Low-cost oven compression molding device and method

Abstract

The low-cost oven compression molding device comprises a forming mold, the forming mold is divided into an upper mold body and a lower mold body, the upper mold body and the lower mold body are positioned and spliced through a positioning pin, and a part cavity is formed in the interior; a plurality of mounting holes are evenly distributed in the edge of the upper die, a plurality of threaded holes are evenly distributed in the edge of the lower die, and bolts penetrate through the mounting holes to be in locking fit with the threaded holes. According to the invention, the uniformly distributed bolts are used for providing corresponding forming pressure for the forming mold, and the drying oven is used as heating curing equipment, so that a traditional heatable press is replaced, and the purchase and use cost of the equipment is greatly reduced; and meanwhile, the forming mold can be independently placed in the drying oven to complete curing, multiple sets of molds can be synchronously formed in the drying oven, and the production flexibility and the production efficiency are greatly improved.

Description

Technical Field

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

[0002] In the field of molding and processing of non-load-bearing composite components, compression molding technology has long held a mainstream application position due to its relatively mature molding process. Traditional compression molding technology has long relied on a heated press as the core equipment, using the pressure output by the press and the heat transferred by the heating plate to achieve the curing and molding of the parts.

[0003] However, during the compression molding process, in order to meet the mold closing accuracy requirements of the press, an additional guide post and guide sleeve structure needs to be designed between the upper and lower molds to ensure mold coaxiality and avoid mold misalignment. At the same time, the flatness deviation of the upper and lower molds and the press panel needs to meet the flatness deviation requirement of 0.02~0.08mm / 1000mm or even higher, which leads to an extended mold processing cycle and increased manufacturing costs.

[0004] Meanwhile, the purchase cost of a dedicated heated press typically ranges from hundreds of thousands to millions of yuan, and equipment maintenance costs are high. Furthermore, the molding process is limited by the press's capacity; when multiple small batches of parts need to be produced simultaneously, the time cost of changing molds is high, resulting in poor production flexibility. Moreover, for parts with complex shapes such as curved surfaces and grooves, the rigid pressure applied by the press can easily lead to uneven stress on the mold, causing bubbles, wrinkles, or dimensional deviations after curing, resulting in a low yield rate. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides a low-cost oven molding apparatus and method, which features low equipment cost, convenient operation, and stable molding quality.

[0006] Therefore, the first technical solution of the present invention is: a low-cost oven molding device, including a molding die, the molding die being divided into an upper die and a lower die, the upper die and the lower die being positioned and assembled by a positioning pin, forming a part cavity inside; a plurality of mounting holes are evenly distributed along the edge of the upper die, and a plurality of threaded holes are evenly distributed along the edge of the lower die, and bolts pass through the mounting holes and lock into the threaded holes. Setting: The preload of a single bolt is F. 预 If the force transmission efficiency of a bolt is η, then the actual clamping pressure F of a single bolt is... 压 =F 预 ×η; During the forming of the part, the total pressure between the upper and lower dies is F. 总 Then the number of bolts n≥F 总 / F 压 n can be an integer.

[0007] Based on the above scheme and as a preferred option: Let the preset autoclave curing pressure of the part be P, and the force-bearing area of ​​the part be A. Then, the total pressure F between the upper and lower molds is... 总 =P×A.

[0008] Based on the above scheme and as a preferred embodiment of the above scheme: the lower mold is provided with at least two positioning pins, and the upper mold is provided with corresponding positioning pin holes, which work in conjunction with the positioning pins.

[0009] Based on the above scheme and as a preferred embodiment of the above scheme: the molding die is provided with at least one temperature monitoring hole, the bottom of the temperature monitoring hole being close to the part cavity; a temperature sensor is provided inside the temperature monitoring hole.

[0010] Based on the above scheme and as a preferred embodiment of the above scheme, it also includes an oven, in which the upper mold and the lower mold are placed after being closed, and a temperature sensor is connected to the temperature controller of the oven.

[0011] Another technical solution of the present invention is: a low-cost oven molding method, using the above-mentioned molding apparatus, comprising the following steps: S1. Stack the prepreg and foam core material according to the designed number of layers and place them into the part cavity of the lower mold; S2. Align the upper mold with the positioning pin of the lower mold, and slowly close the mold until the parting surface is in contact; S3. Use a torque wrench to tighten the bolts in a diagonal sequence. The tightening torque of each bolt should be set according to the pre-set torque to ensure that the bolt preload is evenly transmitted. S4. Place the molding mold into the oven, insert the thermocouple into the temperature monitoring hole of the mold, and connect the other end of the thermocouple to the temperature controller. S5. After molding, remove the molding mold, loosen the bolts in diagonal order, separate the upper mold and the lower mold, remove the molded part, and perform appearance inspection and size measurement.

[0012] Based on the above scheme and as a preferred option: in step S4, thermocouple temperature control is used, the oven curing temperature is increased from room temperature to 120℃ at 3℃ / min, held for 2 hours, and then decreased to below 50℃ at 2℃ / min; during the curing process, the surface temperature is monitored in real time to ensure that the temperature fluctuation is ≤±3℃.

[0013] Compared with the prior art, the beneficial effects of the present invention are: By using evenly distributed bolts to provide the corresponding molding pressure for the molding die and using an oven as a heating and curing device, the traditional heatable press can be replaced, significantly reducing the cost of equipment purchase and use. At the same time, the molding die can be placed independently in the oven to complete the curing, eliminating the limitation of press capacity on the traditional molding process. When multiple small batches of parts need to be produced at the same time, there is no need to switch molds on the press, reducing the changeover time cost. Multiple sets of molds can be formed simultaneously in the oven, greatly improving the flexibility and efficiency of production.

[0014] The forming mold is positioned by locating pins, eliminating the need for high-precision guide pillars and bushings, which significantly reduces the processing accuracy requirements and design complexity of the mold; it also reduces the number of precision machining steps, effectively shortens the mold processing cycle, and reduces the mold manufacturing cost, solving the problems of high processing cost and long cycle of traditional molds.

[0015] The mold is equipped with a temperature monitoring hole near the cavity and a temperature sensor to monitor the surface temperature in real time. At the same time, the oven curing process is designed with stepped heating and cooling curves and strict temperature fluctuation standards to achieve precise temperature control and real-time adjustment during the curing process, ensuring the stability of the curing environment for the parts and further guaranteeing the consistency and reliability of the parts molding.

[0016] When closing the mold, the upper and lower molds are precisely positioned by the positioning pins. With the help of a torque wrench, the bolts are tightened in a diagonal sequence to ensure that the bolt preload is evenly transmitted and the total pressure is precisely controlled. When demolding, the molds can be separated by loosening the bolts in a diagonal sequence. The operation process is simple and convenient, requiring no professional press operation skills, thus lowering the operation threshold and improving the efficiency and controllability of mold closing and demolding.

[0017] The molding device has a simple overall structure and a high degree of standardization of its parts. Through precise calculation of the number of bolts and preload, it can adapt to the molding requirements of non-load-bearing composite materials with different stress areas and different preset curing pressures, and has strong process adaptability and practical application value. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of Example 1; Figure 2 This is an exploded view of the parts in Example 1; Figure 3 This is a structural cross-sectional view of Example 1; Figure 4 This is a schematic diagram of the structure of Example 2; Figure 5 This is an exploded view of the parts in Example 2; Figure 6 This is a cross-sectional view of the structure of Example 2.

[0019] The parts are marked as follows: First upper mold 1, mounting hole 11, first lower mold 2, threaded hole 21, part cavity 3, locating pin 4, locating pin hole 5, bolt 6, temperature monitoring hole 7, second upper mold 8, second lower mold 9. Detailed Implementation

[0020] In the description of this invention, it should be noted that directional terms such as "center", "lateral (X)", "longitudinal (Y)", "vertical (Z)", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", and "counterclockwise" indicate the orientation and positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. They should not be construed as limiting the specific protection scope of this invention.

[0021] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features. Thus, the use of "first" and "second" to define a feature may explicitly or implicitly include one or more of that feature. In the description of this invention, "several" or "a number" means two or more, unless otherwise explicitly specified.

[0022] The low-cost oven molding apparatus described in this embodiment includes a molding die and an oven. The molding die consists of a first upper die 1 and a first lower die 2. The first upper die 1 and the first lower die 2 are provided with molding grooves, which, when assembled, form a part cavity 3. The first lower die 2 is provided with multiple positioning pins 4, and the first upper die 1 is provided with corresponding positioning pin holes 5, which cooperate with the positioning pins 4.

[0023] A plurality of mounting holes 11 are evenly distributed along the edge of the first upper mold 1, and a plurality of threaded holes 21 are evenly distributed along the edge of the first lower mold 2. Bolts 6 pass through the mounting holes and lock into the threaded holes. The molding die is provided with at least one temperature monitoring hole 7 (the hole diameter is adapted to the thermocouple, usually 3~5mm). One end of the temperature monitoring hole 7 is close to the part cavity 3 (≤5mm from the mold surface), and the other end extends to the outside of the mold. It is used to insert a thermocouple to collect the mold surface temperature in real time during the curing process, ensuring that the temperature control accuracy is ≤±3℃. A thermocouple is installed in the temperature monitoring hole 7. After the first upper mold 1 and the first lower mold 2 are closed, they are placed in an oven, and the thermocouple is connected to the temperature controller of the oven. The temperature inside the mold near the part surface is detected by the thermocouple.

[0024] This embodiment employs a bolt pre-tightening mechanism: bolt pre-tightening force is used instead of press pressure, and bolt parameters are determined through quantitative calculation. Parameter 1: Preload F of a single bolt 预 Also known as the allowable tensile force of a single bolt. F 预 = [б] × A s ;

б

[0025] Parameter 2: If the force transmission efficiency of the bolt is η, then the actual tightening pressure F of a single bolt is... 压 =F 预 ×η; Parameter 3: When the part is formed, the preset autoclave curing pressure is P, and the force-bearing area of ​​the part is A. Then the total pressure F between the upper mold and the lower mold is... 总 =P×A. The value of the curing pressure P is determined according to the general requirements of composite material molding processes, based on the material and part structure, and should generally be between 0.1-2.5 MPa. The pressure should ensure mold closure. For products with high requirements for appearance and smoothness, a higher molding pressure should generally be selected. In this method, a pressure of 1.8-2.5 MPa will be used for curing.

[0026] Parameter 4: Number of bolts n≥F 总 / F 压 n can be an integer.

[0027] Example 1: Taking a non-load-bearing foam sandwich component for aerospace applications as an example (e.g.) Figure 1 (as shown) 1) Part specifications: Length 200mm × Width 150mm × Height 20mm, foam core thickness 10mm, part bearing area A is about 0.08㎡; 2) Molding requirements: Curing pressure P is 1.8MPa, curing temperature is 120℃, curing time is 2h, and temperature control accuracy is ≤±3℃; 3) Mold design: The first upper mold and the first lower mold are made of 45# steel. The parting surface is ground to a flatness of ±0.1mm and a fitting clearance of 0.1mm. Two locating pins with a diameter of 10mm are set. Two temperature monitoring holes with a diameter of 5mm are reserved (6mm away from the part surface). The tooling dimensions are: length 690mm × width 510mm × height 110mm.

[0028] Bolt Options and Calculations Bolt specification selection: M12, performance grade 8.8, safety factor 2.0, preload force F per bolt. 预 ≈26KN); Total pressure: Autoclave curing pressure P = 1.8 MPa = 1.8 × 10⁶ Pa, part bearing area A = 0.08 m², total pressure is F 总 =P×A=1.8×106×0.08=1440000N=144KN; Force transmission efficiency: For rigid structures, uniform stress distribution, and short molds, higher values ​​(0.8-0.9) can be used. For flexible structures, uneven stress distribution, and long molds, a lower value (0.6-0.7) should be used.

[0029] Bolt quantity calculation: n=F 总 / F 预 ×0.9=144KN / 26KN×0.9≈6.2 pieces Considering the even distribution of bolts and a more reliable sealing and tightening effect, the number of bolts can be appropriately increased, and 8 bolts can be selected.

[0030] Example 2 The part and mold parameters for this embodiment are as follows: Part specifications: Length 1600mm × Width 72mm × Height 60mm, foam core thickness 55mm, part bearing area A approximately 0.215㎡; Molding requirements: curing pressure 1.8MPa, curing temperature 120℃, curing time 2h, temperature control accuracy ≤±3℃; Mold design: The second upper mold 8 and the second lower mold 9 are made of 45# steel. The parting surface is ground to a flatness of ±0.1mm and a mating clearance of 0.1mm. Two locating pins 4 with a diameter of 25mm are set. Two temperature monitoring holes 7 with a diameter of 5mm are reserved (6mm away from the part surface). The tooling dimensions are: length 1980mm × width 500mm × height 114mm. Bolt selection and calculation: Bolt specification selection: M16, performance grade 8.8, safety factor 2.0, preload force F per bolt. 预 ≈50.24KN); Total pressure: Autoclave curing pressure P = 1800 kPa = 1.8 × 10⁻⁶ 6 Pa, the area of ​​the part subjected to force A = 0.215 m², the total pressure is F 总 =P×A=1.8×10 6 ×0.215=387000N=387KN; Force transmission efficiency: For rigid structures, uniform stress distribution, and short molds, higher values ​​(0.8-0.9) can be used. For flexible structures, uneven stress distribution, and long molds, a lower value (0.6-0.7) should be used.

[0031] Bolt quantity calculation: n=F 总 / F 预 ×0.7=387KN / 50.24KN×0.7≈11 pieces Considering the even distribution of bolts and a more reliable sealing and tightening effect, the number of bolts can be appropriately increased, and 12 bolts can be selected.

[0032] The molding process steps are as follows: S1. Blank preparation: Stack the prepreg (carbon fiber / epoxy resin system) and foam core material according to the design number of layers, and place them into the part cavity of the lower mold to ensure that the blank is free of wrinkles and displacement. S2. Mold Closure and Pressure Application: Align the upper mold with the positioning pin of the lower mold, and slowly close the mold until the parting surface is in contact; use a torque wrench (torque accuracy ±5%) to tighten the bolts in a diagonal sequence, with the tightening torque of each bolt set according to the pre-set value, to ensure that the bolt preload is evenly transmitted. S3. Oven curing: Place the mold assembly in the oven, insert two K-type thermocouples into the temperature monitoring holes of the mold respectively, and connect the other end of the thermocouples to the temperature controller; set the oven curing curve: room temperature → increase the temperature to 120℃ at 3℃ / min → keep at the temperature for 2 hours → decrease the temperature to below 50℃ at 2℃ / min; during the curing process, monitor the surface temperature in real time to ensure that the temperature fluctuation is ≤±3℃; S4. Part Removal: After the oven temperature drops below 50℃, remove the mold assembly, loosen the bolts in diagonal order, separate the upper mold and the lower mold (use the mold lifting screws to lift the upper mold and use a crane to lift the upper mold during separation), remove the molded parts, and perform visual inspection and dimensional measurement.

[0033] In this embodiment, the mold processing cost is reduced by 42% compared to traditional press molds, no press equipment is required in the molding process, the part qualification rate reaches 98%, and the curing temperature fluctuation range is ±2℃, which fully meets the performance requirements of non-main load-bearing components.

[0034] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principle of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A low-cost oven molding apparatus, characterized in that: The mold includes a molding die, which is divided into an upper mold and a lower mold. The upper mold and the lower mold are positioned and assembled by positioning pins to form a part cavity inside. Several mounting holes are evenly distributed along the edge of the upper mold, and several threaded holes are evenly distributed along the edge of the lower mold. Bolts pass through the mounting holes and lock into the threaded holes. Setting: The preload of a single bolt is F. 预 If the force transmission efficiency of a bolt is η, then the actual clamping pressure F of a single bolt is... 压 =F 预 ×η; During the forming of the part, the total pressure between the upper and lower dies is F. 总 Then the number of bolts n≥F 总 / F 压 n can be an integer.

2. The low-cost oven molding apparatus as described in claim 1, characterized in that: If the preset autoclave curing pressure of the part is set to P, and the force-bearing area of ​​the part is A, then the total pressure F between the upper and lower molds is... 总 =P×A.

3. The low-cost oven molding apparatus as described in claim 1, characterized in that: The lower mold is provided with at least two positioning pins, and the upper mold is provided with corresponding positioning pin holes, which work together with the positioning pins.

4. The low-cost oven molding apparatus as described in claim 1, characterized in that: The molding die is provided with at least one temperature monitoring hole, the bottom of which is close to the part cavity; a temperature sensor is provided inside the temperature monitoring hole.

5. The low-cost oven molding apparatus as described in claim 4, characterized in that: It also includes an oven, in which the upper and lower molds are placed after being closed, and a temperature sensor is connected to the oven's temperature controller.

6. A low-cost oven molding method, using the molding apparatus according to any one of claims 1 to 5, characterized in that: Includes the following steps: S1. Stack the prepreg and foam core material according to the designed number of layers and place them into the part cavity of the lower mold; S2. Align the upper mold with the positioning pin of the lower mold, and slowly close the mold until the parting surface is in contact; S3. Use a torque wrench to tighten the bolts in a diagonal sequence. The tightening torque of each bolt should be set according to the pre-set torque to ensure that the bolt preload is evenly transmitted. S4. Place the molding mold into the oven, insert the thermocouple into the temperature monitoring hole of the mold, and connect the other end of the thermocouple to the temperature controller. S5. After molding, remove the molding mold, loosen the bolts in diagonal order, separate the upper mold and the lower mold, remove the molded part, and perform appearance inspection and size measurement.

7. The low-cost oven molding method as described in claim 6, characterized in that: In step S4, thermocouple temperature control is used. The oven curing temperature is increased from room temperature to 120°C at a rate of 3°C / min, and after holding at this temperature for 2 hours, it is decreased to below 50°C at a rate of 2°C / min. During the curing process, the surface temperature is monitored in real time to ensure that the temperature fluctuation is ≤±3°C.

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