacuum flapper valve 332, the fifth vacuum flapper valve 333 and the fourth solenoid valve 335 in the gas circulation filter assembly 33, and the solenoid vacuum belt charge valve 322 in the evacuation assembly 32.

Wherein the oxygen removing step comprises:

after closing the cavity door of the forming cavity 11, the third vacuum flapper valve 43 in the second gas path is opened, and the second solenoid valve 52 and the third solenoid valve 53 in the third gas path are opened, and the other gas path switches are maintained in a closed state;

starting the protective gas output device 20, so that the protective gas output device 20 injects protective gas into the third gas path through the second gas pipe 62, and deoxidizing the pipeline in the third gas path and the inside of the gas circulation filtering assembly 33 by using a normal pressure convection mode; simultaneously, an electromagnetic vacuum belt inflation valve 322 in the vacuumizing assembly 32 is opened, a vacuum pump 323 is started, vacuumizing operation is carried out on the forming cavity 11, the pressure gauge 12 detects the air pressure in the forming cavity 11 in real time, and when the pressure gauge 12 detects that the air pressure in the forming cavity 11 reaches a preset air pressure range, the third vacuum baffle valve 43 in the second air path and the second electromagnetic valve 52 and the third electromagnetic valve 53 in the third air path are closed;

then, the operation of the vacuum pump 323 in the vacuum pumping assembly 32 is stopped, the electromagnetic vacuum belt charging valve 322 is closed, the first electromagnetic valve 51 in the second gas path is opened, so that the protective gas output device 20 injects the protective gas into the forming cavity 11 through the first gas pipe 61, when the pressure gauge 12 detects that the gas pressure in the forming cavity 11 reaches the normal pressure, the first electromagnetic valve 51 in the second gas path is closed, and the protective gas output device 20 is closed, at this time, if the oxygen content in the forming cavity 11 detected by the oxygen transmitter 13 does not reach the preset range, the previous processes of vacuum pumping of the forming cavity 11 and injecting the protective gas are repeated until the oxygen content in the forming cavity 11 reaches the preset range.

In this way, oxygen in the forming cavity 11 can be removed quickly, oxygen in the forming material can be extracted, and protective gas can permeate into the forming material, so that the oxygen content in the forming material is effectively reduced.

In the oxygen removal step, the preset air pressure range is 10 in the present embodiment²Pa～10^-1Pa, which can be adjusted according to actual conditions.

In the oxygen removing step, the air flow rate in the third air path can be adjusted through the air flow rate adjusting valve 70, so that the oxygen discharging process of the third air path and the vacuumizing process of the forming cavity 11 are synchronized on a time node.

In the oxygen removing step, after the forming cavity 11 is subjected to one-time vacuum pumping and protective gas injection operation, when the oxygen transmitter 13 detects that the oxygen content in the forming cavity 11 does not reach the preset range, the preset air pressure range to be reached by the vacuum pumping operation on the forming cavity 11 can be further adjusted, so that when a forming material is subsequently supplemented in the forming cavity 11 to continue printing operation or new printing operation is performed after a printed finished product is taken out, the oxygen removing operation process can enable the oxygen content in the forming cavity 11 to reach the preset range only by performing one-time vacuum pumping and protective gas injection operation on the forming cavity 11.

In the oxygen removing step, as shown in fig. 2, if the filtered gas outlet branch pipe 69 passes through the housing 31 and is connected to the muffler 34 of the inner cavity, after the oxygen removing operation of the selective laser melting system is completed, the exhaust gas of the vacuum pump 323 is released into the inner cavity of the gas circulation device 30 after evacuation, and simultaneously the excess protective gas in the third gas path is retained in the inner cavity of the gas circulation device 30, so that the oxygen concentration in the inner cavity of the gas circulation device 30 can be reduced, and the parts in the evacuation assembly 32 and the gas circulation filter assembly 33 can be protected by the protective atmosphere.

After the step of deoxidizing the selective laser melting system is completed, the gas path switches in the selective laser melting system are all in a closed state again, and at the moment, the steps of printing operation and gas circulating filtration can be carried out.

Wherein, the step of circulating filtration comprises:

and opening the first vacuum flapper valve 41 and the second vacuum flapper valve 42 in the first gas path to communicate the forming cavity 11 with the gas circulation filter assembly 33 in the gas circulation device 33, opening the fourth vacuum flapper valve 332 and the fifth vacuum flapper valve 333 in the gas circulation filter assembly 33 at the moment, starting the gas circulation power device 334 to enable the gas in the first gas path to circularly flow, starting the selective laser melting equipment 10 to perform printing operation, taking away the smoke dust splashed in the forming cavity 11 in a protective gas circulation mode in the printing process, performing circulation filtration through the first filter 331, and refilling the filtered gas into the forming cavity 11 to realize the reuse of the protective gas.

In the step of circulating and filtering, the powder spreading operation and the laser selective melting operation are performed alternately in the printing operation, when the powder spreading operation is performed, the power of the gas circulation power device 334 needs to be reduced, so that the gas flow in the first gas path is reduced to meet the requirement when the powder is spread, the gas circulation power device 334 recovers to normal output power after the powder spreading is completed, for example, when the gas circulation power device 334 is a vortex fan, the vortex fan reduces the rotation speed during the powder spreading so that the gas flow in the first gas path is reduced to meet the requirement when the powder is spread, the rotation speed of the vortex fan is increased to normal rotation speed again after the powder spreading is completed, and the gas flow can be monitored through the flowmeter 80 on the first gas path.

In the step of circulating and filtering, the method also comprises the step of monitoring the air pressure in the forming cavity 11 in real time through the pressure gauge 12, and if the air pressure in the forming cavity 11 is higher than the normal pressure by 2 KPa-5 KPa, the pressure relief valve 14 is started, so that the condition of negative pressure at the air inlet of the gas circulation power device 334 can be prevented.

In the step of circulating and filtering, after the first vacuum flapper valve 41 and the second vacuum flapper valve 42 in the first gas path are opened to communicate the forming cavity 11 with the gas circulating and filtering assembly 33 in the gas circulating device 33, and the gas circulating and power device 334 of the gas circulating and filtering assembly 33 is started to circulate the gas in the first gas path, the method further comprises the steps of measuring the concentration of the oxygen in the forming cavity 11 in real time through the oxygen transmitter 13 to judge whether the protective gas in the forming cavity 11 reaches the concentration required for printing operation, and if the concentration does not reach the requirement, repeating the step of removing oxygen until the protective gas in the forming cavity 11 reaches the concentration required for printing operation.

During the above-described operation of the selective laser melting system, the fourth solenoid valve 335 is always in a closed state.

Further, in the process of the printing operation, if the flow meter 80 detects that the gas flow in the first gas path is lower than the preset threshold, the replacement of the first filter 331 is prompted, and correspondingly, the working process of the selective laser melting system in this embodiment further includes steps of replacing the first filter on line and removing oxygen after the replacement, specifically including:

when the flowmeter 80 detects that the gas flow of the first gas path does not reach the standard and the gas circulation power device 334 normally operates, the industrial personal computer of the selective laser melting system prompts the replacement of the first filter 331, and at the moment, the gas circulation power device 334, the first vacuum baffle valve 41 and the second vacuum baffle valve 42 are closed; the fourth vacuum flapper valve 332 and the fifth vacuum flapper valve 333 are then closed, the first filter 331, the fourth vacuum flapper valve 332 and the fifth vacuum flapper valve 333 are removed in their entirety, and the first filter 331, the fourth vacuum flapper valve 332 and the fifth vacuum flapper valve 333 are replaced with new ones.

After the replacement is completed, if the inside of the replaced first filter 331 is the protective gas, the third electromagnetic valve 53 and the fourth electromagnetic valve 335 are firstly opened, then the second electromagnetic valve 52 and the protective gas output device 20 are opened, so that the protective gas output device 20 injects the protective gas into the third gas path through the second gas pipe 62, the oxygen removal operation is performed on the third gas path again in a normal pressure convection mode, oxygen in the pipe and the inside of the gas circulation power device 334 in the third gas path is removed, then the third electromagnetic valve 53, the fourth electromagnetic valve 335, the second electromagnetic valve 52 and the protective gas output device 20 are closed, and the replaced fourth vacuum flapper valve 332 and the fifth vacuum flapper valve 333 are opened, so that after the gas circulation filtering assembly and the selective laser melting device are restarted, the selective laser melting system can continue the printing operation;

if the inside of the replaced first filter 331 is air, the third solenoid valve 53 and the fourth solenoid valve 335 are opened first, the second solenoid valve 52 and the replaced fourth 332 and fifth 333 vacuum flapper valves are then opened, then the protective gas output device 20 is started, so that the protective gas output device 20 injects protective gas into the third gas path through the second gas pipe 62, the oxygen removal operation is performed again on the third gas path by using the normal pressure convection mode, oxygen in the pipeline in the third gas path, the gas circulation power device 334 and the replaced first filter 331 is removed, the third solenoid valve 53, the fourth solenoid valve 335, the second solenoid valve 52 and the protective gas output device 20 are then closed, after the gas circulation filter assembly and the selective laser melting device are restarted, the selective laser melting system can continue to perform printing operation.

Because the new first filter 331, the fourth vacuum flapper valve 332 and the fifth vacuum flapper valve 333 are in a protective gas protection state in the whole, only the oxygen in the other part of the third gas path needs to be removed after the replacement is completed, compared with the mode that butterfly valves are arranged at two ends of the first filter 331, the first filter 331 and two butterfly valves connected with the first filter 331 in the prior art are replaced, the whole replacement mode of the present application can avoid the influence of the replacement filter on the oxygen content in the forming cavity 11.

Compared with the prior art, the selective laser melting system provided by the embodiment of the invention at least has the following beneficial effects:

1. the method has the advantages that the forming cavity 11 in the selective laser melting system is deaerated by vacuumizing and then injecting protective gas, the deaerating efficiency in the forming material in the forming cavity 11 can be improved, the consumption of the protective gas can be reduced compared with a convection mode, the deaerating speed can be increased, the oxygen concentration in the forming cavity 11 can be monitored in real time by arranging the oxygen transmitter 13, and the automatic adjustment of the oxygen concentration in a circulating gas circuit can be realized; meanwhile, the smoke dust in the forming cavity 11 is taken away in a mode of circulating protective gas, the smoke dust is filtered by the first filter 331, and the filtered gas is refilled into the forming cavity 11, so that the protective gas is reused.

2. The oxygen in the pipeline and the gas circulation filtering component in the third gas path is removed by using a normal pressure convection mode, and is synchronous with the oxygen removal in the forming cavity 11 in time, so that the oxygen removal time can be reduced, and the oxygen removal speed is improved.

3. The filter can be replaced online, the first filter 331, the fourth vacuum flapper valve 332 and the fifth vacuum flapper valve 333 in the gas circulation device 30 can be replaced integrally on the premise of not influencing the oxygen content of the forming cavity 11 during printing and processing, the problem of oxygen concentration increase of a circulation gas path caused by the fact that air in a pipeline at the rear part of the first filter 331 cannot be replaced independently is solved, and the functions of vacuumizing and deoxidizing the forming cavity 11 of the selective laser melting system and the online replacement of the filter can be integrated.

4. The excess protective gas can be charged into the gas circulation device 30 to protect the components inside the gas circulation device 30 from the protective atmosphere.

Example two

Referring to fig. 3, which is a schematic structural diagram illustrating a gas circulation device according to an embodiment of the present invention, the gas circulation device includes a housing 31, and a vacuum pumping assembly 32 and a gas circulation filter assembly 33 which are disposed in an inner cavity of the housing 31, the vacuum pumping assembly 32 is connected to a vacuum pumping inlet pipe 66, and the gas circulation filter assembly 33 is connected to a filter inlet pipe 67 and a filter outlet pipe 68, wherein:

the gas circulation filter assembly 33 is used for cleaning the air in the forming chamber 11 and associated piping in the selective laser melting system and includes a first filter 331, a fourth vacuum flapper valve 332, a fifth vacuum flapper valve 333, a gas circulation power unit 334 and a fourth solenoid valve 335;

the fourth vacuum flapper valve 332, the first filter 331, the fifth vacuum flapper valve 333 and the gas circulation power device 334 are sequentially connected through connecting pipes, the fourth vacuum flapper valve 332 is also connected with the filtering gas inlet pipe 67, the gas circulation power device 334 is also connected with the filtering gas outlet pipe 68, and the filtering gas inlet pipe 67 and the filtering gas outlet pipe 68 are respectively connected to the forming cavity 11 through gas circuit switches;

one end of the fourth electromagnetic valve 335 is communicated with the filtering air inlet pipe 67 through a connecting pipe, and the other end is communicated with a connecting pipe between the fifth vacuum flapper valve 333 and the gas circulation power unit 334 through a connecting pipe, namely, a structure composed of the fourth vacuum flapper valve 332, the first filter 331 and the fifth vacuum flapper valve 333 is connected with the fourth electromagnetic valve 335 in parallel.

Wherein, the gas circulation power device 334 is used for providing a power source for the gas circulation filtration of the selective laser melting system, in this embodiment, the gas circulation power device 334 is a vortex fan;

the first filter 331 is used to filter fumes from the circulating gas of the selective laser melting system to maintain a clean print job environment for the forming chamber 11.

In this embodiment, the fourth solenoid valve 335 and the connecting tube at both ends thereof are used as an auxiliary gas path for performing oxygen removal operation on the gas circulation filter assembly 33 and the related pipelines after replacing the first filter 331, wherein the fourth 332 and fifth 333 vacuum flapper valves are replaced along with the first filter 331, when the first filter 331 is replaced, and, correspondingly, the fourth 332 and fifth 333 vacuum flapper valves are manual vacuum flapper valves in this embodiment, so that the first filter 331, the fourth vacuum flapper valve 332 and the fifth vacuum flapper valve 333 are assembled and disassembled as a whole, the problem of the increase of the oxygen concentration of the circulating gas path of the selective laser melting system caused by the irreplaceability of the air in the pipeline at the rear part of the first filter 331, the integration of the functions of vacuumizing and deoxidizing the forming cavity 11 of the selective laser melting system and the online replacement of the filter can be realized.

Further, in the present embodiment, the vacuum-pumping assembly 32 is used for performing vacuum-pumping treatment on the forming cavity 11 in the selective laser melting system during the process of removing oxygen by the selective laser melting system, and includes a second filter 321, an electromagnetic vacuum belt inflation valve 322, a vacuum pump 323, and a third filter 324, where the second filter 321, the electromagnetic vacuum belt inflation valve 322, the vacuum pump 323, and the third filter 324 are sequentially connected by a connecting pipe, the second filter 321 is further connected to the vacuum-pumping air inlet pipe 66, and the vacuum-pumping air inlet pipe 66 is connected to the forming cavity 11 by an air circuit switch.

Wherein the second filter 321 is used as a pre-filter of the vacuum pump 323 and is used for filtering soot and particulate matters in the gas before the gas in the forming cavity 11 enters the vacuum pump 323 so as to reduce the abrasion of components in the vacuum pump 323;

In the embodiment, the vacuum-pumping assembly 32 pumps the forming cavity 11 of the selective laser melting system through the vacuum pump 323 to finally form the forming cavityA vacuum environment is formed in the cavity 11 to provide a precondition for removing oxygen in the cavity 11 and the forming material, and optionally, in this embodiment, the air pressure in the cavity 11 reaches a medium vacuum pressure after the vacuum process is performed, that is, the air pressure in the cavity 11 reaches 10²Pa～10^-1Pa。

Referring further to fig. 4, fig. 4 is another schematic structural diagram of the gas circulation device provided in this embodiment, the inner cavity of the gas circulation device is further provided with a muffler 34, the muffler 34 is connected to a filtering gas outlet branch pipe 69, the filtering gas outlet branch pipe 69 is connected to the filtering gas pipe 68 through a gas circuit switch (not shown), and the excess protective gas exhausted from the filtering gas pipe 68 can be injected into the gas circulation device 31 and remain in the inner cavity of the gas circulation device, so that the oxygen concentration in the inner cavity of the gas circulation device can be reduced, the parts in the vacuum pumping assembly 32 and the gas circulation filtering assembly 33 can be protected by a protective atmosphere, and the stability of the oxygen concentration in each gas circuit of the selective laser melting system can be maintained for a longer time.

In addition, the related technical contents in the first embodiment can be referred to in the gas circulation device provided by the embodiment of the invention to help understand the structure and function of the gas circulation device provided by the embodiment.

The gas circulation device provided by the embodiment of the invention can be used for vacuumizing the forming cavity in the selective laser melting system, can improve the oxygen removal efficiency in the forming material in the forming cavity, can reduce the loss of protective gas compared with a convection mode, and can accelerate the oxygen removal speed; meanwhile, the smoke dust in the forming cavity is taken away in a mode of circulating protective gas, the smoke dust is filtered by the first filter 331, and the filtered gas is refilled into the forming cavity, so that the protective gas is reused; meanwhile, the online filter replacement can be realized, the first filter 331, the fourth vacuum baffle valve 332 and the fifth vacuum baffle valve 333 in the gas circulation device are integrally replaced on the premise of not influencing the oxygen content of the forming cavity in the printing and processing of the selective laser melting system, the problem of oxygen concentration increase of a circulation gas path caused by the fact that air in a partial pipeline behind the first filter 331 is replaced independently is solved, and the functions of vacuumizing and deoxidizing the forming cavity of the selective laser melting system and the online filter replacement can be integrated into a whole; in addition, redundant protective gas can be filled into the gas circulating device, and the protective atmosphere protection of all components in the gas circulating device is realized.

EXAMPLE III

An embodiment of the present invention further provides a printing method, which is applied to the selective laser melting system of the first embodiment, in this embodiment, it is assumed that all gas path switches in the selective laser melting system are initially in an off state, and as shown in a flow chart shown in fig. 5, the method includes:

s1, keeping a gas circuit switch in the first gas circuit and a gas circuit switch between the protective gas output device and the forming cavity in the second gas circuit closed, and starting a gas circuit switch between the vacuumizing assembly and the forming cavity in the second gas circuit and a gas circuit switch in the third gas circuit;

s2, starting a protective gas output device, carrying out deoxidization operation on the third gas path, and starting a vacuumizing assembly to vacuumize the forming cavity;

s3, detecting whether the air pressure in the forming cavity reaches a preset air pressure range by a pressure gauge, if not, continuing to execute S2, otherwise, executing S4;

s4, closing an air path switch between the vacuumizing assembly in the second air path and the forming cavity and an air path switch in the third air path, and stopping the operation of the vacuumizing assembly;

s5, opening a gas path switch between the protective gas output device and the forming cavity in the second gas path, and injecting protective gas into the forming cavity;

s6, detecting whether the air pressure in the forming cavity reaches normal pressure by a pressure gauge, if not, continuing to S5, otherwise, executing S7;

s7, closing the protective gas output device in the second gas path and a gas path switch between the protective gas output device and the forming cavity;

s8, detecting whether the oxygen content in the forming cavity reaches a preset range by an oxygen transmitter, if not, repeating S1-S8, otherwise, executing S9;

and S9, opening a gas path switch in the first gas path, and starting the gas circulation filtering component and the selective laser melting equipment to perform printing operation and gas circulation filtering operation.

Referring further to fig. 2, another flowchart illustrating a printing method according to an embodiment of the present invention is based on the foregoing steps S1 to S9, and the method further includes:

s10, detecting whether the air flow of the first air path is lower than a preset threshold value by a flowmeter on the first air path, if not, continuing to execute S9, otherwise, executing S11;

s11, stopping the operation of the gas circulation filtering component and the selective laser melting equipment, and closing a gas path switch in the first gas path;

and S12, replacing the filter in the gas circulation filtering assembly and the vacuum baffle valves at two ends of the filter, after the replacement is finished, carrying out oxygen removal operation on the pipeline on the third gas path and the gas circulation filtering assembly, and after the oxygen removal is finished, restarting the gas circulation filtering assembly and the selective laser melting equipment to carry out printing operation and gas circulation filtering operation.

Wherein the process of replacing the filter and vacuum flapper valves across the filter for oxygen scavenging operation and restarting the print job in S12 includes two situations:

the first situation is as follows: if the inside of the filter in the gas circulation filtering assembly after replacement is protective gas, opening a gas circuit switch in a third gas circuit and gas circuit switches on a pipeline which is integrally connected in parallel with the vacuum baffle valves at the two ends of the filter and the filter, and carrying out deoxidization operation; and after deoxygenation is finished, closing the air path switch in the third air path and the air path switches on the pipelines which are integrally connected with the filter and the vacuum baffle valves at the two ends of the filter in parallel, then opening the air path switch in the first air path and the vacuum baffle valves at the two ends of the filter, and restarting the gas circulation filtering assembly and the selective laser melting equipment to perform printing operation and gas circulation filtering operation.

Case two: if the interior of the filter in the gas circulation filtering assembly is air after replacement, opening a gas circuit switch in a third gas circuit and gas circuit switches on a pipeline which is integrally connected with the filter and vacuum baffle valves at two ends of the filter in parallel, and opening the vacuum baffle valves at two ends of the filter to perform oxygen removal operation; and after deoxygenation is completed, closing the gas path switch in the third gas path and the gas path switches on the pipelines which are integrally connected in parallel with the vacuum baffle valves at the two ends of the filter and the filter, then opening the gas path switch in the first gas path, and restarting the gas circulation filtering assembly and the selective laser melting equipment to perform printing operation and gas circulation filtering operation.

The operation of the selective laser melting system provided by the embodiment of the present invention will be described in detail with reference to fig. 1 and 2, and after the selective laser melting system is installed, the steps of the printing method can be divided into an oxygen removal stage and a circulating filtration stage.

Prior to performing the oxygen scavenging stage, it is assumed that all of the pneumatic switches in the selective laser melting system are closed, including the first vacuum flapper valve 41 and the second vacuum flapper valve 42 in the first pneumatic circuit, the first solenoid valve 51 and the third vacuum flapper valve 43 in the second pneumatic circuit, the second solenoid valve 52 and the third solenoid valve 53 in the third pneumatic circuit, the fourth vacuum flapper valve 332, the fifth vacuum flapper valve 333 and the fourth solenoid valve 335 in the gas circulation filter assembly 33, and the solenoid vacuum belt charge valve 322 in the evacuation assembly 32.

Wherein the oxygen removal stage comprises:

In the oxygen removal stage, the predetermined pressure range is 10 in the present embodiment²Pa～10^-1Pa, which can be adjusted according to actual conditions.

In the oxygen removing stage, the air flow rate in the third air path can be adjusted through the air flow rate adjusting valve 70, so that the oxygen discharging process of the third air path and the vacuumizing process of the forming cavity 11 are synchronized on a time node.

In the deoxidizing stage, after the forming cavity 11 is subjected to one operation of vacuumizing and injecting protective gas, and the oxygen transmitter 13 detects that the oxygen content in the forming cavity 11 does not reach the preset range, the preset air pressure range to be reached by the vacuumizing operation of the forming cavity 11 can be further adjusted, so that when forming materials are subsequently supplemented in the forming cavity 11 to continue printing operation or new printing operation is performed after a printed finished product is taken out, the oxygen content in the forming cavity 11 can reach the preset range only by performing one operation of vacuumizing and injecting protective gas on the forming cavity 11 in the deoxidizing operation process.

In the oxygen removing stage, as shown in fig. 2, if the filtered gas outlet branch pipe 69 passes through the housing 31 and is connected to the muffler 34 of the inner cavity, after the oxygen removing operation of the selective laser melting system is completed, the exhaust gas of the vacuum pump 323 is released into the inner cavity of the gas circulation device 33 after vacuum pumping, and simultaneously the redundant protective gas in the third gas path is retained in the inner cavity of the gas circulation device 33, so that the oxygen concentration in the inner cavity of the gas circulation device 30 can be reduced, and the parts in the vacuum pumping assembly 32 and the gas circulation filtering assembly 33 can be protected by protective atmosphere.

And after the deoxygenation stage of the selective laser melting system is completed, the gas path switches in the selective laser melting system are all in a closed state again, and at the moment, the printing operation and the gas circulating filtration stage can be carried out.

Wherein the loop filtration phase comprises:

In the circulating filtration stage, the powder spreading operation and the laser selective melting operation are performed alternately in the printing operation, when the powder spreading operation is performed, the power of the gas circulating power device 334 needs to be reduced, so that the gas flow in the first gas path is reduced to meet the requirement when the powder is spread, the gas circulating power device 334 recovers to normal output power after the powder spreading is completed, for example, when the gas circulating power device 334 is a vortex fan, the vortex fan reduces the rotating speed during the powder spreading so that the gas flow in the first gas path is reduced to meet the requirement when the powder is spread, the rotating speed of the vortex fan is increased to normal rotating speed after the powder spreading is completed, and the gas flow can be monitored through the flowmeter 80 on the first gas path.

In the circulation filtering stage, the method also comprises the step of monitoring the air pressure in the forming cavity 11 in real time through the pressure gauge 12, and if the air pressure in the forming cavity 11 is higher than the normal pressure by 2 KPa-5 KPa, the pressure relief valve 14 is started, so that the condition of negative pressure at the air inlet of the gas circulation power device 334 can be prevented.

In the circulating and filtering stage, after the first vacuum flapper valve 41 and the second vacuum flapper valve 42 in the first gas path are opened to communicate the forming cavity 11 with the gas circulating and filtering assembly 33 in the gas circulating device 33, and the gas circulating and power device 334 of the gas circulating and filtering assembly 33 is started to circulate the gas in the first gas path, the method also comprises the steps of measuring the oxygen concentration in the forming cavity 11 in real time through the oxygen transmitter 13 to judge whether the protective gas in the forming cavity 11 reaches the concentration required for printing operation, and if the oxygen is not required, repeating the oxygen removing stage until the protective gas in the forming cavity 11 reaches the concentration required for printing operation.

Further, in the process of the printing operation, if the flow meter 80 detects that the gas flow in the first gas path is lower than the preset threshold, it will prompt to replace the first filter 331, and correspondingly, the working process of the selective laser melting system in this embodiment further includes a stage of replacing the first filter on line and removing oxygen after replacement, which specifically includes:

Compared with the prior art, the printing method provided by the embodiment of the invention at least has the following beneficial effects:

1. the method has the advantages that the forming cavity 11 in the selective laser melting system is deaerated by vacuumizing and then injecting protective gas, the deaerating efficiency in the forming material in the forming cavity 11 can be improved, the consumption of the protective gas can be reduced compared with a convection mode, the deaerating speed can be increased, the oxygen concentration in the forming cavity 11 can be monitored in real time by arranging the oxygen transmitter 13, and the automatic adjustment of the oxygen concentration in a circulating gas circuit can be realized; meanwhile, the smoke dust in the forming cavity 11 is taken away in a mode of circulating protective gas, the smoke dust is filtered by the first filter 331, the filtered gas is refilled into the forming cavity 11, the protective gas is reused, and therefore the printing quality can be effectively improved.

2. The pipeline in the third gas path and the oxygen in the gas circulation filtering component are removed by utilizing the normal pressure convection mode, and are synchronous with the deoxidization in the forming cavity 11 in time, so that the deoxidization time can be reduced, the deoxidization speed is improved, and the printing time is further saved.

3. The filter can be replaced online, the first filter 331, the fourth vacuum baffle valve 332 and the fifth vacuum baffle valve 333 in the gas circulation device 30 can be replaced integrally on the premise of not influencing the oxygen content of the forming cavity 11 in printing and processing, the problem that the oxygen concentration of a circulation gas path is increased due to the fact that air in a partial pipeline behind the first filter 331 is replaced independently is solved, the functions of vacuumizing and deoxidizing the forming cavity 11 of the selective laser melting system and the online replacement of the filter are integrated, on one hand, the printing quality can be effectively improved, and meanwhile, the printing time can be effectively saved.

4. The redundant protective gas can be filled into the gas circulation device 30, and all components in the gas circulation device 30 are protected by protective atmosphere, so that the printing quality can be effectively improved.

It is to be understood that the above-described embodiments are merely illustrative of some, but not restrictive, of the broad invention, and that the appended drawings illustrate preferred embodiments of the invention without limiting its scope. This invention may be embodied in many different forms and, on the contrary, these embodiments are provided so that this disclosure will be thorough and complete. Although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that various changes in the embodiments and modifications can be made, and equivalents may be substituted for elements thereof. All equivalent structures made by using the contents of the specification and the attached drawings of the invention can be directly or indirectly applied to other related technical fields, and are also within the protection scope of the patent of the invention.

Claims

1. A selective laser melting system, characterized in that the system comprises a selective laser melting device, a protective gas output device and a gas circulation device, wherein the selective laser melting device comprises a forming cavity, a pressure gauge and an oxygen transmitter which are arranged on the wall of the forming cavity; the gas circulation device comprises a shell, and a vacuumizing assembly and a gas circulation filtering assembly which are arranged in an inner cavity of the shell;

the forming cavity and the gas circulation filtering assembly form a first gas path for gas circulation filtering, the protective gas output device, the forming cavity and the vacuumizing assembly form a second gas path for vacuumizing and deoxidizing the forming cavity, the protective gas output device and the gas circulation filtering assembly form a third gas path for deoxidizing other parts except the forming cavity in the first gas path before gas circulation filtering, each gas path comprises a plurality of connecting pieces, the first gas path, the second gas path and the third gas path are interconnected through a part of the connecting pieces, and each connecting piece comprises a connecting pipe and a gas path switch;

the second gas circuit is used for detecting the oxygen content in the forming cavity when the gas pressure in the forming cavity after oxygen removal reaches normal pressure;

the connecting pipe connected with the gas circulation filtering assembly comprises a filtering gas inlet pipe and a filtering gas outlet pipe, and the filtering gas outlet pipe is also connected with a filtering gas outlet branch pipe through a third electromagnetic valve;

the filtering air outlet branch pipe penetrates through the shell and extends to the interior of the shell;

the gas circulation filtering component comprises a first filter and a fourth electromagnetic valve which are arranged in parallel through a connecting pipe, gas in the filtering gas inlet pipe can pass through the first filter and the fourth electromagnetic valve and then enters the filtering gas outlet pipe, and the fourth electromagnetic valve is used for auxiliary deoxidization when the first filter is replaced.

2. The selective laser melting system of claim 1, wherein the gas path switch on the first gas path comprises a first vacuum flapper valve and a second vacuum flapper valve, the gas path switch on the second gas path comprises a first solenoid valve and a third vacuum flapper valve, and the gas path switch on the third gas path comprises a second solenoid valve and a third solenoid valve;

the connecting pipe connected with the protective gas output device comprises a first gas pipe and a second gas pipe, the connecting pipe communicated with the forming cavity comprises a vacuumizing gas outlet pipe, a circulating gas outlet pipe and a circulating gas inlet pipe, and the connecting pipe connected with the vacuumizing assembly comprises a vacuumizing gas inlet pipe;

and the second air delivery pipe is connected with the filtering air inlet pipe through a second electromagnetic valve.

3. The selective laser melting system of claim 2, wherein the gas circulation filter assembly further comprises a fourth vacuum flapper valve, a fifth vacuum flapper valve, and a gas circulation power plant;

4. The selective laser melting system of claim 3, wherein the evacuation assembly comprises a second filter, an electromagnetic vacuum belt inflation valve, a vacuum pump and a third filter, the second filter, the electromagnetic vacuum belt inflation valve, the vacuum pump and the third filter are sequentially connected through connecting pipes, and the second filter is further connected with the evacuation intake pipe.

5. The selective laser melting system of any one of claims 2 to 4, wherein the inner cavity of the housing is further provided with a muffler, and the filtered outlet branch pipe passes through the housing and is connected with the muffler.

6. The selective laser melting system of any one of claims 2 to 4, wherein a flow meter is further mounted on the filtered outlet duct.

7. The selective laser melting system of any one of claims 2 to 4, wherein the first gas delivery conduit is further provided with an air flow rate regulating valve.

8. The selective laser melting system of claim 1, wherein a pressure relief valve is further provided on a wall of the forming chamber.

9. A gas circulation device is applied to a selective laser melting system and is characterized by comprising a shell, and a vacuumizing assembly and a gas circulation filtering assembly which are arranged in an inner cavity of the shell, wherein the vacuumizing assembly is connected with a vacuumizing air inlet pipe, the gas circulation filtering assembly is connected with a filtering air inlet pipe and a filtering air outlet pipe, and the filtering air outlet pipe is also connected with a filtering air outlet branch pipe through a third electromagnetic valve; wherein:

one end of the fourth electromagnetic valve is communicated with the filtering air inlet pipe through a connecting pipe, and the other end of the fourth electromagnetic valve is communicated with a connecting pipe between the fifth vacuum baffle valve and the gas circulation power device through a connecting pipe, and is used for assisting in deoxidizing when the first filter is replaced.

10. The gas circulation device as claimed in claim 9, wherein the evacuation assembly comprises a second filter, an electromagnetic vacuum belt inflation valve, a vacuum pump and a third filter, the second filter, the electromagnetic vacuum belt inflation valve, the vacuum pump and the third filter are sequentially connected through connecting pipes, and the second filter is further connected with the evacuation intake pipe.

11. A gas circulation arrangement according to claim 9 or 10, wherein the gas circulation power means is a vortex fan.

12. A printing method applied to the selective laser melting system according to any one of claims 1 to 8, comprising:

when the pressure gauge detects that the air pressure in the forming cavity reaches the medium vacuum pressure, an air path switch between the vacuumizing assembly and the forming cavity in the second air path and an air path switch in the third air path are closed;

when the air pressure of the oxygen transmitter in the forming cavity reaches the normal pressure, detecting that the oxygen content in the forming cavity does not reach a preset range, and repeating the previous steps until the oxygen content in the forming cavity reaches the preset range;

starting a gas path switch in the first gas path, and starting the gas circulation filtering assembly and the selective laser melting equipment to perform printing operation and gas circulation filtering operation;

when the third gas path is subjected to deoxidization operation, redundant protective gas exhausted by the filtering gas pipe is injected into the shell of the gas circulating device;

after the replacement is completed, the fourth electromagnetic valve and the pipeline connected with the fourth electromagnetic valve are assisted to remove oxygen in the third gas path and the gas circulation filtering assembly, and after the removal of oxygen is completed, the gas circulation filtering assembly and the selective laser melting equipment are restarted to perform printing operation and gas circulation filtering operation.

13. The method of claim 12, wherein the removing oxygen from the tubing in the third gas path and the gas circulation filter assembly, and after removing oxygen, restarting the gas circulation filter assembly and the selective laser melting device for printing and gas circulation filtering comprises: