RU2071882C1 - Method of cutting threads on parts of deep-well pumps - Google Patents

Abstract

FIELD: machining. SUBSTANCE: lateral and longitudinal feeding of a thread cutting tool are controlled. Every time the initial position of the lateral feeding is shifted with respect to the previous one inversely proportional to the number of runs performed. During the first turn of a thread cutting the lateral feeding is then uniformly increased by a value of increasing radial pressing out of a tool. The steady-state thread cutting is then performed, the lateral feeding of a tool being constant. During the last turn the lateral feeding is decreased by the value of the radial pressing out of a tool. Longitudinal feeding increases by a value of the axial pressing out of a tool during the first turn. The steady-state thread cutting is then performed. During the last turn the longitudinal feeding decreases by a value of the increasing axial pressing out of a tool. Required relationships are available in the invention description. EFFECT: simplified method. 2 cl, 1 dwg

Description

 The invention relates to metalworking and can be used for the manufacture of threaded products.

 A known method of threading a threading cutter, receiving a longitudinal feed movement along the axis of the product, numerically equal to the pitch of the thread being cut, and lateral feed to the depth, reported between the aisles (Yakukhin V.G. Stavrov V.A. Thread manufacturing. M. Engineering, 1989, p. 19 23).

 There is a method of extruding threads with a single-thread rolling roller that receives a longitudinal feed movement along the axis of the product, numerically equal to the pitch of the extruded thread, and a transverse feed to a depth that is communicated between the aisles (Scherbyuk N.D. Yakubovsky N.V. Threaded pipe joints of oil grade and downhole motors. M. Nedra, 1974, p. 227 229).

 There is a method of forming threads for moving a thread-forming tool from its initial position along the forming surface of a rotating workpiece by means of longitudinal feeding by successive longitudinal forming passages and a transverse working feed communicated between the passes containing the step of cutting the tool at the first turn of the thread forming, the step of the tool exit at the last turn thread forming and the established stage between them (Granovsky G.I. Gr VG-ray Cutting metals. M. High School, 1985, pp. 258 259 prototype).

However, the known methods of forming threads do not provide high quality products. When each longitudinal forming passage is performed by a thread-forming tool, the radial component P _{y of} the thread forming force at the stage of cutting the tool is unstable and increases from zero at the initial contact of the tool with the workpiece to the maximum constant value achieved at the end of the cutting stage and the beginning of the established stage of thread formation. At the end of the formation of the thread of the required (main) length, the tool is usually brought into the groove for the tool to exit. At the tool exit stage, the radial component of the cutting force begins to decrease in the reverse sequence and at the end of this stage acquires a zero value. The elastic radial relative depressions of the tool from the workpiece at all three stages of the process correspond to a change in the radial component of the cutting force: at the insertion stage they increase from zero to maximum, at the steady-state stage they are set constant, at the tool exit stage they decrease to zero. The resulting diametric dimensions (average and inner diameters) of the thread formed at different stages of the process, i.e. diametric dimensions along the length of the thread, various. This is due to the difference in the relative elastic squeezes of the tool from the workpiece during processing at its three stages: the stage of cutting the tool, the steady-state stage and the stage of the tool exit. When the external thread is formed, its average and internal diameters are formed smaller in the areas obtained at the cutting and tool exit stages than in the thread area obtained at the steady-state stage of the process. When the internal thread is formed, its average and internal diameters are formed larger in the sections obtained at the cutting and tool exit stages than in the thread section obtained at the steady-state stage of the process. Diametric differences in the size of the thread obtained at three different stages of its formation depend on the magnitudes of the forces acting during processing and the rigidity of the technological system used. These differences in the sizes of the average and internal diameters of the thread in three different sections along its length are an organic disadvantage of the known processing methods. The inevitability of the occurrence of this drawback of the resulting thread leads to the assumption adopted by existing state standards governing the quality of the formed threads. In particular, when controlling the dimensions of the external and internal threads, state standards allow the screwing (screwing in) of a threaded threaded gauge onto (a) a part up to the first two turns. This section of the product thread corresponds to the stage of tool insertion, where the average and internal diameters of the external thread are smaller than the permissible smallest sizes, and the average and internal diameters of the internal thread are larger than the permissible largest sizes. Essentially coincident phenomena occur at the opposite end of the threaded product in the thread portion formed at the tool exit stage.

Along with the processing error due to the influence of the forming force of the radial component P _{y of the} radial component P _y and the corresponding elastic depressions of the technological system during each pass of the tool, there is also a processing error due to the action of the axial component P _{x of} force that is not constant during each pass of the tool shaping and the corresponding elastic depressions of the technological system. At the stage of insertion of the tool, its release is directed to the side opposite to the direction of the longitudinal feed, at the stage of exit of the tool to the side coinciding with the direction of the longitudinal feed. The resulting elastic deformations distort the first and last turns of the thread formed at the cutting and exit stages of the tool and manifest themselves in stretching the pitch of the first and last turns of the thread. These errors of the thread pitch, which are formed at the stages of cutting and tool exit, depend on the magnitudes of the forces acting during processing and the rigidity of the technological system used. At the established stage of the process of thread forming, the elastic axial depressions of the tool and the workpiece, as a result of the influence of the axial component of the forming force, are practically absent close to zero and directed towards the longitudinal feed of the tool. The distortion of the step at the first and last turns of the thread as a result of the elastic axial depressions of the tool and the workpiece is a defective thread, reproduced in each shaping passage of the tool. Differences in the thread pitch of the product in three different lengths of the sections formed at the cutting, tool exit and steady state process stages are an organic disadvantage of the known processing methods.

During the shaping of the first and last turns of the thread, processing errors due to changes in the radial P _y and axial P _x components of the cutting force and the corresponding elastic presses are summed, i.e. the errors of the diametrical dimensions (average and inner diameters) of the thread are summed up with the errors of the thread pitch. The combination of these errors, without causing their mutual compensation in the product, leads, however, to the non-obviousness of the marriage on the thread, which is not identified by means of complex control of threaded products used in industry.

 In the existing classification of threads, which divides the threads into fasteners and kinematic (running), thread defects resulting from the described features of the dynamics of the process of thread formation are permissible. In particular, fastening threads do not have high accuracy requirements; kinematic threads are, in some cases, accurate, however, as a rule, they exclude the possibility of using extreme first and last defective threads.

 At the same time, in a number of petroleum engineering products threaded connections are used, which, along with the fastening function, which is basic for fastening threads, perform the function of mutual, very accurate basing of a number of parts to be mated in series. In this case, the exact mutual arrangement of threaded parts sequentially interconnected with each other should be carried out due to technologically difficult to achieve a significant increase in the accuracy of the manufacture of threads on which the parts based on the threads are based. Such petroleum engineering products include deep well pumps. The diametrical dimensions of such products are limited to a certain extent by the diameter of the producing wells, and the length of the significant restrictions has virtually no. Assembling a product of limited diameter and unlimited length is a large series of threaded parts connected in series with each other over mating threaded surfaces into a long product. With such a combination of parts of the deep pump into a single assembly unit, accumulation of errors of basing and relative positioning of the parts is inevitable, which ultimately leads to misalignment of the assembled parts, curvature of the longitudinal axis of the product, violation of the structural radial clearances between the parts, reduce the operational life of the product and reduce the effectiveness of its use.

 The aim of the invention is to improve the quality of the formed threads.

где S_ni величина изменяемой в течение i-го прохода поперечной подачи резьбообразующего инструмента, мм; t_i нормативная величина поперечной подачи резьбообразующего инструмента для i-го прохода, обратно пропорциональная числу проходов (нормативная глубина резания), мм; P_yi радиальная составляющая силы формообразования резьбы для i-прохода, кН; j_y радиальная жесткость металлообрабатывающего станка, кН/мм, а величину продольной подачи инструмента для начала первого и конца последнего оборота резьбоформирования определяют по проходу согласно зависимостям соответственно

где S $\genfrac{}{}{0ex}{}{\text{н}}{\text{oi}}$ и S $\genfrac{}{}{0ex}{}{\text{к}}{\text{oi}}$ продольная подача резьбообразующего инструмента соответственно для начала первого и конца последнего оборотов резьбоформирования i-го прохода, мм; Р продольная подача установившейся стадии резьбоформирования, равная шагу обрабатываемой резьбы, мм; Р_xi осевая составляющая силы формообразования резьбы для начала первого и конца последнего оборотов i-го прохода, кН; j_x осевая жесткость металлообрабатывающего станка, кН/мм.This goal is achieved by the fact that for forming threads, the thread-forming tool is moved from its initial position along the forming surface of the rotating workpiece by longitudinal feeding by successive longitudinal forming passages and a transverse working feed communicated in the gaps between the passes containing the step of cutting the tool on the first turn of the thread forming stage the output of the tool at the last turn of the thread formation and the steady-state stage between they, and the difference of the proposed method is that, in order to improve the quality of the formed threads, the thread-forming tool is installed in the direction of its transverse feed for each subsequent longitudinal forming passage to its original position, shifted by an amount inversely proportional to the number of longitudinal forming passages, reduced by the magnitude of the radial squeezing of the tool of the established stage of threading, then evenly during the first turn of threading increase the transverse feed by the value of the increasing radial tool deposition, carry out the subsequent steady-state stage of thread forming with a constant transverse tool feed and during the last turn of the thread forming uniformly reduce the transverse tool feed evenly by the value of the decreasing radial tool squeeze, while the thread-forming tool is moved in the direction of its longitudinal filing during the first turn of thread forming with increased by the value of the axial pressing of the tool with a feed uniformly reduced during the first turn of the thread forming by the value of the axial pressing of the tool decreasing to zero value is carried out the next steady stage of thread forming with a constant longitudinal feed of the tool equal to the pitch of the formed thread, and during the last turn of the thread forming uniformly reduce the longitudinal feed of the tool by the value of the increasing axial pressing of the tool, and the value of the variable transverse thread feed the forming tool is determined by the passage according to the dependence

where S _{ni is the} value of the thread-forming tool that is changed during the i-th pass of the transverse feed, mm; t _{i is the} standard value of the transverse feed of the thread-forming tool for the i-th passage, inversely proportional to the number of passes (standard depth of cut), mm; P _{yi is the} radial component of the thread forming force for the i-pass, kN; j _{y the} radial stiffness of the metalworking machine, kN / mm, and the longitudinal feed of the tool for the beginning of the first and end of the last turn of the thread forming is determined by the passage according to the dependencies, respectively

where s $\genfrac{}{}{0ex}{}{\text{n}}{\text{oi}}$ and S $\genfrac{}{}{0ex}{}{\text{to}}{\text{oi}}$ longitudinal feed of the thread-forming tool, respectively, for the beginning of the first and end of the last turns of the thread forming of the i-th passage, mm; P is a longitudinal feed of the steady-state stage of thread formation equal to the pitch of the thread being machined, mm; P _{xi is the} axial component of the thread forming force for the beginning of the first and end of the last revolutions of the i-th passage, kN; j _x axial rigidity of the metalworking machine, kN / mm.

 The drawing shows a schematic diagram of the formation of threads by the proposed method and a cyclogram for moving a thread-forming tool, where, as an example, the number of longitudinal forming passes is taken to be 5.

 Description of the proposed method of forming threads is an example of its implementation. To implement the method, well-known technical means are required: a screw-cutting or turning-thread-cutting semiautomatic device and a tool for forming a thread (thread-cutting tool or a single-thread rolling roller). The modes of thread formation are established taking into account specific processing conditions, based on existing standards.

The method of forming threads is carried out by moving the thread-forming tool from its initial position along the forming surface of the rotating workpiece by means of longitudinal feeding by successive longitudinal shaping passages and a transverse working feed communicated between the passes. The thread-forming tool is moved when the first longitudinal forming passage A _{1 is} made from the initial position 1 ₁ to the final position 2 ₁ , after which it is removed from the workpiece by moving B ₁ to position 3 ₁ . Reverse movement C _{1 of the} thread-forming tool to a point 4 ₂ in length is equal to the working movement. The longitudinal shaping passage of the tool comprises a cutting step, during which the sides of the thread profile of the tool successively go into operation one after another (the stage of growth to the maximum values of the radial component P _{R of} the forming force of the thread and the radial squeezing of the tool from the workpiece), the steady-state stage, during which both sides of the thread profile of the tool simultaneously form a thread on the workpiece (the stage of steady-state maximum radial component of the thread forming force s and radial extraction of the tool from the workpiece) and, finally, the step of the tool exit, during which the sides of the thread profile of the tool successively one after another come out of contact with the workpiece (the stage of reduction from the maximum to zero values of the radial component of the forming force of the thread and the radial pressing of the tool from the workpiece).

 The stages of insertion and exit of the tool are limited, respectively, by the first and last turns of the thread forming, between which is the steady-state stage of the process.

The transverse feed D ₂ for performing the second longitudinal forming pass is nominally slightly larger than the retraction value B _{1 of the} tool at the end of the previous pass, which determines the amount of machining allowance in the second pass and the value of the transverse working feed S _n2 . The second longitudinal forming passage is performed from the new position 1 _{2 by} repeating the described sequence of tool movements.

где ΔR_i величина радиального относительного отжатия инструмента от заготовки для i-го прохода, мм;
P_yi радиальная составляющая силы формообразования резьбы для i-го прохода, кН;
j_y радиальная жесткость металлообрабатывающего станка, кН/мм.The sides of the thread profile of the tool enter sequentially one after another to the full depth of processing of each longitudinal passage during the first full revolution of the workpiece. Over this period of time, the radial relative squeezing of the tool from the workpiece as a function of the radial component P _{y of} the thread forming force increases from zero to its maximum steady-state value. The magnitude of this radial extraction or an increase in the radial dimensions of the formed thread is

where ΔR _{i the} value of the radial relative extraction of the tool from the workpiece for the i-th passage, mm;
P _{yi is the} radial component of the thread forming force for the i-th passage, kN;
j _y radial stiffness of the metalworking machine, kN / mm.

 The diametrical dimensions of the thread formed in traditional processing processes are set according to the size of the thread formed in the steady state process. The dimensions of the first and last turns have dips in the average and inner diameters.

When installing a thread-forming tool to perform each longitudinal forming passage to the initial positions of points 1 ₁ .1 ₅ in the proposed processing method, the coordinates of these points are adjusted by the value of the radial pressing ΔR of the tool coming in this passage in the direction of its removal from the workpiece.

где S_ni величина изменяемой в течение i-го прохода поперечной подачи резьбообразующего инструмента, мм;
t_i нормативная величина поперечной подачи резьбообразующего инструмента для i-го прохода, обратно пропорциональная числу проходов (нормативная глубина резания), мм.The magnitude of the adjustable transverse feed threading tool for each of the passes is

where S _{ni is the} value of the thread-forming tool that is changed during the i-th pass of the transverse feed, mm;
t _{i is the} standard value of the transverse feed of a thread-forming tool for the i-th pass, inversely proportional to the number of passes (standard depth of cut), mm.

 Thus, the thread-forming tool is installed in the direction of its transverse feed for each subsequent longitudinal forming passage to the initial position, shifted by an amount inversely proportional to the number of longitudinal forming passages, reduced by the radial squeeze ΔR of the tool of the established thread forming stage. In the position of the tool adjusted by the value ΔR, it begins to cut into the workpiece. Then, during the first turn of the thread forming, the transverse feed is uniformly increased by the value of the increasing radial squeezing of the tool. Thus, at the time of the initial contact of the tool with the workpiece, they begin to work out the maximum correction value ΔR to its zero value, which is reached at the end of the first turn of the thread formation. At the end of the first turn of the thread formation, the tool occupies in the radial direction the position necessary for thread formation at the steady-state stage of the process. This stage is carried out with a constant (unchanged) lateral feed of the tool, which corresponds to the movement of the tool in traditional threading processes. During the last turn of the thread formation, the tool position in the radial direction is again adjusted, while its transverse feed is uniformly reduced in the reverse sequence by the value of the decreasing radial tool depression. The development of the corrective value of the radial displacement ΔR of the tool at the last turn of the thread formation corresponds to the development of the same corrective value of the radial displacement of the tool at the first turn of the thread formation, but differs in the reverse sequence.

 During each longitudinal forming passage, the adjustment of the transverse feed of the tool is carried out continuously at the cutting and exit stages of the tool, which makes it possible to obtain threads with the same diametrical dimensions along its entire length, including sections formed at the cutting and exit stages of the tool.

 When processing external threads, the change in the transverse feed at the first and last turns of the thread forming is directed towards decreasing the diametrical dimensions of the thread of the product, and when processing internal threads towards increasing the diametrical dimensions of the thread of the product.

During thread forming, there is also a processing error caused by elastic axial movements (depressions) of the thread forming tool along the axis of the workpiece. This processing error is due to the impact on the tool of the axial component P _{x the} force of the thread forming. The load on the profile forming part of the tool at the insertion stage (at the first turn of the thread forming) and the stage of the tool exit (at the last turn of the thread forming) is one-sided, because one of the sides of the tool thread profile either comes into full contact with the workpiece at the insertion stage before the other side, or leaves earlier than the other side from full contact with the workpiece being processed at the tool exit stage. As a result of this, the axial tool depressions as a result of the action of the axial component P _x , the thread forming forces change during the first turn of the thread forming process from the highest value when the tool is inserted into the workpiece at the beginning of the first turn, to zero after the end of the first turn of the thread forming process. At the established stage of the process, the sides of the thread profile of the tool perceive a mutually balanced load. Therefore, the axial component of the thread forming force and the corresponding elastic depressions at the steady-state stage are close to zero values. At the last revolution of the thread forming, the axial component and the elastic tool depressions caused by it increase to values corresponding to the values of the axial component of the force and elastic depressions of the first revolution of the thread forming, i.e. at the end of the last turn, they again acquire the highest values.

и

где S $\genfrac{}{}{0ex}{}{\text{н}}{\text{oi}}$ и S $\genfrac{}{}{0ex}{}{\text{к}}{\text{oi}}$ продольная подача резьбообразующего инструмента соответственно для начал первого и конца последнего оборотов резьбоформирования i-го прохода, мм;
Р продольная подача установившейся стадии резьбоформирования, равная шагу обрабатываемой резьбы, мм;
Р_xi осевая составляющая силы формообразования резьбы для начала первого и конца последнего оборотов i-го прохода, кН;
j_x осевая жесткость металлообрабатывающего станка, кН/мм.The processing error at the stages of insertion and exit of the tool is eliminated by changing the speed of its longitudinal feed. At the stage of insertion of the tool at its initial contact with the workpiece (at the beginning of the first turn of threading) and at the stage of exit of the tool at its final contact with the workpiece (at the end of the last turn of threading), the tool is moved with a longitudinal feed equal to each of the longitudinal passes:

and

where s $\genfrac{}{}{0ex}{}{\text{n}}{\text{oi}}$ and S $\genfrac{}{}{0ex}{}{\text{to}}{\text{oi}}$ longitudinal feed of the thread-forming tool, respectively, for the beginning of the first and the end of the last revolution of the thread formation of the i-th passage, mm;
P is a longitudinal feed of the steady-state stage of thread formation equal to the pitch of the thread being machined, mm;
P _{xi is the} axial component of the thread forming force for the beginning of the first and end of the last revolutions of the i-th passage, kN;
j _x axial rigidity of the metalworking machine, kN / mm.

Величины этих осевых упругих отжатий для начала стадии врезания и конца стадии выхода инструмента представляют собой корректирующую величину для традиционной подачи при резьбоформировании, равной шагу Р резьбы за один оборот заготовки. Направление осевого упругого отжатия инструмента на стадии врезания противоположно направлению продольной подачи, а на стадии выхода инструмента совпадает с ней.Dependencies that determine the longitudinal feed of the tool for the beginning of the first S $\genfrac{}{}{0ex}{}{\text{n}}{\text{oi}}$ and the end of the last S $\genfrac{}{}{0ex}{}{\text{to}}{\text{oi}}$ the turns of the thread forming take into account the value of the axial elastic squeezing of the tool from the workpiece for each i-th passage:

The values of these axial elastic squeezes for the beginning of the insertion stage and the end of the tool exit stage are a correction value for the traditional feed during threading, equal to the thread pitch P for one revolution of the workpiece. The direction of the axial elastic pressing of the tool at the insertion stage is opposite to the direction of the longitudinal feed, and at the exit stage of the tool coincides with it.

The thread-forming tool at initial contact with the workpiece, at the beginning of the first turn of the thread forming, is moved with a longitudinal feed S $\genfrac{}{}{0ex}{}{\text{n}}{\text{oi}}$ decelerated by the end of the first turn of the thread formation to a feed rate P equal to the thread pitch per revolution of the workpiece. At the established stage of the process, the longitudinal feed of the tool is equal to the step of the formed thread per revolution of the workpiece. At the exit stage, the tool is moved with a longitudinal feed, increasing from a value equal to the thread pitch per revolution of the workpiece at the beginning of the last revolution of the thread forming, to the value S $\genfrac{}{}{0ex}{}{\text{to}}{\text{oi}}$ at the end of the last turn of threading.

 Correction at the stages of insertion and exit of the tool of the transverse and longitudinal feeds is carried out at each longitudinal forming pass.

 The result of the compensation of dynamic errors that occur at the initial and final stages of thread forming is the elimination of existing thread defects, which are a traditional hidden marriage of the first and last turns of the thread in diametric dimensions (average and inner diameters) and thread pitch.

The modes of threading are set based on the specific processing conditions according to the existing general engineering normative and reference literature. The values of the radial P _y and axial P _x components of the forming force of the thread are determined, based on the processing conditions, according to the general engineering reference literature. The rigidity of metalworking equipment is found in accordance with the type of equipment used in the regulatory literature, etc.

 An example of a specific implementation.

A special external thread was cut on the plunger of the sucker rod pump of production wells. Parameters of the cut thread: outer diameter d 37.348 mm; thread pitch P 1.814 mm; thread profile angle α 60 ^o ; thread length l 17 mm. Thread cutting was carried out using a CNC screw-cutting lathe. 16K20FZ for 5 consecutive longitudinal forming passages of a thread-cutting tool. The workpiece material to be processed is steel 38XMA, having a tensile strength s _of 900 MPa. Cutting speed V 113 m / min. Cooling-lubricating fluid 3% emulsion from emulsol Ukrinol 1. Material of the cutting part of the thread-cutting tool carbide T15K6.

When the cutter was set to its initial position for the execution of each longitudinal forming pass, the radial squeezing of the tool was taken into account, increasing during the first turn of thread forming from zero at the initial contact of the tool with the workpiece to the maximum steady-state value at the end of the first turn of thread forming. The cutting depth t _{i of the} thread-cutting tool according to the regulatory data (6, p. 9, card 1.1.) Was for five passes: t ₁ 0.17 mm; t ₂ 0.43 mm; t ₃ 0.78 mm; t ₄ 1.07 mm; t ₅ 1.23 mm and, consequently, the thickness of the layer cut off by the tip edge of the cutter for five passes (single radial cutting of the tool) was in the passages: S _R1 0.17 mm; S _R2 0.26 mm; S _R3 0.35 mm; S _R4 0.29 mm; S _R5 0.16 mm.

The main component P _{z of} the cutting force according to empirical dependencies (7, p. 70) was in the passages: P _z1 0.74 kN; P _z2 2.34 kN; P _z3 4.89 kN; P _z4 5.67 kN; P _z5 4.28 kN.

The radial P _y (at the steady-state stage of the process) and the axial P _x (at the cutting and tool exit stages) constituting the cutting forces in fractions of the main component P _z cutting forces were defined as P _y P _z / 4 and P _x P _z / 3, which amounted in passages: P _y1 0.19 kN; P _y2 0.59 kN; P _y3 1.22 kN; P _y4 1.42 kN; P _y5 1.07 kN; P _x1 0.25 kN; P _x2 0.78 kN; P _x3 1.63 kN; P _x4 1.89 kN; P _x5 1.43 kN.

The standard rigidity of the used screw-cutting machine mod. 16K20FZ was: j _y 28 kN; j _x 48 kN.

что для каждого из проходов составляло:

Определяемая (коpректируемая) поперечная подача резьбонарезного резца, учитывающая величину его радиального отжатия ΔR_i, определялась по проходам, как
S_ni= t_i- ΔR_i, мм,
что для каждого из проходов составляло:

Рассчитанные величины поперечных подач S_ni резьбонарезного резца по проходам определяли его положение при начальном контакте с заготовкой. К концу первого оборота резьбоформирования поперечная подача резьбонарезного резца, равномерно увеличиваясь, приобретала величину, равную ранее определенной нормативной глубине резания t_i, и составляла для каждого из проходов: S_n1 t₁ 0,17 мм; S_n2 t₂ 0,43 мм; S_n3 t₃ 0,78 мм; S_n4 t₄ 1,07 мм; S_n5 t₅ 1,23 мм.The calculated corrective value of the radial extraction of the tool from the workpiece for the steady-state stage of the process was determined by passes as

that for each of the passes was:

The determined (corrected) transverse feed of the thread-cutting tool, taking into account the value of its radial pressing ΔR _i , was determined by the passages, as
S _ni = t _i - ΔR _i , mm,
that for each of the passes was:

The calculated values of the transverse feeds S _{ni of the} thread-cutting tool along the passages determined its position at initial contact with the workpiece. By the end of the first turn of the thread forming, the transverse feed of the thread-cutting tool, increasing uniformly, acquired a value equal to the previously determined standard depth of cut t _i , and for each of the passes was: S _n1 t ₁ 0.17 mm; S _n2 t ₂ 0.43 mm; S _n3 t ₃ 0.78 mm; S _n4 t ₄ 1.07 mm; S _n5 t ₅ 1.23 mm.

 At this constant for each of the passages of the transverse feed of a thread-cutting tool, thread processing was performed at a steady stage of the process.

(в конце последнего оборота резьбоформирования на каждом проходе резца).Starting from the last turn of the thread forming, the transverse feed along the passages of the thread-cutting tool was again corrected in the reverse sequence as compared to the cutting stage, i.e. decreased uniformly from the above values of the steady-state stage of the process: S _n1 t ₁ 0.17 mm; S _n2 t ₂ 0.43 mm; S _n3 t ₃ 0.78 mm; S _n4 t ₄ 1.07 mm; S _n5 t ₅ 1.23 mm (at the beginning of the last turn of the thread formation at each cutter pass) to the values calculated earlier for the cutting stage:

(at the end of the last turn of the thread formation at each cutter pass).

 The values of the transverse feeds of a thread-cutting tool at various stages of threading along the passages are presented in table. one.

When installing the thread-cutting tool in the initial position for each longitudinal forming passage, along with the value of the radial squeezing of the tool from the workpiece, the value of the axial squeezing of the tool at the stages of its cutting and exit was also taken into account. These depressions as a result of the influence of the axial component P _x the cutting force changed when the tool was inserted from the highest value at the beginning of the first turn of the thread forming process to zero at the end of the first turn of the thread forming process. The steady-state stage proceeded with axial components of the cutting force and axial tool depressions close to zero values. When the tool exits, the axial components of the cutting force and axial depressions increased towards the end of the last turn of the thread forming to the values equal to the highest corresponding to the beginning of the stage of cutting the tool.

что для каждого из проходов составляло:

Определяемая (корректируемая) продольная подача резьбонарезного резца, учитывающая величину его осевого отжатия ΔS_oi для начала первого оборота резьбоформирования, определялась по проходам как
S $\genfrac{}{}{0ex}{}{\text{н}}{\text{oi}}$ = P + ΔS_oi,
что для каждого из проходов составляло:

Рассчитанные величины продольных подач S $\genfrac{}{}{0ex}{}{\text{н}}{\text{oi}}$ резьбонарезного резца являлись подачами инструмента при его начальном контакте с заготовкой. К концу первого оборота резьбоформирования продольная подача резьбонарезного резца, равномерно уменьшаясь, приобретала для каждого из проходов нормативную (некорректируемую) величину, равную шагу нарезаемой резьбы Р 1,814 мм на один оборот заготовки. С такой постоянной продольной подачей осуществлялось нарезание резьбы на установившейся стадии процесса. Начиная с последнего оборота резьбоформирования, продольная подача по проходам резьбонарезного резца снова корректировалась равномерно уменьшалась от значения установившейся стадии резьбоформирования, равного величине шага резьбы за один оборот заготовки (в начале последнего оборота резьбоформирования), до значений S $\genfrac{}{}{0ex}{}{\text{к}}{\text{oi}}$ (в конце последнего оборота резьбоформирования), определявшихся по проходам как
S $\genfrac{}{}{0ex}{}{\text{к}}{\text{oi}}$ = P - ΔS_oi,
что для каждого из проходов составляло:

Величины продольных подач резьбонарезного резца на различных стадиях резьбоформирования по проходам представлены в табл. 1
Для получения сравнительных данных, наряду с нарезанием резьбы предлагаемым способом, проводилось нарезание резьбы резьбонарезным резцом известным, согласно прототипу, способом, т.е. без корректирования поперечной и продольной подач на стадиях врезания и выхода инструмента. Прочие условия осуществления сопоставляемых способов резьбонарезания были одинаковыми. Номинальные значения основных параметров резьбы и отклонения этих значений от номинальных при резьбонарезании сопоставляемыми способами обработки приведены в табл. 2.The calculated corrective value of the axial pressing of the tool from the workpiece for the beginning of the first and end of the last turn of the thread formation was determined by the passages as

that for each of the passes was:

The determined (corrected) longitudinal feed of the thread-cutting tool, taking into account the value of its axial pressing ΔS _oi for the beginning of the first turn of the thread forming, was determined by passes as
S $\genfrac{}{}{0ex}{}{\text{n}}{\text{oi}}$ = P + ΔS _oi ,
that for each of the passes was:

The calculated values of the longitudinal feeds S $\genfrac{}{}{0ex}{}{\text{n}}{\text{oi}}$ thread-cutting tool was the feed of the tool at its initial contact with the workpiece. By the end of the first turn of the thread forming, the longitudinal feed of the thread-cutting tool, evenly decreasing, acquired for each of the passes a standard (non-correctable) value equal to the pitch of the cut thread P 1,814 mm per revolution of the workpiece. With such a constant longitudinal feed, threading was carried out at the steady-state stage of the process. Starting from the last turn of the thread forming, the longitudinal feed along the passages of the thread cutting tool was again corrected to decrease evenly from the value of the steady-state stage of thread forming equal to the value of the thread pitch for one revolution of the workpiece (at the beginning of the last turn of the thread forming), to the values S $\genfrac{}{}{0ex}{}{\text{to}}{\text{oi}}$ (at the end of the last turn of the thread forming), determined by the passages as
S $\genfrac{}{}{0ex}{}{\text{to}}{\text{oi}}$ = P - ΔS _oi ,
that for each of the passes was:

The values of the longitudinal feeds of the thread-cutting tool at various stages of threading along the passages are presented in table. one
To obtain comparative data, along with threading by the proposed method, threading was carried out by a thread-cutting tool known, according to the prototype, by a method, i.e. without adjusting the transverse and longitudinal feeds at the stages of cutting and tool exit. Other conditions for the implementation of comparable threading methods were the same. Nominal values of the main parameters of the thread and deviations of these values from the nominal values when thread cutting by comparable processing methods are given in table. 2.

 Analysis of the data given in table. 2 shows that the compared methods of threading provided obtaining products of unequal quality of thread. The accuracy of the thread obtained by the proposed method is higher than the accuracy of the thread made in a known manner, in the following parameters: average diameter, inner diameter and thread pitch. On the threaded parts obtained by the proposed method, the defects of decreasing the average and internal diameters of the thread and increasing the pitch of the threads at its first and last turns, which took place on the parts made in a known manner, were eliminated.

 The obtained comparative data indicate the possibility of controlling the accuracy of the diametrical dimensions of the thread and its pitch at the stages of cutting and tool exit by introducing at these stages the compensation of elastic displacements of the tool and the workpiece.

 Currently, multi-pass cutting and rolling of external and internal, cylindrical and tapered threads is carried out without compensation for dynamic processing errors that occur at the stages of cutting and tool exit.

Using the proposed method of forming threads provides, in comparison with existing methods, the following technical and economic effect:
improving the quality of the thread of the product in terms of accuracy; reduction of arising systematic production errors of threading and a decrease in the dispersion of the thread sizes of the processed products.

Claims (2)

 1. The method of forming threads, in which the product is rotated, and the threading tool informs the transverse feed and move along the forming surface of the product, making allowance for several passes, characterized in that the transverse and longitudinal feeds on each of the passages are adjusted, while the thread-forming tool in the initial position is shifted in the opposite direction to the feed, by the value of the radial squeezing of the tool in this longitudinal passage, then, during the first revolution of the product, transverse and the longitudinal feed is increased, and at the last revolution of the product is reduced by the value of the radial and axial pressing of the tool, respectively. 2. The method according to claim 1, characterized in that the transverse feed at the i-th passage is adjusted by the value of S _ni , determined by the formula

where t _i is the standard value of the transverse feed of the thread-forming tool for the i-th passage, mm;
P _{yi is the} radial component of the thread forming force for the i-th passage, kN;
j _y is the radial stiffness of the glass, kN / mm,
and the longitudinal feed of the tool to start the first S $\genfrac{}{}{0ex}{}{\text{n}}{\text{oi}}$ and the end of the last S $\genfrac{}{}{0ex}{}{\text{to}}{\text{oi}}$ the speed of threading is determined by the formulas

where P is a longitudinal feed equal to the pitch of the formed thread, mm;
P _{xi is the} axial component of the thread forming force for the beginning and end of the last revolutions of the i-th passage, kN.

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