A four-axis machining method for deep and narrow V-groove structural parts

Abstract

The invention provides a four-axis machining method for a deep narrow V-groove structural part, comprising the following steps: step 1, re-parameterizing the back side and the basin side of the deep narrow V-groove structural part to obtain a re-parameterized surface; step 2, equidistantly offsetting the re-parameterized surface to obtain an offset surface; step 3, discretizing the offset surface to obtain a discrete curve group; step 4, establishing multiple swinging tool planes; step 5, generating a tool axis non-interference feasible domain on any swinging tool plane; step 6, repeating step 5 to obtain a tool axis non-interference feasible domain on each swinging tool plane; and then obtaining a tool axis motion control line; step 7, generating a tool axis extended ruled surface group according to the tool axis motion control line; step 8, generating a tool path file according to the tool axis extended ruled surface group. The method solves the problem that it is difficult to generate a non-interference machining process tool path in the fine machining of existing deep narrow V-groove structural parts.

Description

Technical Field

[0001] The invention belongs to the technical field of four-axis machining of aviation structural parts, and in particular relates to a four-axis machining method for deep and narrow V-groove structural parts. Background Art

[0002] The reduction of aircraft engine weight is of great significance for increasing flight range and energy conservation and emission reduction of aircraft. With the development of material technology, more and more composite materials are being applied to the field of aviation manufacturing. In recent years, in order to achieve weight reduction and efficiency improvement of aircraft engines, turbofan blades have also begun to adopt composite manufacturing technology. In order to improve the impact resistance of composite turbofan blades, a titanium alloy metal reinforcement edge is applied to the leading edge of the composite blade. The inner cavity of the metal reinforcement edge is a complex curved channel part with a deep and narrow V-groove structure. One of its design and structural characteristics is that the feasible domain of the machining tool is extremely narrow. Therefore, it is very easy for the tool and the inner cavity wall of the part to interfere during the machining process. It is difficult to generate interference-free machining process tool paths using the traditional CNC machining tool path generation algorithm based on the curved surface active frame. If the traditional CNC machining tool path generation algorithm based on the curved surface active frame is used to generate the four-axis machining tool path, it is usually necessary to repeatedly adjust the tool axis vector to obtain the interference-free four-axis machining tool axis vector required by the high-precision process. This problem has a profound impact on the compilation efficiency and quality of the machining program and causes the defect of unsatisfactory part machining yield. Summary of the invention

[0003] The purpose of the present invention is to provide a four-axis machining method for deep and narrow V-groove structural parts to solve the problem that it is difficult to generate interference-free machining tool paths in the fine machining of existing deep and narrow V-groove structural parts.

[0004] The present invention adopts the following technical solution: a four-axis machining method for deep and narrow V-groove structure parts, comprising the following steps:

[0005] Step 1, establishing a drawing coordinate system XYZ for a processing model of a deep narrow V-groove structural part, wherein the processing model has a blade back side surface and a blade basin side surface forming a V-shaped angle, and a bottom surface is connected and arranged at the ends of the blade back side surface and the blade basin side surface close to each other; the blade back side surface and the blade basin side surface are respectively re-parameterized to obtain a first multi-parametric surface and a second multi-parametric surface correspondingly;

[0006] Among them, a tangential extension line I is drawn along the blade tip direction for the intersection line of the bottom surface and the blade basin side surface, and the tangential extension line I is the X-axis; a tangential extension line II is drawn toward the blade basin side direction for the edge curve of the bottom surface on the blade tip side, and the plane formed by the tangential extension line II and the X-axis is the XOY plane; a perpendicular line to the X-axis is drawn in the XOY plane, and the Y-axis is determined; according to the right-hand coordinate system rule, the Z-axis is determined through the X-axis and the Y-axis;

[0007] Step 2, equidistantly offset the first multi-parametric curved surface and the second multi-parametric curved surface respectively, and obtain a first offset curved surface and a second offset curved surface accordingly; the offset distance is determined according to the radius value of the tool ball head;

[0008] Step 3, discretizing the first bias surface and the second bias surface respectively, and obtaining a first discrete curve group and a second discrete curve group accordingly;

[0009] Step 4, establishing a plurality of equally spaced knife-swinging planes parallel to the YOZ plane in the region between the first discrete curve group and the second discrete curve group, wherein the plurality of knife-swinging planes constitute a knife-swinging plane group;

[0010] Step 5: Generate a tool axis interference-free feasible domain for four-axis machining of deep and narrow V-groove structure parts on any tool swing plane;

[0011] Step 6, repeat step 5 to obtain the tool axis non-interference feasible domain on each swinging tool plane; then parallel to the XOY plane, establish a section plane at the opening side of the deep narrow V-groove structure part and at a position that does not intersect with the deep narrow V-groove structure part, the section plane intersects with each tool axis non-interference feasible domain, and obtains multiple intersection lines III, and the connection line obtained by connecting the midpoint of each intersection line III is the tool axis motion control line;

[0012] Step 7, the first discrete curve group and the second discrete curve group contain multiple discrete curves, and the tool axis motion control line and each discrete curve are used to generate a ruled surface according to the tool swing plane group, and all the ruled surfaces constitute a tool axis ruled surface group; each ruled surface is then linearly extended along the Z axis toward the inner cavity of the deep narrow V-groove close to the bottom surface, that is, a tool axis extended ruled surface group is generated;

[0013] Step 8: According to the machining interpolation method, the wires of each ruled surface in the tool axis extended ruled surface group are converted into the machining parameters of the line drive mode, that is, the CLS tool path file used for four-axis machining of deep narrow V-groove structure parts is generated.

[0014] Furthermore, in step 3, the first bias surface and the second bias surface include multiple bias surfaces, and the total number of discrete curves in the first discrete curve group and the second discrete curve group is determined according to the maximum value of the height of each bias surface in the Z-axis direction and the discrete spacing between adjacent discrete curves.

[0015] Furthermore, in step 4, the spacing between adjacent swinging knife planes is determined according to the maximum value of the angle formed by the tangent of each discrete curve and the swinging knife plane; the longest discrete curve is selected, and the number of the swinging knife planes is determined in combination with the spacing between adjacent swinging knife planes.

[0016] Furthermore, the specific method of step 5 is:

[0017] Assume that the two sides of any swinging knife plane are intersection line I and intersection line II, intersection line I is the intersection line of the first offset curved surface and the swinging knife plane, and intersection line II is the intersection line of the second offset curved surface and the swinging knife plane;

[0018] Each discrete curve intersects with the swinging knife plane to generate multiple intersection points. All the intersection points located on the intersection line I are assumed to be the knife center point I, and all the intersection points located on the intersection line II are assumed to be the knife center point II. A ray is drawn through each knife center point I to the edge end point on the intersection line II away from the bottom surface, and a ray is drawn through each knife center point II to the edge end point on the intersection line I away from the bottom surface.

[0019] The cutting plane intersects with the corresponding swinging knife plane to generate a swinging knife intersection line;

[0020] Multiple closed planes are formed by the intersection of each ray and the intersection line of the swinging knife. The area obtained by intersecting multiple closed planes is the feasible domain without interference of the knife axis.

[0021] Furthermore, in step 6, the midpoint of each intersection line III is connected by generating a B-spline curve.

[0022] Furthermore, in step 7, the distance each ruled surface extends is equal to the radius of the tool ball head.

[0023] The beneficial effects of the present invention are:

[0024] 1. Efficient programming efficiency improvement: At the algorithm level, the present invention has outstanding advancement. Its unique tool axis motion control line generation mechanism enables the construction of tool position trajectory for the same processing area to be completed with the help of only one tool axis motion control line during the finishing tool path generation process of deep and narrow V-groove structural parts. The traditional method requires calculating the tool axis vector control line one by one for each parameter curve, and the calculation process is cumbersome, complicated and time-consuming. The present invention has completely changed this situation. There is no need to perform a large amount of repetitive tool axis motion control line calculations, which greatly simplifies the programming process, effectively shortens the time required for machining program compilation, significantly improves compilation efficiency, and provides more efficient technical support for actual production and processing.

[0025] 2. Excellent processing quality assurance: The processing method of the present invention performs well in ensuring processing accuracy and quality. The fine machining tool path is generated by the carefully designed tool axis motion control line, which can effectively guarantee the continuity and smoothness of the tool axis motion during the entire processing process. This feature is crucial when processing deep and narrow V-groove structural parts. It effectively avoids the interference of the tool with the inner cavity surface of the part in the non-cutting area. However, traditional processing methods often require multi-segment decomposition of some tool paths due to the difficulty in accurately controlling the motion trajectory of the tool axis without inner cavity interference, which affects the consistency of the surface quality and dimensional accuracy of the parts. The present invention fundamentally solves this problem, ensures the high-quality completion of part processing, meets the requirements of high-precision processes, helps to improve the overall performance and reliability of the product, and has important application value in fields with extremely high precision requirements such as aviation structural parts.

[0026] 3. The present invention divides the inner cavity curved surface of the metal reinforcement edge into regions according to the curved surface characteristics of the composite blade and re-parameterizes the curved surface of each region, and extracts parameters such as the processing area for the inner cavity curved surface of the reinforcement edge corresponding to the side surface of the blade basin and the back side of the blade. The tool axis non-interference feasible domain is calculated based on the extracted processing area, and the tool axis motion mode of the same processing area is generated based on the same tool axis motion control line, and a continuous, smooth and non-interference processing trajectory can be generated through the tool axis motion control line. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the structure of the deep narrow V-groove structural part of the present invention;

[0028] Figure 2 It is a structural schematic diagram of the plane layout of the swinging knife of the present invention;

[0029] Figure 3 It is a schematic diagram of the position of the feasible region without interference of the tool axis of the present invention;

[0030] Figure 4 It is a schematic diagram of the position of the knife axis motion control line of the present invention.

[0031] Among them, 1. Leaf back side, 2. Leaf basin side, 3. Bottom, 4. Swinging knife plane, 5. Swinging knife intersection line, 6. Intersection line I, 7. Intersection line II, 8. Knife center point I, 9. Knife center point II, 10. Ray, 11. Knife axis non-interference feasible domain, 12. Intersection line III, 13. Section plane, 14. Knife axis motion control line. DETAILED DESCRIPTION

[0032] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] In order to improve the impact resistance of the composite turbofan blade, a titanium alloy metal reinforcement edge is applied to the leading edge of the composite blade. The inner cavity of the metal reinforcement edge is a deep and narrow V-groove structure. The deep and narrow V-groove structure part is a complex curved channel part.

[0034] The present invention provides a four-axis machining method for deep and narrow V-groove structural parts, comprising the following steps:

[0035] Step 1: Figure 1 As shown, a drawing coordinate system XYZ is established for the processing model of the deep narrow V-groove structural part, and the processing model is an existing design model of the deep narrow V-groove structural part. The processing model has a blade back side surface 1 and a blade basin side surface 2 forming a V-shaped angle, and a bottom surface 3 is connected and arranged at the ends where the blade back side surface 1 and the blade basin side surface 2 are close to each other; the blade back side surface 1 and the blade basin side surface 2 are re-parameterized respectively, and the first multi-parametric surface and the second multi-parametric surface are obtained correspondingly.

[0036] Among them, a tangential extension line I is made along the tip direction of the blade for the intersection line of the bottom surface 3 and the blade basin side surface 2, and the tangential extension line I is the X-axis; a tangential extension line II is made in the direction of the blade basin side surface 2 for the edge curve of the bottom surface 3 on the blade tip side, and the plane formed by the tangential extension line II and the X-axis is the XOY plane; a perpendicular line to the X-axis is made in the XOY plane, which is the Y-axis; according to the right-hand coordinate system rule, the Z-axis is determined by the X-axis and the Y-axis.

[0037] The blade back side surface 1 is the side that protrudes outward relative to the inside of the V-shaped groove, and the blade basin side surface 2 is the side that is recessed inward relative to the inside of the V-shaped groove; on both sides of the processing model, the angles formed by the blade back side surface 1 and the blade basin side surface 2 are different in size, the side with a relatively larger angle is the tenon side, and the side with a relatively smaller angle is the blade tip side.

[0038] By reasonably establishing the drawing coordinate system and re-parameterizing the back side surface 1 and the basin side surface 2, an accurate mathematical model basis can be provided for the subsequent processing steps, so that the entire processing process is carried out under a unified coordinate system and parameter framework, which is convenient for accurate calculation and control of the tool path, ensuring the accuracy and consistency of processing.

[0039] Step 2: perform equidistant offsets on the first multi-parametric surface and the second multi-parametric surface respectively, and obtain the first offset surface and the second offset surface accordingly; the offset distance is determined according to the radius value of the tool ball head.

[0040] In the four-axis machining method of the present invention, a cylindrical ball-end tool is used to perform four-axis machining on a deep and narrow V-groove structural part, and the tool ball end radius is determined according to the minimum curvature radius of the first offset curved surface and the second offset curved surface. The equidistant offset operation is performed to reserve space for tool machining while considering the tool ball end radius, to ensure that the tool can smoothly cut along the curved surface during machining, to avoid machining interference problems caused by not considering the actual size of the tool, and also to provide an important reference basis for the subsequent determination of the tool center motion curve group, which helps to improve machining accuracy and quality.

[0041] Step 3: Discretize the first offset surface and the second offset surface respectively, and obtain a first discrete curve group and a second discrete curve group accordingly; the first discrete curve group and the second discrete curve group are tool center motion curve groups during tool milling.

[0042] Step 4: Figure 2 A plurality of equally spaced swinging tool planes 4 parallel to the YOZ plane are established in the region between the first discrete curve group and the second discrete curve group, and the plurality of swinging tool planes 4 form a swinging tool plane group. The swinging tool plane 4 is the plane where the tool axis rotates in four-axis machining. The plurality of swinging tool planes 4 can control the direction of tool axis movement in four-axis machining of deep and narrow V-groove structure parts.

[0043] Establishing a swinging tool plane group can effectively limit and guide the rotational movement of the tool axis. By reasonably setting the spacing and number of the swinging tool planes, the tool can cut at the appropriate position and direction during the machining process, ensuring the stability and accuracy of the machining process. It also helps to optimize the machining process and improve machining efficiency.

[0044] Step 5: Generate a tool axis interference-free feasible domain 11 for four-axis machining of deep narrow V-groove structure parts on any swinging tool plane 4. Determine the tool axis interference-free feasible domain 11, that is, find the area on the swinging tool plane 4 where the tool axis can move safely, avoid collision or interference between the tool and other parts of the part during machining, and ensure the safety and reliability of the machining process.

[0045] Step 6: Repeat step 5 to obtain the tool axis interference-free feasible domain 11 on each tool swinging plane 4. Figure 4, parallel to the XOY plane, a section plane 13 is established at the opening side of the deep narrow V-groove structural part and at a position that does not intersect with the deep narrow V-groove structural part. The section plane 13 intersects with each tool axis non-interference feasible domain 11, and obtains multiple intersection lines III12. The connection line obtained by connecting the midpoint of each intersection line III12 is the tool axis motion control line 14. By connecting the midpoints of the intersection lines to generate the tool axis motion control line 14, the feasible domain information on each swinging tool plane 4 can be integrated to provide guidance for the subsequent generation of a continuous, smooth and non-interference tool motion path, thereby ensuring the tool's motion continuity during the entire machining process.

[0046] Step 7, the first discrete curve group and the second discrete curve group contain multiple discrete curves, and the tool axis motion control line 14 and each discrete curve are used to generate a ruled surface according to the swinging tool plane group, and all the ruled surfaces constitute the tool axis ruled surface group; each ruled surface is then linearly extended along the Z axis toward the inner cavity of the deep narrow V-shaped groove close to the bottom surface 3, that is, the tool axis extended ruled surface group is generated. The purpose of generating the tool axis extended ruled surface group is to organically combine the tool axis motion control line 14 with all the discrete curves, construct a complete tool motion geometric model, and provide the necessary geometric basis for the subsequent processing parameter conversion.

[0047] Step 8: According to the machining interpolation method, the wires of each ruled surface in the tool axis extended ruled surface group are converted into the machining parameters of the line drive mode, that is, the CLS tool path file used for four-axis machining of deep narrow V-groove structure parts is generated. The tool path file is converted using the post-processing software of the corresponding four-axis machine tool to obtain the corresponding machine tool code file, and the machine tool code file is imported into the four-axis machine tool and called to realize the machining of deep narrow V-groove structure parts. Finally, the conversion from geometric model to actual machining instructions is realized, so that the machine tool can perform accurate four-axis machining of deep narrow V-groove structure parts according to the predetermined tool path and machining parameters.

[0048] In some embodiments, in step 3, the first bias surface and the second bias surface include multiple bias surfaces, and the total number of discrete curves in the first discrete curve group and the second discrete curve group is determined according to the maximum value of the height of each bias surface in the Z-axis direction and the discrete spacing between adjacent discrete curves.

[0049] In some embodiments, in step 4, the first discrete curve group and the second discrete curve group include multiple discrete curves, and the spacing between adjacent swinging knife planes is determined according to the maximum value of the angle formed by the tangent of each discrete curve and the swinging knife plane 4; the longest discrete curve is selected, and the number of the swinging knife planes 4 is determined in combination with the spacing between adjacent swinging knife planes 4. By considering the angle between the tangent of the discrete curve and the swinging knife plane 4 and the longest discrete curve to determine the spacing and number of the swinging knife planes 4, it can ensure that the layout of the swinging knife planes 4 is more reasonable, which can not only meet the cutting requirements of the tool in different positions and directions, but also avoid the processing error or interference problem caused by improper setting of the swinging knife plane 4, thereby improving the processing accuracy and reliability.

[0050] In some embodiments, the specific method of step 5 is:

[0051] like Figure 3 , assuming that the two sides of any swinging knife plane 4 are intersection lines I6 and II7, respectively, the intersection line I6 is the intersection line of the first offset curved surface and the swinging knife plane 4, and the intersection line II7 is the intersection line of the second offset curved surface and the swinging knife plane 4;

[0052] Each discrete curve intersects with the swinging knife plane 4 to generate multiple intersection points, and the intersection points are the knife center points. Since the knife center points are generated by the intersection of the first discrete curve group and the second discrete curve group with the swinging knife plane 4 respectively, the position of the knife center point can be located on the first offset curved surface or on the second offset curved surface. It is assumed that each intersection point located on the intersection line I6 is the knife center point I8, and it is assumed that each intersection point located on the intersection line II7 is the knife center point II9. A ray 10 is made through each knife center point I8 to the edge end point on the intersection line II7 away from the bottom surface 3, and a ray 10 is made through each knife center point II9 to the edge end point on the intersection line I6 away from the bottom surface 3;

[0053] The section plane 13 intersects with the corresponding swinging knife plane 4 to generate a swinging knife intersection line 5;

[0054] A plurality of closed planes are formed by the intersection of each ray 10 and the swinging knife intersection line 5, and the area obtained by intersecting the plurality of closed planes is the feasible domain 11 of the knife axis without interference.

[0055] In some embodiments, in step 6, a B-spline curve is generated to connect the midpoints of each intersection line III12. The B-spline curve has good smoothness and continuity, and can better fit the ideal motion path of the tool, making the tool move more smoothly and accurately during the machining process, and reducing machining errors caused by discontinuous or rough motion.

[0056] In some embodiments, the distance that each ruled surface extends in step 7 is equal to the radius of the tool ball head.

[0057] Embodiment: When a tool with a ball head diameter of 1.2mm and a taper of 2deg is used for four-axis finishing of a deep and narrow V-groove structure part with a length of 955.4mm, a Z-direction height range of 57.3mm~64.1mm, and a distance range of 2.8mm~18.7mm between the blade basin side surface 2 and the blade back side surface 1, there are a total of 107 tool center lines.

[0058] In the traditional processing method, since the tool axis control line of each tool center line needs to be solved, the tool axis vector of each tool center line needs to be analyzed and adjusted separately, which involves a large number of geometric calculations and iterative processes, and a total of 107 solutions are required. However, by adopting the method of the present invention and following the established steps, only one tool axis motion control line 14 needs to be generated to realize the generation of the tool position trajectory of the target processing area. Through processing simulation analysis and monitoring and measurement during the actual processing process, the tool path generated by the method of the present invention shows excellent continuity and smoothness, without obvious vibration or offset, ensuring the consistency of the processing process and processing accuracy. At the same time, due to the stability of the tool axis motion, the wear of the tool is also effectively controlled, which prolongs the service life of the tool and further reduces the processing cost.

Claims

1. A four-axis machining method for deep and narrow V-groove structural parts, characterized in that: The following steps are involved: Step 1: Establishing a drawing coordinate system XYZ for a processing model of the deep narrow V-groove structural part, wherein the processing model comprises a blade back side surface (1) and a blade basin side surface (2) forming a V-shaped angle, and a bottom surface (3) is connected and arranged at the ends of the blade back side surface (1) and the blade basin side surface (2) close to each other; respectively re-parameterizing the blade back side surface (1) and the blade basin side surface (2) to obtain a first multi-parametric surface and a second multi-parametric surface; Wherein, a tangential extension line I is drawn along the blade tip direction for the intersection line of the bottom surface (3) and the blade basin side surface (2), and the tangential extension line I is the X-axis; a tangential extension line II is drawn in the direction of the blade basin side surface (2) for the edge curve of the bottom surface (3) on the blade tip side, and the plane formed by the tangential extension line II and the X-axis is the XOY plane; a perpendicular line to the X-axis is drawn in the XOY plane, and the Y-axis is determined; according to the right-hand coordinate system rule, the Z-axis is determined by the X-axis and the Y-axis; Step 2, performing equidistant offsets on the first multi-parametric curved surface and the second multi-parametric curved surface respectively, and obtaining a first offset curved surface and a second offset curved surface correspondingly; the offset distance is determined according to the radius value of the tool ball head; Step 3, discretizing the first biased curved surface and the second biased curved surface respectively, and obtaining a first discrete curve group and a second discrete curve group accordingly; Step 4, establishing a plurality of equally spaced swinging knife planes (4) parallel to the YOZ plane in the region between the first discrete curve group and the second discrete curve group, wherein the plurality of swinging knife planes (4) form a swinging knife plane group; Step 5, generating a tool axis interference-free feasible domain (11) for four-axis machining of the deep narrow V-groove structure part on any one of the tool swing planes (4); Step 6, repeating step 5 to obtain a tool axis non-interference feasible domain (11) on each of the tool swinging planes (4); then establishing a section plane (13) parallel to the XOY plane at a position on the opening side of the deep narrow V-groove structural part and not intersecting with the deep narrow V-groove structural part, wherein the section plane (13) intersects with each of the tool axis non-interference feasible domains (11), and obtains a plurality of intersection lines III (12), and the connection line obtained by connecting the midpoint of each of the intersection lines III (12) is the tool axis motion control line (14); Step 7: The first discrete curve group and the second discrete curve group contain a plurality of discrete curves, and the tool axis motion control line (14) and each of the discrete curves are used to generate ruled surfaces according to the tool swinging plane group, and all of the ruled surfaces constitute a tool axis ruled surface group; each of the ruled surfaces is then linearly extended along the Z axis toward the inner cavity of the deep narrow V-shaped groove in a direction close to the bottom surface (3), thereby generating a tool axis extended ruled surface group; Step 8: According to the machining interpolation method, the wires of each ruled surface in the tool axis extended ruled surface group are converted into machining parameters in a line-driven manner, so as to generate a CLS tool path file for four-axis machining of the deep narrow V-groove structure part.

2. A four-axis machining method for deep narrow V-groove structural parts as claimed in claim 1, characterized in that: In step 3, the first offset surface and the second offset surface include multiple offset surfaces, and the total number of discrete curves in the first discrete curve group and the second discrete curve group is determined according to the maximum value of the height of each offset surface in the Z-axis direction and the discrete spacing between adjacent discrete curves.

3. A four-axis machining method for deep narrow V-groove structural parts as claimed in claim 2, characterized in that: In step 4, the spacing between adjacent swinging knife planes (4) is determined based on the maximum value of the angle formed by the tangent of each discrete curve and the swinging knife plane (4); the longest discrete curve is selected, and the number of the swinging knife planes (4) is determined in combination with the spacing between adjacent swinging knife planes (4).

4. A four-axis machining method for deep narrow V-groove structural parts as claimed in claim 3, characterized in that: The specific method of step 5 is: Assume that two sides of any one of the swinging knife planes (4) are intersection lines I (6) and II (7), respectively, the intersection line I (6) is the intersection line of the first offset curved surface and the swinging knife plane (4), and the intersection line II (7) is the intersection line of the second offset curved surface and the swinging knife plane (4); Each of the discrete curves intersects with the swinging knife plane (4) to generate a plurality of intersection points, each of the intersection points located on the intersection line I (6) is assumed to be a knife center point I (8), and each of the intersection points located on the intersection line II (7) is assumed to be a knife center point II (9); a ray (10) is drawn through each knife center point I (8) to an edge end point on the intersection line II (7) away from the bottom surface (3), and a ray (10) is drawn through each knife center point II (9) to an edge end point on the intersection line I (6) away from the bottom surface (3); The section plane (13) intersects with the corresponding swinging knife plane (4) to generate a swinging knife intersection line (5); A plurality of closed planes are formed by the intersection of each ray (10) and the swinging knife intersection line (5), and the area obtained by intersecting the plurality of closed planes is the knife axis interference-free feasible domain (11).

5. A four-axis machining method for deep narrow V-groove structural parts as claimed in claim 4, characterized in that: In step 6, a B-spline curve is generated to connect the midpoints of each intersection line III (12).

6. A four-axis machining method for deep narrow V-groove structural parts as claimed in claim 5, characterized in that: In step 7, the distance that each of the ruled surfaces extends is equal to the radius of the tool ball head.

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