An automated method of milling a tapered bore

Abstract

The present application relates to numerical control machining technical field, especially a kind of automatic milling method of taper hole, comprising the following steps: part clamping on numerical control machining equipment, establish processing coordinate system, use conventional milling method to process part to position;According to the structural characteristics of the taper hole of part and the tool parameters selected, adopt helix method to prepare processing program, form characteristic semi-finishing tool path;Part is semi-finished, and the error value between the theoretical taper surface of taper hole after semi-finishing and actual taper surface is obtained by probe detection, and the processing direction compensation value of taper hole is calculated;According to the compensation value, the processing origin or tool length value is corrected, and finishing is carried out, and the size of taper hole is processed to position.The method compared with the conventional processing mode of this kind of feature, in-depth detailed description and error compensation are carried out for trajectory preparation, parameter selection, and theoretical formula is provided to guide engineering application, which effectively improves the processing quality and efficiency of high-precision taper hole.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of numerical control machining, in particular to an automatic milling method for a tapered hole. BACKGROUND

[0002] With the development of aviation technology, the requirements for new generation of aviation equipment are getting higher and higher. In order to reduce the weight of the aircraft and enhance the structural strength, titanium alloy hanging joint support, titanium alloy special-shaped beam and other composite and integral aircraft structural parts begin to be widely used. The tapered holes of such parts are usually paired and form a precise conical fit with a tapered pin with a PTFE composite liner lubricating layer. The fit has the characteristics of contact self-centering, adjustable fit, easy disassembly, air-tight fit and self-locking fit.

[0003] Currently, engineering and technical personnel mainly focus on part clamping, machining methods and measurement in the research of machining process for the tapered hole feature of titanium alloy parts. In the field of aviation structural parts, the tapered hole feature is usually machined by boring. This process can fully guarantee the accuracy of the tapered hole, such as patent CN202010694453B. However, this method uses boring to process, which requires the use of special equipment with a flat spindle or U-axis cutter for machining. The machining process of the tapered hole and the lug is generally separated. In order to ensure their coordination, special fixtures need to be designed for part clamping and positioning. Although the accuracy is high, it requires a certain cost and increases the process flow. Whether the machining link can efficiently and accurately machine the tapered hole greatly affects the production and assembly of such beams and joint parts, and then affects the assembly structure of the whole machine. Therefore, an automatic milling method for a tapered hole is proposed to ensure that the feature can be formed in the same process as the remaining assembly structure features, which has considerable engineering practical significance. SUMMARY

[0004] To solve the above technical problems, the present application provides an automatic milling method for a tapered hole, which can effectively solve the problem of machining the tapered hole and improve the machining quality and efficiency.

[0005] In order to achieve the above application purpose, the technical scheme provided by the present application is as follows:

[0006] An automatic milling method for a tapered hole, comprising the following steps:

[0007] Step (1). The part is clamped on the numerical control machining equipment, the machining coordinate system is established, and the traditional milling method is used to process the rib top, web, inner and outer shape, lug and tapered cylindrical surface of the part to the right position;

[0008] Step (2). According to the structural characteristics of the tapered hole of the part and the selected tool parameters, the structural characteristics include the taper hole taper half angle α, the tool nose radius r, the spiral line method is used to compile the machining program, the machining parameters are calculated, and the characteristic semi-finishing tool path is formed;

[0009] Step (3). The part is semi-finished, and the error value δ between the theoretical taper surface and the actual taper surface of the tapered hole after semi-finishing is obtained by probe detection, and the machining direction compensation value Δ1 of the tapered hole is calculated by combining the theoretical allowance τ left in the machining direction of the tapered hole taper surface during semi-finishing;

[0010] Step (4). According to the compensation value Δ1, the machining origin or tool length value is corrected, and finishing is carried out, and the tapered hole size is machined in place.

[0011] Further, the part in step (1) is a metal part, including aluminum alloy and titanium alloy, and the tapered hole structure is located on the high lug structure of the part, which is a through hole structure as a whole.

[0012] Further, the numerical control machining equipment in step (1) can be installed and used with a measuring probe to meet the processing requirements of vertical and horizontal conversion.

[0013] Further, the spiral line method in step (2) is suitable for calculating the tool path of regular revolved surface, and the tool path contact point moves spirally along the machined surface. The distance of the tool contact point along the axial direction per revolution is called the pitch, which is represented by the pitch s.

[0014] Further, the spiral line method in step (2) is used to calculate the corresponding spiral line pitch s. When using a ball end mill to cut a tapered hole with a point contact trajectory, the residual area height R max To meet the requirements of the project drawing, the following relationship can be obtained

[0015]

[0016] The transformation formula can be obtained as follows:

[0017]

[0018] Where R max The order of magnitude is specified by the engineering project drawing, and the R max of the relevant features of the machined part shall not exceed the specified value, and the threshold value of the spiral line pitch s is calculated accordingly.

[0019] Further, the machining parameters in step (2) include cutting pitch s (mm), cutting line speed V C (m / min), feed per tooth F z (mm / z), and cutting width A e(mm) four aspects, three machining parameters except the cutting pitch s, the relevant calculation formula is given according to engineering experience, wherein the cutting line speed V C (m / min) is selected according to the following basis:

[0020] V C = n1*n2*n3*n4*80

[0021] The feed per tooth F z (mm / z) is selected according to the following basis:

[0022]

[0023] The cutting width A e (mm) is selected according to the following basis:

[0024] A e ≤0.1

[0025] Wherein, n1 is the machining material correction coefficient, n2 is the part structure correction coefficient, n3 is the tool diameter correction coefficient, and n4 is the tool length-diameter ratio correction coefficient. If the milling tool diameter is D C (mm), the tool working length is L C (mm), the correction coefficient selection table is given according to engineering experience.

[0026] Further, the error value δ of the step (3) is the difference between the theoretical conical surface after semi-finishing and the actual conical surface, which is used to reflect the error between the machined feature and the theory under the actual state of the equipment, and the value is obtained by comparing the difference between the probe measurement result and the theoretical value. Combined with the theoretical allowance τ left in the machining direction of the conical hole conical surface during semi-finishing, the error value δ can be converted to the machining direction of the conical hole, and the compensation value Δ1

[0027]

[0028] Finally, the value is compensated to the machining direction of the conical hole, and the machining origin or tool length value is corrected.

[0029] The beneficial effects of the present application are:

[0030] 1. The method provides a scientific and simple automatic milling method for taper hole, compared with the conventional processing method of such features, the traditional boring of taper hole is changed to automatic milling, and the reference transformation error and tooling manufacturing cost caused by process flow are reduced.

[0031] 2. During machining, the probe measures the semi-finished state to compensate for errors, which eliminates the machining errors caused by tool state, equipment precision, temperature and humidity changes and other environmental changes, and ensures the accuracy of the machining size.

[0032] 3. The automatic milling method of the taper hole is researched deeply, and the formulaic theory is provided, which provides certain theory basis for the processing and research of similar structure. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The assembly schematic view of the taper hole of the automatic milling method of the taper hole.

[0034] Figure 2 The structure illustration of the taper hole in the automatic milling method of the taper hole.

[0035] In the figure, α - taper hole taper half angle.

[0036] Figure 3 The process scheme flow chart in the automatic milling method of the taper hole.

[0037] Figure 4 The spiral line trajectory schematic view in the automatic milling method of the taper hole.

[0038] Figure 5 The row cutting residual height schematic view in the automatic milling method of the taper hole.

[0039] Figure 6 For Figure 5 The enlarged view of A area in the middle.

[0040] In the figure, R max The residual area height formed by processing,

[0041] S - spiral line pitch,

[0042] R - tool tip arc radius,

[0043] α - taper hole taper half angle.

[0044] Figure 7 The measurement error compensation schematic view in the automatic milling method of the taper hole.

[0045] Figure 8 For Figure 7 The enlarged view of A area in the middle.

[0046] In the figure, δ - the difference between the theoretical taper surface and the actual taper surface after semi-finishing,

[0047] Δ1 - the value of correcting the processing origin or tool length value according to the measurement error,

[0048] α - taper hole taper half angle,

[0049] τ - the theoretical allowance of the taper hole taper surface in the processing direction during semi-finishing.

[0050] Figure 9 The correction coefficient selection table of the machining parameters in the automatic milling method of the taper hole described in the present application.

[0051] In the figure, n1—machining material correction coefficient,

[0052] n2—part structure correction coefficient,

[0053] n3—tool diameter correction coefficient,

[0054] n4—tool length-diameter ratio correction coefficient,

[0055] D C —milling tool diameter,

[0056] L C —tool working length. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are for explaining the present application but not limiting the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0058] The specific implementation method of the present application will be described below in combination with the drawings and examples, and the present application is not limited to the embodiments.

[0059] Embodiment 1

[0060] An automatic milling method of a taper hole, comprising the following steps:

[0061] Step (1). The part is clamped on a numerical control machining equipment, a machining coordinate system is established, and the part is processed to the position by using a traditional milling method for rib top, web, inner and outer shape, ear piece, taper hole cylindrical surface and other features;

[0062] Step (2). According to the structural features of the taper hole of the part and the selected tool parameters, the structural features include taper hole taper half angle α, tool tip arc radius r, etc., a spiral line method is used to compile a machining program, main machining parameters are calculated, and a feature semi-finishing tool path is formed;

[0063] Step (3). The part is semi-finished, and the error value δ between the theoretical taper surface and the actual taper surface of the taper hole after semi-finishing is obtained by using a probe to detect, and the machining direction compensation value Δ1 of the taper hole is calculated by combining the theoretical allowance τ left in the machining direction of the taper hole during semi-finishing;

[0064] Step (4). According to the compensation value Δ1, the machining origin or tool length value is corrected, and the fine machining is carried out, and the size of the tapered hole is machined in place.

[0065] Further, the part in step (1) is a metal part, including aluminum alloy and titanium alloy, and the tapered hole structure is as shown in Figure 1 、 2 located on the high ear structure of the part, and the whole presents a through hole structure.

[0066] Further, the numerical control machining equipment in step (1) can be installed and used with a measuring probe to meet the processing of vertical and horizontal conversion.

[0067] Further, the helix method in step (2) is suitable for calculating the tool path of regular revolution surface, and the tool path contact point moves along the machined surface in a spiral motion, as shown in Figure 4 . The distance of the tool contact point along the axial motion per revolution is called the lead, which is represented by the pitch s.

[0068] Further, the helix method in step (2) is used to calculate the corresponding helix pitch s, and when the end milling cutter point contact trajectory is used to cut the tapered hole, the residual area height R max formed by the nose radius needs to meet the project drawing requirements, and the geometric relationship is as shown in Figure 5 、 Figure 6 , and the following relationship is obtained

[0069]

[0070] The transformation formula is obtained as follows:

[0071]

[0072] where the order of magnitude of R max is specified by the engineering project drawing, and the R max of the relevant features of the machined part is required to be within the specified value, and the threshold value of the helix pitch s is calculated accordingly.

[0073] Further, the machining parameters in step (2) include cutting pitch s (mm), cutting line speed V C (m / min), feed per tooth F z (mm / z) and cutting width A e (mm) four aspects, and the three machining parameters except cutting pitch s are given by the relevant calculation formula according to engineering experience, and the selection of cutting line speed V C (m / min) is based on:

[0074] V C = n1*n2*n3*n4*80

[0075] Feed per tooth F z The selection criteria for (mm / z) are as follows:

[0076] F z =n3*0.08

[0077] Cutting width A e The selection criteria for (mm) are as follows:

[0078] A e ≤0.1

[0079] Where n1 is the correction factor for the material being machined, n2 is the correction factor for the part structure, n3 is the correction factor for the tool diameter, and n4 is the correction factor for the tool length-to-diameter ratio. If the milling tool diameter is D... C (mm), the working length of the tool is L C (mm), the correction factor selection table based on engineering experience is as follows: Figure 9 As shown.

[0080] Furthermore, the error value δ in step (3) refers to Figures 7-8 The difference between the theoretical and actual conical surfaces after semi-finishing is shown to reflect the error between the machined features produced under actual equipment conditions and the theoretical value. The value is obtained by comparing the probe measurement result with the theoretical value. Combined with the theoretical allowance τ left for the conical surface of the conical hole in the machining direction during semi-finishing, the error value δ can be converted to the machining direction of the conical hole, and the compensation value Δ1 can be calculated.

[0081]

[0082] Finally, this value is compensated for in the machining direction of the tapered hole, and the machining origin or tool length value is corrected.

[0083] Example 2

[0084] The specific implementation of this patent will be described below with reference to the accompanying drawings and embodiments.

[0085] like Figure 3 The diagram shown is a process flow chart for the automated milling method of tapered holes. The specific implementation process is as follows:

[0086] An automated milling method for tapered holes includes the following steps:

[0087] (1) The part is clamped on the CNC machining equipment, a machining coordinate system is established, and the part is machined to the required position using traditional milling methods, including the top of the rib, web, inner and outer shape, lugs, tapered hole, cylindrical surface, and other features.

[0088] (2) According to the structural features of the tapered hole of the part, the taper angle α of the tapered hole, the tool tip arc radius r, the spiral line method is selected to compile the machining program, and the spiral line pitch s is calculated:

[0089]

[0090] where R max is of the order of magnitude max The engineering project drawing stipulates that the R max of the relevant features of the machined part shall not exceed the specified value. According to the general requirements for high-precision assembly dimensions of aviation structural parts at present, the surface roughness requirement is Ra1.6, the taper angle α of the tapered hole is 12.5°, and the milling cutter with a sharp circular arc radius r of 3mm is usually selected for the machining link. The calculated cutting line pitch s is not greater than 0.1913mm, and s=0.18mm.

[0091] According to relevant engineering processing experience, the remaining main machining parameters, the cutting line speed V C (m / min), the feed per tooth F z (mm / z), and the cutting width A e (mm) are calculated as follows:

[0092] V C = n1*n2*n3*n4*80

[0093] F z = n3*0.08

[0094] A e ≤0.1

[0095] Wherein, for the titanium alloy TC4 material joint part, the machined material correction coefficient n1=1 and the part structure correction coefficient n2=0.5 are selected, at this time, the milling cutter with a diameter D C =16mm and a tool working length L C of 50mm is selected, the cutter diameter correction coefficient n3=0.8 and the cutter length-diameter ratio correction coefficient n4=0.8 are calculated, and the cutting line speed V C =25.6m / min, the feed per tooth F z =0.064, and the cutting width A e =0.1 are further calculated. The relevant parameter calculation results are applied to the machining program compilation to obtain the semi-finishing trajectory.

[0096] (3) The part is semi-finished, and the probe detection is performed to obtain the error value δ between the theoretical tapered surface of the tapered hole and the actual tapered surface after semi-finishing, and the machining direction compensation value Δ1 of the tapered hole is calculated:

[0097]

[0098] If the measured error value δ = 0.1mm, and the cone half angle α is 12.5°, the theoretical allowance τ left in the processing direction of the conical hole taper surface during semi-finishing is 0.2mm, and the compensation value Δ1 = 0.6621mm is calculated.

[0099] (4) The processing origin or the tool length value is corrected according to the compensation value Δ1, finishing is carried out, and the conical hole size processing is in place.

[0100] The application analyzes the automatic milling method of the conical hole, and respectively applies the application to the two main steps of calculating the main processing parameters and error compensation. The skilled in the art can select the processing equipment and process parameters within the scope of the application, and also can ensure the part processing quality and efficiency.

Claims

1. A method of automated milling of a tapered bore, characterized by: Comprising the following steps: Step (1). The part is clamped on the numerical control machining equipment, the machining coordinate system is established, and the traditional milling method is used to process the rib top, web, inner and outer shape, ear piece, and tapered hole cylindrical surface to the position; Step (2). According to the structural features of the tapered hole of the part and the selected tool parameters, the structural features include the taper hole taper half angle , tool nose radius , adopt helix method to compile processing program, calculate processing parameters, form feature semi-finishing tool path; Step (3). Semi-finishing the part, and detecting the part by a probe to obtain the error value δ between the theoretical conical surface and the actual conical surface of the conical hole after semi-finishing, and combining the theoretical allowance τ left in the machining direction of the conical surface during semi-finishing, the machining direction compensation value of the conical hole is calculated ; Step (4). Compensate value The processing origin or tool length value is corrected, and the finishing is carried out. The size of the tapered hole is processed in place. The spiral line method in the step (2) is suitable for the tool path calculation of regular revolving surface, the tool path contact point of which makes spiral motion along the machined surface, and the distance of the tool path contact point along the axial motion per revolution is called the lead, which is represented by the pitch s; The helix method in the step (2) is used to calculate the corresponding helix pitch When using a ball end mill to drill a conical hole with point contact track, the residual area height formed by the nose radius of the tool The following relationship is obtained to meet the project drawing requirements The transformation formula can be obtained: wherein the order of magnitude of the number of turns of the helix is defined by the engineering project drawings, the characteristics of the machined parts do not exceed the values defined, thus calculating the pitch of the helix upper threshold value; The machining parameters in step (2) include cutting pitch (mm), cutting linear speed (m / min), feed per tooth (mm / z), and cutting width (mm). Three machining parameters other than cutting pitch are given by relevant calculation formulas based on engineering experience, wherein the selection of cutting linear speed (m / min) is based on the following equation: feed per tooth The choice of m / z is based on the following: cutting width The selection of the cutting width (mm) is based on: wherein, is a correction coefficient for the machined material, is a correction coefficient for the part structure, is a correction coefficient for the tool diameter, is a correction coefficient for the tool length-diameter ratio, if the milling tool diameter is (mm), and the tool working length is (mm), the correction coefficient is selected from the correction coefficient selection table according to engineering experience.

2. A method of automated milling of a tapered bore according to claim 1, characterized in that: The part in step (1) is a metal part, including aluminum alloy and titanium alloy.

3. The method of claim 1, wherein: The numerical control machining equipment in step (1) can install and use a measuring probe to meet the vertical and horizontal conversion processing.

4. The method of claim 1, wherein: The error value δ of the step (3) refers to the difference between the theoretical conical surface and the actual conical surface after semi-finishing, and is used to reflect the error between the machined feature and the theory under the actual state of the equipment, and the value is obtained by comparing the difference between the measured result of the probe and the theoretical value. By combining the theoretical allowance τ left in the machining direction of the conical hole conical surface during semi-finishing, the error value δ can be converted to the machining direction of the conical hole, and the compensation value is calculated Finally, the value is compensated to the processing direction of the tapered hole, and the processing origin or tool length value is corrected.

5. The method of claim 2, wherein: The tapered hole structure is located on the high ear piece structure of the part, and the whole presents a through hole structure.

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