A binder forming method based on a non-continuous jetting composite structure printing process

Abstract

The application belongs to the technical field of additive manufacturing, and discloses a binder forming method based on a non-continuous jetting composite structure printing process. The method is suitable for binder jetting in an internal solid area and a surface area. The surface of the solid area is completely jetted with the binder, and the jetting thickness is adjustable; the internal area of the solid is jetted in a honeycomb shape. The internal and external parts are printed in a composite structure, which can greatly reduce the binder content of the printed part, improve the printing efficiency, and form stable connection of the blank through the grid structure, so that the strength, rigidity and energy absorption capacity of the blank are obviously increased.

Description

Technical Field

[0001] This invention relates to the field of binder jetting 3D printing technology in additive manufacturing, and particularly to a binder molding method based on a discontinuous jetting composite structure printing process. Background Technology

[0002] With the development of technology, binder jet printing has become an important process in manufacturing. This process features high forming efficiency, adaptability to a wide variety of materials, high material utilization, and a relatively rich range of achievable part geometries. By layering powder and then spraying binder onto the powder bed, specific areas of powder are bonded together. These layers are then printed and stacked to form the desired preform. The preform is then cured, degreased, and sintered to obtain a high-density sample.

[0003] Traditional binder jet printing often adopts a continuous jetting strategy. This method is easy to operate, but it has challenges in controlling the jetting volume and uniformity, especially in terms of the molding of internal structures and the improvement of the strength of the blank. The continuous jetting mode is difficult to achieve differentiated supply of binder in different areas of the component. The binder is prone to local enrichment and over-wetting, resulting in uneven distribution of binder in the blank and decreased interlayer bonding stability. Especially for the forming and processing of components with complex internal structures, it is impossible to control the internal microstructure of the blank as needed, and there are obvious deficiencies in improving the strength and stiffness of the blank [1-2]. Existing technologies lack binder jetting molding schemes that can prepare composite structures in an integrated manner, making it difficult to balance the forming accuracy of the component shape and the internal mechanical properties. Conventional molding processes cannot simultaneously improve the energy absorption capacity of the component through structural design [3].

[0004] Therefore, developing a binder molding method based on discontinuous jetting composite structure printing technology, which uses honeycomb structure inkjet technology in the solid area to achieve integrated fabrication of composite structures throughout the entire component, and simultaneously improves the strength, stiffness and energy absorption capacity of the blank, has become an urgent technical problem to be solved.

[0005] [1] Wang Haoran, Li Xin, Liu Chang. Types, formation mechanisms, effects and elimination methods of defects in binder jetting 3D printing [J]. 3D Printing & Additive Manufacturing, 2024(03):45-53.

[0006] [2]EMADY HN,STEVENS M,ROBINSON J.Understanding the Effect ofPrinting Parameters and Prewetting on Binder Jetting Continuous LineFormation[C] / / Utah Undergraduate Research Conference.Salt Lake City:UtahState University,2024. [3]ZHANG L,WANG Y,LIU H.Mechanical Performance and Microstructure ofSilica Powder–Calcium Binder Systems Fabricated by Binder Jetting 3D Printing[J].Journal of Materials in Civil Engineering,2026,38(4):04026021. Summary of the Invention In view of this, the present invention provides an adhesive molding method based on a discontinuous jetting composite structure printing process.

[0007] To achieve the above objectives, the present invention provides an adhesive molding method based on a discontinuous jetting composite structure printing process, comprising the following steps: Step 1: Establish a printing model. The printing model is constructed by spraying adhesive completely onto the surface area of ​​the solid printing object, and by spraying adhesive in a honeycomb structure onto the internal area of ​​the solid printing object, resulting in an internal honeycomb structure and an overall encapsulated outer surface. Step two: Print the green part according to the printing model; Step 3: The green blank is cured, degreased, and sintered to obtain the sample.

[0008] Preferably, in step two, the printing material for the green part is titanium alloy powder with a particle size range of 5-25μm.

[0009] Preferably, in step two, the printing parameters are set as follows: compaction roller return speed 10-30 mm / s, powder thickness 0.03-0.08 mm, and printing curing time 30-120 s.

[0010] Preferably, in step two, the thickness of the adhesive covering the solid printing surface area of ​​the green part is ≥60μm. This thickness ensures that the surface powder of the component is fully bonded, avoiding surface peeling and flaking, and ensuring the integrity of the outer contour and surface strength of the molded part; if the adhesive coverage thickness is less than 60μm, the surface powder will not bond sufficiently, and surface defects are likely to occur.

[0011] Preferably, in step two, the wall thickness of the honeycomb-shaped region inside the solid printing of the green part covered by the adhesive is ≥10μm. The internal honeycomb region does not need to bear the same load as the surface layer. Appropriately reducing the adhesive coverage thickness ensures the interconnection of the honeycomb structure and maintains structural integrity while reducing the amount of adhesive used. It also leaves pore channels to facilitate the full discharge of organic matter during the subsequent degreasing stage, preventing bubbling and cracking of the green part during degreasing. If the wall thickness is less than 10 μm, the thin honeycomb wall is prone to fracture, losing the load-bearing and energy-absorbing characteristics of the composite structure.

[0012] The honeycomb structure unit has a pore size of 300-900μm and a porosity of 60-90%.

[0013] Preferably, in step three, the curing temperature is 150-200℃ and the time is 1-5h.

[0014] Preferably, in step three, the degreasing is performed as follows: the degreasing heating rate is 1-6℃ / min, the degreasing temperature is 400-600℃, the holding time is 30-150min, the atmosphere is Ar, the vacuum degree is 0.1-1 bar, and the purity is >99.999%.

[0015] Preferably, in step three, the sintering process is as follows: heating to 1000-1360℃ at a rate of 5-10℃ / min, and sintering for 60-240 min.

[0016] Compared with the traditional continuous spray molding process, the present invention can increase the energy absorption capacity of sintered titanium alloy components by 25% to 40% and the bending stiffness of components by 15% to 30%. At the same time, it can effectively suppress the defects of local enrichment of binder, significantly improve the uniformity of internal components of the billet, and simultaneously improve the strength, stiffness and energy absorption capacity of the billet.

[0017] As can be seen from the above technical solutions, compared with traditional continuous spray molding technology, the adhesive molding method of the present invention has the following advantages and breakthroughs: 1. By using a discontinuous spraying strategy, the amount of adhesive sprayed can be differentiated and controlled in different zones, thereby achieving precise control of the composite structure inside and outside the component and overcoming the shortcomings of the traditional continuous spraying process, such as uneven adhesive distribution and inability to design the internal microstructure. 2. The solid region contains an embedded honeycomb composite structure, giving the component excellent strength, stiffness, and energy absorption capacity. Mechanical comparison tests show that, under the same external dimensions, compared to a solid titanium alloy component prepared by continuous spraying, the energy absorption efficiency of the composite structure sample of this invention is improved by more than 26%; detailed comparative experimental test data can be found in the specific embodiments and comparative examples. 3. The honeycomb structure achieves lightweight design, reducing the overall weight of the components by 21% while ensuring load-bearing performance; detailed comparison data of lightweight indicators can be found in the specific implementation examples below; 4. The molding process is highly automated, and the binder can be controlled in different zones, which effectively suppresses defects such as peeling and degreasing cracking of the blank, and significantly improves the yield. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 This is a flowchart of the present invention.

[0020] Figure 2 This is a product structure diagram of Example 1; where 1 is the outer solid shell of the component, and 2 is the internal honeycomb porous area. Detailed Implementation

[0021] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0022] Example 1 First, a three-dimensional model of the titanium alloy sample was designed, cut into CLI format files using slicing software, and then imported into an adhesive jet printer.

[0023] Titanium alloy powder particles with a particle size of 5–25 μm were selected and placed in the powder supply hopper for pre-treatment of powder drying and degassing before printing. The constructed printing model was loaded, with the surface area thickness set to 1 mm and the honeycomb area wall thickness set to 0.2 mm. The printing program was started to carry out 3D printing: during printing, the compaction roller return speed was 30 mm / s, the powder thickness was 0.08 mm, and the printing curing time was 120 s. The binder supply was controlled by partitioning using a discontinuous jetting strategy. The binder coverage thickness on the surface area of ​​the green body was set to 60 μm, and the binder coverage wall thickness in the honeycomb area inside the green body was set to 10 μm. The honeycomb structure unit pore size was 300 μm, and the porosity was 60%. After layer-by-layer printing, a green body was obtained.

[0024] The printed green blank is carefully removed and transferred to a hot air curing oven for curing: the curing temperature is 180℃ and the curing time is 3 hours; after curing, the green blank is transferred to a vacuum degreasing oven, the degreasing heating rate is 5℃ / min, the temperature is raised to 600℃, the holding time is 120 min, the protective atmosphere is high-purity Ar, the vacuum degree is 0.1 bar, and the argon purity is >99.999%; after degreasing, it is transferred to a sintering furnace, the temperature is raised to 1200℃ at a rate of 8℃ / min, the holding sintering time is 180 min, after sintering, it is slowly cooled with the furnace, and the surface floating powder is cleaned to obtain the final titanium alloy composite structure product.

[0025] Sample performance testing: Quasi-static compression test, weight measurement and appearance defect inspection were carried out on the titanium alloy composite component prepared in Example 1; the sample dimensions were 50mm×50mm×20mm; test results: the weight of the component was reduced by 21% compared with the solid component of the same outer dimensions; the energy absorption efficiency of the component was increased by 27%; the billet and sintered finished product had no peeling, degreasing and cracking defects, and the yield was high.

[0026] Example 2 First, a three-dimensional model of the titanium alloy sample was designed, cut into CLI format files using slicing software, and then imported into an adhesive jet printer.

[0027] Titanium alloy powder particles with a particle size of 5–25 μm were selected and placed in the powder supply hopper for pre-treatment of powder drying and degassing before printing. The constructed printing model was loaded, with the surface area thickness set to 2 mm and the honeycomb area wall thickness set to 0.3 mm. The printing program was started to carry out 3D printing: during printing, the compaction roller return speed was 30 mm / s, the powder thickness was 0.08 mm, and the printing curing time was 120 s. The binder supply was controlled by a discontinuous jetting strategy, with the binder coverage thickness on the surface area of ​​the green body set to 60 μm and the binder coverage wall thickness on the honeycomb area inside the green body set to 15 μm. The honeycomb structure unit pore size was 400 μm, and the porosity was 70%. After layer-by-layer printing, a green body was obtained.

[0028] The printed green blank is carefully removed and transferred to a hot air curing oven for curing: the curing temperature is 180℃ and the curing time is 3 hours; after curing, the green blank is transferred to a vacuum degreasing oven, the degreasing heating rate is 5℃ / min, the temperature is raised to 600℃, the holding time is 120 min, the protective atmosphere is high-purity Ar, the vacuum degree is 0.1 bar, and the argon purity is >99.999%; after degreasing, it is transferred to a sintering furnace, the temperature is raised to 1200℃ at a rate of 8℃ / min, the holding sintering time is 180 min, after sintering, it is slowly cooled with the furnace, and the surface floating powder is cleaned to obtain the final titanium alloy composite structure product.

[0029] Sample performance testing: Example 2: The outer dimensions of the component are consistent with those of Example 1. Test results: Due to the increased thickness of the adhesive wall in the honeycomb area, the overall load-bearing stiffness of the component is further improved. The weight of the component is reduced by 16% compared with the solid component, the energy absorption efficiency is increased by 31%, and the finished product has no cracks or peeling defects.

[0030] Comparative Example 1 This comparative example uses a traditional continuous adhesive spraying molding process to construct a three-dimensional model of a solid titanium alloy component with dimensions identical to that of Example 1. The component does not have a honeycomb porous structure inside, and the entire printing area is continuously and fully covered by adhesive spraying. The printing powder, powder particle size, powder spreading parameters, and the entire process parameters of curing-debinding-sintering are all completely consistent with those of Example 1.

[0031] The solid titanium alloy specimens prepared in this comparative example were subjected to the same quasi-static compression, weight, and appearance defect tests as those in the examples. Test results: The specimens are solid structures with high self-weight; the energy absorption efficiency is lower than that of the composite honeycomb components in Examples 1-2 under the same external dimensions; there is localized binder enrichment in the printed blanks, and some specimens show micro-cracks during the degreasing stage; the yield is lower than that of the discontinuous spraying process of this invention.

[0032] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0033] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for forming an adhesive based on a discontinuous jetting composite structure printing process, characterized in that, Includes the following steps: Step 1: Establish a printing model. The printing model is constructed by spraying adhesive completely onto the surface area of ​​the solid printing object, and by spraying adhesive in a honeycomb structure onto the internal area of ​​the solid printing object, resulting in an internal honeycomb structure and an overall encapsulated outer surface. Step two: Print the green part according to the printing model; Step 3: The green blank is cured, degreased, and sintered to obtain the sample.

2. The adhesive molding method according to claim 1, characterized in that, In step two, the printing material for the green part is titanium alloy powder with a particle size range of 5-25μm.

3. The adhesive molding method according to claim 1, characterized in that, In step two, the printing parameters are set as follows: compaction roller return speed 10-30mm / s, powder thickness 0.03-0.08mm, and printing curing time 30-120s.

4. The adhesive molding method according to claim 1, characterized in that, In step two, the thickness of the adhesive covering the solid printing surface area of ​​the green part is ≥60μm.

5. The adhesive molding method according to claim 1, characterized in that, In step two, the wall thickness of the honeycomb-shaped area inside the solid printing of the green part is ≥10μm covered by the adhesive.

6. The adhesive molding method according to claim 1, characterized in that, In step two, the cell size of the honeycomb structure is 300-900 μm, and the porosity is 60-90%.

7. The adhesive molding method according to claim 1, characterized in that, In step three, the curing temperature is 150-200℃ and the time is 1-5 hours.

8. The adhesive molding method according to claim 1, characterized in that, In step three, the degreasing process is as follows: the degreasing heating rate is 1-6℃ / min, the degreasing temperature is 400-600℃, the holding time is 30-150min, the atmosphere is Ar, the vacuum degree is 0.1-1 bar, and the purity is >99.999%.

9. The adhesive molding method according to claim 1, characterized in that, In step three, the sintering process is as follows: heating to 1000-1360℃ at a rate of 5-10℃ / min, and sintering for 60-240 min.

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