Method for processing Z-shaped connecting rib

Abstract

The invention belongs to the technical field of numerical control machining, and relates to a method for machining a Z-shaped connecting rib, which is suitable for machining the Z-shaped connecting rib arranged on a double-sided machining part. According to the method, the size and surface quality of the thin-wall edge strip can be effectively controlled on the premise of ensuring the accuracy of a theoretical appearance surface; the quality problems of high edge strip tearing, edge strip bending and the like in the Z-shaped connecting rib machining process are solved, and the Z-shaped connecting rib machining device is particularly suitable for machining of high and thin edge strips and light-weight parts and has remarkable economic benefits especially in part batch machining. The invention provides a beneficial solution for realizing products with high and thin edge strips and light-weight parts subjected to double-sided processing.

Description

Technical Field

[0001] The present invention belongs to the technical field of numerical control machining, and relates to a method for machining Z-shaped connecting ribs, which is applicable to the machining of Z-shaped connecting ribs provided on double-sided machining parts. Background Art

[0002] With the continuous improvement of the requirements for the integration of aircraft structure and function, lightweight and stealth performance, more and more thin-walled, high-flange and curved structures have emerged in the design of aircraft structural parts. Conventional machining solutions can no longer meet the machining requirements of future aircraft structural parts, and it is necessary to continuously optimize and innovate machining solutions.

[0003] Chinese Patent CN102728878A discloses a numerical control curved surface contour machining Z-type process connection method, specifically: the part is machined in two sides. When finishing the contour of the first side, a square shoulder milling cutter is used to machine all the theoretical contours in place, and the lowest milling plane of the cutter should be 1-2 mm lower than the process connection plane; turn the part over to machine the second side, open a window in the height direction of the flange after rough machining, and finish machining the flange at the window; after the part machining is completed, use a square shoulder milling cutter to cut the process connection thinly, leaving a margin of 0.1-0.2 mm on the side. The final part connection form is a "hanging basket" structure, and the part can be easily broken off by a fitter.

[0004] After being verified by actual application in the production workshop, it is found that this invention is more suitable for machining parts with large weight and normal wall thickness dimensions, but there are some problems in the machining of parts with small weight and high-thin flanges, including: when opening the window synchronously with machining the flange height after rough milling, the high-thin flange will vibrate, resulting in cutting damage to the flange height, and in severe cases, tearing and bending of the flange height; after opening the window, when machining the inner shape of the high-thin flange, the flange trembles, the wall thickness is difficult to guarantee, the surface quality is poor, and there are quality hazards; if the part is light in weight, the part will be lifted when opening the window or cutting the process connection thinly with a square shoulder tool, resulting in cutting damage, tearing, etc. to the flange height, causing the part to be scrapped. This invention is not applicable to the machining of parts with small weight and high-thin flanges. Summary of the Invention

[0005] In order to solve the quality hazard problems such as cutting damage, tearing and bending of the flange height existing in the prior art when machining Z-shaped connecting ribs, the present invention provides a safer and more effective method for machining Z-shaped connecting ribs.

[0006] The technical solution of the present invention is as follows:

[0007] A method for machining Z-shaped connecting ribs, the steps are as follows:

[0008] The first step: Preparation work before machining

[0009] (1.1) Arrangement of machining sequence for front and back sides:

[0010] Analyze the part structure, and set the orientation with the included angle between the flange outer surface and the Z-plane greater than or equal to 90° as the first surface, that is, the open-angle surface of the outer shape is machined on the first surface; try to avoid machining the closed-angle surface of the outer shape on the first surface.

[0011] (1.2) Blank size setting:

[0012] 1.2.1) The thickness dimension of the plate blank is greater than the minimum inclusive dimension of the part height by 3 mm or more, which is used to ensure the connection stiffness and the minimum width for subsequent cutting. When machining the first surface, the minimum inclusive thickness surface of the part should coincide with the thickness surface of the blank, and all thickness allowances are placed on the second surface.

[0013] 1.2.2) The length and width of the blank are greater than the minimum inclusive dimension of the part, and it is ensured that there is enough allowance on the side of the blank with Z-shaped connecting ribs after rough machining to ensure the structural stiffness, that is: H≥D + 12 mm, where H is the allowance on the side of the blank with Z-shaped connecting ribs, D is the diameter of the cutter for rough milling the outer shape, and 12 mm is the additional allowance used to ensure the overall stiffness.

[0014] The second step: Machine the first surface of the part

[0015] Machine all the flange outer shapes that need to be set with Z-shaped connecting ribs in place; and take the web surface as the Z-direction dividing surface, and sequentially complete the machining of the inner shape and the web surface part of the first surface part. The part below the web surface is machined in place on the second surface.

[0016] The requirements during the machining process are as follows:

[0017] 1) For parts with the included angle between the flange outer surface and the Z-plane equal to 90°, a flat-bottom milling cutter with R0 - R0.5 can be used to finish-machine the flange outer surface with a three-axis command. The lowest cutting depth surface of the cutter should be 2 - 3 mm lower than the process connection surface, and this range is defined as the axial process connection area, which is convenient for subsequent unloading of the part.

[0018] 2) For parts with the included angle between the flange outer surface and the Z-plane greater than 90°, when the flange outer surface is a ruled surface, a five-axis dynamic swing angle method can be used for machining, and the side edge of the milling cutter is used to finish-mill the flange outer surface; when the flange outer surface is a complex curved surface, a vertical milling cutter with a bottom corner R1 or more or a ball-end milling cutter can be used to finish-machine the flange outer surface by the method of dense row cutting. Similarly, the axial process connection area is required to be 2 - 3 mm. After the row cutting of the flange outer surface is completed, it can be decided whether to add the step of using a flat-bottom milling cutter with R0 - R0.5 to fill-mill the axial process connection area according to actual needs, which is convenient for subsequent unloading of the part.

[0019] The third step: Turn the blank over and machine the second surface of the part

[0020] (3.1) Rough milling: During rough milling, control the machining range through the numerical control program to avoid machining the flange height.

[0021] (3.2) Finishing milling: Finish the rough-machined parts in (3.1), and continue to keep the edge strip high without machining. For the edge strip wall thickness that needs to be measured, 1-2 windows can be opened above the edge strip height. The window width is equal to the tool diameter D. This can maximize the structural rigidity of the edge strip and avoid vibration during subsequent processing of the edge strip inner shape. When opening the window, the tool should be perpendicular to the edge strip surface, and process from the edge strip inner shape surface to the edge strip outer shape surface.

[0022] (3.3) Cutting the rough material and leaving the process connection ribs: After the parts are processed, use R0 flat-bottom milling cutter to cut thinly for process connection, leaving a 0.3-0.5mm margin on the side. Along the extension direction of the edge strip, evenly distribute the Z-shaped connection ribs and open the window.

[0023] The requirements for opening a window are as follows:

[0024] 1) When the first cut is made, the axial delamination is not allowed. At this time, the processing trajectory is to process along the extension direction of the edge strip until it exceeds the outer surface of the part edge strip by 0.2-0.5mm; the rib height is processed in place. At this time, a gap window has appeared.

[0025] 2) The second tool processing route is to raise the Z value by 0.5-1mm on the basis of the edge strip height, and the "凵"-shaped processing trajectory. The tool feed trajectory is perpendicular to the inner surface of the edge strip, and moves parallel to the extension direction of the edge strip to the set window length distance, and then the tool is cut from the direction perpendicular to the inner surface of the edge strip. Depending on the tool diameter and the amount of raw material, the window width range parallel to the extension direction of the edge strip can exceed the outer surface of the part edge strip by 5-20mm. At this time, axial layered processing can be appropriately performed according to the thickness of the raw material excess.

[0026] 3) Repeat the second cutting process until the window size is processed to the required size.

[0027] Beneficial effects of the present invention:

[0028] The present invention can effectively control the size and surface quality of thin-walled edge strips while ensuring the accuracy of the theoretical outer surface; it can avoid the quality problems of tearing edge strips and bending edge strips when processing Z-shaped connecting ribs, and is particularly suitable for the processing of high-thin edge strips and small-weight parts, especially in batch processing of parts, and has significant economic benefits. The present invention provides a beneficial solution for the realization of products of high-thin edge strips and small-weight parts processed on both sides. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is the first step of the program track for processing Z-shaped connecting ribs;

[0030] Figure 2 It is the second step program track for processing Z-shaped connecting ribs;

[0031] Figure 3 It is the third - step program trajectory for machining the Z - shaped connecting rib;

[0032] Figure 4 It is the combined cross - sectional view of the typical part and the blank;

[0033] Figures 5(a) and 5(b) are the simplified diagrams of the first - side machining;

[0034] Figures 6(a) and 6(b) are the completed diagrams of the second - side machining;

[0035] Figure 7 It is the partial sectional view of the flange height (the partial enlarged view of Figure 6(b)).

[0036] In the figure: 1 - blank, 2 - typical part, 3 - program trajectory. Specific implementation mode

[0037] The following further illustrates the specific implementation mode of the present invention in combination with the attached drawings and technical solutions.

[0038] Taking a typical - structure part as an example, a method for machining a Z - shaped connecting rib according to the present invention has the following specific implementation steps:

[0039] 1. Analyze the structural characteristics of the part, and set the side of the open - angle area of the part's outer shape as the first - side machining. Place the part at the center of the plate blank, and the maximum theoretical outer shape of the part is 50 mm away from the outer edge of the blank. The flange of the part is flush with the upper surface of the blank, and the thickness of the blank is the minimum inclusive dimension of the part height plus 4 mm (see Figure 4 ).

[0040] 2. Preparation procedures before NC machining: Milling the upper and lower planes and right - angled edges of the blank to determine the machining origin.

[0041] 3. Machining the first side: NC - milling the first side of the part to complete the rough - milling and finish - milling of the inner and outer surfaces of the flange, the flange ends, the flange - end corners, and the web (see Figures 5(a) and 5(b)). Among them, the outer shape of the flange is completely machined, and the lowest cutting - depth surface of the tool is 3 mm lower than the process connection surface.

[0042] 4. Turn the part over and machine the second side:

[0043] (1) NC - milling the second side of the part, protecting the flange height, leaving a 2 - mm allowance uniformly on all the un - machined surfaces of the part, and successively rough - machining the inner surface of the flange, the flange ends, the flange - end fillets, and the web.

[0044] (2) Finish - machining the flange ends and the flange - end fillets.

[0045] (3) Finish - machining the web.

[0046] (4) Measure the thickness of the edge strip after rough machining through the fillet position of the edge strip end, adjust the program offset according to the allowance, and fine-machine the inner surface of the edge strip to ensure the wall thickness of the edge strip.

[0047] (5) Cut edge strip high Z-shaped connecting ribs: After the parts are processed, they are connected by R0 flat-bottom milling cutter thinning process, leaving a 0.4mm margin on the side. Along the extension direction of the edge strip, 2 windows of uniform size are opened, leaving 3 Z-shaped connecting ribs (see Figure 1 , Figure 6(a) and Figure 6(b), Figure 7 ).

[0048] The requirements for opening windows are as follows:

[0049] 1) When the first cut is made, axial delamination is not allowed. The first cut is processed along the edge extension direction until it exceeds the edge profile of the part by 0.3mm. The rib height is processed in place, and a gap window has appeared (such as Figure 2 shown).

[0050] 2) The second tool processing route is to raise the Z value by 0.5mm on the basis of the edge strip height, and the "凵"-shaped processing trajectory. The tool mills in from the inner surface of the edge strip, moves parallel to the extension direction of the edge strip for a suitable distance, and then mills out from the inner surface of the edge strip. Depending on the tool diameter and the rough material excess, the processing range in the parallel edge strip extension direction exceeds the part edge strip outer surface by 20mm, which is convenient for measurement. At this time, according to the rough material excess thickness, two axial layered processing (such as Figure 3 shown).

[0051] 3) Repeat the second cutting process until the window size is processed to the required size (such as Figure 3 shown).

[0052] (6) Cut the web connecting reinforcement (see Figures 6(a), 6(b) and Figure 7 ), thus completing all the machining work of the parts.

Claims

1. A method for processing Z-shaped connecting ribs, characterized in that, The steps are as follows: Step 1: Preparation before processing (1.1) Arrangement of machining sequence for front and back sides: Analyze the part structure, and set the orientation with the angle between the flange outer surface and the Z plane greater than or equal to 90° as the first side, that is, complete the machining of the open-angle surface of the outer shape on the first side; avoid machining the closed-angle surface of the outer shape on the first side; (1.2) Setting of blank size: 1.2.1) The thickness dimension of the plate blank is greater than the minimum inclusion dimension of the part height by 3 mm or more, which is used to ensure the connection stiffness and the minimum width for subsequent cutting; when machining the first side, the minimum inclusion thickness surface of the part should coincide with the thickness surface of the blank, and all thickness allowances are placed on the second side; 1.2.2) The length and width of the blank are greater than the minimum inclusion dimension of the part, and ensure that there is enough allowance on the side of the blank with the Z-shaped connecting rib after rough machining to ensure the structural stiffness; Step 2: Machine the first side of the part Machine all the flange outer shapes where the Z-shaped connecting ribs need to be set in place; and use the web surface as the Z-direction dividing surface to sequentially complete the machining of the inner shape and the web surface part of the first-side part, and machine the part below the web surface in place on the second side; Step 3: Turn the blank over and machine the second side of the part (3.1) Rough milling: During rough milling, control the machining range through the numerical control program and avoid machining the flange height; (3.2) Finish milling: Finish machine the rough-machined part in (3.1), and continue to avoid machining the flange height; for those that need to measure and ensure the flange wall thickness dimension, open 1-2 windows above the flange height, and the window width is equal to the tool diameter D; when opening the window, the tool should be perpendicular to the flange surface and machine from the inner shape surface of the flange to the outer shape surface of the flange; (3.3) Cut off the blank and leave the process connecting rib: After the part machining is completed, use a flat-bottom milling cutter with R0 to cut the process connection thinly; along the extension direction of the flange, evenly distribute and leave the Z-shaped connecting ribs and open windows.

2. A method for processing a Z-shaped connecting rib according to claim 1, characterized in that, The requirements during the machining process of Step 2 are as follows: 1) For parts with the angle between the flange outer surface and the Z plane equal to 90°, use a flat-bottom milling cutter with R0-R0.5 to finish machine the flange outer surface with three-axis commands, and the lowest cutting depth surface of the tool is 2-3 mm lower than the process connection surface, and this range is defined as the axial process connection area; 2) For parts with the angle between the flange outer surface and the Z plane greater than 90°, when the flange outer surface is a ruled surface, the five-axis dynamic swing angle method can be used for machining, and finish machine the flange outer surface with the side edge of the milling cutter; when the flange outer surface is a complex curved surface, use a vertical milling cutter with a bottom corner R1 or above or a ball-end milling cutter to finish machine the flange outer surface by the dense row cutting method.

3. A method for processing a Z-shaped connecting rib according to claim 2, characterized in that, In 1), it is required that the lowest cutting depth surface of the tool is 2-3 mm lower than the process connection surface.

4. A method for processing a Z-shaped connecting rib according to claim 2, characterized in that, In 2), it is required that the axial process connection area is 2-3 mm.

5. A method for processing a Z-shaped connecting rib according to claim 2, characterized in that, In 2), after the row cutting of the flange outer surface is completed, decide whether to add the step of using a flat-bottom milling cutter with R0-R0.5 to fill and machine the axial process connection area according to actual needs.

6. A method for processing a Z-shaped connecting rib according to claim 1, characterized in that In 1.2.2), it is required that H≥D + 12 mm, where H is the allowance of the blank on the side of the Z-shaped connecting rib, D is the diameter of the rough milling outer shape tool, and 12 mm is the additional allowance.

7. A method for processing a Z-shaped connecting rib according to claim 1, characterized in that In (3.3), leave a 0.3-0.5 mm allowance on the side during machining.

8. A method for processing a Z-shaped connecting rib according to claim 1, characterized in that, The requirements for opening windows in Step 3 are as follows: 1) When the height of the first cut rib is high, axial delamination is not allowed. At this time, its processing trajectory is to process along the extension direction of the flange until it exceeds the outer surface of the part flange by 0.2 - 0.5 mm; the rib height is processed in place; at this time, a gap window has appeared. 2) The processing route of the second cut is that the Z value is raised by 0.5 - 1 mm on the basis of the flange height, with a U-shaped processing trajectory. The tool feed trajectory mills in perpendicular to the inner surface of the flange and moves parallel to the extension direction of the flange until it reaches the set window length distance, and then exits the tool from the direction perpendicular to the inner surface of the flange; depending on the tool diameter and the blank allowance, the width range of the window parallel to the extension direction of the flange exceeds the outer surface of the part flange by 5 - 20 mm. At this time, axial delamination processing can be appropriately carried out according to the thickness of the blank allowance. 3) Repeat the second cut processing process until the window size is processed to the required size.

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