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WO2025052133A1 - Appareil et procédé de formation par couches d'objets 3d à partir de matériau de construction particulaire - Google Patents

Appareil et procédé de formation par couches d'objets 3d à partir de matériau de construction particulaire Download PDF

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Publication number
WO2025052133A1
WO2025052133A1 PCT/GB2024/052320 GB2024052320W WO2025052133A1 WO 2025052133 A1 WO2025052133 A1 WO 2025052133A1 GB 2024052320 W GB2024052320 W GB 2024052320W WO 2025052133 A1 WO2025052133 A1 WO 2025052133A1
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Prior art keywords
fusing
section
energy
layer
voxels
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English (en)
Inventor
Neil Hopkinson
Marshall LING
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Stratasys Powder Production Ltd
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Stratasys Powder Production Ltd
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/20—Direct sintering or melting
    • B22F10/28—Powder bed fusion, e.g. selective laser melting [SLM] or electron beam melting [EBM]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/30—Process control
    • B22F10/36—Process control of energy beam parameters
    • B22F10/368—Temperature or temperature gradient, e.g. temperature of the melt pool
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/10—Auxiliary heating means
    • B22F12/13—Auxiliary heating means to preheat the material
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/40—Radiation means
    • B22F12/41—Radiation means characterised by the type, e.g. laser or electron beam
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/40—Radiation means
    • B22F12/44—Radiation means characterised by the configuration of the radiation means
    • B22F12/45—Two or more
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F12/00—Apparatus or devices specially adapted for additive manufacturing; Auxiliary means for additive manufacturing; Combinations of additive manufacturing apparatus or devices with other processing apparatus or devices
    • B22F12/90—Means for process control, e.g. cameras or sensors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/10—Processes of additive manufacturing
    • B29C64/141—Processes of additive manufacturing using only solid materials
    • B29C64/153—Processes of additive manufacturing using only solid materials using layers of powder being selectively joined, e.g. by selective laser sintering or melting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/10—Processes of additive manufacturing
    • B29C64/165—Processes of additive manufacturing using a combination of solid and fluid materials, e.g. a powder selectively bound by a liquid binder, catalyst, inhibitor or energy absorber
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/20—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B29C64/264—Arrangements for irradiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/20—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B29C64/264—Arrangements for irradiation
    • B29C64/268—Arrangements for irradiation using laser beams; using electron beams [EB]
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/20—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B29C64/264—Arrangements for irradiation
    • B29C64/291—Arrangements for irradiation for operating globally, e.g. together with selectively applied activators or inhibitors
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/20—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B29C64/295—Heating elements
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y10/00—Processes of additive manufacturing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y30/00—Apparatus for additive manufacturing; Details thereof or accessories therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/30—Process control
    • B22F10/36—Process control of energy beam parameters
    • B22F10/362—Process control of energy beam parameters for preheating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F10/00—Additive manufacturing of workpieces or articles from metallic powder
    • B22F10/30—Process control
    • B22F10/36—Process control of energy beam parameters
    • B22F10/364—Process control of energy beam parameters for post-heating, e.g. remelting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C64/00—Additive manufacturing, i.e. manufacturing of three-dimensional [3D] objects by additive deposition, additive agglomeration or additive layering, e.g. by 3D printing, stereolithography or selective laser sintering
    • B29C64/30—Auxiliary operations or equipment
    • B29C64/386—Data acquisition or data processing for additive manufacturing
    • B29C64/393—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B33—ADDITIVE MANUFACTURING TECHNOLOGY
    • B33Y—ADDITIVE MANUFACTURING, i.e. MANUFACTURING OF THREE-DIMENSIONAL [3-D] OBJECTS BY ADDITIVE DEPOSITION, ADDITIVE AGGLOMERATION OR ADDITIVE LAYERING, e.g. BY 3-D PRINTING, STEREOLITHOGRAPHY OR SELECTIVE LASER SINTERING
    • B33Y50/00—Data acquisition or data processing for additive manufacturing
    • B33Y50/02—Data acquisition or data processing for additive manufacturing for controlling or regulating additive manufacturing processes

Definitions

  • the present disclosure relates to the field of layerwise manufacture of 3D objects from particulate build material, and in particular to the control of fusion of object cross sections. Apparatus and methods of control therefor are disclosed, which may find particular benefits in applications requiring improved parts properties.
  • an object is built up layer by layer from powder material by selectively fusing, or melting, the powder over successive object cross sections. This results in the object being built up within a supportive bed of unfused powder that can be removed at the end of the process by simply brushing and/or blowing the supportive powder off by pressurised gas streams.
  • the object cross sections are typically defined as part of slice data that defines the voxels to be fused for each layer. Selective fusion may be achieved by for example a laser tracing the cross section, or by a printhead printing infrared absorber over the voxels to be fused followed by irradiation with an infrared light source, whereby the absorber causes selective heating.
  • print and fuse processes employ scanning printheads and lamps that can process each layer in a single pass and are thus faster and have high potential for industrial large volume manufacture.
  • fusing energy is provided by non-selective heat sources.
  • the non-selective heat source is typically an elongate infrared lamp that spans the width of the layer and that is operated to provide fusing energy to the object cross sections as it traverses the layer.
  • Print and fuse processes rely on the deposition of absorber to create selectivity, which is typically provided by a printhead scanning over the layer before application of the fuse lamp heating of the printed cross section.
  • the absorber is carbon black, leading to dark grey to black parts in appearance that are challenging to colour, especially to to achieve vibrant colours. Meanwhile, absorbers of lighter or nonblack appearance may be used but these typically lead to drawbacks in mechanical properties.
  • print and fuse processes retain limitations that may be addressed by the present invention disclosed herein.
  • Fig. 1 is a schematic cross section side view through a build bed of an apparatus for the layerwise manufacture of 3D objects according to the invention
  • Fig. 2 is a flow chart of a method of using the apparatus according to the invention.
  • Fig. 3 is a flow chart of a further method of using the apparatus according to the invention.
  • Fig. 4 illustrates temperature deviations of a line of voxels along x
  • Fig. 5 is a variant of Fig. 1 illustrating different fusing energy beams based on the temperature deviations of Fig. 4;
  • Fig. 6 is a variant of Fig. 1 illustrating adjusted fusing energy beams and non-fusing energy beams, each of different energies;
  • Figs. 7A to 7E illustrate different stages of fusing of a digital light projector (DLP) comprising a scrolling digital mirror device (DMD);
  • DLP digital light projector
  • DMD scrolling digital mirror device
  • Fig. 8A illustrates a mask to be applied to a slice for a DMD
  • Fig. 8B illustrates a slice comprising non-fusing heating data
  • Fig. 8C illustrates a schematic top view of a layer heated according to a combination of the slice of Fig. 8B modified by the mask of Fig 8A;
  • Fig. 9 illustrates a series of mask weights used to modify the pixel data of a non-fusing slice
  • Figs. 10A to 10D illustrate a sequence of slices modified by a mask for a scrolling DMD
  • Fig. 11A illustrates the example intensity profile obtained by Figs. 10A to 10D;
  • Fig. 1 IB illustrates a variant of the profile of Fig. 1 IB
  • Fig. 12 illustrates intensity profiles obtained by conventional powder bed fusion apparatus.
  • a “fusing energy beam source” is operable to ‘fuse’ build material by being operated at an energy output and/or wavelength capable of raising the temperature of the build material to or above the melting temperature. In this way, fusion of the build material over object cross sections may be achieved.
  • a “non-fusing energy beam source” is operated at a comparatively lower energy output and/or at a different wavelength, capable of raising the temperature of the build material without it reaching or exceeding the melting temperature.
  • the term ‘non-fusing’ is not intended to define any particular order in the steps of a thermal event sequence. A non-fusing step may be applied at any suitable instance of the process.
  • a “selective” heat source herein is a heat source able to address the layer per voxel or unit control area so as to selectively heat to fuse or warm specific areas of the layer.
  • a “non- selective” heat source herein is a heat source that applies heat over groups of voxels at a time without being configured to selectively heat or fuse specific area of the layer in absence of other means to enhance the absorption of radiation of the non-selective heat source at specific voxels of the layer.
  • Such means may be a printhead selectively applying radiation absorber to specific voxels that are to fuse.
  • Examples of non-selective heat sources are scanning infrared bar heaters conventionally used in print and fuse apparatus, or the overhead heaters fixedly arranged above the layer to help maintain a uniform temperature over the layer.
  • Fig.l which illustrates a schematic cross section side view of a build bed formed from a sequence of layers 160
  • the apparatus 10 comprises two fusing light sources which in combination provide a solution to address or at least reduce the present shortcomings.
  • the apparatus comprises a first fusing source and a second fusing source, at least one of which is a digital light projector (DLP) for providing selective fusing energy.
  • DLP digital light projector
  • the two fusing sources in combination provide selective application of energy and prolonged heating of the fused cross sections to ensure full consolidation and improved quality of the object and unfused material. Applying a combination of such first and second fusing sources allows reducing or omitting the presence of absorber to create selectivity and presents a solution to achieving white or light-coloured objects with improved mechanical properties.
  • the DLP is arranged to provide fusing energy beams to the layer 160 and comprises a digital mirror device (DMD) 240 and a light source 250, such as an infrared light source.
  • the digital mirror device 240 comprises an array of individually addressable mirrors, wherein the light source directs a light beam 450 towards the array and each mirror is configured to receive and redirect an energy beam received from the light source 250 either away from or towards the layer, based on the image slice for a corresponding layer.
  • the mirror When a mirror is in an operative state, the mirror reflects a beamlet of the energy beam towards a corresponding voxel of the layer 160.
  • the mirror When a mirror is in an inoperative state, the mirror reflects the beamlet of the energy beam away from the layer.
  • Such operation of a DMD is well known.
  • the location on the layer and thus the voxel addressed may be altered by altering the position of the array, by moving it across the layer or operating it in scrolling mode to sweep the energy beams of the array across the layer, by altering the angle of the array with respect to the layer surface, and/or by altering the angle of the light source with respect to the array.
  • the apparatus 10 comprises a distributor 290 to distribute each layer of build material; and a first fusing source and a second fusing source, each configured to provide fusing energy based on image slices defining each object cross section to be formed within a corresponding layer, wherein at least one of the first and second fusing sources is configured to provide selective fusing energy to selected object voxels of the layer within the object cross sections.
  • a fusing source is herein described in the form of a digital light projector.
  • the apparatus comprises a controller configured to control the distributor 290 to distribute each layer; to control the first fusing source to fuse selected object voxels to form an object cross section; and to control the second fusing source to further fuse the object voxels fused by the first fusing source.
  • the steps of distributing and fusing by the first and second fusing source are repeated to form the object from a sequence of object cross sections.
  • a method 600 for controlling the apparatus 10 is further illustrated in Fig. 2, which is a flow chart showing at block 610 the step of distributing a layer; at block 650 the step of fusing selected object voxels within the cross section and at block 680 the step of further fusing the object voxels using the second fusing source.
  • the two fusing steps at blocks 650 and 680 may be applied in either order to improve the provision of fusing energy compared to conventional apparatus:
  • Fig. 1 illustrates the DLP as the first fusing source applying the fusing step at voxel resolution at block 620.
  • the further fusing step may be provided by the second fusing source, which is shown in the form of a scanning infrared lamp or non-selective energy source 220 configured to heat the object cross section fused in the first fusing step.
  • Selectivity is achieved by the higher absorber weight per volume within the densified build material of the object cross section after fusing by the DLP.
  • the higher density of the object cross section 150 results in an absorptivity to radiation from the non-selective second fusing source, such as an infrared scanning lamp, that is higher than that of the surrounding undensified build material. Therefore, the further fuse step results in selective fusing of the object cross section without the need of applying absorber with an inkjet printhead.
  • the first fusing source may therefore be the DLP; and the second fusing source may be a non-selective fusing source controlled to further fuse the object cross section after fusing by the DLP.
  • the step of fusing selected object voxels is provided using the DLP at block 650, and before the step of further fusing at block 680, wherein the fusing of selected object voxels causes a densification of build material within the object cross section; wherein the second light source is a non-selective light source and wherein the densification provides selective absorption by the object cross section.
  • further fusing is provided to the object cross section only and not to non-fusing voxels outside the fused object cross section.
  • the build material may comprise an absorber, wherein the amount of the absorber per unit volume in the build material is sufficient to cause fusing within the object cross section by the second fusing source following fusing by the first fusing source, and insufficient to cause fusing within the nonfusing voxels by the second fusing source.
  • the amount of absorber may be less than required in conventional print and fuse apparatus and thus lead to objects lighter in colour or lighter grey.
  • the sequence of steps may be represented by the flow chart of Fig. 2 in which block 650 of selective fusing is applied, by the first fusing source, before a second fusing step at block 680.
  • non-selective heating is applied by a second fusing source that causes further fusing of the cross section and warming without fusing of the unfused build material within the non-fusing area.
  • the first fusing source may be a non-selective fusing lamp
  • the second fusing source a digital light projector comprising a digital mirror device of individually addressable mirrors and a light source, wherein the light source directs light towards the digital mirror device and each mirror redirects an energy beam of the light either away from or towards the layer based on the image slice of a corresponding layer.
  • the apparatus further comprises an absorber deposition device configured to deposit absorber over the object cross section before the step of fusing by the first light source.
  • the controller may be configured to control the absorber deposition device to deposit absorber over the object cross section; and to control the first fusing source to fuse the object voxels of the object cross section and next to control the second fusing source to further fuse some or all object voxels of the object cross section.
  • the amount of absorber or its absorptive properties may be lower than in conventional print and fuse process and may allow nonblack absorbers.
  • the first fusing step in combination with the second, selective fusing step by the DLP may be applied in a gentler manner.
  • the DLP may be operated at a relatively lower power as a result of providing the further fusing step and/or as a result of the object cross section comprising absorber that may enhance the absorption of radiation by the DLP.
  • Allowing the DLP to be operated at lower power reduces the risk of overheating the DMD and prolongs its lifetime.
  • the sequence of steps may be represented by the flow chart of Fig. 2 in which block 650 of selective fusing is applied after block 680 of non- selective further fusing.
  • the provision of the DLP as one of the first and second fusing sources may further improve object quality by allowing provision of different fusing energy beams to different object voxels.
  • the different energy levels may be defined by slice data where the DLP is applied as first fusing source. Additionally, or instead, the different energy levels may be provided or corrected based on thermal feedback from temperature measurements of the fused cross sections, for example following the first fuse step, where the first fusing source is the non- selective fusing source. Different fusing energies based on thermal feedback
  • the apparatus 10 may comprise a thermal sensor 280 configured to measure temperature of the layer 160, after the provision of fusing energy from the first light source (in the form of the non-selective fusing source) and before the provision of fusing energy by the second light source (in the form of the DLP). From the measured temperatures, a fusing thermal profile of the object cross section(s) of that layer defined by the first fusing step may be determined, and compared to a predefined fusing thermal profile for the cross section(s), for example as predetermined from a thermal model.
  • deviations from the predefined fusing thermal profile may be determined and used to define a correction to the fusing energy levels to be provided by some or all of the mirrors of the digital mirror device 240 to corresponding object voxels in the further step of fusing at block 680 of Fig. 2.
  • the controller may be configured to control the thermal sensor 280 and to make the comparisons and determinations; and to control the digital mirror device to provide the corrected different energy levels so as to fine tune the fusing thermal profile of the cross section. In this way, the fusing process may be fine-tuned by the step of further fusing at block 680.
  • Fig. 3 is a flow chart further illustrating this variant method 700 of the method 600 of Fig. 2.
  • FIG. 3 shows at block 710 the step of distributing a new layer, and at block 750 the combined step of depositing absorber over the object cross sectional area of each layer as defined by one or more image slices, and then fusing the object voxels defined by absorber with the first, non-selective fusing source.
  • temperatures of the object cross section are measured using the thermal sensor 280 to determine a fusing thermal profile of the object cross section; which is compared to a predefined fusing thermal profile. Based on the comparison, corrections to the fusing energy levels are determined that are to be applied to the fusing energy beams at a subsequent fusing step by the digital mirror device.
  • the further fusing step carried out by the DLP applies the corrected different fusing energy beams to some or all of the object voxels of the object cross section.
  • the determined different energies are to achieve an improved fusing profile that is closer to or substantially corresponds to the predefined fusing thermal profile.
  • the object cross sections are typically defined as part of slice data that defines the voxels to be fused in each layer comprising one or more object cross sections.
  • the controller 300 controls each micromirror by switching it between the operative and the inoperative state at a switching rate, or duty cycle.
  • the different fusing energy beams 410 provided by the DMD 240 are indicated by arrows.
  • the differences in fusing energy are indicated by the relative thickness of the arrows, wherein the thicker the arrow, the higher the fusing energy of the fusing energy beam provided by a corresponding mirror of the DMD.
  • Fig. 1 the different fusing energy beams 410 provided by the DMD 240 are indicated by arrows.
  • the differences in fusing energy are indicated by the relative thickness of the arrows, wherein the thicker the arrow, the higher the fusing energy of the fusing energy beam provided by a corresponding mirror of the DMD.
  • fusing energy beams 410 1, 410_2, 410_3 different thicknesses are indicated for three of the fusing energy beams, fusing energy beams 410 1, 410_2, 410_3.
  • the outer fusing energy beam 410 3 with respect to the array of mirrors may for example be of higher energy, for example as defined by a higher duty cycle or “ON” time of the mirror, than an inner fusing energy beam 410_l, with respect to the array.
  • a fusing energy beam 410_2 between the outer and inner fusing energy beams 410 1 and 410_3 may provide an energy level intermediate to that of the outer and central fusing energy beams.
  • the mirrors and their operation define the resolution of voxels that may be selectively addressed on the layer.
  • Each mirror of the DMD may be assumed to heat a control area (based on the footprint of the energy beam projected onto the layer by each mirror) and at least the volume of the layer underneath the control area, due to the relatively small layer thickness of the layer.
  • each energy beam is referred to heat a corresponding voxel of at least the top most layer.
  • a “voxel” is referred to as the smallest area selectively addressable by the DMD extending through a layer, wherein the layer may be from 10pm to several 100pm thick or even of the order of microns thick.
  • the build area may be referred to synonymously as the layer 160 due to its relatively small thickness.
  • resolution herein is intended to compare a relatively high resolution, at or exceeding the voxel resolution as may be defined by conventional print heads, and as may be achieved by the DMD, and relatively low resolution as may be provided by an elongate infrared lamp that extends along the width of the layer (along y) or a conventional overhead heater.
  • a non-fusing step may be applied by the DLP when provided as either the first or second fusing source.
  • the first and/or second fusing source when configured to apply selective fusing energy to selected obj ect voxels, may be configured to also apply selective non-fusing energy to selected non-fusing voxels within a non-fusing area outside of the object cross section.
  • the image slices may define the non-fusing area for each layer; wherein the energy levels of the non-fusing energy beams are configured to raise the temperature of the non-fusing voxels to a temperature below the onset of melting.
  • the image slices may define different energy levels for some or all non-fusing voxels so as to define a spatial variation in non-fusing energy level, wherein the spatial variation may be based on one or more of, with respect to the layer stack rather than the slice stack:
  • the energy levels within the peripheral non-fusing area may be different to, such as higher than, the energy levels of the remaining non-fusing area, which may be zero;
  • the control of the DLP to provide non-fusing energy beams may be based on modified image slices that have been modified by one or more masks, as will be described in more detail below.
  • Applying selective fusing energy to selected object voxels during the step of fusing and/or further fusing at blocks 650 or 680 of Fig. 2 or at blocks 780 of Fig. 3 may comprise applying non-fusing energy beams to some or all non-fusing voxels; wherein an energy level of the non-fusing energy beams is configured to raise the temperature of the non-fusing voxels to a temperature below the melting temperature of the build material.
  • the melting point may in some cases be defined by the onset of melting of the build material, at which the material particles become sufficiently viscous to stick to one another. Additionally, or instead, the DLP may be operated based on thermal feedback from the thermal sensor 280 to fine tune the non-fusing energy profile determined using the thermal sensor 280.
  • the thermal sensor 280 may be configured to measure temperature of the nonfusing area before the provision of non-fusing energy beams by the digital light projector; wherein the controller is configured to determine from the measured temperature a nonfusing thermal profile of the non-fusing area; compare the determined non-fusing profile to a predefined non-fusing profile for that layer; and, based on the comparison, determine an energy level to be provided by the digital mirror device to some or all of the non-fusing voxels by corresponding non-fusing energy beams. This will be described further with reference to Figs. 5 and 6.
  • the non-fusing step applied by the DLP may be concurrent or following the step of fusion or further fusion.
  • the apparatus may comprise a further heat source configured to provide nonfusing energy.
  • the heat source may be provided by one or more of the digital light projector; a further digital light projector or a non-selective heat source, configured to provide nonfusing energy to the layer.
  • a non-selective heat source may be mounted behind the distributor to immediately preheat the freshly distributed layer.
  • the further heat source may be operated to heat the non-fusing area towards or to a predefined target layer temperature that may be close to the melting temperature to prevent curling due to excessive temperature differentials during fusing, and sufficiently below the melting temperature of the build material so as to avoid accidental fusion.
  • the target layer temperature may be chosen to be within 10 °C or 20 °C below the melting temperature.
  • the first or second light source when configured to provide fusing energy beams selectively to individual object voxels may be configured to provide fusing energy beams of different energy levels to the object cross section. This is indicated by the different fusing beams 410 in Fig. 1 for example.
  • the initial image slices may define a constant fusing energy level for all object voxels.
  • a model based simulation routine may be applied to determine adjusted slice data based on the initial slices that may determine different fusing energy levels to be applied to some of the object voxels, e.g. in terms of duty cycle, to be provided to each object voxel.
  • the routine may determine thermal impacts on each object cross section to be built based on its environment, determine deviations of the modelled solution from a predefined target temperature and adjust the duty cycle for some or all object pixels to reduce such unwanted deviations.
  • individual duty cycles to be applied for each object voxel of a layer may be determined based on one or more of: the shape and/or area of the object cross section; the shape and/or volume of one or more preceding object cross sections; the shape and/or volume of one or more subsequent object cross sections; and the distance to a neighbouring object cross section and/or to a boundary wall of the build volume as defined by the layer stack, for example.
  • thermal build up may be reduced. This allows control over undesirable effects such as wall growth, caused by unfused powder sticking to an overly hot object wall, adjacent objects affecting one another due to thermal interference, or even joining of adjacent objects.
  • the duty cycle of the fusing energy beam per voxel may be defined for similar effects.
  • the duty cycle may be low at and near the centre of the object volume and increased gradually from the centre outward, with the highest duty cycle defined at the object surface periphery.
  • Narrow sections meanwhile may receive a constant high level of energy (defined in terms of duty cycle, for example) since they are more affected by heat dissipation due to their high surface to volume ratio.
  • Fig. 1 illustrates the DMD 240 applying different fusing energy beams 410 to the object cross section wherein the energy is varied from the centre of the object cross section 150 outwards, so that near the centre the energy of inner fusing energy beams 410 1 is lower compared to outer fusing energy beams 410_3 at the periphery of the object cross section 150.
  • Adjusted energy levels including optionally non-fusing energy levels
  • Fig. 6 shows adjusted energy beams of different energy levels in more detail in a simplified variant of Fig. 1 and in which only the energy beams provided by the DMD, and not the DMD itself, area shown. All features shown and described in relation to Fig. l may equally be present and be applied to Fig. 6.
  • the controller 300 may be configured to control each mirror of the DMD based on adjusted slices to provide the different fusing energy beams 410 to the object cross section 150 and optionally non-fusing energy beams 420 to the nonfusing areas within the layer 160 and outside the object cross section 150.
  • Adjusted levels of energy for the non-fusing and fusing voxels may have been determined based on the considerations described herein, so as to achieve a thermal profile for each layer as determined from simulations of heat impact considering the location, size and shape of the object cross sections for example.
  • the desired temperature level and profile may be different for different object cross section, and may be different for voxels within the non-fusing areas.
  • the optional provision of the non-fusing energy beams 420 is again indicated by dashed arrows.
  • the non-fusing energy beams 420 may be provided by the DMD by operating corresponding mirrors with a shorter operative phase, thus reducing the energy to non-fusing energy levels.
  • a second light source configured to irradiate the DMD at a different wavelength not as readily absorbed as that provided by the fusing light source 250, or a second DLP may be provided that is operable at a different wavelength.
  • Selective and differential non-fusing may be provided by the DMD as is illustrated by selective non-fusing energy beams 420 such that energy beams 420H closest to the periphery of the object cross section 150 are of higher energy compared to energy beams 420L further away from the periphery.
  • non-fusing energy beams 420 may reduce in energy outwards from the object cross section 150 over a peripheral region surrounding the object cross section.
  • Selective non-fusing by the DMD may be applied concurrently with or following fusing of the object cross section.
  • fusing energy beams 41 OH are highest for obj ect voxels near the periphery of the obj ect cross section 150 and fusing energy beam 410L is the lowest for object voxels at the centre of the object cross section 150.
  • Thermal feedback optionally including non-fusing energy beams
  • the apparatus 10 may comprise a thermal sensor such as thermal sensor 280 shown in Fig. 1, arranged above the layer and configured to measure temperatures of the layer. During the build process, the thermal sensor may be used to measure the temperature of, for example, the fused cross sections and/or non-fusing area. A thermal map may be generated to represent the thermal profile over the fused cross sections which may be compared to a target fusing thermal map.
  • the target fusing map may comprise a defined thermal profile map based on “greyscale” information of the adjusted image data, in other words it may comprise more than an average fusing temperature and the threshold range of deviation from the average.
  • a correction mask may be determined that is applied to the modified fusing slice data of a subsequent layer so as to compensate for such excessive deviations in fusing temperature and to converge towards the intended fusing topography.
  • Fig. 4 and Fig. 5 illustrate the method of Fig. 3, in which the DLP is the second fuse source used to provide a further, fine tuning fuse step.
  • the post-fuse temperature profile is measured at block 760.
  • the deviations correspond to a line of temperatures measured along the x- direction measured over a 2-dimensional section along x of the layer 160 of Fig. 5.
  • the layer 160 comprises fused cross sections 150A, 150B and 150C.
  • the predefined fusing thermal profile may be different for different object cross sections 150A, 150B and 150C.
  • the predefined fusing thermal profile may be higher than for the largest cross section 150B, for example to compensate for the higher heat leakage from the narrow cross section 150C.
  • the non-fusing areas 130 A, 13 OB may be fine tuned in non-fusing temperature based on a voxel- specific desired temperature determined according to the considerations described herein.
  • Fig. 5 is a simplified variant of a cross section side view through layers 160 of Fig. 1 irradiated with energy beams by a digital mirror device 240, with fusing energy beams 410 and optionally concurrently with non-fusing energy beams 420.
  • Fig. 4 measured deviations from a predefined fusing profile are shown in Fig. 4.
  • deviations of a measured non-fusing profile across non-fusing areas 130A and 130B from a predefined non-fusing profile may be determined, and 150C being fused in Fig. 5, measured deviations from a predefined fusing profile are shown in Fig. 4.
  • Fig. 5 is a simplified variant of a cross section side view through layers 160 of Fig. 1 irradiated with energy beams by a digital mirror device 240, with fusing energy beams 410 and optionally concurrently with non-fusing energy beams 420.
  • the determined deviations are all below the predefined respective profile temperature for all voxels measured. This is indicated by the x-axis crossing the y-axis above the measured deviations; i.e. the measured temperature deviations are all negative in the example shown, although this is not essential.
  • the step of further fusing by the digital mirror device 240 is to apply additional heat to both object voxels and non-fusing voxels by applying energy beams as determined based on the measured deviations.
  • the predefined fusing profile will be at an overall higher temperature level than the predefined non-fusing profile.
  • the determined energy level to be applied by the DMD to the fusing voxel may be expected to be higher than that to be applied to the non-fusing voxel.
  • Fig. 5 illustrates the determined fusing energy beams 410 to achieve a temperature within a range of the predefined temperature target of a respective predefined target profile based on the deviations in Fig. 4.
  • the arrow line thickness indicates relative energy levels for fusing energy beams 410 and non-fusing energy beams 420, such that thin to thick arrows indicate low to high energy.
  • the first cross section 150A is determined to deviate the most from its fusing target temperature and receives the highest energy fusing energy beams 410A.
  • the narrow cross section 150C was determined to deviate the least from its desired fusing target temperature and receives the lowest fusing energy beam 410C.
  • the temperature of object cross section 150B deviates from the desired fusing target over the largest range compared to the other two object cross sections, and the fine tuning fusing energy beams 410B differ the most from one another compared to fine tuning fusing energy beams 410A and 410C.
  • Figs. 4 and 5 are merely for illustration and do not suggest actual ranges or energy differences. Shown in dashed lines are optional non-fusing energy beams 420 that may be applied concurrently or sequentially by the DMD to the non-fusing areas such as 130A, 130B, based on the deviations determined in Fig. 4.
  • non-fusing energy beams may also be of different energies so as to fine tune the temperature of the nonfusing areas to achieve improved object properties.
  • the predefined fusing profile may be based on similar or the same considerations as those made to determined adjusted image slices as described with reference to Fig. 6, for example, and as further described herein.
  • the predefined non-fusing profile may be based on similar or the same considerations as those described herein to arrive at adjusted nonfusing energy levels to generate adjusted image slices.
  • Such predefined profile may be determined using model based simulations that were developed empirically for a given build material, for example. Directionality, scrolling and delays between thermal events
  • the build material at the point of distribution is at a lower temperature than the top most processed layer it is to cover.
  • the step of distributing may therefore be referred to as a ‘cold’ thermal event.
  • the steps of non-fusing and fusing meanwhile are ‘hot’ thermal events after each of which the layer starts to cool again.
  • Distribution of each new layer preferably occurs before the fused, hot, object cross sections of the (previous) layer cool to become too viscous to allow adequate adhesion with the new layer.
  • the timing of the distribution step may thus be carefully controlled with respect to the temperature of the fused object cross section.
  • the step of distributing a new layer is initiated before the step of fusing (e.g. the traverse of a fusing energy source over the layer) is complete.
  • At least one of the first and second fusing source may be configured to scroll across the layer while providing fusing energy and/or further fusing energy to object voxels, and optionally while providing non-fusing energy to non-fusing voxels.
  • the first and second fusing source may be configured to scroll across the layer in the first direction while providing fusing energy and/or further fusing energy to object voxels, and optionally while providing non-fusing energy to non-fusing voxels.
  • the steps of fusing and further fusing may be provided by the first and second light source while traversing the layer so as to progressively fuse and further fuse the object cross section during their respective traverse; wherein the steps of distributing, fusing and further fusing are applied along the same direction.
  • the DMD and the non-selective fusing source may be arranged on the same carriage as and behind the distributor 290, for example.
  • Image slice data may be used to determine locations at which an underlying object cross section contributes to the heating of a subsequent layer. Additionally, it may be used to determine how best to condition a new layer for optimal fusing of object cross sections in a subsequent layer. This is illustrated in Figs. 7A to 7E, which illustrate different stages of a traverse of the DMD over the layer in a simplified variant of the apparatus of Fig. 1, and in which the DLP may be controlled to additionally provide selective non-fusing energy beams ahead of or behind the distributor and/or the other fusing energy source.
  • the DMD 240 is arranged to scroll over the layer 160 along the x-direction from left to right, as indicated by the open arrow, so as to progressively provide fusing energy beams 410 to corresponding voxels within object cross section 150 along the x-direction.
  • the scrolling DMD or a further DLP comprising a scrolling DMD is arranged to provide non-fusing energy beams 420 to regions of the layer that are not to fuse.
  • Fig. 7A illustrates the scrolling DMD as it begins its traverse over the layer 160, and optionally being controlled by controller 300 to provide non-fusing energy beams 420 of different non-fusing energies.
  • a lower energy may be provided in the form of non-fusing energy beams 420L up to a region 130P, which is a peripheral region just outside an object cross section 150 that is to be formed.
  • Non-fusing energy beams 420H may be provided to the peripheral region 130P. which may also vary such that the closer a voxel is located within the peripheral region 130P to the object cross section to be formed, the higher the energy. In this example this is indicated by an inward non-fusing energy beam 420H2 which is of higher non-fusing energy than outward non-fusing energy beam 420H1.
  • the DMD provides fusing energy beams 410 to begin fusing the object cross section 150 while non-fusing energy beams 420 are provided concurrently to voxels upstream of the object cross section 150, with respect to the scrolling direction.
  • Fig. 7C illustrates how the scrolling DMD may apply fusing energy beams 410 of different energies to corresponding voxels within the object cross section 150, for example the fusing energy may be reduced towards the centre of the cross section 150.
  • This is not specifically labelled in this Figure but may for example be as indicated by the thickness of the fusing energy beams 410 in Fig. 6.
  • Figs. 7D and 7E further illustrate stages of the DMD during its traverse and the different fusing energy beams provided depending on its position over the layer, and the optional different non-fusing energy beams 420.
  • the micromirror array may thus be controlled to provide non-fusing energy beams are provided and fusing energy beams to the layer 160. It can be seen how different mirrors of the array are operated to address the same voxel during the traverse of the DMD. In this way, each non-fusing voxel may receive a selective non-fusing boost concurrent with the provision of fusing energy beams following for example a preheating step by a non-selective preheating lamp.
  • the DMD(s) may begin their traverse before the distributor has completed its traverse over the layer along the same direction (e.g. along x).
  • the velocities at which each traverse the layer may be the same, constant velocity.
  • the application of the DMD is however not limited to a unidirectional thermal cycle; improved results may be obtained in which thermal events are applied in an opposing or orthogonal direction to other thermal events.
  • multi-directional processes which may generate larger thermal deviations from the predefined thermal profile across each layer, fine tuning of fusing energy and/or nonfusing energy may be advantageously provided by the DMD.
  • each voxel which is defined by the area of a single pixel of the two dimensional image or slice being projected onto the layer, is controlled through a combination of projection duration (global), light source intensity (global), and greyscale value (local to pixel).
  • projection duration global
  • light source intensity global
  • greyscale value local to pixel
  • a combination of exposing sequential images or adjusting greyscale value may be carried out.
  • each voxel is instead associated with an entire row (along x) of mirrors, where the time each control area is associated with an individual pixel is equal to the projected pixel length divided by the scrolling speed.
  • each voxel is defined by the projected pixel width (along y) and a combination of scroll speed, image projection frequency, and projected pixel length (along x).
  • the images or slices being projected are synchronized with the scroll speed such that while the projection moves along the x axis, the projected object geometry remains in a fixed position on the layer for the duration over which the projected area overlaps with the voxel.
  • the reference frame fixed to the voxel the position of features within the projected image are synchronized with the scrolling to maintain a consistent position on the layer surface. In this way, object geometries and compensations related to object geometry can be controlled.
  • the reference frame fixed to the micromirror array the position of features within the slice are fixed to the pixel location regardless of scrolling. This allows application of e.g. calibrations such as uniformity masks, scaling, etc. which are independent of object geometry.
  • Image slices for a digital mirror device may be modified by one or more masks for the temporal control for a DMD in scrolling mode, and/or spatial control of irradiation intensity, at each object voxel and/or non-fusing voxel.
  • the image slices may be modified based on one or more masks applied to the different energy levels, wherein each mask is associated with one of the frame of the layer and the frame of the digital mirror device, and wherein modified different energy levels are provided to the object cross section during the step of fusing selected object voxels.
  • the modification may be made to adjusted slice data comprising adjusted fusing energy levels and optionally adjusted non-fusing energy levels as described herein. This will now be described with reference to Figs.
  • FIG. 8A A simple example of an image slice 6000 comprising a plurality of fusing pixels defining an object model cross section 6500 is shown in Fig. 8A.
  • a fusing energy level defined for each fusing pixel may in this simple example be the same for each object pixel.
  • the area surrounding the object model cross section 6500 is a non-fusing slice area 6300 defining “non-fusing areas” over which voxels in the layer are not to fuse.
  • the slices are prepared typically from obj ect models that have been placed or nested within a virtual build volume which is based on the real build volume of the apparatus.
  • the virtual build volume is a 3D volume within which certain compensations may be applied to account for shrinkage and deformation during processing of the object.
  • the virtual build volume is divided into a sequence of slices, which are the 2D images defined to map to a corresponding layer of the build process.
  • a fusing mask 5000 as illustrated by way of example in Fig. 8B is provided.
  • the fusing mask comprises data to modify that of the fusing pixels of each slice.
  • the shading from light to dark, from left to right, along the x-direction indicates a linear variation of weights increasing from low to high.
  • the weights may be factors varying from 0 to 1 as the shading changes from white to black. Therefore, a constant energy level defined for the fusing pixels of the model cross section 650 would be modified by the mask by multiplying each energy level with a corresponding weight.
  • the modified slice 7000 of Fig. 3C illustrates the modified model cross section 7500 over which the modified energy level now gradually increases from left to right. This is further illustrated in Fig.
  • the mask may be associated with the reference frame of the DMD.
  • the weights of the mask map onto a corresponding micromirror.
  • the row Pn of Fig. 9 may instead be thought of as representing a row of n mirrors.
  • the mask data value remains the same irrespective of the slice data.
  • Figs. 10A to 10D shows four different stages of a traverse of the DMD 240 over the layer 160 in a variant of the apparatus 10 of Fig. 1.
  • the DMD 240 addresses an object cross section 150 progressively with six mirrors of its array, aligned one after the other in the direction of the traverse.
  • the mask 5000 defining the weights a inset at the top left of Fig. 10A, each mirror along x is operated with a specified weight for that mirror.
  • each Figure further shows modified fusing pixel data of the modified slice 7000 corresponding to the position at which the DMD is operated above the layer.
  • the modified slice 7000 is identified by the time step at which is it applied, where the time difference between successive mirrors providing fusing energy beams to a given voxel remains constant since the speed of the DMD is constant.
  • the scale of the x-axis of the layer 160 is not the same as that of the modified slice 7000 since modified slice 7000 shows only an extract to focus on the modified pixels.
  • the unmodified fusing slice data 6000 may in this example have specified a constant duty cycle of 100% for each pixel.
  • the variation in weight is superimposed on the modified slice, in which the y-axis of the slice is parallel to the vertical axis of the weight value.
  • the modified energy level for each pixel of the cross section 150 which in this example is formed from four successive pixels Pl to P4, is indicated by its shading at each stage. As before, white indicates the lowest energy level of a modified pixel and black the highest energy level.
  • the six mirrors may for example have been assigned weights 0.9, 0.8, 0.7, 0.6, 0.5 and 0.4, from right to left.
  • the DMD 240 has just started at starting time tl to address the first voxel of the object cross section 150, with the first mirror.
  • the first voxel is shown in black to indicate fusing, and the first mirror at the leading edge of the DMD provides a fusing energy beam 410 according to the first modified pixel Pl.
  • the second modified pixel P2 defines the location and energy level of the second voxel to the right of the first voxel, and is fused by the first mirror at a duty cycle of 90%.
  • the shading of the first modified pixel Pl is slightly lighter than that of the second modified pixel P2.
  • the DMD 240 is addressing all four voxels at the same time based on the modified fusing slice 7000(t4).
  • the fourth voxel at right edge of the cross section 150 is heated by the first mirror, at 90% duty cycle.
  • the DMD 240 is addressing all four voxels with a different set of mirrors, mirrors six to three from left to right, based on the modified fusing slice 7000(t6).
  • the first voxel is now heated by the sixth mirror at the trailing edge of the array.
  • the fourth voxel is now heated by the third mirror operated at a duty cycle of 70%.
  • the second and third voxels are heated by respective fifth mirror at 50% and fourth mirror at 60% duty cycle.
  • a linear power profile may be provided to each voxel in this way during the traverse of the DMD over it, as illustrated by the graph of Fig. 11A for the first voxel for example.
  • the times t3 and t5 not illustrated in Figs 10A to 10D are also included in this Fig. 11 A. This is a simple illustration of how a linear power profile may be achieved applying the method according to the invention.
  • the position of each pixel within the modified slice data is different to reflect the changing position of the DMD with respect to the layer.
  • the slice and modified slice is fixed to the reference frame of the layer so that object cross section remains in the same position for each position of the DMD.
  • the location of the first, second, third and fourth pixel changes in each slice when the DMD is provided in a scrolling mode.
  • the mask may be defined to achieve any desirable intensity profile for each non-fusing or fusing voxel over the duration of heating when applied in combination with a scrolling DMD. This provides a simple process that allows full control over the intensity profile for each voxel of the layer. Improved mechanical properties may be provided that are not achievable with conventional powder bed fusion apparatus.
  • Different masks may be defined for different layers such that different energy levels can be individually assigned in any direction of the layer, per non-fusing area and/or per object cross section, either through varying the gradient between different y axis positions or by associating a specific mask to certain groups of the plurality of slices during the slicing operation to ensure that the variation of energy applied throughout the DMD pass is optimal for each individual object, or non-fusing area.
  • FIG. 11B An improved intensity profile is shown in Fig. 11B, which may be achieved by designing a suitable mask 5000 and associating it with the frame of reference of the DMD as it scrolls over the layer according to the method of operation of Figs. 10A to 10D.
  • Such an intensity profile may rapidly achieve melting while maintaining the build material in a low viscosity state over a maximised duration without overheating of the fused material, therefore reducing the risk of build material degradation.
  • conventional powder bed fusion processes achieve intensity profiles illustrated in Fig. 12. For example, laser sintering may only achieve fusing by applying a very short and intense fusing intensity profile illustrated by the solid line in Fig. 12.
  • the intensity delivered to each voxel is designed to overheat over a very short timeframe of the order of milliseconds or less.
  • the particles typically reach full consolidation over a duration of of order of seconds. Since this process therefore needs to continue beyond the application of the laser beam for the particles to reach full consolidation, the material needs to effectively be overheated to ensure it remains long enough in a sufficiently low viscous state.
  • the resulting high temperatures can lead to material degradation in the form of chain scission and/or oxidation within the fused cross section, leading to weaker parts.
  • a relatively lower and broader intensity profile shown by the dashed line in Fig. 12 is typically provided, for example by a scanning infrared lamp, leading to a relatively slow heat up phase and relatively low fusing temperature. Application allows irradiation intensity control over the duration each voxel is heated.
  • the fusing energy source 250 of the DLP may be an infrared laser, for example.
  • the DMD 240 may comprise a single micromirror array arranged to simultaneously address each voxel of the entire layer surface from a static position.
  • the DMD may comprise an array of mirrors fewer in number than the voxels on the layer surface, and may be arranged on a scanning (or “scrolling”) gantry above the layer to successively address rows of voxels along the y-direction as the DMD is moved (scrolled or scanned) above the layer surface, as is illustrated in Figs. 6A to 8C.
  • the DMD may be mounted to a galvanometer for example, and the controller may be configured to vary the angle of the array with respect to the layer surface.
  • the digital light projector may comprise a group of DMD arrays 240, each receiving a portion of the slice, in the form of sub-slices, that are synchronised to project a reconstructed slice from the sub-slices.
  • This mode of operation is also known as tiling.
  • Adjacent arrays may jointly irradiate the overlap section in any conventional manner known from “printhead stitching”, where neighbouring sections are addressed in any suitable pattern by both subarrays so as to obscure otherwise visible or measurable overlap joints.
  • Both the first light source and the second light source may be configured to apply selective fusing energy to the object voxels, wherein the method further comprises, between the steps of fusing and further fusing: measuring temperatures of the object cross section to determine a fusing thermal profile of the object cross section; comparing the measured fusing temperature profile to a predefined fusing temp thermal profile; determining different energy levels to be provided by the digital mirror display based on the comparison during the step of further fusing; wherein the step of further fusing is a step of further fusing selected object voxels based on the determined different energy levels.
  • the thermal sensor 280 may be a thermal camera of sufficiently high resolution to capture the temperature of each layer at or near voxel resolution.
  • the thermal sensor may be arranged stationary above the layer as shown in Fig 1.
  • the thermal sensor may be a line scan camera having an elongate array of sensor pixels arranged to move above the layer, in a direction perpendicular to the direction of elongation of the array, to measure the temperature of the layer surface line by line.
  • the line scan camera may for example follow the distributor and/or the fusing radiation source.
  • a thermal map may be reconstructed from the multiple line scans taken to represent the temperature of the entire layer.
  • the thermal map generated may be used to control the DMD to provide the different fusing energy beams to object cross sections of the layer.
  • Fig. 1 shows an apparatus 10 that may optionally comprise an overhead heater 270 arranged above the build area and configured to maintain the layer at the target preheat temperature.
  • an overhead heater typically has an array of individually controllable heating elements, each element addressing a plurality (or “zone”) of voxels over a relatively large region on the build bed.
  • the heating elements may be ceramic heater tiles and able to respond rapidly changes in control, thus the DMD enables a fast-acting correction at high resolution while the overhead heater is continuously operated to maintain the layer at the target layer temperature.
  • the overhead heater 270 may comprise four or more heater elements, for example at least one above each comer of a rectangular build area, or one above and along each side of the build area.
  • the controller 300 may be configured to control the heater elements of the overhead heater based on a temperature distribution of the layer as measured by the thermal sensor 280.
  • the thermal sensor 280 may be controlled to measure temperatures of the layer after respective blocks 620 or 720 of non-fusing, for example, and before the respective steps of fusing the object cross section at block 650 or 750.
  • the overhead heater 290 may be controlled continuously to maintain the layer temperature at the average layer target temperature throughout the layer cycle.
  • the DLP may optionally provide fusing, and optionally nonfusing, energy beams to the layer based on temperature measurements made after the step of fusing at blocks 650, 750, such that the different energies of the fusing, and optionally non-fusing, energy beams are determined based on the measurements made following the steps of fusing at block 650, 750, for example at block 760 of Fig. 3.
  • the DMD or a low resolution infrared non-fusing lamp may be applied to preheat or warm the layer immediately after a new layer is distributed, at the optional block 620 in Fig. 2 or optional block 720 in Fig. 3.
  • the infrared digital light projector may comprise a first micromirror array arranged to preheat the build area at blocks 620 or 720, behind the distribution device with respect to the direction of distribution, and a second DMD array arranged to fuse at voxel resolution at block 650 or 750, and/or at block 770 of Fig. 3.
  • a preheating step at block 620 of the method 600 of Fig. 2 or at block 720 of the method 700 of Fig. 3 may be provided by a scanning infrared lamp that follows the distributor to immediately heat the freshly distributed layer.
  • the controller 300 may be a computer or microprocessor provided with a program that, when executed, causes the steps of the methods disclosed herein.
  • a computer program may be provided comprising instructions which, when the program is executed by the controller 300, e.g. a computer, cause the controller or computer to carry out the method and its variants as described herein.
  • the controller may be configured to control any one or any combination of components to provide the method steps for controlling the apparatus 10 as described herein.

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  • Optics & Photonics (AREA)
  • Mechanical Engineering (AREA)
  • Toxicology (AREA)
  • Health & Medical Sciences (AREA)
  • Plasma & Fusion (AREA)
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Abstract

L'invention concerne un appareil de fabrication par couches d'objets 3D à partir d'un matériau de construction particulaire, l'appareil comprenant un distributeur destiné à distribuer chaque couche de matériau de construction ; une première source de fusion et une seconde source de fusion, chacune étant conçue pour fournir une énergie de fusion sur la base de tranches d'image définissant chaque section transversale d'objet à former au sein d'une couche correspondante, au moins une source parmi la première et la seconde source de fusion étant conçue pour fournir une énergie de fusion sélective à des voxels d'objet sélectionnés de la couche au sein des sections transversales d'objet ; et un dispositif de commande configuré pour : commander la distribution, par le distributeur, d'une couche ; commander, dans l'un ou l'autre ordre, la fusion, par la première source de fusion, des voxels d'objet sélectionnés pour la formation d'une section transversale d'objet et la fusion supplémentaire, par la seconde source de fusion, des voxels d'objet fondus par la première source de fusion ; et répéter la distribution, la fusion et la fusion supplémentaire afin de former l'objet à partir d'une séquence de sections transversales d'objet. L'invention concerne également un procédé de fonctionnement de l'appareil.
PCT/GB2024/052320 2023-09-07 2024-09-06 Appareil et procédé de formation par couches d'objets 3d à partir de matériau de construction particulaire Pending WO2025052133A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB2313642.7A GB2633355A (en) 2023-09-07 2023-09-07 Apparatus and method for layerwise formation of 3D objects from particulate build material
GB2313642.7 2023-09-07

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WO2025052133A1 true WO2025052133A1 (fr) 2025-03-13

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1648686B1 (fr) * 2003-07-25 2009-12-02 Loughborough University Enterprises Limited Procede et appareil pour frittage selectif d'un materiau particulaire
WO2017132664A1 (fr) * 2016-01-28 2017-08-03 Seurat Technologies, Inc. Système et procédé de fabrication additive et de traitement thermique spatial
US10137500B2 (en) * 2013-08-02 2018-11-27 Rolls-Royce Plc Method of manufacturing a component
WO2019117886A1 (fr) * 2017-12-13 2019-06-20 Hewlett-Packard Development Company, L.P. Prédiction du comportement thermique à partir d'une carte de tons continus
US20230055872A1 (en) * 2021-08-20 2023-02-23 General Electric Company Irradiation devices with optical modulators for additively manufacturing three-dimensional objects

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US11117194B2 (en) * 2017-03-15 2021-09-14 Applied Materials, Inc. Additive manufacturing having energy beam and lamp array
US11230058B2 (en) * 2019-06-07 2022-01-25 The Boeing Company Additive manufacturing using light source arrays to provide multiple light beams to a build medium via a rotatable reflector

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1648686B1 (fr) * 2003-07-25 2009-12-02 Loughborough University Enterprises Limited Procede et appareil pour frittage selectif d'un materiau particulaire
US10137500B2 (en) * 2013-08-02 2018-11-27 Rolls-Royce Plc Method of manufacturing a component
WO2017132664A1 (fr) * 2016-01-28 2017-08-03 Seurat Technologies, Inc. Système et procédé de fabrication additive et de traitement thermique spatial
WO2019117886A1 (fr) * 2017-12-13 2019-06-20 Hewlett-Packard Development Company, L.P. Prédiction du comportement thermique à partir d'une carte de tons continus
US20230055872A1 (en) * 2021-08-20 2023-02-23 General Electric Company Irradiation devices with optical modulators for additively manufacturing three-dimensional objects

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GB202313642D0 (en) 2023-10-25
GB2633355A (en) 2025-03-12

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