A method and device for processing an inverted conical hole and an aluminum double fork arm knuckle lower swing arm

Abstract

A kind of aluminum double fork arm steering knuckle lower swing arm inverted taper hole processing method and device, adopt drill bit, ball head milling cutter, dovetail milling cutter, single blade reverse scraper, after drilling in closing end, minimum radius allowance is controlled at 0.3mm, ball head milling cutter is according to three-dimensional solid cone spiral side milling wide mouth end, dovetail milling cutter is according to layered way and is carried out semi-finishing and is connected with wide mouth end, after processing, the allowance is controlled as 0.05mm, finally utilize single blade reverse scraper and do finishing, the order is first circle arc feed and retreat tool and do circular interpolation processing, after processing, the allowance is 0.01mm, second circle is also arc feed, after removing the remaining allowance, do third circle arc interpolation finishing tool processing without retreat tool, after processing, arc retreat tool, then tool returns to center position according to the calculation result spindle back direction and is pulled back to finish taper surface, without cutting allowance, simply with finishing tool to finish processing, to reach the purpose of improving surface quality.Thus can replace expensive angle head and realize stable and efficient processing.

Description

Technical Field

[0001] This invention relates to a reverse conical hole machining process, more specifically to a reverse conical hole machining method and apparatus, and also to an aluminum double wishbone steering knuckle lower control arm obtained therefrom. Background Technology

[0002] With the technological advancements in the automotive industry, double wishbone steering knuckles, previously found primarily in high-end vehicles, are increasingly being adopted in mid-range and even low-to-mid-range models, especially in new energy vehicles. The lower control arm of these steering knuckles is often designed with an inverted conical bore structure. Because the tapered end of this structure is closer to the outside of the part while the wide end faces inward, tool interference during machining has always been a major challenge. Previous solutions have primarily involved angle head reversal machining or back-scraping machining. Both solutions have clear advantages and disadvantages: angle head machining meets quality requirements but is too expensive and has a long procurement cycle; back-scraping machining has lower costs and a shorter procurement cycle but is unstable and makes it difficult to ensure stable mass production. Therefore, achieving low-cost, efficient, and stable machining has become an increasingly prominent requirement for the processing of such products. Summary of the Invention

[0003] To address the aforementioned problems, the present invention aims to provide an economical, stable, and efficient method and apparatus for machining inverted conical holes. Thus, by innovatively employing a clever process of "rough machining + semi-finishing with a facing head + reverse scraping and interpolation finishing + reverse pulling and smoothing," low-cost, high-efficiency, and stable machining is achieved.

[0004] According to one aspect of the present invention, a method for machining an inverted conical hole is provided, the inverted conical hole having a constricted end and a wide end, the method comprising the following steps: a roughing step, using a drill bit to rough drill the inverted conical hole from the constricted end; a semi-finishing step, using a ball end mill to semi-finish one side of the wide end and using a dovetail end mill to semi-finish one side of the constricted end, such that the semi-finished areas on these two sides are joined together; and a finishing step, using a single-edged back scraper to perform final finishing from the constricted end.

[0005] According to another aspect of the present invention, a machining apparatus for a conical hole is provided for implementing the above-described machining method for a conical hole, comprising: a roughing unit for rough drilling the conical hole from the concave end using a drill bit; a semi-finishing unit for semi-finishing one side of the conical hole from the wide end using a ball end mill and semi-finishing one side from the concave end using a dovetail end mill, such that the semi-finished areas on both sides are joined together; and a finishing unit for final finishing from the concave end using a single-edged back scraper.

[0006] To achieve the aforementioned objectives, this invention employs a through-hole roughing drill bit, a wide-end semi-finishing ball end mill, a narrow-end semi-finishing dovetail end mill, and a finishing single-edged back scraper to perform machining in a manner of "roughing + semi-finishing + finishing". After rough drilling, the minimum radius allowance (at the tapered end) is controlled at 0.3mm. The wide-mouth end ball end mill is used for three-dimensional conical helical side milling, controlling the minimum allowance of the upper part to 0.05mm. The tapered end dovetail end mill is used for semi-finishing in layers and then joined with the wide-mouth end, controlling the remaining allowance to 0.05mm. Finally, a single-edged backscraper is used for finishing. The sequence is: the first round (or repeat) of circular infeed and retraction for circular interpolation, resulting in a remaining allowance of 0.01mm; the second round of circular infeed to remove the remaining allowance, followed by a third round of circular interpolation finishing without retraction, to remove any remaining high points from the second round; after finishing, the tool retracts in a circular arc, then returns to the center position and is back-pulled in the Z+ direction (spindle retraction direction) to finish the conical surface, with no cutting allowance, using only the full edge for finishing to improve surface quality. This achieves stable and efficient machining by replacing expensive angle heads with inexpensive tools. Attached Figure Description

[0007] Figure 1 A schematic cross-sectional view of the inverted cone hole of the lower control arm of the aluminum double wishbone steering knuckle is shown.

[0008] Figure 2 A schematic diagram of a through-hole roughing drill bit is shown.

[0009] Figure 3 A schematic diagram of a ball end mill with a wide-mouth semi-finishing end is shown.

[0010] Figure 4 A schematic diagram of a dovetail milling cutter for semi-finishing the tapered end is shown.

[0011] Figure 5 A schematic diagram of the structure of a finishing single-edged back scraper is shown.

[0012] Figure 6 , Figure 7 The diagrams schematically show the comparison of the structure before and after machining the inverted conical hole.

[0013] Figure 8 The diagram schematically illustrates the working state of the drill bit during rough machining of a through hole.

[0014] Figure 9 This diagram schematically illustrates the working state of a ball end mill during the semi-finishing of a wide-mouth end.

[0015] Figure 10 The diagram schematically illustrates the working state of the dovetail milling cutter during the semi-finishing of the closing end.

[0016] Figure 11 The diagram schematically illustrates the working state of a single-edged back scraper during finishing.

[0017] Figure 12 A schematic diagram of the configuration of the inverted conical hole machining apparatus according to an embodiment of the present invention is shown. Detailed Implementation

[0018] Exemplary embodiments of the present invention will now be described in detail with reference to the accompanying drawings. The exemplary embodiments described below and illustrated in the drawings are intended to teach the principles of the invention, enabling those skilled in the art to implement and use the invention in various environments and for various applications. Therefore, the scope of protection of the invention is defined by the appended claims, and the exemplary embodiments are not intended, and should not be considered, a limiting description of the scope of protection of the invention. Furthermore, for ease of description, the dimensions of the various parts shown in the drawings are not necessarily drawn to actual scale. The references to orientations or positional relationships shown in the drawings, such as upper and lower halves corresponding to the size of the cone aperture, are merely for the purpose of facilitating the description of the invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the invention. Numerical parameters in this specification and the appended claims may be approximate values ​​and can be varied according to the desired characteristics of the subject matter or the specific application. Moreover, any numerical range stated herein is intended to include all subranges contained therein, and a numerical range expressed as "numerical value A to numerical value B" refers to a range including endpoints numerical values ​​A and B. Those skilled in the art will understand that the terms “S1” to “S7” in the embodiments of the present invention are only used to distinguish different steps, units or modules, and do not represent any specific technical meaning, nor do they indicate the necessary logical order between them.

[0019] The mass production of double wishbone steering knuckles, which are increasingly used in the automotive industry, has long been plagued by high costs and low stability in machining the lower control arm tapered hole. According to this invention, for the lower control arm tapered hole 1 with a constricted end 6 and a wide end 7 (see...),... Figure 1 This invention proposes a novel machining process for a conical hole (also known as a tapered hole or cone hole), comprising the following steps. While the example described here is a tapered hole in the lower control arm of an aluminum double wishbone steering knuckle, the invention is not limited to this and can be applied to the machining of other tapered hole structures, even when not affected by tool interference.

[0020] Step S1: Use a drill bit to rough drill the inverted conical hole from the closing end to remove the cylindrical excess material enclosed by the inner wall of the conical hole.

[0021] As one of the cutting tools used for machining parts, the drill bit can be Figure 2The illustrated through-hole roughing drill bit 2 (also simply called the drill bit). According to the various cutting tools of the invention, a wide-end semi-finishing ball end mill 3 is also included (see...). Figure 3 Also known as ball end mill, semi-finishing dovetail end mill 4 (see Figure 4 Also known as a dovetail milling cutter), finishing single-edge back scraper 5 (see Figure 5 All of these (also known as single-blade back scrapers) can be designed and manufactured according to the size requirements of the drawings of the parts to be processed.

[0022] Here, the diameter of drill bit 2 can be designed according to the size of the tapered end, ensuring that the machining allowance is ≤0.3mm. The main function of this design is to quickly remove the allowance through cutting. More specifically, as... Figure 8 As shown, the inverted conical hole 1 is rough drilled from the constriction end 6 using drill bit 2 to achieve maximum internal cutting. Preferably, the rough drilling speed is 7000-8000 RPM, and the feed linear speed is 0.2-0.26 mm / rev (millimeters per revolution); the minimum radius allowance at the constriction end after rough machining is less than 0.3 mm.

[0023] In step S2, the ball end mill 3 and dovetail end mill 4 are used to continue semi-finishing the tapered hole from opposite ends. This is to minimize and more evenly control the remaining machining allowance of the tapered hole, which helps to ensure a stable machining state for the subsequent finishing single-edge back scraper 5.

[0024] More specifically, such as Figure 9 As shown, a ball end mill 3 is used to perform semi-finishing from one side of the wide end 7 using, for example, a three-dimensional conical spiral toolpath 8, to remove most of the excess material from the upper half of the conical hole. By arranging the shank of the ball end mill 3 at an angle relative to the axis of the conical hole, the ball end portion on the tip side of the shank can easily enter the wide end 7 for milling without interfering with surrounding parts.

[0025] Moreover, such as Figure 10 As shown, a dovetail end mill 4 is used to perform semi-finishing on the lower half of the tapered hole from the constricted end 6 side using, for example, a layered interpolation toolpath 9. This removes most of the excess material from the lower half and achieves alignment with the semi-finishing performed on the wide end 7 side, a process known as "joint" semi-finishing. Preferably, during semi-finishing, the ball end mill 3 or dovetail end mill 4 operates at a speed of 2000–3000 RPM and a feed rate of 0.15–0.2 mm / rev; the minimum allowance after joint semi-finishing is less than 0.05 mm. Here, "joint" is not limited to the alignment of the two tool working areas; it can also involve multiple tools, as long as their respective semi-finishing areas can be appropriately aligned.

[0026] Here, using two cutting tools to machine the entire conical surface instead of a single dovetail tool can avoid the phenomenon that the rigidity is weak due to the large length-to-diameter ratio of the tool, which leads to the instability of the semi-finishing allowance. Furthermore, by using a ball-end tool to machine the conical spiral, the maximum machining residual height can be achieved, thus enabling precise and stable control of the machining allowance (0.05mm).

[0027] Here, the structure of each tool can be designed according to the size of the tapered hole to ensure that they can cooperate with each other to completely cover the tapered surface and have sufficient rigidity to meet the requirements of rapid machining. The main function of this design is to ensure the accuracy and stability of the finishing allowance by setting the tool path (the three-dimensional tapered helical tool path 8 from the wide end side of the ball end mill 3 and the layered interpolation tool path 9 from the narrow end side of the dovetail end mill 4).

[0028] Step S3: Use a precision single-edged back scraper to perform final finishing on the inverted conical hole in a predetermined manner.

[0029] More specifically, such as Figure 11 As shown, a finishing single-edged back scraper 5 is used to perform final finishing from the converging end 6. Preferably, the finishing speed is 2000-3000 RPM, and the feed rate is 0.1-0.15 mm / rev. The finishing is performed after the aforementioned semi-finishing, removing the remaining allowance in three layers, and finally adding a Z+ direction (spindle retraction direction) back scraper to meet dimensional accuracy and surface coloring requirements. That is, the tool enters from the converging end 6 to process the entire tapered hole, which presents a tool deflection problem. Therefore, the design uses a single-edged back scraper with three interpolations plus one Z+ direction back scraping to control the tool deflection effect. For example, the remaining 0.05 mm allowance can be removed by two circular interpolations, the high point of the previous interpolation can be removed by the third circular interpolation, and finally, a Z+ direction (spindle retraction direction) full-edge back scraping is performed.

[0030] Thus, in the finishing single-edge back scraper tool path, a reverse-pull finishing tool consisting of 3 circular interpolations and 1 Z+ direction (spindle retraction direction) is used. The specific steps are: S4, the first circular interpolation removes 0.04mm of the allowance (0.01mm remaining), which removes most of the allowance to ensure the subsequent machining allowance and reduces the cutting force of the subsequent machining, thus weakening the machining deflection; S5, the second circular interpolation removes 0.01mm of the allowance (0mm remaining), which is used to stably complete the final machining with a smaller cutting force. S6, the third circular interpolation cycle does not remove excess material in the program design; it repeats the path of the second cycle. Its purpose is to cut away any excess material that was not completely removed due to tool retraction, minimizing the amount of excess material removed. S7, after completing the circular interpolation, the tool's rotation axis retracts to the taper hole axis position. According to the dimensional calculations, a Z+ direction (spindle retraction direction) reverse scraping and finishing cut is performed. In the program design, this also does not remove excess material; its purpose is to use the cutting edge to remove high points during the circular interpolation cutting process, thereby achieving a smooth taper surface. Each circular interpolation entry and exit is a tangential circular arc entry and exit, avoiding the drastic changes in cutting force caused by vector direction cutting, which could lead to vibration and affect the taper surface quality.

[0031] In this way, the tool structure can be designed according to the taper hole size, so that it has maximum rigidity while meeting the structural dimensions, reducing tool deflection, and combined with the tool path designed in this patent, the goal of meeting the drawing requirements can be achieved.

[0032] Technical Effects: According to the processing scheme of the present invention, a through-hole roughing drill bit, a wide-end semi-finishing ball end mill, a narrow-end semi-finishing dovetail end mill, and a finishing single-edged back scraper can be designed and manufactured according to the dimensional requirements of the part drawing. The through-hole roughing drill bit is used to rough drill the lower swing arm tapered hole from the narrow end. The ball end mill is used to perform semi-finishing from the wide end side to remove most of the excess material in the upper half of the tapered hole. The dovetail end mill is used to perform semi-finishing from the narrow end to the lower half of the tapered hole, and then docks with the wide end semi-finishing to remove most of the excess material in the lower half. Finally, the single-edged back scraper is used for final finishing from the narrow end.

[0033] Furthermore, machining parameters can be adjusted according to actual cutting conditions, and the tool structure can be arbitrarily adjusted according to the size of the tapered hole, making it widely applicable. Therefore, according to the process scheme of this invention, the main function of roughing is to quickly remove excess material and achieve high-efficiency machining; the main function of semi-finishing is to control the stability of the finishing allowance; and the design of the finishing stage focuses on improving the surface finish. This method ensures product quality while avoiding the high-cost, long-cycle machining methods using angled heads, achieving a win-win situation for both quality and efficiency.

[0034] More specifically, in order to solve the typical problem of low machining efficiency and surface quality that cannot meet product requirements due to the limitation of tool rigidity causing vibration during the machining process, the following machining scheme is designed: After rough drilling, the minimum radius allowance (end 6) is controlled below 0.3mm; the ball end mill 3 performs three-dimensional conical helical side milling on the wide end, controlling the minimum allowance of the upper part below 0.05mm; the dovetail end mill 4 performs semi-finishing on the end in layers and connects it with the wide end 7; the machined end mill... The allowance is controlled to be below 0.05mm. Finally, a single-edged back scraper 5 is used for finishing. The sequence is as follows: the first circle is a circular infeed and retraction for circular interpolation machining. After machining, the allowance is below 0.01mm. The second circle is a circular infeed to remove the remaining allowance. Then, without retraction, the third circle is a circular interpolation finishing to remove the high points left over from the first circle. After machining, the tool is retracted in a circular arc. Then, the tool returns to the center position and the Z+ direction is reverse-pulled to finish the conical surface according to the calculation results. There is no cutting allowance. It is a simple finishing process to improve the surface quality.

[0035] Figure 9 This is a schematic diagram of the structure of an inverted conical hole processing device provided in an exemplary embodiment of the present invention. Figure 4 As shown, it includes:

[0036] Rough machining unit: Use a drill bit to rough drill the tapered hole from the concave end;

[0037] Semi-finishing unit: The ball end mill 3 is used to perform semi-finishing on one side of the inverted conical hole from the wide end 7 side, and the dovetail end mill 4 is used to perform semi-finishing on the other side from the narrow end 6 side, so that the semi-finished areas on one side are connected with the semi-finished areas on the other side.

[0038] Finishing unit: The final finishing is performed from the closing end using a single-edged reverse scraper.

[0039] The inverted conical hole machining apparatus according to the present invention can advantageously avoid interference during conical hole machining, and is particularly suitable for spindle anti-interference design in the field of machining center manufacturing technology.

[0040] For those skilled in the art, the specific meanings of the terms used in this application will be understood according to the specific circumstances. Although the invention has been described with reference to various specific embodiments, it should be understood that modifications can be made within the spirit and scope of the described inventive concept. Therefore, it is intended that the invention be limited to the described embodiments but will have the full scope defined by the language of the appended claims.

Claims

1. A method of machining a reverse taper hole having a closed end (6) and a wide open end (7), the method comprising the steps of: In the roughing step, a rough drill is performed from the closed end using a drill bit (2); In the semi-finishing step, a ball end mill (3) is used to semi-finish one side of the wide end (7), and a dovetail end mill (4) is used to semi-finish one side of the narrow end (6), so that the semi-finished areas on both sides are joined together; in the finishing step, a single-edged back scraper (5) is used to finish the tapered hole from the narrow end. In the semi-finishing step, the ball end mill (3) is used to perform semi-finishing from the wide end (7) side with a three-dimensional conical spiral toolpath (8); the shank of the ball end mill (3) is arranged at an angle relative to the axis of the conical hole, so that the ball end portion on the top side of the shank enters the wide end (7) for milling; the dovetail end mill (4) is used to perform semi-finishing from the narrow end (6) side with a layered interpolation toolpath (9); the rotational speed of the ball end mill (3) or the dovetail end mill (4) is 2000-3000 RPM, the feed is 0.15-0.2 mm / rev, and the minimum allowance after the semi-finishing area is less than 0.05 mm.

2. The method of claim 1, wherein The inverted conical hole is the lower control arm inverted conical hole of the aluminum double wishbone steering knuckle.

3. The method of claim 1 or 2, wherein The diameter of the drill bit (2) is determined by ensuring that the minimum radius allowance at the closing end after the roughing step is ≤0.3mm; and / or, in the roughing step, the drilling speed is 7000~8000RPM and the feed linear speed is 0.2~0.26mm / rev.

4. The method of claim 1 or 2, wherein In the finishing step, the remaining material after the semi-finishing step is removed in three layers, and finally a Z+ direction reverse scraper is added, where Z+ direction indicates the spindle retraction direction; and / or, in the finishing step, the rotational speed of the single-edged reverse scraper (5) is 2000-3000 RPM, and the feed linear speed is 0.1-0.15 mm / rev.

5. The method of claim 4, wherein The remaining 0.05mm after the semi-finishing step is removed by two circular interpolations. The high point of the previous interpolation is removed by a third circular interpolation. Finally, the Z+ direction is used for back scraping. The infeed and retraction of each circular interpolation are circular arc cuts in and out in the tangential direction.

6. The method of claim 5, wherein The finishing process also includes the following steps: the first circular interpolation removes 0.04mm of excess material, leaving 0.01mm of excess material; the second circular interpolation removes 0.01mm of excess material; the third circular interpolation repeats the second path; after the third circular interpolation is completed, the rotation axis of the single-edged back scraper returns to the position of the tapered hole axis, and the Z+ direction back scraping and finishing are calculated according to the dimensions.

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