Powder supply system for laser metal deposition and method for refilling powder supply

Abstract

Examples relate to a powder supply system comprising: a powder feeder connectable to a laser metal deposition apparatus, the powder feeder comprising a supply hopper for storing powder, a first powder outlet through which the powder is to be supplied to the laser metal deposition apparatus, and a first powder inlet through which the powder is to be supplied to the laser metal deposition apparatus; a refill hopper for storing additional powder, the refill hopper including a second powder outlet connected to the first powder inlet, the additional powder being supplied to the supply hopper through the second powder outlet; and a pressure generating device for generating an operating pressure level within the feed hopper. The system also includes a controller that, upon receiving the refill signal during normal operation of the powder feeder, causes a pressure level to be generated within the refill hopper that is substantially equal to the operating pressure level, and causes additional powder to be transferred from the refill hopper to the feed hopper.

Description

Technical Field

[0001] The present invention generally relates to additive manufacturing techniques, such as additive layered manufacturing processes that use metal or ceramic powders to form a build or coat a part surface. More specifically, the present invention relates to a powder feed system for a laser metal deposition manufacturing process and a method for refilling a powder feeder of the powder feed system. Background Art

[0002] LMD, also known as laser cladding, is a direct energy deposition (DED) process in which a laser source is used to produce a concentrated beam that is focused on the surface of a substrate (workpiece) and produces a molten pool on the substrate. The material in the form of powder or wire is ejected through one or more delivery nozzles and enters the focused laser beam. In the case where the added material is a powder (e.g., metal or ceramic powder), the blown powder meets the laser beam and is absorbed and integrated into the molten pool, thereby being deposited on the substrate surface. An XYZ positioning mechanism typically moves the substrate relative to the laser to produce part layers layer by layer. The technology allows for the additive manufacturing of medium and large-sized complex geometric parts layer by layer and has a high deposition rate (up to 10Kg / h or even higher). LMD typically uses data computer-aided design (CAD) software or a 3D object scanner to guide the hardware to deposit materials.

[0003] Powder particles injected into the laser beam are sucked from the supply system through a cylindrical inlet to the supply nozzle. Existing powder feeders use a mechanical structure to deliver a metered powder flow. Typically, the powder is extracted or pushed out of the powder reservoir by the action of a rotating wheel driven by a motor. Such supply systems must maintain a constant pressure (e.g., 1.5 bar or higher) in their reservoirs or hoppers to avoid fluctuations in the powder flow, which may cause powder to be supplied at inconsistent rates. These fluctuations may also cause quality control problems that otherwise require a consistent powder flow. Ensuring that powder is effectively and consistently supplied to the gas powder flow at the powder delivery nozzle is critical to laser cladding to ensure that high-quality parts are obtained.

[0004] However, the reservoirs or hoppers of existing powder feeders have limited capacity to store powder (the hopper volume is typically in the range of 1.1 to 5 liters), so since they must maintain a constant pressure within a very specific margin, laser cladding will stop every time the hopper becomes empty and they must be refilled. Depending on the volume of the hopper and the deposition rate, this refilling operation may be performed every few hours. This makes the manufacturing process inefficient and may produce discontinuities in the resulting parts. Some solutions have tried to overcome this problem by including additional powder feeders, wherein the corresponding hoppers of these additional powder feeders are connected in parallel to the corresponding laser cladding equipment, and which powder feeder supplies the deposition nozzle is controlled by inserting switches, valves or similar devices. In this way, the system has a main powder feeder and a backup powder feeder, which will operate when the remaining powder feeders empty their hoppers. This solution is inefficient, expensive, not suitable for situations where there is not enough space available to install multiple powder feeders, and introduces large variability in the deposited surface obtained, because these powder feeders may not deposit exactly the same amount of powder (deposition rate is grams per minute) onto the substrate.

[0005]

[0006] Therefore, there remains a need in the art for a powder feed system, particularly a system useful in high rate manufacturing processes, that can provide a constant and continuous supply of powder at a consistent rate and in an amount sufficient to manufacture large size parts. Summary of the invention

[0006] The first object of the present invention is a powder supply system, which includes a powder feeder connectable to an LMD device, the powder feeder including a supply hopper for storing powder, a first powder outlet and a first powder inlet, and the powder will be supplied to the LMD device through the first powder outlet. As used herein, the LMD device may refer to any device or system capable of producing a molten pool at the surface of a workpiece (while adding powder melted by a laser to the molten pool), such as a laser cladding machine, a deposition laser head or nozzle, etc. The powder feeder may preferably be a positive displacement feeder, which uses a rotating disk that collects powder in small holes or grooves. Alternatively, the powder feeder may be a spiral powder feeder, a flow powder feeder including a defined vibrating motion drive to meter the powder material, or any other known type of powder feeder. At some point, the powder is blown into a powder supply line, where a gas such as argon or nitrogen transports the powder to the desired outlet point at the deposition nozzle through a powder supply hose.

[0007] The powder feed system also includes a pressure generating device to generate an operating pressure level inside the feed hopper. The operating pressure level inside the feed hopper can typically be in the range of 1.5 bar to 6 bar, but other pressure levels can be used to ensure an appropriate pressure difference between the hopper contents and the powder carrier gas flow used to move the fluidized powder out of the hopper and toward the deposition nozzle. Although in some embodiments, the pressure generating device can be a single pressure source that generates pressure levels in the two hoppers, such as a piston screw pump, a differential pressure generator, a pressurized bottle (gas cylinder) storing the gas, etc., in some other embodiments, different pressure sources can be used to generate the two pressure levels. Preferably, the pressure source will be a pressurized gas source.

[0008] The powder feed system further comprises at least one refill hopper configured to store additional powder and comprising a second powder outlet fluidly connected to the first powder inlet, through which the additional powder is provided to the feed hopper. The refill hopper may have a wide variety of shapes and volumes, depending on the system in which it will be installed and the requirements of the particular additive manufacturing process. Preferably, the refill hopper may have a volume selected to store up to 400 kg of powder, or even more. The additional powder will be the same powder as that stored in the feed hopper.

[0009] The powder feed system also includes a controller configured to, during normal operation of the powder feeder, upon receiving a first refill signal, cause the pressure generating device to generate a pressure level in the refill hopper that is substantially equal to the operating pressure level in the supply hopper, and cause at least a portion of the additional powder to be transferred from the refill hopper to the supply hopper. As used herein, "normal operation of the powder feeder" refers to the regular operation of the feeder to provide the required powder dose to the LMD device. In this way, the refill hopper refills the supply hopper at any time during normal operation of the supply hopper without having to stop the LMD process. By equalizing the pressure in the two hoppers before transferring the powder from the refill hopper to the supply hopper, the pressure at the supply hopper is not affected during the powder transfer, thereby avoiding fluctuations in the powder flow rate at the outlet of the powder feeder. This maintains the powder flow at a constant and consistent rate, ensuring that the powder is constantly and continuously deposited onto the corresponding substrate and ensuring that high-quality parts are obtained. Additionally, by performing the refilling of the hopper of the powder feeder during its normal feeding operation and thus without having to stop the powder feed, the additive manufacturing process, in particular the laser metal deposition process, fed by the powder feeder does not have to be interrupted at any time. This increases the overall efficiency of the cited manufacturing process.

[0010] Once a predetermined amount of powder has been transferred from the refill hopper to the supply hopper, the refill hopper may be depressurized.

[0011] As used herein, a controller may be a CNC controller, a PLC or the like, or any other device that includes the necessary hardware and software to perform the functions disclosed herein.

[0012] In some embodiments, the powder supply system includes a first flow control device, which is located between the supply hopper and the refill hopper to control the transmission of additional powder. The flow control device can be integrated into a conduit, a tube or a hose that communicates the first powder inlet of the supply hopper with the second powder outlet of the refill hopper. The first flow control device is configured to allow or prevent powder from being transmitted toward the supply hopper from the refill hopper. As an example, the first flow control device can be a solenoid valve or a pneumatic valve, and more preferably a diaphragm solenoid valve or a diaphragm pneumatic valve. In some other embodiments, the valve can be a pinch valve, which is closed in its normal position and opened when pressurized, and vice versa.

[0013] In some embodiments, the powder feed system includes a first flow meter located between the feed hopper and the refill hopper, preferably downstream of the first flow control device, to monitor the amount of additional powder delivered to the feed hopper. This allows for better control of the amount of powder delivered from the refill hopper to the feed hopper, and therefore better control of the amount of powder remaining inside both hoppers.

[0014] In some embodiments, the powder supply system includes a second flow meter located at the outlet of the powder supply to monitor the powder flow rate to be provided to the laser metal deposition device. This allows for better control of the amount of powder provided to the LMD device.

[0015] In some embodiments, the powder feeder includes a first level sensor for monitoring the powder level in the feed hopper. The first level sensor may be located on the cover of the feed hopper. Alternatively, the first level sensor may be externally connected to the portion of the feed hopper located between the rotating disk and the container. In another alternative, the powder feeder may include a weighing sensor to weigh the powder in the feed hopper, thereby estimating the amount of remaining powder. The use of a level sensor simplifies the monitoring of the amount of remaining powder because the measurement is independent of the specific physical and chemical characteristics of the powder filling the hopper, such as density. Various sensors can be used for point detection of solids, including vibration, rotating paddles, mechanical (diaphragms), microwave (radar), capacitance, optical, pulsed ultrasonic and ultrasonic level sensors. For the case where the first level sensor is placed between the rotating disk of the feed hopper and the container, the sensor may be a laser sensor configured to measure the powder level of the glass passing through the container. This avoids having to drill holes in the feed hopper to place the level sensor.

[0016] In some embodiments, the first refill signal received at the controller is a signal issued by the first level sensor indicating that the powder level in the feed hopper is below a first predetermined threshold. Alternatively, the first refill signal may be a signal generated by a user to force a refill of the feed hopper. The first level sensor may also issue a stop signal indicating that the powder level in the feed hopper has reached a "full" level, so the controller may cause the refill hopper to stop transferring powder to the feed hopper. For example, the controller may turn off the first flow control device.

[0017] In some embodiments, the refill hopper includes a second powder inlet through which powder is provided from an external powder source. The external powder source may be a powder deposit from which powder may be provided by gravity, by blowing the powder (e.g., injecting gas), or by some other propulsion device (such as a peristaltic pump or any other device or system capable of propelling powder from an external source to the refill hopper). The second powder inlet will preferably be located on the lid of the refill hopper. The refill hopper may also include another powder inlet for manually introducing powder.

[0018] In some embodiments, the second powder inlet of the refill hopper can be positioned adjacent to the longitudinal center axis of the refill hopper. Preferably, the second powder inlet will be positioned in line with the longitudinal center axis of the refill hopper. In this case, the agitator, which will also be positioned in line with the longitudinal center axis of the refill hopper, can be actuated by a motor that is eccentric and connected to the agitator by inserting a transmission device (such as a transmission belt with toothed gears, etc.). The more centered the second powder inlet is in the refill hopper, the more uniform the powder storage in the refill hopper, and the better the Gaussian distribution of the powder particles will be.

[0019] In some embodiments, the powder supply system includes a cyclone hopper as an additional external powder source. The cyclone hopper can be fluidly connected to the third powder inlet of the refill hopper and is configured to provide powder to the refill hopper. The third powder inlet will preferably be located on the cover of the refill hopper. Preferably, when the powder distribution in the refill hopper is out of range or control, the cyclone hopper will supply the refill hopper. For example, when the user detects more than usual powder blockage in the refill powder (meaning that the powder distribution in the refill hopper is out of range or control) (this is usually caused by the powder particles not presenting a proper Gaussian distribution), he can activate the cyclone hopper to supply the refill hopper, which also stores powder, and deactivates the current external powder source. In this case, the traditional external powder source can also be fluidly connected to the cyclone hopper, so the powder stored in the external powder source circulates inside the cyclone hopper to improve its particle distribution before being supplied to the refill hopper. Alternatively, the external powder source and the cyclone hopper can be two independent powder hoppers. The cyclone hopper ensures that the powders supplied to the refill hopper maintain a proper Gaussian distribution between their particles.

[0020] In some embodiments, the powder supply system includes a second flow control device located upstream of the second powder inlet to control the powder transmission from an external powder source. The flow control device can be integrated into a conduit, a pipeline or a hose that communicates the second powder inlet of the refill hopper with an external powder source, and can be opened and closed to allow or prevent powder from passing through. As an example, the second flow control device can be a solenoid valve or a pneumatic valve, and more preferably a diaphragm solenoid valve or a diaphragm pneumatic valve. In some other embodiments, the valve can be a pinch valve, which is closed in its normal position and opened when pressurized, and vice versa.

[0021] In some embodiments, the refill hopper includes a second level sensor, such as a vibration, rotary paddle, mechanical (diaphragm), microwave (radar), capacitance, optical, pulsed ultrasonic, and ultrasonic level sensor, to monitor the powder level within the refill hopper. The second level sensor may be located on the lid of the refill hopper. Alternatively, the refill hopper may include a weighing sensor to weigh the powder within the refill hopper, whereby the amount of remaining powder may be estimated.

[0022] In some embodiments, the controller is configured to cause powder to be provided from an external powder source to the refill hopper via a second powder inlet in response to receiving a second refill signal. That is, the controller may cause gas injection to blow powder from an external powder source, or may activate a peristaltic pump to supply powder, and may also open a valve at the inlet of the refill hopper.

[0023] In some embodiments, the second refill signal is a signal received from a second level sensor indicating that the powder level in the refill hopper is below a second predetermined threshold or a signal received from a user. In any of these cases, the controller can activate a corresponding propulsion device to feed powder from an external powder source to the refill hopper, or powder can be manually added to the refill hopper. In addition, the controller can cause the second flow control device to open to allow the powder to pass. The second level sensor can also send a stop signal indicating that the powder level in the refill hopper has reached a "full" level, so the controller can cause the external powder source to stop feeding powder to the refill hopper. For example, the controller can turn off the second flow control device or deactivate the gas injection or peristaltic pump.

[0024] In some embodiments, the powder hopper and the refill hopper include respective first and second pressure sensors to monitor the pressure levels within the respective supply hopper and refill hopper, respectively. These pressure sensors are used to monitor the pressure levels inside the hoppers at any time and particularly during the refilling operation.

[0025] In some embodiments, the supply hopper and the refill hopper include first and second gas inlets, respectively, fluidly connected to the pressure generating device.

[0026] In some embodiments, the supply hopper and the refill hopper are configured to store metal powders (stainless steel, silver, copper nickel, titanium, cobalt, metal oxides, etc.), ceramic powders (carbides, nitrides, oxide ceramics, etc.), or a combination of both. The metal powders may be made of a single metal component, a combination of multiple metal components, alloys, and any combination thereof. The ceramic powders may be made of a single ceramic component or a combination of multiple ceramic components. Due to the toxicity of these powders, the powder supply system disclosed herein is designed to be preferably airtight.

[0027] In some embodiments, the refill hopper comprises a container for storing the powder and a lid for closing the container. The container has an upper cylindrical section and a lower inverted frustoconical section. Although preferably the upper section of the container will be cylindrical, in some other embodiments, the upper section may have a different geometry, such as a frustoconical geometry, a trapezoidal geometry, or any other geometry. Although preferably the lower section of the container will be frustoconical, in some other embodiments, the lower section may be substantially conical. The inclined sidewalls of the lower inverted frustoconical section will preferably have an angle greater than 60° relative to the horizontal plane. This inclination of the sidewalls of the lower section of the container ensures that the flowability of the powder in the lower inverted frustoconical section is substantially constant, so that the powder does not adhere to the wall of the container and falls towards the lower part of the container where the powder outlet is located. More preferably, the angle will be 70° relative to the horizontal plane.

[0028] In some embodiments, at least one of the supply hopper and the refill hopper comprises an electrically actuated agitator to move the powder. Preferably, both hoppers comprise electrically actuated agitators. The agitators may be driven by an electric motor located on the respective cover of the hopper and by a corresponding rotating axial shaft inserted. The agitator may be any known agitator capable of moving the powder near the powder outlet to minimize clogging and powder segregation and ensure continuous supply of the powder.

[0029] In some embodiments, the electrically actuated agitator may be a screw conveyor configured to convey powder upward from an area located near the respective powder outlets of the feed hopper and the refill hopper, respectively. By doing so, powder segregation in an area closer to the respective powder outlets is reduced.

[0030] The agitator of the refill hopper extends from the lid of the refill hopper to the area of ​​the powder outlet of the refill hopper in close proximity thereto. The closer the free end of the agitator is to the powder outlet, the better it is positioned. The distance between the free end of the agitator and the powder outlet will depend on the size of the cross section of the agitator in the area and the size of the cross section of the powder outlet, but they will preferably be designed to minimize the distance. The agitator can be divided into an upper part, a central part and a lower part corresponding to the upper part, the central part and the lower part of the refill hopper. For example, these parts can correspond to approximately three equal thirds, wherein the length of the agitator and the container of the refill hopper can be divided into three thirds. In some other examples, these parts can have different lengths relative to the total length of the agitator and the hopper, respectively, and the length between them can be slightly different.

[0031] In some embodiments, the agitator of the refill hopper comprises a cone connected to the central part of the agitator. The cone is connected to the agitator by its apex and is open towards the bottom of the container. The cone is open at its base, i.e., it does not have a base that closes the cone. The side walls of the cone have an angle greater than 60° relative to the horizontal. Preferably, the angle is 70° relative to the horizontal. The cone causes a zigzag effect in the powder stored in the refill hopper, resulting in mixing of the powder particles in the central area of ​​the refill hopper.

[0032] In some embodiments, the agitator includes a first stirring rod and a second stirring rod. Both stirring rods correspond to the bottom of the agitator and are close to the free end of the agitator. The free end of the agitator is the end of the agitator that is located next to the powder outlet. In addition, these stirring rods are located at different distances from the free end of the agitator. In other words, the two stirring rods are located at different heights relative to the free end of the agitator. Preferably, the length of these stirring rods is slightly smaller than the inner diameter of the corresponding part of the refill hopper. The rotation of these stirring rods causes the powder located near the powder outlet to move to avoid clogging. In fact, the closer the free end of the stirring rod rotates relative to the inner wall of the container, the stirring rod most effectively avoids powder clogging.

[0033] In some embodiments, the agitator includes a third stirring rod and a fourth stirring rod. The two stirring rods also correspond to the lower part of the agitator, but are close to the central part of the agitator. The third stirring rod and the fourth stirring rod are also positioned at different distances from the free end of the agitator. In other words, these stirring rods are located between the cone and the first stirring rod and the second stirring rod. Preferably, the length of these stirring rods is slightly smaller than the inner diameter of the corresponding part of the refill hopper. The rotation of the stirring rod causes the powder located between the cone and the first stirring rod and the second stirring rod to move to promote its descent toward the powder outlet. The closer the free end of the stirring rod rotates relative to the inner wall of the container, the more effectively the stirring rod promotes the powder to descend downward.

[0034] In some embodiments, the agitator further comprises a screw coupled to an upper portion of the agitator. The diameter of the screw is slightly smaller than the inner diameter of a corresponding portion of the refill hopper. The rotation of the screw prevents large powder particles from adhering to the sidewall in the upper portion of the refill hopper.

[0035] In some embodiments, the powder feed system includes a heating pad or heating jacket at least partially covering the outer surface of at least one of the feed hopper and the refill hopper.By heating the powder, humidity inside the hopper is minimized, thereby reducing powder segregation.

[0036] In some embodiments, at least one vibration motor is coupled to the outer surface of the refill hopper. The vibration motor may be operated when a blockage is detected (when the first flow control device is opened to allow powder transfer, the flow meter may not detect the powder transfer) and when the powder is to be replaced and the refill hopper needs to be cleaned. Alternatively or in combination with the vibration motor, the refill hopper may also include an additional gas inlet through which pressurized gas (preferably air) is injected to clean the hopper. The additional gas inlet may be located in the cover of the refill hopper or in its sidewall and may be connected to an air compressor.

[0037] In some embodiments, the refill hopper and the supply hopper may include respective pressure relief valves to control or limit the maximum pressure level inside both hoppers.

[0038] A second object of the present invention is a method for refilling a feed hopper of a powder feed system. The method comprises providing a powder feed system as described above, wherein the feed hopper has been pressurized at an operating pressure level to provide powder to an LMD device. As described above, the LMD device may refer to any device capable of depositing metal and / or ceramic powder onto a substrate by melting, such as a laser cladding machine, a deposition head or a nozzle, etc.

[0039] Then, during normal operation of the powder feeder of the powder feed system, the method further comprises:

[0040] receiving a first refill signal at the controller. The refill signal indicates that the feed hopper is to be refilled and may be issued by a user, for example, when the user visually detects that the powder level in the feed hopper is low or when a first level sensor or a weighing sensor of the feed hopper detects that the powder level in the hopper is low (e.g., below a first predetermined threshold);

[0041] pressurizing the refill hopper via the pressure generating device until the pressure level within the refill hopper is substantially equal to the operating pressure level in the supply hopper. That is, the controller instructs the pressure generating device to generate a pressure within the refill hopper that is equal to the operating pressure level in the supply hopper;

[0042] At least a portion of the additional powder stored in the refill hopper is caused to transfer to the supply hopper. This may be caused by opening a flow control device located between the supply hopper and the refill hopper and by means of gravity, some propulsion mechanism, a small pressure difference between the two hoppers, or a combination thereof. Once a predetermined amount of powder has been transferred from the refill hopper to the supply hopper, the refill hopper may be depressurized.

[0043] In some embodiments, the method comprises pressurizing the refill hopper at a pressure level equal to or at most 1 bar, preferably at most 0.5 bar, more preferably at most 0.2 bar higher than the operating pressure level in the supply hopper.

[0044] In some embodiments, the method includes receiving a second refill signal at the controller. The second refill signal indicates that the powder level inside the refill hopper is low. The controller then causes powder to be transferred from an external powder source to the refill hopper. The controller may cause gas injection to blow powder from the external powder source, or may activate a peristaltic pump to feed powder. In addition, the controller may also instruct to open a second flow control device located between the refill hopper and the external powder source to allow the powder to enter.

[0045] In some embodiments, the second refill signal is a signal received from a second level sensor indicating that the powder level within the refill hopper is below a second predetermined threshold or a signal received from a user. In any of these cases, the controller can activate a corresponding propulsion device to feed powder from an external powder source to the refill source, or powder can be manually added to the refill hopper. The second level sensor can also send a stop signal indicating that the powder level within the refill hopper has reached a "full" level, so the controller can stop the external powder source from feeding powder to the refill hopper. For example, the controller can turn off the second flow control device or stop gas injection or deactivate the peristaltic pump.

[0046] The powder supply system and method for supplying powder described herein have several advantages and / or differences compared to previous devices and techniques. Specifically, a system and method are provided that are capable of providing a constant, continuous, consistent and stable powder flow at a low flow rate required for an additive manufacturing process (such as an LMD process). It avoids fluctuations in the powder flow that may cause quality control problems. In addition, the relatively expensive multiple powder feeders used in the prior art are replaced by cheaper refilling hoppers that can refill the powder feeder multiple times as needed and do not introduce fluctuations in the powder flow provided to the additive manufacturing device. Finally, the solution disclosed herein avoids having to stop the manufacturing process during normal operation of the powder feeder to refill the hopper by refilling the supply hopper, and does not affect its normal function. This solution is particularly useful for high-speed additive manufacturing processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] To complete the description and to provide a better understanding of the invention, a set of drawings are provided. Said drawings form an integral part of the description and illustrate embodiments of the invention which should not be interpreted as limiting the scope of the invention but merely as examples of how the invention may be performed.

[0048] The accompanying drawings include the following figures:

[0049] Figure 1 A perspective front view of a powder feed system according to a specific embodiment of the present invention is shown.

[0050] Figure 2A A first embodiment of a pressure generating subsystem is shown. Figure 1 A three-dimensional front view of a powder supply system.

[0051] Figure 2B A second embodiment including a pressure generating subsystem is shown. Figure 1 A three-dimensional front view of a powder supply system.

[0052] Figure 3 Shows Figure 1 and Figure 2A Detailed perspective view of the cover of the feed hopper.

[0053] Figure 4 A perspective view of a refill hopper according to a specific embodiment of the present invention is shown.

[0054] Figure 5 Shows Figure 4 A plan view of the lid of the refill hopper.

[0055] Figure 6 Shows Figure 4 A cross-sectional plan view of a refill hopper along its longitudinal axis.

[0056] Figure 7 A flow chart is shown of a method for refilling a powder hopper of a powder feed system according to certain embodiments of the present invention.

[0057] Figure 8 A perspective view of a refill hopper according to another specific embodiment of the present invention is shown.

[0058] Fig. 9 Shows Figure 8 A cross-sectional view of a refill hopper along its longitudinal axis.

[0059] Fig.10 The embodiment according to the present invention is shown Fig. 9 A three-dimensional diagram of a stirrer. DETAILED DESCRIPTION

[0060] Figure 1 1 shows a perspective front view of a powder supply system 100 according to a specific embodiment of the present invention. It should be understood that Figure 1 The system 100 may include additional components, and some of the components described herein may be removed and / or modified without departing from the scope of the described system 100. Additionally, implementation of the system 100 is not limited to such embodiments.

[0061] The powder supply system 100 comprises a powder supply device 101, in particular a disc powder supply device, which in turn comprises a supply hopper 102 for storing powder and a cabinet 103, which carries the supply hopper 102 and stores the electric, electronic and mechanical components for managing the powder supply operation. The supply hopper 102 is formed by a container 104 for storing powder and a supply disk 105 having an annular groove (not shown in the figure). The rotation of the supply disk 105 enables the groove filled with powder to reach the opposite side of the container 104, at which time the carrier gas (argon or nitrogen) uses a suction unit to pick up the powder by sucking the powder out of the groove. Preferably, an antistatic hose can be used to supply the powder to the laser cladding nozzle (not shown in the figure). The supply hopper 102 also includes an agitator 106, the rotation control of which is actuated by a rotary motor 107 located on the upper cover 108 of the supply hopper. Agitator 106 rotates inside container 104 at a defined distance from a spreader unit (not shown in this figure) and helps to ensure a continuous supply of powders that do not flow well or tend to drip badly. Different types of agitators can be used, such as standard agitators or agitators with pins or small plates.

[0062] The pressurized gas supplied to the feed hopper 102 is provided by a pressure generator 111, such as a piston screw pump, a differential pressure generator connected to a gas source (e.g., argon or nitrogen), or a pressurized bottle in which the gas is stored, wherein a pressure gauge is inserted to regulate the delivery pressure. The pressure generator 111 is directly connected to the cabinet 103 so that the pressurized gas passes through the cabinet 103 and reaches the feed hopper 102 via a gas inlet (not shown) located in the lower part of the feed hopper 102. The pressure generator 111 generates a pressure level of, for example, 6 bar pressure, which can preferably be reduced to 1.5 bar by a pressure regulator before entering the feed hopper 102 (other pressure levels can be generated by the pressure generator 111 and supplied to the feed hopper 102, depending on the specific application and the reinforcement used in the container 104), which is the operating pressure level used by the powder feeder 101 for its normal operation. The gas injected to generate said pressure can only leave the supply hopper 102 from the suction unit and via the powder outlet through which powder will be supplied to the laser cladding nozzle. The supply hopper 102 also comprises a powder inlet 112 through which powder is received from a refill hopper 113 .

[0063] The refilling hopper 113 also includes a rotary agitator (not shown in the figure), which may have the same architecture as the agitator 106 of the supply hopper 102 or may be different. The agitator may also be actuated by a rotary motor (not shown in the figure) located on the cover (not shown) of the refilling hopper 113. The powder outlet 114 of the refilling hopper 113 is connected to the powder inlet 112 of the supply hopper 102 through an antistatic hose 115 and a flow control device (particularly a pinch valve 116 that opens or closes the valve using pressurized air). The refilling hopper 113 also includes a gas inlet 117 connected to a hose 118, which is supplied by the same pressure generator 111. Alternatively, the refilling hopper 113 and the supply hopper 102 may be connected to different pressure generators, respectively.

[0064] Preferably, the refill hopper 113 may have a volume selected to store up to 400 kg of powder or even more. The powder stored in the refill hopper 113 is the same powder stored in the container 104 of the supply hopper 102, and it may be a metal powder (stainless steel, silver, copper nickel, titanium, cobalt, metal oxides, etc.), a ceramic powder (carbide, nitride, oxide ceramic, etc.), or a combination of both. The metal powder may be made of a single metal component, a combination of multiple metal components, an alloy, and any combination thereof. The ceramic powder may be made of a single ceramic component or a combination of multiple ceramic components.

[0065] During normal operation of the powder feeder, when the controller 119 receives a signal indicating that the amount of powder in the supply hopper 102 is low, it instructs the pressure generator 111 to also provide a pressure of 1.5 bar in the refill hopper 113 to equalize the pressure levels in the two hoppers 102, 113. The controller 119 will then also deactivate (the pinch valve 116 is pressurized to keep it closed) a compressor (not shown) connected to the pinch valve 116 so that the pinch valve 116 opens and at least a portion of the powder stored in the refill hopper 113 can be transferred to the supply hopper 102 by the action of gravity. Once the supply hopper 102 has been refilled, the controller 119 activates the compressor to close the pinch valve 116 and stops the pressure generator 111 from providing pressure inside the refill hopper 113. All components and connections of the powder supply system 100 used to transfer the powder are airtight to avoid leakage due to the high toxicity of the powder.

[0066] Thus, the container 104 of the supply hopper 102 is refilled by the refill hopper 113 in a continuous manner and without introducing pressure variations in the supply hopper 102 which could cause fluctuations in the powder flow rate at the outlet of the powder feeder 101. This avoids having to interrupt the powder feeding process performed by the powder feeder 101 to refill it, and therefore avoids having to interrupt the additive manufacturing process performed by the LMD device fed by said powder feeder 101.

[0067] Although Figure 1 Specific shapes and arrangements of components forming powder feed system 100 are shown, but other designs and architectures may be used. Figure 1 , controller 119 is shown as a separate element located outside of cabinet 103 , but it may be the same controller used to manage the remaining elements of powder supply system 100 , and it may be housed inside the cabinet 103 .

[0068] Similarly, although Figure 1 A disk powder feeder 101 and a pinch valve 116 are shown, but other powder feeders and other electric or pneumatic valves based on different feeding technologies may be used. Figure 1 In the embodiment shown, only one refill hopper 113 is connected to a single supply hopper 102 , but in some other embodiments, more than one refill hopper 113 may be connected to one or more supply hoppers 102 of the same powder feeder 101 .

[0069] Figure 2A A first embodiment of a pressure generating subsystem is shown. Figure 1 A perspective front view of the powder supply system 100 .

[0070] This embodiment of the pressure generation subsystem comprises a pressure generator 111 which is directly connected to the cabinet 103 so that the pressurized gas provided by the pressure generator 111 is supplied at a pressure of 6 bar and then reduced to 1.5 bar before entering the supply hopper 102 by a pressure regulator (not shown) preferably located inside the cabinet 103. There is a connection for supplying pressurized gas inside the cabinet 103 between the pressure regulator and the supply hopper 102. The pressure generator 111 is further managed by a controller 119.

[0071] In such an embodiment, the supply hopper 102 includes a gas outlet 109 that fluidly connects the supply hopper 102 with the refill hopper 113 through an interposed valve 123 (e.g., an electric valve or a solenoid valve), which is designed to cut off or allow the flow of a fluid (particularly a gas such as nitrogen or argon). Therefore, when the controller 119 receives a signal indicating that the amount of powder in the supply hopper 102 is low, it instructs the valve 123 to allow pressurized gas to be transmitted from the pressure generator 111 via the supply hopper 102 toward the refill hopper 113 until the pressure in the refill hopper 113 is equal to the pressure level in the supply hopper 102. Then, the controller 119 also deactivates the compressor (not shown) connected to the pinch valve 116 (the pinch valve 116 is pressurized to keep it closed), so that the pinch valve 116 opens, and at least a portion of the powder stored in the refill hopper 113 can be transferred to the supply hopper 102 by the action of gravity. In such an embodiment, there is also a flow meter 122 at the outlet of the pinch valve 116 to control the amount of powder delivered to the feed hopper 102. Once the feed hopper 102 has been refilled, the controller 119 activates the compressor to close the pinch valve 116 and instructs valve 123 to close.

[0072] The embodiment also includes an external powder source 126 and a cyclone hopper 127, which is connected to the lid of the refill hopper through a corresponding powder inlet (not shown in the figure). The external powder source 126 can be a powder deposit from which powder can be provided by gravity, by blowing the powder (e.g., injecting gas), or by a propulsion device such as a peristaltic pump or any other device or system capable of propelling powder from an external source to the refill hopper. The cyclone hopper 127 can be a powder deposit with a cyclone that uses centrifugal force to mix the powder particles from its deposit to ensure that the powder particles present a Gaussian distribution at its outlet.

[0073] Figure 2B A second embodiment including a pressure generating subsystem is shown. Figure 1 A perspective front view of the powder supply system 100 .

[0074] In this second embodiment of the pressure generating subsystem, the pressure generator 111 is directly connected to the cabinet 103 through which the pressurized gas reaches the supply hopper 102. The pressure generator 111 is also directly connected to the refill hopper 113 by inserting another valve 124 (electric valve or solenoid valve). The gas provided by the pressure generator 111 can be at a pressure of 6 bar and can be reduced to 1.5 bar before entering the supply hopper 102 by a pressure regulator (not shown) located inside the cabinet 103 or integrated into the pressure generator 111. The gas provided to the refill hopper 113 can also be provided by the pressure generator 111 at a pressure of 6 bar, and it can be reduced to 1.5 bar by a pressure regulator (not shown) integrated into the pressure generator 111. The pressure regulator for the gas provided to the refill hopper 113 can be configured to provide the gas at a pressure slightly higher than the pressure provided to the supply hopper 102. For example, the gas provided to the refill hopper 113 can be at any pressure in the range of 1.5-2.5 bar. This pressure difference between the two hoppers will facilitate the transfer of powder from the refill hopper 113 to the supply hopper 102. The pressure generator 111 is also managed by the controller 119.

[0075] When the controller 119 receives a signal indicating that the amount of powder in the supply hopper 102 is low, it instructs the valve 124 to allow gas to be transferred from the pressure generator 111 toward the refill hopper 113 until the pressure level in the refill hopper 113 is equal to or slightly higher than the pressure level in the supply hopper 102. The controller 119 will then also deactivate the compressor (not shown) connected to the pinch valve 116 (the pinch valve 116 is pressurized to keep it closed) so that the pinch valve 116 opens and at least a portion of the powder stored in the refill hopper 113 can be transferred to the supply hopper 102 by the action of gravity. In such an embodiment, there is also a flow meter 122 at the outlet of the pinch valve 116 to control the amount of powder transferred to the supply hopper 102. Once the supply hopper 102 has been refilled, the controller 119 activates the compressor to close the pinch valve 116 and instructs the valve 124 to close.

[0076] and Figure 2A As in , this embodiment also includes an external powder source 126 and a cyclone hopper 127 fluidly connected to the refill hopper 113.

[0077] Figure 3 Shows Figure 1 and Figure 2A Detailed perspective view of the cover 108 of the supply hopper 102.

[0078] The lid 108 comprises a rotary motor 107 for actuating the agitator 106, a powder inlet 112 connected to a hose 115, a pressure sensor 120 for monitoring the pressure level in the container 104 of the supply hopper 102, and a level sensor 121 for monitoring the amount of powder in the container 104 of the supply hopper 102, the powder being received from the refill hopper 113 through the hose 115. The pressure sensor 120 may be a strain gauge, a piezoelectric sensor, a capacitive sensor, a manometer or any other sensor capable of monitoring the pressure level in the container 104. In turn, the level sensor 121 may be an ultrasonic level sensor, a capacitive level sensor, an optical level sensor or any other sensor capable of monitoring the level of the powder in the container 104. The pressure sensor 120 and the level sensor 121 are communicatively connected to the controller 119, thereby providing both measurements in a continuous or periodic manner. The lid further comprises a gas outlet 109 connected to a hose 125, through which the pressurized gas previously injected into the supply hopper 102 is conveyed towards the refill hopper 113. In this case, there is a valve 123 downstream of the gas outlet 109 to shut off or allow the flow of pressurized gas to the refill hopper 113 .

[0079] Figure 4 A perspective view of a refill hopper 200 according to a particular embodiment of the present invention is shown. It should be understood that Figure 4 The refill hopper 200 may include additional components, and some of the components described herein may be removed and / or modified without departing from the scope of the described refill hopper 200. Additionally, implementation of the refill hopper 200 is not limited to this embodiment.

[0080] The refill hopper 200 comprises a container 201 for storing powder, the container 201 having an upper cylindrical section 202 and a lower inverted frustoconical section 203 terminating in a powder outlet 204 of the hopper 200, through which the powder is supplied to the supply hopper via a corresponding hose, pipe or tube, such as Figure 1and FIG. 2 . The refill hopper 200 also includes a support structure 205 that is designed to rest on a flat surface (e.g., a floor). The support structure is entirely optional and may have different designs. The cover 206 of the refill hopper 200 includes a first powder inlet 207 (shown as having a removable threaded closure) through which powder can be manually supplied by a user and a second powder inlet 211 through which powder can be received from an external powder source. The external powder source may be a powder deposit from which powder may be provided by gravity, by blowing powder (e.g., injecting gas), or by some other propulsion device such as a peristaltic pump or any other device or system capable of propelling powder from an external source to the refill hopper 200. The lid 206 also has a rotary motor 208 for actuating an agitator (not shown), screws 209 for coupling the lid 206 to the container 201, a pressure sensor 210, a plurality of gas inlets 212 through which pressurized gas (usually air) is injected to clean the container 201 when the powder in use is replaced by another powder, a gas inlet 213 connected to a hose 214 through which a gas such as argon or nitrogen is injected to pressurize the interior of the container 201, a pressure relief valve 215, and a level sensor (not shown in this figure). There is also a vibration motor 216 coupled to the outer surface of the container 201, which can be operated when a blockage is detected (the flow meter located downstream of the powder outlet 204 may not detect the passage of powder) and when the powder is to be replaced and the container 201 needs to be cleaned.

[0081] Figure 5 Shows Figure 4 206 of the refill hopper 200. The cover 206 of the refill hopper 200 includes a manual powder inlet 207, an automatic powder inlet 211, a rotary motor 208, eight screws 209, a pressure sensor 210, four gas inlets 212 for cleaning purposes, a gas inlet 213 for pressurizing the interior of the container 201, a pressure reducing valve 215, and a level sensor 217. The pressure sensor and the level sensor may be for Figure 3 The same type of sensor described in the cover of the feed hopper.

[0082] Although Figure 4 and Figure 5 A specific structure and arrangement of the elements of the refill hopper 113 is shown, but in some other embodiments, there may be a different number of gas inlets, powder inlets, sensors, or screws, and they may be located at different locations in the hopper 113. For example, there may be a gas inlet 212 located in the side wall of the cylindrical section 202 of the container 201 for cleaning purposes.

[0083] Figure 6 Shows Figure 4 A cross-sectional view of the refill hopper 200 along its longitudinal axis.

[0084] It shows an agitator 219 inside the container 201, which has a longitudinal section 220, which has a stirring member 221 in its lower end and is connected to the rotating shaft 218 through its opposite end. The stirring member 221 is formed by two inverted truncated cone parts connected to each other. The rotating shaft 218 is connected to the rotating motor 208 and is actuated by the rotating motor 208. There is a sealing gasket between the circular flange 223 around the upper edge of the container 201 and the cover 206 to keep the container 201 airtight. In addition, the cover 206 has a sealing structure 222, which has an opening for the rotating shaft 218 to pass through. There will be another seal between the sealing structure 222 and the rotating shaft 218 to avoid powder from entering the internal space defined by the sealing structure 222 and the inner surface of the cover 206, and thus prevent powder from entering the rotating motor 208. Agitator 219 rotates adjacent the outlet opening 204 of the inverted frustoconical section 203 of the container 201 to minimize powder segregation and ensure a continuous supply of powders that do not flow well or tend to drip poorly.

[0085] Although Figure 6 An agitator 219 having this particular geometry and shape is shown, but other agitators with different geometries and shapes may be used. For example, the agitator may have a pin or small plate at its free end, or may be a screw conveyor that conveys the powder upward from an area closer to the outlet opening 204. Other architectures and designs of the agitator are also possible, as long as they minimize clogging, powder segregation, and ensure a continuous supply of powder. In addition, the architecture and design of the agitator of the refill hopper 200 may be the same or different from the architecture and design of the agitator of the supply hopper.

[0086] Figure 7 A flow chart is shown of a method 300 for refilling a powder hopper of a powder feed system, according to certain embodiments of the present invention.

[0087] At step 301 of method 300, a powder supply system as previously described is provided. A supply hopper of the powder supply system is pressurized at an operating pressure level of the powder supply (e.g., 1.5 bar), so that the powder feeding device can operate normally to supply powder to a corresponding laser cladding device performing an additive manufacturing process.

[0088] At step 302 of method 300, a first refill signal is received at a controller during normal operation of a powder feeder of a powder feed system. The first refill signal indicates that the amount of powder in the feed hopper is low and therefore must be refilled. The first refill signal may be issued by a user, for example, when he visually detects that the powder level in the feed hopper is low or when a level sensor or load cell of the feed hopper detects that the powder level in the hopper is low (e.g., below a first predetermined threshold).

[0089] At step 303 of method 300, the controller instructs the pressure generating device to pressurize the refill hopper so that the pressure level in the refill hopper is substantially equal to the operating pressure level in the supply hopper. In particular, the controller can instruct a corresponding flow control device (e.g., an electric valve or a pneumatic valve) located between the pressure generating device and the refill hopper to allow the pressurized gas generated by the pressure generating device to be transferred to the refill hopper until the pressure levels in the two hoppers are substantially equal. In some embodiments, the pressure in the refill hopper may be up to 1 bar higher than the operating pressure level in the supply hopper, preferably up to 0.5 bar higher, and more preferably up to 0.2 bar higher. The greater the pressure difference between the two hoppers, the easier it is to transfer powder from the refill hopper to the supply hopper, but it may also produce more fluctuations in the powder in the supply hopper, which may affect the supply hopper flow.

[0090] At step 304 of method 300, the controller causes at least a portion of the additional powder stored in the refill hopper to be transferred to the supply hopper. The controller can cause the transfer by opening a flow control device (e.g., a pinch valve) in a hose, pipe, or tube connecting the two hoppers. Gravity, some propulsion device, a pressure difference between the two hoppers, or a combination thereof will help the powder to be transferred from one hopper to another hopper via the hose, pipe, or tube. A level sensor or a weighing sensor for the supply hopper can also send a stop signal indicating that the powder level in the supply hopper has reached a "full" level, so the controller can close the flow control device to stop supplying powder to the supply hopper.

[0091] The refilling process is performed during the normal feeding operation of the powder feeder without interrupting the additive manufacturing process performed by the corresponding laser cladding device. Once the refilling operation is completed, the refill hopper can be depressurized.

[0092] At step 303 of method 300 , the overpressure relief valve of the refill hopper will ensure that no overpressure is generated inside the refill hopper.

[0093] In addition, the controller may receive a second refill signal indicating that the powder level in the refill hopper is low, in particular below a second predetermined threshold. The signal may be generated by a level sensor or a weighing sensor of the refill hopper or directly by the user. The controller may then cause the powder to be transferred from an external powder source to the refill hopper. To this end, the controller may activate a corresponding propulsion device to feed the powder from the external powder source to the refill hopper. The level sensor or the weighing sensor may also emit a stop signal indicating that the powder level in the refill hopper has reached a "full" level, so the controller may cause the external powder source to stop feeding powder to the refill hopper. Alternatively, in response to the second refill signal (which may light an indicator light or may generate a sound or any other warning signal), the user may manually feed powder to the refill hopper. The stop signal may generate another warning signal or may deactivate a previously activated warning signal, thus notifying the user that the refill hopper is full and that he may stop manually filling the refill hopper. During the filling operation of the refill hopper, the flow control device located between the hoppers will be closed to prevent any turbulence or pressure changes that may be caused by the filling operation inside the supply hopper.

[0094] Figure 8 A perspective view of a refill hopper 400 according to a particular embodiment of the present invention is shown. It should be understood that Figure 8 The refill hopper 400 may include additional components, and some of the components described herein may be removed and / or modified without departing from the scope of the described refill hopper 400. Additionally, implementation of the refill hopper 400 is not limited to this embodiment.

[0095] Figure 8 The refill hopper 400 is very similar to Figure 4 The refill hopper 200 comprises a container 401 having an upper cylindrical section 402 and a lower inverted frustoconical section 403 terminating in a powder outlet 404 of the hopper 400, through which powder is supplied to the supply hopper via a corresponding hose, pipe or tube, such as Figure 1 and 2. Although Figure 4 In the refill hopper 200, the upper cylindrical section 202 is longer than the lower inverted frustoconical section 203, but in Figure 8 In the refill hopper 400, the situation is just the opposite. Figure 8The ratio between the lengths of the two parts in reduces the powder adhesion and clogging near the powder outlet 404. The refill hopper 400 also includes a support structure 405, which is designed to rest on a flat surface (e.g., a floor). The support structure 405 is completely optional and can have different designs. The cover 406 includes a first powder inlet 407 (which is shown without a removable threaded closure) and a second powder inlet 411, and the powder can be manually supplied by the user through the first powder inlet 407, and the powder can be received from an external powder source through the second powder inlet 411. The external powder source can be a powder deposit, and the powder can be provided from the powder deposit by gravity, by blowing the powder (e.g., injecting gas), or by some other propulsion device such as a peristaltic pump or any other device or system capable of propelling powder from an external source to the refill hopper 400. The cover 406 also includes a third powder inlet 433 to connect to a cyclone hopper (not shown in this figure). The lid 406 also has a rotary motor 408 for actuating an agitator (not shown in this figure), a screw 409 for coupling the lid 406 to the container 401, a pressure sensor 410, a plurality of gas inlets 412 through which pressurized gas (usually air) is injected to clean the container 401 when the powder in use is replaced by another powder, a gas inlet 413 connected to a hose 414 through which gas (e.g. argon or nitrogen) is injected to pressurize the interior of the container 401, and a pressure relief valve 415 and a level sensor (not shown in this figure), wherein the pressure relief valve 415 is used to protect the pressurized container 401 during an overpressure event. There is also a vibration motor 416 coupled to the outer surface of the container 401, which can be operated when a blockage is detected (a flow meter located downstream of the powder outlet 404 may not detect the powder transfer, resulting in the activation of the vibration motor) and when the powder is to be replaced and the container 401 needs to be cleaned. Each of the upper cylindrical section 402 and the lower inverted frustoconical section 403 includes a cylindrical protrusion 435 on its outer surface in which a corresponding capacitive sensor (not shown) is housed. The capacitive sensors are configured to monitor the powder level within the refill hopper 400. These capacitive sensors mounted on the outer surface of the sections 402, 403 provide a more reliable powder level measurement and are Figure 5 and Figure 6 An alternative to a powder level sensor 217 located in the lid of the refill hopper is shown.

[0096] Fig. 9 Shows Figure 8 A cross-sectional view of the refill hopper 400 along its longitudinal axis.

[0097] An agitator 419 is shown inside the container 401, the agitator 419 having a main section 418, wherein a stirrer section 420 is coupled to the lower portion of the main section 418. The main section 418 is coupled to and actuated by the rotary motor 408. There is a sealing gasket between the circular flange 423 around the upper edge of the container 401 and the lid 406 to keep the container 401 airtight. In addition, the lid 406 has a sealing structure 422, which has an opening 424 through which the main section 418 of the agitator 419 passes. There will be another seal between the sealing structure 422 and the main section 418 to avoid powder from entering the internal space defined by the sealing structure 422 and the inner surface of the lid 406, and thus prevent powder from entering the rotary motor 408. This embodiment also includes an additional gas inlet 412 for cleaning purposes located in the side wall of the cylindrical section 402 of the container 401. The inclined walls of the lower inverted frustoconical section 403 form an angle α of 70° with respect to the horizontal, although they may form any other angle greater than 60°.

[0098] The agitator 419, more specifically the main section 418 of the agitator 419, includes a screw 425 connected to its upper section. In this particular embodiment, the screw 425 is located corresponding to the lower portion of the upper cylindrical section 402 and the upper portion of the lower inverted frustoconical section 403. The diameter of the screw 425 is such that the outer edge of the screw 425 rotates close to the inner surface of the container 401 to avoid larger powder particles from adhering to the inner surface.

[0099] The agitator 419 further comprises a cone 426 connected to its central portion. In this particular embodiment, the cone 426 is located corresponding to the central portion of the lower inverted frustoconical section 403. The cone 426 is connected to the main section 418 of the agitator 419 by its apex and is open towards the bottom of the container 401. The side walls of the cone have an angle β of 70° with respect to the horizontal plane, although they can form any other angle greater than 60°. The cone causes a zigzag effect in the powder stored in the refill hopper, resulting in mixing of the powder particles in the central area of ​​the refill hopper.

[0100] The stirrer 419 further includes a first stirring rod 427 and a second stirring rod 428. The two stirring rods 427, 428 are located corresponding to the lower portion of the stirrer 419 and close to the free end of the stirrer 419. Figure 8 Only one of the two bars 427, 428 is shown, as the other does not appear in the cross-sectional view. In such an embodiment, these first stirring bars 427 and second stirring bars 428 are coupled to the stirring member section 420. As in Fig.10As can be seen in the figure, the two stirring bars 427, 428 are positioned at different distances from the free end of the stirrer 419. The rotation of these stirring bars 427, 428 causes the movement of powder located near the powder outlet 404 to avoid blockages, minimize powder segregation and ensure a continuous supply of powders that do not flow well or tend to drip poorly.

[0101] In addition, the stirrer 419 includes a third stirring rod 429 and a fourth stirring rod 430. The two stirring rods 429, 430 are also located corresponding to the lower portion of the stirrer 419, but close to the central portion of the stirrer 419. Figure 8 Only one of the two strips 429, 430 is shown, as the other does not appear in the cross-sectional view. Fig.10 As can be seen in FIG. 4 , the third stirring rod 429 and the fourth stirring rod 430 are also positioned at different distances from the free end of the stirrer 419. The length of these stirring rods 429, 430 is slightly smaller than the inner diameter of the corresponding part of the refill hopper 400. The rotation of the stirring rods 429, 430 causes the movement of the powder located between the cone 426 and the first stirring rod 427 and the second stirring rod 428 to promote its descent toward the powder outlet 404.

[0102] In this particular embodiment, the lower inverted frustoconical section 403 includes an interchangeable outlet nozzle 433, which is connected to the rest of the lower inverted frustoconical section 403 by means of a flange 432. In this way, the powder outlet 404 can be exchanged in an easy and quick manner. In addition, by removing the interchangeable outlet nozzle 433, the lower region of the lower inverted frustoconical section 403 can be easily cleaned, and the agitator section 420, which is detachably connected to the main section 418, can also be cleaned and exchanged if necessary. For example, when the interchangeable outlet nozzle 433 is replaced so that the powder outlet 404 has a different size, the agitator section 420 of the agitator 406 should be replaced so that its geometry and size are adapted to the new powder outlet 404.

[0103] Fig.10 The embodiment according to the present invention is shown Fig. 94. A perspective view of an agitator 419 of the present invention. The figure depicts a first stirring rod 427 and a second stirring rod 428 coupled to the agitator section 420 of the agitator 419 and a third stirring rod 429 and a fourth stirring rod 430 coupled to the main section 418 of the agitator 419. The figure also depicts a spiral 425 and a cone 426 coupled to the main section 418 of the agitator 419 and an electric rotary motor 408 coupled to the agitator 419 via an insertion transmission 431. In this particular embodiment, the first stirring rod 427 and the second stirring rod 428 and the third stirring rod 429 and the fourth stirring rod 430 respectively form a 90° angle between them. However, in some other embodiments, these rods may form different angles between them.

[0104] Although Fig.10 An agitator 419 having a particular geometry, shape, and elements coupled thereto is shown, but other agitators having different geometries, shapes, and coupling elements may be used. For example, the agitator may have a pin or small plate at its free end, or may be a screw conveyor that transports the powder upward from an area closer to the outlet opening 404. Other architectures and designs of the agitator are also possible, as long as they minimize clogging, powder segregation, and ensure a continuous supply of powder. Additionally, the architecture and design of the agitator 419 of the refill hopper 400 may be the same or different from the architecture and design of the agitator of the supply hopper.

[0105] In this article, the term "include" and its derivatives (such as "comprising" etc.) should not be understood to exclude the meaning, that is, these terms should not be interpreted as excluding the possibility that the described and defined elements can include other elements, steps, etc. The term "another" as used herein is defined as at least the second or more. Unless otherwise specified, the term "connection" used herein is defined as a direct connection without any intermediate element or an indirect connection with at least one intermediate element. Two elements can be mechanically, electrically or communicatively linked through a communication channel, path, network or system.

[0106] The present invention is obviously not limited to the specific embodiments described herein, but also covers any variation (e.g. regarding the choice of materials, dimensions, components, configuration, etc.) that may be considered by a person skilled in the art within the general scope of the invention as defined in the claims.

Claims

1. A powder supply system (100), comprising: a powder feeder (101) connectable to a laser metal deposition apparatus, the powder feeder comprising a feed hopper (102) for storing powder, a first powder outlet and a first powder inlet (112), the powder to be fed to the laser metal deposition apparatus through the first powder outlet; at least one refill hopper (103) configured to store additional powder and comprising a second powder outlet (114) fluidly connected to the first powder inlet (112), the additional powder being provided to the supply hopper (102) through the second powder outlet; a pressure generating device (111) configured to generate an operating pressure level within the supply hopper (102); as well as A controller (119) configured to, during normal operation of the powder feeder (101), upon receipt of a first refill signal, cause the pressure generating device (111) to generate a pressure level in the refill hopper (113) that is substantially equal to the operating pressure level in the supply hopper (102), and to cause at least a portion of the additional powder to be transferred from the refill hopper (113) to the supply hopper (102).

2. The powder feeding system (100) according to claim 1, comprising a first flow control device (116), the first flow control device (116) being located between the feeding hopper (102) and the refilling hopper (113) to control the delivery of the additional powder, wherein The first flow control device (116) is preferably a solenoid valve or a pneumatic valve, more preferably a diaphragm solenoid valve or a diaphragm pneumatic valve.

3. A powder supply system (100) according to any one of the preceding claims, comprising a first flow meter (122), which is located between the supply hopper (102) and the refill hopper (113), preferably downstream of the first flow control device (116), to monitor the amount of additional powder delivered to the supply hopper (102).

4. A powder feeding system (100) according to any one of the preceding claims, comprising a second flow meter, which is located at the outlet of the powder feeder (102) to monitor the powder flow rate to be provided to the laser metal deposition device.

5. The powder feeding system (100) according to any one of the preceding claims, wherein: The powder feeder (101) comprises a first level sensor (121) for monitoring the powder level within the feed hopper (102).

6. The powder feeding system (100) according to any one of the preceding claims, wherein: The first refill signal is a signal received from the first level sensor (121) indicating that the powder level in the feed hopper (102) is below a first predetermined threshold or a signal received from a user.

7. The powder feeding system (100) according to any one of the preceding claims, wherein: The refill hopper (113, 200) comprises a second powder inlet (211) through which powder is provided from an external powder source.

8. The powder feed system (100) according to claim 7, comprising a second flow control device, the second flow control device being located upstream of the second powder inlet (211) to control the powder delivery from the external powder source, wherein The second flow control device (211) is preferably a solenoid valve or a pneumatic valve, and more preferably a diaphragm solenoid valve or a diaphragm pneumatic valve.

9. The powder supply system (100) according to claim 7 or 8, wherein: The second powder inlet (211) is located proximate to, and preferably coincident with, the longitudinal axis of the refill hopper (113).

10. A powder supply system (100) according to any one of claims 7 to 9, comprising a cyclone hopper (127) as an additional external powder source, the cyclone hopper (127) being fluidly connected to a third powder inlet (434) of the refilling hopper (113) and being configured to provide powder to the refilling hopper (113).

11. The powder feeding system (100) according to any one of the preceding claims, wherein: The refill hopper (113, 200) comprises a second level sensor (217) for monitoring the level of powder within the refill hopper (113, 200).

12. The powder feeding system (100) according to any one of the preceding claims, wherein: The powder feeder (101) includes a first pressure sensor (120) for monitoring the pressure level inside the feed hopper (102), and the refill hopper (113, 200) includes a second pressure sensor (210) for monitoring the pressure level inside the refill hopper (113, 200).

13. The powder feeding system (100) according to any one of the preceding claims, wherein: The supply hopper (102) and the refill hopper (113) respectively comprise a first gas inlet and a second gas inlet (117) fluidly connected to the pressure generating device (111).

14. The powder feeding system (100) according to any one of the preceding claims, wherein: The supply hopper (102) and the refill hopper (113) are configured to store metal powder, ceramic powder, or a combination of both.

15. The powder feeding system (100) according to any one of the preceding claims, wherein: The refill hopper (113, 200) comprises a container (201) for storing the powder, the container (201) having an upper cylindrical section (202) and a lower inverted frustoconical section (203), the lower inverted frustoconical section (203) having an angle greater than 60° relative to the horizontal plane, and preferably, the angle is 70° relative to the horizontal plane.

16. The powder feeding system (100) according to any one of the preceding claims, wherein: The refill hopper (113) includes an electrically-actuated agitator (106) configured to move powder stored within the refill hopper (113).

17. The powder supply system (100) according to claim 16, wherein: The agitator (106) comprises a cone (426) connected to a central portion of the agitator (106), wherein a side wall of the cone (426) has an angle greater than 60° relative to the horizontal plane, and preferably, the angle is 70° relative to the horizontal plane.

18. The powder supply system (100) according to claim 16 or 17, wherein: The agitator (106) includes a first stirring rod (427) and a second stirring rod (428), wherein the first stirring rod (427) and the second stirring rod (428) are located at a lower portion of the agitator (106) and are positioned close to a free end of the agitator (106), and the first stirring rod (427) and the second stirring rod (428) are located at different distances from the free end of the agitator (106).

19. The powder supply system (100) according to claim 18, wherein: The agitator (106) includes a third stirring rod (429) and a fourth stirring rod (430), wherein the third stirring rod (429) and the fourth stirring rod (430) are located at the lower part of the agitator (106) and are positioned close to the central part of the agitator (106), and the third stirring rod (429) and the fourth stirring rod (430) are located at different distances from the free end of the agitator (106).

20. The powder supply system (100) according to any one of claims 16 to 19, wherein: The agitator (106) includes a screw (425) coupled to an upper portion of the agitator (106), wherein the diameter of the screw (425) is similar to an inner diameter of an upper portion of the refill hopper (113).

21. A method (300) for refilling a powder hopper of a powder feed system, characterized in that The method comprises providing (301) a powder feed system according to any one of the preceding claims, the feed hopper being pressurized at an operating pressure level to provide powder to an additive manufacturing device, and Wherein, during normal operation of the powder feeder of the powder feed system, the method further comprises: receiving (302) a first refill signal at the controller; pressurizing (303) the refill hopper by the pressure generating device until the pressure level inside the refill hopper is substantially equal to the operating pressure level in the supply hopper; and At least a portion of the additional powder stored in the refill hopper is transferred (304) to the supply hopper.

22. The method (300) according to claim 13 comprises pressurizing the refilling hopper at a pressure level equal to or at most 1 bar higher than the operating pressure level in the supply hopper, preferably at most 0.5 bar higher, and more preferably at most 0.2 bar higher.

23. The method (300) according to claim 13 or 14, comprising: receiving at the controller a second refill signal, the second refill signal preferably being a signal received from the second level sensor indicating that the level of powder within the refill hopper is below a second predetermined threshold or a signal received from a user; and Powder is transferred from an external powder source to the refill hopper.

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