Patent Application
20230173585
This disclosure is directed to three-dimensional (3D) object printers that eject melted metal drops to form objects and, more particularly, to the formation of metal support structures with the ejected metal used to form objects in such printers.
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 a vessel in 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 operating actuators so 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 a constant 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.
In the 3D object printing systems that use elastomer materials, temporary support structures are formed by using an additional ejector to eject drops of a different material to form supports for overhang and other object features that extend away from the object during formation of the object. Because these support structures are made from materials that are different than the materials that form the object they can be designed not to adhere or bond well with the object. Consequently, they can be easily separated from the object feature that they supported during object manufacture and removed from the object after object formation is finished. Such is not the case with metal drop ejecting systems. If the melted metal used to form objects with the printer is also used to form support structures, then the support structure bonds strongly with the features of the object that need support while they solidify. Consequently, a significant amount of cutting, machining, and polishing is needed to remove the supports from the object. Coordinating another metal drop ejecting printer using a different metal is difficult because the thermal conditions for the different metals can affect the build environments of the two printers. For example, a support structure metal having a higher melting temperature can weaken or soften the metal forming the object or a support metal structure having a lower melting temperature than the object can weaken when the object feature made with the higher temperature melted metal contacts the support structure. Being able to form support structures that enable metal drop ejecting printers to form metal object overhangs and other extending features would be beneficial.
A new method of operating a 3D metal object printer forms support structures that do not adhere tightly to object features supported by the structures. The method includes detecting a portion of a support structure layer to be formed with an ejector head configured to eject melted metal drops through a nozzle toward a planar member, and operating a magnetic field generator to generate a magnetic field through which the ejected melted metal drops pass before being received at the planar member.
A new 3D metal object printer forms support structures that do not adhere tightly to object features supported by the structures. The new 3D metal object printer includes an ejector head configured to eject melted metal drops through a nozzle, an magnetic field generator configured to generate a magnetic field at the nozzle, planar member positioned to receive melted metal drops ejected from the ejector head, and a controller operatively connected to the magnetic field generator, the controller being configured to operate the magnetic field generator to generate a magnetic field through which the ejected melted metal drops pass before being received at the planar member.
The foregoing aspects and other features of a method that forms support structures that do not adhere tightly to object features supported by the structures and a 3D metal object printer that implements the method are explained in the following description, taken in connection with the accompanying drawings.
For a general understanding of the 3D metal object printer and its operation as disclosed herein as well as the details for the printer and its operation, reference is made to the drawings. In the drawings, like reference numerals designate like elements.
With further reference to
The ejector head 140 is movably mounted within Z-axis tracks for movement of the ejector head with respect to the platform 112. One or more actuators 144 are operatively connected to the ejector head 140 to move the ejector head along a Z-axis and are operatively connected to the platform 112 to move the platform in an X-Y plane beneath the ejector head 140. The actuators 144 are operated by a controller 148 to maintain an appropriate distance between the orifice 110 in the baseplate 114 of the ejector head 140 and a surface of an object on the platform 112.
Moving the platform 112 in the X-Y plane as drops of molten metal are ejected toward the platform 112 forms a swath of melted metal drops on the object being formed. Controller 148 also operates actuators 144 to adjust the distance between the ejector head 140 and the most recently formed layer on the substrate to facilitate formation of other structures on the object. While the molten metal 3D object printer 100 is depicted in
A controller 148 operates the switches 152. One switch 152 can be selectively operated by the controller to provide electrical power from source 156 to the heater 160, while another switch 152 can be selectively operated by the controller to provide electrical power from another electrical source 156 to the coil 164 for generation of the electrical field that ejects a drop from the nozzle 108. Because the heater 160 generates a great deal of heat at high temperatures, the coil 164 is positioned within a chamber 168 formed by one (circular) or more walls (rectilinear shapes) of the ejector head 140. As used in this document, the term “chamber” means a volume contained within one or more walls within a metal drop ejecting printer in which a heater, a coil, and a removable vessel of a 3D metal object printer are located. The removable vessel 104 and the heater 160 are located within such a chamber. The chamber is fluidically connected to a fluid source 172 through a pump 176 and also fluidically connected to a heat exchanger 180. As used in this document, the term “fluid source” refers to a container of a liquid having properties useful for absorbing heat. The heat exchanger 180 is connected through a return to the fluid source 172. Fluid from the source 172 flows through the chamber to absorb heat from the coil 164 and the fluid carries the absorbed heat through the exchanger 180, where the heat is removed by known methods. The cooled fluid is returned to the fluid source 172 for further use in maintaining the temperature of the coil in an appropriate operational range.
The controller 148 of the 3D metal object printer 100 requires data from external sources to control the printer for metal object manufacture. In general, a three-dimensional model or other digital data model of the object to be formed is stored in a memory operatively connected to the controller 148. The controller can selectively access the digital data model through a server or the like, a remote database in which the digital data model is stored, or a computer-readable medium in which the digital data model is stored. This three-dimensional model or other digital data model is processed by a slicer implemented with a controller to generate machine-ready instructions for execution by the controller 148 in a known manner to operate the components of the printer 100 and form the metal object corresponding to the model. The generation of the machine-ready 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 representation, which in turn can be processed to generate machine instructions, such as g-code, for fabrication of the object by the printer. As used in this document, the term “machine-ready instructions” means computer language commands that are executed by a computer, microprocessor, or controller to operate components of a 3D metal object additive manufacturing system to form metal objects on the platform 112. The controller 148 executes the machine-ready instructions to control the ejection of the melted metal drops from the nozzle 108, the positioning of the platform 112, as well as maintaining the distance between the orifice 110 and a surface of the object on the platform 112.
Using like reference numbers for like components and removing some of the components not used to form metal support structures that do not adhere too tightly to the object during formation, a new 3D metal object printer 100′ is shown in
As shown in
Melted metal drops that land on a surface with little or no kinetic energy have reduced bond strength. This reduced bond strength is thought to arise from lower drop velocities reducing the effectiveness of wetting and coalescence between melted metal drops. Operating the electromagnetic coil 204 lowers the velocities of the drops that pass through the magnetic field so it reduces the ability of the drops to bond to one another. A steady magnetic field produced by current passing through the coil is perpendicular to the motion of the ejected drops. This field induces eddy currents in the drops, which in turn induces a Lorentz force in a direction opposite to the motion of the drop. This Lorentz force acts to dampen the motion of the drop and the mechanical energy is dissipated as heat. The dampening force is proportional to the velocity of the drop. Thus, a uniform magnetic field across a gap of about 10 mm between the nozzle and the drop landing surface causes a melted metal drop having a 500 micron diameter that was ejected with an initial velocity of 3.5 m/s to have a reduced velocity and time of flight that is a function of the magnetic field strength.
The graph of
The controller 148′ can be implemented with one or more general or specialized programmable processors that execute programmed instructions. The instructions and data required to perform the programmed functions can be stored in memory associated with the processors or controllers. The processors, their memories, and interface circuitry configure the controllers to perform the operations previously described as well as those described below. These components can be provided on a printed circuit card or provided as a circuit in an application specific integrated circuit (ASIC). Each of the circuits can be implemented with a separate processor or multiple circuits can be implemented on the same processor. Alternatively, the circuits can be implemented with discrete components or circuits provided in very large scale integrated (VLSI) circuits. Also, the circuits described herein can be implemented with a combination of processors, ASICs, discrete components, or VLSI circuits. During metal object formation, image data for a structure to be produced are sent to the processor or processors for controller 148′ from either a scanning system or an online or work station connection for processing and generation of the signals that operate the components of the printer 100′ to form an object on the platform 112.
A process for operating the 3D metal object printer 100′ to form metal support structures that weakly attach to object features is shown in
It will be appreciated that variants of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems, applications or methods. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements may be subsequently made by those skilled in the art that are also intended to be encompassed by the following claims.
