Patent Application
20180345371
The present disclosure generally relates to additive manufacturing apparatuses and methods. More specifically, the present disclosure relates to apparatuses and methods that enable additive manufacturing on a large-scale format or reduce the amount of powder necessary to build radial-shaped objects. These apparatuses and methods are useful but are not limited to the additive manufacturing of components of an aircraft engine.
Additive manufacturing (AM) encompasses a variety of technologies for producing components in an additive, layer-wise fashion. In powder bed fusion which is one of the most popular AM technologies, a focused energy beam is used to fuse powder particles together on a layer-wise basis. The energy beam may be either an electron beam or laser. Laser powder bed fusion processes are referred to in the industry by many different names, the most common of which being selective laser sintering (SLS) and selective laser melting (SLM), depending on the nature of the powder fusion process. When the powder to be fused is metal, the terms direct metal laser sintering (DMLS) and direct metal laser melting (DMLM) are commonly used.
Referring to
Selected portions 107 of the powder layer are irradiated in each layer using, for example, laser beam 108. After irradiation, the build plate 102 is lowered by a distance equal to one layer thickness in the object 109 being built. A subsequent layer of powder is then coated over the last layer and the process repeated until the object 109 is complete. The laser beam 108 movement is controlled using galvo scanner 110. The laser source (not shown) may be transported from a laser source (not shown) using a fiber optic cable. The selective irradiation is conducted in a manner to build object 109 an accordance with computer-aided design (CAD) data.
Powder bed technologies have demonstrated the best resolution capabilities of all known metal additive manufacturing technologies. However, since the build needs to take place in the powder bed, the size of object to be built is limited by the size of the machine's powder bed. Increasing the size of the powder bed has limits due to the needed large angle of incidence that can lower scan quality, and weight of the powder bed which can exceed the capabilities of steppers used to lower the build platform. In view of the foregoing, there remains a need for manufacturing apparatuses and methods that can handle production of large objects with improved precision and in a manner that is both time- and cost-efficient with a minimal waste of raw materials.
In a first aspect, the present invention relates to an additive manufacturing apparatus that includes at least one build unit comprising a powder delivery mechanism, a powder recoating mechanism and an irradiation beam directing mechanism; a rotating build platform; and a positioning mechanism configured to provide independent movement of the at least one build unit in at least two dimensions that are substantially parallel to the rotating build platform. Preferably, the rotating build platform is vertically stationary. Preferably, the rotating build platform has an annular configuration.
In some embodiments, the positioning mechanism is further configured to provide independent movement of the at least one build unit in a third dimension that is substantially perpendicular to the rotating build platform. In one embodiment, the positioning mechanism is further configured to provide independent movement of the at least one build unit around at least one rotational axis.
In some embodiments, the build unit further includes a gas-flow mechanism configured to provide a substantially laminar gas flow to at least one build area within the build platform.
In some embodiments, the irradiation beam directing mechanism further comprises a laser source or an electron source. Accordingly, The irradiation beam directing mechanism emits and directs a laser beam at an angle that is substantially perpendicular to a build area within the build platform. Alternatively, the irradiation beam directing mechanism emits and directs an electron beam at an angle that is substantially perpendicular to a build area within the build platform.
In certain embodiments, the powder delivery mechanism includes a powder dispenser. The powder dispenser includes at least one powder storage compartment, and at least a first gate and a second gate. The first gate is operable by a first actuator to allow opening and closing of the first gate. The second gate is operable by a second actuator to allow opening and closing of the second gate. Each of the first gate and the second gate is configured to control the dispensation of powder from the at least one storage compartment onto a build surface within the build platform.
In a second aspect, the present invention relates to a method of manufacturing at least one object. The method includes steps of: (a) rotating a build platform; (b) depositing powder from at least one build unit; (c) irradiating at least one selected portion of the powder to form at least one fused layer; and (d) repeating at least step (d) to form the object. The build unit is moved in a radial direction during the manufacture of the at least one object. In some embodiments, the method further includes a step of leveling of the at least one selected portion of the powder.
In a third aspect, the present invention relates to a method of manufacturing at least one object. The method includes steps of: (a) rotating a build platform; (b) depositing powder from at least one build unit; (c) irradiating at least one selected portion of the powder to form at least one fused layer; and (d) repeating at least step (d) to form the object. The build unit is moved in a radial direction during the manufacture of the at least one object and a build wall retains unfused powder about the at least one object.
The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. For example, the present invention provides a preferred method for additively manufacturing certain components of metal objects, and preferably these components and these objects are used in the manufacture of jet aircraft engines. In particular, large, annular components of jet aircraft engines can be advantageously produced in accordance with this invention. However, other components of an aircraft may be prepared using the apparatuses and methods described herein.
The present invention provides an apparatus and embodiments of the apparatus that can be used to perform powder-based additive layer manufacturing of a large object. Examples of powder-based additive layer manufacturing include but are not limited to selective laser sintering (SLS), selective laser melting (SLM), direct metal laser sintering (DMLS), direct metal laser melting (DMLM) and electron beam melting (EBM) processes.
An additive manufacturing apparatus provided herein includes a mobile build unit assembly, which is configured to include several components that are essential for additively manufacturing high-precision, large-scale objects. These build components include, for example, a powder recoating mechanism and an irradiation beam directing mechanism. The build unit is advantageously attached to a positioning mechanism that allows two- or three-dimensional movement (along x-, y- and z-axes) throughout the build environment, as well as rotation of the build unit in a way that allows leveling of the powder in any direction desired. The positioning mechanism may be a gantry, a delta robot, a cable robot, a robotic arm, a belt drive, or the like.
Aside from the mobile build unit, an additive manufacturing apparatus of the present invention also includes a rotating build platform. Preferably, this build platform has a substantially circular configuration but is not so limited. Since the build unit of the apparatus is mobile, this eliminates the need to lower the build platform as successive layers of powder are built up, as it is in conventional powder bed systems. Accordingly, the rotating platform of the present invention is preferably vertically stationary.
Importantly, since there are two mobile components in the additive manufacturing apparatuses of the present invention, namely the build unit and the build platform, it is important to coordinate, for example, the speed and/or direction of the irradiation beam directing mechanism with, for example, the rotational speed and/or rotational direction of the build platform.
The dashed lines AB, EF and IJ represent imaginary co-linear fused layers on respectively the outer grown build envelope 224, built object 230 and inner grown build envelope 226 if the build platform 210 was non-rotating; whereas the solid lines CD, GH and KL represent that actual and corresponding co-linear fused layers formed.
The compensation scheme generally takes account of the fact that the angular velocity is constant but the surface velocity of the powder bed increases in the direction away from the center of rotation. Compensation may also cause the beam to slow when writing in the direction of rotation and speed up when writing against the direction of travel. It should be appreciated that alternative or additional schemes may be utilized to compensate for the rotational movement of the build platform 210.
The build unit 302 may be configured to include several components for additively manufacturing a high-precision, large-scale object or multiple smaller objects. A mobile build unit may include, for example, a powder delivery mechanism, a powder recoating mechanism, a gas-flow mechanism with a gas-flow zone and an irradiation beam directing mechanism.
The positioning mechanism 325 may be an X-Y-Z gantry has one or more x-crossbeams 325X (one shown in
The rotating build platform 310 may be a rigid and ring-shaped or annular structure (i.e. with an inner central hole) configured to rotate 360° around the center of rotation W. The rotating build platform 310 may be secured to an end mount of a motor 316 that is operable to selectively rotate the rotating build platform 310 around the center of rotation W such that the build platform 310 moves in a circular path. The motor 316 may be further secured to a stationary support structure 328. The motor may also be located elsewhere near the apparatus and mechanically connected with the build platform via a belt for translating motion of the motor to the build platform.
Advantageously, a selective recoating mechanism according to an embodiment of the present invention allows precise control of powder deposition using powder deposition device (e.g. a hopper) with independently controllable powder gate plates as illustrated, for example, in
Additional details for a build unit that can be used in accordance with the present invention may be found in U.S. patent application Ser. No. 15/406,444, titled “Additive Manufacturing Using a Dynamically Grown Build Envelope,” with attorney docket number 037216.00061, and filed Jan. 13, 2017; U.S. patent application Ser. No. 15/406,467, titled “Additive Manufacturing Using a Mobile Build Volume,” with attorney docket number 037216.00059, and filed Jan. 13, 2017; U.S. patent application Ser. No. 15/406,454, titled “Additive Manufacturing Using a Mobile Scan Area,” with attorney docket number 037216.00060, and filed Jan. 13, 2017; U.S. patent application Ser. No. 15/406,461, titled “Additive Manufacturing Using a Selective Recoater,” with attorney docket number 037216.00062, and filed Jan. 13, 2017; U.S. patent application Ser. No. 15/406,471, titled “Large Scale Additive Machine,” with attorney docket number 037216.00071, and filed Jan. 13, 2017, the disclosures of which are incorporated herein by reference.
Representative examples of suitable powder materials can include metallic alloy, polymer, or ceramic powders. Exemplary metallic powder materials are stainless steel alloys, cobalt-chrome, aluminum alloys, titanium alloys, nickel based superalloys, and cobalt based superalloys. In addition, suitable alloys may include those that have been engineered to have good oxidation resistance, known “superalloys” which have acceptable strength at the elevated temperatures of operation in a gas turbine engine, e.g. Hastelloy, Inconel alloys (e.g., IN 738, IN 792, IN 939), Rene alloys (e.g., Rene N4, Rene N5, Rene 80, Rene 142, Rene 195), Haynes alloys, Mar M, CM 247, CM 247 LC, C263, 718, X-750, ECY 768, 282, X45, PWA 1483 and CMSX (e.g. CMSX-4) single crystal alloys. The manufactured objects of the present invention may be formed with one or more selected crystalline microstructures, such as directionally solidified (“DS”) or single-crystal (“SX”).
This written description uses examples to disclose the invention, including the preferred embodiments, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. Aspects from the various embodiments described, as well as other known equivalents for each such aspect, can be mixed and matched by one of ordinary skill in the art to construct additional embodiments and techniques in accordance with principles of this application.
