Patent Publication Number: US-2023141628-A1

Title: Large area deposition type additive manufacturing equipment

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application claims the benefit of Taiwanese Patent Application No. 110141743 filed on Nov. 10, 2021, the contents of which are incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a technical field of additive manufacture, and more particularly to an additive manufacturing equipment configured to deposit raw material in a large area and reduce drag force between the product and the raw material tank. 
     Description of the Related Art 
     Additive manufacturing process, also named as three-dimensional printing, can be applied to various objects having a complicated shape and not easily manufactured by traditional processing technique. The additive manufacturing technology has many kinds of process, such as the fused deposition modeling, the photopolymerization, the powder bed fusion, the binder jetting, the material jetting, the laminated object manufacturing, and the direct energy deposition, wherein the photopolymerization has become an important process. Different from the additive manufacturing process using metal material, the photopolymerization has applications for the market of the products more used in our daily life, which includes the fields in health caring, automobile industry, aerospace &amp; national defense field, architecture and education. The photopolymerization plays an important role in the development of the additive manufacturing technology. 
     The photopolymerization process can be performed by a top-down type system or a bottom-up type system. The top-down type system has a light source located above a raw material tank (vat), and light from the light source travels downwards into the raw material for curing one layer of liquid photocurable material on a carrying platform, and the carrying platform moves downwards for curing the next layer of the liquid photocurable material. The bottom-up type system has the light source located under the raw material tank, and light from the light source travels upwards to pass through and enter a bottom of the raw material tank. The liquid photocurable material in the raw material tank is cured for one layer on the carrying platform by the light, and afterwards the carrying platform moves upwards, thereby curing the next layer of the liquid photocurable material thereon. 
     As for the conventional bottom-up type system of photopolymerization process, because the deposition region is close to the bottom of the raw material tank, the cured material is adhered to the bottom of the tank. The cured material must be separated from the bottom of the tank and liquid photocurable material flows to fill the region previously occupied by the cured material before the formation of the next layer of the photocurable material. For this purpose, the carrying platform have to move up and then down to a position spaced from the bottom of the raw material tank by a distance corresponding to one layer of the photocurable material to be cured. Therefore, such a conventional photopolymerization process using the bottom-up type system has a low production rate and small production capability. 
     Moreover, as the conventional photopolymerization process uses UV light sources, such as light emitting diode of UV light, the cost of the equipment is increased. The UV light sources may also reduce the service life of a liquid crystal panel serving as a photomask. Another conventional photopolymerization equipment uses a lens array for converging light from the light source. However, the lens array has a higher cost and occupies a considerable space. The most important problem of conventional photopolymerization equipment mentioned above is the non-uniform light intensity, which usually occurs at the boundary or interactions of the lens array. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a large area deposition type additive manufacturing equipment which solves the problems of low production rate and insufficient production capability, and also solves the problem of high cost, low service life and non-uniform light intensity for the light source. 
     The invention provides a large area deposition type additive manufacturing equipment. The large area deposition type additive manufacturing equipment in accordance with an exemplary embodiment of the invention includes a light source module, a dynamic photomask module, a raw material tank and a deposition module. The light source module includes a plurality of light emitting members arranged in an array; a light diffusion member including a plurality of first micro-structure configured to diffuse light; a light enhancement member including a plurality of second micro-structure configured to converge the light; and a light emitting angle limiter including a plurality of third micro-structure configured to limit a light emitting angle of the light. The dynamic photomask module is disposed above the light source module and generates a plurality of photomasks over time. The raw material tank includes a peripheral wall, a bottom wall and a transparent member, wherein the peripheral wall is connected to the bottom wall, and the transparent member is disposed on the bottom wall, and a liquid photocurable raw material is stored in the raw material tank. The deposition module includes a carrying platform and a driving member driving the carrying platform along a first direction to approach or move away from the bottom wall, wherein the carrying platform has a deposition surface facing the bottom wall. The light emitting members emit light to pass through the light diffusion member, the light enhancement member and the light emitting angle limiter to form a curing light having an collimated emitting angle, the curing light travels through the transparent member and reaches the liquid photocurable raw material, the liquid photocurable raw material is cured and deposited to the carrying platform layer by layer, and the light emitting angle ranges less than +30° with respect to a normal line of an incident plane of the light emitting angle limiter. 
     In another exemplary embodiment, the first micro-structure is granular, the second micro-structure is prism-shaped, and the third micro-structure is louver-shaped. 
     In yet another exemplary embodiment, the peripheral wall is detachably connected to the bottom wall, the bottom wall has a first opening to which the transparent member is disposed, and the dynamic photomask module corresponds the first opening. 
     In another exemplary embodiment, the dynamic photomask module is surrounded by the peripheral wall and disposed near the first opening, and the curing light passes through the transparent member and the dynamic photomask module sequentially. 
     In yet another exemplary embodiment, the carrying platform has a plurality of through holes through which the liquid photocurable raw material flows. 
     In another exemplary embodiment, the deposition module further includes an ultrasonic oscillator disposed on a surface of the carrying platform opposite to the deposition surface. 
     In yet another exemplary embodiment, the deposition module further includes a weight sensor disposed at the connection of the driving device and the carrying platform, and the weight sensor is configured to detect a load of the carrying platform. 
     In another exemplary embodiment, the driving device includes a bracket, a rail and a driving member, the carrying platform is disposed on the bracket, the driving member drives the bracket to move on the rail along the first direction. 
     In yet another exemplary embodiment, the large area deposition type additive manufacturing equipment further includes a control module configured to control a speed of the carrying platform according to the detection of the weight sensor. 
     In another exemplary embodiment, the light emitted from the light emitting members is visible light, and the liquid photocurable raw material is cured by visible light. 
     The large area deposition type additive manufacturing equipment of the present invention is provided with the carrying platform of large area, the large bracket, the large rail and the driving member of large power, whereby the additive manufacturing equipment of bottom-up type is able to form a plurality of products on the carrying platform in one process. The ultrasonic oscillators vibrate the product, thereby separating the product from the bottom of the raw material tank. The weight sensor detects a load of the carrying platform to regulate the speed of the carrying platform so as to reduce the drag force generated between the product and the raw material tank, thereby preventing the product separated from the carrying platform. In the present invention, the carrying platform does not need to move up and down for separation of the product from the raw material tank before the formation of the next layer as what is performed in the conventional additive manufacturing equipment. Therefore, the production rate is increased to obtain a sufficient production ability. 
     Moreover, the large area deposition type additive manufacturing equipment of the present invention is also provided with light sources of visible light, and the liquid photocurable material is cured by the visible light. As the UV light is replaced by the visible light, the cost of the equipment is reduced, and the problem of reduction in service life of the equipment caused by UV light is also solved. In addition, as the light source module of the present invention includes the light diffusion member, the light enhancement member and the light emitting angle limiter, uniform light intensity and a small light emitting angle are obtained, thereby obtaining products of uniform quality. 
     A detailed description is given in the following embodiments with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG.  1    is a perspective view of an embodiment of a large area deposition type additive manufacturing equipment of the present invention; 
         FIG.  2    is a side view of the large area deposition type additive manufacturing equipment of  FIG.  1    and an enlarged view of a light source module; 
         FIG.  3    is an exploded view of the large area deposition type additive manufacturing equipment of  FIG.  1   ; 
         FIG.  4    is an exploded view of another embodiment of a raw material tank of the large area deposition type additive manufacturing equipment of the present invention; 
         FIG.  5    is a block diagram of the large area deposition type additive manufacturing equipment of  FIG.  1   ; and 
         FIG.  6    depicts light emitting angle distribution of the light source module of the large area deposition type additive manufacturing equipment of  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. 
     Referring to  FIGS.  1 ,  2  and  3   , an embodiment of a large area deposition type additive manufacturing equipment is disclosed. The large area deposition type additive manufacturing equipment of the present invention is a bottom-up type system and includes a light source module  10 , a dynamic photomask module  20 , a raw material tank  30  and a deposition module  40 . Liquid photocurable material is stored in the raw material tank  30 . The deposition module  40  moves downwards into the raw material tank  30 . The light source module  10  is disposed under the raw material tank  30  and configured to emit light. The light passes through the dynamic photomask module  20  and reaches the liquid photocurable material in the raw material tank  30 . A layer of liquid photocurable material is cured by the light in a specific position and attached to the deposition module  40 . Afterwards, the deposition module  40  move upwards, and the liquid photocurable material flows back to fill a space originally occupied by the layer of cured product. The light source module  10  emits light again to cure the liquid photocurable material at the same position so as to form the next layer of the product. 
     The light source module  10  includes a plurality of light emitting members  11 , a light diffusion member  12 , a light enhancement member  13  and a light emitting angle limiter  14 . The light emitting members  11  are arranged in an array. The light diffusion member  12  includes a plurality of first micro-structures configured to diffuse light. The light enhancement member  13  includes a plurality of second micro-structures configured to converge light. The light emitting angle limiter  14  includes a plurality of third micro-structures configured to limit a light emitting angle at which the light emits from the light source module  10 . The light passes through the light diffusion member  12 , the light enhancement member  13  and the light emitting angle limiter  14  sequentially to become a curing light having a light emitting angle. The curing light passes through a transparent member  33  disposed on a bottom of the raw material tank  30  and the dynamic photomask module  20  to reach the liquid photocurable material in the raw material tank  30 . The liquid photocurable material is cured by the light and deposited on a carrying platform  41  of the deposition module  40 . 
     The light emitting member  11  of the present embodiment is a light emitting diode. A plurality of light emitting diodes are disposed on a circuit board and arranged in an array. The light emitting diodes of the present embodiment are arranged in an array of 6×9, and current-limiting resistances are connected to the light emitting diodes to promote uniformity of illuminance. The light emitting diodes of the present embodiment emit a light having wavelength of 460 nm to 470 nm, visible blue light. As no UV light source is used, the cost of equipment is reduced, and the service life of light emitting diodes and the members constituting the optical path of the light, such as the dynamic photomask module  20 , is increased. The persons operating the equipment are also protected to prevent injury caused by the UV light possibly happened in the conventional equipment. Moreover, the light emitting members  11  are divided into multiple groups, and each group is disposed in a control region. A control module  50  described in the following paragraphs controls the light emitting members  11  to emit light in certain specific control regions or in all control regions. The light emitting members  11  corresponding to the part of the liquid photocurable material not intended to be cured are controlled to give off no light. In this way, the service life of the light emitting members  11  is increased, and undesired material curing or residues generation caused by increased sensitivity of the liquid photocurable material after a long-term operation of the equipment is thus prevented. 
     The light diffusion member  12  exemplarily has a substrate of polyethylene terephthalate (PET). Irregularly-shaped particles or grains are filled into the substrate to constitute the first micro-structure. Light is diffused by the particles or grains when light enters the substrate, whereby the light from the point lint sources, the light emitting diodes, is diffused by the light diffusion member  12  to become light as emitted from a planar light source. 
     The light enhancement member  13  has a plurality of second micro-structures of prism shape. The light diffused by the light diffusing member  12  enters the light enhancement member  13 . The diffused light is refracted by the second micro-structures and thus converged, whereby the light intensity in the front direction (facing the raw material tank  30  is increased. 
     The light emitting angle limiter  14  has a plurality of third micro-structures of microlouver-shape. The third micro-structures have black color (colored by black dye), which absorbs light. The part of the converged light leaks in large angle is blocked and absorbed by the third micro-structures when the large angle leakage light enters the light emitting angle limiter  14 . The light emitting angle limiter  14  of the present embodiment limits the light emitting from the light source module  10  at an angle ranging within ±30° with respect to a central line (the normal line of an incident plane of the light emitting angle limiter  14 ). Although total light quantity is reduced by the light emitting angle limiter  14  due to the absorption, the disorderly traveling light having a large emitting angle is eliminated, which may cause the liquid photocurable material cured in undesired positions, which become defects of a product. 
     The dynamic photomask module  20  is disposed above the light source module  10  and generates a plurality of photomask patterns. The dynamic photomask module  20  of the present embodiment is a liquid crystal panel which maintains a high resolution (for example 7680×4320) for a large area deposition. The photomask patterns correspond to the desired curing position of each layer. The liquid crystal molecules allow the light to pass or not, whereby the light cures the liquid photocurable material in the desired positions. 
     The raw material tank  30  includes a peripheral wall  31 , a bottom wall  32  and a transparent member  33 . The peripheral wall  31  is detachably connected to the bottom wall  32 , and the transparent member  33  is mounted to the bottom wall  32 . The liquid photocurable material is stored in the raw material tank  30 . The bottom wall  32  is a part of a base which has a length and a width greater than that of the peripheral wall  31 . The peripheral wall  31  has a height 15 to 25 times as large as a thickness of the carrying platform  41 . The height of the peripheral wall  31  is also greater than that of the conventional raw material tank to avoid the liquid photocurable material sprinkling out of the raw material tank  30 . 
     The bottom wall  32  has a first opening  321  on which the transparent member  33  is disposed. The dynamic photomask module  20  corresponds to the first opening  321 . The transparent member  33  of the present embodiment is a transparent glass plate. Light from the light source module  10  can pass through the transparent member  33  and enter the raw material tank  30 . The raw material tank  30  further includes a quick-detach plate  34  engaging the first opening  321 . The quick-detach plate  34  has a second opening  341  on which the transparent member  33  is mounted. The dynamic photomask module  20  is disposed above the light source module  10  and also mounted to the second opening  341 . The dynamic photomask module  20  is disposed in the raw material tank  30  and surrounded by the peripheral wall  31 . Light from the light source module  10  passes through the transparent member  33  and the dynamic photomask module  20  sequentially. As the dynamic photomask module  20  is mounted to the quick-detach plate  34 , and the quick-detach plate  34  is mounted to the first opening  321  of the bottom wall  32 . As shown in  FIG.  4   , the dynamic photomask module  20  can replace liquid crystal panels of different sizes based on requirements, or consist of multiple small liquid crystal panels combined to provide a complete photomask pattern. The quick-detach plate  34  of different sizes can also be used for adapting to the dynamic photomask module  20  of different sizes. 
     The deposition module  40  includes a carrying platform  41  and a driving device  42 . The driving member  42  drives the carrying platform  41  to move along a first direction to approach or depart from the bottom wall  32 . The carrying platform  41  has a deposition surface  411  opposite to the bottom wall  32 . The driving device  42  includes a bracket  421 , a rail  422  and a driving member  423 . The rail  422  is disposed on the bottom wall  32  and located outside the peripheral wall  31 . The rail  422  extends along the first direction Z. The carrying platform  41  is disposed on the bracket  421  movably disposed on the rail  422 . The driving member  423  drives the bracket  421  to move forwards and backwards on the rail  422  along the first direction Z. The driving member  423  includes exemplarily a servo motor and a screw rod on which the bracket  421  is screwed. The bracket  421  is moved along the first direction Z through the rotation of the screw rod. 
     The carrying platform  41  has a larger size, such as a length larger than 32 inches. Therefore, multiple identical or different products can be deposited on the carrying platform  41  in one additive manufacturing process. The carrying platform  41  has a plurality of through holes  412  allowing the liquid photocurable material to flow through and fill the space originally occupied by the cured material, thereby completely covering the cured layer of the product and waiting for formation of the next layer. 
     The deposition module  40  further includes a plurality of ultrasonic oscillators  43  disposed on a surface of the carrying platform  41  opposite to the deposition surface  411 . The ultrasonic oscillators  43  are arranged in an array. When one layer of the liquid photocurable material is cured between the carrying platform  41  and the bottom of the raw material tank  30  (the dynamic photomask module  20  and a liner film on the dynamic photomask module  20 ), and a portion of the cured material is attached to the bottom of the raw material tank  30 , the ultrasonic oscillators  43  are activated to provide vibration which is transmitted to the cured material, thereby separating the cured material from the bottom of the raw material tank  30  (the liner film on the dynamic photomask module  20 ). Afterwards, the carrying platform  41  moves upwards, and the liquid photocurable material flows back through the through holes  412  to fill the space originally occupied by the cured material. The ultrasonic oscillators  43  of the present embodiment are arranged on the entire carrying platform  41 . For the purpose of clear presentation of the carrying platform  41 ,  FIG.  1    shows only the ultrasonic oscillators  43  disposed on a half portion of the carrying platform  41 . The ultrasonic oscillators  43  can also be mounted to the peripheral wall  31  or the bottom wall  32  to speed the flow of the liquid photocurable material. 
     The deposition module  40  further includes a weight sensor  44  disposed at a connection of the carrying platform  41  and the driving device  42  to detect a load of the carrying platform  41 . The weight sensor  44  is exemplarily a stress/strain gauge. Speed and displacement of the carrying platform  41  driven by the driving device  42  is determined according to the load of the carrying platform  41  detected by the weight sensor  44 . The separation of the product from the carrying platform  41  due to higher moving speed and induced larger drag force is thus prevented. 
     Referring to  FIG.  5   , the large area deposition type additive manufacturing equipment of the present embodiment further includes a control module  50  configured to control the speed of the carrying platform  41  based on the load of the carrying platform  41  detected by the weight sensor  44 . The control module  50  includes a processor  51  which can be microprocessor chip. The processor  51  is also connected to a computing device  52 . The processor  51  transmits control commands to the computing device  52 , and the computing device  52  transmits photomask patterns to the liquid crystal display panel of the dynamic photomask module  20 . The processor  51  is also connected to a relay  53  controlling the circuits of the light source module  10 . The relay  53  enables the circuits of the light source module  10  opened or closed so that the light emitting members  11  emit light or not. The processor  51  can also control the light emitting members  11  in specific regions or in all control regions to emit light. The processor  51  is also connected to the driving member  423  of the driving device  42  to control the rotational speed of the servo motor so as to control the moving speed of the carrying platform  41 . 
     The large area deposition type additive manufacturing equipment of the present invention is provided with the carrying platform of large area, the large bracket, the large rail and the driving member of large power, whereby the additive manufacturing equipment of bottom-up type is able to form a plurality of products on the carrying platform in one process. The ultrasonic oscillator vibrates the product, thereby separating from the bottom of the raw material tank. The weight sensor detects a load of the carrying platform to regulate the speed of the carrying platform so as to reduce the drag force generated between the product and the raw material tank, thereby preventing the product separated from the carrying platform. In the present invention, the carrying platform does not need to move up and down for separation of the product from the raw material tank before the formation of the next layer as what is performed in the conventional additive manufacturing equipment. Therefore, the production rate is increased and the production ability is higher. 
     Moreover, the large area deposition type additive manufacturing equipment of the present invention is also provided with light source of visible light, and the liquid photocurable material is cured by the visible light. As the UV light is replaced by the visible light, the cost of the equipment is reduced, and the problem of reduction in service life of the equipment caused by UV light is also solved. 
     Referring to  FIG.  6   , the light from the light source module  10  is diffused by the light diffusion member  12  to obtain uniform light as emitting from a planar light source (see (a) of  FIG.  6   ). Two light enhancement members  13  converge the diffused light, and the light intensity at an angle near the normal line is increased through certain light collecting mechanisms (see (b) and (c) of  FIG.  6   ). The light emitting angle limiter  14  eliminates the light traveling at a large incident angle in two lateral sides (see (d) of  FIG.  6   ). Therefore, light from the light source  10  has a uniform light intensity and a small light emitting angle, thereby obtaining photocured products of uniform quality. 
     While the invention has been described by way of example and in terms of preferred embodiment, it is to be understood that the invention is not limited thereto. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.