A non-uniform allowance boundary-based thin-walled fitting part pair trajectory generation method

Abstract

The application discloses a kind of thin wall fitting piece pair shape track generation method based on non-uniform allowance boundary, it is related to the field of aircraft assembly digitization processing technology.This method receives fitting edge, target boundary and non-uniformly distributed gap allowance, discrete sampling and establishes frame;With constant radial depth, the target boundary is offset as allowance layer by equal interval in the gap direction, and the number of layers is rounded up from the ratio of the thickest allowance and the depth;Each layer only cuts in the material section where the allowance is greater than its offset distance, and when the allowance has multiple peaks, the same layer is divided into multiple sections and the empty area is raised.The tool center is offset by a tool radius from the layer, and the tool axis is in the difference direction, which restricts each layer from exceeding the target boundary.The offset of the last layer is zero, and the entire edge is shaped along the target boundary, connected in order and set in and out of the tool.The application maintains stable cutting force with constant radial depth, adapts to non-uniform allowance in material section, does not exceed cutting, and ensures target shape with the last layer shaping, solving the problem of non-uniform allowance adaptation and stable cutting force.

Description

Technical Field

[0001] This invention relates to the field of digital machining technology for aircraft assembly, and more specifically, to a method for generating the conformal trajectory of thin-walled mating parts based on non-uniform margin boundaries. Background Technology

[0002] Thin-walled mating parts for aircraft skins, such as cabin doors, covers, and movable surfaces, mate with corresponding openings on the fuselage. After assembly, the mating edges must fit snugly against the target shape and meet the design requirements for surface seam clearance. Due to factors such as manufacturing errors, clamping deformation, and assembly deviations, these mating parts often have excess material remaining relative to the target shape after assembly. This excess material must be milled away along the mating edge using the side edge of an end mill to bring the mating edge to the target shape—a process known as profile trimming. The amount of excess material removed is not uniform along the mating edge: the thickness of excess material varies in different areas, and in some areas it is even close to zero, with very little material left to remove. Furthermore, these mating parts have thin walls and poor rigidity, making them susceptible to deformation and vibration from the cutting forces during milling, thus affecting machining quality.

[0003] Therefore, the trimming trajectory for thin-walled mating parts must simultaneously meet three requirements. First, alignment, meaning trimming the entire mating edge to the target shape along the target boundary; second, stable cutting force, meaning maintaining a stable cutting force during milling to suppress deformation and chatter of the thin-walled part. In end mill side cutting, the cutting force is mainly determined by the radial depth of cut; and third, no overcutting, meaning that in areas where the allowance is close to zero, no cut should cross the target boundary or cut into the target shape to avoid irreversible overcutting.

[0004] Existing methods for generating mating edge trimming trajectories mainly fall into the following categories. The first category involves geometry-driven, full-circle layered machining. This method uses the mating edge or target boundary as the driving geometry, moving the tool along the driving geometry in a full circle, and layering using contour surfaces or constant offsets. The trajectory of this method is determined by the driving geometry and is unaware of the non-uniform distribution of allowance along the mating edge: each layer advances with the same depth of cut along the entire circle, resulting in insufficient layer counts in areas with thick allowance and potential overcutting of the target boundary in areas with thin allowance. Furthermore, regardless of whether there is still allowance on a certain section of the mating edge, each layer moves along the entire circle, resulting in inefficient movement in areas with no allowance. Especially in areas with near-zero allowance, the constant full-circle advance easily crosses the target boundary, causing overcutting. In addition, contour machining, which is based on layering by height on a three-dimensional surface, is not only unaware of the non-uniform allowance along the mating edge when applied to trimming along a mating boundary line, but also easily crosses the target boundary in areas with near-zero allowance.

[0005] The second type involves reconstructing the surface based on measured point clouds and then laying out the trajectory using conventional toolpath patterns. This involves 3D scanning of the mating parts, reconstructing the surface, or extracting boundaries, and then laying out the toolpath using conventional patterns such as isoparametric lines and isostatic heights. Although this method uses measured data instead of theoretical numerical models, its toolpath pattern is still determined by geometry and is independent of the amount of allowance in each part. Furthermore, its isostatic height and other patterns are aimed at controlling the machining residue on curved surfaces, rather than trimming the edges to the correct shape along a mating boundary line with non-uniform allowances, and it does not address overcutting in areas where the allowance is close to zero.

[0006] The third type is the allowance-driven method, which adapts to non-uniform allowances by varying the depth of cut. To ensure that the amount of material removed by the tool changes with the allowance, the radial depth of cut is adjusted along the mating edge. A larger depth of cut is used where the allowance is thicker, and a smaller depth of cut is used where the allowance is thinner, removing the non-uniform allowance in one or several passes. Although this method adapts to the non-uniform distribution of the allowance, the continuous variation of the radial depth of cut along the mating edge causes fluctuations in the cutting force during milling. For mating parts with thin walls and poor rigidity, fluctuations in cutting force can easily cause uneven deformation and chatter, which is detrimental to machining quality. Furthermore, this method is mostly used to generate offset profiles with varying distances for subsequent machining, and does not directly provide layered toolpaths.

[0007] The aforementioned methods share the following shortcomings. First, the geometry-driven method, which determines the trajectory based on driving geometry, cannot adapt to non-uniformly distributed allowances along the mating edge. It may result in uneven allowance thickness, insufficient layering, cutting beyond the target boundary, or idling where there is no allowance left. Second, methods adapting to non-uniform allowances rely on changing the radial depth of cut, causing the cutting force to fluctuate along the mating edge, which is detrimental to suppressing deformation and chatter in thin-walled parts. Third, none of the above methods specifically address overcutting in areas where the allowance is close to zero. In summary, existing technologies struggle to balance adapting to non-uniform allowances with maintaining stable cutting forces: adapting to non-uniform allowances requires changing the depth of cut, causing cutting force fluctuations; maintaining a constant depth of cut requires advancing along the entire circumference, which is unsuitable for non-uniform allowances; and none of them simultaneously satisfy the requirements of conformation, stable cutting forces, and overcutting.

[0008] Therefore, a method for generating the profile trimming trajectory of thin-walled mating parts is needed: while maintaining a constant radial depth of cut for each cut, thus ensuring stable cutting force, this method should adapt to the non-uniformly distributed allowance along the mating edge, only cutting in areas where allowance remains, trimming the entire mating edge to the target shape, and ensuring that areas with near-zero allowance are not cut. Thus, a method for generating the profile trimming trajectory of thin-walled mating parts based on non-uniform allowance boundaries is proposed to solve the above problems. Summary of the Invention

[0009] To solve the above-mentioned technical problems, the present invention provides a method for generating the alignment trajectory of thin-walled mating parts based on non-uniform allowance boundaries. This method maintains stable cutting force with constant radial cutting depth, adapts to non-uniform allowance in the material section, avoids overcutting, and ensures the target shape by aligning with the last layer. It simultaneously meets the three requirements of alignment, stable cutting force, and no overcutting.

[0010] The specific plan is as follows: A method for generating the conformal trajectory of a thin-walled mating part based on a non-uniform allowance boundary, wherein excess material must be removed from the mating edge of the thin-walled mating part and fitted to fit the target boundary, and the removed clearance allowance is non-uniformly distributed along the mating edge. The method includes the following steps: Step 1, Discrete sampling of the allowance boundary: Discretize the mating edge into a series of sampling points along the arc length of the mating edge, and establish a local frame at each sampling point consisting of the tangential direction, the gap direction and the step direction. The tangential direction is the tool feed direction, the gap direction is along the gap width direction from the target boundary to the side of the excess material, the radial cutting depth of the tool is measured along the gap direction, and the step direction is the tool axis direction. Step 2, equal depth offset layering of the excess material: Based on the target boundary, offset the excess material side along the gap direction at equal intervals with a fixed radial depth. The total number of offset layers is the rounded-up value of the ratio of the maximum gap allowance to the radial depth, thus constructing several excess material layers. Step 3: Determine the material section of each allowance layer: For each allowance layer, determine the material section of the mating edge arc segment where the gap allowance is greater than the offset distance of the allowance layer relative to the target boundary. Step 4, Tool position calculation: On the material section of each of the remaining material sub-layers, offset the tool center from the remaining material sub-layer along the gap direction towards the side of excess material by a tool radius to obtain the tool center trajectory of the remaining material sub-layer, and constrain the side edge of the tool after offset not to cross the target boundary. Step 5, final layer shape refinement along the target boundary: the remaining layer with a zero offset distance relative to the target boundary is taken as the final layer, and its tool center trajectory is only expanded by one tool radius. The tool moves along the entire mating edge and is directly refined to the target shape. Step 6, connecting and transitioning the cutting tools of each layer: Connect the cutting tool trajectories on the material sections of each layer in the order from the outside to the inside to form a single cutting tool trajectory. Set the advance and retraction tools at both ends of each material section. The gaps between unconnected arc segments in the same layer are skipped by lifting the tool.

[0011] Preferably, the local frame in step one is constructed according to the following formula: , ; In the formula, For the first The arc length parameter of each sampling point along the mating edge. For the mating edge curve with arc length as a parameter in The point at that location, To cooperate with the side The guide vector for the arc length, To coordinate with the edge in the first Unit tangential at each sampling point, For the first The out-of-plane normal at each sampling point is used as the step difference direction. For the first The gap directions at each sampling point constitute a right-handed orthogonal system.

[0012] Preferably, in step one, the sampling interval is adaptively determined according to the curvature of the mating edge, and the sampling interval is reduced where the curvature is large.

[0013] Preferably, in step two, the first... The gap margin for each sampling point is The radial depth of cut is The total number of layers and the remaining layers are determined by the following formula: , , ; In the formula, This represents the total number of floors. To round up, For the first Each level of residual capacity In the direction of the gap, For the first The offset distance of each residual layer relative to the target boundary This is the arc length parameter along the mating edge.

[0014] Preferably, in step three, the first The material section of each layer with remaining capacity is determined by the following formula: ; In the formula, For the first Each remaining layer of material-rich section To allow for clearance along the mating edges, the final layer is not cut according to the above formula, and its material section... Take the entire mating edge to traverse the entire target boundary.

[0015] Preferably, in step four, the first The tool center trajectory and overcut constraint of each layer of allowance are determined by the following formula: , , ; In the formula, For the first The tool core trajectory of each layer with a remaining margin For the tool radius, The clearance allowance is along the mating edge; the right side of the inequality indicates that none of the allowance layers exceed the target boundary, and only the last layer satisfies this constraint when the clearance allowance is close to zero.

[0016] Preferably, in step five, the trajectory of the blade core in the final layer is determined by the following formula: ; In the formula, The final tool center trajectory is offset by only one tool radius relative to the target boundary. This ensures that the side edge of the cutting tool moves precisely along the target boundary.

[0017] Preferably, in step six, when the material section of the same allowance layer consists of several unconnected arc segments, except for lifting the cutter to skip in the gap between segments, the continuous cutter path between segments is maintained by overlapping or smooth transition in the form of full-length or overlapping sections, which are sensitive to the continuity of the cutter path.

[0018] Preferably, the side cutting edge height of the cutting tool covers the entire wall thickness along the step direction of the mating edge. The cutting tool moves along the mating edge once to remove the current allowance layer in one go along the entire wall thickness direction without axial separation. The layering is only performed along the gap direction according to the radial cutting depth.

[0019] Preferably, the thin-walled fitting is a cabin door, cover, or movable surface of an aircraft skin.

[0020] The beneficial effects of this invention are as follows: Unlike methods that adapt to non-uniform allowances by changing the radial depth of cut, causing the cutting force to fluctuate along the mating edge, this invention uses a constant radial depth of cut to offset each layer. The machining of each allowance layer is advanced with the same radial depth of cut, and the cutting force does not fluctuate with the thickness of the allowance. This suppresses the deformation and chatter of thin-walled mating parts during machining, and maintains the stability of the cutting force while adapting to non-uniform allowances.

[0021] Unlike methods that use driving geometry to determine the trajectory and move the cutter in layers along the mating edge, this invention determines the material section based on whether there is still material on each layer of the allowance. This causes each layer to shrink layer by layer as the allowance is unevenly distributed along the mating edge, and the cutter only moves along the arcs where there is still material. When the allowance rebounds or has multiple peaks, the material section of the same layer is automatically cut into several arcs, and the cutter skips the gaps between the segments. This adapts to the uneven distribution of the allowance and avoids empty runs where there is no allowance. The trajectory is adaptively cut according to the distribution of the allowance rather than generated along a fixed driving geometry.

[0022] For areas with near-zero margin, this invention uses the constraint that the offset distance of each margin layer does not exceed the gap margin at that location, so that no layer crosses the target boundary and cuts into the target shape. The first cut at the area with near-zero margin is the last layer along the target boundary. This avoids overcutting caused by constant advancement along the mating edge across the target boundary at the near-zero margin.

[0023] In this invention, excess material is removed layer by layer with a constant radial depth of cut, leaving a uniform allowance along the mating edge for the final layer. The final layer runs along the entire mating edge of the target boundary and is precisely shaped by using the side edge of an end mill to fit the target boundary. The rough removal adapts to non-uniform allowances, while the fine finishing ensures the target shape. The division of labor is clear. Thus, this invention, while maintaining a constant radial depth of cut for each cut and a stable cutting force, simultaneously satisfies three requirements: shaping along the target boundary, suppressing thin-wall deformation, and avoiding cutting at locations with near-zero allowances. This solves the problem in existing technologies where it is difficult to balance adapting to non-uniform allowances and maintaining stable cutting forces. Attached Figure Description

[0024] Figure 1 This is a flowchart of the method for generating the shape trajectory of thin-walled mating parts based on non-uniform margin boundaries according to the present invention; Figure 2 This is a schematic diagram of the machining object and the side milling method of the end mill provided as an example in an embodiment of the present invention; Figure 3 This is a schematic diagram of the allowance boundary and local frame provided as an example in an embodiment of the present invention; Figure 4 This is an exemplary schematic diagram of offset layering with equal cutting depth and fixed number of layers provided in an embodiment of the present invention; Figure 5 This is an exemplary schematic diagram of the layered shrinkage and multi-segmentation of the material sections with remaining material in each layer, provided in an embodiment of the present invention. Figure 6 This is a partially enlarged schematic diagram of tool position calculation provided as an example in an embodiment of the present invention; Figure 7 This is an exemplary schematic diagram of overcutting constraints and final layer shape refinement provided in an embodiment of the present invention; Figure 8This is an exemplary schematic diagram of the connection and output of the tool core trajectories of each layer provided in an embodiment of the present invention; Figure 9 This is a schematic diagram illustrating two methods of inter-segment transition provided in an embodiment of the present invention: skipping over the knife and overlapping and walking fully.

[0025] The reference numerals in the appendix of this invention are as follows: 1. Parts to be repaired; 2. Reference parts; 3. Mating edges; 4. End mills. Detailed Implementation

[0026] Because existing methods for generating trimming trajectories for thin-walled mating parts either use mating edges or target boundaries as the driving geometric layering method, failing to detect non-uniformly distributed allowances along the mating edges, resulting in insufficient layering or cutting beyond the target boundary in areas with varying allowance thickness, and idling in areas with no allowance; or adapting to non-uniform allowances by changing the radial depth of cut, causing the cutting force to fluctuate along the mating edges, which is not conducive to suppressing deformation of thin-walled parts; and none of these methods specifically address overcutting in areas where the allowance is close to zero, there are problems such as difficulty in balancing adapting to non-uniform allowances and maintaining stable cutting forces, and difficulty in ensuring proper alignment and overcutting. This invention achieves stable cutting force, adaptive removal of non-uniform allowance, and non-overcutting alignment in areas with near-zero allowance by following the steps of discrete sampling of allowance boundaries, equal depth of cut offset layering of allowance, determination of material sections in each allowance layer, tool position calculation, final layer alignment and fine finishing along the target boundary, and tool position connection and trajectory transition of each layer. Under the premise of maintaining a constant radial depth of cut for each cut and thus maintaining stable cutting force, each layer adaptively shrinks along the non-uniformly distributed allowance along the mating edge, only moves the tool in arc segments where there is still allowance, and aligns the final layer along the target boundary without each layer exceeding the target boundary.

[0027] The present invention will now be described in further detail with reference to the accompanying drawings.

[0028] This embodiment discloses a method for generating the shape trajectory of thin-walled mating parts based on non-uniform margin boundaries, such as... Figure 2 As shown, the processing object and processing method include: part to be repaired 1, reference part 2, mating edge 3, and end mill 4. In this embodiment, part to be repaired 1 is an aircraft cabin door, and reference part 2 is the door frame opening on the fuselage that mates with it. After the two are assembled, excess material must be removed from the mating edge 3 of part to be repaired to fit the target shape and meet the design requirements for the surface seam gap. The amount of gap removed is not uniformly distributed along the mating edge 3. Part to be repaired 1 is a thin-walled skin-like part with thin walls and poor rigidity. The cutting force during processing can easily cause deformation and vibration.

[0029] In this embodiment, the end mill 4 is a cylindrical end mill with a diameter of 8mm and a radius of... The excess material is milled away along the mating edge 3 using its side edge, i.e., side edge milling; during machining, the cutter axis cuts in along the step direction and the side edge cuts in along the seam width direction; the side edge height of the end mill 4 covers the entire wall thickness of the mating edge 3 along the step direction. The workpiece coordinate system and the surface model of the part to be repaired 1 have been calibrated, and the calibration method will not be described in detail here, as it does not constitute a limitation of this invention.

[0030] Please see Figure 1 The method for generating the profile trajectory of thin-walled mating parts based on non-uniform margin boundaries includes the following steps: Step 1, Discrete sampling of the allowance boundary: Receive the measured mating edge 3 of the part to be repaired 1, the target boundary and the clearance allowance along the mating edge 3, and discretize the mating edge 3 into a series of sampling points along the arc length of the mating edge 3. At each sampling point, establish a local frame composed of the tangential direction, the clearance direction and the step direction. The tangential direction is the feed direction of the end mill 4, the clearance direction is along the gap width direction from the target boundary to the side of the excess material, the radial cutting depth of the end mill 4 is measured along the clearance direction, and the step direction is the cutter axis direction.

[0031] Please see Figure 3 In this step, the sampling interval is adaptively determined according to the curvature of mating edge 3, and the basic step size is used along the arc length. Discretize the sample and refine it in areas of high curvature to reduce the sampling interval. The sampling interval is determined by the following formula: ; In the formula: For the first Each sampling interval; Based on the step size, this embodiment takes ; For the first The arc length parameter of each sampling point along mating edge 3, To coordinate with side 3 in Curvature at that point; The encryption coefficient is used. In this embodiment, the perimeter of the mating edge 3 is... Approximately 430 sampling points were obtained through discrete sampling, with denser sampling at locations with greater curvature, such as the four corners of the hatch. At each sampling point... Establish a local frame, constructed according to the following formula: , ; In the formula, For the measured curve of mating side 3 with arc length as the parameter, The point at that location, To coordinate with side 3 in The guide vector for the arc length, To coordinate with side 3 in the first The unit tangential direction at each sampling point, i.e., the feed direction of the end mill 4; For the first The out-of-plane normal at each sampling point, i.e. the step difference direction, is also the cutter axis direction of the end mill 4; Depend on and The cross product yields the result along the seam width direction from the target boundary towards the side with excess material, i.e., the first... The direction of the gap at each sampling point , and The three constitute a right-handed orthogonal system; the sampling direction of side 3 is taken to make The direction pointing towards the side with excess material. This setting ensures that subsequent offset layering, tool center offset, and depth of cut are all along the gap direction. This process decouples the feed direction and the tool axis direction.

[0032] Step 2, equal depth offset layering of the allowance: with a fixed radial depth as the spacing and the target boundary as the reference, the excess material side is offset layer by layer at equal intervals along the gap direction to generate a set of mutually parallel and constant spacing allowance layers. The total number of offset layers is the rounded-up value of the ratio of the gap allowance of the thickest part to the radial depth.

[0033] Please see Figure 4 In this step, a fixed radial depth of cut is given for each cut. The number of layers required for each sampling point and the total number of layers in the entire field are determined by the following formula: , ; In the formula: For the first The number of layers required to remove excess material at each sampling point; This is the clearance allowance at that point; A fixed radial depth of cut for each cut; To round up; This represents the total number of layers in the remaining area. This is the allowance for the thickest part, of which This is the clearance allowance along the mating edge 3. This refers to the arc length parameter along the mating edge 3. In this embodiment, the clearance allowance is mostly located along the mating edge 3. maximum value And in areas where the value is close to zero, take ,have to ; where the allowance is thicker thinner areas Approaching zero .

[0034] Using the target boundary as a reference, along the gap direction towards the side with excess material... Equivalent offsets are used to construct the remaining space in layers. The layer is represented by the following formula: , ; In the formula: For the first Layered allowance is divided into layers; The direction of the gap at the sampling point; For the first The offset distance of the layer relative to the target boundary along the gap direction. As the outermost layer with the largest offset distance, This is the last layer, with an offset distance of zero, meaning it coincides with the target boundary, and the spacing between adjacent layers is constant. In this embodiment, the offset distances of each layer relative to the target boundary are as follows: , , , This setup ensures that each layer is machined at a constant radial depth of cut. The cutting force does not fluctuate with the change in allowance thickness, thereby suppressing the deformation and chatter of thin-walled parts. This is what distinguishes this invention from the method of adapting to non-uniform allowance by changing the radial depth of cut.

[0035] Step 3: Determine the material-rich sections of each allowance layer: For each allowance layer, determine the material-rich sections of the mating edge 3 arc segment where the clearance allowance is greater than the offset distance of the allowance layer relative to the target boundary. That is, along the mating edge 3, determine which arc segments still have allowance above the layer and need to be cut, and which arc segments have no allowance and should be skipped, thus obtaining the material-rich sections of the layer.

[0036] Please see Figure 5 , No. The material-rich section of the layer is determined by the following formula: ; In the formula, For the first A material-containing section with a allowance in each layer, meaning the clearance allowance is greater than the offset distance of that layer, and there is still material on the mating edge of the layer in the arc segment. Only in Internal tooling for material removal The arc segments beyond this level have no margin and cannot be cut. From this formula, it can be seen that the outermost levels ( Smaller, offset distance The larger ( The shorter the layer, the more it covers only the thickest portion; the closer the layer is to the target boundary. The longer the layer; the last layer is not cut according to the above method, and its material section Take the entire mating edge 3 to traverse the entire target boundary. In this embodiment, the outermost layer... Only the coverage margin reaches The above is a short paragraph, each layer The clearance shrinks layer by layer as the thickness of the allowance decreases. When the clearance allowance curves back along the mating edge 3 or exhibits multiple peaks, the arc segment with allowance on the same layer is interrupted by the arc segment without allowance. It consists of several unconnected arc segments, which break at the valley, such as... Figure 5 The diagram shows a section on each side of the mid-to-zero valley. This configuration ensures that each layer of machining is performed only along the arc segment where there is still a margin along the mating edge 3, without tool movement in empty areas. The trajectory adaptively trims according to the margin distribution, which not only adapts to non-uniform margins but also avoids empty cutting in areas where there is no margin. This is what distinguishes this invention from the method of tool movement along the entire circle of the driving geometry.

[0037] Step 4, Tool position calculation: On the material section of each allowance layer, offset the tool center from the allowance layer along the gap direction towards the side of excess material by a tool radius to obtain the tool center trajectory of the allowance layer, and constrain the side edge of the end mill 4 to not cross the target boundary after offset.

[0038] Please see Figure 6 In this step, the first The tool center trajectory for each layer of allowance is calculated using the following formula: , ; In the formula: For the first The blade's trajectory in each layer; The radius of the end mill 4 is shown in this embodiment. ; This is the distance between the blade center and the target boundary along the gap direction, i.e., the offset distance at the layer. In addition, offset the radius of the end mill 4. This ensures that the four side edges of the end mill are precisely positioned on the desired surface, removing the material above that surface. Each tool position is controlled by the cutter center. With the tool axis vector Composition, feed along the tangential direction In this embodiment, the distances between each layer of the blade core and the target boundary are as follows: , , , To ensure that no layer of processing cuts into the target shape, the offset of each layer must satisfy the following no-cutting constraint: ; In the formula: the left side of the inequality indicates that the layer offset distance is not negative, that is, it is not offset outside the target boundary; the right side indicates that the layer offset distance does not exceed the gap margin at that point, that is, the layer does not cross the target boundary and cut into the target shape. In areas where the gap margin is close to zero, only the last layer ( This constraint is satisfied, meaning the first cut at this location is the final layer, processed directly along the target boundary. Other layers with positive offsets will not be cut at this location because they exceed the allowance. This setup ensures that areas with near-zero allowance will not be overcut by any layer crossing the target boundary, consistent with the determination of the material section in step three—the near-zero area is only the final layer. cover.

[0039] Step 5, final layer for fine finishing along the target boundary: the remaining layer with a zero offset distance from the target boundary is taken as the final layer. Its tool center trajectory is only expanded by one tool radius, so that the side edge of the end mill 4 fits the target boundary and moves along the entire mating edge 3 to directly finish to the target shape.

[0040] Please see Figure 7 In this step, the last layer ( ) layer offset distance The trajectory of the blade center is calculated using the following formula: ; In the formula, The final tool center trajectory is offset by only one tool radius relative to the target boundary. This ensures that the four side edges of the end mill are exactly along the target boundary. Movement, in this embodiment, the distance between the last layer of the blade core and the target boundary is... The last layer contains material. The entire mating edge 3 is covered, so the final layer runs along the entire target boundary, shaping the entire mating edge 3 to the target shape. Each layer in steps two through four removes excess material layer by layer with a constant radial depth, leaving a uniform allowance along the mating edge 3 for the final layer (the value of which does not exceed one radial depth). The final layer refines along the target boundary on this uniform allowance, thus determining the final alignment accuracy. This method ensures that the alignment of the entire mating edge 3 is completed in one fine-tuning by the final layer, with uniform removal at all points. This differs from the coarse removal of the aforementioned layers—coarse removal adapts to non-uniform allowances, while alignment refinement ensures the target shape, and the two have a clear division of labor.

[0041] Step Six: Tool Position Connection and Trajectory Transition: Following the layer sequence from the outside in, connect the tool center trajectories on the material sections of each allowance layer sequentially to form a single tool position trajectory. Set the advance and retraction tools at both ends of each material section. Skip the gaps between unconnected arc segments within the same allowance layer by lifting the tool. For sections sensitive to toolpath continuity, maintain continuity between segments using overlapping or smooth transitions. Finally, output the tool center position and corresponding tool axis vector.

[0042] Please see Figure 8 and Figure 9 In this step, according to The layering sequence from the outside in divides each layer into material sections. The toolpaths on the upper part are connected sequentially to form a single toolpath, with advance and retraction tools set at both ends of each material-containing section. When a certain layer of material-containing section... When the material is broken into several arc segments due to excess material backflow or multiple peaks, the interval between segments is an empty area where there is no excess material above that level. The tool is lifted and quickly skipped over this empty area, without moving within it. This is the standard method for transitioning between segments. Figure 9 The tool is lifted and skipped as shown; for sections sensitive to toolpath continuity, toolpath continuity can also be maintained between sections by overlapping or smooth transitions. This is a workaround for inter-section transitions, such as... Figure 9 The overlapping section is shown in the diagram. The final output toolpath is an ordered sequence of the tool center position and the corresponding tool axis vector in each material-containing section: , , ; In the formula: For the first The position of the cutting core on the material-containing section; This corresponds to the tool axis vector. The tool path drives the machine tool, causing the end mill 4 to remove non-uniform allowance layer by layer with a constant radial depth, only removing material from the material section, and shaping the entire mating edge 3 of the thin-walled mating part along the target boundary from the last layer. This setting allows the arc segment trajectories of each layer, along with the tool advance and retraction and the transition between segments, to form a single complete trajectory. Empty areas are skipped by tool lifting to avoid empty cutting, and flexible overlaps are used to ensure continuity. The trajectory is generated according to the allowance distribution rather than along a fixed drive geometry.

[0043] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or step transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for generating the conformal trajectory of a thin-walled mating part based on a non-uniform allowance boundary, wherein excess material must be removed from the mating edge of the thin-walled mating part and fitted to fit the target boundary, and the removed clearance allowance is non-uniformly distributed along the mating edge, characterized in that, The method includes the following steps: Step 1, Discrete sampling of the allowance boundary: Discretize the mating edge into a series of sampling points along the arc length of the mating edge, and establish a local frame at each sampling point consisting of the tangential direction, the gap direction and the step direction. The tangential direction is the tool feed direction, the gap direction is along the gap width direction from the target boundary to the side of the excess material, the radial cutting depth of the tool is measured along the gap direction, and the step direction is the tool axis direction. Step 2, equal depth offset layering of the excess material: Based on the target boundary, offset the excess material side along the gap direction at equal intervals with a fixed radial depth. The total number of offset layers is the rounded-up value of the ratio of the maximum gap allowance to the radial depth, thus constructing several excess material layers. Step 3: Determine the material section of each allowance layer: For each allowance layer, determine the material section of the mating edge arc segment where the gap allowance is greater than the offset distance of the allowance layer relative to the target boundary. Step 4, Tool position calculation: On the material section of each of the remaining material sub-layers, offset the tool center from the remaining material sub-layer along the gap direction towards the side of excess material by a tool radius to obtain the tool center trajectory of the remaining material sub-layer, and constrain the side edge of the tool after offset not to cross the target boundary. Step 5, final layer shape refinement along the target boundary: the remaining layer with a zero offset distance relative to the target boundary is taken as the final layer, and its tool center trajectory is only expanded by one tool radius. The tool moves along the entire mating edge and is directly refined to the target shape. Step 6, connecting and transitioning the cutting tools of each layer: Connect the cutting tool trajectories on the material sections of each layer in the order from the outside to the inside to form a single cutting tool trajectory. Set the advance and retraction tools at both ends of each material section. The gaps between unconnected arc segments in the same layer are skipped by lifting the tool.

2. The method for generating the conformal trajectory of thin-walled mating parts based on non-uniform margin boundaries according to claim 1, characterized in that, The local frame in step one is constructed according to the following formula: ， ； In the formula, For the first The arc length parameter of each sampling point along the mating edge. For the mating edge curve with arc length as a parameter in The point at that location, To cooperate with the side The guide vector at the arc length, To coordinate with the edge in the first Unit tangential at each sampling point, For the first The out-of-plane normal at each sampling point is used as the step difference direction. For the first The direction of the gap at each sampling point , and The three form a right-handed orthogonal system, and the sampling direction of the edges is taken to make... The direction pointing towards the side with excess material.

3. The method for generating the conformal trajectory of thin-walled mating parts based on non-uniform margin boundaries according to claim 1, characterized in that, In step one, the sampling interval is adaptively determined according to the curvature of the mating edge, and the sampling interval is reduced where the curvature is large.

4. The method for generating the conformal trajectory of thin-walled mating parts based on non-uniform margin boundaries according to claim 2, characterized in that, In step two, let the first... The gap margin for each sampling point is The radial depth of cut is The total number of layers and the remaining layers are determined by the following formula: ， ， ； In the formula, This represents the total number of floors. To round up, For the first Each level of residual capacity In the direction of the gap, For the first The offset distance of each residual layer relative to the target boundary This is the arc length parameter along the mating edge.

5. The method for generating the profile trajectory of thin-walled mating parts based on non-uniform margin boundaries according to claim 4, characterized in that, In step three, the first The material section of each layer with remaining capacity is determined by the following formula: ； In the formula, For the first Each remaining layer of material-rich section To allow for clearance along the mating edges, the final layer is not cut according to the above formula, and its material section... Take the entire mating edge to traverse the entire target boundary.

6. The method for generating the profile trajectory of thin-walled mating parts based on non-uniform margin boundaries according to claim 5, characterized in that, In step four, the first The tool center trajectory and overcut constraint of each layer of allowance are determined by the following formula: ， ， ； In the formula, For the first The tool center trajectory of each layer of the remaining margin. For the tool radius, The clearance allowance is along the mating edge; the right side of the inequality indicates that none of the allowance layers exceed the target boundary, and only the last layer satisfies this constraint when the clearance allowance is close to zero.

7. The method for generating the conformal trajectory of thin-walled mating parts based on non-uniform margin boundaries according to claim 6, characterized in that, In step five, the trajectory of the blade core in the final layer is determined by the following formula: ； In the formula, The final tool center trajectory is offset by only one tool radius relative to the target boundary. This ensures that the side edge of the cutting tool moves precisely along the target boundary.

8. The method for generating the conformal trajectory of thin-walled mating parts based on non-uniform margin boundaries according to claim 1, characterized in that, In step six, when the material section of the same allowance layer consists of several unconnected arc segments, except for lifting the cutter to skip in the gap between segments, the continuous cutter path between segments is maintained by overlapping or smooth transition in the form of full-length or overlapping sections, which are sensitive to the continuity of the cutter path.

9. The method for generating the conformal trajectory of thin-walled mating parts based on non-uniform margin boundaries according to claim 1, characterized in that, The side cutting edge height of the cutting tool covers the entire wall thickness along the step direction of the mating edge. The cutting tool moves along the mating edge once to remove the current allowance layer in one go along the entire wall thickness direction without axial separation. The layering is only performed along the gap direction according to the radial cutting depth.

10. The method for generating the conformal trajectory of thin-walled mating parts based on non-uniform margin boundaries according to claim 1, characterized in that, The thin-walled fittings are aircraft skin-like components such as doors, covers, or movable surfaces.

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