Patent Application
20180169756
The present disclosure generally relates to methods for additive manufacturing that utilize supports in the process of building an object, as well as novel supports to be used within these AM processes.
Additive manufacturing (AM) processes generally involve the buildup of one or more materials to make a net or near net shape (NNS) object, in contrast to subtractive manufacturing methods. Though “additive manufacturing” is an industry standard term, AM encompasses various manufacturing and prototyping techniques known under a variety of names, including freeform fabrication, 3D printing, rapid prototyping/tooling, etc. AM techniques are capable of fabricating complex objects from a wide variety of materials. Generally, a freestanding object can be fabricated from a computer aided design (CAD) model. A particular type of AM process uses an energy beam, for example, an electron beam or electromagnetic radiation such as a laser beam, to sinter or melt a metal powder material, creating a solid three-dimensional object in which particles of the powder material are bonded together. Different material systems, for example, engineering plastics, thermoplastic elastomers, metals, and ceramics are in use. Laser sintering or melting is a notable AM process for rapid fabrication of functional objects, prototypes and tools.
Selective laser sintering, direct laser sintering, selective laser melting, and direct laser melting are common industry terms used to refer to produce three-dimensional (3D) objects by using a laser beam to sinter or melt a fine metal powder. These processes may be referred to herein as metal powder additive manufacturing. More accurately, sintering entails fusing (agglomerating) particles of a powder at a temperature below the melting point of the powder material, whereas melting entails fully melting particles of a powder to form a solid homogeneous mass. The physical processes associated with laser sintering or laser melting include heat transfer to a powder material and then either sintering or melting the metal powder material.
Metal powder additive manufacturing processes create layers of molten metal or an agglomeration of metal over already formed layers of hardened metal. Where the hardened metal is under the new layer, the hardened metal supports the new layer. One challenge of additive manufacturing is building surfaces that are not vertical such as unsupported horizontal surfaces or vertically angled surfaces, i.e., those angled relative to horizontal with no support therebelow. More specifically, where a portion of the new layer is not over a previously formed, now hardened metal, the non-heated metal powder thereabout provides insufficient support and gravity negatively impacts the object's final shape. In order to address this situation, during metal powder additive manufacture of a metallic object, it is known to also form supports as part of the metallic object to support the otherwise unsupported surfaces. For example, supports may be formed in fuel nozzles, such as those used in gas turbines, to maintain separation between parts, e.g., spaced, concentric tubular components in close proximity to one another. In many applications, the supports are removed from the final metallic object, e.g., where operation using the object does not allow for the presence of the supports or support breakage may cause other damage. In these situations, the supports are removed through post-AM processes such as machining or chemical processes. In some cases, supports built into the metallic object are allowed to remain in the object. In this case, stresses, such as thermal stress observed during operation of the metallic object, may be allowed to break the supports. The breakage may be allowed, for example, to improve operation by allowing for more freedom of movement during stresses observed within the object. It is difficult, in some applications, to ensure that the supports are configured to break during operation in a manner that does not otherwise impact the object. While these challenges have been described relative to metal powder additive manufacturing, they are also present in other forms of additive manufacturing.
A first aspect of the disclosure provides a self-breaking support for a vertically opposed first and second surfaces of an object, the self-breaking support comprising: a first base coupled to the first surface and extending towards the second surface; a second base coupled to the second surface and extending towards the first surface; and a self-breaking link coupling the first base to the second base, the self-breaking link including a body and a weakened zone in the body.
A second aspect of the disclosure provides a method for manufacturing a metallic object, the method comprising: forming the metallic object with a self-breaking support using a metal powder additive manufacturing process, the self-breaking support including: a first base coupled to a first surface of the metallic object and extending towards a second surface of the metallic object that is vertically opposed to the first surface, a second base coupled to the second surface and extending towards the first surface, and a self-breaking link coupling the first base to the second base, the self-breaking link including a body and a weakened zone in the body; and allowing the self-breaking link to break during cooling of at least a portion of the metallic object during the forming.
The illustrative aspects of the present disclosure are designed to solve the problems herein described and/or other problems not discussed.
These and other features of this disclosure will be more readily understood from the following detailed description of the various aspects of the disclosure taken in conjunction with the accompanying drawings that depict various embodiments of the disclosure, in which:
It is noted that the drawings of the disclosure are not to scale. The drawings are intended to depict only typical aspects of the disclosure, and therefore should not be considered as limiting the scope of the disclosure. In the drawings, like numbering represents like elements between the drawings.
As an initial matter, in order to clearly describe the current disclosure it will become necessary to select certain terminology when referring to and describing an object manufactured as described herein. When doing this, if possible, common industry terminology will be used and employed in a manner consistent with its accepted meaning. Unless otherwise stated, such terminology should be given a broad interpretation consistent with the context of the present application and the scope of the appended claims. Those of ordinary skill in the art will appreciate that often a particular object may be referred to using several different or overlapping terms. What may be described herein as being a single part may include and be referenced in another context as consisting of multiple components. Alternatively, what may be described herein as including multiple components may be referred to elsewhere as a single part.
In addition, several descriptive terms may be used regularly herein, and it should prove helpful to define these terms at the onset of this section. These terms and their definitions, unless stated otherwise, are as follows. A “metallic object” as used herein may include any material thing including a metal or metal alloy formed by a metal powder additive manufacturing process, and an “object” can include any material thing formed by additive manufacturing processes, perhaps using materials other than metal such as but not limited to polymers and ceramic composites. Approximating language, as used herein throughout the specification and claims, may be applied to modify any quantitative representation that could permissibly vary without resulting in a change in the basic function to which it is related. Accordingly, a value modified by a term or terms, such as “about,” “approximately” and “substantially,” are not to be limited to the precise value specified. In at least some instances, the approximating language may correspond to the precision of an instrument for measuring the value. Here and throughout the specification and claims, range limitations may be combined and/or interchanged, such ranges are identified and include all the sub-ranges contained therein unless context or language indicates otherwise. “Approximately” as applied to a particular value of a range applies to both values, and unless otherwise dependent on the precision of the instrument measuring the value, may indicate +/−10% of the stated value(s). “Substantially vertical” may be +/−5° from vertical, and “substantially perpendicular” as applied to two structures may be 85° to 95°. “Substantially triangular” may refer to a shape having three major sides but with some variation in the shape of the sides, or the number of additional minor sides provided. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or objects, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, objects, and/or groups thereof. “Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
As indicated above, the disclosure provides a self-breaking support for a vertically opposed first and second surfaces during additive manufacturing of an object, and in particular, a metallic object formed using metal powder additive manufacturing. A method for manufacturing a metallic object is also described.
To illustrate an example of an additive manufacturing process,
AM control system 104 is shown implemented on computer 130 as computer program code. To this extent, computer 130 is shown including a memory 132, a processor 134, an input/output (I/O) interface 136, and a bus 138. Further, computer 130 is shown in communication with an external I/O device/resource 139 and a storage system 141. In general, processor 134 executes computer program code, such as AM control system 104, that is stored in memory 132 and/or storage system 141 under instructions from code 120 representative of object 102. While executing computer program code, processor 134 can read and/or write data to/from memory 132, storage system 141, I/O device 139 and/or AM printer 106. Bus 138 provides a communication link between each of the objects in computer 130, and I/O device 139 can comprise any device that enables a user to interact with computer 130 (e.g., keyboard, pointing device, display, etc.). Computer 130 is only representative of various possible combinations of hardware and software. For example, processor 134 may comprise a single processing unit, or be distributed across one or more processing units in one or more locations, e.g., on a client and server. Similarly, memory 132 and/or storage system 141 may reside at one or more physical locations. Memory 132 and/or storage system 141 can comprise any combination of various types of non-transitory computer readable storage medium including magnetic media, optical media, random access memory (RAM), read only memory (ROM), etc. Computer 130 can comprise any type of computing device such as a network server, a desktop computer, a laptop, a handheld device, a mobile phone, a pager, a personal data assistant, etc.
Additive manufacturing processes begin with a non-transitory computer readable storage medium (e.g., memory 132, storage system 141, etc.) storing code 120 representative of object 102. As noted, code 120 includes a set of computer-executable instructions defining object 102 that can be used to physically generate the object, upon execution of the code by system 100. For example, code 120 may include a precisely defined 3D model of object 102 and can be generated from any of a large variety of well-known computer aided design (CAD) software systems such as AutoCAD®, TurboCAD®, DesignCAD 3D Max, etc. In this regard, code 120 can take any now known or later developed file format. For example, code 120 may be in the Standard Tessellation Language (STL) which was created for stereolithography CAD programs of 3D Systems, or an additive manufacturing file (AMF), which is an American Society of Mechanical Engineers (ASME) standard that is an extensible markup-language (XML) based format designed to allow any CAD software to describe the shape and composition of any three-dimensional object to be fabricated on any AM printer. Code 120 may be translated between different formats, converted into a set of data signals and transmitted, received as a set of data signals and converted to code, stored, etc., as necessary. Code 120 may be an input to system 100 and may come from a part designer, an intellectual property (IP) provider, a design company, the operator or owner of system 100, or from other sources. In any event, AM control system 104 executes code 120, dividing object 102 into a series of thin slices that it assembles using AM printer 106 in successive layers of powder. In the DMLM example, each layer is melted or sintered to the exact geometry defined by code 120 and fused to the preceding layer. Subsequently, object 102 may be exposed to any variety of finishing processes, e.g., minor machining, sealing, polishing, assembly to another part, etc.
As shown best in the cross-sectional perspective view of an end of a fuel nozzle 142 in
While tubes 146, 148 are coupled in selected locations (at build platform 118 (
Each base 172, 174 may take any form necessary to support or position self-breaking support 170 where support of surfaces during metal powder additive manufactured is desired. In one example, shown in
Weakened zone 184 may include any manner of physical structure capable of causing body 180 to break under a desired stress. In the example shown in the enlarged front view of
Self-breaking support 170 can take a variety of alternative forms, which can be selected based on a number of factors such as but not limited to: any number of characteristics of first and second surfaces 154, 156, e.g., distance therebetween, relative angles, angle of each, etc.; the desired amount of support necessary; and/or the desired stress required to break the support. In
In another embodiment, shown in side views in
First base 172 and second base 174 can have any shape necessary to ensure they are securely formed with surfaces 154, 156. In embodiments shown herein, each base has a substantially triangular cross-section (excepting where body 180 extends therefrom). Where, for example, surfaces 154, 156 are not planar, bases 172, 174 can take a variety of alternative shapes to accommodate secure formation thereof with the surfaces. It is noted that while bases 172, 174 are generally vertically aligned in
Weakened zone 184 may also take a variety of alternative forms. For example, in
A method for manufacturing an object 102, and in particular a metallic object, according to embodiments of the disclosure may include forming object 102 with self-breaking support 170, as described herein, using a metal powder additive manufacturing process (as in
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiment was chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.
