阅读说明：本技术 一种液压偶件精密珩磨孔径预测及控制方法 (Hydraulic coupling part precision honing aperture prediction and control method ) 是由 杨长勇 苏浩 何鸿宇 吴超迪 傅玉灿 丁文锋 徐九华 于 2021-05-07 设计创作，主要内容包括：本发明公开了一种液压偶件精密珩磨孔径预测及控制方法,步骤是：获取珩磨油石的加工参数及几何参数与珩前底孔孔径值；建立珩磨材料去除体积预测模型,考虑停留时间对越程段材料去除体积的影响,得到改进后的珩磨材料去除率公式,初步计算珩磨材料去除率Q-(m)与D-(s)值；根据初始珩后孔径分布,计算出越程段停留时间取值；建立珩磨材料去除体积改进预测模型,并预测珩磨材料去除率及珩后孔径值；开展正交珩磨试验,针对珩磨试验数据进行显著性分析,分析各工艺参数对材料去除率及珩后孔径差的影响,并验证模型的准确性。结果表明：增设合适的停留时间并采用最佳工艺参数进行珩磨加工,可满足珩后孔径一致性要求,并增大珩磨材料去除率。(The invention discloses a method for predicting and controlling a precision honing aperture of a hydraulic coupling part, which comprises the following steps: acquiring processing parameters and geometric parameters of honing oilstones and aperture values of bottom holes before honing; establishing a honing material removal volume prediction model, considering the influence of the residence time on the skip segment material removal volume to obtain an improved honing material removal rate formula, and primarily calculating the honing material removal rate Q m And D s a value; calculating the value of the retention time of the over-travel section according to the initial post-honing pore size distribution; establishing a honing material removal volume improvement prediction model, and predicting the honing material removal rate and the post-honing aperture value; and carrying out orthogonal honing test, carrying out significance analysis on honing test data, analyzing the influence of each process parameter on the material removal rate and the post-honing aperture difference, and verifying the accuracy of the model. The results show that: adds proper residence time and adopts the optimal technological parameters to carry out honing processing, thus meeting the requirement of honing the holeThe diameter consistency is required, and the removal rate of the honing material is increased.)

1. A method for predicting and controlling the aperture of a precision honing of a hydraulic coupling part is characterized by comprising the following steps:

step S1, obtaining the processing parameters and the geometric parameters of the honing oilstone and the aperture value of the pre-honing bottom hole; the parameter is the total length l of the oilstone_sWidth b, upper overrun amount l_uLower overrun amount l_dInitial bore diameter d of the valve₀Reciprocating velocity V_aRotational speed V_n；

Step S2, establishing a honing material removal volume prediction model, considering the influence of the residence time on the skip segment material removal volume, obtaining an improved honing material removal rate formula, and primarily calculating the honing material removal rate Q_mAnd D_sA value;

step S3, calculating the value of the retention time of the over-travel section according to the pore size distribution after the initial honing;

step S4, establishing a honing material removal volume improvement prediction model, and predicting the honing material removal rate and the post-honing aperture value;

and step S5, carrying out orthogonal honing test, carrying out significance analysis on honing test data, analyzing the influence of each process parameter on the material removal rate and the post-honing aperture difference, and comparing the material removal rate and the post-honing aperture difference of the honing test with the simulation result of the prediction model to verify the accuracy of the model.

2. The method for predicting and controlling the precise honing bore diameter of the hydraulic coupling part according to claim 1, wherein in step S2), the theoretical formula of the removal rate of the honed material is as follows:

when 0. ltoreq. z < (l)_s-l_d) When the temperature of the water is higher than the set temperature,

when (l)_s-l_d)≤z＜l_sWhen the temperature of the water is higher than the set temperature,

when l is_s≤z＜(H-l_s) When the temperature of the water is higher than the set temperature,

when (H-l)_s)≤z＜(H-l_s+l_u) When the temperature of the water is higher than the set temperature,

when (H-l)_s+l_u) When z is less than or equal to H,

according to the difference of the height position of the oilstone in the valve sleeve hole, the material removal rate formula can be decomposed into five parts, wherein V_aIs the reciprocating speed, F_hrIs a positive pressure of oilstone_uAnd l_dRespectively an upper overrun amount and a lower overrun amount, b is the width of the oilstone, H is the height of the workpiece hole, l_sExpressed as the length of the oilstone, the material removal rate is expressed as Q_mIndicating that z represents the height position of the oilstone in the inner hole, and the contact load ratio K can be calculated;

the functional relationship exists between the oilstone positive pressure and the honing pressure, and the expression is as follows:

wherein mu₁Denotes the coefficient of sliding friction, mu, between cemented carbides₂The coefficient of sliding friction between CBN and hard alloy is represented by phi in the angle of taper, m in the number of oilstones, P_rFor honing pressure, S_kThe cross-sectional circle area of the expansion cone rod.

3. The method for predicting and controlling the precise honing bore diameter of the hydraulic coupling part according to claim 1, wherein in step S3, the determination process of the overrun period residence time value is as follows:

in order to predict the aperture distribution after honing, the method needs to be realized by utilizing the size of a front bottom hole of honing and combining a theoretical formula of removal rate of honing materials; firstly, measuring the size of a front bottom hole of the honing by using a pneumatic measuring instrument at a specific interval along the height direction of an inner hole, and obtaining a value D of the front hole diameter of the honing through nonlinear fitting₀And combining the predicted value with the predicted value of the material removal volume at different height positions to calculate the aperture value D after honing_hThe expression is as follows:

the height position of the hole after honing is mainly divided into three parts: an upper overrun section, a middle area and a lower overrun section; taking the average aperture value of the middle area of the hole as the ideal aperture after honing, and respectively carrying out numerical operation on the average aperture value and the aperture values at the upper and lower overrun sections to obtain the retention time of the single-stroke overrun section, wherein the expression is as follows:

wherein t is_d、t_uRespectively the residence time of the lower overrun section and the residence time of the upper overrun section,is the average pore diameter of the central region of the pores, D_iRepresents the aperture value at any height position of the overrun section, h is unit height,representing the average material removal rate, i is the count value at different height positions of the hole, and n represents the number of reciprocating strokes in the honing process.

4. The method for predicting and controlling the precise honing bore diameter of the hydraulic coupling part according to claim 1, wherein in step S4, the process of establishing the honing material removal volume prediction model is as follows:

the honing material removal rate formula shows that the maximum value of the material removal rate appears at the honing overrun starting and stopping point, the top end and the bottom end of the inner hole obtain the minimum values of the material removal rate, and the difference can be specifically expressed as:

because the added retention time of the overrun section will cause the extra increase of the material removal volume of the overrun section, the specific expression of the improved honing material removal rate formula is as follows:

based on the honing material removal rate improvement prediction formula, establishing a honing material removal volume improvement prediction model, predicting the distribution condition of the aperture after honing, and showing the following results: the addition of the retention time can reduce the material removal volume difference between the over-travel section and the middle area and improve the aperture consistency after honing.

5. The method for predicting and controlling the precise honing bore diameter of the hydraulic coupling part according to claim 1, wherein in step S5, the significance analysis of the honing test data is to fit a honing process parameter regression formula with the honing test data, and the expression is as follows:

wherein D_sRepresenting the aperture difference after honing, wherein alpha, beta, gamma and epsilon are fitting coefficients related to the removal rate of the honing material, and b, c, d and e represent fitting coefficients related to the aperture difference after honing;

substituting the material removal rate and the aperture difference of the honed hole in a neural network for optimization iteration, inputting each process parameter, setting the number of neurons in the hidden layer to be 10, randomly selecting 70% of samples as training data, 15% of samples as verification data, testing the rest 15% of samples, and obtaining an output solution as the optimal process parameter after circulation.

Technical Field

The invention relates to the technical field of finish machining of holes made of materials difficult to machine, in particular to a method for predicting and controlling the hole diameter of precision honing of a hydraulic coupling.

Background

The honing is a fine processing technology which utilizes the contact extrusion of honing oilstone and the cylindrical surface of an inner hole and cuts off materials along a spiral track, the processing materials mainly comprise cast iron and hardened steel, the processing dimensional tolerance grade is IT 7-IT 4, the surface roughness can reach 0.32-0.08 mu m, and the honing is widely applied to the production of cylinder holes, oil cylinder holes and hydraulic cylinder holes. During honing, the honing head does circumferential rotation movement and axial reciprocating movement, and expansion and contraction of the expansion cone rod in the honing head are controlled under hydraulic control, so that oilstone radially expands and retracts, oilstone abrasive particles are in contact extrusion with the surface of a workpiece, and the purpose of removing materials on the surface of an inner hole is finally achieved.

Factors affecting the removal rate of the honing material are: honing rod reciprocating speed, honing rod rotating speed, reciprocating feeding amount, honing over-travel amount, oilstone grain diameter, mesh number and the like. The removal volume of the honing material can be calculated by measuring the aperture before and after honing by the pneumatic measuring instrument, and the removal rate of the honing material can be obtained by comparing the volume with the honing time. In 2015, a paper entitled "research on removal rate of nickel-based superalloy honing material" published by Huangda Shunshi journal of Nanjing university of aerospace, and honing orthogonal experiments were developed in the paper to study the change law of removal rate of honing material. The test result shows that: the material removal rate is obviously influenced by the reciprocating feeding amount and the particle size and the mesh number of the oilstone, and the material removal rate is not obviously influenced by the axial reciprocating speed, the rotating speed of the honing rod and the overtravel amount. In addition, since the machining parameters fail to predict the honing material removal rate, only qualitative analysis is made and no quantitative characterization is performed. In addition, the relation between the material removal rate and the hole diameter precision after honing is not provided, the honing process often has the problem of poor hole diameter consistency after honing, the high processing efficiency of the sheet surface is required to seriously affect the hole processing precision and the surface quality, and therefore, the key for solving the problem is to improve the processing efficiency to the maximum extent on the premise of ensuring the high precision and the high consistency of the holes.

Disclosure of Invention

The invention provides a method for predicting and controlling precise honing bore diameter of a hydraulic coupling part, which belongs to a honing method for controlling bore size. The honing process parameter optimization regression formula is fitted by using the honing test data and the prediction result, a process parameter optimization model is established, the precision control of the honing aperture is realized, and the aperture consistency is improved.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

a method for predicting and controlling the aperture of a precision honing of a hydraulic coupling part comprises the following steps:

step S1, obtaining the processing parameters and the geometric parameters of the honing oilstone and the aperture value of the pre-honing bottom hole;

step S2, construct the material removal rate formula and initially calculate Q_mAnd D_sA value;

the expansion taper rod and the oilstone are subjected to force transmission through the wedge-shaped structure, and because the expansion taper rod is kept in an expansion state in the honing process, the oilstone and the surface of a workpiece are always in contact extrusion, and therefore the axial pressure of the expansion taper rod is converted into the radial pressure of the oilstone.

Wherein F_hrDenotes the positive radial pressure of the oilstone, μ₁Denotes the coefficient of sliding friction, mu, between cemented carbides₂The coefficient of sliding friction of CBN and hard alloy is represented by phi of the angle of taper and the number of oilstone stripsExpressed by m, P_rFor honing pressure, S_kThe cross-sectional circle area of the expansion cone rod.

According to the research and analysis of the movement and stress of the honing oilstone and the simulation result of the contact of the honing oilstone and the inner hole, a theoretical formula of the removal rate of the honing material is deduced, and the theoretical formula can be specifically expressed as

When 0. ltoreq. z < (l)_s-l_d) When the temperature of the water is higher than the set temperature,

when (l)_s-l_d)≤z＜l_sWhen the temperature of the water is higher than the set temperature,

when l is_s≤z＜(H-l_s) When the temperature of the water is higher than the set temperature,

when (H-l)_s)≤z＜(H-l_s+l_u) When the temperature of the water is higher than the set temperature,

when (H-l)_s+l_u) When z is less than or equal to H,

wherein V_aRepresenting the reciprocating velocity,/_uAnd l_dRespectively an upper overrun amount and a lower overrun amount, b is the width of the oilstone, H is the height of the workpiece hole, l_sExpressed as the length of the oilstone, the material removal rate is expressed as Q_mAnd Z represents the height position of the central mass point of the oilstone in the inner hole, and the contact load ratio is represented by K.

Measuring the size of the honing front bottom hole along the height direction of the inner hole at a specific interval by using a pneumatic measuring instrument, and obtaining the value D of the honing front hole diameter at different height positions of the hole through nonlinear fitting₀The combination of the material removal rate with the corresponding height can obtain the aperture D after honing_hExpression of whichIs of the formula

Step S3, calculating the value of the retention time of the over-travel section according to the pore size distribution after the initial honing;

the height position of the hole after honing is mainly divided into three parts: an upper overrun section, a middle area and a lower overrun section. Taking the average aperture value of the middle area of the hole as the ideal aperture after honing, and respectively carrying out numerical operation on the average aperture value and the aperture values at the upper and lower overrun sections to obtain the retention time of the single-stroke overrun section, wherein the expression is

Wherein t is_d、t_uRespectively the residence time of the lower overrun section and the residence time of the upper overrun section,is the average pore diameter of the central region of the pores, D_iThe aperture value of any height position of the overrun section is represented, h is unit height,for the average material removal rate, i is a count value at different height positions of the hole, and n represents the number of reciprocating strokes in the honing process.

It should be noted that t is_dAnd t_uThe value cannot be a negative value, and when the retention time is less than 0.1s, the influence effect of the retention time on the removal volume of the skip section material can be ignored.

Step S4, establishing a honing material removal volume prediction model, and predicting the honing material removal rate and the post-honing aperture value;

calculating the removal rate range value of the honing material, and the specific expression is

Because the added retention time of the overrun section will cause the extra increase of the material removal volume of the overrun section, the specific expression of the improved honing material removal rate formula is as follows:

step S5, developing a honing orthogonal test and fitting a honing process parameter optimization regression formula;

and analyzing the influence of each process parameter on the material removal rate and the post-honing aperture difference, and comparing the removal rate of the honing experimental material and the post-honing aperture difference with the simulation result of the prediction model to verify the accuracy of the model. Meanwhile, the honing test data is utilized to fit a honing process parameter optimization regression formula, and the expression is

Wherein the aperture difference after honing is D_sAlpha, beta, gamma and epsilon are all honing material removal rate fitting coefficients, while b, c, d and e represent post-honing aperture difference fitting coefficients, and the material removal rate and the aperture difference of the post-honing hole of the honing test are compared with the simulation result of the pre-measured model to verify the accuracy of the model.

Substituting the removal rate of the honing test material and the aperture difference after honing into a neural network for optimization iteration, inputting each process parameter, setting the number of neurons in the hidden layer as 10, randomly selecting 70% of samples as training data, 15% of samples as verification data, using the remaining 15% of samples for testing, and obtaining an output solution as an optimal process parameter after circulation.

The results show that: the proper residence time is added, and the optimal technological parameters are adopted for honing, so that the requirement of aperture consistency after honing can be met, and the removal rate of honing materials is increased.

The invention has the advantages that:

(1) the model can be calibrated under the condition of carrying out a small number of honing tests, and the proper retention time can be added according to the size distribution rule of the bottom holes before honing to adjust the removal rate of the honing material at different height positions of the holes, so that the control of the precision of the hole diameter after honing is realized. The optimal process parameters can be obtained by utilizing the honing process parameter optimization regression formula, so that the aperture consistency after honing is ensured, the material removal rate can be properly improved, the production cost of enterprises is reduced, and the production efficiency is improved.

(2) In the process of establishing the honing pore size distribution prediction model, the influence of the state of the honing front bottom hole on the precision of the honing rear pore size is considered, the size of the honing front bottom hole at different height positions of the hole is analyzed, the retention time value which is required to be added in the overrun section is calculated, and the retention time value is used for establishing the honing pore size prediction model.

(3) And testing and verifying the honing test data by using a neural network, iteratively optimizing to obtain optimal process parameters, and carrying out honing processing by using the optimized process parameters to ensure the consistency of the bore diameter after honing and improve the removal rate of the honing material.

Drawings

Fig. 1 is a pictorial view of a honing device employed in the invention;

FIG. 2 is a schematic diagram of the movement of the honing oilstone; 1-oilstone, 2-valve pocket;

FIG. 3 is a force analysis graph of the expanding cone pressure and the oilstone positive pressure;

FIG. 4 is a flow chart of residence time calculation;

FIG. 5 is a graph comparing experimental post-honing hole and prediction model results;

FIG. 6 is a flow chart of process parameter optimization.

Detailed Description

The invention is further illustrated with reference to the figures and examples.

As shown in fig. 2, the schematic diagram of the movement of the honing oilstone is that the movement of the honing oilstone is a combined movement formed by combining the outward expansion movement, the axial reciprocating movement and the rotary movement of the oilstone 1, under the influence of the reverse acceleration, the movement process of firstly accelerating, then uniformly decelerating and finally decelerating the oilstone is carried out, and the height of the surface of the hole exposed out of the valve sleeve 2 when the end surface of the oilstone is at the overtravel dead point position is used as the overtravel amount.

The total length of the whetstone 1 is denoted by l_sWidth b, wherein the amount of upward overrun is l_uThe lower overrun amount is l_dThe initial bore diameter of the valve is d₀Reciprocating at a speed V_aV for rotational speed_nAnd (4) showing.

Fig. 3 is a stress analysis diagram of the expanding cone pressure and the oilstone positive pressure, wherein the expanding cone pressure is determined by the honing pressure and the cross-sectional area of the cone rod. Assuming expanding cone pressure F_kAngle of taper and angle of taperAnd the conditions such as the respective friction coefficients are known. When the honing head moves downwards integrally, the friction force F borne by the oilstone working surface_haUpward direction, the expansion cone is always in an outward expansion state, and the positive pressure F_hrThe direction always points to the axis, and the oilstone block bears the support reaction force F at the moment_a3Downward; when the honing head integrally moves upwards, the expansion cone is still in an outward expansion state, F_haIn the downward direction, F_a3Upwards.

And (4) deducing a theoretical formula of the removal rate of the honing material according to research and analysis of the motion and stress of the honing oilstone and the simulation result of the contact of the oilstone and the inner hole.

Measuring the size of the honing front bottom hole along the height direction of the inner hole by using a pneumatic measuring instrument, and obtaining the value D of the honing front hole diameter at different height positions of the hole through nonlinear fitting₀。

The initial post-honing aperture value can be calculated by a material removal rate formula and combining the size of the pre-honing bottom hole, and the expression is as follows:

FIG. 4 shows a flow chart of residence time calculation, which divides the holes after honing into (0, l) according to different height positions of the holes_s-l_u], (l_s-l_u,H-l_s+l_d],(H-l_s+l_d,H]And thirdly, taking the average aperture value of the middle area of the hole as an ideal aperture size, and respectively calculating with the aperture values in the upper and lower overrun sections to obtain the material removal volume difference value of the overrun sections, and further judging and calculating the retention time.

If the material removal volume of the middle area of the hole is larger than the material removal volume value of a certain overrun section, the dwell time needs to be increased in the overrun section; if the material removal volume value of the middle area is smaller than the material removal volume of a certain over-travel section, the over-travel section does not need to set the retention time, and the specific expression of the retention time is calculated as follows:

wherein t is_d、t_uRespectively the residence time of the lower overrun section and the residence time of the upper overrun section,is the average pore diameter of the central region of the pores, D_iRepresents the aperture value at any position of the overrun section, h is the unit height,for the average material removal rate, i is a count value at different height positions of the hole, and n represents the number of reciprocating strokes in the honing process.

It should be noted that t is_dAnd t_uThe value cannot be negative, and when the retention time is less than 0.1s,the effect of the residence time on the volume of material removed during the overrun period can be neglected.

The honing material removal rate tolerance value can be specifically expressed as:

establishing a honing material removal volume prediction model, and considering the influence of the residence time on the removal volume of the overrun section material, obtaining an improved honing material removal rate formula, wherein the expression is as follows:

honing test is carried out on DMF180 center by CoolEXAct honing tool developed by DIAHON company, 4 blocks of CBN oilstones with abrasive density of 200#/230# (average abrasive size of 64 μm) as multi-layer sintered superhard abrasive are mounted on the honing tool, and the tool is mainly applied to rough honing after boring and honing, and the size D of a bottom hole before honing is₀Between phi 6.975-6.981 mm, surface roughness R_a0.8 to 1.6 μm, and a hole length H of 60 mm.

Considering no oilstone abrasion and material plastic deformation generated in the honing process, the ideal aperture value after honing is phi 6.992-6.995 mm, the aperture difference after honing is less than 4 mu m, and the surface roughness is less than 0.4 mu m. Length of honing stone l_sIt is taken to be 30mm and the width b is chosen to be 1.5 mm.

An orthogonal honing test is carried out according to the table 1, corresponding model simulation operation is carried out, and in order to verify the model accuracy, the error value is calculated by adopting the following formula:

TABLE 1 honing orthogonal test variable table

The average error is 7.9%, the error of the model is always less than 10% by observation, which indicates that the prediction accuracy of the model can meet the requirement.

With V_a＝3m/min、P_r＝1.5Mpa、l＝10mm、n_sThe experimental honed holes were compared to the model simulation results, which are shown in fig. 4, for an example of a process parameter combination at 1365 rpm.

And (3) carrying out significance analysis on honing test data, researching the influence of each process parameter on the removal rate of the honing material and the aperture difference after honing, and comparing the removal rate of the honing test material and the aperture difference after honing with the simulation result of the prediction model to verify the accuracy of the model, as shown in figure 5.

Fitting a honing process parameter optimization regression formula by using honing test data, wherein the expression is

Wherein the aperture difference after honing is D_sAlpha, beta, gamma and epsilon are all fitting coefficients related to the removal rate of the honing material, and b, c, d and e are fitting coefficients related to the aperture difference after honing.

Fig. 6 is a process parameter optimization flow chart, firstly, a post-honing hole meeting the standard in the orthogonal test data is screened as a target aperture, secondly, the removal rate of the honing material and the aperture difference after the honing are substituted into a neural network for multiple cycle iterations, and finally, the optimal process parameters capable of meeting the requirements of the material removal rate and the aperture precision are output.

The results show that: when V is_aIs 3 to 5m/min, P_r1.5 to 2MPa, l is 10mm, n_sWhen the diameter is 1365r/min, the removal rate of the honing material can be increased on the premise of ensuring the requirement of aperture consistency (less than 3 μm) after honing.