High-precision thickness processing method for composite material surrounding frame plate of civil aircraft

Abstract

This invention relates to the field of CNC machining technology for aerospace composite materials, specifically to a high-precision thickness machining method for composite material frame panels of civil aircraft. The method includes: S1: initial clamping; S2: after the initial clamping, finishing the inner and outer contours to the final width and reserving process lugs, and rough machining the surface thickness to the reserved finishing allowance; S3: machining secondary positioning holes on the process lugs and removing the part; S4: adding a secondary positioning structure to the tooling; S5: using the secondary positioning holes of the part and the secondary positioning holes of the tooling for positioning, followed by secondary clamping and vacuum compaction; S6: finishing the surface to the theoretical thickness.

Description

Technical Field

[0001] This invention relates to the field of CNC machining technology for aerospace composite materials, specifically to a high-precision thickness machining method for composite material frame panels of civil aircraft. It is applicable to the machining of large-size, thin-plate aerospace composite material structural components with strict thickness tolerance requirements. Background Technology

[0002] Composite material frame parts for civil aircraft are characterized by large size, low rigidity, and high thickness tolerance requirements. The blank size of the part targeted by this invention is approximately 1m × 1m × 15mm, with a required final machining thickness of 10mm and a tolerance of ±0.15mm.

[0003] Traditional machining processes generally employ a method of completing the contour and surface machining in one setup: ① Apply 0.4mm double-sided tape to the CNC machining equipment; ②Use the 2-φ12 positioning holes reserved during the laying and molding of composite material blanks and the tooling positioning pins for positioning and bonding; ③ Manually press and compact the parts with both hands to ensure they fit snugly against the tooling; ④ Use a D12 solid carbide keyway end mill to machine the inner and outer contours to the dimensions; ⑤ Use a B12 2-flute PCD diamond tool to finish the profile in one pass; ⑦ Use alcohol to remove the adhesive and remove the parts.

[0004] This process has obvious flaws: ① Manual pressing cannot guarantee uniform adhesion of large-sized parts. Air bubbles and gaps are easily generated between the tape and the parts and tooling. During processing, the parts may warp slightly, resulting in serious thickness deviations. ② All machining is completed in one clamping, and systematic errors such as positioning gaps and tape deformation cannot be compensated; ③ In actual processing, the thickness fluctuation range reached 9.61mm to 10.15mm, which exceeded the tolerance requirements, resulting in a high scrap rate and high production costs, and failing to meet the demand for stable mass production of aerospace parts. Summary of the Invention

[0005] Purpose of the invention: This invention provides a high-precision thickness processing method for composite material frame panels of civil aircraft, which solves the problem of large thickness tolerance of composite material frame panels in a single clamping process.

[0006] Technical solution: A method for high-precision thickness processing of composite material frame panels for civil aircraft includes: S1: Initial clamping; S2: After the initial clamping, finish the inner and outer contours to the final width and reserve the process lugs, and rough machine the surface thickness to the reserved finishing allowance; S3: Machining secondary positioning holes on the process lug and removing the part; S4: The tooling is equipped with a secondary positioning structure; S5: After positioning using the secondary positioning holes of the part and the secondary positioning holes of the tooling, clamp the parts again and vacuum compact them. S6: The surface is finished to the theoretical thickness.

[0007] Furthermore, S1 specifically refers to: Apply 0.4mm double-sided tape to the CNC machining fixture and clean excess material from the surface of the fixture and the lower surface of the composite material blank; then, through the 2mm pre-reserved opening on the blank... The φ12 positioning hole is attached to the tooling positioning pin for positioning and then pressed firmly.

[0008] Furthermore, in S2, the finishing allowance is 0.5mm.

[0009] Furthermore, S2: specifically refers to: The inner and outer contours are machined to the final width using a D12 solid carbide keyway cutter, with a pre-reserved process lug. The surface is rough-machined using a B12 2-flute PCD diamond tool, with a finishing allowance reserved in the thickness direction.

[0010] Furthermore, S3: specifically refers to: Use a φ10 drill bit to machine two φ10 positioning holes on the process lug; use alcohol to remove the part from the tooling and clean the tooling of any remaining double-sided tape.

[0011] Furthermore, S4: specifically: With the process of protruding ears 2 Using the φ10 positioning hole as a reference, machine 2 holes at the corresponding positions on a CNC machine. A φ10 positioning hole is provided with a positioning pin.

[0012] Furthermore, S5: specifically: Re-attach new 0.4mm double-sided tape to the tooling; through 2 The φ10 positioning hole and the secondary positioning pin of the tooling are precisely positioned; the upper surface of the part is pressed and compacted by vacuum adsorption to ensure that the part, tape and tooling are completely fitted without gaps.

[0013] Furthermore, S5: specifically: The profile was finished using a B12 2-flute PCD diamond tool to remove the 0.5mm allowance and achieve the final thickness.

[0014] Beneficial effects: 1) The product thickness accuracy has been significantly improved, with thickness fluctuation reduced from 0.54mm to within 0.1mm, fully meeting the ±0.15mm tolerance; 2) The parts qualification rate has been improved from a low level under traditional processes to 100%; 3) Reduce scrap and rework, and lower the loss of composite material raw materials and processing costs; 4) It has strong process stability and can be widely applied to similar large-size thin-plate composite material aerospace structural parts. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 Schematic diagram of composite material preform structure; Figure 2 A schematic diagram of the finished product and the blank. Detailed Implementation

[0017] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0018] This invention addresses the problem that traditional single-clamping processes cannot guarantee the thickness tolerance of composite material frame panels within ±0.15mm. It provides a high-precision processing technology involving secondary positioning, secondary bonding, step-by-step processing, and vacuum compaction, achieving stable and qualified thickness and significantly improving the part qualification rate.

[0019] like Figure 1 and Figure 2 A high-precision thickness processing technology for composite material frame panels of civil aircraft includes the following steps: 1. Initial clamping Apply 0.4mm double-sided tape to the CNC machining fixture and clean excess material from the surface of the fixture and the lower surface of the composite material blank; then, through the 2mm pre-reserved opening on the blank... The φ12 positioning hole is attached to the tooling positioning pin for positioning and then manually pressed to compact it.

[0020] 2. Finishing of inner and outer contours and roughing of surface The inner and outer contours are machined to a width of 40±0.15mm using a D12 solid carbide keyway end mill, with a pre-reserved process lug. The surface is rough-machined using a B12 2-flute PCD diamond tool, with a 0.5mm finishing allowance in the thickness direction.

[0021] 3. Machin the secondary positioning holes and remove the part. Use a φ10 drill bit to machine two φ10 positioning holes on the process lug; use alcohol to remove the part from the tooling and clean the tooling of any remaining double-sided tape.

[0022] 4. Add a secondary positioning structure to the tooling. With the process of protruding ears 2 Using the φ10 positioning hole as a reference, machine 2 holes at the corresponding positions on a CNC machine. A φ10 positioning hole is provided with a positioning pin.

[0023] 5. Secondary clamping and vacuum compaction Re-attach new 0.4mm double-sided tape to the tooling; through 2 The φ10 positioning hole and the secondary positioning pin of the tooling are precisely positioned; the upper surface of the part is pressed and compacted by vacuum adsorption to ensure that the part, tape and tooling are completely fitted without gaps.

[0024] 6. Surface finishing The profile was finished using a B12 2-flute PCD diamond tool to remove the 0.5mm allowance and achieve the final thickness.

[0025] 7. Test passed Remove the part and use a micrometer to check the thickness. The thickness is stable at 9.85mm to 9.95mm, which meets the tolerance requirement of 10±0.15mm.

[0026] In summary, this invention employs a step-by-step processing method: after the contour is finely machined, the surface is first rough-machined with a 0.5mm allowance to avoid the accumulation of errors from the first machining stage leading to thickness deviations; secondary positioning holes are added: φ10 positioning holes are added based on the machined contour, significantly improving the positioning accuracy of the secondary clamping; secondary bonding with new adhesive tape avoids bonding errors caused by the decreased adhesion and deformation of old adhesive tape; vacuum compaction replaces manual pressing: achieving uniform bonding of large-sized parts and completely eliminating air bubbles and local gaps.

[0027] Example: Raw material dimensions: approximately 1000mm × 1200mm × 15mm Finished frame outline dimensions: 40±0.15mm Finished product thickness: 10±0.15mm Adhesion method: 0.4mm double-sided tape Positioning method: 2 φ12 pre-drilled hole positioning +2 φ10 secondary precision positioning Processing equipment: 5-axis CNC machining center Cutting tools: D12 solid carbide keyway end mill, B12 2-flute PCD diamond end mill, φ10 drill bit A high-precision thickness processing technology for composite material frame panels of civil aircraft is disclosed. The rough machining of the profile allows for a thickness allowance of 0.5mm. Secondary clamping employs vacuum adsorption for compaction, replacing manual pressing. New 0.4mm double-sided adhesive tape is used for secondary clamping to ensure bonding rigidity and adhesion accuracy. The specific steps include: 1) Initial clamping: Apply 0.4mm double-sided tape to the CNC machining center and pass it through the 2mm pre-reserved opening on the composite material blank. The φ12 positioning hole is positioned and glued to the tooling positioning pin, and then manually pressed to compact it; 2) Rough machining of contour and profile: Use a D12 solid carbide keyway end mill to machine the inner and outer contours to 40±0.15mm, and use a B12 2-flute PCD diamond tool to rough machine the profile, leaving a 0.5mm finishing allowance in the thickness direction; 3) Preparation of secondary positioning holes: Use a φ10 drill bit to machine two φ10 positioning holes on the part, then remove the part from the tooling and clean the tooling residue tape; 4) Secondary positioning modification of tooling: Machining matching positioning pins at the corresponding φ10 positioning hole positions of the parts on the CNC machining set; 5) Secondary clamping: Re-attach new 0.4mm double-sided tape to the fixture, and clamp it using 2... The φ10 positioning hole is precisely positioned with the secondary positioning pin of the tooling, and the part is compacted by vacuum method; 6) Surface finishing: Use a B12 2-flute PCD diamond tool to remove the reserved 0.5mm allowance and machine to the final thickness of 10±0.15mm.

[0028] To address the problems of poor fit and positioning errors leading to thickness deviations and low pass rates in traditional single-clamping processes, this invention employs a method of secondary positioning, secondary bonding, step-by-step machining, and vacuum compaction: first, the contour is finely machined and the surface is rough-machined (leaving a 0.5mm allowance); then, secondary positioning holes are machined; a fine positioning structure is added to the tooling; after replacing the adhesive tape, a second vacuum clamping is performed; and finally, the surface is finely machined. This invention can stably control the thickness of parts within 9.95mm to 10.05mm, meeting the tolerance requirement of 10±0.15mm, achieving a 100% pass rate. It is suitable for high-precision machining of large-size aerospace composite thin-plate parts.

[0029] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A method for high-precision thickness processing of composite material frame panels for civil aircraft, characterized in that, include: S1: Initial clamping; S2: After the initial clamping, finish the inner and outer contours to the final width and reserve the process lugs, and rough machine the surface thickness to the reserved finishing allowance; S3: Machin a secondary positioning hole on the process lug and remove the part; S4: The tooling is equipped with a secondary positioning structure; S5: After positioning using the secondary positioning holes of the part and the secondary positioning holes of the tooling, clamp the parts again and vacuum compact them. S6: The surface is finished to the theoretical thickness.

2. The high-precision thickness processing method for composite material frame panels of civil aircraft according to claim 1, characterized in that, S1, specifically: Apply 0.4mm double-sided tape to the CNC machining fixture and clean excess material from the surface of the fixture and the lower surface of the composite material blank; then, through the 2mm pre-reserved opening on the blank... The φ12 positioning hole is attached to the tooling positioning pin for positioning and then pressed firmly.

3. The method of claim 1, wherein the method further comprises: In S2, the finishing allowance is 0.5mm.

4. The method of claim 1, wherein, S2: Specifically: The inner and outer contours are machined to the final width using a D12 solid carbide keyway cutter, with a pre-reserved process lug. The surface is rough-machined using a B12 2-flute PCD diamond tool, with a finishing allowance reserved in the thickness direction.

5. The method of claim 1, wherein the method further comprises: S3: Specifically: Use a φ10 drill bit to machine two φ10 positioning holes on the process lug; use alcohol to remove the part from the tooling and clean the tooling of any remaining double-sided tape.

6. The method for high-precision thickness processing of composite material frame panels for civil aircraft according to claim 1, characterized in that, S4: Specifically: With the process of protruding ears 2 Using the φ10 positioning hole as a reference, machine 2 holes at the corresponding positions on a CNC machine. A φ10 positioning hole is provided with a positioning pin.

7. The method for high-precision thickness processing of composite material frame panels for civil aircraft according to claim 1, characterized in that, S5: Specifically: Re-attach new 0.4mm double-sided tape to the tooling; through 2 The φ10 positioning hole and the secondary positioning pin of the tooling are precisely positioned; the upper surface of the part is pressed and compacted by vacuum adsorption to ensure that the part, tape and tooling are completely fitted without gaps.

8. The method for high-precision thickness processing of composite material frame panels for civil aircraft according to claim 1, characterized in that, S5: Specifically: The profile was finished using a B12 2-flute PCD diamond tool to remove the 0.5mm allowance and achieve the final thickness.

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