Patent Application
20230339024
The device and method disclosed in this document relates to three-dimensional (3D) object printers and, more particularly, to optical systems for laser-assisted drop-on-demand 3D metal object printers.
Unless otherwise indicated herein, the materials described in this section are not admitted to be the prior art by inclusion in this section.
Three-dimensional printing, also known as additive manufacturing, is a process of making a three-dimensional solid object from a digital model of virtually any shape. Many three-dimensional printing technologies use an additive process in which an additive manufacturing device ejects drops or extrudes ribbons of a build material to form successive layers of the part on top of previously deposited layers. Some of these technologies use ejectors that eject UV-curable materials, such as photopolymers or elastomers, while others melt plastic materials to produce thermoplastic material that is extruded to form successive layers of thermoplastic material. These technologies are used to construct three-dimensional objects with a variety of shapes and features. This additive manufacturing method is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling.
Recently, some 3D object printers have been developed that eject drops of melted metal from one or more ejectors to form 3D metal objects. These printers have a source of solid metal, such as a roll of wire, macro-sized pellets, or metal powder, and the solid metal is fed into a heated receptacle of the printer where the solid metal is melted and the melted metal fills the receptacle. The receptacle is made of non-conductive material around which an electrical wire is wrapped to form a coil. An electrical current is passed through the coil to produce an electromagnetic field that causes a drop of melted metal at the nozzle of the receptacle to separate from the melted metal within the receptacle and be propelled from the nozzle. A platform is configured to move in a X-Y plane parallel to the plane of the platform by a controller that operates actuators so that melted metal drops ejected from the nozzle form metal layers of an object on the platform. The controller operates another actuator to alter the position of the ejector or platform to maintain an appropriate distance between the ejector and an existing layer of the metal object being formed. This type of metal drop ejecting printer is called a magnetohydrodynamic (MHD) printer.
While magnetohydrodynamic printing has made great progress, the parts fabricated from conventional magnetohydrodynamic printing systems often exhibit inconsistencies with respect to build strength, adhesion, porosity, surface finish, cracking, fractures, Z-height errors, and the like. In view of the foregoing, secondary or post-printing processes, such as machining and finishing, are often implemented to address the inconsistencies in the objects fabricated from conventional magnetohydrodynamic printing systems. These post-printing processes, however, greatly reduce productivity and correspondingly increase the cost of fabricating the part via magnetohydrodynamic printing.
An additive manufacturing device for fabricating a part is disclosed. The additive manufacturing device comprises a platen having a surface configured to support the part during fabrication of the part. The additive manufacturing device further comprises an ejector head arranged above the surface of the platen. The ejector head is configured to eject droplets of a molten build material toward the surface of the platen to fabricate the part. The additive manufacturing device comprises an optical system having at least one structure configured to redirect light between (i) a first location in a fabrication environment situated between the platen and the ejector head and (ii) a second location.
A method for fabricating a part using an additive manufacturing device is also disclosed. The method comprises ejecting, using an ejector head, droplets of a molten build material toward a platen to fabricate a part within a fabrication environment situated between the platen and the ejector head. The method further comprises redirecting light between a first location within the fabrication environment and at least one second location that is external to the fabrication environment. The redirecting includes at least one reflection of the light. At least one of a light source and a light sensor is positioned at the least one second location. The light includes at least one of (i) light generated by the light source and redirected onto at least one of the part and the droplets, (ii) light reflected from at least one of the part and the droplets and redirected onto the light sensor, and (iii) thermally emitted light from at least one of the part and the droplets and redirected onto the light sensor. The method further comprises at least one of controlling and monitoring at least one characteristic of at least one of the part and the droplets using the at least one of the light source and the light sensor.
The foregoing aspects and other features of the additive manufacturing device are explained in the following description, taken in connection with the accompanying drawings.
For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the embodiments illustrated in the drawings and described in the following written specification. It is understood that no limitation to the scope of the disclosure is thereby intended. It is further understood that the present disclosure includes any alterations and modifications to the illustrated embodiments and includes further applications of the principles of the disclosure as would normally occur to one skilled in the art which this disclosure pertains.
The 3D object printer 100 includes an ejector head 104 and a build platform 106. As used herein, the term “ejector head” refers to the housing and components of a 3D object printer that melt, eject, and regulate the ejection of melted drops of build material for the production of 3D objects. The ejector head 104 includes a body 110 (which may also be referred to as a pump chamber), one or more heating elements 112, and one or more metallic coils 114, which are operably coupled with one another. The heating elements 112 are at least partially disposed about the body 110, and the metallic coils 114 are at least partially disposed about the body 110 and/or the heating elements 112. The body 110 has an inner surface 120 defining an inner vessel 122 thereof. The body 110 defines a nozzle 124 disposed at a first end of the body 110, which extends through an opening defined in a heat shield 132. As used herein, the term “nozzle” means a structure defining an orifice that is fluidically connected to a volume or vessel containing melted build material and that is configured for the expulsion of melted drops of build material from the volume or vessel. The head shield 132 is arranged between the body 110 of the ejector head 104 and the build platform 106. The nozzle 124 has an orifice 134 at an end of the portion thereof that extends through the opening of the heat shield 132, via which the ejector head 104 ejects droplets of build material onto a substrate 116 to fabricate a part 118. As used herein, the term “part” means an object of manufacture made with a 3D metal drop ejecting apparatus.
The build platform 106 comprises at least a platen 128, such as heated platen 128 having a heating element 136, onto which the ejector head 104 ejects droplets of build material to form the part 118. As used herein, the substrate 116 refers the surface upon which the ejector head 104 ejects new droplets of build material. Thus, at least for an initial layer of build material, the substrate 116 refers to a top surface of the platen 128 and, for subsequent layers of material, the substrate 116 refers to a surface of the previously deposited build material and/or a surface of the partially fabricated part 118.
In an exemplary operation of the 3D object printer 100, a build material (e.g., metal) from a source 126 of bulk material (e.g., bulk metal) is directed to the inner vessel 122 of the body 110. As used herein, the term “bulk material” means build material available in aggregate form, such as metal wire of a commonly available gauge, macro-sized metal pellets, and metal powder. As used herein, the term “vessel” means a hollow volume having a receptacle configured to hold a liquid or solid substance. In at least one embodiment, the build material includes one or more metals and/or alloys thereof. The heating elements 112 at least partially melt the build material contained in the inner vessel 122 of the body 110. In particular, the build material may be a solid metal, and the heating elements 112 heat the body 110 and thereby heat the metal from a solid to a liquid (e.g., molten metal). As used herein, the term “metal” means a metal as defined by the periodic chart of elements or alloys formed with these metals. Illustrative metal build materials include, but are not limited to, aluminum, aluminum alloys, brass, bronze, chromium, cobalt-chrome alloys, copper, copper alloys, iron alloys (Invar), nickel, nickel alloys (Inconel), nickel-titanium alloys (Nitinol), stainless steel, tin, titanium, titanium alloys, gold, silver, molybdenum, tungsten, or the like, or alloys thereof, or any combination thereof.
The metallic coils 114 are coupled with a power source (not shown) configured to facilitate the ejection of melted droplets of the build material onto the substrate 116. In particular, the metallic coils 114 and the power source coupled therewith are configured to generate a magnetic field that generates an electromotive force within the body 110 that generates an induced electrical current in the molten metal disposed in the body 110. The magnetic field and the induced electrical current in the molten metal creates a radially inward force on the liquid metal, known as a Lorentz force, which creates a pressure at the nozzle 124. The pressure at the nozzle 124 expels the molten metal through the orifice 134 and out of the nozzle 124 toward the substrate 116 and/or the build platform 106 in the form of one or more droplets to thereby form at least a portion of the part 118.
With continued reference to
The computing system 108 is operably and/or communicably coupled with any one or more of the components of the 3D object printer 100. Particularly, the computing system 108 is at least operably and/or communicably coupled with one or more switches 142 configured to operate the metallic coils 114 to eject melted droplets of the build material onto the substrate 116, as discussed above (e.g., by connecting and disconnecting the metallic coils 114 from the power source).
Additionally, the computing system 108 is operably and/or communicably coupled with actuators 138, 140 configured to move certain components of the 3D object printer 100 independently from one another or together with one another. Particularly, in at least one embodiment, any one or more components of the 3D object printer 100 may move independently with respect to one another. For example, in some embodiments, the ejector head 104 and the platen 128 of the build platform 106 (or any other components of the 3D object printer 100) are configured move independently from one another along an X-axis, a Y-axis, and/or a Z-axis. Similarly, any two or more components of the 3D object printer 100 may be coupled with one another such that the two or more components move with one another. For example, the ejector head 104 may be coupled with one or both of the laser heating system 102 and the optical monitoring system 130 via respective mounts or the like (not shown). In this way, movement or translation of the ejector head 104 along the X-axis, the Y-axis, and/or the Z-axis results in a corresponding movement or translation of the laser heating system 102 and/or the optical monitoring system 130 along the X-axis, the Y-axis, and/or the Z-axis, respectively.
In some embodiments, the computing system 108 is configured to the operate actuator(s) 138 to move the ejector head 104 at least along the Z-axis. Particularly, in one embodiment, the ejector head 104 is movably mounted within Z-axis tracks or a similar mechanism (not shown) configured for movement of the ejector head 104 (and any other components fixedly mounted thereto) relative to the platen 128 of the build platform 106. The actuator(s) 138 are configured to move the ejector head 104 along the Z-axis by way of the Z-axis tracks. The computing system 108 operates these actuator(s) 138 to maintain an appropriate distance in the Z-direction between the orifice 134 of the nozzle 124 and the substrate 116. In further embodiments, the ejector head 104 is similarly configured to also move along the X-axis and/or the Y-axis.
In some embodiments, the computing system 108 is configured to the operate actuator(s) 140 to move at least the platen 128 of the build platform 106 along an X-Y plane defined by the X-axis and the Y-axis. Particularly, in one embodiment, the platen 128 is movably mounted within X-axis and Y-axis tracks or similar mechanisms (not shown) configured for movement of the platen 128 (and any other components fixedly mounted thereto) relative to the ejector head 104. The actuator(s) 140 are configured to move the platen 128 of the build platform 106 along the X-Y plane by way of the X-axis and Y-axis tracks. The computing system 108 operates these actuator(s) 140 to provide the necessary X-Y positioning of the substrate 116 with respect to the orifice 134 of the nozzle 124. In further embodiments, the platen 128 of the build platform 106 is similarly configured to also move along the Z-axis.
In an exemplary operation of the 3D object printer 100, in order to fabricate the part 118, the computing system 108 operates the actuator(s) 138 to position the orifice 134 of the nozzle 124 over the substrate 116 at a defined distance from in the Z-direction the substrate 116 (e.g., between 4 mm and 8 mm). Next, the computing system 108 operates the switches 142 to cause the nozzle 124 to eject molten metal droplets of onto the substrate 116 to begin forming the part 118. Simultaneously or sequentially with ejecting the molten metal droplets, the computing system 108 also operates the actuators 140 to move the platen 128 of the build platform 106 in the X-Y plane to, thereby, form swaths or layers of melted metal on the substrate 116 to form the part 118. As each layer of metal is deposited onto the substrate 116, the computing system 108 operates the actuator(s) 138 to maintain an appropriate distance in the Z-direction between the orifice 134 and the substrate 116. (e.g., between 4 mm and 8 mm). In alternate configurations, the computing system 108 may similarly move the ejector head 104 in the X-Y plane or move the move the platen 128 along the Z-axis.
In the exemplary operation of the 3D object printer 100, the computing system 108 requires data from external sources to facilitate the fabrication the part 118. In general, a three-dimensional model or other digital model of the part 118 that is to be fabricated is stored in a memory operatively connected to the computing system 108. In one embodiment, the computing system 108 is configured to access the digital model through a server or the like, a remote database in which the digital model is stored, or a computer-readable medium in which the digital model is stored. In one embodiment, the computing system 108 (or another processor or controller) processes the digital model to generate machine instructions for execution by the computing system 108 in a known manner to operate the components of the 3D object printer 100 to form the part 118 corresponding to the model. The generation of the machine instructions can include the production of intermediate models, such as when a CAD model of the device is converted into an STL data model, a polygonal mesh, or other intermediate representations, which in turn can be processed to generate machine instructions, such as g-code, for fabrication of the object by the 3D object printer 100. As used herein, the term “machine instructions” means computer language commands that are executed by a computer, microprocessor, or controller to operate components of a 3D object additive manufacturing system. The computing system 108 executes the machine instructions to control the ejection of the melted metal drops from the nozzle 124, to control the positioning of the platen 128, and to control the positioning of the ejector head 104, as discussed above.
As mentioned above, the 3D object printer 100 advantageously includes a laser heating system 102. It should be appreciated that forming structures with molten metal droplets is a complex thermo-fluidic process that involves re-melting, coalescence, cooling, and solidification. Voids and cold lap (lack of fusion) are caused by poor re-melting and insufficient metallurgical bonding under inappropriate temperatures at the interface formed between the molten metal droplets and previously deposited material or substrates (e.g., droplets). This interfacial temperature is primarily a function of the droplet temperature and the surface temperature of the previously deposited material or substrate. Obtaining and retaining accurate part shape and Z-height are also negatively impacted by the same factors. An interfacial temperature that is too low results in the formation of voids and cold laps from insufficient re-melting and coalescence. Conversely, if the interfacial temperature is too high, the new droplets flow away from the surface of previously deposited material before solidification, which leads to the malformation of part shape and Z-height error.
The interfacial temperature can be managed by controlling the initial droplet temperature, the build part surface temperature, the build plate temperature, drop frequency, and part Z-height. These factors can be controlled at some level through process parameter optimization, but the thermal processes involved may be too slow to keep up with the changes and dynamics that occur during part printing that can result in unacceptable interfacial temperatures.
To address the aforementioned issues, the computing system 108 is configured to operate the laser heating system 102 to modify interfacial temperatures and/or temperature gradients of a substrate and/or an area proximal the substrate to control grain size, growth, and/or structure of the metal forming the part 118. For example, in one embodiment, the laser heating system 102 is operated to modify interfacial temperatures and/or temperature gradients of ejected molten metal on the substrate 116 to control grain size, growth, and/or structure of the metal forming the part 118, thereby improving build strength, adhesion, porosity, and/or surface finish, and preventing cracks and fractures in the article.
With continued reference to
The laser(s) 144 of the laser heating system 102 may include any suitable laser that is configured to sufficiently heat the substrate 116 and/or an area proximal the substrate 116. In at least one embodiment, the type of the laser(s) 144 utilized may be at least partially dependent on the build material, such as the type of metal being deposited to fabricate the article 118. In another embodiment, the type of the laser(s) 144 utilized at least partially depends on a rate at which the drops are deposited on the substrate 116 or the deposition rate. In at least some embodiments, the laser(s) 144 are configured to generate a thin pencil-like laser beam with a diameter of, for example 0.5 mm. In at least some embodiments, the laser(s) 144 are configured to generate a diffraction limited laser beam (low beam parameter product (BPP)). In one embodiment, the laser(s) 144 include a fiber laser. For example, commercially available 1070 nm fiber lasers can provide high power, low divergence beam, beam profile shaping, and CW/Pulse modulation. A 1070 nm, 0.5 mm diameter fiber laser beam has a depth of focus of 168 mm or more.
In an exemplary embodiment, the laser(s) 144 may have an irradiance of from about 1 W/cm2 to about 1 MW/cm2. It should be appreciated that much lower power lasers or laser arrays could also be used depending on the application, metal, configuration and spot size. It should further be appreciated that any one or more of the lasers 144 may include a combination of power and optical configurations, including collimated and non-collimated lasers, that may achieve the desired irradiance.
The computing system 108 is configured to operate the laser heating system 102 to heat at least a portion of the substrate 116 and/or an area proximal the substrate 116. For example, the laser heating system 102 is configured to heat at least a portion of the platen 128, a portion of the part 118, respective surfaces thereof, and/or areas proximal thereto. The laser heating system 102 may heat the portion of the substrate 116 before, during, and/or after deposition of the one or more drops of the molten metal on the substrate 116 and/or an area proximal the substrate 116.
In an exemplary embodiment, the laser heating system 102 heats a portion of the substrate 116 corresponding to the deposition of melted drops and/or the melt pool, before and/or during the deposition of the drops on the substrate 116. It should be appreciated that the deposition of the drops on the substrate 116 may create or form a melt pool on the substrate 116, and the laser heating system 102 is configured to at least partially modulate (e.g., increase, decrease, alter, etc.) an interfacial temperature or a temperature gradient of the melt pool to thereby control one or more properties of the resulting solid metal forming the part 118. For example, modulating the temperature gradient of the melt pool may allow the 3D object printer 100 to control a grain size, grain growth, grain structure, grain orientation, and/or grain boundaries, of the resulting solid metal forming the part 118. It should be appreciated that metal grain formation, structure, and/or properties (e.g., size, growth, orientation, boundaries, etc.) may at least partially determine one or more mechanical properties of the resulting portion of the part 118. For example, the grain formation and/or structure may at least partially determine a yield stress, ductility, hardness, fatigue life, or combinations thereof, of the resulting solid metal forming the part 118. As such, the laser heating system 102 is configured to at least partially heat the portions of the substrate 116 to thereby controls one or more properties of the solid metal forming the part 118.
In some embodiments, the computing system 108 is configured to operate the laser heating system 102 to heat a portion of the substrate 116 that is adjacent or proximal the deposition of melted drops and/or the melt pool. For example, the laser heating system 102 is configured to at least partially heat a portion of the substrate 116 adjacent to or outside of the deposition of melted drops and/or the melt pool. It should be appreciated that heating the portion of the substrate 116 near, proximal, or adjacent the deposition of the drops and/or the melt pool may reduce surface roughness and/or provide improved surface finishing capabilities as compared to a surface without heating from the targeted hearing system 102.
In some embodiments, the computing system 108 is configured to operate the laser heating system 102 to reheat or re-melt a previously deposited drop or section of the part 118 to control the interfacial temperature and/or temperature gradient of the melt pool as the molten metal drops and the previously deposited metals are coalescing to thereby improve the mechanical and/or build qualities of the part 118. It should be appreciated that an amount of heat or thermal energy needed to sufficiently control the temperature gradient of the melt pool may be minimal as a temperature of the part 118 and/or the melt pool or the coalescing region thereof is already maintained at a relatively high temperature. As such, the laser heating system 102 may be cost effectively operated and provide sufficient thermal energy to control the temperature gradient of the melt pool. It should further be appreciated that the laser heating system 102 may be operated in an on-line manner such that productivity is not reduced. For example, the laser heating system 102 may be operated alongside the other components of the 3D object printer 100 to provide articles 118 with improved properties and without an off-line secondary or post-printing process.
In some embodiments, the laser heating system 102 directly heats an area having a diameter of from about 0.025 mm to about 2.0 mm. For example, the output (e.g., laser beam) of the laser heating system 102 may have a diameter or a major axis of from about 0.025 mm to about 2.0 mm.
In some embodiment, the computing system 108 is configured to operate the laser heating system 102 such that the substrate 116, the area proximal the substrate 116, and/or near the part 118 being fabricated is maintained at a temperature of from about 200° C. to about 600° C. It should be appreciated that all or substantially all the components of the laser heating system 102 is configured to operate in the temperatures of the substrate 116, the area proximal the substrate 116, and/or near the part 118. It should be appreciated that the droplet and substrate temperatures will be different for different metals.
In some embodiments, the computing system 108 is configured to operate the laser heating system 102 to heat the substrate 116 and/or the area proximal the substrate 116 to a temperature of at least about 60% to about 100% of a melting point of the build material. For example, the laser heating system 102 is configured to heat the substrate 116 and/or the area proximal the substrate 116 to a temperature of at least about 95% of the melting point of the build material. In another example, the laser heating system 102 is configured to increase a temperature of the substrate 116 and/or the area proximal the substrate 116 (e.g., a coalescence area or melt pool) about ±10% of a melting point of the build material.
As mentioned above, the 3D object printer 100 advantageously includes an optical monitoring system 130. The optical monitoring system 130 may, for example, include one or more illuminators and/or one or more sensors configured to measure droplet temperatures, build part temperatures, build plate temperatures, substrate temperatures, build part shape, build part Z-height, droplet size, droplet rate, or the like, or any combination thereof. These measurements may enable various types of feedback control to be implemented by the computing system 108. Particularly, in some embodiments, the optical monitoring system 130 is configured to communicate with the computing system 108 to provide feedback measurements. In some embodiments, the computing system 108 operates the components of the 3D object printer 100 with reference to the feedback measurements in a closed-loop manner. Additionally, these measurements enable the computing system 108 to monitor the operation of the 3D object printer 100 for conditions that may result in a printed object 118 having inferior quality, such as non-uniform drop ejection (also referred to as drop jitter).
Additionally, in the illustrated embodiments, the optical monitoring system 130 includes an optical sensor 148. The optical sensor 148 is a sensor configured to receive reflected light and/or thermally emitted light (i.e., thermal radiation) from the fabrication environment of the 3D object printer 100, for example light reflected from and/or thermal radiation emitted from the substrate 116 or from melted droplets as they are ejected from the nozzle 124. This optical sensor 148 can serve a variety of purposes, including measuring droplet temperatures, build part temperatures, build plate temperatures, substrate temperatures, build part shape, build part Z-height, droplet size, droplet rate, or the like. To this end, the optical sensor 148 may, for example, comprise a pyrometer, an imaging camera, a photodiode, infrared sensors, or the like, or combinations thereof. In some embodiments, the optical monitoring system 130 comprises a plurality of optical sensors 148 of various types and purposes. In addition, it should be appreciated that the sensors of the optical monitoring system 130 are not limited only to optical sensors and may include additional sensors for measuring various other aspects of the operation of the 3D object printer 100.
It will be appreciated that the type of light generated by the optical illuminator 146 will vary depending on the type of the optical illuminator 146 and depending on the purpose of the illumination. Accordingly, the beam of light 150 may, for example, comprise visible light, ultra-violet light, infrared light, or even a laser beam. In the illustration of
In some embodiments, the optical illuminator 146 may be omitted from optical monitoring system 130 and the optical sensors 148 may be configured to only measure thermally emitted light (i.e., thermal radiation) from the fabrication environment of the 3D object printer 100. Particularly, it will be appreciated by those of ordinary skill in the art that some characteristics of the droplets or the ejection process, such as temperature, can be measured without any optical illumination.
In some embodiments, the computing system 108 is configured to operate the optical illuminator 146 to shine light into the fabrication environment of the 3D object printer 100 and operates the optical sensor 148 to measure droplet temperatures, build part temperatures, build plate temperatures, substrate temperatures, build part shape, build part Z-height, droplet size, droplet rate, or the like.
Although not illustrated in
It should be appreciated that, in many embodiments of the 3D object printer 100, there are significant spatial and structural constraints that make it challenging to provide a direct optical path for the ingoing and outgoing light between the target location and optical devices of the laser heating system 102 and the optical monitoring system 130. For instance, in many embodiments, the 3D object printer 100 operates with a very small distance between the substrate 116 and the head shield 132 of the ejector head 104, e.g., between 4 mm and 8 mm, leaving little space to suitably arrange the optical devices to provide a direct optical path to and from the target location. Additionally, in many embodiments, the structure of the ejector head 104 is also quite wide (e.g., the heat shield 132 may be greater than 50 mm wide) such that it obstructs arranging the optical devices to provide a direct optical path that has a low angle of incidence (AOI) with a target location on the surface of the substrate 116 (e.g., less than 80 degrees). As used herein, angles of incidence of a light beam with a surface are measured relative to an orthogonal incidence with the surface (i.e., a 0° angle of incidence refers to an incidence of the light beam with that is parallel with the surface normal).
As a result, in such embodiments, the only arrangement of the optical devices of the laser heating system 102 and the optical monitoring system 130 to provide direct optical path is one in which the light beam has a very high, near glancing, angle of incidence with the target location.
To overcome these challenges, one or both of the laser heating system 102 and the optical monitoring system 130 include respective optical systems having at least one structure configured to guide or redirect the light beam of the optical device 160 between the target location with the fabrication environment and the location at which the optical device 160 is arranged. The structures of the optical system may comprise any structure configured to reflect, refract, shape, or focus a light beam generated by a light source and/or reflected or thermally emitted from the target location. Examples of such structures include transparent material bodies, such as prisms, optical rods, light guides, optical lenses, optical filters and the like, as well as optically reflective bodies, such as mirrors and other structures having reflective coatings or layers. It should be appreciated that the terms “transparent” and “reflective” are used with respect to the particular light beam with which the structure is utilized. Particularly, as used herein with respect to the structures of the optical system, the term “transparent” means that the material or structure allows for transmission of light therein at the frequency/wavelength of the light beam with which the structure is utilized. Likewise, as used herein with respect to the structures of the optical system the term “reflective” means that the material or structure reflects light at the frequency/wavelength of the light beam with which the structure is utilized.
By way of the below examples, it should be understood that an arbitrary combination and arrangement of optical structures can be combined to guide light beam(s), such as laser beams, illumination beams, reflected light beams, thermal radiation, etc., as necessary according the structural and spatial constraints of the 3D object printer 100. Essentially similar optical structures can be utilized to guide light into the fabrication environment and out of the fabrication environment, regardless of the type of light or the purpose of the light.
In at least some embodiments, the optical system of the laser heating system 102 or of the optical monitoring system 130 includes at least one transparent rod via which the light beam travels along a longitudinal axial direction thereof. In general, the transparent rod is configured to receive the light beam from the optical device 160 or provide the light beam to the optical device 160 at a first end. The light beam travels through the transparent rod along the longitudinal axial direction from the first end to a second end. The light beam exits or enters the transparent rod at the second end. In at least some embodiments, the second end of the first transparent rod has an angled end face with an angle relative to the longitudinal axis of the transparent rod. The angle of the angled end face is configured to cause a total internal reflection (TIR) of the light beam such that the light beam is redirected with respect to the longitudinal axis and exits or enters via a side surface of the second end that is proximate to angled end face.
The first end 208 of the body 206 receives a light beam 212 from the optical device 160 and/or provides the light beam 212 to the optical device 160 (not shown). The second end 206 has an angled end face 204 with an angle relative to the longitudinal axis of the elongated body 206. The angle of the angled end face 204 is configured to cause a total internal reflection (TIR) of the light beam 212 such that the light beam 212 is redirected with respect to the longitudinal axis. The light beam 212 travels between a target location 216 on the substrate 116 and enters or exits the transparent rod 202 via a side surface 214 of the second end 210 that is proximate to angled end face 204. In at least one embodiment, the angle of the angled end face 204 relative to the longitudinal axis of the elongated body 206 is about 45°, such that the light beam is redirected at an angle which is orthogonal to the longitudinal axis of the elongated body 206 (i.e., with a reflection that is about 90°).
In at least some embodiments, the transparent rod 202 has a rotation such that the angled end face 204 is oriented to reflect the light beam 212 such that the light beam 212 reaches or is reflected or thermally emitted from the target location with a non-zero angle of incidence. In the illustrated embodiment, the transparent rod 202 has a rotation such that the light beam 212 reaches or is reflected or thermally emitted from the target location 216 with an angle of incidence of about 45°.
In at least some embodiments, a portion of the outer surface the elongated body 206, in particular the side surface 214 from which that the light beam 212 exits or enters the transparent rod 202, has a different shape or radius of curvature than the rest of the outer surface of the body 206. Particularly,
In a further embodiment, a portion of the outer surface the elongated body 206, in particular the side surface 214 from which that the light beam 212 exits or enters the transparent rod 202, has a radius of curvature that is configured to partially focus the light beam in the plane of incidence, thereby circularizing the beam footprint for a non-zero angle of incidence. Particularly,
With reference to
In the illustrated embodiment, the target location of the light beam 212 is a location at or near where the molten metal droplets are deposited and is accordingly, in alignment with the orifice 134 of the nozzle 124 in the X-direction and Y-direction and located at a predetermined distance from the orifice 134 in the Z-direction. Accordingly, as shown in
Although not illustrated in the
The first end 308 of the body 306 receives a light beam 312 from the optical device 160 and/or provides the light beam 312 to the optical device 160 (not shown). The second end 306 has an angled end face 304 with an angle relative to the longitudinal axis of the elongated body 306. The angle of the angled end face 304 is configured to cause a total internal reflection (TIR) of the light beam 312 such that the light beam 312 is redirected with respect to the longitudinal axis. The light beam 312 travels between a target location 316 on the substrate 116 and enters or exits the transparent rod 302 via a side surface 314 of the second end 310 that is proximate to angled end face 304.
However, in at least one embodiment, in contrast to the transparent rod 202 discussed above, the angle of the angled end face 304 relative to the longitudinal axis of the elongated body 306 is less than about 45° (e.g., about 30°), such that the light beam 312 is redirected at an angle which is non-orthogonal to the longitudinal axis of the elongated body 306 (i.e., with a reflection that less than about 90°). In at least one embodiment, the light beam 312 is redirected at an angle which is obtuse with respect to a direction of travel of the light beam 312 within the elongated body 306. As a result of the obtuse reflection angle, the light beam 312 exits or enters the body 306 through the side surface 314 of the second end 310 with a non-zero angle of incidence with the side surface 314. Accordingly, the light beam 312 is refracted as it exits or enters the transparent rod 302. Since the refractive index of the material of the body 306 is generally greater than that of the surrounding air, the refraction of the light beam is generally such that the angle of the light beam 312 becomes closer to parallel to the longitudinal axis of the transparent rod 302. In this way, the angle of incidence of the light beam 312 with the target location 316 on or proximate to the substrate 116 depends on the angle of the angle of the angled end face 304, as well as the refractive index of the material of the body 306. This is in contrast with the transparent rod 202 discussed above, which achieves a non-zero angle of incidence by rotation of the transparent rod 202. In the illustrated embodiment, the angle of the angled end face 304 and the refractive index of the material of the body 306 are such that the light beam 312 reaches or is reflected or thermally emitted from the target location 316 with an angle of incidence of about 45°.
In at least some embodiments, a portion of the outer surface the elongated body 306, in particular the side surface 314 from which that the light beam 312 exits or enters the transparent rod 302, has a different shape or radius of curvature than the rest of the outer surface of the body 306. Particularly, the side surface 314 may be shaped in such a manner as to shape the light beam 312 to have a circular beam footprint at the target location with a particular non-zero angle of incidence (e.g., about 45°).
As in other illustrated embodiments, the target location of the light beam 312 is in alignment with the orifice 134 of the nozzle 124 in the X-direction and Y-direction and located at a predetermined distance from the orifice 134 in the Z-direction. Thus, as shown in
Although not illustrated in the
In some embodiments, the optical system of the laser heating system 202 includes multiple transparent rods that are optically and mechanically connected together with one or more transparent joints. Each transparent joint of the optical system has body that includes at least one angled surface configured cause at least one total internal reflection (TIR) of the light beam within transparent joint that redirects the light beam from an end of a transparent rod to an end of another transparent rod that is arranged at a different angle or direction. It should be appreciated that the multiplicity of transparent rods and transparent joints can be manufactured together as a single part or subsequently joined together using a suitable technique. With reference to
By way of the above examples, it should be understood that an arbitrary number of transparent rods and transparent joints of various configurations can be combined to operate as a light guide that navigates light beam(s), such as laser beams, illumination beams, reflected light beams, thermal radiation, etc., as necessary according the structural and spatial constraints of the 3D object printer 100. In some embodiments, the transparent rods of the optical system can be configured to periscope through the other structures of the 3D object print 100 (e.g., periscope through the heat shield 132 via small vertical opening).
In at least some embodiments, the optical system of the laser heating system 102 includes at least one reflective rod via which the light beam is reflected. In general, the reflective rod has a first end with an angled end face, which has a reflective coating or is otherwise composed of a reflective material. The optical device 160 is arranged or the light beam thereof is directed such that the light beam is output toward the angled end face of the reflective rod. The light beam is reflected by the angled end face of the reflective rod to, thereby, redirect the light beam toward a target location on or proximate to the substrate 116. In at least some embodiments, the angle of the angled end face relative to a longitudinal axis of the reflective rod is about 45 degrees, such that the light beam is reflected at an angle which is orthogonal to a longitudinal axis of the reflective rod when the light beam travels parallel to or colinear with the longitudinal axis to reach the angled end face.
The angle of the angled end face 504 is configured to reflect a light beam 512 such that the light beam 512 is redirected toward or received from a target location 516 on the substrate 116. In at least one embodiment, the angle of the angled end face 504 relative to the longitudinal axis of the elongated body 506 is about 45°, such that the light beam 512 is reflected between an optical path that is orthogonal to the longitudinal axis of the elongated body 506 and an optical path that is parallel to or colinear with the longitudinal axis to reach the angled end face 516 (i.e., a reflection that is about 90°).
In at least some embodiments, the reflective rod 502 has a rotation such that the angled end face 504 is oriented to reflect the light beam 512 such that the light beam 512 reaches or is reflected from the target location with a non-zero angle of incidence. In the illustrated embodiment, the reflective rod 502 has a rotation such that the light beam 512 reaches or is reflected from the target location 516 with an angle of incidence of about 45°.
In at least some embodiments, angled end face 504 may have shape or radius of curvature that is configured to shape the light beam 512 to have a circular beam footprint at the target location with a particular non-zero angle of incidence (e.g., about) 45°, in a similar manner as discussed above with respect to
With reference to
As in other illustrated embodiments, the target location of the light beam 312 is in alignment with the orifice 134 of the nozzle 124 in the X-direction and Y-direction and located at a predetermined distance from the orifice 134 in the Z-direction. Thus, as shown in
Although not illustrated in the
As noted above, in at least some embodiments, the structures of the optical system are at least partially embedded within a component of the ejector head 104 or within any other component of the 3D object printer 100. Particularly, contamination of the structures of the optical system is often a concern with designing the 3D object printer 100. The surfaces of the structures of the optical system could be exposed to ejected metal droplets, ejected metal satellites, metal splattering from build part and metal sputtering, or metal evaporation from build part 118.
The rod 602 is embedded within the heat shield 132 by way of a bore 604 or channel that is drilled or otherwise defined in the heat shield 132. The bore 604 is suitably dimensioned and shaped to accommodate the body of the rod 602. In embodiments having multiple rods, multiple bores or other corresponding voids are defined in the heat shield 132 and/or other components of the ejector head 104 to accommodate each component of the optical system.
In the embodiments in which the rod 602 is a transparent rod, a light beam 612 exits or enters the rod 602 from a side surface, in the same manner discussed above with respect to the transparent rod 202 and the transparent rod 302. A narrow bore 606 or channel is drilled or otherwise defined in the heat shield 132 to connect the bore 604 with an opening 608 defined in a bottom surface of the heat shield 132 that faces the platen 128. The light beam 612 travels from the side surface of the rod 602 via the narrow bore 606, exits or enters the heat shield 132, and travels toward the target location on or proximate to the substrate 116.
Similarly, in embodiments in which the rod 602 is a reflective rod, the laser (not shown) is arranged to output the light beam 612 through the bore 604 toward the reflective angled end face of the rod 602 or receive the light beam 612 from the reflective angled end face via the bore 604. The light beam 612 is reflected by the reflective angled end face of the rod 602, in the same manner discussed above with respect to the reflective rod 502. The light beam 612 travels between reflective angled end face of the rod 602 and the target location on or proximate to the substrate 116 via the narrow bore 606. In this way, the rod 602 and any other structures of the optical system are protected from exposure to metal contamination.
The narrow bore 606 is sized to accommodate the width of the light beam 612 and is angled to accommodate the angle at which the light beam 612 travels between the rod 602 and the target location on or proximate to the substrate 116. In general, the narrow bore 606 is sized to provide some tolerance with respect to the angle, alignment, and size of the light beam 612. However, in a practical implementation, mechanical adjustments may be required to compensate for fabrication and assembly tolerances and accurately orient the rod 602 with respect to the target location.
In one embodiment, in order to accommodate such mechanical adjustments, the laser heating system 102 includes one or more actuators (not shown) configured to rotate the rod 602 within the bore, or reposition the rod 602 longitudinally within the bore 604. These actuators can be operated manually by hand or controlled electronically by the computing system 108. By adjusting the rod 602 axially and/or longitudinally, the actuator(s) provide mechanical degrees of freedom to accurately orient the rod 602 with respect to the target location, even in the presence of fabrication and assembly tolerances.
As mentioned above, an optical device, such as the laser 144 of the laser heating system 102, the optical illuminator 146 of the optical monitoring system 130, or the optical sensor 148 of the optical monitoring system 130, is suitable coupled with or arranged with respect to the structures of the optical systems as necessary to project light into the fabrication environment or receive light reflected or thermally emitted from the fabrication environment. In some embodiments, the optical devices are coupled with the structures of the optical systems with one or more of a collimator, beam expansion optics, a focusing lens, an optical isolator, and folding optics. Below, several arrangements are described for coupling a light source, such as the laser 144 or the optical illuminator 146, with various optical systems and structures. However, it will be appreciated by those of skill in the art that essentially similar arrangements can be utilized to couple a light receiver, such as the optical sensor 148, with the various optical systems and structures.
The method 900 begins with ejecting droplets of a molten build material to fabricate a part within a fabrication environment (block 910). Particularly, the computing system 108 operates the actuator(s) 138 to position the orifice 134 of the nozzle 124 over the substrate 116 at a defined distance from in the Z-direction the substrate 116 (e.g., between 4 mm and 8 mm). Next, the computing system 108 operates the switches 142 to cause the nozzle 124 to eject molten metal droplets of onto the substrate 116 to begin forming the part 118. Simultaneously or sequentially with ejecting the molten metal droplets, the computing system 108 also operates the actuators 140 to move the platen 128 of the build platform 106 in the X-Y plane to, thereby, form swaths or layers of melted metal on the substrate 116 to form the part 118. As each layer of metal is deposited onto the substrate 116, the computing system 108 operates the actuator(s) 138 to maintain an appropriate distance in the Z-direction between the orifice 134 and the substrate 116. (e.g., between 4 mm and 8 mm). In alternate configurations, the computing system 108 may similarly move the ejector head 104 in the X-Y plane or move the move the platen 128 along the Z-axis.
Next, the method 900 continues with providing a light source and/or a light sensor that is positioned at at least one second location that is external to the fabrication environment (block 920). Particularly, the 3D object printer 100 is provided with one or both of the laser heating system 102 and the optical monitoring system 130. The laser heating system 102 includes at least one laser 144 configured to generate at least one laser beam. The optical monitoring system 130 includes at least one optical illuminator 146 configured to generate at least one light beam and at least one optical sensor 148 configured to receive and measure at least one reflected light beam and/or emitted thermal radiation.
Next, the method 900 continues with redirecting light between a first location in the fabrication environment and the at least one second location, the redirecting including at least one reflection of the light (block 930). Particularly, light is redirected by reflection using at least one structure of at least one optical system between a target location within the fabrication environment and the location(s) at which optical devices are situated external to the fabrication environment. The optical systems and structures used to redirect the light may include any of the optical systems, optical structures, transparent rods, reflective rods, discussed or suggested herein. In at least some embodiments, the light includes light generated by the laser 144 and/or the optical illuminator 146 and redirected onto a target location on the part 118 and/or the droplets of build material as they are ejected toward the platen 128. In at least some embodiments, the light includes light reflected and/or thermally emitted from a target location on the part 118 and/or the droplets of build material as they are ejected toward the platen 128, which is redirected onto the optical sensor 148.
Finally, the method 900 continues with controlling and/or monitoring at least one characteristic of the part and/or the droplets using the light source and/or the light sensor (block 940). Particularly, the computing system 108 is configured to operate the laser heating system 102 to heat at least a portion of the substrate 116 and/or an area proximal the substrate 116. In at least some embodiments, the laser heating system 102 heats a portion of the substrate 116 to control one or more characteristics or properties of the solid metal forming the part 118. In some embodiments, the computing system 108 is configured to operate the laser heating system 102 to reheat or re-melt a previously deposited drop or section of the part 118 to control the interfacial temperature and/or temperature gradient of the melt pool as the molten metal drops and the previously deposited metals are coalescing to thereby improve the mechanical and/or build qualities of the part 118.
Additionally, in some embodiments, the computing system 108 is configured to operate the optical illuminator 146 to shine light into the fabrication environment of the 3D object printer 100 and operates the optical sensor 148 to measure droplet temperatures, build part temperatures, build plate temperatures, substrate temperatures, build part shape, build part Z-height, droplet size, droplet rate, or the like. These measurements enable various types of feedback control to be implemented by the computing system 108. Particularly, in some embodiments, the optical monitoring system 130 is configured to communicate with the computing system 108 to provide feedback measurements. In some embodiments, the computing system 108 operates the components of the 3D object printer 100 with reference to the feedback measurements in a closed-loop manner. Particularly, in some embodiments, the computing system 108 operates the nozzle 124 with reference to the feedback measurements to control characteristics of the droplets of molten material ejected from the nozzle 124. Additionally, in some embodiments, the computing system 108 operates the laser heating system 102 with reference to the feedback measurements to control temperature characteristics of the part 118.
As used throughout, ranges are used as shorthand for describing each and every value that is within the range. Any value within the range may be selected as the terminus of the range. In addition, all references cited herein are hereby incorporated by reference in their entireties. In the event of a conflict in a definition in the present disclosure and that of a cited reference, the present disclosure controls.
Additionally, all numerical values are “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art. It should be appreciated that all numerical values and ranges disclosed herein are approximate values and ranges, whether “about” is used in conjunction therewith. It should also be appreciated that the term “about,” as used herein, in conjunction with a numeral refers to a value that may be ±0.01% (inclusive), ±0.1% (inclusive), ±0.5% (inclusive), ±1% (inclusive) of that numeral, ±2% (inclusive) of that numeral, ±3% (inclusive) of that numeral, ±5% (inclusive) of that numeral, ±10% (inclusive) of that numeral, or ±15% (inclusive) of that numeral. It should further be appreciated that when a numerical range is disclosed herein, any numerical value falling within the range is also specifically disclosed.
As used herein, the term “or” is an inclusive operator, and is equivalent to the term “and/or,” unless the context clearly dictates otherwise. The term “based on” is not exclusive and allows for being based on additional factors not described, unless the context clearly dictates otherwise. In the specification, the recitation of “at least one of A, B, and C,” includes embodiments containing A, B, or C, multiple examples of A, B, or C, or combinations of A/B, A/C, B/C, A/B/B/B/B/C, A/B/C, etc. In addition, throughout the specification, the meaning of “a,” “an,” and “the” include plural references. The meaning of “in” includes “in” and “on.”
While the disclosure has been illustrated and described in detail in the drawings and foregoing description, the same should be considered as illustrative and not restrictive in character. It is understood that only the preferred embodiments have been presented and that all changes, modifications and further applications that come within the spirit of the disclosure are desired to be protected.
