Selective laser sintering with localized heating by area exposure

Abstract

A selective heating system for heating a layer of the printing material on the print bed of a selective laser sintering printer contains a processing module, a light source, and a lens. The processing module stores print patterns to print a three-dimensional object. The light source emits light corresponding to the print patterns. The lens focuses light corresponding to the print patterns onto the printing material on the print bed.

Description

INTRODUCTION

[0001] The present disclosure relates to additive manufacturing and in particular to systems and methods for selective laser sintering (SLS) of a powder to produce a three-dimensional part (3D part).

[0002] Selective laser sintering (SLS) is a process of fusing a printing material, usually a powder, layer by layer to create a 3D object. SLS printers use lasers, lamps, and / or resistance heatbeds to heat the powder, and lasers to fuse layers of powder together to create a 3D printed object.

[0003] Typically, all printing material on the build platform is heated just below its melting point using heating coils or infrared lamps. The material is maintained at this elevated temperature throughout the printing process to make it easier for the laser to melt the thermoplastic powder, thus reducing the amount of energy required and preventing the printed parts from warping due to temperature gradients. Once heated, the printing process begins. The thermoplastic powder is spread using a distributor or roller, creating a thin, uniform layer on the build platform. The laser then selectively heats the thermoplastic powder in specific sections of the build platform to melt the powder into a defined geometry.The printing process is repeated, with the part growing larger with each layer. Unsintered printing material accumulates and encases the 3D printed part. This unsintered material is removed after printing is complete. A percentage of the unsintered material, heated to just below the melting point of the printing material, is unusable for future print jobs and must be discarded. The percentage of material that must be discarded can range from 20% to 100%, resulting in significant waste and increasing the manufacturing cost of a 3D printed part.

[0004] Thus, while current SLS printers fulfill their intended purpose, there is a need for a new and improved system and process for selective laser sintering. A new and improved system and process that address the high percentage of printing material waste would be particularly desirable. SUMMARY

[0005] According to several aspects, a process for printing a three-dimensional object includes depositing a printing material onto a build platform, spreading the deposited material across the build platform to form a homogeneous layer, and projecting a print pattern onto this layer. The print pattern defines the cross-sectional area of ​​the three-dimensional object. Furthermore, projecting the print pattern heats the printing material within the patterned area from ambient temperature to a temperature below the material's melting point. Additionally, the process involves melting the heated printing material with a laser and solidifying the molten material to form the cross-sectional area of ​​the three-dimensional object.

[0006] According to an additional aspect of the present disclosure, distributing the deposited printing material further includes rolling the deposited printing material to form the homogeneous layer.

[0007] According to another aspect of the present disclosure, the projection of the printed pattern onto the layer of the printing material is carried out using a digital light processing projector.

[0008] According to another aspect of the present disclosure, the projection of the printed pattern onto the layer of the printing material is carried out using a laser diode arrangement.

[0009] According to another aspect of the present disclosure, melting the heated printing material further comprises laser heating of the printing material from a temperature below the melting temperature to the melting temperature of the printing material.

[0010] According to another aspect of the present disclosure, solidifying the layer of molten printing material includes cooling the layer of molten printing material.

[0011] According to another aspect of the present disclosure, printing the three-dimensional object further comprises printing multiple cross-sectional areas onto multiple layers of printing materials.

[0012] According to another aspect of the present disclosure, the cross-sectional areas are formed using several sequential printing patterns.

[0013] According to another aspect of the present disclosure, the cross-sectional areas are formed using the printing pattern.

[0014] From several perspectives, a selective laser sintering printer for printing a three-dimensional object includes a build bed to support a first layer of the printing material and a selective heating system to project a print pattern onto this first layer. The print pattern defines a cross-sectional area of ​​the three-dimensional object. Projecting the print pattern heats the first layer of printing material within the projected pattern from ambient temperature to a temperature below the material's melting point. The printer also includes a laser to melt the heated first layer of printing material to form a section of the three-dimensional object, and a build volume.

[0015] According to an additional aspect of the present disclosure, the printer further includes a rolling element for distributing the deposited printing material in order to form a homogeneous layer.

[0016] According to another aspect of the present disclosure, the selective heating system further includes a digital light processing projector to project the print pattern onto the first layer of the printing material.

[0017] According to another aspect of the present disclosure, the printer further includes a control module. The control module contains commands to control the laser to heat the first layer of the printing material from a temperature below the melting point to the melting point of the printing material.

[0018] According to another aspect of the present disclosure, the control module further contains commands to change the print patterns from a first print pattern to a second print pattern when a second layer of the printing material is deposited on top of the first layer of the printing material on the print bed.

[0019] According to another aspect of the present disclosure, the printer further includes a motor to move the print bed in a vertical direction, thereby adjusting the print volume to accommodate the three-dimensional object.

[0020] From several perspectives, a selective heating system for heating a layer of printing material on the print bed of a selective laser sintering printer includes a computing module containing a processor and memory for storing print patterns, a light source configured to emit light corresponding to the print patterns, and a lens to receive the emitted light corresponding to the print patterns. The lens focuses the print patterns onto the layer of printing material applied to the print bed. Furthermore, the focused print patterns heat the layer of printing material.

[0021] In yet another aspect of the present disclosure, the memory further contains instructions to focus the printing patterns onto the layer of the printing material in order to heat the layer of the printing material from an ambient temperature to a higher temperature below a melting temperature of the printing material.

[0022] According to an additional aspect of the present disclosure, the light source further includes a digital light processing projector to project the print pattern onto the layer of the printing material.

[0023] According to another aspect of the present disclosure, the light source further includes a laser diode arrangement to project the print pattern onto the layer of the printing material.

[0024] Further areas of application will become apparent from the description provided here. It should be understood that the description and specific examples serve only for illustration and are not intended to limit the scope of this disclosure. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described here serve only for illustration and are not intended to limit the scope of the present disclosure in any way; they show: Fig. 1 a schematic representation of a selective laser sintering printer (SLS printer) according to an embodiment of the present disclosure; Fig. 2A a partial top view of a printed pattern projected onto a layer of the printing material deposited on a print bed of the SLS printer, according to an embodiment of the present disclosure; Fig. 2B a schematic representation of a side view of the print bed having additional layers of a printing material which have been successively deposited on layers of a printing material, wherein some of the layers have sintered sections, according to an embodiment of the present disclosure, and Fig. 3 a flowchart illustrating a method for printing a three-dimensional object using an SLS printer, according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0026] The following description is merely exemplary and is not intended to limit the present disclosure, application or uses.

[0027] With reference to Fig. Figure 1 shows a schematic representation of the SLS printer 100 according to an embodiment of the present disclosure. The printer comprises a print base 101, a frame 102, a print bed assembly 103, a container 104, a roller element 106, a selective heating system 108, a laser 110, and a print volume 112. The components of the SLS printer 100 are described in detail below.

[0028] The print base 101 is mounted in a horizontal plane and can be positioned on a solid surface such as a production table or floor. The print base 101 can be rectangular or square, as required, to support the frame 102 and the print bed assembly 103. The print base 101 is configured to support the frame 102 and the print bed assembly 103.

[0029] Frame 102 contains vertical support elements 118a, 118b, 118c (not shown), and 118d (not shown) and horizontal elements 120a, 120b (not shown), 120c (not shown), and 120d (not shown). One end of the vertical elements 118a-118d is positioned and attached at the corners of the perimeter of the print base 101. The horizontal elements 120a-120d are connected to and attached to the other end of the vertical elements 118a-118d. Thus, the horizontal elements 120a-120d are positioned above the print bed assembly 103 and provide a means to support the components of the SLS printer 100 above the print bed assembly 103, as described in more detail below.

[0030] The print bed assembly 103 comprises a build plate 122, a motor 124, and a housing 126. The build plate 122 is used to support the three-dimensional object during printing. The build plate is supported by the housing 126. The housing 126 is supported by the print base 101 and is extendable and foldable in the vertical direction 128. The housing 126 is attached to a central section of the print base 101 and to a central section of the build plate 122. The motor 124 is located under the build plate 122 and is coupled to the housing 126 to move the housing 126 vertically. Thus, the build plate 122 moves up and down in the vertical direction 128 by extending and contracting the housing 126.

[0031] Container 104 is a funnel-shaped structure with an inlet 132, an outlet 134, and a holding container 135. The inlet receives printing material 136 for use during a printing process. The outlet 134 serves as an exit point for the printing material 136, which is to be deposited onto the build plate 122 of the print bed assembly 103 during the printing process. The holding container 135 is positioned between the inlet 132 and the outlet 134. The holding container 135 holds the required amount of printing material 136 necessary to print the 3D object. The outlet 134 also includes a valve 144, which has a closed and an open state. In the closed state, the valve 144 prevents the printing material 136 from flowing out of container 104. The valve 144, when open, allows the printing material 136 to flow out of the container 104.In one embodiment of the present disclosure, the valve 144 is selectably switchable from the closed state to the open state in order to dispense a printing material onto the print bed. The printing material 136 can be made from, but is not limited to, polymers such as nylon 11 and nylon 12, composites such as glass-filled nylon, carbon fiber nylon, thermoplastic polyurethane, polycarbonate, polypropylene, metal powder, and ceramics.

[0032] The rolling element 106 comprises a rolling element body 146 and an axle 148. The rolling element body 146 is cylindrical and has a through-bore extending along its length for the rolling element axle 148 to pass through. In one embodiment of the present disclosure, the rolling element 106 includes a control mechanism (not shown) configured to roll and press the rolling element body 146 along the entire construction plate 122. The rolling element 106 is used to distribute the deposited printing material 136 onto the construction plate 122 to form a thin, dense, homogeneous layer 145. The rolling element 106 comprises a rolling element body 146 and a rolling element axle 148.

[0033] The selective heating system 108 is supported above the construction plate 122 by the horizontal elements 120a-120d of the frame 102. The selective heating system 108 includes a computing module 158, a lens 162, and a light source projector 163. The computing module 158 contains a processor and memory and is used to store a print pattern 164 and instructions 165. In one embodiment of the present disclosure, the computing module 158 stores several print patterns 164 required to print the three-dimensional object. The instructions 165 contain information about the sequence and duration for projecting the print patterns 164. The lens 162 is used to scale and project the light emitted by the light source 163. Furthermore, the light source 163 receives the print pattern 164 from the computing module 158 and emits light that corresponds to the print pattern 164.The print pattern 164 is then projected by the lens 162 onto the layer 145 of a printing material 136 on the build plate 122. In one embodiment of the present disclosure, the print pattern 164 is projected onto the build plate 122 for a period of time in order to heat the printing material 136 to a near-melting temperature. In one embodiment of the present disclosure, the selective heating system 108 is, for example, a digital low-pressure sodium (DLP) projector. In another embodiment of the present disclosure, the selective heating system 108 is, for example, a laser diode array.

[0034] The laser 110 is mounted on the horizontal elements 120a-120d of the frame 102. The laser 110 includes a laser gun 176, a galvanometer 178, a control module 180, and a communication module 182. The laser gun 176 emits a laser beam 184 onto the layer 145 of a printing material 136. The beam 184 heats the printing material 136 from near-melting temperature to melting temperature. The temperature increase causes the particles of the printing material 136 exposed to the laser beam 184 to sinter and fuse with neighboring particles. The galvanometer 178 orients the laser gun 176, enabling it to direct the laser beam 184 to different locations on the build plate 122. The control module 182 determines and controls the orientation of the galvanometer 178. The communication module 182 connects the selective heating system 108 to the laser 110 via communication technology.Furthermore, the communication module 182 has access to the print pattern 164 and commands 172, which are stored in the computing module 158 of the selective heating system 108. The communication module 182 can be operated to send the print pattern 164 to control a module 180, which uses the print pattern 164 to determine a control procedure necessary to orient the laser gun 176 so that the beam 184 is emitted in the print pattern 164. The laser 110 can be, for example, a carbon laser, a fiber laser, or any laser suitable for heating and melting the printing material 136.

[0035] The print volume 112 defines the effective print volume of the SLS printer 100. The print volume 112 is adjustable by moving the print bed assembly 103 upwards or downwards in the vertical direction. In one embodiment of the present disclosure, the print volume 112 increases, for example, when the print bed assembly 103 moves vertically relative to the printer base 101. Additionally, the present disclosure provides that the print volume 112 is adjustable to a final volume sufficient to contain all the layers 145 required to complete the printing of the three-dimensional object.

[0036] Now, with reference to Fig. Figure 2A illustrates a partial top view of the print pattern 164, which is projected onto a layer 145 of a printing material 136 distributed on the build plate 122 of the print bed arrangement 103, according to an embodiment of the present disclosure. The print pattern 164 defines several selectively heated sections 168 in the print area 166. The selectively heated sections 168 represent the cross-sectional geometry of the 3D object to be produced. The selective heating system 108 heats the selectively heated sections 168 to near-melting temperature. The laser 110 is directed towards the selectively heated sections 168 and further heats them to the melting temperature of the printing material to form the sintered areas 186. The sintered sections 168 represent the final cross-sectional geometry of the printed object.

[0037] Now, with reference to Fig. Figure 2B shows a schematic representation of a first, second, and third layer 145a-c of a printing material 136 deposited on the construction plate 122 according to an embodiment of the present disclosure. The first layer 145a has a first sintered area 186a defined by a first print pattern of the print pattern 164 projected by the selective heating system 108. The second layer 145b has a second sintered area 186b defined by a second print pattern of the print pattern 164 projected by the selective heating system 108. The third layer 145c has a selectively heated section 168 defined by a third print pattern of the print pattern 164 projected by the selective heating system 108.The first and second sintered areas 186a and 186b, and the selectively heated section 168, are bordered by unheated printing material 136, which is removed when printing is complete. The first sintered area 186a and the second sintered area 186b are fused to form a section of the 3D object. The selectively heated section 168 in the third layer 145c is heated by the selective heating system 108 to a temperature below the melting point of the printing material 136, without heating the printing material 136 adjacent to the selectively heated section 168.

[0038] With reference to Fig. Figure 3 is a method for printing a three-dimensional object with the SLS printer 100, generally referred to as 300, according to an embodiment of the present disclosure. In the present disclosure, the method 300 enables the printer 100 to print the three-dimensional object completely. Furthermore, the method 300 and the systems described above enable the printing of complex parts, including, but not limited to, connecting elements and cylindrical shafts.

[0039] In one embodiment of the present disclosure, the method 300 for selective laser sintering printing begins in block 302.

[0040] In block 304 with additional reference to Fig. 1 The printing material 136 is deposited from the container 104 onto the construction plate 122 of the print bed arrangement 103.

[0041] In block 306, the rolling element 106 distributes the printing material 136 evenly on the top surface 128 of the construction plate 122, forming a thin dense layer 145 of the printing material 136.

[0042] In block 308 with additional reference to Fig. 1 and Fig. 2. The print pattern 164 is projected onto layer 145. As mentioned above, projecting the print pattern 164 for a certain period of time increases the temperature of the printing material 136 in the selectively heated sections 168 of the printing area 166, which are defined in the print pattern 164. The printing material 136 outside the print pattern 164 and the selectively heated sections 168, which are not exposed to the light source 163 of the selective heating system 108, is not heated by the selective heating system 108.

[0043] In block 310, the temperature of the printing material 136 is checked. In one embodiment of the present disclosure, the temperature of the printing material 136 is determined by measuring the amount of heat radiated from the selectively heated section 168. In another embodiment of the present disclosure, the temperature of the printing material 136 is not determined; instead, the printed pattern 164 is projected onto the layer 145 of a printing material 136 for a predetermined duration in order to raise the temperature of the printing material 136 to a predetermined temperature, e.g., near its melting point.

[0044] In block 312 with additional reference to Fig. 1 and Fig. 2 The printing material 136 is sintered in the optionally heated section 168 using the laser 110, forming the sintering area 186.

[0045] In block 314 with additional reference to Fig.2. The sintered areas 186 are solidified. In one embodiment of the present disclosure, the sintered section 184 is solidified by switching off the light source projector 163 and the laser 110, which allows the printing material to cool down.

[0046] In block 316, the SLS printer 100 checks whether the printing process is complete. In one embodiment of the present disclosure, the printer 100 receives a message from the computing module 158 of the light source projector 163 indicating whether there are multiple layers 145 to be printed. The printing process is considered complete when the processor and memory of the computing module 158 indicate that the last layer has been dispensed, heated, and sintered.

[0047] The printing process ends in block 318.

[0048] The systems and methods of the present disclosure offer several advantages. These include a significant reduction in wasted printing material 136. Selective heating of the layer 145 of printing material 136 in specific areas preserves the quality of the printing material 136 in the unheated areas, thereby making the printing material 136 reusable.

[0049] Selective heating could also increase the number and variety of printing materials that can be used for SLS printing. For example, insulating materials such as fiberglass absorb and retain heat, which makes such materials unsuitable for SLS printing. Advantageously, heating selected areas with the selective heating system of the present disclosure overcomes the problems that arise with insulating materials during SLS printing.

[0050] The description of the present revelation is merely exemplary, and it is intended that variations that do not deviate from the main content of the present revelation remain within its scope. Such variations should not be considered a deviation from the idea and scope of the present revelation.

Claims

[1] Method for printing a three-dimensional object, the method comprising: Deposition of a printing material onto a print bed; Distributing the deposited printing material on the printing bed to form a homogeneous layer of printing material; Projecting a print pattern onto the layer of the printing material, wherein the print pattern defines a cross-sectional area of ​​the three-dimensional object and the projection of the print pattern heats the printing material in the projected print pattern from a first ambient temperature to a second higher temperature below a melting temperature of the printing material; Melting the heated printing material with a laser, and Solidifying the molten printing material that forms the cross-sectional area of ​​the three-dimensional object. [2] Method according to claim 1, wherein the distribution of the deposited printing material further comprises rolling the deposited printing material to form the homogeneous layer. [3] Method according to claim 1, wherein the projection of the printed pattern onto the layer of the printing material is carried out using a digital light processing projector. [4] Method according to claim 1, wherein the projection of the print pattern onto the layer of the printing material is carried out using a laser diode arrangement. [5] Method according to claim 1, wherein the melting of the heated printing material further comprises laser heating of the printing material from the second temperature to the melting temperature of the printing material. [6] Method according to claim 5, wherein the solidification of the layer of molten printing material comprises cooling the layer of molten printing material. [7] Method according to claim 2, wherein the printing of the three-dimensional object further comprises printing multiple cross-sectional areas onto multiple layers of printing materials. [8] Method according to claim 7, wherein the multiple cross-sectional areas are formed using multiple sequential printing patterns. [9] Method according to claim 7, wherein the multiple cross-sectional areas are formed using the printing pattern. [10] Selective laser sintering printer for printing a three-dimensional object, the printer comprising: a print bed to support a first layer of the printing material; a selective heating system for projecting a print pattern onto the first layer of the printing material, wherein the print pattern defines a cross-sectional area of ​​the three-dimensional object and the projection of the print pattern heats the first layer printing material in the projected print pattern from a first ambient temperature to a second higher temperature below a melting temperature of the printing material; a laser to melt the heated first layer of the printing material to form a section of the three-dimensional object; and a pressure volume.

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