A method for predicting electrode feed speed during electrochemical finishing of inner channel surface

Abstract

A method for predicting the feeding speed of an electrode for electrolytic finishing machining of an inner flow channel surface, using a roughness measuring device to measure the initial wave crest height and initial wave valley height of the actual inner surface; according to the electrolytic machining process requirements, the microscopic wave crest material dissolution speed, material removal amount and actual machining gap, the wave valley material dissolution speed, material removal amount and actual machining gap at the observation point are calculated according to the machining voltage and the theoretical machining gap; according to the microscopic wave crest material dissolution speed, material removal amount and actual machining gap, and the wave valley material dissolution speed, material removal amount and actual machining gap, the microscopic wave crest height and wave valley depth at the next moment at the observation point are calculated; it is determined whether the sum of the microscopic wave crest height and the wave valley depth meets the machining requirement roughness, if yes, the number of steps of the current iteration is recorded, and the time required for electrolytic machining of a unit length of the inner flow channel is calculated, and then the feeding speed is predicted; a theoretical basis is provided for the selection of electrolytic machining parameters of the inner flow channel.

Description

Technical Field

[0001] The invention relates to the technical field of electrolytic finishing of inner flow channel surface, and in particular to a method for predicting electrode feeding speed during electrolytic finishing of inner flow channel surface. Background Art

[0002] With the development of additive manufacturing technology, various internal flow channel parts have appeared in the fields of aerospace, molds, biomedicine, etc. These channels are mainly used for fluid medium transmission and cooling, and the surface quality of their inner walls has an important impact on the working stability of the equipment and the quality of product molding. However, the surface of metal parts manufactured by additive manufacturing is rough due to the adhesion of powder, steps and spheroidization effects, and they need to be post-finished to meet the requirements of internal flow channel design.

[0003] Electrolytic machining has the characteristics of high efficiency, low electrode loss, stress-free machining, and good surface integrity. It is suitable for finishing machining of various difficult-to-machine metal materials. When electrolytic machining the inner surface, the cathode does not feed along the radial direction of the inner flow channel, and there is a constant gap between the cathode and the workpiece surface. If the feed speed is too high, the tool cathode will have a short machining time on the same part of the inner flow channel surface, and the peaks and troughs of the roughness will not have enough time to be electrochemically dissolved, and the surface quality improvement effect of the workpiece will not be obvious; if the feed speed is too low, the tool cathode will have a long machining time on the same part of the inner flow channel surface, and the peaks and troughs of the roughness can be fully dissolved, but it is possible that the inner flow channel aperture size will be out of tolerance and the machining efficiency will be low. Therefore, there is an urgent need for a method to predict a reasonable feed speed to improve the surface quality and machining efficiency of the inner flow channel. Summary of the invention

[0004] In response to the needs of the prior art, the present invention provides a method for predicting electrode feed speed during electrolytic finishing machining of an inner flow channel surface, aiming to predict a reasonable feed speed to improve the surface quality of the inner flow channel and the electrolytic machining efficiency.

[0005] A method for predicting electrode feed speed during electrolytic finishing of inner flow channel surface, characterized in that it comprises the following steps:

[0006] Step 1: Take the ideal inner surface of the inner flow channel as the roughness measurement benchmark, and use the roughness measurement device to measure the initial peak height of the actual inner surface. δ f0 and initial trough height δ g0 ;

[0007] Step 2: According to the electrolytic machining process requirements, preset the machining voltage U, theoretical machining gap Δ, and cathode size L in the feed direction;

[0008] Step 3: Calculate the material dissolution rate, material removal amount and actual processing gap of the micro-wave crest at the observation point, the material dissolution rate, material removal amount and actual processing gap of the wave trough at the observation point according to the processing voltage U and the theoretical processing gap Δ;

[0009] Step 4: Calculate the micro-peak height and trough depth at the next moment at the observation point based on the micro-peak material dissolution rate, material removal amount and actual processing gap, as well as the trough material dissolution rate, material removal amount and actual processing gap;

[0010] Step 5: Determine whether the sum of the micro-peak height and the trough depth meets the roughness requirement of the processing. If yes, record the number of steps n of the current iteration and calculate the time T required for electrochemical processing per unit length of the inner flow channel, T= dt n, and go to step 6; otherwise, go to step 4;

[0011] Step 6: Predict the feed speed based on the processing time T v , the formula is as follows:

[0012] v =L / T.

[0013] Further: In step 3, calculate the actual machining gap of the micro-wave peak near the observation point at time t=0 y f (0) and material dissolution rate v af (0), actual machining clearance of trough y g (0) and material dissolution rate v ag (0), the calculation formula is as follows:

[0014] crest: ;

[0015] trough: ;

[0016] Further: Calculate the dissolution rate of the microscopic peak material at time t=j v af (j) Material removal amount dy f and actual machining clearance y f (j+1), dissolution rate of trough material v ag (j) Material removal amount dy g and actual machining clearance y g (j+1), the calculation formula is as follows:

[0017] crest:

[0018] ;

[0019] ;

[0020] ;

[0021] trough:

[0022] ;

[0023] ;

[0024] ;

[0025] Where, κ is the conductivity of the electrolyte, and are the current efficiencies at the peak and trough respectively, and ω is the volume electrochemical equivalent of the inner flow channel parts.

[0026] Further: The height of the microscopic peak at time t=j+1 δ f(j+1) and trough height δ g(j+1) for:

[0027] Peak height: ;

[0028] Trough height: .

[0029] Further: dt is a discrete unit step and satisfies: .

[0030] Furthermore, the cross-section of the inner flow channel is circular, rectangular or square; the trajectory of the inner flow channel is straight or curved.

[0031] Further, the processing voltage U is 10V ~ 25V.

[0032] Further, the processing gap Δ is 0.2mm ~ 0.5mm.

[0033] Further, the feed speed predicted in step 6 is the speed when the cathode feed processing is completed once. When multiple reciprocating motion processing is required, the reciprocating motion feed speed V1 is equal to the product of the number of reciprocating motions N1 and the predicted feed speed v, that is: V1=N1*v.

[0034] Further: Steps 3 to 6 are implemented by MATLAB numerical simulation software.

[0035] The beneficial effects of the present invention are as follows: based on initial conditions such as theoretical processing gap, initial wave peak height and initial wave valley height, MATLAB is used for discrete and iterative solution to obtain the dissolution rate of wave peak and wave valley materials at any time and the actual processing gap, the heights of wave peaks and wave valleys when the roughness required for processing is satisfied are deduced from the actual processing gap, the processing time required for a unit length of the inner flow channel is calculated based on the iteration step size and number of times, and finally the feed speed is determined by the size of the cathode in the feed direction, thereby providing a theoretical basis for the selection of electrolytic processing parameters for the inner flow channel. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 Schematic diagram of electrochemical machining of internal flow channels;

[0037] Figure 2 The roughness change process of the inner flow channel surface during electrochemical machining;

[0038] Figure 3 Numerical solution flow chart;

[0039] Figure 4 The trend diagram of machining voltage and time required under different theoretical machining gaps;

[0040] Figure 5 The changing trend of processing voltage and time required under different processing requirements;

[0041] Figure 6 Variation trend of machining voltage and time required under different original surface roughness;

[0042] Figure 7 Cathode feed speed under different theoretical machining gaps. DETAILED DESCRIPTION

[0043] The present invention is described in detail below in conjunction with the accompanying drawings. The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be interpreted as limiting the present invention. The directional terms such as left, middle, right, top, and bottom in the embodiments of the present invention are only relative concepts or are based on the normal use state of the product, and should not be considered as restrictive.

[0044] A method for predicting the electrode feed speed of an inner flow channel surface electrolytic finishing machining, wherein the cross-sectional shape of the inner flow channel is circular, rectangular, or square; the inner flow channel trajectory is linear or curved; and the method comprises the following steps:

[0045] Step 1: Figure 1As shown, the ideal inner surface 3 of the inner flow channel is used as the roughness measurement reference, and the maximum height R of the profile of the actual inner surface 4 is measured by using the roughness measurement device. Z0 , initial peak height δ f0 and initial trough height δ g0 ;

[0046] Step 2: According to the electrolytic machining process requirements, preset the machining voltage U, theoretical machining gap Δ, and the size L of the cathode 2 in the feed direction, and consult the literature to obtain the electrolyte conductivity κ , current efficiency η , Volume electrochemical equivalent of inner flow channel parts ω etc. initial conditions;

[0047] Step 3: Figure 2 As shown, the actual machining gap of the micro peak 5 near the observation point A at time t=0 is calculated y f (0) and material dissolution rate v af (0), actual machining clearance of trough 6 y g (0) and material dissolution rate v ag (0), the calculation formula is as follows:

[0048] crest: ;

[0049] trough: ;

[0050] Step 4: Calculate the jth step (discrete unit step length is dt )t=j time micro peak 5 material dissolution rate v af (j) Material removal amount dy f and actual machining clearance y f (j+1), dissolution rate of material in trough 6 v ag (j) Material removal amount dy g and actual machining clearance y g (j+1), the calculation formula is as follows:

[0051] crest:

[0052] ;

[0053] ;

[0054] ;

[0055] trough:

[0056] ;

[0057] ;

[0058] ;

[0059] in, and are the current efficiencies at the peak and trough, respectively;

[0060] Step 5: Calculate the j+1th step (discrete unit step length is dt )The microscopic peak height at time t=j+1 δ f(j+1) and trough height δ g(j+1) And judge whether the roughness R meets the processing requirements ZZ , the calculation formula is as follows:

[0061] Peak height: ;

[0062] Trough height: ;

[0063] Judgment formula whether it is established;

[0064] If the equation is true, the calculation ends and the number of iteration steps is j+1; if not, the next iteration calculation is continued until the equation is true;

[0065] Step 6: Get the processing requirement R from step 5 ZZ The number of steps n required for iteration is used to calculate the time T required for electrochemical machining per unit length of the inner flow channel. The calculation formula is as follows:

[0066] T= dt n, where ;

[0067] Step 7: Predict the feed speed based on the processing time T obtained in step 6 v , the formula is as follows:

[0068] v =L / T; In addition, the predicted feed speed is the speed when the cathode is fed once to complete the processing. When multiple reciprocating motions are required, the reciprocating motion feed speed V1 is equal to the product of the number of reciprocating motions N1 and the predicted feed speed v, that is: V1=N1*v; Among them, steps 3 to 7 are implemented by MATLAB numerical simulation software.

[0069] When electrochemical machining the inner flow channel, the theoretical machining gap remains constant, and at the same feed speed, the machining voltage is determined by the real-time machining gap and the surface roughness required for machining, while the real-time machining gap is affected by the theoretical machining gap and the original surface roughness. Therefore, in order to determine the reasonable machining voltage, the MATLAB numerical calculation software is used according to Figure 3 The process shown in the figure is iterated to solve the changing trends of machining voltage and required machining time under different theoretical machining gaps, original surface roughness and surface machining required roughness. Figure 4 , Figure 5 and Figure 6 shown.

[0070] Figure 4 The surface roughness value R under different theoretical machining gaps Z The variation trend of the time required for machining with the voltage when the machining gap is reduced from 40μm to 10μm. Under the same theoretical machining gap, the machining time increases linearly and slowly with the decrease of machining voltage, but when the voltage is reduced to a certain value, the machining time increases significantly. When the theoretical machining gaps are 0.3mm, 0.4mm, 0.5mm and 0.6mm, respectively, when the machining voltage is reduced from 40V to 25V, the required machining time only increases by 29.82s, 43.68s, 40.98s and 48.54s, respectively. When the machining voltage is lower than 5V, 10V, 12.5V and 15V, respectively, the required machining time increases significantly, and the predicted cathode feed speed decreases rapidly.

[0071] Figure 5 The theoretical machining clearance is 0.4 mm, and the surface machining requires a roughness value R Z The changing trend of machining voltage and required machining time when the surface roughness is reduced from 32μm to 6μm, 8μm, 10μm and 12μm. Under the same machining voltage, as the surface roughness required decreases, the required machining time increases; under the same surface roughness required, as the machining voltage decreases, the required machining time increases slowly and linearly, but when the machining voltage is lower than 10V, the required machining time increases significantly, and the cathode feed speed is predicted to be very small, which affects the machining efficiency.

[0072] Figure 6 The change trend of machining voltage and required machining time when the theoretical machining gap is 0.3mm and the surface roughness decreases by 10μm from 40μm, 32μm and 24μm respectively. Under the same original surface roughness, as the voltage decreases, the required machining time increases slowly and linearly, but when the voltage is lower than a certain value, the slope of the curve decreases and the trend of increasing the required machining time becomes larger, especially when the voltage continues to decrease to 7.5V, the slope of the curve decreases significantly and the required machining time increases significantly.

[0073] From the above analysis, it can be seen that the reasonable voltage range is between 10V and 25V. The specific value should take into account factors such as the theoretical processing gap, the original processing surface roughness value and the processing requirement roughness value.

[0074] Figure 7 The cathode feed speed is when the roughness of the original surface of the inner flow channel workpiece is reduced to 10μm under different theoretical machining gaps when the voltage is 12V and the roughness is reduced to 10μm. As the theoretical machining gap decreases, the current density between the cathode and the inner flow channel surface increases, the material dissolution rate per unit time increases, and the required feed speed increases slowly and linearly. When the gap is reduced to 0.5mm, the slope of the curve decreases, especially when the gap continues to decrease to 0.2mm, the slope of the curve decreases significantly linearly. When the theoretical machining gap increases from 0.8mm to 0.5mm, the feed speed only increases by 1.03mm / min. Therefore, the reasonable machining gap is 0.2mm to 0.5mm.

[0075] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for predicting electrode feed speed during electrolytic finishing of inner channel surface, characterized in that: The following steps are involved: Step 1: Taking the ideal inner surface of the inner flow channel as the roughness measurement benchmark, use the roughness measurement device to measure the initial peak height δ of the actual inner surface f0 and the initial trough height δ g0 ; Step 2: According to the electrolytic machining process requirements, preset the machining voltage U, theoretical machining gap Δ, and the cathode size L in the feed direction; Step 3: Calculate the material dissolution rate, material removal amount and actual processing gap of the micro-wave crest at the observation point, the material dissolution rate, material removal amount and actual processing gap of the wave trough at the observation point according to the processing voltage U and the theoretical processing gap Δ; Calculate the actual machining gap y of the microscopic wave peak near the observation point at time t = 0 f (0) and material dissolution rate v af (0), actual machining gap y in the trough g (0) and material dissolution rate v ag (0), the calculation formula is as follows: Peak: y f (0) = Δ - δ f0 ; v af (0) = 0; Trough: y g (0) = Δ + δ g0 ; v ag (0) = 0; Calculate the dissolution rate v of the microscopic peak material at time t=j af (j) Material removal amount dy f and the actual machining gap y f (j+1), dissolution rate of trough material v ag (j) Material removal amount dy g and the actual machining gap y g (j+1), the calculation formula is as follows: crest: of f =v af (j)·dt: the f (j+1)=y f (j)+d f =y f (j)+v af (j)·dt: trough: of g =v ag (j)·dt: the g (j+1)=y g (j)+d g =y g (j)+v ag (j)·dt: Where, κ is the conductivity of the electrolyte, η g and η f are the current efficiencies at the peak and trough, respectively; ω is the volume electrochemical equivalent of the inner flow channel parts; Step 4: Calculate the micro-peak height and trough depth at the next moment at the observation point based on the micro-peak material dissolution rate, material removal amount and actual processing gap, as well as the trough material dissolution rate, material removal amount and actual processing gap; Microscopic peak height δ at time t = j + 1 f(j+1) and trough height δ g(j+1) for: Peak height: δ f(j+1) =Δ-y f (j+1); Valley height: δ g(j+1) =y g (j+1)-Δ; Step 5: Determine whether the sum of the micro-peak height and the trough depth meets the roughness requirement of machining. If yes, record the number of steps n of the current iteration, calculate the time T required for electrochemical machining of the unit length of the inner flow channel, T = dt n, and execute step 6; otherwise, execute step 4; Step 6: According to the processing time T, predict the feed speed v, the formula is as follows: v=L / T.

2. The method for predicting electrode feed speed during electrolytic finishing of inner flow channel surface according to claim 1, characterized in that: dt is the discrete unit step and satisfies: dt≤0.0001min.

3. The method for predicting electrode feed speed during electrolytic finishing of inner flow channel surface according to claim 1, characterized in that: The cross-sectional shape of the inner flow channel is circular, rectangular or square; the trajectory of the inner flow channel is straight or curved.

4. The method for predicting electrode feed speed during electrolytic finishing of inner flow channel surface according to claim 1, characterized in that: The processing voltage U is 10V~25V.

5. The method for predicting electrode feed speed during electrolytic finishing of inner flow channel surface according to claim 1, characterized in that: The processing gap Δ is 0.2mm~0.5mm.

6. The method for predicting electrode feed speed during electrolytic finishing of inner flow channel surface according to claim 1, characterized in that: The feed speed predicted in step 6 is the speed when the cathode feed processing is completed once. When multiple reciprocating motion processing is required, the reciprocating motion feed speed V1 is equal to the product of the number of reciprocating motions N1 and the predicted feed speed v, that is: V1 = N1*v.

7. The method for predicting electrode feed speed during electrolytic finishing of inner flow channel surface according to claim 1, characterized in that: Steps 3 to 6 are implemented by MATLAB numerical simulation software.

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