Cutting processing method of organic glass multi-deep cavity shell

Abstract

This invention discloses a machining method for multi-cavity acrylic shells, relating to the field of precision machining. The method includes: clamping the part in a special fixture and applying a clamping force of 0.3MPa-0.45MPa; performing three-step layered milling—roughing, semi-finishing, and finishing—on right angles to form a transitional structure with progressively decreasing arc radii; selecting a single cavity, machining the front side to 50% depth, flipping the fixture, and machining the reverse side to the remaining 50%; completing the single cavity and then machining the remaining cavities sequentially; when machining cavities with a depth-to-diameter ratio ≥10, applying a high-pressure airflow of 0.6MPa-0.7MPa and using an intermittent feed method with a 2mm feed followed by retraction for chip removal. This invention effectively solves the problems of corner chipping, deformation, and difficult chip removal in the machining of multi-cavity acrylic shells by combining precise clamping, gradient fillet transition, alternating machining of the front and back sides of a single cavity, and high-pressure intermittent chip removal, significantly improving the product qualification rate.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology, specifically to a cutting method for a multi-cavity plexiglass shell. Background Technology

[0002] PMMA (polymethyl methacrylate) is the preferred material for aerospace connector housings, precision instrument housings, and small deep-cavity components in optical equipment due to its excellent optical properties, insulation, and machinability. A typical multi-cavity housing component has an overall rectangular parallelepiped structure, as shown in the figure. Figure 1 As shown, a square groove is provided on one side of the outer wall, and multiple long strip-shaped deep cavities (or deep cavity holes or deep holes) are provided inside. A very thin isolation wall (only 0.7-1.0 mm thick) is formed between adjacent long strip-shaped deep cavity holes. The length direction of the deep cavity is perpendicular to the outer side of the square groove.

[0003] In actual production, this specific part structure presents an extremely challenging technical bottleneck for existing conventional CNC cutting processes: Firstly, thin-walled interference and edge chipping are frequent problems. Acrylic glass is a brittle polymer material, which is prone to stress concentration during machining. Due to the extremely small spacing between deep cavities and the extremely thin partition walls, the brittle material is very prone to chipping along the direction of the deep cavities when machining inner right angles or grooves. Moreover, chipping often occurs in the finishing stage, directly leading to the scrapping of the entire part.

[0004] Secondly, the specific structure makes it difficult to suppress deep cavity deformation. Due to the interference between the square groove on the outer wall and the deep cavity hole inside, the overall rigidity distribution of the part is extremely uneven. The existing machining process usually adopts the traditional process of "machining the whole side and then flipping it over" (that is, machining all the deep cavities on the front side first and then flipping it over to machine the reverse side). This causes the extremely thin isolation wall that has been machined on the front side to completely lose its support when machining the reverse side. Under the combined action of cutting force and clamping force of the fixture, the thin wall is very prone to "tool deflection" and elastic rebound, resulting in serious exceedance of form and position tolerances.

[0005] Third, the clamping methods are crude and lack thin-walled anti-pinch structures. Existing general-purpose flat-jaw vises or simple clamps cannot quantitatively control the clamping force during clamping. They are prone to causing pre-deformation due to excessive pressure directly crushing the thin-walled parts, or causing the parts to loosen during processing due to insufficient pressure.

[0006] Fourth, chip removal from deep cavities with large aspect ratios is extremely difficult. The ends of strip-shaped holes within parts often require the drilling of cooling or fastening vias with an aspect ratio ≥10. During deep cavity machining, acrylic chips easily adhere to the cutting tool, preventing the removal of cutting heat. Existing simple air-blowing methods cannot effectively remove chips from the bottom of the hole, scratching the hole wall and resulting in an extremely low machining pass rate for holes with large aspect ratios. Furthermore, this can easily lead to tool jamming and part cracking.

[0007] Therefore, there is an urgent need for a processing method and special fixture that can precisely control the clamping force, achieve smooth flipping, and be combined with a specific layered chip removal process to solve the problem of high systematic processing scrap rate caused by the special structure and brittleness of the material. Summary of the Invention

[0008] To address the problems existing in the prior art, the present invention aims to provide a machining method for multi-cavity acrylic shells. By organically combining layered milling, controlled clamping, alternating single-cavity machining, and intermittent chip removal in deep cavities, this method achieves high-precision, low-scrap batch processing with a simple process logic, effectively avoiding problems such as chipping, deformation, and tool sticking and scratches in deep cavities that occur during the machining of acrylic parts.

[0009] The objective of this invention is achieved through the following technical solution: A machining method for a multi-cavity acrylic shell includes the following steps: clamping the part to be machined onto a special fixture and applying a clamping force of 0.3 MPa to 0.45 MPa; performing layer milling at the right-angle intersections of the part, sequentially performing roughing, semi-finishing, and finishing, and reserving cutting allowances between each adjacent machining stage; the roughing process forms a first arc transition at the right angle, the semi-finishing process processes the first arc transition into a second arc transition with progressively decreasing radii, and the finishing process... The two-circular-arc transition machining is a blunt structure as required by the design; select a single deep cavity on the part, first machine the front side of the deep cavity to 50% of the total depth of the deep cavity, then flip the fixture so that the reverse side of the part faces upward, and machine the reverse side of the deep cavity to 50% of the total depth of the deep cavity. After completing the machining of a single deep cavity, machine the remaining deep cavities in sequence; when machining deep cavities with a depth-to-diameter ratio greater than or equal to 10, apply a directional high-pressure airflow of 0.6MPa to 0.7MPa to the hole position, and adopt an intermittent feed method of retracting the tool once after each preset feed distance to remove chips.

[0010] This technical solution precisely controls the clamping force within a narrow range of 0.3-0.45 MPa, avoiding pre-deformation of thin-walled parts due to excessive clamping force. Utilizing a layered milling process of "rough-semi-finish-finish" with a decreasing radius at right angles effectively disperses stress concentration in brittle materials during machining. Combined with a process sequence of "alternating machining 50% depth on both sides of a single cavity," the machined thin-walled part provides support during subsequent reverse machining, significantly reducing tool deflection and chatter. Simultaneously, the use of a high-pressure airflow of 0.6-0.7 MPa, coupled with intermittent feed, ensures that debris in deep cavities with a length-to-diameter ratio ≥10 is forcibly expelled, preventing heat buildup, tool sticking, and hole wall scratches.

[0011] Furthermore, during rough machining, a 0.25mm allowance is reserved, and the radius of the first arc transition is R1.2mm; during semi-finishing, a 0.15mm allowance is removed, and the radius of the second arc transition is R0.8mm; during finishing, the remaining 0.1mm allowance is removed, and the radius of the chamfered structure is R0.5mm. This preferred parameter gradient can maximize the release of the internal stress of the acrylic glass, while leaving a stable cutting allowance for finishing.

[0012] Furthermore, in the intermittent feed method, the preset distance for each feed is 2mm. This distance, combined with high-pressure airflow, ensures that the fine debris generated during each cut in the deep cavity is completely blown out by the airflow at the moment of tool retraction, effectively preventing debris from compressing and scratching the hole wall.

[0013] Furthermore, a single-flute end mill is used in the roughing stage of deep cavity machining; and a large helix angle end mill with a helix angle of 45° is used in the finishing stage of layer milling. The single-flute end mill can reduce cutting resistance and heat during roughing; while the large helix angle end mill can provide a smoother chip removal path and a smoother surface finish during finishing.

[0014] Furthermore, when finishing the inner right-angle region of the part, the tool performs axial feed milling along the longitudinal axis of the inner right angle. Axial milling can prevent the side edge from chipping or the part edge from breaking due to excessive radial force at the right angle.

[0015] Furthermore, in the layered milling step, the depth of cut for each layer is 0.1 mm to 0.15 mm. This small depth of cut further reduces cutting forces and protects the dimensional stability of the thin-walled structure.

[0016] Furthermore, during the process of clamping the part to be processed onto the special fixture, the L-shaped step positioning structure on the back plate of the special fixture forms an insertion positioning fit with the square groove on the outer wall of the part.

[0017] Furthermore, during the process of clamping the part to be processed onto the special fixture, the clamping member is pushed by the clamping screw on the front plate of the special fixture to clamp the part along the length of the deep cavity of the part; the clamping member and the clamping screw are connected in an axially limited and circumferentially rotatable manner. This rotatable connection ensures that when the clamping screw is tightened, the pressure plate remains stationary when in contact with the surface of the part, avoiding scratches on the brittle acrylic surface caused by hard rotational friction.

[0018] Furthermore, during the process of flipping the special fixture to make the reverse side of the part face up, the special fixture is driven to rotate 180° around the horizontal axis, and locked after being flipped into place. This ensures the rigidity of subsequent cutting operations and prevents the part from vibrating during reverse machining.

[0019] Furthermore, when driving the special fixture to flip, the driving torque is transmitted through the frame structure of the special fixture, and the radial offset at both ends of the fixture body is constrained by the coaxial positioning structure to maintain rotational synchronization and coaxiality during the flipping process. The coaxial positioning structure avoids twisting of the fixture due to asynchrony at both ends during the flipping process, significantly improving the reference repeatability positioning accuracy for front and back surface machining. The beneficial effects of this invention are: (1) Significant anti-corner chipping effect: Through the three-step rounded corner transition process of "rough-semi-fine-fine", the stress concentration at the right angle is completely eliminated, effectively reducing the corner chipping rate.

[0020] (2) Excellent anti-deformation effect: By controlling the clamping force within an extremely narrow range of 0.3-0.45MPa and combining the strategy of “50% alternating processing of the front and back sides of a single cavity”, the problem of chattering after the thin wall loses support is effectively solved, and the form and position tolerance of the deep cavity is strictly controlled.

[0021] (3) Stable quality of deep cavity machining: By using a specific air pressure of 0.6-0.7MPa for high-pressure chip removal and intermittent feed with a step distance of 2mm, the problem of tool sticking and scratching in large depth-to-diameter holes is solved, and the quality of hole wall machining is greatly improved.

[0022] (4) Easy to promote and apply: The complete set of process parameters and tooling has been solidified and formed into standardized operation instructions, which breaks away from the traditional processing mode that relies on manual experience and is suitable for the mass and automated production of acrylic parts in aerospace and other precision instrument industries. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the part described in this invention.

[0024] Figure 2 This is a top view of the special fixture described in this invention.

[0025] Figure 3 This is a three-dimensional structural diagram of the clamping body described in this invention.

[0026] As shown in the figure: 1A-First mounting base, 1B-Second mounting base, 2-Active rotary chuck, 3-Driven rotary chuck, 4-Drive motor, 5-Clamping body, 6-Rear plate, 7-Stepped positioning part, 8-Front plate, 9-Clamping screw, 10-Clamping component, 11-Left plate, 12-Right plate, 13-Fasting bolt, 14-Machine tool worktable, 15-Part, 151-Square slot, 152-Deep cavity, 18-Positioning pin. Detailed Implementation

[0027] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The described embodiments are merely some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings of this specification are merely for illustrative purposes to aid those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by the invention, should still fall within the scope of the technical content disclosed herein. Furthermore, the terms such as "upper," "lower," "left," "right," and "middle" used in this specification are merely for clarity and are not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Example 1

[0030] like Figures 1 to 3 As shown, this embodiment provides a machining method for a multi-cavity acrylic shell, including the following steps: S1. The part 15 to be processed is clamped onto a special fixture. This special fixture is fixed to the machine tool worktable 14 and includes: A drive motor 4 is mounted on the machine tool worktable 14, and a first mounting base 1A and a second mounting base 1B are respectively bolted to the machine tool worktable 14. A driving rotary chuck 2 is rotatably mounted on the first mounting base 1A via bearings, and a gear set is disposed therein. A driven rotary chuck 3 is rotatably mounted on the second mounting base 1B via bearings. The driving rotary chuck 2 is connected to the drive motor 4 via the gear set. The bearings in the first mounting base 1A and the second mounting base 1B respectively support the central shafts of the driving rotary chuck 2 and the driven rotary chuck 3.

[0031] The active rotary chuck 2 is equipped with a locking structure. This locking structure is an integrated pneumatic or hydraulic brake (a standard configuration of commercially available four-axis CNC rotary tables). A rotary joint is located on the central shaft of the active rotary chuck 2, which connects to both an external air / hydraulic source and the brake inside the chuck. Because the rotary joint has a moving annular sealing channel, the pressure difference from the external air / hydraulic source is consistently transmitted to the internal brake during the rotation of the active rotary chuck 2, and the air / hydraulic paths do not become entangled. When the drive motor 4 drives the active rotary chuck 2 to rotate the fixture 5 to the target angle, the CNC system issues a command to control the external air or hydraulic source to supply pressure to the brake inside the active rotary chuck 2 via the rotary joint. The brake locks the central shaft of the active rotary chuck 2, locking the fixture 5 at the current angle, ensuring the rigidity and accuracy of subsequent cutting operations.

[0032] A frame-type clamping body 5 is provided between the first mounting base 1A and the second mounting base 1B. The left and right ends of the clamping body 5 are detachably connected to the active rotary chuck 2 and the driven rotary chuck 3, respectively, and can rotate around a horizontal axis under the drive of the drive motor 4 to achieve a rotation from 0° to 180°. The clamping body 5 is assembled from four plates: a front plate 8, a rear plate 6, a left plate 11, and a right plate 12. The left plate 11 and the right plate 12 are detachably connected one-to-one to the driven rotary chuck 3 and the active rotary chuck 2, respectively (the left plate 11 is detachably connected to the driven rotary chuck 3 by two screws, and the right plate 12 is detachably connected to the active rotary chuck 2 by two screws). The joints between the plates are detachably connected by at least two fastening bolts 13. A coaxial positioning component is provided between the active rotary chuck 2 and the driven rotary chuck 3. The coaxial positioning component includes two coaxially arranged guide shafts, which respectively form a clamping engagement with the active rotary chuck 2 and the driven rotary chuck 3, and are respectively inserted into the preset slots of the left plate 11 and the right plate 12, thereby providing precise coaxial guidance and support when the clamping body 5 is flipped.

[0033] A stepped positioning part 7 is provided on the rear end (rear plate 6) of the fixture body 5 on the side (front side) facing the part 15, for insertion and positioning with the square groove on the outer wall of the part. The stepped positioning part 7 is an L-shaped stepped groove provided at the upper and lower ends of the rear end (rear plate 6) of the fixture body 5 facing the part 15, and the distance between the stepped surfaces of the two stepped positioning parts 7 is adapted to the distance between the upper and lower groove walls of the square groove on the outer wall of the part to be processed. A positioning pin 18 is also provided on the front side wall of the rear end (rear plate 6) of the fixture body 5, which is used to abut against the side wall of the part 15 to assist in positioning in the left and right directions.

[0034] A clamping screw 9 and a clamping member 10 (located inside the clamping body 5) are provided at the front end (front plate 8) of the clamping body 5. The clamping member 10 is used to clamp the part 15 onto the front side wall of the rear end of the clamping body 5 (i.e., the front side wall of the rear plate 6). The clamping member 10 and the clamping screw 9 are connected by an axial limiting and circumferentially rotatable manner (the clamping member 10 is movably sleeved on the end of the clamping screw 9, and an axial limiting snap ring / step structure is provided between the two, and a clearance fit is provided in the circumferential direction to achieve relative rotation). The axial clamping direction of the clamping screw 9 is parallel to the length direction of the deep cavity 152 that will be machined inside the part 15, so that the force direction during clamping is consistent with the length direction of the deep cavity 152, avoiding the lateral component force causing pre-deformation of the thin wall on the side of the deep cavity 152 during clamping.

[0035] When clamping the part, the square groove 151 on the outer rear wall of part 15 is inserted into the stepped positioning parts 7 at both ends of the rear plate 6, and the two stepped surfaces form a limit in the Z-axis direction. Then, the clamping screw 9 on the front plate 8 is tightened, pushing the clamping member 10 at its end against the front side wall of the part. Because the clamping member 10 and the clamping screw 9 are connected in an axially limited and circumferentially rotatable manner, the clamping member 10 does not rotate with the screw during tightening, thus preventing scratches on the acrylic surface. The operator uses torque control to ensure that the clamping force applied to the part is maintained between 0.3 MPa and 0.45 MPa.

[0036] S2. After positioning and controlled clamping, start the machine tool to perform layer milling at the intersecting right angles of part 15. During roughing, the tool leaves a 0.25mm allowance at the right angle and controls the toolpath to form a first arc transition with a radius of R1.2mm at that point to release the initial stress of the brittle material at the sharp corner. In the semi-finishing stage, the tool removes 0.15mm of allowance and further processes the aforementioned arc transition with a radius of R1.2mm into a second arc transition with a radius of R0.8mm to further disperse residual stress. In the finishing stage, the tool removes the remaining 0.1mm of allowance, finally forming a chamfered edge structure with a radius of R0.5mm as required by the design drawings. Throughout the layer milling process, the depth of cut per layer is controlled to be 0.1mm to 0.15mm. In the finishing stage, a large helix angle end mill with a helix angle of 45° is used to ensure a sharp cutting edge.

[0037] S3. After completing the layered milling, the machine tool enters the single-cavity alternating machining stage. The first target deep cavity on part 15 is selected. The CNC program controls the tool to first machine the front side of the cavity, cutting to 50% of its total depth. Then, the CNC system issues a command, driving motor 4 to rotate the active rotary chuck 2 180°, causing the fixture 5 and part 15 to flip along the horizontal axis. At this point, the reverse side of the same deep cavity faces upwards. The machine tool then machines the reverse side of the same deep cavity to the remaining 50% depth. After machining this single deep cavity, the machine tool switches to the next deep cavity sequentially, repeating the above "front 50% → flip 180° → reverse 50%" operation process until all deep cavities are machined.

[0038] S4. When machining the deep cavity of part 15 with a depth-to-diameter ratio ≥ 10, the pre-set nozzle on the side of the machine tool spindle starts working, applying a directional high-pressure airflow of 0.6MPa to 0.7MPa to the hole to be machined. Simultaneously, the CNC program uses the G83 intermittent feed command, setting the tool to rapidly retract once every 2mm axial feed. At the moment of retraction, the high-pressure airflow forces the fine acrylic glass debris generated at the bottom of the hole out of the hole, preventing debris accumulation and friction against the hole wall, and also effectively carrying away cutting heat, preventing tool sticking. A single-flute end mill is used in the roughing stage of the deep cavity to reduce the contact area; in the finishing stage of the inner right-angle area, a plunge milling process with the tool feeding axially along the longitudinal axis of the inner right angle is used to ensure the integrity of the inner right angle.

[0039] The machining method described in this embodiment is used to process acrylic multi-cavity shell parts. Specifically, it employs a precise clamping force of 0.3MPa to 0.45MPa, alternating machining of 50% on both sides of a single cavity, a gradient fillet transition from R1.2mm to R0.8mm to R0.5mm, and a high-pressure airflow of 0.6MPa to 0.7MPa combined with intermittent feed at 2mm increments. Testing revealed that the vertical dimensional deviation of the deep cavities in the finished parts was controlled within 0.04mm, the rate of exceeding form and position tolerances and the rate of edge chipping were reduced to below 2%, the deep cavity machining pass rate increased to over 97%, and the overall product pass rate increased to over 95%, effectively solving the industry pain points of chipping, deformation, and poor deep cavity quality. Example 2

[0040] The difference between this embodiment and Embodiment 1 lies in the tooling and parameter matching for deep cavity chip removal. In this embodiment, a double-edged spiral drill bit with a special chip removal groove design is used in the deep cavity finishing stage. When the drill bit retracts after every 2mm of feed, it can generate a stronger suction effect, which, together with the 0.65MPa directional high-pressure airflow, forms an internal and external pressure difference, further improving the efficiency of removing small chips from the deep cavity.

[0041] The other steps in this embodiment are the same as in Embodiment 1, and will not be repeated here.

[0042] Comparative Example 1 The same model of acrylic multi-cavity shell parts were machined using existing conventional processes, namely rough clamping with general-purpose flat-jaw vises, layer-by-layer milling, and conventional air blowing for chip removal. Testing revealed that the maximum vertical dimensional deviation of the deep cavities was 0.13mm, the form and position tolerance exceedance rate was 35%, the edge chipping rate was 38%, the deep cavity machining pass rate was only 65%, and the overall product pass rate was 62%.

[0043] Comparative experiment: To verify the technical effect of Example 1, the applicant conducted comparative tests on the same type of plexiglass multi-cavity shell parts, using the existing conventional process of Comparative Example 1 (general flat-jaw clamping, full-surface layer milling, conventional air blowing chip removal) and the process described in Example 1. The main quality indicators are compared in Table 1.

[0044] Table 1. Comparison of key processing quality indicators between this embodiment and existing conventional processes.

[0045] As can be seen from the comparison data in the table above, when using the existing conventional process of Comparative Example 1, the clamping force cannot be precisely quantified and controlled, and the thin wall loses support after the entire surface is machined. The maximum vertical dimensional deviation of the deep cavity is 0.13mm, and the form and position tolerance exceedance rate is as high as 35%. At the same time, the one-time molding of brittle materials at right angles results in a chipping rate as high as 38%, and the simple air blowing chip removal results in a deep cavity machining qualification rate of only 65%. The superposition of defects in each link results in an overall product qualification rate of only 62%.

[0046] By employing the process described in Embodiment 1 of this invention, precise clamping force of 0.3MPa to 0.45MPa controls pre-deformation during clamping; alternating machining of 50% on both the front and back sides of a single cavity avoids chattering caused by the loss of support in thin-walled structures; gradient fillet transitions of R1.2mm → R0.8mm → R0.5mm disperse cutting stress at right angles; and high-pressure airflow of 0.6MPa to 0.7MPa combined with intermittent feed at 2mm increments solves the chip removal problem in deep cavities. With the synergistic effect of these techniques, the dimensional deviation of the deep cavity is reduced to within 0.04mm, the chipping rate and the rate of exceeding dimensional tolerances are both reduced to below 2%, and the pass rate for deep cavity machining is increased to over 97%, ultimately resulting in a significant leap in the overall product pass rate from 62% to over 95%.

[0047] Other aspects of this invention that are not detailed herein are all conventional techniques known to those skilled in the art.

[0048] It should be noted that the terms “comprising,” “including,” or any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0049] The scope of protection of this invention is not limited to the technical solutions disclosed in the specific embodiments. Any modifications, equivalent substitutions, improvements, etc., made to the above embodiments based on the technical essence of this invention shall fall within the scope of protection of this invention.

Claims

1. A method for machining a multi-cavity acrylic shell, characterized in that, Includes the following steps: The part to be processed is clamped on a special fixture and a clamping force of 0.3MPa to 0.45MPa is applied. The parts are milled in layers at the right angles, and roughing, semi-finishing and finishing are performed in sequence, with cutting allowances reserved between each adjacent machining stage; the roughing creates a first arc transition at the right angle, the semi-finishing processes the first arc transition into a second arc transition with a smaller radius, and the finishing processes the second arc transition into a blunt structure as required by the design. Select a single deep cavity on the part, first machine the front side of the cavity to 50% of the total depth of the cavity, then flip the fixture so that the back side of the part is facing up, and machine the back side of the cavity to 50% of the total depth of the cavity. After completing the machining of a single deep cavity, machine the remaining deep cavities in sequence. When machining deep cavities with a depth-to-diameter ratio greater than or equal to 10, a directional high-pressure airflow of 0.6 MPa to 0.7 MPa is applied to the hole, and an intermittent feed method is adopted, in which the tool retracts once after each preset feed distance to remove chips.

2. The machining method for the multi-cavity plexiglass shell according to claim 1, characterized in that: During rough machining, a 0.25mm allowance is reserved, and the radius of the first arc transition is R1.2mm; during semi-finish machining, a 0.15mm allowance is removed, and the radius of the second arc transition is R0.8mm; during finish machining, the remaining 0.1mm allowance is removed, and the radius of the chamfered structure is R0.5mm.

3. The machining method for the multi-cavity plexiglass shell according to claim 1, characterized in that: In the intermittent feed method, the preset distance for each feed is 2mm.

4. The machining method for multi-cavity organic glass shells according to claim 1, characterized in that: In the roughing stage of deep cavity machining, a single-flute end mill is used; in the finishing stage of layer milling, a large helix angle end mill with a helix angle of 45° is used.

5. The machining method for a multi-cavity acrylic shell according to claim 1, characterized in that: When finishing the inner right-angle area of ​​a part, the tool performs a plunge milling operation with axial feed along the longitudinal axis of the inner right angle.

6. The machining method for a multi-cavity acrylic shell according to claim 1, characterized in that: In layer milling, the depth of cut for a single layer is 0.1 mm to 0.15 mm.

7. The machining method for the multi-cavity acrylic shell according to any one of claims 1-6, characterized in that: During the process of clamping the part to be processed onto the special fixture, the L-shaped step positioning structure on the back plate of the special fixture forms an insertion positioning fit with the square groove on the outer wall of the part.

8. The machining method for a multi-cavity acrylic shell according to claim 7, characterized in that: During the process of clamping the part to be processed onto the special fixture, the clamping member is pushed by the clamping screw on the front plate of the special fixture to clamp the part along the length of the deep cavity of the part; the clamping member and the clamping screw are connected in an axially limited and circumferentially rotatable manner.

9. The machining method for a multi-cavity acrylic shell according to claim 8, characterized in that: During the process of flipping the special fixture to make the reverse side of the part face up, the special fixture is driven to rotate 180° around the horizontal axis, and the fixture is locked after it is flipped into place.

10. The machining method for a multi-cavity acrylic shell according to claim 9, characterized in that: When driving the special fixture to flip, the driving torque is transmitted through the frame structure of the special fixture, and the radial offset of both ends of the fixture is constrained by the coaxial positioning structure to maintain rotational synchronization and coaxiality during the flipping process.

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