Three-dimensional printing head with stirring needle cold end sealing structure

Abstract

The invention discloses a three-dimensional printing head with a stirring needle cold end sealing structure, and belongs to the field of mechanical structures. The main body structure comprises a heat dissipation body, a heating block, a temperature difference sleeve and a heat insulation sealing gasket. According to the assembly relation, the heat dissipation body with the material through holes is communicated with the heating block through the throat pipes; the upper end of the temperature difference sleeve is inserted into the middle hole of the radiator, and the lower end of the temperature difference sleeve is inserted into the middle hole of the heating block; the motor is fixed to the top of the heat dissipation body, and a motor shaft drives the stirring needle to rotate in the forward direction and the reverse direction. The stirring needle penetrates through an inner hole of the temperature difference sleeve, then penetrates through a hole in the middle of the heating block and extends into the public melt cavity and the nozzle, the upper end of the temperature difference sleeve is a heat conduction contact end, and a gap between the lower end of the temperature difference sleeve and the middle hole of the heating block is sealed by a heat insulation sealing gasket; and the method can be widely applied to the technical field of color mixing type FDM-3D printing.

Description

Technical Field

[0001] The present invention belongs to the field of mechanical manufacturing, and more precisely, it is a special sealing structure for a stirring needle specifically used in an FDM-3D printer. Background Art

[0002] The present invention is directed to FDM-3D printing technology: specifically, Fused Deposition Modeling (FDM). Rapid prototyping Method, abbreviated as FDM.

[0003] The basic structure and operating principle of an FDM-3D printer are described as follows:

[0004] It mainly includes a feeding mechanism, a mechanical stage for carrying the extruder for 2D or 3D movement (horizontal X-axis and Y-axis movement and vertical Z-axis drive), or the extruder remains stationary in the (Z-axis direction), and the movement in the Z-axis direction is completed by the lifting of an independent workbench; currently, the 3D mechanical systems for driving and addressing the extruder in FDM-3D printers are divided into: a robotic arm 3D displacement system, a belt or lead screw-driven (X, Y-axis) 2D mechanical transmission + (Z-axis) lifting workbench system, a vertical 3 lead screw-driven (commonly known as the "る method") displacement drive system using a connecting rod to connect the extruder platform, etc. There is also a structural housing for maintaining the above-mentioned moving components; there is also an electronic control system for supporting the movement of the mechanical system. The working conditions are as follows: Under the control of the electronic system, according to the cross-sectional profile information of the product part, the extruder makes X-Y plane movement, and the workbench adjusts its height. At the start of printing, the workbench plane is located at the nozzle position of the hot melt nozzle. The thermoplastic filamentous material is sent to the hot melt nozzle by the wire feeding mechanism, heated and melted into a semi-liquid state in the nozzle, and then extruded out, selectively coated on the workbench, and quickly cooled to form a thin slice profile about 0.1 - 8 mm thick. After one layer of cross-section forming is completed, the workbench descends a certain height, and then the next layer of cladding is carried out, as if "drawing" the cross-section and profile layer by layer. In this way, a three-dimensional product part is finally formed.

[0005] The structural details are as follows: the extruder is the core component of FDM rapid prototyping technology, and the components of the extruder include the feeder part (also called wire feeder, pusher, etc.) and the extrusion nozzle part: throat, heating metal body, heating rod and temperature sensor and other components. Most of them use heating rod to heat the metal block, squeeze the plastic wire through the inlet end of the throat, and then guide it through the throat to reach the heating part of the metal block to melt and then enter the nozzle area. The melted plastic wire is under the action of the subsequent wire feeding (piston) pressure. Extruded from the nozzle and squeezed onto the printing table. The throat of the extruder is made of stainless steel to reduce its thermal conductivity. Some stainless steel throats are lined with Teflon. Due to the long-term heating and printing of the extruder, the temperature inside the throat rises, causing the material inside the tube to be in a molten state. When the printing stops and the cooling is done, the material will stick to the tube. The next time the machine is restarted to print, the sticky material inside the tube cannot melt immediately, causing the throat to be blocked. The throat is lined with Teflon so that the material inside the throat will not melt and stick, which can greatly improve the plugging problem. At the same time, the author adds a heat sink and a fan to the extruder, mainly to reduce the temperature of the upper part of the throat, prevent plugging problems, and also dissipate heat for the extruder. The heated and melted plastic filament is squeezed from the nozzle onto the printing table. If you want to reduce the plastic from warping and shrinking due to a sudden drop in temperature, you can use a hot bed printing table. There are four common types of nozzle diameters at the bottom of the extruder: 0.2mm, 0.3mm, 0.4mm, and 0.5mm. The most widely used nozzle on the market is 0.4mm. After selecting the nozzle diameter, you must also set the corresponding parameters in the software during printing, such as the print layer height and print speed in the slicing software, to achieve higher printing quality and accuracy.

[0006] The circuit part includes: The circuit part includes: The role of the 3D printer circuit part in the printer is to control the coordinated, orderly and complete operation of the entire printing process. Modify some parameters in the firmware as needed to meet the printing requirements.

[0007] At present, the color mixing technology of FDM-3D printing technology still has defects: for the sealing problem of the stirring needle under a simple structure, the high-temperature fluororubber rubber ring is also difficult to last long. Although the ball head seal has excellent temperature resistance and durability, it is difficult to obtain good continuous sealing under actual wear and vibration. A more reliable sealing structure is needed to make significant progress in the problem of color mixing and sealing. [Summary of the invention]

[0008] The purpose of the present invention is to solve the problem of thermal balance sealing structure of a stirring needle of an FDM-3D printer under a simple structure.

[0009] Features of the present invention: It is a kind of low-temperature pipeline based on a cold base to reduce the temperature of the molten material, which can neither prevent the rotation of the stirring needle nor have a compact structure. Summary of the invention:

[0011] The main structure of the 3D printing head corresponding to the cold-end sealing structure of the stirring needle of the 3D printing head of the present invention includes: a heat sink, a heating block, a temperature difference sleeve, and a heat-insulating gasket; Assembly relationship: The heat sink with a material passage hole is connected to the heating block through multiple throat pipes. Similarly, the temperature difference sleeve is made of metal material, and the heat-conducting contact end of the temperature difference sleeve is tightly fitted and connected to the corresponding middle hole of the heat sink, aiming to facilitate good heat dissipation. The tight-fitting methods include welding, bonding, interference fit, and spiral (spiral fit of screw and nut) fit; The lower end of the temperature difference sleeve and the middle hole of the heating block (3) are hermetically connected through a heat-insulating gasket with poor heat conduction. The heat-insulating gasket has a certain tightness and strength to withstand the pressure of the internal molten material, so as to avoid overflow of materials and excessive heat conduction; The shaft of the motor is connected to the stirring needle to drive the stirring needle to rotate forward and backward, but does not restrict the axial displacement of the stirring needle; The pushing screw at the tip of the stirring needle cooperates with the inner hole of the nozzle. When rotating forward and backward, it will boost the flow direction of the molten material, respectively boosting the discharge or back-drawing of the molten material. The sealing ball head part (under the thrust of the spring) is pressure-fitted with the inner conical surface of the temperature difference sleeve and has the characteristic of self-running-in; The spring applies an upward axial thrust by pushing the retaining ring fixedly connected to the motor (extended) shaft; However, the sealing ball head part is an optional structure. Another way is not to make the sealing ball head structure, nor to make the inner conical surface structure of the temperature difference sleeve, and thus there is no need for a spring, becoming a simple column and shaft tube fit. It only depends on the cold-end sealing structure of the stirring needle of the present invention;

[0012] In detail: The heating rod can be pressed by the pressing piece and closely attached to the bottom of the heating block or inserted into the prefabricated hole of the heating block for power-on heating of the heating block; Each material wire inlet hole of the heating block serves as a material passage connecting each throat pipe. The end of the material passage of the heating block is processed with a material outlet hole leading to the common molten material cavity (multiple color materials correspond to multiple outlet holes); The conduit inside the heat sink is connected between the lock nozzle screw hole fixed on the upper part of the heat sink and the corresponding hole of the throat pipe at the lower part of the heat sink, playing the role of transmitting the material wire; The Teflon guide hose starts from the lower end of the lock nozzle and ends at the bottom of the sub-molten material cavity on the heating block (the sub-molten material cavity is located at the part of the molten material cavity outside the end of the throat pipe), playing the role of sealing and smoothing the material wire; When the material wire is pushed by the pusher (or feeder), after passing through the lock nozzle, (radiator) conduit, and throat pipe, it enters the material wire inlet hole of the heating block, is melted in each sub-molten material cavity, and then enters the common molten material cavity; Finally, the stirring needle stirs the molten materials converged from all paths. The thread at the front end of the stirring needle is an optional structure. In the case of having a thread, rotating forward or backward can boost the ejection of the material or boost the recovery of the material (commonly known as back-drawing in the industry).

[0013] Brief description of the principle of the cold-end seal of the stirring needle in the present invention: Due to the heat dissipation of the heat sink, the temperature of the temperature difference sleeve decreases from bottom to top, that is, the temperature at the sealing conical surface in contact with the sealing ball head of the stirring needle is relatively high; the uppermost end of the temperature difference sleeve is tightly fitted into the central hole at the bottom of the heat sink, and the heat will be transferred out and the temperature will decrease. Since the temperature of the temperature difference sleeve decreases from bottom to top, a temperature gradient from bottom to top is generated. If there is overflow between the sealing ball head of the stirring needle and the sealing conical surface, the overflow will flow along the gap between the stirring needle and the inner wall of the temperature difference sleeve. However, as the temperature decreases, the viscosity of the molten material will increase, achieving the purpose of preventing material leakage.

[0014] Furthermore, the motor can also be placed inside the heat sink, exactly creating space at the central part of the heat sink, which is beneficial for reducing the external volume.

[0015] Furthermore, the Teflon guide hose, as an optional component, is selectively used. It can be completely replaced by processing a coating (such as Teflon) on the inner walls of the conduit and the throat tube, so that the Teflon guide hose is not used.

[0016] Advantages of the present invention:

[0017] For the first time, a sealing structure that utilizes the temperature gradient, has low cost, is durable and simple, and has a small volume is developed. [Description of the Drawings]

[0018] Figure 1 Schematic diagram of a 3D printing head with a cold-end seal structure of the stirring needle.

[0019] Figure 2 Cross-sectional view of a 3D printing head with a cold-end seal structure of the stirring needle.

[0020] Figure 3 Exploded schematic diagram of a 3D printing head with a cold-end seal structure of the stirring needle.

[0021] Figure 4 Schematic diagram of the connection between the temperature difference sleeve, the heat sink and the heating block.

[0022] Figure 5 Partial cross-sectional schematic diagram of the temperature difference sleeve, the heat sink and the heating block.

[0023] Annotation of the attached drawings:

[0024] 1 Throat tube

[0025] 2 Heat sink

[0026] 3 Heating block

[0027] 3-1 Common molten material cavity

[0028] 3-2 Filament inlet hole

[0029] 3-3 Material Passing Channel

[0030] 3-4 Melt Discharge Hole

[0031] 3-5 Melt Separation Chamber

[0032] 3-6 Stirring Needle Insertion Hole

[0033] 4 Temperature Difference Sleeve

[0034] 4-1 Heat Conducting Contact End

[0035] 4-2 Heat Insulating Contact End

[0036] 5 Heat Insulating Sealing Pad

[0037] 6 Motor

[0038] 7 Motor Shaft

[0039] 8 Stirring Needle

[0040] 8-1 Pushing Screw

[0041] 8-2 Sealing Ball Head

[0042] 9 Spring

[0043] 10 End Face Bearing

[0044] 11 Heating Rod

[0045] 12 Nozzle

[0046] 13 Retaining Ring

[0047] 14 Conduit

[0048] 15 Teflon Feeding Hose

[0049] 16 Nozzle Lock

[0050] 17 Fixing Screw

[0051] 18 Feed Wire

[0052] 19 Pressing Plate

[0053] 20 Motor Mounting Base

[0054] 21 Upper Heat Dissipation Body

[0055] 22 Heat Shield

[0056] 23 Heating Rod Lead

[0057] 24 Teflon Hose

[0058] 25 Spray Hole

[0059] [Implementation Case]

[0060] The following further describes the present invention with reference to the accompanying drawings in connection with the preferred embodiments:

[0061] As Figure 1 , Figure 2 , Figure 3 , Figure 4 shown:

[0062] The main structure of a three-dimensional printing head with a cold-end sealing structure for a stirring needle includes: a heat sink (2), a heating block (3), a thermocouple sleeve (4), etc.; a throat tube (1), a fixing screw (17), and a thermocouple sleeve (4) are connected between the heat sink (2) and the heating block (3); the heat-conducting contact end (4-1) of the thermocouple sleeve (4) is tightly fitted into the corresponding hole of the heat sink (2) (which is beneficial for good heat dissipation), while the outer wall of the heat-insulating contact end (4-2) of the thermocouple sleeve (4) is hermetically connected to the inner wall of the stirring needle insertion hole (3-6) (or the so-called middle hole) of the heating block (3) through a heat-insulating gasket (5) with poor heat conductivity (such as fluororubber) (the heat-insulating gasket has a certain tightness to withstand the pressure of the internal molten material to prevent excessive heat transfer from the heating block); the motor (6) fixed on the motor fixing seat (20) is connected to the stirring needle through a shaft (which can be a long needle integrated with the motor shaft), driving the stirring needle to rotate forward and backward, but not restricting the axial displacement of the stirring needle; the material-pushing spiral (8-1) part of the stirring needle (8) is inserted and matched with the inner hole of the nozzle (12) (when rotating forward and backward, it is respectively matched with the discharge or back-drawing of the molten material) until it approaches the spray hole (25). The sealing ball head (8-2) part is in sealing cooperation with the inner wall sealing cone surface of the thermocouple sleeve (4) and has the characteristic of self-running-in; the spring (9) applies an upward axial thrust to the retaining ring (13) fixedly connected to the motor shaft (7) through the push-up end face bearing (10) to provide the sealing pressure between the sealing ball head of the stirring needle and the inner wall sealing cone surface of the thermocouple sleeve (4); the heating rod (11) connected to the heating rod lead (23) is pressed tightly against the bottom of the heating block (3) by a pressing piece for heating; the material wire inlet hole (3-2) of the heating block (3) serves as a material passing channel (3-3) to connect the throat tube (1), and a molten material outlet hole (3-4) leading to the common molten material cavity (3-1) is processed at the end of the material passing channel (3-3) (5 color materials correspond to 5 outlet holes); the conduit (14) inside the heat sink (2) is connected between the screw hole of the nozzle (16) of the upper heat sink (21) fixed on the heat sink (2) and the corresponding hole of the throat tube at the lower part of the heat sink (2), playing the role of conveying the material wire (18); the Teflon guide hose (15) starts from the lower end of the nozzle (16) and ends at the bottom of the sub-molten material cavity (3-5) on the heating block, playing the role of sealing and smoothing the material wire; the heat shield (22) is made of heat-insulating material to prevent the heat of the heating block from overflowing. The Teflon hose (24) is respectively inserted into the nozzle and the conduit (14) until each sub-molten material cavity (3-5).

[0063] In particular Figure 4 As shown: The temperature of the temperature difference sleeve (4) is lower towards the upper part, that is, the temperature at the sealing conical surface in contact with the sealing ball head (8-2) of the stirring needle is relatively high; the uppermost end of the temperature difference sleeve (4) is tightly fitted into the central hole at the bottom of the heat sink (2), and the heat will be transferred out and the temperature will decrease. Since the temperature of the temperature difference sleeve (4) is lower towards the upper part, a temperature drop gradient from bottom to top is generated. If there is overflow between the sealing ball head (8-2) of the stirring needle and the sealing conical surface, the overflow material will flow along the gap between the stirring needle and the inner wall of the temperature difference sleeve (4). However, as the temperature drops, the viscosity of the molten material will increase more and more, thereby generating a greater viscous resistance, and the purpose of preventing material leakage is achieved.

[0064] As Figure 5 shown:

[0065] To further elaborate on the anti-overflow principle of the present invention: First, a necessary condition requires that the heat-conducting contact end (4-1) at the upper end of the temperature difference sleeve be tightly fitted to the heat sink (2); while the heat-insulating contact end (4-2) at the lower end of the temperature difference sleeve should be as adiabatic as possible from the heating block (3), that is, through the heat-insulating gasket (5) in the gap (in this figure, an annular heat-insulating gasket (ring) is used); in this way, a temperature difference is generated on the temperature difference sleeve. The lower end of the temperature difference sleeve is closer to the heating block (3) and thus has a higher temperature, and the upper end of the temperature difference sleeve is closer to the heat sink (2) and thus has a lower temperature; in actual use, the temperature of the heating block (3) is between 200 - 400 degrees, and the heat sink (2) after air cooling is between 60 - 90 degrees; thus, the temperature of the temperature difference sleeve from top to bottom often ranges between 100 degrees and 200 degrees. The sealing ball head (8-2) of the stirring needle (8) also plays an auxiliary sealing role due to the pressure.

Claims

1. Three-dimensional printing head with a cold-end sealing structure for a stirring needle, the main structure comprising: Heat sink, heating block, temperature difference sleeve, heat insulation gasket; Assembly relationship: The heat sink with a material passing hole is connected to the heating block through multiple throat pipes; The upper end of the temperature difference sleeve is inserted into the middle hole of the heat sink, and the lower end of the temperature difference sleeve is inserted into the middle hole of the heating block; The motor is fixed on the top of the heat sink or placed inside the heat sink, and the motor shaft drives the stirring needle to rotate forward and backward; After passing through the inner hole of the temperature difference sleeve, the stirring needle passes through the hole in the middle of the heating block and extends into the common melting cavity and the nozzle; The heating rod is tightly attached to the bottom of the heating block or inserted into the prefabricated hole of the heating block for heating; The material wire inlet hole of the heating block serves as a material passing channel to connect the throat pipe, and a material melting outlet hole leading to the common melting cavity is processed at the end of the material passing channel; The conduit inside the heat sink is connected between the lock nozzle screw hole fixed on the upper part of the heat sink and the corresponding hole of the throat pipe at the lower part of the heat sink, playing the role of conveying the material wire; The Teflon guide hose can be not used as an optional component, starting from the lower end of the lock nozzle and ending at the bottom of the sub-melting cavity on the heating block; Each color material wire is inserted into the feeding hole at the top of the heat sink, passes through the guide pipeline and then through the material wire inlet hole of the heating block, melts in the sub-melting cavity, passes through the material passing channel, and finally enters the common melting cavity through the material melting outlet hole; The position of the sealing ball head is in pressure fit with the inner conical surface of the temperature difference sleeve under the thrust of the spring and has the characteristic of self-running-in; The spring applies an upward axial thrust by pushing the retaining ring fixedly connected to the extended shaft of the motor; However, the position of the sealing ball head is an optional structure. Another way is not to make the sealing ball head structure and not to make the inner conical surface structure of the temperature difference sleeve, so the spring is not needed, and it becomes a simple fit between the column and the shaft tube, relying solely on the cold end sealing structure of the stirring needle of the present invention; Its characteristic lies in that: The material of the temperature difference sleeve of the 3D printing head is a metal material. The upper end of the temperature difference sleeve is a heat-conducting contact end, tightly fitted and connected to the corresponding middle hole of the heat sink. The tight fitting methods include welding, bonding, interference fit, and screw fit; The gap between the lower end of the temperature difference sleeve and the middle hole of the heating block is sealed by an adiabatic heat insulation gasket; The principle of the cold end seal of the stirring needle is as follows: Due to the heat dissipation of the heat sink, the temperature of the temperature difference sleeve becomes lower and lower upwards, that is, the temperature at the sealing conical surface in contact with the sealing ball head part of the stirring needle is relatively high; The uppermost end of the temperature difference sleeve is tightly fitted to the central hole at the bottom of the heat sink, and the heat will be conducted out and the temperature will decrease. Since the temperature of the temperature difference sleeve becomes lower and lower upwards, a temperature drop gradient from bottom to top is generated. If there is overflow of the material between the sealing ball head part of the stirring needle and the sealing conical surface, the overflow material will flow along the gap between the stirring needle and the inner wall of the temperature difference sleeve. However, as the temperature decreases, the viscosity of the molten material will increase more and more, achieving the purpose of preventing material leakage.

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