RU2036068C1 - Method of control of process of combined machining and surface plastic deformation - Google Patents

Abstract

FIELD: mechanical engineering. SUBSTANCE: total frictional force of machine tool carriage, maximum and minimum values of cutting force radial component are preliminarily determined, and stabilization of unchuckings is accomplished by machining with maintaining of relation: [const≅ P_y+P_dcosα≅ const+2F] and provision of the variation of cutting force radial component from P_{y min} to (P_{y min}-2F), where P_y - cutting force radial component, N; P_d - strain force applied to deforming member, N; α - angle of setting of deforming member relative to cutting tool, deg; F - total frictional force of carriage, N; P_{y max} and P_{y min} - maximum and minimum values of cutting force radial component, respectively, N. EFFECT: facilitated procedure. 4 cl, 5 dwg, 1 tbl

Description

 The invention relates to mechanical engineering and can be used in enterprises when turning, planing, boring and milling workpieces from structural and difficult to process materials.

Known methods of process control with combined processing by cutting and surface plastic deformation [1]
A known processing method closest in technical essence to the invention [2] in which the stabilization of the squeezes is carried out by applying to the deforming element an additional deformation force equal to the change in the radial component of the cutting force, wherein the value of the deformation force is taken in the range from 0.7 P _opt to 1 , 3 P _opt , where P _{opt is the} deformation force.

A disadvantage of the known control method is that the control method does not take into account the friction forces in the machine system and cannot be implemented when changes in the cutting force exceed the above range of changes in the deformation force, which reduces the accuracy of the processing. In addition, the increased range of changes in the deformation force from R _d1 to R _d2 determines the obtaining of a treated surface that is heterogeneous in quality, the value of which will vary widely from R _a1 to R _a2 .

 The aim of the invention is the expansion of technological capabilities by improving the quality and accuracy of processing.

This is achieved by preliminarily determining the total friction force of the machine support, the largest and smallest values of the radial component of the cutting force and the nature of its change over time when cutting, and stabilization of the depressions is carried out by maintaining the ratio
const ≅ P _y + P _d cosα ≅ const + 2 F, and ensuring optimal deformation forces in the time interval corresponding to a change in the radial component of the cutting force from P _уmin to Р _{у max} 2F, where Р _{у is the} radial component of the cutting force, N; R _{d the} deformation force applied to the deforming element H; α installation angle of the deforming element relative to the cutter, deg; F the total friction force of the caliper, N; _Umax P, P _ymin respectively the maximum and minimum values of the radial component of the cutting forces, N.

Moreover, stabilizing is performed expeller by applying additional deformation element deforming force, changing its value at the opposite phase with respect to a change in the radial component of the cutting force while maintaining the same angle α with maintaining ratio P _umax P _ymin ≥ P _ext cos α≥ P _ymax P _ymin 2F, where F _ext additional deformation force applied to the deforming member, N.

(P_ymax + P_ymin) F, где Р_ср. среднее значение радиальной составляющей силы резания, Н.In addition, the processing is carried out with the coincidence in time of the optimal deformation force and the radial component of the cutting force equal to
R _cf

(P _ymax + P _ymin ) F, where P _cf. the average value of the radial component of the cutting force, N.

In addition, processing is performed with the angle α in opposite phase with respect to a change in the radial component of the cutting force and maintaining ratio P _umax P _ymin ≥ P _{opt (cos α min -cosα max) ≥} P ymax P ymin 2F, where F _opt optimal force deformation, N; α _min , α _{max the} smallest and largest installation angle of the deforming element, deg.

In FIG. 1 shows a schematic diagram of a device for controlling a process by the proposed method; in FIG. 2 the same, side view showing the relative position of the cutter and the deforming element during shaft processing (α≅ ± 90 ^о ); in FIG. 3 graphs of changes in surface roughness depending on the magnitude of the projection of the deformation force on the direction of the radial cutting force; in FIG. 4 graph of the movement of the caliper during its load and unloading by radial force; in FIG. 5 is a graph of changes in radial cutting force and strain force over time.

 The method of controlling the process of combined processing is as follows.

When machining part 1 with cutter 2 due to fluctuation in stock, hardness of the processed material, etc. cutting force varies. Suppose that its radial component P _y , as the most affecting the accuracy of processing, varies from P _{y min} to P _{y max} . The time variability of the force P _y determines various elastic depressions of the body 3 of the caliper 4, as the most pliable node of the machine system, directly associated with obtaining parts of a certain accuracy.

 As a result, the size of the workpiece surface will fluctuate, which reduces the accuracy of processing. In addition, a deforming element, for example, a roller 5, processing surface plastic deformation (PPD) and located after the cutter will have a different interference with respect to the surface to be treated, i.e. processing will occur with different deformation forces, which, given the hyperbolic nature of the dependence on the deformation forces, will lead to a spread in its magnitude.

Initially, experimentally or analytically determine the largest and smallest values of the radial component of the cutting force and the nature of its change in time when cutting with the cutter and the total friction force of the most malleable unit of the support machine system in which the tools are mounted. To eliminate or significantly reduce the elastic vibrations of the caliper together with the cutter, the processing is carried out with the following ratio
const ≅ P _y + P _d cos α≅ const + 2F, (1)
The forces P _y and P _d equal:
P _y P _min + Δ P _d (2) where P _{y min is the} smallest value of the radial component of the cutting force (the constant part of the power P _y ); Δ P _{y is the} variable part of the force.

R _d P _opt + P _add , (3) where P _{opt is the} optimal deformation force that ensures the minimum roughness of the treated surface (a constant part of the force R _d ); P _additional additional deformation force (variable part of the force P _d ).

Then we rewrite relation (1) in the form
const ≅ P _ymin + Δ P _y + P _opt cosα +
+ P _add cos α≅ const + 2F. (4)
Relations (1) and (4) can be fulfilled due to: a periodic change in the force P _add with a constant angle α; periodic changes in the angle α at a constant value of R _d P _opt (P _add 0); due to changes and P _add and angle α
Consider the first option.

Then P _min + P _opt cos α const and expression (4) can be represented as follows
0 ≅Δ P _y + P _add cos α≅ 2F (5) or
-ΔP _y ≅ P _add cos α≅ 2F Δ P _y (6)
From the expressions (5) and (6) it follows that the additional deformation force P _add should change in antiphase with respect to the change in the radial component of the cutting force while keeping the angle α unchanged
Since (Δ P) _max P _ymax P _ymin and considering the above expressions (5) and (6) can be represented as: P _ymax P _ymin ≥ P _ext cos α≥ P _ymax P _ymin
2F, (7) where
(P _{ext cos α) max P ymax P ymin} ;
(P _{ext cos α) min P ymax P ymin} 2F, where F _ymax, P _ymin respectively the maximum and minimum values of the radial component of the cutting force; P _additional additional deformation force applied to the deforming element. That is, to improve the oscillations of the radial component of the cutting force P _y to the deforming element 5, for example a roller, by means of the adjusting mechanism 6 (Fig. 1), an additional force P _{add is} applied, which reduces the fluctuations in the force P _y. The additional deformation force P _add on the parts is created by a screw, cam, etc. and transmitted by means of a spring 7 (FIG. 1).

 To determine the magnitude of the adjusting effect of the adjusting mechanism 6 on the deforming roller 5, the housing 3 has a protrusion 8 in contact with the elastic beam 9. According to the indications of the indicator 10, fixing the deviation (deflection) of the beam 9, turn the knob of the adjusting mechanism 6, changing the magnitude of the radial force on the roller and maintaining the indicator in a certain range, this ensures the fulfillment of relation (7).

To determine the total friction force F of the caliper, graphs of the elastic displacements of the tool are constructed together with the caliper against the radial load P _y (Fig. 4) when they are loaded (curve 11, Fig. 4) and unloaded (curve 12). The magnitude of the force 2F is shown in the graph of figure 4. When the force changes from P _уmax to Р _уmin (unloading), the support together with the cutter 2 and the housing 3 will move to the part by the value Δ у ₁ у ₂ . The line of displacements of the cutter during unloading (with a decrease in the force P _y ) is represented by the section AB curve 12. When the load increases from P _min to P _{y max the} support will also move by the same value Δ y ₁ y ₂ . The line of movement of the cutter under load (with an increase in P _y ) is represented by section CE of curve 11.

As can be seen from figure 4, a decrease in the load on the caliper from P _max to P _max 2F does not lead to movement of the caliper, i.e. he is motionless at this change in load. Since the cutter and the roller are located on one side of the part, due to the change in the force effect of the roller on the support of the machine, the load can be maintained in the indicated range, i.e. we load the caliper while reducing the radial load during cutting, which increases the accuracy of processing due to the absence of elastic movements of the caliper. Therefore, an additional force P _{add is} applied to the deforming element of the roller 3, changing in antiphase with the radial force of the cutter and supplementing the minimum radial force to a value equal to or greater than P _ymax 2F.

Consider the second option for stabilizing the squeezes. Then P _уmin const and expression (4) with P _add 0 can be represented as:
0 ≅Δ P _y + P _opt cos α≅ 2F (8) or
ΔP _y ≅ P _opt cos α≅ 2F Δ P _y (9)
It follows from expressions (8) and (9) that the projection of the optimal deformation force on the direction of the radial component of the cutting force should change in antiphase compared to the change in the variable part of the radial component of the cutting force. Since P _opt const, this can only be achieved by changing the angle from α _min to α _max . Since Δ P _max P _ymin and taking into account the above, expressions (8) and (9) can be represented as:
P _ymax P _ymin ≥ P _opt (cos α _{min
cos α max) ≥ P ymax P} ymin 2F, ( 10) where P _opt optimal deforming force; α _min , α _{max the} smallest and largest installation angles of the deforming element relative to the axis of the part during processing, respectively.

The greatest projection of the deformation force
P ₃ P _opt cos α _min (11)
From the point of view of obtaining the smallest range of changes in the angle P ₁ P ₃ (P _max P _min 2F) P _opt cos α _max ;
(12)
cos α _max P ₁ / P _opt (13)
The second option is more difficult to constructively, but it provides the best quality of the processed surface.

Thus, using the proposed options, the change in the total radial force acting on the caliper from the side of the cutter and the deforming element, subject to the relations (1), (7) and (10), will be limited by the limits Р _уmax and Р _уmax 2F (segment АЕ on 4), and the radial movement of the caliper with the cutter, equal to ₁ , will not change, i.e. the cutter will remain motionless. If we accept the tolerance on the processing error in diameter equal to δ, then we can assume the difference in the readings of indicator 10 (Fig. 1) by δ / 2, i.e. Y ₃ Y ₁ δ / 2 (Fig. 4). Following the indication of the indicator 10, through the adjusting mechanism 6 achieve the fulfillment of the ratio (1) with an error equal to δ / 2.

After the first stage of controlling the process of combined processing, when the accuracy of processing is achieved, it is necessary to perform the second stage of control, which ensures the best purity of the treated surface. The dependence of the surface roughness on the deformation force is parabolic in nature and therefore there is an optimal deformation force P _opt , which ensures the smallest roughness of the treated surface. On the other hand, with an increase in the amplitude of the oscillations of P _{additional, the} surface heterogeneity in terms of its roughness increases, so it is necessary to strive for a minimum range of variation of P _additional . These conditions are provided if the moment in time of the projection of the optimal deformation force on the direction of the radial component of the cutting force is within the time interval of the change in this force, determined by the minimum Р _уmin and the maximum, reduced by twice the total friction force, Р _уmax 2F by its values.

In FIG. 5, the change in the radial component of the cutting force with time is represented by curve 16, and the change in the deformation force of curve 17. This time interval is located between the time τ ₁ and τ ₂ , τ ₂ and τ ₃ on the graph (Fig. 5) of the change in the radial force Ru f (τ ) Points A and B, B ₁ and A _{1 are the} extreme points of the intervals.

 Two limiting cases and many intermediate ones are possible, one of which is optimal.

In the first case, processing occurs when the projection of the deformation force on the direction of the radial component of the cutting force changes from P ₁ to P ₃ (Figs. 3, 5), where the force P ₁ P _opt cos α corresponds to the minimum roughness of the treated surface, equal to R _a3 . The roughness of the machined surface changes from R _a3 R _amin to R _a1 (curve 13, Figure 3), and R _ext cos α P _ymax P _ymin 2F.

In the second case, the processing occurs when the projection of the deformation force on the direction of the radial component of the cutting force changes from P ₁ to P ₃ (Fig. 3.5), where the force P ₃ P _opt cos α corresponds to the minimum roughness of the machined surface, equal to R _a3 . The roughness of the machined surface is changed by R _a1 to R _a3 (curve 14), and R _ext cos α P _ymax P _ymin 2F.

(P_ymax 2F P_ymin),
P_cp

(P_ymax + P_ymin) F. (11) Т.е. имеет место совпадение во времени действия оптимального усилия деформирования и радиальной составляющей силы резания, определяемой из выражения (11). Величина отклонения проекции дополнительной силы оптимального значения Р₂ составляет половину величины для первого и второго случаев и равна
(Р_доп cos α)'

(P₃ P₂)

(P_ymax P_ymin 2F).In the third, optimal case, processing occurs when the force P _add cos α also changes from P ₁ to P ₃ (Fig. 3), but the smallest surface roughness is achieved when the projection moment of the optimal deformation force projection on the direction of the radial component of the cutting force coincides with the moment the time of occurrence of the variable radial component of the cutting force equal to (figure 5)
P _cf P _ymin +

(P _ymax 2F P _ymin ),
P _cp

(P _ymax + P _ymin ) F. (11) i.e. there is a coincidence in time of the action of the optimal deformation force and the radial component of the cutting force, determined from expression (11). The deviation of the projection of the additional force of the optimal value of P ₂ is half the magnitude for the first and second cases and is equal to
(P _add cos α) '

(P ₃ P ₂ )

(P _ymax P _ymin 2F).

The roughness of the machined surface varies from R _a2 <R _a1 to R _a3 = R _amin (curve 15), i.e., the treatment provides the smallest spread in the roughness of the machined surface.

 A method of automatically controlling the process of combined processing of cutting and PPD is as follows.

The oscillations of the radial component of the cutting force P _y during processing causes elastic vibrations of the housing 3, which are then transmitted through the protrusion 8 to the beam 9 and are monitored by sensors D ₁ and D ₂ . The signals from the sensors D ₁ and D _{2 are} amplified by the amplifier and fed to the comparing device SU, where they are compared with the signals of the master device memory. In the event of a mismatch of signals in magnitude and sign, a command is sent to the actuator MI, which controls the adjusting mechanism 6, which regulates the movement of the deformation roller 5 to establish an acceptable mismatch of the signals of the master and the comparison devices. Thus, during processing, the condition for fulfilling relation (1) is constantly maintained.

^{PRI me} R 1. Make a shaft of steel grade 45 with a diameter of 80 ^-0.03 mm 400 mm long. The part is machined with a combination tool (CI), consisting of a circular tool with a diameter of 42 mm and a profile roller with a diameter of 42 mm. Processing Modes: V 125 m / min; S 0.28 mm / rev; t 0.4 mm; R _opt 800 N. The angle of installation of the roller α 0. Before processing, determine the value of the total friction force F 50 N, the values of the radial component of the cutting force: P _ymax 900 N; _Rumin 600 N. Produce stabilization of the squeezes due to the application of additional deformation forces.

 The first case.

P ₁ P _opt cos α 800 ˙ cos0 ^o 800 H;
_Additional P ^min P P _{ymin ymax} 2F 900600
100,200 N;
R ₃ R ₁ + R _ext ^min P ₁ + (P _ymax P _ymin 2F) + 800 (900 600 100) 1000 N;
R _a3 0.3 μm; R _a1 1.0 μm.

 The second case.

P ₃ P _opt cos α 800 H; P ₁ P ₃ P _add ^min 800 (900 600 100) 600 N;
R _a3 0.3 μm; R _a1 1.0 μm.

 The third case.

P ₂ P _opt cos α 800 H; P _add ^min P _ymax 2F P _ymin 900 600 100 200 N.

R _a3 0.3 μm; R _a2 0.4 μm.

Having calibrated the deflection of the beam 9 (Fig. 1) by a certain force P ₁ and P ₃ using indicator 10 (division value 0.001 mm) and adjusting mechanism 6, we carry out the processing according to the selected case conditions. The processing results are summarized in table.

PRI me R 2. For the processing conditions of the shaft of example 1 to stabilize the squeezes by changing the angle α. Determine the change in the angle α if α _min 20 ^about .

P ₃ P _opt ˙ cos α _min 800 ˙ cos 20 ^o 752 N.

P ₁ P ₃ P _add ^min ; P _add ^min P _max P _min 2F 900 600 100 200 N.

P ₁ 752 200 552 N.

0,69.P ₁ P _opt ˙ cos α _max ; cos α _max

0.69.

α _max 46.37 ^about .

By varying the angle α from 20 to ^about 46.37 achieve stabilizing wrung cutter.

 The proposed processing method is simple to implement, extends the technological capabilities of the combined processing. Tests of the proposed method showed its effectiveness in the processing of shafts. The method provides an increase in accuracy by 1.5-2 times in comparison with the known methods, takes into account the condition of the equipment during combined processing of CI and reduces the dispersion of the roughness of the treated surface due to a decrease in the additional deformation force as compared with the amplitude of oscillations of the radial component of the cutting force.

Claims (4)

1. METHOD FOR CONTROLLING THE PROCESS OF COMBINED CUTTING AND SURFACE-PLASTIC DEFORMATION, including determining the optimal deformation force that provides the smallest roughness, measuring deviations of the elastic depressions of the technological system that arise as a result of changes in the radial component of the deformation of the cutting force and the simultaneous cutting force and deformation of the cutting force parts by cutting and deforming elements located on one side of the part, characterized in that, with the purpose of expanding technological capabilities by improving the quality and accuracy of processing, preliminarily determine the total friction force of the machine support, the largest and smallest values of the radial component of the cutting force and the nature of its change in time when cutting, and stabilization of the squeezes is carried out by introducing processing with maintaining
const ≅ P _y + P _d cosα ≅ const + 2F
and ensuring optimal deformation forces at time intervals corresponding to changes in the radial component of the cutting force from

where P is _the radial component of the cutting force, N;
P _{d the} deformation force applied to the deforming element, N;
α installation angle of the deforming element relative to the cutter, deg;
F the total friction force of the caliper, N;

respectively, the largest and smallest values of the radial component of the cutting force, N. 2. The method according to claim 1, characterized in that the stabilization of the squeezes is carried out by applying an additional deformation force to the deforming element, changing its values in antiphase with respect to the change in the radial component of the cutting force while maintaining the angle α unchanged while maintaining the ratio

where P _{d about p the} additional deformation force applied to the deforming element, N. 3. The method according to claims 1 and 2, characterized in that the processing is carried out with a coincidence in time of the action of the optimal deformation force and the radial component of the cutting force equal to

where P _{with p is the} average value of the radial component of the cutting force, N. 4. The method according to claim 1, characterized in that the processing is carried out with a change in the angle α in antiphase with respect to the change in the radial component of the cutting force and withstanding the ratio

where P _{o p t} the optimum deformation force H;
α _min , α _{max the} smallest and largest installation angle of the deforming element, deg.

Images