Method and apparatus for manufacturing UHMWPE structures incorporating graphene

Abstract

A method for manufacturing a graphene-incorporated UHMWPE structure, the method comprising the step of i. providing a build chamber having a vertically movable platform defining a build plate, on which SLS In a 3D printing process, powder material may be sintered layer by layer, and the method further includes: ii. preheating a build chamber; iii. reducing the pressure in the build chamber and / or supplying an inert gas into the build chamber; iv. depositing a UHMWPE powder layer on a build plate to define a print bed; v. exposing a selected area of ​​the UHMWPE powder layer to at least one first laser light source to create a sintered region of the UHMWPE powder layer; vi. exposing a selected area of ​​the UHMWPE powder sintered region to at least one second laser light source to induce graphene formation derived from the UHMWPE powder; vii. lowering the platform by one step corresponding to the thickness of the UHMWPE powder layer and depositing a further UHMWPE powder layer thereon; and viii. repeating steps (v) to (vii) until the structure is complete.

Description

Technical Field

[0001] The present invention relates to a method and apparatus for manufacturing a UHMWPE structure incorporating graphene using additive manufacturing techniques, and more particularly to a method for manufacturing improved body armor.

Background Art

[0002] Ultra-high molecular weight polyethylene (UHMWPE) is a high-performance polymer having a low coefficient of friction, very good wear resistance, high toughness and impact resistance, as well as high chemical resistance and good biocompatibility. It is used in the shipbuilding industry, the fiber industry, and also in biomedical applications. It has also been found to provide advantageous properties when used in the manufacture of body armor due to its light weight and good ballistic resistance.

[0003] However, UHMWPE parts cannot be easily manufactured by conventional plastic manufacturing techniques such as injection molding or extrusion because of their very high melt viscosity due to extremely long polymer chains.

[0004] Selective laser sintering (SLS) is an additive manufacturing technique that uses a laser as a power and heat source to sinter powder materials (usually nylon or polyamide). The laser is directed at points in the subsequent layer of powder material on the print bed at positions defined by a 3D model so as to bond the powder materials layer by layer to create a solid structure. Since UHMWPE has transparency and a highly aggregated structure, it is difficult to process UHMWPE using SLS technology, and the finished product has a high porosity, poor material uniformity, and it becomes impossible to create thin sheets for flexible circuits.

[0005] Also, although UHMWPE provides good ballistic resistance, body armor made of UHMWPE generally cannot stop bullets from large-caliber weapons without excessive thickness.

Summary of the Invention

[0006] According to a first aspect of the present invention, a method is provided for manufacturing a graphene-incorporated UHMWPE structure, the method comprising the step of i. providing a build chamber having a vertically movable platform defining a build plate, on which SLS In a 3D printing process, powder material may be sintered layer by layer, and the method further includes: ii. preheating a build chamber; iii. reducing the pressure in the build chamber and / or supplying an inert gas into the build chamber; iv. depositing a UHMWPE powder layer on a build plate to define a print bed; v. exposing a selected area of ​​the UHMWPE powder layer to at least one first laser light source to create a sintered region of the UHMWPE powder layer; vi. exposing a selected area of ​​the UHMWPE powder sintered region to at least one second laser light source to induce graphene formation derived from the UHMWPE powder; vii. lowering the platform by one step corresponding to the thickness of the UHMWPE powder layer and depositing a further UHMWPE powder layer thereon; and viii. repeating steps (v) to (vii) until the structure is complete.

[0007] In a preferred embodiment, the at least one first laser light source includes a non-focused IR laser light source extending over the selected region of the UHMWPE powder layer and one or more focused UV lasers adapted to sinter the contour and / or details of the selected region of the UHMWPE powder layer.

[0008] The second laser light source may include one or more focused UV lasers adapted to induce graphene formation on a selected area of ​​the print bed.

[0009] The method may further include the step of pressing the UHMWPE powder layer deposited on the build plate after exposing the selected region of the UHMWPE powder layer to the at least one first laser light source. The UHMWPE layer may be pressed using a heated roller adapted to traverse the build plate.

[0010] The method may further include detecting a local downward displacement of the heating roller while it is moving across the print bed, followed by adding additional powder, and optionally repeating sintering in the region where the displacement of the heating roller indicates the presence of voids in the UHMWPE layer, before repeating the step of moving the heating roller across the print bed.

[0011] The method preferably includes the step of preheating the build chamber in a separate preheating chamber before transferring the build chamber into the printer housing containing the first and second laser light sources. The method may further include the step of cooling the build chamber in the second chamber by transferring the build chamber into the second chamber after the construction is complete. The preheating chamber, the second chamber, and the printer housing may include cooperating doors, which allow the build chamber to be transferred between them while maintaining a reduced pressure and / or inert gas atmosphere in the preheating chamber, the second chamber, and the printer housing.

[0012] A further aspect of the present invention provides an apparatus for manufacturing a graphene-incorporated UHMWPE structure, the apparatus comprising a build chamber having a vertically movable platform defining a build plate, on which powder material can be sintered layer by layer in an SLS 3D printing process, the apparatus further comprising a printer housing capable of enclosing the build chamber, the housing incorporating heating means for heating the build chamber, means for reducing the pressure inside the housing and / or supplying an inert gas into the housing, a powder supply system adapted for depositing a UHMWPE powder layer on the build plate, a first laser system adapted for sintering a selected region of the top layer of UHMWPE powder to define a print bed on the build plate of the build chamber, and a second laser system adapted for inducing graphene formation on the print bed.

[0013] The at least one first laser light source may include a non-focused IR laser light source extending over the selected region of the UHMWPE powder layer, and one or more focused UV lasers adapted to sinter the contours and / or details of the selected region of the UHMWPE powder layer.

[0014] The second laser light source may include one or more focused UV lasers adapted to induce graphene formation on a selected area of ​​the print bed.

[0015] The powder supply system may include a powder storage hopper mounted on a gantry above the build plate within the enclosure. To measure the flow rate of powder from the lower end of the powder storage hopper, a dosing wheel may be connected to the outlet of the powder storage hopper at the top of the enclosure. The powder storage hopper may be adapted to move parallel to the build plate while the dosing wheel is operated, thereby causing the powder flow to accumulate adjacent to the build plate. To spread the powder flow across the print bed, it is preferable that a roller is mounted within the enclosure so as to traverse the print bed. The roller preferably includes a heating means for heating the outer surface of the roller.

[0016] The roller may be adapted to press downward against the print bed as it traverses the print bed, thereby allowing the roller to pass over each freshly sintered layer on the print bed and press downward against the layer, ensuring sufficient adhesion between layers and reducing the porosity of the sintered structure.

[0017] Preferably, the roller includes means for detecting local downward displacement of the roller during its movement on the print bed following the sintering of the powder on the print bed, the detection means providing feedback to the control system of the apparatus, the control system being adapted to repeat sintering over areas where the displacement of the heated roller indicates the presence of voids and / or incomplete sintering in the UHMWPE layer, before optionally repeating the step of adding additional powder and moving the roller across the print bed.

[0018] The control system may be programmed to scan the surface of the material on the print bed to identify which areas are properly sintered and which are not, when the deflection of the roller indicates the presence of voids and / or incomplete sintering in the UHMWPE layer. Then, without the build plate descending to start the next layer, an additional powder layer is spread on the print bed, and the further sintering process is repeated, focusing on the identified under-sintered areas. After the further sintering step is complete, the control system may be programmed to scan the surface again to determine if any improperly sintered areas remain. If so, the control system may again move the roller across the print bed to apply further pressure to the structure to adhere the layer, and this process may be repeated until the feedback mechanism determines that the sintering is sufficient.

[0019] The apparatus may further include a preheating chamber, in which the build chamber may be preheated before being transferred into the printer housing containing the first and second laser light sources. A second chamber may be provided, in which the build chamber may be transferred after the construction is completed in the printer housing to be cooled. The second chamber may include a second preheating chamber. The preheating chamber and the second chamber are preferably portable and adapted to move relative to the printer housing. The preheating chamber, the second chamber, and the printer housing preferably include cooperating doors, which allow the build chamber to be transferred between them while maintaining a reduced pressure and / or inert gas atmosphere in the preheating chamber, the second chamber, and the printer housing.

[0020] Here, an apparatus for manufacturing a graphene-incorporated UHMWPE structure according to an embodiment of the present invention will be described with reference to the accompanying drawings, merely as an example. [Brief explanation of the drawing]

[0021] [Figure 1] This is a perspective view of a 3D printing apparatus for manufacturing a graphene-incorporated UHMWPE structure according to an embodiment of the present invention. [Figure 2] This is a cross-sectional view of the apparatus shown in Figure 1. [Figure 3] This is a detailed view of area A in Figure 2. [Figure 4] Figure 1 is a schematic diagram of the laser assembly of the device shown in Figure 1. [Figure 5] Figure 5 is a detailed schematic diagram of the mirror system for the IR laser in the laser assembly. [Figure 6] Figure 4 is a further schematic diagram of the IR laser system in the laser assembly. [Figure 7] Figure 4 is a schematic diagram of the UV sintered laser in the laser assembly. [Modes for carrying out the invention]

[0022] As shown in the drawings, an apparatus for manufacturing a graphene-incorporated UHMWPE structure according to an embodiment of the present invention includes a sealed printer housing 2 adapted to be filled with an inert gas such as nitrogen, and a build chamber 4 may be disposed therein.

[0023] A print bed 6 is defined on top of a vertically movable platform inside the build chamber 4, the platform defines a build plate, and on the build plate within the build chamber, a structure is created layer by layer by selective laser sintering (SLS) in a 3D printing process. A powder supply system 10 is provided above the build chamber 4 within the housing to supply a layer of UHMWPE powder onto the print bed 6 of the build chamber.

[0024] Heating means (not shown) are provided within the printer housing 2 to heat and maintain the temperature of the build chamber 4 at a temperature just below the melting point of the powder. A liquid nitrogen storage tank 8 may be disposed in the lower region of the printer housing 2.

[0025] A laser assembly is mounted above the build chamber 4 at the top of the printer housing 2, and the laser assembly includes a first laser system adapted to heat a selected area of the topmost layer of powder on the print bed 6 at a temperature just below or exactly at the melting point of the material, thereby fusing (sintering) the particles within the selected area of the topmost layer of powder together and to the already sintered material of the underlying layer. The unfused powder supports the sintered structure during printing, eliminating the need for a dedicated support structure.

[0026] In a preferred embodiment, the first laser system includes an infrared (IR) laser 10 whose output is reflected and pulsed, but not focused, to the top layer of powder on the print bed via appropriate mirrors and lenses 12 to cover a two-dimensional area on the print bed. As shown in Figure 5, the IR laser 10 is preferably pulsed at 1 Hz to 1 GHz with respect to a first sinusoidal mirror 12A, which is fitted to move slowly across the beam in the same direction as the mirror's wave. After being reflected by the first mirror 12A, the laser pulse may be directed to a second stationary sinusoidal mirror 12B positioned at 90 degrees to the first mirror 12A. This reflects the laser pulse into a one-dimensional line that can be scanned on the print bed 6. As shown in Figure 6, this pulse path is directed onto a liquid crystal on silicon (LCOS) screen 12D via a series of lenses 12C. This screen 12D displays the desired pattern of this particular print layer and reflects only pulses within these areas. This reflection is then directed onto the print bed 6, sintering the top layer of powder on the print bed 6 as determined by the pattern on the LCOS screen. This process sinters the powder to define the body into the desired shape.

[0027] The IR laser 10 may include a 100W CO2 laser, which is pulsed at 1Hz to 1GHz and slightly focused to widen the beam size to approximately 1mm through a series of glass lenses. The beam is then directed to a first sinusoidal holographic mirror 12A (wavelength 10 micrometers), which moves parallel to the mirror's wave at a constant speed of 1mm per second. After being reflected by this mirror, the laser pulse is directed to a second sinusoidal mirror 12B positioned at a 90-degree angle to the first mirror. This arrangement is advantageous because the laser pulse can spread from a fixed point of approximately 1mm to a series of random points within an area of ​​approximately 330mm x 330mm. The IR laser can be controlled by a variable pulse rate to ensure that it strikes almost every part of the selected area of ​​the print bed 6 at least once, thereby ensuring that the entire powder layer within the selected area is sintered. After being reflected from the second mirror, the pulses are directed to the LCOS screen 12D, which displays only the selected area desired for sintering on the print bed 6. This ensures that only pulses within this area are reflected onto the print bed 6, and that the correct area is sintered.

[0028] The first laser system preferably further includes a separate ultraviolet laser system 14 provided for more precisely creating structural details (e.g., the edges of a desired structure). In one embodiment, four UV lasers 14A, 14B, 14C, and 14D may be provided, each UV laser emitting a focused beam toward its own rotating mirror pair 15A, 15B, 15C, and 15D, with one mirror of each pair rotating in the x-plane and the other mirror of each pair rotating in the y-plane, thereby allowing the focused beams from each UV laser 14A, 14B, 14C, and 14D to be directed to any point within a quarter area of ​​the print bed 6 assigned to each. This makes it possible to sinter precise edges of the structure.

[0029] The combination of pulsed sintering (IR laser 10) and cold working (UV laser 14) makes it possible to create complex shapes very quickly and accurately.

[0030] UV lasers 14A, 14B, 14C, and 14D may each include a 351nm excimer laser XeF (xenon fluoride). UV lasers do not heat and melt materials, resulting in a very different reaction with materials compared to IR lasers. Instead, UV lasers deliver a very precise and localized amount of energy to break down and reform bonds in materials.

[0031] By using these four UV lasers, one in each quadrant of the build plate, to sinter the edges of a structure with a given powder layer, each laser can easily cover the entire area of ​​that quadrant, efficiently drawing around the edges of the structure's shape with high precision.

[0032] The apparatus includes a second laser system for inducing graphene formation in a selected layer of sintered powder on a print bed 6, if it is desired to incorporate graphene material into the finished structure, wherein the graphene is derived from the UHMWPE powder by a laser-induced graphene (LIG) process.

[0033] A second laser system may include a further arrangement of UV lasers and mirrors, having a structural arrangement relative to the UV lasers of the first laser system, and the second laser system comprises four UV lasers 16, each covering a quarter area of ​​the print bed 6. Each laser is directed using x-movable mirrors and y-movable mirrors, so that each laser beam can be directed as needed. Lasers in the second laser system may include a KrF (krypton fluoride) 248 nm laser. The output from these lasers is directed onto the already sintered material to create the desired shape of graphene. This may be to cover the entire already sintered material in a layer, or to cover only a portion of the sintered layer and something in between of any desired shape. As shown in Figure 4, the UV sintered laser 14 and the UV graphene laser 16 may be associated with a common set of optical rotating mirrors to direct the resulting beams onto the print bed 6.

[0034] After sintering the powder in the top layer and optionally forming graphene in a selected area of ​​the top layer, the platform is then lowered into the build chamber by one layer, typically 50-200 microns, to deposit an additional powder layer on top of the build plate, and the process is repeated.

[0035] In the embodiment shown in the drawings, the powder supply system 10 includes a powder storage hopper located at the top of the build chamber, which is adapted to supply a thin layer of powder onto the print bed.

[0036] In the most well-known SLS printers, powder is supplied to the build plate by providing a powder storage chamber of the same size as the build chamber along the build plate. A piston from below raises the powder level in the powder storage chamber to just above the level of the build plate, and rollers are used to spread this layer of powder from the powder storage chamber across the build plate. However, this system requires the powder storage chamber to be located adjacent to the build chamber, which significantly increases the printer footprint and further complicates system maintenance.

[0037] In this invention, this problem is solved by providing a powder storage hopper 17 in a gantry located above the build plate within the housing. To measure the flow rate of powder from the lower end of the powder storage hopper, a dispensing wheel may be connected to the outlet of the powder storage hopper at the top of the housing.

[0038] The powder storage hopper, once filled, is adapted to move parallel to the build plate while operating a dosing wheel, thereby accumulating the powder flow adjacent to the build plate. A roller 18 may be provided to spread this powder flow across the print bed 6. This powder supply system requires a dosing wheel and a precise control system to ensure even distribution of powder across the build plate, but the powder supply system significantly reduces the printer footprint and simplifies powder storage.

[0039] In the above configuration, rollers 18 are provided to move the powder across the print bed 6. The rollers 18 may be made of metal and are preferably internally heated. The rollers 18 are preferably motor-driven to move back and forth across the build plate. Additional actuators or motors may be provided at each end of the rollers 18 to press the rollers 18 against the build plate and apply pressure to each powder layer.

[0040] The Roller 18 can perform multiple functions.

[0041] In the above state, the roller 18 is used first to spread the powder layer over the print bed 6 before the powder layer is sintered.

[0042] After each powder layer has been sintered, a second function of the roller 18 may be utilized. In this second function, the heated roller 18 can pass over each sintered layer on the print bed and press downward against the layer, preferably with a pressure of 0.5 to 6 bar. The purpose of this is to ensure sufficient adhesion between layers and to reduce the porosity of the sintered structure.

[0043] The roller 18 may also be associated with a feedback mechanism that includes means for detecting the vertical displacement of the roller toward the build plate. This feedback mechanism can facilitate the identification of excessive porosity in the sintered structure and / or the identification of layers of the structure that are not properly fused. Detection of local downward displacement of the roller as it traverses the print bed can indicate areas of layers with poor porosity or poor sintering. Once this is detected, the roller 18 may be moved aside the print bed, and the surface of the material on the print bed may be scanned, for example, using a lidar, to identify which areas of the part have been properly sintered and which areas have not been properly sintered. Once this is established by the scanning step, a further layer of powder may be spread on the print bed using the roller 18 without lowering the build plate and starting the next layer. The laser sintering process may then be repeated, focusing on the areas that are poorly sintered. After this laser sintering step is complete, the surface may be scanned again. If problems still exist, the roller may traverse the print bed again, applying further pressure to the structure to adhere the layers, and this process may be repeated until the feedback mechanism determines that sintering is sufficient.

[0044] If the feedback mechanism, specifically the scan step, determines that sintering was successful, the problem detected by displacement may be determined to be layer adhesion and / or porosity further beneath the structure. In such a case, the rollers may be operated to apply greater pressure to the print bed and complete more cross-sections on the print bed until the feedback mechanism determines that the pressure applied by the rollers across the structure on the build plate is uniform. At this point, the build plate may be moved down one level, and the formation of the next layer may begin.

[0045] Most SLS printers utilize a manual system for moving the build chamber through the printer. In these systems, the build chamber typically needs to be manually positioned inside the printer through a front door, and it remains stationary during the heating, printing, and subsequent cooling processes. The advantages of such known systems include a simplified internal mechanism due to manual movement, as it eliminates the need for moving parts to assist in positioning the print bed relative to the sintered laser footprint, thus enabling accurate and reproducible prints. This lack of additional mechanism also reduces the overall footprint and cost of the printer.

[0046] A major drawback of such known SLS printers is that the build chamber 4 must remain stationary within the printer during heating and cooling to ensure uniform cooling of the resulting sintered structure and prevent deformation of the formed structure. Large prints can take up to 24 hours, which can result in up to 50% printer downtime, as typical prints can have heating times of over 1 hour and cooling times of over 10 hours.

[0047] Some known systems attempt to solve this problem by creating larger internal chambers within the printer to accommodate multiple chambers at once, thus reducing machine downtime and allowing multiple chambers to be printed sequentially. However, this significantly increases the printer's footprint and the amount of power required to heat the larger internal volume of the machine.

[0048] This problem is solved in the apparatus according to a preferred embodiment of the present invention by heating and cooling each build chamber in a separate portable preheating chamber 20 located outside the printer housing. This preheating chamber is preferably separate from the printer housing 2 of the apparatus and may be adapted to be connected to the main printer housing 2. The preheated build chamber 4 can be moved from the preheating chamber 20 to the inside and outside of the housing 2 through cooperating insulating doors 22 provided on one or both sides of the housing (preferably via the inlet and outlet sides) and on the cooperating side of the preheating chamber 20, thereby allowing the print / sintering process to start immediately.

[0049] When the preheated build chamber 4 is transferred from the preheating chamber 20 into the printer housing 2, the respective doors 22 can be closed and sealed. A second preheating chamber 20 may be located on the opposite side of the housing 2, adjacent to the exit door of the housing 2, and the same process may be performed to transfer the build chamber 4 currently present in the housing 2, containing the completed print / structure, into the second preheating chamber, allowing the build chamber to cool slowly without having to remain inside the main printer housing during the cooling process, significantly reducing machine downtime.

[0050] The preheating chamber 20 is preferably adapted to preheat the build chamber 4 and to be filled with an inert gas, preferably nitrogen. This prepares the preheated build chamber for transfer into the main housing, allowing printing / sintering to begin as soon as the previous print is complete and removed from the main housing into an additional portable preheating chamber, significantly speeding up manufacturing time by reducing downtime. All these processes are repeated until the print is complete, at which point the door to the exit area opens and the build chamber is moved to its own cooling and depressurization section. A new, empty build chamber is then moved into the build area.

[0051] The powder used in the device contains ultra-high molecular weight polyethylene (UHMWPE) as its base polymer. This is a rare material for SLS printing because it is colorless and has a low melting point. Most polymers used in SLS printing, such as nylon 11, are dark or black. This is because they absorb the laser much better and facilitate the sintering process. Because UHMWPE is colorless, it can be difficult to sinter. Furthermore, its very low melting point (130°C to 136°C) makes it difficult to sinter without completely melting the material. These factors make UHMWPE an unsuitable choice for SLS 3D printing, and therefore it is often not considered as a polymer for this process.

[0052] This invention overcomes these problems by blurring the focus of the IR laser beam used in sintering. This uses the same energy but over a much wider area, preventing the material from melting completely. This laser is used for most parts. The process is designed to gently poke the material so that it forms bonds between the powder particles. The heated environment in the build chamber sets the material near its melting point, requiring only a small amount of additional energy to initiate bonding between the powder particles.

[0053] If necessary, the layers may be treated after sintering to form graphene. This process involves scribing over a desired area using a second laser system to remove hydrogen atoms from the UHMWPE, leaving only carbon. The energy from the laser causes these carbon atoms to interbond, forming a graphene sheet that covers the entire desired area of ​​the print bed.

[0054] The aforementioned apparatus can be advantageously used to manufacture body armor, and graphene sheets can be integrated into the UHMWPE structure to improve the ballistic performance of the body armor. It is also conceivable that the apparatus can be used to manufacture a number of other UHMWPE products that can provide enhanced mechanical and / or electrical properties by benefiting from the incorporation of graphene embedded within the structure.

[0055] The present invention is not limited to the embodiments described herein, but may be amended or modified without departing from the scope of the invention as defined by the appended claims.

Claims

1. A method for manufacturing a UHMWPE structure incorporating graphene, wherein the method is: i. The method includes the step of providing a build chamber having a vertically movable platform defining a build plate, on which powder material can be sintered layer by layer in an SLS 3D printing process, and the method further includes ii. A step of preheating the build chamber, iii. The steps of reducing the pressure in the build chamber and / or supplying an inert gas into the build chamber, iv. A step of depositing a UHMWPE powder layer on the build plate so as to define the print bed, v. The step of exposing a selected region of the UHMWPE powder layer to at least one first laser light source in order to create a sintered region of the UHMWPE powder layer, vi. A step of exposing a selected region of the UHMWPE powder sintered region to at least one second laser light source to induce graphene formation derived from the UHMWPE powder, vii. The step of lowering the platform by one step corresponding to the thickness of the UHMWPE powder layer and depositing another UHMWPE powder layer on top of it, viiii. The steps (v) to (vii) are repeated until the above structure is completed, The method, including the method described above.

2. The method according to claim 1, wherein the at least one first laser light source comprises a non-focused IR laser light source extending over the selected region of the UHMWPE powder layer and one or more focused UV lasers adapted to sinter the contour and / or details of the selected region of the UHMWPE powder layer.

3. The method according to claim 1 or 2, wherein the second laser light source includes one or more focused UV lasers adapted to induce the graphene formation on a selected area of ​​the print bed.

4. The method according to any prior claim, further comprising the step of pressing the UHMWPE powder layer deposited on the build plate after exposing the selected region of the UHMWPE powder layer to the at least one first laser light source.

5. The method according to claim 4, wherein the UHMWPE layer is pressed using a heated roller adapted to traverse the build plate.

6. The method according to claim 5, comprising the step of detecting a local downward displacement of the heating roller while the heating roller is moving on the print bed, followed by adding additional powder, and optionally repeating sintering in a region where the displacement of the heating roller indicates the presence of voids in the UHMWPE layer, before repeating the step of moving the heating roller across the print bed.

7. The method according to any prior claim, further comprising the step of preheating the build chamber in a separate preheating chamber before transferring the build chamber into a printer housing including the first laser light source and the second laser light source.

8. The method according to claim 7, further comprising the step of cooling the build chamber in a second chamber by transferring the build chamber into a second chamber after the completion of the aforementioned structure.

9. The method according to claims 7 and 8, wherein the preheating chamber, the second chamber, and the printer housing include cooperating doors, thereby enabling the build chamber to be moved between them while maintaining a reduced pressure and / or inert gas atmosphere within the preheating chamber, the second chamber, and the printer housing.

10. An apparatus for manufacturing a UHMWPE structure incorporating graphene, wherein the apparatus is The apparatus comprises a build chamber having a vertically movable platform defining a build plate, on which powder material can be sintered layer by layer in an SLS 3D printing process, and the apparatus further comprises A housing capable of enclosing the aforementioned build chamber, The housing incorporates a heating means for heating the build chamber, Means for reducing the pressure inside the housing and / or supplying an inert gas into the housing, A powder supply system adapted to deposit a UHMWPE powder layer onto the build plate, A first laser system adapted to sinter a selected region of the top layer of UHMWPE powder to define a print bed on the build plate of the build chamber, A second laser system adapted to induce graphene formation on the print bed, The apparatus comprising the above.

11. The apparatus according to claim 10, wherein the at least one first laser light source comprises a non-focused IR laser light source extending over the selected region of the UHMWPE powder layer and one or more focused UV lasers adapted to sinter the contour and / or details of the selected region of the UHMWPE powder layer.

12. The apparatus according to claim 10 or 11, wherein the second laser light source includes one or more focused UV lasers adapted to induce the graphene formation on a selected area of ​​the print bed.

13. The apparatus according to any one of claims 10 to 12, wherein the powder supply system comprises a powder storage hopper mounted on a gantry located above the build plate within the housing.

14. The apparatus according to claim 13, wherein a dispensing wheel is connected to the outlet of the powder storage hopper at the top of the housing in order to measure the flow rate of powder from the lower end of the powder storage hopper.

15. The apparatus according to claim 14, wherein the powder storage hopper is adapted to move parallel to the build plate while the dispensing wheel is in operation, so that the powder flow accumulates adjacent to the build plate.

16. The apparatus according to claim 15, wherein a roller is mounted inside the housing so as to traverse the print bed in order to spread the powder flow across the print bed.

17. The apparatus according to claim 16, wherein the roller includes a heating means for heating the outer surface of the roller.

18. The apparatus according to claim 17, wherein the roller is adapted to press downward against the print bed when traversing the print bed, so that the roller can pass over each sintered layer on the print bed and press downward against the layer, ensuring sufficient adhesion between layers and reducing the porosity of the sintered structure.

19. The apparatus according to claim 18, wherein the roller includes means for detecting a local downward displacement of the roller during its movement on the print bed following the sintering of the powder on the print bed, the detection means providing feedback to a control system of the apparatus, the control system being adapted to repeat sintering over areas where the displacement of the heating roller indicates the presence of voids and / or incomplete sintering in the UHMWPE layer, before optionally repeating the step of adding additional powder and moving the roller across the print bed.

20. The apparatus according to claim 19, wherein the control system is programmed to identify which areas are properly sintered and which areas are not properly sintered by scanning the surface of the material on the print bed when the deflection of the roller indicates the presence of voids and / or incomplete sintering in the UHMWPE layer, and then, without the build plate descending to start the next layer, a further powder layer is spread on the print bed, and the further sintering process is repeated, focusing on the identified insufficiently sintered areas.

21. The apparatus according to claim 20, wherein the control system is programmed to determine, after the further sintering step is completed, whether any improperly sintered areas remain by scanning the surface again, and if so, the control system may again move the roller across the print bed to apply further pressure to the structure to adhere the layer, and this process may be repeated until the feedback mechanism determines that the sintering is sufficient.

22. The apparatus according to any one of claims 10 to 21, further comprising a preheating chamber, wherein the build chamber can be preheated in the preheating chamber before it is transferred into the printer housing, which includes the first laser light source and the second laser light source.

23. The apparatus according to claim 22, further comprising a second chamber, wherein after the structure is completed in the printer housing, the build chamber can be transferred into the second chamber and cooled therein.

24. The apparatus according to claim 23, wherein the preheating chamber, the second chamber, and the printer housing include cooperating doors, thereby enabling the build chamber to be moved between them while maintaining a reduced pressure and / or inert gas atmosphere within the preheating chamber, the second chamber, and the printer housing.

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