CN113733554A

CN113733554A - Method and device for forming high molecular parts by microwave and infrared radiation in composite mode

Info

Publication number: CN113733554A
Application number: CN202110966968.XA
Authority: CN
Inventors: 魏青松; 张净凯; 李继康; 毛贻桅; 赵丹雷
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2021-08-23
Filing date: 2021-08-23
Publication date: 2021-12-03

Abstract

The invention belongs to the additive manufacturing related technical field, and discloses a method and a device for forming a high molecular part by microwave and infrared radiation, wherein the method comprises the following steps of (1) preheating a powder bed on which premixed high molecular powder is paved by microwave and infrared radiation; the premixed polymer powder comprises a polymer material and a first radiation absorbing material, wherein the first radiation absorbing material comprises a microwave radiation absorbing material; (2) selectively laying a second radiation absorbing material onto the powder bed; the second radiation absorbing material comprises an infrared radiation absorbing material or comprises an infrared radiation absorbing material and a microwave radiation absorbing material; (3) sintering the powder bed by radiating the powder bed at least once by adopting infrared radiation alone or infrared radiation and microwave simultaneously; (4) and (4) repeating the steps (2) to (3) until the polymer part is manufactured. The invention realizes the high-speed, high-precision and high-quality forming of the high-molecular parts.

Description

Method and device for forming high molecular parts by microwave and infrared radiation in composite mode

Technical Field

The invention belongs to the technical field related to additive manufacturing, and particularly relates to a method and a device for forming a high-molecular part by microwave and infrared radiation in a composite mode.

Background

The polymer is also called polymer, plastic and the like, has the advantages of light weight, insulation, low melting point, easy processing and the like, and has large demand and dominates in the market of material increase manufacturing consumables. Currently, additive manufacturing technologies suitable for polymers include Fused Deposition Modeling (FDM), Stereolithography (SLA), Selective Laser Sintering (SLA), droplet jetting (3 DP), and the like. The forming principle and the used materials of the technologies are different, wherein FDM needs to prepare high polymer consumables into filaments or particles with a certain diameter, and the forming table is small, low in speed and difficult to form large-size parts; SLA does not need to be melted when forming the liquid photosensitive resin, and the temperature resistance and the strength of the material have certain limitations; SLS takes powdery macromolecules as raw materials, but high-energy laser beams are needed to apply heat to the powder, point-by-point scanning of point light spots reduces forming efficiency, and optical devices such as a laser, a vibrating mirror and a focusing mirror have high cost; 3DP utilizes high accuracy shower nozzle to spray the binder to polymer powder bed shaping face, and liquid binder plays the bridging effect after permeating the solidification in the powder bed, and the shaping is fast, but the part performance depends on the characteristic of binder, and the binder is mostly the organic solvent that has certain toxicity.

There are many researchers now proposing additive manufacturing methods based on droplet ejection of a surface sintered or bulk sintered powder bed, and patent WO2005011959 discloses a method of selectively incorporating particulate material using infrared imaging, by selectively supplying a quantity of radiation absorber material to the powder bed using a print head, and then supplying radiation energy to the entire powder bed using, for example, infrared lamps, the radiation absorber material absorbing electromagnetic radiation and converting it into heat energy to be transferred to the surrounding powder to cause sintering at an elevated temperature. Patent EP3388169 discloses a method and a system for producing a three-dimensional object, which utilizes the principle that exposure of the optically resonant particles to radiation causes optical resonance to heat up and transfer heat to the surrounding powder material to effect sintering.

The method can realize the selective sintering of the polymer powder bed without an optical focusing device and technology, but the energy supply mode and direction are single. The whole powder bed is mainly subjected to two types of energy input from the surface to the inside by upper surface radiation and bottom plate heat conduction, and because the depth of heat radiation penetrating into the powder bed is limited, and the upper surface is directly exposed in the air, most of heat is dissipated by convection and cannot be transferred downwards, the heat conductivity of the polymer powder is poor, and the speed of upward heat transmission of the bottom plate is low. Along with the printing process, the height of the formed powder is increased, the area far away from the forming surface does not receive radiation energy any more for a long time, the heat is gradually dissipated to the periphery, the whole powder forms a temperature gradient with low internal temperature and high upper and lower surface temperatures, and finally the performance of parts at different positions of the powder bed is different, especially large-volume parts are easy to warp and deform, or cracks occur due to internal stress, and even the parts cannot be formed.

EP1459871 discloses a method for producing three-dimensional objects by selective heating using microwave radiation, whereby a susceptor is selectively applied to a powder bed, and the susceptor is heated by microwave radiation and heat is transferred to the surrounding matrix powder to cause it to sinter at an elevated temperature. On one hand, the manufacturing process described in the patent does not include a powder bed preheating process step, the warpage deformation phenomenon often occurring in powder bed additive manufacturing can occur, and on the other hand, because the air in the direct exposure of the powder bed surface dissipates heat fast, the surface temperature is lower than the interior when only microwaves are used as an energy source, the surface is heated and sintered by enough energy, meanwhile, the interior can be overheated, and heat leakage to the surrounding non-forming area finally causes the dimensional error of the part. Still for example patent CN107262714 discloses a microwave sintering 3D printing device and technology suitable for many materials, and this patent uses multichannel spiral feeding mechanism and vibrates the whitewashed head and send out work raw and other materials powder and the transparent powder of microwave as the support to printing the plane, adopts upper substrate layer-by-layer compaction, the mode shaping work piece of once only microwave sintering at last. The parts manufactured by the method are integrally heated and cooled, and uneven deformation and shrinkage cannot occur, but the scheme of the patent is difficult to ensure the powder laying precision and efficiency at the same time, and is not beneficial to the mass production of the parts.

In summary, the conventional powder bed additive manufacturing method for polymer parts has the defects of high device cost, low forming speed, low precision and the like, and the conventional surface sintering and bulk sintering methods have the defects that uniform temperature field distribution of a powder bed is difficult to realize and prepared parts are easy to generate warping deformation and the like.

Disclosure of Invention

Aiming at the defects or improvement requirements of the prior art, the invention provides a method and a device for forming a high-molecular part by microwave and infrared radiation in a composite mode.

To achieve the above object, according to one aspect of the present invention, there is provided a method for forming a polymer part by microwave and infrared radiation, the method comprising the steps of:

(1) preheating a powder bed on which premixed polymer powder is paved by adopting microwave and infrared radiation; the premixed polymer powder comprises a polymer material and a first radiation absorbing material, wherein the first radiation absorbing material comprises a microwave radiation absorbing material;

(2) selectively laying a second radiation absorbing material onto the powder bed; wherein the second radiation absorbing material comprises an infrared radiation absorbing material or the second radiation absorbing material comprises an infrared radiation absorbing material and a microwave radiation absorbing material;

(3) irradiating the powder bed with infrared radiation alone or infrared radiation and microwaves at least once to sinter the region of the powder bed to which the second radiation absorbing material is applied;

(4) and (4) repeating the steps (2) to (3) until the polymer part is manufactured.

Further, the average particle diameter of the polymer powder material is 20 to 150 μm.

Further, the average particle diameter of the polymer powder material is 60 to 80 μm.

Further, the mass ratio of the first radiation absorbing material to the high polymer powder material is 1: 16-1: 200; the ratio of the particle size of the first radiation absorbing material to the particle size of the polymer powder material is 1:100 to 1: 1.

Further, the infrared radiation used during preheating is medium-wave infrared radiation with the wavelength between 2000nm and 4000 nm; the infrared radiation used during sintering is short-wave infrared radiation with the wavelength between 500nm and 1400 nm.

Further, the second radiation absorbing material has a particle size distribution in a range of 20nm to 1000 nm.

Further, in step (2), the second radiation absorbing material is applied to the powder bed by an inkjet print head.

Further, the second radiation absorbing material is homogeneously dispersed in the liquid matrix; the preheating temperature is 5-10 ℃ lower than the sintering temperature of the high polymer powder material.

According to another aspect of the present invention, there is provided an apparatus for microwave and infrared radiation composite forming of polymer parts, the apparatus being adapted to form polymer parts by using the method for microwave and infrared radiation composite forming of polymer parts as described above.

Generally, compared with the prior art, the method and the device for forming the high molecular parts by microwave and infrared radiation in a composite mode have the following beneficial effects:

1. the method takes microwave as a main preheating means to control the integral temperature uniformity of the powder bed, combines infrared radiation and microwave radiation as selective sintering means, and ensures that a non-forming area is almost unchanged while a forming area sprayed with a radiation absorption material is sintered by setting process parameters.

2. The invention combines the advantages of droplet ejection, radiation surface sintering and body sintering, and can realize selective sintering of powder with low cost, high efficiency and high quality to generate three-dimensional objects without expensive laser generators, focusing light paths and other devices.

3. According to the invention, the polymer powder and the radiation absorbing material are premixed, and the infrared radiation and the microwave are utilized to uniformly heat the whole inside and surface of the powder bed, so that the defects of internal temperature gradient of the powder bed and deformation, cracks and the like caused by the internal temperature gradient of the powder bed easily in the existing heating method are avoided, and meanwhile, a proper amount of radiation absorbing material can play a role in enhancing the polymer raw material.

4. The invention adopts an energy applying mode of compounding microwave and infrared radiation, and selectively applies energy to the high molecular powder in a semi-closed heat dissipation environment to control the whole temperature distribution, thereby relieving the defects of warping deformation, cracks and the like caused by uneven temperature distribution in the powder bed easily generated by the existing heating method.

5. The average particle size of the high polymer powder material is selected to be 20-150 microns, the porosity of a powder bed is too large due to too large powder particle size, large shrinkage is easy to occur in the subsequent sintering process, or the material flow cannot fill the pores in time, so that a formed part has more pores and the surface is too rough, and the powder flowability is poor due to too small powder particle size, so that the powder laying quality is poor.

6. The second radiation absorbing material has good stability when dispersed in a liquid matrix, and does not cause the problem of blockage of the jet orifice of the printing head due to particle agglomeration in the process of storage or printing.

Drawings

FIG. 1 is a schematic flow chart of a method for forming a polymer part by microwave and infrared radiation composite provided by the invention;

FIG. 2 is a schematic view of an apparatus for forming polymer parts by microwave and infrared radiation in accordance with the present invention;

fig. 3 is a schematic view of a showerhead provided by the present invention.

The same reference numbers will be used throughout the drawings to refer to the same or like elements or structures, wherein: 200-forming cavity, 201-powder bed, 211 a-forming platform bottom plate, 211 b-forming platform lifting rod, 211 c-forming platform side wall, 212 a-powder storage chamber bottom plate, 212 b-powder storage chamber lifting rod, 212 c-powder storage chamber side wall, 202-raw material powder, 213-powder laying device, 214-powder recovery chamber, 221-spray head, 222 a-first auxiliary agent storage box, 222 b-second auxiliary agent storage box, 223a-X direction moving mechanism, 223b-Y direction moving mechanism, 224 a-first liquid auxiliary agent, 224 b-second liquid auxiliary agent, 213-powder laying device, 231 a-preheating infrared radiation lamp tube, 231 b-preheating reflecting cover, 232 a-sintering microwave generating source, 232 b-sintering microwave guiding device, 233 a-sintered infrared radiation lamp, 233 b-sintered reflector, 234 a-sintered microwave generating source, 234 b-sintered microwave directing means, 241-formed plane temperature detector, 242-powder bed temperature detector, 250-computer control unit, 301-droplet ejection head, 302-ejection range, 303-area of formed plane.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. In addition, the technical features involved in the embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

Referring to fig. 1, the method for forming a polymer part by microwave and infrared radiation composite provided by the present invention mainly includes the following steps:

s1, mixing the polymer powder material with the first radiation absorbing material to obtain a pre-mixed polymer powder material.

Specifically, the polymer powder material comprises a crystalline polymer powder material and a non-crystalline polymer powder material, and the sintering temperature of the polymer powder material is between 50 and 300 ℃, preferably between 60 and 250 ℃. The sintering temperature is a melting temperature of the crystalline polymer or a glass transition temperature of the amorphous polymer.

The polymer powder material comprises non-crystalline polymer material and crystalline polymer material, such as non-crystalline polymer material such as polycarbonate, polystyrene, polymethyl methacrylate, polyvinyl alcohol, styrene-acrylonitrile copolymer, polyvinyl chloride, etc.; and the like, polyamide, thermoplastic polyurethane elastomer, high-density polyethylene, polyether block amide, polyformaldehyde, polylactic acid and other crystalline high-molecular materials.

The average particle size of the high polymer powder material is 20-150 microns, the excessive powder particle size can cause the excessive porosity of a powder bed, the large shrinkage is easy to occur in the subsequent sintering process or the material flow cannot timely fill the pores, so that the formed part has more pores and the surface is too rough, the too small powder particle size can cause the powder flowability to be poor, and the powder laying quality to be poor, and preferably, the particle size is 60-80 microns.

The first radiation absorbing material comprises a microwave radiation absorbing material, or the first radiation absorbing material comprises a microwave radiation absorbing material and an infrared radiation absorbing material. Wherein the first radiation absorbing material is used for absorbing radiation energy so as to preheat the whole powder bed to enable the powder bed to reach a preheating temperature.

Compared with microwave radiation absorbing materials, the high polymer powder materials are generally microwave transparent materials, can be completely transmitted by microwaves and can neither reflect nor absorb the microwaves.

The microwave radiation absorbing material is carbon material such as carbon black, graphite, carbon fiber, etc., ceramic material such as silicon carbide, barium titanate, etc., magnetic metal micro powder such as Fe, Co, Ni and alloy powder thereof, etc., ZnO, MnO₂、SnO₂、TiO₂And the like, or conductive polymer materials such as aniline, polypyrrole, polythiophene, polyacetylene, and the like.

The infrared radiation absorbing material is a metal nanoparticle, a semiconductor tube thermal conversion material, an organic photo-thermal material or a carbon-based material, wherein the metal nanoparticle is an Au nanoparticle, an Ag nanoparticle, a Cu nanoparticle, an Al nanoparticle, an In nanoparticle, a Pd nanoparticle, a Pt nanoparticle or a Bi nanoparticle; semiconductor photothermal conversion material into TiO₂、Ti₂O₃Oxides of Ti, Cu, etc₂Cu sulfide such as xS, copper selenide (Cu)₂xSe) and copper telluride (Cu)₂xTe) or the like, or WO₃～x、MoO₃X, etc. The organic photo-thermal material is organic conjugated polymer such as polypyrrole, polyaniline, polythiophene and polydopamine, or organic micromolecule such as porphyrin and indocyanine. The carbon-based material is carbon black, graphite, carbon nanotubes or graphene.

The infrared radiation absorbing material is a material which has an absorption rate of more than 90% in an infrared region and converts absorbed infrared radiation into heat energy. Preferably, the first radiation absorbing material is preferably a microwave radiation absorbing material, so as to achieve a good overall preheating effect, and may or may not contain a small amount of infrared radiation absorbing material, that is, if the first radiation absorbing material includes an infrared radiation absorbing material and a microwave radiation absorbing material, the mass of the microwave radiation absorbing material is far greater than that of the infrared radiation absorbing material.

The mixing method of the first radiation absorbing material and the polymer powder material is a ball milling method, a coprecipitation method, a stirring mixing method or a low-temperature crushing method, and preferably the ball milling method. The mass ratio of the first radiation absorbing material to the polymer powder material is 1: 16-1: 200, and preferably, the mass ratio of the first radiation absorbing material to the polymer powder material is 1: 20-1: 100.

The ratio of the particle size of the first radiation absorbing material to the particle size of the polymer powder material is 1:100 to 1: 1; preferably, the ratio of the particle size of the first radiation absorbing material to the particle size of the polymer powder material is 1: 20-1: 5; the particle size is the median particle size of the powder.

S2, uniformly paving the premixed polymer powder material on a powder bed, and preheating the powder bed by adopting microwave and infrared radiation to reach the preheating temperature.

Specifically, the single-layer powder spreading thickness adopted by powder spreading is 0.05-0.2 mm, the preferable single-layer powder thickness is 0.7-0.16 mm, and experiments prove that the single-layer powder thickness is within the numerical range, and the formed part blank has higher dimensional accuracy and strength.

The wavelength of the infrared radiation emitted by the infrared radiation generator for preheating overlaps with the absorption peak of the formed polymer powder, in which case the infrared radiation used for preheating can be efficiently absorbed by the polymer powder. Preferably, the infrared radiation during preheating is medium wave infrared radiation with a wavelength between 2000nm and 4000 nm.

The preheating temperature is 5-10 ℃ lower than the sintering temperature of the polymer powder, wherein the sintering temperature is the melting temperature of the crystalline polymer or the glass transition temperature of the amorphous polymer.

And S3, selectively paving a second radiation absorption material on the powder of the powder bed according to the section information of the part to be formed, wherein the second radiation absorption material comprises an infrared radiation absorption material, or the second radiation infrared absorption material comprises an infrared radiation absorption material and a microwave radiation absorption material.

Specifically, the second radiation absorbing material is applied to the powder bed through an inkjet printing head, the inkjet printing head is a piezoelectric type spray head or a bubble type spray head, and the number of the printing heads can be three or more, so as to improve the forming efficiency.

The second radiation absorbing material, which may be the same or different type than the first radiation absorbing material, comprises an infrared radiation absorbing material or comprises an infrared radiation absorbing material and a microwave radiation absorbing material, and the area to which the second radiation absorbing material is applied absorbs radiation and is converted to thermal energy better than the rest of the powder bed.

The second radiation absorbing material is dispersed in a liquid matrix in a mode of one or a combination of several of ball milling, ultrasonic oscillation, mechanical stirring, sanding and the like, and the liquid matrix comprises several of deionized water, organic solvent, dispersing agent, wetting agent, surfactant, pH regulator, microbial inhibitor, defoaming agent and the like or is used.

The particle size distribution range of the second radiation absorption material is 20 nm-1000 nm; the preferred second radiation absorbing material has a particle size distribution in the range of 20nm to 100 nm. The second radiation absorbing material has good stability when dispersed in a liquid matrix, and does not cause the problem of blockage of the jet orifice of the printing head due to particle agglomeration in the process of storage or printing.

S4, the powder bed is treated at least once with infrared radiation alone or in combination with microwave radiation, so that the region to which the second radiation absorbing material is applied is densified after reaching the sintering temperature.

Specifically, the powder bed may be treated using an infrared radiation generator alone or simultaneously with the microwave generator, depending on the composition of the second radiation absorbing material in step S3.

The radiation generator processes the powder bed one or more times, and the times and the power used for the processes depend on the temperature distribution of the forming plane; the desired temperature profile is a non-forming zone (i.e., the powder in the area where the second radiation absorbing material is not applied) that is treated to a temperature 2c to 10 c below the sintering temperature, and a forming zone (i.e., the powder in the area where the second radiation absorbing material is applied) that is treated to a temperature 2c to 10 c above the sintering temperature.

The infrared radiation generator used in the sintering step may be the same as or different from the infrared radiation generator used in the preheating step, and preferably, the infrared radiation generator used in this step has a wavelength different from that of the preheating; the peak value of the emission wavelength distribution curve of the infrared radiation generator for sintering coincides with the peak value of the infrared absorption wavelength distribution curve of the infrared radiation absorption material, in this case, the photothermal conversion efficiency of the infrared radiation absorption material is higher, and simultaneously, the peak value of the emission wavelength distribution curve of the infrared radiation generator for sintering is staggered with the peak value of the radiation absorption wavelength distribution curve of the polymer powder to be formed, so that the energy absorption difference between a forming area and a non-forming area is increased. Preferably, the infrared radiation of the infrared radiation generator for sintering is short-wave infrared radiation with a wavelength between 500nm and 1400 nm.

The infrared radiation generator used in the sintering step is fixed or movable, and preferably, the infrared radiation generator is movable and closer to the powder bed than the infrared radiation generator for preheating, in which case the radiation can be uniformly applied to the entire powder bed with a smaller volume of the radiation generator.

S5, repeating the steps S2, S3 and S4 until the whole polymer part is manufactured, and then taking out the polymer part after the whole polymer part is cooled and carrying out subsequent treatment or direct use.

Specifically, in the process of repeating the steps S2, S3 and S4, the process parameters of each step are adjusted in real time according to the temperature distribution condition of the forming surface so as to ensure the uniformity of the whole temperature of the powder bed; the process parameters include the power, frequency and processing time of the microwave generator, the power, radiation time of the infrared radiation lamp, the application amount of the second radiation absorbing material, and the like.

In the process of repeating the steps S2, S3 and S4, adjusting the process parameters of each step in real time according to the temperature distribution condition of the forming surface so as to ensure the uniformity of the whole temperature of the powder bed; the process parameters include the power, frequency and processing time of the microwave generator, the power, radiation time of the infrared radiation lamp, the application amount of the second radiation absorbing material, and the like.

After the forming process is finished, the cooling method of the powder bed comprises natural cooling and forced cooling, wherein the forced cooling refers to air cooling or water cooling of the other side of the material contacted with the powder bed; preferably, the powder bed is slowly and naturally cooled after molding, so that the defects that the powder bed has temperature gradient from inside to outside in the cooling process, the formed part is warped and deformed and the like are avoided.

The present invention is further illustrated in detail by the following specific examples.

Example 1

A method for forming a polymer part by microwave and infrared radiation comprises the following steps:

s1, screening out 800g of thermoplastic polyurethane elastomer powder with the average particle size of 40-60 mu m, 70g of silicon carbide powder with the average particle size of 5-10 mu m and 10g of copper sulfide powder with the average particle size of 400-600 nm by using mesh screens with different mesh numbers respectively, putting the screened out powder into a ball mill, and mechanically mixing for 24 hours to obtain uniformly mixed polymer powder.

S2: laying the mixed powder into a thin layer of 0.05mm, and starting a preheating infrared radiator and a preheating microwave generator to preheat the powder bed to ensure that the surface and the side wall of the powder bed reach 100-110 ℃.

And S3, according to the cross-section information obtained by the processing model of the computer component, selectively applying a liquid matrix with a second radiation absorption material on the powder bed by an auxiliary agent application module, wherein the second radiation absorption material is nano carbon black particles accounting for 5 percent of the mass fraction of the auxiliary agent and has the average particle diameter of 20 nm-40 nm.

S4, the powder bed is treated by using a sintered infrared radiator and a sintered microwave generator, the temperature of the non-forming area is raised to 110-120 ℃, and the temperature of the powder containing the second radiation absorbing material reaches 130-140 ℃, and plastic flow occurs and the powder is bonded with each other.

S5: and repeating the steps S2, S3 and S4, timely adjusting the power and the processing time of preheating radiation in the step S2, the type and the amount of ink of the auxiliary agent applying module in the step S3, the power and the processing time of sintering radiation in the step S4 and other process parameters according to temperature data acquired by the thermal imager and the thermocouple until the whole part is manufactured, and taking out the part after the whole part is cooled along with the powder bed for subsequent processing or direct use.

Example 2

s1 Polymer blend powder having an average particle size of 60nm to 80 μm was prepared by coprecipitation using 1000g of polymethyl methacrylate powder, 40g of copper nanoparticles having an average particle size of 600nm to 800nm, and 10g of polypyrrole powder.

S2: laying the mixed powder into a 0.2mm thin layer, and starting a preheating infrared radiator and a preheating microwave generator to preheat the powder bed to ensure that the surface and the side wall of the powder bed reach 90-95 ℃.

And S3, according to the cross-section information obtained by the processing model of the computer component, selectively applying a liquid matrix with a second radiation absorbing material on the powder bed by an auxiliary agent applying module, wherein the second radiation absorbing material comprises copper nanoparticles accounting for 4% of the mass fraction of the auxiliary agent and graphite accounting for 1% of the mass fraction of the auxiliary agent, and the average grain diameter is 300 nm-500 nm.

S4, the powder bed is processed by using a sintering infrared radiator and a sintering microwave generator, the temperature of the non-forming area is raised to 110-115 ℃, and the temperature of the powder containing the second radiation absorption material reaches 125-130 ℃, so that plastic flow occurs and the powder are bonded together.

Example 3

s1, respectively screening 2000g of polyamide powder with the average particle size of 70-100 microns, 5g of ferroferric oxide powder with the average particle size of 5-10 microns and 5g of copper sulfide powder with the average particle size of 400-600 nm by using mesh screens with different mesh numbers, putting the screened powder into a ball mill, and mechanically mixing for 24 hours to obtain uniformly mixed polymer mixed powder.

S2: laying the mixed powder into a thin layer of 0.07mm, and starting a preheating infrared radiator and a preheating microwave generator to preheat the powder bed to ensure that the surface and the side wall of the powder bed reach 100-110 ℃.

And S3, according to the cross-section information obtained by the processing model of the computer component, selectively applying a liquid matrix with a second radiation absorbing material on the powder bed by an auxiliary agent applying module, wherein the second radiation absorbing material is black titanium dioxide accounting for 5% of the mass fraction of the auxiliary agent, and the average grain diameter of the second radiation absorbing material is 800 nm-1000 nm.

S4, the powder bed is treated with a sintered infrared radiator and a sintered microwave generator, the non-forming zone temperature is raised to 160 ℃ to 170 ℃, and the powder containing the second radiation absorbing material reaches 180 ℃ to 190 ℃ and plastic flow occurs and adheres to each other.

Referring to fig. 2 and 3, the present invention further provides an apparatus for microwave and infrared radiation composite forming of polymer parts, the apparatus includes a powder supply module, an auxiliary agent application module, a radiation generation module, a temperature detection module located in a forming cavity 200, and a computer control assembly 250 located outside the forming cavity 200, wherein the powder supply module, the auxiliary agent application module, the radiation generation module, and the temperature detection module are respectively connected to the computer control assembly 250.

The powder supply module includes a forming table, a powder storage chamber, a powder laying device 213, and a powder recovery chamber 214. The forming platform comprises a forming platform bottom plate 211a, a forming platform lifting rod 211b and a forming platform side wall 211c, the forming platform bottom plate 211a and the forming platform side wall 211c form a cavity with an open upper part, the high polymer powder material to be sintered and formed is placed in the cavity to form a powder bed 201, and the plane of the surface of the powder bed 201 is a forming plane. The forming platform base plate 211a is connected to the forming platform lifting rod 211b and can move in a direction perpendicular to the forming plane under the driving of the forming platform lifting rod 211 b.

In another embodiment, the forming platform may be a detachable structure, and may be moved to a specific position or detached from the specific position by a guide rail slider, a polished rod slider, or the like, and may be positioned and fixed by a positioning hole, a guide post, a clamping groove, a magnet, or the like.

The powder storage chamber is located on the side or above the side of the forming station, which stores the raw material powder 202 to be formed. In some embodiments, the powder storage chamber may be identical in structure to the forming platform and located to the side of the forming platform; the powder storage chamber includes a powder storage chamber bottom plate 212a, a powder storage chamber lift rod 212b, and a powder storage chamber side wall 212c, the raw material powder 202 is stored in an upper open cavity formed by the powder storage chamber bottom plate 212a and the powder storage chamber side wall 212c, the powder storage chamber bottom plate 212a is connected to the powder storage chamber lift rod 212b, and the powder storage chamber bottom plate 212a can be lifted by the powder storage chamber lift rod 212b and push the raw material powder 202 inside to exceed a forming plane, then a powder laying device 213 removes the raw material powder 202 exceeding the forming plane and lays it flat on an upper surface of the forming platform, and excess powder enters the powder recovery chamber 214.

In some embodiments, the powder placement device 213 may be a doctor blade, a powder placement roller, or a combination thereof. It will be appreciated that the powder storage chamber may be located above or laterally above the forming table, as long as a metered amount of powder can be delivered to the interior of the powder laying device 213 or an area that can be operated to lay down powder. In some embodiments, the powder storage chamber may also be an upper powder dropping structure, and the powder is moved by powder dropping, belt conveying, screw conveying, gas conveying, and the like.

The auxiliary agent applying module comprises a spray head 221, an auxiliary agent storage box and a spray head moving mechanism, wherein the spray head 221 is respectively connected with a first auxiliary agent storage box 222a and a second auxiliary agent storage box 222b, and the first auxiliary agent storage box 222a is used for storing a first liquid auxiliary agent 224a containing an infrared radiation absorbing material and a second liquid auxiliary agent 224b containing a microwave radiation absorbing material.

It is understood that in other embodiments, one or more of the additive storage cartridges may be provided, the liquid additive in the same additive storage cartridge may contain both the infrared radiation absorbing material and the microwave radiation absorbing material, and the liquid additives in different additive storage cartridges may contain the same amount of the same kind of radiation absorbing material or different amounts of the different kinds of radiation absorbing material.

The second radiation absorbing material has good stability when dispersed in a liquid matrix, and the problem of blockage of the jet orifice of the printing head caused by particle agglomeration in the storage or printing process is avoided.

The head 221 uses a droplet ejection head in which a first auxiliary agent storage cartridge 222a and a second auxiliary agent storage cartridge 222b correspond to different rows of droplet ejection holes, and a head moving mechanism includes an X-direction moving mechanism 223a and a Y-direction moving mechanism 223b to drive the X-direction movement and the Y-direction movement of the head 221, respectively, to move the head 221 to an arbitrary position on a forming plane. The sprayer moving mechanism can be in a sliding rail sliding block mode, a ball screw mode, a hydraulic rod mode and the like.

The powder placement device 213 is connected to the X-direction movement mechanism 223a of the head movement mechanism, and is driven by the X-direction movement mechanism 223 a. In other embodiments, the powder layering device 213 may have a separate moving mechanism, and the moving direction thereof may be the same as or different from that of the head moving mechanism.

When the nozzle 221 is used, the nozzle 221 can apply the auxiliary agent to any position of the molding plane by moving the nozzle moving mechanism once along the length direction of the molding plane.

The radiation generation module comprises a radiation preheating module and a radiation sintering module; the radiation preheating module is used for preheating a forming plane in the forming process so that the temperature of the plane reaches a temperature suitable for forming, and preheating the whole powder so as to reduce the temperature gradient of the whole powder; the radiation sintering module is used for applying energy to the forming plane and/or the powder whole body, so that the temperature of the area receiving the radiation absorbing material applied by the radiation auxiliary agent applying module is raised to be above the sintering point to form the whole body.

The radiation generation module comprises a preheating infrared radiator, a preheating microwave generator, a sintering infrared radiator and a sintering microwave generator, wherein the preheating microwave generator is positioned right above the forming platform, and the preheating infrared radiator is positioned on two sides of the preheating microwave generator. The preheating infrared radiator includes an infrared radiation lamp 231a and a preheating reflection cover 231b, and the infrared radiation lamp 231a generates medium wave infrared radiation having a wavelength peak of 2500nm and irradiates the powder bed of the forming plane under the action of the preheating reflection cover 231 b. The preheating microwave generator comprises a preheating microwave generating source 232a and a preheating microwave guide device 232b, the preheating microwave generating source 232a generates microwave radiation of 2450Hz, the microwave radiation passes through the preheating microwave guide device 232b and then is emitted to the forming platform in parallel to enter the powder bed 201, microwave absorbing materials in the powder generate dielectric loss under the action of microwave electromagnetic, the microwave energy is converted into heat energy to enable the temperature of the powder around the microwave absorbing materials to be increased, the content and the types of the microwave absorbing materials are different, and the heat generated after the microwave absorption is different.

The sintered infrared radiator includes a sintered infrared radiation lamp 233a and a sintered reflecting housing 233b, and can generate short-wave infrared radiation having a wavelength peak of 1000nm, and the sintered microwave generator includes a sintered microwave generating source 234a and a sintered microwave guide 234b, and can generate microwave radiation of 2435 Hz.

The positions of the preheating infrared radiator and the preheating microwave generator are relatively fixed, and the sintering infrared radiator and the sintering microwave generator are connected with the X-direction moving mechanism 223a of the nozzle moving mechanism and driven by the X-direction moving mechanism 223 a. The action width of the sintering infrared radiator and the sintering microwave generator is the same as or slightly wider than that of the forming platform, and the sintering infrared radiator and the sintering microwave generator can be moved to be right above any area in the powder bed 201 to apply any power radiation under the drive of the X-direction moving mechanism 223 a. In some other examples, the sintered infrared radiator and the sintered microwave generator may have separate moving mechanisms, the moving directions of which may be the same as or different from those of the shower head moving mechanism.

The temperature detection module comprises a forming plane temperature detector 241 and a powder bed temperature detector 242, wherein the forming plane temperature detector 241 is used for measuring the real-time temperature distribution of a forming plane in the forming process and feeding back the obtained temperature data to the computer control component 250. The computer control unit 250 processes the received data and controls the actions of the powder supply module, the aid application module and the radiation generation module in the subsequent forming process according to the processing result.

In this embodiment, the forming plane temperature detector 241 is a thermal imager, the powder bed temperature detector 242 is a thermocouple, and the forming plane temperature detector 241 is located above the forming platform, and captures the temperature distribution of the powder on the forming platform at a certain angle. The powder bed temperature detectors 242 are located in the forming table bottom plate 211a and the forming table side wall 211c to collect real-time temperatures lateral and below the powder bed.

The computer control module 250 is used for processing the three-dimensional model of the part and temperature feedback data, controlling the laying of powder, the movement of the spray head and the ink-jet action, and controlling the opening and closing of the radiation generation module and the power according to the temperature feedback data.

Analysis revealed that: when infrared radiation is used independently for selective sintering, the whole powder bed can be heated through the infrared radiation on the upper surface and a heating plate on the bottom (or the side surface), because the penetration depth of the infrared radiation is shallow, and the upper surface is directly exposed in the air to dissipate heat quickly, the temperature of the powder bed is actually kept mainly by the heat conduction of the bottom, but the heat conductivity of the high polymer powder is poor, a temperature gradient from bottom to top can be formed after the powder bed is formed to a certain height, the part can be deformed and has internal stress after being taken out, under some conditions, the surface temperature is too low, and the energy of the infrared radiation can not even melt a forming area.

When microwave is used alone for selective sintering, the microwave can penetrate through the high polymer powder to heat the microwave absorbing material in the powder bed, if only the microwave is used as a heat source, when the microwave absorbing material content of each layer of the powder is consistent, the heat obtained by the microwave is the same, but because the upper surface is exposed in the air for faster heat dissipation, when the surface obtains enough heat for powder melting, the heat obtained in the interior is excessive, and even the surrounding (non-forming area) powder is melted and bonded together, so that the surface precision is reduced.

The invention provides a method for forming a high molecular part by microwave and infrared radiation in a composite mode.

It will be understood by those skilled in the art that the foregoing is only a preferred embodiment of the present invention, and is not intended to limit the invention, and that any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A method for forming a high molecular part by microwave and infrared radiation in a composite mode is characterized by comprising the following steps:

2. The method for composite forming of polymer parts by microwave and infrared radiation according to claim 1, wherein: the average particle diameter of the polymer powder material is 20-150 mu m.

3. The method for microwave and infrared radiation composite forming of polymer parts according to claim 2, characterized in that: the average grain diameter of the polymer powder material is 60-80 μm.

4. The method for composite forming of polymer parts by microwave and infrared radiation according to claim 1, wherein: the mass ratio of the first radiation absorbing material to the high polymer powder material is 1: 16-1: 200; the ratio of the particle size of the first radiation absorbing material to the particle size of the polymer powder material is 1:100 to 1: 1.

5. A method of composite forming of polymer parts by microwaves and infrared radiation according to any one of claims 1 to 4, wherein: the infrared radiation used during preheating is medium-wave infrared radiation with the wavelength between 2000nm and 4000 nm; the infrared radiation used during sintering is short-wave infrared radiation with the wavelength between 500nm and 1400 nm.

6. A method of composite forming of polymer parts by microwaves and infrared radiation according to any one of claims 1 to 4, wherein: the second radiation absorbing material has a particle size distribution range of 20nm to 1000 nm.

7. A method of composite forming of polymer parts by microwaves and infrared radiation according to any one of claims 1 to 4, wherein: in step (2), the second radiation absorbing material is applied to the powder bed by an inkjet print head.

8. The method for composite forming of polymer parts by microwave and infrared radiation according to claim 7, wherein: the second radiation absorbing material is uniformly dispersed in the liquid matrix; the preheating temperature is 5-10 ℃ lower than the sintering temperature of the high polymer powder material.

9. A device for microwave and infrared radiation composite forming of polymer parts is characterized in that: the device is used for forming the polymer part by adopting the method for forming the polymer part by combining the microwave and the infrared radiation according to any one of claims 1 to 8.