CN113001971A

CN113001971A - Vacuum environment-oriented heat-resistant energy-saving FDM printing head

Info

Publication number: CN113001971A
Application number: CN202110252084.8A
Authority: CN
Inventors: 杨杰; 黎静; 张祺; 马红林; 吴文杰; 高霞
Original assignee: Chongqing University; Chongqing Institute of Green and Intelligent Technology of CAS
Current assignee: Chongqing University; Chongqing Institute of Green and Intelligent Technology of CAS
Priority date: 2021-03-08
Filing date: 2021-03-08
Publication date: 2021-06-22
Anticipated expiration: 2041-03-08
Also published as: CN113001971B

Abstract

The invention discloses a heat-resistant energy-saving FDM printing head facing a vacuum environment. In a vacuum non-convection environment, a stable and energy-saving heat resistance mode is adopted, the passive temperature control characteristic of a high heat resistance material is utilized, and the conduction contact area is optimally designed in a matching manner, so that the passive heat resistance device is rapidly cooled, and the material blockage is prevented. On one hand, the problem of air cooling failure in a vacuum environment is solved, system accessories and power consumption increase caused by liquid cooling are avoided, and equipment miniaturization is facilitated; on the other hand, the heat of the heater is prevented from being dissipated by the heat dissipation mechanism to the maximum extent, and heat loss is reduced. The FDM printing head is suitable for space additive manufacturing, meets the extrusion forming of polymers and composites thereof, metal alloys and composites thereof, inorganic non-metals and composites thereof under the constraint conditions of extravehicular vacuum environment and limited space resources, and is beneficial to continuous, low-consumption and reliable melting/melting deposition additive manufacturing in the space environment.

Description

Vacuum environment-oriented heat-resistant energy-saving FDM printing head

Technical Field

The invention belongs to the field of space additive manufacturing, and particularly relates to a vacuum environment-oriented heat-resistant energy-saving FDM printing head.

Background

With the continuous development of the aerospace technology, space tasks such as deep space exploration base construction, space station function expansion, high-resolution earth observation and the like increasingly enhance the requirements on large-scale, light-weight and high-strength space structures/facilities, but are limited by rocket carrying capacity, severe mechanical conditions in the launching process and high carrying cost, and the traditional operation mode of 'ground manufacturing launching and space expansion application' is difficult to use. The extra-cabin orbital additive manufacturing, namely the additive manufacturing developed in the extra-cabin space environment of a space station, can break through the rocket envelope and the carrying capacity limitation, greatly reduces the launching cost, is an effective way for realizing the in-orbit construction of large space structures/facilities, and becomes one of the key core technologies for competing for the high point of the space detection strategy in the world astronautics.

Unlike in-cabin rail additive manufacturing, in addition to the effects of spatial microgravity, off-cabin rail additive manufacturing, represented by Fused Deposition Modeling (FDM) technology, faces harsh environmental challenges of vacuum, thermal radiation, charged particle radiation, ultraviolet radiation, temperature alternation, and the like. Especially along with the change of the height of the orbit, the vacuum degree of the space orbit environment reaches 10^-3～10^-12pa, not only possibly causing the printed material to sublime, decompose, outgas,The heat transfer process among parts such as extruded materials, radiators, hot melt cavities, hot melt nozzles and the like and systems in the melt extrusion process is changed essentially due to the fact that the radiation becomes the only heat transfer mode among non-contact objects due to the lack of the heat convection and heat conduction action of air; with the disappearance of the convection medium, the forced convection fan cooling printing head in the traditional melt extrusion molding cannot be used.

Meanwhile, different from ground additive manufacturing, extravehicular on-track melting/melting deposition forming is not only seriously influenced by space extreme environment, but also faces rigorous limitation of space resources, namely limit constraints on multiple aspects such as the volume, weight, power and the like of a printing system/equipment. Therefore, for melting/melting deposition forming of high melting point polymers and composites thereof, metal alloys and composites thereof, and inorganic non-metals and composites thereof, active temperature control type print heads represented by single-stage or multi-stage liquid cooling/gas cooling, and relatively complex circulation pipelines and additional accessories such as switch valves, pump bodies and the like bring extra volume, weight and power loss, and are not beneficial to melting/melting deposition additive forming in an extravehicular vacuum environment.

In addition, the air cooling/liquid cooling heat dissipation method has the problem of power loss, and dissipates the heat energy applied to melting/melting materials. Based on this, even if a large-area copper ring radiator is used to replace air cooling/liquid cooling, the vacuum radiation heat dissipation scheme proposed by related U.S. researches cannot solve the problem of power loss, and simultaneously, the volume and the weight of the printing head are increased, so that extra-cabin material increase forming under the condition of space extreme power constraint is not facilitated.

In the prior art, as disclosed in patent application No. CN112373035A, a precise temperature control 3D print head suitable for high temperature thermoplastics and a method for using the same are disclosed, the print head includes: the device comprises a vacuum high-efficiency heat insulation cylinder, a heat insulation pad, a ventilation cylindrical support, a heating block, a heating rod, a thermal sensor, an overlong printing head, a porous cooling pipe and a heat insulation sleeve; the upper part of the vacuum high-efficiency heat insulation cylinder is fixedly connected with the ventilation cylinder-shaped support through the heat insulation pad. The invention can realize the heat insulation and preservation of the installation of the high-temperature printing head, the control of the temperature of the printing head and the control of the local printing environment, improves the temperature control precision, can better control the cooling crystallization process of a printed product, improves the product forming quality, and can be applied to the field of 3D printing of high-temperature special engineering plastics. However, the patent is not suitable for the vacuum environment because the air heat convection and heat conduction function is lacked under the constraint conditions of the vacuum environment outside the cabin and the limited space resources.

At present, extra-cabin on-track melting/melting deposition forming additive manufacturing is in the initial stage of technical development, namely, the concept design is converted to an engineering prototype, in an extra-cabin vacuum environment, under the constraints of the volume, weight and power of a printing system/equipment, the temperature control problem caused by heat transfer change is overcome, and in an environment without air convection and conduction, the continuous low-consumption extrusion material of an extrusion printing head is ensured, so that the key technical bottleneck which must be overcome in extra-cabin on-track additive manufacturing is formed; the method has very important significance for the research on the basic scientific problems of the influence of the melting behavior and the heat-dominated forming process change on the precision and the strength of the extravehicular large-scale additive part in the material extrusion process, and the exploration practice of engineering problems of extravehicular additive manufacturing equipment/system development, extravehicular large-scale space structure in-orbit construction and the like.

Disclosure of Invention

The invention provides a vacuum environment-oriented heat-resistant energy-saving FDM printing head, which aims to solve the technical problems involved in a melting/melting deposition additive forming extrusion process due to the lack of air heat convection and heat conduction action, limitation of system volume, weight, power consumption and the like under the constraint conditions of an extravehicular vacuum environment and limited space resources. Therefore, the invention adopts the following technical scheme:

the invention discloses a heat-resistant energy-saving FDM printing head facing a vacuum environment. The connecting guider is an inlet for the material to be extruded to enter the printing head and provides a mechanical interface for connecting the printing head with the printing system; the upper end of the passive heat resistor is connected with the connecting guider, the lower end of the passive heat resistor is fixed with the heater, after the wire enters the passive heat resistor, the shorter part of the lower part is softened by the thermal action material of the heater, and the longer part of the upper part keeps solid and transmits continuous extrusion thrust under the thermal cooling action of the passive heat resistor; the heater provides a heat source for melting/fusing the material and feeds back the heating temperature; the nozzle is connected with the heater, and the material is extruded after being melted/melted in the nozzle liquid cavity.

The passive heat resistor adopts a heat-resistant design, and in a vacuum non-convection environment, the passive temperature control characteristic of a high-heat-resistant material is utilized, and the optimal design of the heat conduction contact area is combined, so that the passive heat resistor realizes a rapid cooling function, and the material blockage is avoided; meanwhile, the passive heat resistor prevents heat from being uploaded, the heat of the heater is limited to be dissipated by the heat dissipation mechanism to the maximum extent, and heat loss is reduced.

In the invention, the center of the heat resistance guide seat and the heat resistance block of the heat resistance device is centered and penetrates through the hole with equal section for materials to pass through.

In the invention, the heat resistance device is made of heat resistance materials, the heat conductivity of the heat resistance guide seat, the heat resistance screw I and the heat resistance screw II is less than 20W/(m.K), and the heat conductivity of the heat resistance block is less than 10W/(m.K).

In the invention, the heat resistance block structure comprises one or more of a solid structure, a frame structure, a shell structure and a hollow topological structure.

In the invention, the connecting surface of the heat resistor and the heater has a high-temperature sealing function, so that material leakage is prevented.

In the invention, in the heater, a heating block is connected with a heating element and a heat sensing element, and a central leak-proof sealing pipe is in threaded connection with a nozzle; the heating elements are symmetrically distributed on two sides of the nozzle to rapidly and uniformly heat materials in the nozzle; the heat sensing element feeds back the melting/fusing temperature of the material in real time.

In the invention, the inner wall of the circular hole of the heat resistor through which the material passes and the inner wall of the liquid cavity of the nozzle are both provided with high-temperature-resistant lubricating coatings, so that the frictional resistance between the material and the inner wall is reduced.

In the invention, the material range suitable for the vacuum printing head is one or more of polymer and composite material thereof, metal alloy and composite material thereof, inorganic nonmetal and composite material thereof.

In the invention, the melting point of the material suitable for the vacuum printing head is not higher than 800 ℃.

In the invention, the material forms suitable for the vacuum printing head comprise wires and strips.

In the invention, the cross section shapes of the wires comprise circles, triangles, quadrangles and polygons, and the cross section shapes of the strips comprise ellipses, triangles, quadrangles and polygons.

Has the advantages that:

the invention provides a vacuum environment-oriented heat-resistant energy-saving FDM printing head, which adopts a stable and energy-saving heat-resistant mode to effectively and passively control temperature, and realizes continuous, low-consumption and reliable melting/melting extrusion for various materials under the dual constraints of extreme environment and strict resource limitation. Wherein:

1. by utilizing the passive temperature control characteristic of a high-heat-resistance material and combining the optimization of the heat conduction contact area, the heat-resistance type passive temperature control is realized on the upper part of the heater of the printing head, the material is ensured to have enough strength to transmit thrust on the premise of no active cooling, the material in the nozzle hot-melt cavity is fully melted/melted, the blockage caused by too low heat dissipation efficiency is avoided, the material is smoothly extruded, and the special working condition of vacuum outside the cabin is fully adapted.

2. According to the change of the melting points of different materials, the passive heat resistor is matched with the corresponding heat resistant material, the contact area is optimized, the optimal temperature gradient of the different materials in the working interval of the printing head can be kept, the vacuum extrusion molding requirements of various materials such as polymers and composite materials thereof, metal alloys and composite materials thereof, inorganic non-metals and composite materials thereof and the like are met, and the diversification of the printing materials is realized.

3. The heat resistance passive temperature control mode not only solves the problem that the heat of the heater is uploaded and dissipated by a cooling system, reduces the energy loss caused by the heat, but also reduces the extra power consumption generated by active heat dissipation modes such as air cooling/liquid cooling and the like; in addition, the passive heat resistor does not need to be added with additional accessories, the volume and the weight of the printing head are reduced, meanwhile, the system reliability is increased, and the strict resource constraint requirement of manufacturing outside a space cabin is met.

Drawings

FIG. 1 is a schematic structural diagram of a heat-resistant energy-saving FDM print head facing a vacuum environment constructed according to a preferred embodiment of the invention;

FIG. 2 is a central cross-sectional view of the printhead of FIG. 1;

FIG. 3 is a cross-sectional view of the screw connection of the passive heat resistor and the heater of FIG. 1;

FIG. 4 is a schematic structural view of a thermal block constructed in accordance with a preferred embodiment of the present invention;

fig. 5 is a schematic diagram of the working principle of the heat-resistant energy-saving FDM printing head facing to the vacuum environment.

The parts of the drawing are marked as follows:

1. the heat insulation device comprises a connecting guide device, 2 a passive heat resistor, 3 a heater, 4 a nozzle, 34 a heat sensing element, 35a heat sensing fixing screw, 11 a lubricating conduit, 12 a conduit joint, 13 a connecting seat, 21 a heat insulation guide seat, 22 a heat insulation block, 31 a heating block, 32 a heating element, 33 a set screw, 23 heat insulation screws I and 24 a heat insulation screw II.

Detailed Description

The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that all the directional indicators (such as upper, lower, left, right, front and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.

In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 1 is a schematic structural diagram of a heat-resistant energy-saving FDM printing head facing a vacuum environment according to a preferred embodiment of the present invention; FIG. 2 is a central cross-sectional view of the printhead of FIG. 1; FIG. 3 is a cross-sectional view of the screw connection of the passive heat resistor and the heater of FIG. 1; fig. 4 is a schematic view of a thermal block constructed in accordance with a preferred embodiment of the present invention. The invention provides a vacuum environment-oriented heat-resistant energy-saving FDM printing head which is composed of a connecting guider 1, a passive heat resistor 2, a heater 3 and a nozzle 4. Wherein:

the guide 1 includes a lubrication guide tube 11, a guide tube joint 12, and a connection seat 13. The lubricating conduit 11 is fixed by a cutting sleeve type pipe connection mode of the conduit joint 12, passes through the conduit joint 12 and the connecting seat 13, and is aligned with the heat-resisting guide seat 21; the external thread at the lower side of the conduit joint 12 is connected with the internal thread hole of the connecting seat 13; the material enters the printing head from the lubricating conduit 11, and in order to reduce the frictional resistance between the material and the pipe wall, the lubricating conduit 11 uses a lubricating material, such as polytetrafluoroethylene, an inorganic self-lubricating coating and the like; threaded holes are symmetrically distributed on a flange table of the connecting seat 13 and used for mechanically connecting the printing head with a printing system; the guider 1 and the passive heat resistor 2 are connected with the external thread of the heat-resistant guide seat 21 through the internal thread of the connecting seat 13.

The passive heat resistor 2 comprises a heat-resistant guide seat 21, a heat-resistant block 22, a heat-resistant screw I23 and a heat-resistant screw II 24. The heat resistance guide seat 21 and the heat resistance block 22 of the heat resistance device 2 are fixed through a connecting screw I23, the centers of the two are aligned, and the two penetrate through a circular hole with the same diameter for materials to pass through; the heat resistance device 2 is fixedly connected with the heater 3 through a heat resistance screw II 24.

When the material is polylactic acid (PLA) or acrylonitrile-butadiene-styrene copolymer (ABS) wire material with the diameter of 1.75mm, TC4 titanium alloy material can be used for the heat-resisting guide seat 21, the connecting screw I23 and the connecting screw II24, and calcium silicate heat-resisting material can be used for the heat-resisting block 22; the diameter of the wire passing round holes of the heat-resistant guide seat 21 and the heat-resistant block 22 is 2mm, and the inner wall of the wire passing round holes is coated with a polytetrafluoroethylene coating to reduce resistance; the joint surface of the heat resistor 2 and the heater 3 is coated with sealant which can resist 250 ℃ to prevent the material leakage.

The heater 3 includes a heating block 31, a heating element 32, a set screw 33, a heat sensing element 34, and a heat sensing set screw 35. The heating block 31 is of a symmetrical structure, and a leak-proof sealing pipe thread through hole is arranged in the center and connected with the nozzle 4; the heating elements 32 are symmetrically distributed on two sides of the nozzle 4 and are fixed in through holes of the heating block 31 by the set screws 33, so that materials in the nozzle can be rapidly and uniformly heated; when the polymer composite material is melted, the heating element 32 can use a ceramic heating rod, the outer wall of the ceramic heating rod is in interference fit with the inner wall of the through hole of the heating block 31, the contact heat conduction area is increased, and the heating efficiency is improved; the heat sensing element 34 is connected in the heating block 31 through a heat sensing fixing screw 35, and feeds back the melting temperature of the material in real time.

Fig. 5 is a schematic diagram illustrating the working principle of a heat-resistant energy-saving FDM printhead facing a vacuum environment according to the present invention. Under the active pushing and twisting action of the motor and the feeding roller, the material enters the printing head from the lubricating conduit 11 connected with the guider 1, penetrates through the passive heat resistor 2 and the heater 3 and reaches the nozzle 4. In a vacuum environment, when the temperature of the heater is raised to the melting temperature of the material, the material in the liquid cavity of the nozzle is melted/melted under the action of heat; the material close to the heater 3 at the lower part of the passive heat resistor is in a melting/melting softening state, and the middle and upper longer parts keep a solid state and transmit the extrusion thrust of the wire feeding motor under the action of passive heat resistor cooling, so that continuous extrusion is realized.

When the material to be extruded is a polyether ether ketone (PEEK) wire material with the diameter of 1.75mm, the heat resistance block 22 is made of silicate, and the contact surface of the passive heat resistor 2 and the heater 3 is optimized to be smaller than 15mm multiplied by 10 mm; in a vacuum atmosphere, when the temperature of the heating block 31 reaches 350 ℃, the distance between the heat resistance block 22 and the heating block 31 is about 10mm, the temperature of the wire passing through the inner wall of the circular hole is reduced to 80 ℃, the temperature of the tail end of the heat resistance block 22 is reduced to about 24 ℃, the heat resistance effect is better realized, and the continuous and stable extrusion of the PEEK wire in vacuum is ensured.

The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.

Claims

1. The utility model provides a hinder energy-conserving formula FDM and beat printer head towards vacuum environment which characterized in that: comprises a connecting guider (1), a passive heat resistor (2), a heater (3) and a nozzle (4), wherein,

the connecting guider (1) is an inlet for the material to be extruded to enter the printing head and provides a mechanical interface for connecting the printing head with a printing system; the upper end of the passive heat resistor (2) is connected with the connecting guider (1), the lower end of the passive heat resistor is fixed with the heater (3), after wires enter the passive heat resistor (2), the lower short part of the wires is softened by the heat action material of the heater (3), and the upper middle long part of the wires keeps solid and transmits continuous extrusion thrust under the passive heat-resistant cooling action; the heater (3) provides a heat source for melting/fusing materials and feeds back heating temperature; the nozzle (4) is connected with the heater (3), and materials are extruded after being melted/melted in a nozzle liquid cavity;

the passive heat resistor (2) adopts a heat resistance design, and in a vacuum non-convection environment, the passive temperature control characteristic of a high heat resistance material is utilized, and the optimal design of a heat conduction contact area is combined, so that the passive heat resistor (2) realizes a rapid cooling function, and material blockage is avoided; meanwhile, the passive heat resistor (2) prevents heat from being uploaded, the heat of the heater (3) is limited to be dissipated by the heat dissipation mechanism to the maximum extent, and heat loss is reduced.

2. The vacuum environment-oriented heat-resistant energy-saving FDM print head of claim 1 wherein: the center of the heat resistance guide seat (21) of the heat resistance device (2) is centered with the center of the heat resistance block (22), and the heat resistance guide seat penetrates through the holes with equal cross sections to allow materials to pass through.

3. The vacuum environment-oriented heat-resistant energy-saving FDM print head of claim 1 or 2, wherein: the heat resistance device (2) is made of a heat resistance material, the heat conductivity of the heat resistance guide seat (21), the heat resistance screw I (23) and the heat resistance screw II (24) is less than 20W/(m.K), and the heat conductivity of the heat resistance block (22) is less than 10W/(m.K).

4. A heat-resistant energy-saving FDM printhead facing a vacuum environment as claimed in any one of claims 1 to 3 wherein: the structure of the heat resistance block (22) comprises one or more of a solid structure, a frame structure, a shell structure and a hollow topological structure.

5. A heat-resistant energy-saving FDM printhead facing a vacuum environment as claimed in any one of claims 1 to 4 wherein: the connection surface of the heat resistor (2) and the heater (3) has a high-temperature sealing function, so that material leakage is prevented.

6. The vacuum environment-oriented heat-resistant energy-saving FDM print head of claim 1 wherein: in the heater (3), a heating block (31) is connected with a heating element (32) and a heat sensing element (34), and a central leakproof sealing pipe is in threaded connection with a nozzle (4); the heating elements (32) are symmetrically distributed on two sides of the nozzle (4) to rapidly and uniformly heat materials in the nozzle; the heat sensing element (34) feeds back the melting/fusion temperature of the material in real time.

7. A heat-resistant energy-saving FDM printhead facing a vacuum environment as claimed in any one of claims 1 to 6 wherein: the inner wall of the round hole of the heat resistor (2) through which the material passes and the inner wall of the liquid cavity of the nozzle (4) are both provided with high-temperature lubricating coatings, so that the frictional resistance between the material and the inner wall is reduced.

8. A heat-resistant energy-saving FDM printhead facing a vacuum environment as claimed in any one of claims 1 to 6 wherein: the material range suitable for the vacuum printing head is one or more of polymer and composite material thereof, metal alloy and composite material thereof, inorganic nonmetal and composite material thereof.

9. A heat-resistant energy-saving FDM printhead facing a vacuum environment as claimed in any one of claims 1 to 6 wherein: the melting point of the material suitable for the vacuum printing head is not higher than 800 ℃.

10. A heat-resistant energy-saving FDM printhead facing a vacuum environment as claimed in any one of claims 1 to 6 wherein: the material form suitable for the vacuum printing head comprises wires and strips.

11. The vacuum environment-oriented heat-resistant energy-saving FDM print head of claim 10, wherein: the cross section shapes of the wires comprise circles, triangles, quadrangles and polygons, and the cross section shapes of the strips comprise ellipses, triangles, quadrangles and polygons.