US20140319734A1

US20140319734A1 - Real time manufacturing of softening polymers

Info

Publication number: US20140319734A1
Application number: US14/261,327
Authority: US
Inventors: Walter Voit; Taylor Ware; James Amato; Michael Moussa; Phillip Brent Duncan; Bryan Bell; Cary Baur; Benjamin R. Lund; Duck J. Yang
Original assignee: University of Texas System; Syzygy Memory Plastics Corp
Current assignee: University of Texas System; Syzygy Memory Plastics Corp
Priority date: 2013-04-24
Filing date: 2014-04-24
Publication date: 2014-10-30
Also published as: US9931771B2; US20160200044A1; US20140323647A1

Abstract

Embodiments of the invention is directed to a manufacturing process to mold and cast custom softening polymers into complex shaped devices, said process comprising the steps of: creating a 3D mold or shell; injecting the shell with a polymer or pre-polymer; cooling or curing the polymer in a short period of time; and forming a device.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §119(e) of U.S. Provisional Patent Application No. 61/815,603 filed Apr. 24, 2013, and U.S. Provisional Patent Application No. 61/815,607 filed Apr. 24, 2013 which are incorporated herein by reference in its entirety as if fully set forth herein.

FIELD OF THE INVENTION

Embodiments of the claimed invention are directed to a method for building custom products out of softening polymers.

BACKGROUND OF THE INVENTION

3D printing or additive manufacturing is a process of making a three-dimensional solid object of virtually any shape from a digital model. 3D printing is achieved using an additive process, where successive layers of material are laid down in different shapes. 3D printing is also considered distinct from traditional machining techniques, which mostly rely on the removal of material by methods such as cutting or drilling (subtractive processes).
A 3D printer is a limited type of industrial robot that is capable of carrying out an additive process under computer control.
The 3D printing technology is used for both prototyping and distributed manufacturing with applications in architecture, construction, industrial design, automotive, aerospace, military, engineering, dental and medical industries, biotech (human tissue replacement), fashion, footwear, jewelry, eyewear, education, geographic information systems, food, and many other fields.
In light of the multiple uses that 3D printing lends itself to, it would be beneficial to use some of the advantages of this technique to build custom product using a variety of materials.

SUMMARY OF THE INVENTION

An embodiment of the invention is directed to a manufacturing process to mold and cast custom softening polymers into complex shaped devices, said process comprising the steps of: creating a 3D mold or shell; injecting the shell with a polymer or pre-polymer; cooling or curing the polymer in a short period of time; and forming a device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a flowchart of different manufacturing options for creating a custom softening earphone in accordance with embodiments of the invention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

An exemplary embodiment of the invention is directed to a manufacturing process to mold and cast custom softening polymers into complex shaped devices, said process comprising the steps of: creating a 3D mold or shell; injecting the shell with a polymer; curing the polymer in a short period of time; and forming a device.
An embodiment of the claimed invention is directed to a method for rapidly building custom products out of softening polymers. This technology uses a combination of scanning and/or 3D printing along with materials design technologies. Most softening polymers, such as shape memory polymers described in the literature or materials, suffer from major limitations that preclude their use in such a real-time manufacturing environment. Some limitations include high cure stresses, long polymerization times, improper viscosity of the monomer solutions, the inability of some systems to cure in aerobic environments and even toxicity of monomers. Softening materials, materials that undergo a large change in modulus between two variable use temperatures, room temperature and body temperature, and especially polymers that soften to moduli below Shore A 50, have not to our knowledge been successfully used in a real-time manufacturing paradigm that combines scanning and 3D printing. To our knowledge these have not been used as thermoplastics for fused deposition printing, or as mixtures of mutually miscible monomers and additives for curing during stereolithography, reaction injection molding or real-time casting into complex 3D shells.
A further embodiment of the claimed invention is directed to a method for direct stereolithography of softening polymer systems, such that materials can be molded directly in a 3D environment based on a complex 3D CAD model. In the past, materials compatible with this paradigm have traditionally been highly multi-functional materials such as the epoxy SU-8 which can be rapidly spot cured with a laser in specific spatial constructions. A manufacturing process is described herein that is able to use a material that changes in modulus by at least 2× between room temperature and body temperature. We describe a manufacturing paradigm for materials in which this modulus change occurs to hardness below Shore A 50, below Shore A 30, below Shore A 20 and below Shore A 10. In one embodiment the materials' modulus changes by more than 100× between room temperature and body temperature. Furthermore, after polymerization, the material can be viscoelastic at both room temperature and body temperature leading to interesting processing modifications to deal with time-dependent polymer mechanics.
Another embodiment of the claimed invention is directed to a method that allows for the printing of a sacrificial polymer shell which is filled (through injection, casting, or some other means) with a custom blend of mutually miscible monomers which are subsequently polymerized optionally around a prefabricated component, such as the custom electronics of an earphone attached to a specially designed tube used to keep monomer from the airway that will ultimately lead from the speaker to the eardrum. This embodiment is set forth in FIGS. 1 and 2. This enables customization of part of the device and mass manufacture of device components that can be identical across devices. This manufacturing paradigm also is possible with materials, which once polymerized, possess a modulus change occurs as a function of temperature to hardness plateaus below Shore A 50, below Shore A 30, below Shore A 20 and below Shore A 10. In one embodiment the materials' modulus changes by more than 100× between room temperature and body temperature.
Yet another embodiment of the claimed invention is directed to a third manufacturing paradigm in which we can alternatively or simultaneously print a sacrificial polymer shell layer-by-layer and fill and cure or partially cure a secondary softening polymer that begins to fill the growing shell as the shell is being manufactured. This can also be accomplished by printing the shell and filling the shell around one or more prefabricated parts that are fully or partially within the boundary created by the shell. We believe this approach can be extremely useful for creating large parts or parts from polymers (softening or not) without the UV transparency necessary to cure through thick layers. In this way, a surface can be cured one layer at a time where the penetration depth of the curing radiation (e.g. UV) through the material is greater than the thickness of the layer. In yet another embodiment of the layer-by-layer curing within a custom 3D shell, the layers can be only partially cured such that reactive groups remain on the surface of the partially cured layer and are able to effectively form covalent crosslinks with the next layer. In this way, a structurally sound, well-formed network can be created across custom parts leading to increases in materials properties such as ultimate tensile strength and toughness.
An additional embodiment of the claimed invention is the design of a 3D printer or print head configuration that allows for this aforementioned paradigm. The 3D printing will include the ability to print an external shell (likely through Fused Deposition Modeling), to fill the shell with a mutually miscible mixture of photopolymerizable monomers and necessary additives (likely through reaction injection molding or injection casting) and the cure the shell layer by layer with a UV source. In more sophisticated versions of this machine it is conceivable that the various layers could be printed out of different materials that in turn could bind together within the framework created by the outer shell. In this way, laminate structures could be created with very interesting anisotropic properties and excellent interlayer adhesion. Specifically, if the UV cure is only a partial cure, such as can be demonstrated with certain thiol-ene, thiol-ene/acrylate and thiol-epoxy systems, these variable interlayers may approach or exceed the materials properties of a monolithically cured polymer or copolymer.
In an embodiment of the invention, a custom designed 3D printer is able to print a thin shell in a custom geometry around prefabricated components such as an earphone connected to an air tube to exclude the mixture of mutually miscible monomers that fill the space inside the shell and outside of the tube and component before the monomers are cured. The monomers are cured by a UV source either on the print head that can cure the monomers layer by layer as the part is being printed, or after several layers or after the entire shell has been filled. This curing profile is dependent on the size of the part, the penetration of the UV radiation, the UV transparency of the shell material and the UV transparency of the monomers themselves and the UV transparency of the cured polymer inside of the shell.
An exemplary embodiment of the claimed invention is directed to a manufacturing process to mold and cast custom softening polymers into complex shapes wherein: a 3D mold or shell is created from CAD file, custom (ear) impression, or custom scan; the shell is injected with rapidly curing polymer; and the polymer is allowed to cure in about 15 minutes (or shorter/longer depending on use). In embodiment of the invention, the material is very soft (e.g. less than 50 shore A) and/or has softening ability (e.g. ˜20-200% change in modulus from room temp to body temp).
In a further embodiment, a polymer manufacturing process is provided wherein a 3D CAD created from custom (ear) impression, or custom scan; and a part is directly printed from using FDM, SLA, or inkjet printing techniques. The material is very soft (e.g. less than 50 shore A) and/or has softening ability (e.g. >20% change in modulus from room temp to body temp); 1 cures rapidly (less than 10 minutes) under exposure to UV or heat upon printing; and is capable of being directly printed onto audio components.
An alternative embodiment is for the design of custom dental aligners or other personalized dental equipment. In this example, a human mouth is scanned or an impression is made and subsequently scanned. The scan is transferred to a program that trims the scan and creates a shell model that represents an allowable boundary of the scan. This shell is then 3D printed using stereolithography or fused deposition molding techniques. (In another embodiment, the mold is directly cast around the impression). The shell is then optionally placed around a bundle of custom electronics that includes speakers, microphones, cables, and optionally a variety of other sensors including but not limited to heart rate monitors, blood pressure monitors, pH monitors, and other analyte monitors. In a more specific such embodiment, a patient's mouth is scanned and a series of molds are made from the existing scan in such a way as to guide teeth back to some predetermined position for cosmetic, aesthetic, functional, health or other reasons. The first mold is printed and a polymer or prepolymer is cooled or cured therein such that the resulting device exerts a specific force onto the patients' teeth and jaws to guide remodeling. Additional parts are likewise fabricated such that the one-time or several-time molds can be rapidly and cheaply manufactured. This is very important because the costs incurred to make metal injection molds using subtractive processes are unduly expensive for low numbers of uses. In addition, often directly printing devices by additive means leads to tradeoffs in the choice of polymer or prepolymer system that may not be conducive for the final application. For instance, optical clarity plays a huge role in this dental aligning application and being able to decouple the polymer properties from the scanning and printing of the custom mold can be very beneficial. In one such embodiment, the mold can be 3D printed from commercially available metals, ceramics prepolymers or polymers, and filled with different prepolymers or polymers which are more likely to be able to hit the demanding application specifications than 3D printable resins. For instance, polymers with greater than about 85% transmission through about a 500 micron to 1 mm film with an elongation of break above about 50% and yield strength of about 48 MPa and a glassy modulus above about 1 GPa can be achieved in many non-3D printed resins. One such prepolymer is a monomer resin of thiols and alkenes which when polymerized possesses high optical clarity, low or zero-cure stresses, delayed network gelation and excellent mechanical properties. When a material such as this is developed toward a 3D printing resin, additives, reactive diluents, colorants, dyes, and other agents may be necessary for printing but not for the application itself. This invention finds a clever way around this quite difficult issue and can present a way to reduce yellowing of the final part.
In a further embodiment of this invention, the final molds can have shape memory properties, such that instead of requiring many multiples of molds (up to 40 in some cases), only one or a much smaller number of dental aligners can be made in the manner described above and utilize the shape memory effect to gradually or periodically reshape the mold and control the applied forces on the teeth and jaw.
Another embodiment of the invention is for the design of a toy, novelty item, bobble head doll, action FIGURE or other likeness. The target object to be scanned, photographed or otherwise converted into a 3D geometry or superposition of 2D geometries, may be but is not limited to a target person, pet, animal, body part, household item or toy, case for consumer electronics, sculptures, artwork or other physical or intellectual creative endeavor.
In certain embodiments of the invention, the injection system is built directly into 3D printer (i.e. able to position and automate casting or reaction injection molding); and the material is liquid or gel system capable of injection into shell. In certain embodiments, the injection and/or finishing can also be designed separately from 3D printer. Additionally, finishing can be accomplished through polish, liquid epoxy, etching, micro-milling, cryomilling, solution dipping, coating or surface functionalization
In some embodiments, the material is optionally formed around prefabricated components. In an embodiment for the manufacture of an earphone, a sound tube is connected and automatically positioned at the target center to cast around (for earphones). The shell is printed directly on to the audio component or the shell is attached to the audio component prior to the injection of the material. The material is typically UV curable or thermally curable and could contain colorants or thermochromic dyes. In certain embodiments, subtractive processing may be used to create semi-custom styles (e.g. sport fit of earphone that lets in some sound). Alternately, the incorporation of sensors (e.g. heart rate, O₂, temp) and connection to phone for sports performance or health monitoring (another potential embodiment).
FIG. 1 shows a schematic process for the design of a custom earphone with a softening material. In a first process, the following steps are followed:
Data collection:

- Digital scanning of ear canal;
- Take impression of ear canal, scan impression

Data filtering:

- Trim and filter scanned data
- Trim and smooth physical ear impression (no scan required)

Mold Production:

- 3D print the custom device mold (FDM)
- 3D print the custom device mold (SLA)
- Cast mold directly from physical impression

Custom Device:

- 3D print device directly (no mold production required)
- Cast the device into mold created by FDM, SLA or from physical impression

Automation/Integration:

- Software algorithm to recognize changes in geometry of ear canal to trim the data just outside the ear canal and inside the ear canal prior to negative draft
- Software algorithm to produce an outward shell of the data so that inner surface matches the inner surface of ear canal.
- Software algorithm to orient and skew the mold impression to avoid overhangs greater than threshold of print quality required for FDM printing (commonly, but not limited to, 45 degrees)
- Software algorithm to produce features for custom devices, selectable by technician, including, but not limited to, holes and geometry for audio tubes, electrical components, audio speakers, and hearing aid components.
- Custom additive or subtractive manufacturing hardware capable of producing a mold using an additive manufacturing technique (including but not limited to FDM and SLA), followed by assembly of electrical components, injection of curable liquid resin into the mold and rapid curing of the resin to produce custom-fit devices (see attached diagram)
- Custom additive manufacturing hardware capable of directly producing custom ear-canal devices incorporating other components including, but not limited to, audio tubes, electrical components, audio speakers and hearing aid components.

The claimed invention is directed to a comprehensive, real-time manufacturing paradigm in which devices are made from softening polymers that comprises several steps:

- a) Laser scanning, acoustic scanning, thermal scanning, or otherwise capturing of a 3D image of a part, body part, component, space, relevant subject matter or specified mold or impression made to represent said part;
- b) A software algorithm to trim and shell scanned data;
- c) A method, such as wireless data transfer, to send the 3D model to a 3D printer;
- d) Printing a material shell of an optionally sacrificial material;
- e) Optionally positioning the material shell around prefabricated components, which could include other components made through this disclosed process, or materials such as but not limited to custom electronics, stiff structural materials or encapsulated biological materials;
- f) Casting a combination of mutually miscible monomers into the shell that are subsequently fully or partially polymerized in the custom mold;
- g) Optionally deforming a partially polymerized device further and completing the polymerization process to achieve extraordinary shapes; and
- h) Performing any necessary post processing steps on the device, such as custom finishing, polishing, and milling.

A preferred embodiment of the invention is the design of custom earphones. In this example, a human ear canal is scanned or an impression is made and subsequently scanned. The electronic scan is transferred to a program that trims the scan and creates a shell model that represents an allowable boundary of the scan. This shell is then 3D printed using stereolithography or fused deposition molding techniques. In another iteration, a physical shell is cast around the physical ear impression. This shell is then placed around a bundle of custom electronics that includes speakers, microphones, cables and optionally a variety of other sensors including but not limited to heart rate monitors, blood pressure monitors, pH monitors, and other analyte monitors.
Other embodiments are directed to a custom manufacturing process for creating a custom earphone for a user in less than 3 hours and more preferably less than 1 hour, less than 30 minutes, less than 20 minutes, less than 15 minutes, less than 10 minutes, and less than 5 minutes.
A further embodiment is directed to a custom manufacturing process for creating an earphone with a softening polymer interface that can be completed in less than 30 minutes.
While particular embodiments of the present disclosure have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are with the scope of this disclosure.

Claims

What is claimed is:

1. A manufacturing process to mold and cast custom softening polymers or prepolymers into complex shaped devices, said process comprising the steps of:

creating a 3D mold or shell;

injecting the shell with a polymer or prepolymer;

cooling the polymer melt or curing the prepolymer in a short period of time; and

forming a device.

2. The process of claim 1, wherein the shell geometry is generated using a laser scan, a physical impression, splicing of pictures taken from multiple angles, image processing and interpolation from a single picture or an alternative scanning of the object to be molded.

3. The process of claim 1, wherein the shell is manufactured by additive means such as fused filament fabrication, stereolithography, digital light projection based selective curing, inkjet printing, selective laser sintering or selective deposition lamination.

4. The process of claim 1, further comprising using a software algorithm to trim and shell scanned data.

5. The process of claim 1, further comprising transferring data to send the 3D model to a 3D printer by wireless or wired means.

6. The process of claim 1, further comprising printing a material shell of an optionally sacrificial material.

7. The process of claim 1, further comprising positioning the material shell around prefabricated components such as but not limited to custom electronics, stiff structural materials or encapsulated biological materials.

8. The process of claim 1, wherein the polymer comprises a combination of mutually miscible monomers that are subsequently fully or partially polymerized in the shell.

9. The process of claim 1, wherein the polymer or prepolymer is cured by a UV source or other optical energy sources.

10. The process of claim 1, further comprising optionally deforming a partially polymerized device further and completing the polymerization process to achieve extraordinary shapes.

11. The process of claim 1, further comprising performing post processing steps on the device, such as custom finishing, polishing, and milling.

12. The process of claim 1, wherein the process is used to manufacture earplugs, earphones, bluetooth devices, hearing aids and other personalized audio equipment.

13. The process of claim 1, wherein the process is used to manufacture dental aligners or other personalized dental equipment or devices.

14. The process of claim 1, wherein the process is used to manufacture end-use products with the requisite properties such as but not limited to mechanical, thermal, electrical, piezoelectric, optical, structural, biological, or chemical to directly be used in manufacturing environments.

15. The process of claim 1, wherein the process is used to manufacture biomedical devices including but not limited to syringes, catheters, valves, stents, suture anchors, needles, bandages, arterial clamps, punctual plugs, septal plugs, synthetic bones, synthetic cartilage, synthetic tendons, custom prosthetics, tissue phantoms, scaffolds, or cellular scaffolds of specific shapes.

16. The process of claim 1, wherein the injecting process used is injection molding, blow molding, vacuum assisted resin transfer molding, reactive injection molding, foaming or casting.

17. The process of claim 11, wherein the post-finishing or polishing is performed by laser ablation.

18. The process of claim 12, wherein the audio equipment is coated with one or more compounds that resist bacteria growth, boost immune system, and enhance compatibility of the audio equipment with human organs.

19. The process of claim 13, wherein the dental equipment is coated with one or more compounds that resist bacterial growth, boost immune system and enhance compatibility of the dental equipment with human organs.

20. The process of claim 15, wherein the biomedical devices are coated with one or more compounds that resist bacterial growth, boost immune system and enhance compatibility of the biomedical devices with human organs.