Extrusion nozzle assembly of a 3D printer and control method thereof

Abstract

The application discloses an extrusion nozzle assembly of a 3D printer, which comprises an extruder (1), a throat pipe (2) and a heating body (3); the heating body (3) is provided with a nozzle (4); the extrusion nozzle assembly further comprises a heat sink (5) and a heat insulation sleeve (6); the heat sink (5) is matched with the throat pipe (2) and is used for heat dissipation of the throat pipe (2); the heat insulation sleeve (6) is matched with the heating body (3) and is used for heat preservation and heat insulation of the heating body (3); the extrusion nozzle assembly further comprises at least one stress sensor (7); when the nozzle collides with a model on a printing platform after the 3D printer is started, the further action of the 3D printer can be stopped according to the feedback of the stress sensor, so that the hardware and precision of the 3D printer are effectively protected.

Description

Technical Field

[0001] The present invention relates to the technical field of 3D printing, and in particular to an extrusion nozzle assembly of a 3D printer and a control method thereof. Background Art

[0002] Fused Deposition Modeling (FDM) was invented by Scott Crump of Stratasys in the late 1980s. It is another widely used 3D printing technology, following stereolithography (SLA) and layer-by-layer prototyping (LOM). In 1992, Stratasys launched the 3D Modeler, the world's first FDM-based 3D printer, marking the commercialization of FDM technology.

[0003] FDM works by heating and melting filamentary thermoplastic material through a nozzle equipped with a micro-nozzle at the bottom, typically with a nozzle orifice diameter of 0.2 to 0.6 mm. Under computer control, the nozzle moves to a designated position based on the 3D model data, extruding the molten liquid material and eventually solidifying it. The ejected material is then deposited on the previously solidified material, and the final product is formed through layer-by-layer accumulation.

[0004] Before a 3D printer can operate, it is necessary to set the data such as the spacing between the layers of the three-dimensional model and the width of the path. The slicing engine then slices the three-dimensional model and generates a printing path. Under computer control, the print head moves in the X-axis and Y-axis directions according to the horizontal layering data, while the vertical movement in the Z-axis direction is completed by the raising and lowering of the printing platform. At the same time, the filamentary material is sent to the hot melt chamber by the extruder. After being heated and melted, it is extruded from the nozzle and adhered to the work surface, where it quickly cools and solidifies. The printed material is quickly fused to the previous layer. When each layer is completed, the workbench drops to a lower level, and the printer continues to print the next layer. This process is repeated until the entire object is printed.

[0005] Currently, 3D printers based on FDM technology do not have a collision protection function for the extrusion nozzle. When there is a solidified but not peeled model on the printing platform, the 3D printer will still start running the nozzle printing according to the normal path. When the nozzle runs along the XY axis, it is bound to collide with the model. In particular, 3D printers with a power-off resume function record the nozzle coordinates before the power outage through the program. After the power is restored, the 3D printer automatically moves the nozzle to the coordinates before the power outage and continues printing. However, if the coordinate storage before the power outage fails or is incorrect, the printing nozzle will collide with the model during the movement process, which can easily lead to the X-axis or Y-axis motor being blocked and burned, the extrusion nozzle assembly, and the distortion and deformation of the X and / or Y axis, causing great damage to the hardware and precision of the 3D printer. Summary of the Invention

[0006] The present invention aims to solve one of the technical problems in the related art at least to a certain extent: to provide an extrusion nozzle assembly of a 3D printer and a control method thereof.

[0007] To this end, one object of the present invention is to provide an extrusion nozzle assembly for a 3D printer, comprising an extruder, a throat and a heating body; a hot melt cavity is provided in the heating body, one end of the throat is connected to the output end of the extruder, and the other end is connected to the hot melt cavity of the heating body; a nozzle connected to the hot melt cavity is provided on the heating body, and the extrusion nozzle assembly also includes a heat sink and a thermal insulation sleeve; the heat sink cooperates with the throat to dissipate heat from the throat; the thermal insulation sleeve cooperates with the heating body to keep the heating body warm and insulated; the extrusion nozzle assembly also includes at least one stress sensor.

[0008] As an optimization, the stress sensor includes a substrate and a strain gauge; the strain gauge is adhered to the surface of the substrate.

[0009] Mounting pieces are provided on the upper and lower sides of the base plate; the base plate and the mounting pieces are connected via at least one spring piece.

[0010] The front side of the substrate is flat, and the back side is concave; the strain gauge is attached to the front side of the substrate, and the sensitive grid of the strain gauge is sensitive to stress changes caused by the expansion and contraction of the substrate in the up and down directions.

[0011] The spring piece is "S"-shaped, the front and rear surfaces of the spring piece are both planes parallel to the front surface of the substrate, and the distance between the front and rear surfaces of the spring piece is equal to the maximum distance between the front and back surfaces of the substrate; the left and right surfaces of the spring piece are both curved surfaces, and the distance between the left and right surfaces of the spring piece is smaller than the distance between the front and rear surfaces of the spring piece.

[0012] As an optimization, the thickness of the upper and lower ends of the substrate is greater than the thickness in the middle.

[0013] As an optimization, the mounting plates at both ends of the stress sensor are fixed on the heat sink and the thermal insulation sleeve respectively.

[0014] The extrusion nozzle assembly includes two stress sensors, and the front surfaces of the substrates of the two stress sensors are respectively arranged parallel to the front and side surfaces of the thermal insulation sleeve; when the extrusion nozzle assembly is installed on the 3D printer, the front surface of the substrate of one stress sensor faces the positive direction of the Y-axis, and is used to detect the stress generated on the substrate of the stress sensor when the force in the Y-axis direction is applied to the nozzle; the front surface of the substrate of the other stress sensor faces the positive direction of the X-axis, and is used to detect the stress generated on the substrate of the stress sensor when the force in the X-axis direction is applied to the nozzle.

[0015] As an optimization, the extruder is provided with a motor for driving it to extrude consumables; the motor is provided with a sheet metal frame; the sheet metal frame is provided with a model cooling fan; the model cooling fan is provided with an air guide nozzle; the outlet of the air guide nozzle is arranged toward the nozzle and the printing platform.

[0016] The thermal insulation sleeve is made of thermal insulation materials, such as porous ceramics, mica, glass fiber, etc.

[0017] As an optimization, the side wall of the heat insulation sleeve is connected to the air guide nozzle through a fixing plate.

[0018] The extruder is a double-gear extruder.

[0019] The heating body is provided with a heating wire and a thermocouple temperature sensor, which are connected to the main controller signal through a driving circuit.

[0020] The electrodes of the strain gauge are electrically connected to the main controller of the 3D printer via a Wheatstone bridge.

[0021] The extrusion nozzle assembly further includes a heat dissipation fan for accelerating the heat dissipation of the heat sink;

[0022] The heat sink is provided with heat dissipation fins, the heat dissipation fan is provided on the side of the extruder, and the air outlet of the heat dissipation fan is directly facing the gap between the heat dissipation fins.

[0023] Another object of the present invention is to provide a method for controlling an extrusion nozzle assembly of a 3D printer, comprising the following steps:

[0024] 1) When the 3D printer is just started, the printing platform is first lowered to the lowest zero position, and the main controller reads the initial values ​​of the stress sensor in the X-axis direction and the stress sensor in the Y-axis direction and stores the initial values, which are recorded as X and Y respectively. base , Y base ;

[0025] 2) During the working process of the 3D printer, the main controller periodically reads the current values ​​of the stress sensor in the X-axis direction and the stress sensor in the Y-axis direction, which are recorded as X and Y respectively. c , Y c , substitute the following formula to calculate A c ,

[0026] 3) When A c >A set When the 3D printer stops printing and lowers the printing platform to the lowest zero position; A set To set the threshold, A set According to the normal printing process of the 3D printer c The maximum value depends on A set >A during normal printing of the model c Maximum value.

[0027] The present invention has the following beneficial effects: the extrusion nozzle assembly of the present invention realizes a collision protection function. When the nozzle collides with the model on the printing platform after starting the 3D printer, or when the incorrect nozzle coordinates cause the nozzle to collide with the unfinished model on the printing platform due to power failure and resumption, the further action of the 3D printer can be stopped according to the feedback of the stress sensor, thereby effectively protecting the hardware and precision of the 3D printer. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the three-dimensional structure of the extrusion nozzle assembly in the embodiment.

[0029] Figure 2 Schematic diagram of the three-dimensional structure of the extrusion nozzle assembly in the embodiment.

[0030] Figure 3 Schematic diagram of the three-dimensional structure of the extrusion nozzle assembly in the embodiment.

[0031] Figure 4 Schematic diagram of the main structure of the extrusion nozzle assembly in the embodiment.

[0032] Figure 5 Schematic diagram of the side structure of the extrusion nozzle assembly in the embodiment.

[0033] Figure 6 Schematic diagram of the exploded structure of the extrusion nozzle assembly in the embodiment.

[0034] Figure 7 Schematic diagram of the exploded structure of the extrusion nozzle assembly in the embodiment.

[0035] Figure 8 Schematic diagram of the stress sensor structure of the extrusion nozzle assembly in the embodiment.

[0036] Figure 9Schematic diagram of the deformation state of the stress sensor of the extrusion nozzle assembly in the embodiment.

[0037] Figure 10 Schematic diagram of the explosion structure of the heating body and the thermal insulation sleeve of the extrusion nozzle assembly in the embodiment.

[0038] Figure 11 Schematic diagram of the cross-sectional structure of the heating body and the thermal insulation sleeve of the extrusion nozzle assembly in the embodiment.

[0039] Among them, 1. Extruder; 2. Throat; 3. Heating element; 4. Nozzle; 5. Heat sink; 6. Thermal insulation sleeve; 7. Stress sensor; 71. Base plate; 72. Strain gauge; 73. Mounting plate; 74. Spring plate; 8. Motor; 9. Sheet metal frame; 10. Model cooling fan; 101. Air guide nozzle; 11. Cooling fan. DETAILED DESCRIPTION

[0040] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0041] Example 1

[0042] Now combined Figure 1-11 An extrusion nozzle assembly of a 3D printer is described, comprising an extruder 1, a throat 2 and a heating body 3; a hot melt cavity is provided in the heating body 3, one end of the throat 2 is connected to the output end of the extruder 1, and the other end is connected to the hot melt cavity of the heating body 3; a nozzle 4 connected to the hot melt cavity is provided on the heating body 3, and the extrusion nozzle assembly also includes a heat sink 5 and a thermal insulation sleeve 6; the heat sink 5 cooperates with the throat 2 to dissipate heat to the throat 2, specifically, the throat 2 passes through the heat sink 5 and is in close contact with it; the thermal insulation sleeve 6 cooperates with the side wall of the heating body 3 to keep the heating body 3 warm; the extrusion nozzle assembly also includes two stress sensors 7.

[0043] like Figure 8 As shown, the stress sensor 7 includes a substrate 71 and a strain gauge 72. The strain gauge 72 is adhered to the surface of the substrate 71. Preferably, the strain gauge 72 is completely covered and sealed with silicone rubber.

[0044] Mounting pieces 73 are provided on the upper and lower sides of the base plate 71. The base plate 71 and the mounting pieces 73 are connected by three spring pieces 74. The base plate 71, the mounting pieces 73 and the spring pieces 74 are integrally cut and formed from a metal sheet.

[0045] The front side of the substrate 71 is flat, and the back side is concave; the strain gauge 72 is attached to the front side of the substrate 71, and the sensitive grid of the strain gauge 72 is sensitive to the stress change caused by the expansion and contraction of the substrate 71 in the vertical direction. Figure 9 The deformation direction shown is the sensitive direction of the sensitive grid of the strain gauge 72.

[0046] The spring piece 74 is in an "S" shape, and the front and rear surfaces of the spring piece 74 are both planes parallel to the front surface of the substrate 71. The distance between the front and rear surfaces of the spring piece 74 is equal to the maximum distance between the front and back surfaces of the substrate 71; the left and right surfaces of the spring piece 74 are both curved surfaces, and the distance between the left and right surfaces of the spring piece 74 is smaller than the distance between the front and rear surfaces of the spring piece 74. The thickness of the upper and lower ends of the substrate 71 is greater than the thickness in the middle. The mounting pieces 73 at both ends of the stress sensor 7 are respectively fixed on the heat sink 5 and the thermal insulation sleeve 6; the distance between the heat sink 5 and the thermal insulation sleeve 6 is greater than the distance between the upper and lower end surfaces of the substrate 71. Figure 8-9 As shown, the structure of the stress sensor 7 enables the substrate 71 to Figure 9 The bending deformation in the longitudinal direction shown produces the maximum expansion and contraction. However, due to the structural characteristics of the spring piece 74, the displacement deformation of the upper and lower mounting plates 73 of the stress sensor 7 in the width direction has little effect on the deformation of the substrate 71. In addition, the sensitive grid of the strain gauge 72 is sensitive to the stress changes caused by the expansion and contraction of the substrate 71 in the vertical direction. This makes the stress sensor 7 more sensitive to the deformation direction.

[0047] The front surfaces of the substrates 71 of the two stress sensors 7 are arranged parallel to the front and side surfaces of the thermal insulation sleeve 6, respectively. When the extrusion nozzle assembly is installed on the 3D printer, the front surface of the substrate 71 of one stress sensor 7 faces the positive direction of the Y-axis, and is used to detect the stress generated on the substrate 71 of the stress sensor 7 when a force in the Y-axis direction is applied to the nozzle 4. The front surface of the substrate 71 of the other stress sensor 7 faces the positive direction of the X-axis, and is used to detect the stress generated on the substrate 71 of the stress sensor 7 when a force in the X-axis direction is applied to the nozzle 4. When the nozzle 4 collides with a model while operating along the XY-axis plane, the heater 3 causes the thermal insulation sleeve 6 to misalign with the heat sink 5, thereby generating stress on the substrate 71 of the stress sensor 7. By calculating the magnitude of the change vector of the stress data from the two sensors in the XY-axis plane, the force vector acting on the nozzle 4 in the XY-axis plane can be reflected. By comparing the magnitude of the force vector acting on the nozzle 4 during normal operation with the magnitude of the force vector acting on the nozzle 4, it can be determined whether the nozzle 4 has collided with an obstacle such as a model.

[0048] The extruder 1 is provided with a motor 8 for driving it to extrude consumables; the motor 8 is provided with a sheet metal frame 9; the sheet metal frame 9 is provided with a model cooling fan 10; the model cooling fan 10 is provided with an air guide nozzle 101; the outlet of the air guide nozzle 101 is arranged toward the nozzle 4 and the printing platform.

[0049] The insulation sleeve 6 is made of porous ceramic insulation material. The sidewalls of the insulation sleeve 6 are connected to the air guide nozzle 101 via a fixing plate. The inner wall of the insulation sleeve 6 engages with the heater 3 via flanges at its upper and lower ends. An annular hollow area is defined between the inner wall of the insulation sleeve 6 and the outer wall of the heater 3, enhancing the insulation effect.

[0050] The extruder 1 includes a filament material input port and an extrusion port. The extruder 1 is an extruder for an FDM 3D printer, such as a double-gear extruder, which is commercially available and belongs to the prior art and will not be described in detail here.

[0051] A heating wire and a thermocouple temperature sensor are provided in the heating body 3. The heating wire and the thermocouple temperature sensor are connected to the main controller signal through a driving circuit.

[0052] The electrodes of the strain gauge 72 are electrically connected to the main controller of the 3D printer via a Wheatstone bridge.

[0053] The extrusion nozzle assembly further includes a cooling fan 11 for accelerating heat dissipation from the heat sink 5. The heat sink 5 is provided with cooling fins, and the cooling fan 11 is disposed on the side of the extruder 1, with the air outlet of the cooling fan 11 facing the gaps between the cooling fins, thereby enhancing the heat dissipation effect.

[0054] Example 2

[0055] This embodiment describes a method for controlling the extrusion nozzle assembly of the 3D printer of Embodiment 1 in the 3D printer, including the following steps:

[0056] 1) When the 3D printer is just started, the printing platform is first lowered to the lowest zero position, and the main controller reads the initial values ​​of the stress sensor 7 in the X-axis direction and the stress sensor 7 in the Y-axis direction and stores the initial values, which are respectively recorded as X base , Y base ;

[0057] 2) During the working process of the 3D printer, the main controller periodically reads the current values ​​of the stress sensor 7 in the X-axis direction and the stress sensor 7 in the Y-axis direction, which are recorded as X and Y respectively. c , Y c , substitute the following formula to calculate A c ,

[0058] 3) When A c>A set When the 3D printer stops printing and lowers the printing platform to the lowest zero position; A set To set the threshold, A set According to the normal printing process of the 3D printer c The maximum value depends on A set >(A during normal printing of the model c maximum value).

[0059] When used specifically, A set A collected by the user during the normal printing process of the 3D printer c The maximum value depends on the value of A. max , A set =w*A max , w>1, w is adjusted according to the required collision sensitivity.

[0060] The above control method can prevent the hardware and precision damage of the 3D printer caused by accidental nozzle collision to the greatest extent after starting the 3D printer.

[0061] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

[0062] Various changes and modifications will undoubtedly become apparent to those skilled in the art upon reading the foregoing description. Therefore, the appended claims should be construed to encompass all changes and modifications within the true intent and scope of the present invention. Any and all equivalents within the scope of the claims should be considered to be within the intent and scope of the present invention.

Claims

1. An extrusion nozzle assembly for a 3D printer, comprising an extruder (1), a throat (2) and a heating body (3); a hot melt cavity is provided in the heating body (3); one end of the throat (2) is connected to the output end of the extruder (1), and the other end is connected to the hot melt cavity of the heating body (3); a nozzle (4) is provided on the heating body (3) and is connected to the hot melt cavity, characterized in that: The extrusion nozzle assembly further comprises a heat sink (5) and a heat insulating sleeve (6); the heat sink (5) cooperates with the throat (2) for dissipating heat from the throat (2); the heat insulating sleeve (6) cooperates with the heating body (3) for thermal insulation of the heating body (3); the extrusion nozzle assembly further comprises at least one stress sensor (7); the stress sensor (7) comprises a substrate (71) and a strain gauge (72); the strain gauge (72) is adhered to the surface of the substrate (71); mounting pieces (73) are provided on the upper and lower sides of the substrate (71); the substrate (71) and the mounting piece (73) are connected by at least one spring piece (74); the substrate (71) The front surface is a plane, and the back surface is a concave surface; the strain gauge (72) is pasted on the front surface of the substrate (71), and the sensitive grid of the strain gauge (72) is sensitive to the stress change caused by the expansion and contraction of the substrate (71) in the up-down direction; the spring piece (74) is "S"-shaped, and the front and rear surfaces of the spring piece (74) are both planes parallel to the front surface of the substrate (71), and the distance between the front and rear surfaces of the spring piece (74) is equal to the maximum distance between the front and rear surfaces of the substrate (71); the left and right surfaces of the spring piece (74) are both curved surfaces, and the distance between the left and right surfaces of the spring piece (74) is smaller than the distance between the front and rear surfaces of the spring piece (74); the thickness of the upper and lower ends of the substrate (71) is greater than the thickness in the middle; The mounting pieces (73) at both ends of the stress sensor (7) are fixed to the heat sink (5) and the heat insulation sleeve (6) respectively; when the nozzle (4) collides with the model on the printing platform after the 3D printer is started, or when the wrong nozzle coordinates cause the nozzle (4) to collide with the unfinished model on the printing platform when the power is cut off and the printing is resumed, the further action of the 3D printer is stopped according to the feedback of the stress sensor (7).

2. The extrusion nozzle assembly of a 3D printer according to claim 1, characterized in that: The extrusion nozzle assembly comprises two stress sensors (7), and the front surfaces of the substrates (71) of the two stress sensors (7) are respectively arranged parallel to the front surface and the side surface of the heat insulation sleeve (6); when the extrusion nozzle assembly is installed on the 3D printer, the front surface of the substrate (71) of one stress sensor (7) faces the positive direction of the Y axis, and is used to detect the stress generated on the substrate (71) of the stress sensor (7) when a force in the Y axis direction is applied to the nozzle (4); the front surface of the substrate (71) of the other stress sensor (7) faces the positive direction of the X axis, and is used to detect the stress generated on the substrate (71) of the stress sensor (7) when a force in the X axis direction is applied to the nozzle (4).

3. The extrusion nozzle assembly of a 3D printer according to claim 2, characterized in that: The extruder (1) is provided with a motor (8) for driving the extruder to extrude consumables; the motor (8) is provided with a sheet metal frame (9); the sheet metal frame (9) is provided with a model cooling fan (10); the model cooling fan (10) is provided with an air guide nozzle (101); the outlet of the air guide nozzle (101) is arranged toward the nozzle (4) and the printing platform.

4. The extrusion nozzle assembly of a 3D printer according to claim 3, characterized in that: The heat-insulating sleeve (6) is made of a heat-insulating material, and the side wall of the heat-insulating sleeve (6) is connected to the air guide nozzle (101) via a fixing plate; a heating wire and a thermocouple temperature sensor are provided in the heating body (3); the heating wire and the thermocouple temperature sensor are connected to the main controller signal via a driving circuit; and the electrodes of the strain gauge (72) are electrically connected to the main controller of the 3D printer via a Wheatstone bridge.

5. The extrusion nozzle assembly of a 3D printer according to claim 4, characterized in that: The extrusion nozzle assembly further includes a cooling fan (11) for accelerating the heat dissipation of the heat sink (5); the heat sink (5) is provided with cooling fins, and the cooling fan (11) is arranged on the side of the extruder (1), and the air outlet of the cooling fan (11) is directly opposite the gap between the cooling fins.

6. A method for controlling the extrusion nozzle assembly of a 3D printer according to any one of claims 2 to 5, comprising the following steps: 1) After the 3D printer is started, the printing platform is first lowered to the lowest zero position, and the main controller reads the initial values ​​of the stress sensor (7) in the X-axis direction and the stress sensor (7) in the Y-axis direction and stores the initial values, which are respectively recorded as X base ,Y base ; 2) During the working process of the 3D printer, the main controller periodically reads the current values ​​of the stress sensor (7) in the X-axis direction and the stress sensor (7) in the Y-axis direction, which are respectively recorded as X c ,Y c , substitute the following formula to calculate A c , 3) When A c >A set When the 3D printer stops printing and lowers the printing platform to the lowest zero position; A set To set the threshold, A set According to the normal printing process of the 3D printer c The maximum value depends on A set >A during normal printing of the model c Maximum value.

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