Patent Application
20160250808
This invention relates generally to printing three dimensional (3D) objects, and more particularly to printing a 3D object using a 3D printer depositing a stack of layers of print material.
Additive and subtractive manufacturing technologies enable computer designs, such as CAD files, to be made into 3D objects. 3D printing, also known as additive manufacturing, typically includes depositing, curing, fusing, or otherwise forming a material into sequential cross-sectional layers of the 3D object. For example, fused deposition modeling techniques include melting a filament of print material and extruding the print material out of a dispenser that is moved in the x-, y-, and z-axes relative to a print pad. The print material is generally deposited in layers in the x- and y-axes to form cross-sectional layers that are stacked along the z-axis to form the 3D object.
3D objects that do not have a planar down-facing surface typically must be supported in some or all areas below the 3D objects. In addition, some additive manufacturing techniques cannot print a 3D object directly onto the print pad because such direct contact between the printed object and the print pad can cause surface flaws on the contacting surface of the printed object or may cause difficulty in the separation of the printed object from the print pad.
Various conventional methods have been developed to provide a mechanical support for printing different parts of the object. For example, one method uses special material selected to be either very brittle when cooled to the room temperature or soluble in another liquid, see, e.g., U.S. 2013/0236706. However, those methods require an application of force to remove the support structure and/or a liquid bath necessitating protracted immersion and agitation of the printed object to adequately dissolve away the support material.
Another method reducing the interface between the printed object and the support structure to a set of fine points, thereby reducing the force necessary to break and to separate the support structure, see, e.g., U.S. 2013/0307193. However, the additional extrusion material must be sufficiently strong to support the printed object, which can create a situation where breaking away the support material may also break portions of the final printed part. This makes the removal of the support material difficult and may require skilled labor, which negates many of the advantages of 3D printing.
Some embodiments of the invention are based on recognition that it is not necessary to cool the printing material completely to provide a structural support for the subsequent printed layers. Instead, it is sufficient to cool the material only below the glass transition temperature. When the heat from hot extruded print material is removed sufficiently fast, the material becomes structurally strong reducing the need for an additional support or at least without a need for prolonged additional support.
Usually, the structures supporting overhanging parts of the printed object provide both mechanical support for printing the print material and serve as a heat sink to cool the print material below the glass transition temperature Tg. In fact, the supporting structure is attached, i.e., bonded, to the printed material to provide multi-directional support preventing deformation of the print material in all directions and to facilitate the cooling.
Some embodiments are based on additional realization that when the print material is rapidly cooled, there is no need for mechanical support in all directions, but only into the direction of sagging, e.g., a direction of a force of gravity. Such a mechanical support can be provided without attaching the support structure to the printed object. It is sufficient that the supporting structure support the print material from beneath, and let the cooling print material constrain itself in the other directions.
These realizations allow using a non-sticking material between layers of the support structure and the layers of printed object. A support structure covered with non-sticking material can provide vertical mechanical support to the printed layers without being attached to the printed layers, and serves as a heat transfer medium for cooling of the hot print material, which in turn prevents structural deformations in other directions within a plane of the layer.
Accordingly, one embodiment of the invention discloses a method for printing a three dimensional (3D) object using a 3D printer depositing a stack of layers of print material, such that each layer is bonded to at least a portion of another layer in the stack forming the object. The method includes providing a support layer of material; covering at least a portion of the support layer with a non-sticking material having a property selected to reduce bonding of the print material to the non-sticking material and to the support layer; and depositing a layer of the print material on the support layer including the portion of the support layer covered with the non-sticking material.
Another embodiment discloses a three dimensional (3D) printer for 3D objects by depositing a stack of layers of print material, such that each layer is bonded to at least a portion of another layer in the stack forming the object. The printer includes an extrusion nozzle for dispersing print material; an applicator for depositing non-sticking material having a property selected to reduce bonding of the print material to the non-sticking material; and a processor for coordinating a movement of the extrusion nozzle and a movement of the applicator, such that a printing of an object includes printing at least a portion of a layer of the print material on at least a portion of a support layer covered with the non-sticking material.
The printer 100 also includes an applicator 104 for depositing non-sticking material 105 having a property selected to reduce bonding of the print material to the non-sticking material. For example, the non-sticking material can be oil. The printer 100 also includes a processor 110 for coordinating an operation of the extrusion nozzle and an operation of the applicator. In various embodiments, the processor controls the operations such that a printing of an object includes printing at least a portion of a layer of the print material on at least a portion of a support layer covered with the non-sticking material.
For example, at some point of time during the printing, as shown in
At a different point of the printing, as shown in
In some embodiments, at least two motors coordinate movements of the extrusion nozzle and the applicator, such that the extrusion nozzle and the applicator interchange their positions during the movements. In some embodiments, the upward movement 125 of the nozzle 103 is optional and can be omitted when the placement locations for the release agent 108 are pre-sorted so the nozzle 103 does not perform a contacting traversal of an already-coated area.
In one embodiment, the applicator 104 is a contacting applicator for applying the non-sticking material via a mechanical contact with at least a portion of the support layer. The contacting applicator can include a porous material such as foam rubber, cotton, wool, felt, or porous thermoset fiber, to provide both a reservoir for the release agent and a soft, compliant contacting surface. In this embodiment, an optional reservoir 108 can be added to supply the non-sticking material 105 to the applicator 104 via a channel 107, which can be a tube, a wick, or other means, whether pumped or allowed to flow by gravity or capillary action.
Some embodiments are based on a realization that when the print material is rapidly cooled, there is no need for mechanical support in all directions, but only into the direction of sagging, e.g., a direction of a force of gravity. Such a mechanical support can be provided without attaching the support structure to the printed object. It is sufficient that the supporting structure support the print material from beneath, and let the cooling print material constrain itself in the other directions.
This realization allows using a non-sticking material between layers of the support structure and the layers of printed object. A support structure covered with non-sticking material can provide vertical mechanical support to the printed layers without being attached to the printed layers, and serves as a heat transfer medium for cooling of the hot print material, which in turn prevents structural deformations in other directions within a plane of the layer.
In various embodiments, the non-sticking material is selected to have properties to reduce bonding of the print material to the non-sticking material and to the underlying support layer. For example, in some embodiments, the non-sticking material is liquid or powder preserving its state after forming the object. Examples of the non-sticking material include oil, such as cooking oil, mold release material, talcum powder and mica dust.
In some embodiments, the non-sticking material is selected to be easily removed from the final object, by, e.g., washing or evaporation. For example, in one embodiment, the volatility of non-sticking material is selected to be positive in a room temperature, e.g., the temperature around 20° C.
Additionally or alternatively, some embodiments heat to the printed object to a temperature sufficient to evaporate the non-sticking material without deforming the printed object. There are many non-sticking materials usable in the various embodiments of the invention. Some commonly available non-sticking materials include no-stick cooking spray, 3-in-1 oil that can be removed with soap and water, and Sprayon Dry Film Release Agent MR-311, which can be selected for its durability and lubricity.
After the layer of print material is deposited, the method can further dispense 340 a set of layers of the print material on the layer of the print material to form the object. In such a manner, each layer is bonded to at least a portion of another layer in the stack forming the object.
In some embodiments, the support layer is printed 360 with the print material and form a part of the object detached from another part of the object. In another embodiment, the support layer is also printed 360 but do not form the part of the object and subsequently removed or separated 350 from the layer of the print material to form the object. The non-sticking material prevents bonding of the print material to the support layer to facilitate such a separation. Additionally or alternatively, the support layer can be a surface of a structure manufactured by different means other than printing. For example, the support structure can be separately manufactured, e.g., using metal or other rigid material, and reused for printing multiple objects.
Similarly, a spring clip with a zero unspring opening height can be fabricated as a single piece and used to hold cloth, paper, insulation, plastic film in the final assembly without requiring a second clamping element. Fabricating such a clip with the conventional printing is difficult due to the need of forming near zero gap for the desired rest position of the spring clip jaws.
Although the invention has been described by way of examples of preferred embodiments, it is to be understood that various other adaptations and modifications can be made within the spirit and scope of the invention. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the true spirit and scope of the invention.
