A build material supply system for a device for layer-wise manufacturing of 3D objects from build material

Abstract

A build material supply system is provided for an apparatus for manufacturing 3D objects from build material layers, comprising a dispensing device for supplying dispensing amounts of build material to a work surface, the dispensing amounts including layer quantity and excess quantity; a buffer tank for mixing the build material; an excess quantity return chamber for receiving excess build material; a supply tank for fresh build material; a build material pump; and a controller; wherein the inlet of the build material pump is connected to the supply tank via a first valve, and in a first embodiment: the inlet of the build material pump is connected to the excess quantity return chamber via a second valve and to the buffer tank via a third valve; the outlet of the pump is connected to the buffer tank via a fourth valve and to the inlet of the dispensing device via a fifth valve; wherein the controller is connected to the pump and the valves and is configured to: (i) control the first valve, the second valve, and the fourth valve to close, control the third valve and the fifth valve to open, and control the pump to operate so as to allow build material to be dispensed. (ii) Controlling the third and fifth valves to close, controlling the first and fourth valves to open, and controlling the pump to operate, so as to allow fresh build material to flow from the supply tank into the buffer tank; and (iii) Controlling the third and fifth valves to close, controlling the second and fourth valves to open, and controlling the pump to operate, so as to allow excess build material to flow from the excess return chamber into the buffer tank; and in a second embodiment: the inlet of the build material pump is connected to the outlet of the excess return chamber; the outlet of the pump is connected to the inlet of the buffer tank; and the outlet of the buffer tank is connected to the inlet of the dispensing device; wherein the controller is connected to the pump and the first valve and is configured to control the first valve to open and control the pump to operate, so as to allow fresh build material to flow from the supply tank into the buffer tank and allow excess build material to flow from the excess return chamber into the buffer tank. A method for delivering build material through a build material system is also provided.

Description

Technical Field

[0001] This invention relates to a build material supply system for an apparatus for manufacturing three-dimensional (3D) objects by layering build material, wherein any remaining build material after layer formation is recycled in situ. A method for delivering build material via the build material supply system and its controller is also disclosed. Background Technology

[0002] As additive manufacturing technology continues to advance, increasingly challenging applications require new solutions. The repeatability and reliability of the mechanical and visual quality of objects in the build process necessitate consistent build material properties for each layer to ensure that the thermal processes experienced by each layer remain identical. Changes in build material properties, such as aging, can affect the melting temperature of the build material and lead to overheating or underheating of the molten layer in powder bed fusion processes. Maintaining consistent mixing of recycled and fresh build materials is particularly important in equipment where build materials are recycled in situ. Another challenge is keeping the build material in a free-flowing state before use for layer formation to achieve reliable batching and ensure the formation of layers with uniform density and thickness. Various build material supply systems are known, such as feed beds and auger feed systems. In these systems, build materials are typically neither mixed nor recycled in situ; instead, they are collected as waste, removed from the equipment, readjusted and mixed, and then fed back to the equipment for new build processes. Known equipment applies in-situ recycling by conveying build materials via augers and other rotating components. However, these augers and other rotating components are difficult to maintain and may not be able to properly deliver all types of powder. Other equipment that applies in-situ recycling uses build material pumps, but these cannot adequately manage build materials from different sources. Therefore, improvements are still needed to provide build material supply systems suitable for industrial and sustainable handling of objects. Utility Model Content

[0003] This utility model is described in the following aspects.

[0004] 1. A build material supply system for an apparatus for manufacturing 3D objects by layering build materials, the build material supply system comprising:

[0005] - A dispensing device configured to supply a dispensing amount of building material to the working surface of the device, the dispensing amount including a layer amount and an excess amount remaining to form a layer;

[0006] - A buffer tank, which is configured to mix building materials for supply to the dispensing device;

[0007] - Excess material return chamber, which is used to receive excess building materials from the distribution device;

[0008] - A supply tank, which is used to hold fresh building materials in order to replenish the buffer tank;

[0009] - A construction material pump for conveying construction materials within the construction material supply system; and

[0010] - Controller;

[0011] The inlet of the building material pump is connected to the supply tank via a first valve, to the excess return chamber via a second valve, and to the buffer tank via a third valve; and the outlet of the pump is connected to the buffer tank via a fourth valve and to the inlet of the dispensing device via a fifth valve.

[0012] The controller is coupled to the building material pump and the first valve, the second valve, the third valve, the fourth valve, and the fifth valve, and is configured to:

[0013] - Control the first valve, the second valve, and the fourth valve to close, control the third valve and the fifth valve to open, and control the pump to operate, so as to allow the building material to flow from the buffer tank through the pump to the dispensing device along the dispensing flow path;

[0014] - Control the third and fifth valves to close, control the first and fourth valves to open, and control the pump to operate, allowing fresh build material to flow along the supply flow path from the supply tank through the pump and into the buffer tank; and

[0015] - Control the third and fifth valves to close, control the second and fourth valves to open, and control the pump to operate, so as to allow excess build material to flow from the excess return chamber through the pump and into the buffer tank along the excess return flow path;

[0016] In order to control the ratio of fresh building material to excess building material delivered to the buffer tank.

[0017] 2. The build material supply system according to aspect 1, wherein the dispensing device includes a dispensing chamber coupled to the outlet of the pump and configured to receive build material from the buffer tank via the pump; the dispensing device further includes an overflow chamber coupled to the dispensing chamber and configured to receive an excess amount of build material transferred from the buffer tank to the dispensing chamber when the build material in the dispensing chamber reaches a predefined level; wherein the overflow chamber is coupled to the inlet of the pump via a sixth valve, and wherein the controller is configured to control the third and fifth valves to close, control the sixth and fourth valves to open, and control the pump to operate to allow excess build material to flow from the overflow chamber through the pump to the buffer tank along an excess supply return flow path.

[0018] 3. The construction material supply system according to aspect 1, wherein the batching device includes a batching chamber and a bypass chamber, the bypass chamber having bypass inlets and bypass outlets at both ends of an intermediate section, the intermediate section including one or more intermediate outlets, wherein the bypass inlets are connected to the outlet of the pump via the fifth valve and the bypass outlets are connected to the inlet of the buffer tank, and wherein the batching chamber includes one or more batching chamber inlets configured to receive construction material from the bypass chamber and connected to the one or more intermediate outlets to form a Or multiple intermediate flow paths; such that when the controller controls the first valve, the second valve, and the fourth valve to close and controls the third valve and the fifth valve to open and controls the pump to operate, the building material is caused to flow along the batching flow path from the buffer tank through the pump to the bypass chamber of the batching device, and along the one or more intermediate flow paths from the bypass chamber to the batching chamber, so as to supply the building material from the buffer tank to the batching chamber, and cause the excess supply building material to return directly from the bypass chamber to the buffer tank along the direct excess supply return flow path.

[0019] 4. The construction material supply system according to aspect 3, wherein the bypass outlet is connected to the inlet of the buffer tank via a sixth valve; such that when the controller controls the first valve, the second valve, and the fourth valve to close and controls the third valve, the fifth valve, and the sixth valve to open and controls the pump to operate, construction material is caused to flow along the batching flow path and the one or more intermediate flow paths, and excess construction material is caused to return to the buffer tank along the direct excess supply return flow path.

[0020] 5. The construction material supply system according to aspect 4, wherein the bypass outlet is further connected to the inlet of the construction material pump via a seventh valve, wherein the controller is connected to the seventh valve and is configured to:

[0021] (i) Control the third valve, the fifth valve and the sixth valve to open, while controlling the first valve, the second valve, the fourth valve and the seventh valve to close, and controlling the pump to operate, so as to allow the building material to flow along the batching flow path and allow the over-supply building material to return directly from the bypass chamber to the buffer tank along the direct over-supply return flow path;

[0022] (ii) Control the third valve and the sixth valve to close and control the fifth valve and the seventh valve to open and control the pump to operate, so as to allow the build material to circulate from the bypass chamber through the build material pump and return to the bypass chamber, so as to reuse the excess supply of build material to fill the batching chamber;

[0023] (iii) Control the fifth valve and the seventh valve to close and control the pump to operate, and:

[0024] - Control the opening of the second and fourth valves to allow excess build material to flow back into the buffer tank along the excess flow path; and

[0025] - Control the opening of the first valve and the fourth valve to allow fresh building material to flow into the buffer tank along the supply flow path.

[0026] 6. A build material supply system for an apparatus for manufacturing 3D objects by layering build materials, the build material supply system comprising:

[0027] - A dispensing device configured to supply a dispensing amount of building material to the working surface of the device, the dispensing amount including a layer amount and an excess amount remaining to form a layer;

[0028] - A buffer tank, which is configured to mix building materials for supply to the dispensing device;

[0029] - Excess material return chamber, which is used to receive excess building materials from the distribution device;

[0030] - A supply tank, which is used to hold fresh building materials in order to replenish the buffer tank;

[0031] - A construction material pump for delivering construction materials within the construction material supply system; and a controller;

[0032] The inlet of the building material pump is connected to the supply tank via a first valve, and the inlet of the building material pump is connected to the outlet of the excess return chamber; the outlet of the pump is connected to the inlet of the buffer tank; and the outlet of the buffer tank is connected to the inlet of the dispensing device.

[0033] The controller is coupled to the pump and the first valve and is configured such that:

[0034] - Control the opening of the first valve and control the operation of the pump to allow fresh build material to flow along the supply flow path from the supply tank through the pump and into the buffer tank; and

[0035] - Operate the pump to allow excess build material to flow from the excess return chamber through the pump and into the buffer tank along the excess return flow path;

[0036] In order to control the ratio of fresh building material to excess building material delivered to the buffer tank.

[0037] 7. The material supply system according to aspect 6, wherein the inlet of the pump is connected to the excess return chamber via a second valve, and wherein the controller is connected to the second valve.

[0038] 8. The construction material supply system according to aspect 6 or aspect 7, wherein the dispensing device includes a dispensing device inlet configured to receive construction material from the outlet of the buffer tank, wherein the controller is coupled to the dispensing device and configured to control the dispensing device to release the dispensing amount.

[0039] 9. A build material supply system according to any of the foregoing aspects, wherein the controller controls the first valve to close to cut off the supply flow path and controls the pump to operate, and controls the second valve to open, if present, to allow the excess build material to flow along the excess amount return flow path.

[0040] 10. A construction material supply system according to any one of aspects 1 to 8, wherein the controller controls the opening of the first valve and, if present, the fourth valve and / or the second valve, to allow excess construction material and fresh construction material to flow simultaneously along the supply flow path and the excess return flow path.

[0041] 11. The building material supply system according to aspect 10 of aspect 2, wherein the controller further controls the sixth valve to open to allow an oversupply of building material to flow into the buffer tank simultaneously from the overflow chamber along with the excess building material and the fresh building material, while controlling the third valve and the fifth valve to close to cut off the material flow path.

[0042] 12. The construction material supply system according to aspect 11, wherein the sixth valve is a variable valve, and wherein the controller is configured to control the sixth valve to partially open so as to impose a higher flow resistance on the excess supply construction material flow returning through the excess supply flow path compared with the flow resistance of the excess construction material flow returning along the excess amount flow path.

[0043] 13. A construction material supply system according to any one of aspects 10 to 12, wherein the supply flow path is configured to have a higher flow resistance to the construction material flow than the excess return flow path.

[0044] 14. A construction material supply system according to any one of aspects 10 to 13, wherein the first valve is a variable valve, wherein the controller is configured to control the first valve to partially open so as to impose a higher flow resistance on the flow of fresh construction material through the supply flow path compared with the flow resistance of the excess construction material flow along the excess return flow path and, if present, with the flow resistance of the excess supply construction material flow along the excess supply return flow path.

[0045] 15. A build material supply system according to any one of aspects 1 to 8, wherein the controller is configured to prioritize the flow of build material to the buffer tank by applying the following order: first, allowing excess build material to flow along the excess amount return flow path by controlling the first valve to be at least partially closed; second, allowing excess supply build material to flow along the excess supply return flow path if present, while controlling the first valve and the second valve to be at least partially closed; and third, allowing fresh build material to flow along the supply flow path while controlling the first valve to be at least partially open.

[0046] 16. The build material supply system according to any of the preceding aspects, wherein the buffer tank includes a fill level sensor configured to detect the fill level of build material inside the buffer tank, and wherein the controller is configured to open and close the supply flow path based on the detected build material level inside the buffer tank.

[0047] 17. A method for delivering build material through a build material supply system of an apparatus for manufacturing 3D objects by layering build material, the method comprising:

[0048] (a) Activate the build material pump and simultaneously open the feed flow path from the buffer tank to the feed device to deliver the build material from the buffer tank to the feed device;

[0049] (b) Dispensing the amount of building material into the working surface of the equipment, the amount of material including the amount of material used to form the layer and the excess amount remaining to form the layer;

[0050] (c) Receiving excess building materials in the excess return room;

[0051] (d) Operate the build material pump while opening the excess return flow path to return excess build material from the excess return chamber to the buffer tank;

[0052] (e) Activate the build material pump while simultaneously opening the supply flow path from the supply tank to the buffer tank to deliver build material from the supply tank to the buffer tank until a predetermined filling duration has elapsed or a predefined filling level is detected in the buffer tank; and

[0053] (f) The excess amount is mixed with the building material in the buffer tank.

[0054] 18. The method according to aspect 17, comprising operating the building material pump continuously from step (a) to step (f).

[0055] 19. The method according to aspect 17 or 18, comprising closing the excess return flow path and the supply flow path before opening the ingredient flow path at step (a), closing the ingredient flow path and at least partially closing the supply flow path when opening the excess return flow path at step (d), and at least closing the ingredient flow path when opening the supply flow path at step (e).

[0056] 20. The method according to any one of aspects 17 to 19, comprising detecting the fill level of the build material in the buffer tank and / or the level of excess build material in the excess return chamber, and controlling the duration of the excess return path being open during step (d) and / or the duration of the supply path being open during step (e).

[0057] 21. The method according to any one of aspects 17 to 20, wherein the building material delivered to the dispensing device at step (a) comprises an excess amount of building material; wherein step (b) further comprises a step (b1) allowing the excess amount to flow out of the dispensing device and a step (b2) activating the pump while opening another flow path from the dispensing device to the buffer tank to return the excess amount to the buffer tank.

[0058] 22. The method according to aspect 21, wherein step (b1) includes allowing the excess supply to flow into the overflow chamber, and wherein step (b2) is applied when detecting the fill level of the excess supply material in the overflow chamber, and / or after detecting that the level of excess build material in the excess return chamber has dropped below a predefined excess build material level, such that the excess build material is returned to the buffer tank before the excess supply build material is returned to the buffer tank.

[0059] 23. The method according to any one of aspects 17 to 22, wherein excess building material is returned to the buffer tank in step (d) before fresh building material is conveyed from the supply tank to the buffer tank in step (e).

[0060] 24. The method according to any one of aspects 17 to 22, wherein steps (d) and (e) are applied simultaneously, and optionally includes at least partially opening the respective flow path to change the flow resistance of the respective flow path such that the amount of excess build material flowing into the buffer tank is at a predefined ratio to the amount of fresh build material.

[0061] 25. The method according to aspect 23 or aspect 24, wherein for multiple repetitions of steps (a) to (f), steps (d) and (e) are controlled such that the predefined ratio remains substantially constant during the multiple repetitions. Attached Figure Description

[0062] Now refer to the attached diagram, in which:

[0063] Figure 1 This is a block diagram illustrating the flow path of the construction material through the construction material supply system according to the first embodiment of the present invention;

[0064] Figure 2 This is a block diagram of the flow path of the construction material through the construction material supply system according to the second embodiment of the present invention;

[0065] Figures 3A-3D It shows Figure 1 Various variations of flow paths;

[0066] Figure 4 It is through according to Figure 1 A schematic cross-section of a material recycling system with a flow path;

[0067] Figure 5 It shows Figure 4 A variant of the system, which is applicable to Figure 3D The flow path;

[0068] Figure 6It is a 3D illustration of the exterior of the buffer tank;

[0069] Figure 7A and 7B yes Figure 6 A schematic cross-section of the variant;

[0070] Figures 8A to 8D This is a 3D illustration of the implementation scheme inside the buffer tank;

[0071] Figure 9A It is a 3D representation of a variation of a dispensing device with a bypass for constructing materials;

[0072] Figure 9B and 9C Is it through Figure 9A Different 3D cuts in the ingredient preparation room and bypass;

[0073] Figure 10 yes Figure 1 Includes Figures 9A-9C Variation of the flow path of the batching device;

[0074] Figure 11 yes Figure 10 The variant flow path;

[0075] Figures 12A to 12D The schematic diagram illustrates the applicable implementation based on Figure 2 Equipment for the flow path;

[0076] Figure 13 yes Figure 2 A variation of the block diagram; and

[0077] Figure 14 This is a flowchart of the operation method according to this utility model.

[0078] In the accompanying drawings, similar elements are always indicated by similar reference numerals. Detailed Implementation

[0079] Reference Figures 1 to 14 This invention describes a build material supply system for an apparatus for manufacturing 3D objects by layering build materials, a method of using the same, and variations thereof, wherein the build material supply system allows for in-situ reuse of remaining build material from the forming layer.

[0080] In the first embodiment and referenced Figure 1 , Figure 1This is a block diagram illustrating the flow path of construction material through a construction material supply system 10 according to a first embodiment of the present invention. The construction material supply system 10 includes: a dispensing device 40 configured to supply a dispensing amount of construction material to the working surface of the device, the dispensing amount including a layer amount and an excess amount remaining after forming a layer; a buffer tank 50 configured to mix the construction material for supply to the dispensing device 40; an excess return chamber 60 for receiving excess construction material; a supply tank 80 for holding fresh construction material to replenish the buffer tank 50; a construction material pump 90 for conveying construction material within the construction material supply system 10; and a controller 100. The inlet of the construction material pump 90 is connected to the supply tank 80 via a first valve 280, to the excess return chamber 60 via a second valve 260, and to the buffer tank 50 via a third valve 250; and the outlet of the construction material pump 90 is connected to the buffer tank 50 via a fourth valve 210 and to the inlet of the dispensing device 40 via a fifth valve 220. Controller 100 is coupled to build material pump 90 and the valves, and is configured to control third valve 250 and fifth valve 220 to close, at least cutting off the dispensing flow path from buffer tank 50 through pump 90 to dispensing chamber 40; optionally, control first valve 280 to close, optionally cutting off the supply flow path from supply tank 80 through pump 90 to buffer tank 50; control second valve 260 and fourth valve 210 to open, opening the excess return flow path from excess return chamber 60 through pump 90 into buffer tank 50; and control pump 90 to operate. This allows excess build material to flow along the excess return flow path, for example, for a predefined excess return duration or based on a minimum excess build material level sensed in excess return chamber 60.

[0081] Furthermore, the controller 100 is configured to close the third valve 250 and the fifth valve 220 to cut off the feed flow path, open the first valve 280 and the fourth valve 210, and control the pump operation. This allows fresh build material to flow along the supply flow path from the supply tank 80 through the pump 90 and into the buffer tank 50, either during the filling duration or based on reaching a fill level sensed within the buffer tank 50.

[0082] Furthermore, the controller 100 is configured to close the first valve 280, the second valve 260, and the fourth valve 210 to cut off the supply flow path and the excess return flow path, control the third valve 250 and the fifth valve 220 to open, and control the operation of the pump 90. This allows the build material to flow along the dispensing flow path, for example, during the dispensing duration or based on reaching a predefined dispensing level within the dispensing device 40.

[0083] Therefore, the ratio of fresh building material delivered to buffer tank 50 to excess building material delivered to buffer tank 50 can be controlled. Furthermore, it can be ensured that the building material in buffer tank 50 is replenished with fresh material to replace the amount of layers removed from the building material supply system 10 to form layers.

[0084] In the second embodiment and with reference to Figure 2 , Figure 2 This is a block diagram illustrating the flow path of build material through a build material supply system 10 according to a second embodiment of the present invention. The build material supply system 10 includes: a dispensing device 40 configured to supply a dispensing amount of build material to a working surface of the device, the dispensing amount including a layer amount and an excess amount remaining to form a layer; a buffer tank 50 configured to mix the build material for supply to the dispensing device 40; an excess return chamber 60 for receiving excess build material from the dispensing device; a supply tank 80 for holding fresh build material to replenish the buffer tank 50; a build material pump 90 for conveying build material within the build material supply system 10; and a controller 100. The inlet of the pump 90 is connected to the supply tank 80 via a first valve 280 and to the outlet of the excess return chamber 60. The outlet of the pump 90 is connected to the inlet of the buffer tank 50; and the outlet of the buffer tank 50 is connected to the inlet of the dispensing device 40. Therefore, in this embodiment, the buffer tank supplies build material directly to the dispensing device 40, rather than via pump 90. Controller 100 is coupled to pump 90 and first valve 280 and is configured to optionally control first valve 280 to close, thereby optionally cutting off the supply flow path from supply tank 80 through pump 90 to buffer tank 50; and to activate pump 90. This allows excess build material to flow from excess return chamber 60 through pump 90 and into buffer tank 50, for example, during a predefined excess return duration or based on a minimum excess build material level sensed within excess return chamber 60.

[0085] Furthermore, controller 100 is configured to control first valve 280 to open the supply flow path and control pump 90 to operate, allowing fresh build material to flow along the supply flow path, either during the filling duration or based on reaching a predefined fill level sensed within buffer tank 50. Since in the second embodiment, build material is supplied directly from the buffer tank rather than via pump 90 to the batching chamber, an outlet valve between the pump and the buffer tank is not required.

[0086] Therefore, the ratio of fresh building material delivered to buffer tank 50 to excess building material delivered to buffer tank 50 can be controlled. Furthermore, it can be ensured that the building material in buffer tank 50 is replenished with fresh material to replace the amount of layers removed from the building material supply system 10 to form layers.

[0087] In both embodiments, the controller may be configured to control the amount of ingredients dispensed by the dispensing device. In both embodiments, the buffer tank 50 may include a sensor configured to detect the fill level of the build material within the buffer tank 50, and the controller may be configured to receive the sensed fill level from the sensor and open the supply flow path when it is determined that the sensed build material level is below a predetermined threshold level.

[0088] refer to Figure 14 The flowchart also provides a method 800 for conveying construction materials through a construction material supply system 10 of the first and second embodiments, the method comprising:

[0089] (a) At box 810, the build material pump 90 is activated, simultaneously opening the feed flow path from buffer tank 50 to feed device 40 to deliver build material from buffer tank 50 to feed device 40. This can be applied for a predefined feed flow duration or until the build material level in feed device 40 has reached a predetermined feed level.

[0090] (b) At box 820, a quantity of build material is dispensed onto the working surface of the device, the quantity including the amount used to form the layer and any excess material remaining to form the layer. The repetition frequency of this box defines the cycle time required to form the layer;

[0091] (c) At frame 830, receive excess construction material in excess return chamber 60;

[0092] (d) At box 840, activate the build material pump 90 while simultaneously opening the excess return flow path to return excess build material from the excess return chamber 60 to the buffer tank 50. This can be applied for a predefined excess return duration or until the build material level in the excess return chamber 60 has dropped below a predefined minimum level.

[0093] (e) At box 860, the build material pump 90 is activated, simultaneously opening the supply flow path from supply tank 80 to buffer tank 50 to deliver build material from supply tank 80 to buffer tank 50 until a predetermined filling duration has elapsed or until a predefined filling level is detected in buffer tank 50; and

[0094] (f) At box 870, mix the excess with the building material in buffer tank 50.

[0095] The method may include detecting one or more of the following: the fill level of build material in buffer tank 50, the level of excess build material in excess return chamber 60, and / or the level of build material in the dispensing device. Optionally, steps (a) to (d) at boxes 810 to 840 may be repeated once or more, or until a predetermined duration has elapsed, or until the level of build material in the buffer tank and / or excess return chamber is detected to have dropped below a corresponding threshold level, before proceeding to step (e) at box 860, replenishing the buffer tank with fresh build material. Not every step at boxes 840 to 860 may exist in every cycle.

[0096] The construction material system and the method of conveying construction material through the system may be particularly advantageous in equipment where excess construction material may have undergone some degree of aging and property changes, for example, where the excess return amount is heated to near the melting temperature as it transfers across the working surface and the construction surface of the equipment. In addition to the supply tank 80, a buffer tank 50 is provided to allow for the maintenance of consistent properties of the construction material mixture throughout the construction process by controlling the ratio of excess construction material to fresh construction material flowing into the buffer tank, through proper operation of the flow path and valves. In the case of powder bed melting processes, excess construction material undergoes relatively high processing temperatures close to the melting temperature of the material and may have already degraded. While in-situ reuse of excess construction material increases the utilization rate of the construction material, it is important to ensure that degraded material is fed back in a manner that ensures it does not affect the overall properties of the construction material in the buffer tank 50 throughout the construction process. Therefore, excess build material can be fed back into buffer tank 50 in a controlled circulation manner along with fresh build material from supply tank 80, thereby ensuring that the build material mixture within buffer tank 50 remains substantially consistent throughout the build process. This is not possible with a single tank. Furthermore, buffer tank 50 is arranged to mix build materials, thus providing the dispensing device with homogeneous build material of consistent quality. The supply tank 80 disclosed herein may not require a mixing function. The mixing step (f) at block 870 can be applied sequentially in all disclosure blocks of the method described herein.

[0097] In some of the following figures, controller 100 is not shown but is equally applicable as described herein.

[0098] Variations of the first embodiment

[0099] Reference Figure 4 Examples of 3D printing equipment in the form of a powder bed fusion apparatus are described, the powder bed fusion apparatus being configured to reuse build materials in situ and including a variation of the build material supply system according to the first embodiment. Figure 4 It includes information about Figure 1 A schematic cross-section of the side view of the components of the device 1 describing the construction material supply system 10. It should be noted that... Figure 4 In the diagram, the dispensing path 140 is shown from left to right, and therefore the dispensing device 40 and the return chamber 60 are now located on the left and right sides of the building area, respectively. Figure 1 and Figure 2 The diagram shown is a mirror image. The mixed build material and the build material of the composition suitable for forming the layer are provided to the buffer tank 50. The dispensing device includes a dispensing chamber disposed below the working surface 8 of the device. The working surface includes a build region 12, which is the topmost surface of the build volume 14, supported on a build platform (not shown) within the container wall, and includes the complete cross-section of the object 2 to be formed. The dispensing device includes a dispensing outlet within the working surface, and a dispensing blade 412 is rotatably disposed above the dispensing outlet. An excess return chamber 60 is further provided on the side of the build region opposite to the side where the dispensing outlet is located. A certain amount of build material is dispensed from the dispensing chamber 410 to the working surface by rotating the dispensing blade to scoop out a dispensing amount of build material from the dispensing chamber 410 and holding the dispensing amount above the working surface. A spreading device 32, shown here as a roller, moves from left to right to spread the dispensing amount of build material along a dispensing path 140.

[0100] The buffer tank 50 is configured to intermittently or continuously mix the building materials in order to maintain the building materials in a homogeneous and preferably free-flowing state. Inlet and outlet valves, indicated by the box, are connected to the pump, and as... Figure 1 Such markings. Controller 100 can control valves to open the dispensing flow path, which includes a buffer tank to pump section 150 and a pump to dispensing device section 120, to allow build material to flow from the buffer tank through pump 90 and into dispensing chamber 410. The dispensing amount includes an excess of build material, which prevents underfeeding and is pushed into the excess return chamber 60 by the device's dispensing device 32. It should be noted that, for example, the dispensing amount including layer quantity and excess quantity remaining after layer formation can include an additional amount spread on the working surface outside the build area range.

[0101] The controller can control valves to open excess return flow paths along the excess return to pump section 160 and pump to buffer tank section 110 to allow excess build material to travel back to buffer tank 50. The controller 100 can also control valves to open supply flow paths along the supply tank to pump section 180 and pump to buffer tank section 110 to allow fresh build material to flow into buffer tank 50. Therefore, the equipment including the build material supply system 10 enables the immediate in-situ reuse of excess build material during the equipment's build process.

[0102] Figure 5 It shows Figure 4 A variation of the device, wherein the dispensing device 40 further includes an overflow chamber 470 connected to the dispensing chamber 410 via an overflow outlet 472, the overflow outlet being arranged below the level of the dispensing outlet. As the dispensing chamber is filled with build material from dispensing paths 120, 150 and reaches the level of the overflow outlet, excess build material flows through the overflow outlet 472. This arrangement of the dispensing device 40 allows the amount of build material in the dispensing chamber to be self-regulating or passively regulated, and ensures that for each level, a consistent amount of build material is dispensed to the working surface 8. The build material transferred from the dispensing chamber is divided into a dispensing amount and an excess supply amount, flowing along a first path 140A (dispensing path) toward the excess return chamber and along an overflow return path including an overflow to pump flow path section 140B and a pump to buffer flow path section 110. All other components, as per [reference to other components], flow towards the excess return chamber. Figure 4 As stated and referenced. Overflow can be immediately returned to buffer tank 50 via the excess supply return flow path.

[0103] therefore, Figure 4 and 5 The build material delivery mechanism is configured in the form of a build material pump 90 (e.g., a diaphragm pump) and a valve system to allow opening and closing of the flow path described herein. This build material supply system 10 can advantageously replace auger and rigid pipe systems for efficient movement of build material along a flow path that includes a dispensing flow path, an excess return flow path, a supply flow path, and an optional overflow return flow path. Build material supply systems using augers and rigid pipes can be difficult to seal and access, potentially due to localized compaction of the build material after idle time or due to the inhalation of small objects, and can be difficult to maintain and repair.

[0104] It has been found that the construction material supply system disclosed herein and its operating method according to the present invention allow for the reliable supply of a substantially stable, uniform consistency of mixed construction material to the batching device 40 by configuring the supply system such that the pump 90 delivers a stable flow of excess construction material back to the construction material and fresh construction material, and optionally a stable flow of overflow construction material to the buffer tank 50.

[0105] Next turn Figures 3A to 3D , showed Figure 4 The flow path of the construction material supply system, and optional Figure 5 Overflow chamber 470. Figure 4 and Figure 5 The components of the building material supply system are schematically shown in the form of boxes, with arrows between the boxes indicating the flow direction along various paths. For simplicity, Figure 1The controller 100 is not shown, but it is also connected to the valve and the pump and is configured to control the operation of the pump and to establish the open and closed positions of the valve within the material flow path.

[0106] exist Figures 3A to 3D In the diagram, the bold outline of the flow path indicates the open flow path through which the building material can flow, while the normal outline of the flow path indicates the closed path through which the building material cannot flow.

[0107] Figure 3A It shows Figure 1 A variant of the system, wherein overflow chamber 470 is optional, as indicated by the dashed outline. The build material supply system 10 includes a first group 310 consisting of at least three inlet valves 250, 260, and 280, located between a pump and a corresponding one of the buffer tank 50, excess return chamber 60, and supply tank 80. Each inlet valve can be individually connected to the pump via a dedicated inlet flow path, or can be connected to a combined inlet flow path 130_IN, as shown here. A second group 320 consists of outlet valves 210 and 220, respectively arranged between the outlet of pump 90 and the buffer tank 50 and the dispensing device 40. Each outlet valve can be individually connected to the pump via a dedicated outlet flow path, or can be connected to a combined outlet flow path 130_OUT, as shown here. A controller is connected to the first valve 280, the second valve 260, and the third valve 250, all of which are inlet valves used to control the flow of build material into pump 90. The controller is further connected to a fourth valve 210 and a fifth valve 220, which are outlet valves used to control the flow of building material leaving the pump 90.

[0108] Figure 3A The feed flow path is indicated in bold. To ensure that the mixture of excess return and fresh build material remains consistent within the buffer tank, the inlet valves 260 and 280, located between the excess return chamber 60 and the supply tank 80 and the pump 90, are closed, while the inlet valve 250, located between the buffer tank 50 and the pump 90, is open. The outlet valve 210 between the pump and the buffer tank 50 is closed, and the outlet valve 220 between the pump and the feed device is open. When the pump is controlled to start operating, it causes build material to flow from the buffer tank 50 through the pump and into the feed chamber 410 of the feed device 40.

[0109] Figure 3BThe excess return flow path is indicated in bold. To open the excess return flow path, inlet valves 250 and 280, located between buffer tank 50 and supply tank 80 and pump 90 respectively, are closed, and inlet valve 260, located between excess return chamber 60 and pump 90, is open. Outlet valve 220 between pump and batching device is closed, and outlet valve 210 between pump and buffer tank 50 is open. When the pump is controlled to start operation, it causes building material to flow from excess return chamber 60 through pump 90 and into buffer tank 50.

[0110] Figure 3C The supply flow path is indicated in bold. To open the supply flow path, inlet valves 250 and 260, located between buffer tank 50 and excess return chamber 60 and pump 90 respectively, are closed, and inlet valve 280, located between supply tank 80 and pump 90, is open. Outlet valve 220 between pump and batching device is closed, and outlet valve 210 between pump and buffer tank 50 is open. When the pump is controlled to start operating, it causes fresh building material to flow from supply tank 80 through pump 90 and into buffer tank 50.

[0111] Turning Figure 3D The variant of the material supply system 10 further includes, for example, Figure 5 The overflow chamber 470, connected to the batching chamber 410, is shown. The first set of inlet valves further includes a sixth valve 240 located between the overflow chamber 470 and the pump 90. The flow from the batching chamber 410 to the overflow chamber 470 is schematically indicated by a flow path segment 140B that flows out of the batching chamber 410 and continues through the overflow chamber 470 to the sixth valve 240.

[0112] Figure 3D The overflow return flow path is indicated in bold. To open the overflow return flow path, inlet valves 250, 260, and 280, located between buffer tank 50, excess return chamber 60, and supply tank 80 and pump 90, respectively, are closed, and inlet valve 240, located between overflow chamber 470 and pump 90, is open. Outlet valve 220 between pump and batching device is closed, and outlet valve 210 between pump and buffer tank 50 is open. When the pump is controlled to start operation, it causes building material to flow from overflow chamber 470 through pump 90 and into buffer tank 50.

[0113] Therefore, the dispensing device of the build material supply system of the first embodiment may include: a dispensing chamber 410, which is coupled to the outlet of the pump and configured to receive build material from the buffer tank 50 via the pump 90; the dispensing device 40 further includes an overflow chamber 470, which is coupled to the dispensing chamber 410 and configured to receive an excess amount of build material transferred from the buffer tank 50 to the dispensing chamber 410 when the build material in the dispensing chamber reaches a predefined level; wherein the overflow chamber 470 is coupled to the inlet of the pump 90 via a sixth valve 240, and wherein the controller 100 is configured to at least control the third valve 250 and the fifth valve 220 to close to cut off the dispensing flow path, and to control the sixth valve 240 and the fourth valve 210 to open and control the pump to operate to open an excess supply return path from the overflow chamber through the pump to the buffer tank. This allows the excess build material to flow along the excess supply return flow path.

[0114] Any or all of the inlet valves may be variable valves and operate as will be further explained below. Regarding the construction material supply system of a variant of the first embodiment including the overflow chamber 470, method 800 and as... Figure 14 The optional box 850, indicated by the dashed outline, may include activating the build material pump while simultaneously opening the excess supply return flow path to return excess build material from the dispensing unit to the buffer tank. This can be applied for a predefined overflow return duration or until the build material level in the overflow chamber has dropped below a predefined minimum level.

[0115] Next, a variation of the dispensing device 40 of the first embodiment will be described. One of the challenges of using a build material pump is to reduce or prevent the environment that pushes build material into the dispensing device, which includes a dispensing chamber 410 into which the build material is pumped under a burst of increased gas pressure. Furthermore, the pump can supply large quantities of build material very efficiently over a short period, making careful control of the amount supplied to the dispensing chamber, whether by active or passive means. Therefore, the authors of this invention have developed a variation of the dispensing device 40 that includes a build material bypass connected to the dispensing chamber 410 via multiple dispensing chamber inlets that control the flow of build material into the dispensing chamber 410 and significantly reduce or completely prevent the generation of powder or dust in the dispensing chamber. Figure 9AA 3D view of this variant of the dispensing device 40, viewed from above, is shown. The dispensing chamber 410 is represented as an elongated trough-shaped container configured to include dispensing blades (not shown) to be installed and rotatable about axis 414. Build material is supplied into the dispensing chamber from a plurality of inlet ports 436. Each inlet port is connected to a bypass outlet port 438 via an inlet flow path 440. As shown herein, the outlet ports 438 are arranged along the length of a middle section of the bypass pipe 430. Each inlet path 440 has significantly higher flow resistance than the bypass 430; preferably, the combined flow resistance of the inlets is greater than the flow resistance of the bypass pipe between its inlet and outlet. When build material is pumped from the bypass inlet 432 through the bypass, it is forced to flow into the plurality of outlet ports 438 arranged along the length of the middle section, each port being connected to the inlet 436. The batching chamber inlet 436 is preferably arranged along the lower portion of the batching chamber and configured such that the building material enters the batching chamber in a substantially horizontal direction or tangentially to the curvature of the trough, in order to avoid pushing the material into the environment of the batching chamber and into the aforementioned workspace. The building material can be circulated back into the buffer tank 50 from the bypass outlet 434. The inlet path 440 is in Figure 9B and Figure 9C It is shown in more detail in the middle. Figure 9B and Figure 9C A deeper cut through the bottom plate of the mixing chamber is shown to expose the outlet port and inlet path 440 in the bypass chamber 430. It has been found that excess amounts of fast-flowing gas can be prevented from entering the mixing chamber 410 by selecting appropriate flow resistance, for example, between each intermediate bypass outlet and the corresponding mixing chamber inlet, and by selecting appropriate diameters and lengths for each inlet path 440. Instead, the gas can flow primarily or entirely along the bypass chamber 430 and exit through the bypass outlet 434.

[0116] Therefore, a dispensing device 40 is provided, comprising a dispensing chamber 410 and a build material bypass chamber 430. The dispensing chamber 410 includes one or more build material inlets 436 connected to one or more intermediate outlets 438 of an intermediate section of the bypass chamber 430, wherein the intermediate section is arranged between the bypass chamber inlet 432 and the bypass chamber outlet 434. The bypass chamber inlet 432 is configured to receive build material from a build material source, such as a buffer tank 50, and the bypass chamber outlet 434 is configured to release build material from the bypass chamber 430. The one or more intermediate outlets 438 are indicated by reference hereinafter. Figure 10 and 11One or more batching chamber inlet paths 440 of the described combined flow path 120B are connected to one or more batching chamber inlets 436. The batching chamber inlet paths 440 are configured to present a flow resistance to the build material flow that is higher than the flow resistance of the bypass chamber between inlet 432 and outlet 434 of the bypass chamber 430. Furthermore, the combined flow resistance of the plurality of batching chamber inlet paths 440 may be higher than the flow resistance of the bypass chamber between inlet 432 and outlet 434 of the bypass chamber 430, each batching chamber inlet path 440 being arranged between outlet port 438 and batching chamber inlet 436. Each of the plurality of outlet ports 438 may be connected to a corresponding batching chamber inlet 436. One or more batching chamber inlets 436 may be arranged near the lower gravity section of the batching chamber 410, for example, at or near the gravity bottom of the batching chamber 410, and / or may be arranged to provide build material flow into the batching chamber at an angle having a component parallel to the inner wall of the batching chamber. For example, the batching chamber entrance 436 can be arranged to point along or toward the bottom of the batching chamber 410. In this way, the generation of building materials suspended in the environment of the batching chamber can be reduced.

[0117] Furthermore, the amount of build material supplied to the mixing chamber 410 can be self-regulated by balancing the flow path resistance between each outlet port 438 and the corresponding mixing chamber inlet 436 relative to a fill level higher than the inlet level within the mixing chamber. Alternatively, the fill level can extend to the underside of the mixing blades, which can be horizontal during filling and close the mixing outlets leading to the workspace. The mixing blades can be used to provide resistance to the flow through the mixing chamber inlet, thereby blocking the supply of additional build material. Alternatively, for some build materials, the weight of the build material itself can be used, since the build material inside the mixing chamber will eventually block the inlet 436 and increase the flow resistance to exceed the maximum flow resistance, thus stopping the flow through the inlet path 440. A build material level sensor can be located in the mixing chamber and connected to the controller so that the controller can close the mixing flow path when the sensor detects that a predefined fill level has been reached. Alternatively, the mixing chamber 410 may further include an overflow outlet coupled to an overflow chamber 470, as referenced herein. Figure 3D and Figure 5 This method can be applied to passively adjust the amount of build material in batching chamber 410 to a predetermined fill level, and thus allows the build material to be continuously circulated along the pump to batching path 120 without overfilling the batching chamber. Alternatively, the build material can be intermittently traversed through bypass 430 to supply a predefined amount of build material to the batching chamber within a given number of layer cycles.

[0118] Typically, the length of the dispensing chamber 410 (along the rotation axis of the dispensing blades) is the same as or greater than the width of the building area 12, which is parallel to the axis of the dispensing blades and perpendicular to the dispensing direction of the dispensing device. It may be advantageous that the building material inside the dispensing chamber 410 is uniformly distributed along its length, such that the amount of material dispensed to the working surface is uniformly distributed along one side of the building area. As shown, multiple dispensing chamber inlets 436 can be arranged along the length of the dispensing chamber, which improves the uniform distribution of the building material inside the dispensing chamber 410.

[0119] In another variation of the material supply system 10 according to the first embodiment, the dispensing device 40 may include a dispensing chamber and a bypass chamber 430, the bypass chamber 430 having bypass inlets 432 and bypass outlets 434 at both ends of an intermediate section, wherein the intermediate section includes one or more intermediate outlets 438. Further reference... Figure 10 , Figure 10 The diagram illustrates the flow path of a modified build material supply system, where a bypass inlet 432 is connected to the outlet of pump 90 via a fifth valve 220, and a bypass outlet 434 is connected to the inlet of buffer tank 50 or another inlet. The batching chamber 410 may include one or more batching chamber inlets 436 configured to receive build material from the bypass chamber 430 and connected to one or more intermediate outlets 438 to form one or more intermediate flow paths 440. A controller controls the opening of the third valve 250 and the fifth valve 220, and controls the closing of the first valve 280, the second valve 260, and the fourth valve 210. When the controller controls pump 90 to operate, build material is caused to flow along the batching flow path from buffer tank 50 through pump 90 to bypass chamber 430, and along the intermediate flow path 440 (in... Figure 10 The flow path (indicated by combined flow path 120B) flows from bypass chamber 430 to batching chamber 410. Furthermore, an excess supply flows from bypass chamber 430 along excess supply return flow path 140C, and then directly from bypass chamber 430 to buffer tank 50 along direct bypass return path 140C. The open batching flow path and excess supply return path are indicated in bold.

[0120] Preferably, one or more intermediate flow paths are configured to have a flow resistance substantially higher than the flow resistance from the bypass inlet to the bypass outlet, such that gas from the pump flows primarily from the bypass inlet to the bypass outlet. Alternatively or additionally, the combined flow resistance of one or more intermediate flow paths may be substantially higher than the flow resistance from the bypass inlet to the bypass outlet, such that gas from the pump flows primarily from the bypass inlet to the bypass outlet.

[0121] exist Figure 11 shown Figure 10In a variant, the bypass outlet can be further connected to the inlet or another inlet of the buffer tank 50 via a sixth valve 240C1; such that when the controller further controls the opening of the sixth valve 240C1, an excess supply flow is caused to originate from the bypass chamber 430 and flow directly from the bypass chamber to the buffer tank 50 along the direct excess supply return flow path 140C1. This allows the controller to cut off the excess supply return path when the supply path and / or excess return path are opened.

[0122] Optionally, such as Figure 11 As shown, the bypass outlet can be further connected to the inlet of the building material pump 90 via a seventh valve 240C2, wherein a controller is connected to the seventh valve 240C2 and is configured to:

[0123] (i) Control the opening of the third valve 250, the fifth valve 220, and the sixth valve 240C1, while controlling the closing of the first valve 280, the second valve 260, the fourth valve 210, and the seventh valve 240C2, and controlling the pump to operate, so as to allow the build material to flow along the batching flow path, and to allow the excess build material to return directly from the bypass outlet to the buffer tank 50 along the direct excess supply return flow path 140C1 without passing through the pump and Figure 10 This is shown in bold. It supplies construction materials to the auxiliary chamber 430;

[0124] (ii) Control the first valve 280, the second valve 260, and the fourth valve 210 to remain closed, control the third valve 250 and the sixth valve 240C1 to close, and control the fifth valve 220 and the seventh valve 240C2 to open, and control the pump to operate to allow build material to circulate from the bypass chamber 430 through the build material pump 90 and return to the bypass chamber 430, so as to continue to reuse the excess supply of build material to fill the batching chamber along the recirculated excess supply return path 140C2. Figure 11 This is shown in bold. This reuses and depletes the recycled building materials through the bypass chamber 430;

[0125] (iii) Control the fifth and seventh valves to close, control the pump to operate, and in sequence or simultaneously:

[0126] - Control the opening of the second valve 220 and the fourth valve 240C2 to allow excess build material to flow into the buffer tank 50 along the excess return path;

[0127] - Control the opening of the first valve 280 and the fourth valve 210 to allow fresh build material to flow into the buffer tank 50 along the supply flow path;

[0128] Repeat steps (i) to (iii).

[0129] Regarding the construction material supply system of the variant of the first embodiment including the bypass chamber 430, method 800 and as... Figure 14 The optional box 850, indicated by the dashed outline, may include activating the build material pump while simultaneously opening an excess supply return flow path to return excess build material from the dispensing unit to the buffer tank, either directly or via pump 90. This can be applied for a predefined excess supply return duration, or only until the build material level in the bypass chamber has dropped below a predefined minimum level.

[0130] Therefore, in the construction material system and its variants according to the first embodiment, where the construction material delivered to the dispensing device at block 810 includes an excess supply of construction material, step (b) at block 820 may further include a step (b1) allowing the excess supply to flow out of the dispensing device, and a step (b2) at block 850 operating the pump while opening another flow path from the dispensing device to the buffer tank 50 to return the excess supply to the buffer tank 50. The method may include returning the excess supply directly to the buffer tank 50, wherein the dispensing device includes, as in... Figure 10 The bypass room 430 shown, or via, as Figure 3D The sixth valve and pump 90 shown return excess supply to buffer tank 50, where the dispensing device includes overflow chamber 470. Alternatively, another flow path can be opened sequentially: from bypass chamber 430 to pump 90 and back to dispensing device 40, to reuse the excess supply in the dispensing device.

[0131] Step (b2) at box 850 may not be applied at each repetition of the multiple repetitions of the cycle from box 810 to 850. Alternatively, box 850 may be applied for a predetermined duration shorter than the duration of step (d) at box 840, or when it is detected that the level of building material in the buffer tank and / or excess return chamber has dropped below a corresponding predetermined level, so that the excess building material is returned to the buffer tank for reuse before the excess building material is returned to the buffer tank.

[0132] The method may include first returning excess build material to buffer tank 50 at box 840, then returning excess supply material (if present) to buffer tank at box 850, and supplying fresh build material from the supply tank at box 860; wherein the step at box 860 is initiated to maintain the build material in the buffer tank at a ratio of excess build material to fresh build material that is substantially uniform. For example, the controller may initiate box 860 after detecting that the fill level in buffer tank 50 has reached the minimum fill level.

[0133] Variations of the second embodiment

[0134] Now refer to Figures 12A to 12D and Figure 13The second embodiment is described. In an implementation of the second embodiment, build materials can be dispensed from above rather than below the work surface, and the dispensing device 40 can supply directly from the buffer tank 50 without having to pass through the build material pump. See reference... Figure 2 The construction material pump 90 is used to transfer construction material from the excess chamber 60 and the supply tank 80 to the buffer tank 50 in a manner similar to that described above and using at least one inlet valve 280 between the supply tank 80 and the pump 90.

[0135] Figure 12A This is a schematic cross-section of a side view of the buffer tank 50 arranged above the working surface 8. The inlet 510 of the buffer tank 50 is configured as described above to be connected to the outlet of the supply tank 80 via a first valve and a pump 90, and as referenced... Figure 2 The outlet is connected to the excess return chamber 60. The outlet 520 of the buffer tank 50 can be a hole in the bottom plate of the buffer tank, such as... Figure 12A As shown. The buffer tank outlet 520 is connected to a dispensing device 40, which is functionally equivalent to the dispensing device described above, and is configured to dispense a quantity of build material from the buffer tank 50 onto the working surface 8. Thereafter, a layer of the dispensed material is distributed onto the build area by a spreading device to form layers, and excess material is pushed into the return chamber 60. Various known methods can be used to dispense a consistent amount of build material for each layer. In this example dispensing device 40, in the outlet section, the buffer tank outlet 520, the rotatable metering disc 442, and the fixed release disc 446 are stacked on top of each other from top to bottom. These metering discs 442 and release discs 446... Figure 12C The offset planar diagram shows the metering position when the discs are stacked. The metering discs are arranged to rotate about a vertical axis at their center. The metering discs may include an aperture 444, as shown, and are configured to receive build-up material from the buffer tank through the buffer tank outlet 520 when the metering discs rotate to align the aperture 444 with the buffer tank outlet 520. Figure 12A As shown. The release orifice 448 is not aligned with the metering orifice 444. Construction material flows through the buffer tank outlet into the metering orifice, and when the metering orifice 444 is filled with construction material from the buffer tank, the disc rotates to the release position to align the metering orifice with the release orifice 448, while simultaneously blocking the buffer tank outlet 520. This is in Figure 12B The instructions indicate that the disc is aligned with... Figure 12DThe diagram is shown in an offset plan view. The build-up material flows from metering orifice 444 to release orifice 448, and from the release orifice through a release portion, such as guide tube 542, onto the working surface 8. Guide tube 452 prevents excessive build-up material from being released into the environment. The disc may include more than one orifice, allowing the build-up material to be released in multiple portions. Alternatively, the disc may be arranged to release build-up material at different locations along the length of the dispensing device. Other known variations may utilize a rotatable rod with opposing grooves instead of a metering disc and a release disc.

[0136] This variation of the dispensing device 40 eliminates the need to manage pressurized gas from a pump within the dispensing device. Furthermore, the dispensing amount is controlled by a metering disc and a release disc, eliminating the need to return excess material from an overflow chamber or bypass chamber to the buffer tank. The buffer tank 50 may include a built-in level sensor to refill the buffer tank to a predefined fill level from the excess return chamber and the supply tank, as will now be referenced. Figure 13 As stated above.

[0137] Figure 13 It is shown Figure 2 A block diagram of a variation of the flow path, wherein another inlet valve 260 may be provided between the excess return chamber 60 and the pump 90. As previously stated, for Figure 2 The build material supply system 10, with its buffer tank, supplies build materials directly to the batching device 40, rather than via a pump 90. The arrangement of the build material supply system according to the second embodiment allows for the supply of a homogeneous build material mixture with consistent properties to the batching device by managing the amount of excess and fresh build material fed into the buffer tank. Figure 13 This is a block diagram illustrating the flow of build material through the build material supply system 10, with arrows indicating the flow direction as previously described. A controller 100 is shown coupled to a combination frame 330, which includes a dispensing device and a buffer tank, as well as a build material level sensor 540. The controller can be configured to control the dispensing device to dispense the amount of build material. The controller is further coupled to a first set of inlet valves 310, including a first valve 280, and can be further configured to control the supply flow path from the supply tank 80 via the first valve 280, through the pump 90, and into the buffer tank 50 by causing the first valve to open and causing the pump to operate. Thus, build material is allowed to flow into the buffer tank 50: from the supply tank to the first valve along flow path segment 180; from the pump to the buffer tank along a common pump inlet segment 130_IN and along flow path segment 110. The buffer tank 50 is coupled to a dispensing device 40, which includes a dispensing chamber in the form of, for example, an orifice 448.

[0138] exist Figure 2In this variant, a set of inlet valves includes a second valve 260, and the inlet of pump 90 is connected to the excess return chamber 60 via the second valve 260. A controller is connected to the second valve 260 and configured to control the first valve 280 to at least partially close and control the second valve 260 to open, allowing excess build material to flow along the excess return flow path. Subsequently, the controller can cause the second valve 260 to close and cause the first valve 280 to fully open, allowing fresh material to flow along the supply flow path. Thus, when the first valve is controlled to open, the controller can control the second valve 260 to cut off the excess return flow path segment 160 from the excess return chamber to the pump. This allows excess build material to be returned to the buffer tank sequentially, and fresh build material to fill the buffer tank. Furthermore, cutting off the excess return flow path prevents accidental suction caused by excess return when the first inlet valve 280 between the supply tank and the pump is open, and thus improves control over the ratio of excess return to fresh build material supplied to the buffer tank. This further allows the pump to operate to mix the build-up materials in buffer tank 50 when the first valve is closed. (As for...) Figures 12A to 12D The dispensing device may include a dispensing device inlet in the form of a metering orifice and configured to receive build material from the outlet of a buffer tank, wherein a controller is coupled to the dispensing device and configured to control the dispensing device to release the dispensing amount. For example, the dispensing device may release the dispensing amount of build material toward a working surface under gravity.

[0139] A combined inlet path 130_IN can be provided from two valves. Alternatively, the two flow paths can be connected to the pump separately, as shown in Figure 3.

[0140] Prioritization and timing of material construction in the flow path

[0141] In this document, “fresh” build material may comprise a predefined mixture of virgin and reused materials from one or more previous build processes, such as a virgin:reuse ratio of 30:70 or 20:80. For most build materials, due to thermal aging, it is preferred or required that the virgin:reuse ratio supplied to the batching chamber does not change significantly enough during the build process to substantially alter the thermal properties of the build material. In powder bed fusion processes, it is important that the properties of the build material supplied to the batching chamber and used to form each layer do not change significantly during the build process. Significant changes in the reused contents can alter the thermal properties of the build material, which in turn will lead to different responses of the build material layers to the thermal cycles applied to the molten layers. For example, the melting temperature of the build material may shift to a higher temperature than the temperature the process was calibrated for, and the thermal energy applied to the cross-section of the object within the molten layer may not cause the same degree of melting as in previous layers. This can lead to gradual changes in the mechanical and potential visual properties of the object. Any significant deviation from a reliable, uniform process will result in inconsistent materials and thus reduced yields due to the discarding of unsuitable materials, which can be avoided by controlling and timing the amount of build material supplied to the buffer tank 50 from various sources.

[0142] When build materials are exposed to high temperatures, particularly near their melting point, thermal aging, such as degradation or polymer chain growth, can occur. For example, nylon PA11 has a melting temperature of approximately 200°C. PA11 build material within the flow path between valves, and for example in the dispensing chamber, can reach a temperature of 100-140°C before being dispensed onto the working surface 8. When the dispensing amount is applied to a previously built area to form a new layer, the dispensing amount is spread onto the hot surface of the existing build volume, which can be maintained at a build bed temperature of approximately 180°C. Therefore, the dispensing amount is much lower than the build bed temperature, and to prevent warping and curling of the underlying molten cross-section, the new layer is typically preheated immediately to reach or approach the build bed temperature. This can be accomplished by arranging heat bars, such as infrared linear lamps, to follow the dispensing device as it preheats the new layer during its formation. Excess material prior to the dispensing device will also become heated through contact with the underlying build volume and will therefore experience the highest thermal shock of powder to the buffer tank within the supply system. It is generally desirable to reuse excess build material first. Since the excess amount is typically relatively small compared to the amount in the buffer tank, it can be immediately returned to the buffer tank and mixed with the buffer tank construction material. Meanwhile, in Figure 4 In the case of a system, the primary source of build materials within the buffer tank can be from a supply tank, which comprises build materials with predefined properties. Figure 5In the case of a system, the system includes an additional flow path for the batching overflow 470, and the overflowed build material can also be returned to the buffer tank 50 before build material from the supply tank 80 is required. The overflow material from the batching overflow 470 can have lower heat exposure than the excess build material and can be returned to the buffer tank 50 after the excess material has been returned to the buffer tank 50.

[0143] In this document, excess overflow chambers, overflow chambers, and bypass chambers can be configured to hold a certain amount of building material before it needs to be conveyed from these chambers to the buffer tank. Therefore, it is possible to sequentially convey the building material and apply certain order and / or flow control. The building material supply system according to two embodiments can provide a building material conveying method in which a controller controls a first valve to close to cut off the supply flow path and controls the pump to operate, and, if present, controls a second valve to open to allow excess building material to flow along the excess return flow path. Subsequently, the controller can control the second valve to close and control the first valve to open to refill the buffer tank with fresh building material, thus applying a sequential filling method that improves control over the amount of excess returned and the amount of fresh building material transferred to the buffer tank 50. Alternatively, excess returned building material can be returned to the buffer tank while fresh building material is being conveyed from the supply tank to the buffer tank 50.

[0144] Regarding the first embodiment and its variations, in order to allow excess build material and fresh build material to flow simultaneously along the supply flow path and the excess return flow path, the controller can control the third and fifth valves to close, control the first valve 280 and the second valve 260 to open, and activate the pump. In a variation of the first embodiment that includes the overflow chamber 60, the controller can further control the sixth valve 240 to open to allow excess supply build material, along with excess build material and fresh build material, to flow simultaneously from the overflow chamber 470 into the buffer tank 50, while controlling the third valve 250 and the fifth valve 220 to remain closed to keep the dispensing flow path closed.

[0145] Regarding the second embodiment, the controller can control the opening of the first valve 280 to allow excess build material and fresh build material to flow simultaneously along the supply flow path and the excess return flow path. In the absence of the optional second valve 260, or with the second valve present and open, excess build material can easily return once it falls into the excess return chamber 60 and can be mixed with the fresh supply material as it travels through the pump 90. With the second valve 260 present, the controller 100 can control both the first and second valves to independently control the flow of excess return build material and supply build material.

[0146] The section between the overflow or bypass and the build material pump can be restricted to provide higher flow resistance to the build material flow compared to the flow from the excess return chamber to the pump. For example, the first valve 280, the second valve 260, and / or the sixth valve 240 can be variable valves. Regarding the first embodiment, the controller 100 can be configured to control the sixth valve 240 to partially open and the second valve 260 to fully open, thereby imposing higher flow resistance to the excess build material flow through the excess supply return flow path compared to the flow resistance of the excess build material flow along the excess return flow path. Regarding the first embodiment and its variations, the first valve 280 can be opened only partially to restrict flow and generate higher flow resistance to the fresh build material flow through the supply flow path compared to the flow resistance of the excess build material flow along the excess supply return flow path.

[0147] Regarding these two embodiments and their variations, the supply flow path can be configured to have a higher flow resistance to the flow of build material than the excess return flow path. The first valve 280 can be a variable valve, and the controller 100 can be configured to control the first valve 280 to open only partially in order to restrict the flow and generate a higher flow resistance to the flow of fresh build material through the supply flow path compared to the flow resistance of excess build material flow along the excess return flow path.

[0148] In both embodiments and their corresponding variations, the flow of build material to the buffer tank can be prioritized, and the controller can be configured to apply the following sequence: First, excess build material is allowed to flow along the excess return path by controlling the first valve to be at least partially closed, for example until the excess build material from the excess return chamber drops below a first predetermined level; second, with respect to a variation of the first embodiment, excess supply build material is allowed to flow along the excess supply return path while controlling the first and second valves to be at least partially closed, for example until the excess supply build material in the overflow chamber 470 or bypass chamber 430 drops below a second predetermined level; and third, fresh build material is allowed to flow along the supply flow path while controlling the first valve to be at least partially open, for example until the build material in the buffer tank reaches a predetermined fill level.

[0149] Additionally, regarding the first embodiment and its variations, controlling the flow of build material to the buffer tank may include: first, controlling the second and fourth valves to open while controlling the first, third, fifth, and sixth valves (if present) to close, to allow excess build material to flow along the excess return flow path; second, if present, controlling the sixth and fourth valves to open while controlling the first, second, third, and fifth valves to close, to allow excess build material to return to the buffer tank along the excess supply return flow path; third, controlling the first and fourth valves to open to replenish the buffer tank with fresh build material along the supply flow path, while controlling the second, third, fifth, and sixth valves (if present) to close.

[0150] Pump 90 can be operated intermittently to deliver excess return building material from excess return chamber 60 along the excess return flow path to buffer tank 50, and the pump can be timed relative to the delivery of excess supply building material along the excess supply flow path and fresh building material along the supply flow path, so that the amount of excess material entering the buffer tank remains constant within a given time period. Alternatively, the building material pump can be controlled to operate continuously within the cycle of boxes 810 to 870. The excess return flow path and the supply flow path can be closed before the batching flow path is opened at box 810 to ensure that building material does not immediately enter the batching flow path and does not mix with the building material in the buffer tank. When the excess return flow path is opened at box 840, the batching flow path can be closed and the supply flow path can be at least partially closed. When the supply flow path is opened at box 860, the batching flow path can be at least closed. This improves the uniformity of the build material within buffer tank 50, but depending on how excess and fresh build material are fed into the buffer tank, it may not be necessary to mix the added build material before conveying it along the dispensing flow path from the buffer tank to the dispensing device. For example, when build material is fed into the buffer tank in the upper section and exits into the dispensing flow path in the lower section, the build material may not immediately reach the buffer tank outlet before being mixed with the existing material. The steps at blocks 840 and 860 can be applied simultaneously and may optionally include at least partially opening the respective flow paths to change the flow resistance of the respective flow paths, such that excess build material preferably flows along the excess amount return flow path to the buffer tank, or first over the fresh build material along the supply flow path starting from supply tank 80, and in order to maintain a substantially uniform ratio of excess to fresh build material within the buffer tank.

[0151] In a variation of the method, steps at boxes 810 through 860 can be applied sequentially, with each step existing in each cycle. Alternatively, the step of dispensing build material from the dispensing chamber at box 820 can be controlled independently of the remaining steps managing the supply of build material to buffer tank 50 and the return of build material from said buffer tank, so that the build process for the object occurs within a fixed cycle duration without delay. The step of receiving excess build material in the excess return chamber 60 at box 830 depends on box 820. Meanwhile, box 840, which conveys excess build material along the excess return flow path, box 850 (if present), which conveys excess supply build material along the overflow return path, the direct excess supply flow path, or the recirculated excess supply flow path, and / or box 860, which conveys fresh build material along the supply flow path, can be controlled independently of boxes 810 and 820. For example, these boxes can be applied sequentially in fewer cycles compared to the number of dispensing cycles at box 810. Alternatively, box 860 can be applied after repeating the steps at boxes 840 and 850 (if present). At box 860, fresh build material is delivered to refill the buffer tank and replace the amount lost in the forming layer.

[0152] The duration for which each flow path is open during this period can be predefined or dynamically controlled based on measurements of the build material levels included in various containers and chambers. Measurements can be provided by one or more build material level sensors or mass sensors arranged within the buffer tank 50 and configured to measure the amount of build material in the buffer tank and optionally further in one or more of an excess return chamber, a batching chamber, and an overflow chamber (if present). The controller 100 can be configured to receive data from the build material level sensors or mass sensors configured to measure the amount of build material in the buffer tank 50. Based on the measured amounts, the controller 100 can control the timing and duration of the delivery of excess build material, overflow build material, and fresh build material into the buffer tank 50. For example, the timing of delivering build material from various sources to the buffer tank can be adjusted during the build process in response to the measured amount of build material in the buffer tank.

[0153] For each layer, the deficit in the build material supply system is the amount used to form the layer on the working surface 8 and the build area 12 during the layer cycle. The surplus can be significantly smaller than the deficit for each layer cycle. Compared to the surplus, a relatively large amount of overflow build material can be generated. The controller can control the supply flow path, the surplus return path, and the excess supply flow path, such that only excess build material and excess supply build material are alternately returned to the buffer tank 50 once or more before the supply flow path is opened to allow fresh build material from the supply tank to flow into the buffer tank. To shorten the time that build material entering the buffer tank needs to be mixed into the existing build material, alternatively, the supply cycle may include multiple instances of a fixed or variable duration during which overflow material is to be delivered to the buffer tank, while there may only be one instance or fewer instances during which excess material and / or fresh build material is delivered to the buffer tank 50.

[0154] In another variation of the method, boxes 810 and 820 can be applied in each loop. Boxes 840 and 860 can be applied alternately in each loop. With box 850 present, the three boxes can be applied alternately within a loop, such that each box is applied every two loops.

[0155] Loop 1: Open the ingredient flow path to fill the ingredient chamber; then close the ingredient flow path (box 810) and open the excess return flow path. Close the excess return flow path (box 840). Dispense the ingredients (box 810).

[0156] Cycle 2: Open the ingredient flow path to fill the ingredient chamber; close the ingredient flow path (box 810). Open the oversupply return flow path and close the oversupply return flow path (box 850). Dispense the ingredients (box 810).

[0157] Cycle 3: Open the batching flow path to fill the batching chamber; close the batching flow path (box 810). Open the supply flow path, close the supply flow path (box 860). Batch the ingredients (box 810).

[0158] The process can then be repeated three times over the duration of the build-up process. For example, for a 10-second cycle between repeating boxes 820, the feed flow path can be open for up to 5 seconds for each layer at box 810. Additionally, one of boxes 840 and 860, and box 850 (if present), can be applied alternately for up to 4 seconds in each cycle, such that each box is applied every other layer, or every two layers if box 850 is present.

[0159] Buffer tank

[0160] In the block diagram described herein, a common inlet flow path 130_IN is shown entering the pump 90 from a set of inlet valves 310, and a common outlet flow path 130_OUT is shown leaving the pump 90 and entering a set of outlet valves 320; conversely, the pump may include multiple inlets and outlets to allow flow paths to be grouped in different ways or to provide separate flow paths to and from the pump.

[0161] Furthermore, the valve shown in the figure can be configured as a 2-way, 3-way, or 4-way valve, having more than one inlet and one outlet on the pump inlet side, and more than one outlet on the pump outlet side. The valve can be a one-way or two-way valve, and / or the valve can be a variable or simple on / off valve. It has been found, for example, that butterfly valves can be adequately controlled in variable positions to regulate the amount of build material flowing through various flow paths.

[0162] The pump can operate continuously, or only when it causes one or more of the following flow paths to open: the batching flow path, the excess return flow path, the oversupply return flow path, and the supply flow path. In the preferred method of operation, the pump can operate continuously.

[0163] Figure 6 This is a 3D view of an example buffer tank in the form of a cylindrical container 50 having an upper feeder 510 and a lower outlet 520. The top surface of the container 50 includes an exhaust port 530 comprising a filter screen configured to release gas from the container while preventing build material from leaving through the exhaust port. The feeder 510 and outlet 520 are arranged tangentially to the circumference of the container. When the pump 90 is operated, build material is pressurized and delivered into the container 50 via the feeder 510 at a tangential angle to the circumference, such that the build material introduced into the container is conveyed in a circulatory manner. The outlet is arranged such that powder material circulating along the inner container wall is conveyed out of the container in the circulation direction within the container. Any excess gas or air is released via the exhaust port 530. Thus, pump operation can be used to mix the build material transferred to the buffer tank 50 with the retained build material to produce a homogeneous mixture and to keep the build material in a free-flowing state before causing it to flow through the outlet 520 to the dispensing chamber 410. Alternatively, a mixer may be placed inside the buffer tank 50 to mix the building materials and keep them in a free-flowing state.

[0164] Figures 8A to 8D yes Figure 6 A 3D illustration of an implementation scheme for a mixing buffer tank 50. Figure 8AThis is a cross-sectional view along the axis of the outer cylindrical wall 550 of the buffer tank. Along this axis, a rotation shaft 570 supports a mixing device 580 arranged in the lower section inside the buffer tank. This mixing device is configured to lift and mix the building material from the bottom of the tank, keeping it in a free-flowing, homogeneous state. The top section of the buffer tank includes a partial inner wall 560, thus forming a double wall for the upper portion of the tank. The partial inner wall 560 provides an inlet passage for the buffer tank inlet 510. Figure 8B This is illustrated in more detail below. When the build material is pumped into the buffer tank at a tangential angle to the outer and inner walls along the channel, the generation of build material dust within the buffer tank 50 is reduced. This variant of the buffer tank may not require a filtered exhaust port because the outlet is shielded from dust. The build material descends towards the bottom plate of the buffer tank and is mixed with the retained build material by the rotation of the mixing device 580. Figure 8C The middle section is shown in a side view mounted on the rotating shaft 570, and in Figure 8D The image is shown in 3D view. The mixing device includes lifting blades 582 extending radially from the shaft for lifting the build material away from the bottom plate of the buffer tank. Helical frame sections 584A and 584B, fixed to the shaft 570 by horizontal supports 588, connect the lower portion to the lifting blades and an upper mixing section, which includes stirring blades 586 that convey the lifted build material toward the shaft. Therefore, the buffer tank 50 can be arranged to continuously mix the build material and prevent dust generation due to the build material being pumped in through inlet 510.

[0165] The buffer tank may further include a fill level sensor that detects when the fill level has been reached. Figure 8A A mechanical version of the fill level sensor 540 is shown, in which a paddle extends vertically downwards from the upper tank section into the tank, originating from a mechanical switch. The paddle is hinged at a switching section such that when build material reaches the fill level, the build material pushes the paddle and causes it to swing from its vertical position to an angled position. This switches the switch to allow detection that the fill level has been reached. Upon receiving a signal indicating that the fill level has been reached from the switch, a controller coupled to the fill level sensor can close the filling path into inlet 510.

[0166] Figure 7AA build container with an inlet 510 positioned below the outlet 520 is shown. Additionally, the inlet 510 may have a higher flow resistance than the outlet 520. As build material enters the buffer tank 50, the internal build material level rises and begins to cover the inlet area entering the buffer tank. At a predetermined maximum level LM, the amount of build material inside the buffer tank is sufficient to provide flow resistance against additional build material entering the buffer tank 50. This arrangement provides a self-regulating build material level within the buffer tank. The level LM can be predefined by providing appropriate flow resistance through the inlet pipe 510. Any overpressurized gas can exit through the top vent 530.

[0167] Therefore, the buffer tank can be configured to mix build materials by including a mechanical stirring device and / or including an inlet and an outlet, said inlet and outlet being arranged such that when the controller causes build materials to flow into the buffer tank, the build materials are mixed by the pressure of compressed gas from a pump. This can further maintain the build materials in a fluidized state. The inlet into the buffer tank can be arranged to induce eddies inside the buffer tank, such that several streams of gas and build materials from the pump can be introduced into the buffer tank, such that the added build materials can be mixed into the existing build materials inside the buffer tank solely by the action of the pump, and such that step (e) can include operating the build material pump to mix the build materials in the buffer tank. The buffer tank can include a fill level sensor configured to detect the fill level of the build materials inside the buffer tank, and wherein the controller is configured to open and close the supply flow path based on the detected build material level inside the buffer tank. Controller 100 can be configured to control components of the material supply system described herein to perform the methods described herein and variations thereof.

[0168] The buffer tank can be further heated, for example by placing thermally conductive foil around the outer wall and / or by passing heated gas through the buffer tank in addition to pumping, such as by allowing heated gas to permeate from the bottom of the tank through the building material.

Claims

1. A construction material supply system for an apparatus for manufacturing 3D objects by layering construction materials, characterized in that, The construction material supply system includes: - A dispensing device configured to supply a dispensing amount of building material to the working surface of the device, the dispensing amount including a layer amount and an excess amount remaining to form a layer; - A buffer tank, which is configured to mix building materials for supply to the dispensing device; - Excess material return chamber, which is used to receive excess building materials from the distribution device; - A supply tank, which is used to hold fresh building materials in order to replenish the buffer tank; - A construction material pump for conveying construction materials within the construction material supply system; and - Controller; The inlet of the building material pump is connected to the supply tank via a first valve, to the excess return chamber via a second valve, and to the buffer tank via a third valve; and the outlet of the building material pump is connected to the buffer tank via a fourth valve and to the inlet of the dispensing device via a fifth valve. The controller is coupled to the building material pump and the first valve, the second valve, the third valve, the fourth valve, and the fifth valve, and is configured to: - Control the first valve, the second valve, and the fourth valve to close, control the third valve and the fifth valve to open, and control the construction material pump to operate, so as to allow the construction material to flow from the buffer tank through the construction material pump to the batching device along the batching flow path; - Control the third and fifth valves to close, control the first and fourth valves to open, and control the build material pump to operate, allowing fresh build material to flow along the supply flow path from the supply tank through the build material pump and into the buffer tank; and - Control the third and fifth valves to close, control the second and fourth valves to open, and control the build material pump to operate, so as to allow excess build material to flow from the excess return chamber through the build material pump and into the buffer tank along the excess return flow path; In order to control the ratio of fresh building material to excess building material delivered to the buffer tank.

2. The construction material supply system according to claim 1, characterized in that, The batching device includes a batching chamber connected to the outlet of the build material pump and configured to receive build material from the buffer tank via the build material pump; The batching device further includes an overflow chamber connected to the batching chamber and configured to receive an excess supply of build material transferred from the buffer tank to the batching chamber when the build material in the batching chamber reaches a predefined level; The overflow chamber is connected to the inlet of the build material pump via a sixth valve, and the controller is configured to close the third and fifth valves, open the sixth and fourth valves, and operate the build material pump to allow excess build material to flow from the overflow chamber through the build material pump to the buffer tank along the excess supply return flow path.

3. The construction material supply system according to claim 1, characterized in that, The batching device includes a batching chamber and a bypass chamber, the bypass chamber having bypass inlets and bypass outlets at both ends of an intermediate section, the intermediate section including one or more intermediate outlets, wherein the bypass inlets are connected to the outlet of the building material pump via the fifth valve and the bypass outlets are connected to the inlet of the buffer tank, and wherein the batching chamber includes one or more batching chamber inlets configured to receive building material from the bypass chamber and connected to the one or more intermediate outlets to form one or more intermediate flow paths; such that when the controller closes the first, second, and fourth valves and opens the third and fifth valves and controls the building material pump to operate, building material is caused to flow along the batching flow path from the buffer tank through the building material pump to the bypass chamber of the batching device, and along the one or more intermediate flow paths from the bypass chamber to the batching chamber, so as to supply building material from the buffer tank to the batching chamber, and cause excess building material to return directly from the bypass chamber to the buffer tank along a direct excess supply return flow path.

4. The construction material supply system according to claim 3, characterized in that, The bypass outlet is connected to the inlet of the buffer tank via a sixth valve; such that when the controller closes the first, second, and fourth valves and opens the third, fifth, and sixth valves and operates the build material pump, the build material is caused to flow along the batching flow path and the one or more intermediate flow paths, and excess build material is caused to return to the buffer tank along the direct excess supply return flow path.

5. The construction material supply system according to claim 4, characterized in that, The bypass outlet is further connected to the inlet of the building material pump via a seventh valve, wherein the controller is connected to the seventh valve and is configured to: (i) Control the third valve, the fifth valve and the sixth valve to open, while controlling the first valve, the second valve, the fourth valve and the seventh valve to close, and controlling the construction material pump to operate, so as to allow the construction material to flow along the batching flow path and allow the excess supply construction material to return directly from the bypass chamber to the buffer tank along the direct excess supply return flow path; (ii) Control the third valve and the sixth valve to close and control the fifth valve and the seventh valve to open and control the construction material pump to operate, so as to allow the construction material to circulate from the bypass chamber through the construction material pump and return to the bypass chamber, so as to reuse the excess supply of construction material to fill the batching chamber; (iii) Control the fifth valve and the seventh valve to close and control the construction material pump to operate, and: - Control the opening of the second and fourth valves to allow excess build material to flow into the buffer tank along the excess amount return flow path; and - Control the opening of the first valve and the fourth valve to allow fresh building material to flow into the buffer tank along the supply flow path.

6. The construction material supply system according to any one of claims 1 and 3-5, characterized in that, The controller controls the opening of the first valve and, if present, the fourth valve and / or the second valve, to allow excess build material and fresh build material to flow simultaneously along the supply flow path and the excess return flow path.

7. The construction material supply system according to claim 2, characterized in that, The controller controls the opening of the first valve and, if present, the fourth valve and / or the second valve, to allow excess build material and fresh build material to flow simultaneously along the supply flow path and the excess return flow path.

8. The construction material supply system according to claim 7, characterized in that, The controller further controls the sixth valve to open to allow an excess supply of building material, along with the surplus building material and the fresh building material, to flow simultaneously from the overflow chamber into the buffer tank, while controlling the third and fifth valves to close to cut off the material flow path.

9. The construction material supply system according to claim 8, characterized in that, The sixth valve is a variable valve, wherein the controller is configured to partially open the sixth valve to impose a higher flow resistance on the excess supply build material flow returning through the excess supply flow path compared to the flow resistance of the excess build material flow along the excess return flow path.

10. The construction material supply system according to claim 6, characterized in that, The supply flow path is configured to have higher flow resistance to the flow of building materials than the excess return flow path.

11. The construction material supply system according to any one of claims 7 to 9, characterized in that, The first valve is a variable valve, wherein the controller is configured to partially open the first valve to impose a higher flow resistance on the flow of fresh building material through the supply flow path compared with the flow resistance of excess building material flow along the excess return flow path and, if present, with the flow resistance of excess supply building material flow along the excess supply return flow path.

12. The construction material supply system according to claim 2, characterized in that, The controller is configured to prioritize the flow of build material to the buffer tank by applying the following order: first, allowing excess build material to flow along the excess amount return flow path by controlling the first valve to be at least partially closed; second, allowing excess supply build material to flow along the excess supply return flow path if present, while controlling the first valve and the second valve to be at least partially closed. Third, fresh building material is allowed to flow along the supply flow path while the first valve is controlled to open at least partially.

13. A construction material supply system for an apparatus for manufacturing 3D objects by layering construction materials, characterized in that, The construction material supply system includes: - A dispensing device configured to supply a dispensing amount of building material to the working surface of the device, the dispensing amount including a layer amount and an excess amount remaining to form a layer; - A buffer tank, which is configured to mix building materials for supply to the dispensing device; - Excess material return chamber, which is used to receive excess building materials from the distribution device; - A supply tank, which is used to hold fresh building materials in order to replenish the buffer tank; - A construction material pump for conveying construction materials within the construction material supply system; and - Controller; The inlet of the building material pump is connected to the supply tank via a first valve, and the inlet of the building material pump is connected to the outlet of the excess return chamber; the outlet of the building material pump is connected to the inlet of the buffer tank; and the outlet of the buffer tank is connected to the inlet of the dispensing device. The controller is coupled to the building material pump and the first valve, and is configured to: - Control the opening of the first valve and control the operation of the build material pump to allow fresh build material to flow along the supply flow path from the supply tank through the build material pump and into the buffer tank; and - Operate the build material pump to allow excess build material to flow from the excess return chamber through the build material pump and into the buffer tank along the excess return flow path; In order to control the ratio of fresh building material to excess building material delivered to the buffer tank.

14. The construction material supply system according to claim 13, characterized in that, The inlet of the building material pump is connected to the excess return chamber via a second valve, and the controller is connected to the second valve.

15. The construction material supply system according to claim 13 or claim 14, characterized in that, The dispensing device includes a dispensing device inlet configured to receive building material from the outlet of the buffer tank, wherein the controller is coupled to the dispensing device and configured to control the dispensing device to release the dispensing amount.

16. The construction material supply system according to claim 14, characterized in that, The controller controls the first valve to close in order to cut off the supply flow path and controls the build material pump to operate, and controls the second valve to open in order to allow the excess build material to flow back along the excess flow path, if present.

17. The construction material supply system according to any one of claims 1-5, 7-10, 12-14, and 16, characterized in that, The buffer tank includes a fill level sensor configured to detect the fill level of the build material inside the buffer tank, and wherein the controller is configured to open and close the supply flow path based on the detected build material level inside the buffer tank.

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