Method for forming a fibre-wound engine housing with form and position tolerances

Abstract

This invention discloses a method for correcting the form and position tolerances of a fiber-wound engine housing. A front joint positioning fixture is connected to the front joint of the housing, and a rear joint positioning fixture is connected to the rear joint of the housing. The method involves detecting the coaxiality, perpendicularity, and spacing of the front joints, and marking the high and low points where perpendicularity exceeds the tolerance. Using the high point of the rear joint as a reference, the method adjusts the low point by tightening the adjusting screws near the low point of the rear joint and the rear joint positioning fixture, pulling the low point outwards to the high point. The correction fixture fully utilizes the tensile and non-compressive characteristics of the front and rear joints to adjust the low point of the out-of-tolerance joint to the reverse limit. The adjusted housing is then subjected to low-temperature heating, which causes the epoxy resin in the composite layer to undergo permanent deformation, thereby stabilizing the housing dimensions. The perpendicularity tolerances of the front and rear joints meet the design and process requirements, achieving the correction purpose and avoiding product scrap due to excessive perpendicularity of the housing.

Description

Technical Field

[0001] This invention relates to the field of fiber-wound engine housing manufacturing technology, specifically to a fiber-wound engine housing form and position tolerance correction method. Background Technology

[0002] After the fiber-wound engine housing is manufactured, the front connector is typically used to install the ignition cartridge, and the rear connector is used to install the engine nozzle. Due to the thrust line angle deviation requirements and the influence of internal pressure during engine operation, the verticality of the front and rear connectors is subject to high standards after the fiber-wound engine housing is manufactured.

[0003] Currently, there are two main technological methods for controlling the perpendicularity and coaxiality accuracy of the front and rear joints of fiber-wound engine casings. One method involves pre-machining allowances on the end faces and outer diameters of the front and rear joints (including the end faces and outer diameters of skirts with dimensional tolerances). Machining is then performed after the casing is fabricated and undergoes a hydrostatic test, ensuring the perpendicularity and coaxiality accuracy of the front and rear joints (including the end faces and outer diameters of skirts with dimensional tolerances). This method ensures relatively stable and reliable accuracy through machining after the casing dimensions and shape are stable. However, the overall casing machining requires advanced equipment and skilled operators, resulting in relatively high processing costs.

[0004] Another, and more commonly used, method involves machining all dimensions of the front and rear joints to the correct position before the insulation structure is fabricated and installed. Through precise mandrel machining and process control of the insulation structure and winding, the perpendicularity and coaxiality of the front and rear joints after shell fabrication are ultimately guaranteed. However, this method is affected by factors such as mandrel machining precision, thickness deviations of the front and rear end caps, deviations in fiber winding alignment and coaxiality of the front and rear joints, shell curing stress, and hydrostatic testing. Although monitoring of perpendicularity and coaxiality at each stage of the process is strengthened, occasional instances still occur where the perpendicularity of the front and rear joints exceeds design specifications. This is especially true for the rear joint, which requires higher precision; excessive perpendicularity can lead to the scrapping of the entire shell, resulting in significant economic losses. Summary of the Invention

[0005] The purpose of this invention is to address the technical problem of excessive perpendicularity of the front and rear joints of the fiber-wound solid rocket motor casing, and to provide a forming method for correcting the geometric tolerances of the perpendicularity of the front and rear joints of the fiber-wound engine casing.

[0006] To achieve the above objectives, the fiber-wound engine housing form and position tolerance correction forming method designed in this invention includes a correction fixture comprising a mandrel, a front connector positioning fixture, and a rear connector positioning fixture; the specific correction forming method is as follows:

[0007] 1) Housing installation

[0008] After the mandrel passes through the housing axially, the front connector positioning fixture is connected to the front connector of the housing. The front clamping nut axially clamps the front connector positioning fixture until it fits against the front connector and is fixed to the mandrel. The rear connector positioning fixture is connected to the rear connector of the housing. The rear connector positioning fixture is axially locked to the mandrel by the rear clamping nut, and a gap is left between the rear connector positioning fixture and the rear connector.

[0009] 2) Size inspection

[0010] After the housing is installed on the alignment fixture, check the coaxiality, perpendicularity, and spacing of the front connectors, and mark the high and low points where the perpendicularity exceeds the tolerance.

[0011] 3) Verticality adjustment

[0012] Using the high point of the rear connector as a reference, by tightening the adjusting screws near the low point of the rear connector and the positioning fixture of the rear connector, the low point is pulled outward to adjust to the high point, achieving an upper tolerance of verticality of +0.2mm.

[0013] 4) Heating and Shaping

[0014] Place the core mold shell into the oven and heat it to 60℃-80℃ at a heating rate of 0.5~1℃ / min, and hold it at that temperature for 4~8 hours; after heating, cool it to room temperature and remove it from the oven.

[0015] 5) Testing

[0016] Loosen the connecting screws and adjusting screws on the front connector, rear connector and front connector positioning fixture; check the spacing, perpendicularity and coaxiality of the front connector and rear connector of the adjusted housing.

[0017] 6) If the verticality does not meet the requirements, repeat steps 3 to 5 until it does.

[0018] Furthermore, in step 1), both the front connector positioning fixture and the rear connector positioning fixture are mounted on the mandrel by keys for circumferential constraint of the housing.

[0019] Furthermore, in step 1), the front connector positioning fixture is connected to the front connector positioning fixture by connecting screws, and the rear connector positioning fixture is connected to the rear connector positioning fixture by adjusting screws.

[0020] Furthermore, in step 1), the width of the gap is 2~5mm.

[0021] Furthermore, in step 3), after the verticality adjustment, the verticality of the rear connector is checked again to ensure that the low point becomes the high point and reaches the upper limit of the verticality tolerance of +0.2mm.

[0022] Compared with the prior art, the present invention has the following advantages: The present invention makes full use of the characteristics of the front and rear joints being under tension but not under pressure by using a straightening tooling to adjust the reverse limit of the low point of the out-of-tolerance joint by pulling, and then heating the adjusted shell at low temperature. The epoxy resin in the composite layer is stabilized and permanently deformed by the low temperature heating, thereby stabilizing the shell size and ensuring that the perpendicularity tolerance of the front and rear joints meets the design and process requirements, thus achieving the purpose of straightening and avoiding product scrap due to out-of-tolerance shell perpendicularity. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the alignment and installation using alignment fixtures in this invention. Detailed Implementation

[0024] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0025] Methods for correcting the form and position tolerances of fiber-wound engine casings, such as Figure 1 The calibration fixture shown includes a mandrel 9, a front connector positioning fixture 2, and a rear connector positioning fixture 5; the specific calibration method is as follows:

[0026] 1) Housing installation

[0027] After the mandrel passes through the housing axially, the front connector positioning fixture 2 is connected to the front connector 1 of the housing. The front clamping nut 3 axially clamps the front connector positioning fixture 2 until it fits against the front connector 1 and is fixed to the mandrel, thus providing radial and axial constraints on the housing. The rear connector positioning fixture 5 is connected to the rear connector 7 of the housing. The rear connector positioning fixture 5 is axially locked to the mandrel 9 by the rear clamping nut 4, and a gap 10 of 2~5mm is left between the rear connector positioning fixture 5 and the rear connector 7 for perpendicularity correction. The rear connector is radially positioned by the hole-shaft fit.

[0028] Both the front connector positioning fixture 2 and the rear connector positioning fixture 5 are keyed onto the mandrel 9 for circumferential constraint of the housing, preventing the housing from rotating during the alignment process.

[0029] To prevent damage to the shell surface during the installation of the alignment fixture, the front connector positioning fixture 2 is first positioned and connected to the front connector 1 using the connecting screw 8, and the rear connector positioning fixture 5 is positioned and connected to the rear connector 7 using the adjusting screw 6.

[0030] 2) Size inspection

[0031] The alignment fixture with the shell installed is hoisted onto a winding machine or horizontal lathe (or laser tracker) to check the coaxiality, perpendicularity, and spacing of the front connectors. High and low points with excessive perpendicularity are checked and marked.

[0032] 3) Verticality adjustment

[0033] Using the highest point of the rear connector as a reference (0 value), by tightening the adjusting screws near the lowest point of the rear connector and the positioning fixture of the rear connector, the lowest point (e.g., -0.5) is pulled outward to the highest point, achieving an upper tolerance of +0.2mm for verticality;

[0034] After the verticality adjustment, the verticality of the rear joint was checked again, and it met the requirement that the low point becomes the high point and reaches the upper limit of the verticality tolerance +0.2.

[0035] 4) Heating and Shaping

[0036] Place the core mold shell into the oven and heat it to 60℃-80℃ at a heating rate of 0.5~1℃ / min. Hold it at this temperature for 4~8 hours to allow the resin to undergo permanent deformation and ensure the stability of the adjusted shell dimensions. After heating, cool it to room temperature +20℃ before removing it from the oven.

[0037] 5) Testing

[0038] Loosen the connecting screws and adjusting screws on the front and rear connectors and the front and rear connector positioning fixtures to allow the housing to be in a free axial position. Use a winding machine, horizontal lathe (or laser tracker) to check the spacing, perpendicularity, and coaxiality of the front and rear connectors of the adjusted housing.

[0039] 6) If the verticality does not meet the requirements, repeat steps 3 to 5 until it does.

[0040] This invention utilizes a calibration fixture to fully leverage the tensile and non-compressive characteristics of the front and rear joints. It adjusts the low-point pull of the out-of-tolerance joint to the reverse limit and then heats the adjusted shell at a low temperature. This low-temperature heating causes the epoxy resin in the composite layer to undergo permanent deformation, thereby stabilizing the shell dimensions and ensuring that the perpendicularity tolerance of the front and rear joints meets the design and process specifications. This achieves the calibration purpose and avoids product scrap due to out-of-tolerance shell perpendicularity.

Claims

1. A method for correcting the form and position tolerances of a fiber-wound engine housing, characterized in that: The calibration fixture includes a mandrel (9), a front connector positioning fixture (2), and a rear connector positioning fixture (5); the specific calibration method is as follows: 1) Housing installation After the mandrel passes through the housing axially, the front connector positioning fixture (2) is connected to the front connector (1) of the housing. The front clamping nut (3) axially clamps the front connector positioning fixture (2) until the front connector positioning fixture (2) fits against the front connector (1) and is fixed to the mandrel. The rear connector positioning fixture (5) is connected to the rear connector (7) of the housing. The rear connector positioning fixture (5) is axially locked to the mandrel (9) by the rear clamping nut (4), and a gap (10) is left between the rear connector positioning fixture (5) and the rear connector (7). The front connector positioning fixture (2) is positioned and connected to the front connector (1) by the connecting screw (8), and the rear connector positioning fixture (5) is positioned and connected to the rear connector (7) by the adjusting screw (6). 2) Size inspection After the housing is installed on the alignment fixture, check the coaxiality, perpendicularity, and spacing of the front connectors, and mark the high and low points where the perpendicularity exceeds the tolerance. 3) Verticality adjustment Using the high point of the rear connector as a reference, by tightening the adjusting screws near the low point of the rear connector and the positioning fixture of the rear connector, the low point is pulled outward to adjust to the high point, achieving an upper tolerance of verticality of +0.2mm. 4) Heating and Shaping Place the core mold shell into the oven and heat it to 60℃-80℃ at a heating rate of 0.5~1℃ / min, and hold it at that temperature for 4~8 hours; after heating, cool it to room temperature and remove it from the oven. 5) Testing Loosen the connecting screws and adjusting screws on the front connector, rear connector and front connector positioning fixture; check the spacing, perpendicularity and coaxiality of the front connector and rear connector of the adjusted housing. 6) If the verticality does not meet the requirements, repeat steps 3 to 5 until it does.

2. The fiber-wound engine housing form and position tolerance correction forming method according to claim 1, characterized in that: In step 1), the front connector positioning fixture (2) and the rear connector positioning fixture (5) are both mounted on the mandrel (9) by keys for circumferential constraint of the housing.

3. The fiber-wound engine housing form and position tolerance correction forming method according to claim 1, characterized in that: In step 1), the width of the gap (10) is 2~5mm.

4. The fiber-wound engine housing form and position tolerance correction forming method according to claim 1, characterized in that: In step 3), after the verticality is adjusted, the verticality of the rear connector is checked again to ensure that the low point becomes the high point and reaches the upper limit of the verticality tolerance of +0.2mm.

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