Patent Publication Number: US-11642853-B2

Title: Deviant control in additive manufacturing

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. application Ser. No. 16/077,320 filed Aug. 10, 2018, which is a national stage of international application no. PCT/US2017/013914 filed Jan. 18, 2017, each incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     Additive manufacturing machines produce 3D objects by building up layers of material. Some additive manufacturing machines are commonly referred to as “3D printers.” 3D printers and other additive manufacturing machines make it possible to convert a CAD (computer aided design) model or other digital representation of an object into the physical object. The object model data may be processed into slices each defining that part of a layer or layers of build material to be formed into the object. 
    
    
     
       DRAWINGS 
         FIGS.  1  and  2    are elevation and plan views, respectively, illustrating one example of an additive manufacturing machine. 
         FIGS.  3 - 18    present a sequence of elevation and plan views illustrating one example of a process for thermal control using machine  10  shown in  FIGS.  1  and  2   . 
         FIGS.  19 - 21    illustrate example thermographs corresponding to the object slice shown in  FIGS.  2 ,  10 , and  18   , respectively. 
         FIGS.  22 - 27    are flow diagrams illustrating example additive manufacturing processes. 
         FIG.  28    is a block diagram illustrating one example of processor readable medium with deviant control instructions thereon to help form an object during additive manufacturing. 
         FIG.  29    is a block diagram illustrating one example of an additive manufacturing machine implementing a controller with thermal control instructions to help form an object during additive manufacturing. 
     
    
    
     The same part numbers designate the same or similar parts throughout the figures. The figures are not necessarily to scale. 
     DESCRIPTION 
     In some additive manufacturing processes, heat is used to fuse together the particles in a powdered build material to form a solid object. Heat to fuse the build material may be generated, for example, by applying a liquid fusing agent to a thin layer of powdered build material in a pattern based on the object slice and then exposing the patterned area to fusing light. Light absorbing components in the fusing agent absorb light energy to help sinter, melt or otherwise fuse the build material into a slice of the object. The process is repeated layer by layer and slice by slice to complete the object. Other functional agents may be used to produce the desired characteristics of an object. For example, detailing agents may be used to enhance or inhibit fusing in certain regions of an object, coloring agents may be used for different color objects or different colors in a single object, and other agents may be used to affect physical properties such as ductility and conductivity. 
     The way in which liquid functional agents interact with one another and their cumulative effect on the build material during additive manufacturing may be difficult to predict. For example, cyan, magenta and yellow coloring agents may absorb fusing light differently from one another, and much differently from a black fusing agent, and thus contribute relatively more or less fusing heat. In addition, dispensing even small quantities of any liquid agent can cool the affected work area noticeably during manufacturing. Thus, the competing thermal effects of each agent may influence the quality and characteristics of the object. 
     A new technique has been developed to help correctly balance the effects of multiple liquid functional agents during additive manufacturing. In one example, an additive manufacturing process includes, while making the object, measuring temperatures at multiple locations in the object, mapping any “hot” regions and any “cold” regions, and modifying the process control data to dispense a different quantity of at least one of the functional agents at the locations corresponding to each of the hot and cold regions, to reduce or eliminate the unwanted condition. For example, the quantity of fusing agent may be decreased at the hot regions for less heat and increased at the cold regions for more heat, to bring the temperatures into an acceptable range. Adjustments may made and their effects measured iteratively slice by slice while making the object or the adjustments may be made and their effects measured when making the object again. 
     Examples are not limited to detecting and correcting temperature deviations. Although temperature is comparatively easy to detect “on the fly” as an indicator of meaningful object properties, other parameters could be used. For example, it may be desirable in some implementations to detect color, density or conductivity. Accordingly, these and other examples shown in the figures and described below illustrate but do not limit the scope of the patent, which is defined in the Claims following this Description. 
     As used in this document, “and/or” means at least one of the connected things; “cold” and “low temperature” mean below a temperature threshold; a “coloring agent” means a substance that colors a build material; a “detailing agent” means a substance that inhibits or prevents or enhances fusing a build material, for example by modifying the effect of a fusing agent; “deviant” means not acceptable; a “fusing agent” means a substance that causes or helps cause a build material to sinter, melt or otherwise fuse; “hot” and “high temperature” mean above a temperature threshold; a “lamp” means any device that emits light; “light” means electromagnetic radiation of any wavelength; a “liquid” means a fluid not composed primarily of a gas or gases; a “processor readable medium” means any non-transitory tangible medium that can embody, contain, store, or maintain instructions for use by a processor and may include, for example, circuits, integrated circuits, ASICs (application specific integrated circuits), hard drives, random access memory (RAM), read-only memory (ROM), and memory cards and sticks; and “work area” means any suitable structure to support or contain build material for fusing, including underlying layers of build material and in-process slice and other object structures. 
       FIGS.  1  and  2    are elevation and plan views, respectively, illustrating one example of an additive manufacturing machine  10 .  FIGS.  3 - 18    present a sequence of elevation and plan views showing one example of a process for thermal control using machine  10 . Referring first to  FIGS.  1  and  2   , additive manufacturing machine  10  includes a first, “fuser” carriage  12  and a second, “dispenser” carriage  14 . Carriages  12  and  14  move back and forth, for example on rails  16 , over a work area  18  at the direction of a controller  20 . Controller  20  represents 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 machine  10 . 
     Fuser carriage  12  carries a layering device  22 , a property detector  24 , and a fusing lamp  26 . Dispenser carriage  14  carries an inkjet printhead assembly or other suitable liquid dispensing assembly  28  to dispense multiple liquid functional agents. In the example shown, dispensing assembly  28  includes two dispensers  30  and  32 . Each dispenser  30 ,  32  may dispense one or multiple functional agents, including for example, a fusing agent, a detailing agent and multiple coloring agents. 
     Work area  18  represents any suitable structure to support or contain build material for fusing, including underlying layers of build material and in-process slice and other object structures. For a first layer of build material, for example, work area  18  may be formed on the surface of a platform  34  that moves up and down to accommodate the layering process. For succeeding layers of build material, for example as shown in  FIG.  1   , work area  18  may be formed on an underlying object structure  36 , which may include unfused build material  38  and build material that has been fused into an object slice  40 . 
     In the example shown in  FIGS.  1  and  2   , layering device  22  is implemented as a roller  22  that moves between a deployed position (shown in  FIG.  1   ) to layer build material as carriage  12  moves over work area  18  and a retracted position (shown in  FIG.  5   ) to not layer build material as carriage  12  moves over work area  18 . Layering roller  22  may rotate freely as it is moved over work area  18 , freewheeling clockwise or counter-clockwise depending on the direction of travel, or roller  22  may be driven rotationally in either direction (co-rotated or counter-rotated). Other implementations for a layering device  22  are possible including, for example, a blade or a device that dispenses build material directly over the work area in a layer. 
     In the example shown in  FIGS.  1  and  2   , property detector  24  is implemented as a thermal imaging device  24 , such as an infrared camera or other suitable device for measuring temperatures in an object slice  40 . Temperature measurements from device  24  are mapped to the corresponding locations in slice  40  to form a thermal map of the slice. Depending on the capabilities of the thermal imaging device  24 , temperature mapping may be performed by device  24  and mapping data transmitted to controller  20  for processing, or temperature mapping may be performed by controller  20 . One example of a temperature map  41  for object slice  40  in  FIGS.  1  and  2    is shown in  FIG.  19   . To represent temperature on a black and white line drawing, “isotemp” lines are used to show different temperature regions. Higher temperature regions in the object slice are depicted by more dense groupings of lines and lower temperature regions are depicted by less dense groupings of lines. Map  41  shows a hot region  42  near the center of slice  40  and a cold region  44  along one edge of slice  40 . 
     Although a single fusing lamp  26  is depicted, multiple fusing lamps may be used, for example to enable a greater range of fusing light. 
     In  FIGS.  1  and  2   , fuser carriage  12  is parked on one side of work area  18  (the left side in  FIGS.  1  and  2   ) and dispenser carriage  14  is parked on the other side of work area  18  (the right side in  FIGS.  1  and  2   ). In this example, a ribbon  46  of build material powder  38  has been deposited along a left side deck  48  adjacent to work area  18 . In  FIGS.  3  and  4   , fuser carriage  12  is moving to the right in a first pass, indicated by motion arrows  50 , with roller  22  deployed to layer build material  38  in a layer  52  over work area  18  (underlying structure  36 ). Although a powdered build material  38  is depicted by stippling in the figures, any suitable fusable build material may be used. 
     In  FIGS.  5  and  6   , fuser carriage  12  and dispenser carriage  14  are moving to the left in a second pass, indicated by motion arrows  56 , with layering roller  22  retracted and fusing lamp  26  turned on to pre-heat build material  38  in layer  52 . In other examples, build material  38  is not pre-heated or it is pre-heated with a heating lamp separate from the fusing lamp. Other pre-heating configurations are possible. 
     Still referring to  FIGS.  5  and  6   , dispenser  30  on dispenser carriage  14  following fuser carriage  12  dispenses a fusing agent  58  on to build material  38  in layer  52  in a pattern  60  corresponding to the desired object slice. For example, a lesser quantity of fusing agent  58  may be dispensed at the location of hot region  42  in slice  40  to lower the temperature in the corresponding region of the new slice and a greater quantity of fusing agent  58  may be dispensed at the location of cold region  44  in slice  40  to raise the temperature in the corresponding region in the new slice. Although only a fusing agent  58  is shown, other functional agents may be dispensed from one or both dispensers  30 ,  32  on to build material  38  as dispenser carriage  14  is moved to the left over work area  18  in  FIGS.  5  and  6   . 
     In  FIGS.  7  and  8   , as dispenser carriage  14  is moved to the right in a third pass, indicated by motion arrows  62 , dispenser  32  dispenses a coloring agent  64  on to build material  38  in layer  52 . Although only a coloring agent  64  is shown, other functional agents may be dispensed from one or both dispensers  30 ,  32  on to build material  38  as dispenser carriage  14  is moved to the right over work area  18  in  FIGS.  7  and  8   . Also in this third pass, fuser carriage  12  follows dispenser carriage  14  over work area  18  with fusing lamp  26  turned on to irradiate patterned build material  60  with fusing light to fuse patterned build material into a second object slice  66 . Thermal imaging device  24  is turned on to measure temperatures in slice  66 . 
     In  FIGS.  9  and  10   , fuser carriage  12  and dispenser carriage  14  have reached the right side of work area  18  after forming second slice  66  and a ribbon  46  of build material  38  has been dispensed to supply deck  48  on the right side of work area  18  in preparation for making the next slice. One example of a thermal map  67  for object slice  66  in  FIGS.  9  and  10    is shown in  FIG.  20   . Although map  67  shows a hot region  68  near the center of slice  66  and a cold region  70  along one edge of slice  66 . However, the lesser quantity of fusing agent  58  dispensed at the location of hot region  42  in the preceding slice  40  has lowered the temperature in the corresponding region  68  of the new slice  66 , as indicated by the less dense isotemp lines in region  68 , and a greater quantity of fusing agent  58  dispensed at the location of cold region  44  in the preceding slice  40  has raised the temperature in the corresponding region  70  in the new slice  66 , as indicated by the more dense isotemp lines in region  70 . 
     The sequence of operations is repeated for the next slice, as shown in  FIGS.  11 - 18   . In  FIGS.  11 - 12  and  13 - 14   , fuser carriage  12  and dispenser carriage  14  are moving to the left in a first pass, indicated by motion arrows  56 . In  FIGS.  11  and  12   , roller  22  is deployed to layer build material  38  in a next layer  74  over work area  18  (now underlying structure  76 ) and fusing lamp  26  is turned on to pre-heat build material  38  in layer  74 . In  FIGS.  13  and  14   , as carriages  12 , and  14  continue across work area  18 , dispenser  30  dispenses a fusing agent  58  on to build material in layer  74  in a pattern  78  corresponding to the next object slice. For example, a lesser quantity of fusing agent  58  may be dispensed at the location of hot region  68  in slice  66  to lower the temperature in the corresponding region of the new slice and a greater quantity of fusing agent  58  may be dispensed at the location of cold region  70  in slice  66  to raise the temperature in the corresponding region in the new slice. Although only a fusing agent  58  is shown, other functional agents may be dispensed from one or both dispensers  30 ,  32  on to build material layer  74  as dispenser carriage  14  is moved to the left over work area  18  in  FIGS.  13  and  14   . 
     In  FIGS.  15  and  16   , as dispenser carriage  14  moves to the right in a second pass, indicated by motion arrows  62 , dispenser  32  dispenses a coloring agent  64  on to build material in layer  74 . Although only a coloring agent  64  is shown, other functional agents may be dispensed from one or both dispensers  30 ,  32  on to build material layer  74  as dispenser carriage  14  is moved to the right over work area  18  in  FIGS.  15  and  16   . Also in this second pass, fuser carriage  12  follows dispenser carriage  14  over work area  18  with fusing lamp  26  turned on to irradiate patterned build material  78  with fusing light to fuse patterned build material into a third object slice  80 . Thermal imaging device  24  is turned on to measure temperatures in slice  80 . 
     In  FIGS.  17  and  18   , fuser carriage  12  and dispenser carriage  14  have reached the right side of work area  18  after forming third slice  80 . One example of a thermal map  81  for object slice  80  in  FIGS.  17  and  18    is shown in  FIG.  21   . In map  81  there are no hot or cold regions. 
     The sequence of operations may continue for each succeeding layer of build material, slice by slice, until the object is completed. 
     The configuration and operating sequence of machine  10  in  FIGS.  1 - 18    is just one example. Other suitable machine configurations and other operating sequences are possible. For example, an additive manufacturing machine  10  may include more or fewer carriages that move in-line with one another or perpendicular to one another, and with more or fewer agent dispensers, lamps and thermal imaging devices. 
       FIG.  22    illustrates one example of an additive manufacturing process  100 , such as might be implemented with a machine  10  shown in  FIGS.  1  and  2   . Referring to  FIG.  22   , an object is made slice by slice at block  101 , including dispensing a first quantity of each of multiple liquid functional agents on to a layer of fusable build material and then irradiating the layer of build material, for example as shown in the sequence of operations illustrated in  FIGS.  1 - 18   . A deviant region in a slice is identified while making the object, at block  102 , for example by identifying a hot region  42  and/or a cold region  44  on a temperature map in  FIG.  19   . And then, at block  103 , a second quantity different from the first quantity of at least one of the functional agents is dispensed into a location corresponding to the deviant region, for example by dispensing a greater or lesser quantity of a fusing agent  58  as shown in  FIGS.  5  and  13   , and/or a lesser quantity or a greater quantity of a coloring agent  64 , as shown in  FIGS.  7  and  15   . 
     Dispensing a different quantity of one or more of the functional agents at block  103  in process  100  may be implemented by making the adjustment in the next slice of the same object, as shown at block  104  in  FIG.  23   , or by making the adjustment in the next object, as shown at block  105  in  FIG.  24   , or a combination of both succeeding slice and succeeding object adjustments. 
     Blocks  102  and  103  in process  100  may be implemented for a group of multiple slices rather than for individual slices. For example, it may be desirable in some manufacturing operations to measure and map the temperatures in every 2 nd  or 3 rd  or 4 th  slice as a sufficiently accurate indicator of the temperatures in each of the individual slices in the group, and then adjusting the quantity of agent(s) to correct any temperature deviant regions in the succeeding 2 nd  or 3 rd  or 4 th  slice and/or in the corresponding group of slices when making the next object. 
       FIG.  25    illustrates another example of an additive manufacturing process  110 , such as might be implemented with a machine  10  shown in  FIGS.  1  and  2   . Referring to  FIG.  25   , process  110  includes making a slice of an object based on process control data, including dispensing a quantity of each of multiple liquid functional agents on to a layer of fusable build material according to the process control data and then irradiating the layer of build material (block  111 ), and determining if there is a hot region in the slice (block  112 ). If it is determined there is a hot region in the slice, then modifying the process control data to dispense a different quantity of at least one of the functional agents at a location corresponding to each hot region to cool the slice at that location (block  113 ). Process  110  also includes determining if there is a cold region in the slice (block  114 ) and, if it is determined there is a cold region in the slice, then modifying the process control data to dispense a different quantity of at least one of the functional agents at the location of each cold region to heat the slice at that location (block  115 ). The acts of making (block  111 ), determining (blocks  112  and  114 ), and modifying (blocks  113  and  115 ) are repeated for succeeding slices until it is determined that there are no hot regions and no cold regions (block  116 ). The object can then be made again (and repeatedly) according to the last modified process control data. 
       FIG.  26    illustrates another example of an additive manufacturing process  120 , such as might be implemented with a machine  10  shown in  FIGS.  1  and  2   . Referring to  FIG.  26   , process  120  includes making an object based on process control data, including dispensing a quantity of each of multiple liquid functional agents on to a fusable build material in a pattern to form patterned build material and to irradiate the patterned build material (block  121 ) and, while making the object, measuring temperatures at multiple locations in the object (block  122 ). Process  120  also includes mapping the measured temperatures to form a temperature map of the object (block  123 ), modifying the process control data based on the temperature map (block  124 ) and then making the object again based on the modified process control data, including dispensing a different quantity of at least one of the functional agents on to the build material (block  125 ). Process control data for a group of multiple slices may be modified based on a temperature map for each of the individual slices in the group. 
       FIG.  27    illustrates another example of an additive manufacturing process  130 , such as might be implemented with a machine  10  shown in  FIGS.  1  and  2   . Referring to  FIG.  27   , process  130  includes layering build material over a work area (block  131 ), dispensing a first quantity of each of the fusing agent and a coloring agent on to a layer of build material in a pattern corresponding to an object slice (block  132 ), and irradiating the patterned build material to fuse build material into the slice (block  133 ). Process  130  also includes mapping temperatures in the slice (block  134 ), identifying any regions of low temperature in the slice and any regions of high temperature in the slice (block  135 ), and repeating the sequence of layering, dispensing, irradiating, mapping and identifying for multiple successive layers of build material to make the object (block  136 ) and then making the object again layer by layer and slice by slice including dispensing a second quantity different from the first quantity of the fusing agent and/or the coloring agent into the regions of low temperature and into the regions of high temperature (block  137 ). 
       FIG.  28    is a block diagram illustrating a processor readable medium  82  with deviant control instructions  84  to help manufacture an object. For one example, instructions  84  may include instructions to execute process  100  in  FIG.  22   . For other examples, instructions  84  may include instructions to execute process  110  in  FIG.  25   , process  120  in  FIG.  26   , or process  130  in  FIG.  27   . 
     Processor readable medium  82  with deviant control instructions  84  may be implemented, for example, in a CAD computer program product, in an object model processor, and/or in a controller for an additive manufacturing machine. Process control data to adjust the quantity of fusing agents, color agents and/or other liquid functional agents may be generated “on the fly”, for example, by processor readable instructions executed on the additive manufacturing machine controller. 
       FIG.  29    is a block diagram illustrating one example of an additive manufacturing machine  10  implementing a controller  20  with deviant control instructions  84 . In this example, deviant control instructions  84  include instructions to control thermal deviations, for example as shown in  FIGS.  1 - 18  and  25 - 27   . Referring to  FIG.  29   , machine  10  includes controller  22 , a work area  18 , a build material layering device  22 , a first fusing or other functional agent dispenser  30 , a second coloring or other functional agent dispenser  32 , a thermal imaging device  24  and a fusing lamp  26 . Build material layering device  22  layers build material over work area  18  and may include, for example, a device to dispense the build material and a blade, brush or roller to spread the build material for each layer. Agent dispensers  30  and  32  dispense respective agents selectively at the direction of controller  20 , for example as described above with reference to  FIGS.  5 ,  7 ,  13  and  15   . While any suitable dispensers  30 ,  32  may be used, inkjet printheads are sometimes used in additive manufacturing machines because of the precision with which they can dispense fusing, detailing, coloring and other functional agents and their flexibility to dispense different types and formulations of such agents. 
     As noted above, controller  20  represents 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 machine  10 . In particular, controller  20  includes a processor readable medium  82  with thermal control instructions  84  and a processor  86  to read and execute instructions  84 . Thermal imaging device  24  may be implemented as an infrared camera or other suitable device for measuring temperatures in an object slice. Temperature measurements from device  24  may be mapped to the corresponding locations in the slice to form a thermal map of the slice. Depending on the capabilities of the thermal imaging device  24 , temperature mapping may be performed by device  24  and mapping data transmitted to controller  20  for processing and/or temperature mapping may be performed by controller  20 . 
     In one example, an additive manufacturing process includes: making an object slice by slice, including dispensing a first quantity of each of multiple liquid functional agents on to a layer of fusable build material and then irradiating the layer of build material; while making the object, identifying a deviant region in a slice; and dispensing a second quantity different from the first quantity of at least one of the functional agents into a location corresponding to the deviant region. 
     In one example, the process described may include, while making the object, measuring a material property of each slice or group of slices in the object and where identifying a deviant region in a slice includes identifying a deviant region from the property measurements. 
     In one example, measuring a material property in the process described, may include measuring a temperature of each slice or group of slices in the object. 
     In one example, in the process described may include dispensing a second quantity different from the first quantity of at least one of the functional agents into a location corresponding to the deviant region includes dispensing a second quantity different from the first quantity of at least one of the functional agents into a location in the next slice corresponding to the deviant region. 
     In one example, in the process described may include identifying a deviant region in the object includes identifying regions of low temperature in the object and regions of high temperature in the object, and dispensing a second quantity different from the first quantity of at least one of the functional agents into a location corresponding to the deviant region includes dispensing a second quantity different from the first quantity of at least one of the functional agents into locations corresponding to the regions of low temperature and the regions of high temperature. 
     In one example, in the process described may include making the object includes dispensing a fusing agent and multiple coloring agents each having a different light absorbability, and dispensing a second quantity different from the first quantity of at least one of the functional agents into a location corresponding to the deviant region includes dispensing a second quantity different from the first quantity of the fusing agent and/or at least one of the coloring agents into locations corresponding to the regions of low temperature and into locations corresponding to the regions of high temperature. 
     In one example, in the process described may include dispensing a second quantity different from the first quantity of at least one of the functional agents into a location corresponding to the deviant region includes dispensing a second quantity greater than the first quantity of the fusing agent into each location corresponding to a region of low temperature and dispensing a second quantity lesser than the first quantity of the fusing agent into each location corresponding to a region of high temperature. 
     In one example, in the process described may include dispensing a second quantity different from the first quantity of at least one of the functional agents into a location corresponding to the deviant region includes making the object again slice by slice including dispensing a second quantity different from the first quantity of at least one of the functional agents into a location corresponding to the deviant region. 
     In one example, in the process described may include identifying a deviant region in the object includes identifying regions of low temperature in the object and regions of high temperature in the object and making the object again slice by slice includes dispensing a second quantity different from the first quantity of at least one of the functional agents into locations corresponding to the regions of low temperature and the regions of high temperature. 
     In one example, in the process described may include making the object includes dispensing a fusing agent and multiple coloring agents each having a different light absorbability and making the object again includes dispensing a second quantity different from the first quantity of the fusing agent and/or at least one of the coloring agents into locations corresponding to the regions of low temperature and into locations corresponding to the regions of high temperature. 
     In one example, in the process described may include making the object again includes dispensing a second quantity greater than the first quantity of the fusing agent into each location corresponding to a region of low temperature and dispensing a second quantity lesser than the first quantity of the fusing agent into each location corresponding to a region of high temperature. 
     As noted above, the examples shown in the figures and described herein illustrate but do not limit the scope of the patent, which is defined in the following Claims. 
     “A”, “an” and “the” used in the claims means at least one. For example, “a” deviant region means at least one deviant region and “the” deviant region means the at least one deviant region.