Additive manufacturing apparatus and method of controlling constant pressure and constant oxygen in a chamber thereof

Abstract

The application discloses an additive manufacturing device and a constant pressure and constant oxygen control method of a chamber thereof, wherein the additive manufacturing device comprises a working chamber, a control system, an inflation valve, a flow proportional inflation valve, a small-flow exhaust valve, at least two exhaust valves, an air inlet and an air outlet which are arranged on the working chamber, and a circulating air system which is connected between the air inlet and the air outlet, and the exhaust flow range of the small-flow exhaust valve is 10-20 L / min; when the oxygen content is reduced to a target oxygen content value, the inflation valve, the small-flow exhaust valve and all the exhaust valves are closed, the flow proportional inflation valve is continuously opened, and PID adjustment is performed according to the chamber pressure, so that the pressure is constantly kept in the allowed range of a target pressure value. The additive manufacturing device and the constant pressure and constant oxygen control method of the chamber thereof can not only maintain the oxygen content but also stabilize the system pressure, and meanwhile, the flow proportional inflation valve only keeps a small opening degree in the state that the chamber pressure and the oxygen content reach the target pressure value and the target oxygen content value respectively, so that the inert gas consumption is greatly reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of 3D printing, in particular to an additive manufacturing device and a method for controlling constant pressure and oxygen content of a chamber thereof. BACKGROUND

[0002] The basic process of the selective laser sintering process is that a powder feeding device feeds a certain amount of powder to a workbench, a powder spreading roller spreads a layer of powder material on the upper surface of the powder bed containing the formed part in the forming cylinder, a heating device heats the powder to a set temperature, a galvanometer system controls the laser to scan the solid part of the powder layer according to the cross-section profile of the layer, so that the powder is melted and bonded with the underlying formed part; when a layer of cross-section is sintered, the workbench is lowered by one layer thickness, and the powder spreading roller spreads a layer of uniform and dense powder on the top, and a new layer of cross-section is scanned and sintered, and after a plurality of layers of scanning and stacking, the entire part manufacturing is completed.

[0003] In the above-mentioned technology, the forming chamber needs to maintain extremely low oxygen content and constant system pressure, and the low oxygen content can avoid the reaction of the powder with oxygen to cause a fire, and the constant system pressure can improve the stability of the formed workpiece. At present, the forming chamber uses a solenoid valve to control the filling and discharge of inert gas, in order to maintain the oxygen content in the chamber, the inert gas filling valve can only be opened all the time, which will cause the pressure in the chamber to rise, and when the exhaust threshold is reached, the exhaust solenoid valve is opened to release pressure, at this time the pressure will decrease rapidly. This method will always open the filling valve, and the consumption of inert gas is large, and when the exhaust valve is opened to release pressure, the pressure in the system chamber fluctuates greatly, and it is impossible to maintain a stable system pressure.

[0004] In order to solve the problem of large gas consumption of the above-mentioned method, an improved method has appeared, which changes the filling port solenoid valve to a flow proportional valve, and controls the filling flow according to the pressure of the chamber. This improved method achieves the purpose of constant system pressure, but at this time the oxygen content is out of control and will gradually rise, so it is difficult to achieve the purpose of maintaining oxygen content and stable system pressure at the same time. SUMMARY

[0005] In view of this, the present application provides an additive manufacturing device and a method for controlling constant pressure and oxygen content of a chamber thereof, which solves the defect that the oxygen pressure of the prior art cannot be considered at the same time, and at the same time when the chamber pressure and oxygen content reach the target pressure value and the target oxygen content value, the flow proportional filling valve will only maintain a small opening, so the consumption of inert gas is greatly reduced.

[0006] In order to achieve the above-mentioned purpose, the application provides an additive manufacturing equipment, which comprises a working cavity, a control system, and an inflation valve, a flow proportional inflation valve, a small-flow exhaust valve, at least two exhaust valves, an air inlet and an air outlet provided on the working cavity, wherein the air inlet and the air outlet are connected with a circulating air system, and the exhaust flow range of the small-flow exhaust valve is 10-20 L / min; wherein the control unit controls the cavity pressure and the oxygen content of the working cavity to be maintained at a target pressure value and a target oxygen content value respectively by the following methods:

[0007] The inflation valve, the flow proportional inflation valve, the small-flow exhaust valve and all the exhaust valves are opened, the flow proportional inflation valve is inflated at the maximum flow to rapidly reduce the oxygen content in the cavity;

[0008] When the oxygen content is reduced to the target oxygen content value, the inflation valve, the small-flow exhaust valve and all the exhaust valves are closed, the flow proportional inflation valve is continuously opened, and the PID adjustment is performed according to the cavity pressure to keep the pressure constant in the allowable range of the target pressure value;

[0009] When the oxygen content rises, the small-flow exhaust valve is opened, the flow proportional inflation valve is adjusted according to the cavity pressure to increase the inflation amount, so that the oxygen content is reduced, and when the oxygen content is reduced to the target oxygen content value, the small-flow exhaust valve is closed, so that the cavity pressure and the oxygen content of the working cavity are maintained in the allowable error range of the target pressure value and the allowable error range of the target oxygen content value respectively.

[0010] As a further preferred scheme of the application, the equipment further comprises a pressure gauge and an oxygen sensor for detecting the pressure and the oxygen content in the working cavity respectively.

[0011] The application further provides a cavity constant-pressure constant-oxygen control method of the above-mentioned additive manufacturing equipment, which comprises the following steps:

[0012] Before the additive manufacturing equipment starts printing, the inflation valve, the flow proportional inflation valve, the small-flow exhaust valve and all the exhaust valves are opened, the flow proportional inflation valve is inflated at the maximum flow to rapidly reduce the oxygen content in the cavity;

[0013] When the oxygen content is reduced to the target oxygen content value, the inflation valve, the small-flow exhaust valve and all the exhaust valves are closed, the flow proportional inflation valve is continuously opened, and the PID adjustment is performed according to the cavity pressure to keep the pressure constant in the allowable range of the target pressure value, and the additive manufacturing equipment starts printing;

[0014] In the printing process of the additive manufacturing, when the oxygen content rises and reaches the Up value, the small flow exhaust valve is opened, the flow proportional inflation valve is PID adjusted according to the chamber pressure to increase the inflation amount, so that the oxygen content is reduced, and after the oxygen content is reduced to the target oxygen content value, the small flow exhaust valve is closed, so that the chamber pressure of the working cavity and the oxygen content are respectively maintained in the allowable error range of the target pressure value and the allowable error range of the target oxygen content value; wherein,

[0015] The Up value is higher than the Low value by more than 0.05%, and the Low value is the target oxygen content value.

[0016] As a further preferred embodiment of the present application, the method further comprises:

[0017] When the oxygen content rises and reaches the Alarm value, the additive manufacturing equipment stops printing and issues an oxygen content too high alarm; wherein the Alarm value is higher than the Up value by more than 0.2%.

[0018] As a further preferred embodiment of the present application, the method further comprises:

[0019] When the chamber pressure is greater than P2, the small flow exhaust valve and at least one exhaust valve are opened, and if the chamber pressure successfully drops, the small flow exhaust valve and at least one exhaust valve are closed, and the additive manufacturing equipment normally prints; wherein,

[0020] P2 is higher than P1 by more than 2kPa, and P1 is the target pressure value.

[0021] As a further preferred embodiment of the present application, the method further comprises:

[0022] When the chamber pressure continues to rise and is greater than P3, the additive manufacturing equipment stops printing and issues a chamber pressure too high alarm, and simultaneously opens the small flow exhaust valve and all exhaust valves for pressure relief; wherein,

[0023] P3 is higher than P2 by more than 2kPa.

[0024] As a further preferred embodiment of the present application, the exhaust flow range of the small flow exhaust valve is smaller than the exhaust flow range of the exhaust valve, and the total flow of the small flow exhaust valve and all exhaust valves is greater than the total flow of the flow proportional inflation valve and all inflation valves.

[0025] As a further preferred scheme of the present application, the target oxygen content value is 0.05%, the Up value is 0.15%, the Alarm value is 0.35%, P1 is 3 kPa, P2 is 5.5 kPa, and P3 is 8 kPa; the rated flow of the inflation valve is 100 L / min, the adjustable range of the flow proportional inflation valve is 0-100 L / min, the rated flow of the small-flow exhaust valve is 20 L / min, and the rated flow of the exhaust valve is 100 L / min.

[0026] The additive manufacturing equipment and the constant pressure and oxygen control method thereof of the present application, by comprising a working cavity, a control system, and an inflation valve, a flow proportional inflation valve, a small-flow exhaust valve, at least two exhaust valves, an air inlet and an air outlet provided on the working cavity, and a circulating air system connected between the air inlet and the air outlet, and by the specific control of the control system on the above-mentioned inflation valve, flow proportional inflation valve, small-flow exhaust valve and at least two exhaust valves, i.e. according to the pressure and oxygen content in the working cavity respectively detected by the pressure gauge and oxygen sensor, the opening and closing of the inflation valve, small-flow exhaust valve and at least two exhaust valves are adjusted and controlled in real time, and the automatic adjustment of the flow proportional inflation valve is controlled, which solves the defect that the oxygen pressure cannot be considered simultaneously in the prior art, and the present application can not only maintain the oxygen content but also stabilize the system pressure, and at the same time when the chamber pressure and oxygen content reach the target pressure value and target oxygen content value respectively, the flow proportional inflation valve will only maintain a small opening, so the consumption of inert gas is greatly reduced. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the specific embodiments of the present application or the technical solutions in the prior art, the drawings needed in the specific embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0028] Figure 1 is a structural schematic diagram of an embodiment of the additive manufacturing equipment provided by the present application;

[0029] Figure 2 is a flowchart of the constant pressure and oxygen control method of the additive manufacturing equipment chamber of the embodiment of the present application;

[0030] Figure 3 is a chamber oxygen content trend graph under the constant pressure and oxygen control method of the additive manufacturing equipment chamber according to the embodiment of the present application.

[0031] The marks in the figure are as follows:

[0032] 1. Inflation valve, 2. Flow ratio inflation valve, 3. Small flow exhaust valve, 4. First exhaust valve, 5. Second exhaust valve, 6. Pressure gauge, 7. Air outlet, 8. Air inlet, 9. Oxygen sensor. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] like Figure 1 As shown, the additive manufacturing equipment of the present invention includes a working chamber, a control system, and an inflation valve 1, a flow ratio inflation valve 2, a small flow exhaust valve 3, at least two exhaust valves (excluding the small flow exhaust valve 3), an air inlet, and an air outlet disposed on the working chamber. A circulating air system is connected between the air inlet and the air outlet. The exhaust flow rate of the small flow exhaust valve 3 is in the range of 10-20 L / min. The control unit controls the chamber pressure and oxygen content of the working chamber to maintain target pressure and target oxygen content values, respectively, through the following methods:

[0035] Open inflation valve 1, flow ratio inflation valve 2, small flow exhaust valve 3 and all exhaust valves. Flow ratio inflation valve 2 inflates at maximum flow rate to rapidly reduce the oxygen content in the chamber.

[0036] When the oxygen content drops to the target oxygen content value, close inflation valve 1, small flow exhaust valve 3 and all exhaust valves, while the flow ratio inflation valve 2 remains open and is PID regulated according to the chamber pressure to keep the pressure constant within the allowable range of the target pressure value.

[0037] When the oxygen content increases, the small flow exhaust valve 3 is opened. The flow ratio inflation valve 2 is adjusted by PID according to the chamber pressure to increase the inflation volume and reduce the oxygen content. After the oxygen content drops to the target oxygen content value, the small flow exhaust valve 3 is closed so that the chamber pressure and oxygen content of the working chamber are maintained within the allowable error range of the target pressure value and the allowable error range of the target oxygen content value, respectively.

[0038] In this embodiment, there are two exhaust valves, such as... Figure 1 As shown, it includes a first exhaust valve 4 and a second exhaust valve 5. In specific implementations, depending on the volume of the working chamber, the number of exhaust valves can also be designed to be three or more, and there is no limitation on it here.

[0039] In the embodiment, the device further comprises a pressure gauge 6 and an oxygen sensor 9 for detecting the pressure and oxygen content in the working chamber, respectively.

[0040] It should be noted that the additive manufacturing device of the present application also comprises existing components such as powder laying device, scanning system, etc., which are not described in detail herein.

[0041] As shown in Figure 2 and Figure 3 The present application also provides a method for controlling the constant pressure and oxygen content of the chamber of the additive manufacturing device, which comprises the following steps:

[0042] Before the additive manufacturing device starts printing, open the inflation valve 1, the flow proportional inflation valve 2, the small flow exhaust valve 3 and all exhaust valves, and the flow proportional inflation valve 2 is inflated at the maximum flow rate to rapidly reduce the oxygen content in the chamber;

[0043] When the oxygen content decreases to the target oxygen content value, close the inflation valve 1, the small flow exhaust valve 3 and all exhaust valves at the t1 time point, continue to open the flow proportional inflation valve 2, and perform PID adjustment according to the chamber pressure to keep the pressure constant within the allowed range of the target pressure value, and the additive manufacturing device starts printing;

[0044] During the printing process of the additive manufacturing, the oxygen content in the forming chamber may increase due to the influence of the circulating air inlet and outlet 7 or the air tightness of the chamber, etc., and when the oxygen content rises and reaches the Up value as shown in Figure 3 At the t2 time point, open the small flow exhaust valve 3, and the flow proportional inflation valve 2 performs PID adjustment according to the chamber pressure to increase the inflation amount and reduce the oxygen content. When the oxygen content decreases to the target oxygen content value, close the small flow exhaust valve 3 at the t3 time point to maintain the chamber pressure of the working chamber within the allowed error range of the target pressure value and the oxygen content within the allowed error range of the target oxygen content value, for example, the chamber pressure is kept constant around the target pressure value (P1), and the oxygen content in the chamber is basically maintained between the Up value and the Low value; wherein,

[0045] The Up value is higher than the Low value by more than 0.05%, and the Low value is the target oxygen content value. It should be noted that the target oxygen content value can be obtained by the designer according to the requirements of the printing material in the chamber and combined with experiments, which is not described in detail herein. The above-mentioned allowed error range is a general parameter in the industry, which belongs to the prior art and is not described in detail herein.

[0046] If the air tightness of the additive manufacturing device fails or the oxygen in the external environment enters the chamber, it may cause the oxygen content to rise greatly. Preferably, in order to avoid the influence of the above factors on the normal work of the additive manufacturing device, i.e. to ensure the reliability of the additive manufacturing device, the method further comprises:

[0047] When the oxygen content rises and reaches the Alarm value, the additive manufacturing equipment stops printing and issues an alarm of too high oxygen content; wherein the Alarm value is higher than the Up value by more than 0.2%.

[0048] As a further preferred scheme of the present application, the method further comprises:

[0049] In order to further avoid the influence of other device failures on the normal printing of the equipment, i.e., to further ensure the normal printing of the equipment, preferably, if the additive manufacturing equipment has a failure such as uncontrolled inflation valve 1, resulting in continuous rise of the chamber pressure, the chamber pressure needs to be controlled, when the chamber pressure is greater than P2, the small-flow exhaust valve 3 and at least one exhaust valve are opened, if the chamber pressure successfully drops, the small-flow exhaust valve 3 and at least one exhaust valve are closed, and the additive manufacturing equipment normally prints; wherein P2 is higher than P1 by more than 2kPa, and the P1 is a target pressure value.

[0050] When the chamber pressure continues to rise and is greater than P3, the additive manufacturing equipment stops printing and issues an alarm of too high chamber pressure, while the small-flow exhaust valve 3 and all exhaust valves are opened for pressure relief; wherein,

[0051] P3 is higher than P2 by more than 2kPa. The P2 is an exhaust pressure value, and P3 is an alarm pressure value. It should be noted that the specific value of the target pressure value can be obtained by the designer according to the requirements of the printing material in the cavity and combined with experiments, which is not specifically described here.

[0052] In a specific implementation, the exhaust flow range of the small-flow exhaust valve 3 is smaller than the exhaust flow range of the exhaust valve, and the total flow of the small-flow exhaust valve 3 and all exhaust valves is greater than the total flow of the flow proportional inflation valve 2 and all inflation valves 1.

[0053] In order to ensure the system stability of the additive manufacturing equipment, preferably, the target oxygen content value is 0.05%, the Up value is 0.15%, the Alarm value is 0.35%, P1 is 3kPa, P2 is 5.5kPa, and P3 is 8kPa; the rated flow of the inflation valve 1 is 100L / min, the adjustable range of the flow proportional inflation valve 2 is 0-100L / min, the rated flow of the small-flow exhaust valve 3 is 20L / min, and the rated flow of the exhaust valve is 100L / min.

[0054] Although the embodiments of the present application are described in conjunction with the drawings, various modifications and changes can be made by those skilled in the art without departing from the spirit and scope of the present application, and such modifications and changes fall within the scope defined by the appended claims.

Claims

1. A method for controlling constant pressure and oxygen in the chamber of an additive manufacturing equipment, characterized in that, The additive manufacturing equipment comprises a working cavity, a control system, and an inflation valve, a flow proportional inflation valve, a small-flow exhaust valve, at least two exhaust valves, an air inlet, an air outlet, a pressure gauge, and an oxygen sensor arranged on the working cavity, wherein the air inlet and the air outlet are connected with a circulating air system, the exhaust flow range of the small-flow exhaust valve is 10-20 L / min, the pressure gauge and the oxygen sensor are used to detect the pressure and the oxygen content in the working cavity respectively, and the control method comprises the following steps: Before the additive manufacturing equipment starts printing, the inflation valve, the flow proportional inflation valve, the small-flow exhaust valve, and all the exhaust valves are opened, the flow proportional inflation valve is inflated at the maximum flow to rapidly reduce the oxygen content in the cavity, and the additive manufacturing equipment starts printing when the oxygen content is reduced to the target oxygen content value. When the oxygen content rises to the Up value, the small-flow exhaust valve is opened, the flow proportional inflation valve is adjusted according to the cavity pressure to increase the inflation amount and reduce the oxygen content, and when the oxygen content is reduced to the target oxygen content value, the small-flow exhaust valve is closed to maintain the cavity pressure and the oxygen content in the working cavity in the allowable error range of the target pressure value and the target oxygen content value respectively. The Up value is higher than the Low value by more than 0.05%, and the Low value is the target oxygen content value. When the cavity pressure is greater than P2, the small-flow exhaust valve and at least one exhaust valve are opened, and if the cavity pressure is successfully reduced, the small-flow exhaust valve and at least one exhaust valve are closed, and the additive manufacturing equipment normally prints; wherein P2 is higher than P1 by more than 2 kPa, and P1 is the target pressure value. The method further comprises:

2. The method of claim 1, wherein, When the oxygen content rises to the Alarm value, the additive manufacturing equipment stops printing and issues an oxygen content too high alarm; wherein the Alarm value is higher than the Up value by more than 0.2%. The method further comprises:

3. The method of claim 2, wherein, When the cavity pressure continues to rise and is greater than P3, the additive manufacturing equipment stops printing and issues a cavity pressure too high alarm, and simultaneously opens the small-flow exhaust valve and all the exhaust valves for pressure relief; wherein P3 is higher than P2 by more than 2 kPa. The exhaust flow range of the small-flow exhaust valve is smaller than that of the exhaust valve, and the total flow of the small-flow exhaust valve and all the exhaust valves is greater than the total flow of the flow proportional inflation valve and the inflation valve. The target oxygen content value is 0.05%, the Up value is 0.15%, the Alarm value is 0.35%, P1 is 3 kPa, P2 is 5.5 kPa, and P3 is 8 kPa; the rated flow of the inflation valve is 100 L / min, the adjustable range of the flow proportional inflation valve is 0-100 L / min, the rated flow of the small-flow exhaust valve is 20 L / min, and the rated flow of the exhaust valve is 100 L / min.

4. The method of claim 1, wherein, ​ 5. The method according to any one of claims 1 to 4, characterized in that, ​

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