A Method of Variable Spindle Speed ​​NC Turning and Repairing External Threads with Different Leads

Abstract

A method for CNC turning and repairing external threads with different leads with variable spindle speed, comprising: using the starting point S of the tool on a reference workpiece at the speed of the spindle speed n 0 , n 2 Turning leads are all P 0 The helix T 0 , T 2 ;Position tool tip at point A 0 ;Turn the spindle to an angular position so that the tool tip points to T 0 ;Move the tool tip so that it points to T 0 Adjacent T 2 and positioned at point A 2 ;pass A 0 and A 2 Calculate the coordinates of T 0 , T 2 Between the axial or circumferential deviation, corrected at the spindle speed n 2 The following thread turning repair program to eliminate the axial or circumferential deviation; remove the reference workpiece; install the workpiece to be repaired and turn the spindle to the angle position; move the tool tip to point B at the bottom of the thread to be repaired; Repair the axial offset distance or circumferential deviation between the required tool starting point E' and the tool starting point E set by the turning repair program; eliminate the axial offset distance or circumferential deviation; execute the adjusted program. This method can realize the maintenance of external threads with different leads under variable spindle speed.

Description

technical field [0001] The invention relates to a thread maintenance method, in particular to a method for variable-spindle speed numerical control turning external threads with different leads. Background technique [0002] A large number of threads are processed and repaired by oil drilling technology service companies every year. Oil pipe thread repair service itself is very necessary for the drilling industry to control equipment costs. Maintenance can prolong the service life of oil pipes and save equipment investment. The technical key point of oil pipe thread repair is to machine along the original helical line of the thread, not to completely remove and reprocess. [0003] For a long time, the industry has generally used special pipe lathes to process threads. Its advantages are simple structure and strong applicability. Its disadvantages are also obvious. The labor intensity of operators is high, the working environment is poor, and there are occupational risks such...

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Problems solved by technology

However, the purpose of this method is to solve the thread disorder phenomenon before and after the speed change in the process of forming the thread, and the starting point of the tool before changing the spindle speed is known; The process belongs to different processing processes. In the process of thread repair and maintenance, the position information of the thread to be repaired is unknown. Therefore, this document is not applicable to the thread repair process, and it does not give how to avoid thread disorder during thread repair. buckle method

[0006] 2. There is a tool setting problem in the process of CNC turning and maintenance of threads: the installation of each thread to be repaired on the machine tool is random, that is, the currently installed thread is quite different from the previous installation in terms of position and angle. Most of the processing position data set in the previous program are meaningless to the current processing, and updating all these data will greatly reduce the labor efficiency of the operator, increase the error rate of the program, and increase the risk of damage to the workpiece thread and maintenance equipment

None of these methods can accurately find the starting point of car repair at one time, and the efficiency is low, so it is only suitable for individual car repair

[0009] (2) Special function expansion technology of the system: the earliest available reference materials in China are documents (Wang Ke, Tang Zongjun, Zhao Wenzhen. Several technical problems in pipe thread numerical control processing [J]. Petroleum Machinery, 1998, 26(11) : 42-43), the general idea is to increase the measurement and feedback functions on the CNC lathe equipment until the layout of the machine tool is completely changed. This method is not economical

[0011] This idea has not been widely adopted by relevant enterprises for the following reasons: Due to the characteristics of heavy load cutting, harsh working conditions, various workpiece forms and variable thread types in the oil pipe thread turning repair, the processing equipment used in this process has been determined. It has the requirements of simple structure, convenient operation, stability and reliability, and easy maintenance. However, this method complicates the structure of the equipment due to the need for additional equipment, and the cost of purchase, use, and maintenance is high. The exposure of the location increases the probability of equipment damage and failure. , reducing the stability, reliability and convenience of operation of CNC lathes, therefore, this method is unacceptable for oil companies that have a large demand for thread turning repairs

[0012] (4) Special system function technology: literature (Zhang Dewu, Gong Junyan, Zhang Hui, Zhao Haiyuan. Application of Siemens 828D in CNC pipe thread lathe for thread repair[J]. Metal Processing: Cold Working, 2015(2): 71- 72), literature (Tang Zongjun, Gu Yanling. Continued cutting of existing threads on CNC lathes [J]. Manufacturing Technology and Machine Tools, 2003(12): 96-97), literature (Ma Bin, Yu Li. FAGOR system's crease repair function Application on pipe thread special machine [J]. CNC Machine Tool Market, 2007 (12): 108-110) respectively introduced the application of the thread repair function provided by Siemens 828D, FAGOR and NUM systems, which can complete the relevant position calculation and The work of setting the coordinate system saves some manual labor, but it does not have the ability to detect the position of the thread to be repaired. For the thread repaired, the characteristic parts of the thread to be repaired are different each time. Therefore, this Technology usually requires the installation of position detection devices on CNC lathes, resulting in increased equipment costs; at the same time, this type of system is limited by its own functions and application range, and can only be applied on CNC lathes with corresponding systems. Not applicable on lathes, not universally applicable

[0013] (5) Marking zero signal technology: literature (Cai Shanle, Ma Zhihong. CNC lathe manual thread tool setting [J]. Machine Tools and Hydraulics, 2004 (9): 177-178), literature (Meng Shengcai. When repairing threads on CNC lathes The problem of tool setting [J]. Electromechanical Engineering Technology, 2008,37(4):100-102+112), literature (Fan Fanghong, Shi Jinyan. Discussion and application of the method of automatic positioning and repairing thread of CNC lathe spindle[J]. Manufacturing Technology and Machine Tools, 2015(4):173-176) and literature (Wan Fawei, Zhao Junyou, Cao Qingyuan, Wang Futao, Cao Jianming, Han Xueyi. Research on oil drill pipe thread repair technology[J]. Machine Tool and Hydraulics, 2017,45(2 ):15-19), the idea is to mark the zero signal of the spindle. This method has an insurmountable shortcoming, that is, the distance between the measurement point on the thread corresponding to the zero signal and the cutting start point is not an integer multiple of the lead. Therefore, As a result, the calculated starting point is inaccurate and needs to be corrected, which is inherently determined by the thread feed operation principle of the CNC machine tool

However, in actual operation, this method still has the following disadvantages: 1. It is difficult to ensure that the "flat plate" is perpendicular to the spindle in actual operation, which reduces the accuracy of subsequent tool setting; 2. The distance L1 cannot be obtained directly from the machine tool. Manual measurement is difficult to guarantee the measurement accuracy of L1. If instrument measurement is used, the equipment structure will be complicated; 3. This method also needs to detect and calculate "rotation angle difference", but most of the CNC lathe systems in the prior art do not have a spindle The phase angle display function, therefore, limits the scope of application of this method; to detect the "rotation angle difference", it is necessary to use a detection instrument, or to modify or modify the machine tool, which will complicate the repair operation of each thread, increase the cost input, and reduce the cost. Ergonomics; in addition, the introduction of "corner difference" complicates position calculation

Therefore, the existence of "flat plate" and "corner difference" in this method makes it cumbersome to operate, low in efficiency, and low in tool setting accuracy.

[0016] The Chinese invention patent application with the publication number CN109799783A discloses a method, a control device and a CNC machine tool for repairing a threaded pipe body by a CNC machine tool. The method obtains the thread track data of the threaded pipe and compares it with the program data of the CNC machine tool. Calculate the data difference between the program thread line and the thread line to be repaired. This method belongs to the "thread contour scanning detection technology". It is necessary to add other systems to obtain the information mentioned in the method and simulate turning the thread, which leads to the complexity of the equipment; at the same time , this method needs to obtain the angle of the CNC machine tool spindle encoder and the machine tool, which makes the whole tool setting process more complicated

In addition, it does not give a method on how to avoid thread disorder during thread maintenance

[0017] The Chinese invention patent application with the publication number CN104148752A discloses a method for automatically extracting and eliminating deviations in CNC thread grinding tool setting and grinding. The method automatically calculates the synchronous following error of the Z axis and the A axis as the deviation, which is equivalent to The most commonly used test method for thread repairing on CNC lathes relies on the operator to visually measure the distance between the tool and the existing thread teeth, and then repeatedly adjusts and eliminates the distance. The process is relatively complicated; and most of the existing CNC lathe systems do not It has the functions of continuous multi-point and multi-dimensional collection, recording, storage and calculation of data, so it limits the scope of application of this method

In addition, this method is suitable for turning and repairing threads with the same lead, but does not give a method of how to repair threads with different leads in batches

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