WO2019055645A1

WO2019055645A1 - Three-dimensional parts made by additive manufacturing using release coatings on the build surface

Info

Publication number: WO2019055645A1
Application number: PCT/US2018/050865
Authority: WO
Inventors: Anthony FIORE III; Shabbir Attarwala; Ikpreet GROVER; Jesse Davis; Joseph B. Schulz; Andrew Scott; Daniel I. Shaw; Brian NOONAN
Original assignee: Henkel IP & Holding GmbH
Priority date: 2017-09-18
Filing date: 2018-09-13
Publication date: 2019-03-21

Abstract

Provided herein are methods for making three dimensional parts by addtive manufacturing using release coatings on the build surface.

Description

THREE-DIMENSIONAL PARTS MADE BY ADDITIVE MANUFACTURING USING RELEASE COATINGS ON THE BUILD SURFACE

BACKGROUND

Field

[0001] Provided herein are methods for making three-dimensional parts by additive manufacturing using release coatings on the build surface.

Brief Description of Related Technology

[0002] Additive manufacturing is fast becoming a viable alternative to traditional manufacturing techniques and in some cases the only practical alternative for making complex parts.

[0003] One draw back to additive manufacturing is the ability to quickly and easily removing the printed part from the build substrate without damaging the printed part, the build substrate or both. Attempts have been made in the past to address the issue. To date none are believed to be without there own draw backs.

[0004] US Patent Application Publication No. US 2016/0075091 provides for the removal of an object produced by depositing a material, layer-by-layer by an additive manufacturing process, onto a surface of a substrate without mechanically contacting the object with a device or chemically contacting the object. Here, removal of the object from the substrate can be accomplished by flexing or bending the substrate. The substrate can be configured to elastically deform in response to a load applied to the sheet causing a deflection at a center of the sheet in an amount of at least about 12 mm and/or the sheet to have a radius of curvature that is less than or equal to about 305 mm.

[0005] US Patent Application Publication No. US 2016/0332387 provides for a device for removing a 3D print from a build plate of a 3D printer comprising a substantially flat sheet of flexible material of sufficient size to receive and hold deposits of print material from the 3D printer, where the sheet of flexible material accommodates repeated flexing without fracturing and without loss of the

substantially flat disposition, is removably placed atop the build plate of the 3D printer prior to the printing process, and has a top surface that is textured to prevent the 3D print from moving on the sheet of flexible material during the printing process; and a means for preventing movement of the sheet while atop the build plate of the 3D printer and during the printing process.

[0006] US Patent No. 7,195,472 (John) is directed to and claims an apparatus for the separation of a material layer that is hardened on a flat plane, which serves as a reference, the apparatus comprising: a layer of a flexible, elastic separating film arranged between the flat plane and the material layer, where the film does not adhere to the plane and where a gaseous or liquid medium can flow between the film and the plane, either

where the flat plane has a surface facing the film, and the surface comprises a certain surface roughness to ensure supply or removal of the medium; or

where the film has a surface facing the plane, the surface comprising a microstructure to ensure supply or removal of the medium.

[0007] US Patent No. 7,052,263 (John) is directed to and claims an apparatus for manufacturing a three-dimensional object by solidifying in layers a liquid material which can be solidified under the influence of light at locations corresponding to the cross-section of the object in a layer. The apparatus comprises: a trough for holding the liquid material over a transparent plate; a light source; a device for projecting an area of light onto a surface of the liquid material in contact with a resilient layer selected from a solid resilient material having the properties of silicone according to a cross-section of the object to solidify the liquid material exposed by the light in accord with the cross-section; and a positioning device for positioning the object being formed relative to the trough for forming additional layers of the object. The trough comprises a surface layer where the solidified material sticks to the surface layer less than to the transparent plate. The '263 patent indicates that "[i]t is crucial that the resilient layer 9 is made of a material to which the polymerisable material 11 sticks less than to the transparent bottom plate 8 after polymerisation."

[0008] Notwithstanding the state of the art it would be desirable to facilitate the facile printing and removal from the build substrate of a three-dimensional part without damaging either the part or the build substrate and permitting for repetitive prints without requiring an additional application of a release coating. In addition it would be desirable for the chosen release coating to be in the liquid - rather than solid - state for ease of application as well as convenience for the size, geometry and contours of the build substrate without having to cut to size a solid release coating. SUMMARY

[0009] These desires are satisfied by the present invention.

[0010] Whereas in the past, a three-dimensionally printed part would need to be removed from the build surface by flexing or bending the surface or using conventional mechanical scrapers, this invention avoids potentially destructive measures to the so-formed part or the surface techniques and provides a method that treats the surface prior to printing with a release coating to facilitate part removal and maintain the integrity of the part as it is removed from the build surface.

[0011] In addition, through the use of the inventive methods, the three- dimensional part may first be printed onto the build substrate. This is no small matter because in an effort to release a printed part from the build substrate the ability to print the part itself may be compromised. Thus, it is essential that the part is capable of being formed against which must be balanced the ability to remove from the build substrate the printed part with a minimum of force. The present invention has achieved such a balance.

[0012] This breakthrough also reduces labor and improves throughput, as more parts can be printed with less energy spent removing the printed part. And more parts can be printed before subsequent applications of a release coating material needs to be made to the surface of the build substrate.

[0013] The surface finish of the printed part is also improved because it has not been altered through a bending of the build surface or the use of mechanical scrapers to physically separate the part from the build surface. This also obviates the need to treat the surface of the printed part to imperfections due to the removal process.

[0014] The significance of this breakthrough becomes even more pronounced after repeated printings because heretofore the build surface begins to show deterioration which leads to an uneven surface on which the part is printed.

[0015] In one aspect, provided herein is a method of facilitating the removal from a build substrate of a three-dimensional part made by additive manufacturing. This method includes the steps of:

Disposing onto at least a portion of a surface of the build substrate a release coating material; Performing additive manufacturing using a resin to form a three- dimensional part on the build substrate, where the three-dimensional part is made according to data indicating a pre-determined pattern; and

Removing the so-formed part from the build substrate.

[0016] In another aspect, provided herein is a method of forming a three- dimensional part. Here, the method includes the steps of:

Providing onto at least a portion of a surface of a build substrate a release coating material;

Sequentially disposing a flowable resin onto the build substrate and solidifying the disposed flowable resin to form a series of intermediate, non-flowable shapes that progress into the three-dimensional part, where the three-dimensional part is made according to data indicating a pattern pre-determined by software code; and

Removing the so-formed part from the build substrate.

[0017] In yet another aspect, provided herein is a method of forming a three- dimensional part. In this method, the steps include:

Providing a carrier and an optically transparent member having a build surface, wherein the carrier and the build substrate define a build region

therebetween;

Providing onto at least a portion of the build surface a release coating material;

Providing to the build region a thermoset resin;

Exposing the build region to radiation in the electromagnetic spectrum appropriate to transmit through the optically transparent member to form a non- flowable three-dimensional intermediate part and advancing the carrier away from the build substrate to continue to form successive forms of the non-flowable three- dimensional intermediate part, all of which according to data indicating a pattern predetermined by software code; and

Subsequent to the exposure to radiation in the electromagnetic spectrum, exposing the so-formed three-dimensional intermediate part to elevated temperature conditions for a time sufficient to cure the thermoset resin into the three- dimensional part. BRIEF DESCRIPTION OF THE FIGURE

[0018] FIG. 1 depicts a bar chart showing the torque (in-lbs) required to release from the buildhead a printed object made from Formlabs Tough Resin on a Formlabs 1+ printer, with and without a release coating material.

DETAILED DESCRIPTION

[0019] As noted above, a method of facilitating the removal from a build substrate of a three-dimensional part made by additive manufacturing is provided herein. The method includes the steps of:

Disposing onto at least a portion of a surface of the build substrate a release coating material;

Performing additive manufacturing using a resin to form a three- dimensional part on the build substrate; and

Removing the so-formed part from the build substrate.

[0020] Additive manufacturing is performed to form the three-dimensional part according to data indicating a pre-determined pattern.

[0021] The release coating material comprises silanol terminated

polydimethylsiloxane. In addition to the silanol terminated polydimethylsiloxane, at least one of tris(n-methylamino)methylsilane.and wax may also be included.

[0022] While the release coating material may be applied directly to the build surface, ordinarily it is applied as a solution or dispersion in a liquid carrier. The liquid carrier may be aqueous and/or solvent based.

[0023] The release coating material may be present at a concentration in the liquid carrier in an amount of about 0.05 to about 10 weight percent, such as about 2.5 to about 5 weight percent.

[0024] The chosen release agent should have a contact angle measurement of greater than 75°C but less than 108°C.

[0025] The resin may be thermoplastic or thermosetting.

[0026] The resin may be exposed to elevated temperature conditions prior to disposing on the build substrate to assist in application. Particularly in the case of thermoplastic resins, doing is desirable in order to facilitate disposition. Here, the temperature chosen should be greater than room temperature plus about 70°C. [0027] Any of a variety of thermoplastic resins may be used. For instance, polyamides, acrylonitrile butadiene styrene resins, polybutylene, polyethylene, polyvinylchloride and nylons are ordinarily used.

[0028] The resin may also be thermosetting - that is to say, curable. In case of thermosetting resins, one of more cure modalities may be used to cure the resin. For instance, exposure to radiation in the electromagnetic spectrum may be used. The radiation in the elctromagnetic spectrum may be selected from IR, VIS, UV and UV/VIS.

[0029] Indeed, radiation at one portion of the spectrum may be used initially, followed by radiation in another portion of the spectrum. Or, radiation in the electromagnetic spectrum may be used together with exposure to elevated temperature conditions. The elevated temperature should be chosen with an eye toward the cure temperature of the resin used and its cure profile with the cure package selected.

[0030] Depending on the chemistry of the resin, the cure package may vary widely in both nature and amount. For instance, where the resin is curable through (meth)acrylate functionality, the cure package may be chosen to be one triggered by exposure to radiation in the electromagnetic spectrum or elevated temperature conditions, or both.

[0031] Where an elevated temperature condition is chosen to cure the resin, the temperature chosen should be greater than room temperature plus about 70°C, though desirably less than about 180°C.

[0032] In another aspect, a method of forming a three-dimensional part is provided. Here, the method includes the steps of:

Sequentially disposing a flowable resin onto the build substrate and solidifying the disposed flowable resin to form a series of intermediate, non-flowable shapes that progress into the three-dimensional part; and

Removing the so-formed part from the build substrate.

[0033] As above, the three-dimensional part is made according to data indicating a pattern pre-determined by software code. [0034] Solidifying the disposed flowable resin may involve exposure to conditions appropriate to render the flowable resin non-flowable. When solidifying a flowable resin that is thermoplastic, this ordinarily involves exposing the resin to elevated temperature conditions to facilitate its disposition on the build substrate. After disposition, the resin needs to be rendered non-flowable. This is ordinarily accomplished by exposing the so-disposed resin to temperature conditions below that which was used to facilitate the disposition.

[0035] Irrespective of whether the resin chosen is thermoplastic or

thermosetting, once the three-dimensional part has been formed it needs to be removed from the build surface for subsequent use. The inventive methods achieve removal of the so-formed without resorting to mechanically contacting the so-formed part with a device or contorting the substrate.

[0036] One way for disposing resin onto the build substrate to form a three- dimensional part is to deposit the resin in a layer-by-layer manner, where after disposition of each layer of resin the resin is solidified to maintain its shape prior to disposition of the subsequent layer until the three-dimensional part is formed and then removed from the build substrate.

[0037] Another way for disposing resin onto the build substrate to form a three- dimensional part is by:

therebetween;

Providing to the build region a thermoset resin;

Subsequent to the exposure to radiation in the electromagnetic spectrum, exposing the so-formed three-dimensional intermediate part to elevated temperature conditions for a time sufficient to cure the thermoset resin into the three- dimensional part.

[0038] In this way, a thermoset resin is used and as the part is forming the resin is exposed to radiation in the electromagnetic region appropriate to cure the resin in its intermediate form.

[0039] In the inventive methods, the release coating material disposed on the build substrate facilitates removal of the three-dimensional part, desirably using less than 30 in-lb force. The following examples are illustrative.

EXAMPLES

[0040] In the examples, a Form 1+ Printer was used to print parts in the shape of a hexagonal nut dimensioned 1" per side x ½" in the Z direction. Indeed, nine of such nuts were printed on the build surface using Formlabs Tough Resin, which is promoted as a photopolymer resin having a combination of (meth)acrylated oligomers, (met)acrylated monomers, acrylated monomers, and a photoinitiator. Prior to printing the build surface was either not coated with a release agent, or coated with a release agent such as Teflon, polyvinyl alcohol, wax or with one of three release agents, each of which being based on a silicone material (CAS # 1432471-92-5) in the range of 0.95% to 1.38% and one of which also having petroleum wax called FREWAX in an amount of 2.48%. FREWAX itself is reported by the manufacturer to contain 2.475% of clay-treated microcrystalline wax and 1.3709% of siloxanes/silicones-silyl-oxy-terminated, diluted in hydrocarbon solvent.

[0041] The use of a release agent on the build surface changes the surface energy of the build surface. The change is intended to lower the energy of the surface, which in turn should result in the three-dimensionally printed part adhering less to the surface than would otherwise occur without the release coating. For instance, the use of wax as a release coating creates a surface with an energy of 35 dynes / sq cm. The use of Teflon creates a surface with an energy of 18 dynes / sq cm. The use of polyvinyl acetate creates a surface with an energy of 37 dynes / sq cm. The use of any of the three silicone based materials creates a surface with an energy in the vicinity of 24 dynes / sq cm. See ASTM Std. D-2578.

[0042] The higher the dynes / sq cm number the more force is expected to be required to remove the printed part from the build surface, whereas the lower the number the less force is expected to be required to remove the printed part from the build surface. Thus, given these values, one would expect that a Teflon release coating would permit a printed part to be removed from the build surface with the least amount of force and a polyvinyl acetate release coating would require the most amount of force to remove a printed part from the build surface.

[0043] In a similar manner, contact angle measurements using water as a liquid may also be useful in setting expectations about surface energy and the degree of adherence to a surface with and without release coatings. For instance, polyvinyl acetate demonstrates a contact angle measurement of 60.6°, wax demonstrates a contact angle measurement of 108.9° and Teflon demonstrates a contact angle measurement of 109.2°. Polydimethylsiloxane has a reported contact angle measurement of 107.2°; the contact angle measurements for the FREKOTE release coatings and FREWAX release coating are expected to be within this vicinity.

[0044] Here, one would expect a higher contact angle measurement to result in a lower amount of force to remove a printed part from the build surface compared with a lower contact angle measurement.

[0045] The Form 1+ Printer was set at Castable, 0.1 mm. The term "castable refers to the material setting, which is a requirement to choose a pre-loaded material setting for each print. The "0.1 mm" refers to the printer resolution, or thickness of each layer of the print. The print takes 3 hours and 14 minutes to complete at these settings.

[0046] The 9 hexagonal nuts were printed on the build surface in a three by three pattern. Once printing was complete, the parts were removed from the build surface using a torsiometer giving a reading of torque strength in inch-lbs. A 21 mm socket was attached to the torsiometer. The torsiometer operates by allowing the user to select a torque wrench add-on between the maximum and minimum force would be required to remove the printed hexagonal nut. Here, 50 in-lb or 200 in-lb torque wrench was used. The torsiometer was operated in peak hold mode as this selection displays the highest torque applied.

[0047] The hexagonal nuts were printed in sets of nine. Multiple sets of the hexagonal nuts were printed for evaluation. For the first group, four sets of nine hexagonal nuts were printed directly on the build surface; that is, no release coating was applied to the build surface prior to the start of printing. For the second through fourth groups, a release coating was applied to the build surface prior to the start of printing. For the second group, five sets of nine hexagonal nuts were printed after applying FREKOTE 770 NC to the build surface prior to the printing of each set. For the third and fourth groups three sets of nine hexagonal nuts were printed after applying a release coating. For the third group, FREWAX was used; and for the fourth group, FREKOTE 55 NC was used.

[0048] In addition, a fourth, fifth, and sixth group of hexagonal nuts were printed in sets of nine with three additional release agents applied to the build surface prior to printing. Release Agent D is Teflon; Release Agent E is polyvinyl acetate and Release Agent F is wax.

[0049] Tables 1-6 below capture the results of the force required to remove the printed parts from the build surface in each group. FIG. 1 depicts this data in a bar chart format.

[0050] Table 1 captures data of a control where no release agent was disposed on the surface of the build surface.

Table 1

[0051] On average about 107 in-lb was required to remove the printed part from the build surface.

[0052] Table 2 captures data where a FREKOTE release agent was disposed on the surface of the build surface. Table 2

[0053] On average about 24.5 in-lb was required to remove the printed part from the build surface.

[0054] Table 3 captures data where another FREKOTE release agent was disposed on the surface of the build surface.

Table 3

[0055] Here too on average about 24.6 in-lb was required to remove the printed part from the build surface.

[0056] Table 4 captures data where FREWAX release agent was disposed on the surface of the build surface. Table 4

[0057] On average about 28 in-lb was required to remove the printed part from the build surface.

[0058] Table 5 captures data of a control where Teflon (Printable Dry Spray - A4) was used as a release agent disposed on the surface of the build surface.

Table 5

[0059] On average about 80.1 in-lb was required to remove the printed part from the build surface. [0060] Table 6 captures data of a control where polyvinyl acetate

(commercially available from Fiber Glass Coatings, Inc.) was used as a release agent disposed on the surface of the build surface.

Table 6

[0061] Some of the intended parts did not print, while others that did print could not be removed from the build surface without breaking the printed part. For those printed parts that could be removed undamaged, on average about 62.5 in-lb was required to remove the printed part from the build surface.

[0062] Where wax (commercially available as STONER-E412 Wax Pattern Release) was used as a release agent disposed on the surface of the build surface, no parts printed. Consequently, no data could be collected.

[0063] From the data captured in these Tables and shown in FIG. 1 , instead of what would have been expected, it may be seen that the release agents useful in the practice of the inventive methods are capable of both (1) permitting a three dimensional part to be printed (in the case of wax itself, parts could not be

successfully printed) and (2) permitting the printed part to be removed from the build surface using less than 30 in-lb force, such as less than 28 in-lb force, desirably less than 25 in-lb force. In addition, the chosen release agent should have a contact angle measurement of greater than 75° but less than 108°, such as greater than 90° but less than 108°, desirably greater than 100° but less than 107.8°.

Claims

What is Claimed is:

1. A method of facilitating the removal from a build substrate of a three- dimensional part made by additive manufacturing, comprising the steps of:

Performing additive manufacturing using a resin to form a three-dimensional part on the build substrate, said three-dimensional part made according to data indicating a pre-determined pattern; and

Removing the so-formed part from the build substrate.

2. The method of Claim 1 , wherein the release coating material comprises silanol terminated polydimethylsiloxane.

3. The method of Claim 1 , wherein the release coating material comprises silanol terminated polydimethylsiloxane and at least one of tris(n-methylamino)methylsilane and wax.

4. The method of Claim 1 , wherein the resin is thermoplastic.

5. The method of Claim 1 , wherein the resin is curable.

6. The method of Claim 1 , wherein the resin is curable by one or more cure modalities.

7. The method of Claim 1 , wherein the resin is curable by exposure to radiation in the electromagnetic spectrum.

8. The method of Claim 1 , wherein the additive manufacturing is performed by exposing the resin to an elevated tempertaure condition.

9. The method of Claim 8, wherein the elevated temperature condition is greater than room temperature plus about 70°C.

10. The method of Claim 1 , wherein the release agent has a contact angle measurement of greater than 75°C but less than 108°C.

11. The method of Claim 1 , wherein the printed three-dimensional part is removed from the build surface using less than 30 in-lb force.

12. A method of forming a three-dimensional part, comprising the steps of:

Sequentially disposing a flowable resin onto the build substrate and solidifying the disposed flowable resin to form a series of intermediate, non-flowable shapes that progress into the three-dimensional part, said three-dimensional part made according to data indicating a pattern pre-determined by software code; and

Removing the so-formed part from the build substrate.

13. The method of Claim 12, wherein solidifying the disposed flowable resin involves exposure to conditions appropriate to render the flowable resin non- flowable.

14. The method of Claim 12, wherein solidifying the disposed flowable resin involves exposure to radiation in the electromagnetic spectrum appropriate to render the flowable resin non-flowable.

15. The method of Claim 12, wherein solidifying the disposed flowable resin involves exposure to radiation in the electromagnetic spectrum appropriate to cure the resin.

16. The method of Claim 12, wherein solidifying the disposed flowable resin involves exposure to radiation in the elctromagnetic spectrum is selected from IR, VIS, UV and UV/VIS.

17. The method of Claim 1 , wherein the so-formed part is removed from the substrate without mechanically contacting the so-formed part with a device or contorting the substrate.

18. The method of Claim 12, wherein the so-formed part is removed from the substrate without mechanically contacting the so-formed part with a device or contorting the substrate.

19. The method of Claim 1 , wherein release agent has a contact angle

measurement of greater than 75°C but less than 108°C.

20. The method of Claim 12, wherein the printed three dimensional part is removed from the build surface using less than 30 in-lb force.

21. A method of forming a three-dimensional part, comprising the steps of:

therebetween;

Providing to the build region a thermoset resin;

Exposing the build region to radiation in the electromagnetic spectrum appropriate to transmit through the optically transparent member to form a non- flowable three dimensional intermediate part and advancing the carrier away from the build substrate to continue to form successive forms of the non-flowable three dimensional intermediate part, all of which according to data indicating a pattern predetermined by software code; and

Subsequent to the exposure to radiation in the electromagnetic spectrum, exposing the so-formed three dimensional intermediate part to elevated temperature conditions for a time sufficient to cure the thermoset resin into the three dimensional part.

22. The method of Claim 1 , wherein release agent has a contact angle measurement of greater than 75°C but less than 108°C.

23. The method of Claim 21 , wherein the printed three-dimensional part is removed from the build surface using less than 30 in-lb force.