Thermal compensation of laser energy transfer for additive manufacturing

Abstract

A manufacturing system includes a printer chamber having a printer bed supporting manufacturing materials and an internal heating system supported by the printer chamber. The internal heating system is configured to direct patterned thermal energy to the printer bed and the supported manufacturing materials. An external heating system is supported by or positioned near the printer chamber and is configured to direct patterned thermal energy to the printer bed and any supported manufacturing materials.

Description

[0001] Cross-references to related patent applications

[0002] This disclosure is part of a non-provisional patent application claiming the benefit of priority to U.S. Patent Application No. 63 / 039,315, filed on June 15, 2020, which is incorporated by reference in its entirety. Technical Field

[0003] The present disclosure generally relates to systems and methods for thermally controlled additive manufacturing. In one embodiment, the manufacturing bed, walls, and ceiling can be thermally controlled to compensate for heat losses.

[0004] background

[0005] Traditional component machining typically relies on removing material by drilling, cutting, or grinding to form a part. In contrast, additive manufacturing (also known as 3D printing) typically involves the sequential layer-by-layer addition of material to build a part. Starting with a 3D computer model, additive manufacturing systems can be used to create complex parts from a variety of materials.

[0006] An additive manufacturing technology called powder bed fusion (PBF) uses one or more focused energy sources, such as lasers or electron beams, to gradually form 3D printed parts by drawing patterns in a thin layer of powder by melting the powder and bonding it to the layer below. The powder can be plastic, metal, glass or ceramic. This technology is very precise and can usually achieve feature sizes as small as 150um-300um. Typically, the process is carried out with the substrate temperature starting from room temperature or some moderately elevated temperature such as 250°C. When printing materials such as steel with a melting point of around 1400°C, the laser must melt the powder and the substrate during the layer printing process. Since both parts start at temperatures close to room temperature, they must undergo temperature cycles of around 1000 degrees Celsius. When this process is repeated for all parts of the layer to be printed, thermal stresses can be established within the part. In addition, depending on the amount of average laser power, this heat load of the printing process causes the temperature of the build plate to increase. The temperature increase during the printing process can be significant and depends on the number of parts and the geometry of the parts being printed. This inter-layer difference in average heat load can lead to unforeseen errors such as spatially dependent thermal warping in all three dimensions, higher residual stresses, and even cracking of the printed part. These factors reduce the accuracy, strength, and usefulness of the finished 3D part.

[0007] Additive manufacturing systems may also require that 3D prints be removed from the controlled printing environment when the 3D print is removed from the print chamber. This can have an adverse impact on 3D prints that require heat treatment ovens for post-process cooling and / or subsequent stress relief, annealing, or heat treatment. While additive manufacturing systems can preheat the print plate and / or maintain the print at a set temperature in the print chamber during printing, temperature control is typically not available outside of the print chamber. Unfortunately, when 3D prints are removed from the print chamber, their temperature is typically uncontrolled and, in many systems, exposed to uncontrolled air. These factors can affect the material properties of the 3D print. Additionally, 3D prints are often too hot to be removed from the print chamber immediately and must therefore remain in the print chamber for several hours after the print is completed. This occupies the print chamber and prevents the system from starting new print jobs.

[0008] Improved thermal control systems for fixed or cartridge-based print chambers are needed. This can include providing isothermal conditions, or alternatively, providing patterned heat flux that can reduce errors such as spatially dependent thermal warpage or higher residual stresses in all three dimensions.

[0009] Overview

[0010] A manufacturing system includes a printer chamber having a printer bed supporting manufacturing materials and an internal heating system supported by the printer chamber. The internal heating system is configured to direct patterned thermal energy to the printer bed and the supported manufacturing materials. An external heating system is supported by or positioned near the printer chamber and is configured to direct patterned thermal energy to the printer bed and any supported manufacturing materials.

[0011] In one embodiment, the printer chamber further includes an ink cartridge.

[0012] In one embodiment, the internal heating system further comprises at least one of a heating element and a cooling element.

[0013] In one embodiment, the external heating system further comprises an infrared heating element.

[0014] In one embodiment, the external heating system further comprises a heated air flow.

[0015] In one embodiment, the external heating system further comprises at least one pointing laser.

[0016] In one embodiment, the external heating system further comprises at least one directed laser to provide non-patterned heating.

[0017] In one embodiment, the external heating system further comprises at least one directed laser to provide patterned heating.

[0018] In one embodiment, the external heating system further comprises at least one pointing laser using recycled light.

[0019] In one embodiment, the sensor further comprises a pyrometer.

[0020] In one embodiment, the sensor further comprises a camera.

[0021] In another embodiment, a manufacturing system includes a printer chamber having a printer bed supporting a layer of printable material. A primary laser source may be directed at a sub-portion of the layer of printable material on the printer bed to print a part pattern. A secondary heating system is configured to direct patterned heat energy into the layer of printable material.

[0022] In one embodiment, the patterned thermal energy is determined at least in part by the pattern of the part being printed.

[0023] In one embodiment, the patterned thermal energy is substantially inversely proportional to the fraction of the pattern being printed.

[0024] In one embodiment, the secondary heating system further comprises a second light emitting heating element.

[0025] In one embodiment, the second light emitting heating element further comprises at least one of an arc lamp, an infrared lamp, an LED heating system, and a laser heating system.

[0026] In one embodiment, the secondary heating system further comprises a patterned heating element supported by the printer chamber.

[0027] In one embodiment, the patterned heating element supported by the printer chamber further comprises at least one of an array of resistive heating cartridges, a heating fluid in a channel, an electrically controlled plasma source, an arc heater, an induction heater, and a microwave heater. In all of these embodiments, the cooling element or heating element may be built into the printer bed or surrounding structure, or projected from a distance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Non-limiting and non-exhaustive embodiments of the present disclosure are described with reference to the following figures, wherein like reference numerals refer to like parts throughout the various figures unless otherwise specified.

[0030] Figure 1A A thermally controlled additive manufacturing system is shown;

[0031] Figure 1B shows a thermally controlled print plate on the Z-stage before printing begins;

[0032] Figure 1Cshows a printed part buried in powder on a print plate as the Z stage moves downward, with embedded heating devices positioned in the print plate and print walls;

[0033] Figure 1D A thermally controlled cartridge system is shown;

[0034] Figure 1E The use of segmented infrared heaters for patterned heating is shown;

[0035] Figure 1F The use of segmented top-down or angled airflow for patterned heating is shown;

[0036] Figure 1G The use of segmented cross-bed gas flow for patterned heating is shown;

[0037] Figure 1H The use of an additional heating laser for patterned heating is shown;

[0038] Fig. 1I The use of an additional heating laser for non-patterned heating is shown;

[0039] Figure 1J The use of additional heating laser derived from recycled or discarded light for patterned heating is shown;

[0040] Figure 1K A thermal imaging system using a camera and a pyrometer is shown;

[0041] Figure 2 A process flow of an additive manufacturing system for thermal control is shown; and

[0042] Figure 3 A demonstration of a constant heat load based on multiple patterned and applied heat loads is shown.

[0043] Detailed Description

[0044] In the following description, reference is made to the accompanying drawings which form a part of the specification and which are shown therein by way of illustration of specific exemplary embodiments in which the present disclosure may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the concepts disclosed herein, and it is understood that the various disclosed embodiments may be modified and other embodiments may be utilized without departing from the scope of the present disclosure. Therefore, the following detailed description is not to be considered in a limiting sense.

[0045] Figure 1AA thermally controlled additive manufacturing system 1A is shown. A print chamber 2A holds a print plate 3A, which may support powder or other additive or subtractive manufacturing material. A print engine 5A capable of directing a laser, electron beam, or other directed energy 5A is positioned externally relative to the print chamber and is used to heat the manufacturing material on the print plate. Sensors 6A may be used to calibrate or provide feedback control during manufacturing.

[0046] The external heating system 7A and / or the internal heating system 8A can be used to adjust or control the temperature of the print chamber 2A, the material temperature, or the temperature of the part being manufactured on the print plate. Both the external heating system 7A and / or the internal heating system 8A can be operated to provide differential or patterned heating or cooling using an array of heating or cooling elements, a segmented structure, a partitioned structure, a scannable structure, or a selected on / off operation. In some embodiments, an isothermal temperature is maintained, while in other embodiments, a patterned heating system can be used to select predetermined temperatures in different selected areas.

[0047] For example, an external patterned heating system can involve the use of components mounted or positioned externally that direct heat flux from above into the print chamber. The patterning component can be one or more heat lamps, one or more lasers (diode, fiber, solid state, etc.), convective flow, or other types of heating elements. Patterning can be achieved by static masks, spatial light modulators such as liquid crystal displays, light valves, optically addressed light valves, micromirror arrays, thermally activated patterned resonators. Heater components such as heat lamps or heating elements can generate patterns by using a large array of elements and controlling which elements in the array are turned on and off and controlling their emission through optical devices such as lenses, reflectors, etc. to redirect light to the bed in a desired pattern. Convective flow can be patterned by using an array of nozzles through which gas flows at a controlled temperature desired / determined by the control system.

[0048] In some embodiments, the print plate 3A on which the printing process is performed contains internal heating elements, such as resistive heating cartridges, heated cooling fluid in cooling channels, electrically controlled plasma sources such as arcs, induction heaters, microwave heaters, or other heat generating devices mounted within the print chamber or in contact with the print bed or chamber. Additionally, the print plate 3A may contain temperature sensing devices, such as RTDs, thermocouples, pyrometers, or other temperature sensing devices, which then communicate with the printer control system to modulate the heat flux to the print plate. The same logic is applied to the print wall, except that the heaters are variably controlled based on the print wall height and the position of the print in the process.

[0049] Sensor 6A may include a pyrometer, a thermal camera, or a visual camera. In some embodiments, the camera may capture video and static images to provide a virtual window. The camera and lights may illuminate and image in multiple wavelengths of light (e.g., IR, visible light, or UV). The camera may be an array of several cameras that may record static and / or video images from many different angles with one or many wavelengths of light. The lights may be an array of one or more lights that illuminate the print chamber 2A and print plate 3A from many angles and at many different wavelengths.

[0050] In some embodiments, both the external heating system 7A and the print engine 4A may use one or more laser sources. Possible laser types include, but are not limited to, gas lasers, chemical lasers, dye lasers, metal vapor lasers, solid-state lasers (e.g., optical fibers), semiconductor (e.g., diode) lasers, free electron lasers, gas dynamic lasers, "nickel-like" samarium lasers, Raman lasers, or nuclear pumped lasers.

[0051] The gas laser may include a laser such as a helium-neon laser, an argon laser, a krypton laser, a xenon ion laser, a nitrogen laser, a carbon dioxide laser, a carbon monoxide laser, or an excimer laser.

[0052] The chemical laser may include a laser such as a hydrogen fluoride laser, a deuterium fluoride laser, a COIL (chemical oxygen iodine laser), or an Agil (all gas phase iodine laser).

[0053] Metal vapor lasers may include lasers such as helium cadmium (HeCd) metal vapor lasers, helium mercury (HeHg) metal vapor lasers, helium selenium (HeSe) metal vapor lasers, helium silver (HeAg) metal vapor lasers, strontium vapor lasers, neon copper (NeCu) metal vapor lasers, copper vapor lasers, gold vapor lasers, or manganese (Mn / MnCl2) vapor lasers. Rubidium or other alkali metal vapor lasers may also be used. Solid-state lasers may include, for example, ruby ​​lasers, Nd:YAG lasers, NdCrYAG lasers, Er:YAG lasers, neodymium YLF (Nd:YLF) solid-state lasers, neodymium-doped yttrium vanadate (Nd:YVO4) lasers, neodymium-doped calcium yttrium borate Nd:YCa4O(BO3)3 or simply Nd:YCOB, neodymium glass (Nd:glass) lasers, titanium sapphire (Ti:sapphire) lasers, thulium YAG (Tm:YAG) lasers, ytterbium YAG (Yb:YAG) lasers, ytterbium 2O3 (glass or ceramic) lasers, ytterbium-doped glass lasers (rods, sheets) / fragments (plate / chip and fiber), holmium YAG (Ho:YAG) laser, chromium ZnSe (Cr:ZnSe) laser, cerium-doped lithium strontium (or calcium) aluminum fluoride (Ce:LiSAF, Ce:LiCAF), promethium-doped 147 phosphate glass (147Pm+3: glass) solid-state laser, chromium-doped chrysoberyl (alexandrite) laser, erbium-doped and erbium-ytterbium co-doped glass laser, trivalent uranium-doped calcium fluoride (U:CaF2) solid-state laser, divalent samarium-doped calcium fluoride (Sm:CaF2) laser or F-center laser.

[0054] Semiconductor lasers may include laser medium types such as GaN, InGaN, AlGaInP, AlGaAs, InGaAsP, GaInP, InGaAs, InGaAsO, GaInAsSb, lead salts, vertical cavity surface emitting lasers (VCSELs), quantum cascade lasers, hybrid silicon lasers, or combinations thereof.

[0055] In operation, the heating devices in the print plate, print wall, and above the print plate can be used to apply the desired thermal conditions to initiate printing. Throughout the printing process, the heat load on the print layer is a variable that depends on the part geometry. Using the internal heating system 8A of the heating devices in the print plate, print wall, and also using the external heating system 7A above the print plate, the temporal modulation of the thermal conditions in the printed part can be provided in situ. In some embodiments, using the internal heating system 8A of the heating devices in the print plate, print wall, and also using the external heating system 7A above the print plate, the spatial modulation of the thermal conditions in the printed part can be provided in situ. Using the internal heating system 8A of the heating devices in the print plate, print wall, and also using the external heating system 7A above the print plate, it can be used to apply the necessary thermal conditions to the completed printed part to minimize thermal stress and optimize the thermal history in the part.

[0056] Once the printing process is complete, heating devices can be used to control cooling of the part, or the cover / thermal insulation can be closed over the top of the print chamber 2A to maintain an even cooling rate from all sides. Preheating powder or other manufacturing materials before and during printing also allows for a reduction in the print energy required to achieve the same print rate, or similarly, an increase in the print rate for a given fixed print energy.

[0057] Figure 1B System 1B is shown in more detail, having a thermally controlled print plate positioned on a Z stage before printing begins. Initially, there is no powder or part to be printed on the print plate 2B. Laser energy 14B can be directed to the material to be printed on the print plate 2B. The print plate 2B can contain a heater cartridge 3B and a temperature sensing device for controlling the temperature of the print plate 2B. Alternatively, the print plate can be fixed to and thermally connected to a daughter plate containing heating and sensing capabilities. In this case, item 2B is the daughter plate and the print plate (not shown) will be located above 2B. Below the print plate 2B, an insulator 4B reduces heat loss. Below the insulator 4B is a cooling tube containment plate 5B, which contains coolant flow channels 6B. This coolant flow protects sensitive and precise system components from overheating. The entire print plate assembly is connected to the z-axis motor by a connecting shaft 7B. Heat flow 8B from patterned elements, unpatterned elements or other radiating elements is incident on the print plate 2B from above. The magnitude of the heat flow 8B can be selected to be inversely proportional to the laser energy 14B to better maintain isothermal conditions. The printer side wall 9B contains a heater element 10B. The outside of the printer side wall 9B is an insulating layer 11B, and the outside of the insulating layer 11B is a printing wall cooling tube side wall 12B containing a coolant flow 13B.

[0058] Figure 1CA system 1C is shown having a printed part 20C buried in powder 15C on a print plate when the Z stage moves downward, wherein embedded heating devices are positioned in the print plate and print wall. Laser energy 14C proportional to the material to be printed is incident on a print plate 2C, which contains a heater cartridge 3C and a temperature sensing device for controlling the temperature of the print plate 2C. Alternatively, the print plate can be fixed to and thermally connected to a daughter board containing heating and sensing capabilities. In this case, item 2B is the daughter board, and the print plate (not shown) will be located above 2B. Below the print plate 2C, an insulator 4C reduces heat loss. Below the insulator 4C is a cooling tube housing plate 5C, which contains a coolant flow channel 6C. The entire print plate assembly is connected to the z-axis motor via a connecting shaft 7C. A heat flux 8C from a patterned element, an unpatterned element, or other radiating element is incident on the print plate 2C from above. The magnitude of the heat flux 8C can be inversely proportional to the laser energy 1C. Printer side wall 9C contains heater elements 10C. Outside of printer side wall 9C is an insulating layer 11C, outside of which is a print wall cooling tube side wall 12C containing coolant flow channels 13C. A printed part 14C on the print plate is supported by the print plate 2C and surrounded by powder 15C. Conductive heat 16C from a heater cartridge in the print plate is applied to the printed part 20C. Conductive heater 17C from a heater cartridge in the print wall is applied to the printed part and surrounding powder.

[0059] Figure 1D A thermally controlled cartridge system is shown. A 3D printing cartridge 1D useful in an additive manufacturing system is shown in partial cross-section. The 3D printing cartridge (hereinafter referred to as the "cartridge") separates all "dirty" printing functions from the rest of the system's functions and the operator environment. "Dirty" refers to wherever powder is present, processed for printing, or where soot is generated. Whenever the cartridge 1D is connected to a companion device such as a print station, powder station, or storage station, the companion device can provide the services required to operate the cartridge based on which companion device the cartridge is matched with (for example, a print station allows full control of the cartridge, while a storage station may only provide heating power and gas recirculation, as well as use of a camera and light). The cartridge 1D is designed to be sealed when disconnected from the companion device, and may include an auxiliary heating or cooling system to allow precise thermal conditions within the cartridge.

[0060] The cartridge 1D is built around a bed or substrate 24D and may include segmented or patterned internal heaters. Fresh powder for a new print is stored in a powder hopper 2D which has the capacity to store all the powder required for a full volume print. Fresh powder is metered onto the substrate through a powder door 23D. The powder is swept across the plate by a powder disperser 4D using a powder spreading knife. A powder disperser drive 5D moves the powder disperser back and forth across the print plate 12D.

[0061] Window 3D seals the top of the cartridge 1D, preventing powder or gas from leaking out, and allowing a laser beam (not shown) to pass through it to weld the powder. Window 3D allows access to the cartridge to load print plates, unload prints, clean and repair cartridge components (seals, spreader knives, etc.). The interior of the cartridge 1D can be illuminated and imaged by a camera and light 22D. The camera and light can be inside or outside the sealed chamber, or both inside and outside the sealed chamber, and can be positioned to take pictures of the scene inside the cartridge and / or focus on the scene, which is particularly the print plate. The camera and light can also be mounted on a motion stage, allowing the user to pan or zoom items of interest during the printing process. The camera can be used in conjunction with secondary printing diagnostics such as pyrometers, motion detectors, photodiodes, thermal cameras, or other sensors to automatically detect events and pan / zoom the camera to focus on locations of interest. In some embodiments, the operator can view the camera image in an electronic or virtual window instead of directly viewing it through a physical port or window in the cartridge.

[0062] Inert gas is supplied to the ink cartridge by gas supply pipe 6D, so that printing can be performed in any atmosphere that is most favorable to each printing. Gas return pipe 7D removes inert gas. Gas passes through HEPA filter 8D, and this HEPA filter 8D removes impurities (soot, suspended powder nanoparticles, etc.). Then, gas enters the gas reclaimer (not shown) installed on the supporting equipment. When the ink cartridge is disconnected from the supporting equipment, gas supply port 9D and gas return port 10D are sealed to keep the atmosphere inside the ink cartridge. Subsequently, by removing oxygen, water vapor, etc. by other equipment, purify gas.

[0063] The Z axis lowers the print plate after each layer is printed so that a new layer of powder can be unfolded and subsequently printed. In this design, the Z axis frame 11D holds the Z axis components. The print plate (also known as the build plate) 12D is where the powder is welded during printing. The print plate heater 13A contains a heating mechanism for the print plate 12D and can also insulate and / or cool the sealing plate 14D. The sealing plate 14D carries a seal 15D that confines the powder to the Z axis frame 11D. The Z axis base plate 16D closes the lower end of the Z axis frame 11D and has features to contain any powder that may slip from the seal 15D. The plunger 17D has an interface so that the plunger 17D can be remotely, automatically and accurately connected to the Z axis drive. The plunger seal 18D cooperates with the base plate 16D and further seals the ink cartridge 1D to prevent powder and / or gas leakage.

[0064] The interface board 19D contains all the inputs and outputs for the ink cartridge (compressed air, power, input and output signals, gases, cooling water, etc.). The ink cartridge is designed to make all of these connections when it is connected to a matching device. The interface may also contain a mechanism for electronically identifying each ink cartridge when it is mated with a matching device. Rollers 20D allow the ink cartridge 1D to roll onto the mating track of the mating device. Forklift tubes 21D allow the ink cartridge to be picked up and moved by a forklift.

[0065] In one embodiment, the ink cartridge 1D may include an electronic identification, such as an electronically readable memory 25D or other electronically readable markings, such as additional text or a barcode. The memory 25D may provide electronic information about the ink cartridge, or the ink cartridge component may be used to identify its brand, model, type, powder type, or any other limiting details about the unit, its subcomponents, or its intended use. This information may be used to inform the print engine of the material to be printed, the desired atmosphere (pressure and temperature), or other printing-related aspects so that the print engine may be adjusted as needed to accommodate the print cartridge, sub-cartridge, or sub-assembly. The changes caused may involve an action, such as automatic exchange of an internal lens assembly, adjustment of the z height / final optical projection of a lens assembly, adjustment of laser parameters such as power per unit area, pulse shape, pulse duration, pulse repetition rate, wavelength, spatial pulse shape, tile size, spatial energy distribution within a tile, modification of data diagnostics, data feedback algorithms, printing process feedback algorithms, or algorithmic changes to how tiles are placed during the printing process. Electronic information from the electronic memory 25D associated with the print cartridge or sub-cartridge can be read by the printer, de-powder station or storage rack to collect data on how many prints have occurred and other key metrics such as the number of disperser cycles, z-axis adjustments, temperature cycles, pressure cycles, or other attributes experienced by the cartridge or sub-cartridge along the way. This information can also be stored in a central database by the print engine, one of the subsystems, the factory automation system, the de-powder station, the cartridge storage station, the cartridge itself, or other supporting / interface equipment.

[0066] Figure 1EA system 1E is shown that supports the use of a segmented infrared heater suitable for use with a print chamber for patterned heating. Laser energy 17E proportional to the material to be printed is incident on a print plate 2E, which contains a heating cartridge 3E and a temperature sensing device for controlling the temperature of the print plate 2C. Below the print plate 2E, an insulator 4E reduces heat loss. Below the insulator 4E is a cooling tube containment plate 5E, which contains a coolant flow 6E. The entire print plate assembly is connected to the z-axis motor via a connecting shaft 7E. A heat flow 8E from a patterned radiating element is incident on the print plate 2E from above. The magnitude of the heat flow 8E can be inversely proportional to the laser energy 17E. The printer side wall 9E contains a heater element 10E. Outside the printer side wall 9E is an insulating layer 11E, and outside the insulating layer 11E is a print wall cooling tube side wall 12E containing a coolant flow 13E. The printed part 14E on the print plate is supported by the print plate 2E and surrounded by powder 15E. Conductive heat 16E from the heater cartridge in the print plate is applied to the printed part 20E. The conductive heater 17E from the heater cartridge in the print wall is applied to the printed part and the surrounding powder. In this embodiment, multiple segments of infrared heaters 18E are mounted above the print plate 2E. Each segment is independently controlled so that multiple parts of the print plate can be heated. This mechanism can spatially regulate the temperature distribution on the print plate caused by the print surface variations between layers. All infrared heater segments can also work together to temporally modulate the total heat load changes caused by the inter-layer variations in the laser energy delivered to the bed. The heaters receive power from a power supply 19E and can be connected in series or in parallel.

[0067] Figure 1F The use of segmented top-down or angled airflow for patterned heating is shown. In this embodiment, the print chamber and general operation of system 1F are similar to those described above with respect to Figure 1E As described, where like numbers represent like structures. In this embodiment, vertical airflow 18F can provide additional heating to the top surface. Using a segmented approach, the spatially related temperature can be tuned to a certain extent. This can be achieved by a series of units that are grouped together, or from a unit with multiple sub-sections.

[0068] Figure 1G The use of segmented cross-bed gas flow for patterned heating is shown. In this embodiment, the print chamber and general operation of system 1G are similar to those described above with respect to Figure 1E As described above, where like numbers represent like structures. In this embodiment, horizontal airflow 18G can provide additional heating to the top surface. As printing proceeds, the temperature of the airflow can be adjusted based on changes in the heat load.

[0069] Figure 1H An additional heating laser for patterned heating in system 1H is shown. System 1H includes a print chamber system including a print plate 2H, a heater cartridge 3H inside the print plate, an insulator 4H below the print plate, a cooling tube receiving plate 5H, and a cooling tube for holding a coolant 6H. Z-axis connecting shaft 7H is connected to the motor. Print wall or side wall 8H contains a heater cartridge 9H. There is an insulator 10H outside the print wall, a cooling tube receiving side wall / plate 11H, and a cooling tube 12H for holding a coolant. Printed parts 13H are formed on the print plate by powder 14H spread on the print plate. Conductive heat 15H from the heater cartridge in the print plate and / or conductive heat 16H from the heater cartridge in the print wall can be used at least in part to maintain thermal conditions in system 1H. Laser energy 17H can be proportional to the print tile fill fraction (2×2mm-10×10mm).

[0070] Additional laser sources provide focused energy to heat smaller and more specific areas of the printing plate. The laser beam delivery can be fixed and the optics are built to project to fill the entire plate, or the laser can be mounted on a scanning device so that the laser can scan to cover the entire printing plate. The laser can be patterned using a spatial light modulator such as an optically addressed light valve, DMD or other patterning device. The laser may need to be homogenized before the SLM to allow high uniformity of the beam. The homogenizer can be a reflective tube, a TIR tube, a diffraction element, a lenslet array or the like. The geometry of the homogenizer is typically square, but can be any geometry configured to fit the pattern.

[0071] The component includes an additional laser source 18H (scanning and / or fixed and patterned). A light beam 19H is emitted from the laser source and directed to a relay optical assembly 20H between the laser source 18H and the laser homogenizer 21H. In some embodiments, an image relay optical assembly 34H is located between the laser homogenizer and the light valve. The homogenized light beam 22H emitted from the laser homogenizer is directed to a patterned addressing light source 23H for a 445nm wavelength light valve. The blue light 24H emitted from the patterned addressing light source is directed to a blue / IR combiner 25H to colinearly align the blue and IR lasers / light sources. The light valve 26H for patterning the supplementary thermal laser source passes some light to a polarizer 27H for rejecting unused light that is not included in the pattern. The component may also include an electric drive source 28H for light valve operation, which forms a patterning unit assembly 29H together with components 25H, components 26H, and components 27H. Light from the patterning unit assembly 29H is directed to the image relay optics assembly 30H for relaying the light valve patterned image to the powder bed. A steering mirror 31H is used to direct light into the build chamber, or otherwise control where the laser goes. The laser beam 32H can be reflected from the scanning mirror and focused onto a sub-portion of the print bed for thermal management of the print bed. Alternatively, a laser beam 33H reflected from a fixed reflector can be focused onto the entire print bed area (or a large portion thereof).

[0072] Fig. 1I The use of an additional heating laser for non-patterned heating is shown; in this embodiment, the print chamber of system II is similar to that described previously with respect to Figure 1HAs described, where like numbers represent like structures. As shown, the laser area printer may include an input from a uniformed image plane 18I. The laser has been uniformed to reach the plane by a reflective tube, a TIR tube, a diffractive optical device, a lenslet array, or a similar mechanism. A beam 19I having a single majority polarization state propagates from plane 18I to an image relay optical component 21I, which changes the beam size at plane 19I and reconstructs its intensity distribution on a light valve 26I. On the path to the light valve 26I, the beam 19I also passes through a beam combiner 25I, which combines a 445nm patterned blue light 24I emitted from a projector unit 23I with a 1000 / 1064nm infrared beam 19I. Both beams are incident on the light valve 26I, which allows the pattern on the blue beam 24I to be transferred to the infrared beam 19I in polarization space. This action of the light valve 26I creates two majority polarization states in the light beam in the desired pattern according to the dynamically adjustable projector unit 23I. Upon hitting the polarizer 27I, the light beam is split into a negative image and a positive image. The positive image is transmitted to the optical image relay lens assembly 30I, which relays the light valve positive image to the print bed in the desired tile size by reflecting off from the movable gimbaled mirror 20I. F-θ optics may be present between the mirror 20I and the print bed in some configurations. The negative image reflects off from the polarizer 27I to be incident on the mirror 22I, which directs the negative image light to the image relay 24I, which couples the light into the waste light homogenizer 35I. In some cases, the mirror 22I is also a dichroic filter, allowing 1064nm light to pass through it and only reflecting 1000nm light. The goal in this case is to use separate methods to homogenize different types of laser light. Tube homogenizers are suitable for homogenizing relatively long pulse, low coherence, low intensity light, while diffraction elements are more suitable for homogenizing low divergence, high coherence light. At the output of the waste light homogenizer 35I, the homogenized image is passed to the final waste light image relay, which performs an image relay operation between the output of the waste light homogenizer 35I and the print bed. The image relay can be fixed or dynamically adjustable to change the focus. The focus can be tight so that a small part of the bed is illuminated, or the focus can be large so that the entire bed is illuminated. The final turning mirror 31I can be fixed or allowed to move to further accommodate the supplementary heat transfer process.

[0073] Figure 1J The use of additional heating laser light derived from recycled or discarded light for patterned heating is shown. In this embodiment, the print chamber of system II is similar to that described above with respect to Figure 1H and Fig. 1I As described, where like numbers represent like structures. The figure shows a configuration for a laser area printer starting from an input homogenized image plane 18J. The laser has been homogenized by a reflective tube, a TIR tube, a diffractive optical device, a lenslet array or a similar mechanism to reach this plane. A beam 19J with a single majority polarization state propagates from plane 18J to an image relay optical component 21J, which changes the beam size at plane 19J and reconstructs its intensity distribution on a light valve 26J. On the way to the light valve 26J, the beam 19J also passes through a beam combiner 25J, which combines a 445nm patterned blue light 24J emitted from a projector unit 23J with a 1000 / 1064nm infrared beam 19J. Both beams are incident on a light valve 26J, which allows the pattern on the blue beam 24J to be transferred to the infrared beam 19J in polarization space. This action of the light valve 26J forms two majority polarization states in the light beam of the desired pattern according to the dynamically adjustable projector unit 23J. Upon hitting the polarizer 27J, the light beam is split into a negative image and a positive image. The positive image is transmitted to the optical image relay lens assembly 30J, which relays the light valve positive image to the print bed in the desired tile size by reflecting off from the movable gimbaled mirror 20J. F-θ optics may be present between the mirror 20J and the print bed in some configurations. The negative image reflects off from the polarizer 27J to be incident on the mirror 22J, which directs the negative image light to the image relay 24J, which couples the light into the waste light homogenizer 35I. In some cases, the mirror 22J is also a dichroic filter, allowing 1064nm light to pass through it and only reflecting 1000nm light. The goal in this case is to use separate methods to homogenize different types of laser light. Tube homogenizers are suitable for homogenizing relatively long pulse, low coherence, low intensity light, while diffraction elements are more suitable for homogenizing low divergence, high coherence light. At the output of the waste light homogenizer 35J, the homogenized image is passed to the image relay for relaying to the second patterning unit assembly, which reconstructs the waste image homogenizer 35J output to the second light valve. The positive image of this new light valve is allowed to transmit through the entire waste light patterning unit assembly to the final image relay optical device 38J, which performs an image relay operation between the waste energy light valve output and the print bed. The image relay can be fixed or dynamically adjustable to change the focus. The focus can be tight so that a small part of the bed is illuminated, or the focus can be large so that the entire bed is illuminated. The final turning mirror 31J can be fixed or allowed to move to further accommodate the supplementary heat transfer process.

[0074] Figure 1KA thermal imaging system using a camera and a pyrometer is shown; detailed thermal imaging can be achieved on each layer of the print if desired. In one embodiment, a color CCD or CMOS camera 7K is used to image a print bed 4K containing the printed article on a print substrate or print plate 5K. The resolution of the camera 7K is selected to be sufficient to resolve the features of the part being printed to determine if there are temperature differences across the layer. For example, if we choose a 16 megapixel camera (4000×4000 pixels), the camera can be used to image a 40 cm bed, providing a nominal pixel resolution of 100 microns. A 64 megapixel camera (8000×8000) can be used to provide a pixel resolution of 50 microns. In operation, due to the very high speeds associated with some embodiments of the additive manufacturing system, the average temperature of the print bed is relatively high. The bed 4K will glow visibly or in an infrared camera system. Even a modest temperature of 500 degrees Celsius will produce a black body curve, whose emission at 1050nm is similar to the red light visible to people at 700 degrees Celsius. Alternatively, one can use a FLIR type camera. The temperature in the image can be calibrated by using an optical pyrometer 2K to benchmark the temperature at a single location 6I in the print bed. By taking some temperature measurements with the pyrometer and correlating these measurements with the corresponding images, a spatial temperature distribution of the bed can be created at low cost. Once calibrated, the pyrometer is no longer strictly required and the image can be used as an independent monitor of the bed temperature. Images taken at the beginning and end of each recoat can be used to track recoat uniformity, print health, and print temperature uniformity. If the temperature is too low or too high, the control system can be used to correct the temperature non-uniformity or overall amplitude by potentially adjusting the surface heating level with spatial correlation or adjusting the bed / wall heating level as needed to maintain the isothermal environment required for printing. Typically, windows 3K are required to protect the imaging devices 2K and 7K from any powder, soot, dust or other particles that may fall off the print bed 4K during the printing process.

[0075] Figure 2 A process flow 200 and selected components of an additive manufacturing system for thermal control are shown. In this embodiment, part geometry and print heat load history 202 are fed as input parameters. A feedforward controller 204 uses the part geometry and print heat load history to actively generate control signals. Heater cartridges in the print wall 206 heat the printed part and the surrounding powder. Radiant heaters 208 heat the printed part and the surrounding powder. Heater cartridges in the print plate 210 heat the printed part and the surrounding powder. The printed part 212 is supported by the print plate and surrounded by powder. Laser energy 214 is applied to the powder layer 216 to melt the powder and promote the solidification process.

[0076] Figure 3 A display of heat loads on different parts of a printed housing is shown, where a combination of heat loads from different sources is balanced to maintain a substantially isothermal condition for the printed part. Isothermal manufacturing conditions can reduce inter-layer differences in average heat load, prevent or reduce spatially correlated thermal warping in all three dimensions, reduce higher residual stresses, and even prevent cracking of printed parts. Such isothermal conditions are provided for the average heat load from the laser energy as shown in the graph 300, which is a function of time or the number of layers on the bed. Supplemental energy 302 is required to balance the heat load 306 from the patterned laser so that the total heat load on the bed is constant (dashed isothermal line 307). For example, heat load 303 is applied to the print plate from below. Heat load 304 is applied to a heater on a side wall at 1 / 3 of the print wall. Heat load 305 is applied to a heater on a side wall at 2 / 3 of the print wall. When these heat loads are added together, a substantially constant heat load 307 is generated. In some embodiments, the amount of patterned thermal energy that provides the heat load is at least partially determined by the part pattern being printed. Additionally, the supplied patterned thermal energy may be provided in an amount that is substantially inversely proportional to the portion of the pattern being printed. Typically, printing a relatively large part or layer sub-portion (relative to the print chamber or print bed) will require little supplied patterned heating energy, while printing a small part or layer sub-portion will require a large amount of supplied patterned heating energy.

[0077] Many modifications and other embodiments of the present invention will occur to those skilled in the art who have benefited from the foregoing description and the teachings presented in the associated drawings. Therefore, it should be understood that the present disclosure is not limited to the specific embodiments disclosed, and modifications and other embodiments are considered to be included within the scope of the appended claims. It should also be understood that other embodiments of the present invention can be implemented without the elements / steps specifically disclosed herein.

Claims

1. A manufacturing system comprising: a printer chamber having a printer bed supporting a manufacturing material, the printer chamber having an inner wall, an insulating layer located outside the inner wall, and an outer wall located outside the insulating layer; an internal contact heating system built into the printer chamber and configured to direct patterned thermal energy onto the printer bed and supported build material; as well as an external heating system for the printer chamber, the external heating system being configured to direct patterned thermal energy onto the printer bed and any supported manufacturing material; Wherein, the internal contact heating system comprises: a heating element within the interior wall of the printer chamber; and A cooling element is within the outer wall of the printer chamber.

2. The manufacturing system according to claim 1, wherein: The printer chamber also includes an ink cartridge.

3. The manufacturing system according to claim 1, wherein: The external heating system also includes an infrared heating element.

4. The manufacturing system according to claim 1, wherein: The external heating system also includes a heated air flow.

5. The manufacturing system according to claim 1, wherein: The external heating system also includes at least one pointing laser.

6. The manufacturing system according to claim 1, wherein: The external heating system also includes at least one directed laser to provide non-patterned heating.

7. The manufacturing system according to claim 1, wherein: The external heating system also includes at least one directed laser to provide patterned heating.

8. The manufacturing system according to claim 1, wherein: The external heating system also includes at least one pointing laser using recycled light.

9. The manufacturing system according to claim 1, further comprising a sensor, wherein: The sensor includes a pyrometer.

10. The manufacturing system of claim 1, further comprising a sensor, wherein: The sensor includes a camera.

11. A manufacturing system comprising: a printer chamber having a printer bed supporting a layer of printable material, the printer chamber having an inner wall, an insulating layer located outside the inner wall, and an outer wall located outside the insulating layer, a primary laser source that can be directed toward a sub-portion of the layer of printable material on the printer bed to print a part pattern; as well as A secondary heating system configured to direct patterned thermal energy into the layer of printable material, wherein the secondary heating system comprises an internal contact heating system comprising a heating element within the inner wall of the printer chamber and a cooling element within the outer wall of the printer chamber.

12. The manufacturing system according to claim 11, wherein: The patterned thermal energy is determined at least in part by the pattern of the part being printed.

13. The manufacturing system according to claim 11, wherein: The patterned thermal energy is adjusted based on the printed pattern to provide thermal uniformity.

14. The manufacturing system according to claim 11, wherein: The patterned thermal energy is used to compensate for spatial thermal non-uniformities in the printed heat source.

15. The manufacturing system according to claim 11, wherein: The patterned thermal energy is adjusted multiple times during printing based on the pattern being printed to provide thermal uniformity.

16. The manufacturing system according to claim 11, wherein: The secondary heating system also includes a second light emitting heating element.

17. The manufacturing system according to claim 16, wherein: The second light emitting heating element also includes at least one of an arc lamp, an infrared lamp, an LED heating system, or a laser heating system.

18. The manufacturing system according to claim 11, wherein: The secondary heating system also includes a patterned heating element supported by the printer chamber.

19. The manufacturing system according to claim 18, wherein: The patterned heating element supported by the printer chamber also includes at least one of an array of resistive heating cartridges, a heating fluid in a channel, an electrically controlled plasma source, an arc heater, an induction heater, or a microwave heater.

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