Patent Application
20230302730
The present invention relates generally to a dual-wavelength light engine for DLP 3D printing with photo-inhibition. More particularly, the present invention relates to a setup configured to independently and locally control activation and inhibition of a polymerization process.
A 3D printing apparatus may be used for the manufacturing of a 3D object such as a 3D dental object with a desired shape through exposing a photocurable substance with light that may transform monomers and oligomers of the photocurable substance into polymers. Those polymers may then make up the body of a 3D (three-dimensional) solid.
In an aspect a 3D printing system is disclosed. The 3D printing system may comprise a first light source and a second light source combined in one light engine. The light sources may comprise LEDs (light emitting diodes). Light from two LEDs radiating at wavelengths matched for polymerization inhibition and polymerization activation may be mixed by a dichroic mirror before being spatially structured by a digital mirror device (DMD). Behind the DMD, the mixed light mask may be projected to a vat by an optical system comprising one or more lenses.
In an aspect, the 3D printing system may comprise two LEDs emitting different wavelengths, the dichroic mirror combining the light of the two LEDs, the DMD configured to create the irradiation mask and the optical system forming the projection. However the two LEDs or light sources may be combined into one, i.e., one LED or light source may emit two wavelengths.
In an aspect, the irradiation mask may be a patterned illumination that may be projected through a transparent glass window of a vat containing photopolymerizable resin to initiate polymerization of the resin while illumination at a second wavelength may inhibit the polymerization reaction in a layer of adjustable thickness adjacent to the glass window, eliminating adhesion of the solidified layer to the bottom of the vat and enabling continuous operation. The non-adhesion may enable the continuous printing. However, a stepwise printing process is also applicable herein and may benefit from the non-adhesion.
In another aspect, identical irradiation masks may be provided for both wavelengths, i.e., for both the photoinhibition and photopolymerization reactions. Further, the system may require one optics only that forms the image used to illuminate the resin, and the setup may alleviate the problem of lingering inhibition radicals by projecting the structured illumination pattern for the wavelength that causes inhibition to only a confined area corresponding to a cross section or layer of the 3D object being printed.
The wavelengths will depend on the characteristics of the photo-initiator and -inhibitor in the resin, in particular their absorption spectra. Hence, it's a question of matching the characteristics of the resin and the projector system. It is preferable that the emittance spectra of the light sources providing the two wavelengths do not overlap and there may be multiple combinations that work well.
In yet another aspect, a 3D printing system is disclosed. The 3D printing system may comprise a first light source configured to emit a first light beam having a first wavelength, a second light source configured to emit a second light beam having a second wavelength, a dichroic mirror disposed in an optical path of the 3D printing system and configured to superimpose the first and second beams, a digital micromirror device (DMD) configured to spatially structure the superimposed first and second light beams into a spatial pattern as a spatially structured superimposed light beam, and an optical system configured to project the spatially structured superimposed light beam onto a resin disposed in a vat to independently control (by the setting the relative light intensities of the first and second light beams) activation and inhibition of a polymerization process of the resin in first and second volume respectively above a region of the resin defined by the spatial pattern imposed by the DMD. The DMD may be disposed between the dichroic mirror and the optical system.
In another aspect, a method may be disclosed. The method may comprise emitting, by a first light source of a 3D printing system, a first light beam having a first wavelength; emitting, by a second light source, a second light beam having a second wavelength; superimposing, by a dichroic mirror disposed in an optical path of the 3D printing system, the first and second light beams; spatially structuring the superimposed light beams, by a digital micromirror device (DMD) disposed between the dichroic mirror and an optical system, into a spatial pattern as a spatially structured superimposed light beam; and projecting, by the optical system, the spatially structured superimposed light beam onto a resin disposed in a vat to independently control activation and inhibition of a polymerization process of the resin in a first and second volume respectively above a region of the resin defined by the spatial pattern imposed by the DMD.
In yet another aspect, a non-transitory computer readable storage medium may be disclosed. The non-transitory computer readable storage medium may store a program which, when executed by a computer system, causes the computer system to perform a procedure that controls a process executed by the 3D Printing system comprising emitting, by a first light source of a 3D printing system, a first light beam having a first wavelength; emitting, by a second light source, a second light beam having a second wavelength; superimposing, by a dichroic mirror disposed in an optical path of the 3D printing system, the first and second light beams; spatially structuring the superimposed light beams, by a digital micromirror device (DMD) disposed between the dichroic mirror and an optical system, into a spatial pattern as a spatially structured superimposed light beam; and projecting, by the optical system, the spatially structured superimposed light beam onto a resin disposed in a vat to independently control activation and inhibition of a polymerization process of the resin in a first and second volume respectively above a region of the resin defined by the spatial pattern imposed by the DMD.
Further, the wavelengths may be chosen according to the characteristics of the photo-initiator and -inhibitor in the resin, in particular their absorption spectra. In an embodiment, the emittance spectra of the light sources providing the two wavelengths may not overlap or may not overlap significantly and thus a plurality of combinations may be possible. More specifically, not overlapping or not overlapping significantly may mean that, the spectra of the two light sources are well separated or the peak wavelengths with defined tolerances (e.g. tolerances of 3 nm, or 5 nm or 10 nm) are distinct. In an embodiment, a wavelength of about 385 nm (e.g. a peak wavelength of the LED is 385 nm with a tolerance of 3 nm, for example, or 5 nm, or 10 nm″) may be used for the initiation and a wavelength of about 405 nm (e.g. a peak wavelength of the LED is 405 nm with a tolerance of 3 nm, for example, or 5 mm, or 10 nm″) may be used for the inhibition. Further, light sources other than LEDs, such as lamps or lasers may also be used for DLP (digital light processing) projectors. However, light from such sources may be further processed using filters or converters to generate a narrow spectrum around the desired wavelength.
To easily identify the discussion of any particular element or act, the most significant digit or digits in a reference number refer to the figure number in which that element is first introduced.
The illustrative embodiments recognize that a user such as dental practitioner may use a 3D printing system to print an object such as a dental object. The object may be printed with an additive manufacturing process which may include techniques such as fused deposition modelling (FDM), selective laser sintering (SLS), stereolithography (SL) and digital light processing (DLP).
In a DLP 3D printing process, a setup may be constructed comprising two independent light sources radiating at different wavelengths, wherein one light source may be a mask projector providing irradiation masks for a curing reaction and a second light source may provide an unstructured light field causing the inhibition reaction. The illustrative embodiments recognize that, because the second light source may provide an unstructured light field only rather than a mask, an inhibition reaction may occur across the full printing area within a layer of resin at the bottom of a vat and not only in the area where material is solidified by the first light source. This may introduce lingering inhibiting radicals, that may limit the achievable printing speed in a continuous printing process. The illustrative embodiments further recognize that for such a setup, two separate light sources may require two independent optics that may have to be aligned.
The illustrative embodiments disclose, as shown in
In the 3D printing system 100, the first light source 102 may be configured to emit a first light beam 126 having a first wavelength. The second light source 104 may be configured to emit a second light beam 126 having a second wavelength. The 3D printing system 100 may be configured to provide identical irradiation masks for both wavelengths, i.e., for both the photoinhibition and photopolymerization reactions. The 3D printing system 100 may further use only one optics (optical system 112) in the optical path 130 that projects the spatially structured superimposed light beam to an area of a photocurable substance (photosensitive resin) corresponding to a cross section of a 3D object being printed and may thus potentially prevent or reduce lingering inhibition radicals that may slow down printing speed. More specifically, the 3D printing system may comprise only one optical pathway 134 of the optical path 130, said optical pathway being disposed behind the DMD 110 and being dedicated to projecting the spatially structured superimposed light beam to the vat. Thus, a structured image may be projected to the vat for photoinhibition and photopolymerization by one optical system in the pathway 134 as opposed to a plurality of different structured images being projected by a plurality of different corresponding optical systems disposed in different corresponding pathways.
The 3D printing system may thus configure the DMD and the optical system 112 to confine photochemical activation and inhibition reactions of the polymerization process of the photosensitive resin to a region of the photosensitive resin corresponding to a cross section of an object being printed. Though the 3D printing system may have one optical system configured to project the spatially structured superimposed light beam, the 3D printing system may also comprise additional optical elements configured to form the light beams of the two light sources that impinge on the DMD, which optical elements may be placed in between the light sources and the dichroic mirror and/or between the dichroic mirror and the DMD.
The 3D printing system 100 may further comprise the dichroic mirror 106 disposed in an optical path 130 of the 3D printing system 100 and configured to superimpose the first and second beams. The 3D printing system 100 may also comprise the digital micromirror device 110 (DMD) configured to spatially structure the superimposed first and second light beams into a spatial pattern as a spatially structured superimposed light beam 108. An optical system 112 of the 3D printing system 100 may be configured to project the spatially structured superimposed light beam 108 onto the photosensitive resin 116 disposed in a vat 114 to independently control activation and inhibition of the polymerization process of the resin in a region 132 of the resin defined by the spatial pattern imposed by the DMD. The region 132 may be an area that corresponds to a layer or cross section of the object 118 being printed. The area may be illuminated, and a volume solidified may be defined by the area and the thickness of the layer to be printed. In the 3D printing system 100, the DMD may be disposed between the dichroic mirror 106 and the optical system 112. The optical system 112 may be configured to deliver a sharp image with defined size to the bottom of the vat 114. In some embodiments, the optical system 112 may comprise a plurality of lenses configured to tune sharpness and/or size of projected images.
In the 3D printing system 100, the first wavelength of the first light source 102 may be configured to photochemically activate polymerization via a photo-initiator of the photosensitive resin 116 at a first volume extending above said region 132 of the resin defined by a first thickness 204. The second wavelength may be configured to inhibit said polymerization via a photo-inhibitor of the photosensitive resin at second volume extending above said region 132 which volume is defined by a second thickness 202 of the photosensitive resin 116, wherein said second volume is a “dead zone”. The second volume may be located adjacent to the bottom 206 of the vat 114 as shown in
Turning now to
Having described the 3D printing system 100 and process 300, reference will now be made to
In one example embodiment herein, at least some components of the 3D printing system 100 may form or be included in the computer system 400 of
The display interface 408 (or other output interface) may forward text, video graphics, and other data from the communication infrastructure 402 (or from a frame buffer (not shown)) for display-on-display unit 414. For example, the display interface 408 may include a video card with a graphics processing unit or may provide an operator with an interface for controlling the 3D printing apparatus.
The computer system 400 may also include an input unit 410 that may be used, along with the display unit 414 by an operator of the computer system 400 to send information to the computer processor 406. The input unit 410 may include a keyboard and/or touchscreen monitor. In one example, the display unit 414, the input unit 410, and the computer processor 406 may collectively form a user interface.
One or more steps of printing a 3D object, such as a 3D dental object, may be stored on a non-transitory storage device in the form of computer-readable program instructions. To execute a procedure, the computer processor 406 loads the appropriate instructions, as stored on storage device, into memory and then executes the loaded instructions.
The computer system 400 may further comprise a main memory 404, which may be a random-access memory (“RAM”), and also may include a secondary memory 418. The secondary memory 418 may include, for example, a hard disk drive 420 and/or a removable-storage drive 422 (e.g., a floppy disk drive, a magnetic tape drive, an optical disk drive, a flash memory drive, and the like). The removable-storage drive 422 reads from and/or writes to a removable storage unit 426 in a well-known manner. The removable storage unit 426 may be, for example, a floppy disk, a magnetic tape, an optical disk, a flash memory device, and the like, which may be written to and read from by the removable-storage drive 422. The removable storage unit 426 may include a non-transitory computer-readable storage medium storing computer-executable software instructions and/or data.
In further illustrative embodiments, the secondary memory 418 may include other computer-readable media storing computer-executable programs or other instructions to be loaded into the computer system 400. Such devices may include removable storage unit 428 and an interface 424 (e.g., a program cartridge and a cartridge interface); a removable memory chip (e.g., an erasable programmable read-only memory (“EPROM”) or a programmable read-only memory (“PROM”)) and an associated memory socket; and other removable storage units 428 and interfaces 424 that allow software and data to be transferred from the removable storage unit 428 to other parts of the computer system 400.
The computer system 400 may also include a communications interface 412 that enables software and data to be transferred between the computer system 400 and external devices. Such an interface may include a modem, a network interface (e.g., an Ethernet card or an IEEE 802.11 wireless LAN interface), a communications port (e.g., a Universal Serial Bus (“USB”) port or a FireWire® port), a Personal Computer Memory Card International Association (“PCMCIA”) interface, Bluetooth®, and the like. Software and data transferred via the communications interface 412 may be in the form of signals, which may be electronic, electromagnetic, optical or another type of signal that may be capable of being transmitted and/or received by the communications interface 412. Signals may be provided to the communications interface 412 via a communications path 416 (e.g., a channel). The communications path 416 carries signals and may be implemented using wire or cable, fiber optics, a telephone line, a cellular link, a radiofrequency (“RF”) link, or the like. The communications interface 412 may be used to transfer software or data or other information between the computer system 400 and a remote server or cloud-based storage (not shown).
One or more computer programs or computer control logic may be stored in the main memory 404 and/or the secondary memory 418. The computer programs may also be received via the communications interface 412. The computer programs include computer-executable instructions which, when executed by the computer processor 406, cause the computer system 400 to perform the methods as described hereinafter. Accordingly, the computer programs may control the computer system 400 and other components of the 3D printing apparatus.
In another embodiment, the software may be stored in a non-transitory computer-readable storage medium and loaded into the main memory 404 and/or the secondary memory 418 using the removable-storage drive 422, hard disk drive 420, and/or the communications interface 412. Control logic (software), when executed by the computer processor 406, causes the computer system 400, and more generally the 3D Printing system 100, to perform the some or all of the methods described herein.
Lastly, in another example embodiment hardware components such as ASICs, FPGAs, and the like, may be used to carry out the functionality described herein. Implementation of such a hardware arrangement so as to perform the functions described herein will be apparent to persons skilled in the relevant art(s) in view of this description.
