Patent Description:
Fluidization is a widely used process in various industries to achieve continuous powder flowability in controllable manner. Most common way for powder fluidization is gas fluidization, where solid powder particles are transformed into a fluid-like state through suspension in a gas. Gas fluidization of small solid particles has been widely used in a variety of industrial applications because of its capability of continuous powder handling and good mixing. However, in some applications, such as for example any technology or processes that are implemented under vacuum, gas fluidization may not be done. For example, additive manufacturing technology, such as an electron-beam melting (EBM) technology, takes place under vacuum, in which products are manufactured by melting metal powder, layer by layer, with an electron beam as a heat source. The EBM process usually consists of three major steps:.

Conventional dispensers for dispensing the metal powder are known from <CIT>, <CIT>, <CIT>, and <CIT>. The dispenser of <CIT> has the features specified in the preamble of claim <NUM>.

The metal powder particles are usually dispensed from a storing container under the action of gravity. However, flow characteristics of the powders in general have a tendency to prevent flow of the powder through small holes due to the fact that the powder particles tend to agglomerate into larger particles. This may disrupt the flowability of the powder and stable supplying rate and accuracy of the amount of the provided powder.

In one aspect, an apparatus for dispensing a powdered material is provided. The dispensing apparatus has the features specified in claim <NUM>.

In yet another aspect, an additive manufacturing system is provided. The system comprises the features specified in claim <NUM>.

In addition to the aspects described above, further aspects and embodiments will become apparent by reference to the drawings and study of the following detailed description.

Throughout the drawings, reference numbers may be re-used to indicate correspondence between referenced elements. The drawings are provided to illustrate example embodiments described herein and are not intended to limit the scope of the invention. Sizes and relative positions of elements in the drawings are not necessarily drawn to scale. For example, the shapes of various elements and angles are not drawn to scale, and some of these elements are arbitrarily enlarged and positioned to improve drawing legibility. I is a perspective cross-sectional view of an example of an apparatus for dispensing powdered material showing a dispensing orifice.

<FIG> illustrates an apparatus for dispensing powdered material <NUM> having a dispenser <NUM> and a vibration system <NUM>. The dispenser <NUM> has a housing <NUM> that defines an inner cavity <NUM> into which the powdered material is inserted. The inner cavity <NUM> has an inlet <NUM> and a dispensing opening <NUM>. A bottom 14a of the inner cavity <NUM> can be slanted such that the powdered material is directed under gravity toward a passage/channel <NUM> that connects the inner cavity <NUM> and the dispensing opening <NUM>. The passage <NUM> can have smaller cross-section so that it can direct the flow toward the dispensing opening <NUM>. In some implementations, the passage <NUM> can have tapered configuration toward the dispensing opening <NUM>. The powdered material from the inner cavity <NUM> flows through the passage <NUM> and out from the dispensing opening <NUM>. The passage <NUM> is curved. The dispensing opening <NUM> can have various dimensions and shapes depending on the size and/or shape of the material's particles. The inner cavity <NUM> can also include a level sensor (not shown) which measures the level of the powdered material in the inner cavity <NUM> of the dispenser <NUM> and can trigger opening of a valve to refill the dispenser <NUM> when the material level in the cavity <NUM> is low, below a threshold. Thus, by using a level sensor, the apparatus <NUM> can be used in continuous manner to continuously dispense desired amounts of powdered material. The level sensor can be an optical, inductive or mechanical type of known sensors. The dispensing apparatus <NUM> can comprise at least one storage container <NUM> (see <FIG>, <FIG>) that has at least one outlet in fluid communication with the inner cavity <NUM> of the dispenser <NUM>. The storage container stores the powdered material so that the dispenser <NUM> can be refiled when required. The level sensor can for example send a signal to a controller <NUM> (<FIG>) so that when the level of the material is under some pre-determined value the controller <NUM> can open the outlet of the storage container to refile the inner cavity <NUM> of the dispenser <NUM>.

The vibration system <NUM> is adjacent to the dispenser <NUM> and can comprise a vibrator <NUM> and a driver <NUM> to drive the vibrator <NUM>. For example, the vibrator <NUM> can have a movable head <NUM> and the driver <NUM> can drive the head <NUM> back- and-forward in linear fashion. A sleeve <NUM> with an inner guide can be anchored to the housing <NUM>. The inner guide of the sleeve <NUM> is sized such that a head <NUM> can move back-and-forward therein therefore providing tapping action to the housing <NUM> of the dispenser <NUM> therefore vibrating the dispenser <NUM>. Such continuing vibrations of the dispenser <NUM> provide that the powdered material continuously flows out through the dispensing opening <NUM>. The curved geometry of the passage <NUM>, for some powdered materials, can allow the powdered material to flow only during vibrations while stop flowing without vibration due to the piling of the material on the curved section of the passage <NUM>. The dispenser <NUM> can comprise a pivot <NUM> around which the dispenser <NUM> can turn or swing to dispense the material out of the dispensing opening <NUM> rotation.

Persons skilled in the art would understand that the sleeve <NUM> can be omitted and the moving head <NUM> can provide tapping motion to the dispenser <NUM> without being guided by the sleeve <NUM>. The vibrator can be driven mechanically (e.g. a mechanical arm or a cam connected to the head and driven by a motor) or electromagnetically. For example, and as illustrated in the example shown in <FIG>, the driver <NUM> can comprise one or more coils 18a that are in electrical communication to a power source (not shown) to provide current pulses to the coils 18a and a permanent magnet 18b that drives the head <NUM> of the vibrator <NUM> back and forth in linear fashion depending on the direction of the current in the coils 18a. This is for illustration purposes only, and the head <NUM> can be driven in linear or rotational manner (e.g. by using a cam) as long as it provides a continuing periodic vibration to the dispenser <NUM>. In case where the vibration systems comprise a vibrator that is driven in rotational manner, the frequency of the vibrations is defined as rounds-per-minute (RPM). Alternatively, for small (light) sizes of dispenser <NUM>, the vibration system <NUM> can be an ultrasonic generator to generate ultrasound vibrations of the dispenser <NUM>. The apparatus <NUM> further comprises a controller <NUM> (<FIG>) configured to control the driver <NUM> of the vibration system <NUM> to adjust the frequency, amplitude and/or the duration of the vibration of the dispenser <NUM>.

<FIG> illustrates another embodiment of an apparatus for dispensing the powdered material <NUM> where the dispensing opening is configured as a dispensing slot <NUM>. The dispensing slot <NUM> has an elongated L-shaped passage/channel <NUM> with closed ends and opened face. The channel <NUM> is in fluid communication with the inner cavity <NUM> of the dispenser <NUM>, such that the powdered material is dispensed out through the slot <NUM> as a curtain <NUM> of fluidized powdered material (see <FIG>), during vibration of the dispenser <NUM>, as described herein above with respect to the apparatus <NUM> of <FIG>. The opening of the slot <NUM> can have different sizes (narrower or wider) and different cross-sections depending on the size of the material's particles.

In some implementations, which are outside the scope of the claims, the dispensing slot <NUM> can comprise a vertical, straight channel 24a (see <FIG>) instead of L-shaped channel <NUM> shown in <FIG>. In some mode of operations, an edge <NUM> of the dispensing slot <NUM> can be used for leveling the powdered material <NUM> on a powder bed (not shown). For example, a point of rotation (pivoting) <NUM> of the dispenser slot <NUM> can be positioned as close as possible to the edge <NUM> of the slot <NUM>. The dispensing slot <NUM> can also be closer to the pivot <NUM>. At the beginning of the operation the edge of the nozzle of the dispensing slot <NUM> can be brought in contact with the powder bed, then the dispensing slot <NUM> can be lifted to a pre-determined distance from the powder bed, e.g. <NUM> away from the powder bed. As the vibrator <NUM> generates vibrations of the dispenser <NUM> it triggers flow of the powdered material on the powder bed while the edge is leveling the powdered layer preventing any layer inconsistence. In addition, the vibration of the dispenser <NUM> may cause tapping motion of the edge of the slot <NUM> to the powder bed further enhancing the continuous flow and compacting of the powdered material.

<FIG> illustrates another embodiment of an apparatus for dispensing the powdered material <NUM> with a direct drive <NUM>. The direct drive <NUM> comprises a permanent magnet <NUM> that is directlly connected to the housing <NUM> of the dispenser <NUM> and a coil <NUM>. The coil <NUM> is operatively coupled to a power source (not shown) so that when a current flow in the coil <NUM> it generates magnetic field. The magnetic field of the coil <NUM> reacts with the magnetic field of the permanent magnet <NUM>, attracting or repelling depending on the direction of the current flow, thus directly vibrating (pushing/pulling) the dispenser <NUM> and the dispensing slot <NUM>. A spring <NUM> can be added at the back of the permanent magnet <NUM> to stabilize the dispenser <NUM> when there is no current in the coil <NUM>. In addition, a displacement sensor <NUM> positioned close to the dispenser <NUM> is added to measure the mechanical movement (displacement) of the dispenser <NUM> during operation. The displacement sensor sends an input signal to the controller <NUM>. Optionally, another displacement sensor (not shown) can be added in proximity to the storage container <NUM> to measure the mechanical vibration (displacement) of the storage container <NUM>.

The apparatus for dispensing powdered materials <NUM>, <NUM> has been tasted and the flow rates of the powdered material have been measured. For example, a titanium (Ti) metal powder has been put in the inner cavity <NUM> of the dispenser <NUM>. Different sizes of dispensing opening <NUM>/dispensing slot <NUM> have been used to test the flowability of the metal powder through different sizes of outlet. In addition, the experiments were conducted at different frequencies with constant or optimized amplitude. <FIG> graphically illustrates results from some of the experiments showing the flowing rate of the metal powder in grams per second. A dash-dot line <NUM> represents a flowing rate in grams per second when a <NUM> diameter hole was used, a dotted line <NUM> represents the flowing rate when <NUM> diameter hole was used and a dashed line <NUM> represents the flowing rate when <NUM> diameter hole was used. In all three cases the vibration system <NUM> was set up to provide vibrations of <NUM> frequency and constant amplitude. As can be noticed from the graph, in all three cases represented by lines (<NUM>, <NUM>, <NUM>) a continuous flow of the metal powder has been obtained with flow rate increasing with the increase of the size of the opening <NUM>/<NUM>, as expected. In order to evaluate the effect of the vibration frequency on the flow rate, further tests were conducted changing the frequency to <NUM> (a broken line <NUM>) and to <NUM> (a solid line <NUM>). In the first case (line <NUM>), a <NUM> diameter hole was used, while in the second case (line <NUM>) a <NUM> long, <NUM> wide slot was used. The amplitude and the phase of the vibrations were also adjusted and optimized through experimentation to provide higher flow rate. First, an optimal frequency for a given opening/slot configuration is established and then an amplitude at such frequency is optimized. The amplitude is defined as the tapping force/power. For example, if the power source provides more current to the coils 18a, the obtained tapping force on the dispenser <NUM> will be stronger, resulting in higher amplitude of the vibration to push the powder through the dispensing opening or slot <NUM>/<NUM>. The optimization of the frequency (length of the stroke) and the amplitude (power of the stroke) for a given powdered material can be done through an experimental iteration. Comparing the line <NUM> with the line <NUM> it can be noticed that increasing the frequency of the vibration and optimizing the amplitude increases the flow rate to almost double for the same size of opening (<NUM> diameter) and same powdered material. It can also be noticed that using a dispensing slot <NUM> instead of single opening <NUM> increases the flow rate, which is expected because of the bigger dispensing area.

The apparatus for dispensing the powdered material <NUM>, <NUM>, <NUM> can further comprise at least one storage container <NUM> (<FIG>) that is in fluid communication with the inner cavity <NUM> of the dispenser <NUM>. When the apparatus is in an operational mode, the storage container <NUM> is configured to provide powdered material to the inner cavity <NUM> of the dispenser <NUM> in continuous manner at a pre-determined rate depending on the flow rate of the dispensing material out of the dispenser. In one implementation, a level sensor can be provided in the inner cavity <NUM> of the dispenser so that when the powdered material in the cavity <NUM> is below the pre-determined level the sensor opens a valve/outlet between the storage container <NUM> and the dispenser <NUM> to provide additional quantity of powdered material into the dispenser <NUM>.

In operation, the powdered material is put in the dispenser <NUM> and then the controller <NUM> (<FIG>) sets up the frequency and amplitude of the vibrations to be applied to the dispenser <NUM>. When the vibration system <NUM>, <NUM> is triggered, the dispenser <NUM> starts to vibrate, providing a continuous flow of powdered material out of the dispenser <NUM>. <FIG> illustrates one example of the control system <NUM> of the dispensing system <NUM>, <NUM>, <NUM>. The controller <NUM> is in communication with the dispenser <NUM> so that it can adjust dispenser's oscillation e.g., frequency and amplitude of dispenser's vibration. The controller <NUM> can also be in communication with the storage container <NUM>. The controller receives as input a flow rate (weight flow) of the powdered material 101a out of the dispenser <NUM> and a flow rate of the powdered material 101b out of the storage container. The controller <NUM> is in communication with the dispenser's displacement sensor 102a and the level sensor 106a about the respective mechanical movement of the dispenser <NUM> and the amount of powdered material in the dispenser <NUM>. In some implementations, a displacement sensor 102b and a level sensor 106b can be provided to measure the displacement of the storage container <NUM> and the amount of powder material therein. The mechanical displacement of the dispenser <NUM> and/or the tank <NUM> can vary during the operation, due to for example, the change of the amount of powder in the container <NUM> and/or the inner cavity <NUM> of the dispenser <NUM>. Therefore, the controller <NUM> can also be in communication with the storage container's displacement sensor 102b and the level sensor 106b to receive signals about the respective mechanical movement and the amount of powdered material in the storage container <NUM>. A processing unit <NUM> of the controller <NUM> receives instructions (input parameters) of the powdered material and the desired flow rate (weight rate) of the powdered material that needs to be dispensed in the powder bed. Various input parameters can be set directly or through a digital interface. Depending on the size of the dispensing opening <NUM>, <NUM> and the powder material density, the frequency is adjusted in relation to the powder size (e.g., in a range of <NUM> to <NUM>). Typically, a larger powder (<NUM> to <NUM>) requires lower frequencies and a finer powder (<NUM> to <NUM>) requires higher frequencies. The vibration, such as the frequency and the amplitude of the displacement of the dispenser <NUM> is set in relation to a target flow rate, the size of the dispensing opening <NUM>, <NUM> and the powder size. The processing unit <NUM> receives a signal from the displacement sensor 102a that measures the displacement of the dispenser <NUM> and compares such data to the target displacement (desired flow rate) and adjusts such displacement by adjusting the current <NUM> in the driver (e.g. coil 18a, <NUM>). Thus, the controller <NUM> can control/adjust the trajectory (wave form) of the dispenser <NUM> in real-time based on the signals received from the displacement sensor 102a. The controller <NUM> also receives signals from the level sensor 106a and 106b to control the amount of the powdered material in the dispenser <NUM> and the storage container <NUM>. For example, if the fill level in the dispenser <NUM> (or in some implementations the fill level in the storage container <NUM>) is below a certain threshold, the controller <NUM> will send a signal (trigger) to refill the dispenser <NUM> and/or the storage container <NUM>. For example, a valve/outlet between the dispenser <NUM> and the container <NUM> will open and close based on the trigger signal from the controller <NUM>. Once the dispensing flow rate is set, the processing unit <NUM> can set (calculates) the required dispensing displacement (distance) and frequency of the dispenser <NUM> and will adjust the current in the driver coil to control in real-time the actual displacement (vibration) of the dispenser <NUM>. Displacement distance of the dispenser <NUM> can vary from <NUM> to <NUM> and in case of large feed (flow) rates the displacement can be for example <NUM> of mm.

In one implementation, the controller <NUM> can receive the input parameters, such as the size of the dispensing opening, the material (size of the powder) and flow (weight) rate, and can set the frequency and displacement of the dispenser <NUM> by calculating optimal settings. The start - stop of the feeding can be controlled by external time-triggers or the operation time schedule can be part of the controller.

The apparatus for the dispensing powdered materials <NUM>, <NUM>, <NUM> can be used in different industries, such as for example, in the pharma industry for dispensing a small amount of medicament in controlled and accurate fashion, in the food or chemical industry for delivering accurate amounts of ingredients/reactants, in the additive manufacturing industry for providing (and spreading in same cases) the powdered material on the powder bed or in the welding industry (e.g. plasma ark welding).

<FIG> illustrates one example of an additive manufacturing system <NUM> that employs the dispensing apparatus <NUM>, <NUM>, <NUM>. The system <NUM> can be an electron-beam melting system (EBM) or a selective laser melting system (SLM) and can comprise an energy source <NUM>, such as for example, an electron-beam gun <NUM> or a laser, and a working chamber (not shown) coupled to the energy source <NUM>. In case when the system <NUM> is an EBM system, the working chamber is a vacuum chamber. A work platform (not shown) is positioned in the chamber and a powder bed <NUM> is positioned on the work platform. The work platform can be moved in Z-direction up and down to provide layer-by-layer structure of the product. The apparatus for dispensing the powdered material <NUM> is also positioned within the chamber to dispense a controllable amount of powdered material <NUM> onto the powdered bed <NUM>. The energy source <NUM> can generate an energy beam <NUM> that is focused, using a focusing means (not shown), onto the powder dispensed onto the powder bed <NUM>, melting such powdered material and producing small volume of melt pool <NUM>. The dispensing apparatus <NUM>, <NUM>, <NUM> can be mounted on a moving platform (not shown) and can be at some pre-determined distance above the power bed <NUM>. The moving platform can move the dispensing apparatus <NUM> in X and/or Y directions, so that a layer of the powdered material can be laid on the powder bed <NUM> without using a spreader, such as a rake or a comb that is usually used in the known additive manufacturing systems. In some implementation, the dispensing apparatus <NUM>, <NUM>, <NUM> can be stationary and the work platform can move the powder bed <NUM> in X and/or Y directions such that the layer of the powdered material is laid on the power bed <NUM>. The energy beam <NUM> can be focused using a focus lens and/or coils to converge the beam radially to form a focal spot. The energy beam <NUM> can further be deflected (using a deflection lens and/or coils) to change the direction or path of the beam <NUM> to a different focal spot to melt the powder deposited at such different focal spot forming another melt pool. The melting pools are then rapidly solidified forming a layer of a product. Then this process is repeated to add additional powder layers and get a layer-by-layer fabrication of the work product. In one implementation, the dispensing apparatus and the energy source <NUM> can be synchronized, such that as the dispensing apparatus dispense the powder on the powder bed <NUM>, it is simultaneously melted by the energy beam <NUM>. This means that the controller (e.g., controller <NUM>) controls the triggering time of the dispensing apparatus and the energy source <NUM> such that the pulse of the energy beam and the dispensing time (vibration pulse) are synchronized. The vibration and the beam pulses can be for example at the rate of <NUM> - <NUM>.

The powdered material used in the additive manufacturing system <NUM> needs to be conductive to avoid being displaced by electrostatic charging when the electron beam is focused onto the powder. In order to increase the conductivity of the metal powder the powder bed <NUM> is preheated at predetermined temperatures (e.g., between <NUM> ° - <NUM> depending on the material). In one embodiment, illustrated in <FIG>, the powdered material is preheated before entering the dispenser <NUM>. For example, the powdered material exiting the storage container <NUM> can enter an elongated heater <NUM>, such as for example electrically heated tube <NUM>. The heater <NUM> can be inclined so that the powdered material can flow in the tube under gravity or the material flow, down the heater <NUM>, can be facilitated by vibrating the heater <NUM> at predetermined frequency. The outlet of the heater <NUM> is in fluid communication with the inner cavity of the dispenser <NUM>. The powdered material preheated in the heater <NUM>, to a predetermined temperature, enters the dispenser <NUM> and through the dispensing opening is positioned on the powder bed <NUM>. In some implementations, the heater can be positioned in the dispenser, e.g., around the inner cavity <NUM> or in proximity to the dispensing opening to pre-heat the dispensed powdered material.

<FIG> illustrate another embodiment of the dispensing apparatus <NUM> that uses a pulse generator <NUM> to increase the electric conductivity of the powdered material. The pulsed generator <NUM> is positioned adjacent to the dispenser <NUM> at some vertical distance above the dispensing slot <NUM>. The powder conductivity can be improved using the Branly effect. Namely, a high voltage power supply and a waveform generator is used to cause the potential differential charge between the pulse generator terminals to create electromagnetic pulses of electrical discharges (e.g., arcs) which improves the electric conductivity of the powder when the electromagnetic field travel through the exposed powder.

<FIG> and <FIG> illustrate another embodiment of a dispensing apparatus <NUM> for dispensing a mixture of two (or more) powdered materials (e.g. an alloy). The dispensing apparatus <NUM> comprises the dispenser <NUM> and the vibration system <NUM>/<NUM> same as the one described herein above with respect to the <FIG>. The dispensing apparatus <NUM> can further comprise at least two storage containers <NUM>. In the illustrated example, the dispensing apparatus <NUM> comprises two storage containers <NUM>, each containing different powdered material, however there can be more or less than two storage containers depending whether the material to be dispensed is a mixture or two or more substances or a single substance. A mixing chamber <NUM> is provided between the storage containers <NUM> and the dispenser <NUM>. The mixing chamber <NUM> has at least two inlets <NUM> (see <FIG>), each inlet <NUM> being in fluid communication with an outlet of a respective storage container <NUM>. The mixing chamber <NUM> is connected to the dispenser <NUM> and comprises one or more outlets <NUM> that are in fluid communication with the inner cavity of the dispenser <NUM> to deliver the mixed powder into the dispenser <NUM>. As the dispenser <NUM> vibrates, the mixing chamber <NUM> vibrates too therefore mixing the particles of the two (or in some cases more than two) powdered materials. In some implementations, the mixing chamber <NUM> can have two or more intersecting channels <NUM> to direct the powders to multiple intersecting sections <NUM> where the powders mix. The channels <NUM> can be curved to allow the powders to flow only during vibrations however, persons skilled in the art would understand that the intersecting channels can be straight or curved without departing from the scope of the invention. In one implementation, a heater (not shown) can be added to preheat the powder in the mixing chamber <NUM>.

<FIG> illustrate an example of another embodiment of a dispensing apparatus <NUM>. The dispensing apparatus <NUM> is similar to the apparatus <NUM> of <FIG> with the dispensing slot <NUM> to provide a curtain of fluidized powdered layer <NUM> (<FIG>). The dispenser <NUM> further comprises a shutter <NUM> that is configured to slide a predetermined distance in a vertical Z-direction, such that when the shutter <NUM> is in a first position (see <FIG>), it is blocking a portion of the slot <NUM>, such that the curtain of the fluidized powder layer is interrupted. When the shutter is in a second position (see <FIG>), the slot <NUM> is not blocked and a continuous curtain of powder layer is provided. The shutter <NUM> is connected to a driver <NUM> that is configured to drive the shutter up and down between the first and the second positions. The driver can be controlled by a controller (e.g. the controller <NUM>) that can be pre-programmed to timely adjust the position of the shutter <NUM>. The driver <NUM> can be an electromagnetic or a mechanical without departing from the scope of the invention.

Conditional language used herein, such as, among others, "can," "could," "might," "may," "e.g.," and the like, unless specifically stated otherwise, or otherwise understood within the context as used, is generally intended to convey that certain embodiments include, while other embodiments do not include, certain features, elements and/or steps. Thus, such conditional language is not generally intended to imply that features, elements and/or steps are in any way required for one or more embodiments or that one or more embodiments necessarily include logic for deciding, with or without operator input or prompting, whether these features, elements and/or steps are included or are to be performed in any particular embodiment. No single feature or group of features is required for or indispensable to any particular embodiment.

Claim 1:
An apparatus for dispensing (<NUM>, <NUM>, <NUM>, <NUM>) a powdered material (<NUM>) comprising:
- a dispenser (<NUM>) having a housing (<NUM>) defining an inner cavity (<NUM>) with an inlet (<NUM>) and a dispensing opening (<NUM>, <NUM>);
- a vibrating system (<NUM>) having a driver (<NUM>, <NUM>), the vibrating system (<NUM>) being in communication to the dispenser (<NUM>) to provide a continuing periodic oscillation of the dispenser (<NUM>); and
- a controller (<NUM>) in communication with the driver of the vibrating system (<NUM>) to control a frequency and an amplitude of the vibrations of the dispenser (<NUM>),
characterized in that the apparatus further comprises
- a displacement sensor (<NUM>, 102a) coupled to the dispenser (<NUM>) and configured to measure mechanical displacement rate of the dispenser (<NUM>) and provide an input signal to the controller (<NUM>) about the measured displacement rate of the dispenser (<NUM>),
wherein the controller (<NUM>) is configured to compare the measured displacement rate with a predetermined target displacement rate and amount of powdered material in the dispenser (<NUM>) and to adjust the frequency and/or the amplitude of the vibrations based on the input signal from the displacement sensor (<NUM>) such that the measured displacement rate matches the target displacement rate,
wherein the dispenser (<NUM>) has a curved channel (<NUM>) or an elongated L-shaped channel (<NUM>) formed between the inner cavity (<NUM>) and the dispensing opening (<NUM>, <NUM>), and
wherein the powdered material (<NUM>) continuously flows out through the dispensing opening (<NUM>, <NUM>) during vibration of the dispenser (<NUM>).