WO2021183263A1

WO2021183263A1 - Additively manufactured products having a matte surface finish

Info

Publication number: WO2021183263A1
Application number: PCT/US2021/018178
Authority: WO
Inventors: Mohamed Imran Jameel
Original assignee: Carbon, Inc.
Priority date: 2020-03-13
Filing date: 2021-02-16
Publication date: 2021-09-16

Abstract

A method of making an object by additive manufacturing, the object having a matte finish on a surface thereof, is described herein. The method includes the steps of: (a) producing an intermediate object by light polymerization of a dual cure resin in an additive manufacturing process, the object having excess unpolymerized resin retained on a surface thereof; (b) separating a portion of the excess unpolymerized resin from the object while leaving a thin film of unpolymerized resin on the surface; (c) contacting the thin film to an absorbent sheet to remove additional excess unpolymerized therefrom; and then (d) further curing the intermediate object to produce an object having a matte finish on the surface.

Description

ADDITIVELY MANUFACTURED PRODUCTS HAVING A MATTE SURFACE FINISH

Mi l l) OF THE INVENTION

[0001] The present invention concerns methods of surface finishing objects produced by additive manufacturing.

BACKGROUND

[0002] A group of additive manufacturing techniques sometimes referred to as "stereolithography" creates a three-dimensional object by the sequential polymerization of a light polymerizable resin. Such techniques may be "bottom-up" techniques, where light is projected into the resin on the bottom of the growing object through a light transmissive window, or "top down" techniques, where light is projected onto the resin on top of the growing object, which is then immersed downward into the pool of resin.

[0003] The recent introduction of a more rapid stereolithography technique known as continuous liquid interface production (CLIP), coupled with the introduction of "dual cure" resins for additive manufacturing, has expanded the usefulness of stereolithography from prototyping to manufacturing (see, e.g., US Patent Nos. 9,211,678; 9,205,601; and 9,216,546 to DeSimone et al.; and also J. Tumbleston, D. Shirvanyants, N. Ermoshkin et ah, Continuous liquid interface production of 3D Objects, Science 347, 1349-1352 (2015); see also Rolland et al., US Patent Nos. 9,676,963, 9,453,142 and 9,598,606).

[0004] A problem encountered with the production of objects from dual cure resins is that washing of the objects to remove excess resin prior to second cure can alter the chemistry of the objects (see, e.g., US Patent No. 20,471,656 to McCall et al.). While this can be avoided by cleaning excess resin by techniques such as wiping or spinning (see. e.g. PCT Patent Application Pub. No. WO 2019/209732 to Murillo and Dachs), these can leave a film on the object which — when subsequently cured — imparts a glossy surface finish to the object. For many products, consumers perceive a glossy finish as inferior, or for some applications (such as where the object contacts the skin or clothing of a user) a glossy finish can have undesirable performance characteristics. Accordingly, there is a need for techniques that impart a matte surface finish to such objects.

SUMMARY [0005] A method of making an object by additive manufacturing, the object having a matte finish on a surface thereof, is described herein. The method includes the steps of: (a) producing an intermediate object by light polymerization of a dual cure resin in an additive manufacturing process, the object having excess unpolymerized resin retained on a surface thereof; (b) separating a portion of the excess unpolymerized resin from the object while leaving a thin film of unpolymerized resin on the surface; (c) contacting the thin film to an absorbent sheet to remove additional excess unpolymerized therefrom; and then (d) further curing the intermediate object to produce an object having a matte finish on the surface. [0006] In some embodiments, the producing step (a) is carried out by bottom-up or top-down stereolithography .

[0007] In some embodiments, the separating step (b) is carried out by spinning ( i.e ., centrifugal separation), blowing with a compressed gas, gravity draining, or a combination thereof.

[0008] In some embodiments, the contacting step (c) is carried out manually or with a mechanical press.

[0009] In some embodiments, the further curing step (d) is carried out by heating, microwave irradiating, contacting to water, or a combination thereof.

[0010] In some embodiments, the object comprises a lattice.

[0011] In some embodiments, the object comprises a cushion ( e.g ., a midsole).

[0012] In some embodiments, the object comprises a body contact surface (e.g., a cushion such as a seat cushion, a helmet liner, an arm rest, a head rest, a handle, a steering wheel, or component thereof), optionally but in some embodiments preferably with the matte finish on the body contact surface.

[0013] In some embodiments, the object comprises a skin contact surface, optionally but in some embodiments preferably, with the matte finish on the skin contact surface.

[0014] In some embodiments, the object is comprised of polyurethane, polyurea, or a copolymer thereof; epoxy; silicone; cyanate ester; or a combination thereof.

[0015] In some embodiments, the surface on which the matte finish is to be imparted is planar, irregular (e.g, curved), or a combination thereof.

[0016] In some embodiments, the object is transparent, translucent, or pigemented (e.g, with a white, black, cyan, magenta, or yellow pigment, or a combination thereof).

[0017] In some embodiments, the object of steps (b), (c) and (d) is unwashed (i.e., is not contacted to a solvent at any point during production thereof).

[0018] Also described herein are objects produced by the processes described herein. [0019] Also disclosed herein is an apparatus useful for imparting a matte finish to an object produced by additive manufacturing. The apparatus includes: (a) a frame; (b) a press; (c) a press drive interconnecting the press and the frame; (d) a mount connected to the frame on wich an object produced by additive manufacturing can be removably engaged; (e) an absorbent sheet dispenser operatively associated with the frame and configured for dispensing an absorbent sheet between the object and the press.

[0020] In some embodiments, the object is carried by a carrier platform on which the object was produced by additive manufacturing, and the mount is configured to engage the carrier platform.

[0021] In some embodiments, the carrier platform includes a unique identifier ( e.g an NFC tag, an RFID tag, etc.), and the frame has a unique identifier reader operatively associated therewith and positioned to read the unique identifier.

[0022] In some embodiments, the press includes a buffer configured to conform the absorbent sheet to the object when the object has an irregular surface portion on which the matte finish is to be imparted.

[0023] In some embodiments, the buffer comprises a constant force compression lattice.

[0024] The foregoing and other objects and aspects of the present invention are explained in greater detail in specification set forth below. The disclosures of ail United States patent references cited herein are to be incorporated herein by reference.

BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1A is a perspective view of a lattice cushion produced by additive manufacturing having a surface onto which a matte finish may be imparted.

[0026] Figure IB is a top plan view of the lattice cushion of Figure 1 A.

[0027] Figure 1C is a side view of the lattice cushion of Figure 1A.

[0028] Figure ID is an alternate side view of the lattice cushion of Figure 1A.

[0029] Figure 2 is a flow chart illustrating one embodiment of a process as described herein. [0030] Figure 3 is a schematic illustration of a portion of the steps of one embodiment of a process as described herein.

[0031] Figure 4 schematically illustrates an apparatus useful for carrying out a portion of the process described herein.

PET AIRED DESCRIPTION

[0032] The present invention is now described more fully hereinafter with reference to embodiments of the invention. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the scope of the invention to those skilled in the art.

[0033] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms "a," "an" and "the" are intended to include plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprised of," "comprises" or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements components and/or groups or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups or combinations thereof.

[0034] As used herein, the term "and/or" includes any and all possible combinations of one or more of the associated listed items, as well as the lack of combinations when interpreted in the alternative ("or").

[0035] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly-used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the specification and claims and should not be interpreted in an idealized or overly formal sense unless expressly so defined herein. Well- known functions or constructions may not be described in detail for brevity and/or clarity. [0036] It will be understood that, although the terms first, second, etc., may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. Rather, these terms are only used to distinguish one element, component, region, layer and/or section, from another element, component, region, layer and/or section. Thus, a first element, component, region, layer or section discussed herein could be termed a second element, component, region, layer or section without departing from the teachings of the present invention.

[0037] 1. RESINS AND ADDITIVE MANUFACTURING STEPS.

[0038] Dual cure resins are preferred for carrying out the present invention. Such resins are known and described in, for example, US Patent Nos. 9,676,963, 9,453,142 and 9,598,606 to Rolland et al. Particular examples of suitable dual cure resins include, but are not limited to, Carbon Inc. medical polyurethane, elastomeric polyurethane, rigid polyurethane, flexible polyurethane, cyanate ester, epoxy, and silicone dual cure resins, all available from Carbon, Inc., 1089 Mills Way, Redwood City, California 94063 USA.

[0039] Techniques for producing an intermediate object, or “green” intermediate, from such resins by additive manufacturing are known. Suitable techniques include bottom-up and top- down additive manufacturing, generally known as stereolithography. Such methods are known and described in, for example, U.S. Patent No. 5,236,637 to Hull, US Patent Nos. 5,391,072 and 5,529,473 to Lawton, U.S. Patent No. 7,438,846 to John, US Patent No. 7,892,474 to Shkolnik, U.S. Patent No. 8,110,135 to El-Siblani, U.S. Patent Application Publication No. 2013/0292862 to Joyce, and US Patent Application Publication No. 2013/0295212 to Chen et al. The disclosures of these patents and applications are incorporated by reference herein in their entirety.

[0040] In some embodiments, the additive manufacturing step is carried out by one of the family of methods sometimes referred to as continuous liquid interface production (CLIP). CLIP is known and described in, for example, US Patent Nos. 9,211,678; 9,205,601; 9,216,546; and others; in J. Tumbleston et al., Continuous liquid interface production of 3D Objects, Science 347, 1349-1352 (2015); and in R. Janusziewcz et al., Layerless fabrication with continuous liquid interface production, Proc. Natl. Acad. Sci. USA 113, 11703-11708 (2016). Other examples of methods and apparatus for carrying out particular embodiments of CLIP include, but are not limited to: Batchelder et al., US Patent Application Pub. No. US 2017/0129169 (May 11, 2017); Sun and Lichkus, US Patent Application Pub. No. US 2016/0288376 (Oct. 6, 2016); Willis et al., US Patent Application Pub. No. US 2015/0360419 (Dec. 17, 2015); Lin et al., US Patent Application Pub. No. US 2015/0331402 (Nov. 19, 2015); D. Castanon, S Patent Application Pub. No. US 2017/0129167 (May 11, 2017); L. Robeson et al., PCT Patent Pub. No. WO 2015/164234 (see also US Patent Nos. 10,259,171 and 10,434,706); C. Mirkin et al., PCT Patent Pub. No. WO 2017/210298 (see also US Pat. App. US 2019/0160733); B. Feller, US Pat App. Pub. No. US 2018/0243976 (published Aug. 30, 2018); M. Panzer and J. Tumbleston, US Pat App Pub. No. US 2018/0126630 (published May 10, 2018); and K. Willis and B. Adzima, US Pat App Pub.

No. US 2018/0290374 (Oct. 11, 2018).

[0041] Objects produced by such processes, and to which the matte finish may be imparted, may comprise a solid structure, a hollow structure, a lattice structure ( e.g ., a strut lattice and/or a surface lattice), or any combination thereof. A non-limiting example of a suitable object is a flexible or elastic lattice cushion comprised of a strut lattice structure 22, as shown in Figures 1A-1D. The matte finish reduces the glossiness of the object. Thus, the surface of the object may have a matte appearance instead of a glossy appearance.

[0042] The surface to which the matte finish is imparted may comprise some or all of the surface of the object, but in some embodiments comprises one side of the object, such as surface 22’ in Figures 1A-1D. Note that, while the illustrated embodiment shows a perforated, or lattice, surface, in other embodiments the surface to which the matte finish is imparted may be solid or continuous. Where the surface is solid, it may be formed over an object that is solid throughout, hollow, contains a lattice ( e.g ., a surface “skin” over a lattice), etc., including combinations thereof.

[0043] 2. RESIDUAL RESIN SEPARATION AND CONTACT TO ABSORBENT SHEET.

[0044] After the object is formed by additive manufacturing, resin retained on the surface thereof is partially removed. This removal may be by any suitable technique, including simply gravity draining, but spinning of the part sufficient to centrifugally separate some of the resin is preferred, and blowing the resin off with a compressed gas (e.g., air, nitrogen, etc.), either manually or by passing the object under an air knife, is also preferred.

[0045] As noted above and shown in the flow chart set forth in Figure 2, methods of imparting a matte finish to an object produced by additive manufacturing, can include the steps of:

(a) producing (11) an intermediate object by light polymerization of a dual cure resin in an additive manufacturing process, the object having excess unpolymerized resin retained on a surface thereof;

(b) separating a portion of the excess unpolymerized resin from the object while leaving a thin film of unpolymerized resin on the surface (for example, by spin cleaning

(12));

(c) contacting the thin film to an absorbent sheet (13) to remove additional excess unpolymerized therefrom (14); and then

(d) further curing the intermediate object to produce an object having a matte finish on the surface (for example, by baking (15)).

[0046] While in the flow chart of Figure 2 the separating step (b) is carried out by spinning (i.e., centrifugal separation), the separating step may be carried out by other techniques, such as by blowing with a compressed gas, gravity draining, or a combination thereof.

[0047] While the contacting step (c) can in some cases be carried out manually, in other embodiments it can be carried out with the aid of a press (21) as illustrated in Figures 3A- 3C.

[0048] The surface on which the matte finish is to be imparted is planar, irregular ( e.g ., curved, as illustrated in Figures 3A-3C), or a combination thereof.

[0049] As shown in Figure 4, also disclosed herein is an apparatus useful for imparting a matte finish to an object produced by additive manufacturing. The apparatus generally includes: (a) a frame or chassis 25; (b) a press 21; (c) a manual, mechanical, electromechanical or pneumatic press drive (27) interconnecting the press and the frame; (d) a mount 26 such as a clamp and/or alignment connected to the frame on wich an object produced by additive manufacturing can be removably engaged; and (e) an absorbent sheet dispenser 23’ operatively associated with the frame and configured for dispensing an absorbent sheet between the object and the press.

[0050] In some embodiments, such as illustrated in Figure 4, the object is carried by a carrier platform 31 on which the object was produced by additive manufacturing, and the mount 26 is configured to engage the carrier platform. Such a platform can include a unique identifier (e.g., an NFC tag, an RFID tag, etc.) 32, and the frame can include a unique identifier reader 33 operatively associated therewith and positioned to read the unique identifier. The unique identifier and unique identifier reader may record data concerning the treatment of the object on the apparatus to a database 34, along with other production data concerning the object, for future reference, optimization, quality control or the like.

[0051] In the illustrated embodiment, the press includes a buffer such as compression lattice 21’ configured to conform the absorbent sheet to the object when the object has an irregular surface portion on which the matte finish is to be imparted. The compression lattice may be a constant force compression lattice, such as described in US Patent No. 10,384,494 to McCluskey. In the alternative, the buffer may be an array of retractable posts or “fingers”, optionally with an overlying sheet. In still other embodiments the buffer may be eliminated and the press itself custom made to conform to the specific objects being treated, or the buffer may be custom made to conform to the specific objects being treated, and mounted on a general purpose press.

[0052] While the illustrated embodiments show an absorbent sheet being applied to one side of an object, it will be appreciated that the absorbent sheet may be applied to multiple sides or even all sides of an object by techniques such as wrapping, using two absorbent sheets (one above and one below), sequentially applying sheets to different regions of the object, or combinations thereof.

[0053] Absorbent sheet 23 may comprise any suitable material or combination of materials. The sheet may be single ply or multi-ply, and may optionally have an adhesive coating on a back surface, or in selected regions of the front surface, to secure the sheet in place during application to prevent slippage or uneven application. The absorbent sheet may be biodegradable or inert, and may comprise a woven material, a non-woven material, or a combination thereof. The absorbent sheet may comprise natural fibers, synthetic fibers, or a combination thereof ( e.g ., absorbent fibers combined with a tear-resistant reinforcing network). The absorbent sheet may comprise paper, cotton, jute, rayon, polyester, acrylonitrile, nylon, or a combination thereof. The absorbent sheet may sponge material, polyurethane foam, or a combination thereof. The absorbent sheet may have a thickness that is sufficient to absorb and retain the aqueous composition. The absorbent sheet may have a thickness in the range from about 0.01 or 0.2 centimeters to about 0.4 or 0.5 centimeters. The absorbent sheet may be provided in the form of a folded stack, roll, or any other suitable configuration, optionally with perforations or the like to facilitate dispensing thereof. Numerous examples of absorbent sheets are known, including but not limited to those set forth in US patents nos. 10,455,838; 9,863,095; 9,822,285; 9,661,826; 7,735,180; and 7,662,257.

[0054] 3. FURTHER CURING.

[0055] Once the intermediate object has progressed through the steps described above, the object is then further cured, such as by heating, microwave irradiating, contacting to water ( i.e ., a “moisture cure”), or some combination thereof {see, for example, US Patent Nos. 9,676,963, 9,453,142 and 9,598,606 to Rolland et ah). Heating may be active heating {e.g., baking in an oven, such as an electric, gas, solar oven or microwave oven, or combination thereof), or passive heating {e.g, at ambient (room) temperature). Active heating will generally be more rapid than passive heating and is typically preferred, but passive heating — such as simply maintaining the intermediate at ambient temperature for a sufficient time to effect further cure — may in some embodiments also be employed.

[0056] In preferred embodiments, the object of steps (b), (c) and (d) is unwashed throughout the process {i.e., is not contacted to a excess solvent at any point during production thereof), though in other embodiments a small amount of solvent may be used to facilitate removal and/or absorption of the residual resin. In such embodiments, rather than use as a wash, the solvent is preferably provided in such an amount that it is absorbed by the absorbent sheet, rather than generating a liquid waste stream which must also be cleaned or disposed of.

[0057] Numerous different types of objects can be produced as described herein. For example: [0058] In some embodiments, the object comprises a cushion ( e.g ., a midsole).

[0059] In some embodiments, the object comprises a body contact surface (e.g., a cushion such as a seat cushion, a helmet liner, an arm rest, a head rest, a handle, a steering wheel, or component thereof, optionally but in some embodiments preferably with the matte finish on the body contact surface.

[0060] In some embodiments, the object comprises a skin contact surface, optionally (but in some embodiments preferably) with the matte finish on the skin contact surface.

[0061] Depending on the choice of dual cure resin(s), the object may (for example) be comprised of polyurethane, polyurea, or a copolymer thereof; epoxy; silicone; cyanate ester; or a combination thereof, and the object may be transparent, translucent, or pigmented (e.g, with a white, black, cyan, magenta, or yellow pigment, or a combination thereof).

[0062] The foregoing is illustrative of the present invention, and is not to be construed as limiting thereof. The invention is defined by the following claims, with equivalents of the claims to be included therein.

Claims

WHAT IS CLAIMED IS:

1. A method of making an object by additive manufacturing, the object having a matte finish on a surface thereof, the method comprising the steps of:

(a) producing an intermediate object by light polymerization of a dual cure resin in an additive manufacturing process, said object having excess unpolymerized resin retained on a surface thereof;

(b) separating a portion of said excess unpolymerized resin from said object while leaving a thin film of unpolymerized resin on said surface;

(c) contacting said thin film to an absorbent sheet to remove additional excess unpolymerized therefrom; and then

(d) further curing said intermediate object to produce an object having a matte finish on said surface.

2. The method of claim 1, wherein said producing step (a) is carried out by bottom-up or top-down stereolithography.

3. The method of any preceding claim, wherein said separating step (b) is carried out by spinning ( i.e ., centrifugal separation), blowing with a compressed gas, gravity draining, or a combination thereof.

4. The method of any preceding claim, wherein said contacting step (c) is carried out manually or with a mechanical press.

5. The method of any preceding claim, wherein said further curing step (d) is carried out by heating, microwave irradiating, contacting to water, or a combination thereof.

6. The method of any preceding claim, wherein said object comprises a lattice.

7. The method of any preceding claim, wherein said object comprises a cushion ( e.g ., a midsole).

8. The method of any preceding claim, wherein said object comprises a body contact surface (e.g., a cushion such as a seat cushion, a helmet liner, an arm rest, a head rest, a handle, a steering wheel, or component thereof), optionally but in some embodiments preferably with said matte finish on said body contact surface.

9. The method of any preceding claim, wherein said object comprises a skin contact surface, optionally but in some embodiments preferably, with said matte finish on said skin contact surface.

10. The method of any preceding claim, wherein said object is comprised of polyurethane, polyurea, or a copolymer thereof; epoxy; silicone; cyanate ester; or a combination thereof.

11. The method of any preceding claim, wherein said surface on which said matte finish is to be imparted is planar, irregular ( e.g ., curved), or a combination thereof.

12. The method of any preceding claim, wherein said object is transparent, translucent, or pigemented (e.g., with a white, black, cyan, magenta, or yellow pigment, or a combination thereof).

13. The method of any preceding claim, wherein said object of steps (b), (c) and (d) is unwashed (i.e., is not contacted to a solvent at any point during production thereof).

14. An object produced by the method of any preceding claim.

15. An apparatus useful for imparting a matte finish to an object produced by additive manufacturing, comprising:

(a) a frame;

(b) a press;

(c) a press drive interconnecting said press and said frame;

(d) a mount connected to said frame on wich an object produced by additive manufacturing can be removably engaged;

(e) an absorbent sheet dispenser operatively associated with said frame and configured for dispensing an absorbent sheet between said object and said press.

16. The apparatus of claim 15, wherein said object is carried by a carrier platform on which said object was produced by additive manufacturing, and said mount is configured to engage said carrier platform.

17. The apparatus of claim 15 or 16, wherein said carrier platform includes a unique identifier ( e.g an NFC tag, an RFID tag, etc.), and said frame has a unique identifier reader operatively associated therewith and positioned to read said unique identifier.

18. The apparatus of claim 15 to 17, wherein said press includes a buffer configured to conform said absorbent sheet to said object when said object has an irregular surface portion on which said matte finish is to be imparted.

19. The apparatus of claim 18, wherein said buffer comprises a constant force compression lattice.