CN109692967B

CN109692967B - Bulk powder for 3D printing and preparation method and printing method thereof

Info

Publication number: CN109692967B
Application number: CN201910118795.9A
Authority: CN
Inventors: 侯春树
Original assignee: Zhongshengde Investment Shenzhen Co ltd
Current assignee: Zhongshengde Investment Shenzhen Co ltd
Priority date: 2019-02-15
Filing date: 2019-02-15
Publication date: 2022-06-17
Anticipated expiration: 2039-02-15
Also published as: CN109692967A

Abstract

The invention provides bulk powder for 3D printing, a preparation method thereof and a printing method thereof. The bulk powder for 3D printing is a bulk particle, and the bulk particle comprises the following components in percentage by weight: 90-98% of powder and 2-10% of binder; wherein the particle size distribution D90 of the powder is 0.3-35 μm. The solid content of the 3D printing bulk powder is remarkably improved, the relative density after sintering can reach more than 97%, the grain size distribution D90 of the bulk particles is 50-200 mu m, the grain size distribution of the powder is fine, the improvement of the sintering density of the product and the mechanical property are facilitated, the sintering density of the prepared 3D printing bulk powder is high, the using amount of the binder is small, and the preparation process is simplified. The 3D printing method provided by the invention has the advantages of reduced energy consumption, high printing speed, high safety and reduced production cost, and can be widely used for 3D printing.

Description

Bulk powder for 3D printing and preparation method and printing method thereof

Technical Field

The invention relates to the technical field of 3D printing, in particular to bulk powder for 3D printing and a preparation method and a printing method thereof.

Background

The 3D printing (3D printing) technology is also called a three-dimensional printing technology, and is a technology for constructing an object by using a bondable material such as powder or plastic and the like in a layer-by-layer printing manner on the basis of a digital model file. It can directly produce parts with any shape from computer graphic data without machining or any die, thus greatly shortening the development period of products, improving productivity and reducing production cost. Products such as lamp housings, body organs, jewelry, football boots customized to the player's foot shape, racing car parts, solid state batteries, and cell phones, violins, etc. customized for an individual can be manufactured using this technique.

The 3D printing technique is actually a general term for a series of rapid prototyping techniques, and the basic principle thereof is laminate manufacturing, in which a rapid prototyping machine forms the cross-sectional shape of a workpiece by scanning in an X-Y plane, and performs displacement of the slice thickness intermittently in a Z coordinate, to finally form a three-dimensional part. At present, the rapid prototyping technologies in the market are classified into a 3DP (three-dimensional display) technology, an SLA (full Service-Level array) stereo light curing technology, an SLS (full Selective Laser Sintering) Selective Laser Sintering technology, a DMLS (full Direct Metal Laser-Sintering) Direct Metal Laser Sintering technology, an FDM (full Deposition Modeling) Fused Deposition Modeling technology, and the like.

The 3D printing technology of metal parts, being the leading and most potential technology in the entire 3D printing system, is an important development direction of advanced manufacturing technology. The metal 3D printing technology is divided into 3 types according to the adding mode of metal powder: 1) the method is widely adopted by equipment manufacturers and various departments and institutes at present, comprises a powder flow conveyed by a laser irradiation nozzle, laser engineering net forming of laser and conveyed powder working simultaneously, and the method is used more domestically at present; 2) selective laser melting technology; 3) the electron beam melting technique, which uses an electron beam to melt a metal powder spread in advance, is similar to the principle of the type 1 except that a heat source is used.

3D printing technology was first applied on plastic materials. The FDM fusion lamination forming technology is the main mode at present, and is characterized in that hot melt materials are heated and melted, meanwhile, a three-dimensional spray head selectively coats the materials on a workbench under the control of a computer according to sectional profile information, and a layer of section is formed after the materials are rapidly cooled. After the formation of one layer is finished, the machine workbench descends by one height (namely the layering thickness) to continue the formation until the whole solid modeling is formed. The forming material has various types, the formed part has higher precision and low price, and the forming die is mainly suitable for forming small plastic parts. However, the plastic products produced in this way are not very strong and do not meet the customer's requirements. In order to increase the strength of products and improve the performance of the products, the DMLS technology adopts alloy powder materials as raw materials, and the raw materials are fused by energy laser after metal is focused, and then 3D printing and laminating are carried out. The method has the characteristics of high precision, high strength, high speed, smooth surface of a finished product and the like, is generally applied to the aerospace and industrial accessory manufacturing industries, and can be used for high-order die design and the like. However, laser sintering equipment is complex, energy consumption in the preparation process is high, factors such as product resolution, equipment cost, product appearance requirements and mass production capacity are comprehensively considered, and the laser sintering equipment cannot be widely popularized and applied at present and is not suitable for being used by high-melting-point non-metal materials. Therefore, the current 3D printing method of non-metallic materials generally uses SLA (Service-Level agent) stereo light curing technology to meet the current industrial requirements, and the process needs to be performed by processes such as molding, degreasing, sintering and the like. In addition, the sintering shrinkage rate of the product is large and the thermal deformation is large due to the slurry state.

CN106270510A discloses a method for manufacturing metal/alloy parts by printing with a plastic 3D printer, which comprises the steps of raw material sintering pretreatment, raw material coating, powder reduction, 3D printing, degreasing, sintering and the like, wherein the main adhesive is Polyformaldehyde (POM), the adhesive with the content of 8-12 wt% is not only added, but also a special degreasing process is needed to finish the product, and the irregular shape of the crushed powder is not beneficial to the powder spreading action. CN109026916A discloses a 3D printing method, comprising: mixing a powdery material to be processed and a powdery nylon material; melting the nylon material by adopting a selective laser sintering technology to bond the material to be processed to form a green body; heating the green body for thermal degreasing to volatilize the nylon material; heating the green body to a sintering temperature of the material to be processed to sinter the green body; the ambient temperature of the green body is reduced to room temperature to obtain a dense part. Although both methods combine powder injection molding and 3D printing technologies, the feeding mode is powdery or irregular, and the following disadvantages are mainly present: the particles are irregular, so the fluidity is not good, and the addition amount of the binder is too much (up to 8-12 wt%). When the laser beam is used for melting the adhesive and combining the adhesive with the lower layer into a whole, the powdery or granular feed is irregular in shape, so that the adhesive cannot be effectively and uniformly coated, the uneven surface thickness and the too low bulk density of the product are easily caused, and the sintering shrinkage variation is large; meanwhile, the excessive adhesive needs special degreasing process and equipment support.

In the prior art, a high-power laser device is used as a method for manufacturing metal parts by using a 3D printing technology, and the popularization strength is limited because the device cost is high, the operation safety and the equipment maintenance cost are high and the unit price of metal raw powder is high due to the power of 2000W-10000W. Therefore, it is necessary to provide a powder of a PM (powder metallurgy) ultrafine powder having a high density, a high mechanical property, sintering characteristics and a low cost. Therefore, the invention integrates the new processes of DMLS, FDM and traditional powder metallurgy sintering, takes the advantages of high resolution function of DMLS, fast printing and FDM type polymer binder mode and high homogeneity of traditional powder metallurgy sintered products, and forms a new process combination.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide the bulk powder for 3D printing, the preparation method and the printing method thereof, and the prepared bulk powder for 3D printing has the advantages of high solid content, high sintering density, small particle size, quick printing, low price and high safety, and can be widely applied to 3D printing.

One of the purposes of the invention is to provide a bulk powder for 3D printing, and to achieve the purpose, the invention adopts the following technical scheme:

the 3D printing bulk powder is bulk particles, and the bulk particles comprise the following components in percentage by weight:

90 to 98 percent of powder

2-10% of a binder;

wherein the particle size distribution D90 of the powder is 0.3-35 μm; the particle size distribution D90 of the agglomerate particles is 50-200 μm.

According to the 3D printing bulk powder provided by the invention, the powder material is beneficial to promoting the sintering density of the product and improving the mechanical property along with the increase of the solid content and the use of the powder with smaller particle size; the binder has a lower dosage than the feed content for injection molding (MIM), so a special degreasing process is not needed, the prepared 3D printing bulk powder has a sintered density of more than 90% and a high density (relative density of more than 97%), wherein the particle size D90 of the bulk powder is 50-200 mu m, the particle size distribution D90 of the bulk particles is 50-200 mu m, the flowability and stability of powder paving of a powder mass on a workbench can be improved, and the used raw materials are low in price and can be widely applied to 3D printing.

In the invention, the agglomerate particle comprises the following components in percentage by weight:

90-98% of powder, for example, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97% or 98% by weight of the powder.

2-10% of binder, for example, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% by weight of binder.

Wherein D90 of the powder is 0.3-35 μm, for example, D90 of the powder is 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 29 μm, 30 μm, 33 μm, 31 μm, or the like. If the particle size of the powder is too large, D90 is larger than 35 μm, the sintering temperature is high during sintering, and the sintering can be dense, so the energy consumption is large, the particle size of the powder is small, and the sintering densification and the sintering temperature reduction are facilitated.

In the present invention, the D90 of the 3D printing bulk powder is 50 to 200 μm, for example, D90 of the 3D printing bulk powder is 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm or 200 μm.

According to the invention, the bulk powder for 3D printing is prepared from the following components in percentage by weight:

the bulk powder for 3D printing is a bulk particle, the powder is agglomerated into a powder dough after a granulation process under the action of a solvent, a binder and a dispersing agent, and after the solvent is volatilized under the action of temperature, the binder forms a layer of polymer film on the surface of the powder dough and forms a bulk particle at the same time.

Specifically, the bulk particles comprise the following components in percentage by weight:

18-30% of the powder, for example, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, or 30% by weight of the powder.

0.6 to 10% of a binder, for example, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, 8.5%, 9%, 9.5%, or 10% by weight of the binder.

60 to 80% of a solvent, for example, 60%, 61%, 62%, 63%, 64%, 65%, 66%, 67%, 68%, 69%, 70%, 71%, 72%, 73%, 74%, 75%, 76%, 77%, 78%, 79%, or 80% by weight of the solvent.

0.01 to 0.05% of a dispersant, for example, 0.01%, 0.02%, 0.03%, 0.04%, or 0.05% by weight of a dispersant.

In the invention, the powder is metal powder or ceramic powder. The solvent comprises an aqueous solvent and an organic solvent; the adhesive comprises paraffin series and thermosetting series, the adhesive, the dispersing agent and the solvent are matched with each other for use, so that the offset effect of misuse is avoided, for example, when the powder is metal powder, the solvent is an organic solvent, and the adhesive and the dispersing agent are both made of materials suitable for metal powder in the field; when the powder is ceramic powder, the solvent can be selected from aqueous solvent and/or organic solvent, and the adhesive and the dispersant are all materials suitable for ceramic powder in the field. Preferably, the D90 of the metal powder is 1 to 35 μm, for example, the D90 of the metal powder is 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, 15 μm, 16 μm, 17 μm, 18 μm, 19 μm, 20 μm, 21 μm, 22 μm, 23 μm, 24 μm, 25 μm, 26 μm, 27 μm, 28 μm, 29 μm, 30 μm, 31 μm, 32 μm, 33 μm, 34 μm or 35 μm. Preferably, the ceramic powder has a D90 of 0.3 to 2 μm, for example, the ceramic powder has a D90 of 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, or 2 μm.

Wherein the metal powder is any one or a mixture of at least two of a stainless steel material, an iron-based material, a magnetic material, a non-ferrous metal material and a high-specific gravity metal material; typical but non-limiting combinations of the mixtures are stainless steel materials, mixtures of ferrous materials, stainless steel materials, mixtures of non-ferrous materials, mixtures of ferrous materials, magnetic materials, mixtures of non-ferrous materials, stainless steel materials, ferrous materials, mixtures of magnetic materials, non-ferrous materials, mixtures of high specific gravity metal materials, mixtures of ferrous materials, magnetic materials, non-ferrous materials, high specific gravity metal materials, mixtures of stainless steel materials, ferrous materials, magnetic materials, non-ferrous materials, high specific gravity metal materials.

Preferably, the non-ferrous metal material is any one or a mixture of at least two of copper alloy, aluminum alloy and titanium alloy; typical but non-limiting combinations of the mixtures are copper alloys, mixtures of aluminum alloys, mixtures of copper alloys, titanium alloys, mixtures of aluminum alloys and titanium alloys, mixtures of copper alloys, aluminum alloys and titanium alloys.

Preferably, the high specific gravity metal material is a tungsten alloy.

The ceramic powder is any one or a mixture of at least two of an oxide ceramic material, a carbide ceramic material, a nitride ceramic material and a graphite material; typical but non-limiting combinations of said mixtures are oxide ceramic materials, mixtures of carbide ceramic materials, mixtures of oxide ceramic materials, nitride ceramic materials, mixtures of oxide ceramic materials, graphite materials, mixtures of carbide ceramic materials, nitride ceramic materials, mixtures of carbide ceramic materials, graphite materials, mixtures of nitride ceramic materials and graphite materials, oxide ceramic materials, carbide ceramic materials, a mixture of nitride ceramic materials, a mixture of oxide ceramic materials, carbide ceramic materials and graphite materials, a mixture of oxide ceramic materials, nitride ceramic materials and graphite materials, a mixture of carbide ceramic materials, nitride ceramic materials and graphite materials, a mixture of oxide ceramic materials, carbide ceramic materials, nitride ceramic materials and graphite materials.

Preferably, the oxide ceramic material is any one or a mixture of at least two of alumina ceramic, zirconia ceramic and piezoelectric ceramic; typical but non-limiting combinations of such mixtures are mixtures of alumina ceramics, zirconia ceramics, mixtures of alumina ceramics, piezoelectric ceramics, mixtures of zirconia ceramics and piezoelectric ceramics, mixtures of alumina ceramics, zirconia ceramics and piezoelectric ceramics.

Preferably, the piezoelectric ceramics are lead zirconate titanate (PZT) ceramics series and/or Strontium Bismuth Titanate (SBT) ceramics series.

Preferably, the carbide ceramic material is any one or a mixture of at least two of silicon carbide ceramic, tungsten carbide ceramic, vanadium carbide ceramic, titanium carbide ceramic, tantalum carbide ceramic and boron carbide ceramic;

preferably, the nitride ceramic material is any one of aluminum nitride ceramic, silicon nitride ceramic, boron nitride ceramic, titanium nitride ceramic and chromium nitride ceramic or a mixture of at least two of the same.

The binder is paraffin binder and/or thermosetting binder; the content of the binder is far lower than the dosage of 13.5-17 wt% in CN106270510A in the prior art, and the content of the macromolecular binder is low, and a Polyformaldehyde (POM) material is not selected, so that special degreasing processes such as catalytic degreasing and the like are not needed, and degreasing and sintering treatment can be directly performed according to a traditional powder metallurgy sintering mode.

Preferably, the paraffin-based binder is a low-temperature paraffin-based binder and/or a high-temperature paraffin-based binder; preferably, the high temperature paraffin-based binder is any one or a mixture of at least two of polyethylene WAX (PE-WAX), polypropylene WAX (PP-WAX) and vinyl acetate and ethylene copolymer WAX (EVA-WAX).

Preferably, the thermosetting plastic binder is any one of or a mixture of at least two of phenol resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin and polyurethane. Typical but non-limiting combinations of the mixtures are mixtures of phenol-formaldehyde resins, urea-formaldehyde resins, mixtures of phenol-formaldehyde resins, melamine resins, mixtures of urea-formaldehyde resins, melamine resins, mixtures of epoxy resins, silicone resins, mixtures of phenol-formaldehyde resins, urea-formaldehyde resins, melamine resins, mixtures of epoxy resins, silicone resins and polyurethanes, mixtures of melamine resins, unsaturated polyester resins, epoxy resins, silicone resins and polyurethanes, mixtures of phenol-formaldehyde resins, urea-formaldehyde resins, melamine resins, unsaturated polyester resins, epoxy resins, silicone resins and polyurethanes, the mixture is not limited to the above combinations but may be other combinations of the above raw materials, only some of which are listed, and is not listed here for reasons of space.

The second purpose of the invention is to provide a preparation method of the bulk powder for 3D printing, which comprises the following steps: and mixing the powder with the binder according to the proportion, and granulating to obtain the bulk powder for 3D printing.

According to the preferable scheme, 18-30% of powder, 0.6-10% of binder, 60-80% of solvent and 0.01-0.05% of dispersant are uniformly mixed according to weight percentage to form suspension-shaped slurry, and the bulk powder for 3D printing of the bulk particles is obtained through a spray granulation process, a rolling granulation process or a fluidized bed granulation process.

The spray granulation of the present invention refers to a granulation method in which a slurry or a solution is sprayed into a granulation tower, and the slurry or the solution is dried and agglomerated under the action of hot air spray, thereby obtaining spherical granules.

The specific process of spray granulation is as follows: according to the weight percentage, stirring and mixing 18-30% of powder, 0.6-10% of binder, 60-80% of solvent and 0.01-0.05% of dispersant uniformly to obtain suspension slurry, combining the suspension slurry with a feeding port end of spray drying equipment or pouring the suspension slurry into a spray trough, continuously spraying the suspension slurry out of an upper spray head, and performing heat exchange in a downward deposition process under the action of gravity through contact with a lower hot air inlet so as to dry the mixed material into a spherical shape, wherein the solvent is volatilized, and the binder forms spherical particles with a layer of high polymer film on the surface of a powder dough to obtain the spherical powder for 3D printing of the spherical particles.

The preparation method can control the size and roundness of the powder dough by controlling the content of the solvent, the spraying pressure and the spraying speed during spray granulation, and is beneficial to 3D printing speed and sintering characteristics.

Preferably, the spray is a centrifugal spray having a pressure of 0.6 to 5MPa, for example, a pressure of 0.6MPa, 0.7MPa, 0.8MPa, 0.9MPa, 1MPa, 1.5MPa, 2MPa, 2.5MPa, 3MPa, 3.5MPa, 4MPa, 4.5MPa, 5 MPa; the temperature of the air inlet of the centrifugal spray is 300-350 ℃, for example, the temperature of the air inlet is 300 ℃, 310 ℃, 320 ℃, 330 ℃, 340 ℃ and 350 ℃; the evaporation amount is 30-90 kg/h, for example, 30kg/h, 40kg/h, 50kg/h, 60kg/h, 70kg/h, 80kg/h, 90 kg/h.

Preferably, the drying temperature is 100 to 170 ℃, for example, the drying temperature is 100 ℃, 110 ℃, 120 ℃, 130 ℃, 140 ℃, 150 ℃, 160 ℃ and 170 ℃.

The invention also aims to provide a printing method of the bulk powder for 3D printing, which comprises the following steps:

1) using the bulk powder for 3D printing as a raw material, and printing a green body with a preset shape by using a 3D printer;

2) sintering the green body obtained in the step 1) to obtain a formed part.

According to the 3D printing method provided by the invention, the powder injection molding technology and the 3D printing technology are combined to obtain the high-fluidity spherical powder for 3D printing with high solid content powder, and when the high-fluidity spherical powder is applied to 3D printing, the printing equipment uses low-power laser equipment or electron beam equipment, so that expensive printer equipment is not needed.

In the step 1), the 3D printer adopts a mode of heating, melting and powder spreading by laser beams or electron beams to print.

Preferably, in step 1), the power of the laser beam or electron beam is 15W to 200W, for example, a laser engraving machine, which is much lower than the high power of 2000W to 10000W of a laser machine used in DMLS technology. The main difference is that the power of the molten polymer of the present invention is much lower than that of DMLS molten metal.

Preferably, in the step 2), the sintering temperature is 1200-1900 ℃, and the sintering time is 2-3 h; for example, the sintering temperature can be 1200 ℃, 1250 ℃, 1300 ℃, 1350 ℃, 1400 ℃, 1450 ℃ or 1500 ℃, 1600 ℃, 1700 ℃, 1800 ℃ or 1900 ℃, and the sintering time can be 2h, 2.1h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.7h, 2.8h, 2.9h or 3h, etc. During sintering, the ceramic powder can be sintered in an atmospheric furnace, and the metal powder can be sintered in a vacuum or atmospheric furnace.

Preferably, in the step 2), a post-processing step is further included after the sintering; the skilled person can perform post-processing on the sintered part according to actual conditions, and the post-processing mode can be selected independently, for example, the post-processing is sand blasting, polishing, wire drawing, water electroplating, sputtering or evaporation and the like.

As a preferable aspect of the present invention, the printing method includes the steps of:

1) the method comprises the following steps of taking bulk powder for 3D printing as a raw material, adopting a 3D printer to spread powder, heating and melting the powder by using a laser beam or an electron beam to finish one-layer printing, spreading a next layer of powder on the printed printing layer, printing the next layer, and circularly printing a green body with a preset shape in such a way;

2) sintering the green body obtained in the step 1) at 1200-1900 ℃ for 2-3 h, and post-processing the sintered part to obtain a formed part.

According to the printing method, the 3D printing bulk powder is used as a raw material, the advantages of high resolution of DMLS laser beams and the advantages of materials used in an FDM mode are mainly combined, heating and melting treatment can be carried out through low-power laser equipment and electron beam equipment, complex and expensive laser heating equipment is not needed, low sintering temperature is adopted, energy consumption is reduced, production cost is reduced, and the 3D printing method is beneficial to launching and popularization in the 3D printing market.

The recitation of numerical ranges herein includes not only the above-recited numerical values, but also any numerical values between non-recited numerical ranges, and is not intended to be exhaustive or to limit the invention to the precise numerical values encompassed within the range for brevity and clarity.

Compared with the prior art, the invention has the beneficial effects that:

(1) the 3D printing bulk powder material has the advantages that the solid content of the powder material is remarkably improved, the solid content can reach more than 90 wt% after spray granulation and drying, the powder with smaller particle size and D90 of 0.3-35 mu m is used as a raw material, the improvement of the sintering density of the product is facilitated, the particle size distribution D90 of the prepared 3D printing bulk powder material bulk particles is 50-200 mu m, the density is high, the relative density can reach more than 95%, the sintering density is high, the using amount of a binder is small, and the preparation process is simplified.

(2) The preparation method of the bulk powder for 3D printing provided by the invention has the advantages that the solid content of the powder material in the bulk powder for 3D printing is obviously improved, the powder content can reach more than 90 wt% after spray granulation and drying, and the method is simple and easy to implement; the size and roundness of the powder agglomerate can be controlled by controlling the content of the solvent, the spraying pressure and the spraying speed during spraying granulation, and the 3D printing speed and the sintering characteristic can be improved.

(3) According to the 3D printing method, the bulk powder for 3D printing is used as a raw material, the traditional powder spraying granulation technology and the 3D printing technology are combined, complex products with high resolution can be printed faster than FDM type products, the development process is shortened, and mass production and popularization are achieved.

(4) According to the 3D printing method, the high-molecular binder is heated and melted by the low-power laser equipment or the electron beam equipment, complex and expensive laser heating equipment is not needed, the energy consumption is reduced, the production cost is reduced, and the method can be widely applied to 3D printing.

Drawings

FIG. 1 is a process flow diagram of a 3D printing method of the present invention;

FIG. 2 is a schematic diagram of the structure of the agglomerate grains of the agglomerate powder for 3D printing according to the present invention;

fig. 3 is a schematic view of the agglomerated particle of the agglomerated powder for 3D printing according to the present invention.

The reference numbers are as follows:

100-powder; 200-bulk particles; 300-polymer film.

Detailed Description

The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached figures 1, 2 and 3.

For the purpose of facilitating an understanding of the present invention, the present invention will now be described by way of examples. It should be understood by those skilled in the art that the examples are only for the understanding of the present invention and should not be construed as the specific limitations of the present invention.

The 3D printing method disclosed by the invention comprises the following steps as shown in figure 1:

(1) preparing slurry: firstly, uniformly stirring 18-30 wt% of powder, 0.6-10 wt% of binder, 60-80 wt% of solvent and 0.01-0.05 wt% of dispersant in a stirring tank to form a suspension slurry state;

(2) spray granulation: joining the slurry obtained in the step (1) with a feeding port end of spray drying equipment or pouring the slurry into a spray tank, setting the drying temperature to be 100-170 ℃, the air inlet temperature to be 300-350 ℃, the evaporation capacity to be 30-70 kg/h, the spray pressure to be 0.6-5 MPa and the rotating speed to be 60-19000 rpm, continuously spraying the slurry out through an upper spray head, contacting with hot air from a lower hot air inlet in the downward deposition process under the action of gravity and carrying out heat exchange, heating and evaporating the solvent, then returning the solvent to a solvent recovery area to be condensed into liquid, and forming a spherical powder mass by the binder and the powder mass and then enabling the powder mass to reach a bottom powder collection area; drying the atomized slurry into spherical powder, the powder has the sintering property of the ultra-fine powder and high fluidity during forming, as shown in FIG. 3;

(3)3D printing and forming: the high-fluidity and high-compactness powder dough is printed according to a DMLS operation mode: paving a thin layer of powder on a working table, paving a second layer of powder upwards after the focused laser beam draws a shape according to a product structure, and repeating the powder paving-laser melting and bonding actions until the product is finished after the focused laser beam draws a shape according to the product structure to finally obtain a blank product (GREEN PARTS);

(4) and (3) high-temperature sintering: directly placing the green blank obtained in the step (3) in a high-temperature sintering furnace, and sequentially setting the temperature and the heating rate to sinter the green blank into a high-density product; the sintering temperature is between 1200 ℃ and 1900 ℃ and the temperature is kept for 2 to 3 hours; the product with the relative density of more than 97 percent can be obtained;

(5) post-processing treatment: and (3) performing post-processing treatment on the surface of the product sintered at high temperature in the step (4) according to requirements, such as: sand blasting, polishing, wire drawing, water plating, sputtering or vapor deposition (PVD).

The shape of the 3D printing bulk powder prepared by the invention is shown in figures 2 and 3. 100 is powder, 200 is bulk particle, and a layer of polymer film 300 is attached on the surface of the powder. Liquid slurry formed by the powder under the action of a solvent, a binder and a dispersant is subjected to spray granulation and drying, the solvent is volatilized and then is agglomerated into a powder ball, and the binder forms a layer of polymer film on the surface of the powder.

Example 1

The bulk powder for 3D printing of the embodiment is in a spherical shape after spray granulation, the particle size distribution D90 of 316 metal powder is 22-25 μm, and the particle size distribution D9080-120 μm of the powder bulk is formed after the spray granulation process. The alcohol solvent mainly plays a role as a carrier and is responsible for combining the metal powder and the binder into a whole.

The contents of the components are as follows according to the weight percentage:

the D90 is formed into powder with the particle size of 80-120 mu m by spraying, drying and granulating, wherein the powder accounts for 95 percent, and the adhesive accounts for 5 percent.

After the 3D printing forming of the green body is carried out for 3 hours at 1360 ℃ of the traditional 316L sintering curve, the sintering density of 7.85g/cm can be obtained³(relative density 99%) of the product.

Example 2

The agglomerated powder for 3D printing of the embodiment is in a spherical shape after spray granulation, the particle size distribution D90 of the 316 metal powder is 22-25 μm, and the particle size distribution D9080-120 μm of the agglomerated powder formed after the spray granulation process. The alcohol solvent plays a main role as a carrier and is responsible for combining the metal powder and the binder into a whole.

the granules are sprayed, dried and granulated to form D9080-120 mu m powder lumps, wherein 90% of the powder accounts for the powder, and 10% of the adhesive accounts for the adhesive.

After the 3D printing forming of the green body is carried out for 3 hours at 1360 ℃ of the traditional 316L sintering curve, the sintering density of 7.85g/cm can be obtained³(relative density 99%) product.

Example 3

The pelletized powder for 3D printing of this example is spherical after spray granulation, and yttrium-stabilized zirconia (3Y-ZrO)₂) The particle size distribution D90 of the powder is 0.3-0.5 μm, and the particle size distribution D9080-120 μm of the powder mass is formed after the spray granulation process. The ultrapure aqueous solvent plays a major role here as a carrier, responsible for stabilizing the yttrium-stabilized zirconia (3Y-ZrO)₂) The powder and the binder are combined into a whole.

the granules are sprayed, dried and granulated to form D9080-120 mu m powder lumps, wherein the powder accounts for 92.5 percent, and the adhesive accounts for 7.5 percent.

3D printing to form a blank, and stabilizing zirconium oxide (3Y-ZrO) with conventional yttrium₂) After the sintering curve is kept at 1450 ℃ for 3 hours, the sintered density of 6.01g/cm can be obtained³(relative density 99%) product.

Example 4

The bulk powder for 3D printing of this example is in a spherical shape after spray granulation, and yttrium-stabilized zirconia (3Y-ZrO)₂) The particle size distribution D90 of the powder is 0.3-0.5 μm, and the particle size distribution D9080-120 μm of the powder mass is formed after the spray granulation process. The ultrapure aqueous solvent plays a major role here as a carrier, responsible for stabilizing the yttrium-stabilized zirconia (3Y-ZrO)₂) The powder and the binder are combined into a whole.

Example 5

The 3D printing bulk powder material is in a spherical shape after spray granulation, the particle size distribution D90 of the ceramic silicon carbide powder is 0.5-1 μm, and the particle size distribution D9080-120 μm of the powder bulk formed after the spray granulation process. The ultrapure water solvent plays a main role here as a carrier, responsible for integrating the ceramic powder with the binder.

the mixture is sprayed, dried and granulated to form D9080-120 mu m powder, wherein 89% of the powder and 11% of the binder are contained.

The green body is formed by 3D printing through a traditional ceramic sintering process, and the sintering density of 3.05g/cm can be obtained after the sintering curve is maintained at 1900 ℃ for 2 hours³(relative density 95%) product.

Comparative example 1

This comparative example is different from example 1 in that D90 of the powder was 80 μm, and the rest was the same as example 1.

In order for the resulting agglomerate particles to be useful for 3D printing, a sintering temperature of 1390 ℃ or higher is required.

Comparative example 2

The comparative example differs from example 1 in that the binder is 25% by weight and the percentage of binder addition is subtracted equally from the percentage of 316L metal powder, alcohol solvent and dispersant, respectively, to ensure that the sum of the total percentages is unchanged, all else being the same as example 1.

In order to obtain the bulk particles for 3D printing, the content of the binder is too high, which not only needs to increase the degreasing process time, but also increases the sintering variation due to large shrinkage during sintering, which complicates the process.

Comparative example 3

The main difference between this comparative example and example 1 is that the PE-WAX adhesive is replaced with an adhesive mainly composed of polyoxymethylene engineering plastic, and the rest is the same as that of example 1.

In order to obtain a printing material applied to 3D printing, the weight percentage of the binder taking polyformaldehyde engineering plastic as a main body needs to be increased to 12%, so that a special catalytic degreasing device and a special catalytic degreasing process are needed in a comparison example, the process is complicated, and the operation safety and the production cost are increased.

The present invention is illustrated by the above-mentioned examples, but the present invention is not limited to the above-mentioned detailed process equipment and process flow, i.e. it is not meant to imply that the present invention must rely on the above-mentioned detailed process equipment and process flow to be practiced. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.

Claims

1. A printing method of bulk powder for 3D printing without a special degreasing process is characterized by comprising the following steps:

2) sintering the green body obtained in the step 1) to obtain a formed part;

the bulk powder for 3D printing is a bulk particle, and the bulk particle is prepared from the following components in percentage by weight:

18 to 30 percent of powder

0.6 to 5 percent of binder

60 to 80 percent of solvent

0.01-0.05% of a dispersant;

the powder is metal powder or ceramic powder, and the binder is paraffin binder and/or thermosetting binder;

wherein the particle size distribution D90 of the powder is 0.3-35 μm; the particle size distribution D90 of the agglomerate particles is 50-200 mu m;

the special degreasing process comprises catalytic degreasing.

2. The printing method according to claim 1, wherein the metal powder has a D90 of 1 to 35 μm.

3. The printing method according to claim 1, wherein the ceramic powder has a D90 of 0.3 to 2 μm.

4. The printing method according to claim 1, wherein the metal powder is any one of a stainless steel material, an iron-based material, a magnetic material, a non-ferrous metal material, a high specific gravity metal material, or a mixture of at least two of them.

5. The printing method of claim 4, wherein the non-ferrous material is any one of a copper alloy, an aluminum alloy, and a titanium alloy or a mixture of at least two thereof.

6. The printing method of claim 4, wherein the high specific gravity metallic material is a tungsten alloy.

7. The printing method according to claim 1, wherein the ceramic powder is any one of an oxide ceramic material, a carbide ceramic material, a nitride ceramic material and a graphite material or a mixture of at least two of the oxide ceramic material, the carbide ceramic material, the nitride ceramic material and the graphite material.

8. The printing method of claim 7, wherein the oxide ceramic material is any one of alumina ceramic, zirconia ceramic, and piezoelectric ceramic or a mixture of at least two thereof.

9. The printing method according to claim 8, wherein the piezoelectric ceramic is of lead zirconate titanate ceramic family and/or of bismuth strontium titanate ceramic family.

10. The printing method of claim 7 wherein the carbide ceramic material is any one of or a mixture of at least two of a silicon carbide ceramic, a tungsten carbide ceramic, a vanadium carbide ceramic, a titanium carbide ceramic, a tantalum carbide ceramic, and a boron carbide ceramic.

11. The printing method of claim 7, wherein the nitride ceramic material is any one of or a mixture of at least two of an aluminum nitride ceramic, a silicon nitride ceramic, a boron nitride ceramic, a titanium nitride ceramic, and a chromium nitride ceramic.

12. The printing method according to claim 1, wherein the paraffin-based binder is a low temperature paraffin-based binder and/or a high temperature paraffin-based binder.

13. The printing method according to claim 12, wherein the high temperature paraffin-based binder is any one or a mixture of at least two of polyethylene wax, polypropylene wax, and vinyl acetate and ethylene copolymer wax.

14. The printing method according to claim 1, wherein the thermosetting plastic-based binder is any one of or a mixture of at least two of phenol resin, urea resin, melamine resin, unsaturated polyester resin, epoxy resin, silicone resin, and polyurethane.

15. The printing method of claim 1, wherein the solvent is an aqueous solvent or an organic solvent.

16. The printing method according to claim 1, wherein the 3D printing dough is prepared by: and mixing the powder with the binder according to the proportion, and granulating to obtain the bulk powder for 3D printing.

17. The printing method of claim 16, wherein 18-30% by weight of the powder, 0.6-5% by weight of the binder, 60-80% by weight of the solvent, and 0.01-0.05% by weight of the dispersant are uniformly mixed, and the 3D printing agglomerated powder is obtained through a granulation process.

18. The printing method of claim 17, wherein the granulation process is spray granulation, tumbling granulation, or fluid bed granulation.

19. The printing method according to claim 18, wherein the specific process of spray granulation is as follows: according to the weight percentage, 18-30% of powder, 0.6-5% of binder, 60-80% of solvent and 0.01-0.05% of dispersing agent are uniformly stirred and mixed to obtain suspension slurry, the suspension slurry is jointed with a feed inlet end of spray drying equipment or poured into a spray trough, the suspension slurry is continuously sprayed out from an upper spray head, and is subjected to downward deposition under the action of gravity and is contacted with a lower hot air inlet to carry out heat exchange, so that the mixed material is dried into a spherical shape, the solvent is volatilized, and the binder forms a layer of bulk particles with a high polymer film on the surface of a powder dough to obtain the bulk powder for 3D printing.

20. The printing method according to claim 19, wherein the temperature of the spray drying is 100 to 170 ℃.

21. The printing method according to claim 19, wherein the spraying manner is centrifugal spraying, the pressure of the centrifugal spraying is 0.6-5 MPa, the temperature of an air inlet of the centrifugal spraying is 300-350 ℃, and the evaporation amount is 30-90 kg/h.

22. The printing method according to claim 1, wherein in the step 1), the 3D printer performs printing by adopting a mode of heating, melting and powder laying by using a laser beam or an electron beam.

23. The printing method according to claim 22, wherein in step 1), the power of the laser beam or the electron beam is 15W to 200W, and the focusing size of the laser beam is 0.01 mm to 0.02 mm.

24. The printing method according to claim 1, wherein in the step 2), the sintering temperature is 1200-1900 ℃, and the sintering time is 2-3 h.

25. The printing method according to claim 1, wherein in step 2), the step of post-processing is further included after the sintering.

26. The printing method of claim 25, wherein the post-processing is sand blasting, polishing, wire drawing, water plating, sputtering, or evaporation.

27. A printing method according to claim 1, characterized in that it comprises the steps of:

1) the method comprises the following steps of taking bulk powder for 3D printing as a raw material, adopting a 3D printer to spread the powder, heating and melting a binder on the surface layer of the powder by using a laser beam or an electron beam to finish one layer of printing, spreading a next layer of powder on the printed printing layer, performing next layer of printing, and circularly printing a green body in a preset shape in such a way;