Patent Publication Number: US-2022219395-A1

Title: Independently movable carriages carrying respective energy sources

Description:
BACKGROUND 
     In three-dimensional (3D) printing, an additive printing process may be used to make 3D solid parts from a digital model. Some 3D printing techniques are considered additive processes because they involve the application of successive layers or volumes of a build material, such as a powder or powder-like build material, to an existing surface (or previous layer). 3D printing often includes solidification of the build material, which for some materials may be accomplished through use of heat, a chemical binder, and/or an ultra-violet or a heat curable binder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features of the present disclosure are illustrated by way of example and not limited in the following figure(s), in which like numerals indicate like elements, in which: 
         FIG. 1  shows a block diagram of an example system that may include a first carriage and a second carriage that may carry various components for fabricating 3D objects; 
         FIGS. 2A-2C , respectively, show an example 3D fabrication system at various stages of operation in the formation of portions of a 3D object; 
         FIGS. 3A-3C , respectively, show alternative operations that the 3D fabrication system may implement during formation of the portion of the 3D object; 
         FIG. 4  shows a block diagram of an example 3D fabrication system having a servicing station; 
         FIG. 5  shows a flow diagram of an example method for controlling movement of a first carriage and a second carriage, the first carriage and the second carriage each including a respective energy source; 
       and 
         FIG. 6  shows a block diagram of an example computer readable medium that may have stored thereon machine readable instructions that when executed by a controller, may cause the controller to control movement of a first carriage and a second carriage, in which the first carriage and the second carriage each includes a respective energy source. 
     
    
    
     DETAILED DESCRIPTION 
     For simplicity and illustrative purposes, the present disclosure is described by referring mainly to examples. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. It will be readily apparent however, that the present disclosure may be practiced without limitation to these specific details. In other instances, some methods and structures have not been described in detail so as not to unnecessarily obscure the present disclosure. 
     Throughout the present disclosure, the terms “a” and “an” are intended to denote at least one of a particular element. As used herein, the term “includes” means includes but not limited to, the term “including” means including but not limited to. The term “based on” means based at least in part on. 
     Disclosed herein are systems, methods, and 3D fabrication systems for controlling the formation of portions of 3D objects using carriages that each carries a respective energy source, Particularly, the systems disclosed herein may include a first carriage that may carry a laying device and a first energy source and a second carriage that may carry an agent delivery device and a second energy source. The first carriage and the second carriage may be independently movable with respect to each other. As such, for instance, controllers of the systems may independently move the first carriage with respect to the second carriage. The controllers may also move the first carriage and the second carriage together during either or both of a first pass and a second pass of the first carriage and the second carriage across a build area. 
     Through implementation of the features of the present disclosure, energy, e.g., fusing energy and/or warming energy, may be applied during each pass of the first carriage and the second carriage. In this regard, following deposition of an agent onto a build material layer, fusing energy may be applied four times during two passes of the first carriage and the second carriage. A first pass may include movement of the first carriage and the second carriage from a first side to a second side of a build area and a second pass may include movement of the first carriage and the second carriage from the second side to the first side of the build area. In addition, independent movement of the first carriage and the second carriage in one direction may be construed as a single pass. Thus, for instance, a sufficient amount of energy to cause build material in a build material layer to be joined together may be applied through two passes of the first carriage and the second carriage. Thus, for instance, 3D objects may be fabricated in a shorter length of time and with a relatively smaller number of passes, which may result in reduced energy usage and time savings. 
     Reference is first made to  FIG. 1 .  FIG. 1  shows a block diagram of an example system  100  that may include a first carriage and a second carriage that may carry various components for fabricating three-dimensional (3D) objects, in which the first carriage may be independently movable with respect to the second carriage. It should be understood that the example system  100  depicted in  FIG. 1  may include additional features and that some of the features described herein may be removed and/or modified without departing from the scope of the system  100 . 
     The system  100  may be a 3D fabrication system or a portion a 3D fabrication system. The 3D fabrication system may also be termed a 3D printing system, a 3D fabricator, or the like, and may be implemented to fabricate 3D objects through selective binding and/or solidifying of build material  102 , which may also be termed build material particles, together. The build material  102  may be formed into a build material layer  104  on a build area  106  during fabrication of a 3D object. 
     The build material  102  may include any suitable material for use in forming 3D objects. The build material  102  may include, for instance, a polymer, a plastic, a ceramic, a nylon, a metal, combinations thereof, or the like, and may be in the form of a powder or a powder-like material. Additionally, the build material  102  may be formed of particles or powder, which may have dimensions, e.g., widths, diameters, or the like, that are generally between about 5 μm and about 100 μm. In other examples, the build material particles may have dimensions that are generally between about 30 μm and about 60 μm. The particles may have any of multiple shapes, for instance, as a result of larger particles being ground into smaller particles. In some examples, the particles may be formed from, or may include, short fibers that may, for example, have been cut into short lengths from long strands or threads of material. In addition, or in other examples, the particles may be partially transparent or opaque. According to one example, a suitable build material may be PA12 build material commercially known as V1R10A “HP PA12” available from HP Inc. 
     As shown, the system  100  may include a first carriage  110 , in which the first carriage  110  may carry a laying device  112  and a first energy source  114 . The laying device  112  may spread, spray, or otherwise form the build material  102  into a build material layer  104 . By way of example, the laying device  112  may be a roller, a spreader, or the like, that may spread the build material  102  into the build material layer  104  as the first carriage  110  is moved across the build area  106  as indicated by the arrow  116 . As another example, the laying device  112  may be a sprayer, or the like, that may sprinkle the build material  102  to form the build material layer  104  as the first carriage  110  is moved across the build area  106  as indicated by the arrow  116 . According to examples, the build area  106  may be provided on a movable platform, which may be moved in a direction away from the first carriage  110  during formation of successive build material layers  104 . 
     The first energy source  114  may output energy  118 , e.g., in the form of light and/or heat. As such, for instance, the first energy source  114  may output energy  118  onto the build material layer  104  as first carriage  110  is moved across the build area  106 . 
     The system  100  may also include a second carriage  120 , in which the second carriage  120  may carry an agent delivery device  122  and a second energy source  124 . The agent delivery device  122  may be a suitable type of agent dispenser that may controllably deposit an agent  126 , for instance, in the form of droplets. By way of particular example, the agent delivery device  122  may be a printhead having a plurality of nozzles in which droplet ejectors, e.g., resistors, piezoelectric actuators, and/or the like, may be provided to eject droplets of an agent through the nozzles. In any regard, the agent delivery device  122  may be controlled to selectively deposit the agent  126  onto locations of the build material layer  104  at which build material  102  is to be binded together to form a portion of a 3D object. 
     According to examples, the agent  126  may be a fusing and/or a binding agent to selectively bind and/or solidify the particles of build material  102 . In particular examples, the agent  126  may be a chemical binder, a thermally curable binder, and/or the like. In other particular examples, the agent  126  may be a fusing agent that may increase the absorption of energy to selectively fuse the particles of build material  102 . 
     According to one example, a suitable fusing agent may be an ink-type formulation including carbon black, such as, for example, the fusing agent formulation commercially known as V1Q60A “HP fusing agent” available from HP Inc. In one example, such a fusing agent may additionally include an infra-red light absorber. In one example such fusing agent may additionally include a near infra-red light absorber. In one example, such a fusing agent may additionally include a visible light absorber. In one example, such a fusing agent may additionally include a UV light absorber. Examples of fusing agents including visible light enhancers are dye based colored ink and pigment based colored ink, such as inks commercially known as CE039A and CE042A available from HP Inc. 
     According to examples, the second carriage  120  may carry an additional agent delivery device that may controllably output another type of agent. The other type of agent may be an agent having a different color than the agent  126  outputted by the agent delivery device  122 , a different formulation from the agent  126 , and/or the like. By way of example, the other agent delivery device may output a detailing agent, which may, for instance, function as a cooling agent that may be applied onto the build material layer  104  to reduce and control the occurrence of thermal bleed from the build material  102  that is being heated. According to one example, a suitable detailing agent may be a formulation commercially known as V1Q61A “HP detailing agent” available from HP Inc. 
     In any regard, the second energy source  124  may output energy  128  as the second carriage  120  is moved across the build area  106  in a first direction  116  to cause the particles of build material  102  on which the agent  126  has been deposited to bind together and/or melt and subsequently fuse together. That is, the second energy source  124  may apply energy  128  onto the build material layer  104  and the deposited agent  126  as the second carriage  120  is moved with the agent delivery device  122  in a lead position. In addition, the first energy source  114  may apply energy  118  onto the build material layer  104  and the deposited agent  126  as the first carriage  110  and the second carriage  120  are moved with the second carriage  120  in a lead position. In this regard, energy  118 ,  128  may be applied onto the build material layer  104  as the first carriage  110  and the second carriage  120  are moved in either of the directions denoted by the arrow  116 . 
     According to examples, the first energy source  114  and the second energy source  124  may each output heating energy that may warm the build material layer  104  and/or may output fusing energy that may cause the build material  102  on which the agent  126  has been deposited to join together. The warming energy may be of sufficient strength to maintain the build material  102  within a predefined range of temperatures, in which an upper limit temperature of the predefined range may be a melting point temperature of the build material  102 , an activation temperature of a thermally activated chemical binder, or the like. In addition, a lower limit temperature of the predefined range may be a temperature from which the build material  102  upon which the agent  126  has been deposited to reach a melting point temperature of the build material  102  when fusing energy is applied to the build material  102  and the agent  126 , In this regard, the fusing energy may be of sufficient strength to cause the build material  102  on which the agent  126  has been deposited to bind together, e.g., melt and fuse, cause a chemical binder to activate, or the like. 
     According to examples, the first energy source  114  may include a fusing lamp and a heating lamp and the second energy source  124  may include a fusing lamp. In other examples, the second energy source  124  may also include both a fusing lamp and a heating lamp. As such, for instance, the first energy source  114 , and in examples, the second energy source  124 , may apply both the warming energy and the fusing energy onto the build material layer  104  and any agent  126  deposited on the build material layer  104  as the first carriage  110  is moved across the build area  106 . In addition, the second energy source  124  may apply fusing energy onto the build area  106  and deposited agent  126  as the second carriage  120  is moved across the build area  106 . As the first carriage  110  and the second carriage  120  may be scanned across the build area  106  in both directions indicated by the arrow  116  and the first energy source  114  and the second energy source  124  may remain active during the scans, the build material  102  in the build material layer  104  may receive warming and fusing energy multiple times during each of the scans. In addition, the agent delivery device  122  may be positioned at a location that is between the first energy source  114  and the second energy source  124  such that the agent delivery device  122  may deliver the agent  126  while moving in both directions indicated by the arrow  116 . Moreover, the first energy source  114  and the second energy source  124  may apply fusing energy as the agent delivery device  122  delivers the agent  126  in both directions. 
     According to examples, the fusing lamps in the first energy source and the second energy source may have a different color temperature as compared with the heating lamp in the first energy source. That is, for instance, the fusing lamps may output a different spectral power distribution than the heating lamp. Particularly, the heating lamp may produce energy having wavelengths that the build material  102  more readily absorbs and the fusing lamps may produce energy having wavelengths that the agent  126  more readily absorbs. By way of particular example, the fusing lamps may have a  2700 K color temp which may produce energy in the near-IR part of the color spectrum and the warming lamps may have a  1800 K color temp lamp that may have energy content in the mid-IR range where the build material  102  may be more absorptive. 
     The system  100  may further include a controller  130  that may control movement of the first carriage  110  and the second carriage  120 . That is, for instance, the controller  130  may control actuators, motors, or the like, that may independently control movement of the first carriage  110  and the second carriage  120  across the build area  106 . That is, the controller  130  may cause the first carriage  110  and the second carriage  120  to move concurrently with each other or independently with respect to each other. The controller  130  may also, in some examples, control the timings at which the agent delivery device  122  may deposit the agent  126  onto the build material layer  104  to form portions of a 3D object in the build material layer  104 . 
     The controller  130  may be a semiconductor-based microprocessor, a central processing unit (CPU), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), and/or other suitable hardware device. Although not shown, the system  100  may include a memory that may have stored thereon machine-readable instructions (which may also be termed computer readable instructions) that the controller  130  may execute. The memory may be an electronic, magnetic, optical, or other physical storage device that contains or stores executable instructions. The memory may be, for example, Random Access memory (RAM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), a storage device, an optical disc, and the like. The memory, which may also be referred to as a computer readable storage medium, may be a non-transitory machine-readable storage medium, where the term “non-transitory” does not encompass transitory propagating signals. 
     Reference is now made to  FIGS. 2A-2C , which respectively show an example 3D fabrication system  200  at various stages of operation in the formation of portions of a 3D object. It should be understood that the example 3D fabrication system  200  depicted in  FIGS. 2A-2C  may include additional features and that some of the features described herein may be removed and/or modified without departing from the scope of the 3D fabrication system  200 . 
     As shown, the 3D fabrication system  200  may include the components of the system  100  as well as other components. The other components may include a mechanism  202  along which the first carriage  110  and the second carriage  120  may move across the build area  106 . The mechanism  202  may be any suitable mechanism by which and/or which may cause the first carriage  110  and/or the second carriage  120  to be moved. For instance, the mechanism  202  may include an actuator, a belt, and/or the like that may cause the first carriage  110  and/or the second carriage  120  to be moved and that the controller  130  may control to move the first carriage  110  and/or the second carriage  120 . 
     The other components may also include decks  204  and  206  from which build material  102  may be supplied for formation into a build material layer  104 . For instance, the deck  206  may supply an amount of build material  102  on top of the deck  206  that the laying device  112  may push the build material  102  over the build area  106  as the first carriage  110  is moved in a first direction  208  as shown in  FIG. 2A . In other examples, however, the laying device  112  may spray or otherwise deposit the build material  102  onto the build area  106  as the first carriage  110  is moved in the first direction  208 . In addition, as the first carriage  110  is moved in the first direction  208 , the first energy source  114  may apply energy  118 , e.g., warming energy, onto the build material layer  104 , for instance, to warm the build materials  102  in the build material layer  104  to an intended temperature. 
     Turning now to  FIG. 2B , the second carriage  120  may also be moved in the first direction  208 . The controller  130  may cause the first carriage  110  and the second carriage  120  to be moved together in the first direction  208 , for instance, as a first pass across the build area  106 . In addition, the controller  130  may control the agent delivery device  122  to selectively deposit an agent  126  onto the build material layer  104  as the second carriage  120  is moved in the first direction  208 . That is, the controller  130  may control the agent delivery device  122  to deposit the agent  126 , e.g., droplets of the agent  126 , onto selected areas of the build material layer  104  that are to be joined together to form part of a 3D object in that build material layer  104 . 
     In addition, the second energy source  124  may apply energy  128 , e.g., fusing energy, onto the deposited agent  126  and the build material layer  104  as the second carriage  120  is moved in the first direction  208  to cause the adjacent build material  102  on which the agent  126  has been deposited to become joined together. That is, for instance, the applied energy  128  may cause the build material  102  onto which the agent  126  has been deposited to melt, e.g., reach a melting point temperature, and subsequently fuse together as the build material  102  solidifies. In other examples, the applied energy  128  may cause the deposited agent  126  to become thermally activated and thus bind the build material  102  together. 
     The first carriage  110  and the second carriage  120  may continue to move in the first direction  208  until, for instance, the second energy source  124  is positioned over and/or beyond the deck  204 . In addition, following the second carriage  120  reaching this position, as shown in  FIG. 2C , the controller  130  may cause the second carriage  120  to move in a second direction  210 . As the second carriage  120  is moved in the second direction  210 , the second energy source  124  may output energy, e.g., fusing energy, onto the applied agent  126  to further cause the adjacent build material  102  on which the agent  126  has been applied to join together. 
     In addition, the controller  130  may cause the first carriage  110  to move in the second direction  210 . The controller  130  may cause the second carriage  120  and the first carriage  110  to be moved together, or separately, in the second direction  210 , for instance, as a second pass across the build area  106 . In addition, the first energy source  114  may apply energy  118 , e.g., fusing energy and warming energy, onto the applied agent  126  and the build material layer  104 , to further cause the build material  102  onto which the agent  126  has been deposited to become joined together. In this regard, fusing energy may be applied onto the build material  102  four times during two passes of the first carriage  110  and the second carriage  120  across the build area  106 . 
     According to examples, following movement of the first carriage  110  and the second carriage  120  in the second direction  210 , the controller  130  may cause the build area  106  to be moved vertically, e.g., in a direction away from the first carriage  110 . In addition, the operations outlined with respect to  FIGS. 2A-20  and the lowering of the build area  106  may be repeated until portions of a 3D object are fabricated. 
     Turning now  FIGS. 3A and 3B , there are shown alternative operations that the 3D fabrication system  200  may implement during formation of the portion of the 3D object. That is, as shown in  FIG. 3A , the second carriage  120  may be moved in the second direction  210  independently from the first carriage  110 . In addition, the agent delivery device  122  may selectively deposit the agent  126  onto the same and/or different areas of the build material layer  104  at which the agent  126  was selectively deposited during the first pass. 
     As shown in  FIG. 3B , the controller  130  may cause the build area  106  to move in a direction away from the first carriage  110 , e.g., in the direction  300 . The build area  106  may be moved a distance that is equal to a height of the build material layer  104 . That is, for instance, the build area  106  may be provided on a movable platform (not shown) and the controller  130  may cause an actuator of the movable platform to move the platform in the direction  300 . 
     As shown in  FIG. 30 , the controller  130  may cause the first carriage  110  to move in the second direction  302  independently of the second carriage  120 . As the first carriage  110  is moved in the second direction  302 , the first energy source  114  may apply energy  118 , e.g., fusing energy, onto the applied agent  126  and the build material layer  104 . In addition, the deck  204  may have provided build material  102  or the laying device  112  may otherwise cause a next build material layer  304  to be formed. The first carriage  110  may be moved across the build area  106  until, for instance, the first carriage  110  reaches the second carriage  120  such that the next build material layer  304  may be formed. In addition, the first carriage  110  may be moved in the first direction during a next pass as shown in  FIG. 2A , and the laying device  112  may apply build material  102  to form the next build material layer  304 . In some examples, the laying device  112  may form a portion, e.g. a bottom half, of the next build material layer  304  as the first carriage  110  moves in the second direction  302  and the laying device may form the remaining portion, e.g., a top half, of the next build material layer  304  as the first carriage  110  moves in the first direction  208 . In any regard, following the movement of the first carriage  110  from one side to the other side of the build area  106 , the operations shown in  FIGS. 2A, 2B, and 3A-30  may be repeated until portions of the 3D object are formed. 
     According to examples, following movement of the first carriage  110  and the second carriage  120  from one side of the build area  106  to the other side of the build area  106  as shown in  FIGS. 2A and 2B , the controller  130  may cause the second carriage  120  to be moved following expiration of a predefined time period. The predefined time period may be based on, for instance, the rate at which the build material  102  may cool, which may itself be based on a number of factors including, for instance, the ambient temperature of a build chamber in which the build material  102  is provided, the volume of agent  126  applied to the build material layer  104 , the increase in temperature caused through application of energy  118 ,  128  onto the build material layer  104 , etc. Thus, for instance, the predefined time period may be relatively shorter in instances in which the build material  102  may be cooled at a relatively faster rate and may be relatively longer in instances in which the build material  102  may be cooled at a relatively slower rate. 
     Similarly, the controller  130  may control the timing at which the first carriage  110  begins to move in the second direction  302  following movement of the second carriage  120  based on the rate at which the build material  102  may cool. In other words, the timing may be based on a timing that may maintain the build material  102  at or above a predetermined temperature during the fabrication process on the build material layer  104 . Thus, for instance, the controller  130  may cause the first carriage  110  to begin to move in the second direction  302  prior to the second carriage  120  reaching the other side of the build area  106  or may cause the first carriage  110  to begin to move in the second direction  302  following the second carriage  120  reaching the other side of the build area  106 . 
     Turning now to  FIG. 4 , there is shown a block diagram of an example 3D fabrication system  400  having a servicing station  402 . As shown in  FIG. 4 , the second carriage  120  may be positioned over a servicing station  402 . The servicing station  402  may include components for servicing the agent delivery device  122 . Servicing may include cleaning or other operations to improve the operations of the agent delivery device  122 . In some examples, the controller  130  may cause the second carriage  120  to be positioned with respect to the servicing station  402  such that the agent delivery device  122  may be serviced at set times, after a set number of printing operations, as needed, etc. In any regard, while the second carriage  120  is being serviced, the controller  130  may cause the first carriage  110  to move across the build area  106  such that the first energy source  114  may continuously apply energy  118  onto the build material layer  104  to, for instance, maintain the build material  102  in the build material layer  104  at or above a predetermined temperature. 
     Turning now to  FIG. 5 , there is shown a flow diagram of an example method  500  for controlling movement of a first carriage and a second carriage, the first carriage  110  and the second carriage  120  each including a respective energy source  114 ,  124 . It should be understood that the method  500  depicted in  FIG. 5  may include additional operations and that some of the operations described therein may be removed and/or modified without departing from the scope of the method  500 . The description of the method  500  is also made with reference to the features depicted in  FIGS. 1-4  for purposes of illustration. Particularly, the controller  130  may execute some or all of the operations included in the method  500 . 
     At block  502 , the controller  130  may cause a first carriage  110  and a second carriage  120  to move in a first direction  208  across a build area  106  during a first pass. During the first pass, a laying device  112  on the first carriage  110  may form a build material layer  104  and a first energy source  114  on the first carriage  110  to output energy  118 . 
     At block  504 , the controller  130  may cause an agent delivery device  122  on the second carriage  120  to selectively deposit an agent  126  onto the build material layer  104 . Moreover, a second energy source  124  on the second carriage  120  may output energy  128  to heat the build material layer  104  and the deposited agent  126 , 
     At block  506 , the controller  130  cause the first carriage  110  and the second carriage  120  to move in a second direction  210 ,  302  across the build area  106  during a second pass. During the second pass, the second energy source  124  and the first energy source  114  may output energy to heat the build material layer  104  and the deposited agent  126 . In some examples, the first carriage  110  and the second carriage  120  may move together during the first pass and the second pass. However, in other examples, the first carriage  110  and the second carriage  120  may be moved separately with respect to each other during either or both of the first pass and the second pass. For instance, during the second pass, the first carriage  110  may move after expiration of a predefined period of time from when the second carriage  120  is begun to move. 
     According to examples, the controller  130  may cause the second carriage  120  to move to a service station  402  as shown in  FIG. 4 , for instance, according to a set schedule, as needed, etc. As discussed herein, the controller  130  may cause the first carriage  110  to move across the build area  106  and the first energy source  114  to output energy  118  on the build material layer  104  while the agent delivery device  122  is being serviced to, for instance, maintain the temperature of the build material  102  at or above a predetermined temperature. 
     According to examples, the controller  130  may cause the agent delivery device  122  to selectively deposit an agent onto the build material layer  104  during the second pass as discussed herein above with respect to  FIG. 3A . In addition, the controller  130  may cause a platform on which the build area  106  is provided to be moved vertically away from the first carriage  110  as shown in  FIG. 3B . Moreover, the controller  130  may cause the first carriage  110  to move in the second direction  302 , in which the first energy source  114  may output energy  118  onto the build material layer  104  and the deposited agent  126  and the laying device  112  may form another build material layer  304  as the first carriage  110  is moved in the second direction  302  as shown in  FIG. 30 . 
     Some or all of the operations set forth in the method  500  may be contained as utilities, programs, or subprograms, in any desired computer accessible medium. In addition, the method  500  may be embodied by computer programs, which may exist in a variety of forms. For example, the method  500  may exist as machine-readable instructions, including source code, object code, executable code or other formats. Any of the above may be embodied on a non-transitory computer readable storage medium. 
     Examples of non-transitory computer readable storage media include computer system RAM, ROM, EPROM, EEPROM, and magnetic or optical disks or tapes. It is therefore to be understood that any electronic device capable of executing the above-described functions may perform those functions enumerated above. 
     Turning now to  FIG. 6 , there is shown a block diagram of an example computer readable medium  600  that may have stored thereon machine readable instructions that when executed by a controller, may cause the controller to control movement of a first carriage  110  and a second carriage  120 , in which the first carriage  110  and the second carriage  120  each includes a respective energy source  114 ,  124 . It should be understood that the computer readable medium  600  depicted in  FIG. 6  may include additional instructions and that some of the instructions described herein may be removed and/or modified without departing from the scope of the computer readable medium  600  disclosed herein. The computer readable medium  600  may be a non-transitory computer readable medium. The term “non-transitory” does not encompass transitory propagating signals. 
     The computer readable medium  600  may have stored thereon machine readable instructions  602 - 606  that a controller, such as the controller  130  depicted in  FIGS. 1-4 , may execute. The computer readable medium  600  may be an electronic, magnetic, optical, or other physical storage device that contains or stores executable instructions. The computer readable medium  600  may be, for example, Random Access memory (RAM), an Electrically Erasable Programmable Read-Only Memory (EEPROM), a storage device, an optical disc, and the like. 
     The controller may fetch, decode, and execute the instructions  602  to control a first carriage  110  to move from a first side to a second side of a build area  106 . As discussed herein, the first carriage  110  may support a laying device  112  to form a build material layer  104  over the build area  106  and a first energy source  114  to apply energy  118  onto the build material layer  104 . The controller may fetch, decode, and execute the instructions  604  to control a second carriage  120  to move concurrently with the first carriage  110 . The second carriage  120  may support an agent delivery device  122  to selectively deposit an agent  126  onto the build material layer  104  and a second energy source  124  to apply energy  128  onto the build material layer  104  and the deposited agent  126 . The controller may fetch, decode, and execute the instructions  606  to control the second carriage  120  and the first carriage  110  to move from the second side to the first side, in which the second energy source  124  and the first energy source  114  may apply energy  118 ,  128  onto the build material layer  104  and the deposited agent  126 . According to examples, the controller  130  may cause the agent delivery device  122  to selectively deposit the agent  126  onto the build material layer  104  during movement from the second side to the first side, in which the first energy source  114  may apply energy onto the build material layer  104  and the deposited agent  126 . 
     Although described specifically throughout the entirety of the instant disclosure, representative examples of the present disclosure have utility over a wide range of applications, and the above discussion is not intended and should not be construed to be limiting, but is offered as an illustrative discussion of aspects of the disclosure. 
     What has been described and illustrated herein is an example of the disclosure along with some of its variations. The terms, descriptions and figures used herein are set forth by way of illustration and are not meant as limitations. Many variations are possible within the scope of the disclosure, which is intended to be defined by the following claims—and their equivalents—in which all terms are meant in their broadest reasonable sense unless otherwise indicated.