A 3D printing device having a favorable geometry of a build area

Abstract

The present invention relates to a 3D printing device having a build area with a favorable geometry. The build area has an X-axis and a Y-axis that form a build field, as well as a Z-axis. In the build area, the dimensional ratio is Y > X > Z. The ratio of Y:X is between 1.1 and 3.0, preferably between 1.2 and 2.0.

Description

Technical Field

[0001] The present invention relates to a 3D printing device having a favorable geometry of a build area. Background Art

[0002] European Patent EP 0 431 924 B1 describes a method for producing a three-dimensional object based on computer data. In this process, a thin layer of particulate material is deposited on a platform by a recoater, and an adhesive material is selectively printed on this thin layer of particulate material by a print head. The particulate areas on which the adhesive is printed adhere and solidify under the influence of the adhesive and an optional additional hardener. Next, the build platform is lowered by one layer thickness or the recoater / print head unit is raised, and a new layer of particulate material is applied, and this new layer of particulate material is printed on the build platform as described above. These steps are repeated until a certain desired height of the object is reached. Thus, the printed area and the solidified area form a three-dimensional object (3D part, molded article).

[0003] After completion, the object made of the solidified particulate material is embedded in loose particulate material and is subsequently released from the loose particulate material. For this purpose, for example, a suction device can be used. This leaves the desired object, which must then be freed of any residual powder, for example, by brushing off the residual powder.

[0004] Other powder-based rapid prototyping processes, such as selective laser sintering or electron beam sintering or high-speed sintering, work in a similar manner, also applying loose particulate material layer by layer and selectively solidifying the particulate material using a controlled physical radiation source.

[0005] Hereinafter, all these processes will be summarized by the term "three-dimensional printing method" or "3D printing method".

[0006] In known 3D printer devices, the build field and the build area are customized according to other requirements of the machine. The main design goal may also be to provide a specific build volume in order to print corresponding small parts or large parts.

[0007] In different 3D printing processes such as laser sintering, inkjet bonding, high-speed sintering, etc., depending on the different applications of the process or different process conditions are required, which determines further machine design and other process parameters. The build material and the print components used also have an impact here.

[0008] In particular, the build volume of known 3D printers is affected by many factors. On the one hand, the parts to be printed impose some requirements on this. For example, if a customer wants to produce a part with a main dimension of 500 mm, then the build volume of the 3D printer should have at least that dimension in one direction.

[0009] On the other hand, when choosing the build volume, process parameters such as build volume speed must also be considered. The build volume speed determines how long it takes for a 3D printer to process the full build volume. Advantageously, in industrial 3D printers, the build volume and build volume speed are chosen relative to each other so that a full job can be printed within 24 hours and the system can be started with a new job. In this case, the 3D printer can operate in a single shift with high utilization. However, this is provided that the 3D printer can run unattended overnight. If the build volume speed of the 3D printer is very high compared to the build volume, the build volume can also be chosen so that one job can be completed during the day shift of 8 - 10 hours and another job can be completed overnight in less than 14 hours. Further reducing the ratio of build volume to build volume speed requires the presence of multi - shift operators or automating the pre - and post - processing operations to take advantage of higher productivity.

[0010] In addition, the build volume of a 3D printer is also defined by process limitations. Figure 1 The schematic diagram in [reference] shows, for example, a commercially available device for laser sintering. In this case, the laser 105 is deflected by the mirror device 106 before passing through the protective glass and / or lens system 107 to draw the pattern 102 on the build field surface 101.

[0011] When the laser impinges on the particulate material, the material is sintered and the molded article 102 is formed layer by layer. The processing chamber is bounded at the top by the lid 108 to maintain the temperature and prevent convection. A square process surface is typically preferred for the device. The reason is that due to the size of the expensive protective glass 107 and the focus loss of the laser beam at the maximum deflection angle, the working range of the laser optics is limited. Therefore, a typical build field size is 200 mm 2 to 400 mm 2 . Larger sizes make temperature management more difficult, which requires the build site temperature to be kept as constant as possible. In addition, the additional cost of the larger optics required to focus the laser and the additional laser power required are disproportionate to the build area obtained.

[0012] Indeed, there are some devices on the market that have two laser systems and can double the operable process surface in one dimension. However, quality loss is expected because it has proven difficult to align at the junction of the two laser fields.

[0013] In another 3D printing process known in the art as "high-speed sintering", the curing of the particulate material is achieved by the input of infrared radiation. The particulate material is thus physically bonded by a fusing process. In this case, the advantage that colorless plastic materials have relatively poor absorption of thermal radiation is utilized. By introducing an IR receptor (absorbent) into the plastic material, the absorption can be increased several times. The IR radiation can be introduced in various ways, for example, by a bar-shaped infrared lamp that moves uniformly over the build area. Selection is made by specifically printing each layer with the IR receptor.

[0014] Thus, at the printing location, the IR radiation is better coupled into the particulate material than in the non-printed areas. This results in selective heating within the layer above the melting point and thus in selective solidification. This process is described, for example, in EP1740367B1 and EP1648686B1.

[0015] Since no laser system is used in the 3D printing process using high-speed sintering, the above limitations of laser sintering do not apply in this case.

[0016] However, it can be noted that in known 3D printers, the geometry and size of the build area are not always optimally selected relative to other machine and process characteristics.

[0017] This can have an adverse effect on the process speed or / and other machine and process parameters, which may lead to a suboptimal process and involve disadvantages in terms of cost-effectiveness, quality, or other drawbacks.

[0018] Therefore, an object of the present invention is to provide a device that is improved in terms of the geometry of the build area or / and the size of the build surface or / and the size of the build area for a 3D high-speed sintering process or a 3D laser sintering process, or at least alleviates or completely avoids the disadvantages of the prior art.

[0019] Therefore, another object of the present invention is to provide a device that improves the geometry of the build area or / and the size of the build surface or / and the size of the build area and the interaction with other process parameters in a 3D high-speed sintering process or a 3D laser sintering process, or the device at least alleviates or helps to completely avoid the disadvantages of the prior art. Summary of the Invention

[0020] On the one hand, the present disclosure relates to a 3D printing device having an optimized geometry of a build area for a high-speed sintering process or a laser sintering process or a sintering process or a multi-jet fusion process, wherein the dimensional ratio of the geometric axes of the build area is Y>X>Z and / or wherein the ratio of Y:X is between 1.1 and 3.0.

[0021] On the other hand, the present disclosure relates to a 3D printing device for a high-speed sintering process or a laser sintering process or a sintering process or a multi-jet melting process, wherein the build area is characterized by an X-axis and a Y-axis forming the build area, and a Z-axis, wherein in the build area the dimensional ratio is Y > X > Z and / or wherein the ratio of Y:X is between 1.1 and 3.0.

[0022] On the other hand, the present disclosure relates to a combination of the geometry of the build area disclosed herein and a dual-cooling sintering assembly, wherein a first closed cooling air circuit is coupled to a second cooling air circuit preferably based on a fluid.

[0023] On the other hand, the present disclosure relates to a high-speed sintering process or a laser sintering process or a sintering process or a multi-jet melting process for producing a molded article by applying and selectively curing particulate material, the process comprising all further process steps as well as the process equipment necessary for a 3D printing process, the process being carried out in a build area which is characterized by an X-axis and a Y-axis forming the build area, and a Z-axis, wherein in the build area the dimensional ratio is Y > X > Z and / or wherein the ratio of Y:X is between 1.1 and 3.0. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 A prior art sintering machine with a laser is shown.

[0025] Figure 2 Shows the influence of the individual dimensions of the process field on the processing speed in additive manufacturing using a high-speed sintering process.

[0026] Figure 3 Shows the cooling time t c And the ratio to the one-dimensional magnification factor, where X and Y are constant.

[0027] Figure 4 Shows that, according to the above figures, when viewed as a whole, the preferred dimensional ratio of Y > X > Z accordingly results, as schematically shown here. It shows the individual layers of the building process, as well as the shaped part created on the surface.

[0028] Figure 5 Shows an exemplary concept of an additive manufacturing device for use with a high-speed sintering process, which results from consideration of the dimensional ratio of the process field disclosed herein; views from above (XY plane) and from the front (XZ plane) are shown here.

[0029] Figure S2 Shows a cross-section of the sintering assembly device obtained according to the build field geometry in the XZ plane.

[0030] Figure S3 Shows a side view (YZ plane) of a sintering unit with an air flow.

[0031] Figure S4 Shows a front view of a sintering unit in the XZ plane with a fan.

[0032] Figure H1 Shows a panel heater of the prior art.

[0033] Figure H2 Shows an infrared panel heater with time and local control and the resulting surface temperature.

[0034] Figure H3 Shows a transmitter unit according to the present disclosure, and also shows an exemplary arrangement of a measuring instrument.

[0035] Figure H4 Shows an exemplary transmitter unit according to the present disclosure, which has an arrangement of infrared emitter groups combined into separate heating circuits.

[0036] Figure H5 Schematically shows an exemplary embodiment of a transmitter in a transmitter unit with closed-loop control according to the present disclosure.

[0037] List of reference numerals

[0038] 101 Square pellet surface

[0039] 102 Molded product

[0040] 103 One layer of granular material

[0041] 104 Laser beam

[0042] 105 Laser generation

[0043] 106 Deflection mirror

[0044] 107 Protective glass, and if necessary, lens system

[0045] 108 Top of the build area

[0046] Figure 5

[0047] 501 Build field surface

[0048] 502 Molded product

[0049] 503 Print head with print modules, the print modules being arranged in a comb-like manner along the Y direction over the total width of the build area

[0050] 504 Single print module

[0051] The gap between the 505 printing modules is only required to move slightly in the Y direction when the print head moves back and forth on the build field surface, so as to fully wet it without gaps when moving back and forth on the build area surface.

[0052] 506 A device, arranged below, for cleaning the printing module during coating

[0053] 507 A single sintering emitter

[0054] 508 A sintering emitter assembly

[0055] 509 A recoater unit

[0056] Figure S2

[0057] S201 A heat sink

[0058] S202 A side wall

[0059] S203 A primary spectrum converter

[0060] S204 A secondary spectrum converter

[0061] S205 Airflow through the heat sink

[0062] S206 A reflector

[0063] S207 An emitter

[0064] S208 A support cover through which coolant flows

[0065] Figure S3

[0066] S301 A support cover through which coolant flows

[0067] S302 A cavity above the reflector, equipped with a heat sink

[0068] S303 A fan

[0069] S304 Airflow

[0070] S305 A primary radiation transducer

[0071] S306 A secondary radiation transducer

[0072] S307 Airflow through the central side wall groove of the component

[0073] Figure S4

[0074] S401 A support cover through which coolant flows

[0075] S402 An emitter

[0076] S403 Fan

[0077] S404 Cavity in the short side wall for the short side of the air flow

[0078] S405 Air flow

[0079] S406 Secondary radiation transducer

[0080] S407 Primary radiation transducer

[0081] S408 Cavity between the two radiation transducers

[0082] S409 Reflector

[0083] Figure H1

[0084] H101 Infrared emitter

[0085] H102 Object surface

[0086] H103 Infrared emitter temperature in the X direction

[0087] H104 Generated object surface temperature distribution

[0088] H105 Optimal temperature range

[0089] H106 Region below the optimal temperature in the X direction

[0090] H107 Infrared pyrometer

[0091] H108 Infrared emitter assembly

[0092] Figure H2

[0093] H201 Infrared emitter

[0094] H202 Object surface

[0095] H203 Calculated required temperature of the infrared emitter in the X direction

[0096] H204 Generated object surface temperature distribution

[0097] H205 Discretization of the required surface temperature and calculation of the power settings for each infrared emitter

[0098] H206 Infrared pyrometer

[0099] H207 Thermal imaging camera

[0100] Figure H3

[0101] H301 Emitter Assembly

[0102] H302 Thermal Imaging Camera

[0103] H303 Infrared Emitter

[0104] H304 Temperature Sensor

[0105] H305 Infrared Pyrometer

[0106] Figure H4

[0107] H400 Emitter Assembly

[0108] H401 - H406 Infrared emitters are combined into respective heating circuits. Detailed Implementation Manner

[0109] The object of the present application is achieved by a 3D printing device for a high - speed sintering process or a laser sintering process or a sintering process or a multi - jet fusion process, characterized in that the build area is characterized by the X - axis, Y - axis and Z - axis forming the build area, wherein in the build area there is a dimensional ratio of Y>X>Z and / or wherein the ratio of Y:X is between 1.1 and 3.0, preferably between 1.2 and 2.0.

[0110] The object of the present application is achieved by a high - speed sintering process or a laser sintering process or a sintering process or a multi - jet fusion process for producing a molded article by applying particulate material and selectively curing, the process comprising all further process steps and process devices necessary for a 3D printing process, the process being carried out in a build field, the build area being characterized by the X - axis and Y - axis and Z - axis forming the build area, wherein in the build area the dimensional ratio is Y>X>Z and / or wherein the ratio of Y:X is between 1.1 and 3.0, preferably between 1.2 and 2.0.

[0111] Hereinafter, several terms will be defined more precisely. Otherwise, the terms used shall have the meanings known to those skilled in the art.

[0112] "Layer building process" or "3D printing process" or "3D process" or "3D printing" in the sense of the present disclosure are respectively processes known in the prior art by which three - dimensional parts are built, and these processes are compatible with the process components and devices described herein.

[0113] As used in this disclosure, "binder jetting" refers to the process of applying powder in layers onto a build platform, printing one or more liquids onto the cross-section of the parts on that powder layer, changing the position of the build platform by one layer thickness relative to the previous position, and repeating these steps until the part is complete. In this context, binder jetting also refers to a layer construction process that requires further processing of the components, such as layer-by-layer exposure, for example, layer-by-layer exposure with infrared or ultraviolet radiation.

[0114] In the "high-speed sintering process" as defined in this disclosure, a thin layer of plastic particles, such as PA12 or TPU, is applied onto a preferably heated build platform (build field). Next, an inkjet printhead moves over a large area of the platform and wets the area of the build field with infrared light-absorbing ink (IR absorber, IR receptor) to create a prototype. Then, the build platform is irradiated with infrared light. The wetted area absorbs heat, causing the underlying powder layer to sinter. However, the unprinted powder remains loose. After sintering, the build platform is lowered by one layer thickness. This process is repeated until the construction of the part is complete. Then, the sintered part is cooled in a controlled manner within the build area before it can be removed and unpacked. In this regard, in addition to the sintering lamp, it may also be advantageous to use top lamps or emitter assemblies that use different wavelength spectra, and the wavelength spectra are substantially non-overlapping. In one variant, in addition to the IR absorber, a so-called refining agent can also be printed, and the agent is used to cool the area printed with it. A variant of the high-speed sintering process is also called the melt jetting process, in which the printhead jets a thermally conductive fluid (commonly called "flux", corresponding to the absorber) onto a layer of particulate material. Immediately after printing, a heat source (infrared) is applied. The area coated with the flux is heated more strongly compared to the powder without this liquid. Therefore, the desired area is fused. Then, another additive, also called a refining agent, is used for heat insulation. This selective imprint appears around the area where the flux or absorber has been printed. The additive is intended to promote the formation of sharp edges. This goal is achieved by making the temperature difference between the printed powder and the unused powder more obvious. The process using these two printing liquids can also be called the multi-jet fusion process.

[0115] The "laser sintering process" used in this invention refers to a 3D printing process that uses a laser to selectively cure particulate materials.

[0116] A "3D formed article", "molded article" or "part" in the sense of this disclosure refers to any three-dimensional object that is manufactured by the method according to this invention or / and by the device according to this invention and exhibits dimensional stability.

[0117] The "building area" is the geometric location where the bed of particulate material is continuously raised by repeatedly applying the particulate material during the building process, where, when applying the continuous principle, the bed passes through this space. The building area is typically delimited by a bottom (i.e., the building platform), walls, and an open top surface (i.e., the building plane). In the continuous principle, there are usually conveyor belts and restricting side walls. The building area can also be designed in the form of a so-called work box, which constitutes a unit that can be moved into and out of the device and allows for batch production. After completing one process, one work box is removed to allow a new work box to be immediately moved into the device, thereby increasing the production volume and thus improving the performance of the device. The building area can also be described using the X, Y, and Z axes.

[0118] In the sense of the present disclosure, all flowable materials known in 3D printing can be used, "building material" or "particulate material" or "powder" or "powder bed", in particular flowable materials in the form of powders, slurries, or fluids. These can include, for example, sand, ceramic powder, glass powder, and other powders of inorganic or organic materials, such as metal powders, plastic materials, wood particles, fiber materials, cellulose, or / and lactose powder, as well as other types of organic powdered materials. The particulate material is preferably a free-flowing powder when dry, but sticky, cut-resistant powders can also be used. This adhesiveness can also be due to the addition of binder materials or auxiliary materials, such as binders. The addition of a liquid can cause the particulate material to flow freely in the form of a slurry. Generally, in the sense of the present disclosure, the particulate material can also be referred to as a fluid.

[0119] In this application, the particulate material and the powder are used synonymously.

[0120] "Particulate material application" is the process of generating a defined powder layer. This can be carried out in a continuous principle on the building platform (building field) or on an inclined plane relative to the conveyor belt. The particulate material application will also be referred to as "recoating" hereinafter.

[0121] In the sense of the present disclosure, "selective liquid application" or "selective binder application" can be carried out relative to the particulate material application, either after each particulate material application or multiple times at irregular intervals, depending on the requirements of the molded article and the optimization of the molded article production. In this case, a cross-sectional image of the desired article is printed.

[0122] The "device" for performing the method according to the present disclosure can be any known 3D printing device including the required parts. Common parts include recoaters, building fields, devices for moving the building field or other parts in a continuous process, work boxes, metering devices, and heating and / or radiation devices, as well as other parts known to those skilled in the art. Therefore, these known parts will not be described in detail herein.

[0123] The building material according to the present disclosure is always applied in a "defined layer" or "layer thickness", which is adjusted individually according to the building material and process conditions. For example, the layer thickness is 0.05 - 5 mm, preferably 0.06 - 2 mm or 0.06 - 0.15 mm, particularly preferably 0.06 - 0.09 mm.

[0124] As used in the present disclosure, a "recoater" or "material application device" refers to a unit through which a fluid such as particulate material, such as mineral or metallic material or plastic, particulate form of wood or a mixture thereof, is applied to the building field. The unit may consist of a fluid container and a fluid application unit. According to the invention, the fluid application unit includes a fluid outlet and a "doctor blade device". The doctor blade device may be a doctor blade. However, any other suitable doctor blade device that can be conceived may be used. For example, a rotating roller or a nozzle is also conceivable. The material can be fed through the container in a free-flowing manner or through an extruder screw, pressurization or other material conveying means.

[0125] A "doctor blade" as defined in the present disclosure is a substantially flat part made of metal or other suitable material, located at the outlet opening of the recoater, and through which the fluid is distributed onto the building platform and smoothed. The recoater may have one or two or more doctor blades. The doctor blade may be an oscillating blade that performs oscillations in the sense of a rotational movement when excited. In addition, the oscillation can be turned on and off by means for generating the oscillation. Depending on the arrangement at the outlet opening, the doctor blade is arranged "substantially horizontally" or "substantially vertically" within the meaning of the present disclosure.

[0126] As used in this disclosure, a "feed container" or "preheating container" is a container that holds particulate material and delivers a quantity of particulate material to a recoater after each layer or any number of layers. To this end, the feed container can advantageously extend across the entire width of the recoater. The feed container is provided at its lower end with a closure that prevents accidental escape of the particulate material. The closure can be configured, according to the prior art, as, for example, a rotary feeder, a simple slide, or other suitable mechanism. The feed container, as defined in this disclosure, can contain more than one layer of particulate material. Preferably, the feed container even contains particulate material for applying 20 layers or more. The particulate material is supplied in large quantities in the form of silos or big bags via a conveying line, or is manually filled into the container. The filling is preferably carried out through an opening in the top edge. This allows the particulate material to be conveyed in the feed container by gravity, so that no additional conveying means need be provided in the container. The feed container can also have a vibration mechanism to prevent bridging of the particulate material in the container. The feed container has a region for receiving the particulate material, typically located between the side walls and the closure. According to this disclosure, it is advantageous to arrange a heating device in the region for receiving the particulate material. The heating device is arranged such that the particulate material flows around the heating device, thereby improving the heating of the particulate material. The feed container can be fixed, in which case the feed container can be located, for example, above the stop position of the recoater or above the construction site. The recoater can then be moved towards or below the feed container to refill it again with pre-tempered particulate material as needed and / or to control the amount of the refill. However, the feed container can also be detachably or non-detachably connected to the recoater. For design or / and cost reasons, it may also be advantageous for the recoater not to be heatable. The recoater can then have passive insulation. However, if preheated particulate material is delivered to the recoater in an amount that is substantially equal to or 1.2 to 2 times the layer amount, the recoater may not be heated at all and no insulation is provided, thus allowing it to be applied with little residence time in the recoater and thus substantially no heat loss.

[0127] As used in this disclosure, a "coolant" is a device capable of cooling the emitter unit, such as water or other liquids or a blower air stream.

[0128] A "heating phase" in the sense of this disclosure means heating the equipment at the start of the process. Once the actual temperature of the equipment reaches a stable value, the heating phase is completed.

[0129] The "cooling phase" in the sense of the present disclosure refers to the time required to cool the particulate material to such an extent that the parts contained therein do not undergo any significant plastic deformation when they are removed from the build area, or the "cooling phase" in the sense of the present disclosure refers to the time that must be waited before a molded article produced by a sintering process can be removed from the build area without damage to them. The cooling time is typically specified as the shortest time required to achieve maximum cooling outside the build area, and is typically specified such that the hottest location in the volume of the build area is safely below the thermal deformation temperature of the material used.

[0130] An "absorbent" or "IR absorbent" or "IR receptor" in the sense of the present disclosure is a medium that can be processed by an inkjet printhead or any other device operating in a similar matrix fashion, which enhances the radiation for local heating of the build material. The absorbent can also be in particulate form, such as black toner. The absorbent can be applied uniformly or selectively in different amounts. For example, the absorbent can be applied as a mixture of absorbents having different absorption maxima, or different absorbents can be applied independently, for example one after another, in an alternating manner or in a predetermined sequence. Thus, applying different amounts can control the strength of the build material and selectively achieve different strengths in, for example, the molded article to be produced and the sheath surrounding the molded article. The strength range is from the strength of the part itself to only slightly higher than the strength of the build material on which no absorbent is printed. This allows for temperature control in the build field / build area and also allows for easy removal of the sheath surrounding the produced part when needed, which is for the purpose of temperature control.

[0131] "Absorption" in the sense of the present disclosure refers to the build material absorbing thermal energy from the radiation. Absorption depends on the type of powder and the wavelength of the radiation.

[0132] An "energy input device" in the sense of the present disclosure refers to an energy source that inputs energy into the build area or / and the particulate material or / and the area printed with the absorbent. For example, this can be an energy source for temperature control or heating of the particulate material, even before the absorber input. It can also include a fixed or moving radiation source that irradiates the build field. If the radiation source is used for curing after the absorbent input, the absorbent is adapted to the type of radiation and preferably optimized. This is to create a heating difference between the "activated" and "non-activated" powders. "Activated" means that, through the absorber printed therein, the temperature in these areas is elevated compared to other areas in the build area and the area of the particulate material without the printed absorber.

[0133] "IR heating" as used in the present disclosure specifically refers to the irradiation of the build field by an IR emitter. The IR emitter can be static or can move over the build field by means of a displacement unit. Using an absorber, IR heating causes different temperature rises in the build area.

[0134] As used in this disclosure, an "IR emitter" is a source of infrared radiation. Typically, an incandescent filament in a quartz or ceramic housing is used to generate the radiation. Depending on the materials used, the radiation will produce different wavelengths. Additionally, the wavelength of such emitters also depends on their power.

[0135] As used in this disclosure, a "ceiling light" or "emitter assembly" or "emitter unit" or "radiation unit" or "heating radiator" or "build field heater" is a radiation source that is installed above the build field and forms a functional unit. The wavelength of the emitted electromagnetic radiation is fixed, and its radiation flux can be adjusted. The emitter unit is a functional unit that emits electromagnetic radiation of a specific spectrum. It can contain a single emitter or a large number of emitters, and the emitters can be controlled individually or in groups. Optionally, it substantially covers the entire build field and is installed at a certain position in the device, or it is smaller than the build field and can move over the build field.

[0136] "Sintering" or "melting" in the sense of this disclosure is a term for the partial coalescence of particles in a powder. In this system, the increase in strength is related to sintering.

[0137] The term "sintering window" in the sense of this disclosure refers to the temperature difference between the melting point that occurs when the powder is first heated and the solidification point during subsequent cooling.

[0138] The "sintering temperature" used in this disclosure is the temperature at which the powder first begins to melt and bond.

[0139] The "peripheral region" as used in this disclosure refers to the region of the emitter assembly that is located at the edge of the emitter assembly and can be separated from the inner region. In this case, the peripheral region and the inner region form the total area of the emitter assembly, and this total area refers to the surface position where the emitter unit is installed.

[0140] The "inner region" as used in this disclosure refers to the region of the emitter assembly that is located inside the emitter assembly and can be separated from the peripheral region.

[0141] The "peripheral region of the build area" in the sense of this disclosure refers to the edge of the build field of the build area.

[0142] The "inner region of the build area" in the sense of this disclosure refers to the region of the build field of the build area that can be separated from the peripheral region of the build field.

[0143] As used herein, the "3D printer" or "printer" or "3D printing device" refers to a device capable of performing a 3D printing process. A 3D printer in the sense of the present disclosure includes a device for applying a build material, such as a fluid like particulate material, and a solidification unit, such as a print head or an energy input device, such as a laser or a heating 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 each case. Alternatively, the term "device" may be chosen.

[0144] The "build field" is a plane or, in a broad sense, a geometric location where a bed of particulate material is continuously built up during the build process by repeated coating with particulate material. The build field is typically bounded by a bottom (i.e., the "build platform"), walls, and an open top surface (i.e., the build plane). The build field forms part of the build area.

[0145] The "printing" or "3D printing" process in the sense of the present disclosure encompasses operations of material application, selective curing or imprinting, and working height adjustment, and occurs in an open or closed processing or build area.

[0146] The "receiving plane" in the sense of the present disclosure refers to the plane on which the build material is applied. According to the present disclosure, the receiving plane can always be freely accessed in one spatial direction by linear movement.

[0147] According to the present disclosure, "spreading" or "applying" or "depositing" refers to any way of dispersing particulate material. For example, a larger amount of powder can be placed at the starting position of a coating channel, and the powder can be distributed or spread into the layer volume by a blade or a rotating roller.

[0148] The "print head" or device for selective curing in the sense of the present disclosure typically consists of various components. Among these components can be print modules. The print module has a large number of nozzles from which "adhesive" is ejected as droplets in a controlled manner onto the build field. The print module is aligned with the print head. The print head is aligned with the machine. This allows the positions of the nozzles to be assigned to the machine coordinate system. The plane in which the nozzles are located is usually referred to as the nozzle plate. Another way of selective curing can also be one or more lasers or other radiation sources or heating lamps. An array of such radiation sources, such as a laser diode array, can also be considered. In the sense of the present disclosure, selective implementation is allowed separately from the curing reaction. Thus, a print head or one or more lasers can be used to selectively process the layer, and other layer processing devices can be used to initiate the curing process. In one embodiment, an IR absorber is printed on the particulate material and then cured using an infrared source. The "print head" can have one or more print modules that are mounted in the assembly in a special arrangement.

[0149] According to the DOD principle, the assembly as a whole is used to wet the surface with a liquid (printing liquid) - in this case the particulate material on the build field.

[0150] The "printing module" used in this disclosure refers to a unit that applies a liquid to a surface according to the DOD principle by means of a so-called inkjet process.

[0151] The "layer processing device" in the sense of this disclosure refers to any device suitable for achieving a certain effect in a layer. This can be a unit such as the aforementioned print head or laser, or a heat source in the form of an IR emitter, or other radiation sources such as a UV emitter, for example. Devices for deionizing or ionizing the layer can also be envisaged. The common feature of all layer processing devices is that their area of action is linearly distributed over the layer, and like other layering units such as print heads or recoaters, they must be guided across the build field to reach the entire layer.

[0152] As used in this disclosure, "drop-on-demand" or "DOD" or "DOD principle" refers to a method of applying a liquid to a surface, whereby the liquid becomes active only at those positions where application is required.

[0153] The "sintering emitter assembly" or "sintering assembly" or "sintering lamp" as used in this disclosure refers to a device that selectively heats the surface of particulate material wetted by an IR receptor to a temperature above the melting temperature by means of electromagnetic radiation. The "sintering assembly" as used in this disclosure is an energy input device capable of heating process powder (microparticulate building material, particulate material) above its sintering temperature. The assembly can be stationary. In a preferred embodiment, the "sintering assembly" moves through the build area in such a way that, in coordination with other equipment devices, a useful layer build with selective curing can be performed.

[0154] The "radiation transducer" within the meaning of this disclosure is an element that changes a particular spectrum of electromagnetic radiation in the basic characteristics of the wavelength intensity distribution when exposed to that spectrum.

[0155] The "peak wavelength" in the sense of this disclosure is the wavelength of electromagnetic radiation that approximates the Planck spectrum and has the highest intensity and follows Wien's displacement law. The peak wavelength can also represent the wavelength with the highest intensity for emitters that do not follow the Planck distribution.

[0156] As used in this disclosure, "overspill" refers to the additional space required when the assembly moves completely from one end of the build field to the other along a linear axis without creating a shadow on the build area.

[0157] Within the meaning of the present disclosure, the "coupling" of a cooling circuit or of a cooling circuit to a cooling member is an operation in which two functionally different parts have a coupling point or connection point at which heat exchange can occur. For example, according to the present disclosure, a closed air cooling circuit is coupled to a liquid-based cooling circuit. Thus, the air cooling circuit can, for example, receive heat from a radiation transducer, and this heat is transferred to the liquid cooling circuit and then conveyed directly or possibly via another coolant to the environment. Thereby, when using a closed-loop control circuit, the temperature at the radiation transducer, for example, can be set to or maintained at a target temperature.

[0158] As defined in the present disclosure, a "closed" air cooling circuit means that the air in the circuit circulates substantially within the circuit and no air is supplied from the outside. In a specific embodiment, the circuit is sealed so that contaminants such as particles of construction material do not enter the circuit and thus no maintenance of the circuit is required.

[0159] An "air cooling circuit" in the sense of the present disclosure means the circulation of air in a tube system of a sintering assembly, where the air or gas is circulated, for example, by means of other devices such as fans.

[0160] A "liquid-based cooling circuit" as defined in the present disclosure is a closed circuit whose coolant is a liquid, such as water, oil or other known liquid coolants.

[0161] An "expansion of the surface" as used in the present disclosure means any means for increasing the surface area for cooling purposes, such as fins, ribs, etc. to increase the cooling capacity.

[0162] A "cooling member" as used in the present disclosure means a heat exchanger.

[0163] Detailed description of the invention

[0164] The various aspects and advantageous embodiments of the present disclosure will be described in more detail below.

[0165] The object of the present application is achieved by means of a 3D printing device for a high-speed sintering process or a laser sintering process or a sintering process or a multi-jet fusion process, characterized in that the build area is characterized by an X-axis and a Y-axis and a Z-axis forming a build field, where in the build area there are dimensions such that Y > X > Z and / or where the ratio of Y:X is between 1.1 and 3.0, preferably between 1.2 and 2.0.

[0166] The object of the present application is achieved by a high-speed sintering process or a laser sintering process or a sintering process or a multi-jet fusion process for producing a molded article by applying and selectively solidifying particulate material, the process comprising all further process steps and process means necessary for a 3D printing process, the process being carried out in a build area, the build area being characterized by an X-axis and a Y-axis forming the build area, and a Z-axis, wherein in the build area the dimensional ratio is Y>X>Z and / or wherein the ratio of Y:X is between 1.1 and 3.0, preferably between 1.2 and 2.0.

[0167] The solution of the present invention has the advantage that the process time and the printing cycle can be optimized and shortened, whereby the cost-effectiveness of the 3D printing process can be increased compared to known high-speed sintering processes and / or laser sintering processes and / or sintering processes. In addition, improved temperature management can be achieved in the process according to the invention, which promotes advantages in terms of quality. In this way, unsintered and unbonded particulate material can also be preserved and recycled in some cases.

[0168] Other preferred aspects and embodiments of the present disclosure are disclosed in the dependent claims.

[0169] The build area dimensions can be selected according to the above. It may be advantageous if the build area has a dimension in the Y direction of 50 cm or greater and a dimension in the Z direction of 50 cm or less, more preferably if the build area has a dimension in the Y direction of 60 cm or greater and a dimension in the Z direction of 40 cm or less.

[0170] Alternatively, a 3D printing device according to the present disclosure has a dimension of the X-axis of the build area greater than 50 cm, a dimension of the Y-axis of the build area greater than 50 cm, and a dimension of the Z-axis of the build area of 50 cm or less, more preferably a dimension of the X-axis of the build area greater than 55 cm, a dimension of the Y-axis of the build area greater than 60 cm, and a dimension of the Z-axis of the build area of 50 cm or less, and particularly preferably a dimension of the X-axis of the build area of 60 cm or greater, a dimension of the Y-axis of the build area of 100 cm or greater, and a dimension of the Z-axis of the build area of 40 cm or less, which may be advantageous.

[0171] In this case, it may be advantageous if the movable components in a 3D printing device according to the present disclosure are narrow, preferably the recoater, the print head and / or the sintering emitter assembly are narrow in the X direction, preferably overall smaller than the build field in the X direction, and particularly preferably smaller than the build field by 80% in the X direction.

[0172] Configure the 3D printing device according to the present disclosure with respect to the X-axis and Y-axis based on other design features. Preferably, the recoater, print head, and / or sintering emitter assembly extends substantially along length Y and travels along the X-axis.

[0173] In a 3D printing device according to the present disclosure, it may be particularly advantageous if the printing module and the print head are specifically designed to achieve better heat distribution or / and better heat management. For example, the printing modules of the print head can be arranged in a comb-like manner. This means that the strips are printed first in one pass, the parallel strips remain unprinted, and the previously unprinted strips are then printed in a second pass. Such a printing process can also be called intermittent. The advantage of this is that a large area can be printed with a relatively short travel distance, thus saving time.

[0174] During temperature management and temperature setting processes, it may be beneficial to obtain favorable printing results if further heat dissipation or heat regulation devices are provided. A 3D printing device according to the present disclosure can include such devices, wherein the 3D printing device includes means for heat dissipation, preferably where one or more or all of the heat-carrying elements are coupled to a coolant.

[0175] Preferably implement a 3D printing device according to the present disclosure, wherein the means for heat dissipation is air or gas or gas mixture or coolant, such as oil-based, water or water-based mixture, or a heat system pipe.

[0176] In a 3D printing device according to the present disclosure, preferably, the sintering assembly is cooled by air or gas or gas mixture or / and coolant or / and through a heat pipe.

[0177] In a 3D printing device according to the present disclosure, it may be preferred that the sintering assembly is characterized by a closed air cooling circuit and a liquid-based cooling circuit, and wherein air circulates in the closed air cooling circuit, preferably through a ventilation device in the air cooling circuit, or / and coolant, or / and is cooled through a heat pipe.

[0178] In a 3D printing device according to the present disclosure, it may be preferred that the liquid-based cooling circuit is arranged on the side facing away from the build field or / and is coupled to another coolant, preferably an external coolant.

[0179] In a 3D printing device according to the present disclosure, preferably, the closed air cooling circuit is at least partially guided past the radiation transducer, preferably where the air cooling circuit is at least partially guided between two radiation transducers.

[0180] In a 3D printing device according to the present disclosure, the means for increasing the surface area can preferably be arranged in the air cooling circuit, preferably where cooling ribs, cooling fins, cooling coils or cooling spirals are coupled to the liquid-based cooling circuit.

[0181] In a 3D printing device according to the present disclosure, the IR emitter may preferably be arranged between the primary and secondary radiation transducers and the liquid-based cooling circuit, and optionally a reflector is arranged between the IR emitter and the liquid flow cooling member.

[0182] In a 3D printing device according to the present disclosure, the liquid-based cooling circuit may preferably be cooled by a liquid flow cooling member outside the sintering assembly, which is preferably a support cover.

[0183] In a 3D printing device according to the present disclosure, the cavities for closing the air cooling circuit may preferably be located between the primary radiation transducer and the secondary radiation transducer and between the primary radiation transducer and the support cover. Preferably, an enlarged portion of the surface of the liquid flow cooling member is arranged therein, and optionally a cavity is located in the side wall of the sintering assembly, and all the cavities communicate with each other to form a closed air cooling circuit.

[0184] In a 3D printing device according to the present disclosure, preferably, a reflector is arranged in the cavity between the primary radiation transducer and the support cover.

[0185] In a 3D printing device according to the present disclosure, the closed air cooling circuit is not connected to the ambient air.

[0186] In a 3D printing device according to the present disclosure, preferably, the 3D printing device includes one, two or more radiation transducers, preferably the primary and / or secondary radiation transducers.

[0187] In a 3D printing device according to the present disclosure, it may be preferable that the 3D printing device includes emitters of broadband electromagnetic radiation of different wavelengths, the spectra of which deviate from each other to a considerable extent. Preferably, a long-wave IR emitter with a peak wavelength between 3 μm and 5.5 μm is combined with an emitter in the short-wave infrared range with a peak wavelength between 0.7 μm and 2 μm, or a long-wave IR emitter is combined with an emitter of incoherent electromagnetic radiation with a narrow spectrum between 0.3 μm and 1.5 μm, preferably in the visible light range, or a broadband mid-wave IR radiator between 3 μm and 1.6 μm is combined with a short-wave IR emitter with a peak wavelength between 0.7 μm and 1.6 μm. Any suitable emitter can be used, such as a ceramic emitter, a panel-type emitter, a quartz halogen emitter, a quartz tungsten emitter, a heating conductor, a quartz glass tube, a carbon emitter, a near-infrared emitter, an LED array of different wavelengths, a gas discharge lamp, an incandescent lamp or / and a heating wire.

[0188] In a 3D printing device according to the present disclosure, it may be preferable that the 3D printing device includes an additional emitter assembly (emitter unit), where the emitter assembly is characterized in that it is an array of a plurality of emitters, where the temperature of each emitter is individually controllable, or a subset of emitters is combined into a group, where the temperature of each group of emitters is controllable. It may also be advantageous to combine several emitters into a group, and these emitters are co-regulated in terms of their temperature.

[0189] In a 3D printing device according to the present disclosure, it may be preferable that a target temperature is set at each emitter or emitter group, provided that the power (watts) of the emitter is not set as the target parameter.

[0190] In a 3D printing device according to the present disclosure, it may be preferable that substantially each emitter or emitter group in the emitter assembly (emitter unit) is set to a different target temperature.

[0191] In a 3D printing device according to the present disclosure, preferably, the emitter assembly includes a control circuit for adjusting the target temperature of each emitter or / and for adjusting the target temperature on the build field.

[0192] In a 3D printing device according to the present disclosure, it may be preferable that the emitter assembly uses an algorithm to achieve the target temperature on the build field through target temperature adjustment in the emitter assembly, or / and where the target temperature adjustment is achieved by defining the emitters as a subset of emitters combined into groups.

[0193] In a 3D printing device according to the present disclosure, it may be preferable that the emitter assembly includes at least one thermal imaging camera pointing to the build field and / or at least one infrared pyrometer and / or at least one temperature sensor, where the temperature sensor is preferably a thermocouple or a resistance thermometer. Preferably, the thermal imaging camera can be used for local measurement recording, while the infrared pyrometer can be used for calibration of absolute values.

[0194] In a 3D printing device according to the present disclosure, it may be preferable that the thermal imaging camera is used for local measurement recording, while the infrared pyrometer is used for calibration of absolute temperature values.

[0195] In a 3D printing device according to the present disclosure, it may be preferable that it includes an emitter assembly (emitter unit), where the target temperature on the build field can be adjusted by setting the target temperature of each emitter in the emitter assembly.

[0196] On the other hand, the present disclosure relates to a high-speed sintering process or a laser sintering process or a sintering process or a multi-jet fusion process for producing a molded article by applying and selectively curing particulate material, the process comprising all further process steps and process apparatus required for a 3D printing process, the process being carried out in a build area which is characterized by an X-axis and a Y-axis and a Z-axis forming the build area, wherein in the build area there are dimensions such that Y > X > Z and / or wherein the ratio of Y:X is between 1.1 and 3.0, preferably between 1.2 and 2.0.

[0197] In the apparatus and method according to the present disclosure, it is further preferred that a feed container is included or used in the apparatus.

[0198] In such a process, advantageously, the features of the above-mentioned 3D printing apparatus according to the present disclosure can equally be used, and thus the features of an advantageous process according to the present disclosure are characterized by any feature or combination of features claimed for the apparatus or features of the apparatus.

[0199] In particular, a process may be preferred in which the process is carried out in a build area which is characterized in that the recoater extends substantially along the length Y and moves in the X direction.

[0200] Furthermore, a process according to the present disclosure may be preferred and advantageous in which the process is carried out using an apparatus in which the recoater, the print head and / or the sintering emitter assembly are narrower in the X direction, preferably overall smaller than the build field in the X direction, particularly preferably smaller than the build field in the X direction by 80%.

[0201] Furthermore, a process according to the present disclosure may be preferred and advantageous in which the process is carried out using an apparatus in which the recoater, the print head and / or the sintering emitter assembly extend substantially along the length Y and / or move along the X axis.

[0202] Furthermore, a method according to the present disclosure may be preferred and advantageous in which the process is carried out using an apparatus in which the print modules of the print head are arranged in a comb-like manner.

[0203] Furthermore, a process according to the present disclosure may be preferred and advantageous in which the process is carried out using an apparatus in which the 3D printing apparatus includes means for heat dissipation, preferably wherein one or more or all of the heat-carrying elements are coupled to a coolant.

[0204] Furthermore, a process according to the present disclosure may be preferred and advantageous in which the process is carried out using an apparatus in which the means for heat dissipation is air or a gas or a gas mixture or a coolant, such as an oil-based water or a water-based mixture, or a heat pipe system.

[0205] Furthermore, the process according to the present disclosure may be preferred and advantageous, wherein the process is carried out using a device comprising a sintering assembly, wherein the sintering assembly is cooled by air or gas or a gas mixture or / and a coolant or / and by a heat pipe.

[0206] Furthermore, the process according to the present disclosure may be preferred and advantageous, wherein the 3D printing device comprises one, two or more radiation transducers, preferably primary and / or secondary radiation transducers.

[0207] Furthermore, the process according to the present disclosure may be preferred and advantageous, wherein the 3D printing device comprises emitters of broadband electromagnetic radiation of different wavelengths, the spectra of which deviate considerably from each other, preferably a long-wave IR emitter with a peak wavelength between 3 μm and 5.5 μm, in combination with an emitter in the short-wave infrared range with a peak wavelength between 0.7 μm and 2 μm, or a long-wave IR emitter, in combination with an emitter of incoherent electromagnetic radiation with a narrow spectrum between 0.3 μm and 1.5 μm and in the visible light range, or a broadband mid-wave IR radiator between 3 μm and 1.6 μm, in combination with a short-wave IR emitter with a peak wavelength between 0.7 μm and 1.6 μm.

[0208] In the device and process according to the present disclosure, it is further preferred that the device comprises or uses a feed container.

[0209] Other aspects of the present invention and further exemplary descriptions of the present invention

[0210] The various aspects of the present disclosure will be described below by way of example and these aspects should not be construed as limiting. Furthermore, any aspects of the exemplary drawings shown below can be used in any combination.

[0211] Generally speaking, the build area of a 3D printer can be divided into two areas, namely a two-dimensional build area (X-axis and Y-axis) and the Z-axis.

[0212] The design of the build field focuses on selective printing using Cartesian coordinates. For this purpose, build fields that are substantially square or rectangular are found in prior art systems. In the literature, build fields using cylindrical coordinates are also available. However, it is more difficult to implement in practice because most parts to be printed are easier to describe using Cartesian coordinates than cylindrical coordinates, and thus it becomes more difficult to convert and optimize the utilization of the build field.

[0213] In the high-speed sintering process in 3D printing, there is also the fact that the temperature management of the build field is achieved by emitters, which tend to be provided in the form of lines or surfaces. In this regard, the build field in a high-speed sintering plant will also tend to have a square or rectangular shape. This also basically applies to the other 3D printing processes mentioned above and should also be understood in this way for the following explanations.

[0214] Furthermore, the build field will be selectively printed with an absorber. This is typically done using a print head operating according to the DOD (Drop-on-Demand) principle. Such a print head has an array of nozzles that can be individually controlled. To print a complete image with the absorber, depending on the number of nozzles and the area to be printed, such a print head is guided through the build field on one or two axes. Importantly, the absorber is applied to all printed areas at approximately the same resolution. This is also easier to represent by the Cartesian movement of a print head using linear axes than using cylindrical coordinates.

[0215] The layout of the build field can vary. A square or rectangular build field can be distinguished. The same build surface will be used for comparison. The optimization here takes a lot of processing time.

[0216] It should be noted that in the high-speed sintering process, each layer is produced by three operations: coating, printing, and sintering. For each of these three operations, different components must be guided across the entire build field. In principle, the components can move through different or combined axis systems, depending on the design.

[0217] Coating is performed by a linear recoater that moves at a uniform speed on an axis over the build area, applying a new layer to the build field. The coating speed depends on the design of the recoater and is typically in the range of 80 mm / s to 400 mm / s.

[0218] Sintering is again carried out by a radiation source, which is usually also linear and extends across the entire side of the build field. The radiation source should move through the build field at a uniform speed transverse to the linear propagation direction, just like the recoater. Depending on the power of the lamp and the material to be processed, the speed can also reach 80 mm / s to 400 mm / s.

[0219] Due to similar requirements in terms of movement, the emitter can move together with the recoater. In this case, sintering and coating can be carried out simultaneously. However, coating can also occur when the coupled coating / sintering unit moves in one direction, and the sintering process can also occur when the unit moves in the other direction.

[0220] The absorber is printed by a print head that typically operates according to the DOD principle. For reasons of printing speed, multiple print modules are combined for this purpose, which combine individually controllable nozzles to form a nozzle array.

[0221] Depending on the embodiment, the printhead consisting of one or more such arrays then moves across the build field in a zigzag pattern or only along one axis. If the printhead extends across the entire side of the build field and has the required resolution in that direction, it is possible for the printhead to move only along one axis. If the printhead is narrower, the printhead must be guided across the build field multiple times and move between directions perpendicular to the direction of travel.

[0222] In a preferred embodiment, the printhead is provided with a nozzle array in a comb-like manner so that it spans the entire side of the build field, but must be moved laterally once to print across the entire build field in two passes. Here, only by two passes, the lateral movement of the printhead is minimized.

[0223] The printing speed is typically from 300 mm / s to 600 mm / s, which is faster than the coating speed or the sintering speed. Generally, through the ingenious arrangement of the printhead and its movement axes, the time of the printing movement can be at least partially integrated into the coating / sintering process.

[0224] When considering the layer time t min it must be taken into account that the components attached to the respective axes have an extension in the direction of movement and must be included in the calculation, because the components as a whole sweep across the surface of the build field and must provide space for the components of the opposite axis at their reversal points. In addition, the acceleration ramps and deceleration ramps must be considered. These additional travel lengths on both sides of the build field will be referred to as overrun hereinafter. Since the coating application is the slowest movement in the production process of the molded article, it is preferable to select a rather short travel length for the recoater and make all components as narrow as possible in the coating direction to minimize the overrun.

[0225] Assuming a square build field, the overrun is added to both sides of the recoater travel, so it is easy to see that a rectangular build field coated on its short side can be processed in a shorter time.

[0226] On the other hand, as Figure 2 (2) shows, as long as the printing unit used is also scaled, the dimension transverse to the direction of travel of the recoater can be neglected in terms of time loss. However, the shortest time for moving and positioning the printhead is necessary. If the printing unit is not as wide as the build field, a positioning time must be added to this time t PH but this is generally less than the time loss in the coating direction, because the repositioning speed is not affected by any process-related limitations other than mechanical stress.

[0227] However, in terms of temperature management during the building process, a square build field is generally more suitable than a rectangular build field because the edge effect is less obvious.

[0228] Considering the above two points, the build field for mechanical optimization in terms of process time for high-speed sintering processes or any other 3D printing processes mentioned in this article tends to be rectangular in shape, and the shape factor, i.e., the ratio of the long side to the short side of the rectangle, should be relatively small, in the range of 1.2 to 2, to limit edge effects.

[0229] In Figure 2 (3)'s layering direction, denoted here by Z, the total processing duration is linearly related to the Z dimension. That is, doubling the Z dimension also means doubling the total processing time. The feed rate in the Z direction is defined by the time of the entire layer cycle and is proportional to the thickness of the layer. Added to the feed time are t start and t end , which are due to the fact that the entire device must be heated and the particulate material cake must be cooled down before the produced molded article can be removed. These times must be added to the time required to create the starting and ending layers to thermally insulate the molded article from the environment and, in the case of the starting layer, achieve temperature and control equilibrium. Compared to the influence of the other two dimensions on the build time, the Z dimension takes this into account the most. This is because, unlike the Z dimension, the length of the build field in the coating direction also linearly affects the determination of the build time, but with a lower coefficient. Doubling the length in the coating direction also results in an increase in the build time. Since the additional lateral length along this axis is independent of the dimensional change, the increase in the build time will be less than 2 times. If the print head is scaled up proportionally at the same time, the expansion of the build field transverse to the coating direction has no effect on the build time.

[0230] In these aspects, the Z dimension is the most critical dimension in the Cartesian build area and should be chosen as the smallest of the three dimensions to minimize the build time as much as possible. A reasonable lower limit is defined by the range of the part to be built. However, the advantage of the Z dimension is that it can be variably selected for each job, and the system only defines the maximum size.

[0231] Figure 3 The graphs in c do not refer to the direct generation time of the molded article, but to the cooling time t c , which is important for removal. For illustration purposes, it is assumed here that the X and Y dimensions are constant.

[0232] The cooling time of the powder cake can be calculated using the differential equation of heat conduction by the finite element method. The spatio-temporal evolution of the temperature field T(x, y, z, t) is given by the following relation:

[0233]

[0234] where ρ is the density of the material, c is the heat capacity, and λ is the thermal conductivity. The change in heat flux (in W / m 2 units) through the volume boundary surface A depends on the two boundary surfaces Tw to T ∞The temperature difference and heat transfer coefficient α:

[0235]

[0236] Especially on the surface of the powder compact, according to the Stefan - Boltzmann law, heat transfer coupling with the environment occurs through thermal radiation:

[0237]

[0238] The so - called T 4 law is based on the size of the surface A, the temperature - dependent emissivity ε(T), and the Stefan - Boltzmann constant σ.

[0239] Obviously, when the volume increases linearly, there is a non - linear relationship for the cooling time. The reason is that the thermal conductivity λ of the granular material used is small, and heat transfer can occur maximally on the surface of the granular material volume, but as the volume increases, these increases are relatively small. In addition, the heat content is also proportional to the volume. Therefore, several advantages are achieved by keeping the at least one - dimensional cuboid granular material cake small. Designing another dimension smaller than the previous one is also beneficial. Above the critical limit denoted here by z max the cooling time of the granular material cake is greater than the degradation time t d of the granular material. This means that a loss in the mechanical properties of the produced molded article must be anticipated, and the unprinted granular material can no longer be returned to the layering process. Anyway, the long cooling time before the produced molded article can be removed is undesirable for the production operation. The length of the cooling time relative to the build time also increases the number of required job bins, since the system can advantageously load a new job bin after printing and then print another job. In addition, the cooling time should not be significantly longer than 24 hours so that the operators using one system in a single - shift operation can be utilized evenly.

[0240] Figure 2 Graphically shows the influence of the individual dimensions of the process field on the processing speed in additive manufacturing using the high - speed sintering process.

[0241] Therefore, in an overall view, a preferred dimensional ratio of Y>X>Z such as Figure 4is schematically shown. The various layers of the build process are shown, as well as the molded part created on the surface. The standard market size of the plastic molded article can reach 1 meter in one direction. Since this market will be served in an additive manufacturing process such as a high-speed sintering process, the process field size of this magnitude seems reasonable, at least in one spatial dimension. Based on these considerations, this dimension can be called Y to maintain naming consistency. This results in a range for the X dimension of <1 meter. Additionally, again following the productivity paradigm, the Z direction should be the smallest. However, it should also be less than z max , which results in values between 150 mm and 400 mm when using commercially available particulate materials such as Voxeljet HSS PA12 powder type B or HSS PP powder type A. The reason is that the removal temperature is relatively low, approximately 40 °C, compared to the processing temperature of 170 °C or 130 °C for the high-speed sintering process using PP powder type A. This value in the Z direction also depends on the expansion in the X direction, which is limited since X>Z should apply.

[0242] According to the present disclosure, on the one hand, it may be useful and advantageous to combine the above-described build area design and geometry definable by the X, Y, and Z axes with other devices that provide or support improved heat dissipation. Similarly, on the one hand, it may be useful to design the sintering assembly in a specific manner, specifically designed to actively influence the build area design while also improving other devices and improving the process flow related to the build area design.

[0243] The shape of the sintering assembly stems from considerations of the build field geometry. In order to minimize the time loss in the X direction when the sintering assembly sweeps across the process field and to minimize the commutation distance included therein, the requirement in terms of shape is that the assembly be as narrow as possible in the X direction. However, long and relatively narrow sintering devices pose special challenges in terms of temperature management, which can only be solved by special types of designs.

[0244] Due to the large footprint of the assembly, the heat generated by the secondary effects on the emitter unit and the absorption spectra from the two spectral converters can no longer be solved by a conventional cooling device with a fluid flow device cover. As a result, the spectral converter overheats, which in turn leads to unnecessary secondary radiation or a significant shortening of the lifespan of the emitter unit.

[0245] This can only be solved by improving the coupling between the heat generated and the heat dissipated. The heat cannot simply be transferred outside the assembly, for example, by air cooling through a connected fan, because this would cause contamination of the assembly space and make the supply and discharge of air difficult, since the device is in continuous motion and performs thousands of cycles of sweeping across the process field during a single build process.

[0246] This problem can be solved by using a transmitter assembly that connects all heating elements to the coolant through a closed air circulation system. For example, air circulation can be generated by a fan and / or supplying compressed air and using a diffuser.

[0247] Figure 5 An exemplary concept of an additive manufacturing device based on a high-speed sintering process is described, which takes into account the dimensional ratios of the process field. It shows a top view (XY plane) and a front view (XZ plane). In an exemplary embodiment, the build area has dimensions of 600x1000x400 mm 3 。

[0248] In an exemplary embodiment, a sintering assembly is described according to the present disclosure and advantageously combined with the present disclosure for build area design, which is equipped with an independent air circulation S205, as Figure S2 schematically shown in a cross-sectional view of the device in the XZ plane. The air in the assembly is guided through the cavity between the spectral converters S203, S204 and over the cooling ribs S201 connected to the cooling lid. This allows for a significant increase in heat dissipation efficiency through the lid through which water flows. In addition, continuous air flow dissipates heat more evenly, which is beneficial for the local continuity of the emitted radiation spectrum.

[0249] Having Figure S3 The sintering assembly in a side view (YZ plane) with the air flow shown in has grooves S307 on the side walls through which the cooling air passes. This ensures that the spectral converter is adequately cooled at its hottest point, as it is furthest from the heat-conducting component. The air flow S304 is generated and maintained by the fan S303. Clearly visible is the important aspect of the continuous air flow circulating in the sealed housing. Thus, the transmitter assembly, although having high power and a suitable spectrum, can also operate in an environment with a high risk of contamination, such as being contaminated with dust.

[0250] Combining the transmitter assembly for build field temperature control with the geometry and dimensions of the above-described build area may be useful according to the specific requirements of the 3D printing device and its required design specifications.

[0251] This also allows for optimizing on-site temperature control.

[0252] Therefore, different transmitter powers can be used to compensate for the non-uniform temperature distribution on the object surface H202, as Figure H2As shown. In this case, a combination of individual infrared emitters H201 in the peripheral area of the emitter assembly forms a dedicated heating circuit that operates at a higher power compared to those circuits in the center of the assembly. In the present example, 5 different surface temperatures H205 of the panel-type infrared emitter H201 are outlined. The surface temperatures are as close as possible to the position-dependent heating curve H205 previously calculated based on geometric and physical factors. The result is a relatively uniform temperature field H204 on the object surface. To control the generated temperature, an infrared pyrometer H206 is used again, but this time in combination with a thermal imaging camera H207 that is capable of recording the temperature distribution on the object surface with spatial resolution. The measurement data from the thermal imaging camera can now be used to targetedly control the individual panel-type emitters, thereby compensating for the non-uniformity of the local constancy of the object surface temperature, especially including its peripheral area. Each individual emitter is assigned a corresponding area element on the object surface. In one embodiment, the infrared pyrometer is used for absolute value correction, thus ensuring prevention of temperature drift in the measurements of the thermal imaging camera and ensuring the temporal constancy of the temperature field.

[0253] Just as Figure H3 in the case of the assembly (H301) of individual emitters (H303) shown in, the control of the thermal imaging camera (H302) and the infrared pyrometer (H305) does not simply adjust the power of individual heating elements.

[0254] The temperature of each individual heating element is measured by a temperature sensor (H304) integrated in the heating element and fed as a measured value to the control system. If the control system is designed as a PID controller, it can be used to minimize the time required for the emitter to reach the target temperature. A prerequisite for this is that there is sufficient reserve in the heating power of each individual heating element. For example, an emitter with a maximum power of 650 watts can be used, but to reach an equilibrium emitter temperature, 200 watts are already reached. Then, the controller is able to maximize the set power until the target temperature is reached and only reduce it back to the steady-state condition for a short time after reaching the target temperature. As a result, the response time can be reduced to well below 20 seconds, which is within the layer cycle time of a sintering printer. Thus, the system can now react in a timely manner to temperature fluctuations.

[0255] Furthermore, this process can significantly reduce the long heating time, and the time until reaching the steady state is only one quarter.

[0256] In an exemplary arrangement of the emitter assembly, each has four thermal imaging cameras H302 and infrared pyrometers H305 to enable non-contact surface temperature measurement of an object with as small an angular error as possible and to keep the distance between the assembly and the object surface small. A smaller distance results in higher energy efficiency. H304 is a conventional temperature sensor, such as a thermocouple or resistance thermometer, which continuously measures the surface temperature of the infrared emitter, and due to the Stefan-Boltzmann law, thus, the radiant power, and together with the other two measuring devices provides input values for setpoint control. The target temperature of each heating element is calculated using the following relationship:

[0257]

[0258] C 12 = ε1·ε2·F 12

[0259] The heat flow between the emitter and the corresponding building field element at temperature T1 should be minimized by adjusting its temperature T2. In addition to the emission factor ε2 of the emitter ε2 and the particulate material on the building field ε1, the so-called view factor F 12 and F 21 are decisive. The view factor describes the orientation of two surfaces relative to each other, where F 21 represents the radiant flux from the emitter to the building field, and F 12 represents the reverse path. The solution for the target temperature of each heating element can be achieved by solving the resulting differential equations using the finite element method.

[0260] If a larger surface is to be covered, multiple emitter fields can be arranged in a staggered manner, i.e., in a combined arrangement, without any problems. By overlapping the measurement ranges of the thermal imaging cameras and infrared pyrometers, calibration data can be further generated, thereby improving the measurement accuracy of the instruments used by comparing the obtained measurement data. Thus, almost any geometry and size of the building field are possible without including another complex and expensive design step.

[0261] Based on symmetry considerations, in one embodiment according to the present disclosure, as Figure H4As shown, emitter groups of the emitter assembly (H400), namely (H401) to (H406), can be formed, and each emitter can be controlled together. Therefore, the workload and cost can be saved, without being mainly restricted by the constancy of the object surface temperature, and the control algorithm is simpler. Therefore, it makes sense to consider emitter (H401) separately at the second-order discontinuity (i.e., the corner of the object surface to be heated), because due to the colder environment, a stronger heat flow will occur there. A similar situation occurs when considering the edges (H405) and (H406) of the object surface to be heated, where these two edges are separated to compensate for the temperature difference between the front and back of the device. (H203) and (H204) perform this operation for this internal area. Then, the maximum symmetry center in the middle of the assembly is covered by (H402). Combining several individual emitters can also have a beneficial effect on the measurement accuracy. For example, multiple temperature sensors can be evaluated within a group, and the average value is used to balance the manufacturing tolerances.

[0262] In addition, Figure H5 An embodiment of the corresponding control is schematically shown, which can be applied to Figure H3 and Figure H4 the example embodiments shown. The change in the object surface temperature distribution is measured by a thermal imaging camera. The area elements are also covered by infrared pyrometers. The average value of the temperatures of the area elements measured by the thermal imaging camera is taken, and this average value is compared with the value measured by the pyrometer. Then the camera is readjusted until the two values are equal. Subsequently, the obtained correction factor is applied to the remaining measurement data. Then the corrected data is transmitted to the control system of the heating element through an algorithm. The task of this algorithm is to assign a corresponding area element to each individual emitter. In addition, the overlap of the area elements is also considered here. The reason is that due to the formed radiation cone, a single emitter also reaches adjacent area elements. In addition, the algorithm must consider the geometric arrangement of the individual emitters, because adjacent emitters will affect each other. In the worst case, this may cause unwanted oscillations in the output of each heating circuit over time

[0263] The algorithm calculates the target temperature of each heating element and sends the target temperature to the controller of each heating circuit. Taking a traditional PID controller as an example, the controller compares the target temperature value and the actual temperature value, and ensures that the specified target temperature of the infrared emitter is reached in the shortest possible time and the deviation is as small as possible by controlling the power supplied to these emitters.

[0264] Next, the temperature distribution is measured again and the process is restarted. Preferably, one cycle of the entire control system occurs at the defined time of each layer cycle of the building process, so that the measurement is not hindered by units such as sintering devices, recoaters, and print heads, which move on the building field surface at this time.

[0265] Figure H5 Schematically shows an embodiment of the control according to the present disclosure, in which the change in the temperature distribution on the surface of the object is measured by a thermal imaging camera and the temporal change is compensated by an infrared pyrometer, and the absolute temperature value can be corrected. The obtained measurement data are fed into an algorithm that uses these data to calculate the target temperature of each infrared emitter and passes them to a PID controller.

[0266] In addition, Figure H5 schematically shows an embodiment of the corresponding control, as it can be applied to Figure H3 and Figure H4 the example embodiments in.

[0267] The solver algorithm is used to calculate the target temperature of each heating element, which is calculated based on the physical relationships describing the heat flow. The view factor F ij represents an important component here.

[0268] The view factor describes the orientation of two surfaces relative to each other, where F 21 represents the radiative flux from the emitter to the build field, and F 12 represents the reverse path. The view factor for two finite surfaces facing each other has the general formula

[0269]

[0270] Thus, the view factor F ij is defined by the finite relative surfaces A i and A j of the emitter and the build field respectively, as well as the angles, cosΘ i and cosΘ j of their respective unit normals to these surfaces, and the distance R ij between the surfaces relative to each other.

[0271] At this point, the emitter unit according to the present disclosure can be designed such that the emitter not only illuminates the area element, i.e., the area (sub - area) of the build field, but also illuminates the entire build field. Thus, the main radiation is projected onto the core area (area element), and in addition, the radiation also impinges around this core area. Similarly, each area element of the entire build field exchanges radiation with the emitter or emitter assembly. This now applies to each individual emitter in the emitter unit. The geometric arrangement of the emitters, such as their size, distance to the build field, and distance from each other, is described by the above - mentioned view factor, just as the geometry of the build field to be heated, i.e., its orientation, length, and width.

[0272] Since it is known which materials are used, the emissivity, which mainly depends on the temperature, can be taken into account during design and operation, i.e., when performing the 3D printing process.

[0273] In addition, the heat flow due to convection and conduction in the particulate material and the emitter assembly is temperature-dependent and is included in the calculations for the design and operation of the emitter assembly according to the present disclosure. This applies in particular to the build field and the peripheral regions of the emitter assembly, since convection and heat conduction occur more frequently here due to discontinuities. In addition, additional heat conduction can be considered due to the position of the emitter assembly and the coolant required for shielding from the machine housing.

[0274] As a result, a complex set of coupled inhomogeneous differential equations is generated. The task of the solver algorithm is now to solve this system of equations by determining the eigenvalue of the temperature assigned to the radiant heaters based on the input of the measured temperature values, thereby minimizing the total heat flow between the calculated emitter and the build field by including the build field set temperature. to a minimum.

[0275] The solution of these target temperatures (T_n,soll) for each emitter n can be achieved by solving the system of equations using a solver of the finite element process. Due to the advancement of the computing power of modern computer systems and the optimization of the individual calculation steps, such a solver can complete the calculation within the time of one layer cycle.

[0276] The target values calculated for the individual emitters are now transmitted to a set of controllers, the task of which is to set these target temperatures at the emitters in the shortest possible time.

[0277] The controllers, exemplarily designed as conventional PID controllers, compare the target temperature value with the actual temperature value (T_n,ist) and ensure that the target temperature of the specified emitter (e.g., infrared emitter) is reached in the shortest possible time by controlling the electrical power (P_n) supplied to these emitters by changing the applied average voltage, thereby achieving the smallest possible deviation.

[0278] Once the target temperature is reached at the emitter, the temperature distribution is measured again. By comparing the measured values with the calculated values, a correction factor can now be derived and included in future calculations. Thus, the system is able to respond dynamically to manufacturing tolerances and disturbances in the structure, such as changes in environmental conditions or changes in the particulate material composition due to the aging of recycled materials added to the printing process. Aging phenomena of the device itself are also automatically corrected. It also avoids running the 3D printer for weeks as is usually the case in the prior art.

[0279] Preferably, a cycle of the entire control system occurs at the defined time of each layer cycle of the build process so that measurements are not impeded by units such as sintering devices, recoaters, and print heads that move across the build field during this time. Changes in interaction with the radiation field or temperature changes of components used during the layering process no longer have an impact because the shadow of the build field can be masked depending on time and location.

[0280] This has the advantage that, compared to the prior art, no adjustment and / or calibration of the equipment is required. In addition, the 3D printer can operate stably even under fluctuating environmental conditions, and thus can operate in areas with higher or lower ambient temperatures. This brings a cost advantage as it eliminates costs for, for example, ambient air conditioning.

[0281] During the printing process, the sintering process of the surface of the particulate material wetted with IR receptors (IR absorbers) corresponding to the cross-section of the molded article to be produced introduces additional energy through the sintering unit, resulting in a temperature increase there. In addition, the molded article parts that have been created change physical parameters such as the thermal conductivity of the particulate material or the emissivity of the printing surface. In prior art equipment, this repeatedly leads to the interruption of the printing process and even damage to the machine due to uncontrollable process conditions.

[0282] In this example, the position of the part in the build area is known. Therefore, the cross-sectional view data for IR receptor application is already available and can be fed to and considered by the solver algorithm. The latter is now able to react dynamically to different filling degrees of the surface of the particulate material. In principle, this process can also be used to automatically place the molded article in the build area in an optimized manner. This eliminates the time-consuming and complex step of manually placing the molded article into the virtual build area. This can save a significant amount of time and cost. For example, there is no need for training in part placement and fine-tuning required for sintering machine operation. In the prior art, in order to ensure optimal orientation and parameterization, the molded article was often created many times, which is so-called "phantom jobs" in this field. Eliminating these multiple pre-test prints can significantly reduce manufacturing costs.

[0283] In addition, the required repeatability, which is important for industrial production, can be achieved, so that more stringent tolerances can be applied to the produced molded articles. Therefore, an improvement in quality is also achieved.

[0284] If a larger surface is to be covered, several emitter fields (overlapping fields covered by a set of emitters or different emitter units) can easily be staggered. By overlapping the measurement ranges of the thermal imaging camera and the infrared pyrometer, calibration data can be further generated, thereby improving the measurement accuracy of the instruments used by comparing the obtained measurement data. Thus, almost any geometric shape and size of the constructed field are possible without including another complex and expensive design step.

Claims

1. A 3D printing device for a sintering process or a multi-jet fusion process, characterized in that, The 3D printing device includes: a sintering emitter assembly, a build area characterized by an X-axis, a Y-axis, and a Z-axis that form a build field, wherein in the build area there are dimensions such that Y > X > Z, and the dimension of the build area in the Z direction is 50 cm or less, and the sintering emitter assembly is generally smaller than the build field in the X direction.

2. The 3D printing device according to claim 1, wherein, The recoater extends substantially along the length Y and moves in the X direction, or / and wherein the dimension of the build field in the Y direction is 50 cm or greater, or / and wherein the ratio of Y:X is between 1.1 and 3.

0.

3. The 3D printing device according to claim 1, wherein, the recoater, the print head, and / or the sintering emitter assembly extend substantially along the length Y and travel along the X-axis, or / and wherein the printing modules of the print head are arranged in a comb-like manner.

4. The 3D printing device according to claim 1, characterized in that, The 3D printing device includes means for heat dissipation, or / and wherein the means for heat dissipation is a gas or a coolant, or / and wherein the sintering emitter assembly is cooled by a gas or / and a coolant or / and through a heat pipe.

5. The 3D printing device according to claim 1, wherein, wherein the sintering emitter assembly is characterized by a closed air cooling circuit and a liquid-based cooling circuit, and wherein a gas circulates in the closed air cooling circuit, or / and wherein the liquid-based cooling circuit is arranged on a side facing away from the build field or / and in connection with an additional coolant, or / and wherein the closed air cooling circuit is at least partially guided past a radiation transducer, or / and wherein means for increasing the surface area are arranged in the air cooling circuit.

6. The 3D printing device according to claim 5, wherein, an IR emitter is arranged between the primary and secondary radiation transducers and the liquid-based cooling circuit, and optionally, a reflector is arranged between the IR emitter and the liquid flow cooling member, or / and wherein the liquid-based cooling circuit is cooled by a liquid flow cooling member outside the sintering emitter assembly, or / and wherein the closed air cooling circuit has no connection to the ambient air, or / and wherein the 3D printing device includes one, two, or more radiation transducers.

7. The 3D printing device according to claim 1, characterized in that, The 3D printing device includes emitters of broadband electromagnetic radiation of different wavelengths, the spectra of which are offset from each other.

8. The 3D printing device according to claim 1, wherein, wherein the 3D printing device includes an additional emitter unit, wherein the emitter unit is characterized by an array of a plurality of emitters, wherein a subset of the emitters is combined into a group, wherein each group includes at least one emitter and one temperature sensor, the temperature sensor being integrated on at least one emitter to measure its own temperature, and the temperature sensor feeding back the measured value to a control system to regulate the temperature of the group.

9. The 3D printing device according to claim 8, characterized in that, wherein a target temperature is set at each emitter or emitter group.

10. The 3D printing device according to claim 8, wherein, the temperature of each emitter is individually controllable, the temperature of each group of emitters is controllable, or / and The emitter unit includes a closed-loop control circuit for adjusting a target temperature on the build field.

11. The 3D printing device according to claim 8, characterized in that, The emitter unit includes at least one thermal imaging camera pointing at the build field and / or at least one infrared pyrometer and / or at least one temperature sensor.

12. The 3D printing device according to claim 11, characterized in that, The thermal imaging camera is used for local measurement recording, and the infrared pyrometer is used for calibrating the absolute temperature value.

13. The 3D printing device according to claim 8, characterized in that, An emitter unit is included, wherein the target temperature on the build field can be adjusted by setting the target temperature of each group or each emitter in the emitter unit.

14. A sintering process for producing a molded article by applying and selectively curing particulate material, characterized in that the process is carried out in a build area, which is characterized by an X-axis and a Y-axis forming a build field, and a Z-axis, wherein there are dimensions Y > X > Z in the build area, and the dimension of the build area in the Z-direction is 50 cm or less, the process uses a 3D printing device, the 3D printing device comprising: a sintering emitter assembly, the sintering emitter assembly being generally smaller than the build field in the X-direction.

15. The sintering process according to claim 14, wherein wherein the build field has a dimension of 60 cm or more in the Y-direction, and the build area has a dimension of 50 cm or less in the Z-direction, or / and where the ratio of Y:X is between 1.1 and 3.0.

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