Patent Description:
Additive manufacturing techniques, such as, directed energy deposition (DED), may be used to fabricate components by depositing material layer-by-layer or volume-by-volume successively along a build direction based on a digital representation of the component. Example techniques for DED may include directing an energy beam (e.g., a laser beam) at a region of a substrate of the component to form an advancing molten pool and delivering material from a spray nozzle to the advancing molten pool. The melt pool is then simultaneously deposited onto the substrate to form a deposited volume or layer of the material.

Blown powder DED typically utilizes a metallic powder of selected particle size and composition that is blown at or adjacent to the melt pool. A distance between a tip of the spray nozzle and a material deposition point is typically known as "stand-off distance". It may be vital to accurately and quickly determine a powder flow rate through the spray nozzle as the powder flow rate may influence geometry, porosity, crack, and mechanical properties of the deposited components. Further, variation of the powder flow rate with the stand-off distance may be important for a deposition stability and a powder catchment efficiency.

Techniques for measurement of powder flow rate are well known. Traditionally, an operator injects an inert gas into a measurement chamber and the spray nozzle of selected dimensions dispenses a powder through a single size hole feature. The measurement chamber is then evacuated, and a weight of the powder collected from the single size hole feature is measured using an external scale. All these operations are carried out manually by using dedicated plastic gloves.

Depending on specifications and condition of the spray nozzle, different size hole features may be required. With the traditional measurement systems, the measurement chamber needs to be evacuated in order to implement new size hole features with different dimensions. Further, the stand-off distance needs to be changed during the measurement process to determine an optimum stand-off distance for improving efficiency. The above measurement process may need to be repeated until the optimum stand-off distance is determined. Thus, the measurement chamber may need to be evacuated each time the weight of the powder is determined (using the external scale) with the varying stand-off distance. This causes the entire measurement process to be time consuming and not suitable for production.

German patent application <CIT> discloses a method for measuring powder flows of a laser welding tool. The method involves successive use of multiple covers having orifices of different sizes, wherein every orifice is arranged in the working region of the laser welding tool, for every cover a powder jet is applied for a predetermined period, and the powder mass which has passed through each orifice is weighed.

United States patent application <CIT> discloses an analysis system for a powder jet of an additive manufacturing machine, the powder jet comprising powder and gas. The analysis system has a separation device that has a separator element that has a circular side wall defining a cylinder and at least one separation wall suitable for separating the inner volume of the separator element into n equal portions that are symmetric with respect to the axis of symmetry of the cylinder. The separator element is suitable for receiving an initial powder jet at the centre of the separator element, on the at least one separation wall, in order to separate the initial powder jet into n powder jet portions. The analysis system also has means for detecting the quantity of powder in each powder jet portion.

United States patent <CIT> discloses a method of calibrating a high energy beam with a material source. The method involves using the high energy beam to provide an aperture, depositing material from the material source towards the aperture for a selected length of time and collecting the material which passes through the aperture, and adjusting the position and/or alignment of the material source relative to the high energy beam dependant on a comparison of the amount of material collected with a predetermined value.

According to a first aspect, there is provided a measurement apparatus for measuring a flow rate of a powder as set out in claim <NUM>.

The measurement apparatus of the present invention includes the fixture plate disposed within and mounted to the casing. The fixture plate includes the plurality of pinhole members. The diameters of the cylindrical holes of the plurality of pinhole members are different from each other. This may allow the flow rate of the powder to be measured using different diameters of the cylindrical holes.

The nozzle may dispense the powder selectively into the cylindrical hole of each pinhole member. Specifically, the measurement apparatus may be programmed to selectively position the nozzle above the cylindrical hole of each pinhole member for dispensing the powder. Thus, the measurement apparatus may allow automatic measurement of the flow rate of the powder, thereby eliminating the traditional manual process. This may enhance a repeatability of the measurement process.

The weighing scale is disposed within the casing underneath the fixture plate. Thus, the casing may not require to be evacuated for determining the weight of the powder received in the powder collector after passing through the corresponding pinhole member. This may allow measurement data to be obtained quickly and accurately. Furthermore, a stand-off distance may be modified during the measurement process for determining the optimum stand-off distance. Thus, the flow rate of the powder from the nozzle may be measured multiple times, each time at a different distance between a tip of the nozzle and the tip of the corresponding pinhole member.

In some embodiments, each pinhole member further includes a frustoconical external surface extending from the top surface and tapering towards the tip. Each pinhole member further includes a frustoconical internal surface spaced apart from and coaxial with the frustoconical external surface. The frustoconical internal surface extends from the bottom surface beyond the top surface and fully defines the discharge passage, such that the discharge passage is frustoconical and tapers from the bottom surface towards the cylindrical hole. The frustoconical external surface may allow extra powder that does not pass through the cylindrical hole to clear off from the tip of the corresponding pinhole member. The frustoconical internal surface of the discharge passage may allow the powder received from the cylindrical hole to unrestrictedly pass through the fixture plate and get collected in the powder collector.

In some embodiments, each pinhole member further includes a cylindrical connecting passage fluidly communicating the cylindrical hole with the discharge passage, such that the discharge passage tapers from the bottom surface to the cylindrical connecting passage. A diameter of the cylindrical connecting passage is at least twice the diameter of the cylindrical hole. The cylindrical connecting passage may allow the powder received within the cylindrical hole to smoothly pass to the discharge passage.

In some embodiments, an axial length of the cylindrical hole is at least twice an axial length of the cylindrical connecting passage. An axial length of the discharge passage is at least thrice the axial length of the cylindrical hole. This may allow unrestricted flow of the powder from the cylindrical hole to the discharge passage in an accurate manner.

In some embodiments, the cylindrical hole, the cylindrical connecting passage, and the discharge passage are coaxial with each other. This may allow the powder received within the cylindrical hole to flow through the fixture plate in an unrestricted manner.

In some embodiments, each pinhole member further includes a conical portion tapering from the top surface to the tip and forming the frustoconical external surface and at least a portion of the frustoconical internal surface. The conical portion includes a top section disposed at the tip. The top section fully defines the cylindrical hole and the cylindrical connecting passage. The conical portion may allow extra powder that does not pass through the cylindrical hole to clear off from the tip of the corresponding pinhole member. Further, the top section may fluidly couple the cylindrical hole with the cylindrical connecting passage.

In some embodiments, a height of the conical portion from the top surface is less than a thickness of the main body between the top surface and the bottom surface. This may allow the conical portion to extend away from the top surface, thereby defining the frustoconical external surface and at least the portion of the frustoconical internal surface.

In some embodiments, a minimum diameter of the discharge passage is greater than the diameter of the cylindrical hole. This may allow the powder received within the cylindrical hole to flow to the discharge passage in an unrestricted manner.

In some embodiments, the fixture plate further includes a wide member spaced apart from each pinhole member and extending at least partially from the top surface. The wide member includes a wide distal end spaced apart from the top surface and a wide cylindrical passage extending from the wide distal end to the bottom surface at least partially through the main body. The wide cylindrical passage has a wide diameter that is at least five times the diameter of the cylindrical hole of each pinhole member. The nozzle is configured to dispense the powder selectively into the wide cylindrical passage of the wide member. The powder collector is configured to receive at least a portion of the powder from the wide cylindrical passage of the wide member. The wide diameter of the wide cylindrical passage may allow unrestricted flow of the powder received from the nozzle to the powder collector, thereby enabling determination of a total powder flow mass dispensed by the nozzle in a predetermined period of time.

In some embodiments, the wide member further includes a wide conical portion extending from the top surface and including a wide frustoconical external surface. Thus, the wide conical portion defines at least a portion of the wide cylindrical passage. The wide frustoconical external surface may allow extra powder that does not pass through the wide cylindrical passage to clear off from a top opening of the wide cylindrical passage.

In some embodiments, the measurement apparatus further includes one or more positioning features disposed on the top surface. The one or more positioning features may allow calibration of a position of the nozzle with respect to the fixture plate.

In some embodiments, the measurement apparatus further includes a support structure fixedly coupled to the casing. The fixture plate is adjustably mounted to the support structure. The support structure may support the fixture plate within the casing in a reliable manner while allowing the fixture plate to be adjusted relative to the casing.

In some embodiments, the casing includes a bottom wall, one or more side walls extending from the bottom wall, and a top wall coupled to the one or more side walls opposite to the bottom wall. The weighing scale is disposed on the bottom wall. The support structure is coupled to one of the side walls. The one of the side wall may allow the support structure to be fixedly coupled to the casing. The bottom wall may allow the weighing scale to be placed within the casing, thereby eliminating use of external scales for the measurement process.

In some embodiments, the support structure includes a first member fixedly coupled to the one of the side walls of the casing. The support structure further includes a second member including a vertical portion adjustably coupled to the first member and a horizontal portion extending parallel to the top surface. The fixture plate is adjustably coupled to the horizontal portion. The support structure further includes a pair of arms. Each of the pair of arms includes a first arm end coupled to the vertical portion and a second arm end coupled to the horizontal portion. The first member may allow the support structure to be fixedly coupled to the casing. The vertical portion may be adjusted relative to the first member and the fixture plate may be adjusted relative to the horizontal portion when required.

In some embodiments, the vertical portion of the second member is adjustable relative to the first member along a first direction substantially parallel to the top surface. The fixture plate is adjustable relative to the horizontal portion along a second direction substantially parallel to the top surface and perpendicular to the first direction. This may allow the fixture plate to be adjusted relative to the casing in both the first direction and the second direction.

In some embodiments, the casing is filled with an inert gas. This may eliminate contamination of the powder within the measurement apparatus.

According to a second aspect, there is provided a method for measuring a flow rate of a powder as set out in claim <NUM>.

The method may allow the flow rate of the powder to be measured using different diameters of the cylindrical holes. The nozzle may dispense the powder into the cylindrical hole of the one pinhole member. Specifically, the nozzle may be programmed to position the nozzle above the cylindrical hole of the one pinhole member for dispensing the powder. Thus, the method may allow automatic measurement of the flow rate of the powder. This may enhance the repeatability of the measurement process. Further, the casing may not require to be evacuated for determining the weight of the powder collected in the powder collector after passing through the corresponding pinhole member since the weighing scale is disposed within the casing underneath the fixture plate. This may allow the measurement data to be determined quickly and accurately.

In some embodiments, the fixture plate further includes a wide member spaced apart from each pinhole member and extending at least partially from the top surface. The wide member includes a wide distal end spaced apart from the top surface and a wide cylindrical passage extending from the wide distal end to the bottom surface at least partially through the main body. The wide cylindrical passage has a wide diameter that is at least five times the diameter of the cylindrical hole of each pinhole member. The method further includes positioning the nozzle above the wide member at the predetermined distance from the wide distal end of the wide member prior to positioning the nozzle above the one pinhole member. The method further includes dispensing the powder through the at least one delivery channel for the predetermined period of time. The method further includes recording, via the weighing scale, the weight of the powder received in the powder collector. The method may allow determination of the total flow rate of the powder in the predetermined period of time since the wide diameter of the wide cylindrical passage may allow unrestricted flow of the powder received from the nozzle to the powder collector.

In some embodiments, the method further includes resetting the weighing scale prior to positioning the nozzle above the one pinhole member. This may allow accurate measurement of the weight of the powder received in the powder collector after the powder is dispensed into the one pinhole member.

In some embodiments, the method further includes modifying the predetermined distance of the nozzle from the tip of the one pinhole member. Thus, the method may allow the predetermined distance to be modified during the measurement process for determining the optimum stand-off distance.

<FIG> is a schematic top perspective view of a measurement apparatus <NUM> for measuring a flow rate of a powder <NUM>. The measurement apparatus <NUM> includes a casing <NUM>. In some embodiments, the casing <NUM> may be an hermetically sealed casing. In some embodiments, the casing <NUM> is filled with an inert gas IG. This may eliminate contamination of the powder <NUM> within the measurement apparatus <NUM>. Examples of the inert gas IG may include, but are not limited to, argon, helium, hydrogen, nitrogen, carbon dioxide, or any combination thereof.

In some embodiments, the casing <NUM> may be made from a plastic (e.g. acrylonitrile butadiene styrene, polylactic acid, polyethylene terephthalate, high-density polyethylene, polyvinyl chloride, polymethyl methacrylate, or the like), a metal (e.g. aluminium, brass, bronze, copper, steel, or the like), an alloy, a combination of both a plastic and a metal, or the like. The casing <NUM> includes a bottom wall <NUM>, one or more side walls <NUM> extending from the bottom wall <NUM>, and a top wall <NUM> coupled to the one or more side walls <NUM> opposite to the bottom wall <NUM>. Specifically, the casing <NUM> includes four side walls 107a, 107b, 107c, 107d. The bottom wall <NUM> and the top wall <NUM> are coupled to the side walls 107a, 107b, 107c, 107d to form a hermetically sealed housing. In some embodiments, the one or more side walls <NUM> of the casing <NUM> may be substantially transparent.

The measurement apparatus <NUM> further includes a nozzle <NUM> movably disposed within the casing <NUM>. In some embodiments, the measurement apparatus <NUM> may further include arrangements (not shown) for moving the nozzle <NUM> within the casing <NUM>. For example, the arrangements for moving the nozzle <NUM> may include a computer numeric control (CNC) machine. In some embodiments, the measurement apparatus <NUM> may be programmed to move the nozzle <NUM> within the casing <NUM>.

In some embodiments, the nozzle <NUM> may be a part of a laser blown powder direct energy deposition (LBP-DED) system (not shown). LBP-DED is an additive manufacturing (AM) process in which successive layers or volumes of material are typically deposited on a substrate of a component along a build direction based on a digital representation of the component. LBP-DED systems generally include directing an energy beam, i.e. a laser beam, at a region of the substrate of the component to form an advancing molten pool. A metallic powder is blown into the melt pool (e.g. via the nozzle <NUM>) and then simultaneously deposited onto the substrate to construct the component in a layer-by-layer manner. It should be understood that DED systems may also utilize any other type of energy beam.

LBP-DED systems may use powder of selected particle size and composition that is blown at or adjacent to the melt pool. During deposition, spatial distribution of the powder (referred to herein as a nozzle distribution pattern) may determine an actual delivery region in which the powder is delivered. When the actual delivery region is not substantially similar to a target delivery region, i.e., in or around the advancing molten pool, deposition defects may occur. For example, the powder may be left partially or fully unmelted, or otherwise unincorporated in the melt pool, or less powder than intended may be incorporated in the melt pool, leading to smaller than intended material addition. In either case, deviation from an expected amount of powder incorporation may lead to defects in the formed component, such as voids, inclusions, unwanted material phases or microstructures, poor cohesion, chambers that include residual, unjoined material, unintended vibration frequencies during operation of the component, blocked channels or openings, audible sound, such as rustling or rattling during use, or the like.

The geometry, porosity, crack, and mechanical properties of the components produced by LBP-DED systems depend on operational parameters, such as feed rate of the powder and incident laser power intensity. The feed rate of the powder is directly related to a distance between the nozzle <NUM> and a material deposition point, typically known as stand-off distance. An optimum stand-off distance may improve a deposition stability and a powder catchment efficiency, which is a percentage of the powder that reaches the melt pool. Therefore, before actual laser powder deposition, it is important to know the flow rate of the powder.

The measurement apparatus <NUM> may allow measurement of the flow rate of the powder <NUM> dispensed by the nozzle <NUM> as a function of a distance between a tip of the nozzle <NUM> and a common plane. The measurement apparatus <NUM> may allow determination of the nozzle distribution pattern by direct measurements of the powder <NUM> dispensed by the nozzle <NUM>. The nozzle <NUM> includes at least one delivery channel <NUM> (shown in <FIG> and <FIG>) configured to dispense the powder <NUM>. The flow rate of the powder <NUM> may need to be determined during the operational life of the nozzle <NUM>, e.g. after a given service cycle. Determination of accurate flow rate of the powder <NUM> may improve the powder catchment efficiency. This may improve an overall efficiency of the LBP-DED systems.

The measurement apparatus <NUM> further includes a fixture plate <NUM> disposed within and mounted to the casing <NUM>. In some embodiments, the measurement apparatus <NUM> further includes a support structure <NUM> fixedly coupled to the casing <NUM>. The fixture plate <NUM> is adjustably mounted to the support structure <NUM>. The support structure <NUM> may support the fixture plate <NUM> within the casing in a reliable manner while allowing the fixture plate <NUM> to be adjusted relative to the casing <NUM>. In some embodiments, the support structure <NUM> is coupled to one of the side walls <NUM>. In the illustrated embodiment of <FIG>, the support structure <NUM> is fixedly coupled to the side wall 107c.

The fixture plate <NUM> includes a main body <NUM> including a top surface <NUM> facing the nozzle <NUM> and a bottom surface <NUM> spaced apart from and opposite to the top surface <NUM>. The fixture plate <NUM> further includes a plurality of pinhole members <NUM> extending at least partially from the top surface <NUM> and spaced apart from each other. In the illustrated embodiment of <FIG>, the plurality of pinhole members <NUM> include four pinhole members 150a, 150b, 150c, 150d. However, it should be understood that the plurality of pinhole members <NUM> may include any number of the pinhole members <NUM>.

In some embodiments, the fixture plate <NUM> further includes a wide member <NUM> spaced apart from each pinhole member 150a, 150b, 150c, 150d and extending at least partially from the top surface <NUM>. In some embodiments, the nozzle <NUM> is configured to dispense the powder <NUM> selectively into the wide member <NUM>. Further, the nozzle <NUM> is configured to dispense the powder <NUM> selectively into each pinhole member 150a, 150b, 150c, 150d. In some embodiments, the nozzle <NUM> is configured to dispense the powder <NUM> for a predetermined period of time.

In some embodiments, the measurement apparatus <NUM> further includes one or more positioning features <NUM> disposed on the top surface <NUM> of the fixture plate <NUM>. In some embodiments, the nozzle <NUM> may further include a sensor (e.g., an imaging sensor, such as a camera) that determines a position of the nozzle <NUM> with respect to the fixture plate <NUM>. For example, the sensor may be disposed on or within the nozzle <NUM> and may be configured to determine the position of the nozzle <NUM> with respect to the one or more positioning features <NUM>. In some embodiments, the one or more positioning features <NUM> may allow calibration of the position of the nozzle <NUM> with respect to the fixture plate <NUM>.

The measurement apparatus <NUM> further includes a weighing scale <NUM> disposed within the casing <NUM> underneath the fixture plate <NUM>. In some embodiments, the weighing scale <NUM> is disposed on the bottom wall <NUM> of the casing <NUM>. The bottom wall <NUM> may allow the weighing scale <NUM> to be placed within the casing <NUM>, thereby eliminating use of external scales for the measurement process. The measurement apparatus <NUM> further includes a powder collector <NUM> disposed on the weighing scale <NUM> and facing the fixture plate <NUM>. The powder collector <NUM> is configured to receive at least a portion of the powder <NUM> from the wide member <NUM>. Further, the powder collector <NUM> is configured to receive at least a portion of the powder <NUM> from each pinhole member <NUM>. The weighing scale <NUM> may indicate a weight of the powder <NUM> received in the powder collector <NUM>.

<FIG> is a schematic partial bottom perspective cut-away view of the measurement apparatus <NUM>. Some components, e.g., the nozzle <NUM>, the weighing scale <NUM>, and the powder collector <NUM> of the measurement apparatus <NUM> are not shown for the purpose of illustration. In some embodiments, the support structure <NUM> includes a first member <NUM> fixedly coupled to the one of the side walls 107c of the casing <NUM>. The first member <NUM> may allow the support structure <NUM> to be fixedly coupled to the casing <NUM>. In some embodiments, the support structure <NUM> further includes a second member <NUM> including a vertical portion <NUM> adjustably coupled to the first member <NUM> and a horizontal portion <NUM> extending parallel to the top surface <NUM>.

In some embodiments, the support structure <NUM> further includes a pair of arms <NUM>. Each of the pair of arms <NUM> includes a first arm end <NUM> coupled to the vertical portion <NUM> and a second arm end <NUM> coupled to the horizontal portion <NUM>. The pair of arms <NUM> may provide support to the horizontal portion <NUM> and the fixture plate <NUM>. In some embodiments, the first arm end <NUM> is fixedly coupled to the vertical portion <NUM> and the second arm end <NUM> is fixedly coupled to the horizontal portion <NUM>.

In some embodiments, the vertical portion <NUM> of the second member <NUM> is adjustable relative to the first member <NUM> along a first direction P1 (also shown in <FIG>) substantially parallel to the top surface <NUM>. In some embodiments, the vertical portion <NUM> is coupled to the first member <NUM> via one or more vertical fasteners <NUM>. In some embodiments, each vertical fastener <NUM> is received through a corresponding vertical slot <NUM> of the vertical portion <NUM>. In some embodiments, the vertical slot <NUM> of the vertical portion <NUM> may extend along the first direction P1. Thus, the vertical slot <NUM> may allow the vertical portion <NUM> to be adjusted relative to the first member <NUM> along the first direction P1.

In some embodiments, the fixture plate <NUM> is adjustably coupled to the horizontal portion <NUM>. In some embodiments, the fixture plate <NUM> is adjustable relative to the horizontal portion <NUM> along a second direction P2 (also shown in <FIG>) substantially parallel to the top surface <NUM> and perpendicular to the first direction P1. In some embodiments, the fixture plate <NUM> is coupled to the horizontal portion <NUM> via one or more horizontal fasteners <NUM>. In some embodiments, each horizontal fastener <NUM> is received through a corresponding horizontal slot <NUM> of the horizontal portion <NUM>. In some embodiments, the horizontal slot <NUM> of the horizontal portion <NUM> may extend along the second direction P2. Thus, the horizontal slot <NUM> may allow the fixture plate <NUM> to be adjusted relative to the horizontal portion <NUM> along the second direction P2. Thus, the fixture plate <NUM> may be adjusted relative to the casing <NUM> in both the first direction P1 and the second direction P2.

<FIG> and <FIG> are schematic top and bottom perspective views of the fixture plate <NUM>, respectively. <FIG> and <FIG> are schematic partial sectional views of the fixture plate <NUM> taken along a section line A-A' and a section line B-B' shown in <FIG>, respectively. In the illustrated embodiment of <FIG>, only the pinhole members 150a, 150b are visible. The features described with reference to the pinhole members 150a, 150b are also equally applicable to the other pinhole members 150c, 150d.

Referring to <FIG>, in the illustrated embodiments, the main body <NUM> of the fixture plate <NUM> is substantially rectangular-shaped. However, in alternative embodiments, the main body <NUM> may include any suitable shape. Further, the main body <NUM> is substantially planar or flat.

Each pinhole member 150a, 150b, 150c, 150d from the plurality of pinhole members <NUM> includes a tip <NUM> (shown in <FIG>, <FIG> and <FIG>) spaced apart from the top surface <NUM>, a cylindrical hole <NUM> (shown in <FIG>) extending from the tip <NUM> towards the top surface <NUM>, and a discharge passage <NUM> (shown in <FIG> and <FIG>) extending from the bottom surface <NUM> at least partially through the main body <NUM> and disposed in fluid communication with the cylindrical hole <NUM>.

The cylindrical hole <NUM> of each pinhole member 150a, 150b, 150c, 150d has a diameter D1 (shown in <FIG>) and is configured to receive the powder <NUM> (shown in <FIG>) from the nozzle <NUM> (shown in <FIG>). The nozzle <NUM> is configured to dispense the powder <NUM> selectively into the cylindrical hole <NUM> of each pinhole member 150a, 150b, 150c, 150d. The powder collector <NUM> (shown in <FIG>) is configured to receive at least the portion of the powder <NUM> from the discharge passage <NUM> of each pinhole member 150a, 150b, 150c, 150d.

The diameters D1 of the cylindrical holes <NUM> of the plurality of pinhole members <NUM> are different from each other. For example, the diameters D1 of the cylindrical holes <NUM> of the plurality of pinhole members 150a, 150b, 150c, 150d are about <NUM>, <NUM>, <NUM>, and <NUM>, respectively. Thus, the flow rate of the powder <NUM> (shown in <FIG>) may be tested using different sizes of cylindrical holes <NUM>.

As shown in <FIG>, in some embodiments, each pinhole member 150a, 150b, 150c, 150d further includes a frustoconical external surface <NUM> extending from the top surface <NUM> and tapering towards the tip <NUM>. In some embodiments, each pinhole member 150a, 150b, 150c, 150d further includes a frustoconical internal surface <NUM> spaced apart from and coaxial with the frustoconical external surface <NUM>. In some embodiments, the frustoconical internal surface <NUM> extends from the bottom surface <NUM> beyond the top surface <NUM> and fully defines the discharge passage <NUM>, such that the discharge passage <NUM> is frustoconical and tapers from the bottom surface <NUM> towards the cylindrical hole <NUM>.

In some embodiments, each pinhole member 150a, 150b, 150c, 150d further includes a cylindrical connecting passage <NUM> fluidly communicating the cylindrical hole <NUM> with the discharge passage <NUM>, such that the discharge passage <NUM> tapers from the bottom surface <NUM> to the cylindrical connecting passage <NUM>. In some embodiments, the cylindrical hole <NUM>, the cylindrical connecting passage <NUM>, and the discharge passage <NUM> are coaxial with each other. This may allow the powder <NUM> (shown in <FIG>) received within the cylindrical hole <NUM> to flow through the fixture plate <NUM> in an unrestricted manner.

In some embodiments, a diameter D2 of the cylindrical connecting passage <NUM> is at least twice the diameter D1 of the cylindrical hole <NUM>. This may allow the powder <NUM> (shown in <FIG>) received within the cylindrical hole <NUM> to easily flow to the cylindrical connecting passage <NUM>. In some embodiments, a minimum diameter D3 of the discharge passage <NUM> is greater than the diameter D1 of the cylindrical hole <NUM>. In the illustrated embodiment of <FIG>, the minimum diameter D3 of the discharge passage <NUM> is equal to the diameter D2 of the cylindrical connecting passage <NUM>. This may allow the powder <NUM> (shown in <FIG>) received within the cylindrical hole <NUM> to flow to the discharge passage <NUM> in an unrestricted manner.

In some embodiments, an axial length L1 of the cylindrical hole <NUM> is at least twice an axial length L2 of the cylindrical connecting passage <NUM>. In some embodiments, an axial length L3 of the discharge passage <NUM> is at least thrice the axial length L1 of the cylindrical hole <NUM>. This may allow unrestricted flow of the powder <NUM> (shown in <FIG>) from the cylindrical hole <NUM> to the discharge passage <NUM> in an accurate manner.

In some embodiments, each pinhole member 150a, 150b, 150c, 150d further includes a conical portion <NUM> tapering from the top surface <NUM> to the tip <NUM> and forming the frustoconical external surface <NUM> and at least a portion of the frustoconical internal surface <NUM>. In some embodiments, a height H1 of the conical portion <NUM> from the top surface <NUM> is less than a thickness H2 of the main body <NUM> between the top surface <NUM> and the bottom surface <NUM>. This may allow the conical portion <NUM> to extend away from the top surface <NUM>, thereby defining the frustoconical external surface <NUM> and at least the portion of the frustoconical internal surface <NUM>. In some embodiments, the height H1 of the conical portion <NUM> of each pinhole member 150a, 150b, 150c, 150d is similar to each other. In some embodiments, the conical portion <NUM> includes a top section <NUM> disposed at the tip <NUM>. In some embodiments, the top section <NUM> fully defines the cylindrical hole <NUM> and the cylindrical connecting passage <NUM>.

As shown in <FIG>, in some embodiments, the fixture plate <NUM> further includes the wide member <NUM> extending at least partially from the top surface <NUM>. In some embodiments, the wide member <NUM> includes a wide distal end <NUM> spaced apart from the top surface <NUM> and a wide cylindrical passage <NUM> extending from the wide distal end <NUM> to the bottom surface <NUM> at least partially through the main body <NUM>.

In some embodiments, the wide cylindrical passage <NUM> has a wide diameter WD that is at least five times the diameter D1 (shown in <FIG>) of the cylindrical hole <NUM> of each pinhole member 150a, 150b, 150c, 150d. For example, the wide diameter WD may be about <NUM>. In some embodiments, the wide member <NUM> further includes a wide conical portion <NUM> extending from the top surface <NUM> and including a wide frustoconical external surface <NUM>. In some embodiments, a height H3 of the wide conical portion <NUM> from the top surface <NUM> is equal to the height H1 (shown in <FIG>) of the conical portion <NUM> (shown in <FIG>) from the top surface <NUM>. In some embodiments, a taper angle of the wide frustoconical external surface <NUM> is greater than a taper angle of the frustoconical external surface <NUM> (shown in <FIG>) of each pinhole member 150a, 150b, 150c, 150d.

<FIG> is a schematic partial side view of the measurement apparatus <NUM>. Some components (e.g., the casing <NUM>) of the measurement apparatus <NUM> are not shown for the purpose of illustration. In the illustrated embodiment of <FIG>, the nozzle <NUM> is aligned with a geometric centre of the wide member <NUM>. A tip of the nozzle <NUM> is disposed at a predetermined distance S from the wide distal end <NUM> of the wide member <NUM>. This predetermined distance S is also referred to herein as the stand-off distance.

Referring to <FIG> and <FIG>, the nozzle <NUM> is configured to dispense the powder <NUM> selectively into the wide cylindrical passage <NUM> (shown in <FIG>) of the wide member <NUM> for the same predetermined period of time T. In some embodiments, the powder collector <NUM> is configured to receive at least a portion of the powder <NUM> from the wide cylindrical passage <NUM> of the wide member <NUM>.

In some cases, nearly all the powder <NUM> dispensed by the nozzle <NUM> passes through the wide diameter WD (shown in <FIG>) of the wide cylindrical passage <NUM> since the wide diameter WD is much larger than the diameter D1 (shown in <FIG>) of the cylindrical hole <NUM> (shown in <FIG>) of each pinhole member <NUM>. The weight of the powder <NUM> received by the powder collector <NUM> is then indicated by the weighing scale <NUM>. This represents a total powder flow mass Mt of the powder <NUM> in the predetermined period of time T.

The wide diameter WD of the wide cylindrical passage <NUM> may allow unrestricted flow of the powder <NUM> received from the nozzle <NUM> to the powder collector <NUM>, thereby enabling determination of the total powder flow mass Mt in the predetermined period of time T. Further, the wide frustoconical external surface <NUM> may allow extra powder <NUM> that does not pass through the wide cylindrical passage <NUM> to clear off from a top opening of the wide cylindrical passage <NUM>.

<FIG> is a schematic partial side view of the measurement apparatus <NUM>. Some components (e.g., the casing <NUM>) of the measurement apparatus <NUM> are not shown for the purpose of illustration. In the illustrated embodiment of <FIG>, the nozzle <NUM> is aligned a geometric centre of the pinhole member 150a. However, in alternative embodiments, the nozzle <NUM> may also be aligned with any other pinhole member <NUM>. In some embodiments, the pinhole member <NUM> from the plurality of pinhole members <NUM> may be chosen based on a wear and tear of the nozzle <NUM>. In some embodiments, the tip of the nozzle <NUM> is disposed at the predetermined distance S (or the stand-off distance) from the tip <NUM> of the pinhole member 150a.

Referring to <FIG> and <FIG>, the nozzle <NUM> is configured to dispense the powder <NUM> selectively into the cylindrical hole <NUM> (shown in <FIG>) of the pinhole member 150a for a predetermined period of time T. In some embodiments, the cylindrical hole <NUM> of the pinhole member 150a may receive at least a portion of the powder <NUM> dispensed by the nozzle <NUM>. Depending on an impact direction and a location of grains of the powder <NUM> at an edge of the cylindrical hole <NUM>, the grains may bounce back or pass through the cylindrical hole <NUM>. The grains that bounce back are referred to herein as rebounding grains. Thus, an effective pinhole area Aph may be defined that is smaller than an actual pinhole area (based on the diameter D1 of the cylindrical hole <NUM>). Effective pinhole area Aph may be determined according to the Equation <NUM> provided below: <MAT> where, Dave is a mean diameter of the grains of the powder <NUM> and D1 is the diameter of the cylindrical hole <NUM>.

In some embodiments, the rebounding grains of the powder <NUM> may run-off the conical portion <NUM> (shown in <FIG>) of the pinhole member 150a along the frustoconical external surface <NUM>. Thus, the extra powder <NUM> that does not pass through the cylindrical hole <NUM> may clear off from the tip <NUM> of the pinhole member 150a. The portion of the powder <NUM> received by the cylindrical hole <NUM> in the predetermined period of time T is then received by the powder collector <NUM>. In some embodiments, the cylindrical connecting passage <NUM> may allow the powder <NUM> received within the cylindrical hole <NUM> to smoothly pass to the discharge passage <NUM>. Further, the frustoconical internal surface <NUM> of the discharge passage <NUM> may allow the powder <NUM> to unrestrictedly pass through the fixture plate <NUM>. Subsequently, the weighing scale <NUM> may indicate the weight of powder <NUM> received in the powder collector <NUM>. This weight of the powder <NUM> is referred to herein as a pinhole powder flow mass Mph.

A flow rate Rp through the nozzle <NUM> in the predetermined period of time T for the predetermined distance S and diameter D1 (shown in <FIG>) of the cylindrical hole <NUM> may be determined according to Equation <NUM> provided below: <MAT> where, Mph is the pinhole powder flow mass, Mt is the total powder flow mass, and Aph is the effective pinhole area.

In some embodiments, the flow rate Rp through the nozzle <NUM> may be measured by varying the predetermined distance S (or the stand-off distance) and the diameter D1 of the cylindrical hole <NUM>. Variations of the flow rate Rp may be plotted against the predetermined distance S for the given diameter D1 of the cylindrical hole <NUM>. An example of such a plot is shown in <FIG>.

<FIG> is a graph <NUM> illustrating an example of a variation of the flow rate Rp with respect to the predetermined distance S (or the stand-off distance). The flow rate Rp is shown along the vertical axis or ordinate of the graph <NUM> and the predetermined distance S is shown along the horizontal axis or abscissa of the graph <NUM>. Based on the graph <NUM>, an optimum stand-off distance <NUM> for the given diameter D1 (shown in <FIG>) of the cylindrical hole <NUM> (shown in <FIG>) may be determined.

<FIG> is a flowchart illustrating a method <NUM> for measuring a flow rate of the powder <NUM> (shown in <FIG>, <FIG> and <FIG>). The method <NUM> may be implemented using the measurement apparatus <NUM> of <FIG>, <FIG>, and the fixture plate <NUM> of <FIG>.

Referring to <FIG> and <FIG>, at step <NUM>, the method <NUM> includes providing the casing <NUM>. At step <NUM>, the method <NUM> further includes movably receiving the nozzle <NUM> within the casing <NUM>. The nozzle <NUM> includes the at least one delivery channel <NUM> configured to dispense the powder <NUM>. At step <NUM>, the method <NUM> further includes providing the fixture plate <NUM> disposed within and mounted to the casing <NUM>.

The fixture plate <NUM> includes the main body <NUM> including the top surface <NUM> facing the nozzle <NUM> and the bottom surface <NUM> spaced apart from and opposite to the top surface <NUM>. The fixture plate <NUM> further includes the plurality of pinhole members 150a, 150b, 150c, 150d extending at least partially from the top surface <NUM> and spaced apart from each other. Each pinhole member 150a, 150b, 150c, 150d from the plurality of pinhole members <NUM> includes the tip <NUM> spaced apart from the top surface <NUM>, the cylindrical hole <NUM> extending from the tip <NUM> towards the top surface <NUM>, and the discharge passage <NUM> extending from the bottom surface <NUM> at least partially through the main body <NUM> and disposed in fluid communication with the cylindrical hole <NUM>. The cylindrical hole <NUM> of each pinhole member 150a, 150b, 150c, 150d has the diameter D1 and is configured to receive the powder <NUM> from the nozzle <NUM>. The diameters D1 of the cylindrical holes <NUM> of the plurality of pinhole members <NUM> are different from each other.

In some embodiments, the fixture plate <NUM> further includes the wide member <NUM> spaced apart from each pinhole member 150a, 150b, 150c, 150d and extending at least partially from the top surface <NUM>. The wide member <NUM> includes the wide distal end <NUM> spaced apart from the top surface <NUM> and the wide cylindrical passage <NUM> extending from the wide distal end <NUM> to the bottom surface <NUM> at least partially through the main body <NUM>. The wide cylindrical passage <NUM> has the wide diameter WD that is at least five times the diameter D1 of the cylindrical hole <NUM> of each pinhole member 150a, 150b, 150c, 150d.

At step <NUM>, the method <NUM> further includes providing the weighing scale <NUM> underneath the fixture plate <NUM> within the casing <NUM>. At step <NUM>, the method <NUM> further includes providing the powder collector <NUM> on the weighing scale <NUM> and facing the fixture plate <NUM>. At step <NUM>, the method <NUM> further includes filling the casing <NUM> with the inert gas IG.

At step <NUM>, the method <NUM> further includes positioning the nozzle <NUM> above the cylindrical hole <NUM> at the predetermined distance S from the tip <NUM> of one pinhole member 150a from the plurality of pinhole members <NUM>. In some embodiments, the method <NUM> further includes resetting the weighing scale <NUM> prior to positioning the nozzle <NUM> above the one pinhole member 150a. This may allow accurate measurement of the weight of the powder <NUM> received in the powder collector <NUM> after the powder <NUM> is dispensed into the one pinhole member 150a. At step <NUM>, the method <NUM> further includes dispensing the powder <NUM> through the at least one delivery channel <NUM> for the predetermined period of time T. At step <NUM>, the method <NUM> further includes recording, via the weighing scale <NUM>, the weight of the powder <NUM> received in the powder collector <NUM>.

In some embodiments, the method <NUM> further includes modifying the predetermined distance S of the nozzle <NUM> from the tip <NUM> of the one pinhole member 150a. Thus, the method <NUM> may allow the predetermined distance S to be modified during the measurement process for determining the optimum stand-off distance <NUM>.

In some embodiments, the method <NUM> further includes positioning the nozzle <NUM> above the wide member <NUM> at the predetermined distance S from the wide distal end <NUM> of the wide member <NUM> prior to positioning the nozzle <NUM> above the one pinhole member 150a. In some embodiments, the method <NUM> further includes dispensing the powder <NUM> through the at least one delivery channel <NUM> for the predetermined period of time T. In some embodiments, the method <NUM> further includes recording, via the weighing scale <NUM>, the weight of the powder <NUM> received in the powder collector <NUM>.

Referring to <FIG>, the measurement apparatus <NUM> includes the fixture plate <NUM> disposed within and mounted to the casing <NUM>. The fixture plate <NUM> includes the plurality of pinhole members <NUM>. The diameters D1 of the cylindrical holes <NUM> of the plurality of pinhole members <NUM> are different from each other. This may allow the flow rate of the powder <NUM> to be measured using different diameters of the cylindrical holes <NUM>.

The nozzle <NUM> may dispense the powder <NUM> selectively into the cylindrical hole <NUM> of each pinhole member <NUM>. Specifically, the measurement apparatus <NUM> may be programmed to selectively position the nozzle <NUM> above the cylindrical hole <NUM> of each pinhole member <NUM> for dispensing the powder <NUM>. Thus, the measurement apparatus <NUM> and the method <NUM> of the present invention may allow automatic measurement of the flow rate of the powder <NUM>, thereby eliminating the traditional manual process. This may enhance a repeatability of the measurement process.

Claim 1:
A measurement apparatus (<NUM>) for measuring a flow rate of a powder (<NUM>), the measurement apparatus (<NUM>) comprising:
a casing (<NUM>);
a nozzle (<NUM>) movably disposed within the casing (<NUM>), the nozzle (<NUM>) comprising at least one delivery channel (<NUM>) configured to dispense the powder (<NUM>);
a fixture plate (<NUM>) disposed within and mounted to the casing (<NUM>), the fixture plate (<NUM>) comprising:
a main body (<NUM>) comprising a top surface (<NUM>) facing the nozzle (<NUM>) and a bottom surface (<NUM>) spaced apart from and opposite to the top surface (<NUM>); and
a plurality of pinhole members (<NUM>) extending at least partially from the top surface (<NUM>) and spaced apart from each other, wherein each pinhole member (<NUM>) from the plurality of pinhole members (<NUM>) comprises a tip (<NUM>) spaced apart from the top surface (<NUM>), a cylindrical hole (<NUM>) extending from the tip (<NUM>) towards the top surface (<NUM>), and a discharge passage (<NUM>) extending from the bottom surface (<NUM>) at least partially through the main body (<NUM>) and disposed in fluid communication with the cylindrical hole (<NUM>), wherein the cylindrical hole (<NUM>) of each pinhole member (<NUM>) has a diameter (D1) and is configured to receive the powder (<NUM>) from the nozzle (<NUM>), and wherein the diameters (D1) of the cylindrical holes (<NUM>) of the plurality of pinhole members (<NUM>) are different from each other;
a weighing scale (<NUM>) disposed within the casing (<NUM>) underneath the fixture plate (<NUM>); and
a powder collector (<NUM>) disposed on the weighing scale (<NUM>) and facing the fixture plate (<NUM>);
wherein the nozzle (<NUM>) is configured to dispense the powder (<NUM>) selectively into the cylindrical hole (<NUM>) of each pinhole member (<NUM>), and wherein the powder collector (<NUM>) is configured to receive at least a portion of the powder (<NUM>) from the discharge passage (<NUM>) of each pinhole member (<NUM>).