Powder wetting apparatus and use thereof in methods for producing molded parts layer by layer

Abstract

An apparatus for wetting or conditioning particulate material (102) suitable for additive manufacturing, the apparatus comprising or consisting of a conveying device (103) for particulate material, a liquid-supplying means (101) or / and conditioning agent-supplying means for dispensing liquid or / and conditioning agent, a particle-supplying means and preferably a particle-collecting means.

Description

[0001] Description

[0002] Powder humidification device and its use in processes for the layered construction of molded parts

[0003] The invention relates to a powder humidifier and its use in a method for producing three-dimensional models by means of layer building technology.

[0004] European patent EP 0 431 924 B1 describes a method for producing three-dimensional objects from computer data. A thin layer of particulate material is applied to a build platform using a recoater, and the particulate material (generally a fluid) is selectively printed with a binder material using a print head. The particulate area printed with the binder bonds and solidifies under the influence of the binder and, if necessary, an additional hardener or an additional heat source. The build platform is then lowered by one layer thickness in a build cylinder and covered with a new layer of particulate material, which is also printed as described above. These steps are repeated until a certain desired object height is reached. The printed and solidified areas thus form a three-dimensional object (molded part).

[0005] This object, made from solidified particulate material, is embedded in loose particulate material after completion, and is then removed from it. This is done, for example, using a vacuum cleaner. What remains are the desired objects, which are then freed from the residual powder, for example, by brushing.

[0006] In known additive manufacturing devices and processes, the printing material (powder or particle material) is not always in a favorable form, particularly with regard to its moisture content. This has far-reaching negative effects in terms of clumping and negative impacts on the printing process, and in particular on the quality of the printed products, i.e., the manufactured molded parts. If the powder or particle material used is not sufficiently flowable, problems can arise during particle material application (recoating), as the recoater or the particle material supply can become clogged. This leads to defects in the component and, under certain circumstances, can lead to the termination of the process.

[0007] The flowability of certain particulate materials depends, among other things, on the moisture content of the particulate material. Conditioning the material to the desired moisture content using conventional methods is very complex.

[0008] It was therefore an object of the present invention to reduce or completely avoid the disadvantages of the prior art.

[0009] It was therefore a further object of the present invention to provide a system in which the printing material is essentially of good quality, in particular uniform and with the desired moisture content, and / or can be delivered to the printing process. Brief Summary of the Invention

[0010] In one aspect, the invention relates to a device for moistening or conditioning particulate material suitable for additive manufacturing, comprising or consisting of a conveying device for particulate material, a liquid supply means and / or conditioning agent supply means for dispensing liquid and / or conditioning agent, a particle supply means and preferably a particle collecting means.

[0011] In one aspect, the invention relates to a method for moistening or conditioning particulate material suitable for additive manufacturing, comprising the steps: a. introducing particulate material into a conveying device, b. conveying the particulate material in the conveying device, c. adding liquid and / or conditioning agent directly into the conveying device from a liquid supply means and / or a dispensing means for one or more conditioning agents onto or into the particulate material, d. mixing and homogenizing the liquid with the particulate material during conveying, e. discharging the thus moistened particulate material from the conveying device, f. optionally measuring the moisture in the particulate material before introducing it into or / and discharging it from the conveying device, preferably regulating the dispensing of liquid onto or into the particulate material by means of a control loop, preferably an algorithm.

[0012] Short description of the characters

[0013] Figs. 1 - 5 show various preferred aspects of the invention.

[0014] Detailed description of the invention

[0015] According to the invention, an object underlying the application is achieved by a device according to claim 1 and / or by a method according to claim 10. Further preferred aspects are described in the subclaims.

[0016] In the following, some terms of the revelation will be explained in more detail.

[0017] For the purposes of the disclosure, "layer construction processes" or "3D printing processes" or "3D processes" or "3D printing" are all processes known from the prior art that enable the construction of components in three-dimensional shapes and are compatible with the process components and devices described below.

[0018] "Binder jetting" in the sense of the disclosure means that powder is applied layer by layer to a build platform, the cross-sections of the component on this powder layer are printed with one or more liquids, the position of the build platform is changed by one layer thickness to the last position, and these steps are repeated until the component is finished. Binder jetting also includes layer-by-layer construction processes that require an additional process component, such as layer-by-layer exposure, e.g., with IR or UV radiation.

[0019] In "powder bed fusion" such as the "high-speed sintering process" as defined in the disclosure, a thin layer of plastic granulate, such as PA12 or TPU, is applied to a preferably heated build platform (build area). An inkjet print head then moves over a large area of ​​the platform and wets the areas of the build area with electromagnetic radiation, e.g. infrared light-absorbing ink (absorber), where the prototype is to be created. The build platform is then irradiated with (e.g. infrared) light. The wetted areas absorb the heat, causing it to melt and bond with the underlying powder layer. The unprinted powder, however, remains loose. After sintering, the build platform lowers by one layer thickness. This process is repeated until the build of a component is complete.The sintered parts are then cooled in a controlled manner in the build chamber before they can be removed and unpacked.

[0020] “Laser sintering process” within the meaning of the disclosure is a 3D printing process in which the particulate material is selectively solidified by means of a laser.

[0021] "3D molded part", "molded body" or "component" within the meaning of the disclosure are all three-dimensional objects produced by means of the method according to the invention and / or the device according to the invention which have a dimensional stability.

[0022] "Build space" is the geometric location in which the particulate material bed grows during the build process through repeated coating with particulate material, or through which the bed flows in continuous principles. Generally, the build space is defined by a floor, the build platform, walls, and an open ceiling surface, the build level. Continuous principles usually include a conveyor belt and delimiting side walls. The build space can also be configured by a so-called job box, which is a unit that can be moved into and out of the fixture and allows for batch production. A job box is moved out after the process is completed, and a new job box can be immediately moved into the fixture, thus increasing the production volume and thus the fixture performance.

[0023] All flowable materials known for 3D printing can be used as "building material" or "particle material" or "powder" or "powder bulk" within the meaning of the disclosure, particularly in powder form, as a slurry, or as a liquid. These can be, for example, sands, ceramic powders, glass powders, and other powders made of inorganic or organic materials such as metal powders, plastics, wood particles, fiber materials, celluloses and / or lactose powders, as well as other types of organic, powdery materials. The particulate material is preferably a dry, free-flowing powder, but a cohesive, cut-resistant powder can also be used. This cohesiveness can also be achieved by adding a binder material or an auxiliary material such as a liquid. The addition of a liquid can result in the particulate material in the form of a slurry being freely flowable.In general, particulate material within the meaning of the disclosure can also be referred to as fluids.

[0024] In the present application, particulate material and powder are used synonymously.

[0025] Particle material deposition is the process by which a defined layer of powder is created. This can occur either on the build platform (build field) or on an inclined plane relative to a conveyor belt in continuous processes. Particle material deposition is also referred to as "coating" or "recoating."

[0026] Any known 3D printing device that includes the required components can be used as a "device" for performing a method according to the disclosure. Typical components include a coater, a build field, means for moving the build field or other components in continuous processes, a job box, dosing devices, and heating and irradiation means, as well as other components known to those skilled in the art, which are therefore not described in detail here. In particular, the device can be suitable for a powder bed fusion process, such as high-speed sintering, multijet fusion, and other processes known to those skilled in the art. Furthermore, the device can have a particulate material reservoir, with a device for regulating the humidity being mounted in the particulate material reservoir.A device according to the invention can have several silos for particulate material, wherein a recycling silo receives particulate material from the unpacking process of the parts or from the overflow and / or is cleaned, e.g., sieved, or subjected to other processing steps and, if necessary, also enriched with new, fresh powder. Finally, particulate material for the printing process is conveyed to a machine silo, from which the coater is filled. A conveyor device conveys particulate material into the machine silo and moistens and / or conditions it. This conveyor device can be a screw conveyor or a pneumatic conveyor device, which are specifically adapted to the requirements of moistening and / or conditioning. A screw conveyor according to the invention can be characterized by certain design features, such as the absence of a core or a defined number of openings (e.g.,10 to 100, preferably 20 to 50) in one or more conveyor spirals which allow a backflow of particulate material, which leads to an advantageous mixing and homogenization of the particulate material with the introduced moisture and / or a conditioning agent, so that the particulate material is substantially uniformly moistened and / or conditioned as soon as it leaves the conveyor.

[0027] The "build material" according to the disclosure is always applied in a "defined layer" or "layer thickness," which is individually adjusted depending on the build material and process conditions. It is, for example, 0.05 to 5 mm, preferably 0.07 to 2 mm. A "coater blade" (also "recoater blade") within the meaning of the disclosure is a substantially flat metallic component or component made of another suitable material, located at the outlet opening of the coater, through which the fluid is dispensed onto the build platform and smoothed. A coater can have one or two or more coater blades. A coater blade can be an oscillating blade that performs oscillations in the sense of a rotary motion or an oscillating motion when excited. Furthermore, this oscillation can be switched on and off by a means for generating oscillations.Depending on the arrangement of the outlet opening, the coating blade is arranged "essentially horizontally" or "essentially vertically" within the meaning of the disclosure.

[0028] "Sintering" or "melting" in the context of this disclosure refers to the partial coalescence of the particles in the powder. In this system, sintering is associated with the buildup of strength.

[0029] "3D printer" or "printer" or "3D printing machine" within the meaning of the disclosure refers to the device in which a 3D printing process can take place. A 3D printer within the meaning of the disclosure comprises a means of application for build material, e.g., a fluid such as a particulate material, and a solidification unit, e.g., a print head or an energy input means such as a laser or a heat lamp. Other machine components known to those skilled in the art and components known in 3D printing are combined with the above-mentioned machine components depending on the specific requirements of the individual case. Alternatively, the term "device" can be chosen. "Build field" is the plane or, in a broader sense, the geometric location on or in which a bed of particulate material grows during the build process through repeated coating with particulate material. The build field is often delimited by a floor, the "build platform," by walls, and an open ceiling surface, the build plane.

[0030] The process "printing" or "3D printing" within the meaning of the disclosure refers to the combination of the processes of material application, selective solidification or printing and adjustment of the working height and takes place in an open or closed process or construction space.

[0031] A "receiving plane" within the meaning of the disclosure is the plane onto which building material is applied. According to the disclosure, the receiving plane is always freely accessible in one spatial direction by a linear movement.

[0032] "Spreading" or "applying" or "depositing" within the meaning of the disclosure means any manner by which the particulate material is distributed. For example, a larger quantity of powder may be placed at the starting position of a coating run and distributed or spread into the coating volume by a blade or a rotating roller.

[0033] "Coater" or "recoater" or "material application means" within the meaning of the disclosure is the unit by means of which a particulate material is applied to the build area. This may consist of a storage container and an application unit, wherein, according to the present invention, the application unit comprises an outlet and a "doctoring device." This doctoring device could be a coating blade. However, any other conceivable suitable doctoring device could also be used. Rotating rollers or a nozzle, for example, are also conceivable. The material can be supplied freely via storage containers or extruder screws, pressurization, or other material conveying devices.

[0034] "Layer treatment means" within the meaning of the disclosure are all means suitable for achieving a specific effect in the layer. These can be the aforementioned units such as the print head or laser, but also heat sources in the form of IR radiators or other radiation sources such as UV radiators. Means for de- or ionization of the layer are also conceivable. What all layer treatment means have in common is that their effective zone is distributed linearly across the layer and that, like the other layer units such as the print head or coater, they must be guided across the build field in order to reach the entire layer.

[0035] "Overflow" in the sense of the disclosure refers to the additional space required when an aggregate is moved on a linear axis completely across the construction field from one end to the other without creating any shadow on the construction field.

[0036] "Humidification" in the sense of the invention means adjusting the moisture content in the particulate material by means of the device or method described here. The introduced liquid can advantageously be adjusted to a liquid quantity of 1 to 20 g per 1 kg of particulate material, preferably 2 to 10 g per 1 kg, particularly preferably 5 to 8 g per 1 kg.

[0037] "Conditioning" in the sense of the invention means that an additional component is added to the particulate material. A "conditioning agent" can be used, for example: a flux, an antistatic agent, antioxidants, or a coolant.

[0038] A "conveying means" (conveying device) within the meaning of the invention can be a screw conveyor or a pneumatic conveyor. The screw conveyor can be specifically adapted to the requirements of humidification and / or conditioning. A screw conveyor according to the invention can be characterized by certain design features, such as the absence of a core or a defined number of openings (e.g., 10 to 100, preferably 20 to 50) in one or more conveyor spirals, which allow a backflow of particulate material, leading to advantageous mixing and homogenization of the particulate material with the introduced moisture and / or a conditioning agent, so that the particulate material is substantially uniformly moistened and / or conditioned as soon as it leaves the conveyor. A pneumatic conveyor can effect the transport of particulate material with a gas, preferably air, preferably by means of positive or negative pressure.Conveying generally takes place via pipes, hoses, or fluid troughs (square pipes with aeration bottoms). Special embodiments can include airborne, strand, and plug conveying, or flow conveying. "Adding moisture and / or conditioning agent" or "introducing moisture and / or conditioning agent" within the meaning of the invention can be done into the conveying device / into the particulate material present within the conveying device (e.g., a screw conveyor or pneumatic conveyor) or continuously fed into the conveying device by dispensing it from an additive, such as a hose, pipe system, or nozzle, and can be done passively or actively.

[0039] "Mixing" in the sense of the invention means that the moisture and / or conditioning agent is introduced into or applied to the particulate material, whereby this process takes place within the conveying means and an intimate mixing with the particulate material occurs during the conveying process. This advantageously results in a substantially uniformly moistened and / or conditioned particulate material, which can then be introduced into the printing process and is characterized by the desired properties with regard to moisture and conditioning. This facilitates the printing process and produces advantageous results in the production process of molded parts that cannot be achieved without this moistening and / or conditioning.In particular, with regard to the desired moistening of the particle material, in contrast to known methods and devices, no additional work steps or steps are required, but rather the moistening and conditioning are combined with a conveying step, which keeps the printing process simple in terms of time and construction and does not lead to a prolongation of the process.

[0040] "Homogenization" in the sense of the invention is the uniform distribution and mixing of particulate material with the components moisture and / or conditioning agent and means a substantially uniform distribution of the same in the particulate material. Thus, advantageous uniform advantageous particulate material properties can be achieved with each layer application and thus positive material properties can be maintained substantially throughout the entire molded part.

[0041] A "particle collection means" within the meaning of the invention can be a container compatible with the device, such as a box, a silo, a container, which is preferably closed. Furthermore, it can be characterized by further features of the device according to the invention, which are described below.

[0042] A "measuring means" of moisture and / or conditioning agent in particulate material within the meaning of the invention can be a capacitive moisture sensor or a microwave moisture sensor, which is placed directly in a particulate material reservoir (silo, container). Preferably, the sensor is placed in a container, preferably in a tube, which preferably has an opening at the bottom.

[0043] In this way, the initial humidity and / or the input humidity of the particulate material and / or the conditioning agent can advantageously be determined, and the discharge of the liquid and / or the conditioning agent can preferably be adjusted depending on the actual and target humidity and / or the actual and target values ​​of the particulate material, optionally controlled by an algorithm. The invention and its disclosure are described further below.

[0044] In one aspect, the invention relates to a device for moistening or conditioning particulate material suitable for additive manufacturing, comprising or consisting of a conveying device for particulate material, a liquid supply means and / or conditioning agent supply means for dispensing liquid and / or conditioning agent, a particle supply means and preferably a particle collecting means.

[0045] The invention relates in one aspect to a method for moistening or conditioning particulate material suitable for additive manufacturing, comprising the steps of: a. Introducing particulate material into a conveying device, preferably a conveyor screw, from a particle feed means, preferably a

[0046] Particulate material reservoir by means of a dosing means, b. conveying the particulate material in the conveying means, c. adding liquid and / or conditioning agent into the conveying device from a liquid supply means and / or a dispensing means for one or more conditioning agents onto or into the particulate material, d. mixing and homogenising the liquid with the particulate material during conveying, e. discharging the thus moistened particulate material from the conveying device, optionally into a particle collecting means, f. optionally measuring the moisture in the particulate material before introducing it into and / or discharging it from the conveying device, preferably regulating the dispensing of liquid onto or into the particulate material by means of a control loop, preferably an algorithm.

[0047] Using the device and the method according to the invention, the moisture content and / or the conditioning of the building material (particulate material) can advantageously be adjusted as desired in a simple and reliable manner and thus, for example, the flowability of the particulate material can be improved or even optimized without the need for turbulence or mixing processes in the construction space or in any other way. By means of the invention, the desired moisture content in the building material can be adjusted simply when feeding in the building material and thus, among other things, the flowability can be improved and / or the building material can be conditioned with regard to other parameters (conditioning agent). Furthermore, the device and the method according to the invention bring about good and essentially uniform mixing with liquid and / or conditioning agent in a simple and effective manner.

[0048] In a preferred embodiment, the device comprises a particle trapping means.

[0049] In a further preferred embodiment, the device for moistening or conditioning particulate material suitable for additive manufacturing further comprises one or more means for measuring the moisture content in the particulate material. In a further preferred embodiment, the liquid is water, and the conditioning agent is a flux, an antistatic agent, antioxidants, or a coolant.

[0050] In a further preferred embodiment, the device can be a screw conveyor or pneumatic conveyor as a conveying device.

[0051] In a further preferred embodiment, the liquid supply means may be a pipe, a flexible conduit or a nozzle.

[0052] In a further preferred embodiment, the particle supply means may be a particle reservoir with a dispensing means, the dispensing means preferably being a particle dosing means.

[0053] In a further preferred embodiment, the means for measuring the moisture in the particulate material may be a capacitive moisture sensor or a microwave moisture sensor, which is placed directly in a particulate material reservoir. Preferably, the sensor is placed in a container, preferably in a tube, which preferably has an opening at the bottom.

[0054] In a further preferred embodiment, the device may further comprise a control circuit for measuring the initial humidity and / or input humidity and / or the conditioning agent, and preferably an adjustment of the dispensing of the liquid depending on an actual and target humidity, optionally controlled by an algorithm. In a further preferred embodiment, the device may further comprise a dispensing means for one or more conditioning agents, wherein the conditioning agent is a gas, a gas mixture, a chemical, a mixture, a solution, an emulsion, and / or a suspension.

[0055] In a further preferred embodiment, the conveying device, preferably the conveyor screw, can have one or more openings for liquid supply means and / or conditioning agent supply means for dispensing liquid and / or conditioning agent, preferably wherein the device in the particulate material reservoir further comprises a device for regulating the air humidity in the particulate material reservoir.

[0056] In a further preferred embodiment, the additive manufacturing process can be a powder bed fusion process.

[0057] In a further aspect, the invention relates to a method for moistening or conditioning particulate material suitable for additive manufacturing, comprising the steps of: a. Introducing particulate material into a conveying device, preferably a conveyor screw, from a particle feed means, preferably a

[0058] Particulate material reservoir by means of a dosing means, b. conveying the particulate material in the conveying means, c. adding liquid and / or conditioning agent into the conveying device from a liquid supply means and / or a dispensing means for one or more conditioning agents onto or into the particulate material, d. mixing and homogenising the liquid with the particulate material during conveying, e. discharging the thus moistened particulate material from the conveying device, optionally into a particle collecting means, f. optionally measuring the moisture in the particulate material before introducing it into and / or discharging it from the conveying device, preferably regulating the dispensing of liquid onto or into the particulate material by means of a control loop, preferably an algorithm.

[0059] In a preferred embodiment, the liquid supply means is a pipe, a flexible conduit and / or a nozzle.

[0060] In a preferred embodiment, the particle supply means is a particle reservoir with a dispensing means, preferably a particle dosing means.

[0061] In a preferred embodiment, a capacitive humidity sensor or a microwave humidity sensor is used as a means for measuring the humidity in the particulate material, which is placed directly in a particulate material reservoir. Preferably, the sensor is placed in a container, preferably in a tube, which preferably has an opening at the bottom.

[0062] In a preferred embodiment, the liquid is water and the conditioning agent is a gas, a gas mixture, a chemical, a mixture, a solution, an emulsion and / or a suspension, preferably wherein the liquid and / or the conditioning agent are released in portions or continuously.

[0063] In a preferred embodiment, the liquid and / or the conditioning agent is delivered into or onto the particulate material by means of a pump.

[0064] In a preferred embodiment, the liquid and / or conditioning agent is introduced into the conveying device, preferably the conveyor screw, through one or more openings for liquid supply means and / or conditioning agent supply means.

[0065] In a preferred embodiment, the additive manufacturing process is a powder bed fusion process.

[0066] In a preferred embodiment, a device for regulating the humidity in the particulate material reservoir is further mounted in the particulate material reservoir.

[0067] Preferred embodiments are described below in the figures.

[0068] Figure description Fig. 1: Figure 1 shows a schematic representation of the device for moistening or conditioning particulate material suitable for additive manufacturing. The unconditioned particulate material 102 is combined with the conditioning agent, which is supplied via a nozzle 101, at the beginning of the conveyor screw 103. At the end of the conveyor screw, the particulate material is homogeneously mixed with the conditioning agent 104 by the circulation within the conveyor screw and is thus advantageously prepared for further processing in additive manufacturing. The particulate material thus already emerges from the conveyor screw with the desired moisture content.

[0069] Combining the transport path of a screw conveyor with humidification: The screw conveyor not only handles the task of material transport, but also homogenization and mixing. A defined amount of water is added at the beginning of the screw conveyor, which is automatically distributed evenly throughout the powder along the transport path. Approximately 1 kg of powder is conveyed through the screw every minute and simultaneously brought to the desired moisture content. Approximately 10 g of water per kg of conveyed powder results in a relative humidity of the powder of approximately 50%. The preferred amount of liquid is 2 to 10 g per 1 kg of particulate material. In addition to a predetermined supply of conditioning agent based on empirical values, a control loop would also be possible that controls the amount of conditioning agent based on measurements before and / or after the screw conveyor. Alternatively, recipes could be loaded and executed based on the starting material and its properties.The properties of the raw material can be stored and read using an RFID chip. The moisture content, which can serve as the basis for a control loop, could also be calculated by load cells in the particle and conditioning agent containers based on the weight gain and loss. Alternatively, the current required by the screw conveyor drive motor can provide information about the flowability of the powder. If the powder is free-flowing, the motor requires less power to rotate. Figure description Fig. 2: Figure 2 shows a cross-section of the screw conveyor to illustrate the material flow within the screw. The screw conveyor consists of a cylindrical housing 207 and the spiral 206. This spiral is designed without a core, thus leaving a free space inside the screw 208.At the beginning of the screw, the unconditioned particulate material 201 is introduced directly into the screw along with the conditioning agent 202. The rotation of the spiral conveys the particulate material along the screw 205. The rotating motion of the spiral causes the material to reach the upper points of the spiral and, at the highest point, fall a short distance downwards through the free space in the center of the screw 204. This promotes mixing and homogenization. At the end of the conveying path, the conditioned particulate material then exits the screw 203.

[0070] Screw conveyor design: The screw conveyor used for moistening is 230 cm long and 5 cm in diameter. The screw is curved and has a flat initial pitch. The pitch increases towards the end of the screw and is approximately 300% in the upper section. The feed rate is determined by the speed of the screw. Furthermore, the power consumption of the motor driving the screw can be used to determine the flowability of the powder, allowing the amount of conditioning agent to be adjusted accordingly.

[0071] In addition to water, flow aid could also be used as a conditioning agent. The amount of flow aid could be measured at the beginning of the screw using an infrared sensor, and an appropriate amount of flow aid could be added to the screw as needed.

[0072] Figure description Fig. 3: Figure 3 schematically illustrates the introduction of the conditioning agent at the beginning of the screw conveyor. The conditioning agent is located in a container with a pipe connection below the liquid level 301. The agent is pumped by a hydraulic pump via a hose into a collecting funnel 303 at the base of the screw conveyor. The conditioning agent, in this case distilled water, is injected 307 into the screw conveyor in a defined quantity via an angled nozzle 304. Furthermore, the unconditioned particulate material 306 is introduced into the screw conveyor via the collecting funnel.

[0073] The water is pumped in pulses (through a hose) from a water tank into the screw conveyor. The water quantity can be controlled by the pulse width of the pump's power supply. Controlled by a PWM signal. In the example, the pump that pumps the conditioning agent into the screw conveyor is switched on for 0.01 seconds and discharged for 0.74 to 1.24 seconds, depending on the starting particle material. Different recipes with different water quantities can be used. The water quantity can be adjusted depending on the moisture content of the starting powder. A distinction can be made between build chamber powder and overfeed powder, and the required moisture content can be added accordingly.

[0074] Figure Description Fig. 4: Figure 4 shows the use and structure of a measuring unit for monitoring particle moisture in a container 404 for the particulate material 403. Depending on the fill level of the particulate material, the measuring unit is located in the air or buried in the material. The measuring unit consists of a downwardly open cylindrical protective container 402 and a measuring head 401.

[0075] Capacitive moisture meters, among others, are used for the quick and cost-effective determination of the material moisture content of bulk materials. The filler of a capacitive moisture meter consists of two capacitor plates (electrodes) between which an electric field is created when a voltage is applied. The space between the electrodes is filled with a dielectric (air) that has a specific dielectric constant. If the dielectric constant of the dielectric changes due to a change in humidity, a conclusion can be drawn about the water content in the air. To prevent dirt from affecting the measurement, the electrodes are protected by a protective cap made of a porous material. When measuring the moisture content of bulk materials, the measuring head is inserted into the bulk material, whereby the partial water vapor pressure in the measuring head equalizes with the partial water vapor pressure in the intergranular volume of the bulk material.

[0076] When measuring moisture in powders, it can happen that the powder particles are smaller than the pores of the protective cap. This can lead to the protective cap becoming clogged or to powder particles getting into the measuring head, which can falsify the measurement results. This problem is solved by placing the measuring head (401) in a protective container (402) that is open at the bottom. A storage area forms in the protective container in which no air movement occurs due to a pressure difference. However, the exchange of the water molecules present in the air (air humidity) can take place unhindered due to a difference in the water vapor partial pressures of the intergranular volume, the protective container, and the measuring head. Since the moving mass of the air humidity and its speed are relatively small, no powder particles can be entrained. This means that the measuring head does not come into contact with powder and the measurement results are not falsified.

[0077] Figure description Fig. 5: Figure 5 shows the use of a measuring unit for monitoring the particle moisture content in a container 505 for the particulate material 504 with a connected nebulizer 501 to maintain the moisture content previously introduced into the conveyor screw. Depending on the moisture content measured by the measuring unit 502, a mist 503 is generated and introduced into the container with the particulate material to prevent the conditioned particulate material from drying out.

[0078] List of reference symbols

Claims

Patent claims 1. Device for moistening or conditioning particulate material suitable for additive manufacturing, comprising or consisting of a conveying device for particulate material, a liquid supply means and / or conditioning agent supply means for dispensing liquid and / or conditioning agent, a particle supply means and preferably a particle collecting means.

2. Device for moistening or conditioning particulate material suitable for additive manufacturing, further comprising one or more means for measuring the moisture in the particulate material.

3. Device according to claim 1 or 2, wherein the liquid is water and the conditioning agent is a flux, an antistatic agent, antioxidants or a coolant and / or wherein the conveying device is a screw conveyor or pneumatic conveyor and / or wherein the liquid supply means is a pipe, a flexible line or a nozzle and / or wherein the particle supply means is a particle reservoir with dispensing means, the dispensing means preferably being a particle dosing means.

4. Device according to one of the preceding claims, wherein the means for measuring the moisture in the particulate material is a capacitive moisture sensor or a microwave moisture sensor which is placed directly in a particulate material reservoir, preferably the sensor is placed in a container, preferably in a tube, which preferably has an opening at the bottom.

5. Device according to one of the preceding claims, further comprising a control circuit for measuring the output humidity and / or input humidity and / or of the conditioning agent and preferably an adjustment of the dispensing of the liquid depending on an actual and target humidity, optionally controlled by an algorithm and / or further comprising a dispensing means for one or more conditioning agents, wherein the conditioning agent is a gas, a gas mixture, a chemical, a mixture, a solution, an emulsion and / or a suspension.

6. Device according to one of the preceding claims, wherein the conveying device, preferably the conveyor screw, has one or more openings for liquid supply means and / or conditioning agent supply means for dispensing liquid and / or conditioning agent, preferably wherein the device further has a device for regulating the air humidity in the particulate material reservoir mounted in the particulate material reservoir.

7. Device according to one of the preceding claims, wherein the additive manufacturing process is a powder bed fusion process.

8. A method for moistening or conditioning particulate material suitable for additive manufacturing, comprising the steps of: a. introducing particulate material into a conveyor device, preferably a conveyor screw, from a particle feed means, preferably a Particulate material reservoir by means of dosing means, b. Conveying the particulate material in the conveying means, c. Addition of liquid and / or conditioning agent into the conveying device from a liquid supply means and / or a dispensing means for one or more conditioning agents onto or into the particulate material, d. Mixing and homogenizing the liquid with the particulate material during conveying, e. Discharge of the thus moistened particulate material from the conveying device, optionally into a particle collecting means, f. Optionally measuring the moisture in the particulate material before introduction into and / or discharge from the conveying device, preferably controlling the liquid discharge onto or into the particulate material by means of a control loop, preferably an algorithm.

9. The method according to claim 8, wherein the liquid supply means is a pipe, a flexible line, a nozzle and / or wherein the particle supply means is a particle reservoir with dispensing means, preferably a particle dosing means, preferably wherein a capacitive humidity sensor or a microwave humidity sensor is used as the means for measuring the humidity in the particle material, which is placed directly in a particle material reservoir, preferably the sensor is placed in a container, preferably in a pipe, which preferably has an opening at the bottom.

10. The method according to any one of claims 8 - 9, wherein the liquid is water and the conditioning agent is a gas, a gas mixture, a chemical, a mixture, a solution, an emulsion and / or a suspension, preferably wherein the liquid and / or the conditioning agent are dispensed in portions or continuously, preferably wherein the liquid and / or the conditioning agent are dispensed into or onto the particulate material by means of a pump, preferably wherein the liquid and / or the conditioning agent are introduced into the conveying device, preferably the conveyor screw, through one or more openings for liquid supply means and / or conditioning agent supply means, preferably wherein the additive manufacturing process is a powder bed fusion process, preferably wherein a device for regulating the air humidity in the particulate material reservoir is further mounted in the particulate material reservoir.

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