A preparation method for an inner mold of a composite material helical spring based on 4D printing

Abstract

The present invention relates to a preparation method of a composite material helical spring inner mold based on 4D printing, comprising the following steps: 1), establishing a three-dimensional model of the inner mold; 2), printing an intelligent deformable part: performing 4D printing with hydrogel as the raw material; printing a layer of composite semi-permeable membrane on the end circular cross-section and the middle large-diameter circular cross-section; printing valves on a layer inward from the semi-permeable membrane with a thermosensitive material as the raw material; coating a layer of heat-insulating and waterproof material on the surface except for the circular cross-section; 3), preparing the inner mold: setting a container filled with water and capable of being uniformly heated, putting the printed intelligent deformable part into the container until the water absorption reaches equilibrium, and taking out the inner mold; 4), demolding through external excitation of brine: putting the inner mold after molding into a container filled with brine, the inner mold continuously shrinks, and finally loses water to be less than the minimum diameter of the helical spring and reaches equilibrium, and successful demolding is achieved. The inner mold prepared by the present invention can facilitate the molding and demolding of the helical spring, and can be quickly recycled.

Description

Technical Field

[0001] The present invention relates to a method for preparing a mold, and particularly to a method for preparing an inner mold of a composite material helical spring based on 4D printing, belonging to the technical field of molds.

Background Art

[0002] The 3D printing technology is a rapid prototyping technology proposed in the 1990s of the 20th century. With the development of the 3D printing technology and the field of intelligent materials, the 4D printing technology has emerged, providing new solutions for realizing the intelligence of printed components and reducing the design complexity, etc. The 4D printing technology combines an intelligent material system, adding a time dimension on the basis of the 3D printing technology. When specific changes occur in the external conditions, the printed object will produce pre-designed shape changes or changes in other physical properties over time to achieve intelligent rapid prototyping.

[0003] In recent years, composite material helical springs have been widely used in automotive parts due to their advantages that cannot be compared with steel springs, such as high specific modulus, high specific strength, strong designability, low density, good fatigue performance, and corrosion resistance. However, due to the helical stepped shape of the helical spring, the difficulty of its preparation has been greatly improved. In particular, the forming and demoulding of fiber-reinforced composite material helical springs are the main problems in their preparation. The preparation of each spring requires melting a mold, with high costs and low mechanization, and it is difficult to achieve the rapid mass production of composite material helical springs.

[0004] Therefore, to solve the above technical problems, it is indeed necessary to provide an innovative method for preparing an inner mold of a composite material helical spring based on 4D printing to overcome the defects in the prior art.

Summary of the Invention

[0005] To solve the above problems, the purpose of the present invention is to provide an intelligent and efficient method for preparing an inner mold of a composite material helical spring based on 4D printing, and the prepared inner mold can facilitate the forming and demoulding of the helical spring and can be recycled quickly.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is: a method for preparing an inner mold of a composite material helical spring based on 4D printing, which includes the following process steps:

[0007] 1), establishing a three-dimensional model of the inner mold: according to the preset deformation process and its function, dividing the three-dimensional model into regions, that is, the model is divided into two parts, namely the end part and the middle large-diameter part; the end part is divided into three regions from the surface to the inside in the direction of the circular cross-section, which are the semi-permeable membrane, the thermosensitive material, and the hydrogel;

[0008] 2), Print the intelligent deformable part: Set the printing parameters for the end part, the large-diameter part in the middle, and the three regions. Using hydrogel as the raw material, perform 4D printing on the end part and the large-diameter part in the middle respectively; Print a composite semi-permeable membrane that can only pass water molecules on the circular cross-section of the end and the circular cross-section of the large-diameter part in the middle as the first valve; Print the second valve on the layer inside the semi-permeable membrane with a thermosensitive material as the raw material; Finally, coat a layer of heat-insulating and waterproof material on the surface except for the circular cross-section.

[0009] 3), Under external excitation, prepare the inner mold: Set a container filled with water that can be heated evenly, put the printed intelligent deformable part into the container until the water absorption reaches equilibrium, and take out the inner mold for forming the spiral spring.

[0010] 4), Demold through the external excitation of brine: Put the inner mold after forming into a container filled with brine. The inner mold continuously shrinks and finally loses water until it is smaller than the minimum diameter of the spiral spring and reaches equilibrium, and the demolding is successful.

[0011] The preparation method of the composite material spiral spring inner mold based on 4D printing of the present invention is further as follows: In the step 2), the hydrogel is specifically a carbon nanotube composite hydrogel; The composite semi-permeable membrane is a composite semi-permeable membrane composed of aromatic polyamide and cellulose acetate; The thermosensitive material uses ceramics.

[0012] The preparation method of the composite material spiral spring inner mold based on 4D printing of the present invention is further as follows: In the step 2), when printing the intelligent deformable part, in the way of taking the center as the origin and the diameter diverging, according to the required length in the diameter direction, regulate the proportion of the hydrophilic material and the hydrophobic material content in the hydrogel, and print out a small long tube; Among them, the hydrophilic material content of the end part is a, and the hydrophilic material content of the large-diameter part in the middle is b, and the hydrophilic material content satisfies a / b = Va / Vb, where Va is the volume of the end part and Vb is the volume of the large-diameter part in the middle.

[0013] The preparation method of the composite material spiral spring inner mold based on 4D printing of the present invention is further as follows: The hydrophilic material content in the hydrogel of the large-diameter part in the middle is greater than that of the end part, so that after receiving water excitation, the large-diameter part in the middle expands more than the end part.

[0014] The preparation method of the composite material spiral spring inner mold based on 4D printing of the present invention is further as follows: The step 3) is specifically: Put the intelligent deformable part into water in the range of 10° to 50°, the thermosensitive material shrinks, voids appear, and the hydrogel absorbs water and expands until it reaches equilibrium; Then slowly raise the water temperature to above 60 degrees until the thermosensitive material expands to block the voids.

[0015] The preparation method of the composite material spiral spring inner mold based on 4D printing of the present invention is further as follows: After the inner mold in step 3) is taken out, continue to bake the cross-section of the inner mold with the ceramic part for 20 minutes to make the ceramic expand to completely block the gap.

[0016] The preparation method of the composite material spiral spring inner mold based on 4D printing of the present invention is further as follows: Coat another layer of heat-insulating and waterproof material on the surface of the inner mold obtained in step 3) except for the circular cross-section.

[0017] The preparation method of the composite material spiral spring inner mold based on 4D printing of the present invention is further as follows: The heat-insulating and waterproof material is specifically oil felt or tarpaulin.

[0018] The preparation method of the composite material spiral spring inner mold based on 4D printing of the present invention is further as follows: In step 4), the brine is an NaCl solution with a mass fraction ranging from 10% to 35% and a temperature range of 10° to 50°.

[0019] The preparation method of the composite material spiral spring inner mold based on 4D printing of the present invention is also as follows: Immerse the demolded inner mold in a water container and perform step 3) to enable the inner mold to be used for the forming of spiral springs again.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1. The carbon nanotube composite hydrogel used in the preparation method of the composite material spiral spring inner mold based on 4D printing of the present invention has excellent mechanical properties and good swelling properties at the same time. It can expand after absorbing water and be used for the forming of spiral springs, and can shrink after losing water, facilitating quick demolding.

[0022] 2. The inner mold prepared by the present invention can be recycled quickly, solving the problem in the prior art that one inner mold needs to be melted for making one spiral spring, and can completely solve the mass production problem of composite material spiral springs.

Description of the Drawings

[0023] Figure 1 It is a schematic flow chart of the preparation method of the composite material spiral spring inner mold based on 4D printing of the present invention.

[0024] Figure 2 It is a schematic structural diagram of the composite material spiral spring inner mold of the present invention.

[0025] Figure 3 It is a sectional view of the composite material spiral spring inner mold of the present invention.

[0026] Figure 4 It is a schematic diagram of the intelligent deformable part printed in step 2) of the present invention.

[0027] Figure 5 It is a schematic diagram of the printing method in step 2) of the present invention.

[0028] Figure 6 It is a schematic diagram of the area where the heat-insulating and waterproof material is coated on the inner mold in step 3) of the present invention.

[0029] Figure 7 It is a schematic diagram showing that the intelligent deformation part of the present invention absorbs water to reach equilibrium under the combined excitation of water and temperature in step 3).

[0030] Figure 8 It is a schematic diagram of the intelligent deformation part of the present invention after reaching equilibrium under the excitation of a container filled with low-temperature brine in step 4).

[0031] Figure 9 It is a schematic diagram of the deformation process of the inner mold of the composite material helical spring of the present invention under external excitation.

Detailed implementation manners

[0032] Please refer to the attached Figure 1 to the attached Figure 9 As shown, the present invention is a preparation method of an inner mold of a composite material helical spring based on 4D printing. Among them, the inner mold of the composite material helical spring is a columnar body with a spiral groove shape on the surface, which is composed of a large cylinder in the middle and two small cylinders at both ends. The groove shape is consistent with the thread of the helical spring, and the helical spring can be wound on the inner mold according to the groove shape for the forming of the helical spring.

[0033] The preparation method of the inner mold of the composite material helical spring based on 4D printing includes the following technological steps:

[0034] 1), Establish a three-dimensional model of the inner mold: According to the preset deformation process and its function, divide the three-dimensional model into regions, that is, the model is divided into two parts, namely the end part and the middle large-diameter part. The end part is divided into three regions from the surface to the inside in the direction of the circular cross-section, which are the semi-permeable membrane 1, the thermosensitive material 2, and the hydrogel 3, as shown in the attached Figure 2 and the attached Figure 3 shown.

[0035] 2), Print the intelligent deformation part, as shown in the attached Figure 4 shown: Set the printing parameters of the end part, the middle large-diameter part, and the three regions. Using the hydrogel 3 as the raw material, perform 4D printing on the end part and the middle large-diameter part respectively. The hydrogel can be a carbon nanotube composite hydrogel, an interpenetrating network hydrogel, a topological structure hydrogel, a macromolecular microsphere composite hydrogel, or a nanocomposite hydrogel. In this embodiment, a carbon nanotube composite hydrogel with better mechanical properties and swelling properties is used.

[0036] Such as Figure 5As shown, since the ratio of the hydrophilic material content to the hydrophobic material content in each small long tube in the diameter direction determines the height of the hydrogel expansion in the diameter direction, during printing, in a manner with the center as the origin and the diameter diverging, the ratio of the hydrophilic material content to the hydrophobic material content in the hydrogel is regulated according to the required length in the diameter direction to print out the small long tubes. Among them, the hydrophilic material content at the end part is a, and the hydrophilic material content at the middle large-diameter part is b. A self-deforming device regulated by water is manufactured by utilizing the difference in the hydrophilic material content of the composite gel in the diameter direction, enabling the hydrogel to only expand and become larger or lose water and shrink in the diameter direction of the required length. In this embodiment, the hydrophilic material content satisfies a / b = Va / Vb, where Va is the volume of the end part and Vb is the volume of the middle large-diameter part. The hydrophilic material content in the hydrogel of the middle large-diameter part is greater than that of the end part, so that after receiving water excitation, the middle large-diameter part expands more than the end part.

[0037] Print a composite semi-permeable membrane 1 that can only pass water molecules and prevent salts from entering on the end circular cross-section and the middle large-diameter circular cross-section as the first valve. The composite semi-permeable membrane 1 is a composite semi-permeable membrane made of aromatic polyamide and cellulose acetate, and other types of materials that can only permeate water molecules can also be used.

[0038] Use the thermosensitive material 2 as the raw material to print the second valve on the layer inside the semi-permeable membrane. The thermosensitive material uses materials with obvious thermal expansion and contraction effects such as quartz or ceramics. In this embodiment, the thermosensitive material 2 uses ceramics. When the temperature is lower than 60°, the thermosensitive material 2 shrinks, the gap 4 appears, water flows in from the outside through the semi-permeable membrane 1, and the hydrogels at the end and the middle part both absorb water and expand until they reach the pre-designed shape and reach equilibrium. When the temperature is higher than 60° or higher, the thermosensitive material expands, the gap 4 disappears, and the valve closes.

[0039] Finally, coat a layer of heat-insulating and waterproof material 5 on the surface except for the circular cross-section. The heat-insulating and waterproof material 5 is specifically linoleum or felt

[0040] 3), under external excitation, prepare the inner mold: set a container filled with water and capable of uniform heating, put the printed intelligent deformable part into the container until it absorbs water and reaches equilibrium (as shown in the appendix Figure 7 ), take out the inner mold for spiral spring forming.

[0041] Specifically, put the intelligent deformable part into water in the range of 10° to 50°, the thermosensitive material shrinks, gaps appear, and the hydrogel absorbs water and expands until it reaches equilibrium; then slowly raise the water temperature to above 60° until the thermosensitive material expands to block the gaps.

[0042] Further, after the inner mold is taken out, continue to bake the cross-section of the inner mold with the ceramic part for 20 minutes to make the ceramic expand to completely block the gap. Moreover, a layer of heat-insulating and waterproof material is coated on the surface of the inner mold except for the circular cross-section. As shown in the appendix Figure 6 It is shown that the outer surface of the expanded inner mold is coated with waterproof and heat-insulating paint to prevent water loss and ensure that water can only flow in from the circular cross-section.

[0043] 4), Demolding is carried out through the external excitation of brine: put the inner mold after molding into a container filled with brine. In this embodiment, the brine is an NaCl solution with a mass fraction ranging from 10% to 35% and a temperature range of 10° to 50°. The inner mold continuously shrinks until it finally loses water to be less than the minimum diameter of the helical spring and reaches equilibrium (as shown in the appendix Figure 8 It is shown), and demolding is successfully completed.

[0044] Put the demolded inner mold into a water container and soak it to perform step 3), so that the inner mold can be used for the molding of the helical spring again, achieving the effect of recycling.

[0045] In summary, the preparation method of the inner mold of the composite material helical spring based on 4D printing of the present invention utilizes the osmosis principle of the semi-permeable membrane and the thermal expansion and contraction effect of the thermosensitive material to regulate the water absorption or water loss behavior. After establishing a model, dividing regions, and setting parameters, printing is carried out in a way that diverges by diameter with the center as the origin. By using the different hydrophilic material contents of the composite gel in the diameter direction, a self-deforming device regulated by water is manufactured, so that the hydrogel expands and becomes larger in the diameter direction according to the required length. Brush a layer of waterproof and heat-insulating paint on the outer surface of the inner mold except for the four circular cross-sections, and put the deformable part into an aqueous solution with variable temperature. As shown in the appendix Figure 9 It is shown that when the temperature is lower than 60 degrees, the thermosensitive material shrinks, voids appear, and the hydrogel absorbs water and expands until it reaches equilibrium. Slowly raise the temperature to above 60 degrees until the thermosensitive material expands to block the voids. After taking it out, it is waterproof and heat-insulating again for the molding of the helical spring. During demolding, place the inner mold and the helical spring wound around it in concentrated brine below 60°. The thermosensitive material shrinks, voids appear, and water flows from the inside of the inner mold to the salt container with a high concentration. The inner mold loses water and shrinks to be less than the diameter of the end helical spring and then reaches equilibrium. Remove the helical spring, and demolding is successfully completed.

[0046] The above specific embodiments are only preferred embodiments of this creation and are not used to limit this creation. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this creation shall be included within the protection scope of this creation.

Claims

1. A preparation method of a composite material helical spring inner mold based on 4D printing, characterized in that: It includes the following technological steps: 1), Establish a 3D model of the inner mold: According to the preset deformation process and its functions, divide the area of the 3D model, that is, the model is divided into two parts, namely the end part and the large-diameter middle part; the end part is divided into three regions from the surface to the inside in the direction of the circular cross-section, which are the semi-permeable membrane, the thermosensitive material, and the hydrogel; 2), Print the intelligent deformable part: Set the printing parameters for the end part, the large-diameter middle part, and the three regions. Using the hydrogel as the raw material, perform 4D printing on the end part and the large-diameter middle part respectively; Print a composite semi-permeable membrane that can only pass water molecules on one layer of the circular cross-section of the end and the circular cross-section of the large-diameter middle part as the first valve; Print the second valve on the layer inside the semi-permeable membrane with the thermosensitive material as the raw material; Finally, coat a layer of heat-insulating and waterproof material on the surface except the circular cross-section; 3), Under external excitation, prepare the inner mold: Set up a container filled with water and capable of uniform heating, put the printed intelligent deformable part into the container until the water absorption reaches equilibrium, take out the inner mold for forming the spiral spring; 4), Demold through the external excitation of brine: Put the inner mold after forming into a container filled with brine, the inner mold continuously shrinks, and finally loses water until it is smaller than the minimum diameter of the spiral spring and reaches equilibrium, and successfully demolds.

2. The preparation method of the composite material helical spring inner mold based on 4D printing according to claim 1, characterized in that: In the step 2), the hydrogel is specifically a carbon nanotube composite hydrogel; the composite semi-permeable membrane is a composite semi-permeable membrane made of aromatic polyamide and cellulose acetate; the thermosensitive material is made of ceramics.

3. The preparation method of the composite material helical spring inner mold based on 4D printing according to claim 2, wherein: In the step 2), when printing the intelligent deformable part, in the way of taking the center as the origin and the diameter diverging, according to the length required in the diameter direction, regulate the proportion of the hydrophilic material and the hydrophobic material content in the hydrogel, and print out a small long tube; among them, the hydrophilic material content of the end part is a, and the hydrophilic material content of the large-diameter middle part is b, and the hydrophilic material content satisfies a / b = Va / Vb, where Va is the volume of the end part and Vb is the volume of the large-diameter middle part.

4. The preparation method of the composite material helical spring inner mold based on 4D printing according to claim 3, characterized in that: The hydrophilic material content in the hydrogel of the large-diameter middle part is greater than that of the end part, so that after receiving water excitation, the large-diameter middle part expands more than the end part.

5. The preparation method of the composite material helical spring inner mold based on 4D printing according to claim 1, characterized in that: The step 3) is specifically: Put the intelligent deformable part into water in the range of 10° to 50°, the thermosensitive material shrinks, voids appear, and the hydrogel absorbs water and expands until it reaches equilibrium; Then slowly raise the water temperature to above 60 degrees until the thermosensitive material expands to block the voids.

6. The preparation method of the composite material helical spring inner mold based on 4D printing according to claim 5, characterized in that: After taking out the inner mold in step 3), continue to bake the cross-section of the inner mold with the ceramic part for 20 minutes to make the ceramic expand to completely block the voids.

7. The preparation method of the composite material helical spring inner mold based on 4D printing according to claim 1, wherein: Apply a layer of heat-insulating and waterproof material on the surface of the inner mold prepared in step 3) except the circular cross-section.

8. The preparation method of the composite material helical spring inner mold based on 4D printing according to claim 7, characterized in that: The heat-insulating and waterproof material is specifically linoleum or felt.

9. The preparation method of the composite material helical spring inner mold based on 4D printing according to claim 1, wherein: In the step 4), the brine is an NaCl solution with a mass fraction ranging from 10% to 35%, and the temperature range is within 10° to 50°.

10. The preparation method of the composite material helical spring inner mold based on 4D printing according to claim 1, characterized in that: Put the demolded inner mold into a water container and soak it to perform step 3), so that the inner mold can be used for forming the spiral spring again.

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