WO2016148343A1

WO2016148343A1 - Printing apparatus for building three-dimensional object

Info

Publication number: WO2016148343A1
Application number: PCT/KR2015/006023
Authority: WO
Inventors: Sangyun Lee; Haiseong JEONG
Original assignee: Lg Electronics Inc.
Priority date: 2015-03-19
Filing date: 2015-06-15
Publication date: 2016-09-22
Also published as: KR20160112496A

Abstract

Provided is a 3D printing apparatus. The 3D printing apparatus includes a build tray on which a building object is layered, a printing module movably disposed above the build tray to discharge source ink having a gel state, and a module support supporting the printing module. The printing module includes a head case, a head unit accommodated in the head case, the head unit including a plurality of nozzles for injecting the ink, a roller assembly of which at least a portion is accommodated in the head case, the roller assembly being disposed directly below the head unit and having an outer circumferential surface to which the ink injected from the head unit adheres, and a photocuring lamp accommodated in the roller assembly to emit UV rays.

Description

PRINTING APPARATUS FOR BUILDING THREE-DIMENSIONAL OBJECT

The present disclosure relates to a printing apparatus for building a three-dimensional (3D) object.

3D printing technologies that have recently started to receive attention have enhanced in degree of freedom with respect to a configuration of a product because a mold required in a typical mass production manner is not necessary at all, and also constraint conditions needed for molding the product in the mold are removed. For example, when a product is produced by using injection molding, in order to extract the product from a mold, the product needs to have no undercut and have a predetermined draft angle. Also, a spatially complicated shape of the product is one of limitations that may not be achieved by the mold.

However, the 3D printing technologies may enable a component, which has a shape that is impossible to be molded in the mass production manner using the mold, to be molded and also mold a component even in an assembled state. Thus, components having various conditions may be built.

Like this, the 3D printing technologies have brought radical change in approach to the shape of the product and production of the product to almost resolve difficulties when manufacturing a mock-up or prototype.

The 3D printing technologies may be classified into a photocuring process, a sintering process, a fused deposition modeling (FDM) manner, a color jetting printing manner, a multi jetting printing or polyjet manner in which the photocuring process is mixed with the color jetting printing manner, and a thin film laminating manner (LOM, PLT, PSL) according to the processes.

Also, sources used for the 3D printing technologies may be classified into a solid phase, a liquid phase, and a powder type according to phases of the sources. In detail, the solid phase source is mainly used for the FDM printing apparatus. Poly lactic acid (PLA), acrylonitrile-butadiene-styrene (ABS) resin, and styrene which are thermo-plastic resins are used as main materials of the solid phase source and are processed in a filament form.

Also, the liquid phase source is a gel type source and mainly used for the photocuring process. The power type source is used for a printing apparatus using a selective laser sintering (SLS) manner that is one of a sintering manner. Here, power type polymer or a metal source sintered by a laser is a main material of the power type source.

In the inkjet type 3D printing apparatus according to the related art, an UV-curable lamp is mounted on each of left and right sides of a printing head. Also, when the printing head moves to the right side, the ink may be cured by UV rays irradiated from the left UV lamp. Also, when the printing head moves to the left side, the ink may be cured by the UV rays irradiated from the right UV lamp.

The inkjet type 3D printing apparatus including the above-described constitutions according to the related art may have limitations as follows.

First, since a curing lamp is mounted on each of left and right sides of the printing head, a moving distance of the printing head has to increase by a width of the curing lamp of the printing head. Thus, the printing apparatus may increase in volume. In detail, to cure ink disposed at the rightmost edge and injected from a nozzle part of the printing head, the left curing lamp has to move up to the ink disposed at the rightmost edge. Thus, the printing head further moves in a right direction up to the position at which the ink disposed at the rightmost edge is cured by the left curing lamp. On the other hand, to cure the ink injected to the leftmost edge, the printing head has to move to the left side so that the right curing lamp moves up to the position at which the leftmost ink is cured.

Second, since the curing lamp is mounted on each of the left and right sides of the printing head, a portion of the UV ray irradiated from the pair of curing lamps may be reflected from a build tray to a nozzle of the printing head to cure the ink attached to the nozzle, thereby interrupting the injection of the ink. Also, if the ink attached to the nozzle is cured to block the nozzle, the recycling of the printing head may be impossible. Thus, since the printing head itself has to be replaced, the maintenance costs may increase.

Third, since the printing head injects ink onto the build tray while moving in a left/right or front/rear direction, a dropping point, i.e., a dropping position of the ink injected from the nozzle onto the build tray may get out of a preset point.

Fourth, since the printing head injects ink onto the build tray while moving in a left/right or front/rear direction, ink particles, which are called ink mist, the ink injected from the nozzle may be scattered to block the nozzle.

The present disclosure has been proposed to improve the above-described limitations.

In one embodiment, a 3D printing apparatus includes: a build tray on which a building object is layered; a printing module movably disposed above the build tray to discharge source ink having a gel state; and a module support supporting the printing module, wherein the printing module includes: a head case; a head unit accommodated in the head case, the head unit including a plurality of nozzles for injecting the ink; a roller assembly of which at least a portion is accommodated in the head case, the roller assembly being disposed directly below the head unit and having an outer circumferential surface to which the ink injected from the head unit adheres; and a photocuring lamp accommodated in the roller assembly to emit UV rays.

The details of one or more embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

The 3D printing apparatus according to the embodiment may have following effects.

First, since the curing lamp is mounted on the lower side of the printing head, the left/right width of the printing head may be reduced to decrease the moving distance of the printing head, thereby reducing the printing time.

Second, since the printing head is reduced in width, and the number of curing lamp is reduced, the product may be miniaturized and reduced in manufacturing cost.

Third, since the phenomenon in which the ink attached to the nozzle of the printing head is cured by the light irradiated from the curing lamp does not occur, the replacement of the printing head due to the blocked nozzle may not occur.

Fourth, since a portion of the roller, onto which the ink injected from the nozzle drops, moves together with the printing head in one body, the phenomenon in which the dropping position of the ink changes may be minimized.

Fifth, since the printing head and the roller move in one body, the phenomenon in which a portion of the ink injected from the nozzle is separated into micro particles and scattered may be minimized. Thus, the phenomenon in which the nozzle is blocked, or the surrounding of the printing apparatus are contaminated may be prevented.

Fig. 1 is a perspective view illustrating a 3D printing apparatus according to an embodiment.

Fig. 2 is a view for explaining an operation principle of the 3D printing apparatus according to an embodiment.

Fig. 3 is a perspective view illustrating a printing module constituting the 3D printing apparatus according to an embodiment.

Fig. 4 is a longitudinal cross-sectional view taken along line IV-IV of Fig. 3.

Fig. 5 is a side view of the printing module from which a head case is removed.

Fig. 6 is a cutaway perspective view taken along line VI-VI of Fig. 3.

Fig. 7 is a cutaway perspective view taken along line VII-VII of Fig. 3.

Fig. 8 is a view illustrating a state in which the printing module moves in a first direction during the printing according to an embodiment.

Fig. 9 is a view illustrating a state in which the printing module moves in a second direction during the printing according to an embodiment.

Figs. 10 to 12 are views successively illustrating a process in which each of components constituting the printing module changes in state when the moving direction of the printing module is switched from the first direction to the second direction according to an embodiment.

Hereinafter, a three-dimensional (3D) printing apparatus according to embodiments will be described in detail with reference to the accompanying drawings.

Fig. 1 is a perspective view illustrating a 3D printing apparatus according to an embodiment, and Fig. 2 is a view for explaining an operation principle of the 3D printing apparatus according to an embodiment.

Referring to Figs. 1 and 2, a 3D printing apparatus 10 according to an embodiment may include a frame 11 defining an outer appearance, a base plate 12 vertically partitioning the frame 11, a build tray 13 moving on the base plate 12 in a front/rear (y-axis) direction of the 3D printing apparatus and on which an object to be three-dimensionally printed (hereinafter, referred to as a building object) is layered, a printing module 30 three-dimensionally forming the building object by injecting ink onto the build tray 13 while moving above the base plate 12 in a left/right (x-axis) direction and vertical (z-axis) direction of the 3D printing apparatus, a plurality of source tanks 26 accommodated in a space defined below the base plate 12, and a control box 16 controlling an overall operation of the 3D printing apparatus 10 including an operation of the printing module 30.

Here, the printing module 30 may be movable in the x-axis and z-axis directions by an x-axis moving guide part 15 and a z-axis moving guide part 14.

A mixing tank 25 for making new colors by mixing ink having various colors, which are supplied from the plurality of source tanks 26, with each other may be disposed outside the printing module 30, for example, on one point of the base plate 12. Also, the source tanks 26 and the mixing tank 25 may be fluidly connected to each other by a tube. Also, the mixing tank 25 and the printing module 30 may be fluidly connected to each other by a tube.

Also, a maintenance unit 24 for blotting the ink attached to an ink supply part disposed on the printing module 30 may be disposed on the other point of the base plate 12. The maintenance unit 24 may operate when reaching a time period at which the nozzle of the head unit 22 has to be cleaned. The maintenance unit 24 cleanly blots an ink residue attached to the nozzle of the ink supply part.

In case of the 3D printing apparatus 10 including the above-described constitutions, the printing module 30 may move in the x-axis direction (the right direction in the drawings) along the x-axis moving guide part 15 and then be disposed above the build tray 23. Also, the printing module 30 injects the ink onto the build tray 23 while moving in ±x-axis and ±z-axis directions according to a design drawing provided from a main computer. The injected ink may be cured to layer the designed 3D building object.

Also, the 3D printing apparatus 10 may be programmed so that the maintenance unit 24 operates to clean the ink attached to the bottom surface of the printing module 30 after a power is applied to the printing apparatus 10 to become in a printing standby state or the printing is completed, or before ink having a specific color is entirely injected, and ink having a different color is replaced.

Hereinafter, a structure and function of the printing module according to an embodiment will be described in detail with reference to the accompanying drawings.

Fig. 3 is a perspective view illustrating a printing module constituting the 3D printing apparatus according to an embodiment, Fig. 4 is a longitudinal cross-sectional view taken along line IV-IV of Fig. 3, Fig. 5 is a side view of the printing module from which a head case is removed, Fig. 6 is a cutaway perspective view taken along line VI-VI of Fig. 3, and Fig. 7 is a cutaway perspective view taken along line VII-VII of Fig. 3.

Referring to Figs. 3 to 7, the printing module 30 according to an embodiment may move in the x-axis direction, i.e., a left/right direction on the drawings along the x-axis moving guide part 15, and the x-axis guide part 15 may move in the z-axis direction, i.e., a vertical direction on the drawings along the z-axis moving guide part 14. Thus, the printing module 30 may reciprocately move in the x-axis and z-axis directions. However, the moving structure of the printing module 30 is not limited to the current embodiment. For example, various mechanisms may be applied to the moving structure of the printing module 30. According to the current embodiment, the printing module 30 may be movable in the x-axis and z-axis directions.

In detail, the printing module 30 may include a head unit 32 through which source ink is injected, a head case 31 in which the head unit 32 is accommodated, a roller assembly 33 disposed under the head unit 32, and a module support 38 that is mounted on the x-axis moving guide part 15 to move along the x-axis moving guide part 15.

In detail, the head unit 32 may be provided as one module in which a plurality of printing heads are arranged in the x-axis direction. Alternatively, the head unit 32 may be provided as a single printing head. Also, a plurality of nozzles are arranged on a bottom surface of the printing head in a longitudinal direction of the printing head so that the ink is injected from the nozzles.

Also, head unit 32 is fixed to the module support 38 by a head fixing part (see reference numeral 320 of Fig. 6). In detail, the head fixing part 320 may have one end connected to a rear surface of the head unit 32 and the other end connected to the module support 38 by passing through the rear surface of the head case 31. Also, a through hole (not shown) through which the head fixing part 320 passes is defined in the rear surface of the head case 31. The through hole may have a long hole shape with an oval shape in the x-axis direction, i.e., in a width direction of the head case. This is done because the head case 31 slightly moves in a +x-axis or ?x-axis direction when the printing module 30 moves in the +x-axis or ?x-axis direction in the state where the head unit 32 is fixed. This will be described in detail with reference to the accompanying drawings.

The roller assembly 33 may include an outer roller 331 disposed on the outermost position and an inner roller 332 disposed inside the outer roller 331.

The printing module 30 may further include a photocuring lamp 333 disposed inside the inner roller 332. Here, since the photocuring lamp 333 is disposed inside the inner roller 332, the roller assembly 33 may include the photocuring lamp 333. Alternatively, the photocuring lamp 333 may be distinguished from the roller assembly 33 and thus be defined as a separate component constituting the printing module 30.

In detail, a central shaft 334 passes through a center of the photocuring lamp 333. The central shaft 334 may be supported by the module support 338.

The outer roller 331 may transfer the ink injected from the nozzle of the head unit 32 to the build tray 13. In detail, the ink injected from the nozzle of the head unit 32 may be spaced apart from an outer circumferential surface of the outer roller 331. A distance between the outer circumferential surface of the outer roller 331 and the nozzle of the head unit 32 is very short, and the head unit 32 and the outer roller 331 may move in one body by the module support 38. Thus, a scattering phenomenon of the ink particles, which occurs in the inkjet type 3D printing apparatus according to the related art, may be minimized, and also a phenomenon in which the dropping position of the ink changes may be minimized.

Also, the outer roller 331 may be formed of a transparent material. UV rays irradiated from the photocuring lamp 333 may cure the ink layered on the build tray 13. Also, when the printing module 30 moves in the x-axis direction, the outer roller 331 may rotate in a state where the outer roller 331 is closely attached to the build tray 13. The ink injected onto the outer circumferential surface of the outer roller 331 may be transferred onto the build tray 13.

The inner roller 332 is disposed inside the outer roller 331. When the outer roller 331 rotates, the inner roller 332 may be maintained in a fixed state. However, when the moving direction of the printing module 30 is switched, the inner roller may rotate only by a predetermined angle. Also, the inner roller 332 is formed of an opaque material. Thus, light irradiated from the photocuring lamp 333 may not be irradiated toward the head unit 32. If when the UV rays irradiated from the photocuring lamp 333 is irradiated toward nozzle, the ink injected from the nozzle may be cured, and thus, the head unit has to be replaced.

However, a photo-irradiation hole 332a may be defined in one side of the inner roller 332. The light irradiated from the photocuring lamp 333 may be transmitted to the build tray 13 through only the photo-irradiation hole 332a. Here, the photo-irradiation hole 332a may be formed by cutting a portion of the inner roller 332 in a longitudinal direction of the inner roller 332. As described above, each of the inner roller 332 and the outer roller 331 may have a cylindrical shape having an empty inside with a predetermined thickness and diameter.

The photocuring lamp 333 may be disposed inside the inner roller 332 and have a cylindrical shape having an outer diameter less than that of the inner roller 332. Also, a photo-irradiation part 333a may be disposed on one side of the photocuring lamp 333. Thus, the UV rays may be emitted through the photo-irradiation part 333a. Also, the photo-irradiation part 333a and the photo-irradiation hole 332a of the inner roller 332 may be disposed on the same line. Thus, light emitted from the photo-irradiation part 333a may pass through the photo-irradiation hole 332a and then be irradiated onto a top surface of the build tray 13.

Also, each of the photocuring lamp 333 and the inner roller 332 may rotate at a predetermined angle by the rotation of the central shaft 334 at a predetermined angle. Also, each of the photo-irradiation part 333a and the photo-irradiation hole 332a may be disposed at a position that is spaced a predetermined distance from a tangent at which the outer roller 331 and the build tray 13 contact each other in a left circumferential direction or right circumferential direction of the outer roller 331. Here, the left circumferential direction may represent that the each of the photo-irradiation part 333a and the photo-irradiation hole 332a is disposed at a position that is spaced a predetermined angle from a contact point between the outer roller 331 and the build tray 13 in a clockwise direction or counterclockwise direction.

As illustrated in Fig. 5, the central shaft 334 may rotate forward or backward at a predetermined angle with respect to a vertical line by a rotation member 35 that is disposed in the module support 38.

In detail, rotation member 35 may be mounted inside the module support 38. The rotation member 35 may include a driving motor 351 for generating a rotation force, a driving gear 352 connected to a rotation shaft of the driving motor 351, and a rotation gear 353 gear-coupled to the driving gear 352.

Also, the rotation gear 353 may be fitted into a protrusion that extends from an end of the central shaft 334 to rotate in one body with the central shaft 334. Thus, when the driving motor 351 rotates forward or backward, the rotation gear 353 may finally rotate forward or backward. Also, the rotation direction and amount of the rotation gear 353 may be determined according to those of the driving gear 352. Finally, the rotation direction and amount of the photocuring lamp 333 may be determined.

Also, the inner roller 332 and the photocuring lamp 333 move in one body. Thus, the photocuring lamp 333 and the inner roller 332 may rotate forward or backward at a set angle in one body. As a result, the photo-irradiation part 333a and the photo-irradiation hole 332a may rotate forward or backward in a state where the photo-irradiation part 333a and the photo-irradiation hole 332a match each other.

Here, the rotation member 35 that is a unit for rotating the central shaft 334 is mounted in the module support 38. Although the rotation member 35 is connected to the central shaft 334 in an embodiment, the idea of the present disclosure is not limited thereto.

Also, as illustrated in Fig. 6, one or plurality of elastic members 36 may be provided in the head case 31.

In detail, the elastic member 36 may be provided in a pair on front and rear sides of the head unit 32 or provided on only one of the front and rear sides of the head unit 32.

Also, a hook protrusion 322 may protrude from each of front and rear surfaces of the head unit 32, and a hook protrusion 311 may protrude from an inner circumferential surface of a sidewall constituting the head case 31. The hook protrusion 311 may protrude from a position that is close to each of front and rear ends of the sidewall of the head case 31.

Also, the elastic member 36 may have one end connected to the hook protrusion 311 of the head case 31 and the other end connected to the hook protrusion 322 of the head unit 32.

As illustrated in Figs. 4 and 7, the printing module 30 may further include a push member 34 extending in an “n” shape along a front surface, the outer circumferential surface of the cylindrical part, and a rear surface of the photocuring lamp 333.

In detail, the push member 34 may include a pair of push bodies 341 respectively disposed on the front and rear surfaces of the photocuring lamp 333 and a push lever 342 extending from an outer circumferential surface of each of the pair of push bodies 341 by a predetermined length. The push lever 342 may be provided as a pair of lever shape that respectively extends from the pair of push bodies 341 in a straight-line bar shape.

For another example, the straight-line bar extending along the outer circumferential surface of the cylindrical part of the photocuring lamp 333 may be connected to an end of each of the pair of push bodies 341 to form the push lever 342 having an “n” shape. Thus, a portion of the straight-line bar extending along the outer circumferential surface of the cylindrical part of the photocuring lamp 333 may be closely attached to the sidewall of the head case 31. Also, when the push member 34 rotates, the head case 31 may be pressed by the push member 34 to move in a left or right direction.

For another example, the push member 34 may include a push body 341 disposed on only one surface of the front and rear surfaces of the photocuring lamp 333 and a single push lever 342 extending from the push body 341 in a radius direction of the roller assembly 33.

Also, a central shaft accommodation hole 343 is defined in a center of the push body 341. As illustrated in the drawings, the central shaft accommodation shaft 343 may have an oval shape or a stadium track shape. The push body 341 may be maintained in a stopped state until the central shaft 334 rotates at a predetermined angle. When the central shaft 334 rotates at a predetermined angle, the push body 341 and the central shaft rotate in one body. An operation mechanism of the push member 34 according to the rotation amount of the rotation shaft 334 will be described below in detail with reference to the accompanying drawings.

Fig. 8 is a view illustrating a state in which the printing module moves in the first direction during the printing according to an embodiment.

Referring to Fig. 8, the printing module 30 may perform a printing process while moving in the first direction that is expressed by an arrow. The photo-irradiation part 333a of the photocuring lamp 333 and the photo-irradiation hole of the inner roller 332 may be directed in a second direction opposite to the first direction.

Here, the first direction may be defined as a +x-axis direction or right direction, and the second direction may be defined as a ?x-axis direction or left direction.

In detail, when the printing module 30 performs the printing process while moving in the first direction, a line passing through centers of the photo-irradiation part 333a and the photo-irradiation hole 332a from a center of the central shaft 334 may be disposed at a position that rotates at a predetermined angle from a vertical line passing through the central shaft 334 in a clockwise direction.

Alternatively, the photo-irradiation part 333a and the photo-irradiation hole 332a may be disposed at a rear side with respect to the moving direction of the printing module 30 from the contact point Q1 at which the outer roller 331 and the build tray 13 contact each other.

In this state, when the printing module 30 moves, the outer roller 331 may also rotate in the state where the outer roller 331 contacts the build tray 13. Thus, the ink injected onto the outer roller 331 may be transferred first to the build tray 13, and then, the photo-irradiation part 333a may cure the ink while pass over the ink.

In more detail, the ink injected onto the outer circumferential surface of the transparent outer roller 331 may be transferred to the build tray 13 before reaches the photo-irradiation hole 332a. Also, the inner roller 332 is formed of an opaque material, a phenomenon in which the ink injected onto the outer circumferential surface of the outer roller 331 is cured by the photocuring lamp 333 before being transferred to the build tray 13 may be prevented.

When the printing module 30 performs the printing process while moving in the first direction, the right outer circumferential surface of the cylindrical part of the outer roller 331 may be spaced a predetermined distance from a lower end of the sidewall of the head case 31 to form a gap g. On the other hand, the left outer circumferential surface of the cylindrical part of the outer roller 331 may be maintained in a state where the outer circumferential surface is closely attached to the lower end of the sidewall of the head case 31. Thus, as the outer roller 331 rotates, the ink attached to the outer circumferential surface of the outer roller 331 may be scraped and separated by the lower end of the sidewall of the head case 31. Also, after the outer circumferential surface of the head case 31 is scraped and cleaned by the lower end of the sidewall of the head case 31, the ink may drop from the head unit 32 to adhere.

Also, as the head case 31 moves in the moving direction of the printing module 30, the gap g may be defined in the right side of the cylindrical part of the outer roller 331, and the left outer circumferential surface may be closely attached to the lower end of the sidewall of the head case 31. This is done because of the elastic force of the elastic member 36. The head unit 32 and the roller assembly 33 move in one body, and the head case 31 may move in the left or right direction by the elastic force of the elastic member 36. Thus, when the lever member 34 rotates to push the sidewall of the head case, the elastic member 36 may be extended. When the lever member 34 returns to its original position, the head case 31 may also return to its original position by the restoring force of the elastic member 36. In the current embodiment, when the printing module 30 performs the printing process while moving in the first direction, the elastic member 36 may be in a default state in which an external force is not applied.

Referring to Fig. 9, when the printing module performs the printing process while moving the second direction opposite to the first direction, the rotation shaft 334 rotates in a counterclockwise direction, and thus, the photo-irradiation part 333a and the photo-irradiation hole 332a may be disposed symmetrical to the state of Fig. 8.

In detail, when the printing module 30 moves in the second direction, the printing module 30 may have a symmetrical shape with respect to the vertical surface in comparison that the printing module 30 moves in the first direction. In detail, when the central shaft 334 rotates in the counterclockwise direction, and thus, the push member 34 rotates in the counterclockwise direction.

As a result, the push lever 342 constituting the push member 34 may push the sidewall of the head case 31, and the elastic member 36 may be extended. That is, in the state where an end of the elastic member 36 connected to the head unit 32 is fixed, the elastic member 36 may be extended while an end of the elastic member 36 connected to the head unit 31 moves in the second direction.

As a result, in the drawings, the gap g may be formed between the left outer circumferential surface of the cylindrical part of the outer roller 331 and the lower end of the sidewall of the head case 31, and the right outer circumferential surface of the outer roller 331 may be closely attached to the lower end of the sidewall of the head case 31.

Also, as the central shaft 334 rotates in the counterclockwise direction, the photo-irradiation part 333a and the photo-irradiation hole 332a may be disposed at a rear side of a contact point Q2 between the outer roller 331 and the build tray 13 with respect to the moving direction (the second direction) of the printing module 30. Thus, the ink injected onto the outer roller 331 may be transferred to the build tray 13, and then, be cured by the UV rays irradiated through the photo-irradiation hole 332a.

When comparing Figs. 8 and 9 to each other, when the moving direction of the printing module 30 is switched, it is seen that the rotation amount of photo-irradiation part 333a and photo-irradiation hole 332a is greater than that of the push lever 342. Hereinafter, an occurrence of a difference between the rotation amount of push lever 342 and the rotation amount of inner roller 332 and photocuring lamp 333 will be described with in more detail with reference to the accompanying drawings.

Referring to Fig. 10, Fig. 10 illustrates a state the printing module 30 performs the printing process while moving in the first direction (the right direction). In this state, in order that the printing module 30 moves in the second direction opposite to the first direction, the processes illustrated in Figs. 11 and 12 have to be performed.

A non-explained reference symbol C represents a concentric circle having a rotation trace of the central shaft 334.

Referring to Fig. 11, the central shaft 334 rotates at a set angle θ1 in a counterclockwise direction. Here, the central shaft accommodation hole 343 defined in the center of the push body 341 has an oval shape or track shape. Also, when the central shaft 334 rotates while being maintained in the state where the central shaft 334 contacts a curved part 343a of the central shaft accommodation hole 343, only the photocuring lamp 333 and the inner roller 332 may rotate in one body, and the push member 34 may be maintained in the stopped state. In more detail, since the curved part 343a has the same curvature as that of the concentric circle having the rotation trace of the central shaft 334, when the central shaft 334 rotates along the curved part 343a, the push member 34 may not rotate, but be maintained in the stopped state.

Also, when the central shaft 334 rotates (L1→L2) at a set angle θ1 in the state of Fig. 10, the central shaft 334 may be disposed on a position at which the curved part 343a is ended. Also, when the central shaft 334 rotates at the set angle θ1, the photocuring lamp 333 and the inner roller 332 may also rotate (R1→R2) at the set angle θ1. Thus, the photo-irradiation part 333a and the photo-irradiation hole 332a may move from the left side to a right side with respect to the vertical line passing through the central shaft.

Referring to Fig. 12, when the central shaft 334 further rotates (L2→L3) at a set angle θ2 (θ2〈θ1) in the counterclockwise direction in the state of Fig. 11, the photocuring lamp 333, the inner roller 332, and the push member 34 may further rotate (R2→R3, K1→K2, P1→P2) at the set angle θ2 in one body.

In detail, when the push lever 342 rotates (P1→P2) at the set angle θ2, the sidewall of the head case 31 may be pressed by the push lever 342 to move by a predetermined distance d in the first direction. Thus, the right outer circumferential surface of the cylindrical part of the outer roller 331 may be closely attached to the lower end of the sidewall of the head case 31, and the left outer circumferential surface of the cylindrical part of the outer roller 331 may be spaced a predetermined distance from the lower end of the sidewall of the head case 31 to form a gap g.

In the state of Fig. 12, the printing module 30 may be movable in the second direction.

A waste ink collection device (not shown) may be disposed at a portion at which the lower end the sidewall of the head case 31 and the outer roller 331 contact each other. Thus, ink fragments separated from the outer circumferential surface of the outer roller 331 by being scraped by the lower end of the sidewall of the head case 31 may be collected into a separate collection box without dropping into the build tray 13.

For example, a suction unit including a suction pump and a suction nozzle may be used as the waste ink collection device. Here, the suction nozzle may be movably provided. That is, when the printing module 30 performs the printing process while moving in the first direction, the suction nozzle may be disposed at a portion at which the outer roller 331 and the sidewall of the head case 31 contact each other, i.e., at a left side of the cylindrical part of the outer roller 331.

On the other hand, when the printing module 30 moves in the second direction, the suction nozzle may move in an opposite direction and then be disposed at a right side of the cylindrical part of the outer roller 331.

Also, surface roughness, i.e., roughness of the completed 3D building object may be determined according to a reciprocating speed of the printing module 30 and the intensity of UV ray irradiated from the photocuring lamp 333.

Also, a curing time of the ink may be determined according to the viscosity of the source ink and the intensity of the UV rays. The viscosity of the ink injected from the head unit 32 may be adjusted through an on/off control of a heater (not shown) provided in the head unit (32).

Also, when the ink is injected once onto the head unit 32, a thickness of an ink layer adhering on the outer circumferential surface of the outer roller 331 may be achieved by adjusting the viscosity of the ink. Also, when a thickness of the ink layer that is formed by injecting ink once is thicker, the printing time may be reduced. For example, when the thickness of the ink layer that is formed by injecting the ink once is set to be thick, the intensity of UV rays increases, and the reciprocating speed of the printing module 30 increases, the printing time may be reduced. On the other hand, the surface of the completed result may be rougher. Thus, the reciprocating speed of the printing module 30 may be adjusted to adjust the surface roughness of the printed result.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this disclosure. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawings and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

Claims

A 3D printing apparatus comprising:

a build tray on which a building object is layered;

a printing module movably disposed above the build tray to discharge source ink having a gel state; and

a module support supporting the printing module,

wherein the printing module comprises:

a head case;

a head unit accommodated in the head case, the head unit comprising a plurality of nozzles for injecting the ink;

a roller assembly of which at least a portion is accommodated in the head case, the roller assembly being disposed directly below the head unit and having an outer circumferential surface to which the ink injected from the head unit adheres; and

a photocuring lamp accommodated in the roller assembly to emit UV rays.
The 3D printing apparatus according to claim 1, wherein the roller assembly comprises:

a cylindrical outer roller having an outer circumferential surface to which the ink injected from the head unit adheres; and

an inner roller accommodated in the outer roller, the inner roller having a photo-irradiation hole in one side thereof,

wherein the outer roller rotates in a state where the outer roller contacts the build tray to transfer the ink adhering to the outer circumferential surface to the build tray.
The 3D printing apparatus according to claim 2, wherein the photocuring lamp is accommodated in the inner roller and comprises a photo-irradiation part on one side thereof.
The 3D printing apparatus according to claim 3, wherein the outer roller is transparent, and the inner roller is opaque.
The 3D printing apparatus according to claim 4, wherein the photo-irradiation part is aligned with the photo-irradiation hole in the same line so that the UV rays emitted from the photo-irradiation part passes through the photo-irradiation hole, and the UV rays passing through the photo-irradiation hole is irradiated onto the build tray via the outer roller.
The 3D printing apparatus according to claim 3, further comprising:

a central shaft passing through a center of the photocuring lamp;

a push member disposed outside the roller assembly and connected to the central shaft to rotate at a predetermined angle together with the central shaft, thereby pressing a sidewall of the head case; and

an elastic member connecting the head unit to the head case.
The 3D printing apparatus according to claim 6, further comprising a head fixing part fixing the head unit to the module support,

wherein the central shaft is connected to the module support.
The 3D printing apparatus according to claim 7, wherein the head fixing part has one end connected to a rear surface of the head unit and the other end connected to the module support by passing through the head case.
The 3D printing apparatus according to claim 7, further comprising a rotation member disposed in the module support and connected to the central shaft to rotate the central shaft forward or backward.
The 3D printing apparatus according to claim 9, wherein the rotation member comprises:

a driving motor;

a driving gear connected to a rotation shaft of the driving motor; and

a rotation gear connected to a rear end of the central shaft and engaged with the driving gear.
The 3D printing apparatus according to claim 6, wherein the push member comprises:

a pair of push bodies disposed on at least one surface of front and rear surfaces of the roller assembly and each of which has a central shaft accommodation hole into which the central shaft is inserted; and

a push lever extending from an outer circumferential surface of each of the push bodies to contact the sidewall of the head case.
The 3D printing apparatus according to claim 11, wherein the central shaft accommodation hole has an oval or track shape constituted by a curved part and a straight-line part, and

the curved part has the same curvature as that of a rotation trace of the central shaft.
The 3D printing apparatus according to claim 12, wherein, when an outer circumferential surface of the central shaft rotates at a set angle (θ1) up to an end of the curved part in a state where the outer circumferential surface contacts the curved part so as to switch a moving direction of the printing module, only the inner roller and the photocuring lamp rotate together with the central shaft in one body.
The 3D printing apparatus according to claim 13, wherein, when the outer circumferential surface of the central shaft further rotates at a set angle (θ2) in the state where the outer circumferential surface rotates up to the end of the curved part, the inner roller, and the photocuring lamp, and the push member rotate together with the rotation shaft in one body.
The 3D printing apparatus according to claim 14, wherein, when the push member rotates at the set angle (θ2), the head case horizontally moves by a set distance (d), and

one of lower ends of left and right walls of the head case is separated from the outer roller, and the other one contacts the outer roller.
The 3D printing apparatus according to claim 14, wherein, when the push member rotates at the set angle (θ2), the elastic member extends by the set distance (d).
The 3D printing apparatus according to claim 5, wherein each of the photo-irradiation part and the photo-irradiation hole is spaced a predetermined angle from a contact point, at which the build tray and the outer roller contact each other, in a circumferential direction of the outer roller.
The 3D printing apparatus according to claim 17, wherein the photo-irradiation part and the photo-irradiation hole are disposed at a rear side of the contact point with respect to a moving direction of the printing module.
The 3D printing apparatus according to claim 1, further comprising:

an x-axis moving guide part on which the module support is slidably mounted, the x-axis moving guide part guiding the module support so that the module support moves in an x-axis direction during the printing; and

a z-axis moving guide part on which the x-axis moving guide part slidably mounted, the z-axis moving guide part guiding the x-axis moving guide part so that the x-axis moving guide part moves in a z-axis direction that is perpendicular to the x-axis direction.
The 3D printing apparatus according to claim 19, wherein the build tray slidably moves in a y-axis direction that is perpendicular to the x-axis and z-axis directions during the printing.