Additive manufacturing equipment and cavity constant-pressure and constant-oxygen control method thereof

Abstract

The invention discloses additive manufacturing equipment and a chamber constant-pressure constant-oxygen control method thereof, the additive manufacturing equipment 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, and the inflation valve, the flow proportional inflation valve, the small-flow exhaust valve, the at least two exhaust valves, the air inlet and the air outlet are arranged on the working chamber. The exhaust flow of the small-flow exhaust valve ranges from 10 L / min to 20 L / min; and 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 continues to be opened, and PID adjustment is conducted according to the pressure of the cavity so that the pressure can be kept within the permissible range of the target pressure value. According to the additive manufacturing equipment and the chamber constant-pressure and constant-oxygen control method thereof, the oxygen content can be maintained, the system pressure can be stabilized, meanwhile, when the chamber pressure and the oxygen content reach the target pressure value and the target oxygen content value respectively, the flow proportional inflation valve can only keep the small opening degree, and the inert gas consumption is greatly reduced.

Description

Technical Field

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

[0002] The basic process of selective laser sintering is: the powder feeding device delivers a certain amount of powder to the work surface, the powder spreading roller spreads a layer of powder material on the surface of the powder bed of the forming cylinder containing the formed parts, the heating device heats the powder to the set temperature, and the galvanometer system controls the laser to scan the solid part of the powder layer according to the cross-sectional contour of the layer, so that the powder melts and bonds with the formed part below; when a layer of cross section is sintered, the workbench drops by a layer thickness, and the powder spreading roller spreads a layer of uniform and dense powder on it, and scans and sinters a new layer of cross section, and after several layers of scanning and superposition, the entire part manufacturing is completed.

[0003] In the above technology, the molding chamber needs to maintain an extremely low oxygen content and a constant system pressure. The low oxygen content can prevent the powder from reacting with oxygen and causing a fire, and the constant system pressure can improve the stability of the molded workpiece. At present, the molding chamber uses a solenoid valve to control the filling and discharge of the inert gas. In order to maintain the oxygen content in the chamber, the inert gas filling valve can only be opened all the time. This operation will cause the chamber pressure to rise. After reaching the exhaust threshold, the exhaust solenoid valve opens to release the pressure, and the pressure will drop rapidly at this time. This method will keep the filling valve open, the inert gas consumption is large, and when the exhaust valve is opened to release the pressure, the chamber pressure of the system fluctuates greatly, and it is impossible to maintain a stable system pressure.

[0004] In order to solve the problem of high gas consumption in the above method, an improved method has emerged. The solenoid valve of the inflation port is replaced with a flow proportional valve to control the inflation flow according to the cavity pressure. This improved method achieves the purpose of constant system pressure, but the oxygen content is out of control and will gradually increase. Therefore, it is difficult for this improved method to achieve the purpose of both maintaining the oxygen content and stabilizing the system pressure. Summary of the invention

[0005] In view of this, the present invention provides an additive manufacturing device and a method for controlling constant pressure and oxygen in its chamber, which solves the defect that the prior art cannot take both compressed oxygen and oxygen into account at the same time. At the same time, when the chamber pressure and oxygen content reach the target pressure value and the target oxygen content value respectively, the flow proportional inflation valve will only maintain a small opening, thereby greatly reducing the consumption of inert gas.

[0006] In order to achieve the above-mentioned object, the present invention provides an additive manufacturing device, comprising a working chamber, a control system, and an inflation valve, a flow rate proportional inflation valve, a small flow rate exhaust valve, at least two exhaust valves, an air inlet and an air outlet arranged on the working chamber, wherein a circulating air system is connected between the air inlet and the air outlet, and the exhaust flow rate range of the small flow rate exhaust valve is 10 to 20 L / min; wherein the control unit controls the chamber pressure and oxygen content of the working chamber to be maintained at a target pressure value and a target oxygen content value respectively in the following manner:

[0007] Opening the inflation valve, the flow ratio inflation valve, the small flow exhaust valve and all the exhaust valves, wherein the flow ratio inflation valve inflates at a maximum flow rate to rapidly reduce the oxygen content in the chamber;

[0008] When the oxygen content drops to the target oxygen content value, the inflation valve, the small flow exhaust valve and all exhaust valves are closed, the flow proportional inflation valve continues to be opened, and PID adjustment is performed according to the chamber pressure to keep the pressure constant within the allowable range of the target pressure value;

[0009] When the oxygen content rises, the small flow exhaust valve is opened, and the flow proportional inflation valve performs PID adjustment 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 is closed to maintain the chamber pressure and oxygen content of the working chamber within 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 embodiment of the present invention, the device further comprises a pressure gauge and an oxygen sensor for respectively detecting the pressure and oxygen content in the working chamber.

[0011] The present invention also provides a method for controlling constant pressure and constant oxygen in the chamber of the above-mentioned additive manufacturing equipment, which comprises the following steps:

[0012] Before the additive manufacturing device starts printing, the inflation valve, the flow ratio inflation valve, the small flow exhaust valve and all the exhaust valves are opened, and the flow ratio inflation valve is inflated at the maximum flow rate to rapidly reduce the oxygen content in the chamber;

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

[0014] During the printing process of additive manufacturing, when the oxygen content rises and reaches the Up value, the small flow exhaust valve is opened, and the flow proportional inflation valve performs PID adjustment 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 is closed to maintain the chamber pressure and oxygen content of the working chamber within the allowable error range of the target pressure value and the allowable error range of the target oxygen content value respectively; 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 invention, the method further comprises:

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

[0018] As a further preferred embodiment of the present invention, 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. If the chamber pressure drops successfully, the small flow exhaust valve and at least one exhaust valve are closed, and the additive manufacturing device prints normally; wherein,

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

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

[0022] When the chamber pressure continues to rise and exceeds P3, the additive manufacturing equipment stops printing and issues an alarm for excessive chamber pressure, while opening the small flow exhaust valve and all exhaust valves to release pressure;

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

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

[0025] As a further preferred embodiment of the present invention, 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 rate of the inflation valve is 100L / min, the adjustable range of the flow ratio inflation valve is 0 to 100L / min, the rated flow rate of the small flow exhaust valve is 20L / min, and the rated flow rate of the exhaust valve is 100L / min.

[0026] The additive manufacturing equipment and the control method for constant pressure and oxygen in the chamber thereof of the present invention include a working chamber, a control system, and an inflation valve, a flow ratio inflation valve, a small flow exhaust valve, at least two exhaust valves, an air inlet and an air outlet arranged on the working chamber, wherein a circulating air system is connected between the air inlet and the air outlet, and the inflation valve, the flow ratio inflation valve, the small flow exhaust valve, and the at least two exhaust valves are specifically controlled by the control system, that is, according to the pressure and oxygen content in the working chamber detected by the pressure gauge and the oxygen sensor respectively, the opening and closing of the inflation valve, the small flow exhaust valve, and the at least two exhaust valves are adjusted and controlled in real time, and the flow ratio inflation valve is automatically adjusted, thereby solving the defect that the prior art cannot take into account both pressure and oxygen at the same time. Moreover, the present invention can maintain the oxygen content and stabilize the system pressure. At the same time, when the chamber pressure and the oxygen content reach the target pressure value and the target oxygen content value respectively, the flow ratio inflation valve will only maintain a small opening, thereby greatly reducing the consumption of inert gas. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

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

[0029] Figure 2 It is a flow chart of a method for controlling constant pressure and constant oxygen in a chamber of an additive manufacturing device according to an embodiment of the present invention;

[0030] Figure 3 This is a trend diagram of chamber oxygen content under a constant pressure and constant oxygen control method for an additive manufacturing equipment chamber according to an embodiment of the present invention.

[0031] The following are marked in the figure:

[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 DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work 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 (the at least two exhaust valves herein do not include the small flow exhaust valve 3) arranged on the working chamber, an air inlet and an air outlet, a circulating air system is connected between the air inlet and the air outlet, and the exhaust flow range of the small flow exhaust valve 3 is 10 to 20 L / min; wherein the control unit controls the chamber pressure and oxygen content of the working chamber to be maintained at the target pressure value and the target oxygen content value respectively in the following manner:

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

[0036] When the oxygen content drops to the target oxygen content value, the charging valve 1, the small flow exhaust valve 3 and all the exhaust valves are closed, the flow proportional charging valve 2 continues to be opened, and the PID adjustment is performed according to the chamber pressure to keep the pressure constant within the allowable range of the target pressure value;

[0037] When the oxygen content rises, the small flow exhaust valve 3 is opened, and the flow proportional inflation valve 2 performs PID adjustment 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 to maintain the chamber pressure and oxygen content of the working chamber within the allowable error range of the target pressure value and the allowable error range of the target oxygen content value, respectively.

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

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

[0040] It should be noted here that the additive manufacturing equipment of the present invention also includes existing components, such as a powder spreading device, a scanning system, etc., which will not be elaborated here.

[0041] like Figure 2 and Figure 3 As shown, the present invention also provides a method for controlling constant pressure and constant oxygen in the chamber of the above-mentioned additive manufacturing equipment, which comprises the following steps:

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

[0043] When the oxygen content drops to the target oxygen content value, the inflation valve 1, the small flow exhaust valve 3 and all the exhaust valves are closed at time t1, the flow proportional inflation valve 2 continues to be opened, and the PID adjustment is performed according to the chamber pressure to keep the pressure constant within the allowable range of the target pressure value, and the additive manufacturing device starts printing;

[0044] During the printing process of additive manufacturing, the oxygen content in the molding chamber may increase due to the influence of the circulating air inlet and outlet 7 or the air tightness of the cavity. When the oxygen content rises and reaches Figure 3 When the Up value is shown, the small flow exhaust valve 3 is opened at time t2, and the flow proportional inflation valve 2 performs PID adjustment 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 at time t3 to maintain the chamber pressure and oxygen content of the working chamber within the allowable error range of the target pressure value and the allowable error range of the target oxygen content value, respectively. For example, the chamber pressure is maintained in a constant state near the target pressure value (P1), and the chamber oxygen content is basically maintained between the Up value and the Low value; wherein,

[0045] The Up value is more than 0.05% higher than the Low value, 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 based on the requirements of the printing material in the cavity and combined with experiments, and will not be elaborated here. The above allowable error range is a common parameter in the industry, which belongs to the prior art and will not be introduced in detail here.

[0046] If the airtightness of the additive manufacturing equipment fails, or oxygen from the external environment enters the chamber, the oxygen content may increase significantly. Preferably, in order to avoid the above factors affecting the normal operation of the additive manufacturing equipment, that is, to ensure the reliability of the operation of the additive manufacturing equipment, preferably, the method further includes:

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

[0048] As a further preferred embodiment of the present invention, the method further comprises:

[0049] In order to further prevent other device failures from affecting the normal printing of the equipment, that is, to further ensure the normal printing of the equipment, preferably, if the additive manufacturing equipment has a failure such as loss of control of the inflation valve 1, resulting in a continuous increase in 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 prints normally; wherein, P2 is more than 2 kPa higher than P1, and P1 is the target pressure value.

[0050] When the chamber pressure continues to rise and exceeds P3, the additive manufacturing equipment stops printing and issues an alarm for excessive chamber pressure, and simultaneously opens the small flow exhaust valve 3 and all exhaust valves to release pressure;

[0051] P3 is higher than P2 by more than 2 kPa. P2 is the exhaust pressure value, and P3 is the 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, and will not be elaborated 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 sum of the flow rates of the small flow exhaust valve 3 and all exhaust valves is greater than the sum of the flow rates of the flow proportional inflation valve 2 and all inflation valves 1.

[0053] 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 rate of the inflation valve 1 is 100L / min, the adjustable range of the flow ratio inflation valve 2 is 0-100L / min, the rated flow rate of the small flow exhaust valve 3 is 20L / min, and the rated flow rate of the exhaust valve is 100L / min.

[0054] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. An additive manufacturing device, characterized in that: The invention comprises a working chamber, a control system, and an inflation valve, a flow rate proportional inflation valve, a small flow rate exhaust valve, at least two exhaust valves, an air inlet and an air outlet arranged on the working chamber, wherein a circulating air system is connected between the air inlet and the air outlet, and the exhaust flow rate range of the small flow rate exhaust valve is 10 to 20 L / min; wherein the control unit controls the chamber pressure and oxygen content of the working chamber to be maintained at the target pressure value and the target oxygen content value respectively by the following methods: Opening the inflation valve, the flow ratio inflation valve, the small flow exhaust valve and all the exhaust valves, wherein the flow ratio inflation valve inflates at a maximum flow rate to rapidly reduce the oxygen content in the chamber; When the oxygen content drops to the target oxygen content value, the inflation valve, the small flow exhaust valve and all exhaust valves are closed, the flow proportional inflation valve continues to be opened, and PID adjustment is performed according to the chamber pressure to keep the pressure constant within the allowable range of the target pressure value; When the oxygen content rises, the small flow exhaust valve is opened, and the flow proportional inflation valve performs PID adjustment 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 is closed to maintain the chamber pressure and oxygen content of the working chamber within the allowable error range of the target pressure value and the allowable error range of the target oxygen content value, respectively.

2. The additive manufacturing device according to claim 1, characterized in that: The device also includes a pressure gauge and an oxygen sensor for respectively detecting the pressure and oxygen content in the working chamber.

3. A method for controlling constant pressure and constant oxygen in a chamber of an additive manufacturing device according to claim 1 or 2, characterized in that: The following steps are involved: Before the additive manufacturing device starts printing, the inflation valve, the flow ratio inflation valve, the small flow exhaust valve and all the exhaust valves are opened, and the flow ratio inflation valve is inflated at the maximum flow rate to rapidly reduce the oxygen content in the chamber; When the oxygen content drops to the target oxygen content value, the inflation valve, the small flow exhaust valve and all exhaust valves are closed, the flow proportional inflation valve continues to be opened, and PID adjustment is performed according to the chamber pressure to keep the pressure constant within the allowable range of the target pressure value, and the additive manufacturing equipment starts printing; During the printing process of additive manufacturing, when the oxygen content rises and reaches the Up value, the small flow exhaust valve is opened, and the flow proportional inflation valve performs PID adjustment 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 is closed to maintain the chamber pressure and oxygen content of the working chamber within the allowable error range of the target pressure value and the allowable error range of the target oxygen content value respectively; wherein, The Up value is higher than the Low value by more than 0.05%, and the Low value is the target oxygen content value.

4. The method according to claim 3, characterized in that The method further comprises: When the oxygen content rises and reaches the Alarm value, the additive manufacturing equipment stops printing and issues an alarm indicating that the oxygen content is too high; the Alarm value is more than 0.2% higher than the Up value.

5. The method according to claim 3, characterized in that: The method further comprises: When the chamber pressure is greater than P2, the small flow exhaust valve and at least one exhaust valve are opened. If the chamber pressure drops successfully, the small flow exhaust valve and at least one exhaust valve are closed, and the additive manufacturing device prints normally; wherein, P2 is higher than P1 by 2 kPa or more, and P1 is the target pressure value.

6. The method according to claim 5, characterized in that The method further comprises: When the chamber pressure continues to rise and exceeds P3, the additive manufacturing equipment stops printing and issues an alarm for excessive chamber pressure, while opening the small flow exhaust valve and all exhaust valves to release pressure; P3 is more than 2 kPa higher than P2.

7. The method according to claim 3, characterized in that The exhaust flow range of the small flow exhaust valve is smaller than the exhaust flow range of the exhaust valve, and the sum of the flow rates of the small flow exhaust valve and all exhaust valves is greater than the sum of the flow rates of the flow ratio inflation valve and all inflation valves.

8. The method according to any one of claims 3 to 7, characterized in that: 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 rate of the inflation valve is 100L / min, the adjustable range of the flow ratio inflation valve is 0 to 100L / min, the rated flow rate of the small flow exhaust valve is 20L / min, and the rated flow rate of the exhaust valve is 100L / min.

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