Patent Application
20220379550
This specification relates to bottom-up stereolithographic 3D printing. In particular, the specification relates to bottom-up stereolithography apparatuses and vats for such apparatuses for receiving and holding resin to be cured by electromagnetic radiation transmitted to the vat through a transparent bottom film thereof.
In bottom-up stereolithography printing, the vat holding the curable resin from which the object to be printed is formed shall meet certain requirements.
For example, the transparent bottom film of the vat, through which the curing radiation is received to the vat to cure resin therein shall lie closely against a support surface of the stereolithography apparatus through which support surface the exposure pattern of a layer to be cured is transmitted. For example, no air bubbles should be present between the support surface and the bottom film of the vat. The bottom film shall be rigid and straight enough and it shall be mountable sufficiently firmly to the vat assembly typically comprising a metal frame forming the circumferential side wall of the vat.
On the other hand, the bottom film should be durable enough to enable repetitive cleaning thereof between different production batches. However, due to the cleaning, the bottom film unavoidably wears out gradually and becomes also less transparent. Therefore, the bottom film shall be changed occasionally. This, in turn, requires the mounting of the bottom film to the vat assembly to be releasably.
The above requirements set limitations to the usability of the conventional vat assemblies. Therefore, there is a need for improved vat assembly configurations.
This summary is provided to introduce a selection of concepts that are further described below in the Detailed Description. This Summary is not intended to definitely identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.
In one aspect, a bottom-up stereolithography apparatus (SLA) is disclosed. The SLA comprises a support surface and a vat assembly for forming a vat having a transparent bottom film, the vat being configured to be placed on the support surface to receive and hold a resin curable by electromagnetic radiation transmitted to the vat through the transparent bottom film thereof.
The vat assembly comprises a circumferential first frame part having a first lower surface defining a bottom level of the vat assembly, and a circumferential first inner side surface extending from the first lower surface to an upper level elevated from the bottom level in a thickness direction of the circumferential first frame part and defining a recess within the circumferential first frame part.
The apparatus comprises an air channel and an evacuating arrangement configured to suck air from the recess of the circumferential first frame part via the air channel.
Thereby a receptacle, at least partially formed of a transparent film material and comprising a bowl may be placed in the vat assembly with the bowl in the recess. Then, with the thereby formed vat being placed on the support surface with the first lower surface of the circumferential first frame part against the support surface, air can be evacuated from the recess via the air channel to stretch the bowl against the support surface and the first inner side surface.
The part of the receptacle, which then lies against the support surface, forms the transparent bottom film of the vat.
In a second aspect, a receptacle is disclosed which is at least partially formed of a transparent film material and comprises a bowl.
The receptacle is configured to be placed in a vat assembly in accordance with the first aspect with the bowl in the recess of the vat assembly to form a vat.
In a third aspect, a method is disclosed for forming a vat by placing a receptacle of the second aspect in the vat assembly of the first aspect with the bowl of the receptacle in the recess, and evacuating air from the recess via the air channel to stretch the bowl against the support surface and the circumferential first inner side surface.
The part of the receptacle, which then lies against the support surface, forms the transparent bottom film of the vat.
The accompanying drawings, which illustrate various embodiments, together with the description help to explain the principles of the embodiments. In the drawings:
The detailed description provided below in connection with the appended drawings is intended as a description of a number of embodiments. It is not intended to represent the only forms in which the embodiments may be constructed, implemented, or utilized.
One or more of the embodiments and examples discussed below may advantageously enable, for example, forming a vat for a bottom-up stereolithography apparatus and process utilizing a low-cost disposable receptacle forming the transparent bottom film of the vat.
The vat assembly 100 of
“Stereolithography” refers to a 3D printing technique wherein the actual “printing” of a material layer is based on curing a layer of a curable resin by electromagnetic radiation such as visible or ultraviolet light. Such printing enables accurate manufacturing of various 3D objects. A stereolithography apparatus can also be called a stereolithographic 3D printer, or a stereolithographic additive manufacturing apparatus.
A stereolithography apparatus may be, for example, configured to, or used to, fabricate dental objects, such as dental splints, models, surgical guides, temporary fillings, and orthodontic models with high precision and efficiency.
Additionally, or alternatively, a stereolithography apparatus may be, for example, configured to, or used to, fabricate any other types of 3D-printable objects, such as jewels or various mechanical components or prototypes or spare parts of such.
In bottom-up stereolithography apparatuses and processes, the object to be printed is formed of a curable resin received to and held in a vat having a transparent bottom film. A pattern of electromagnetic radiation is transmitted through the bottom film to the vat to cure a layer of the resin at the bottom of the vat. The object to be printed is formed layer by layer onto a build surface of a build platform which is raised upwards after curing of each layer.
The actual exposure pattern of the curing electromagnetic radiation may be produced, for example, by a radiative element and a masking element partially masking the radiation emitted by the radiative element. Such radiative element and a masking element may be positioned underneath a transparent part of a support surface of a table of the SLA. A radiative element may comprise one or more radiation sources of any appropriate type, such as an array of light-emitting diode (LED) elements. A masking element may comprise, for example, a liquid crystal panel or element.
The vat assembly 100 of
“Circumferential” nature of an object such as a body or a surface refers to a configuration of the object forming a closed loop along a circumference surrounding an open center or inner area or volume. Basically, such circumference may have any shape, such as circular, oval, elliptical, or rectangular. In the example of
The circumferential first frame part has first lower surface 111 defining a bottom level 111′ of the vat assembly, and a first upper surface 112 defining an upper level 112′ elevated from the first lower surface and the bottom level in a thickness direction of the first frame part. The overall circumferential configuration of the first frame part results in the first lower and upper surfaces also being circumferential.
In the example of
The “elevation” of the first upper surface from the first lower surface in a thickness direction of the first frame part refers to the first frame part having a thickness. The first “upper” surface being “elevated” from the first lower surface defines an “upward” direction U of the vat assembly being directed, in a fictitious coordinate system fixed to the vat assembly, from the first lower surface 111 towards the first upper surface 112. Said upwards direction U is marked by an arrow in
The first lower and upper surfaces 111, 112 are connected via or by a circumferential first inner side surface 113.
“Inner” refers to the side of said surface on the inner side of the circumference of the first frame part 110, the first inner side surface 113 thus facing towards the inner volume enclosed by the circumferential first frame part. Said inner volume, defined in the lateral directions by the circumferential first inner side surface 113, forms a recess 114 within the first frame part 110.
Advantageously, the first frame part comprises an air channel 115 which opens to the recess 114 through the circumferential first inner side surface 113.
The air channel 115 “opening” to the recess 114 through the circumferential first inner side surface refers to the air channel having an open end in the form of an opening 116 at the circumferential first inner side surface 113. Air or any other gas can flow between the recess and the air channel through the opening 116.
In the example of
The vat assembly 100 of
Said releasable mounting may be implemented by any other appropriate means, such as one or more screw attachments, clamps, etc.
Other embodiments may be implemented without any second frame part.
The first and the second frame parts 110, 120 may be formed of any appropriate material(s). For example, such material may comprise a metal, such as aluminum or steel, or a plastic material.
The receptacle 130 of
A vat thereby formed and its use in a stereolithography apparatus (SLA) is illustrated in
The stereolithography apparatus 150 of
The SLA has a table 151 forming a support surface 152. The table comprises a radiation transmission part 153 which may comprise a transparent plate enabling radiation from an external radiation source to be transmitted through it. Alternatively, the transmission part 153 may comprise an exposure arrangement producing the curing electromagnetic radiation.
An exposure arrangement may comprise, for example, one or more light emitting diodes (LEDs) possible arranged in an array as a radiation source. An exposure arrangement may further comprise a masking element, such as a liquid crystal panel, to partially mask the radiation emitted by a radiation source. A mask may thereby form the actual exposure pattern for each layer to be cured.
As illustrated in the drawings of
The recess 114 of the first frame part 110, defined by the circumferential first inner side surface 113, has a specific recess shape. Correspondingly, the recess has a specific recess volume. In the example of
The bowl 131 of the receptacle 130 correspondingly has, in its non-stretched rest position, a bowl rest shape substantially following the recess shape and a bowl rest volume slightly smaller than the recess volume of the first frame part 110. The bowl may further have one or more stretched positions.
The bowl rest volume may cover, for example, less than or equal to 95%, for example, less than or equal to 80% of the recess volume. The slightly smaller size of the bowl may enable stretching of the bowl against the first frame part 110 and the support surface 152 as discussed below.
The SLA 150 comprises an evacuating arrangement having an air pipe 154. In the drawing of
The receptacle 130 is formed of a transparent film material which may comprise, for example, fluorinated ethylene propylene FEP. FEP may provide sufficient optical transparency for proper and accurate curing of the layers of the object to be printed by exposure to radiation transmitted through the bottom film 103 of the vat. FEP may also provide sufficient rigidity of the bottom film, and enable manufacturing of the receptacle easily, for example, by thermoforming. The film may have a wall thickness, for example, of about 0.3 mm or less. Even as low thicknesses as 0.1 mm or less may be used.
In other embodiments, it is possible that a receptacle is only partially formed of a transparent film material. Thus, it is possible that only a part of the receptacle, namely the part forming the transparent bottom film in the final vat assembly, is formed of the transparent film material. The rest of the receptacle may then be formed of an opaque or less transparent material.
For effecting the air sucking or evacuating, the evacuating arrangement may comprise any appropriate vacuum means, such as an air pump, connected to the air pipe 154. Instead of an air pump, vacuum means may comprise, for example, any appropriate arrangement with a mechanically adjustable closed volume connected to the air channel to suck or evacuate air from the recess by enlarging the closed volume. Such evacuating arrangement may be integrated to the SLA or to the vat assembly itself.
Several advantages may be achievable by a vat assembly, receptacle, vat, and SLA discussed above with reference to
For example, the vat assembly 100 in which a separate receptable 130 may be placed to easily form the complete vat 101 allow using disposable receptacles. Then, each production batch may be printed, or each printing operation may be carried out, using a disposable receptable. Then, there is no need for cleaning the vat from residual resin.
A disposable receptacle may be filled with resin when in use. In an alternative embodiment, a disposable receptable may be ready filled with a resin beforehand. Such pre-filled receptable may optionally be closed by a film to be removed before use.
Embodiments with the vat assembly 100 having also the second frame part 120 makes forming the vat 101 and changing the receptacle 130 thereof simple.
The air channel 115 of the first frame part 110, allowing evacuating air from the recess 114 and stretching the bowl 131 of the receptacle 130 placed in the vat assembly, further greatly improves the feasibility of the vat assembly 100. First of all, it enables ensuring that the bottom film of the vat lies conformally against the support surface of the SLA onto which the vat is placed even if the bottom part of the bowl itself is not completely straight when the bowl is in its rest position. This allows the receptacle to be formed of a very thin film, which may provide savings in the material costs. Further, the film being stretched against the support surface due to evacuation of air via the air channel may enable controlled peeling of the cured layer off the bottom film of the vat.
In the example vat assembly 110 of
In other embodiments, substantially vertical circumferential first side surfaces without a conical section may be used. In yet other embodiments, a conical section may cover a part of a circumferential first inner side surface only, whereby such conical section is thus not itself circumferential.
Receptacles with bowl rest shapes substantially following the recess shape of a first frame part of a vat assembly may be manufactured, for example, by thermoforming or molding. A conical section of the circumferential first inner side surface of a first frame part may facilitate such manufacturing by enabling thermoforming of molding tools to have a proper draft. A draft may facilitate relieving the completed receptacle from the tool, such as a mold, by means of which the shape of the bowl is defined in the manufacturing process.
In addition to creating the vacuum, the air channel 115 may also be used to adjust the vacuum and the force by which the receptable is pressed against the inner side surface 113 of the first frame part 110 and the support surface 152 of the SLA 150. For example, for raising the build platform 154 after completion of curing a layer of the resin, the vacuum may be slightly relieved. This may allow the bottom film 103 of the vat 101 to bend upwards to facilitate smooth and controlled peeling of the cured layer off the bottom film.
In the example of
In other embodiments, any other appropriate types of upper sealing means may be used. For example, the lower surface of the flange of a receptacle may have a layer of an adhesive or sealing agent, or a gasket, thereon. Such layer or gasket may enable implementation of a vat assembly without any second frame part for pressing the flange of the receptacle between the first upper surface of a first frame part and a second lower surface of the second frame part of the vat assembly. An example of a gasket integrated in the flange of a receptacle is discussed below with reference to
In yet other embodiments, it may be possible to implement vat assemblies and SLA configurations without any upper sealing means.
The first frame part of the example of
In other embodiments, any other appropriate types of lower sealing means may be used. For example, in some embodiments, sealing between the support surface of an SLA and a first frame part of a vat assembly may be achieved by sealing means formed or placed in or on the support surface instead of in or on the first lower surface of a first frame part. Such sealing means may comprise, correspondingly to the sealing means of the example of
It may also be possible to implement vat assemblies and SLA configurations without any lower sealing means.
In the embodiments discussed above with reference to
It is to be noted that the above embodiments and examples are not limiting or exclusive examples of all possible vat assemblies, receptacles, vats, and/or stereolithography apparatuses within the scope of this specification. Instead, any further embodiments and variants thereof may be implemented within the scope of the claims.
For example, the shapes and/or dimensions of the vat assemblies may be different from those of
The vat assembly 300 and receptacle 330 of
Even further variations in the shapes and/or dimensions of the vat assembly are possible in other embodiments. For example, vat assemblies may be implemented having a first frame part without any specific first upper surface. Also then the circumferential first inner surface may extend from the first lower surface to an upper level elevated from the bottom level in the thickness direction. In such embodiments, a receptable placeable in the vat assembly with its bowl in the recess may lack any specific flange extending laterally from the upper rim of the bowl.
In such embodiments, if the vat assembly comprises a circumferential second frame part, that may be shaped and dimensioned so that instead of a flange, some other circumferential mounting part of the receptacle placed in the vat assembly may lie between the first and the second frame parts. “Mounting” refers to such circumferential part serving as a part from which the receptacle may be releasably mounted to the vat assembly by having it pressed between the first and the second frame parts.
On the other hand, in such embodiments, upper sealing means may be used which may form an air-tight sealing between the first frame part and a receptacle in any appropriate location. For example, a gasket may be arranged on the circumferential first inner side surface.
Variations are also possible e.g. in the location of the air channel. One example is illustrated in
The SLA 450
The drawings of
The receptacle 530 of
In the example of
The lid 534 is formed as a thin film which may be formed of, for example, some suitable plastic material. A non-transparent lid may be formed of, for example, a thin foil of aluminum or some other metal.
In the example of
The lid 534 is removable. In the example of
The removable lid 534 enables providing a receptacle which is pre-filled with resin. Then, the user of the SLA may take a ready-to-use receptacle, place it into the vat assembly and peel or rip off the cover thereof. After use, the remaining resin may be cured, and the receptacle together with the cured resin may be disposed as normal waste.
The receptacle 630 of
The receptacle 630 distinguishes from those other receptacles in that it has an upper gasket 642 mounted on the lower surface of the flange 633 of the receptacle.
The upper gasket 642 integrated in the flange 633 may serve for forming a sealing between the receptacle and a vat assembly in a complete vat formed by placing the receptacle 630 in a vat assembly which may be basically in accordance with any of those discussed above. The first frame part of such vat assembly may comprise a circumferential upper sealing groove formed on the first upper surface thereof, in which upper sealing groove the upper gasket 642 of the flange 633 is placeable. Then, differently from the example of
In other embodiments, an upper gasket may lie elsewhere in a receptacle, for example, on the outer surface of the bowl.
It will be understood that the benefits and advantages described above may relate to one embodiment or example or may relate to several embodiments or examples. The embodiments and examples are not limited to those that solve any or all of the stated problems or those that have any or all of the stated benefits and advantages. It will further be understood that reference to ‘an’ item refers to one or more of those items.
The term “comprising” is used in this specification to mean including the feature(s) followed thereafter, without excluding the presence of one or more additional features.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20195976 | Nov 2019 | FI | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/FI2020/050761 | 11/16/2020 | WO |
