A mold forming process of a low-cost radome

Abstract

The application relates to the technical field of composite radome manufacturing, and particularly discloses a low-cost radome mold forming process, which comprises the following steps: step one, initial mold forming: selecting PU hard foam to make an initial mold of a radome mold, wherein the initial mold is a one-time integral lost mold structure, is not provided with a demolding slope, an ejection mechanism and a core-pulling mechanism, and a mold cavity is designed as a continuous smooth curved surface matched with a preset radome; step two, first trial production: forming a radome by using the initial mold, and performing parameter detection on the formed radome to obtain detection data; step three, mold correction: correcting the size, structure or surface state of the initial mold made of PU foam according to the detection data; and step four, iterative optimization: repeating steps two and three; and the low-cost radome mold forming process is used to solve the problems of high cost and long processing cycle of a traditional radome mold.

Description

Technical Field

[0001] This invention relates to the field of composite material radome manufacturing technology, and in particular to a low-cost radome molding process. Background Technology

[0002] A radome is an electromagnetically transparent structure used to protect antenna systems from external environmental influences, and it is widely used in aviation, aerospace, radar, and communication fields. Radomes are typically made of fiber-reinforced resin-based composite materials, which must possess excellent wave-transmitting performance while ensuring mechanical load-bearing capacity. For radomes in the development stage, as the technology is constantly being optimized, the product's shape, size, and structural parameters may change frequently, thus placing high demands on the flexibility, cost, and iteration cycle of the molding molds.

[0003] Currently, metal molds are commonly used for forming radomes, and their processing methods include integral forging, precision milling, and chrome plating. While metal molds can ensure high forming accuracy and surface quality, they also have the following significant drawbacks.

[0004] Firstly, the material and processing costs of metal molds are relatively high. Taking a typical radome as an example, the manufacturing cost of steel molds is high, which is too much of an investment for the research and development phase and makes it difficult to achieve parallel verification of multiple schemes.

[0005] Secondly, the process of metal mold making, from blank forging, rough machining, heat treatment, precision machining to surface treatment, usually takes about 45 days, which seriously restricts the product development progress.

[0006] Finally, during product development, frequent changes to dimensions and structure require each modification to remill, weld, or even reforge the metal mold, resulting in a mold repair cycle of 3-5 days and significant costs per repair. Frequent mold repairs can also lead to localized stress concentration, deformation, or even scrapping of the mold, further increasing development risks and costs.

[0007] In addition to metal molds, existing technologies also use silicone molds and resin molds as alternatives. However, these materials have poor dimensional stability under high-temperature vacuum bag compression molding conditions, making it difficult to meet the requirements of high precision and high wave transmission for radomes.

[0008] Therefore, a low-cost radome molding process is proposed to solve the problems of high cost and long processing cycle of traditional radome molds. Summary of the Invention

[0009] The purpose of this invention is to provide a low-cost mold forming process for radomes to solve the problems mentioned in the background art.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: The present invention provides a low-cost mold forming process for an antenna radome, comprising the following steps: Step 1: Initial mold forming: PU rigid foam is selected to make the initial mold for the radome mold. The initial mold is an integral one-time lost foam structure, without demolding angle, ejection mechanism and core pulling mechanism. The mold cavity is designed as a continuous smooth curved surface that matches the preset radome. Step 2, Initial Trial Production: The radome is formed using the initial mold, and the parameters of the formed radome are tested to obtain test data; Step 3: Mold Modification: Based on the test data, perform local mold modification on the initial mold for making PU foam, and modify the size, structure or surface condition of the mold. Step 4: Iterative optimization: Repeat steps 2 and 3 until the radome produced using the modified mold meets the preset requirements and the final mold is obtained.

[0011] Preferably, before step one, a material shrinkage pre-verification step is included: a scaled-down model is made using PU foam with the same density and process as the initial mold, and its shrinkage is measured after vacuum bag pressing and oven curing treatment. This shrinkage is used as reference data for the initial mold size compensation.

[0012] Preferably, in the shrinkage pre-verification step, the scaling factor of the scaling model is 1:5, and the vacuum degree of the vacuum bag pressure is... The oven curing process is as follows: the temperature is increased to 120℃ at a rate of 1.5℃ / min, and then kept at that temperature for 3 hours before being cooled with the oven.

[0013] Preferably, the density of the rigid PU foam in step one is 55-65 kg / m³, and more preferably 60±5 kg / m³.

[0014] Preferably, the processing of the initial mold in step one includes: splicing multiple PU foam boards to form a blank, performing rough processing with a allowance, and then fine processing to make the dimensional accuracy of the initial mold reach ±0.2mm and the surface roughness Ra≤3.2μm. During the processing of the initial mold, a weakening groove is pre-embedded in the preset segmentation area.

[0015] Preferably, after step one, a surface treatment step is also included: cleaning the surface of the initial mold, repairing with putty and laying a release cloth. The putty repair needs to be done in layers, with each layer not exceeding 1mm in thickness and the total repair thickness not exceeding 3mm. After repair, it needs to be cured at room temperature for 24 hours before fine grinding.

[0016] Preferably, the radome produced in step two uses a quartz fiber reinforced epoxy resin prepreg system with a single-layer cured thickness of 0.2 mm. It is laid in the order of inner surface layer → adhesive film → honeycomb → adhesive film → outer surface layer. The inner and outer surface layers are both made of 0.2 mm quartz fiber prepreg, the adhesive film is 0.12 mm thick, and the honeycomb is 3 mm aramid paper honeycomb. The honeycomb can also be PMI foam or PET foam. The honeycomb is aramid paper honeycomb, PMI foam, or PET foam.

[0017] Preferably, the process parameters for vacuum bag pressing-oven curing in step two are: vacuum degree The curing process involves raising the temperature from room temperature to 80±2℃ at a rate of 1–2℃ / min and holding for 60 minutes, then raising it to 120±2℃ at a rate of 1–2℃ / min and holding for 180 minutes. The entire curing process is carried out under vacuum. After curing, the product should be cooled to <50℃ in the oven before being removed from the mold.

[0018] Preferably, in step three, the local mold repair is carried out by using a precision milling cutter for local repair and / or by using putty or epoxy repair putty for local filling and sanding. The depth of a single repair by the precision milling cutter shall not exceed 0.5mm. After the PU foam mold has been repaired more than 5 times, a full-size inspection should be carried out again, and the mold should be remade if necessary.

[0019] In another aspect of the present invention, the process further includes the molding of the rain cover assembly: a rain cover mold is made of PU foam of the same material as the radome mold, a quartz fiber reinforced epoxy resin prepreg is laid on the rain cover mold, and the same vacuum bagging and curing process is performed on the radome body.

[0020] The beneficial effects of this invention are as follows: This invention uses PU foam as the mold material, replacing traditional steel molds. PU foam material is low in cost and can be quickly machined using CNC, eliminating the need for complex forging, heat treatment, and precision grinding processes. The low mold cost significantly reduces the economic burden during the research and development phase compared to traditional steel molds. PU foam material has a uniform texture and is easy to cut, significantly shortening the initial mold processing cycle compared to traditional steel molds. More importantly, during product development, when changes in size and structure occur, only local CNC adjustments and putty repairs are needed on the PU foam mold. Each mold repair is quick and inexpensive; further fine-tuning can be completed even faster. In contrast, traditional steel molds require long repair times and are costly to repair each time. This invention significantly improves the iterative efficiency of the development phase. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the initial mold forming process according to an embodiment of the present invention; Figure 2This is a schematic diagram of the iterative development cycle of an embodiment of the present invention; Figure 3 This is a schematic diagram of the production process of metal molds according to an embodiment of the present invention; Figure 4 This is a schematic diagram of the PU foam mold process according to an embodiment of the present invention. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0023] Reference Figures 1-4 This invention discloses a low-cost mold forming process for radomes, employing a one-time lost foam casting process using PU foam combined with vacuum bag pressing and oven curing technology. This process is suitable for manufacturing high-transmittance radomes of various shapes and sizes. Compared to traditional steel mold hand lay-up molding, this process offers advantages such as lower mold costs, shorter processing cycles, and lower energy consumption. Especially during product development, where frequent changes in technical specifications and dimensional structures are common, PU foam molds can adapt well to these changes, and mold repair costs are low. This significantly improves production efficiency and technological competitiveness while maintaining electromagnetic and mechanical properties.

[0024] Example 1: Complete Steps for Antenna Radome Mold Forming, Iterative Correction, and Product Manufacturing This embodiment focuses on illustrating the entire process of radome mold making, from initial molding, trial production testing, parameter correction, and repeated iterations, to finally obtaining a mold that meets the requirements. It clearly demonstrates the core benefits of PU foam molds, such as adaptability to frequent changes and low mold repair costs. The specific steps are as follows: 1. Initial mold forming 1.1 Pre-verification of Material Shrinkage Based on the initial dimensions of the radome, a scaled-down model of the radome was fabricated using rigid PU foam with a density of 60±5 kg / m³, with a scaling factor of 1:5. Vacuum bag sealing was then performed using the same process as the final product, with strict control over the vacuum level. The packaged scaled-down model was placed in a hot air circulating oven and heated to 120℃ at a rate of 1.5℃ / min. After holding at this temperature for 3 hours, it was cooled to room temperature with the oven. After unpacking, the key dimensions of the scaled-down model were precisely measured using a coordinate measuring machine. The unilateral shrinkage was measured to be 1.0±0.1mm, which was used as the core reference data for initial mold size compensation. The compensation amount was 1.0±0.1mm for unilateral shrinkage. The shrinkage measurement required linear regression analysis at each key dimension point of the full-size mold to obtain the functional relationship between shrinkage rate and size. When the thickness ratio of the scaled-down model to the full-size mold exceeded 1:3, a step-by-step scaling verification (1:3→1:2→1:1) should be adopted to ensure the accuracy of the shrinkage data and to ensure that the initial mold can initially adapt to the preset product size.

[0025] 1.2 Initial mold structure design and processing Based on the initial radiator size and structure requirements, a one-piece lost foam casting structure was adopted, without draft angles, ejection mechanisms, or core-pulling mechanisms. The mold cavity was designed as a continuous, smooth curved surface to match the pre-designed radiator. The linear expansion coefficient of the rigid PU foam in a 120℃ vacuum environment is [missing information]. Based on this, the mold size compensation amount is determined; the initial mold design is a breakable and separable structure, and during processing, a weakening groove is pre-embedded in the preset division area, with the groove depth being 1 / 3 to 1 / 2 of the mold wall thickness; the parting surface is set at the open flange, retaining only the positioning reference surface, and the rest is a solid foam structure, which simplifies the mold structure while reserving convenient mold repair space for subsequent size and structure changes.

[0026] Mold processing steps: Taking a high-transparency radome with external dimensions of approximately 1200mm×800mm×300mm as an example; Take six 700mm×550mm×80mm PU foam boards and dry them in a 50℃ oven for 2 hours before use to completely eliminate internal stress in the foam and avoid dimensional deformation during subsequent processing and molding. Use two-component polyurethane structural adhesive to splice the foam boards and cure them for 12 hours at room temperature and a contact pressure of 0.02~0.05MPa to form a complete mold blank.

[0027] Rough machining: Use a Φ12~Φ20mm ball end mill to rough machine the blank, leaving a 0.5~1mm allowance for subsequent mold repair and adjustment.

[0028] Finishing: Use a Φ6~Φ10mm precision milling cutter to finish the mold, so that the initial mold size accuracy reaches ±0.2mm and the surface roughness Ra≤3.2μm, thus completing the initial mold forming.

[0029] 1.3 Initial mold surface treatment 1.3.1 Surface cleaning: Use compressed air to thoroughly blow the mold surface and cavity to completely remove dust and debris generated during processing; then use industrial alcohol or acetone to carefully wipe the mold surface to remove oil stains and trace impurities to avoid affecting the subsequent lay-up and molding quality.

[0030] 1.3.2 Putty Repair: For deep dents, knife marks, and joints on the mold surface, use two-component putty for repair. The mixing ratio should be strictly in accordance with resin:hardener = 100:2 (by mass). The thickness of a single application should be ≤1mm. After curing at room temperature for 30 minutes, sand the mold successively with 180-grit, 320-grit, and 600-grit sandpaper. The total repair thickness should not exceed 3mm. After repair, allow 24 hours for curing at room temperature before fine sanding. Repeat the repair and sanding process until the mold surface is smooth, free of pores and unevenness, and the edges and rounded corners are evenly transitioned.

[0031] 1.3.3 Laying the release fabric: Cut the release fabric to ensure that its size is 50-100mm larger than each side of the mold's working surface; spray a low-residue adhesive onto the mold surface at a rate of 80-120g / m², and allow it to dry for 2-3 minutes until it is no longer sticky to the touch; when laying the release fabric, use a rubber scraper to smooth it from the center to the edge, thoroughly removing air bubbles; control the overlap width of the release fabric to 10-20mm, and seal the edges with high-temperature tape to ensure no wrinkles, no air bubbles, and no gaps; the adhesive should be compatible with PU foam and epoxy resin, and it is recommended to use a low-residue polyurethane adhesive to avoid using solvent-based adhesives that may cause foam corrosion, thus ensuring the quality of subsequent demolding and product surface.

[0032] 2. Initial trial production: The radome is formed using the initial mold, and parameters are tested. 2.1 Radome Body Layup and Molding A quartz fiber reinforced epoxy resin prepreg system is used, with a single-layer cured thickness of 0.2mm. The layers are laid from the inside out in the following order: inner surface layer → adhesive film → honeycomb → adhesive film → outer surface layer. The specific layer structure is as follows: the first layer is a 0.2mm quartz fiber prepreg; the second layer is a 0.12mm epoxy structural adhesive film; the third layer is a 3mm aramid paper honeycomb core material; the fourth layer is another 0.12mm epoxy structural adhesive film; and the fifth layer is a 0.2mm quartz fiber prepreg on the outer surface. Each layer is compacted with a roller using approximately 10kg of linear pressure to eliminate interlayer air bubbles. The interface between the honeycomb and the adhesive film is slightly pre-compressed at 80℃ to improve interfacial adhesion.

[0033] After the layup is completed, vacuum bag sealing and sealing tests are performed: the layup preform and mold are placed together on a tray, and the perforated release film, breathable felt, and vacuum bag film are laid in sequence; the vacuum nozzle is installed, the four sides are sealed with sealing strips, and a vacuum is drawn until... Hold the pressure for 15 minutes. If the vacuum level drops by ≤0.002MPa / min, the seal is considered qualified. If it is not qualified, find the leak and reseal.

[0034] The properly packaged preform and mold are transferred into a forced-circulation hot air oven and cured according to the following procedure: The temperature is increased from room temperature to 80±2℃ at a rate of 1–2℃ / min, and held for 60 min; then increased to 120±2℃ at a rate of 1–2℃ / min, and held for 180 min; the vacuum level is maintained throughout the curing process. After curing, allow the material to cool in the oven to below 50°C, then remove it for demolding and cleaning.

[0035] Demolding and Cleaning: Install a pneumatic impact hammer in the pre-defined segmented area of ​​the foam mold (formed by the weakened grooves embedded during processing), and impact along the mold segmentation line with an air pressure not exceeding 0.4MPa to controllably break the PU foam mold along the weakened area; remove large pieces of foam with a wooden or copper shovel, and clean complex cavities and corners with 0.2-0.3MPa high-pressure air in conjunction with a nylon brush, and finally use a sticky roller for fine suction cleaning; after cleaning, use an endoscope to check whether there is any foam residue or scratches on the inner surface of the radome. Only after confirming that there is no damage can the demolding be considered complete, and the radome sample for the first trial production can be obtained.

[0036] 2.2 Parameter Testing of Initial Trial Production Samples Comprehensive parameter testing was conducted on the radome samples produced during the first trial run. The focus was on indicators directly related to mold dimensions and structure, as well as electromagnetic and mechanical properties. Specific testing items and standards are as follows: Dimensional accuracy inspection: The contour, flatness, and wall thickness of the sample are inspected using a coordinate measuring machine. The preset standards are contour tolerance ±0.5mm and wall thickness ±0.1mm. Visual inspection: Under 1000 lx illumination, observe the sample visually with a 5x magnifying glass. The sample should be free of bubbles, cracks, delamination, wrinkles, and missing glue. Non-destructive testing: A-mode ultrasonic testing is used to inspect the honeycomb interlayer, requiring no debonding and no voids; Transmission performance test: In a microwave anechoic chamber, the 2-18 GHz frequency band is tested according to standards, requiring an average transmittance ≥85% and an insertion loss ≤0.8 dB; Mechanical property testing: Test the tensile strength and flexural strength of the sample. The tensile strength is required to be ≥350MPa and the flexural strength is required to be ≥400MPa.

[0037] Test results: The initial trial production sample showed a deviation in outline dimensions exceeding ±0.5mm, uneven wall thickness exceeding ±0.1mm in some areas, and a few minor wrinkles on the surface, which did not meet the preset requirements; the electromagnetic and mechanical properties basically met the standards, indicating that the problem was mainly in the mold size and structural design, and the mold needs to be modified.

[0038] 3. First mold correction: Based on the test data of the first trial production sample, clarify the direction of mold correction: For the deviation of the contour size, according to the specific deviation value detected by the coordinate measuring machine, perform local mold correction on the mold cavity contour based on the initial mold; For the problem of uneven wall thickness, adjust the thickness of the corresponding position of the mold cavity, and refer to the first shrinkage verification data and sample deviation data for the correction amount; For the problem of appearance wrinkles, perform secondary grinding and putty repair on the local uneven areas of the mold surface to ensure the smoothness of the mold cavity surface.

[0039] Mold Repair Process: Since PU foam is used as the mold material, it eliminates the need for complex milling, welding, or reforging required for traditional steel molds. Only a precision milling cutter is needed to locally trim the mold cavity contour, with a single trimming depth not exceeding 0.5mm. Uneven areas are then filled with putty and sanded. Putty repair must be done in layers, with each layer not exceeding 1mm in thickness, and the total repair thickness not exceeding 3mm. After repair, it needs to be cured at room temperature for 24 hours before fine grinding. The entire mold repair process takes only 4-6 hours, resulting in low material costs. Compared to the 3-5 days required for traditional steel mold repair, costs are significantly reduced, and minor changes in size and structure can be quickly accommodated. After more than 5 mold repairs, the PU foam mold should undergo a full-dimensional inspection, and a new mold may be necessary.

[0040] After the mold is repaired, a second surface treatment is performed on the mold (repeating step 1.3) to ensure that the surface quality of the mold meets the standards before proceeding to the second trial production.

[0041] 4. Multiple iterations: mold modification → trial production → inspection, until a qualified mold and product are obtained. 4.1 Second Trial Production and Testing: Using the modified mold, repeat steps 2.1 to 2.2 to conduct a second trial production and obtain the second batch of radome samples. Comprehensive parameter testing of the samples revealed that the outline dimension deviation had been reduced to ±0.4mm, and the wall thickness unevenness problem had been improved. However, slight deviations still existed in some local positions, and although the wave transmission performance met the standards, there was room for improvement. Further mold modification was required.

[0042] 4.2 Second mold correction: Based on the second inspection data, the focus is on correcting the dimensional deviations of the local cavity of the mold, fine-tuning the curvature of the mold cavity surface, and optimizing the smoothness of the mold surface to further reduce product appearance defects. This mold correction only requires fine-tuning of local positions, which once again demonstrates the advantages of convenient and low-cost mold correction of PU foam molds, and is suitable for the parameter fine-tuning needs in the research and development stage.

[0043] 4.3 Subsequent Iterations and Finalization: Repeat the above process of "mold modification → trial production → parameter testing". Based on the test results of each batch of samples, adjust the size, structure, and surface condition of the mold accordingly. Each mold modification only requires local treatment, which is time-saving, low-cost, and does not require discarding the entire mold. Repeat steps two and three 2 to 4 times. After each iteration, measure the local dimensional deviation of the mold until the test results of two consecutive iterations meet all of the following conditions: contour tolerance ≤ ±0.5mm; wall thickness tolerance ≤ ±0.1mm; no defects in appearance; no delamination or voids detected by non-destructive testing. After 3 to 4 iterations of correction, the mold dimensional accuracy stabilized at ±0.2mm. The radome samples produced using this mold met all the preset requirements: contour tolerance ±0.5mm, wall thickness ±0.1mm, no defects in appearance, no delamination or voids in non-destructive testing, average transmittance ≥87%, insertion loss ≤0.8dB, tensile strength ≥350MPa, and bending strength ≥400MPa. Finally, a qualified radome mold and qualified products were obtained.

[0044] 5. Rain Cover Component Molding: After the main radome mold is finalized, a simple foam mold made of the same material as the rain cover is created to meet the dimensional requirements. This allows for quick adaptation to the size and structure of the rain cover. If the rain cover dimensions need to be changed, only a quick modification of the simple foam mold is required, taking only 1-2 hours, resulting in extremely low cost. The rain cover uses 5 layers of 0.2mm quartz epoxy prepreg continuously laid on the simple foam mold, undergoing the same vacuum bagging and curing process as the radome body. Demolding and cleaning are performed simultaneously to ensure the matching accuracy of the rain cover and the radome flange surfaces meets standards, further demonstrating the advantages of PU foam molds in adapting to structural changes and low-cost mold modification.

[0045] Example 2: Traditional steel mold + hand lay-up molding process During the product development stage, traditional steel molds have significant drawbacks when faced with frequent changes in size and structure: the molds are made of 45 steel through forging, tempering, precision machining, and chrome plating, with a processing cycle of about 45 days and a cost of about 220,000 yuan; if the size or structure of the mold needs to be changed, the steel mold needs to be remilled, welded, or forged, with each mold repair taking 3 to 5 days and costing more than 10,000 yuan. Moreover, frequent mold repairs can easily lead to the scrapping of the mold, significantly increasing the development cost and cycle.

[0046] Traditional molding processes involve applying release wax, manual layering, and curing at room temperature for 24 hours, followed by curing at 100°C for 4 hours. Demolding relies on ejector pins and wedges, which can easily lead to scratches and deformation of the radome, requiring frequent mold repairs. The final product has a contour accuracy of only ±2.0mm, numerous surface defects, a high rate of delamination, and consumes 20% more energy than the process of this invention. In contrast, the PU foam mold of this invention can quickly adapt to frequent changes in size and structure during the development stage, and has extremely low mold repair costs and very short time consumption, solving the core pain points of traditional steel molds.

[0047] Example 3: Comparative Test of Continuous Production Using the Process of the Invention The mold, after being finalized according to the process of this invention, continuously produces 10 radomes. The comparison data with the traditional process is shown in the table below:

[0048] The results show that the PU foam mold of the present invention can not only adapt to the frequent changes in size and structure during the development stage through multiple iterations, but also has low mold repair cost and short time consumption. Compared with the traditional steel mold process, it has significant advantages in terms of cost and cycle, and is especially suitable for the needs of the product development stage.

[0049] Example 4: Parameter Adjustment Range Based on Example 1, and considering the potential for further dimensional and structural changes during the development phase, the following parameters can be adjusted within a reasonable range to achieve equivalent results, further demonstrating the adaptability of PU foam molds: The density of PU foam can be selected from 50 to 80 kg / m³, which takes into account both compressive strength and breakage resistance. If the size of the radome is changed significantly, foam boards of the corresponding density can be re-assembled and processed, which is much cheaper than replacing steel molds. Shrinkage verification can be performed using a full-size model. It should be re-measured when the foam batch or oven is changed to ensure the accuracy of dimensional correction and to accommodate the slight differences between different batches of materials. Atomic putty can be replaced with epoxy repair putty, which must be compatible with foam and release cloth, allowing for flexible selection according to mold repair needs and reducing mold repair costs; The number of prepreg layers can be increased or decreased, and the honeycomb thickness can be adjusted from 2 to 6 mm. To adapt to changes in the mechanical performance requirements of the radome, only minor adjustments to the cavity thickness are needed in the mold, without the need for a complete replacement. The curing regime can be adjusted to 80℃ / 1h+120℃ / 2h+140℃ / 1h. Shrinkage needs to be re-verified to adapt to the curing requirements after the change of radome material. The mold does not need to be significantly modified. The thickness of the epoxy film can be adjusted within the range of 0.12 to 0.2 mm, while maintaining the same molding quality, wave transmission and mechanical properties of the honeycomb sandwich structure.

[0050] Material Substitution Notes Quartz fiber can be replaced with low-dielectric fibers such as E-glass fiber, D-glass fiber, and polyimide fiber; aramid paper honeycomb can be replaced with PMI foam and PET foam, requiring matching dielectric properties; extra-large radomes can be processed in sections and bonded as a whole, with shrinkage calculated independently for each section. All these changes in materials and dimensions do not require discarding the original PU foam mold; only partial mold repair or section splicing is needed, further demonstrating the advantages of this process in adapting to frequent changes and minimizing mold repair costs.

[0051] To verify the dimensional stability of rigid PU foam under high temperature and vacuum conditions, a PU foam sample with a density of 60±5 kg / m³ was selected and subjected to high temperature and vacuum conditions at 120℃. Ten heating-cooling cycle tests were conducted under the specified conditions. Each cycle included heating to 120℃, holding at that temperature for 3 hours, and then cooling to room temperature in the furnace. The test results showed that the dimensional change rate of the sample was ≤0.05%, and the coefficient of linear expansion remained stable within a certain range. There was no significant fatigue deformation or dimensional drift caused by internal stress release, fully meeting the accuracy requirements for 3-4 iterations of radome mold repair. The shrinkage rate of different batches of PU foam varies within ±0.15mm; therefore, material shrinkage pre-verification should be performed again when changing foam batches.

[0052] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A low-cost mold forming process for an antenna radome, characterized in that: Includes the following steps: Step 1: Initial mold forming: PU rigid foam is selected to make the initial mold for the radome mold. The initial mold is an integral one-time lost foam structure, without demolding angle, ejection mechanism and core pulling mechanism. The mold cavity is designed as a continuous smooth curved surface that matches the preset radome. Step 2, Initial Trial Production: The radome is formed using the initial mold, and the parameters of the formed radome are tested to obtain test data; Step 3: Mold modification: Based on the test data, perform local mold modification on the initial mold made of rigid PU foam to correct the size, structure or surface condition of the mold. Step 4: Iterative optimization: Repeat steps 2 and 3 until the radome produced using the modified mold meets the preset requirements and the final mold is obtained.

2. The mold forming process for a low-cost radome according to claim 1, characterized in that: Before step one, there is also a material shrinkage pre-verification step: a scaled-down model is made using PU foam with the same density and process as the initial mold. After vacuum bag pressing and oven curing, its shrinkage is measured and used as reference data for the initial mold size compensation.

3. The mold forming process for a low-cost radome according to claim 2, characterized in that: In the material shrinkage pre-verification step, the scaling factor of the scaling model is 1:5, and the vacuum degree of the vacuum bag pressure is... The oven curing process is as follows: the temperature is increased to 120℃ at a rate of 1.5℃ / min, and then kept at that temperature for 3 hours before being cooled with the oven.

4. The mold forming process for a low-cost radome according to claim 1, characterized in that: The density of the rigid PU foam mentioned in step one is 55-65 kg / m³, preferably 60±5 kg / m³.

5. The mold forming process for a low-cost radome according to claim 1, characterized in that: The initial mold processing described in step one includes: splicing multiple PU foam boards to form a blank, performing rough processing with a allowance, and then fine processing to make the dimensional accuracy of the initial mold reach ±0.2mm and the surface roughness Ra≤3.2μm. During the initial mold processing, a weakening groove is pre-embedded in the preset segmentation area.

6. The mold forming process for a low-cost radome according to claim 1, characterized in that: Step one includes a surface treatment step: cleaning the initial mold surface, repairing with putty and laying a release cloth. The putty repair needs to be done in layers, with each layer not exceeding 1mm in thickness and the total repair thickness not exceeding 3mm. After repair, it needs to be cured at room temperature for 24 hours before fine grinding.

7. The mold forming process for a low-cost radome according to claim 1, characterized in that: The radome produced in step two uses a quartz fiber reinforced epoxy resin prepreg system with a single-layer curing thickness of 0.2 mm. It is laid in the following order: inner surface layer → adhesive film → honeycomb → adhesive film → outer surface layer. The inner and outer surface layers are both made of 0.2 mm quartz fiber prepreg, the adhesive film is 0.12 mm thick, and the honeycomb is 3 mm aramid paper honeycomb. The honeycomb can also be PMI foam or PET foam. The honeycomb is aramid paper honeycomb, PMI foam, or PET foam.

8. The mold forming process for a low-cost radome according to claim 1, characterized in that: Step two involves forming the radome using a vacuum bag pressing-oven curing process. The process parameters for this vacuum bag pressing-oven curing are: vacuum degree... The curing process involves raising the temperature from room temperature to 80±2℃ at a rate of 1–2℃ / min and holding for 60 minutes, then raising it to 120±2℃ at a rate of 1–2℃ / min and holding for 180 minutes. The entire curing process is carried out under vacuum. After curing, the product should be cooled to <50℃ in the oven before being removed from the mold.

9. The mold forming process for a low-cost radome according to claim 1, characterized in that: In step three, the local mold repair is carried out by using a precision milling cutter for local repair and / or by using putty or epoxy repair putty for local filling and sanding. The depth of a single milling cut should not exceed 0.5mm. After the PU foam mold has been repaired more than 5 times, a full-size inspection should be carried out again, and the mold should be remade if necessary.

10. The mold forming process for a low-cost radome according to claim 1, characterized in that: The process also includes the molding of the rain cover assembly: a rain cover mold is made of PU foam of the same material as the radome mold, quartz fiber reinforced epoxy resin prepreg is laid on the rain cover mold, and the same vacuum bag pressing and curing process is performed on the radome body.

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