Controllable high-precision photocuring 3D printing method for combustible powder shell

Abstract

The invention discloses a controllable high-precision photocuring 3D printing method for a combustible powder shell, and relates to a forming method for the combustible powder shell. The technical problems that an existing 3D printing combustible powder shell is low in forming precision and high in surface roughness are solved. The method comprises the following steps: uniformly mixing light-cured resin, a photoinitiator, an active diluting monomer, an energetic filler and a light inhibitor to obtain slurry; and then the slurry is added into a material groove of a photocuring 3D printer, 3D printing is conducted, and the controllable high-precision combustible powder shell is obtained. The size precision of the combustible powder shell obtained through 3D printing ranges from 25 micrometers to 50 micrometers, and the average tensile strength ranges from 6 MPa to 7 MPa; the average bending strength is 10 to 11 MPa; the average compression strength is 36 to 40 MPa. The method can be used in the ammunition preparation field.

Description

Technical Field

[0001] The invention relates to a molding method of a combustible powder shell. Background Art

[0002] With the increasing demand for combat performance of weapon systems by modern troops, the research and development of lightweight ammunition has received attention, and lightweight cartridge cases have emerged. Combustible cartridge cases made of combustible materials completely burn out the combustible material part after ignition, eliminating the need for shell extraction, shell ejection and corresponding mechanisms, increasing the rate of fire while also providing a certain amount of launch energy. Since the emergence of combustible cartridge cases, their processing technology has always been the focus of research. The existing combustible cartridge case is a loose, porous, non-homogeneous material, which is mainly prepared by mixing nitrocellulose, paper fiber, adhesive and diphenylamine in a certain proportion and then using a suction filtration molding method. However, this method requires the design of a processing mold first, which not only has low molding precision and a long cycle, but also has poor uniformity and poor mechanical properties.

[0003] 3D printing technology has the advantages of fast speed, high resolution and excellent spatiotemporal control, and has been proven to be a powerful tool for manufacturing models with expected designs and complex structures. However, the current 3D printing technology for combustible shells still has the disadvantages of low molding accuracy and high surface roughness. Summary of the invention

[0004] The present invention aims to solve the technical problems of low molding accuracy and high surface roughness of existing 3D printed combustible shells, and to provide a method for controllable high-precision light-curing 3D printing of combustible shells.

[0005] The method for controllable high-precision light-curing 3D printing of a combustible shell of the present invention is carried out according to the following steps:

[0006] 1. Mix 100 parts of photocurable resin, 5 parts of photoinitiator, 25-80 parts of active diluent monomer, 50-90 parts of energetic filler and 0.1-0.2 parts of photoinhibitor uniformly according to weight ratio to obtain slurry;

[0007] The light-curable resin is one or a combination of polyurethane acrylate, epoxy acrylate, polyester acrylate, and unsaturated polyester;

[0008] The energetic filler is one or a combination of 2,4,6-trinitrotoluene (TNT), hexanitrohexaazaisopentane (CL-20), 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX), and 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX);

[0009] The photoinhibitor is one or a combination of carbon black, titanium dioxide, silicon dioxide, zinc oxide, zinc barium, methyl orange, Sudan III, methylene blue, and rhodamine B;

[0010] 2. Add the slurry into the material tank of the light-curing 3D printer for 3D printing with a layer thickness of 0.025mm to 1.0mm. Use a UV light source with a wavelength of 254 to 435nm and a power of 100 to 120mV for light curing. The exposure time of a single layer is 2 to 3s. After 3D printing, a controllable, high-precision combustible shell is obtained.

[0011] Furthermore, the particle size of the energetic filler described in step 1 is in the range of 30 to 500 μm.

[0012] Furthermore, the photoinitiator described in step 1 is one or a combination of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), ethyl 2,4,6-trimethylbenzoylphosphonate, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (819), and 1-hydroxycyclohexyl phenyl ketone (184).

[0013] Furthermore, the active diluent monomer in step 1 is one or a combination of monofunctional isobornyl methacrylate (IBOMA), ethoxyethoxyethyl acrylate (EOEOEA), and tripropylene glycol diacrylate (TPGDA).

[0014] The slurry formula plays a vital role in the molding of the combustible shell of the present invention. The formula of the combustible shell is mainly composed of four parts: photoinitiator, photocurable resin, reactive diluent monomer, and energetic filler. Photocurable resin is a large part of the photocurable system and a basic component of the combustible shell formula, which determines the basic properties of the cured product, including hardness, flexibility, adhesion and other properties. In the photocurable resin system containing energetic fillers, the introduction of energetic fillers will not only increase the viscosity of the system and easily cause sedimentation, but also the energetic filler crystal particles themselves have too strong scattering ability of ultraviolet light, which will lead to the extension of the curing edge. By adding reactive diluents and photoinhibitors, the controllability of high-precision printing is achieved and the mechanical properties of the material are improved. The dimensional accuracy of the 3D-printed combustible shell of the present invention is 25 to 50 microns, the average tensile strength is 6 to 7MPa; the average bending strength is 10 to 11MPa; and the average compressive strength is 36 to 40MPa.

[0015] The method of the controllable high-precision light-curing 3D printing combustible shell of the present invention prepares the combustible shell by 3D printing, has a simple and rapid processing technology, high structural flexibility, and the prepared combustible shell is uniform and has high mechanical properties. It can be used in the field of ammunition preparation. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a photo of the controllable high-precision combustible cartridge case cover prepared in Example 1;

[0017] Figure 2 This is a scanning electron microscope photograph of the fracture cross section of the controllable high-precision combustible cartridge case upper cover prepared in Example 1;

[0018] Figure 3 This is a tensile performance test curve of the controllable high-precision combustible shell prepared in Example 1;

[0019] Figure 4 This is a curve chart of the bending performance test of the controllable high-precision combustible cartridge prepared in Example 1;

[0020] Figure 5 This is a compression performance test curve of the controllable high-precision combustible cartridge prepared in Example 1;

[0021] Figure 6 This is a photo of the combustible cartridge case cover prepared in Comparative Example 1;

[0022] Figure 7 This is a photo of the combustible cartridge case prepared in Example 2. DETAILED DESCRIPTION

[0023] The following are specific embodiments of the present invention, and the technical solutions of the present invention are further described in conjunction with the embodiments, but the present invention is not limited to these embodiments.

[0024] Embodiment 1: The method of controllable high-precision light-curing 3D printing of a combustible shell in this embodiment is carried out according to the following steps:

[0025] 1. Weigh 100 g of epoxy acrylate, 3 g of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO), 50 g of isobornyl methacrylate (IBOMA), 70 g of 1,3,5-trinitro-1,3,5-triazacyclohexane (RDX) crystal particles with an average particle size of 30 μm, and 0.1 g of methyl orange, and add them into a container in sequence, and stir for 2 h in a dark environment at a rotation speed of 456 r / s to obtain a slurry;

[0026] 2. Pour the slurry into the material tank of the light-curing 3D printer, and perform 3D printing under the conditions of a light source wavelength of 405nm, a power of 120mV, a printed layer thickness of 0.05mm, and a single layer exposure time of 2s to obtain a controllable, high-precision combustible shell.

[0027] The photo of the controllable high-precision combustible shell obtained in this embodiment is shown in Figure 1 As shown, it is the upper cover of the combustible charge shell.

[0028] The size of the upper cover prepared in this embodiment is consistent with the size of the design drawing. The diameter error of the upper cover is 20 microns, which is extremely small. The surface is smooth and delicate without obvious layer patterns. It can accurately restore the tiny details in the design. The layer thickness is uniform and thin, and the material utilization rate is high, so that there is little need for post-processing, or even no post-processing is required, saving time and cost.

[0029] The cross section of the controllable high-precision combustible shell of this embodiment is fixed on the metal copper sheet sample plate by conductive glue. The sample needs to be sprayed with gold before testing, and the spraying time is 50s. The fracture section of the sample is scanned by high-power SEM, and the scanning electron microscope photo of the fracture section is as shown in FIG. Figure 2 As shown, from Figure 2 It can be seen that the RDX solid filler is dispersed more evenly, has good density, and the resin is in a good curing and cross-linking state.

[0030] The mechanical properties of the controllable high-precision combustible shell prepared in this embodiment were tested using a universal testing machine. At room temperature, samples were prepared according to national standard dimensions and tensile, bending and compression performance tests were performed. The tensile performance curve is shown in Figure 3 As shown, from Figure 3 It can be seen that the average tensile strength is 6.462MPa; the bending performance curve is as follows Figure 4 As shown, from Figure 4 It can be seen that the average bending strength is 10.217MPa; the compressive strength performance curve is as follows Figure 5 As shown, from Figure 5 It can be seen that the average compressive strength is 36.091MPa. Figure 3 to Figure 5 It can be seen that the controllable high-precision combustible shell has good mechanical properties.

[0031] Comparative Example 1: This comparative example is different from Example 1 in that the amount of methyl orange added in step 1 is 0, and the other steps and parameters are the same as those in Example 1, to obtain an upper cover of a combustible cartridge case.

[0032] The upper cover of the combustible cartridge case prepared in this comparative example without adding the photoinhibitor methyl orange is shown in the following photo. Figure 6 As shown, from Figure 6 It can be seen that the shape of the upper cover is irregular, the surface is rough, and the shape and size of the combustible charge shell upper cover cannot be precisely controlled.

[0033] Comparative Example 2: This comparative example is different from Example 1 in that the amount of methyl orange added in step 1 is 0.05 g, and the other steps and parameters are the same as those in Example 1, to obtain the upper cover of the combustible cartridge case.

[0034] The combustible cartridge case upper cover prepared in this comparative example under the condition of adding a small amount of the photoinhibitor methyl orange is rough in surface observation with obvious layering and unevenness, with serious loss of details, and unable to accurately present the subtle parts of the design.

[0035] Comparative Example 3: This comparative example is different from Example 1 in that the amount of methyl orange added in step 1 is 0.3 g, and the other steps and parameters are the same as in Example 1 to obtain a combustible cartridge case.

[0036] In this comparative example, a large amount of methyl orange, a light inhibitor, is added, and the absorption of ultraviolet light energy is too strong. The remaining ultraviolet light energy cannot meet the initiation requirements of the photoinitiator, making 3D printing impossible.

[0037] From the comparison between Example 1 and Comparative Examples 1 to 3, it can be seen that only under the condition of adding a suitable amount of photoinhibitor methyl orange can a high-precision 3D-printed combustible shell product be obtained. Under the condition of no photoinhibitor or a small amount of photoinhibitor added, the dimensional accuracy of the 3D-printed combustible shell product is poor. This is because, in the slurry system containing energetic fillers, the energetic fillers scatter ultraviolet light severely, and the scattered energy triggers the curing of the surrounding resin, causing the curing edge to extend. Adding an appropriate amount of photoinhibitor methyl orange can absorb the scattered energy, so that the scattered light of the non-target curing area is suppressed, and the edge of the target curing area is clear, thereby obtaining a 3D-printed combustible shell with controllable accuracy.

[0038] Embodiment 2: The method of controllable high-precision light-curing 3D printing of a combustible shell in this embodiment is carried out according to the following steps:

[0039] 1. Weigh 100 g of polyurethane acrylic resin, 3 g of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (819), 70 g of isobornyl methacrylate (IBOMA), 60 g of 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane (HMX) crystal particles with an average particle size of 35 μm, and 0.2 g of silicon dioxide, and add them into a container in sequence, and stir for 2 h in a dark environment at a rotation speed of 456 r / s to obtain a slurry;

[0040] 2. Pour the slurry into the material tank of the light-curing 3D printer. The wavelength of the light source is 405nm, the power is 120mV, the thickness of the printed layer is 0.05mm, and the exposure time of a single layer is 2s. After 3D printing, a high-precision combustible shell is obtained; it includes an upper cover and a lower body.

[0041] The photo of the controllable high-precision combustible shell obtained in this embodiment is shown in Figure 7As shown in the figure, a is the lower body of the combustible shell, and b is the combustible shell with an upper cover. The sizes of the upper cover and the lower body of the controllable high-precision combustible shell obtained in this embodiment are consistent with the sizes of the design drawings. The outer diameter error of the lower body is 25 microns, which is extremely small. The surface is smooth and delicate without obvious layer patterns, and the tiny details in the design can be accurately restored. The layer thickness is uniform and thin, and the material utilization rate is high, so that there is little need for post-processing, or even no post-processing is required, saving time and cost.

[0042] The controllable high-precision combustible shell of this embodiment was subjected to mechanical property tests. Under room temperature conditions, the tensile, bending and compression performance tests were carried out according to the national standard size sample preparation. The average tensile strength was 6.335MPa; the average bending strength was 10.085MPa; and the average compression strength was 36.147MPa. It can be seen from the test data that the controllable high-precision combustible shell has good mechanical properties.

Claims

1. A method for controllable high-precision light-curing 3D printing of combustible shells, characterized in that: The method proceeds as follows:

1. Mix 100 parts of photocurable resin, 5 parts of photoinitiator, 25-80 parts of active diluent monomer, 50-90 parts of energetic filler and 0.1-0.2 parts of photoinhibitor uniformly according to weight ratio to obtain slurry; The light-curable resin is one or a combination of polyurethane acrylate, epoxy acrylate, polyester acrylate, and unsaturated polyester; The energetic filler is one or a combination of 2,4,6-trinitrotoluene, hexanitrohexaazaisopentane, 1,3,5-trinitro-1,3,5-triazacyclohexane, 1,3,5,7-tetranitro-1,3,5,7-tetraazacyclooctane; The photoinhibitor is one or a combination of carbon black, titanium dioxide, silicon dioxide, zinc oxide, zinc barium, methyl orange, Sudan III, methylene blue, and rhodamine B; 2. Add the slurry into the material tank of the light-curing 3D printer for 3D printing with a layer thickness of 0.025mm to 1.0mm. Use a UV light source with a wavelength of 254 to 435nm and a power of 100 to 120mV for light curing. The exposure time of a single layer is 2 to 3s. After 3D printing, a controllable, high-precision combustible shell is obtained.

2. The method for controllable high-precision light-curing 3D printing of combustible shells according to claim 1, characterized in that: The particle size of the energetic filler described in step 1 ranges from 30 to 500 μm.

3. A method for controllable high-precision light-curing 3D printing of a combustible shell according to claim 1 or 2, characterized in that: The photoinitiator described in step 1 is one or a combination of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide, ethyl 2,4,6-trimethylbenzoylphosphonate, phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide, and 1-hydroxycyclohexyl phenyl ketone.

4. A method for controllable high-precision light-curing 3D printing of a combustible shell according to claim 1 or 2, characterized in that: The active diluent monomer described in step 1 is one or a combination of monofunctional isobornyl methacrylate, ethoxyethoxyethyl acrylate, and tripropylene glycol diacrylate.

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