Patent Application
20140252687
The present disclosure relates to Additive Manufacturing systems and techniques for making three dimensional articles and parts, and more particularly to a system and method for performing Additive Manufacturing using a high power diode system.
The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Additive Manufacturing (“AM”), also referred to as 3D printing, is a manufacturing technique in which material is added sequentially, layer by layer, in order to build a part. This is in contrast to traditional machining, where the part starts as a block of material that is then whittled down to the final desired shape. With AM fabrication, a directed power source is used to agglomerate material (typically powder) into a final, near net-shape article. Three dimensional articles are manufactured one layer at a time as an assemblage of two-dimensional sections. One important advantage of AM fabrication is that complex shapes (e.g. parts with internal features) can be realized. Another important advantage is that the material required is limited to that used to form the final part. Thus, AM fabrication has the benefit of very little material loss. This is especially important for expensive/tightly controlled materials.
The use of AM for metal fabrication is relatively recent. Historically, plastics have been the focus of commercial systems that employ AM. Nevertheless, the use of metals with AM is highly commercially and technologically important because the majority of engineered structures rely heavily on metals. Metal AM requires a relatively high power, highly focused laser beam (typically on the order of 100 W-1000 W) to melt, fuse, and/or sinter metallic powder. The metal powder is typically placed in a powder bed during the AM process. The laser beam is rastered along the powder surface to make a two-dimensional section per pass. Once each layer is completed, the powder bed retracts and new powder is layered on top of the just-completed layer. Considering that a typical layer thickness is only about 50-100 microns, it can be seen how this rastering is the most time consuming step. This is the principal reason why objects that would only take two to three hours to machine using traditional machining methods may take up to eight hours or more using AM. Moreover, due to the necessity of rastering the laser beam, the maximum part size can be limited. Presently a 25 cm×25 cm area part size is the largest part size that can be made with an AM technique that involves rastering the laser beam. Accordingly, there is a strong desire to reduce the time required to manufacture objects, and particularly metal objects, using AM. One important challenge that the present disclosure addresses is overcoming this relatively slow speed necessitated by the raster scanning operation employed with a conventional AM fabrication process.
In one aspect the present disclosure relates to a system for performing an Additive Manufacturing (AM) fabrication process on a powdered material forming a substrate. The system may comprise a diode array for generating an optical signal sufficient to melt or sinter a powdered material of the substrate. A mask may be used for preventing a first predetermined portion of the optical signal from reaching the substrate, while allowing a second predetermined portion to reach the substrate. At least one processor may be used for controlling an output of the diode array.
In another aspect the present disclosure relates to a system for performing an Additive Manufacturing (AM) fabrication process on a powdered material forming a substrate. The system may comprise a diode array for generating a pulsed optical signal sufficient in optical intensity to melt or sinter a powdered material of the substrate. A mask may be interposed between the diode array and the substrate for preventing a first predetermined portion of the pulsed optical signal from reaching the substrate, while allowing a second predetermined portion to reach the substrate. The mask may be configured to be controlled and addressable by a processor to electronically enable selected subportions of the substrate to be masked off. A processor may be used for electronically controlling the mask.
In still another aspect the present disclosure relates to a method for performing Additive Manufacturing (AM). The method may comprise irradiating a powdered layer of a substrate using a pulsed optical signal sufficient to irradiate at least a substantial portion of an entire two dimensional layer within which the substrate is positioned. A mask may be used to selectively block a first subportion of the pulsed optical signal from reaching the first layer of the substrate. A second layer of powdered material may be placed over the first layer. The second layer may be irradiated using the pulsed optical signal while using the mask to selectively block a second subportion of the pulsed optical signal from reaching the second layer of the substrate.
Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. In the drawings:
The following description is merely exemplary in nature and is not intended to limit the present disclosure, application, or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features.
Referring to
In one preferred form the diode array 12 may comprise a single large diode bar. Alternatively a plurality of diode bars located adjacent one another may be used to form the diode array 12. In one preferred form the diode array may be made up of arrays of diode bars each being about 1 cm×0.015 cm to construct a 25 cm×25 cm diode array. However, any number of diode bars may be used, and the precise number and configuration may depend on the part being constructed as well as other factors. Suitable diode bars for forming the diode array 12 are available from Lasertel of Tucson, Ariz., Oclaro Inc. of San Jose, Calif., nLight Corp. of Vancouver, Wash., Quantel Inc. of New York, N.Y., DILAS Diode Laser, Inc. of Tucson, Ariz., and Jenoptik AG of Jena, Germany, as well as many others. The diode array 12 is able to provide a minimum power density of about 10 kW/cm2 and maximum>100 kW/cm2 at two percent duty cycle. This makes it feasible to generate sufficient optical power to melt a wide variety of materials.
It will also be appreciated that a significant advantage of using a diode array comprised of one or more diode bars is that such an assembly is readily scalable. Thus, diode arrays of various sizes can be constructed to meet the needs of making a specific sized part. For example, the diode array 12 may be constructed to have a one square meter area, which would allow correspondingly large scale components to be constructed through an AM fabrication process, provided of course that a suitably sized powder bed is available to support fabrication of the part. Another significant advantage is that the system 10 can be integrated into existing AM fabrication systems with the added benefit of no moving parts. The system 10 allows for the AM fabrication of traditionally difficult to fabricate and join metal such as ODS (oxide dispersion strengthened) steels or any alloy traditionally formed using solid state (i.e. non-melt) processing techniques.
Referring to
In
During an actual AM fabrication operation, a first layer of powdered material may be acted on by the system by pulsing the diode array 12 to melt selected portions (or possibly the entire portion) of the first layer. A subsequent (i.e., second) layer of powdered material may then be added over the layer just acted on by the system 10 and the process would be repeated. The diode array 12 may be pulsed to melt one or more selected subportions (or possibly the entirety) of the second layer of material. With each layer the system 10 electronically controls the pixels of the mask 14 to selectively block specific, predetermined portions of the substrate 20 from being irradiated by the pulsed optical signal from the diode array 12. This process is repeated for each layer, with the computer 18 controlling the mask 14 so that, for each layer, one or more selected subportions (or possibly the entirety) of the powdered material is blocked by the mask 14 from being exposed to the pulsed optical signal. Preferably, an entire two dimensional area of each layer is melted or sintered at once by pulsing the diode array 12. However, it is just as feasible to raster scan the diode array 12 over the two dimensional area in the event the entire two dimensional area cannot be completely irradiated by the diode array.
An alternative to the addressable mask 14 is a non-addressable mask. A non-addressable mask may be a precision cut piece of metal (e.g., tungsten) that would simply block portions of the light beam. While such a machined mask can be used to build simple geometries, the full potential of the system 10 described herein will be maximized if an addressable mask such as mask 14 is used.
Referring to
The systems 10, 100 and 200 are able to melt and sinter each layer in a single “pass” or, put differently, in a single operation by pulsing the diode array 12. The need to raster scan an optical beam dozens, hundreds or more times, back and forth across a surface, is therefore eliminated. This significantly reduces the time required to melt and sinter each layer of powder material during the AM fabrication process.
Referring to
While various embodiments have been described, those skilled in the art will recognize modifications or variations which might be made without departing from the present disclosure. The examples illustrate the various embodiments and are not intended to limit the present disclosure. Therefore, the description and claims should be interpreted liberally with only such limitation as is necessary in view of the pertinent prior art.
The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the U.S. Department of Energy and Lawrence Livermore National Security, LLC, for the operation of Lawrence Livermore National Laboratory.
