CN110216425B - Machining method for precisely machining variable-groove-width threads through single teeth - Google Patents

Abstract

The invention discloses a processing method for precisely processing variable-groove wide threads by single teeth; the invention establishes the compensation of the motion path between the large-size oil pipe and the single-tooth cutter based on the geometric shape of the variable-groove-width thread, completes the rough machining and the finish machining of the internal thread simultaneously, and improves the machining efficiency of the variable-groove-width thread.

Description

A machining method for single-tooth precision machining of variable groove width threads

Technical field:

The invention relates to the field of machining, in particular to a machining method for single-tooth precision machining of variable groove width threads.

Background technique:

The variable groove width threaded connection of oil pipes or gas pipes not only needs to connect the threads tightly, but also has high strength and high sealing performance, which puts forward higher requirements for the machining accuracy of variable groove width threads. At present, turning machining is an effective method for efficient thread machining. However, due to the large length of the tubing, more than 15 meters, and the larger diameter, more than 0.5 meters, in the existing processing technology, comb cutters are used. Turning is performed, but the machine tool is required to clamp the large-size oil pipe thread to rotate for turning, which leads to the change of the kinematic chain transmission and the counterweight ratio of the machine tool, resulting in machining errors and constrains the machining accuracy. The invention provides a single-tooth precision machining method for variable-groove-width threads. Based on the geometry of the variable-groove-width threads, the compensation of the motion path between a large-sized oil pipe and a single-tooth cutter is established, and the internal thread is simultaneously completed. roughing and finishing. The invention can effectively reduce the cost of machining tools and improve the machining efficiency.

Invention content:

The invention discloses a processing method of single-tooth precision machining of variable groove width threads. Based on the geometry of variable groove width threads, the invention establishes the compensation of the motion path between a large-sized oil pipe and a single-tooth tool, and simultaneously completes the Roughing and finishing of internal threads.

For solving the above problems, the technical scheme of the present invention is:

A processing method for single-tooth precision machining of variable groove width threads, comprising the following steps;

Step 1: Obtain the preset relative position of the tool and the workpiece before loading the workpiece; install a non-contact sensor on the worktable and the center of the tool of the machine tool to detect the actual relative position of the tool and the workpiece after the workpiece is loaded;

Step 2: Obtain the relative position and angle error between the tool and the workpiece before and after loading the workpiece; compensate the relative position and angle error between the tool and the workpiece before and after loading the workpiece through the control program of the machine tool;

Step 3. Processing of variable groove width thread size: in a given variable groove width thread, according to the design parameters of the variable groove width thread, the minimum width b ₁ and the maximum width b ₂ of the variable groove width thread are obtained, and the minimum width of the variable groove width thread is obtained. Depth h ₁ , maximum depth h ₂ , the length l ₀ of the variable groove width thread is obtained; then the distance from the initial end of the thread is the width b(x) and depth h(x) of the thread at x, respectively:

Step 4. Determine the tool parameters for processing the variable groove width thread: use a single tooth tool to carry out turning and milling compound processing: the machine tool clamp clamps the workpiece, and the tool moves along the variable groove width thread path under the control of the machine tool control system for turning processing. Under the action of the motorized spindle of the machine tool, the tool carries out a spinning motion, which is a milling motion; the tool is a disc milling cutter; The minimum width b ₁ of the groove width thread, the minimum depth of the machining part in the disc milling cutter is the maximum depth h ₂ of the variable groove width thread; that is, the length of the main cutting edge of the insert is b ₁ , and the length of the secondary cutting edge is h ₂ , so as to complete the processing of variable groove width thread depth at one time, and realize the roughing and finishing of threads;

Step 5. Control of the variable groove width thread processing motion path: Since in the variable groove width thread processing, the width of the blade is set to the minimum width b ₁ of the variable groove width thread, and the remaining part of the width of the thread needs to be processed continuously, so To optimize the machining path:

The first process: under the control of the machine tool control system, the disc milling cutter is processed along the thread curve with the width b ₁ to complete the processing of the thread width b _1. The depth of the thread is controlled by the machine tool control system according to the change of the thread depth curve. deep realization;

The second process: calculate the maximum width b ₃ of the remaining thread that needs to be processed;

同样，切削深度控制按照第一道工序中深度的控制，完成变槽宽螺纹的加工；1) If b ₃ is lower than b ₁ , under the action of the machine tool control system, the control cutting width changes with the thread path according to the following rules:

Similarly, the cutting depth control is based on the depth control in the first process to complete the processing of variable groove width threads;

切削深度按照控制按照第一道工序中深度的控制进行变槽宽螺纹的加工；2) If b ₃ is greater than b ₁ , when calculating at the machining path l ₁ , the remaining cutting width of the thread is b ₁ , and if it is greater than the path l ₁ , the remaining cutting width of the thread is less than b ₁ , then in the machine tool control system Under the action, taking the widest point of the thread as 0 point, the thread path 0-l ₁ is processed according to the cutting width b ₁ , and the cutting width from the path l ₁ to the initial end of the thread changes according to the following rules:

The cutting depth is controlled according to the control of the depth in the first process to process the variable groove width thread;

The third process: analyze the thread path 0-l ₁ , if the maximum remaining processing width of the thread is lower than b ₁ , use the second process 1) to complete the processing of the thread; if the maximum remaining processing width of the thread is greater than b ₁ , then use the second process 2) for processing;

Repeat steps 1), 2) and the third operation to complete the processing of the variable groove width thread.

In a further improvement, the workpiece is an oil pipe or a gas pipe.

As a further improvement, the radius of the arc of the cutting edge of the insert on the disc milling cutter is 0.3 mm.

Further improvement, the preset relative position of the tool and the workpiece before the workpiece is clamped is obtained through the control system of the machine tool itself.

For a further improvement, the second step includes the following steps: establishing a coordinate system oxyz, and in the general coordinate system, testing to obtain the actual position of the tool and the workpiece under different conditions, that is, on the machine tool table, with the vertical direction as the z direction, the tool The cutting feed movement is the y direction, and the cutting depth direction of the tool is the x direction. After the machine tool clamps the workpiece, the displacement error in the x direction is ξ _x , the displacement error in the y direction is ξ _y , and the displacement error in the z direction is ξ _z . The angle error of the deflection movement of the main shaft in the xz plane is ζ _xz , and the rotational angle error of the chuck used for clamping the workpiece is ζ _xzd ;

In the identification of machine tool errors, the relative positions of ideal tool and workpiece P' _t -P' _w in x, y, z directions and angles are: Δx' _wt , Δy' _wt , Δz' _wt , θ'_yz; P ' _t represents the position of the reference point of the tool in the universal coordinate system oxyz where the workpiece is not installed, P _w ' represents the position of the reference point of the workpiece in the universal coordinate system oxyz where the workpiece is not installed; the actual relative position of the tool and the workpiece P _t -P _w The positions and angles in the x, y, z directions are: Δx _wt , Δy _wt , Δz _wt , θ _yz , P _t represents the position of the tool reference point after the workpiece is installed in the general coordinate system oxyz, and P _w represents the general coordinate system. The position of the reference point of the workpiece under the oxyz after the workpiece is installed; the relative position and angle error of the tool and the workpiece before and after the workpiece is installed are:

ξ _x =Δx' _wt -Δx _wt

ξ _y =Δy' _wt -Δy _wt

ξ _z = Δz' _wt -Δz _wt

ζ _yz = θ' _yz -θ _yz (1)

The tool adjustment compensation error ξ _x , ξ _y , ξ _z is performed inside the machine tool, and the above displacement error and angle error ζ _xz are added on the basis of the original control motion to perform motion compensation.

Description of drawings

The accompanying drawings are used to provide a further understanding of the present invention, and constitute a part of the specification, and together with the specific embodiments of the present invention, they are used to explain the present invention, and are not construed to limit the present invention. In the attached image:

Figure 1 is a schematic diagram of the displacement and angle error model of the relative position of the tool and the workpiece before and after modification in the general coordinate system;

Figure 2 is a schematic diagram of a variable groove width thread;

FIG. 3 is a schematic diagram of the blade structure of the disc milling cutter.

Detailed ways:

The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. It should be understood that the embodiments described herein are used to illustrate and explain the present invention, but not to limit the present invention.

(1) After the machine tool is refitted and the large-sized oil pipe is loaded, the counterweight ratio of the machine tool and the response of the transmission chain are changed, which has a great impact on the static error of the machine tool and the machining motion error. Before the modification of this machining center, its assembly, static and other errors have been tested and compensated through the internal program. On this basis, the actual relative position P _t -P _w and the preset relative position P _t '- of the tool and the workpiece after modification are obtained. The position and angle errors of P _w '. The preset relative position of the tool and the workpiece can be obtained by measuring the relative position of the tool and the workpiece before the modification, and the actual relative position of the modified tool and the workpiece can be obtained by measuring the relative position of the modified tool and the workpiece. The actual position of the sensor is detected by a pair of non-contact sensors, one sensor is arranged on the worktable, and the other sensor is arranged in the center of the tool to detect the relative position of the workpiece and the center of the tool. As shown in Figure 1.

First of all, the definition of the machine tool error, let the displacement error in the x direction be ξ _x , the displacement error in the y direction be ξ _y , the displacement error in the z direction is ξ _z , the angle error of the machine tool spindle deflection in the xz plane is ζ _xz , used for clamping The rotation angle error of the chuck for tightening the large size oil pipe is ζ _xzd .

In the identification of machine tool errors, the relative positions of the ideal tool and the workpiece P _t '-P _w ' in the x, y, z directions and angles are: Δx' _wt , Δy' _wt , Δz' _wt , θ' _yz . The position and angle of the actual relative position P _t -P _w of the tool and the workpiece in the x, y, z directions are: Δx _wt , Δy _wt , Δz _wt , θ _yz , respectively. Then the relative position and angle error of the tool and the workpiece before and after the large-size tubing is installed are:

The error caused by this part is compensated by the internal tool adjustment of the machine tool, and the above displacement and angle errors are added on the basis of the original control movement.

(2) Processing of variable groove width thread size. In a given variable groove width thread, according to the design parameters, the minimum width b ₁ , the maximum width b ₂ of the variable groove width thread, the minimum depth h ₁ and the maximum depth h ₂ of the variable groove width thread can be obtained. The schematic diagram of the specific thread is shown in the figure 2 shown. In order to ensure the tight and reliable installation of the threaded connection, the thread depth and width of the variable groove width thread change linearly, and with the length of the thread (thread distance), it is the distance from the initial end of the thread to the end of the thread along the threaded bolt around the oil pipe . According to the design parameters of the variable groove width thread, the length l ₀ of the variable groove width thread can be obtained. Then the distance from the initial end of the thread is the width b(x) and the depth h(x) of the thread at x, respectively:

(3) Tool parameters for processing variable groove width threads. In the processing of variable groove width threads, since the traditional processing method of variable groove width threads is turning with a comb cutter, it is difficult to accurately and precisely process and smoothly transition the width and depth of variable groove width threads. Secondly, due to the long length of the oil pipe, it is difficult to clamp the clamp to the middle position of the oil pipe length, which results in the eccentric movement of the workpiece during machining due to the rotation of the machine tool to clamp the large-sized oil pipe, which reduces the machining accuracy of the oil pipe. The single-tooth tool is used to carry out turning-milling compound machining to solve the above problems. The details are as follows: the machine tool clamps the large-sized oil pipe, and the tool moves along the thread path of variable groove width under the control of the machine tool control system, which is the turning movement. Under the action of the machine tool electric spindle, the spinning motion is carried out, which is the milling motion. The disc milling cutter is used for turning and milling compound machining. The maximum width of the disc milling cutter is the minimum width b ₁ of the variable slot width thread, and the minimum depth of the disc milling cutter is the maximum depth of the variable slot width thread. h ₂ . At the same time, the arc radius of the cutting edge of the insert installed on the disc milling cutter head is 0.3mm. This is because the depth of the thread changes in the processing of threads with different flute widths. If the transition radius of the cutting edge is small, the transition will occur. The chip edge is easy to chip, and if it is large, it is difficult to meet the smooth transition between the bottom surface and the side surface of the thread. Set the length of the main cutting edge of the disc milling cutter to be b ₁ and the length of the secondary cutting edge to be h ₂ , which can complete the processing of variable groove thread depth in one processing, realize the roughing and finishing of the thread, and improve the processing efficiency. The setting of the length of the secondary cutting edge satisfies the requirement of variable groove width machining with minimum width.

(4) Control of the motion path of variable groove width thread machining. Since in the variable groove width thread processing, the width of the insert is set to the minimum width b ₁ of the variable groove width thread, and the remaining part of the width of the thread needs to be processed continuously. The optimized processing path provided by the present invention is:

The first process: under the control of the machine tool control system, the disc milling cutter is processed along the thread curve with the width b ₁ , which completes the processing of the thread width b ₁ , and the depth of the thread changes according to (2) in the machine tool control system. Controlling the depth of cut is achieved.

The second process: after the first process is completed, calculate the maximum width b ₃ of the remaining thread that needs to be processed.

同样，切削深度控制按照第一道工序中深度的控制，完成变槽宽螺纹的加工。1. If the maximum width is lower than b ₁ , under the action of the machine tool control system, the control cutting width changes with the thread path according to the following rules:

Similarly, the depth of cut control is based on the depth control in the first process to complete the processing of variable groove width threads.

切削深度按照控制按照第一道工序中深度的控制进行变槽宽螺纹的加工。2. If the maximum width is greater than b ₁ , when calculating at the machining path l ₁ , the remaining cutting width of the thread is b ₁ , and if it is greater than the path l ₁ , the remaining cutting width of the thread is less than b ₁ , then in the machine tool control system Under the action, the thread path 0-l ₁ is processed according to the cutting width b ₁ , and the cutting width from the path l ₁ to the end of the thread changes according to the following rules:

The cutting depth is controlled according to the control of the depth in the first process to process the variable groove width thread.

3. Analyze the thread path 0-l ₁ , if the maximum remaining processing width of the thread is lower than b ₁ , the thread processing will be completed by the second process 1; if the maximum remaining processing width of the thread is greater than b ₁ , refer to The second step 2 is processed, and then according to the relationship between the processing width of the remaining thread and b ₁ , refer to 3 for thread processing.

According to the above procedures, the main purpose is to avoid the movement of the workpiece and the reciprocating movement of the tool, which will cause processing errors and improve the processing accuracy.

The foregoing has shown and described the basic principles, main features and advantages of the present invention. The protection scope of the present invention is not limited to the above-mentioned embodiments, and all technical solutions under the idea of the present invention belong to the protection scope of the present invention. It should be pointed out that for those skilled in the art, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims (5)

1. a processing method of single-tooth precision machining variable groove width thread, is characterized in that, comprises the steps; Step 1: Obtain the preset relative position of the tool and the workpiece before loading the workpiece; install a non-contact sensor on the worktable and the center of the tool of the machine tool to detect the actual relative position of the tool and the workpiece after the workpiece is loaded; Step 2: Obtain the relative position and angle error between the tool and the workpiece before and after loading the workpiece; compensate the relative position and angle error between the tool and the workpiece before and after loading the workpiece through the control program of the machine tool; Step 3. Processing of the variable groove width thread size: the thread depth and width of the variable groove width thread change linearly. In a given variable groove width thread, according to the design parameters of the variable groove width thread, the smallest variable groove width thread is obtained. The width b ₁ , the maximum width b ₂ , the minimum depth h ₁ and the maximum depth h ₂ of the variable groove width thread, and the length l ₀ of the variable groove width thread is obtained; then the distance from the initial end of the thread is the width b(x) of the thread at x and The depth h(x) are:

Step 4. Determine the tool parameters for processing the variable groove width thread: use a single tooth tool to carry out turning and milling compound processing: the machine tool clamp clamps the workpiece, and the tool moves along the variable groove width thread path under the control of the machine tool control system for turning processing. Under the action of the motorized spindle of the machine tool, the tool carries out a spinning motion, which is a milling motion; the tool is a disc milling cutter; The minimum width b ₁ of the groove width thread, the minimum depth of the machining part in the disc milling cutter is the maximum depth h ₂ of the variable groove width thread; that is, the length of the main cutting edge of the insert is b ₁ , and the length of the secondary cutting edge is h ₂ , so as to complete the processing of variable groove width thread depth at one time, and realize the roughing and finishing of threads; Step 5. Control of the variable groove width thread processing motion path: Since in the variable groove width thread processing, the width of the blade is set to the minimum width b ₁ of the variable groove width thread, and the remaining part of the width of the thread needs to be processed continuously, so To optimize the machining path: The first process: under the control of the machine tool control system, the disc milling cutter is processed along the thread curve with the width b ₁ to complete the processing of the thread width b _1. The depth of the thread is controlled by the machine tool control system according to the change of the thread depth curve. deep realization; The second process: calculate the maximum width b ₃ of the remaining thread that needs to be processed; 1) If b ₃ is lower than b ₁ , under the action of the machine tool control system, the control cutting width changes with the thread path according to the following rules:

Similarly, the cutting depth control is based on the depth control in the first process to complete the processing of variable groove width threads; 2) If b ₃ is greater than b ₁ , when calculating at the machining path l ₁ , the remaining cutting width of the thread is b ₁ , and if it is greater than the path l ₁ , the remaining cutting width of the thread is less than b ₁ , then in the machine tool control system Under the action, taking the widest point of the thread as 0 point, the thread path 0-l ₁ is processed according to the cutting width b ₁ , and the cutting width from the path l ₁ to the initial end of the thread changes according to the following rules:

l ₁ ≤x1≤l ₀ , the cutting depth is controlled according to the depth control in the first process to process the variable groove width thread; The third process: analyze the thread path 0-l ₁ , if the maximum remaining processing width of the thread is lower than b ₁ , use the second process 1) to complete the processing of the thread; if the maximum remaining processing width of the thread is greater than b ₁ , then use the second process 2) for processing; Repeat steps 1), 2) and the third operation to complete the processing of the variable groove width thread. 2 . The method for precision machining of variable groove width threads with a single tooth according to claim 1 , wherein the workpiece is an oil pipe or an air pipe. 3 . 3 . The method for precision machining of variable groove width threads with a single tooth according to claim 1 , wherein the radius of the arc of the cutting edge of the insert on the disc milling cutter is 0.3 mm. 4 . 4. The single-tooth precision machining method for variable groove width threads according to claim 1, wherein the preset relative position of the tool and the workpiece before clamping the workpiece is obtained through the control system of the machine tool itself. 5. The processing method of single-tooth precision machining variable groove width thread as claimed in claim 1, wherein the step 2 comprises the steps of: establishing a coordinate system oxyz, under the universal coordinate system, testing to obtain tools under different conditions With the actual position of the workpiece, that is, on the machine table, the vertical direction is the z direction, the cutting feed movement of the tool is the y direction, and the cutting depth direction of the tool is the x direction. After the machine tool clamps the workpiece, the displacement error in the x direction is ξ _x , the displacement error in the y-direction is ξ _y , the displacement error in the z-direction is ξ _z , the angular error of the deflection motion of the machine tool spindle in the xz plane is ζ _xz , and the rotational angle error of the chuck used for clamping the workpiece is ζ _xzd ; In the identification of machine tool errors, the relative positions of ideal tool and workpiece P' _t -P' _w in x, y, and z directions and angles are: Δx' _wt , Δy' _wt , Δz' _wt , θ'_yz; P ' _t represents the position of the reference point of the tool in the universal coordinate system oxyz where the workpiece is not installed, P' _w represents the position of the reference point of the workpiece in the universal coordinate system oxyz where the workpiece is not installed; the actual relative position of the tool and the workpiece P _t -P _w The positions and angles in the x, y, z directions are: Δx _wt , Δy _wt , Δz _wt , θ _yz , P _t represents the position of the tool reference point after the workpiece is installed in the general coordinate system oxyz, and P _w represents the general coordinate system. The position of the reference point of the workpiece under the oxyz after the workpiece is installed; the relative position and angle error of the tool and the workpiece before and after the workpiece is installed are: ξ _x =Δx′ _wt -Δx _wt ξ _y =Δy′ _wt -Δy _wt ξ _z =Δz′ _wt -Δz _wt ζ _yz = θ′ _yz - θ _yz (1) The tool adjustment compensation error ξ _x , ξ _y , ξ _z is performed inside the machine tool, and the above displacement error and angle error ζ _xz are added on the basis of the original control motion to perform motion compensation.

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