Patent Publication Number: US-2020298470-A1

Title: Formation of three dimensional objects including magnetic material

Description:
BACKGROUND 
     Additive manufacturing is a process used to produce three-dimensional (3D) objects. Additive manufacturing can be performed by extruding a material through a nozzle and depositing (typically layer-by-layer) the material onto a substrate to form an object. In some instances, the material used to form the layers of the 3D object may be referred to herein as “build material.” Extrusion-based additive manufacturing is sometimes called “fused deposition modeling®” (FDM®), which is a trademark of Stratasys Ltd. Of Edina, Minn., “fused filament fabrication” (FFF), or more generally, “3D printing.” 
     Additive manufacturing processes often utilize electronic data that represents an object, such as a computer-aided design (CAD) model of the object, to form the object. The electronic data can be processed by a computing device component of the additive manufacturing apparatus (e.g., a 3D printer) to form the object. For example, an electronic representation of the object can be mathematically sliced into multiple horizontal layers. The horizontal layers can have contours that will produce the shape of the object being formed by the additive manufacturing apparatus. The computing device component can generate a build path to form the contours for each horizontal layer and send control signals to the extrusion portion of the additive manufacturing apparatus to move a nozzle along the build path to deposit an amount of the material to form each of the horizontal layers. The horizontal layers are formed on top of each other to deposit fluent strands or “roads” of the build material in a layer-by-layer manner onto a platform or a build substrate. For example, the additive manufacturing system can move an extrusion head/nozzle, the platform/build substrate, or both the nozzle and platform vertically and horizontally relative to each other to form the object. The build material from which the object is formed hardens shortly after extrusion to form a solid 3D object. 
     SUMMARY 
     This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key or essential features of the claimed subject matter; nor is it to be used for determining or limiting the scope of the claimed subject matter. 
     This application is directed to forming objects that include magnetic material via a 3D printing process. In an implementation, an article can be formed that includes a plurality of layers of a first polymeric material and at least one layer of a second polymeric material having a magnetic material. The article can be formed by depositing a plurality of layers of the first polymeric material onto a surface of a substrate and depositing at least one layer of a second polymeric material onto at least one layer of the plurality of layers of the first polymeric material. An apparatus can be used to form the article, where the apparatus includes a first material source for the first polymeric material and a second material source for the second polymeric material. The apparatus can also include a first extrusion component to deposit the plurality of layers of the first polymeric material onto the surface of the substrate. Additionally, the apparatus can include a second extrusion component to deposit the at least one layer of the second polymeric material onto the at least one layer of the plurality of layers of the first polymeric material. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The detailed description is set forth with reference to the accompanying drawing figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The use of the same reference numbers in different figures indicates similar or identical items or features. 
         FIG. 1  illustrates an example framework to form objects including one or more layers of a polymeric material that include a magnetic material. 
         FIG. 2  illustrates a first example apparatus to form objects including one or more layers of a polymeric material that include a magnetic material and to magnetize the magnetic material. 
         FIG. 3  illustrates a second example apparatus to form objects including one or more layers of a polymeric material that include a magnetic material and to magnetize the magnetic material. 
         FIG. 4  illustrates a first example apparatus to magnetize magnetic material included in a layer of an object by applying a magnetic field to the magnetic material. 
         FIG. 5  illustrates a second example apparatus to magnetize magnetic material included in a layer of an object by applying a magnetic field to the magnetic material. 
         FIG. 6  illustrates an example process to form objects including one or more layers of a polymeric material that include a magnetic material. 
     
    
    
     DETAILED DESCRIPTION 
     The technologies described herein are generally directed to forming objects including one or more layers of a polymeric material that include a magnetic material. In particular, the objects can be produced by forming one or more first layers that include a first polymeric material. The one or more first layers can be free of a magnetic material. Additionally, the object can be produced by forming one or more second layers that include a second polymeric material having a magnetic material. For example, the one or more second layers can include a polymeric material embedded with magnetic particles. The one or more first layers and the one or more second layers can be formed by extruding the first polymeric material and the second polymeric material onto a substrate. The one or more first layers and the one or more second layers can be deposited according to a pattern that is represented by computer readable data. 
     A magnetizing device can be used to magnetize the magnetic material included in the one or more second layers. In an implementation, the magnetizing device can be a component of the apparatus used to produce the one or more first layers and the one or more second layers. In a particular implementation, the magnetizing device can apply a magnetic field to the one or more second layers to align particles of the magnetic material. In this way, the one or more second layers can produce attractive or repulsive forces when placed in proximity with materials that can be influenced by a magnetic field. 
       FIG. 1  illustrates an example framework  100  to form objects including one or more layers of a polymeric material that include a magnetic material. The framework  100  can include a three-dimensional (3D) printing apparatus  102  that can produce an object  104 . In an implementation, the 3D printing apparatus  102  can produce the object  104  by depositing material in layers according to a pattern. For example, the object  104  can include a plurality of layers, such as representative layers  106 ,  108 ,  110 ,  112 ,  114 . The layers  106 ,  108 ,  110 ,  112 ,  114  can include at least one polymeric material. In the illustrative implementation of  FIG. 1 , the layers  106 ,  108 ,  114  can include a first polymeric material. In addition, the layers  110 ,  112  can include a second polymeric material having a magnetic material. 
     The 3D printing apparatus  102  can include one or more extrusion components  116  to form the layers  106 ,  108 ,  110 ,  112 ,  114 . The one or more extrusion components  116  can be coupled to a non-magnetic material source  118 . The non-magnetic material source  118  can store the first polymeric material that is used to form the layers  106 ,  108 ,  114  of the object  104 . The first polymeric material can be free of a magnetic material. As used herein, when a first material is referred to as being “free” of a second material, the first material does not contain any amount of the second material or contains trace amounts of the second material. 
     In addition, the one or more extrusion components  116  can be coupled to a magnetic material source  120 . The magnetic material source  120  can store the second polymeric material that is used to form the layers  110 ,  112  of the object  104 . In an implementation, the one or more extrusion components  116  can include a first extrusion head coupled to the non-magnetic material source  118  and a second extrusion head coupled to the magnetic material source  120 . In a particular implementation, the non-magnetic material source  118  can include a filament of the first polymeric material that can be fed into the first extrusion head of the one or more extrusion components  116  to form the layers  106 ,  108 ,  114 . Also, the magnetic material source  120  can include a filament of the second polymeric material that can be fed into the second extrusion head of the one or more extrusion components  116  to form the layers  110 ,  112 . 
     The first polymeric material can include an amount of one or more polymers, such as an amount of one or more thermoplastic polymers. In an implementation, the first polymeric material can include an amount of one or more polyesters. Additionally, the first polymeric material can include an amount of a glycol-modified polyethylene terephthalate. Further, the first polymeric material can include an amount of a copolymer. To illustrate, the first polymeric material can include an amount of a copolyester. The first polymeric material can also include an amount of a polylactic acid, acrylonitrile butadiene styrene, a polycarbonate, a polyamide, a polyetherimide, a polystyrene, a polyphenylsulfone, a polysulfone, a polyethersulfone, a polyphenylene, a poly(methyl methacrylate), or combinations thereof. 
     The second polymeric material can include more than trace amounts of a magnetic material. The magnetic material included in the second polymeric material can include Neodymium (Nd), in some cases. In addition, the magnetic material included in the second polymeric material can include Niobium (Nb), in some scenarios. Further, the magnetic material included in the second polymeric material can include Boron (B). In still other instances, the magnetic material included in the second polymeric material can include Iron (Fe). In an illustrative implementation, the magnetic material can include a combination of Nd, Fe, and B. For example, the magnetic material included in the second polymeric material can include Nd 2 Fe 14 B. In another illustrative implementation, the magnetic material can include a combination of Nd, Fe, Nb, and B. 
     In an illustrative implementation, the second polymeric material can include an amount of magnetic material included in a range of about 1% by volume to about 5% by volume of a total volume of the second polymeric material. In another illustrative implementation, the second polymeric material can include an amount of magnetic material included in a range of about 2% by volume to about 10% by volume of a total volume of the second polymeric material. In an additional illustrative implementation, the second polymeric material can include an amount of magnetic material included in a range of about 8% by volume to about 20% by volume of a total volume of the second polymeric material. In a further illustrative implementation, the second polymeric material can include an amount of magnetic material included in a range of about 15% by volume to about 30% by volume of a total volume of the second polymeric material. In other illustrative implementations, the second polymeric material can include an amount of magnetic material included in a range of about 25% by volume to about 40% by volume of a total volume of the second polymeric material. In still further illustrative implementations, the second polymeric material can include an amount of magnetic material included in a range of about 35% by volume to about 50% by volume of a total volume of the second polymeric material. In still additional illustrative implementations, the second polymeric material can include an amount of magnetic material included in a range of about 45% by volume to about 60% by volume of a total volume of the second polymeric material. Also, the second polymeric material can include an amount of a magnetic material included in a range of about 55% by volume to about 75% by volume of a total volume of the second polymeric material. Furthermore, the second polymeric material can include an amount of a magnetic material included in a range of about 70% by volume to about 90% by volume of a total volume of the second polymeric material. 
     Further, the second polymeric material can include particles of magnetic material having a d50 of no greater than about 150 micrometers, no greater than about 125 micrometers, no greater than about 110 micrometers, no greater than about 90 micrometers, no greater than about 75 micrometers, or no greater than about 50 micrometers. The second polymeric material can also include particles of magnetic material having a d50 of at least about 2 micrometers, at least about 5 micrometers, at least about 10 micrometers, at least about 20 micrometers, at least about 25 micrometers, or at least about 30 micrometers. In an illustrative example, the second polymeric material can include particles of magnetic material having a d50 included in a range of about 2 micrometers to about 25 micrometers. In another illustrative example, the second polymeric material can include particles of magnetic material having a d50 included in a range of about 3 micrometers to about 10 micrometers. In an additional illustrative example, the second polymeric material can include particles of magnetic material having a d50 included in a range of about 20 micrometers to about 50 micrometers. In a further illustrative example, the second polymeric material can include particles of magnetic material having a d50 included in a range of about 40 micrometers to about 80 micrometers. In still other illustrative examples, the second polymeric material can include particles of magnetic material having a d50 included in a range of about 75 micrometers to about 150 micrometers. 
     In addition to the magnetic material, the second polymeric material can include an amount of one or more polymers, such as an amount of one or more thermoplastic polymers. In an implementation, the second polymeric material can include an amount of one or more polyesters. Additionally, the second polymeric material can include an amount of a glycol-modified polyethylene terephthalate. Further, the second polymeric material can include an amount of a copolymer. To illustrate, the second polymeric material can include an amount of a copolyester. The second polymeric material can also include an amount of a polylactic acid, acrylonitrile butadiene styrene, a polycarbonate, a polyamide, a polyetherimide, a polystyrene, a polyphenylsulfone, a polysulfone, a polyethersulfone, a polyphenylene, a poly(methyl methacrylate), or combinations thereof. 
     In an illustrative implementation, the second polymeric material can include an amount of one or more polymers included in a range of about 10% by volume to about 25% by volume of a total volume of the second polymeric material. In another illustrative implementation, the second polymeric material can include an amount of one or more polymers included in a range of about 20% by volume to about 40% by volume of a total volume of the second polymeric material. In an additional illustrative implementation, the second polymeric material can include an amount of one or more polymers included in a range of about 35% by volume to about 55% by volume of a total volume of the second polymeric material. In a further illustrative implementation, the second polymeric material can include an amount of one or more polymers included in a range of about 50% by volume to about 75% by volume of a total volume of the second polymeric material. In other illustrative implementations, the second polymeric material can include an amount of one or more polymers included in a range of about 70% by volume to about 80% by volume of a total volume of the second polymeric material. In still further illustrative implementations, the second polymeric material can include an amount of one or more polymers included in a range of about 75% by volume to about 85% by volume of a total volume of the second polymeric material. In still additional illustrative implementations, the second polymeric material can include an amount of one or more polymers included in a range of about 80% by volume to about 90% by volume of a total volume of the second polymeric material. Also, the second polymeric material can include an amount of one or more polymers included in a range of about 85% by volume to about 95% by volume of a total volume of the second polymeric material. Furthermore, the second polymeric material can include an amount of a one or more polymers included in a range of about 90% by volume to about 99% by volume of a total volume of the second polymeric material. 
     The first polymeric material and the second polymeric material can include other components, in some cases. For example, the first polymeric material and/or the second polymeric material can include various additives. To illustrate, the first polymeric material, the second polymeric material, or both can include pigment or dye to alter a color of the material. The first polymeric material and/or the second polymeric material can also include other additives that affect the optical properties of the material. 
     The 3D printing apparatus  102  can also include at least one magnetizing device  124  that can magnetize the magnetic material of the layers  110 ,  112 . For example, the at least one magnetizing device  124  can include one or more magnets to apply a magnetic field to the magnetic particles of the layers  110 ,  112 . By applying a magnetic field to the magnetic particles of the layers  110 ,  112 , the magnetic particles of the layers  110 ,  112  can be aligned such that portions of the layers  110 ,  112  have a particular polarity. To illustrate, the layers  110 ,  112  can be magnetized such that respective portions of the layer  110  have a first polarity and a second polarity that is opposite the first polarity and that respective portions of the layer  112  have the first polarity and the second polarity. In this way, the layers  110 ,  112  can exhibit characteristics of magnetized particles. In an illustrative example, the layer  110  can be magnetized such that a first portion of the layer  110  having the first polarity is attracted to a portion of an additional object having the second polarity and is repelled by a portion of an additional object that has the first polarity. Continuing with this example, the layer  110  can include a second portion having the second polarity that is attracted to a portion of an additional object that has the first polarity and is repelled by a portion of an additional object having the second polarity. 
     In some cases, the portions of the layers  110 ,  112  having the first polarity and the second polarity can be arranged in the Z-direction. For example, the layer  112  can have a first sub-layer of magnetized particles that is adjacent to the layer  110  with the first sub-layer having a first polarity and a second sub-layer of magnetized particles that is adjacent to the layer  114  with the second sub-layer having a second polarity. In other cases, the portions of the layers  110 ,  112  having the first polarity and the second polarity can be arranged in the X-direction. To illustrate, the layer  112  can have a first portion of magnetized particles arranged at a first end  126  having the first polarity and a second portion of magnetized particles arranged at a second end  128  having the second polarity. 
     Although the illustrative example of  FIG. 1  shows that the layers  110 ,  112  have magnetic material throughout, in other situations, the layer  110  and/or the layer  112  can partially include magnetic material. For example, the first portion of the layer  110  can have a magnetic material, while a second portion of the layer  110  is free of magnetic material. In other situations, the layer  110  can include multiple portions that include a magnetic material and multiple portions that are free of a magnetic material. 
     The 3D printing apparatus  102  also includes a control system  130  that controls the operation of the one or more extrusion components  116  and the at least one magnetizing device  124 . For example, the control system  130  can send signals to the one or more extrusion components  116  to control the movement of the one or more extrusion components  116  to extrude the first polymeric material from the non-magnetic material source  118  to form one or more layers of the object  104 . The control system  130  can also send signals to the one or more extrusion components  116  to control the movement of the one or more extrusion components  116  to extrude the second polymeric material from the magnetic material source  120  to form one or more additional layers of the object  104 . The control system  130  can also send signals to the at least one magnetizing device  124  to cause the magnetizing device  124  to generate a magnetic field and move the magnetizing device  124  such that the magnetic field is applied to portions of the object  104  that include magnetic material. 
       FIG. 2  illustrates a first example apparatus  200  to form objects including one or more layers of a polymeric material that include a magnetic material and to magnetize the magnetic material. In some instances, the system  200  can be considered a fused deposition modeling® (FDM®) system, a fused filament fabrication (FFF) system, or more generally, a 3D printing system (or 3D printer). 
     The apparatus  200  can include a housing  202  for a number of the components of the apparatus  200 . The housing  202  can be formed from a number of materials, such as one or more metals, one or more polymers, or a combination thereof. The apparatus  200  can also include a first extrusion head  204  and a second extrusion head  206 . The first extrusion head  204  and the second extrusion head  206  can be mounted on a horizontal rail  208 . The first extrusion head  204  and the second extrusion head  206  can move along the horizontal rail  208  in the X-direction. In an implementation, the first extrusion head  204  and the second extrusion head  206  can move along the horizontal rail  208  by the use of one or more stepper motors, one or more servo motors, one or more microcontrollers, one or more belts, combinations thereof, and the like. In some cases, the first extrusion head  204  and the second extrusion head  206  can move in tandem along the horizontal rail  208 . In a particular implementation, the first extrusion head  204  and the second extrusion head  206  can be coupled together. In other cases, the first extrusion head  204  and the second extrusion head  206  can move separately along the horizontal rail  208 . 
     The apparatus  200  can also include a first vertical rail  210  and a second vertical rail  212 . The first extrusion head  204  can move in the Z-direction along the first vertical rail  212  and the second extrusion head  206  can move in the Z-direction along the second vertical rail  214 . In some scenarios, the first extrusion head  204  and the second extrusion head  206  can move in tandem along the first vertical rail  210  and the second vertical rail  212 . In other instances, the first extrusion head  204  and the second extrusion head  206  can move separately along the first vertical rail  210  and the second vertical rail  212 . In a particular implementation, the first vertical rail  210  and the second vertical rail  212  can be arranged to move in the X-direction along the horizontal rail  208 . The first vertical rail  210  and the second vertical rail  212  can move together along the horizontal rail  208 , in some cases, while in other situations, the first vertical rail  210  and the second vertical rail  212  can move separately along the horizontal rail  208 . 
     The first extrusion head  204 , the second extrusion head  206 , or both can move along the horizontal rail  208 , the first vertical rail  210 , and/or the second vertical rail  212  at a speed of at least about 5 mm/second, at least about 10 mm/second, at least about 25 mm/second, at least about 50 mm/second, at least about 75 mm/second or at least about 125 mm/second. In addition, first extrusion head  204 , the second extrusion head  206 , or both can move along the horizontal rail  208 , the first vertical rail  210 , and/or the second vertical rail  212  at a speed no greater than about 400 mm/second, no greater than about 350 mm/second, no greater than about 300 mm/second, no greater than about 250 mm/second, no greater than about 200 mm/second, or no greater than about 150 mm/second. In an illustrative example, the first extrusion head  204 , the second extrusion head  206 , or both can move along the horizontal rail  208 , the first vertical rail  210 , and/or the second vertical rail  212  at a speed included in a range of about 2 mm/second to about 500 mm/second. In another illustrative example, the first extrusion head  204 , the second extrusion head  206 , or both can move along the horizontal rail  208 , the first vertical rail  210 , and/or the second vertical rail  212  at a speed included in a range of about 20 mm/second to about 300 mm/second. In an additional illustrative example, the first extrusion head  204 , the second extrusion head  206 , or both can move along the horizontal rail  208 , the first vertical rail  210 , and/or the second vertical rail  212  at a speed included in a range of about 30 mm/second to about 100 mm/second. 
     The apparatus  200  can also include a first material source  214  that stores a first polymeric material that is free of a magnetic material. The first material source  214  can be coupled to the first extrusion head  204  by a first supply line  216 . In addition, the apparatus  200  includes a second material source  218  that stores a second polymeric material that includes at least one magnetic material. The second material source  218  can be coupled to the second extrusion head  206  by a second supply line  220 . The first polymeric material can be fed into the first extrusion head  204  from the first material source  214  in order to form one or more layers of the first polymeric material on a platform  222  of the apparatus  200 , such as a first layer  224  of an object  226 . In some situations, the platform  222  can also be referred to herein as a substrate. The second polymeric material can be fed into the second extrusion head  206  from the second material source  218  in order to form one or more layers of the second polymeric material on the platform  222 , such as a second layer  228  of the object  226 . In some cases, instead of moving the first extrusion head  204  and/or the second extrusion head  206  along the first vertical rail  210  and the second vertical rail  212 , respectively, while forming the object  226 , the platform  222  can be moved along the first vertical rail  210  and the second vertical rail  212 . In other situations, the first extrusion head  204 , the second extrusion head  206 , and the platform  222  can be moved along the first vertical rail  210  and the second vertical rail  212  during the formation of the object  226 . 
     The platform  222  can be provided as a “working surface” for building the object  226 . In some cases, an additional substrate (not shown) can be mounted on the platform  222  as a working surface for building the object  226  and the one or more layers of the first polymeric material and the second polymeric material can be formed on the additional substrate rather than being formed on the platform  222  itself. During operation of the apparatus  200 , the platform  222  can be initially positioned below the first extrusion head  204  and the second extrusion head  206  in a direction along the Z-axis. The platform  222  and/or the first extrusion head  204  and the second extrusion head  206  can be positioned such that the distance at which a layer of the object  226  is spaced below the first extrusion head  204  and/or the second extrusion head  206  can be a distance allowing for the deposition of fluent strands or “roads” of build material at a desired thickness. In some instances, a distance between the object  226  and the first extrusion head  204  and/or the second extrusion head  206  can be within a range from about 0.02 mm to about 4 mm. As layers of the object  226  are deposited, the first extrusion head  204  and/or the second extrusion head  206  can be positioned a distance in increments in the Z-direction that allows for depositing a next layer of the object  226  at a desired thickness. In some examples, the incremented distance can be about 0.1 mm. 
     Additionally, in some implementations, the platform  222  can be heated to aid in the adhesion of the object  226  to the platform  222  during the formation of the object  226 . In an illustrative example, the platform  222  can be heated at a temperature included in a range of about 30° C. to about 125° C. In another illustrative example, the platform  222  can be heated at a temperature included in a range of about 40° C. to about 90° C. In some instances, the temperature at which the platform  222  is heated can depend on a glass transition temperature of at least one of the build materials being deposited onto the platform  222  to form the object  226 . Further, heating the platform  222  can provide an anti-warping effect on the build material used to form the object  226 . Heating of the platform  222  can be performed by suitable heating elements, such as electrical elements that can be turned on or off, gas heating elements below the platform  222 , or another suitable heating element. In some situations, though, the platform  222  may not be heated. 
     In an implementation, the first material source  214  and the second material source  218  can individually include a material bay or housing containing a spool of build material filament that can be unwound from the spool by a motor or drive unit. In some examples, supplying of the build material through the first supply line  216  and/or the second supply line  218  can be turned on or off, and the build material can be advanced in both forward and backward directions along the first supply line  216  and/or the second supply line  218 . Retraction of the first polymeric material along the first supply line  216  toward the first material source and retraction of the second polymeric material along the second supply line  220  toward the second material source  218  can be advantageous to prevent “drool” at the respective extrusion head  204 ,  206  and/or to recycle unused build material after finishing an object. Moreover, the rate at which the first polymeric material is supplied to the first extrusion head  204  and the rate at which the second polymeric material is supplied to the second extrusion head  206  can be controlled by a drive unit (e.g., worm drive) at varying speeds so that speeds can be increased or decreased. 
     Filaments of the first polymeric material and/or the second polymeric material can have a diameter of at least about 0.5 mm, at least about 1 mm, at least about 1.5 mm, or at least about 2 mm. In addition, filaments of the first polymeric material and/or the second polymeric material can have a diameter no greater than about 7 mm, no greater than about 5 mm, no greater than about 3 mm, or no greater than about 2.5 mm. In an illustrative example, the diameter of first polymeric material and/or the diameter of the second polymeric material can be included in a range of about 0.2 mm to about 10 mm. In another illustrative example, the diameter of the first polymeric material and/or the diameter of the second polymeric material can included in a range of about 1.7 mm to about 2.9 mm. 
     The first extrusion head  204  and the second extrusion head  206  can be configured to extrude material onto the platform  222  during the process of forming the object  226 . The first extrusion head  204  and the second extrusion head  206  can be a suitable type of extrusion head configured to receive material and to extrude the material through a nozzle (or tip) that includes an orifice from which fluent strands or “roads” of the material can be deposited onto the platform  222  in a layer-by-layer manner to form the object  226 . In an implementation, nozzles of varying-sized orifices can be utilized for depositing roads of build material having different thicknesses from the first extrusion head  204  and/or the second extrusion head  206 . 
     In some cases, the first extrusion head  204  can include a heating element that heats the first polymeric material to a temperature that causes the first polymeric material to become flowable before extruding the first polymeric material onto the platform  222 . Additionally, the second extrusion head  206  can include a heating element that heats the second polymeric material to a temperature that causes the second polymeric material to become flowable before extruding the second polymeric material onto the platform  222 . The temperature applied to the first polymeric material in the first extrusion head  204  and the temperature applied to the second polymeric material in the second extrusion head  206  can vary depending on the material being heated. For example, a first temperature can be applied to heat the first polymeric material and a second temperature can be applied to heat the second polymeric material. 
     The temperature applied to heat the first polymeric material in the first extrusion head  204  and/or the temperature applied to heat the second polymeric material in the second extrusion head  206  can be at least about 150° C., at least about 170° C., at least about 190° C., or at least about 210° C. Additionally, the temperature applied to heat the first polymeric material in the first extrusion head  204  and/or the temperature applied to heat the second polymeric material in the second extrusion head  206  can be no greater than about 350° C., no greater than about 300° C., no greater than about 280° C., no greater than about 260° C., or no greater than about 240° C. In an illustrative example, the temperature applied to heat the first polymeric material in the first extrusion head  204  and/or the temperature applied to heat the second polymeric material in the second extrusion head  206  can be included in a range of about 135° C. to about 360° C. In another illustrative example, the temperature applied to heat the first polymeric material in the first extrusion head  204  and/or the temperature applied to heat the second polymeric material in the second extrusion head  206  can be included in a range of about 230° C. to about 290° C. 
     Additionally, the temperature applied to heat the first polymeric material in the first extrusion head  204  and/or the temperature applied to heat the second polymeric material in the second extrusion head  206  can be based on a glass transition temperature of the material. For example, the temperature applied to heat the first polymeric material in the first extrusion head  204  can be within about 2° C. of the glass transition temperature of the first polymeric material and the temperature applied to heat the second polymeric material in the second extrusion head  206  can be within about 2° C. of the glass transition temperature of the second polymeric material. In another example, the temperature applied to heat the first polymeric material in the first extrusion head  204  can be within about 5° C. of the glass transition temperature of the first polymeric material and the temperature applied to heat the second polymeric material in the second extrusion head  206  can be within about 5° C. of the glass transition temperature of the second polymeric material. In an additional example, the temperature applied to heat the first polymeric material in the first extrusion head  204  can be within about 12° C. of the glass transition temperature of the first polymeric material and the temperature applied to heat the second polymeric material in the second extrusion head  206  can be within about 12° C. of the glass transition temperature of the second polymeric material. In a further example, the temperature applied to heat the first polymeric material in the first extrusion head  204  can be within about 25° C. of the glass transition temperature of the first polymeric material and the temperature applied to heat the second polymeric material in the second extrusion head  206  can be within about 25° C. of the glass transition temperature of the second polymeric material. 
     The apparatus  200  also includes a first magnetizing device  230  having a first arm  232  and a first magnetic plate  234 . Additionally, the apparatus  200  includes a second magnetizing device  236  having a second arm  238  and a second magnetic plate  240 . The first magnetizing device  230  and the second magnetizing device  236  can create magnetic fields to magnetize magnetic materials of the object  226 . The first magnetizing device  230  can be disposed on a third vertical rail  242  and the second magnetizing device  236  can be disposed on a fourth vertical rail  244 . The first magnetizing device  230  can move in the Z-direction along the third vertical rail  242  and the second magnetizing device  236  can move in the Z-direction along the fourth vertical rail  244 . In some implementations, the first arm  232  and the second arm  238  can be retractable or otherwise be configured to modify a respective length of the first arm  232  or a respective length of the second arm  238 . Magnetizing magnetic material in the object  226  will be discussed in more detail with respect to  FIG. 4  and  FIG. 5 . 
     The apparatus  200  can include a control system  242 . The control system  242  can include one or more hardware processor devices represented by processor  244  and one or more physical memory devices represented by memory  246 . In some cases, the processor  244  can be a single processing unit or a number of processing units, any of which can include single or multiple computing units or multiple cores. Additionally, the processor  244  can be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, and/or any devices that manipulate signals based on operational instructions. Among other capabilities, the processor  244  can be configured to fetch and execute computer-readable instructions, such as computer readable instructions stored in the memory  246 . 
     The memory  246  can be examples of computer storage media for storing instructions which are executed by the processor  244  to perform various functions. In an example, the memory  246  can generally include both volatile memory and non-volatile memory (e.g., RAM, ROM, or the like). The memory  246  can also include one or more cache memory devices, one or more buffers, one or more flash memory devices, or a combination thereof. Computer storage media includes volatile and non-volatile, removable and non-removable media implemented in any method or technology for storage of information, such as computer readable instructions, data structures, program modules, or other data. Additionally, computer storage media includes, but is not limited to, random access memory (RAM), read only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory or other memory technology, compact disc ROM (CD-ROM), digital versatile disks (DVD) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transmission medium that can be used to store information for access by a computing device. In contrast, communication media can embody computer readable instructions, data structures, program modules, or other data in a modulated data signal, such as a carrier wave. As defined herein, computer storage media does not include communication media. 
     The apparatus  244  can also include one or more additional components  248 . For example, the one or more additional components  248  can include one or more input/output devices, such as a keyboard, a mouse, a touch screen, a display, speakers, a microphone, a camera, combinations thereof, and the like. The one or more additional components  248  can also include one or more communication interfaces for exchanging data with other devices, such as via a network, direct connection, or the like. For example, the communication interfaces can facilitate communications within a wide variety of networks or connections, such as one or more wired networks or wired connections and/or one or more wireless networks or wireless connections. 
     The control system  242  can include, be coupled to, or obtain data from a computer-aided design (CAD) system to provide a digital representation of the object  226  to be formed by the apparatus  200 . Any suitable CAD software program can be utilized to create the digital representation of the object  226 . For example, a user can design, using a 3D modeling software program executing on a host computer, an object having a particular shape with specified dimensions, such as the object  226 , that is to be manufactured using the apparatus  200 . In order to translate the geometry of the object  226  into computer-readable instructions or commands usable by processor  244  or a suitable controller in forming the object  226 , the control system  242  can mathematically slice the digital representation of the object  226  into multiple horizontal layers. The control system  242  can then design build paths along which build material is to be deposited in a layer-by-layer fashion to form the object  226 . 
     The control system  242  can manage and/or direct one or more components of the apparatus  200 , such as the first extrusion head  204  and/or the second extrusion head  206 , by controlling movement of those components according to a numerically controlled computer-aided manufacturing (CAM) program along computer-controlled paths. The movement of the various components, such as the first extrusion head  204 , the second extrusion head  206 , or both, can be performed by the use of stepper motors, servo motors, microcontrollers, combinations thereof, and the like. 
     In an illustrative implementation, the control system  242  can control the supply of the first polymeric material from the first material supply  214  to the first extrusion head  204  and the supply of the second polymeric material from the second material supply  218  to the second extrusion head  206 . As build material is supplied to the first extrusion head  204  and/or the second extrusion head  208 , the control system  242  can direct the movement of the first extrusion head  204  and/or the second extrusion head  206  along the horizontal rail  206 , the first vertical rail  210 , the second vertical rail  212 , or a combination thereof, so that the first extrusion head  204 , the second extrusion head  206 , or both can follow a predetermined build path while depositing build material for each layer of the object  226 . In this sense, the horizontal rail  208 , the first vertical rail  210 , and/or the second vertical rail  212 , such as a gantry, allow the first extrusion head  204  and/or the second extrusion head  206  to move two-dimensionally and/or three-dimensionally in vertical and/or horizontal directions as shown by the arrows in  FIG. 2 . Additionally, or alternatively, the platform  222  can be movable in two-dimensions and/or three-dimensions, and such movement can be controlled by the control system  242  to provide similar relative movement between the platform  222  and the first extrusion head  204  and the second extrusion head  206  so that multiple roads of build material can be deposited by moving the first extrusion head  204 , the second extrusion head  206 , the platform  222 , in a two-dimensional (2D) horizontal plane (i.e., X-Y plane) to form each layer of the object  226 , and then multiple successive layers can be deposited on top of one another by moving the first extrusion head  204 , the second extrusion head  206 , and/or the platform  222  in a vertical Z-direction. 
     The control system  242  can also control the movement of the first magnetizing device  230  along the third vertical rail  242 , the movement of the second magnetizing device  236  along the fourth vertical rail  244 , and/or the movement of the platform  222  such that the first magnetizing device  230  and/or the second magnetizing device  236  can be located proximate to portions of the object  226  that include magnetic material. The control system  242  can also control when a magnetic field is to be generated by the first magnetizing device  230  and the second magnetizing device  236  by providing signals to provide current to the first magnetizing device  230  and/or the second magnetizing device  236 . The control system  242  can control a magnitude of the current provided to the first magnetizing device  230  and/or a magnitude of the current provided to the second magnetizing device  236 . Additionally, the control system  242  can control a duration for which the magnetic field is generated by the first magnetizing device  230  and/or the second magnetizing device  236 . Furthermore, the control system  242  can control a configuration and/or location of the first arm  232 , a configuration and/or location of the second arm  238  to position the first magnetic plate  234  and the second magnetic plate  240  to magnetize portions of the object  226 . 
     The object  226  can be formed in a controlled environment, such as by confining individual ones of the components of the apparatus  200  to a chamber or other enclosure formed by the housing  202  where temperature, and optionally other parameters (e.g., pressure) can be controlled and maintained at a desired level by elements configured to control temperature, pressure, etc. (e.g., heating elements, pumps, etc.). In some instances, the temperature applied to the build material can correspond to a temperature at or above the creep-relaxation temperature of the build material. This can allow more gradual cooling of the build material as it is deposited onto the platform  222  so as to prevent warping of the layers of the object  226  upon deposition. 
     Although  FIG. 2  illustrates one illustrative example of certain components of an additive manufacturing system usable for carrying out the techniques disclosed herein, it is to be appreciated that the configuration and inclusion of certain components shown in  FIG. 2  is one, non-limiting, example of a suitable additive manufacturing system. Namely, other types and configurations of additive manufacturing systems can be utilized with the techniques and materials disclosed herein without changing the basic characteristics of the apparatus  200 , and the apparatus  200  can be implemented as any suitable size for a particular industry or application, such as industrial-sized for commercial object production and/or testing, desktop-sized, handheld for consumer-use, and so on. For example, although the illustrative example of  FIG. 2  shows that the apparatus  200  includes two magnetizing devices and two arms, the apparatus  200  can include a different number of magnetizing devices and a different number of arms. To illustrate, in some cases, the apparatus  200  can include more than two magnetizing devices and more than two arms. In other implementations, the apparatus  200  can be configured to include a single magnetizing device and/or a single arm. 
       FIG. 3  illustrates a second example apparatus  300  to form objects including one or more layers of a polymeric material that include a magnetic material and to magnetize the magnetic material. The apparatus  300  includes components that are the same or similar to corresponding components described with respect to the apparatus  200  of  FIG. 2  with the exception of the arrangement of the magnetizing devices of the apparatus  300 . Thus, the details of many of the components of the apparatus  300  are omitted because the features of these components have been described in detail previously with respect to  FIG. 2 . 
     The apparatus  300  can include a housing  302  for a number of the components of the apparatus  300 . The housing  302  can be formed from a number of materials, such as one or more metals, one or more polymers, or a combination thereof. The apparatus  300  can also include a first extrusion head  304  and a second extrusion head  306 . The first extrusion head  304  and the second extrusion head  306  can be mounted on a horizontal rail  308 . The first extrusion head  304  and the second extrusion head  306  can move along the horizontal rail  208  in the X-direction. In an implementation, the first extrusion head  304  and the second extrusion head  306  can move along the horizontal rail  308  by the use of one or more stepper motors, one or more servo motors, one or more microcontrollers, one or more belts, combinations thereof, and the like. In some cases, the first extrusion head  304  and the second extrusion head  306  can move in tandem along the horizontal rail  308 . In a particular implementation, the first extrusion head  304  and the second extrusion head  306  can be coupled together. In other cases, the first extrusion head  304  and the second extrusion head  306  can move separately along the horizontal rail  308 . 
     The apparatus  300  can also include a first vertical rail  310  and a second vertical rail  312 . The first extrusion head  304  can move in the Z-direction along the first vertical rail  312  and the second extrusion head  306  can move in the Z-direction along the second vertical rail  314 . In some scenarios, the first extrusion head  304  and the second extrusion head  306  can move in tandem along the first vertical rail  310  and the second vertical rail  312 . In other instances, the first extrusion head  304  and the second extrusion head  306  can move separately along the first vertical rail  310  and the second vertical rail  312 . In a particular implementation, the first vertical rail  310  and the second vertical rail  312  can be arranged to move in the X-direction along the horizontal rail  308 . The first vertical rail  310  and the second vertical rail  312  can move together along the horizontal rail  308 , in some cases, while in other situations, the first vertical rail  310  and the second vertical rail  312  can move separately along the horizontal rail  308 . 
     The apparatus  300  can also include a first material source  314  that stores a first polymeric material that is free of a magnetic material. The first material source  314  can be coupled to the first extrusion head  304  by a first supply line  316 . In addition, the apparatus  300  includes a second material source  318  that stores a second polymeric material that includes at least one magnetic material. The second material source  318  can be coupled to the second extrusion head  306  by a second supply line  320 . The first polymeric material can be fed into the first extrusion head  304  from the first material source  314  in order to form one or more layers of the first polymeric material on a platform  322  of the apparatus  300 , such as a first layer  324  of an object  326 . The second polymeric material can be fed into the second extrusion head  306  from the second material source  318  in order to form one or more layers of the second polymeric material on the platform, such as a second layer  328  of the object  326 . In some cases, instead of moving the first extrusion head  304  and/or the second extrusion head  306  along the first vertical rail  310  and the second vertical rail  312 , respectively, while forming the object  326 , the platform  322  can be moved along the first vertical rail  310  and the second vertical rail  312 . In other situations, the first extrusion head  304 , the second extrusion head  306 , and the platform  322  can be moved along the first vertical rail  310  and the second vertical rail  312  during the formation of the object  326 . 
     The platform  322  can be provided as a “working surface” for building the object  326 . In some cases, an additional substrate (not shown) can be mounted on the platform  322  as a working surface for building the object  326 . During operation of the apparatus  300 , the platform  322  can be initially positioned below the first extrusion head  304  and the second extrusion head  306  in a direction along the Z-axis. The platform  322  and/or the first extrusion head  304  and the second extrusion head  306  can be positioned such that the distance at which a layer of the object  326  is spaced below the first extrusion head  304  and/or the second extrusion head  306  can be any suitable distance allowing for the deposition of fluent strands or “roads” of build material at a desired thickness. As layers of the object  326  are deposited, the first extrusion head  304  and/or the second extrusion head  306  can be positioned a distance in increments in the Z-direction that allows for depositing a next layer of the object  326  at a desired thickness. 
     Additionally, in some implementations, the platform  322  can be heated to aid in the adhesion of the object  326  to the platform  322  during the formation of the object  326 . In some instances, the temperature at which the platform  322  is heated can depend on a glass transition temperature of at least one of the build materials being deposited onto the platform  322  to form the object  326 . Further, heating the platform  322  can provide an anti-warping effect on the build material used to form the object  326 . Heating of the platform  326  can be performed by any suitable heating elements, such as electrical elements that can be turned on or off, gas heating elements below the platform  322 , or any other suitable heating element. In some situations, though, the platform  322  may not be heated. 
     In an implementation, the first material source  314  and the second material source  318  can individually include a material bay or housing containing a spool of build material filament that can be unwound from the spool by a motor or drive unit. In some examples, supplying of the build material through the first supply line  316  and/or the second supply line  318  can be turned on or off, and the build material can be advanced in both forward and backward directions along the first supply line  316  and/or the second supply line  318 . Moreover, the rate at which the first polymeric material is supplied to the first extrusion head  304  and the rate at which the second polymeric material is supplied to the second extrusion head  306  can be controlled by a drive unit (e.g., worm drive) at varying speeds so that speeds can be increased or decreased. 
     The first extrusion head  304  and the second extrusion head  306  can be configured to extrude material onto the platform  322  during the process of forming the object  326 . The first extrusion head  304  and the second extrusion head  306  can be any suitable type of extrusion head configured to receive material and to extrude the material through a nozzle (or tip) that includes an orifice from which fluent strands or “roads” of the material can be deposited onto the platform  322  in a layer-by-layer manner to form the object  326 . In an implementation, nozzles of varying-sized orifices can be utilized for depositing roads of build material having different thicknesses from the first extrusion head  304  and/or the second extrusion head  306 . 
     In some cases, the first extrusion head  304  can include a heating element that heats the first polymeric material to a temperature that causes the first polymeric material to become flowable before extruding the first polymeric material onto the platform  322 . Additionally, the second extrusion head  306  can include a heating element that heats the second polymeric material to a temperature that causes the second polymeric material to become flowable before extruding the second polymeric material onto the platform  322 . The temperature applied to the first polymeric material in the first extrusion head  304  and the temperature applied to the second polymeric material in the second extrusion head  306  can vary depending on the material being heated. For example, a first temperature can be applied to heat the first polymeric material and a second temperature can be applied to heat the second polymeric material. 
     The apparatus  300  also includes a first magnetizing device  330  having a first arm  332  and a first magnetic plate  334 . Additionally, the apparatus  300  includes a second magnetizing device  336  having a second arm  338  and a second magnetic plate  340 . The first magnetizing device  330  and the second magnetizing device  336  can create magnetic fields to magnetize magnetic materials of the object  326 . The first magnetizing device  330  and the second magnetizing device  336  can be disposed on the horizontal rail  308 . The first magnetizing device  330  and the second magnetizing device  336  can move in the X-direction along the horizontal rail  308 . In some implementations, the first arm  332  and the second arm  338  can be retractable or otherwise be configured to modify a respective length. Additionally, the first arm  332  can include one or more elbows and the second arm  338  can include one or more elbows that enable the first arm  332  and the second arm  338  to be arranged in a number of configurations to apply a magnetic field to the object  326  and magnetize materials of the object  326  located at a number of positions within the object  326 . Magnetizing magnetic material in the object  326  will be discussed in more detail with respect to  FIG. 4  and  FIG. 5 . 
     The apparatus  300  can include a control system  342 . The control system  342  can include one or more hardware processor devices represented by processor  344  and one or more physical memory devices represented by memory  346 . Among other capabilities, the processor  344  can be configured to fetch and execute computer-readable instructions, such as computer readable instructions stored in the memory  346 . The memory  346  can be an example of computer storage media for storing instructions which are executed by the processor  344  to perform various functions. 
     The apparatus  344  can also include one or more additional components  348 . For example, the one or more additional components  348  can include one or more input/output devices, such as a keyboard, a mouse, a touch screen, a display, speakers, a microphone, a camera, combinations thereof, and the like. The one or more additional components  348  can also include one or more communication interfaces for exchanging data with other devices, such as via a network, direct connection, or the like. For example, the communication interfaces can facilitate communications within a wide variety of networks or connections, such as one or more wired networks or wired connections and/or one or more wireless networks or wireless connections. 
     The control system  342  can include, be coupled to, or obtain data from a computer-aided design (CAD) system to provide a digital representation of the object  326  to be formed by the apparatus. In an implementation, the control system  342  can manage and/or direct one or more components of the apparatus  300 , such as the first extrusion head  304  and/or the second extrusion head  306 , by controlling movement of those components according to a numerically controlled computer-aided manufacturing (CAM) program along computer-controlled paths. The movement of the various components, such as the first extrusion head  304 , the second extrusion head  306 , or both, can be performed by the use of stepper motors, servo motors, microcontrollers, combinations thereof, and the like. 
     In an illustrative implementation, the control system  342  can control the supply of the first polymeric material from the first material supply  314  to the first extrusion head  304  and the supply of the second polymeric material from the second material supply  318  to the second extrusion head  306 . As build material is supplied to the first extrusion head  304  and/or the second extrusion head  308 , the control system  342  can direct the movement of the first extrusion head  304  and/or the second extrusion head  306  along the horizontal rail  308 , the first vertical rail  310 , the second vertical rail  312 , or a combination thereof, so that the first extrusion head  304 , the second extrusion head  306 , or both can follow a predetermined build path while depositing build material for each layer of the object  326 . In this sense, the horizontal rail  308 , the first vertical rail  310 , and/or the second vertical rail  312  allow the first extrusion head  304  and/or the second extrusion head  306  to move two-dimensionally and/or three-dimensionally in vertical and/or horizontal directions as shown by the arrows in  FIG. 3 . Additionally, or alternatively, the platform  322  can be movable in two-dimensions and/or three-dimensions, and such movement can be controlled by the control system  342  to provide similar relative movement between the platform  322  and the first extrusion head  304  and the second extrusion head  306  so that multiple roads of build material can be deposited by moving the first extrusion head  304 , the second extrusion head  306 , the platform  322 , in a two-dimensional (2D) horizontal plane (i.e., X-Y plane) to form each layer of the object  326 , and then multiple successive layers can be deposited on top of one another by moving the first extrusion head  304 , the second extrusion head  306 , and/or the platform  322  in a vertical Z-direction. 
     The control system  342  can also control the movement of the first magnetizing device  330  and the second magnetizing device  336  along the horizontal rail  308  and/or the movement of the platform  322  to be located proximate to portions of the object  326  that include magnetic material. The control system  342  can also control when a magnetic field is to be generated by the first magnetizing device  330  and the second magnetizing device  336  by providing signals to direct current to the first magnetizing device  330  and/or the second magnetizing device  336 . The control system  342  can control a magnitude of the current provided to the first magnetizing device  330  and/or a magnitude of the current provided to the second magnetizing device  336 . Additionally, the control system  342  can control a duration for which the magnetic field is generated by the first magnetizing device  330  and/or the second magnetizing device  336 . Furthermore, the control system  342  can control a configuration and/or location of the first arm  332 , a configuration and/or location of the second arm  338  to position the first magnetic plate  334  and the second magnetic plate  340  to magnetize portions of the object  326 . 
     Although  FIG. 3  illustrates one illustrative example of certain components of an additive manufacturing system usable for carrying out the techniques disclosed herein, it is to be appreciated that the configuration and inclusion of certain components shown in  FIG. 3  is one, non-limiting, example of a suitable additive manufacturing system. Namely, other types and configurations of additive manufacturing systems can be utilized with the techniques and materials disclosed herein without changing the basic characteristics of the apparatus  300 , and the apparatus  300  can be implemented as any suitable size for a particular industry or application, such as industrial-sized for commercial object production and/or testing, desktop-sized, handheld for consumer-use, and so on. For example, although the illustrative example of  FIG. 3  shows that the apparatus  300  includes two magnetizing devices and two arms, the apparatus  300  can include a different number of magnetizing devices and a different number of arms. To illustrate, in some cases, the apparatus  300  can include more than two magnetizing devices and more than two arms. In other implementations, the apparatus  300  can be configured to include a single magnetizing device and/or a single arm. In addition, although  FIG. 3  shows that the first arm  332  has a single elbow and the second arm  338  has a single elbow, arms of the apparatus  300  can include a different number of elbows or no elbows. Further, the apparatus  300  can include components that are alternatives to the elbows that enable the parts of an arm to rotate, such as a hinge or another type of rotatable connector. 
       FIG. 4  illustrates a first example apparatus  400  to magnetize magnetic material included in a layer of an object  402  by applying a magnetic field to the magnetic material. The object  402  can include a first layer  404  including a first polymeric material, a second layer  406  including a second polymeric material, and a third layer  408  including the first polymeric material. The second polymeric material of the second layer  406  can include a magnetic material that can be magnetized by the apparatus  400 . In some cases, the particles of the magnetic material may be unaligned before a magnetic field is applied to the second layer  406  of the object  404 . Additionally, although the illustrative example of  FIG. 4  shows that the object  402  includes two layers of the first polymeric material and one layer of the second polymeric material, the object  402  can have at least one layer of the first polymeric material and at least one layer of the second polymeric material. In a particular implementation, the first layer  404 , the second layer  406 , and the third layer  408  can be formed by extruding the first polymeric material and the second polymeric material onto a platform or other substrate. 
     A magnetic field can be generated by a first magnetizing device  410  and/or a second magnetizing device  412 . In an implementation, a magnetic field can be generated by directing current through a first coil  414  of the first magnetizing device  410  and/or directing current through a second coil  416  of the second magnetizing device  412 . The apparatus  400  can also include a first magnetic plate  418  and a second magnetic plate  420 . When a magnetic field is generated by the first magnetizing device  410  and/or the second magnetizing device  412 , the first magnetic plate  418  can have a first polarity and the second magnetic plate  420  can have a second polarity that is opposite the first polarity. In the illustrative implementation of  FIG. 4 , the magnetic field can be generated in a direction indicated by arrow  422 . In this way, the magnetic particles of the second layer  406  can be aligned according to the direction of the magnetic field such that the second layer  406  includes a first portion  424  having the second polarity and a second portion  426  having the first polarity. Thus, the first portion  424  and the second magnetic plate  420  can have the same polarity and the second portion  426  and the first magnetic plate  418  can have the same polarity. Accordingly, when the first portion  424  is proximate to a portion of additional object including magnetic material having the second polarity, the first portion  424  and portion of the additional object can be repelled from each other. Also, when the first portion  424  is proximate to a portion of an additional object including magnetic material having the first polarity, the first portion  424  and the portion of the additional object can be attracted to each other. 
     Additionally, the apparatus  400  can have a first arm  428  and a second arm  430 . The first arm  428  can be used to position the first magnetizing device  410  and the first magnetic plate  418  and the second arm  430  can be used to position the second magnetizing device  412  and the second magnetic plate  420  to apply a magnetic field to a portion of the object  402  that includes magnetic particles. 
     In a particular implementation, the first magnetic plate  418 , the second magnetic plate  420 , the first arm  428 , and the second arm  430  can be made of high magnetic permeability materials such as a permalloy. Optionally, a magnetic yoke  436  can be added for connecting the first arm  428  and the second arm  430  to reinforce and stabilize a magnetic field generated by the apparatus  400 . The magnetic yoke  436  can also be made of high magnetic permeability materials such as a permalloy, and can also be flexible. 
     The first magnetic device  410  and the first magnetic plate  418  can be moved along a first rail  432  to be proximate to the second layer  406 . In addition, the second magnetic device  412  and the second magnetic plate  420  can be moved along a second rail  434  to be proximate to the second layer  406 . In some cases, a length of the first arm  428  and a length of the second arm  430  can be controlled to move the first magnetic plate  418  and the second magnetic plate  420  within a specified distance of the second layer  406  to apply a magnetic field to the second layer  406  that is sufficiently strong to magnetize the magnetic particles of the second layer  406 . 
     Although, the illustrative example of  FIG. 4  shows the magnetic field being generated in the direction indicated by the arrow  422 , the apparatus  400  can be used to generate a magnetic field in a direction opposite the direction indicated by the arrow  422 . In these situations, the magnetic field can be generated from the first magnetic plate  418  to the second magnetic plate  420  with the first magnetic plate  418  having the second polarity and the second magnetic plate  420  having the first polarity. Also, in these situations, the portions of the second layer  406  can be arranged such that the first portion  424  has the first polarity and the second portion  426  has the second polarity. Furthermore, in some scenarios, the apparatus  400  can be configured to generate a magnetic field in a direction that is perpendicular to the direction indicated by the arrow  422 . That is, the first magnetizing device  410 , the second magnetizing device  412 , the first magnetic plate  418 , the second magnetic plate  420 , the first arm  428 , and the second arm  430  can be arranged to apply a magnetic field along the Z-axis. In this way, the particles of the magnetic material included in the second layer  406  can be aligned in a different manner. In one illustrative example, a first portion of the second layer  406  having particles of a first polarity can be disposed in a direction along the X-axis and adjacent to the first layer  404  and a second portion of the second layer  406  having particles of a second polarity can be disposed in a direction along the X-axis and adjacent to the third layer  408 . In another illustrative example, a first portion of the second layer  406  having particles of a first polarity can be disposed in a direction along the X-axis and adjacent to the third layer  408  and a second portion of the second layer  406  having particles of a second polarity can be disposed in a direction along the X-axis and adjacent to the first layer  404 . Additionally, although the illustrative implementation of  FIG. 4  includes multiple magnetizing devices, in other implementations, the apparatus  400  can include a single magnetizing device that has a coil that is coupled to the first magnetic plate  418  and the second magnetic plate  420 . 
       FIG. 5  illustrates a second example apparatus  500  to magnetize magnetic material included in a layer of an object  502  by applying a magnetic field to the magnetic material. The object  502  can include a first layer  504  including a first polymeric material and a second layer  506  including a second polymeric material. The second polymeric material of the second layer  506  can include a magnetic material that can be magnetized by the apparatus  500 . In some cases, the particles of the magnetic material may be unaligned before a magnetic field is applied to the second layer  506  of the object  504 . Additionally, although the illustrative example of  FIG. 5  shows that the object  502  includes one layer of the first polymeric material and one layer of the second polymeric material, the object  502  can have at least one layer of the first polymeric material and at least one layer of the second polymeric material. In a particular implementation, the first layer  504  and the second layer  506  can be formed by extruding the first polymeric material and the second polymeric material onto a platform or another substrate. 
     A magnetic field can be generated by a first magnetizing device  508  and/or a second magnetizing device  510 . In an implementation, a magnetic field can be generated by directing current through a first coil  512  of the first magnetizing device  508  and/or directing current through a second coil  514  of the second magnetizing device  510 . The apparatus  500  can also include a first magnetic plate  516  and a second magnetic plate  518 . When a magnetic field is generated by the first magnetizing device  508  and/or the second magnetizing device  510 , the first magnetic plate  516  can have a first polarity and the second magnetic plate  518  can have a second polarity that is opposite the first polarity. In the illustrative implementation of  FIG. 5 , the magnetic field can be generated in a direction indicated by arrow  520 . In this way, the magnetic particles of the second layer  506  can be aligned according to the direction of the magnetic field such that the second layer  506  includes a first portion  522  having the second polarity and a second portion  524  having the first polarity. Thus, the first portion  522  and the second magnetic plate  518  can have the same polarity and the second portion  524  and the first magnetic plate  516  can have the same polarity. Accordingly, when the first portion  522  is proximate to a portion of an additional object including magnetic material having the second polarity, the first portion  522  and portion of the additional object can be repelled from each other. Also, when the first portion  522  is proximate to a portion of an additional object including magnetic material having the first polarity, the first portion  522  and the portion of the additional object can be attracted to each other 
     Additionally, the apparatus  500  can have a first arm  526  and a second arm  528 . The first arm  526  can include a first elbow  530  and a second elbow  532 . Also, the second arm  528  can include a third elbow  534  and a fourth elbow  536 . The first arm  526 , the first elbow  530 , and the second elbow  532  can be used to position the first magnetizing device  508  and the first magnetic plate  516  and the second arm  528 , the third elbow  534 , and the fourth elbow  536  can be used to position the second magnetizing device  510  and the second magnetic plate  518  to apply a magnetic field to a portion of the object  502  that includes magnetic particles. 
     In a particular implementation, the first magnetic plate  516 , the second magnetic plate  518 , the first arm  526 , the second arm  528 , the first elbow  530 , the second elbow  532 , the third elbow  534 , and the fourth elbow  536  can be made of high magnetic permeability materials such as a permalloy. Optionally, a magnetic yoke  538  can be added for connecting the first arm  526  and the second arm  528  to reinforce and stabilize a magnetic field generated by the apparatus  500 . The magnetic yoke  538  can also be made of high magnetic permeability materials such as a permalloy, and can be flexible. 
     The first magnetic device  508  and the second magnetic device  510  can be moved along a rail  540  to be proximate to portions of the second layer  506 . In some cases, a length of the first arm  526 , a rotation of the first elbow  530 , and/or a rotation of the second elbow  532  and a length of the second arm  528 , a rotation of the third elbow  534 , and/or a rotation of the fourth elbow  536  can be controlled to move the first magnetic plate  516  and the second magnetic plate  518  within a specified distance of the second layer  506  to apply a magnetic field to the second layer  506  that is sufficiently strong to magnetize the magnetic particles of the second layer  506 . Additionally, although the illustrative implementation of  FIG. 5  includes multiple magnetizing devices, in other implementations, the apparatus  500  can include a single magnetizing device that has a coil that is coupled to the first magnetic plate  516  and the second magnetic plate  518 . 
     Although, the illustrative example of  FIG. 5  shows the magnetic field being generated in the direction indicated by the arrow  522 , the apparatus  500  can be used to generate a magnetic field in a direction opposite the direction indicated by the arrow  522 . In these situations, the magnetic field can be generated from the first magnetic plate  516  to the second magnetic plate  518  with the first magnetic plate  516  having the second polarity and the second magnetic plate  518  having the first polarity. Also, in these situations, the portions of the second layer  506  can be arranged such that the first portion  522  has the first polarity and the second portion  524  has the second polarity. 
     In the flow diagram of  FIG. 6 , each block represents one or more operations. In some cases, at least a portion of the one or more operations of each block can be performed by an apparatus according to computer-executable instructions processed by a control system of the apparatus. In other cases, at least a portion of the one or more operations of each block can be performed manually. The order in which the blocks are described is not intended to be construed as a limitation, and any number of the described operations can be combined in any order and/or in parallel to implement the processes. 
       FIG. 6  illustrates an example process  600  to form objects including one or more layers of a polymeric material that include a magnetic material. At  602 , the process  600  can include depositing a plurality of layers of a first polymeric material onto a surface of a substrate. In some cases, the plurality of layers of the first polymeric material can be extruded onto the substrate. Additionally, the first polymeric material can be free of magnetic materials. In an implementation, a layer of the plurality of layers of the first polymeric material has a thickness of no greater than about 100 micrometers. 
     At  604 , the process  600  can include depositing at least one layer of a second polymeric material onto at least one layer of the plurality of layers of the first polymeric material. The at least one layer of the second polymeric material can include a magnetic material. In an implementation, the magnetic material can include neodymium particles having a particle size less than 100 micrometers. Also, the at least one layer of the second polymeric material can have a thickness of no greater than about 100 micrometers. Furthermore, at least one of the first polymeric material and the second polymeric material can include an acrylonitirile-butadiene-styrene co-polymer 
     In a particular implementation, a first extrusion process can be used to deposit the plurality of layers of the first polymeric material onto the surface of the substrate and a second extrusion process can be used to deposit the at least one layer of the second polymeric material onto the at least one layer of the plurality of layers of the first polymeric material. In some cases, the first extrusion process and the second extrusion process can have different conditions. For example, the first extrusion process can include applying a temperature included in a range of about 210° C. to about 270° C. to the first polymeric material and the second extrusion process can include applying a temperature included in a range of about 180° C. to about 250° C. to the second polymeric material. 
     At  606 , the process  600  can include magnetizing the magnetic material of the at least one layer of the second polymeric material. In an implementation, a magnetic field can be applied to the magnetic material of the at least one layer of the second polymeric material to magnetize the magnetic material. In an example, one or more magnetizing devices can be moved to be disposed proximate to the magnetic material. A magnetic field can then be generated by directing current through a respective coil of at least one magnetizing device to magnetize the magnetic material. In some cases, the magnetic field can be generated by the apparatus used to deposit the magnetic material onto the substrate. In other cases, a device separate from the apparatus used to deposit the magnetic material onto the substrate can magnetize the magnetic material. 
     In an implementation, the at least one magnetizing device can include a first magnetizing device having a first coil and a second magnetizing device including a second coil. In these implementations, the magnetic material of the at least one layer of the second polymeric material can be magnetized by directing current through the first coil, directing current through the second coil, or directing current through the first coil and the second coil. Additionally, the first magnetizing device can be coupled to a first arm and the second magnetizing device can be coupled to a second arm. Furthermore, the first magnetizing device and the second magnetizing device can be coupled to a single rail in some implementations, or to separate rails in other implementations. Magnetizing magnetic material of a layer of the object can include moving the first magnetizing device and/or the second magnetizing device along at least one rail to a location that is proximate to the magnetic material included in a layer of the object. Also, the first arm and the second arm can be moved to respective locations such that enable magnetic plates of the magnetizing devices can apply a magnetic field to portions of a layer of the object that include magnetic material. 
     In an implementation, the magnetic material can be magnetized such that a first portion of particles of the magnetic material are arranged in a first direction and have a first polarity. Additionally, the magnetic material can also be magnetized such that a second portion of particles of the magnetic material are arranged in a second direction and have a second polarity. The second direction can be opposite the first direction and the second polarity can be opposite the first polarity. In an illustrative example, the first portion of the particles of the magnetic material can have a north pole, while the second portion of the particles of the magnetic material can have a south pole. In a particular implementation, the first plurality of particles and the second plurality of particles can be arranged such that the first plurality of particles are disposed adjacent to the second plurality of particles in a direction substantially perpendicular to the surface of the substrate. In another implementation, the first plurality of particles and the second plurality of particles can be arranged such that the first plurality of particles are disposed adjacent to the second plurality of particles in a direction substantially parallel to the surface of the substrate. 
     EXAMPLE CLAUSES 
     A. A method comprising: disposing a plurality of layers of a first polymeric material onto a surface of a substrate; disposing at least one layer of a second polymeric material onto at least one layer of the plurality of layers of the first polymeric material, the at least one layer of the second polymeric material including a magnetic material. 
     B. The method of clause A, wherein: the plurality of layers of the first polymeric material are deposited onto the substrate using a first extrusion process; and the at least one layer of the second polymeric material is deposited onto the at least one layer of the plurality of layers of the first polymeric material using a second extrusion process. 
     C. The method of clause B, wherein: the first extrusion process includes applying a temperature included in a range of about 210° C. to about 270° C. to the first polymeric material; and the second extrusion process includes applying a temperature included in a range of about 180° C. to about 250° C. to the second polymeric material. 
     D. The method of any one of clauses A-C, further comprising magnetizing the magnetic material of the at least one layer of the second polymeric material. 
     E. The method of clause D, wherein: the magnetic material includes a first plurality of particles having a first polarity and a second plurality of particles having a second polarity; and the method further comprises: arranging the first plurality of particles and the second plurality of particles such that the first plurality of particles are disposed adjacent to the second plurality of particles in a direction substantially perpendicular to the surface of the substrate. 
     F. The method of clause D, wherein: the magnetic material includes a first plurality of particles having a first polarity and a second plurality of particles having a second polarity; and the method further comprises: arranging the first plurality of particles and the second plurality of particles such that the first plurality of particles are disposed adjacent to the second plurality of particles in a direction substantially parallel to the surface of the substrate. 
     G. An apparatus comprising: a first material source for a first polymeric material; a second material source for a second polymeric material, the second polymeric material including a magnetic material; a first extrusion component to deposit a plurality of layers of the first polymeric material onto a surface of a substrate; and a second extrusion component to deposit at least one layer of the second polymeric material onto at least one layer of the plurality of layers of the first polymeric material. 
     H. The apparatus of clause G, further comprising at least one magnetizing device to magnetize the magnetic material of the at least one layer of the second polymeric material. 
     I. The apparatus of clause H, wherein the at least one magnetizing device includes a first magnetizing device having a first coil and a second magnetizing device including a second coil, and the magnetic material of the at least one layer of the second polymeric material is magnetized by directing current through the first coil, directing current through the second coil, or directing current through the first coil and the second coil. 
     J. The apparatus of clause I, further comprising: a first arm coupled to the first magnetizing device; and a second arm coupled to the second magnetizing device. 
     K. The apparatus of clause J, further comprising: at least one rail; and a control system including: one or more processors; and one or more computer storage media storing instructions executable by the one or more processors to perform operations comprising: moving the first arm to a first location and moving the second arm to a second location to magnetize the magnetic material of the at least one layer of the second polymeric material. 
     L. The apparatus of clause K, wherein the at least one rail includes a first rail and a second rail, and the operations moving the first arm along the first rail to the first location and the second arm along the second rail to the second location. 
     M. The apparatus of any one of clauses H-L, further comprising: a first rail, wherein the first extrusion component and the second extrusion component are mounted on the first rail; a second rail, wherein the first magnetizing component is mounted on the second rail; and a third rail, wherein the second magnetizing component is mounted on the third rail. 
     N. The apparatus of any one of clauses H-M, further comprising: a rail, wherein the first extrusion component, the second extrusion component, the first magnetizing component, and the second magnetizing component are mounted on the rail. 
     O. An article comprising: a plurality of layers of a first polymeric material; and at least one layer of a second polymeric material having a magnetic material, wherein the at least one layer of the second polymeric material is disposed on at least one layer of the first polymeric material. 
     P. The article of clause O, wherein the magnetic material includes neodymium particles having a particle size less than 100 micrometers. 
     Q. The article of clause P, wherein: a layer of the plurality of layers of the first polymeric material has a thickness of no greater than about 100 micrometers; and the at least one layer of the second polymeric material has a thickness of no greater than about 100 micrometers. 
     R. The article of clause Q, wherein at least one of the first polymeric material and the second polymeric material include an acrylonitirile-butadiene-styrene co-polymer. 
     S. The article of clause Q or R, wherein: the magnetic material includes a first plurality of particles having a first polarity and a second plurality of particles having a second polarity; and the first plurality of particles are disposed adjacent to the second plurality of particles in a direction substantially parallel to a horizontal plane of the object. 
     T. The article of any one of clauses Q, R, or S, wherein: the magnetic material includes a first plurality of particles having a first polarity and a second plurality of particles having a second polarity; the first plurality of particles are disposed adjacent to the second plurality of particles in a direction substantially perpendicular to a horizontal plane of the object. 
     Furthermore, this disclosure provides various example implementations, as described and as illustrated in the drawings. However, this disclosure is not limited to the implementations described and illustrated herein, but can extend to other implementations, as would be known or as would become known to those skilled in the art. Reference in the specification to “one implementation,” “this implementation,” “these implementations” or “some implementations” means that a particular feature, structure, or characteristic described is included in at least one implementation, and the appearances of these phrases in various places in the specification are not necessarily all referring to the same implementation. 
     Although the subject matter has been described in language specific to structural features and/or methodological acts, the subject matter defined in the appended claims is not limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims. This disclosure is intended to cover any and all adaptations or variations of the disclosed implementations, and the following claims should not be construed to be limited to the specific implementations disclosed in the specification.