Patent Description:
3D plastic printed parts may use plastic powder or plastic cord as feedstock, combined with a binder. A UV source or thermal treatment solidifies and shapes the object layer by layer. The final step is to remove the plastic 3D printed object from the build plate with a light force and/or some mild scraping.

3D metal printed parts are printed on a build plate. The feedstock is made of metal powders or combination of powders. The build plate is placed into the 3D printing machine. Once the machine is activated, a blade deposits a layer of metal powder over the build plate. A laser or series of lasers selectively sinters the metal that will become part of the 3D printed object. The first few passes of the laser essentially weld what will become the 3D printing object to the build plate. The blade then deposits new powdered metal across the surface of the build plate. Selective sintering is repeated and the object is created layer by layer.

Once the printing process is complete, the bond between the print material and the build plate will need to be broken for the printed object to be removed from the build plate. The bond between the print material and the surface of the build plate may make it difficult to separate the 3D printed object from the build plate following completion of the print process. To remove print material from the build plate, a user may be required to employ tools such as a band saw or wire electrical discharge machining (EDM) machine, or other means, to mechanically separate the print material from the build plate. <CIT> describes systems, methods and tool for additive manufacturing on a build surface of a pre-existing component. An additive manufacturing tool successively positions layers of powdered materials and selectively fuses the layers of powdered materials to create an additive component on the build surface of the pre-existing component. The pre-existing component is secured in a build plate by a thermal expansion fit during the additive manufacturing process
<CIT> describes a method for additive manufacturing utilizing a build plate with a release layer. The method includes irradiating a first layer of powder in a powder bed to form a first fused region over a support. The first release layer is provided between the first fused region and the support. The method also includes providing a given layer of powder over the powder bed and irradiating the given layer of powder in the powder bed to form a given fused region.

In one embodiment, an additive manufacturing build plate in accordance with claim <NUM> is provided. Some optional or preferred features are set out in dependent claims.

In some implementations, the solid metal or metal alloy is an insert configured to be snapped into the recessed section.

In some implementations, the basin is filled with the solid metal or metal alloy, wherein the solid metal or metal alloy has a solidus temperature that is lower than a solidus temperature of the material forming the top surface, bottom surface, and side walls of the additive manufacturing build plate.

In some implementations, the solid material forms a flat surface flush at top edges of the build plate basin.

In some implementations, the additive manufacturing build plate further comprises: a metal 3D object printed on a surface of the solid metal or metal alloy filling the basin, wherein the solid metal or metal alloy has a solidus temperature that is lower than a solidus temperature of the printed metal 3D object.

In some implementations, the additive manufacturing build plate comprises: a single part including the top surface, the bottom surface, and the sidewalls.

In some implementations, the additive manufacturing build plate comprises: a frame comprising an interior cutout smaller than the recessed section, the frame configured to retain the metal or the metal alloy during a 3D printing process; and a base comprising the recessed section, wherein the frame is configured be affixed on top of the base.

In one embodiment, an additive manufacturing system, comprises: a build plate, comprising: a top surface, a bottom surface, and sidewalls comprised of a material, wherein the top surface, bottom surface, and sidewalls are dimensioned such that the build plate is useable in a 3D printing device; and a recessed section formed through the top surface; and an insert of a solid metal or metal alloy that provides a surface for forming a 3D printed object in the 3D printing device, the insert dimensioned to be inserted into and secured within the recessed section.

In some implementations of the system, the solid metal or metal alloy has a solidus temperature that is lower than a solidus temperature of the material forming the top surface, bottom surface, and side walls of the additive manufacturing build plate.

In some implementations of the system, the build plate comprises: a frame comprising an interior cutout smaller than the recessed section, the frame configured to retain the insert during a 3D printing process, wherein the insert is dimensioned to be inserted into and secured within the recessed section and the interior cutout; and a base comprising the recessed section, wherein the frame is configured be affixed on top of the base.

In one embodiment, a method is provided in accordance with claim <NUM>. Some optional or preferred features are set out in dependent claims.

In some implementations, the method further comprises: printing a 3D printed object onto a surface of the solid metal or metal alloy to form an assembly, wherein the solid metal or metal alloy has a solidus temperature that is lower than a solidus temperature of the 3D printed object.

In some implementations, the 3D printed object is joined metallurgically to the metal or metal alloy during 3D printing.

In some implementations, the method further comprises: heating the assembly above the solidus temperature of the solid metal or metal alloy, thereby melting the metal or metal alloy and releasing the 3D printed object from the build plate.

In some implementations, the method further comprises: collecting, while the assembly is heated, the melting metal or metal alloy draining through the drain hole in a container.

In some implementations, the method further comprises: after draining the melting metal or metal alloy through the drain hole, refilling the recessed section with a refill liquid metal or metal alloy.

In some implementations, the refill liquid metal or metal alloy comprises the metal or metal alloy collected in the container.

In some implementations, the lid is comprised of a material that does not form a bond with the metal or metal alloy.

In some implementations, the method further comprises: removing the lid, thereby exposing a solid phase metal or metal alloy that provides a build surface for a 3D metal printed object.

In one embodiment, a method comprises: obtaining a build plate useable in a 3D printing device, the build plate comprising: a top surface, a bottom surface, and sidewalls comprised of a material; and a recessed section formed through the build plate; and securing, within the recessed section, an insert of a solid metal or metal alloy, wherein the solid metal or metal alloy has a solidus temperature that is lower than a solidus temperature of the material forming the top surface, bottom surface, and side walls of the additive manufacturing build plate.

In some implementations, the method further comprises: after securing the insert, positioning the build plate within a 3D printing device, printing, using the 3D printing device, a 3D printed object onto a surface of the insert; and after printing the 3D printed object, removing the insert with the 3D printed object from the recessed section of the build plate.

In some implementations, the method further comprises: after securing the insert, positioning the build plate within a 3D printing device; printing, using the 3D printing device, a 3D printed object onto a surface of the insert, wherein the solid metal or metal alloy has a solidus temperature that is lower than a solidus temperature of the 3D printed object; and after printing the 3D printed object, melting the insert to release the 3D printed object from the build plate.

In some implementations, the build plate comprises: a frame comprising an interior cutout smaller than the recessed section, the frame configured to retain the metal or the metal alloy during a 3D printing process; and a base comprising the recessed section; and securing the insert, comprises: securing a bottom part of the insert in the recessed section; and after securing the bottom part of the insert: securing a top part of the insert in the interior cutout of the frame; and affixing the frame on top of the base.

In one unclaimed embodiment, a method comprises: obtaining a plate of a solid metal or metal alloy; securing the plate in a 3D printing system; after securing the plate, printing, using the 3D printing system, a 3D printed object onto a surface of the plate to form an assembly, wherein the solid metal or metal alloy has a solidus temperature that is lower than a solidus temperature of the 3D printed object. In some implementations, the 3D printed object is joined metallurgically to plate during 3D printing. In some implementations, the method further comprises: heating the assembly above the solidus temperature of the solid metal or metal alloy, thereby melting the plate and releasing the 3D printed object from the plate. In some implementations the plate includes holes (e.g., screw holes on the corners or some other part of the plate) or some other means for securing it to the 3D printing system during 3D printing.

Other features and aspects of the disclosed technology will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which illustrate, by way of example, the features in accordance with implementations of the disclosed technology. The summary is not intended to limit the scope of any inventions described herein, which are defined by the claims and equivalents.

The present disclosure, in accordance with one or more implementations, is described in detail with reference to the following figures. The figures are provided for purposes of illustration only and merely depict example implementations. Furthermore, it should be noted that for clarity and ease of illustration, the elements in the figures have not necessarily been drawn to scale.

Some of the figures included herein illustrate various implementations of the disclosed technology from different viewing angles. Although the accompanying descriptive text may refer to such views as "top," "bottom" or "side" views, such references are merely descriptive and do not imply or require that the disclosed technology be implemented or used in a particular spatial orientation unless explicitly stated otherwise.

The figures are not exhaustive and do not limit the present disclosure to the precise form disclosed.

There is a need for improving techniques in additive manufacturing for removing workpieces that are essentially welded to a build plate. One challenge is to free the parts without damaging them, but also to protect the build plate so that it can be reused. As noted above, mechanical means, such as by use of a bandsaw or wire EDM, are typically employed to cut and remove a 3D printed from a build plate outside of the 3D printer. The build plate may then be machined separately to remove excess material and return them to a usable state. Such separation techniques, however, may be problematic.

Current mechanical removal approaches may lead to damage of the 3D printed part, damage to the surface of the build plate, and/or injury to the user. First, mechanical removal of the part by cutting may require hours of post processing to bring the 3D printed part back to its desired shape. Second, by cutting the 3D printed part away from the build plate, a portion of the welded part (post) requires grinding to remove that remaining piece from the build plate and to return the build plate to a smooth surface for reuse. This process of ensuring that all printed material is removed from a build plate before beginning a new printing process may be tedious and time consuming, as well as potentially harmful to the build plate. Moreover, mechanical removal techniques such as using a bandsaw or wire EDM require 3D printed parts to have a standoff between the part and the build plate to allow access for the band saw or wire EDM clearance, which requires additional, consumable metal powder.

Although not taught for removal of 3D metal printed/laser sintered parts from a build plate, a chemical removal method has been proposed for separating 3D printed support structures from a 3D printed object. By applying this method, certain areas of a metal additive manufacturing part react chemically when immersed in a corrosive solution. The technique involves a controlled degradation that eats away at the supports while leaving actual part virtually intact. This process may use sodium hexacyanoferrate as a sensitizing agent. Although this chemical etching process of support and part removal may reduce the removal and post processing time of traditional machining, it relies on the application of corrosive chemicals.

To address the aforementioned deficiencies of the art, the present systems and methods described in the disclosure are directed to simplifying 3D printed object removal from a build plate without the use of expensive saws, complex machines, or harsh chemicals. In accordance with implementations of the disclosure, a thermally decomposable build plate may enable the facile release of 3D metal printed parts created by additive manufacturing. During 3D metal printing or laser sintering, a print material may bond onto a surface of the build plate having a lower melting temperature than the print material and the rest of the build plate. Once the printing process is completed, the assembly may be treated with heat, thereby melting the bond surface between the 3D printed object and the build plate, and releasing the 3D printed object.

In contrast to mechanical removal of a 3D printed metal part that often necessitates hours of post processing to reshape and polish the bottom of the object and to resurface the build plate for reuse, by applying the systems and methods described herein, a facile removal of a 3D printed object from a build plate may be enabled without damage to the 3D printed part. Little or no post processing, finishing, reshaping, and/or polishing the 3D printed object may be needed by applying the 3D printed part removal systems and methods disclosed herein. Moreover, by virtue of applying the systems and methods described herein, object removal from a build plate may be accelerated without the use of corrosive chemicals, thereby offering a user additional time and cost-savings in additive manufacturing.

<FIG> shows a perspective view of a build plate <NUM> that can be used for additive manufacturing or 3D printing in accordance with implementations of the disclosure. As shown, build plate <NUM> includes a top surface <NUM>, a bottom surface <NUM> and four sidewalls <NUM> that extend between the top and bottom surfaces. The build plate <NUM>, including the top, bottom, and side surfaces, may be made of copper, stainless steel, tool steel, tin, aluminum, cemented carbide, ceramic, graphite, or some other suitable material. In particular, as further described below, the build plate <NUM> may be made of material (e.g., metal or metal alloy) having a solidus temperature that is substantially higher (e.g., at least <NUM>) than that of a thermally decomposable material that is placed or formed in its recessed section <NUM>, and used to create a bond between build plate <NUM> and a 3D printed object during 3D printing. For example, the build plate <NUM> may have a melting temperature that is greater than <NUM>.

Although depicted in the shape of a rectangular prism or cuboid having sidewalls that extend perpendicularly between the top surface <NUM> and bottom surface <NUM>, it should be noted that in other implementations build plate <NUM> may be some other suitable shape, e.g., a trapezoidal prism, that may be used to implement the 3D printing techniques described herein.

In this example, means for attachment of build plate <NUM> to a 3D printing apparatus are represented by slots or holes <NUM> (e.g., bolt holes) in each corner of top surface <NUM>. Structural protrusions (e.g., bolts or tabs) of the 3D printing apparatus may be inserted into holes <NUM> to hold the build plate <NUM> in place during 3D printing. Although holes <NUM> are illustrated in each corner of top surface <NUM>, it should be appreciated that depending on the implementation, build plate <NUM> may include holes <NUM> and/or protrusions in any suitable location on top surface <NUM>, bottom surface <NUM>, and/or other surface of build plate <NUM> to facilitate attachment to the 3D printing apparatus In some implementations, holes <NUM> may be included on bottom surface <NUM> and not on top surface <NUM> to prevent powdered metal from 3D printing to fall into holes <NUM>.

As depicted, build plate <NUM> includes a mortised or recessed section <NUM> extending through its center. The recessed section <NUM> is illustrated as having surfaces <NUM> (e.g., sidewalls) and a lower surface <NUM>. As further described below, the recessed section <NUM> may be filled with a lower melting temperature metal or metal alloy that provides a thermally decomposable surface for building a 3D printed object.

The recessed section <NUM> may be in the form of a basin with a drain hole that extends all the way through the build plate <NUM> (e.g., from top surface <NUM> through bottom surface <NUM>). This is depicted by <FIG>, which respectively show angled, top, and side views of build plate <NUM>, including a recessed section <NUM> with a drain hole <NUM>. As shown, the recessed section <NUM> is in the form of a basin that slopes downward toward hole <NUM> that extends out the bottom of build plate <NUM>, thereby permitting a material (e.g., liquid metal) to be drained out of build plate <NUM>. In <FIG>, the dashed outlines depict the corner holes <NUM>, drainage hole <NUM>, and basin shapes. The bottom edges of the basin leading to the drainage hole are sloped in this example.

It should be appreciated that although the examples of the disclosure show the lower surface of recessed section <NUM> sloping down at an acute angle toward a centered, circular hole <NUM>, other basin constructions, slope angles, hole locations, and hole shapes may be utilized. For example, in some implementations, the recessed section may be implemented by perpendicularly sloping its sides into a flat bottom having a hole. In some implementations, the hole <NUM> may positioned off center (e.g., close to one of the corners of build plate <NUM>). In some implementations, the hole <NUM> may instead drain through a side wall <NUM> of build plate <NUM>. In some implementations, the hole <NUM> may be rectangular or square.

The recessed section <NUM> may be formed via any suitable machining process such as by using a morticing machine, a metal lathe, a milling machine, a drill, etc. For example, the recessed section <NUM> may be formed by morticing a solid block of metal. Depending on the implementation, the top perimeter and average depth of recessed section <NUM> may be optimized for the 3D printing device and process used with build plate <NUM>. For example, the perimeter of the cutout may be shaped such that it does not interfere with a 3D printing device securing mechanism (e.g., providing sufficient space for holes <NUM>) while providing a large enough surface area to form a 3D printed object. In some implementations, sufficient depth may be provided to optimize cooling and provide for a deeper channel.

<FIG> respectively show angled, top, and bottom views of a build plate <NUM> filled by a solid material <NUM>. As depicted in this example, the material filling recessed section <NUM> forms a flat surface flush to the top edges of the recessed section. As shown by the bottom view in <FIG>, the solid material <NUM> filling the recessed section <NUM> is visible through the drainage hole <NUM>. Although in this example, the solid material <NUM> forms a flat surface flush at the top edges of the build plate basin, in other implementations it may lie below the top edges of the build plate basin.

In implementations, the solid material <NUM> is a solid metal or metal alloy having a melting point lower than that of the material (e.g., metal) of the unfilled build plate <NUM>. The solidus temperature of the metal or metal alloy may be at least <NUM> lower than that of the build plate <NUM>. In some implementations, the differences in melting point may be more significant. For example, in some implementations the solidus temperature of the metal or metal alloy may be at least <NUM> lower, <NUM> lower, <NUM> lower, <NUM> lower, <NUM> lower, <NUM> lower, <NUM> lower, or even more than <NUM> lower than the solidus temperature of the build plate <NUM>.

In some implementations, the solid material <NUM> is a solid metal or metal alloy having a solidus temperature of less than <NUM>. In some implementations, it has a solidus temperature between <NUM> and <NUM>. For example, the solid material <NUM> may be a solder alloy such as tin alloys (e.g., <NUM>. 5Sn3Ag0.5Cu), bismuth alloys (e.g., 58Bi42Sn) or indium alloys (e.g., 52In48Sn). In other implementations, the solid material <NUM> may be a single elemental metal such as tin, bismuth, indium, or others.

<FIG> depict one particular example of a method of forming solid material <NUM> in a recessed section <NUM> of build plate <NUM>, in accordance with implementations of the disclosure. As depicted by <FIG>, which shows a side view of plate <NUM>, a flat plate or lid <NUM> covers the top surface of build plate <NUM>, extending beyond the edges of recessed section <NUM> and the top surface <NUM> of build plate <NUM>. In other implementations, lid <NUM> may extend up to or just beyond the edges of recessed section <NUM>. Lid <NUM> may be held in place using clamps or other suitable mechanical means to create a seal. The material of lid <NUM> may be comprised of a material such that it does not bond with build plate <NUM> but may be mechanically held in place to create an enclosed mold. For example, graphite, polytetrafluoroethylene, ceramic, cemented carbide, copper, stainless steel, tool steel, tin, aluminum, or some other suitable material may be used. The material of build plate <NUM> may be the same as or different from the material of lid <NUM>.

After the lid <NUM> covers the top surface of build plate <NUM>, the build plate <NUM> and lid <NUM> may be inverted, and the recessed section <NUM> may be filled through drain <NUM>. In particular, <FIG> illustrates a side view of the inverted build plate <NUM> and lid <NUM>. A container <NUM> may be used to pour a liquid <NUM> of material (e.g., metal or metal alloy) through drainage hole <NUM> onto lid <NUM>, filling the recessed section <NUM>. Prior to this step, the metal or metal alloy may be heated above its solidus temperature to form liquid <NUM>. In some implementations, the use of a basin with acutely sloped sides may prevent the formation of air pockets when adding a liquid metal <NUM> through hole <NUM>.

In this example implementation, by virtue of adding the liquid metal <NUM> through hole <NUM> with the assembly inverted, any unwanted accumulates (e.g., dross) may float to and settle at the top of the filled recessed section (i.e., where hole <NUM> is), thereby ensuring a clean metal or metal alloy surface is formed where 3D printing occurs.

Once the recessed section <NUM> is filled, the assembly may be cooled, causing liquid <NUM> to solidify (e.g., to form a solid material <NUM>). Thereafter, the lid <NUM> may be removed to expose a smooth, solid phase metal or metal alloy that provides a build surface for a 3D metal printed object. To facilitate removal of lid <NUM> and ensure a smooth surface is formed (e.g., a flat surface flush to the top edges of the build plate recess), the lid <NUM> may be comprised of a material, e.g. graphite, polytetrafluoroethylene, ceramic, copper, stainless steel, tool steel, tin, aluminum, a non-stick metal, or some material that does not bond with liquid <NUM>, before or after the liquid <NUM> solidifies.

It should be appreciated that although <FIG> depict one example technique for forming a solid material <NUM> in a recessed section <NUM> of a build plate <NUM> to provide a surface for a 3D printed object, other techniques are possible. For example, in some implementations a liquid metal or metal alloy may instead be poured from the opposite side, through the top surface of recessed section <NUM>, first filling drain <NUM>. In such implementations, a lid <NUM> may instead cover drain <NUM>. In yet other implementations, drain <NUM> may be on the side of build plate <NUM> (e.g., through a side wall <NUM>), in which case the liquid metal or metal alloy may be poured through the side wall.

In other embodiments, the solid material <NUM> may be a pre-shaped solid insert that may be snapped or otherwise secured into or out of recessed section <NUM>. The insert may be dimensioned such that it fits securely (e.g., occupies substantially all of the open volume) within the recessed section. In such instances, multiple duplicate molds of the solid insert may be formed, with each mold being utilized during a 3D printing process. By way of illustration, <FIG> illustrate inserts that may be used in accordance with implementations of the disclosure. <FIG> shows an insert <NUM> that may be secured in a recess of a single piece build plate that has a rectangular recessed section. <FIG> shows an insert <NUM> that may be secured in a two-piece build plate <NUM>, further discussed below.

A snap-in insert of solid material <NUM> obviates the requirement that an operator of the 3D printing system performs the labor-intensive process of casting the liquid metal <NUM> in advance, to form solid material <NUM> in the recessed section <NUM> of build plate <NUM>. As such, additive manufacturing throughput may be significantly improved on the operator side by utilizing preformed, snap-in inserts. Additionally, the snap-in inserts may make operation of the 3D printing system more convenient and simpler for the operator When an operator completes 3D printing onto a solid material <NUM>, as described herein, the operator may snap the insert of solid material <NUM> out, and subsequently melt the insert to retrieve the 3D printed object. For example, the insert may be snapped out by using a rod or other suitable tool to apply pressure to the insert via hole <NUM>. A throughput advantage that may be realized from snapping out the insert with the 3D printed object is that the operator may quickly resume printing the next 3D metal printed object by snapping in a new insert <NUM>. In some implementations where inserts are utilized, build plate <NUM> may not include hole <NUM>, and some other suitable technique may be utilized to snap the insert out. Alternatively, the insert may be removed by melting it while it is still attached to build plate <NUM>, and collecting the liquid metal via drain hole <NUM> as further described below with reference to <FIG>.

In some implementations, an operator may be supplied a container in which to place an insert (with the 3D printed object) prior to melting The container may be sent back to the manufacturer of the solid insert (or some other party) to recycle the metal/metal alloy or reuse the metal/metal alloy to create a new insert (e.g., for the same user or a different user).

<FIG> illustrates a 3D metal printing process including a 3D metal printing device <NUM> using a metal powder bed <NUM> and a laser <NUM> to form a 3D printed object <NUM> on a build plate <NUM>, in accordance with implementations of the disclosure. Also shown is build plate loading platform <NUM> and optical component <NUM> for directing the output of a laser <NUM>. The metal powder bed <NUM> may comprise aluminum, cobalt, copper, nickel, steel, stainless steel, titanium, vanadium, tungsten carbide, gold, bronze, platinum, silver alloys, cobalt-chromium alloys, refractory metals, a combination thereof, or some other suitable metal or metal alloy for forming 3D printed object <NUM>. The 3D printed object may be laser sintered. Prior to beginning printing, a build plate <NUM> having a top surface including a region with a low melting temperature metal or metal alloy (e.g., top surface of solid material <NUM> filling a recessed section <NUM> as depicted by <FIG>) may be loaded into the 3D metal printing device <NUM>. For example, build plate <NUM> may be placed on a platform <NUM> of device <NUM>.

At the start of printing, a first layer of metal powder may be deposited (e.g., using a doctor blade or wiper blade) over the top surface of build plate <NUM>, including solid material <NUM>. Laser <NUM> or a series of lasers may then lase/sinter the deposited metal powder, causing the first layer of 3D printed object <NUM> to be metallurgically joined to the solid material. Thereafter, additional layers of powdered metal may be deposited by metal powder bed <NUM> and 3D printed object <NUM> may be created layer by layer. The device <NUM> may include a lowering mechanism (e.g., as part of platform <NUM>) apparatus to allow for subsequent metal layers of the 3D printed object <NUM> to be formed. As the apparatus and build plate are lowered, a metal powder layer may be added to the top surface and a laser or laser(s) used to selectively join/sinter areas to the 3D printed object <NUM> below At the completion of the aforementioned 3D printed process, build plate <NUM> with 3D printed object <NUM> may be removed from 3D printing device <NUM>.

The melting temperature of the metal or metal alloy that is used to form 3D printed object <NUM> is higher than that of the solid material <NUM>. For example, similar to the build plate <NUM>, the solidus temperature of the 3D printed object <NUM> may be at least <NUM> higher than the solidus temperature of the metal or metal alloy. In some implementations, the differences in melting point may be more significant. For example, in some implementations the solidus temperature of the 3D printed object <NUM> may be <NUM> higher, <NUM> higher, <NUM> higher, <NUM> higher, <NUM> higher, <NUM> higher, <NUM> higher, or even more than <NUM> higher than the solidus temperature of the metal or metal alloy of solid material <NUM>. In some implementations, the metal powder used to form 3D printed object <NUM> may comprise aluminum, cobalt, copper, nickel, steel, stainless steel, titanium, vanadium, tungsten carbide, gold, bronze, platinum, silver alloys, cobalt-chromium alloys, refractory metals, a combination thereof, or some other suitable metal or metal alloy.

It should be noted that although 3D printing may occur at room temperature, the heat generated by laser <NUM> may increase the temperature of solid material <NUM>. To prevent premature melting of material <NUM> during 3D printing, this increase in temperature may be accounted for when selecting a suitable metal or metal alloy <NUM>. In some implementations, the power of laser <NUM> may be decreased while forming lower layers of 3D printed object <NUM> to prevent overheating of material <NUM> during 3D printing.

<FIG> shows an assembly including the metal 3D printed object <NUM> metallurgically joined onto build plate <NUM> after the completion of 3D printing. In particular, the 3D printed object <NUM> may be joined to a surface of build plate <NUM> containing a low melting temperature solid material <NUM>, as described above.

Following 3D printing, the 3D printed object <NUM> is separated from build plate <NUM>. To this end, the assembly may be heated (e.g., by placing the assembly in an oven) to a temperature above the solidus temperature of the low melting temperature solid material <NUM>, thereby melting away the material and releasing the 3D printed object. The heat source is not limited to that of an oven. In other implementations, the 3D printed object <NUM> may be thermally separated from the solid material <NUM> by a heat source other than an oven such as by blow torch, heated air, heated liquid, hotplate, laser, or any other suitable heat source sufficient to melt the solid material <NUM>, thereby releasing the 3D printed object <NUM>. <FIG> shows a side view in which the low melting temperature metal or metal alloy filling the recessed section <NUM> of the build plate <NUM> is melting and draining (shown as melting liquid <NUM>) through the drain hole <NUM> into container or collection apparatus <NUM> while the 3D printed object <NUM> and the remaining structure of build plate <NUM>, including recessed section <NUM>, remain solid. During this removal process, the 3D printed object <NUM> may be held in place by a tool. In some implementations, this process may be incorporated into a compartment of a 3D printing assembly In an alternate separation method, prior to applying heat, a thin object such as a punch may be placed though drain hole <NUM> on the underside of build plate <NUM> with significant pressure to release the solid metal insert <NUM>, with the 3D printed object <NUM> still attached, from the recessed section <NUM>. The aforementioned combination may be placed into a container with a heated medium or subjected to other thermal treatment to cause the separation of solid metal insert <NUM> from 3D printed object <NUM>. This separation method may be implemented on a preformed insert as described above, or on a solid material <NUM> formed via casting by the operator as described in <FIG>.

In this example, by virtue of having a collection apparatus <NUM> to collect the liquid metal or liquid metal alloy <NUM> during the phase change from solid to liquid, the collected metal or metal alloy may be reused to refill the recessed section <NUM> for future 3D printing operations. For example, the collected metal or metal alloy may be used to fill recessed section <NUM> as described above with reference to <FIG>, in preparation for printing a new 3D object. In another embodiment, the solid material <NUM> may be a pre-shaped solid insert as discussed above, which can be snapped into or out of recessed section <NUM>, eliminating the need to repour liquid metal into the mold for the next printing.

<FIG> depicts the 3D printed object <NUM> after being separated from build plate <NUM> once the material filling recessed section <NUM> is no longer solid and melted away. In some implementations, after separation of the 3D printed object <NUM>, the collected metal or metal alloy may be used to refixture the object <NUM> for polishing, reshaping, and/or grinding, as needed. For example 3D printing parts may be held using a clamping mechanism for post processing. The lower melting point material <NUM> may be used to secure the 3D printed object <NUM> into a vice or clamping mechanism while performing the post processing functions above, so that the clamp does not contact the part <NUM> directly.

<FIG> shows a perspective view of an alternate, multi-part build plate <NUM> that may be used for additive manufacturing or 3D printing, in accordance with implementations of the disclosure. As shown, build plate <NUM> includes a top surface <NUM>, a bottom surface <NUM> and four sidewalls <NUM> that extend between the top and bottom surfaces. The build plate <NUM>, including the top, bottom, and side surfaces, may be made of copper, stainless steel, tool steel, tin, aluminum, cemented carbide, ceramic, graphite, or some other suitable material. In particular, the multiple parts of the build plate <NUM> may be made of material (e.g., metal or metal alloy) having a solidus temperature that is substantially higher (e.g., at least <NUM>) than that of a thermally decomposable material that is placed or formed in its recessed section <NUM>, and used to create a bond between build plate <NUM> and a 3D printed object during 3D printing. For example, the parts of build plate <NUM> may have a melting temperature that is greater than <NUM>.

In contrast to the single-part design of build plate <NUM>, build plate <NUM> includes multiple parts. <FIG> demonstrate an example of how build plate <NUM> may be implemented with multiple parts. As depicted in <FIG>, build plate <NUM> includes base <NUM> and frame <NUM> configured to be attached over the base <NUM>. The frame includes opening <NUM>, and the base <NUM> includes recessed section <NUM>.

In this example, frame <NUM> is used to secure solid material <NUM> in place during the 3D printing process to keep it from lifting from recessed section <NUM> during 3D printing. As illustrated by cross section A-A of <FIG>, in example build plate <NUM> the recessed section <NUM> is wider than the frame opening <NUM>. By virtue of this configuration, frame <NUM> may provide a clamping force to secure a solid material <NUM>. This two-part design may be particularly beneficial when implemented with an insert <NUM> as discussed above. Frame <NUM> may be used to hold down insert <NUM> along the outside edges of bottom portion <NUM> of insert <NUM>, which may curl upwards during sintering if the insert becomes too hot. Additionally, due to the insert part being cast into the exact same size cavity (e.g., in one part or two part build plates), there are frictional forces that may be relied on to hold the solid material in place, using a "press-fit" mechanism However, when friction is not enough to hold the insert in place (e.g., such as when frictional forces are overcome by localized heating), the depicted two part design may add additional retention for the insert by pressing down on the insert's edges.

Frame <NUM> is removably coupled to base <NUM>, and frame <NUM> may be removed from base <NUM> as to allow removal (or insertion) of the solid material. For example, the bottom part <NUM> of insert <NUM> may be first secured into recessed section <NUM> of base <NUM>. Afterward, frame <NUM> may be secured over base <NUM>, and the top part <NUM> of insert <NUM> may be secured in opening <NUM> of frame <NUM>. Frame <NUM> and base <NUM> may be affixed through a number of means, including screws, set screws, pins, dovetail, sliding rails or other interlocking designs.

<FIG> depict a particular example implementation for affixing an example frame 270a and a base 280a of an example build plate 200a. <FIG> shows a perspective view of build plate 200a. <FIG> shows a bottom view and cross-sectional views of build plate 200a. This example utilizes recessed holes <NUM> in frame 270a that may extend through holes in base 280a. Utilizing appropriately sized machine screws, frame 270a and base 280a may be secured via recessed holes <NUM>. In this implementation, recessing the screw flush or below the top surface of build plate 200a (i.e., below the top of frame <NUM>) allows powdered metal to be deposited without interfering with metal powder bed <NUM> of the 3D printing system <NUM>, described below. For example, when a wiper of system <NUM> levels powder across a surface of the printing surface, this may ensure that the wiper is not damaged by the protruding screw.

Build plates consisting of multiple parts, such as build plate <NUM>, may employ various design features to ease separation of frame <NUM> from base <NUM>. The build plate <NUM> may require separation to remove solid material <NUM> without melting the solid material <NUM>. Referring again to <FIG>, this example demonstrates an implementation that incorporates jack screw holes <NUM> in a base 280a to ease separation from a frame 270a. Bolts inserted into the jack screw holes <NUM> and tightened can be used to push the frame 270a away from the base 280a, or to push the base 280a away from the frame 270a. Several design features may also aid in disassembly, including tabs extending from the base <NUM> and/or the frame <NUM> or a nail nick or gap for prying apart the assembly.

It should be noted that although in the examples illustrated herein the build plate <NUM> is composed of two parts - frame <NUM> and base <NUM>, the build plate <NUM> may be made of more than two parts that are affixed using one or more of the aforementioned methods.

In build plate <NUM>, means for attachment of build plate <NUM> to a 3D printing apparatus are represented by slots or holes <NUM> (e.g., bolt holes) in each corner of top surface <NUM>. In this instance, the bolt holes <NUM> may extend through frame <NUM> and base <NUM>. Structural protrusions (e.g., bolts or tabs) of the 3D printing apparatus may be inserted into holes <NUM> to hold the build plate <NUM> in place during 3D printing. Although holes <NUM> are illustrated in each corner of top surface <NUM>, it should be appreciated that depending on the implementation, build plate <NUM> may include holes <NUM> and/or protrusions in any suitable location on top surface <NUM>, bottom surface <NUM>, and/or other surface of build plate <NUM> to facilitate attachment to the 3D printing apparatus In some implementations, holes <NUM> may be included on bottom surface <NUM> and not on top surface <NUM> to prevent powdered metal from 3D printing to fall into holes <NUM>.

The recessed section <NUM> may be in the form of a basin with a drain hole that extends all the way through the build plate <NUM> (e.g., from top surface <NUM> through bottom surface <NUM>). This is depicted by <FIG>, which show angled, top, and cross-sectional side views of build plate <NUM>, including a recessed section <NUM> with a drain hole <NUM>. As shown, the recessed section <NUM> is in the form of a basin that converges toward hole <NUM> that extends out the bottom of build plate <NUM>, thereby permitting a material (e.g., liquid metal) to be drained out of build plate <NUM>. 12C, the dashed outlines depict the corner holes <NUM>, drainage hole <NUM>, and basin shapes. The bottom edges of the basin leading to the drainage hole are flat in this example, although they can also be sloped to allow ease of drainage.

It should be appreciated that although the examples of the disclosure show the lower surface of recessed section <NUM> flat, featuring a centered, circular hole <NUM>, other basin constructions, slope angles, hole locations, and hole shapes may be utilized. For example, in some implementations, the recessed section may be implemented by perpendicularly sloping its sides into a flat bottom having a hole. In some implementations, the hole <NUM> may positioned off center (e.g., close to one of the corners of build plate <NUM>). In some implementations, the hole <NUM> may instead drain through a side wall <NUM> of build plate <NUM>. In some implementations, the hole <NUM> may be rectangular or square.

<FIG> respectively show angled, top, and bottom views of a build plate <NUM> filled by a solid material <NUM>, in accordance with implementations of the disclosure. As depicted in this example, the material filling recessed section <NUM> forms a flat surface flush to the top edges of the recessed section. As shown by the bottom view in <FIG>, the solid material <NUM> filling the recessed section <NUM> is visible through the drainage hole <NUM>. Although in this example, the solid material <NUM> forms a flat surface flush at the top edges of the build plate basin, in other implementations it may lie below the top edges of the build plate basin.

<FIG> depict one particular example of a method of forming solid material <NUM> in a recessed section <NUM> of build plate <NUM>, in accordance with implementations of the disclosure. As depicted by <FIG>, which shows a side view of plate <NUM>, a flat plate or lid <NUM> covers the top surface of build plate <NUM>, extending beyond the edges of recessed section <NUM> and the top surface <NUM> of build plate <NUM>. In other implementations, lid <NUM> may extend up to or just beyond the edges of recessed section <NUM>. Lid <NUM> may be held in place using clamps or other suitable mechanical means to create a seal. The material of lid <NUM> may be comprised of a material such that it does not bond with build plate <NUM> but may be mechanically held in place to create an enclosed mold. For example, graphite, polytetrafluoroethylene, ceramic, cemented carbide, or some other suitable material may be used.

Once the recessed section <NUM> is filled, the assembly may be cooled, causing liquid <NUM> to solidify (e.g., to form a solid material <NUM>). Thereafter, the lid <NUM> may be removed to expose a smooth, solid phase metal or metal alloy that provides a build surface for a 3D metal printed object. To facilitate removal of lid <NUM> and ensure a smooth surface is formed (e.g., a flat surface flush to the top edges of the build plate recess), the lid <NUM> may be comprised of a material, e.g. graphite, polytetrafluoroethylene, ceramic, a non-stick metal, or some material that does not bond with liquid <NUM>, before or after the liquid <NUM> solidifies.

It should be appreciated that although <FIG> depict one example technique for forming a solid material <NUM> in a recessed section <NUM> of a build plate <NUM> to provide a surface for a 3D printed object, other techniques are possible. For example, in some implementations a liquid metal or metal alloy may instead be poured from the opposite side, through the top surface of recessed section <NUM>, first filling drain <NUM>. In such implementations, a lid <NUM> may instead cover drain <NUM>. In yet other implementations, drain <NUM> may be on the side of build plate <NUM> (e.g., through a side wall <NUM>), in which case the liquid metal or metal alloy may be poured through the side wall. In yet other implementations, instead of having an operator cast the liquid metal to form solid material <NUM>, an insert <NUM> may be inserted as described above.

The melting temperature of the metal or metal alloy that is used to form 3D printed object <NUM> is higher than that of the solid material <NUM>. For example, similar to the build plate <NUM>, the solidus temperature of the 3D printed object <NUM> may be at least <NUM> higher than the solidus temperature of the metal or metal alloy. In some implementations, the differences in melting point may be more significant. For example, in some implementations the solidus temperature of the 3D printed object <NUM> may be <NUM> higher, <NUM> higher, <NUM> higher, <NUM> higher, <NUM> higher, <NUM> higher, <NUM> higher, or even more than <NUM> higher than the solidus temperature of the metal or metal alloy of solid material <NUM>. In some implementations, the metal powder used to form 3D printed object <NUM> may comprise aluminum, cobalt, copper, nickel, steel, stainless steel, titanium, vanadium, tungsten carbide, gold, bronze, platinum, silver alloys, cobalt-chromium alloys, refractory metals, a combination thereof, or some other suitable metal or metal alloy.

Following 3D printing, the 3D printed object <NUM> is separated from build plate <NUM>. To this end, the assembly may be heated (e.g., by placing the assembly in an oven) to a temperature above the solidus temperature of the low melting temperature solid material <NUM>, thereby melting away the material and releasing the 3D printed object. <FIG> shows a side view in which the low melting temperature metal or metal alloy filling the recessed section <NUM> of the build plate <NUM> is melting and draining (shown as melting liquid <NUM>) through the drain hole <NUM> into container or collection apparatus <NUM> while the 3D printed object <NUM> and the remaining structure of build plate <NUM>, including recessed section <NUM>, remain solid. During this removal process, the 3D printed object <NUM> may be held in place by a tool. In some implementations, this process may be incorporated into a compartment of a 3D printing assembly.

In this example, by virtue of having a collection apparatus <NUM> to collect the liquid metal or liquid metal alloy <NUM> during the phase change from solid to liquid, the collected metal or metal alloy may be reused to refill the recessed section <NUM> for future 3D printing operations. For example, the collected metal or metal alloy may be used to fill recessed section <NUM> as described above with reference to <FIG>, in preparation for printing a new 3D object.

In an alternate separation method, prior to applying heat, frame <NUM> may be separated from base <NUM>, thereby exposing a top portion of solid material <NUM>. After separating frame <NUM> from base <NUM>, a thin object such as a punch may be placed though drain hole <NUM> on the underside of build plate <NUM> with significant pressure to release the solid material <NUM>, with the 3D printed object <NUM> still attached, from the recessed section <NUM>. The aforementioned combination may be placed into a container with a heated medium or subjected to other thermal treatment to cause the separation of solid metal material <NUM> from 3D printed object <NUM>. This separation method may be implemented on a preformed insert as described above, or on a solid material <NUM> formed via casting by the operator as described in <FIG>.

Claim 1:
An additive manufacturing build plate, comprising:
a top surface, a bottom surface, and sidewalls comprised of a material, wherein the top surface, bottom surface, and sidewalls are dimensioned such that the build plate is useable in a 3D printing device; and
a recessed section formed through the top surface, wherein the recessed section comprises a hole extending through the bottom of the build plate; and
a solid metal or metal alloy disposed in the recessed section to provide a surface for forming a 3D printed object in the 3D printing device, wherein the solid metal or metal alloy has a solidus temperature that is lower than a solidus temperature of the material forming the top surface, bottom surface and sidewalls of the build plate.