March 17, 2016 - 8:41 PM EDT
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Patent Application Titled "System and Method for Determining Beam Power Level along an Additive Deposition Path" Published Online (USPTO 20160059352)

By a News Reporter-Staff News Editor at Journal of Engineering -- According to news reporting originating from

Washington, D.C.
, by VerticalNews journalists, a patent application by the inventor Sparks, Todd Eugene (
Rolla, MO
), filed on September 2, 2014, was made available online on March 10, 2016.

The assignee for this patent application is Product Innovation & Engineering, Llc.

Reporters obtained the following quote from the background information supplied by the inventors: "Additive metal deposition is an industrial technique that builds fully-dense structures by melting powdered or wire metal, via a laser or other energy source, into solidifying beads, which are deposited side by side and layer upon layer upon a work piece substrate. It is known to utilize the process to repair and rebuild a worn or damaged component using a laser to build up structure on the component. The process is particularly useful to add features such as bosses or flanges on subcomponents of fabricated structures. The basic process involves adding layers to the component to create a surface feature on the component via the introduction of depositing material (delivered in the form of injected powder or a wire) into a laser beam. The additive process is known by several names including 'laser cladding,' 'laser metal deposition,' 'direct metal deposition' or 'additive metal layering.'

"Additive metal layering is typically performed by using a computer aided design ('CAD') to map the geometry of a part and then depositing metal, layer-by-layer, on the part. The CAD mapped geometry is input into a computer controlled (robotic) part handler that can manipulate the part in multiple axes of movement during the deposition process. In all of these techniques a heat source (typically an industrial laser beam) is used to create a melt pool into which a wire or powdered feedstock is fed in order to create beads upon solidification. In practice, the heat source is under computer numerical control and is focused onto a workpiece, producing the melt pool. A small amount of powder or wire metal is introduced into the melt pool, building up the part in a thin layer. The beam follows a previously determined toolpath. The toolpath is generated based on the CAD data that computes the needed part layer by layer. The beads are created by means of relative motion of the melt pool and the substrate, e.g. using an industrial robot arm or an XY-table. A part is then built by depositing the beads side by side and layer upon layer. The most popular approach combines a high power laser heat source with metal powder as the additive material.

"Careful tuning of the deposition tool and parameters, such as the powder or wire feed rate, the energy input, and the traverse speed are therefore important in order to obtain layers, which are free from defects such as shape irregularities, lack-of-fusion or cracks. Droplet forming, i.e. globular transfer of the molten metal, is also a common disturbance that affects the geometrical profile of the deposited beads and stability of the additive layers.

"Regulating the necessary needed power is critical to system operation and achieving a high-quality layered end product. The currently known laser additive processes attempt to address deposition quality issues in either of two ways. In this respect, the prior laser additive processes use a constant laser power or one regulated by a feedback (a/k/a 'closed-loop') sensor.

"The issue with using a constant laser power is that the operator has to optimize the power level for a worst case scenario, typically the start of the process. This results in variations in both geometry and material properties as the melt pool size and temperature gradients vary with the local energy balance conditions around the melt pool. Using a constant energy throughout the deposition process is problematic because the additive process changes the geometry of the built structure during the process. Hence, the chosen constant power level represents a compromise selection. For example and as shown in FIG. 1A, at the start of the deposition process, the structure is positioned further from the laser source and too little energy is input into the deposition. At the mid-process point, shown in FIG. 1B, the target structure is closer to the energy source and the appropriate energy is present in the workpiece. However, by the end of the process, as shown, in FIG. 1C, the workpiece is closer to the energy source and too much energy is present in the work site.

"Feedback systems represent an attempt to address the deficits of the constant power system. The typical prior art feedback systems attempt to control the deposition process by monitoring the dimensions of the part or the melt pool during the deposition process. Feedback or closed-loop systems are inherently reactionary, and thus can only react to conditions that have already drifted away from nominal. There is thus a need in the art for an improved method of regulating laser power during the additive process."

In addition to obtaining background information on this patent application, VerticalNews editors also obtained the inventor's summary information for this patent application: "The instant invention addresses the deficits of the prior art by providing for a method of predicting needed laser power during an additive layer process. The calculated predictive levels can then be input into the laser power controller to regulate laser power at intervals during the additive path deposition process. The inventive method is a power schedule calculation method for an additive deposition process using a beam source that calculates optimum beam power for any point P(s) along an additive path that will be traveled to form a build that has a geometry and is formed from deposited material added to a substrate. The inventive method utilizes a calculated idealized geometry for each point P(s) along the additive path. The idealized geometry for each point P(s) comprises a melt pool, hot zone and bulk portion. FIG. 2 is a photograph depicting a real-world machine environment of a substrate undergoing additive metal layering. This image shows the thermodynamic constituents of the workpiece used to formulate an idealized geometry. As shown in FIG. 2 an idealized geometry of the present invention comprises the melt pool, hot zone and bulk structure, which are delineated in the photograph. The pink arrow indicates heat flux entering the environment. The red arrows indicate heat conduction in the workpiece. The blue arrows represent heat lost by the workpiece to the environment.

"The inventive method predicts energy needs along the additive path based upon an improved model of the dynamic geometry and thermodynamics of the build during the additive process. The inventive laser power prediction method can be generally described as using four essential components to calculate needed power during the deposition process to create a thermodynamic model of the deposition system. The four components include: a) an additive path describing the path of the laser through space; b) a geometric representation of the geometry that the additive path is intended to create; c) a description of the thermodynamic characteristics of the manufacturing environment; and d) the thermophysical characteristics of the materials involved.

"The inventive model is used to predict an appropriate input laser power at definable intervals along the laser path. It accomplishes this by using the path and geometric representation of the part being produced to create an idealized geometry that allows for tenable calculations. As shown in FIG. 2, the Idealized geometry comprises three elements: the melt pool, a hot zone around the melt pool, and the rest of the component being constructed. Prior art predictive and feedback systems and methods rely on melt pool characteristics for predictive and feedback control. In contrast, a key element in the model used in the present invention is the hot zone. In particular, the present invention method and system relies upon a good estimator of the hot zone shape and connectivity to the bulk of the structure. Estimating the hot zone is accomplished by intersecting hemispheres oriented in the direction of the tool axis with the part geometry. This technique is shown in FIG. 3.

"The model's advantage over a more conventional Eulerian finite element method ('FEM') mode is demonstrated in FIGS. 4A and 4B. As shown in these figures, the number of calculations (represented by the arrows) necessary to compute the heat conduction through the domain in the inventive model is less than the conventional Eulerian FEM model. Applying the domain-specific knowledge to create the simplified model for predicting laser power allows for the computation of laser power with higher frequency and good numerical stability.

"The present invention also includes a system for fabricating a part on a substrate using a deposition beam source that follows an additive path and that is controlled in accordance with the described laser power prediction method. The system includes a computer-aided design database including a description of the part to be fabricated and a database describing the additive path to be traveled as the part is formed. The additive path is composed of a plurality of points. The system further includes a substrate support for supporting the substrate and manipulating it through space, a metal stock delivery system, (e.g., powdered metal injector/sprayer or wire feed) and a controllable beam source capable of emitting a beam onto the substrate and adapted to form a melt pool thereon and a controller adapted to control power to the beam source. The controller is programmed to regulate energy of the produced beam for any point on the additive path in accordance with the required power predicted for that point by the described calculation methods.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIGS. 1A-1C are photographs showing the beginning, middle and end stages of an additive build process utilizing a constant power to form a build.

"FIG. 2 is a photograph of a substrate undergoing additive metal layering showing the thermodynamic constituents of the workpiece used to formulate an idealized geometry of the present invention.

"FIG. 3 is a diagram showing the hemisphere oriented technique used to

"estimate hot zone shape and connectivity of the bulk of the workpiece structure.

"FIG. 4A depicts the conventional Eulerlan FEM model used to estimate

"heat conduction through a structure. FIG. 4B depicts the simplified method used to estimate heat conduction through a structure that is employed as part of the present invention predictive method.

"FIG. 5A depicts a simplified deposition path utilized when building a wall-shaped structure using additive laser deposition. FIG. 5B is a graph showing predicted needed laser power over time for an additive metal deposition process used to build the wall structure of FIG. 5A. The predicted needed laser power is calculated at various intervals along the additive path process according to the present invention calculation technique.

"FIG. 6A depicts a simplified deposition path utilized when building a cylindrical-shaped structure using additive laser deposition. FIG. 6B is a graph showing predicted needed laser power over time for an additive metal deposition process used to build the cylindrical structure of FIG. 6A. The predicted needed laser power is calculated at various intervals along the additive path process according to the present invention calculation technique.

"FIG. 7 depicts a preferred embodiment system for fabricating a part on a substrate using a deposition beam source that follows an additive path and that is controlled in accordance with the described laser power prediction method.

"FIGS. 8A-8C are flow charts of an embodiment of the method for

"controlling beam power according to the present invention predictive technique."

For more information, see this patent application: Sparks, Todd Eugene. System and Method for Determining Beam Power Level along an Additive Deposition Path. Filed September 2, 2014 and posted March 10, 2016. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=7143&p=143&f=G&l=50&d=PG01&S1=20160303.PD.&OS=PD/20160303&RS=PD/20160303

Keywords for this news article include: Product Innovation & Engineering Llc.

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Source: Equities.com News (March 17, 2016 - 8:41 PM EDT)

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