1. A method for forming an object having a three-dimensional target shape, comprising:
- a) providing a build powder, a support powder, a binder and a container and wherein said build powder is bindable by said binder and said support powder is substantially not bindable by said binder;
b) dispensing said build powder and said support powder into said container in a sequence of layers of build powder patterned with support powder that collectively form the three-dimensional shape in build powder, supported directly by support powder;
c) applying the binder to the build powder, thereby forming said object, made of build powder and binder; and
d) separating said object from said support powder.
A method for forming an object having a three-dimensional target shape, that makes use of a build powder, a support powder and a binder. The build powder is more strongly bound by the binder than is the support powder. The build powder and the support powder are dispensed in a sequence of layers of build powder patterned with support powder that collectively form the three-dimensional shape in build powder, and the binder is applied to the deposited build powder, thereby forming the object of build powder and binder. Finally, the formed object is separated from the support powder.
- 1. A method for forming an object having a three-dimensional target shape, comprising:
a) providing a build powder, a support powder, a binder and a container and wherein said build powder is bindable by said binder and said support powder is substantially not bindable by said binder; b) dispensing said build powder and said support powder into said container in a sequence of layers of build powder patterned with support powder that collectively form the three-dimensional shape in build powder, supported directly by support powder; c) applying the binder to the build powder, thereby forming said object, made of build powder and binder; and
d) separating said object from said support powder.
- View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20)
This application is a continuation of U.S. patent application Ser. No. 15/889,664, filed Feb. 6, 2018, which itself is a continuation of international application PCT/US17/52593 filed on Sep. 20, 2017, which claims benefit of provisional application U.S. Ser. No. 62/397,549, filed on Sep. 21, 2016, all of which are incorporated by reference as if fully set forth herein.
The present invention is in the field of 3D printers for the manufacture of objects.
Although three-dimensional (3D) printing does currently exist, much of this technology is expensive to use, and the range of materials that are useable in a particular printer are usually quite limited. This creates an encumbrance, especially for those wishing to produce metal parts through 3D printing.
One example is US Published Application No. 2015/0210010, in which liquid or gel substances are deposited and then cured. The use of liquids and gels limits material selection. For example, it is impractical to dispense most metals as liquids because of their high melting temperatures, and tendency to oxidize when molten and exposed to air. Also, US Published Application No. 2002/0145213, discloses the deposition of layers of build powder, and the selective deposition of binder powder interspersed into the build powder. But using this method, it is virtually impossible to get the thorough mixture of bind powder with build powder that is necessary to create a uniform printed object, without porosities. Further, if the build and binder powders are similar, the unbound build powder may tend to sinter together at the temperatures necessary to activate the bind powder, causing great difficulty in freeing the printed object from the surrounding sintered powder. But if the bind powder and build powder are dissimilar, the different material qualities can cause undesirable properties in the resultant 3D printed object. Both of these references appear to disclose systems in which a curing operation is required after the deposition of each layer, a step that prolongs the process and adds to the complexity and expense of the required machinery.
In a first separate aspect, the present invention may take the form of a method for forming an object having a three-dimensional target shape, that makes use of a build powder, a support powder and a binder. The build powder is more strongly bound by the binder than is the support powder. The build powder and the support powder are dispensed in a sequence of layers of build powder patterned with support powder that collectively form the three-dimensional shape in build powder, and the binder is applied to layers of build and support powder and permitted to cure, thereby forming the object of build powder and binder. Finally, the support powder is removed from the formed object.
In a second separate aspect, the present invention may take the form of an apparatus for making three-dimensional physical objects, that includes a frame and a pan. A build powder pourer is at least partially filled with build powder and a support powder pourer is at least partially filled with support powder, each of the pourers having a dispensing opening and a dispensing plug, controllably covering the dispensing opening. A pourer-movement and dispensing plug-actuating assembly is supported by the frame over the pan, and includes a movement element that is selectively attachable to the build powder pourer and alternately to the support powder pourer and is also capable to controllably move an attached pourer in three orthogonal dimensions and to control the dispensing plug. A computer assembly, including an input for receiving a target three-dimensional shape, controls the pourer-movement and dispensing plug-actuating assembly to move the pourers and selectively open the plugs, thereby causing powder to be poured into the pan, and to thereby create in the pan a sequence of layers of build powder patterned with support powder that collectively forms the target shape in build powder.
Definition: the term, “metal” is used in this application, encompasses metal alloys.
For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Any alterations and further modifications in the described embodiments, and any further applications of the principles of the invention as described herein are contemplated as would normally occur to one skilled in the art to which the invention relates.
Note: where there are a set of like elements, labelled N.1-N.4 (where N is an integer), an arbitrary one of these will be labelled, for example N, where it does not matter which one of N.1-N.4 is being referred to. For example, if an arbitrary one of pourers 10.1-10.4 is being referred to, it will be referenced by “10”.
The 3D printer uses a build powder and a support powder to build up 3D objects in the pan 4, layer by layer. Each layer consists of a region or multiple regions filled with build powder while the rest of the pan area in that layer is filled with support powder. In one embodiment, some part of a region might be skipped during pouring of a layer and filled later when pouring a layer above it, to increase the speed of the pouring process. After all layers have been poured, the build powder is bound by a binder, resulting in a 3D object, which is then separated from the support powder. The powders may be made from any appropriate material, provided that the following requirements are met:
1. Build and support powders are pourable, or at least arrangeable into a desired pattern by an appropriate mechanism.
2. Build powder is strongly bindable by the binder.
3. Support powder is far less strongly bindable by the binder that is the build powder.
4. Build and support powders remain mostly in solid particulate form during the process, to prevent shape distortion.
It is also important that the ambient gas is chosen appropriately to facilitate the above requirements. For example, if oxidation would negatively impact bindability of the build powder by the binder, the ambient gas should be selected to prevent oxidation. For example, in some embodiments the ambient gas is argon. In these embodiments the mechanism is enclosed in an air-tight chamber. In an alternative embodiment a substance that binds with oxygen, such as carbon in the form of coke, is put in the pan 4 before it is heated
In a preferred embodiment, iron powder is used as the build powder, silicon dioxide powder is used as the support powder, and molten iron-carbon alloy with high carbon content is used as a binder. Iron-carbon alloys of varying carbon content may be used, although a carbon content of 4.3% has the advantage of having the lowest melting temperature—about 1147 degrees Celsius. This alloy is commonly available as “Pig Iron,” and is henceforth referred to simply as “Pig” in this text. In this embodiment, the powders are poured in such a way that the top layer has exposed build powder.
After the 3D pattern of iron powder and SiO2 powder has been created, a separator 110, having a through-hole is placed over the powder and a piece of Pig and a piece of carbon, such as coke, are placed on the separator, in such manner to avoid deforming the build powder shape. The pig should cover the hole in the separator 110, which should be above the surface of exposed build powder, to avoid SiO2 powder blocking the flow of molten pig. The pan 4 is then filled the rest of the way with SiO2 powder (in some methods, sand). The piece of carbon is needed to convert oxygen into carbon monoxide when heated, to prevent oxidation of the iron. The pan 4 is closed with a lid, transferred to a kiln, and heated. The kiln temperature is chosen to be above the melting temperature of Pig but below the melting temperature of the iron powder. When the temperature gets high enough, the Pig melts and soaks through the iron powder by capillary action, but the Pig does not soak the silicon dioxide powder, which resists wetting by molten iron. The pan is held at that temperature for a certain length of time, referred to as the hold time. During the hold time, the carbon atoms of the molten Pig diffuse into the particles of the iron powder, thus equalizing the carbon content. Longer hold times result in a better diffusion. After the pan is cooled down, the printed object is separated from the support powder and the remains of the Pig are cut off. Preferably, the printed object is designed such that it has an additional narrow neck at the top and a flat pad above it, such that the molten Pig would soak the object through the pad and the neck, making it easier to cut or break the neck separating the object from the pad and the remains of the Pig. The resulting material of the printed object is carbon steel. Further post-processing and heat treatment can be used to achieve desired properties and dimensions.
In another embodiment, the build powder is copper powder, the support powder is silicon dioxide, and the binder is copper-silver alloy.
In additional embodiments, instead of using a molten material as the binder, a chemical process is used to bind the particles of the build powder.
In one embodiment, the build powder is cement, the support powder is silicon dioxide, and the binder is water, which soaks the cement and causes binding.
In another embodiment, an epoxy is used as the binder. The build powder is a polymer such as, for example, Polytetrafluoroethylene (PTFE), Polyether ether ketone (PEEK), Nylon, Acrylonitrile Butadiene Styrene (ABS), Polylactic Acid (PLA), Polyoxymethylene (POM), Polycarbonate (PC), Polyvinyl Chloride (PVC), Polyethylene terephthalate (PET), Polyethylene (PE), Polypropylene (PP), Polystyrene (PS), Poly(methyl methacrylate) (PMMA), Polybenzimidazole (PBI), Polyethersulfone (PES), Polyetherimide (PEI), Polyphenylene oxide (PPO), or Polyphenylene sulfide (PPS), and the support powder is another polymer from the same list. The polymer used for support powder is non-wettable by the epoxy; the polymer used for build powder is wettable by the epoxy.
In another embodiment, a glue is used as the binder instead of epoxy. The glue can be either chemical or thermal.
In another embodiment, heat is used to bind the particles of the build powder. The build powder is selected to have a glass transition temperature that is lower than the glass transition temperature of the support powder. The temperature used for binding is chosen to be above the glass transition temperature of the build powder and sufficient to strongly bind the build powder particles together, but not high enough to strongly bind the support powder particles, so that the support can be separated from the object without breaking it. The temperature selected should be below the melting point of either of the two powders to prevent shape distortion.
In another embodiment, multiple build powders of different colors are used to create colorful objects.
Referring again to
Referring now to
Fork assembly 5 also includes plug rod rotating stepper motor 1.S that rotates a claw 21. When carriage 15 is lowered, claw 21 engages with and rotates knob 22 (
In one embodiment, there are four pourers: two for support powder and two for build powder. Of the two pourers for each type of powder, one has a smaller hole 20 for higher resolution pouring, and one has a larger hole 20 for faster pouring.
Referring first to
The above noted movement of arm 150 is effected by a DC Motor 151 (
The fork assembly 105, rides vertically on a vertical tube 186 (
In one example the following parameters were used to produce a high carbon steel 3D printed object.
Build powder: IRON100
The specification, and ordering information for IRON100 can be found on the Internet at: http://www.iron-powder.com/wp-content/uploads/2014/03/IRON100_Specifications.pdf
Following is some information concerning IRON100:
Chemical Analysis (by Weight)
Flow rate 29.00 sec/50 g
Particle size <212 microns.
Median particle size: 100 microns.
The specification for OK85, a product of USSilica, can be found at the following Internet address, and is also reproduced below.
Grain Shape: Round
Melting Point: 3100 Degrees F.
Typical Chemical Analysis: SiO2 (Silicon Dioxide) 99.8%
Particle size: <425 microns.
Median particle size: 150 microns.
Available in an Ingot Size (Approx):
185×120×55 mm (7.25″×4.7×2.5)
5.54 kb (12 lbs.)
Pourer hole diameter: 1 mm for the smaller hole and 4 mm for the bigger hole.
Pourer horizontal moving speed while pouring (in millimeters per second):
Ramp: 600 degrees Celsius per hour
Hold temperature: 1250 degrees Celsius
Hold time: 4 hours
In another example similar parameters were used, except the following:
The OK85 powder was filtered to remove 25% of the largest and 5% of the smallest particles.
The IRON100 powder was filtered to remove 20% of the smallest particles.
Pourer hole diameter: 1 mm for the smaller hole and 2 mm for the bigger hole.
Pourer horizontal moving speed while pouring (in millimeters per second):
Ramp: 600 degrees Celsius per hour
Hold temperature: 1180 degrees Celsius
Hold time: 2 hours
Referring, now, to
The present invention finds industrial applicability in the manufacture of objects via 3D printing.
While a number of exemplary aspects and embodiments have been discussed above, those possessed of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.