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WO2024246120A1 - Système de transport de produits en vrac et procédé de transport de produits en vrac - Google Patents

Système de transport de produits en vrac et procédé de transport de produits en vrac Download PDF

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Publication number
WO2024246120A1
WO2024246120A1 PCT/EP2024/064754 EP2024064754W WO2024246120A1 WO 2024246120 A1 WO2024246120 A1 WO 2024246120A1 EP 2024064754 W EP2024064754 W EP 2024064754W WO 2024246120 A1 WO2024246120 A1 WO 2024246120A1
Authority
WO
WIPO (PCT)
Prior art keywords
conveying
bulk material
gas
powder
tank
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
PCT/EP2024/064754
Other languages
German (de)
English (en)
Inventor
Daniel KOPSCHINSKI
Martin Robert BENTZ-VON DOGLOW
Marcel OVERBERG
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Nikon SLM Solutions AG
Original Assignee
Nikon SLM Solutions AG
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from DE102023114326.3A external-priority patent/DE102023114326B3/de
Priority claimed from DE102023114305.0A external-priority patent/DE102023114305A1/de
Priority claimed from DE102023114306.9A external-priority patent/DE102023114306A1/de
Application filed by Nikon SLM Solutions AG filed Critical Nikon SLM Solutions AG
Publication of WO2024246120A1 publication Critical patent/WO2024246120A1/fr
Anticipated expiration legal-status Critical
Pending legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/20—Direct sintering or melting
    • B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B13/00—Grading or sorting solid materials by dry methods, not otherwise provided for; Sorting articles otherwise than by indirectly controlled devices
    • B07B13/14—Details or accessories
    • B07B13/18—Control
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/70—Recycling
    • B22F10/73—Recycling of powder
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/80—Data acquisition or data processing
    • B22F10/85—Data acquisition or data processing for controlling or regulating additive manufacturing processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/50—Means for feeding of material, e.g. heads
    • B22F12/57—Metering means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/80—Plants, production lines or modules
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/90—Means for process control, e.g. cameras or sensors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/10—Processes of additive manufacturing
    • B29C64/141—Processes of additive manufacturing using only solid materials
    • B29C64/153—Processes of additive manufacturing using only solid materials using layers of powder being selectively joined, e.g. by selective laser sintering or melting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/30—Auxiliary operations or equipment
    • B29C64/307—Handling of material to be used in additive manufacturing
    • B29C64/321—Feeding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/30—Auxiliary operations or equipment
    • B29C64/357—Recycling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y40/00—Auxiliary operations or equipment, e.g. for material handling
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y50/00—Data acquisition or data processing for additive manufacturing
    • B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65G—TRANSPORT OR STORAGE DEVICES, e.g. CONVEYORS FOR LOADING OR TIPPING, SHOP CONVEYOR SYSTEMS OR PNEUMATIC TUBE CONVEYORS
    • B65G53/00—Conveying materials in bulk through troughs, pipes or tubes by floating the materials or by flow of gas, liquid or foam
    • B65G53/34—Details
    • B65G53/66—Use of indicator or control devices, e.g. for controlling gas pressure, for controlling proportions of material and gas, for indicating or preventing jamming of material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B1/00—Sieving, screening, sifting, or sorting solid materials using networks, gratings, grids, or the like
    • B07B1/46—Constructional details of screens in general; Cleaning or heating of screens
    • B07B1/50—Cleaning
    • B07B1/54—Cleaning with beating devices
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B07—SEPARATING SOLIDS FROM SOLIDS; SORTING
    • B07B—SEPARATING SOLIDS FROM SOLIDS BY SIEVING, SCREENING, SIFTING OR BY USING GAS CURRENTS; SEPARATING BY OTHER DRY METHODS APPLICABLE TO BULK MATERIAL, e.g. LOOSE ARTICLES FIT TO BE HANDLED LIKE BULK MATERIAL
    • B07B2220/00—Type of materials being separated
    • B07B2220/02—Plastics
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/50—Means for feeding of material, e.g. heads
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/70—Gas flow means
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F2202/00—Treatment under specific physical conditions
    • B22F2202/15—Use of fluidised beds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P10/00—Technologies related to metal processing
    • Y02P10/25—Process efficiency

Definitions

  • the invention relates to a bulk material conveying system and a method for conveying bulk material.
  • the invention particularly relates to the conveying of raw material powder in a system for producing a three-dimensional workpiece by irradiating layers of the raw material powder with electromagnetic radiation or particle radiation (for example a system for selective laser melting).
  • the molding compound can initially be present as granules, as powder or as liquid molding compound and can be solidified selectively or, in other words, site-specifically as a result of the irradiation.
  • the molding compound can be a bulk material such as raw material powder.
  • the molding compound can comprise, for example, ceramic, metal or plastic materials and also material mixtures thereof.
  • a variant of generative layer construction processes concerns the so-called laser beam melting in the powder bed (also: selective laser melting), in which metallic and/or ceramic raw material powder materials in particular are solidified into three-dimensional workpieces by irradiation with a laser beam.
  • raw material powder material in the form of a raw material powder layer to a carrier and to irradiate it selectively and in accordance with the geometry of the workpiece layer currently being produced.
  • the laser radiation penetrates the raw material powder material and solidifies it, for example as a result of heating, which causes melting or sintering.
  • a new layer of unprocessed raw material powder material is applied to the workpiece layer already produced.
  • Known coating arrangements or powder application devices can be used for this purpose.
  • the now topmost and still unprocessed raw material powder layer is then irradiated again.
  • the workpiece is then built up layer by layer, with each layer defining a cross-sectional area and/or a contour of the workpiece.
  • CAD or comparable workpiece data in order to produce the workpieces essentially automatically.
  • the present disclosure is generally directed to a bulk material conveying system for conveying bulk material.
  • the bulk material can be raw material powder for use in one of the systems described above for producing a three-dimensional workpiece.
  • a so-called pneumatic conveying system is typically used.
  • a gas flow of conveying gas for example air or a protective gas such as argon or an air-protective gas mixture
  • a conveying device e.g. a pump or a blower
  • the conveying line can in particular form a closed circuit so that the gas flow is conveyed in a circle (so-called conveying circuit).
  • a predetermined dose of bulk material per unit time is fed into the gas flow from a source tank by means of a dosing device. It is also possible for bulk material from several source tanks to be fed into the gas flow at the same time.
  • a gas-bulk material mixture is conveyed through the conveying line to a point in the conveying circuit where a separating device (for example a cyclone) is located.
  • a separating device for example a cyclone
  • the bulk material is separated from the gas-bulk material mixture as completely as possible and fed to a target tank.
  • a cyclone can be located above the target tank, whereby the separated bulk material falls into the target tank due to gravity (so-called gravity conveying).
  • a problem with pneumatic bulk material conveying is that operating parameters of the system and/or a property of the bulk material (for example a material of a bulk material powder used and its conveying properties) can change during operation or between individual conveying processes.
  • certain operating parameters of the bulk material conveying system must be adjusted, in particular the speed of the gas flow, which is determined by the conveying device.
  • Another operating parameter of the bulk material conveying system that may need to be adjusted is the dose of bulk material per unit time that is conveyed into the gas flow.
  • the object of the invention is therefore to provide a bulk material conveying system and a corresponding method for conveying bulk material, which solve at least one of the problems described above or a problem related thereto.
  • a reliable and simple determination of a target value of the gas velocity is desirable, which can react to a change in one or more operating parameters.
  • the invention therefore relates to a bulk material conveying system, in particular for conveying raw material powder in a system for producing a three-dimensional workpiece by irradiating layers of the raw material powder with electromagnetic radiation or particle radiation.
  • the bulk material conveying system comprises a conveying line which is designed to convey a gas flow and, at least in sections, a bulk material flow driven by the gas flow, and a dosing device which is designed to supply the gas flow with a predetermined dose of bulk material per unit of time. The dose is determined by a control value applied to the dosing device.
  • the bulk material conveying system further comprises a conveying device which is designed to convey the gas flow through the conveying line and at least one measuring device for measuring at least one characteristic of the gas flow.
  • the bulk material conveying system further comprises a control device which is designed to determine a gas density of the gas flow based on the measured at least one characteristic of the gas flow, determine a bulk material mass flow of the bulk material flow, based on the control value applied to the dosing device, determining a target velocity of the gas flow based on the gas density and based on the bulk material mass flow, and controlling the conveying device to convey the gas flow at the determined target velocity.
  • a control device which is designed to determine a gas density of the gas flow based on the measured at least one characteristic of the gas flow, determine a bulk material mass flow of the bulk material flow, based on the control value applied to the dosing device, determining a target velocity of the gas flow based on the gas density and based on the bulk material mass flow, and controlling the conveying device to convey the gas flow at the determined target velocity.
  • the bulk material conveying system can be set up to convey the bulk material pneumatically.
  • the system can in particular be a system for selective laser melting or sintering, which has, for example, one or more of the features described above.
  • the system can be a system for selective electron beam melting.
  • the conveyor line can, for example, comprise one or more pipes and/or one or more hoses and/or one or more connectors.
  • the conveyor line can be powder-tight and in particular gas- and powder-tight, so that no gas or powder can enter or leave the conveyor line (from the side) - except through the openings in the conveyor line.
  • conveying line is designed in sections to convey a bulk material flow driven by the gas flow can mean that only one section of an entire conveying circuit formed by the conveying line is designed to convey a gas-bulk material mixture.
  • the remaining part of the conveying circuit essentially only conveys gas (conveying gas), for example air, protective gas or an air-protective gas mixture.
  • the control value can be a voltage, a current, a pulse or another suitable signal (in particular an electrical signal) which can be varied in order to vary the dose delivered by the dosing device.
  • the conveying device can be a pump or a blower.
  • one or more filter devices can be provided in the conveying circuit which is formed by the conveying line, in particular for filtering bulk material or bulk material residues remaining in the gas flow.
  • the control device can comprise a computer, for example.
  • the control device can comprise a processor and a memory, wherein a program is stored on the memory which, when executed, causes the processor to carry out the method according to the second aspect.
  • the term bulk material mass flow is used here to indicate a physically quantifiable mass flow of the bulk material being conveyed (in kg/s). In contrast, the term bulk material flow describes (only) the presence of bulk material being conveyed through the conveying line.
  • the determination steps can each include one or more calculations. Measured variables, but also stored variables (for example standard values) can be included in the respective calculation.
  • the conveying device can be controlled in such a way that it reduces or increases the speed of the conveyed gas flow. In particular, for example, increasing the voltage applied to the conveying device can lead to the speed of the gas flow being increased. Since the gas flow conveys the bulk material, the speed of the gas flow also determines the speed of the conveyed bulk material.
  • the gas density can be determined based on at least one of the following parameters of the gas flow: oxygen content, pressure, temperature, dew point and humidity.
  • a corresponding sensor can be provided in the gas stream, which is set up to measure the respective parameter.
  • the gas density p can be determined using the following formula: where pmess is a measured pressure of the gas stream, Tmess is a measured temperature of the gas stream, p n is a predetermined normal pressure, T n is a predetermined normal temperature and pmixture is given by the following formula: where pair is a known density of air which is part of the gas stream, Pprotective gas is a known density of a protective gas which is part of the gas stream, oxygen contentair is a known oxygen content of the air and oxygen contentmeasured is a measured oxygen content of the gas stream.
  • Pmess and Tmess can each be measured by suitable sensors arranged in the gas flow. At least one or both of the sensors required for this can be arranged downstream of the conveying device, in particular between the conveying device and a source tank from which the bulk material is conveyed. In particular, at least one or both of the sensors can be arranged immediately downstream of the conveying device.
  • the normal pressure and the normal temperature can be predetermined standard values, for example the normal pressure can be 1013.25 mbar and the normal temperature can be 293.15 K. However, normal pressure and/or normal temperature can also be measured values of the ambient pressure or the ambient temperature.
  • the protective gas can be argon, for example, where the density Pprotective gas corresponds to a known density of the gas argon.
  • the density of air, the density of the protective gas used and the oxygen content of the air can be looked up in the relevant tables in the specialist literature.
  • the oxygen content of the air can also be a measured oxygen content of the ambient air.
  • Oxygen content measurement can be carried out by a suitable sensor arranged in the gas flow.
  • the sensor required for this can be arranged upstream of the conveying device, between a target tank into which the bulk material is conveyed, and the conveying device.
  • the sensor can be arranged immediately upstream of the conveying device.
  • the control value applied to the dosing device can be a motor speed of a motor of the dosing device, in particular a motor for driving a conveyor screw of the dosing device.
  • control value can also be a current or a voltage that is applied to the motor.
  • control value can represent any (e.g. electrical) signal that is suitable for changing the dose (more precisely: dose per time) delivered by the dosing device and in particular for setting it to a predetermined value.
  • the dosing device can, as described above, comprise a conveyor screw that is designed to is to convey bulk material from the original tank.
  • the dosing device can comprise at least one of the following elements: a rotary valve, a dosing slide and a valve, in particular a valve with a variable opening diameter.
  • Determining the desired velocity v S0 n of the gas flow may include calculating a saltation velocity based on the determined gas density and the determined bulk material mass flow. Determining the desired velocity Vsoii may be done using the following formula: desired ⁇ saltation "F ⁇ safety where Vsaitation is the calculated saltation velocity of the bulk material being conveyed and vsafety is a predetermined safety velocity.
  • the saltation speed can be a speed below which particles of the bulk material being conveyed (for example powder) start to fall down and accumulate on a bottom of the conveying line. To ensure that this does not happen, a predetermined safety speed can be added to the calculated saltation speed. In a way, this forms a safety margin from the saltation speed, which ensures that no deposition of bulk material takes place in the conveying line. As an alternative to adding the safety speed, the saltation speed can be multiplied by a safety factor.
  • Calculating the saltation rate can be done using the following formula: where M s is the determined bulk material mass flow in kg/s, g is a predetermined acceleration due to gravity in m/s 2 , D is a diameter of the conveying line in m, p is the determined gas density of the gas flow in kg/m 3 and a and b are parameters each dependent on a particle diameter d of the bulk material.
  • the predetermined acceleration due to gravity can correspond to the acceleration due to gravity on the earth's surface of 9.81 m/s 2 .
  • the parameters a and b can each be a predetermined and/or pre-stored constant for a respective bulk material.
  • the parameter a and/or the parameter b can be determined as a function of the particle diameter d of the bulk material used.
  • a formula for calculating the parameter a and/or a formula for calculating the parameter b can be dependent on the particle diameter d.
  • the particle diameter d can be taken from a specification of the bulk material used.
  • the particle diameter d can be stored, for example, in a memory of the control device.
  • a table can be stored in a memory of the control device in which the respective values for the particle diameter d of the respective powder are stored for different powder materials. In this way, a respective particle diameter d can be used when calculating the target speed.
  • the control of the conveying device for conveying the gas flow can be carried out at the determined target speed using a speed sensor for measuring a speed of the gas flow and a control loop, in particular comprising a PID controller.
  • a PID controller is a proportional-integral-derivative controller, whereby PID control is well known in control engineering for setting and maintaining a predetermined value (in this case the gas velocity) constant.
  • the control device can further be configured to determine whether at least one measured characteristic of the bulk material conveying system is above a predetermined maximum value for the respective characteristic, and if the at least one measured characteristic is above the predetermined maximum value, reducing the control value of the dosing device by a predetermined value.
  • the bulk material conveying system can comprise one or more sensors for measuring the respective parameter. Determining whether the at least one measured parameter is above the predetermined maximum value and the corresponding adjustment of the control value can be carried out after the steps of determining a gas density, determining a bulk material mass flow, determining a target speed and controlling the conveying device. These steps can be carried out again after adjusting the control value with the new control value. Thus, the determination (and if necessary adjustment) of the target speed and - if necessary - the adjustment of the control value can be carried out alternately. Reducing the control value means that the dosing device outputs a smaller dose of bulk material per unit time.
  • the control device can further be configured to increase the control value of the dosing device by a predetermined value if the at least one measured parameter is below the predetermined maximum value.
  • control value is increased by the predetermined value.
  • the control value can only be increased if all of the determined parameters do not exceed their associated maximum value. Increasing the control value means that the dosing device dispenses a higher dose of bulk material per unit of time.
  • the at least one parameter may include at least one of the following parameters: conveying speed, pump outlet pressure, pump power and dose of bulk material per unit time.
  • the respective parameter can be measured, for example, using a sensor provided for this purpose or determined in another way.
  • the parameter can be calculated based on at least one input value (e.g. an applied voltage) which is applied to an element of the powder conveying system (e.g. the conveying device).
  • the control device can be set up to terminate a conveying process by stopping the conveying device if at least one of the following events is detected: a source tank from which bulk material is removed by means of the dosing device is empty, a target tank into which the bulk material is conveyed is full, a predetermined maximum delivery time is exceeded and a total pressure loss of the conveying gas exceeds a predetermined limit.
  • the respective event can be detected, for example, using a corresponding sensor.
  • the events can be detected as follows.
  • a source tank from which bulk material is taken by means of the dosing device is empty; this can be determined using a corresponding level sensor (e.g. a capacitive sensor, a radar sensor, an ultrasonic sensor or an optical sensor).
  • a target tank into which the bulk material is conveyed is full; this can be determined using a corresponding level sensor (e.g. a capacitive sensor, a radar sensor, an ultrasonic sensor or an optical sensor).
  • a predetermined maximum conveying time has been exceeded; this can be determined using a corresponding timer that is started when conveying is started.
  • a total pressure loss of the conveying gas exceeds a predetermined limit value; this can be determined using one or more pressure sensors in the conveying line.
  • the bulk material conveying system may further comprise a pressure equalization tank coupled to the conveying line downstream of the conveying device and upstream of the dosing device.
  • the pressure compensation vessel can be designed to reduce an overpressure at an outlet of the conveying device (e.g. a pump).
  • the overpressure vessel can be provided at the outlet of the conveying device.
  • the bulk material conveying system can comprise at least a first conveying circuit for conveying raw material powder from a main storage facility into a first tank of the system for producing a three-dimensional workpiece by irradiating layers of the raw material powder with electromagnetic radiation or particle radiation.
  • a lower outlet of the first tank can be coupled to an upper inlet of an intermediate tank of the system, wherein a manufacturing process in a process chamber of the system is fed with powder from the intermediate tank.
  • An upper inlet of the main storage facility can be coupled to an outlet of a sieve for sieving the raw material powder.
  • the main storage can, for example, be a storage or tank permanently installed in the bulk material conveying system.
  • the main storage can be located at a lower height than the first tank.
  • the first conveying circuit can be activated by the control device by opening at least one valve, so that the conveying device conveys gas through this first conveying circuit.
  • the bulk material conveying system can be designed in such a way that powder can be fed to the sieve from a buffer container which is located above the sieve. Powder can be conveyed into the buffer container, for example, by means of a second conveying circuit from an overflow tank of the system and/or from an external tank.
  • the bulk material conveying system can comprise at least a second conveying circuit for conveying raw material powder from an overflow tank into a buffer tank.
  • the overflow tank can be configured to receive excess powder from the process chamber of the system for producing a three-dimensional workpiece by irradiating layers of the raw material powder with electromagnetic radiation or particle radiation.
  • a lower outlet of the buffer tank can be coupled to an inlet of a sieve for sieving the raw material powder.
  • the second conveying circuit can be activated by the control device by opening at least one valve so that the conveying device conveys gas through this second conveying circuit.
  • the overflow tank can be arranged, for example, in a lateral area next to a construction cylinder of the system, with the overflow tank being open at the top so that the excess powder can be pushed into the overflow tank, for example by means of a powder application device.
  • the bulk material conveying system may comprise at least a third conveying circuit for conveying raw material powder from an external tank into a buffer container.
  • the external tank may be detachably coupled or coupled to the bulk material conveying system.
  • a lower outlet of the buffer container may be coupled to an inlet of a sieve for sieving the raw material powder.
  • the third delivery circuit can be activated by the control device by opening at least one valve so that the delivery device can deliver gas through this third
  • the third conveyor circuit can be operated simultaneously with the second conveyor circuit, so that powder from the external tank and powder from the overflow tank are mixed together in an adjustable mixing ratio.
  • the mixing ratio can be set, for example, by the respective dosing devices of the respective containers (external tank, overflow tank).
  • the dosing device can be located at the outlet of each source tank and a cyclone can be located at the inlet of each target tank for separating the raw material powder from the gas stream and for feeding the raw material powder into the target tank.
  • the dosing device allows the bulk material flow to be introduced into the gas flow and the cyclone allows the bulk material to be removed from the gas flow again.
  • the invention relates to a method for conveying bulk material, in particular for conveying raw material powder in a system for producing a three-dimensional workpiece by irradiating layers of the raw material powder with electromagnetic radiation or particle radiation.
  • the method comprises conveying a gas flow and a bulk material flow driven by the gas flow through a conveying line and supplying a predetermined dose of bulk material per unit of time through a dosing device. The dose can be determined by a control value applied to the dosing device.
  • the method further comprises conveying the gas flow through the conveying line using a conveying device and measuring at least one characteristic of the gas flow using a measuring device.
  • the method further comprises determining a gas density of the gas flow based on the measured at least one characteristic of the gas flow and determining a bulk material mass flow of the bulk material flow based on the control value applied to the dosing device.
  • the method further comprises determining a desired velocity of the gas flow based on the gas density and based on the bulk material mass flow and controlling the conveying device to convey the gas flow at the determined desired velocity.
  • the bulk material conveying system according to the first aspect can be used for this purpose be configured to carry out the method for conveying bulk material according to the second aspect.
  • the gas density can be determined based on at least one of the following parameters of the gas flow: oxygen content, pressure, temperature, dew point and humidity.
  • the gas density p can be determined using the following formula: where pmess is a measured pressure of the gas stream, Tmess is a measured temperature of the gas stream, p n is a predetermined normal pressure, T n is a predetermined normal temperature and pmixture is given by the following formula: where pair is a known density of air which is part of the gas stream, Pprotective gas is a known density of a protective gas which is part of the gas stream, oxygen contentair is a known oxygen content of the air and oxygen contentmeasured is a measured oxygen content of the gas stream.
  • the control value applied to the dosing device can be a motor speed of a motor of the dosing device, in particular a motor for driving a conveyor screw of the dosing device.
  • Determining the desired velocity v S0 n of the gas flow may comprise calculating a saltation velocity based on the determined gas density and the determined bulk material mass flow, and determining the desired velocity Vsoii may be performed using the following formula: desired ⁇ saltation "F ⁇ safety where Vsaitation is the calculated saltation velocity of the bulk material being conveyed and vsafety is a predetermined safety velocity.
  • Calculating the saltation rate can be done using the following formula: where M s is the determined bulk material mass flow in kg/s, g is a predetermined acceleration due to gravity in m/s 2 , D is a diameter of the conveying line in m, p is the determined gas density of the gas flow in kg/m 3 and a and b are parameters each dependent on a particle diameter d of the bulk material.
  • Controlling the conveying device for conveying the gas flow at the determined target speed can be carried out using a speed sensor for measuring a speed of the gas flow and a control loop, in particular comprising a PID controller.
  • the method may further comprise: determining whether at least one measured characteristic of the bulk material conveying system is above a predetermined maximum value for the respective characteristic, and if the at least one measured characteristic is above the predetermined maximum value, reducing the control value of the dosing device by a predetermined value.
  • the method may further comprise, if the at least one measured parameter is below the predetermined maximum value, increasing the control value of the dosing device by a predetermined value.
  • the at least one parameter may include at least one of the following parameters: conveying speed, pump outlet pressure, pump power and dose of bulk material per unit time.
  • the method may further comprise terminating a conveying operation by stopping the conveying device if at least one of the following events is detected: a source tank from which bulk material is removed by means of the dosing device is empty, a target tank into which the bulk material is conveyed is full, a predetermined maximum conveying time is exceeded and a total pressure loss of the conveying gas exceeds a predetermined limit value.
  • the method may comprise conveying raw material powder through at least a first conveying circuit from a main storage facility into a first tank of the system for producing a three-dimensional workpiece by irradiating layers of the raw material powder with electromagnetic radiation or particle radiation.
  • a lower outlet of the first tank may be coupled to an upper inlet of an intermediate tank of the system, wherein a production process in a process chamber of the system is fed with powder from the intermediate tank.
  • An upper inlet of the main storage facility may be coupled to an outlet of a sieve for sieving the raw material powder.
  • the method may comprise conveying raw material powder through at least one second conveying circuit from an overflow tank into a buffer tank.
  • the overflow tank may be configured to receive excess powder from the process chamber of the system for producing a three-dimensional workpiece by irradiating layers of the raw material powder with electromagnetic radiation or particle radiation.
  • a lower outlet of the buffer tank may be coupled to an inlet of a sieve for sieving the raw material powder.
  • the method may include conveying raw material powder through at least a third conveying circuit from an external tank into a buffer container.
  • the external tank may be detachably coupled or coupled to the bulk material conveying system.
  • a lower outlet of the buffer container may be coupled to an inlet of a sieve for sieving the raw material powder.
  • the dosing device can be located at the outlet of each source tank.
  • a cyclone can be located at the inlet of each target tank to separate the raw material powder from the gas stream and to feed the raw material powder into the target tank.
  • the system described here for producing a three-dimensional workpiece by irradiating layers of the raw material powder with electromagnetic radiation or particle radiation can, for example, comprise a carrier device for applying the powder in several layers so that a powder bed is formed. Furthermore, one or more powder application devices can be provided for applying the powder and, if necessary, for applying powder of different materials. A separate powder application device can be provided for each material.
  • the carrier device can be moved vertically by means of a lifting device. down so that the top layer of powder always remains at the same height in relation to a construction chamber of the system.
  • the system can comprise one or more irradiation units.
  • the irradiation units each comprise a beam source (in particular a laser beam source) and an optics with one or more optical components for shaping and deflecting the beam (e.g.
  • the beam source can be located outside the respective irradiation unit, with the beam being fed to the irradiation unit via an optical conductor (e.g. glass fiber).
  • an optical conductor e.g. glass fiber
  • Figure 1 a system for producing a three-dimensional workpiece by
  • Irradiating layers of a raw material powder with electromagnetic radiation or particle radiation which is equipped with a bulk material conveying system
  • Figure 2 a schematic representation of a dosing device in the form of a
  • Conveyor screw where parameters of the conveyor screw are specified for calculating a mass flow conveyed by the conveyor screw
  • Figure 3 a flow chart of a limit control process
  • Figure 4 a schematic representation of a bulk material conveying system for a selective laser melting plant, which enables at least three conveying processes a, b and c;
  • Figure 5 a representation in which the conveying process a of the system of Fig. 4 is highlighted;
  • Figure 6 a representation in which the conveying process b of the system of Fig. 4 is highlighted.
  • Figure 7 a representation highlighting the conveying process c of the system of Fig. 4.
  • Fig. 1 shows a system 1100 for producing a three-dimensional workpiece by irradiating layers of a raw material powder with electromagnetic radiation or particle radiation.
  • the system 1100 is a system for producing a three-dimensional workpiece by means of an additive manufacturing process in which a raw material powder is used, for example selective laser melting or selective laser sintering.
  • the bulk material conveying system of the present disclosure is described below in connection with an above-mentioned system, the bulk material conveying system or the method for conveying bulk material is not limited to use in connection with an additive manufacturing system.
  • the advantages resulting from the bulk material conveying system or the associated method presented here are generally applicable to situations in which bulk material is conveyed by means of pneumatic conveying.
  • the system 1100 comprises a carrier 1002 and a powder application device 1003 for applying a raw material powder 1004 to the carrier 1002.
  • the carrier 1002 and the powder application device 1003 are located within a process chamber 1011, which can be sealed from the ambient atmosphere, i.e., from the environment of the process chamber 1011.
  • the system 1100 further comprises an irradiation device 1005 for selectively irradiating electromagnetic radiation or particle radiation onto the raw material powder 1004, which has been applied to the carrier 1002.
  • the process chamber 1011 i.e. the powder application device 1003, is supplied with raw material powder 1004 by means of a bulk material conveying system 1001, which is described in detail below.
  • the bulk material conveying system 1001 is a powder conveying system.
  • the bulk material conveying system 1001 comprises a powder storage 1006 in which the raw material powder 1004, which is supplied to the process chamber 1011, is stored.
  • the powder storage 1006 is connected to a conveying line 1007 via a metering device 1008.
  • a gas stream 1009 is conveyed through the conveying line 1007 by means of a conveying device 1019 along a direction which is indicated by an arrow in Fig. 1.
  • a conveying device 1019 along a direction which is indicated by an arrow in Fig. 1.
  • the conveying device 1009 is designed in the form of a vacuum pump.
  • the dosing device 1008 is designed to dispense a desired dose of raw material powder 1004 into the gas stream 1009 flowing through the conveyor line 1007.
  • the dosing device 1008 comprises a first powder valve 1021, which is provided with a continuously variable flow cross-section, so that the amount of powder 1004 that is introduced into the gas stream 1009 per unit of time via a dosing opening 1023 of the dosing device 1008 can be continuously varied.
  • a control value can be applied to the dosing device 1008 by a control device 1040 described further below, which determines the dose dispensed per time.
  • the control value determines the cross-section and thus the dose.
  • the valve 1021 can be replaced by a conveyor screw with an associated motor for driving the conveyor screw.
  • the control value determines the speed of the motor and thus the dose delivered.
  • the raw material powder-gas mixture flowing through the conveying line 1007 downstream of the dosing device 1008 is conveyed to a cyclone 1010 which serves as a separating device.
  • the cyclone 1010 comprises an inlet 1020 which enables a tangential inflow of the raw material powder-gas mixture into a conical separation chamber 1022.
  • Powder particles 1004 which fall out of the rotating flow of the raw material powder-gas mixture which forms within the conical separation chamber 1022 are discharged from the cyclone 1010 by means of a powder outlet 1024 which is located in a lower region of the cyclone 1010.
  • These powder particles 1004 are fed to the process chamber 1011, i.e. the powder application device 1003, by means of a connecting line 1026 which connects the powder outlet 1024 of the cyclone 1010 with a powder inlet 1028 of the process chamber 1011.
  • a second powder valve 1030 is provided in the connecting line 1026.
  • the second powder valve 1030 is also equipped with a continuously variable flow cross-section, so that the amount of powder 1004 that is fed to the process chamber 1011 from the powder outlet 1024 of the cyclone 1010 can be continuously varied.
  • the second powder valve 1030 can also (like the first powder valve) be replaced by a conveyor screw with an associated motor.
  • powder is thus conveyed from an original tank formed by the powder reservoir 1006 into a target tank, wherein the target tank can be viewed, for example, as the volume of the connecting line 1026 below the powder valve 1030.
  • this volume represents a powder container for the powder application device 1003, from which the powder application device 1003 is supplied with powder for the application of individual layers.
  • this powder reservoir (and thus the target tank) can be integrated into the powder application device 1003.
  • the gas which was separated from the powder particles 1004 in the cyclone 1010 is fed back into the conveying line 1007 via a gas outlet 1032 of the cyclone 1010.
  • the gas outlet 1032 is arranged in an upper part of the cyclone 1010.
  • a filter unit 1014 is arranged in the conveyor line 1007 downstream of the cyclone 1010.
  • the filter unit 1014 comprises a replaceable filter 1013 which is adapted to filter out remaining raw material powder particles 1004 which are in the gas stream 1009 leaving the gas outlet 1032.
  • the bulk material conveying system 1001 further comprises a measuring device 1050 for measuring a characteristic of the gas flow which is conveyed in the conveying line 1007.
  • the measuring device 1050 is arranged immediately downstream of the conveying device 1019 and the measuring device 1050 is a pressure sensor for measuring a pressure (gas pressure) within the conveying line 1007.
  • further measuring devices 1015, 1016, 1017 and 1018 are provided along the conveying line 1007.
  • the measuring device 1018 is a temperature sensor for measuring a temperature of the gas flow.
  • the measuring device 1015 is an oxygen sensor for measuring an oxygen content of the gas flow.
  • the measuring devices 1016 and 1017 can each be further sensors for measuring one of the aforementioned properties (pressure, temperature, oxygen content).
  • the measuring devices 1016 and 1017 can each be, independently of one another, a sensor for measuring a flow rate, a presence of bulk material (e.g. capacitive sensor or ultrasonic sensor), a dew point, etc. Apart from the measuring devices 1050 and 1015 to 1018, fewer or several sensors can be provided. Furthermore, the measuring devices can be provided at another location in the conveyor line.
  • the pressure sensor 1050, the temperature sensor 1018 and the oxygen sensor 1015 are particularly relevant for the functioning of the control device 1040 described here (see below).
  • the bulk material conveying system 1001 comprises a control device 1040.
  • the control device 1040 controls the operation of the elements of the bulk material conveying system, in particular all elements that can be controlled.
  • the control device 1040 controls the conveying device 1019 and can control it in particular in such a way that a predetermined flow rate of the conveyed gas is set, for example by applying a voltage value set by the control device 1040.
  • the control device 1040 is able to increase or decrease the flow rate by a predetermined value.
  • the control device 1040 also controls the dosing device 1008.
  • the control device 1040 applies a predetermined control value to the dosing device 1008, which results in the dosing device releasing a predetermined dose of raw material powder per unit of time into the gas flow.
  • the control device 1040 is able to increase or decrease a currently conveyed dose by a predetermined value.
  • the control device 1040 also receives the measurement data from all measuring devices.
  • the control device 1040 also controls the valve 1030.
  • the control device 1040 can also be configured to control the entire operation of the system 1010, i.e. the exposure by means of the irradiation device 1005, the powder application by means of the powder application device 1003, lowering of the carrier 1002, etc.
  • the controller 1040 To determine a suitable setpoint of the gas velocity in the delivery line 1007 and to set a velocity corresponding to the setpoint, the controller 1040 performs the following steps:
  • the control device 1040 calculates a gas density of the gas flow based on a measured characteristic of the gas flow. There are several ways in which a gas density of the gas flow can be determined (for example calculated or estimated) using one or more measured characteristics. One possibility is shown below as an example.
  • the control device 1040 uses a measured pressure (measured by the pressure sensor 1050), a measured temperature (measured by the temperature sensor 1018) and a measured oxygen content (measured by the oxygen sensor 1015).
  • the values for normal pressure and normal temperature can also be replaced by measured values of the environment (surrounding atmosphere) of the bulk material conveying system.
  • pmixture is obtained from the following formula: where pair is a known density of air which is part of the gas stream, Pprotective gas is a known density of a protective gas which is part of the gas stream, oxygen content air is a known oxygen content of the air and oxygen content measurement is the oxygen content of the gas flow.
  • Pprotective gas is a known density of a protective gas which is part of the gas stream
  • oxygen content air is a known oxygen content of the air
  • oxygen content measurement is the oxygen content of the gas flow.
  • the oxygen content of the ambient atmosphere can be measured and used.
  • the control device 1040 determines a bulk material mass flow of the bulk material flow based on the control value applied to the dosing device 1008.
  • the bulk material mass flow is a powder mass flow.
  • the mass flow is specified in kg/s, for example.
  • the determination of the bulk material mass flow depends on the dosing device 1009 used and in particular on its geometry.
  • an associated volume flow of the bulk material being conveyed can be calculated or read from a table, for example, depending on an applied control value (e.g. rotation speed of a conveyor screw).
  • an applied control value e.g. rotation speed of a conveyor screw
  • there can be a linear dependency between the control value and the volume flow whereby a factor that characterizes the linear dependency can have been determined beforehand by means of calibration.
  • the desired mass flow in kg/s can be calculated using a known density (kg/m 3 ) of the bulk material being conveyed.
  • a calibration table or a way of calculating the volume flow based on a given control value can be found, for example, in a manual or a specification of the dosing device 1009.
  • the dosing device 1009 can be calibrated to determine a dependency between control value and volume flow.
  • the bulk material mass flow can also be calculated.
  • a corresponding calculation is shown below using the example of a screw conveyor.
  • the bulk material mass flow is calculated using the following formula:
  • M s is the bulk material mass flow
  • D z is an outer diameter of the screw conveyor
  • Gw is a height of the screw wall
  • H w ,i is a first screw spacing
  • e is a thickness of the screw wall
  • n m is a rotation speed of the screw conveyor
  • i is a transmission ratio
  • p s is a bulk density.
  • Fig. 2 shows a screw conveyor and associated parameters.
  • the controller 1040 determines a desired velocity of the gas flow based on the gas density determined in step A and based on the bulk material mass flow determined in step B.
  • Determining the target velocity v S0 n of the gas flow may include calculating a saltation velocity based on the determined gas density and the determined bulk material mass flow. Determining the target velocity v S0 n is carried out according to one embodiment using the following formula: target ⁇ saltation " ⁇ safety where Vsaitation is the calculated saltation velocity of the conveyed bulk material and vsafety is a predetermined safety velocity.
  • the saltation speed is a speed below which particles of the bulk material being conveyed (e.g. powder) begin to fall down and accumulate on a bottom of the conveying line 1007.
  • a predetermined safety speed is added to the calculated saltation speed. In a way, this forms a safety margin from the saltation speed, which ensures that no deposition of bulk material takes place in the conveying line 1007.
  • a predetermined safety factor can be multiplied by the saltation speed (e.g. 1.1 or 1.2).
  • the saltation rate is calculated by the controller 1040 using the following formula:
  • M s is the specific bulk material mass flow in kg/s
  • g is a predetermined acceleration due to gravity in m/s 2
  • D is a diameter of the conveyor line in m
  • p is the specific gas density of the gas flow in kg/m 3
  • a and b are parameters that are each dependent on a particle diameter d of the bulk material.
  • the parameters a and b can, for example, each be stored as constants for the bulk material used in a memory of the control device. Furthermore, at least one of the two parameters a and b can be calculated, whereby the respective calculation is dependent on the particle diameter d of the bulk material used.
  • the particle diameter d is taken from a specification of the bulk material used, for example a data sheet of the powder used.
  • the particle diameter d can also be stored, for example, in a memory of the control device 1040.
  • a table can be stored in the memory of the control device 1040 in which the respective values for the particle diameter d of the respective powder are stored for different powder materials. In this way, a respective particle diameter d can be used when calculating the target speed by entering or selecting the powder used via a user interface of the control device 1040.
  • the control device 1040 controls the conveying device 1019 to convey the gas flow at the target speed determined in step C.
  • a signal with a predetermined voltage value or a predetermined frequency is applied to the conveying device 1019, it being known that the voltage value or the frequency leads to the desired conveying speed of the conveying device 1019.
  • a control loop can be used which provides a measured gas velocity value a speed sensor is taken into account.
  • sensor 1016 or 1017 can be a corresponding speed sensor.
  • a PID controller can be used to regulate the desired value of the target speed.
  • an operating point for bulk material conveyance i.e. a conveying speed of the conveying gas and thus a conveying speed of the conveyed bulk material
  • this involves using data that is stored for different types of powder in a memory of the control device 1040 (for example, the bulk density and the particle diameter of the powder).
  • it is possible to react to changing operating parameters, in particular to changes in measured values, for example the oxygen content, the pressure and/or the temperature within the conveying line 1007. It is also possible to react to a change in the conveyed mass flow of the bulk material by adjusting the speed of the gas flow.
  • the above steps A to D which are carried out by the control device 1040, can be followed by a so-called limit value control.
  • this is optional and only the determination of the target speed can be carried out according to steps A to D.
  • the control device 1040 is set up to determine whether at least one measured parameter of the bulk material conveying system 1001 is above a predetermined maximum value for the respective parameter. If the at least one measured parameter is above the predetermined maximum value, the control device 1040 reduces the control value of the dosing device 1008 by a predetermined value so that it releases a smaller dose of bulk material per unit of time into the gas stream.
  • FIG. 3 shows a flow chart of a process performed by the controller 1040 after determining the target speed and controlling the conveyor.
  • step 1202 it is checked whether a measured conveyor speed is below a predetermined maximum value.
  • a speed sensor in the gas stream or in the gas-powder mixture stream is used, for example the sensor 1016 or 1017 in Fig. 1.
  • step 1204 it is queried whether a measured pump outlet pressure is below a predetermined maximum value.
  • a pressure sensor in the gas stream downstream of the pump 1019 is used, for example the sensor 1050 in Fig. 1.
  • step 1206 it is queried whether a pump power consumed by the pump 1019 is below a predetermined maximum value.
  • step 1208 in which it is queried whether a dose of bulk material dispensed by the dosing device 1008 per time is within a predetermined maximum range.
  • step 1208 If it is determined in step 1208 that the dose of bulk material dispensed per time is not within the predetermined maximum range ("no" after step 1208), then in step 1210 it is checked whether the dose is below the predetermined maximum range. If this is the case ("yes"), then in step 1212 the dose is increased by a predetermined value. If this is not the case ("no" after step 1210), then in step 1214 the dose is reduced by a predetermined value.
  • step 1216 checks whether the dose is less than a predetermined minimum. If this is not the case ("no"), the process is terminated. However, if this is the case ("yes" after step 1216), filter cleaning is carried out in step 1218.
  • the process also proceeds to the reduction of the dose of the dosing device 1008 according to step 1214 if in at least one of the queries 1202, 1204 and 1206 the result is "no" and thus a corresponding maximum value has been reached or exceeded.
  • a source tank 1006 from which bulk material is removed by means of the dosing device 1008 is empty
  • a target tank into which the bulk material is conveyed (or a corresponding cyclone 1010) is full, a predetermined maximum conveying time is exceeded and a total pressure loss of the conveying gas exceeds a predetermined limit value.
  • step A the method performed by the control device 1040 returns to step A (see above).
  • Fig. 4 shows a schematic representation of a bulk material conveying system which is used for conveying raw material powder in a system 1100 for producing a three-dimensional workpiece by irradiating layers of the raw material powder with electromagnetic radiation or particle radiation.
  • the bulk material conveying system of Fig. 4 represents a more detailed representation of a bulk material conveying system compared to Fig. 1, wherein certain components are shown and provided with reference numerals that may also be present in the system of Fig. 1, but are not explicitly described.
  • system of Fig. 4 also represents a more complex embodiment of a bulk material conveying system of the type described herein, in particular since several conveying processes can be carried out within the system, i.e. conveying processes from different source tanks to different destination tanks.
  • conveying processes from different source tanks to different destination tanks.
  • the exact structure and functioning of the bulk material conveying system is described below.
  • the method comprising steps A to D for adjusting a conveying speed can also be carried out in connection with the system of Fig. 4.
  • the bulk material conveying system of Fig. 4 also comprises a control device (not shown) for controlling the individual components of the system of Fig. 4.
  • the system 1100 corresponds, for example, to the system 1100 of Fig. 1 and - generally speaking - for example to a generally known system for additive manufacturing by means of selective laser melting or selective laser sintering.
  • Fig. 4 only the process chamber of the system 1100 is shown.
  • Raw material powder is fed by means of a loader 2104 from an intermediate tank 2102 (also: hopper) of the system 1100 to the process chamber (more precisely, a powder application device or a coater in the process chamber 1011).
  • Excess powder from the additive manufacturing process can be collected in a front overflow tank 2 or a rear overflow tank 3. This is in particular powder that is not needed when coating a new powder layer and is thus pushed by a powder application device into one of the overflow tanks 2 or 3.
  • An inlet valve 19 or 17 is located at an inlet of the respective powder tanks 2 or 3.
  • the overflow tanks 2 and 3 each comprise an outlet valve 34 or 25. Furthermore, a powder sensor 35 or 26 is provided in the area of the respective outlet of the overflow tanks 2 and 3. This monitors the inlet of an associated dosing device in the form of a dosing screw (or conveyor screw) 36 or 27. A powder sensor 37 or 28 is also provided at the outlet of the respective dosing screw 36 or 27.
  • the overflow tanks 2 and 3 each comprise an upper powder sensor 31 or 22 and a lower powder sensor 32 or 23 for monitoring the fill level of the respective overflow tank 2 or 3.
  • weighing cells 33 or 24 are provided on the respective overflow tanks 2 or 3.
  • a valve 30 or 21 is located on a respective upper side of the overflow tanks 2 or 3. The respective overflow tank 2 or 3 is connected to the pressure sensor 30 or 21.
  • valve 38 or 29 is connected to a delivery line.
  • another valve 38 or 29 at the respective access to the delivery line.
  • the process chamber is connected via corresponding valves 20 or 18 for pressure equalization to a line which connects the valve 30 or 21 with the valve 38 or 29.
  • the powder is conveyed from the overflow tanks 2 and 3 into a buffer tank 4 via the conveying line.
  • a cyclone 42 is located above the buffer tank 4 to separate the powder.
  • the conveying gas flows through the conveying line into a filter 41, where remaining powder particles are filtered out.
  • a compressed gas supply 39 is in contact with the filter 41, which can be switched on by the control device.
  • the conveying circuit leads back to the conveying device 79, which is provided in the form of a pump 79.
  • the path of the conveying gas, starting from the valve 40, leads in this order via a pump protection filter 74, a dew point sensor 75, an oxygen sensor 76, a redundant oxygen sensor 77 and a pressure sensor 78, more precisely a pressure sensor 78 on the pump suction side.
  • the conveying gas flows further via a pressure sensor 80 on the pump pressure side (not shown separately on the pump pressure side in the schematic representation of Fig. 4).
  • a pressure compensation tank 84 is provided downstream of the pressure sensor 80. This is equipped with an inert gas supply 82 and a safety valve 83.
  • the pressure compensation tank 84 serves to prevent excessive overpressure on the pump pressure side, i.e. downstream of the pump 79.
  • an exhaust valve 81 is provided, via which gas can be released from the conveying line. Further downstream of pressure compensation tank 84 there is a speed and temperature sensor 86. After venting access via valves 88 and 87, there is a possibility of directing the conveying gas to convey powder from a main reservoir 6 by opening a valve 72 and/or to convey powder from an external tank 8 and/or from one or both of the overflow tanks 2 and 3 by opening a valve 73.
  • valve 72 When valve 72 is opened, the conveying gas, after powder from the main reservoir 6 has been introduced into the gas flow via valve 60, flows to a cyclone 9, which is located above a first tank 1. Powder can be separated there for conveying into the first tank 1.
  • the conveying gas flows via the cyclone 42 and through filter 41 back to the pump 79, in the way described above (including via several sensors).
  • valve 73 When valve 73 is opened, powder from an external tank 8 can be added to the flow of conveying gas by a metering device 70 (conveyor screw 70). Furthermore, powder from the overflow tank 3 and/or powder from the overflow tank 2 can be added via the conveyor screw 27 and/or via the conveyor screw 36.
  • the conveying gas-powder mixture then flows - as previously described - to the cyclone 42, where it can be conveyed into the buffer container 4.
  • Powder leaving the conveyor screw 58 of the main storage 6 can be fed via a valve 60 either to the conveying gas of the conveying line which is associated with the valve 72, or alternatively or additionally via a valve 61 to the conveying gas of the conveying line which is associated with the valve 73.
  • Powder that is separated by the cyclone 9 enters the first tank 1 via an inlet valve 12. From there it is conveyed via an outlet valve 16 into an intermediate tank 2102 (also: hopper), for example by means of gravity conveying. From the intermediate tank 2102 it can be fed via the loader 2104 to the process chamber 1011 of the system 1100 and used in the additive manufacturing process.
  • an intermediate tank 2102 also: hopper
  • Powder which is separated by the cyclone 42 passes through an inlet valve 44 into a buffer container 4. From the buffer container 4, the powder can be fed through an outlet valve 48 to a sieving device 5 (by means of gravity conveyance).
  • the sieving device 5 serves to filter out larger particles and impurities from the powder, in particular if the powder which is fed to the sieving device 5 has already been used in an additive manufacturing process and, for example, comes from one or both of the overflow tanks 2 or 3.
  • the screening device 5 comprises a dosing device 49 in the form of a conveyor screw 49 in order to feed powder to be screened in a metered manner to an ultrasonic sieve 50 of the screening device 5.
  • Sieved powder or sieved particles pass through a line into an oversize container 7.
  • the sieved powder enters the main storage 6 via an inlet valve 52. From the main storage 6, the powder can be fed via an outlet valve 56 and via the conveyor screw 58 of the conveyor line for pneumatic conveying into the first tank 1, as described above.
  • an external tank 8 can be connected to the conveyor line, which can be a movable tank, for example, which can be connected to the conveyor line by means of a suitable interface.
  • a movable tank can be connected to the external tank 8 via an inlet valve 63 of the external tank 8, so that, for example, fresh powder can be fed to the system.
  • Powder from the external tank 8 is fed to the conveyor screw 70 via an outlet valve 67 of the external tank 8 and via an inlet valve 68 of a conveyor screw 70. From there, the powder enters the conveyor line and is conveyed by the gas flow when valve 73 is open.
  • Each of the powder containers 1, 2, 3, 4, 6 and 8 has an inlet valve 12, 19, 17, 44, 52 and 63 and an outlet valve 14, 34, 25, 48, 56 and 67.
  • each of the powder containers 1, 2, 3, 4, 6 and 8 also has a valve 10 or 11, 30, 21, 43, 51 and 62. Via these pressure equalization valves, the respective powder container is connected via a respective pressure equalization line to the conveying line in which the gas flow of the conveying gas flows, except in the case of the first tank 1, whose pressure equalization line is connected to the intermediate tank.
  • the pressure equalization lines of the powder containers 2, 3, 4, 6 and 8 are connected to the conveyor line via an associated valve 38, 29, 8 (the same for containers 4 and 6) and 87.
  • each of these powder containers 1, 2, 3, 4, 6 and 8 comprises an upper powder sensor 13, 31, 22, 45, 53 and 64 and a lower powder sensor 14, 32, 23, 46, 54 and 65.
  • each of the powder containers 1, 2, 3, 4, 6 and 8 is provided with load cells 15, 33, 24, 47, 55 and 66. These are used to weigh the respective container and thus also serve to determine the fill level of the respective container.
  • a powder sensor 35, 26, 57 and 69 is provided at the inlet of the conveyor screws 36, 27, 58 and 70 and a powder sensor 37, 28, 59 and 71 is provided at the outlet of the conveyor screws 36, 27, 58 and 70.
  • the individual elements of the bulk material conveying system shown in Fig. 4 are listed again below using their reference symbols, although this list does not claim to be complete.
  • the bulk material conveying system comprises at least three conveying circuits a to c.
  • the conveying circuits share the conveying line in which the conveying gas circulates, at least in sections.
  • two of the conveying processes can run in parallel, in particular the conveying processes b and c described below. This leads to a mixing (blending) of powder from the overflow tanks 2 and 3 and the external tank 8, with the powder mixing in the buffer container 4.
  • powder is conveyed from the main storage 6 (origin tank) into the first tank 1 (target tank).
  • the conveying in the conveying process a includes the prior opening of the valves 56 and 60.
  • the powder in the main storage 6 is powder that was previously sieved by the sieving device 5. From the The powder can then be fed from the first tank 1 to the additive manufacturing process in the process chamber.
  • the powder is fed into the conveyor line via the conveyor screw 58 and is separated in the cyclone 9.
  • the conveyor gas flows back to the pump 79 via the filter 41.
  • the conveying process b powder is conveyed from the overflow tank 2 (original tank) and/or the overflow tank 3 (original tank) into the buffer tank 4 (target tank).
  • the conveying in the conveying process b includes the prior opening of the valves 25 and 34.
  • the powder in the overflow tanks is contaminated powder that was not solidified in the additive manufacturing process.
  • the contaminated powder is fed from the buffer tank 4 to the sieve device 5.
  • the powder is brought into the conveying line via the conveyor screws 36 and 27 and is separated in the cyclone 42.
  • the conveying gas flows back to the pump 79 via the filter 41.
  • powder is conveyed from the external tank 8 (source tank) into the buffer tank 4 (target tank).
  • the conveying in the conveying process c includes the prior opening of the valves 67 and 68.
  • the powder in the external tank 8 is possibly contaminated powder that is fed into the process from outside. However, it can also be uncontaminated, fresh powder.
  • the powder conveyed from the buffer tank 4 into the buffer tank is fed to the sieve device 5.
  • the powder is brought into the conveying line via the conveyor screw 69 and is separated in the cyclone 42.
  • the conveying gas flows back to the pump 79 via the filter 41.
  • a method can be carried out which determines the gas velocity (target velocity) and which adjusts the pump 79 so that it conveys the conveying gas at the determined target velocity.
  • the steps A to D explained above can be carried out by a control device of the bulk material conveying system.
  • sensor data from the pressure sensor 80, the temperature sensor 86 and the oxygen sensor 76 are used to determine the gas density of the gas flow.
  • the geometry of the respective conveyor screw, which is located at the outlet of the respective source tank, is taken into account when calculating the bulk material mass flow.
  • the speed of the gas conveyed by the pump 79 is regulated using the speed sensor 86, for example by means of a PID control.
  • a limit control according to Fig. 3 can be implemented in connection with each of the conveying processes a to c (see the description above).
  • the closed powder circuits according to the conveying processes a to c can have the advantage, among other things, that a system operator has to intervene manually in the process as little as possible and comes into contact with the powder as little as possible, which, for example, poses health risks and can pose a risk of explosion or ignition for certain types of powder.
  • the automatic adjustment of the conveying speed can have the advantage that an optimal operating point (i.e. an optimal conveying speed) can be set quickly and easily for different types of powder and/or different process conditions.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Optics & Photonics (AREA)
  • Mechanical Engineering (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Sustainable Development (AREA)
  • Analytical Chemistry (AREA)
  • Automation & Control Theory (AREA)
  • Plasma & Fusion (AREA)
  • Combined Means For Separation Of Solids (AREA)
  • Air Transport Of Granular Materials (AREA)

Abstract

L'invention concerne un système de transport de produits en vrac, destiné en particulier à transporter une matière première pulvérulente dans une installation permettant de fabriquer une pièce tridimensionnelle par irradiation de couches de matière première pulvérulente par rayonnement électromagnétique ou par rayonnement de particules. Le système de transport de produits en vrac comprend une conduite de transport qui est conçue de manière à transporter un flux gazeux et au moins par endroits un flux de produits en vrac entraîné par le flux gazeux, et un dispositif de dosage qui est conçu de manière à acheminer une dose prédéfinie de produits en vrac par période jusqu'au flux gazeux. La dose est déterminée par une valeur de commande appliquée au dispositif de dosage. En outre, le système de transport de produits en vrac comprend un dispositif de transport qui est conçu de manière à transporter le flux gazeux à travers la conduite de transport et au moins un dispositif de mesure destiné à mesurer au moins une grandeur caractéristique du flux gazeux. Le système de transport de produits en vrac comprend en outre un dispositif de commande qui est conçu de manière à déterminer une densité de gaz du flux gazeux, sur la base de ladite au moins une grandeur caractéristique mesurée du flux gazeux, à déterminer un flux massique de produits en vrac du flux de produits en vrac, sur la base de la valeur de commande appliquée au dispositif de dosage, à déterminer une vitesse de consigne du flux gazeux, sur la base de la densité de gaz et sur la base du flux massique de produits en vrac et à commander le dispositif de transport afin de transporter le flux gazeux à la vitesse de consigne déterminée.
PCT/EP2024/064754 2023-05-31 2024-05-29 Système de transport de produits en vrac et procédé de transport de produits en vrac Pending WO2024246120A1 (fr)

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
DE102023114326.3A DE102023114326B3 (de) 2023-05-31 2023-05-31 Verfahren zur Steuerung des Betriebs einer Siebvorrichtung, Siebvorrichtung, Pulveraufbereitungssystem und Anlage zur Herstellung von dreidimensionalen Werkstücken
DE102023114326.3 2023-05-31
DE102023114305.0A DE102023114305A1 (de) 2023-05-31 2023-05-31 Pulverfördersystem zum Fördern von Rohmaterialpulver zu einer Anlage zum Herstellen eines dreidimensionalen Werkstücks
DE102023114305.0 2023-05-31
DE102023114306.9 2023-05-31
DE102023114306.9A DE102023114306A1 (de) 2023-05-31 2023-05-31 Schüttgutfördersystem und Verfahren zum Fördern von Schüttgut

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WO2024246120A1 true WO2024246120A1 (fr) 2024-12-05

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PCT/EP2024/064747 Pending WO2024246118A2 (fr) 2023-05-31 2024-05-29 Procédé pour commander le fonctionnement d'un dispositif de tamisage, dispositif de tamisage, système de préparation de poudre et installation de fabrication de pièces tridimensionnelles
PCT/EP2024/064744 Pending WO2024246115A1 (fr) 2023-05-31 2024-05-29 Système de transport de poudre pour transporter une matière première pulvérulente jusqu'à une installation de fabrication de pièce tridimensionnelle
PCT/EP2024/064754 Pending WO2024246120A1 (fr) 2023-05-31 2024-05-29 Système de transport de produits en vrac et procédé de transport de produits en vrac

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PCT/EP2024/064747 Pending WO2024246118A2 (fr) 2023-05-31 2024-05-29 Procédé pour commander le fonctionnement d'un dispositif de tamisage, dispositif de tamisage, système de préparation de poudre et installation de fabrication de pièces tridimensionnelles
PCT/EP2024/064744 Pending WO2024246115A1 (fr) 2023-05-31 2024-05-29 Système de transport de poudre pour transporter une matière première pulvérulente jusqu'à une installation de fabrication de pièce tridimensionnelle

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