Patent ID: 12202197

The same part numbers designate the same or similar parts throughout the figures.

DESCRIPTION

Additive manufacturing machines make a 3D object through the solidification of one or more layers of a build material. Additive manufacturing machines make objects based on data in a 3D model of an object generated, for example, with a CAD computer program product. The model data is processed into slices each defining that part of a layer or layers of build material to be solidified. Examples of additive manufacturing described below use a technique sometimes referred to as “light area processing” (LAP) in which an ink or other suitable coalescing agent is dispensed on to a layer of build material in the desired pattern and then exposed to light. Light absorbing components in the coalescing agent absorb light to generate heat that sinters, melts or otherwise coalesces the patterned build material, allowing the patterned build material to solidify.

LAP heating may occur in two steps. First, the build material is heated to and maintained at temperature just below its coalescing temperature, for example with a combination of resistive heaters and a lower intensity heater lamp. Second, a coalescing agent is “printed” or otherwise dispensed on to the build material in the desired pattern and exposed to a higher intensity coalescing lamp emitting light absorbed into the patterned build material. Presently, halogen lamps emitting light over a broad spectrum are usually used in both steps. Accordingly, carbon black ink is often used as the coalescing agent to absorb light over a broad spectrum to generate enough heat to effectively coalesce the patterned build material. The use of black ink, however, limits the color of the manufactured objects to black and grey.

A variety of different color objects may be manufactured with LAP using colored and colorless inks that have high light absorption within a narrow band of wavelengths. Colorless inks that absorb only infrared light may be particularly desirable coalescing agents because they enable manufacturing objects that are the same color as the starting build material. The colorless dyes described in the international patent applications filed by Hewlett-Packard Development Company in September 2014 under PCT/US2014/057882 and PCT/US2014/057863 and titled 3-Dimensional Printing, for example, have been developed for use as ink based LAP coalescing agents. Broad band halogen lamps, however, may be inadequate for heating build material patterned with colored and colorless inks because only a small portion of the light emitted falls within the band of wavelengths where high light absorption occurs, and thus the amount of absorbed radiative energy may be inadequate to heat the patterned build material to a coalescing temperature. In addition, light emitted outside this band of wavelengths may have undesirable heating effects.

New LAP lighting techniques have been developed to manufacture color objects (other than black and grey) using color and colorless coalescing agents, including the colorless dyes described in the PCT/US2014/057882 and PCT/US2014/057863 patent applications. Examples of the new techniques utilize monochromatic light covering the peak light absorption of the coalescing agent to develop the heat needed to reach coalescing temperatures. In one example, an additive manufacturing process includes dispensing a liquid coalescing agent on to build material in a pattern corresponding to an object slice and then exposing the patterned build material to monochromatic light within a band of wavelengths that includes a peak light absorption of the coalescing agent. Although the intensity of the monochromatic light needed for adequate heating may vary depending on the characteristics of the build material and coalescing agent, it is expected that monochromatic light with a spectral intensity at least 1×1012Wm−3sr−1(watts per cubic meter per steradian) will be sufficient for many implementations.

In another example, a carriage assembly for an additive manufacturing machine carries an array of individually addressable monochromatic light sources along with an inkjet printhead to dispense the coalescing agent. Individual light sources may be energized selectively to illuminate only patterned build material to limit unwanted effects on surrounding build material and to reduce power consumption. Also, the array may include a single set of monochromatic light sources (only one wavelength band) corresponding to a coalescing agent with an absorption peak within the band, or multiple sets of light sources (multiple wavelength bands) to accommodate a greater range of coalescing agents. The use of a monochromatic lighting array enables an integrated carriage assembly to carry both the printhead(s) and the light sources for immediate, targeted lighting.

The electronic instructions to control monochromatic lighting in an additive manufacturing machine may reside on a processor readable medium implemented, for example, in a CAD computer program product, in an object model processor, or in the controller for the additive manufacturing machine.

These and other examples described below and shown in the figures illustrate but do not limit the scope of this disclosure, which is defined in the Claims following this Description.

As used in this document: “coalesce” means to become a coherent mass by heating, for example by sintering or melting; a “coalescing agent” means a substance that causes or helps cause a build material to coalesce; a “coalescence modifier agent” means a substance that inhibits or prevents coalescence of a build material, for example by modifying the effect of a coalescing agent; “monochromatic” means within a band of wavelengths 30 nm or narrower; “polychromatic” means a band of wavelengths broader than 30 nm; and a “slice” means one or more slices of a multi-slice object or the object itself for a single slice object.

The sequence of sections presented inFIGS.1-9illustrate one example for manufacturing a three dimensional object10shown inFIG.9.FIGS.10and11are flow diagrams illustrating example additive manufacturing processes100and130, respectively, implemented in the example ofFIGS.1-9. Referring first toFIG.1, in this example a supply12of powdered build material14is held on a delivery piston16in a supply bed18. A roller or other suitable layering device20moves build material14from supply bed18to a receiving piston22in a manufacturing bed24, as indicated by arrow26. Pistons16and22move up and down, respectively, as build material14is moved from supply bed18to manufacturing bed24. Any suitable build material14may be used to make the desired solid object, which may be hard or soft, rigid or flexible, elastic or inelastic. Also, while a powdered build material14is depicted by particles28in this example, suitable non-powdered build materials could be used.

Referring now also toFIG.10, a first layer30of build material14is formed in manufacturing bed24as shown inFIG.1(block102inFIG.11). In some implementations, it may be desirable to pre-heat build material14, particularly in the first few layers, to help keep each layer flat during coalescence and solidification. Individual layers of build material14may be pre-heated in manufacturing bed24, as shown inFIG.1(block104inFIG.10), or build material14may be pre-heated in supply bed18, or a combination of heating in both beds18and24. “Pre-heating” in this context refers to heating before light is applied to coalesce build material for coalescence, as described below with reference toFIG.4. While the pre-heating temperature will vary depending on the characteristics of build material14, the pre-heating temperature usually will be 20° C. to 50° C. below the melting point or the sintering point for a nylon12powdered build material. Any suitable heater32may be used. In the example shown inFIG.1, heater32includes a heating lamp positioned over bed24. In other examples, heater32may include a resistive heater in the powder bed used alone or with a heating lamp.

InFIG.2, a coalescing agent34is dispensed on to build material14in layer30in a pattern corresponding to the first object slice (block106inFIG.10), for example with an inkjet type dispenser36. This pattern for coalescing agent34is depicted by an area38of dense stippling in the figures. If desired, a coalescence modifier agent40may be dispensed on to build material14in layer30for example with an inkjet type dispenser44, as shown inFIG.3(block108inFIG.10). Modifier agent40blocks or neutralizes the effects of the coalescing agent and may be applied before or after coalescing agent (or both before and after) to help control the degree of coalescence of targeted areas of build material for improved dimensional accuracy and overall quality of the manufactured object. In the example shown inFIG.3, modifier agent40is dispensed on to an area42covering the area where a second object slice will overhang the first slice. Overhang area42covered by coalescence modifier agent40is depicted by light stippling in the figures. Coalescence modifier agent40may also be dispensed on to other areas of build material layer30to help define other aspects of the object slice, including interspersed with the pattern of the coalescing agent to change the material characteristics of the slice. Although two dispensers36,44are shown, agents34and40could be dispensed from the same dispensers integrated into a single device, for example using different printheads (or groups of printheads) in a single inkjet printhead assembly.

Coalescing agent34includes a light absorbing component to absorb light to generate heat that sinters, melts or otherwise coalesces patterned build material38. The rate of light absorption for different types of coalescing agents34will vary over different parts of the electromagnetic spectrum depending on the characteristics of the light absorbing component. For example, a yellow colorant may have a peak light absorption at about 450 nm wavelength light. A cyan colorant, by contrast, may have a peak light absorption at about 700 nm wavelength light. Black ink may have high absorption across a broad band of wavelengths compared to high absorption for yellow and cyan across narrow bands of wavelengths.

As noted above, it may not always be desirable to use black ink as a coalescing agent34. However, because other colors absorb light across a narrower band of wavelengths, the time it takes to generate coalescing heat with a polychromatic, halogen lamp using cyan ink, for example, may be too long to be practical for additive manufacturing. Heating time may be reduced to practical levels for cyan and other color inks, and even for colorless inks, by using monochromatic light matching the color absorption band of coalescing agent34. Thus, inFIG.4, the area of layer30patterned with coalescing agent34is exposed to monochromatic light46from a light source48to coalesce build material patterned with coalescing agent34, allowing the patterned build material to solidify and form first object slice50(block110inFIG.10). In one example, as described in the more detail below, light source48is configured to emit monochromatic light46within a band of wavelengths that includes the peak light absorption of coalescing agent34with sufficient intensity to coalesce patterned build material. Any suitable light source48may be used to emit monochromatic light including, for example, LEDs, laser diodes and other sources that emit monochromatic light directly as well as light sources that emit monochromatic light by filtering, splitting, dispersing, refracting or otherwise producing monochromatic light from polychromatic light.

The process may be repeated for second and subsequent layers to form a multi-slice object. For example, inFIG.5a second layer52of build material14is formed in manufacturing bed24over first layer30(block112inFIG.10) and pre-heated (block114inFIG.10). InFIG.6, a coalescing agent34is dispensed on to build material14in layer52in a pattern54corresponding to the second object slice (block116inFIG.10), including along the edge of an area56overhanging first slice50. InFIG.7, a coalescence modifier agent40is dispensed on to build material14in layer52in area58to help prevent the unwanted coalescence and solidification of build material along the edge of the overhang (block118inFIG.10). InFIG.8, the area54of layer52patterned with coalescing agent34is exposed to monochromatic light46to coalesce build material and form second object slice60overhanging first slice46(block120inFIG.10).

Agent dispensers36and44may be carried back and forth across manufacturing bed24together with light source48, as indicated by arrows62inFIGS.1-8, on a single carriage or on two or more separate carriages. Also, it may be possible in some implementations to use stationary agent dispensers36,44and/or light sources48. Coalescing agent34dispensed on to build material14in second layer52may be the same as or different from the coalescing agent dispensed on to first layer30. Accordingly, monochromatic light46to coalesce patterned build material in second layer52may be the same or different wavelength from the light to coalesce patterned build material in first layer30. Also, while distinct first and second slices50and60are shown inFIG.8, the two slices actually fuse together into a single part upon coalescing and solidification of the second slice. The now fused slices50,60may be removed from manufacturing bed24as a finished object10shown inFIG.9. Although a simple two-slice object10is shown, the same process steps may be used to form more complex, multi-slice objects.

FIG.11illustrates another example of an additive manufacturing process130. Referring toFIG.11, a liquid coalescing agent is dispensed on to build material in a pattern corresponding to a slice (block132) and patterned build material is exposed to monochromatic light within a band of wavelengths that includes a peak light absorption of the coalescing agent (block134). The wavelength of the monochromatic light will vary depending on the peak absorption of the light absorbing component in the coalescing agent. Several examples are described below with reference to the graphs shown inFIGS.14and15. Also, the intensity of the monochromatic light should be great enough to allow the patterned build material to reach a coalescing temperature within a practical period of time. Thus, as shown inFIG.12, exposing patterned build material to monochromatic light in block134ofFIG.11may be performed, for example, by exposing patterned build material to monochromatic light with a spectral intensity at least 1×1012Wm−3sr−1. Referring toFIG.13, in one specific example described below, exposing patterned build material to monochromatic light in block134ofFIG.11may be performed by exposing patterned build material to monochromatic light with a spectral intensity at least 1×1012Wm−3sr−1to raise the temperature of the patterned build material 20° C. to 50° C. in a quite practical time of 1 second or less.

Several examples of coalescing agent and matching monochromatic light to generate coalescing heat are described below with reference to the graphs ofFIGS.14and15.FIG.14shows light absorption as a function of wavelength for black, yellow, magenta, cyan and colorless ink coalescing agents. A colorant acts as the light absorbing component in each ink which, for the color inks represented inFIG.14, is a color pigment. The pigment based inkjet inks represented inFIG.14are commercially available from Hewlett-Packard Company as C8750 (black), C4905 (yellow), C4904 (magenta), and C4903 (cyan). A colorless dye acts as the light absorbing component in the colorless dye based ink represented inFIG.14. Two such dyes are described in the PCT/US2014/057882 and PCT/US2014/057863 patent applications noted above.

FIG.15shows spectral intensity as a function of wavelength for several examples of commercially available light sources that emit monochromatic light near the peak absorptions for the color coalescing agents shown inFIG.14. (Suitable light sources that emit monochromatic light near the peak absorption for the colorless coalescing agent shown inFIG.14are not yet readily available commercially.)FIG.15also shows the spectral intensity of a 2500K halogen lamp relative to the monochromatic light sources.

A colorless ink such as that represented inFIG.14will absorb 60% or more light in the band of 800 nm to 1350 nm, including 808 nm light emitted by the infrared laser diode inFIG.15. A yellow ink such as that represented inFIG.14will absorb 60% or more light in the band of 380 nm to 500 nm, including the 450 nm light emitted by the blue laser diode and the 470 nm light emitted by the blue LED inFIG.15. A magenta ink such as that represented inFIG.14will absorb 60% or more light in the band of 420 nm to 600 nm, including the 590 nm light emitted by the yellow LED inFIG.15. A cyan ink such as that represented inFIG.14will absorb 60% or more light in the band of 520 nm to 700 nm, including the 590 nm light emitted by the yellow LED and the 640 nm red LED inFIG.15. A black ink such as that represented inFIG.14will absorb 60% or more light across the full spectrum of visible light (380 nm to 700 nm), including light emitted by any of the color LEDs and laser diodes inFIG.15.

As shown inFIG.15, the spectral intensity of the monochromatic light is significantly higher at or near peak absorption than the spectral intensity of the polychromatic light emitted by a 2500K halogen lamp. It has been demonstrated that monochromatic light sources such as the LEDs and laser diodes represented inFIG.15produce enough energy to generate the heat needed to coalesce polymer build materials when matched to the proper light absorbing component in the coalescing agent. In one example, a nylon12build material powder that coalesces at about 185° C. is pre-heated to about 150° C., patterned with a yellow ink fromFIG.14, and exposed to a blue LED emitting 470 nm light from a distance less than 2 cm. The yellow ink absorbing nearly 100% of the incident light should generate sufficient heat to reach the coalescing temperature of about 185° C. at least 10 times faster than with a 2500K halogen lamp. If the patterned build material is exposed to a blue laser diode emitting 450 nm light, the coalescing temperature may be reached even faster. While the threshold absorption for adequate heating will vary depending on the build material and the monochromatic light source, it is expected that sufficient heat may be generated in an exposure time less than 1 second if the coalescing agent absorbs incident light at a rate of 60% or more for matching light with a spectral intensity at least 1×1012Wm−3sr−1.

FIG.16is a block diagram illustrating a processor readable medium64with instructions66to control lighting during the manufacture of a 3D object. A processor readable medium64is any non-transitory tangible medium that can embody, contain, store, or maintain instructions for use by a processor. Processor readable media include, for example, electronic, magnetic, optical, electromagnetic, or semiconductor media. More specific examples of suitable processor readable media include a hard drive, a random access memory (RAM), a read-only memory (ROM), memory cards and sticks and other portable storage devices.

Lighting instructions66include instructions to control monochromatic lighting during the manufacture of a 3D object, for example by exposing patterned build material to monochromatic light at block134inFIG.11-13. Instructions66may include other lighting instructions, for example instructions to pre-heat build material at block104inFIG.10with a heating lamp32inFIGS.1-8. Processor readable medium64with instructions66may be implemented, for example, in a CAD computer program product, in an object model processor, or in a controller for an additive manufacturing machine. Control data to inhibit solidification can be generated, for example, by processor readable instructions on the source application, usually a CAD computer program product, in an object model processor, or by processor readable instructions on the additive manufacturing machine.

FIG.17is a block diagram illustrating one example of an additive manufacturing machine68implementing a controller70with lighting instructions66. Referring toFIG.17, machine68includes controller70, a manufacturing bed or other suitable support24, a roller or other suitable build material layering device20, a coalescing agent dispenser36, a coalescence modifier agent dispenser44, a heater32and a light source48. The in-process object structure is supported on support24during manufacturing. In some machines68, support24is movable at the urging of controller70to compensate for the changing thickness of the in-process structure, for example as layers of build material are added during manufacturing.

Build material layering device20layers build material on support24and on the in-process structures and may include, for example, a device to dispense the build material and a blade or roller to distribute the build material uniformly to the desired thickness for each layer. Coalescing agent dispenser36dispenses coalescing agent selectively at the direction of controller70on to build material, for example as described above with reference toFIGS.2and6. Coalescence modifier agent dispenser44dispenses modifier agent selectively at the direction of controller70on to build material, for example as described above with reference toFIGS.3and7. While any suitable dispensers36,44may be used, inkjet printheads are often used in additive manufacturing machines because of the precision with which they can dispense agents and their flexibility to dispense different types and formulations of agents. Manufacturing machine68may include a heater32if it is desired to pre-heat the build material. Manufacturing machine36includes a light source48to apply light energy to coalesce build material treated with coalescing agent, for example as described above with reference toFIGS.5and8.

Controller70represents the processor (or multiple processors), the associated memory (or multiple memories) and instructions, and the electronic circuitry and components needed to control the operative elements of machine68. In particular, controller70includes a memory72having a processor readable medium64with lighting instructions66and a processor74to read and execute instructions66. For example, controller70would receive control data and other instructions from a CAD program to make an object and execute local lighting instructions66as part of the process of making the object.

Alternatively, lighting instructions66may be embodied in a processor readable medium64separate from controller70, for example as part of a CAD computer program product shown inFIG.18. Referring toFIG.18, an additive manufacturing system76includes an additive manufacturing machine68operatively connected to a CAD computer program product78with lighting instructions66residing on a processor readable medium64. Any suitable connection between machine68and CAD program product78may be used to communicate instructions and control data to machine68including, for example, a wired link, a wireless link, and a portable connection such as a flash drive or compact disk.

FIG.19illustrates one example of a carriage assembly79for an additive manufacturing machine such as machine68shown inFIGS.17and18. Referring toFIG.19, carriage assembly79includes a carriage80carrying agent dispensers36,44and a light source48. Carriage80is movable back and forth over manufacturing bed24to dispense coalescing and modifier agents34,40, for example as shown inFIGS.2-3and6-7, and to expose patterned build material to monochromatic light46, for example as shown inFIGS.4and8. In the example shown inFIG.19, agent dispensers36and44are configured as elongated inkjet printheads that span the width of bed24with an array of nozzles82through which the agents are dispensed on to build material supported on bed24, or that span so much of the width of bed24corresponding to a build zone88for layering and coalescing the build material. While two printheads36,44with only a single line of dispensing nozzles are shown, other configurations are possible. For example, more or fewer printheads could be used each with a different array of dispensing nozzles, including printheads and nozzles to dispense multiple different color (or colorless) coalescing agents.

Also, in the example shown, light source48is configured as a pair of light bars84that span the width of bed24with an array of individually addressable LEDs, laser diodes or other monochromatic light sources86, or that span so much of the width of bed24corresponding to a build zone88for layering and coalescing the build material. Each of the light sources86or each of multiple groups of the light sources86is individually addressable in the array to emit light selectively independent of any other light source in the array or of any other group of light sources in the array. Each light bar84is positioned outboard of agent dispensers36,44to enable illuminating patterned build material on bed24immediately after dispensing an agent34,40, if desired, when carriage80is moving in either direction across bed24. Individual light sources86may be energized selectively at the direction of the controller70to illuminate only patterned build material to limit unwanted effects on surrounding build material and to reduce power consumption. In addition, each light bar84may include a single set of monochromatic lights (only one wavelength band) corresponding to coalescing agents with absorption peaks within that band, or multiple sets of lights (multiple wavelength bands) to accommodate a greater range of coalescing agents. Other suitable lighting configurations are possible. For example, light source48may be supported on a carriage distinct from the carriage supporting the agent dispenser(s). For another example, light source48may be configured as a stationary array of monochromatic light sources86covering build zone88.

In one example, each light bar84includes a line of monochromatic red light sources, a line of monochromatic green light sources and a line of monochromatic blue light sources to cover corresponding absorption peaks for cyan, magenta, and yellow coalescing agents, respectively. Lines or other arrays of multiple monochromatic light sources enable manufacturing an object with different color parts using a single light source48. Thus, for example, a first color (or colorless) coalescing agent34may be dispensed at block106inFIG.10and exposed to a corresponding first color (or colorless) monochromatic light46at block110, and a second color (or colorless) coalescing agent34dispensed at block116and exposed to a corresponding second color (or colorless) monochromatic light46at block120. Other processes are possible. For another example, dispensing a coalescing agent at one or both blocks106and116may include patterning build material with multiple, different coalescing agents34and exposing the different patterns to corresponding multiple, different monochromatic light46to obtain different colors within the same layer of build material.

While a powdered polymer build material is often used for additive manufacturing, other suitable build materials may be used, including metals and other non-polymers and/or liquids, pastes, and gels. Suitable coalescing agents include water or solvent based dispersions with a light absorbing component. As one example, the coalescing agent may be an ink that includes colored or colorless pigments or dyes as the light absorbing component.

Suitable coalescence modifier agents may separate individual particles of the build material to prevent the particles from joining together and solidifying as part of the slice. Examples of this type of coalescence modifier agent include colloidal, dye-based, and polymer-based inks, as well as solid particles that have an average size less than the average size of particles of the build material. The molecular mass of the coalescence modifier agent and its surface tension should be such that it enables the agent to penetrate sufficiently into the build material to achieve the desired mechanical separation. In one example, a salt solution may be used as a coalescence modifier agent. In other examples, inks commercially known as CM996A and CN673A available from Hewlett-Packard Company may be used as a coalescence modifier agent. Suitable coalescence modifier agents may act to modify the effects of a coalescing agent by preventing build material from reaching its coalescing temperature during heating. A fluid that exhibits a suitable cooling effect may be used as this type of coalescence modifier agent. For example, when build material is treated with a cooling fluid, heat in the build material may be absorbed evaporating the fluid to help prevent build material from reaching its coalescing temperature. Thus, for example, a fluid with a high water content may be a suitable coalescence modifier agent. Other types of coalescence modifier agent may be used.

“A” and “an” used in the Claims means one or more.

The examples shown in the figures and described above illustrate but do not limit the scope of this disclosure, which is defined in the following Claims.