Machining method for weak-rigidity long-barrel shell

Abstract

The invention discloses a machining method for a weak-rigidity long barrel shell. The specific process route comprises the steps of blanking, rough machining, heat treatment, pre-spinning machining, spinning forming, gas truck benchmark, outer shape finish turning and inner shape finish turning. And a pneumatic chuck turning reference procedure is added after spinning, the overall straightness of the part is improved by utilizing the high precision of a pneumatic chuck, and a reference is provided for grabbing and clamping of numerical control finish turning. During finish turning, exploration tests are carried out for many times, the optimal clamping force is found, and the deformation of the clamped product is minimum. And grabbing and clamping point positions with consistent outer diameters are selected during grabbing and clamping, so that the product roundness is improved. During turning, the tail top is added, the influence of turning force on the coaxiality of a product is weakened, finish turning is divided into two steps of outer diameter turning and inner diameter turning, the coaxiality requirement is improved through internal control, and the precision required by the product is achieved after finish turning by adjusting the positions of the center frame and the tail top for multiple times.

Description

Technical Field

[0001] The invention relates to a machining method for a weak-rigidity long cylindrical shell, belonging to the technical field of mechanical processing. Background Art

[0002] During the product development process, a large number of weak-rigidity long cylindrical shells are important components of weapons. The commonly used process flow for this type of components is: cutting → rough processing → heat treatment → pre-machining → spinning → fine turning. Spinning is used to ensure the wall thickness and uniformity of the cylindrical part of the product. Fine turning after spinning ensures the size of the centering part and the coaxiality of the entire product. During fine turning, two points are fixed (i.e., the port and the cylindrical part) and the mouth and the centering part are machined.

[0003] A certain type of metal part is a weak rigid long cylindrical shell with an outer diameter of Φ100 to Φ110 mm, an aspect ratio of 18 to 20, a cylindrical wall thickness of 1.5 to 2.0 mm, two left and right sections, and a multi-section centering section in the middle. The coaxiality of the cylindrical section to the centering sections at both ends is required to be ≤Φ0.5, and the coaxiality of the middle centering section to the centering sections at both ends is required to be ≤Φ0.2. According to the above machining process, after spinning, the cylindrical part of the part has reached the thin-walled size required by the product, and the overall coaxiality is small. However, after spinning, even if soft claws are used to fix the parts, it is very easy to cause the parts to bend and deform due to improper setting of the gripping force, and the coaxiality increases. Moreover, due to the inconsistency between the outer diameters of the fixed point mouth and the cylindrical part, it is easy to have coaxiality deviation after turning, resulting in the scrapping of the parts. Therefore, developing a machining method suitable for such parts has become an urgent problem to be solved. Summary of the Invention

[0004] The purpose of the present invention is to solve the problem of difficulty in machining a weak rigidity long cylindrical shell with high coaxiality requirements, and to provide a machining method for a weak rigidity long cylindrical shell.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] The present invention provides a machining method for a weak rigid long cylindrical shell, wherein the specific process route is: blanking → rough machining → heat treatment → pre-spinning machining → spinning forming → air truck base → fine turning of the outer shape → fine turning of the inner shape;

[0007] After spinning, a pneumatic chuck turning process is added. The high precision of the pneumatic chuck is utilized to improve the overall straightness of the part and provide a reference for the gripping process during CNC finishing. During finishing, multiple trials are conducted to find the optimal gripping force to minimize deformation after gripping. Gripping points with consistent outer diameters are selected during gripping to improve product roundness. During turning, a tail jack is added to reduce the impact of turning forces on product coaxiality. Finish turning is divided into two steps: outer diameter turning and inner diameter turning. Internal control is used to enhance coaxiality requirements. By repeatedly adjusting the position of the center rest and tail jack, the required product accuracy is achieved after finishing.

[0008] The specific contents of the invention are as follows:

[0009] Step 1: Cutting

[0010] The selected material has uniform wall thickness and sufficient length to facilitate further rough processing.

[0011] Step 2: Rough machining

[0012] Black skin and other defects on the turning surface

[0013] Step 3: Heat Treatment

[0014] Improve product mechanical properties to meet product requirements

[0015] Step 4: Pronation machining

[0016] According to the product drawing and the thinning rate of the material, the spinning blank drawing that fits the spinning core rod is designed, and the blank is turned before spinning. The quality of the spinning blank directly affects the spinning effect, so the consistency of the spinning blank must be ensured.

[0017] Step 5: Spinning

[0018] According to the final finished product drawing, design the spinning process drawing, the cylindrical part and the product Figure 1 The centering part should leave enough allowance for subsequent turning (3 to 8 mm in the diameter direction). The overall length of the product can leave a allowance of 16 to 80 mm according to the actual route. The coaxiality can be internally controlled according to specific requirements, and the coaxiality requirement can be increased by Φ0.5 to 1.

[0019] Step 6: Gas Truck Benchmark

[0020] When turning the base, a pneumatic chuck is used to clamp the parts, and the parts are aligned through the centering parts at both ends. After turning the base, the straightness and roundness of the parts are better guaranteed, providing protection for subsequent fine turning.

[0021] Step 7: Finishing the shape

[0022] After testing, the deformation during machining was minimized when the hydraulic chuck force was adjusted to 0.5-0.7 MPa, the center frame clamping force was 0.7-0.9 MPa, and the top force was 0.1-0.2 MPa.

[0023] Soft claw fixes the centering part at the starting end ( Figure 1 A in the middle), the top supports the centering part at the end ( Figure 1 M), the center of the frame is placed in the middle centering part ( Figure 1 C in the middle), it is required that there is a centering part between this centering part and the soft claw fixing part to ensure that the other centering parts are aligned with the centering part of the clamping part ( Figure 1The coaxiality of A, C, and M in the middle is ≤ Φ0.1, the coaxiality of the cylindrical part to the centering part at the clamping position is ≤ Φ0.4, and the size of the centering part at the end of the turning and the unclamped position is ≤ Φ0.1.

[0024] Step 8: Fine turning the inner shape

[0025] Remove the center and move the center frame to the end centering part ( Figure 1 M in the middle), flat end face to product size, and inner dimension of the end after turning.

[0026] Beneficial effects:

[0027] This method can significantly improve the product qualification rate. The qualification rate before the improvement is 25-30%, and the qualification rate after the improvement can reach 85-92%. The present invention effectively improves the problems such as large runout, uneven wall thickness, low straightness, and poor roundness caused by spin finishing, and better ensures product quality and consistency.

[0028] The present invention can systematically solve the problem of machining such weak rigidity long cylindrical thin-walled shells with high coaxiality requirements, and can be extended to the machining of various products in this series, thereby reducing economic losses caused by scrapped parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the structural diagram of the part to be processed;

[0030] Figure 2 Schematic diagram of the clamping position in the method of the present invention;

[0031] Figure 3 Schematic diagram of the spinning blank in the method of the present invention. DETAILED DESCRIPTION

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0033] Example

[0034] Take a part with two centering parts in the middle as an example. The outer diameter is Φ105mm, the aspect ratio is 20, the wall thickness of the cylindrical part is 1.8mm, there are 4 centering parts, 2 on the left and right sections and 2 in the middle. The coaxiality of the cylindrical part to the centering parts at both ends is required to be ≤Φ0.45, and the coaxiality of the middle centering part to the centering parts at both ends is required to be ≤Φ0.2. The specific method is as follows:

[0035] Step 1: Cutting

[0036] Step 2: Rough machining

[0037] Leave enough allowance for subsequent heat treatment and rough machining

[0038] Step 3: Heat Treatment

[0039] Breaking strength after heat treatment ≥1000Mpa

[0040] Step 4: Pronation machining

[0041] according to Figure 3 Machining the spun blank ensures the coaxiality and consistency of the spun blank.

[0042] Step 5: Car benchmark (refer to the figure Figure 2 )

[0043] 1. Clamp and align the centering part ①, hold the air clamp at a distance of 400±5 from the end face ④, ensure that the runout difference between the centering part ② and the root of the air clamp is ≤Φ0.1, turn the outer diameter of the centering part ④, and chamfer it;

[0044] 2. Turn around, clamp the centering part ④, hold the air clamp at a position 400±5 from the end face ①, ensure that the runout difference between the centering part ③ and the root of the air clamp is ≤Φ0.1, and turn the outer diameter of the centering part ①;

[0045] Step 6: Car appearance (see figure Figure 2 )

[0046] Set the clamping force of the CNC lathe to 0.6MPa, the clamping force of the center stand to 0.8MPa, and the center force of the tailstock to 0.2MPa

[0047] Fix the centering part ① with soft claws, support the centering part ④ with the centering center, set up the center frame (③ centering part), ensure that the coaxiality of the ② and ④ centering parts to the ① and ③ centering parts is ≤ Φ0.1, and the coaxiality of the cylindrical part to the ① and ③ centering parts is ≤ Φ0.4, and turn the diameters of the ② and ④ centering parts.

[0048] Step 7: Car interior shape (see figure Figure 2 )

[0049] Remove the center, move the center frame to the ④ centering part, level the total length, and turn the internal dimensions.

Claims

1. A machining method for a weak rigid long cylindrical shell, characterized in that: The specific process route is: blanking → rough machining → heat treatment → pre-spinning machining → spinning → air truck base → fine turning of the outer shape → fine turning of the inner shape; The pneumatic car benchmark process is: using a pneumatic chuck to clamp the part, aligning the part through the centering parts at both ends, and then performing the benchmark; The finishing process of the shape turning is as follows: the soft claws are fixed to the centering part at the starting end of the part, the top tip is supported on the centering part at the end end, and the center frame is placed on the middle centering part, and then the shape is finished turning; The hydraulic chuck force is adjusted to 0.5-0.7Mpa, the center stand clamping force is 0.7-0.9Mpa, and the center force is 0.1-0.2Mpa. The process of fine turning the inner shape is as follows: removing the top, moving the center frame to the centering part of the end, flattening the end surface to the product size, and fine turning the inner shape size of the end.

Images