CN113665100B - Co-rotating conical double-screw fused deposition modeling extrusion type 3D printing nozzle - Google Patents

Abstract

The present invention provides a co-rotating conical twin-screw fused deposition molding extrusion type 3D printing nozzle, which mainly includes a driving mechanism connected in sequence, a transmission mechanism and a screw extrusion mechanism, and the screw extrusion mechanism includes a co-rotating Conical twin-screw assembly, barrel and extrusion head; this device is mainly aimed at two or more raw material components with relatively high content, and can be directly added to the co-rotating Conical twin-screw fused deposition modeling extrusion 3D printing nozzles are used for FDM printing to form parts, so as to avoid damage to the performance of parts caused by multiple processing of raw materials (twin-screw blending, single-screw extrusion, 3D printing) At the same time, the pretreatment process of printing materials is omitted, which greatly improves the production efficiency.

Description

A co-rotating conical twin-screw fused deposition molding extrusion 3D printing nozzle

technical field

The invention belongs to the technical field of 3D printing devices, and in particular relates to a co-rotating conical twin-screw fused deposition molding extrusion type 3D printing nozzle, which can be applied to the technical field of fused deposition molding 3D printing.

Background technique

3D printing is a manufacturing method that is increasingly valued by the scientific and engineering community. It is based on digital model files, using powdered metal or plastic and other bondable materials to construct objects by stacking and accumulating layer by layer. Technology. This technology is widely used in industrial design, aerospace, automobile manufacturing and many other fields. Fused deposition modeling (FDM) is one of the most common technologies in the field of 3D printing. The working principle of traditional FDM printers is: the filaments made of thermoplastic polymers such as ABS and PLA are used as printing consumables after being sized and sent to the printer through rollers. It enters the heating zone of the nozzle for melting, and the unmelted wire above acts as a plunger to push the molten material, extruding it from the nozzle, and depositing it layer by layer on the build plate to form a three-dimensional structure. FDM printing technology has many advantages, such as simple operation, low material cost, safe manufacturing environment, etc.

At present, most of the traditional FDM printers are printed by conveying wire materials. This kind of printer has the following disadvantages: it has high requirements on the fluidity, shrinkage and strength of the material, resulting in very limited materials for traditional FDM printers. Commonly used are only PLA, ABS, etc.; the polymer filament near the heating zone is softened due to heat transfer, and for materials with poor stiffness, a certain thrust cannot be applied to extrude the molten material, so it cannot be used for FDM molding; and the filament The required filament preparation process increases raw material costs.

In view of these problems existing in the traditional FDM technology, some researchers have proposed an improved technical scheme of using pellets or powder instead of printing filaments based on the technical principles and characteristics of FDM printing. For example, by improving the nozzle of the FDM printer and adopting the technical principle of single-screw extrusion inside the nozzle, a smooth extrusion effect can be achieved for pellets or powder. However, it still has the following disadvantages: because the extrusion screw generally adopts an ordinary straight screw structure, the plasticizing effect on plastic pellets or powders that require a large compression ratio is poor; in order to ensure the transportation, melting and homogenization of materials , the screw requires a larger aspect ratio (usually 25 to 30), which will lead to an increase in the length of the screw and increase the overall size and weight of the extrusion equipment; the material is directly extruded after being plasticized in the extrusion screw At this time, the material will maintain the spiral movement in the barrel due to inertia, which will easily cause the deformation of the printed part and reduce the accuracy of the shape and size of the printed part.

The inventor of the present invention has previously authorized a patent "a conical screw extrusion equipment suitable for FDM printers" (application number 201620058778.2) discloses a conical single-screw extrusion equipment suitable for FDM printers, which uses The conical screw structure greatly reduces the required aspect ratio and improves the plasticizing effect through the conical structure, which is suitable for plastic pellets or powders that require a large compression ratio. However, the inventors of the present invention have found through long-term application and practice that the above-mentioned patented equipment still relies on the friction between the screw and the barrel for conveying materials, and the printing effect is very poor when using powder materials as raw materials, and pellets are usually used as raw materials. For composite materials and mixtures, the preparation of pellets usually requires a process such as twin-screw extruder mixing and granulation. The processing procedure is still relatively cumbersome. The problem of loss.

In addition, there are also inventions similar to screw extrusion FDM printing nozzles in the prior art. For example, the Chinese invention patent application "A Twin-screw Material Extrusion Device for 3D Printing" (application number 201911158971.8) discloses a 3D The twin-screw material extruding device for printing, its structure is mainly that the driving screw and the driven screw are arranged in the melting shell and meshed with each other, the two screws are connected by a synchronous transmission mechanism, and the driving screw and the driven screw are adjacent to the thrust bearing There is a thrust transmission mechanism between them. Through the above-mentioned structure, it realizes the applicability of the powder as a raw material, and can add various auxiliary agents to the main material to carry out extrusion printing together.

With the advancement of material science research, single polymer parts can no longer meet the high performance and functional requirements, while composite parts filled with mixed materials or high content fillers have better mechanical properties and functional properties, but This kind of material is usually composed of two or more components with relatively high content, which is very different from the process condition characteristics of additives that only need to be added in a small amount. Therefore, the preparation of such materials usually adopts a processing process such as twin-screw extruder mixing and granulation to ensure sufficient melt blending or uniform dispersion. However, when it is applied to fused deposition modeling 3D printing raw materials, Because of the characteristics of secondary melt blending caused by FDM technology, it is easy to damage the mechanical properties and functional properties of this type of material, thus affecting the performance of 3D printed parts.

Contents of the invention

In order to solve the above-mentioned problems in the background technology, the present invention provides a co-rotating conical twin-screw fused deposition molding extrusion 3D printing nozzle, which is mainly aimed at two or more raw material components with relatively high content, It can be directly added to the co-rotating conical twin-screw fused deposition molding extrusion type 3D printing nozzle of the present invention to carry out FDM printing and forming parts without the pretreatment process steps of melt blending, thereby avoiding multiple processing of raw materials (twin-screw Blending, single-screw extrusion, 3D printing), the performance of the part is damaged, and the pretreatment process of printing raw materials is omitted, which greatly improves the production efficiency.

In order to achieve the above object, the present invention is realized by adopting the technical solution consisting of the following technical measures.

A co-rotating conical twin-screw fused deposition molding extrusion type 3D printing nozzle mainly includes a driving mechanism connected in sequence, a transmission mechanism and a screw extrusion mechanism, and the screw extrusion mechanism includes a co-rotating conical twin-screw components, barrels and extrusion heads,

The conical twin-screw assembly that rotates in the same direction includes two conical screws that rotate in the same direction. The conical screw includes a threaded section and a connecting section. The connecting section is connected to the transmission mechanism. The length of the threaded section is 85-95mm. The inner diameter of the screw in the threaded section changes linearly from 9.6-9.8mm at the feed end to 4.9-5.1mm at the discharge end, and the depth of the screw groove of the threaded section also changes linearly from 6.4-6.6mm at the feed end to 1.8-2.0mm at the discharge end. mm, the pitch is 6-7mm, the width of the flight is 0.8-1.2mm, and the overall structure is tapered;

The two conical screws rotating in the same direction are in clearance fit, and the angle between the axis lines of the screws is 5-7°;

The inner cavity of the barrel is a "∞"-shaped channel, which is in clearance fit with the co-rotating conical twin-screw assembly, and the barrel is provided with a feeding port;

The extrusion head is fixedly connected with the discharge end of the barrel.

The main inventive point of the present invention is that for two or more raw material components with relatively high content, they can be directly added to the co-rotating conical twin-screw of the present invention without the process steps of twin-screw melt blending and single-screw extrusion. The fused deposition modeling extrusion 3D printing nozzle performs FDM printing to form parts, so as to avoid the performance damage defects caused by multiple processing of raw materials, and at the same time omit the pretreatment process, which greatly improves the production efficiency.

In order to achieve the above purpose, the inventors of the present invention combined the results of computer virtual simulation and actual production experience, and by limiting the co-rotation mode of the twin-screw assembly, the meshing part has a strong shearing effect on the mixed material when the twin-screws rotate in the same direction. The technical principle greatly enhances the screw's ability to melt and mix materials. At the same time, through the combination of six sets of process parameters including the length of the thread section, the linear change of the inner diameter of the screw and the depth of the screw groove, the screw pitch, the screw edge and the angle between the twin-screw axis line in the twin-screw assembly, the combination of the mixed material in the twin-screw assembly is guaranteed. The threaded segments are capable of adequate melt blending.

Further, in order to ensure that the mixed materials can be fully melt-blended in the co-rotating conical twin-screw assembly, the screw speed of the co-rotating conical twin-screw assembly is 10-30r/min; at the same time, those skilled in the art according to It can be known from common knowledge that the greater the screw torque, the stronger the shearing force on the material, and when targeting two or more high-content raw material components, it is necessary to ensure that a certain shearing force intensity can be ensured so that multiple groups The raw materials are melted and blended smoothly, but the screw torque is mainly determined by the output torque of the drive motor, and a high-power drive motor usually means greater equipment space and cost, and the overall stability and structure of the 3D printing nozzle are more demanding. Substantial growth. The inventor of the present invention summed up through a large number of experiments and long-term work experience. In order to better illustrate the present invention and provide a design scheme that can be used for reference and is practical, it is not aimed at the three-dimensional operation of fused deposition extrusion 3D printing. On the premise of redesigning the overall structure such as the platform, it is preferable to use a stepper motor with a maximum output torque of 2.3-2.5N·m. At this time, the melt-blending processing time of the mixed material in the thread section is about 60-120s, which basically meets the melt-blending process requirements of common multi-component mixed plastics or high-filler filled plastics on the market.

Wherein, the driving mechanism is to provide co-rotating power to the two conical screws in the co-rotating conical twin-screw assembly respectively through the transmission mechanism. Those skilled in the art can choose suitable dual driving equipment according to the existing technology. The unconnected transmission mechanism provides rotational power to the two conical screws respectively, or a single drive device is selected, and the transmission device provides rotational power to the two conical screws respectively. In order to make the two screws rotate in the same direction and have the best shear force effect at the meshing point, the selection of the above-mentioned driving mechanism needs to make the two screws have the characteristics of rotating at the same speed and with the same torque. Those skilled in the art of the transmission mechanism can also select a suitable transmission mode according to the prior art.

In order to better illustrate the present invention and provide a preferred technical solution with smaller equipment space requirements, the driving mechanism is mainly composed of a stepping motor and a motor reducer connected to it for transmission.

Based on the above preferred technical solution, the transmission mechanism is selected to adopt worm gear transmission, the transmission mechanism is mainly composed of a worm wheel and a worm, the worm is connected to the output end of the motor reducer, and the transmission section of the tapered screw is fixedly connected with a worm gear , The worm is driven from the side meshing with the worm gear. The worm drives the two worm gears to rotate at the same time, so that the twin screws rotate in the same direction at the same speed and with the same torque.

Furthermore, in order to improve the co-rotation stability of the twin screws, the transmission mechanism also includes a screw connecting shaft, the connecting section of the conical screw is fixedly connected with one end of the screw connecting shaft, and the other end of the screw connecting shaft is fixedly connected with The worm gear is driven by the worm gear meshing with the worm gear from the side. The worm drives the two worm gears to rotate at the same time, so that the twin screws can rotate in the same direction at the same speed and with the same torque through the screw connecting shaft. In actual industrial design, the screw connection shaft can also be fixed by multiple bearings to further increase the rotation stability of the twin-screw.

In addition, considering the long-term operation requirements of industrial conversion equipment, it is also possible to choose to set up a cooling water circulation channel in the transmission mechanism to reduce the heat transfer effect of the barrel and avoid overheating damage.

Wherein, in order to cooperate with the feeding end of the threaded section of the conical screw, a feeding port is provided on the side wall of the barrel, and the feeding port is located above the feeding end of the threaded section.

Generally, in order to melt and blend the mixed material in the thread section, those skilled in the art can select an appropriate heating method for raising the temperature of the barrel according to the existing technology. For better illustration and to provide a suitable technical solution, an electric heating coil is also provided on the barrel.

Generally speaking, the overall practical operation of the co-rotating conical twin-screw fused deposition molding extrusion 3D printing nozzle also includes power supply and fixing parts, etc. Those skilled in the art can choose a suitable combination according to the existing technology collocation method. In terms of overall structural design, the technical solution of the present invention is essentially aimed at the innovation of the screw extrusion mechanism and the matching drive mechanism and transmission mechanism. Other structural designs can preferably refer to the prior art, such as the inventor of the present invention who previously applied for a patent "A conical screw extrusion device suitable for FDM printers" (application number 201620058778.2).

The present invention also provides a matching 3D printing process adapted to the above co-rotating conical twin-screw fused deposition molding extrusion 3D printing nozzle, which mainly includes the following steps:

(1) According to the required ratio of raw materials, the pellets or powders of various raw materials are evenly mixed as a mixed material;

(2) Gradually pour the mixture obtained in step (1) through the feeding port of the barrel, and set the screw speed of the co-rotating conical twin-screw fused deposition molding extrusion-type 3D printing nozzle at 10-30r/min, drive The output torque of the motor is 2.3-2.5N m;

(3) Print and prepare according to the three-dimensional digital model of the required product, the printing speed is 600-4800mm/min, and the temperature of the hot bed is 40-80°C.

Generally, as described in step (1), the granules or powders of various raw materials are uniformly mixed, and as a mixed material, it is usually simple stirring and mixing so that the granules or powders of various raw materials can be mixed, for example, in the experiment Under room preparation conditions, usually put the pellets or powder in the same container, shake and mix evenly. In actual industrial production, those skilled in the art can use conventional stirring and mixing equipment in the prior art to perform mixing operations on raw materials. It is worth noting that the above-mentioned uniform mixing is usually the mixing between pellets and pellets, and between powders and powders. If you choose to mix pellets and powders, it is easy to cause uneven mixing due to the large particle size difference. , affect the mechanical properties of the actual printed parts.

Usually, the mixed material obtained in step (1) is gradually poured in through the feeding port of the barrel as described in step (2). In a preferred technical solution, the mixed material can be conveniently added by installing a hopper on the feeding port. , and the mixed material does not exceed 1/2 of the height of the hopper when the mixed material is poured in, so as to control the adding rate of the mixed material.

In order to better illustrate the present invention, and provide several specific supporting 3D printing processes adapted to the equipment of the present invention:

For fused deposition modeling 3D printing of polypropylene/hexagonal boron nitride (PP/h-BN) composite materials as printing materials, it mainly includes the following steps:

(1) taking polypropylene as a matrix, and using hexagonal boron nitride with a mass fraction of 20 to 40 wt% as a filler, mixing the powders of the above two components evenly as a mixed material;

(2) Gradually pour the mixed material obtained in step (1) through the feed port of the barrel, and set the screw speed of the corotating conical twin-screw fused deposition molding extrusion 3D printing nozzle to 20r/min, and the drive motor The output torque is 2.3N m;

(3) Print and prepare according to the three-dimensional digital model of the required product, set the printing speed to 3000mm/min, and the temperature of the hot bed to 80°C.

For fused deposition modeling 3D printing of polylactic acid/thermoplastic polyurethane (PLA/TPU) blends as printing materials, it mainly includes the following steps:

(1) taking polylactic acid polymer as the continuous phase, and thermoplastic polyurethane with a mass fraction of 10 to 50 wt% as the dispersed phase, mixing the pellets of the above two components evenly, as a mixed material;

(2) Gradually pour the mixed material obtained in step (1) through the feeding port of the barrel, and set the screw speed of the corotating conical twin-screw fused deposition molding extrusion 3D printing nozzle at 15r/min, and the driving motor The output torque is 2.3N m;

(3) Print and prepare according to the three-dimensional digital model of the required product, set the printing speed to 1800mm/min, and the temperature of the hot bed to 50°C.

Among them, in the above-mentioned specific supporting 3D printing process, the specific selection of each component in the printing raw material adopts the specific selection suitable for fused deposition modeling 3D printing disclosed in the prior art.

It can be clearly seen that using the co-rotating conical twin-screw fused deposition molding extrusion 3D printing nozzle of the present invention, when targeting two high-content mixed raw material systems, it can directly Printing the parts, so as to avoid the defects of the performance of the parts caused by the secondary melt blending of FDM technology, and at the same time omit the pretreatment process of the melt blending of printing materials, which greatly improves the production and preparation efficiency.

It is worth noting that the specific process parameters defined in the present invention are obtained based on the combination of computer virtual simulation results and actual production experience, wherein the specific parameter settings of the co-rotating conical twin-screw assembly are determined by the linearity of the inner diameter of the screw and the depth of the screw groove. The change can ensure that there is sufficient torque to provide shear force, and at the same time, the mixed material has sufficient melt extrusion time in the entire thread section. If the overall cone angle of a single screw is further increased or the angle between the axes of two screws is increased, the overall structural size and weight of the entire equipment will be affected. It greatly affects the printing accuracy, and it needs to be adapted to the drive mechanism with a larger input torque, which increases the overall cost; if the overall cone angle of a single screw is reduced or the axis angle of two screws is increased, it will significantly affect the high content Due to the melt blending effect of multi-component raw materials, especially powder materials, the printed parts are prone to defects such as interface fractures and other mechanical properties degradation.

The above-mentioned specifically defined process parameters were also obtained by the inventor of the present invention after computer virtual simulation and actual production comparison, and were further revised in actual production tests, and the limited protection scope was proposed based on experimental facts.

Instructions attached

Fig. 1 is a schematic structural view of a co-rotating conical twin-screw fused deposition molding extrusion 3D printing nozzle in Example 1 of the present invention.

Fig. 2 is a schematic structural view of a conical screw in a co-rotating conical twin-screw fused deposition molding extrusion 3D printing nozzle in Example 1 of the present invention.

3 is a schematic structural view of a driving mechanism in a co-rotating conical twin-screw fused deposition molding extrusion 3D printing nozzle according to Embodiment 1 of the present invention.

Fig. 4 is a schematic diagram of the appearance structure of a co-rotating conical twin-screw fused deposition molding extrusion 3D printing nozzle in Example 1 of the present invention.

Fig. 5 is a photo of a co-rotating conical twin-screw fused deposition molding extrusion 3D printing nozzle in Example 1 of the present invention.

Fig. 6 is a photograph of the printed product obtained in Application Example 1 of the present invention as a sample for tensile strength testing.

In the figure, 1-temperature control nozzle; 2-nozzle connector; 3-barrel; 4-conical screw A; 5-conical screw B; 6-feeding hopper; 7-barrel heat insulation layer; 8-cooling Water circulation channel; 9-axis fixed plate; 10-worm gear A; 11-worm gear B; 12-bearing fixing piece; 13-screw connecting shaft A; 14-screw connecting shaft B; 15-bearing end cover; 16-electric heating coil A; 17-electric heating coil B; 18-worm; 19-worm fixing piece; 20-drive connecting plate; 21-motor reducer; 22-stepping motor.

Detailed ways

The present invention will be further described below by way of embodiments and in conjunction with the accompanying drawings. It is worth noting that the given embodiments cannot be construed as limiting the protection scope of the present invention, and some non-essential improvements and adjustments made by those skilled in the art according to the content of the present invention should still belong to the protection scope of the present invention.

Example 1

In this embodiment, a co-rotating conical twin-screw fused deposition molding extrusion type 3D printing nozzle, as shown in Figure 1, includes a sequentially connected drive mechanism, a transmission mechanism and a screw extrusion mechanism. The screw extrusion The mechanism includes a co-rotating conical twin-screw assembly, a barrel and an extrusion head,

The corotating conical twin-screw assembly, as shown in Figure 2, includes two corotating conical screws (conical screw A and conical screw B), and the conical screw includes a threaded section and a connecting section , the connection section is connected with the transmission mechanism, the length of the thread section is 90mm, the inner diameter of the screw of the thread section is linearly changed from 9.67mm at the feed end to 5mm at the discharge end, and the groove depth of the thread section is also 6.5mm from the feed end Linearly change to 1.8mm at the discharge end, the screw pitch is 6.32mm, the screw edge width is 1mm, and the overall structure is tapered;

The two conical screws rotating in the same direction are in a clearance fit, and the angle β between the axis lines of the screws is 6°;

The inner cavity of the barrel is a "∞" shaped channel, which is matched with the conical twin-screw assembly rotating in the same direction. A hopper is provided outside the feeding port, and electric heating coils (electric heating coil A and electric heating coil B) are fixed on the outside of the barrel;

The extrusion head includes a temperature-control nozzle, and the temperature-control nozzle is fixedly connected to the discharge end of the barrel through a nozzle connector. The nozzle connector is provided with an inner cavity that communicates with the nozzle and the barrel, and the shape of the inner cavity is Extension of the shape of the barrel cavity;

The transmission mechanism includes a worm wheel (worm gear A and worm wheel B), a worm and a screw connecting shaft (screw connecting shaft A and screw connecting shaft B), and shaft fixing plates and bearing fixtures for stabilizing the two ends of the screw connecting shaft respectively, and The casing of the transmission mechanism is composed of the shaft fixing plate and the bearing fixing piece;

The connecting section of the conical screw is fixedly connected to one end of the screw connecting shaft, and is stabilized by the bearing provided on the shaft fixing plate at the fixed connection, and the other end of the screw connecting shaft is fixedly connected with a worm wheel near the end, and the worm is connected from the The side is meshed with the worm gear; the worm drives the two worm gears to rotate at the same time, so that the twin screws can rotate in the same direction at the same speed and with the same torque; The other end of the stabilizing screw connection shaft;

The shaft fixing plate is fixedly connected to the barrel, and a layer of barrel heat insulation is provided at the joint to reduce the high temperature transmission of the barrel;

The shaft fixing plate is also provided with a cooling water circulation channel to reduce the heat transfer effect of the barrel and avoid overheating damage;

A bearing end cover is also arranged on the bearing fixing part to facilitate maintenance and disassembly;

The drive mechanism, as shown in accompanying drawing 3, includes a stepper motor and a motor reducer that are connected to each other, and also includes a worm screw fixture and a drive connection plate. The stepper motor is transmitted to the drive motor reducer, and is decelerated by the motor The output shaft of the drive is transmitted to the worm, and the worm fixing part includes bearings, which play the role of stabilizing the worm, and the drive connecting plate respectively connects the worm fixing part and the motor reducer together, which acts as a flange and can also be used as a worm Bearing caps for the bearings in the fixture.

Example 2

In this embodiment, a co-rotating conical twin-screw fused deposition molding extrusion type 3D printing nozzle comprises sequentially connected drive mechanisms, transmission mechanisms and screw extrusion mechanisms, and the screw extrusion mechanisms include co-rotating conical twin-screw assembly, barrel and extrusion head,

The corotating conical twin-screw assembly, as shown in Figure 2, includes two corotating conical screws (conical screw A and conical screw B), and the conical screw includes a threaded section and a connecting section , the connection section is connected with the transmission mechanism, the length of the thread section is 85mm, the inner diameter of the screw of the thread section is linearly changed from 9.6mm at the feed end to 4.9mm at the discharge end, and the groove depth of the thread section is also 6.4mm at the feed end. The mm linearly changes to 1.8mm at the discharge end, the screw pitch is 6mm, the screw edge width is 0.8mm, and the overall structure is tapered;

The two conical screws rotating in the same direction are clearance fit, and the angle between the axis lines of the screws is 7°;

The inner cavity of the barrel is a "∞" shaped channel, which is matched with the conical twin-screw assembly rotating in the same direction. A hopper is provided outside the feeding port, and electric heating coils (electric heating coil A and electric heating coil B) are fixed on the outside of the barrel;

The extrusion head includes a temperature-control nozzle, and the temperature-control nozzle is fixedly connected to the discharge end of the barrel through a nozzle connector. The nozzle connector is provided with an inner cavity that communicates with the nozzle and the barrel, and the shape of the inner cavity is Extension of the shape of the barrel cavity;

The driving mechanism includes a double driving device, which respectively provides rotational power to the two conical screws through a non-connected transmission mechanism, and is transmitted to the transmission mechanism through the driving mechanism;

The drive mechanism includes two sets of stepping motors and motor reducers that are connected in transmission with each other. The stepping motors are transmitted to the drive motor reducer, and are then transmitted to the transmission mechanism by the output shaft of the motor reducer.

Example 3

In this embodiment, a co-rotating conical twin-screw fused deposition molding extrusion type 3D printing nozzle, as shown in Figure 1, includes a sequentially connected drive mechanism, a transmission mechanism and a screw extrusion mechanism. The screw extrusion The mechanism includes a co-rotating conical twin-screw assembly, a barrel and an extrusion head,

The corotating conical twin-screw assembly, as shown in Figure 2, includes two corotating conical screws (conical screw A and conical screw B), and the conical screw includes a threaded section and a connecting section , the connecting section is connected with the transmission mechanism, the length of the threaded section is 95mm, the inner diameter of the screw of the threaded section is linearly changed from 9.8mm at the feed end to 5.1mm at the discharge end, and the depth of the screw groove of the threaded section is also 6.6mm at the feed end. The mm linearly changes to 2.0mm at the discharge end, the screw pitch is 7mm, the screw edge width is 1.2mm, and the overall structure is tapered;

The two conical screws rotating in the same direction are in a clearance fit, and the angle β between the axis lines of the screws is 5°;

The inner cavity of the barrel is a "∞" shaped channel, which is matched with the conical twin-screw assembly rotating in the same direction. A hopper is provided outside the feeding port, and electric heating coils (electric heating coil A and electric heating coil B) are fixed on the outside of the barrel;

The extrusion head includes a temperature-control nozzle, and the temperature-control nozzle is fixedly connected to the discharge end of the barrel through a nozzle connector. The nozzle connector is provided with an inner cavity that communicates with the nozzle and the barrel, and the shape of the inner cavity is Extension of the shape of the barrel cavity;

The transmission mechanism includes a worm wheel (worm gear A and worm wheel B), a worm and a screw connecting shaft (screw connecting shaft A and screw connecting shaft B), and shaft fixing plates and bearing fixtures for stabilizing the two ends of the screw connecting shaft respectively, and The casing of the transmission mechanism is composed of the shaft fixing plate and the bearing fixing piece;

The connecting section of the conical screw is fixedly connected to one end of the screw connecting shaft, and is stabilized by the bearing provided on the shaft fixing plate at the fixed connection, and the other end of the screw connecting shaft is fixedly connected with a worm wheel near the end, and the worm is connected from the The side is meshed with the worm gear; the worm drives the two worm gears to rotate at the same time, so that the twin screws can rotate in the same direction at the same speed and with the same torque; The other end of the stabilizing screw connection shaft;

The shaft fixing plate is fixedly connected to the barrel, and a layer of barrel heat insulation is provided at the joint to reduce the high temperature transmission of the barrel;

The shaft fixing plate is also provided with a cooling water circulation channel to reduce the heat transfer effect of the barrel and avoid overheating damage;

A bearing end cover is also arranged on the bearing fixing part to facilitate maintenance and disassembly;

The drive mechanism, as shown in accompanying drawing 3, includes a stepper motor and a motor reducer that are connected to each other, and also includes a worm screw fixture and a drive connection plate. The stepper motor is transmitted to the drive motor reducer, and is decelerated by the motor The output shaft of the drive is transmitted to the worm, and the worm fixing part includes bearings, which play the role of stabilizing the worm, and the drive connecting plate respectively connects the worm fixing part and the motor reducer together, which acts as a flange and can also be used as a worm Bearing caps for the bearings in the fixture.

Example 4

In this embodiment, a co-rotating conical twin-screw fused deposition molding extrusion type 3D printing nozzle, as shown in Figure 1, includes a sequentially connected drive mechanism, a transmission mechanism and a screw extrusion mechanism. The screw extrusion The mechanism includes a co-rotating conical twin-screw assembly, a barrel and an extrusion head,

The corotating conical twin-screw assembly, as shown in Figure 2, includes two corotating conical screws (conical screw A and conical screw B), and the conical screw includes a threaded section and a connecting section , the connection section is connected with the transmission mechanism, the length of the thread section is 85mm, the inner diameter of the screw of the thread section is linearly changed from 9.6mm at the feed end to 4.9mm at the discharge end, and the groove depth of the thread section is also 6.4mm at the feed end. The mm linearly changes to 1.8mm at the discharge end, the screw pitch is 6mm, the screw edge width is 0.8mm, and the overall structure is tapered;

The two co-rotating conical screws are clearance fit, and the angle β between the screw axes is 7°; the inner cavity of the barrel is a "∞"-shaped channel, and the gap between the co-rotating conical twin-screw assembly is Cooperate, the described material barrel is provided with feeding mouth, and simultaneously feeding mouth is positioned at the feeding end top of screw thread section, and is provided with feeding hopper outside feeding mouth, and the outer side of feeding barrel is fixed with electric heating coil (electric heating coil A and electric heating coil A and heating coil B);

The extrusion head includes a temperature-control nozzle, and the temperature-control nozzle is fixedly connected to the discharge end of the barrel through a nozzle connector. The nozzle connector is provided with an inner cavity that communicates with the nozzle and the barrel, and the shape of the inner cavity is Extension of the shape of the barrel cavity;

The transmission mechanism includes a worm wheel (worm gear A and worm wheel B), a worm and a screw connecting shaft (screw connecting shaft A and screw connecting shaft B), and shaft fixing plates and bearing fixtures for stabilizing the two ends of the screw connecting shaft respectively, and The casing of the transmission mechanism is composed of the shaft fixing plate and the bearing fixing piece;

The connecting section of the conical screw is fixedly connected to one end of the screw connecting shaft, and is stabilized by the bearing provided on the shaft fixing plate at the fixed connection, and the other end of the screw connecting shaft is fixedly connected with a worm wheel near the end, and the worm is connected from the The side is meshed with the worm gear; the worm drives the two worm gears to rotate at the same time, so that the twin screws can rotate in the same direction at the same speed and with the same torque; The other end of the stabilizing screw connection shaft;

The shaft fixing plate is fixedly connected to the barrel, and a layer of barrel heat insulation is provided at the joint to reduce the high temperature transmission of the barrel;

The shaft fixing plate is also provided with a cooling water circulation channel to reduce the heat transfer effect of the barrel and avoid overheating damage;

A bearing end cover is also arranged on the bearing fixing part to facilitate maintenance and disassembly;

The drive mechanism, as shown in accompanying drawing 3, includes a stepper motor and a motor reducer that are connected to each other, and also includes a worm screw fixture and a drive connection plate. The stepper motor is transmitted to the drive motor reducer, and is decelerated by the motor The output shaft of the drive is transmitted to the worm, and the worm fixing part includes bearings, which play the role of stabilizing the worm, and the drive connecting plate respectively connects the worm fixing part and the motor reducer together, which acts as a flange and can also be used as a worm Bearing caps for the bearings in the fixture.

Application example 1

This application example is fused deposition modeling 3D printing using polypropylene/hexagonal boron nitride (PP/h-BN) composite material as the printing material, and using co-rotating conical twin-screw fused deposition molding extrusion as described in Example 1 Type 3D printing nozzle, which mainly includes the following steps:

(1) taking polypropylene as a matrix, and using hexagonal boron nitride with a mass fraction of 35 wt% as a filler, mixing the powders of the above two components evenly as a mixed material;

(2) Gradually pour the mixed material obtained in step (1) through the feed port of the barrel, and set the screw speed of the corotating conical twin-screw fused deposition molding extrusion 3D printing nozzle to 20r/min, and the drive motor The output torque is 2.3N m;

(3) Print and prepare according to the three-dimensional digital model of the desired product, set the printing speed to 3000mm/min, the temperature of the hot bed to 80°C, and the temperature of the nozzle to 220°C.

The final printed product was used as a sample to test its performance.

The results of mechanical properties show that the tensile strength of the composite material can reach 36MPa, the Young's modulus can reach 2250MPa, and the notched impact strength can reach 6.5kJ/m ² .

Scanning electron microscope (SEM) images show that the dispersion of fillers in PP/h-BN composites is good, indicating that the effect of the twin-screw nozzle melt blending is good.

Application Comparative Example 1

This application example is fused deposition modeling 3D printing using polypropylene/hexagonal boron nitride (PP/h-BN) composite material as printing raw material, and using traditional fused deposition 3D printing technology (HORI Z300 FDM printer), the main Include the following steps:

(1) taking polypropylene as a matrix, and using hexagonal boron nitride with a mass fraction of 35 wt% as a filler, mixing the powders of the above two components evenly as a mixed material;

(2) The mixed material obtained in step (1) is granulated by twin-screw melt extrusion to obtain mixed pellets, wherein the process parameters of twin-screw melt extrusion granulation are: the temperature from the hopper to the machine head is 150, 170, 180, 200, 200, 200, 200, 200, 190°C, the screw speed is 120rpm.

(3) The mixed pellets obtained in step (2) were prepared by printing according to the three-dimensional digital model of the required product, the printing speed was set at 3000mm/min, the temperature of the hot bed was 80°C, and the temperature of the nozzle was 220°C.

The final printed product was taken as a sample, and its mechanical properties were tested. The tensile strength of the composite material was 35MPa, the Young's modulus was about 2200MPa, and the notched impact strength was 7kJ/m ² .

Application example 2

This application example is fused deposition modeling 3D printing using a polylactic acid/polybutylene succinate (PLA/PBS) blend as a printing material, and uses the co-rotating conical twin-screw fused deposition described in Example 1 Forming the extruded 3D printing nozzle mainly includes the following steps:

(1) take the polylactic acid polymer as the continuous phase, and the mass fraction is 40wt% polybutylene succinate as the dispersed phase, and the pellets of the above two components are mixed uniformly as the mixed material;

(2) Gradually pour the mixture obtained in step (1) through the feeding port of the barrel, and set the screw speed of the corotating conical twin-screw fused deposition molding extrusion-type 3D printing nozzle to 15r/min, and the drive motor The output torque is 2.3N m;

(3) Print and prepare according to the three-dimensional digital model of the required product, set the printing speed to 1800mm/min, and the temperature of the hot bed to 60°C. The nozzle temperature was 200°C.

The final printed product was used as a sample to test its performance.

The results of mechanical properties show that the tensile strength of the PLA/PBS blend can reach 44MPa, the Young's modulus can reach 1450MPa, and the notched impact strength is 6.8kJ/m ² .

Application Comparative Example 2

This application example is fused deposition modeling 3D printing using polylactic acid/polybutylene succinate (PLA/PBS) blends as printing materials, and using traditional fused deposition 3D printing technology (HORI Z300FDM printer), It mainly includes the following steps:

(1) take polylactic acid as the continuous phase, and the mass fraction is 40wt% polybutylene succinate as the dispersed phase, and the pellets of the above two components are mixed uniformly as a mixed material;

(2) The mixed material obtained in step (1) is granulated by twin-screw melt extrusion to obtain mixed pellets, wherein the process parameters of twin-screw melt extrusion granulation are: the temperature from the hopper to the machine head is 120, 150, 180, 180, 190, 190, 200, 200, 180°C, the screw speed is 80rpm.

(3) The mixed pellets obtained in step (2) were prepared by printing according to the three-dimensional digital model of the required product, the printing speed was set at 1800mm/min, the temperature of the hot bed was 60°C, and the temperature of the nozzle was 200°C.

The final printed product was used as a sample to test its performance.

The results of mechanical properties show that the tensile strength of the composite material can reach 42.5MPa, the Young's modulus can reach 1330MPa, and the notched impact strength is 6.68kJ/m ² .

Application example 3

This application example is fused deposition modeling 3D printing using a polylactic acid/polybutylene succinate (PLA/PBS) blend as a printing material, and uses the co-rotating conical twin-screw fused deposition described in Example 1 Forming the extruded 3D printing nozzle mainly includes the following steps:

(1) take the polylactic acid polymer as the continuous phase, and the mass fraction is 20wt% polybutylene succinate as the dispersed phase, and the pellets of the above two components are mixed uniformly as the mixed material;

(2) Gradually pour the mixed material obtained in step (1) through the feeding port of the barrel, and set the screw speed of the corotating conical twin-screw fused deposition molding extrusion 3D printing nozzle at 15r/min, and the driving motor The output torque is 2.3N m;

(3) Print and prepare according to the three-dimensional digital model of the desired product, set the printing speed to 1800mm/min, and the temperature of the hot bed to 60°C. The nozzle temperature was 200°C.

The final printed product was used as a sample to test its performance.

The results of mechanical properties show that the tensile strength of the PLA/PBS blend can reach 56MPa, the Young's modulus can reach 1900MPa, and the notched impact strength can reach 4kJ/m ² .

Application Comparative Example 3

This application example is fused deposition modeling 3D printing using polylactic acid/polybutylene succinate (PLA/PBS) blends as printing materials, and using traditional fused deposition 3D printing technology (HORI Z300FDM printer), It mainly includes the following steps:

(1) take polylactic acid as continuous phase, mass fraction is 20wt% polybutylene succinate as dispersed phase, the pellets of above-mentioned two components are mixed uniformly, as mixed material;

(2) The mixed material obtained in step (1) is granulated by twin-screw melt extrusion to obtain mixed pellets, wherein the process parameters of twin-screw melt extrusion granulation are: the temperature from the hopper to the machine head is 120, 150, 180, 180, 190, 190, 200, 200, 180°C, the screw speed is 80rpm.

(3) The mixed pellets obtained in step (2) were prepared by printing according to the three-dimensional digital model of the required product, the printing speed was set at 1800mm/min, the temperature of the hot bed was 60°C, and the temperature of the nozzle was 200°C.

The final printed product was used as a sample to test its performance.

The results of mechanical properties show that the tensile strength of the composite material can reach 52MPa, the Young's modulus can reach 1850MPa, and the notched impact strength is 4.1kJ/m ² .

Claims (9)

1. A3D printing process utilizing a co-rotating conical double-screw fused deposition modeling extrusion type 3D printing nozzle is characterized in that the co-rotating conical double-screw fused deposition modeling extrusion type 3D printing nozzle mainly comprises a driving mechanism, a transmission mechanism and a screw extrusion mechanism which are connected in sequence, the screw extrusion mechanism comprises a co-rotating conical double-screw component, a charging barrel and an extrusion head,

the homodromous conical double-screw component comprises two homodromous conical screws, each conical screw comprises a threaded section and a connecting section, each connecting section is in transmission connection with the transmission mechanism, the length of each threaded section is 85-95 mm, the inner diameter of each threaded section is linearly changed from 9.6-9.8 mm of the feeding end to 4.9-5.1 mm of the discharging end, the depth of a screw groove of each threaded section is also linearly changed from 6.4-6.6 mm of the feeding end to 1.8-2.0 mm of the discharging end, the screw pitch is 6-7 mm, the width of a screw edge is 0.8-1.2 mm, and the whole conical structure is formed;

the two conical screws rotating in the same direction are in clearance fit, and the included angle of the axial leads of the screws is 5-7 degrees;

an inner cavity of the charging barrel is an infinity-shaped channel and is in clearance fit with the homodromous rotating conical double-screw component, and a charging opening is formed in the charging barrel;

the extrusion head is fixedly connected with the discharge end of the charging barrel;

the 3D printing process for utilizing the co-rotating conical double-screw fused deposition modeling extrusion type 3D printing nozzle mainly comprises the following steps of:

(1) According to the required raw material proportion, uniformly mixing the granular materials or powder materials of various raw materials to obtain a mixed material; the raw materials are in a mode of taking polypropylene as a matrix and hexagonal boron nitride with the mass fraction of 20-40 wt% as a filler, or in a mode of taking polylactic acid polymer as a continuous phase and thermoplastic polyurethane with the mass fraction of 10-50 wt% as a dispersed phase;

(2) Gradually pouring the mixed material obtained in the step (1) into a charging opening of a charging barrel, setting the screw rotating speed of a co-rotating conical double-screw fused deposition molding extrusion type 3D printing nozzle to be 10-30 r/min, and setting the output torque of a driving motor to be 2.3-2.5 N.m;

(3) Printing according to the three-dimensional digital model of the required product, wherein the printing speed is 600-4800 mm/min, and the temperature of a hot bed is 40-80 ℃.

2. The 3D printing process according to claim 1, wherein: the transmission mechanism is driven by a worm gear and a worm, the transmission mechanism mainly comprises the worm gear and the worm, the worm is connected with the output end of the motor reducer, the transmission section of the conical screw is fixedly connected with the worm gear, and the worm is in meshing transmission with the worm gear from the side face.

3. The 3D printing process according to claim 2, wherein: the transmission mechanism further comprises a screw rod connecting shaft, the connecting section of the conical screw rod is fixedly connected with one end of the screw rod connecting shaft, the other end of the screw rod connecting shaft is fixedly connected with a worm wheel, and the worm is meshed with the worm wheel from the side for transmission.

4. The 3D printing process according to claim 3, wherein: the driving mechanism comprises a stepping motor and a motor reducer which are in transmission connection with each other, and the stepping motor is transmitted to the driving motor reducer and is transmitted to the worm by an output shaft of the motor reducer.

5. 3D printing process according to claim 1 or 2, characterized in that: and a cooling water circulation channel is arranged in the transmission mechanism.

6. The 3D printing process according to claim 1, wherein: the charging barrel is characterized in that a charging opening is formed in the side wall of the charging barrel and is positioned above the feeding end of the threaded section.

7. The 3D printing process according to claim 1, wherein: and the charging barrel is also provided with an electric heating coil.

8. The 3D printing process according to claim 1, wherein:

aiming at fused deposition modeling 3D printing of a polypropylene/hexagonal boron nitride composite material as a printing raw material, the method mainly comprises the following steps:

(1) Taking polypropylene as a matrix, taking 20-40 wt% of hexagonal boron nitride as a filler, and uniformly mixing the powder of the two components to obtain a mixed material;

(2) Gradually pouring the mixed material obtained in the step (1) into a charging opening of a charging barrel, setting the screw rotating speed of a co-rotating conical double-screw fused deposition modeling extrusion type 3D printing nozzle to be 20r/min, and setting the output torque of a driving motor to be 2.3 N.m;

(3) Printing preparation is carried out according to a three-dimensional digital model of a required product, the printing speed is set to 3000mm/min, and the temperature of a hot bed is 80 ℃.

9. The 3D printing process according to claim 1, wherein:

the method mainly comprises the following steps of:

(1) Uniformly mixing granules of the two components to obtain a mixed material, wherein a polylactic acid polymer is used as a continuous phase, and thermoplastic polyurethane with the mass fraction of 10-50 wt% is used as a dispersed phase;

(2) Gradually pouring the mixed material obtained in the step (1) into a charging opening of a charging barrel, setting the screw rotating speed of a co-rotating conical double-screw fused deposition modeling extrusion type 3D printing nozzle to be 15r/min, and setting the output torque of a driving motor to be 2.3 N.m;

(3) Printing preparation is carried out according to a three-dimensional digital model of a required product, the printing speed is set to be 1800mm/min, and the temperature of a hot bed is 50 ℃.

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