Numerical control machining method for sharp edges of outer covering part of car
By combining PowerMILL programming and ball end mill machining strategies through secondary development, the machining challenges of sharp edges, concave corners, and punches with multiple sharp edges and half-cut edges on the outer body panels of automobiles have been solved, achieving high precision and consistency without refinishing, and meeting the precision and appearance requirements of sharp edges for high-end models.
Patent Information
- Application Number
- CN202511804406.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-03
- Publication Date
- 2026-02-13
AI Technical Summary
In the existing technology, the processing of sharp edges of car body panels has problems such as the inability to manually grind within 5mm on both sides of the concave sharp corner, and the edge joint tool breakage in the half of the punch with multiple sharp edges. It is difficult to meet the requirements of high-end cars for the precision, surface quality and appearance consistency of sharp edges.
The PowerMILL programming, developed through secondary development, is used to construct the sharp edge protection surface. Combined with the D30 ball end mill for ultra-semi-finishing and the three-dimensional offset spiral milling strategy of D6 and D1 ball end mills, the programming and trajectory rearrangement are performed to address the sharp edge concave corners and punches with multiple sharp edges and half edges without tool breakage, ensuring the accuracy and consistency of sharp edge machining.
It achieves refinish-free machining of sharp edges and concave corner areas, eliminating tool marks from the large tool to the small tool and tool breakage differences from the joints of multiple sharp edges and half edges of the punch in traditional machining, improving the consistency of sharp edge precision and surface quality, and meeting the requirements of high-end models.
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Figure CN121514832A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of automobile production and processing, and particularly relates to a numerical control machining method for sharp edges of a car outer covering part. BACKGROUND
[0002] With the increasingly small matching round corner requirement of the model edge line and the part, the sharp edge process gradually evolves into a unique sharp edge process. The sharp edge directly determines the high-end texture and brand recognition of the vehicle, and has a key influence on the forming precision, assembly consistency and aerodynamic performance of the covering part.
[0003] The current existing machining technology mainly adopts the conventional numerical control machining idea: the sharp edge concave surface machining is performed according to the process of rough machining by a large knife and fine machining by a small knife, the operation space for subsequent manual repair is reserved by grooving on the concave surface, and no special protection and machining strategy is designed for the sharp edge corner area; the convex die multi-sharp edge machining is performed by adopting the partition programming mode, the sharp edges on both sides are machined to ensure the basic sharpness; the overall machining depends on the default parameters of the conventional programming software, and the machining characteristics of the key areas of the sharp edge are not considered in the tool path planning, and manual repair by a fitter is needed after machining to eliminate the tool joint marks and adjust the surface to meet the basic forming requirement.
[0004] In the traditional machining, the tool joint marks of the large knife and the small knife near the edge line are prone to appear in the strong pressing area of the forming, and the manual repair cannot reach the key area of the sharp corner due to the grooving design on the concave surface, and the tool joint discontinuity appears in the convex die partition machining due to the tool wear, which is difficult to eliminate even by repair, so that the domestic die cannot meet the requirements of the sharp edge precision, surface quality and appearance consistency of the high-end car outer covering part. Therefore, the existing machining method has the problems that the sharp edge concave surface (especially the space within 5mm on both sides of the sharp corner) cannot be repaired by manual repair, and the tool joint discontinuity appears in the convex die multi-sharp edge with a half. SUMMARY
[0005] The present application aims to provide a numerical control machining method for sharp edges of a car outer covering part to solve the technical problems in the prior art that the space within 5mm on both sides of the sharp corner cannot be repaired by manual repair, and the tool joint discontinuity appears in the convex die multi-sharp edge with a half.
[0006] The numerical control machining method for sharp edges of a car outer covering part provided by the present application comprises the following steps: Step 1, for the sharp edge concave surface during the overall machining of the surface, PowerMILL programming is used for machining the surface of the part where the concave surface is located, the sharp edge surface near the edge line of the concave surface is extracted and cut, the normal is upwardly biased to form a sharp edge protection surface, and a machining allowance is obtained; and the super semi-finishing machining with a D30 ball allowance is added between the conventional semi-finishing and finishing machining; Step 2, first adopt D6 ball head cutter, then adopt D1 ball head cutter, respectively according to preset value with same three-dimensional offset strategy from sharp edge middle to single direction spiral follow milling processing, processing range exceeds the range of sharp edge protection surface in step 1; At the same time, the tool path of D1 ball head cutter is layered according to the residual processing amount of D6 ball head cutter, and is combined into uninterrupted processing program to prevent overcutting of sharp edge; Step 3, for the convex mold multi-sharp edge with half truncated edge, the sharp edge is programmed according to the partitioning and the trajectory sequence is rearranged by secondary development tool to realize the non-tool joint break processing.
[0007] Further, the specific steps of step 1 are: Step 1.1, using PowerMILL programming method based on secondary development to process the surface of the sharp edge concave surface, numbering the tool used for programming, so that the output processing program carries the instructions of automatic tool changing, automatic tool changing and automatic tool measuring, realizing the automatic processing of the surface of the sharp edge concave surface; Step 1.2, first extract the sharp edge concave surface in the processing data, cut the sharp edge surface in the preset range near the edge line and offset the normal upward by a preset thickness to form a sharp edge protection surface only used for surface finishing programming; Step 1.3, between the semi-finishing allowance of 0.1mm of the conventional D30 ball head cutter and the finishing allowance of 0mm of the conventional D30 ball head cutter, add the super semi-finishing process of D30 ball allowance; Step 1.4, finally, according to the rule of one program and one tool for each edge, the sharp edge concave surface is finished to eliminate the tool joint mark of traditional large tool to small tool near the edge line.
[0008] Further, in step 1.2, the cutting range of the sharp edge surface is 5-10mm near the edge line, the preset thickness of the normal upward offset is 0.1-0.15mm, and the sharp edge protection surface range is reserved 0.1-0.15mm machining allowance after the surface finishing is completed.
[0009] Further, in step 1.3, the allowance of D30 ball head cutter super semi-finishing is 0.03mm-0.04mm, which is used to reduce the influence of tool wear on machining precision in subsequent finishing, so as to minimize the tool joint mark between sharp edge concave surface and D30 ball head cutter finishing.
[0010] Further, the specific steps of step 2 are: Step 2.1, the processing of sharp edge concave surface corner first adopts D6 ball head cutter, according to preset speed, feed rate, step distance and calculated tolerance, with three-dimensional offset strategy and according to reference line, single direction spiral follow milling processing from sharp edge middle, processing range exceeds the range of sharp edge protection surface in step 1; Step 2.2, again adopt D1 ball head cutter, according to the preset high speed, low feed speed, small step and high precision calculation tolerance, with the same three-dimensional offset strategy from the sharp edge of the middle of the single spiral milling, and the step is set with circular arc cutting in and out; Step 2.3, at the same time, the D1 ball head cutter is processed according to the D6 ball head cutter residual processing amount, which is layered and combined into an uninterrupted processing program to prevent the sharp edge from being overcut.
[0011] Further, in step 2.1, the preset parameters of D6 ball head cutter processing are 10000r / min-11000r / min, 4000mm / min-4500mm / min, 0.2mm, 0.005mm, and the processing range exceeds the sharp edge protection surface allowance range in step 1 by 2-3mm.
[0012] Further, in step 2.2, the preset parameters of D1 ball head cutter processing are 14000-15000r / min, 2000-2500mm / min, 0.05mm, 0.001mm; and except for the Y-shaped edge center track, a single sharp edge is processed continuously by a D1 ball head cutter, and the track has no tool jumping.
[0013] Further, in steps 2.1 and 2.2, the method for obtaining the reference line of the sharp edge recess track is to generate a single-pen clear root calculation track by PowerMILL with the same tool allowance and 0.001mm calculation tolerance at the position where the angle between the two sides of the sharp edge is less than 170°-180°, and the intersection line is obtained as the reference line after biasing to the concave side by the distance of tool radius plus processing allowance.
[0014] Further, in step 2.3, the layering thickness of the D1 ball head cutter starting track is 0.005mm, and after layering, the track is combined with the track generated by the three-dimensional offset strategy into an uninterrupted processing program, which is used to eliminate the local groove defects of the sharp edge caused by tool heat accumulation effect.
[0015] Further, the specific steps of step 3 are: For the convex mold with multiple sharp edges with half truncated edges, the convex mold with multiple sharp edges is programmed by the sharp edge processing method, and the tangential extension surface is made on both sides of the sharp edge during programming, so that the processing track is along the tangential direction. The track in different regions is rearranged according to the unified region sequence through secondary development tool to ensure that the region with half truncated edge is processed sequentially from one side to the other side.
[0016] Beneficial effects: The application provides a numerical control machining method for sharp edges of a car outer covering part.
[0017] The application solves the no-repair machining method for sharp edge concave surfaces and convex molds with half-edge multi-sharp edges, breaks through from ordinary sharp edges (sharp edge concave surface groove, product sharpness cannot be effectively controlled due to machining capacity limitation) to realize strong pressure design of sharp edge concave surface no-empty groove and no-repair machining of convex mold with half-edge multi-sharp edges no-tool joint mark; under the premise of not significantly increasing machining cost, the no-repair machining of the surface near the sharp edge of the ordinary sharp edge mold is realized. BRIEF DESCRIPTION OF DRAWINGS
[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creative labor.
[0019] Figure 1 The flow chart of the numerical control machining method for sharp edges of a car outer covering part provided by the embodiments of the present application is shown in the figure. Figure 2 The sharp edge distribution diagram of the high-end car engine cover outer plate with half-edge in the machining method provided by the embodiments of the present application is shown in the figure. Figure 3 The sharp edge distribution diagram of the high-end car wing plate with Y-shaped edge in the machining method provided by the embodiments of the present application is shown in the figure. Figure 4 The cross-sectional local enlarged view of the sharp edge in the machining method provided by the embodiments of the present application is shown in the figure. Figure 5 The sharp edge reference line cross-sectional schematic diagram of the sharp edge in the machining method provided by the embodiments of the present application is shown in the figure. Figure 6Trajectory diagram of the processing method provided by the embodiment of the present application for the bifurcation of the sharp edge concave Y-shaped edge; Figure 7 Trajectory diagram of the processing method provided by the embodiment of the present application for the anti-cutting processing of the sharp edge concave edge line; Figure 8 Trajectory diagram of the processing method provided by the embodiment of the present application for the rearrangement sequence of the half truncated edge disappearance of the punch.
[0020] Marked as: 1-sharp edge; 2-half truncated edge; 3-half truncated edge disappearance; 4-Y-shaped edge; 5-sharp edge sharp corner; 6-both sides of the concave intersection forming area; 7-reference line section point; 8-tool radius and processing allowance section. DETAILED DESCRIPTION
[0021] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme of the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all the embodiments. The components of the embodiments of the present application described and shown in the drawings can be arranged and designed in various different configurations.
[0022] Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the claimed present application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.
[0023] In the description of the present application, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship when the product of the present application is usually placed, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the present application. In addition, the terms "first", "second", "third" and the like are only used to distinguish the description and cannot be understood as indicating or implying relative importance.
[0024] Some embodiments of the present application will be described in detail below in combination with the drawings. In the case of no conflict, the following embodiments and features in the embodiments can be combined with each other.
[0025] As Figure 1As shown, the present application provides a numerical control machining method for sharp edges of car outer cover, comprising: step 1, for the sharp edge concave surface of the overall machining of the profile, the PowerMILL programming of secondary development is used for machining the profile of the concave surface, the sharp edge surface near the sharp edge concave surface is extracted and cut, the normal is upwardly biased to form a sharp edge protection surface, and a machining allowance is obtained; and the super semi-finishing of D30 ball allowance is added between the conventional semi-finishing and the finishing. Step 1.1, the PowerMILL programming mode based on secondary development is used for profile machining of the sharp edge concave surface, the tool used for programming is numbered, the machining program output carries the instructions of automatic tool changer, automatic tool changer and automatic tool measurement, and the automatic machining of the profile of the sharp edge concave surface is realized. Step 1.2, the sharp edge concave surface in the machining data is extracted, the sharp edge surface in the preset range near the edge line is cut and the normal is upwardly biased by a preset thickness to form a sharp edge protection surface used only for profile finishing programming; the cutting range of the sharp edge surface is 5-10mm near the edge line, preferably 10mm, the preset thickness of the normal upward bias is 0.1-0.15mm, preferably 0.1mm, and the range of the sharp edge protection surface is retained 0.1-0.15mm after the profile finishing is completed, preferably 0.1mm, and the machining allowance.
[0026] Step 1.3, between the conventional D30 ball head tool semi-finishing allowance 0.1mm and the conventional D30 ball head tool finishing allowance 0mm, the super semi-finishing process of D30 ball allowance is added; in step 1.3, the allowance of D30 ball head tool super semi-finishing is 0.03mm-0.04mm, which is used to reduce the influence of tool wear on machining precision in subsequent finishing, and the tool mark between the sharp edge concave surface and the D30 ball head tool finishing is minimized.
[0027] Step 1.4, finally, the profile finishing of the sharp edge concave surface is carried out according to the rule of one program for each edge and one tool, and the tool mark near the edge line of the traditional large tool to small tool is eliminated.
[0028] Specifically, as Figure 2 , Figure 3As shown, the machining mode of PowerMILL programming based on secondary development is used for machining the surface of the concave part, which has the characteristics of facilitating secondary development output tool, using tool number for programming, and making the output program with instructions for automatic tool changing and tool measurement during machining to realize automatic machining. The sharp edge concave surface finish machining needs to have a sharp edge protection surface, which has the characteristics of being processed in place by conventional methods except near the concave surface, and the sharp edge concave surface finish machining uses a special programming method to ensure that each edge has one program, one tool, and no defect for one continuous machining, so as to achieve no rework standard. The traditional method can eliminate the tool joint mark near the edge line from large tool to small tool, the position of the tool joint mark is outside the forming strong pressure area, and the tool joint mark is controlled within a certain range through targeted processing, so as to realize coloring after less rework and ensure the demand of later debugging work. The sharp edge concave surface protection before finish machining in step 1.2 is to extract the sharp edge concave surface from the machining data and cut the sharp edge surface within a range of 10 mm near the edge line, and the normal is upwardly biased by 0.1 mm, which is used only during surface finish machining programming to ensure that there is a 0.1 mm machining allowance in the sharp edge protection surface range after finish machining. The sharp edge concave surface area finish machining preprocessing in step 1.3 is that the sharp edge area is the outer surface of the product area of the workpiece, and between the conventional machining allowance D30 ball allowance 0.1 mm semi-finish and D30 ball allowance 0 mm finish machining, D30 ball allowance 0.03 mm super semi-finish machining is added to minimize the influence of tool wear on machining accuracy and ensure that the tool joint mark between the sharp edge concave surface and the D30 ball allowance 0 mm finish machining is minimized.
[0029] Step 2, for the sharp edge concave surface sharp corner, first use D6 ball nose tool, then use D1 ball nose tool, respectively, according to the preset value, with the same three-dimensional bias strategy, from the middle of the sharp edge, single helix milling processing, the processing range exceeds the allowance range of the sharp edge protection surface in step 1; at the same time, the D1 ball nose tool cutting path is layered according to the residual machining amount of the D6 ball nose tool, and is combined into an uninterrupted machining program to prevent overcutting of the sharp edge; Step 2.1, the sharp edge concave surface sharp corner is first machined by D6 ball nose tool, with three-dimensional bias strategy and according to the reference line, single helix milling processing is carried out from the middle of the sharp edge, and the processing range exceeds the allowance range of the sharp edge protection surface in step 1; in step 2.1, the preset parameters of the D6 ball nose tool machining are rotation speed 10000r / min-11000r / min, preferably 10000r / min, feed speed 4000mm / min-4500mm / min, preferably 4000mm / min, step distance 0.2mm, and calculation tolerance 0.005mm, and the processing range exceeds the sharp edge protection surface allowance range in step 1 by 2-3mm, preferably 2mm.
[0030] Step 2.2, as shown in Figure 6 , Figure 7 , the D1 ball end mill is used again, preset high rotation speed, low feed speed, small step distance and high precision calculation tolerance, and the same three-dimensional offset strategy is used to process the single helix from the sharp edge middle, and the circular arc is set between the step distances for cutting in and cutting out; in step 2.2, the preset parameters of the D1 ball end mill processing are rotation speed 14000-15000 r / min, preferably 14000 r / min, feed speed 2000-2500 mm / min, preferably 2000 mm / min, step distance 0.05 mm, and calculation tolerance 0.001 mm; and in addition to the Y-shaped edge center track, a single sharp edge is continuously processed by one D1 ball end mill, and the track does not have tool jumping.
[0031] The method for obtaining the reference line of the sharp edge concave surface track is to generate a reference line from the track by PowerMILL single-pen root cleaning calculation track with the same tool allowance and calculation tolerance of 0.001 mm at the positions where the angles between the two sides of the sharp edge are less than 170-180°; at the positions where the track cannot be generated, the intersection line is obtained after offsetting to the concave side by the distance of the tool radius plus the machining allowance, as the reference line.
[0032] Step 2.3, the D1 ball end mill tool path is layered according to the residual machining allowance of the D6 ball end mill, and is combined into an uninterrupted machining program to prevent overcutting of the sharp edge. In step 2.3, the layering thickness of the D1 ball end mill tool path is 0.005 mm, and after layering, the track is combined with the track generated by the three-dimensional offset strategy into an uninterrupted machining program to eliminate local groove defects of the sharp edge caused by tool heat accumulation effect.
[0033] Specifically, as shown in Figure 4 , in the design data, the concave edge of the sharp edge is a sharp angle formed by the intersection of the two concave surfaces, and in the programming link, a ball end mill with a reasonable diameter is selected, special programming requirements and methods are used, and the key factors related to the actual processing result and the forming quality are understood and controlled, that is, the control of the sharp angle residual R value after the design data calculation and the machining precision and quality of the two concave surfaces, to ensure the sharpness of the sharp edge and other general quality requirements of the outer surface line of the car product without rework. In order to ensure the machining precision and quality near the sharp edge and the concave surface, the program starts cutting at the sharp edge, processes from one end to the other end, and then finishes the machining outward, which strictly guarantees the sharpness of the sharp edge and the stress of the two sides of the sharp edge during molding to meet the design intention and molding requirements. The lower tool path needs to be tangent to the two sides of the sharp edge, the cutting in and cutting out are connected outside the product area to ensure the sharpness and aesthetics of the sharp edge. as shown in Figure 5As shown, the reference line is calculated considering the tool radius and machining allowance, the included angle between the two sides of the sharp edge is generally between 170 degrees and 180 degrees, and in the part less than 176 degrees, the single pen clear root is calculated by PowerMILL software using the same tool allowance, the method of calculating the trajectory according to the calculation tolerance of 0.001mm, and the trajectory is used to generate the reference line. In the part where the trajectory cannot be generated, the intersection line is obtained as the reference line by offsetting the concave side according to the distance of the tool radius and the machining allowance respectively. Due to the shape of the product and the strong pressure design, there will be local offset near the end of the edge line, and even after the offset surface is extended, the intersection cannot be obtained. At this time, the obtained reference line needs to be extended to the end of the sharp edge concave surface according to the tangential direction. The reference line obtained by the two methods or disconnected needs to be checked at the joint, and the smooth part needs to be kept and the smooth joint needs to be ensured. Extract one reference line for each sharp edge, and place the long and short two of the Y-shaped edge into one reference line; For the anti-overcut processing of sharp edge edge line, due to the slow heat conduction characteristics of small diameter tool, the maximum machining amount is at the tool starting position, and there will be heat accumulation effect in high speed machining process, which causes the tool to stretch and lengthen during machining. The heat accumulation effect is related to the machining amount and duration, and the heat dissipation condition is a dynamic process in which heat generation and heat dissipation are difficult to balance. When the included angle between the two sides of the sharp edge is 170° and the D6 allowance is 0.03mm, the lengthening range of the D1 ball head tool is 0-0.02mm during the machining process of the D1 ball head tool with a machining allowance of 0.04mm from the middle of the sharp edge. A local groove defect with different depths is formed at the sharp edge. The conventional white light, three coordinate and online detection methods cannot detect it. Since the tool is in a non-heat accumulation state before and after machining, the tool length detection data cannot be associated with the occurrence of this defect, and only the debugging expert can find it through visual and fingertip touch methods. After this machining defect enters the debugging process, it will directly affect the quality and sharpness of the sharp edge on the surface of the workpiece, and it cannot be eliminated through research and development, so that the design department obtains the wrong corresponding relationship between the strong pressure and deformation data of the sharp edge surface and the forming result. By using the method of dividing the D1 ball head tool starting trajectory into layers according to the D6 residual machining allowance by 0.005mm, and then using three-dimensional offset strategy to calculate the single helical milling from the middle of the sharp edge according to the reference line, the two are combined into one program to ensure that the machining of the sharp edge is not interrupted.
[0034] Step 3, as shown in Figure 8 For the convex mold with multiple sharp edges with half truncated edges, the sharp edges are programmed and the trajectory order is rearranged by secondary development tool to realize no tool breakage machining. For the convex mold with multiple sharp edges with half truncated edges, the convex mold with multiple sharp edges is programmed according to the sharp edge machining method, and the tangential extension surface is made on both sides of the sharp edge during programming, so that the machining trajectory is along the tangential direction. By using the secondary development tool, the trajectories in different regions are rearranged in sequence according to the unified region to ensure that the half truncated edge region is sequentially machined from one side to the other side.
[0035] Specifically, in order to ensure the sharpness of the sharp edge of the punch, the trajectory is ensured to be machined in a direction approximately perpendicular to the sharp edge during numerical control machining, and the tangential extension surface is made on both sides of the sharp edge during programming, so that the trajectory is fed and withdrawn in the tangential direction, thereby maximizing the sharpness of the sharp edge. Therefore, the punch with a sharp edge needs to be programmed and machined in sections according to the sharp edge. This tool feeding mode is called picking sharp edge machining. In the punch with a half-edge, when the trajectory enters the region where the half-edge disappears, machining discontinuity will be caused due to the tool wear caused by the section machining on both sides of the half-edge. Even if this machining discontinuity is eliminated by hand finishing, coloring defects will still occur on the two adjacent sides, which will make the mold product area debugging coloring unqualified. The secondary development tool has the following functions: rearranging the trajectory order of different regions with the same number of roots according to a unified region, ensuring that the region with a half-edge is sequentially machined from one side to the other side by picking the sharp edge tool feeding mode, and ensuring that there is no finishing debugging coloring failure.
[0036] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.
Claims
1. A CNC machining method for sharp edges of automotive exterior body panels, characterized in that, include: Step 1: For the sharp edges and concave surfaces during the overall machining of the profile, the PowerMILL programming developed in the secondary development is used to machine the profile surface where the concave surface is located. The sharp edges and concave surfaces near the sharp edge edge are extracted and cut off. The upward offset of the normal direction forms a sharp edge protection surface to obtain the machining allowance. Then, a super semi-finishing with a D30 ball allowance is added between the conventional semi-finishing and finishing. Step 2: For the sharp corners of the concave surface of the sharp edge, first use a D6 ball end mill, then use a D1 ball end mill. Both are machined in a single-direction spiral climb mill starting from the middle of the sharp edge with the same three-dimensional offset strategy according to the preset value. The machining range exceeds the allowance range of the sharp edge protection surface in Step 1. At the same time, the starting trajectory of the D1 ball end mill is layered according to the residual machining amount of the D6 ball end mill and merged into an uninterrupted machining program to prevent overcutting of the sharp edge. Step 3: For the part of the punch with multiple sharp edges and half edges, program according to the sharp edge partition and rearrange the trajectory sequence through the secondary development tool to achieve seamless tool breakage machining.
2. The CNC machining method for sharp edges of automotive exterior body panels according to claim 1, characterized in that, The specific steps of step 1 are as follows: Step 1.1: Use the PowerMILL programming method based on secondary development to perform surface machining on the part containing the sharp edge and concave surface. Number the tools used in programming so that the output machining program carries instructions for automatic head changing, automatic tool changing and automatic tool measurement of the machine tool, thereby realizing the automated machining of the surface of the part containing the sharp edge and concave surface. Step 1.2: First, extract the sharp edge concave surface from the processing data, cut the sharp edge surface within a preset range near the edge line and offset it upward in the normal direction by a preset thickness to form a sharp edge protection surface that is only used for surface finishing programming. Step 1.3: Between the standard D30 ball end mill semi-finishing allowance of 0.1mm and the standard D30 ball end mill finishing allowance of 0mm, add a super semi-finishing process with D30 ball allowance; Step 1.4 Finally, follow the rule of one procedure and one tool for each edge to perform fine machining of the concave surface of the sharp edge, eliminating the tool marks near the edge line caused by the traditional large tool to small tool.
3. The CNC machining method for sharp edges of automotive exterior body panels according to claim 2, characterized in that, In step 1.2, the cutting range of the sharp edge surface is 5 to 10 mm near the edge line, the preset thickness of the upward offset of the normal is 0.1 to 0.15 mm, and the sharp edge protection surface range retains a machining allowance of 0.1 to 0.15 mm after the surface finishing is completed.
4. The CNC machining method for sharp edges of automotive exterior body panels according to claim 2, characterized in that, In step 1.3, the allowance for the semi-finishing of the D30 ball end mill is 0.03mm to 0.04mm, which is used to reduce the impact of tool wear on machining accuracy during subsequent finishing and to minimize the tool marks between the sharp edge concave surface and the finishing of the D30 ball end mill.
5. The CNC machining method for sharp edges of automotive exterior body panels according to claim 1, characterized in that, The specific steps of step 2 are as follows: Step 2.1: Machining of sharp edges and concave corners. First, use a D6 ball end mill, according to the preset speed, feed rate, step distance and calculated tolerance, and use a three-dimensional offset strategy and follow the reference line to start the unidirectional spiral milling from the middle of the sharp edge. The machining range exceeds the allowance range of the sharp edge protection surface in Step 1. Step 2.2: Then, using a D1 ball end mill, calculate the tolerance according to the preset high speed, low feed rate, small step distance and high precision, and use the same three-dimensional offset strategy to start the unidirectional helical climb milling from the middle of the sharp edge, and set the arc entry and exit between the step distances. Step 2.3: Simultaneously, the starting trajectory of the D1 ball end mill is layered according to the residual machining amount of the D6 ball end mill and merged into an uninterrupted machining program to prevent overcutting of sharp edges.
6. The CNC machining method for sharp edges of automotive exterior body panels according to claim 5, characterized in that, In step 2.1, the preset parameters for machining the D6 ball end mill are: rotation speed of 10000r / min~11000r / min, feed speed of 4000mm / min~4500mm / min, step distance of 0.2mm, calculated tolerance of 0.005mm, and the machining range exceeds the allowance range of the sharp edge protection surface in step 1 by 2~3mm.
7. The CNC machining method for sharp edges of automotive exterior body panels according to claim 5, characterized in that, In step 2.2, the preset parameters for machining with the D1 ball end mill are: rotational speed of 14000-15000 r / min, feed rate of 2000-2500 mm / min, step distance of 0.05 mm, and calculated tolerance of 0.001 mm; and except for the center trajectory of the Y-shaped edge, a single sharp edge is continuously machined by a single D1 ball end mill, with no tool skipping along the trajectory.
8. The CNC machining method for sharp edges of automotive exterior body panels according to claim 5, characterized in that, In steps 2.1 and 2.2, the reference line for the starting tool path of the concave surface of the sharp edge is obtained by using PowerMILL to perform a single-stroke root clearing calculation path at the part where the included angle between the two sides of the sharp edge is less than 170° to 180° with the same tool allowance and a calculation tolerance of 0.001mm, and generating a reference line from the path; at the part where a path cannot be generated, the intersection line is obtained by offsetting the tool radius plus the machining allowance to the concave side, and used as the reference line.
9. The CNC machining method for sharp edges of automotive exterior body panels according to claim 5, characterized in that, In step 2.3, the layer thickness of the starting trajectory of the D1 ball end mill is 0.005mm. After layering, it is merged with the trajectory generated by the three-dimensional offset strategy into a single uninterrupted machining program to eliminate sharp-edged local groove defects caused by tool heat accumulation effect.
10. The CNC machining method for sharp edges of automotive exterior body panels according to claim 1, characterized in that, The specific steps of step 3 are as follows: For the punch with multiple sharp edges and half edges, the punch is programmed in sections according to the sharp edge machining method. During programming, tangential extension surfaces are made on both sides of the sharp edge so that the machining trajectory is tangentially fed in and out. The trajectory of different areas is rearranged in a unified order by a secondary development tool to ensure that the area with half edges is machined sequentially from one side to the other.