Additive manufacturing power map to mitigate overhang structure

A laser powder bed fusion additive manufacturing system for producing a part by creating a power map that is an intelligent feed forward model to control the laser powder bed fusion additive manufacturing for producing the part and using the power map to control the laser powder bed fusion additive manufacturing for producing the part. This includes an apparatus for producing a part including a powder bed, a laser that produces a laser beam, a proportional integral derivative controller that creates a power map that describes laser power requirements as the laser moves along a path, wherein the laser power requirements prevent defects in the part.

BACKGROUND

Field of Endeavor

The present application relates to additive manufacturing and more particularly to Additive Manufacturing: Power map to mitigate overhang structure.

State of Technology

The challenge is to build an overhang structure using AM, without formation of dross. That is how to maintain a smooth surface at the overhang. These overhang structures can differ in build quality from machine to machine due to the randomness of the dross process.

There is no prior art other than trial and error, and still, this does not produce optimal overhang structure.

The inventors' method uses Intelligent Feed Forward principle by employing an additive manufacturing power map an PID loop within a computational simulation. This helps maintain a constant melt pool depth, by automatically monitoring the laser energy deposition. Hence, since dross is equivalent to randomly produced melt depth that exceeds the accepted roughness threshold, the PID controls the amount of melt depth and keeps it in control, constant, hence avoiding wild fluctuations (dross) and help keep the surface smooth.

SUMMARY

Features and advantages of the disclosed apparatus, systems, and methods will become apparent from the following description. Applicant is providing this description, which includes drawings and examples of specific embodiments, to give a broad representation of the apparatus, systems, and methods. Various changes and modifications within the spirit and scope of the application will become apparent to those skilled in the art from this description and by practice of the apparatus, systems, and methods. The scope of the apparatus, systems, and methods is not intended to be limited to the particular forms disclosed and the application covers all modifications, equivalents, and alternatives falling within the spirit and scope of the apparatus, systems, and methods as defined by the claims.

The inventors' apparatus, systems and methods provide an intelligent feed forward model to control additive manufacturing (AM) laser powder bed fusion process, whereby, the laser crosses an overhang section and creates a smooth overhand inner walls, with little to no dross formation. This is accomplished by controlling the laser power through a computer model. The description below describes using a proportional integral derivative (PID) controller to create a power map. The benefit of the process map is to eliminate dross formation in overhangs built using AM. These rough surface defects are random in nature. Their presence prevent machine to machine reproducibility of same AM parts. Also, they have a deleterious effect on part properties. Removing them is a major need and requirement for future AM machines.

The inventors' apparatus, systems and methods have use in additive manufacturing machines that use energy beams to create AM parts for any application.

The apparatus, systems, and methods are susceptible to modifications and alternative forms. Specific embodiments are shown by way of example. It is to be understood that the apparatus, systems, and methods are not limited to the particular forms disclosed. The apparatus, systems, and methods cover all modifications, equivalents, and alternatives falling within the spirit and scope of the application as defined by the claims.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

Referring to the drawings, to the following detailed description, and to incorporated materials, detailed information about the apparatus, systems, and methods is provided including the description of specific embodiments. The detailed description serves to explain the principles of the apparatus, systems, and methods. The apparatus, systems, and methods are susceptible to modifications and alternative forms. The application is not limited to the particular forms disclosed. The application covers all modifications, equivalents, and alternatives falling within the spirit and scope of the apparatus, systems, and methods as defined by the claims.

The inventors have developed an intelligent feed forward model to control additive manufacturing (AM) laser powder bed fusion process, whereby, the laser crosses an overhang section and creates a smooth overhand inner walls, with little to no dross formation. This is accomplished by controlling the laser power through a computer model. The Applicants will describe using a proportional integral derivative (PID) controller to create a power map. The benefit of the process map is to eliminate dross formation in overhangs built using AM. These rough surface defects are random in nature. Their presence prevent machine to machine reproducibility of same AM parts. Also, they have a deleterious effect on part properties. Removing them is a major need and requirement for future AM machines. The inventor's apparatus, systems and methods will be used in additive manufacturing machines that use energy beams to create AM parts for any application.

Referring now to the drawings and in particular toFIG. 1andFIG. 2, simplified schematic depictions illustrates an object constructed using an AM.FIGS. 1 and 2will be used to demonstrate dross formation in overhangs.FIG. 1illustrates an object constructed using an AM and using a first material and a second material. As illustrated, the depiction inFIG. 1includes a number of components. The components illustrated inFIG. 1are identified and described below.Reference Numeral100—Object.Reference Numeral102—The part of object100consisting of a first material.Reference Numeral104—Simple square openings features to be built into object100.Reference Numeral106—Simple round holes features to be built into object100.
Reference Numeral108—Bridging material of made of a second material used in the AM of object100.

Referring now toFIG. 2, a simplified schematic depiction further illustrates the object100constructed using an AM and helps demonstrate dross formation in overhangs. The components illustrated inFIG. 2are identified and described below.Reference Numeral100—Object.Reference Numeral102—The part of object100consisting of a first material.Reference Numeral104—Simple square openings features to be built into object100.Reference Numeral106—Simple round holes features to be built into object100.Reference Numeral209—Dross or overhang that can occur during AM constructing of a desired object.

The description of the components illustrated inFIG. 2having been completed, the operational aspects of constructing the object100using an AM system that incorporates the inventor's apparatus, systems and methods will now be considered. The bridging material108has been etched/removed leaving the features104and106exposed. A common problem encountered is that dross or overhang209can occur. Dross or overhang209is shown in the features104and106.

Referring now toFIG. 3, a simplified illustration shows the construct of an object using an using an AM system with a first material and a second material. The components illustrated inFIG. 3are identified and described below.Reference Numeral300—System for constructing an object.Reference Numeral302—Object.Reference Numeral304—Build platform.Reference Numeral306—First material.Reference Numeral308—First printhead.Reference Numeral310—First material stream.Reference Numeral312—Second material.Reference Numeral314—Second printhead.Reference Numeral316—Second material stream.Reference Numeral318—Arrows indicating possible movement directions for print heads308and314.Reference Numeral320—Computer/Controller.

The system300for constructing an object is an AM system for producing an object302. The part306of the object302is constructed of the first material306. One or more features made of the second material312are included in the object302.

The system300incudes a build platform304, a first printhead308, and a second printhead314. A first material306is directed into the first printhead308and is extruded from the first printhead308in a first material stream310to produce the part306of the object302. A second material312is directed into the second printhead314and is extruded from the second printhead314in a second material stream316to produce the feature made of the second material312. Relative movement between the build platform304and the first and second printhead308and314is illustrated by the arrows318. A computer/controller320directs operation of the system300to produce the object302.

Referring now toFIGS. 4, 5, and 6; illustrations will be used to further demonstrate dross formation in overhangs.FIG. 4illustrates an object constructed using an AM. The components illustrated inFIG. 4are identified and described below.Reference Numeral400—Object.Reference Numeral402—Layers of melted powder.Reference Numeral404—Layers of bridging material made of a second material.Reference Numeral406—Laser beam.Reference Numeral408—Laser beam path.Reference Numeral410—A single layer of the layers of melted powder402.

FIG. 4illustrates a moment in time in the AM construction of the object400. InFIG. 4an object400being made of a first material and a second material is shown. The first material is the layers of melted powder402. The second material is the layers of the bridging material404. The second material404will eventually be removed to complete the final workpiece/object400. Note that for simplicity only the overall second material404is shown and the individual layers of the second material do not appear.

The laser beam406moves along the laser beam path408to melt the metal powder and form the solidified layers of the object400.FIG. 4illustrates a moment in time in the AM construction of the object400when the single layer410has been applied. The layers of the first material402and the layers of the second bridging material404have been laid down.

Referring now toFIG. 5the object400being constructed using an AM is illustrated. The components illustrated inFIG. 5are identified and described below.Reference Numeral400—Object.Reference Numeral402—Layers of melted powder.Reference Numeral404—Layers of bridging material made of a second material.Reference Numeral406—Laser beam.Reference Numeral408—Laser beam path.Reference Numeral410—A single layer of the layers of melted powder402.Reference Numeral412—An additional layer of the layers of melted powder402.

FIG. 5illustrates another moment in time in the AM construction of the object400. InFIG. 5the object400being made of a first material and a second material is shown. The first material is the layers of melted powder402. The second material is the layers of the bridging material404. The second material404will eventually be removed to complete the final workpiece/object400. Note that for simplicity only the overall second material404is shown and the individual layers of the second material do not appear. InFIG. 5an additional layer412of melted powder is shown being applied on top of the layer410.

The laser beam406moves along the laser beam path408to melt the metal powder and form the solidified layers of the object400.FIG. 5illustrates another moment in time in the AM construction of the object400when the layers of the first material402including the single layer410and the layers of the second bridging material404have been laid down.FIG. 5shows the additional layer412of melted powder being applied on top of the layer410.

Referring now toFIG. 6the object400being constructed using an AM is shown with illustration of dross formation in an overhang. The components illustrated inFIG. 6are identified and described below.Reference Numeral400—Object.Reference Numeral402—Layers of melted powder.Reference Numeral404—Layers of bridging material made of a second material.Reference Numeral406—Laser beam.Reference Numeral408—Laser beam path.Reference Numeral410—A single layer of the layers of melted powder402.Reference Numeral412—An additional layer of the layers of melted powder402.Reference Numeral414—An area where the laser beam power remains constant.Reference Numeral416—Dross/overhang416.

FIG. 6illustrates and further demonstrates dross formation in an overhang. InFIG. 6the object400being made of a first material and a second material is shown. The first material is the layers of melted powder402. The second material is the layers of the bridging material404. The second material404will eventually be removed to complete the final workpiece/object400. Note that for simplicity only the overall second material404is shown and the individual layers of the second material do not appear. InFIG. 6an additional layer412of melted powder has been applied on top of the layer410.

In each pass408of the laser beam406in the areas outside of area414the beam406not only melts/fuses the additional layer412, the laser beam406also fuses the layer412to the layer410below layer412. If the laser beam power remains constant in the area labeled414, too much energy will be applied. This leads to melting into the bridge material40and the formation of dross/overhang416that will remain after removal of the bridging material in a later step of the AM process.FIG. 6shows dross/overhang416extending into the second bridging material404. This dross/overhang416will remain after removal of the bridging material404in a later step of the AM process.

The inventor's additive manufacturing power map mitigates overhang defects by reducing the laser power as the laser beam moves along the area labeled414. A tracer point can be used by a PID controller. By requesting the temperature variable at that point to be equal to melting temperature, the PID controller will control the power to achieve this end.

The inventors' apparatus, systems and methods provide a solution to the problem illustrated inFIGS. 4, 5, and 6. The inventors additive manufacturing power map mitigates overhang structures. The inventors additive manufacturing power map uses an intelligent feed forward model to control additive manufacturing (AM) laser powder bed fusion process, whereby, the laser crosses an overhang section and creates a smooth overhand inner walls, with little to no dross formation. This is accomplished by controlling the laser power through a computer model. A proportional integral derivative (PID) controller creates a power map. The benefit of the process map is to eliminate dross formation in overhangs built using AM. These rough surface defects are random in nature. Their presence prevent machine to machine reproducibility of same AM parts. Also, they have a deleterious effect on part properties. Removing them is a major need and requirement for future AM machines.

Referring now toFIG. 7, an illustration shows the final finished workpiece/object700constructed using an AM and the inventors' power map apparatus, systems and methods. The components illustrated inFIG. 7are identified and described below.

Reference Numeral702—Simple square openings and round hole features built into finished workpiece/object700.

The powder bed fusion system includes an apparatus in which selected areas of a powder bed are solidified in a layer-by-layer manner to form a workpiece. A laser generates a laser beam across the surface of the powder bed to solidify predetermined areas of each layer. Applicants' AM power map mitigates defects when the laser follows a laser path that produces a laser beam path on the powder bed.

The inventors' power map system utilizes the PID (proportional integral derivative) to decrease the laser power and maintain a constant melt depth. Since the energy is accumulating in overhang region, the temperature at the tracer point is maintained fixed. The PID then controls the power by decreasing it, so as to decrease the amount of energy deposited and maintain a constant temperature value at the depth of the tracer point. This in turns guarantees fixed melt pool depth and prevents formation of dross.

Additional details of the inventors' inventors additive manufacturing power map are disclosed in the patent applications identified and described below. The content of the patent applications identified and described below are hereby incorporated herein by reference in their entirety for all purposes.U.S. Provisional Patent Application No. 62/647,358 filed Mar. 23, 2018 entitled “additive manufacturing power map to mitigate overhang structure.”U.S. Provisional Patent Application No. 62/647,375 filed Mar. 23, 2018 entitled “additive manufacturing power map to mitigate defects.”U.S. patent application Ser. No. 16/145,483 filed Sep. 28, 2018 entitled “additive manufacturing power map to mitigate defects.”

Although the description above contains many details and specifics, these should not be construed as limiting the scope of the application but as merely providing illustrations of some of the presently preferred embodiments of the apparatus, systems, and methods. Other implementations, enhancements and variations can be made based on what is described and illustrated in this patent document. The features of the embodiments described herein may be combined in all possible combinations of methods, apparatus, modules, systems, and computer program products. Certain features that are described in this patent document in the context of separate embodiments can also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment can also be implemented in multiple embodiments separately or in any suitable subcombination. Moreover, although features may be described above as acting in certain combinations and even initially claimed as such, one or more features from a claimed combination can in some cases be excised from the combination, and the claimed combination may be directed to a subcombination or variation of a subcombination. Similarly, while operations are depicted in the drawings in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. Moreover, the separation of various system components in the embodiments described above should not be understood as requiring such separation in all embodiments.

Therefore, it will be appreciated that the scope of the present application fully encompasses other embodiments which may become obvious to those skilled in the art. In the claims, reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural and functional equivalents to the elements of the above-described preferred embodiment that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Moreover, it is not necessary for a device to address each and every problem sought to be solved by the present apparatus, systems, and methods, for it to be encompassed by the present claims. Furthermore, no element or component in the present disclosure is intended to be dedicated to the public regardless of whether the element or component is explicitly recited in the claims. No claim element herein is to be construed under the provisions of 35 U.S.C. 112, sixth paragraph, unless the element is expressly recited using the phrase “means for.”

While the apparatus, systems, and methods may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the application is not intended to be limited to the particular forms disclosed. Rather, the application is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the application as defined by the following appended claims.