Patent Description:
Additive manufacturing is a process in which material is built up layer-by-layer to form a component. Additive manufacturing is also referred to by terms such as "layered manufacturing," "reverse machining," "direct metal laser melting" (DMLM), "selective laser sintering" (SLS), stereolithography (SLA), and "<NUM>-D printing. " Such terms are treated as synonyms for purposes of the present invention.

With the present rapid maturation of <NUM>-D printing technology, more accurate printers and modeling tools are becoming commercially available at decreasing cost. One problem associated with this cost decrease is the ease of creating inexpensive replicas that can place inferior components in the market.

In some applications, for example gas turbine engines, particularly aircraft gas turbine engines, counterfeit parts pose a severe risk to engine integrity.

<CIT> discloses system that includes a three-dimensional (3D) printing device.

<CIT> discloses a three-dimensional barcode label.

<CIT> discloses a method, system for encoding or decoding information in physical properties of an object. <CIT> discloses a method for producing a marked object.

This problem is addressed by the physical incorporation of a three-dimensional ("<NUM>-D") identification code into a component using additive manufacturing processes. The invention is defined by the appended Claims.

A first aspect of the invention relates to a component according to claim <NUM>.

Another aspect of the invention relates to a method according to claim <NUM>.

The invention may be best understood by reference to the following description taken in conjunction with the accompanying drawing figures in which:.

Referring to the drawings wherein identical reference numerals denote the same elements throughout the various views, <FIG> depicts an exemplary turbine blade <NUM>. The turbine blade <NUM> includes a conventional dovetail <NUM>, which may have any suitable form including tangs that engage complementary tangs of a dovetail slot in a rotor disk (not shown) for radially retaining the blade <NUM> to the disk as it rotates during operation. A blade shank <NUM> extends radially upwardly from the dovetail <NUM> and terminates in a platform <NUM> that projects laterally outwardly from and surrounds the shank <NUM>. A hollow airfoil <NUM> extends radially outwardly from the platform <NUM> and into the hot gas stream. The airfoil has a root <NUM> at the junction of the platform <NUM> and the airfoil <NUM>, and a tip <NUM> at its radially outer end. The airfoil <NUM> has a concave pressure side wall <NUM> and a convex suction side wall <NUM> joined together at a leading edge <NUM> and at a trailing edge <NUM>. The airfoil <NUM> may take any configuration suitable for extracting energy from the hot gas stream and causing rotation of the rotor disk. By way of example and not of limitation, the turbine blade <NUM> may be formed from a suitable aerospace alloy, such as a nickel- or cobalt-based superalloy, which has acceptable strength at the elevated temperatures of operation in a gas turbine engine. The tip <NUM> of the airfoil <NUM> is closed off by a tip cap <NUM> which may be integral to the airfoil <NUM> or separately formed and attached to the airfoil <NUM>.

The airfoil <NUM> includes an internal cooling circuit which may have any conventional configuration, such as a serpentine circuit. <FIG> is a cross-sectional view of the turbine blade <NUM> showing an example of a suitable circuit. Within the turbine blade <NUM>, a plurality of internal passages <NUM> direct a flow of cooling air. Each such passage <NUM> is connected at one end to a cooling air inlet <NUM> within the shank <NUM>. The inlets <NUM> receive pressurized cooling air from a compressor of a gas turbine engine (not shown) in a conventional manner. At various locations along the passages <NUM> a plurality of cooling holes <NUM> of conventional size and configuration are positioned. These holes <NUM> provide a flowpath for cooling air inside passages <NUM> to the gas stream outside the blade <NUM>. The airfoil <NUM> may incorporate a plurality of trailing edge cooling holes <NUM> (<FIG>), or it may incorporate a number of trailing edge bleed slots (not shown) on the pressure side wall <NUM> of the airfoil <NUM>. The internal passages <NUM> are defined by and separated from each other by a plurality of integral walls <NUM>.

The turbine blade <NUM> may be described generally as including a body having an interior bounded by an exterior surface. The turbine blade is just one example of numerous components which may benefit from the inclusion of an identification code, on an exterior surface or within the interior of the body. Examples of such a code and its manufacture are described below.

<FIG> illustrates an exemplary code <NUM> incorporated into an exposed surface of a component such as the turbine blade <NUM> shown in <FIG>. In the illustrated example, the code <NUM> is incorporated into a forward face <NUM> of the dovetail <NUM>, but the code <NUM> may be formed on any surface where its presence does not affect the function of the component.

For the purposes of convenient description, reference will be made to X, Y, and Z axes, which are three mutually perpendicular directions. The code <NUM> comprises a plurality of cells <NUM> which are laid out in an array of predetermined dimensions in an X-Y plane. In the illustrated example, the cells <NUM> have a rectilinear shape and specifically are quadrilaterals; however any shape which is capable of being manufactured by an additive manufacturing process and scanned by a scanning device, such as a laser or optical scanner, may be used.

Each of the cells <NUM> encodes a data value by way of its height in the Z direction. It will be understood that a commercially available scanning device is able to resolve the Z-height of each cell <NUM> down to a certain minimum resolution. The code <NUM> has a predetermined overall maximum height in the Z-direction, labeled "H". The maximum height H is divided into a predetermined number of increments. In the illustrated example the height H is divided into <NUM> increments, in which case each cell <NUM> can encode one of <NUM> different unique values. These are shown as values <NUM>-<NUM> and A-F corresponding with hexadecimal values. The overall maximum height H and the number of increments may be selected taking into account the Z-direction resolution of the additive manufacturing machine used to create the code <NUM> as well as the Z-direction resolution of the scanning device used to read the code <NUM>.

The code <NUM> is referenced to several datums <NUM> which describe the position, alignment, and scale of the code <NUM>. In the claimed invention, the datums <NUM> comprise additional cells positioned at the far corners (i.e. distal corners) of the code <NUM>. In the illustrated example, the datums <NUM> are identifiable as such by their increased size (i.e. surface area) relative to the other cells <NUM>. They could also be identifiable by having a smaller size or a different shape. For example, three of the datums <NUM> are arranged in an L-shape. The angle of the L-shape identifies a reference corner of the code <NUM> and identifies the X-and Y-directions. The lengths of the legs of the L-shape identify the scale of the code <NUM>.

The substantive content of the code <NUM> may include numerous types of information. Nonlimiting examples include any or all of the following kinds of information: manufacturer name, manufacturer location, manufacturing date, part number, part version, production batch number and/or series code, or serial number. Optionally, the code may include authentication information of arbitrary content relative to the component (e.g. plain or encrypted text, numbers, images, etc.) serving as a "watermark" to identify a genuine component.

The logic used for encoding the substantive content, or stated another way the symbolic relevance of each height increment value, may be selected to suit a particular application. For example, the height increment values may be correlated to numeric values, alphabetical values, alphanumeric values, or other systems of symbols.

<FIG> illustrates an exemplary code <NUM> which may be incorporated into the body of a component such as the turbine blade <NUM> shown in <FIG>. The illustrated example, the code <NUM> is incorporated into the airfoil portion <NUM>.

For the purposes of convenient description, reference will be made to X, Y, and Z axes as described above. which are three mutually perpendicular directions. The code comprises a plurality of cells <NUM> which are laid out in an array of predetermined dimensions in an X-Y plane. In the illustrated example, the cells <NUM> have a rectilinear shape and specifically are parallelepipeds; however any shape which may be manufactured and identified by a scanning device may be used.

The cells <NUM> are identifiable by way of one or more position-independent properties. This refers to properties which may be identified by means of a nondestructive scanning device or process, such as computed tomography ("CT"). This type of process also provides the <NUM>-D spatial resolution required to read the positions of the individual cells <NUM>. One example of a position-independent property is the mass density of a particular cell <NUM>. In the simplest implementation, the cells <NUM> would be identified by having, for example, a much greater density than the surrounding material. In this case each cell <NUM> is binary, encoding one of two values, e.g. a greater density material is either present or not present at a specific X, Y, Z position within the code <NUM>.

The identifiable cells <NUM> may be used in different configurations to encode data. In the example shown in <FIG>, each of the cells <NUM> encodes a data value by way of its binary value for its specific X, Y position. The code <NUM> comprises a number of layers <NUM>, each of which is an independent <NUM>-D code.

The code <NUM> is referenced to one or more datums <NUM> which describe the position, alignment, and scale of the code <NUM>. In the illustrated example, the datums <NUM> are provided in the form of additional cells positioned at the far corners of the code <NUM>. In the illustrated example, datums <NUM> are identifiable as such by their increased size (i.e. volume) relative to the other cells <NUM>. They could also be identified by having a smaller size or a different shape. Collectively the datums <NUM> identify the X, Y, and Z directions and the scale of the code <NUM>.

<FIG> shows the claimed code <NUM> which is divided into columns <NUM> (one example shown) which are laid out in an array of predetermined dimensions in an X-Y plane. The code <NUM> has a predetermined overall maximum height in the Z-direction, labeled "H". The maximum height H is divided into a predetermined number of increments; each column <NUM> comprises a number of cells <NUM> equal to the number of increments. For example the height H may be divided into <NUM> increments, in which case each column <NUM> contains <NUM> cells (capable of encoding <NUM><NUM> combinations). The overall maximum height H and the number of cells <NUM> arrayed along the height H may be selected taking into account the Z-direction resolution of the additive manufacturing machine used to create the code <NUM> as well as the Z-direction resolution of the scanning device used to read the code <NUM>. The code <NUM> is similar to the surface code <NUM> described above in that it is a single unitary code with each "column" (that is, each unique X-Y position) encoding multiple values.

The cells <NUM> encode multiple data values by way of one or more of the position-independent properties described above. One example of a position-independent property that can encode multiple values is the density of a particular cell <NUM>. For example, several different materials with different densities ranked from low to high in a range may be identified. A specific cell may then be created from one of those identified materials. For example, if five different materials with unique densities are identified, each cell <NUM> could encode one of five different unique values. Alternatively, differences in material composition (i.e. alloy) detectable by means such as CT scanning or gamma ray scanning could be used as a basis for encoding multiple data values. Another example of a position-independent property that can encode multiple values is the porosity of a particular cell <NUM>. For example, several different materials with different porosities ranked from low to high in a range may be identified. This same concept of encoding multiple data values using position-independent properties may be incorporated in the codes <NUM> or <NUM> described above.

The code <NUM> is referenced to one or more datums which describe the position, alignment, and scale of the code <NUM>. In the claimed invention, the datums <NUM> are provided in the form of additional cells positioned at the far corners of the code <NUM>. In the illustrated example, datums <NUM> are identifiable as such by their increased size (i.e. volume) relative to the other cells <NUM>. They could also be identified by having a smaller size or a different shape. Collectively the datums <NUM> identify the X, Y, and Z directions and the scale of the code <NUM>.

As described above for the surface code <NUM>, the substantive content of the codes <NUM> or <NUM> may include numerous types of information. Furthermore the logic used for encoding the substantive content may be selected to suit a particular application as described above for the surface code <NUM>.

The datums described above need not be incorporated directly into the codes <NUM>, <NUM>, <NUM>. Optionally, the datums may be incorporated as part of the component. Using the turbine blade <NUM> and code <NUM> as an example, various existing elements may be used as datums. For example, referring to <FIG>, two inboard front corners <NUM> of the dovetail <NUM> and one front corner <NUM> of the platform <NUM> are exterior features that could be readily located using commercially available scanning equipment. These points would be sufficient to constrain the position, orientation, and scale of the turbine blade <NUM>. Once the location and distance between these points are known, this information may be matched to existing data, e.g. a computer-based solid model of the turbine blade <NUM>. A coordinate system of the component X', Y', Z' may then be correlated to the coordinate system X, Y, Z of the code <NUM>.

The codes <NUM>, <NUM>, <NUM> described above may be incorporated into the body of the turbine blade <NUM> or other component in any desired position and orientation that is consistent with the intended function of the component. Stated another way, the coordinate system X, Y, Z of the code <NUM>, <NUM>, <NUM> may be rotated and/or translated away from the coordinate system X', Y', Z', of the component.

This feature is especially helpful for avoiding counterfeit components, as a scan conducted without prior knowledge of the part-based datums would reveal no useful information. It is also possible that the code <NUM>, <NUM>, <NUM> would simply appear to be inclusions or defects in the component.

The codes described above are especially suitable for manufacturing as an integral part of the component as a whole. An additive manufacturing process such as powder-bed additive manufacturing process may be used. In the case of the surface code <NUM>, any conventional type of additive manufacturing machine may be used. In the case of the interior codes <NUM>, <NUM>, is it helpful to use a machine which is capable of applying multiple different materials for each layer of a build.

<FIG> and <FIG> illustrate schematically an exemplary additive manufacturing apparatus <NUM> suitable for carrying out an additive manufacturing process with multiple materials. The apparatus <NUM> may include a build platform <NUM>, an excess powder container <NUM>, a directed energy source <NUM>, a beam steering apparatus <NUM>, and a coater <NUM>, all of which may be enclosed in a housing <NUM>. Each of these components will be described in more detail below.

The build platform <NUM> is a rigid structure providing a planar worksurface <NUM>. The excess powder container <NUM> is an open-topped vessel which lies adjacent to the build platform <NUM>, and serves as a repository for excess powder P.

The directed energy source <NUM> is a device producing radiant energy with suitable power and other operating characteristics to melt and fuse the powder during the build process, described in more detail below. For example, the directed energy source <NUM> may comprise a laser or an electron beam gun.

The beam steering apparatus <NUM> functions so that a beam "B" from the directed energy source <NUM> can be focused to a desired spot size and steered to a desired position in a plane coincident with the worksurface <NUM>. For example, it may comprise one or more mirrors, prisms, and/or lenses and provided with suitable actuators.

The housing <NUM> encloses the working components of the apparatus <NUM> and may be sealed to prevent contamination. The housing <NUM> may be purged with a gas or gas mixture through inlet and outlet ports <NUM> and <NUM>, respectively.

As seen in <FIG>, the coater <NUM> may include a reservoir assembly <NUM> positioned above a dispenser <NUM>. A width of the dispenser <NUM> may be substantially equal to a width W of the build platform <NUM>. The dispenser <NUM> includes one or more elongated troughs (designated <NUM> generally) extending parallel to the width. In the illustrated example, the dispenser <NUM> includes a plurality of troughs <NUM> in a side-by-side arrangement.

Each trough <NUM> includes one or more deposition valves <NUM>. As used herein the term "valve" means any structure having a first position or condition which permits flow of powdered material (referred to as an "open" state), and a second position or condition which blocks flow of powdered material (referred to as a "closed" state). The action of the deposition valve <NUM> may be binary (i.e. on-off) or variable (i.e. open to a variable degree). Nonlimiting examples of suitable devices usable as deposition valves <NUM> include microelectromechanical system ("MEMS") devices or piezoelectric devices. In the illustrated example each trough <NUM> includes a linear array of deposition valves <NUM> extending along the width of the dispenser <NUM>. The size of the deposition valves <NUM> (i.e. their flow area in the open state), the spacing between individual deposition valves <NUM>, and the total number of deposition valves <NUM> may be selected in order to provide a desired spatial resolution and total coverage area. In use, the amount of powder deposited and resulting powder layer thickness may be controlled by the duration that the deposition valves <NUM> are open.

The reservoir assembly <NUM> includes at least one reservoir <NUM> disposed over each trough <NUM>. Each reservoir <NUM> is defined by suitable walls or dividers forming a volume effective to store and dispense a powder P. Each individual reservoir <NUM> may be loaded with a powder P having unique characteristics, such as composition and/or powder particle size. It should be appreciated that the powder P may be of any suitable material for additive manufacturing. For example, the powder P may be a metallic, polymeric, organic, or ceramic powder. It is noted that the reservoir assembly <NUM> is optional and that powder P may be loaded directly into the troughs <NUM>.

Each reservoir <NUM> may incorporate a feed valve <NUM> operable to selectively permit flow of powder P from the reservoir <NUM> into the associated trough <NUM>. The structure of the feed valve <NUM> may be as described above for the deposition valves <NUM>. The feed valves <NUM> may be used to selectively flow powder for various purposes, such as for limiting the amount of powder P in the trough <NUM> (to avoid interfering with operation of the deposition valves <NUM>); or for mixing powders from several different reservoirs <NUM> together in one trough <NUM>.

In the illustrated example, a group of reservoirs <NUM> are arranged in a side-by-side configuration extending parallel to the width W of the dispenser <NUM>. For convenience of description this group may be referred to as a "column" <NUM>. The reservoirs <NUM> within the column <NUM> are grouped above a funnel-shaped collector <NUM> with a single outlet <NUM> which discharges into the respective trough <NUM>. One such column <NUM> and collector <NUM> may be provided for each trough <NUM>. Alternatively, each reservoir <NUM> could be positioned to discharge directly into one of the troughs <NUM>.

It is possible to arbitrarily load each reservoir <NUM> with a unique powder (e.g. a powder having a unique composition and/or particle size). It is also possible to load a group of reservoirs <NUM> with powders having at least one common property. For example, the reservoirs <NUM> of a particular column <NUM> could be loaded with several powders having the same composition but differing powder particle sizes in each individual reservoir <NUM>.

The coater <NUM> is mounted for controlled movement relative to the build platform <NUM> in at least one axis parallel to the worksurface <NUM>, such that powder can be dispensed over a selected area of the build platform <NUM>. In the illustrated example, The width of the dispenser <NUM> is substantially equal to a width of the build platform <NUM>, so no movement is required in the width direction in order to dispense powder in a specified location. The coater <NUM> is mounted to the housing <NUM> using a first actuator <NUM> permitting controlled movement in the "length" direction. The first actuator <NUM> is depicted schematically in <FIG>.

Optionally, the coater <NUM> may include apparatus for controlled movement relative to the build platform <NUM> perpendicular to the worksurface <NUM> (i.e. height) so as to control the distance between the coater <NUM> and the worksurface <NUM>. A second actuator <NUM> is shown schematically for this purpose. Relative movement in the height direction could be produced by movement of the coater <NUM>, the build platform <NUM>, or some combination of the two.

Optionally, the apparatus may include a vibrator <NUM> operable to vibrate the build platform <NUM> and level deposited powder, as described in more detail below. For example, an electromechanical vibrator may be used for this function.

The functions of the apparatus <NUM> may be implemented using an electronic controller <NUM> depicted schematically in <FIG>. For example, one or more processor-based devices such as a microcomputer or programmable logic controller ("PLC") may be used for this purpose. Functional connections of the controller <NUM> to the other components of the apparatus <NUM> are shown as single dashed lines.

The apparatus <NUM> described above is operable to produce a layered component comprising fused powder, where the coater <NUM> can be used to deposit powder having specified characteristics at each specified location within a layer.

Subsequent to deposition, the directed energy source <NUM> is used to melt the deposited powder, which may correspond to a two-dimensional cross-section of the component being built. The directed energy source <NUM> emits a beam "B" and the beam steering apparatus <NUM> is used to steer the focal spot "S" of the beam B over the exposed powder surface in an appropriate pattern. The exposed layer of the powder P is heated by the beam B to a temperature allowing it to melt, flow, and consolidate. This step may be described as "fusing" the powder P. After a layer is fused, the coater <NUM> is moved vertically apart from the build platform <NUM> by a layer increment, and another layer of powder deposited as described above. The directed energy source <NUM> again emits a beam B and the beam steering apparatus <NUM> is used to steer the focal spot S of the beam B over the exposed powder surface in an appropriate pattern. The exposed layer of the powder P is heated by the beam B to a temperature allowing it to melt, flow, and consolidate both within the top layer and with the lower, previously-solidified layer. This cycle of applying powder P and then laser melting the powder P is repeated until the entire component C is complete.

Claim 1:
A component (<NUM>) incorporating a <NUM>-D identification code (<NUM>), comprising:
a component (<NUM>) body having an interior bounded by an exterior surface; and an identification code (<NUM>) formed as a part of the interior, the identification code (<NUM>) including a plurality of cells (<NUM>) arranged in a three-dimensional space within the interior, wherein each of the cells (<NUM>) is configured to encode more than two possible values;
a plurality of additional cells (<NUM>), each additional cell (<NUM>) configured as a datum positioned at a far corner, i.e. a distal corner, of the identification code (<NUM>), wherein the datums identify a size, position, and orientation of the identification code (<NUM>); wherein
wherein each of the plurality of cells (<NUM>) encodes more than two possible values by way of a position of the each of the plurality of cells (<NUM>) along at least one axis of the three-dimensional space;
wherein the cells (<NUM>) are identifiable by one or more position-independent properties.