Patent Publication Number: US-2021187613-A1

Title: Manufacturing system and method for providing variable pressure environment

Description:
PRIORITY DECLARATION 
     The present application claims the priority of an International Patent Application No. PCT/CN2017/105591, entitled “MANUFACTURING SYSTEM AND METHOD FOR PROVIDING VARIABLE PRESSURE ENVIRONMENT”, filed on Oct. 11, 2017, the disclosures of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present disclosure relates to manufacturing technology, and more particularly, to a manufacturing system and method for providing a variable pressure environment, which are applied to additive manufacturing (AM), subtractive manufacturing (e.g., a machining process), or hybrid additive and subtractive manufacturing. 
     BACKGROUND OF THE INVENTION 
     Additive manufacturing technology is a kind of manufacturing technology emerged and rapidly developed in recent years. The field of additive manufacturing using metals as raw materials especially gets more attention due to its potential of directly and rapidly prototyping an engineering part. 
     The additive manufacturing using metals as raw materials may manufacture a part with a complex shape. The basic principle is that the raw materials (such as metal powder, metal wire, etc.) are melted into a liquid state or a semi-solid state through a heating source (such as laser, arc, ion beam, electron beam, etc.), then the liquid or semi-solid raw materials are deposited layer by layer according to a pre-generated slicing path corresponding to a target shape of the part. 
     Due to metallurgical defects of the metals, the part obtained through the additive manufacturing tends to have defects such as pores, micro cracks, etc. In addition, there are a large amount of residual stress in the part obtained through the additive manufacturing. Due to the above-mentioned defects and residual stress, the part is easily deformed and cracked, and has insufficient strength. As such, the part obtained through the additive manufacturing is difficult to be applied to actual projects. 
     In order to cure the above-mentioned deficiencies of the additive manufacturing, the prior art proposes a method of implementing additive manufacturing under a hyperbaric pressure environment. Stability of the hyperbaric pressure environment is required for implementation of this method. However, a conventional apparatus used for the additive manufacturing cannot implement stability control to the hyperbaric pressure environment. 
     SUMMARY OF THE INVENTION 
     According to an example of the present disclosure, a manufacturing system for providing a variable pressure environment includes: 
     a seal pressure vessel; 
     a monitoring apparatus, to monitor an environmental parameter in the seal pressure vessel; 
     a manufacturing apparatus, wherein the manufacturing apparatus is located in the seal pressure vessel; 
     a vacuum pump, wherein the vacuum pump is connected with the seal pressure vessel; 
     a first inert gas source; 
     a storage vessel of inert gas, wherein the storage vessel of the inert gas is connected with the first inert gas source and the seal pressure vessel respectively; 
     a computer numerical control (CNC) system, to control the vacuum pump to vacuumize the seal pressure vessel before the manufacturing apparatus performs manufacturing operations, control, according to feedback of the monitoring apparatus and after the seal pressure vessel is vacuum, the first inert gas source to inject the inert gas into the seal pressure vessel through the storage vessel of the inert gas until a pressure in the seal pressure vessel reaches a hyperbaric pressure, and control, according to the feedback of the monitoring apparatus, the storage vessel of the inert gas to implement dynamic compensation for a positive deviation or a negative deviation of the pressure in the seal pressure vessel compared with a target pressure. 
     According to another example of the present disclosure, a manufacturing method for providing a variable pressure environment includes: 
     at step a1, controlling a vacuum pump to vacuumize a seal pressure vessel; 
     at step a2, controlling a first inert gas source to inject inert gas into the seal pressure vessel in a vacuum state through a storage vessel of the inert gas until a pressure in the seal pressure vessel reaches a hyperbaric pressure; 
     at step a3, performing a manufacturing process in the seal pressure vessel that is under the hyperbaric pressure; 
     at step a4, releasing the hyperbaric pressure in the seal pressure vessel; 
     at step a5, taking out a manufactured part from the seal pressure vessel; 
     wherein when at least one of the step a2 and step a3 is performed, the method further includes: 
     at step b1, controlling the storage vessel of the inert gas to implement dynamic compensation for a positive deviation or a negative deviation of the pressure in the seal pressure vessel compared with a target pressure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram illustrating structure of a manufacturing system, according to an example of the present disclosure; 
         FIG. 2  is a schematic flowchart illustrating a manufacturing method, according to another example of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     To make the objective, technical solution, and advantages of the present disclosure more clearly, examples of the present disclosure are described in detail with reference to the accompanying drawings. 
     Referring to  FIG. 1 , according to an example of the present disclosure, a manufacturing system for providing a variable pressure environment may at least implement the additive manufacturing. The manufacturing system includes a seal pressure vessel  10 , a manufacturing apparatus  20 , a vacuum pump  30 , an inert gas source  40 , a storage vessel of inert gas  50 , a feeding apparatus  60 , a heating source  70 , an inert gas source  80 , and a computer numerical control (CNC) system  90 . 
     Pressure resistance of the seal pressure vessel  10  is within the range between vacuum and 100 bar, in which 1 bar=10 5  Pascal (Pa). For example, the pressure resistance of the seal pressure vessel  10  may be not less than 60 bar. 
     In addition, a monitoring apparatus (not shown in the figure) is configured in the seal pressure vessel  10 , such as a pressure gauge, a thermometer, etc., for monitoring an environmental parameter in the seal pressure vessel  10  in real-time, such as a pressure, a temperature, and the like. In the example shown in  FIG. 1 , the seal pressure vessel  10  includes a base  11  and a cover  12  mounted on the base  11 . 
     The manufacturing apparatus  20  is located in the seal pressure vessel  10 . That is, the manufacturing apparatus  20  is located on the base  11  of the seal pressure vessel  10  and is covered with the cover  12  of the seal pressure vessel  10 . 
     In the example shown in  FIG. 1 , the manufacturing apparatus  20  supports the additive manufacturing and the subtractive manufacturing, i.e., the manufacturing apparatus  20  supports the hybrid additive and subtractive manufacturing. In addition, the manufacturing apparatus  20  includes a working table  21 , a rotating component  22 , an additive manufacturing head  23 , a subtractive manufacturing head  24 , and a moving component  25 . 
     The working table  21  has a surface for placing a workpiece. In addition, a clamp for fixing a manufactured part may be mounted on the working table  21 . 
     The rotating component  22  includes a longitudinal turntable  22   a  which may rotate around a vertical axis parallel to the Z direction, and a lateral turntable  22   b  which may rotate around a horizontal axis parallel to the Y direction. The lateral turntable  22   b  is mounted on a top surface of the longitudinal turntable  22   a . The working table  21  is mounted on a side surface of the lateral turntable  22   b . As such, the rotating component  22  may provide the working table  21  with double rotations around the vertical axis and the horizontal axis through linkage between the longitudinal turntable  22   a  and the lateral turntable  22   b.    
     In the example, the additive manufacturing head  23  uses a laser cladding head. The additive manufacturing head  23  is suspended above the working table  21 . 
     In the example, the subtractive manufacturing head  24  uses an electric spindle that supports the machining process. The subtractive manufacturing head  24  and the additive manufacturing head  23  are suspended above the working table  21  in parallel. 
     The moving component  25  provides translational freedom in three directions for the additive manufacturing head  23  and the subtractive manufacturing head  24  with respect to the working table  21 , in which the three directions include the X direction, the Y direction, and the Z direction. 
     Specifically, the moving component includes a first Z-axis  22   a , a second Z-axis  22   b , an X-axis  22   c , and a Y-axis  22   d . In this case, the additive manufacturing head  23  and the subtractive manufacturing head  24  are respectively mounted on the first Z-axis  22   a  and the second Z-axis  22   b , so that the additive manufacturing head  23  and the subtractive manufacturing head  24  may perform Y-direction movement respectively along the first Z-axis  22   a  and the second Z-axis  22   b . The first Z-axis  22   a  and the second Z-axis  22   b  are mounted on the X-axis  22   c  to cause the additive manufacturing head  23  and the subtractive manufacturing head  24  to perform X-direction movement within a manufacturing dimension range of the working table  21 . The first Z-axis  22   a , the second Z-axis  22   b , and the X-axis  22   c  are integrally mounted on the Y-axis  22   d  through a support structure to cause the additive manufacturing head  23  and the subtractive manufacturing head  24  to perform the Y-direction movement within the manufacturing dimension range of the working table  21 . The Y-axis  22   d  is fixed on the base of the seal pressure vessel  10 . 
     The above-described rotating component  22 , moving component  25 , and subtractive manufacturing head  24  supporting the machining process use a solid lubricant medium or a non-volatile vacuum lubricant medium. 
     In addition, the manufacturing apparatus  20  may further include other structures such as an industrial robot (not shown in  FIG. 1 ). In addition, the industrial robot may also use the solid lubricant medium or the non-volatile vacuum lubricant medium. 
     The feeding apparatus  60  is connected with the additive manufacturing head  23  in the seal pressure vessel  10  through a feeding pipeline Tm to feed raw materials to the additive manufacturing head  23 . In the example shown in  FIG. 1 , the feeding apparatus  60  is a powder-feeding apparatus. That is, the raw materials fed by the feeding apparatus  60  are in the form of a powder. It can be understood that, as an alternative, the feeding apparatus  60  may be a wire-feeding apparatus, that is, the fed raw materials are in the form of a continuous filament. 
     The heating source  70  is connected with the additive manufacturing head  23  in the seal pressure vessel  10  through a heat energy pipeline Th to heat and melt the raw materials fed to the additive manufacturing head  23 . A heating source provided by the heating source  70  may be a laser beam. In this case, the heat energy pipeline Th may be an optical fiber. Alternatively, the heating source provided by the heating source  70  may be an electron beam, an arc, or an ion beam. In this case, the heat energy pipe Th may be a cable. 
     In the example shown in  FIG. 1 , the vacuum pump  30  is connected with the seal pressure vessel  10  through a vacuum pipeline Tv. The storage vessel of the inert gas  50  is connected with the inert gas source  40  and the seal pressure vessel  10  respectively. That is, the storage vessel of the inert gas  50  is connected with the inert gas source  40  through a pressure-supply pipeline Ts, and is connected with the seal pressure vessel  10  through a pressure-increasing pipeline Ti and a pressure-decreasing pipeline Td. In this case, a gas booster pump  506  is configured in the pressure-increasing pipeline Ti. 
     The CNC system  90  controls the vacuum pump  30  to vacuumize the seal pressure vessel  10  before the manufacturing apparatus  20  performs manufacturing operations, and closes the vacuum pipeline Tv after the seal pressure vessel  10  is vacuum. The computer numerical control system  90  also controls, according to feedback of the monitoring apparatus and after the seal pressure vessel  10  is vacuum, the inert gas source  40  to inject inert gas into the seal pressure vessel  10  through the storage vessel of the inert gas  50  until the pressure in the seal pressure vessel  10  reaches a hyperbaric pressure, e.g., 5 MPa. And, the CNC system  90  controls, according to the feedback of the monitoring apparatus, the storage vessel of the inert gas  50  to implement dynamic compensation for a positive deviation or a negative deviation of the pressure in the seal pressure vessel  10  compared with a target pressure. 
     For a situation where a hyperbaric pressure environment is formed, the above-mentioned target pressure may be a fixed value representing a standard pressure of the hyperbaric pressure environment. For a pressure-increasing process forming the hyperbaric pressure environment, the above-mentioned target pressure may be a variable representing a desired pressure-increasing trend. 
     The positive deviation or the negative deviation means that the pressure in the seal pressure vessel  10  may be higher than the target pressure, or may be lower than the target pressure. Accordingly, the compensation refers to a trend of the pressure in the seal pressure vessel  10  to change towards the target pressure. 
     Specifically, the above-described control implemented by the computer numerical control system  90  may be described as follows. That is, injecting of the inert gas into the storage vessel of the inert gas  50  through the pressure-supply pipeline Ts and injecting of the inert gas into the seal pressure vessel  10  through the pressure-increasing pipeline Ti are controlled by the computer numerical control system  90 . 
     That is, the CNC system  90  may control an increment of the pressure inside the storage vessel of the inert gas  50  by controlling an amount of the inert gas injected into the storage vessel of the inert gas  50  by the pressure-supply pipeline Ts. The CNC system  90  may control an increment of the pressure inside the seal pressure vessel  10  by controlling an amount of the inert gas injected into the seal pressure vessel  10  by the pressure-increasing pipeline Ti. 
     In addition, opening and closing of the pressure-increasing pipeline Ti and the pressure-decreasing pipeline Td are also controlled by the CNC system  90 . 
     For example, at a stage of creating the hyperbaric pressure environment at an initial state of the manufacturing process, the pressure-increasing pipeline Ti is opened and the pressure-decreasing pipeline Td is closed, in which only the gas booster pump  506  in the pressure-increasing pipeline Ti is allowed to inject the inert gas into the seal pressure vessel  10 . During the manufacturing process, both the pressure-increasing pipeline Ti and the pressure-decreasing pipeline Td are opened, in which the gas booster pump  506  in the pressure-increasing pipeline Ti is allowed to inject the inert gas into the seal pressure vessel  10  and the pressure-decreasing pipeline Td is allowed to release the inert gas in the seal pressure vessel  10 . 
     The release of the inert gas in the seal pressure vessel  10  performed by the pressure-decreasing pipeline Td is not controlled by the CNC system, but may be controlled by a difference of pressures between the seal pressure vessel  10  and the storage vessel of the inert gas  50 . In addition, the above-described pressure-decreasing pipeline Td may further include a gas filtering apparatus  505 , which is configured to filter and clean the inert gas recycled from the seal pressure vessel  10 . 
     That is, the pressure inside the storage vessel of the inert gas  50  may not be consistent with the pressure inside the seal pressure vessel  10 . As such, the difference of the pressures is allowed between the seal pressure vessel  10  and the storage vessel of the inert gas  50 . Therefore, according to the difference of the pressures between the seal pressure vessel  10  and the storage vessel of the inert gas  50 , an adaptive pressure-relief process may be implemented through the pressure-decreasing pipeline Td. 
     Specifically, referring to  FIG. 1 , a pressure regulating valve  501  controlled by the CNC system  90  is configured in the pressure-supply pipeline Ts. The pressure regulating valve  501  is used for controlling the amount of the inert gas injected into the storage vessel of the inert gas  50  through the pressure-supply pipeline Ts. A pressure regulating valve  502  controlled by the CNC system  90  is configured in the pressure-increasing pipeline Ti. The pressure regulating valve  502  is used for controlling of the CNC system  90  to the amount of the inert gas injected into the seal pressure vessel  10  through the pressure-increasing pipeline Ti. The gas booster pump  506  is configured in the pressure-increasing pipeline Ti. The gas booster pump  506  is configured to fill the seal pressure vessel  10  with the inert gas. A safety valve  503  is configured in the pressure-decreasing pipeline Td. The safety valve  503  is unidirectionally conducted from the seal pressure vessel  10  to the storage vessel of the inert gas  50 . The safety valve  503  is configured to implement the adaptive pressure-relief process through the pressure-decreasing pipeline Td in response to the difference of the pressures between the seal pressure vessel  10  and the storage vessel of the inert gas  50 . 
     When the pressure in the seal pressure vessel  10  forms a positive deviation compared with the target pressure, if the difference of the pressures between the storage vessel of the inert gas  50  and the seal pressure vessel  10  is sufficient to open the safety valve  503 , the positive deviation may be compensated through the adaptive pressure-relief process of the seal pressure vessel  10 . If the pressure inside the seal pressure vessel  10  forms a negative deviation compared with the target pressure after the adaptive pressure-relief process, an increment of the pressure for compensating the negative deviation may be generated for the seal pressure vessel  10  by injecting the inert gas into the seal pressure vessel  10  through the storage vessel of the inert gas  50 . 
     In addition, since the seal pressure vessel  10  is full of the inert gas provided by the inert gas source  40  during the manufacturing process, when the feeding apparatus  60  is a powder-feeding apparatus, the inert gas source  80  may provide, for the feeding apparatus  60 , a gas pressure used for injecting material powder. The inert gas source  80  is controlled by the CNC system  90  to be isolated from the seal pressure vessel  10  when the seal pressure vessel  10  is vacuumized. A type of the inert gas used by the inert gas sources  40  and  80  may be determined according to requirements of a manufactured part, e.g., argon, nitrogen, helium, or the like. 
     Based on the above example, a variable pressure environment may be provided within the seal pressure vessel  10  so as to implement the manufacturing process in the hyperbaric pressure environment. Thus, for a manufacturing process using metals as raw materials, various issues caused by metallurgical defects of the metals can be effectively suppressed. In this case, the storage vessel of the inert gas  50  is safe and stable to the hyperbaric pressure environment, so that a manufacturing process applying a continuous and uniform hyperbaric pressure may be achieved. In addition, the above-described example is universal and may be applied to metal-based additive and subtractive manufacturing, hybrid additive and subtractive manufacturing, ultrasonic hybrid additive manufacturing, etc. Further, in the above-described example, a solid lubricant medium or a non-volatile vacuum lubricant medium is used in the manufacturing system, so as to avoid oil and grease lubrication from splashing in the vacuum environment to pollute the manufacturing environment, and thus the manufacturing system can work normally in the hyperbaric pressure environment. 
     In addition, the above-described example may further perform temperature control on the hyperbaric pressure environment to ensure temperature stability of the hyperbaric pressure environment. 
     Specifically, a temperature adjusting component  504  is configured in the pressure-increasing pipeline Ti to adjust, between the storage vessel of the inert gas  50  and the pressure regulating valve  502 , a temperature of the inert gas to be injected into the seal pressure vessel  10 . 
     For example, the temperature adjusting component  504  may include cooling apparatuses connected in series between the storage vessel of the inert gas  50  and the pressure regulating valve  502 . The cooling apparatuses are configured to cool the inert gas to be injected into the seal pressure vessel  10 . Therefore, the temperature adjusting component  504  may also be referred to as a cooling component. 
     In this case, a temperature adjusting component (not shown in  FIG. 1 ) used for heating the inert gas in the seal pressure vessel  10  may be configured in the seal pressure vessel  10 , which may be referred to as a heating component, such as a preheating coil. The preheating coil may be fixed at a free position in the seal pressure vessel  10  or may be fixed below the working table  21 . 
     Based on the above configuration, when an environment temperature inside the seal pressure vessel  10  is too high, the internal temperature of the seal pressure vessel  10  may be reduced through turning on the temperature adjusting component  504  used for cooling to inject cooled inert gas into the seal pressure vessel  10 . At the same time, the storage vessel of the inert gas  50  recycles an equal amount or a basically equal amount of the inert gas from the seal pressure vessel  10  to maintain pressure balance in the seal pressure vessel  10 . When the environment temperature inside the seal pressure vessel  10  is too low, the environment temperature in the seal pressure vessel  10  may be increased through a preheating coil heater. 
     Referring to  FIG. 2 , in another example, a manufacturing method for providing a variable pressure environment may include operations as follows. 
     At block  211 , a vacuum pump is controlled to vacuumize a seal pressure vessel. 
     At block  212 , a first inert gas source is controlled to inject inert gas into the seal pressure vessel in a vacuum state through a storage vessel of the inert gas until a pressure in the seal pressure vessel reaches a hyperbaric pressure. 
     At block  213 , a manufacturing process is performed in the seal pressure vessel that is under the hyperbaric pressure. 
     In this case, the operation at this step may implement additive manufacturing and/or subtractive manufacturing. 
     For example, at this step, the additive manufacturing may be implemented according to operations described as follows. Raw materials may be fed to the seal pressure vessel. The raw materials fed to the seal pressure vessel may be heated and melted. According to a preset path plan, additive accumulation may be performed using the melted materials. In this case, the fed metal raw materials may be in the form of a powder, and a second inert gas source may be used to provide a gas pressure for injecting raw material powder. Alternatively, the fed metal raw materials may be in the form of a continuous filament. A heating source used for the additive manufacturing at this step may be a laser beam, an electron beam, an arc, or an ion beam. 
     For another example, at this step, the subtractive manufacturing may be implemented by a machining process. 
     At block  214 , the hyperbaric pressure in the seal pressure vessel is released. 
     At block  215 , a manufactured part is taken out from the seal pressure vessel. 
     In the manufacturing method as shown in  FIG. 2 , when the operations at block  212  and block  213  are performed, the method further includes operations as follows. 
     At block  221 , the storage vessel of the inert gas is controlled to implement dynamic compensation for a positive deviation or a negative deviation of the pressure in the seal pressure vessel compared with a target pressure. 
     At block  222 , a temperature in the seal pressure vessel is adjusted. 
     The operation at block  221  may include controlling injection of the inert gas into the storage vessel of the inert gas and controlling injection of the inert gas into the seal pressure vessel. Release of the inert gas in the seal pressure vessel may be controlled by a difference of pressures between the seal pressure vessel and the storage vessel of the inert gas. 
     For example, a first pressure regulating valve for controlling the injection of the inert gas into the storage vessel of the inert gas may be configured between the first inert gas source and the storage vessel of the inert gas, a second pressure regulating valve for controlling the injection of the inert gas into the seal pressure vessel and a gas booster pump for injecting the inert gas into the seal pressure vessel may be configured between the storage vessel of the inert gas and the seal pressure vessel, and a safety valve for releasing the inert gas in the seal pressure vessel may be configured between the storage vessel of the inert gas and the seal pressure vessel. 
     When the pressure in the seal pressure vessel forms a positive deviation compared with the target pressure, if the difference of the pressures between the storage vessel of the inert gas and the seal pressure vessel is sufficient to open the safety valve, the positive deviation may be compensated through an adaptive pressure-relief process of the seal pressure vessel. If the pressure inside the seal pressure vessel forms a negative deviation compared with the target pressure after the adaptive pressure-relief process, an increment of the pressure for compensating the negative deviation may be generated for the seal pressure vessel by injecting the inert gas into the seal pressure vessel through the storage vessel of the inert gas. 
     In order to clean the recycled inert gas, a gas filtering apparatus may be configured between the storage vessel of the inert gas and the seal pressure vessel. 
     In addition, at block  222 , operations of cooling the inert gas to be injected into the seal pressure vessel and heating the inert gas in the seal pressure vessel may be included. 
     The above are several examples of the present disclosure, and are not used for limiting the protection scope of the present disclosure. Any modifications, equivalents, improvements, etc., made under the principle and spirit of the present disclosure should be included in the protection scope of the present disclosure.