High-speed plunge milling method for curved quenched edge

Abstract

The present application relates to a kind of curved quenching edge high-speed plunge milling processing method, including fire after profile rough machining: using end mill to carry out rough machining to quenching profile, to process away the quenching surface layer of highest hardness, most consumed tool;Using end mill adopts radial layered mode, to the profile of quenching black skin surface layer that is processed away, carry out a large amount of machining;Adopting contour or top-down one-way plunge milling, with ball cutter swing angle processing mode, carry out rough machining to the steep region of quenching profile;Using superhard tool, to the gentle profile region after rough machining, carry out semi-finishing;Fire after profile using mirror surface milling cutter carries out bidirectional plunge milling finishing.The present application uses mirror surface milling cutter plunge milling processing to replace end mill side milling, improves traditional quenching profile processing method;Mirror surface milling cutter is applied to profile processing, creates high-speed plunge milling and improves profile processing mode;Quenching after profile processing is divided into three stages, quenching after profile rough machining, second stage and quenching profile finishing.

Description

Technical Field

[0001] This invention belongs to the field of cold stamping trimming die technology, specifically relating to a high-speed milling method for curved surface quenching cutting edge. Background Technology

[0002] Currently, contour trimming followed by quenching is the primary machining method for cold stamping trimming dies. As a relatively mature machining method in the industry, the traditional approach to contour machining involves using a roller mill with its side edge for integral cutting. However, after years of experience, the problems associated with this method have become increasingly apparent. In particular, the increasing demands for automation in manufacturing processes, the precision requirements of presses, and the evolving surface quality requirements of customers have rendered traditional machining methods inadequate.

[0003] Currently, the main body materials for cold-stamping and trimming contours are mostly 7Cr and Cr12, using high-frequency quenching and solid quenching methods. After quenching, the machining tools are solid carbide end mills and superhard end mills, with the machining method being a single cut using the side edge of the end mill. For machining steep areas and deep contours, end mills are insufficient; these are achieved using swivel ball end mills. Existing technology has the following problems: 1. High operator involvement and low labor productivity; 2. High CNC machining and tooling costs; 3. Poor contour accuracy and surface quality, with indentations and tool marks; 4. Large amount of contour refining required; 5. Tool connection issues in swivel ball end milling. Summary of the Invention

[0004] The purpose of this invention is to provide a novel high-speed plunge milling method for curved surface hardening cutting edge machining after contour hardening, so as to solve the problems of contour accuracy, surface quality and high cost.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A high-speed plunge milling method for machining curved, hardened cutting edges includes the following steps:

[0007] A. Rough machining of the outline after firing

[0008] A1. Use an end mill to rough machine the quenched contour to remove the hardest and most tool-consuming quenched surface layer.

[0009] A2. Use an end mill to remove a large amount of the hardened black skin layer from the contour. Use the radial layering method of the end mill to remove a large amount of the hardened contour.

[0010] A3. Rough machining of steep areas of the quenched contour: use equal height or top-down unidirectional plunge milling, and use ball end mills with swivel angle machining method for rough machining.

[0011] B. Post-fired contour semi-finishing

[0012] Using a superhard cutting tool, semi-finishing is performed on the smooth contour area after roughing to ensure that the finishing milling is qualified in one go.

[0013] C. Post-fire contour finishing

[0014] Using a mirror milling cutter for bidirectional plunge milling finish machining ensures that the contour of the cold stamping trimming die for automotive body panels is completed on a vertical spindle.

[0015] Further, in step A1, the end mill may be a used cutting tool.

[0016] Further, in step A2, use a D20 or D16 end mill.

[0017] Further, in step A3, use a D30 ball end mill or a D30 mirror end mill.

[0018] Furthermore, the roughing parameters of the 30 mirror end mill are as follows: allowance 0.08mm, step distance 1mm, speed 3000, feed 3000.

[0019] Further, in step B, use an ultrahard tool that has been used with a D20 or D16.

[0020] Furthermore, in step B, the finishing allowance is between 0.02 and 0.08 mm.

[0021] Further, in step C, use a D30 mirror end mill to extend 120 or 150.

[0022] Further, in step C, the machining parameters are as follows: allowance -0.01mm, step distance 0.5mm, speed 4000, feed 4000, and calculated tolerance 0.01mm.

[0023] Furthermore, the finishing allowance of -0.01mm is taken as the midpoint between the contour machining tolerance of 0 and -0.02mm.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] 1. This invention improves the traditional quenching contour machining method by using mirror milling cutters for plunge milling instead of end mills for side milling;

[0026] 2. Machining Method: Apply mirror milling cutters to contour machining, create high-speed plunge milling, and improve contour machining methods;

[0027] 3. The contour machining after quenching in this invention is divided into three stages. The first stage is rough machining of the contour after quenching, which removes a large amount of the contour and retains a small amount of allowance. The second stage is semi-finishing of the quenched contour to ensure that the finishing allowance is uniform. The third stage is finishing of the quenched contour by insert milling.

[0028] 4. In this invention, the roughing and semi-finishing of the contour in the gentle area (height difference ≤ 90) is completed by using the side edge of the end mill; the roughing and semi-finishing of the contour in the steep area (height difference > 90) is completed entirely by using ball end mills or mirror milling cutters with equal height and plunge milling strategies, ensuring that all contour machining is completed by the vertical spindle of the CNC equipment, replacing the original method of machining the steep contour of the vertical spindle by tilting the angle, and eliminating tool marks. Attached Figure Description

[0029] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 A schematic diagram illustrating the problem of machining a hardened profile with an existing end mill.

[0031] Figure 2 Ball end mill with swing angle machining of steep contours;

[0032] Figure 3 The flowchart of the high-speed plunge milling method for curved surface hardening cutting edge of the present invention. Detailed Implementation

[0033] The present invention will be further described below with reference to embodiments:

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0035] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, in the description of this invention, terms such as "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0036] Currently, the existing tools for cold stamping and trimming contours, and machining after quenching, are solid carbide end mills and superhard end mills. The machining method is a one-cut operation using the side edge of the end mill, which has the following problems: 1. The accuracy of the end mill is greatly affected by wear; 2. The machining method is unreasonable; 3. The machining process is unreasonable.

[0037] To address issue 1, the types and methods of tool usage can be improved to completely eliminate the adverse effects of tool wear on machining and reduce tool costs. Since solid carbide tools are expensive, and once a tool chipps or is damaged and cannot be used, insert-type tool bodies can be considered as a replacement, with the side and bottom cutting edges used separately to reduce tool costs.

[0038] Specifically, this invention applies mirror end mills to the machining of hardened cutting edges. A new type of tool is used, and a laser tool measuring instrument is employed to detect the dimensions and cutting edge length of the new mirror end mill. Based on the actual tool dimensions and standard cutting parameters, a standard tool is created in the programming software for programming simulation. On-site cutting experiments are conducted using this tool. The wear effect of the new mirror end mill is far less than that of an end mill. After multiple rounds of cutting tests, the back chamfer angle and straight edge length of the cutting edge are designed to make it more suitable for machining hardened parts.

[0039] To address problem 2, a new toolpath template can be developed to eliminate surface quality defects such as tool marks. Transverse tool marks on the cutting edge surface have the greatest impact on coloring and mold closing, and are difficult to eliminate, requiring a significant increase in the amount of preparation work. This necessitates the development of new machining methods in conjunction with new cutting tools.

[0040] Specifically, the machining direction designed in this invention is consistent with the stamping direction, which can effectively avoid transverse tool marks left after cutting. This invention develops a special tool for contour milling, realizing high-speed contour milling.

[0041] To address problem 3, this invention achieves automated processing by refining the machining process. An experimental plan was developed, and by exploring different materials and process allowances, the first-pass yield was effectively improved while ensuring the surface quality of the cutting edge.

[0042] Specifically, an experimental plan was first developed, as shown in Table 1. The process of semi-finishing with a D20 alloy cutter (0.05mm margin) and finishing with a D16 superhard cutter (0mm margin) was adjusted to semi-finishing with a D20 alloy cutter (0.05mm margin) and finishing with a D20 superhard cutter (0mm margin) and finishing with a D30 Daijie mirror milling cutter (0mm margin).

[0043] Table 1

[0044]

[0045]

[0046] Before using the new process to finish the cutting edge contour, this invention adds a semi-finishing step to eliminate the residual allowance caused by the semi-finishing tool deflection, ensuring good results in the plunge milling finishing and high surface finish of the cutting edge. At the same time, it eliminates human intervention and achieves automation.

[0047] This invention relates to a high-speed plunge milling method for curved surface hardening cutting edges, used for roughing or semi-finishing, with bidirectional plunge milling for finishing. The machining method includes edge trimming after hardening and the application of mirror milling cutters to curved surface hardening cutting edges. It features a high-speed plunge milling cutting edge, eliminating the need for wobble angle machining on steep cutting edges, thus eliminating tool marks and automating cutting edge machining. This reduces or minimizes the need for cutting edge fitting, improves the surface quality and precision of the cutting edge, and achieves cost reduction and efficiency improvement in machining and fitting.

[0048] This invention involves three stages for contour machining after quenching. The first stage is rough machining of the quenched contour, removing a large amount of material and retaining a small allowance. The second stage is semi-finishing of the quenched contour, ensuring uniform finishing allowance. The third stage is finishing of the quenched contour, using plunge milling. In this invention, the roughing and semi-finishing of contours in gentle areas (height difference ≤ 90°) are completed using the side edge of an end mill; the roughing and semi-finishing of contours in steep areas (height difference > 90°) are completed entirely using ball end mills or mirror milling cutters with equal height and plunge milling strategies. This ensures that all contour machining is completed by a vertical spindle on a CNC machine, replacing the original method of machining steep contours using a tilting angle, and eliminating tool marks.

[0049] Specifically, the method includes the following steps:

[0050] A. Rough machining of the outline after firing

[0051] A1. Using an end mill, you can perform rough machining on the hardened contour using a previously used tool. The purpose is to remove the hardened surface layer, which has the highest hardness and consumes the most tool.

[0052] A2. Use an end mill to remove a large amount of the hardened black skin from the contour. Employ a radial layering machining strategy with the end mill, often using D20 or D16 cutters, to remove a significant amount of the hardened contour.

[0053] A3. Rough machining of steep areas of the quenched contour is performed using a D30 ball end mill or a D30 mirror end mill, employing a unidirectional plunge milling strategy either at the same height or from top to bottom. The aim is to replace the previous method of using a ball end mill with a swivel angle for machining areas that could not be machined with an end mill. After repeated trial cuts and tests, the rough plunge milling parameters for the D30 mirror end mill are as follows: allowance 0.08mm, step distance 1mm, spindle speed 3000 rpm, feed rate 3000 rpm.

[0054] B. Post-fired contour semi-finishing

[0055] Using superhard cutting tools, especially those previously used with D20 or D16, semi-finishing is performed on the gently contoured areas after roughing. The aim is to ensure that the finishing allowance is between 0.02 and 0.08 mm, guaranteeing that the finishing milling pass in one go.

[0056] C. Post-fire contour finishing

[0057] Using a D30 mirror end mill with a 120 or 150mm extension is sufficient to ensure the vertical spindle machining of the cold-stamping trimming die contour for automotive body panels. The machining strategy employed is two-way plunge milling for finishing, with the following parameters: allowance -0.01mm, stepover 0.5mm, spindle speed 4000 rpm, feed rate 4000 rpm, and calculated tolerance 0.01mm. The finishing allowance of -0.01mm is taken as the midpoint between the contour machining tolerance of 0 and -0.02mm.

[0058] Compared with existing technologies, this method has the following advantages:

[0059] 1. The surface quality of the cutting edge is significantly improved after processing. Using existing methods, the cutting edge surface suffers from problems such as tool marks, poor smoothness, and poor perpendicularity, with a pass rate of only 28%. However, this method can effectively eliminate tool marks, resulting in a very good cutting edge surface quality and a pass rate of up to 98.48%.

[0060] 2. Regarding the pass rate of cutting edge machining: Using existing methods, the pass rate is low, requiring multiple rounds of rework. However, this method can achieve a pass rate in one pass, eliminating the need for precision rework.

[0061] 3. Regarding the amount of cutting edge grinding: Using the existing method, the amount of work for a fitter to grind the cutting edge is 8 to 40 hours; while using this method, the fitter does not need to grind the large surface of the cutting edge, and can directly press the cutting edge after grinding the R angle.

[0062] 4. Human-machine interaction: Existing methods involve manual control of the cutting edge, resulting in high labor costs. This method achieves 100% automated cutting edge machining after heating, with UG online inspection, which can improve labor productivity and reduce labor costs.

[0063] 5. Tooling costs: In existing methods, the cutting edge is entirely machined with a cutting tool after firing, resulting in high tooling costs. This method uses precision machining of the cutting inserts, allowing the old cutting edges to be reused, thus improving tool life and extending its lifespan.

[0064] This invention shortens the width of the finishing cutting edge by adding an upper die trimming insert and a hollow cutting edge, reducing it from 30-40mm to 15-25mm. This reduces processing time by 26%, saving an average of 21 hours of CNC machining time per month, resulting in savings of 280,000 yuan in rework costs and 100,000 yuan in processing costs. The workload of grinding and fitting the cutting edge is reduced from 1-4 shifts in the assembly cycle to no longer requiring grinding or fitting on large surfaces, where only a polishing coat is needed. This saves fitters an average of over 20,000 yuan per month. This method achieves 100% automation of the cutting edge, a 98% pass rate, and total cost savings of 620,000 yuan.

[0065] Example 1

[0066] A high-speed plunge milling method for machining curved surfaces with hardened cutting edges is proposed. For the contours in gentle areas (height difference ≤ 90°), roughing and semi-finishing are completed using the side edge of an end mill; for the contours in steep areas (height difference > 90°), roughing and semi-finishing are entirely done using ball end mills. This ensures that all contour machining is completed by the vertical spindle of a CNC machine, replacing the original method of machining steep contours using a tilting cutter and eliminating tool marks. The specific steps include:

[0067] 1. Rough machining of the contour after firing

[0068] 11. Use an end mill to rough machine the quenched contour to remove the hardest and most tool-consuming quenched surface layer.

[0069] 12. Use an end mill to remove a large amount of the hardened black skin layer from the contour. Use a D20 end mill and employ a radial layering machining method to remove a large amount of the hardened contour.

[0070] 13. Rough machining of steep areas of the quenched contour is performed using a D30 ball end mill, employing a constant height or top-down unidirectional plunge milling method with ball end mill tilting. After repeated trial cuts and tests, the roughing parameters for the D30 mirror end mill are as follows: allowance 0.08mm, step distance 1mm, spindle speed 3000, feed rate 3000.

[0071] 2. Post-fired semi-finishing of contours

[0072] The purpose of using a superhard D20 milling cutter to perform semi-finishing on the smooth contour area after roughing is to ensure that the finishing allowance is between 0.02 and 0.08 mm, so as to guarantee that the finishing milling is qualified in one go.

[0073] 3. Post-fired contour finishing

[0074] Using a D30 mirror milling cutter with a 120 or 150mm extension, ensure the vertical spindle machining of the cold-stamping trimming die contour for automotive body panels is completed. Double-sided plunge milling is employed for finishing, with the following parameters: allowance -0.01mm, stepover 0.5mm, spindle speed 4000 rpm, feed rate 4000 rpm, calculated tolerance 0.01mm. The finishing allowance of -0.01mm is taken as the midpoint between the contour machining tolerance of 0 and -0.02mm.

[0075] Note that the above description is merely a preferred embodiment of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and various obvious changes, readjustments, and substitutions can be made without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments, and may include many other equivalent embodiments without departing from the concept of the present invention, the scope of which is determined by the scope of the appended claims.

Claims

1. A high-speed plunge milling method for machining curved surface hardened cutting edges, characterized in that, Includes the following steps: A. Rough machining of the outline after firing A1. Use an end mill to rough machine the quenched contour to remove the hardest and most tool-consuming quenched surface layer. A2. Use an end mill to remove a large amount of the hardened black skin layer from the contour. Use the radial layering method of the end mill to remove a large amount of the hardened contour. A3. Rough machining of steep areas of the quenched contour: Use a D30 ball end mill or a D30 mirror end mill, employing equal-height or top-down unidirectional plunge milling. The purpose is to replace the original end mill method of machining with a ball end mill at an angle, which is not possible with end mills. B. Post-fired contour semi-finishing Using an ultra-hard tool, semi-finishing is performed on the smooth contour area after roughing to ensure that the finishing milling is qualified in one go. C. Post-fire contour finishing Using a mirror milling cutter for bidirectional plunge milling finish machining ensures that the contour of the cold stamping trimming die for automotive body panels is completed on a vertical spindle.

2. The method for high-speed plunge milling of curved surface hardened cutting edges according to claim 1, characterized in that: Step A1, the end mill is a used tool.

3. The method for high-speed plunge milling of curved surface hardened cutting edges according to claim 1, characterized in that: Step A2: Use a D20 or D16 end mill.

4. The high-speed plunge milling method for curved surface hardening cutting edge according to claim 1, characterized in that: Step B: Use a D20 or D16 superhard tool, which is a used superhard tool.

5. The method for high-speed plunge milling of curved surface hardened cutting edges according to claim 1, characterized in that: Step B, the finishing allowance is between 0.02 and 0.08 mm.

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