CN114571019A - Electric spark milling method - Google Patents

Electric spark milling method Download PDF

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CN114571019A
CN114571019A CN202210259872.4A CN202210259872A CN114571019A CN 114571019 A CN114571019 A CN 114571019A CN 202210259872 A CN202210259872 A CN 202210259872A CN 114571019 A CN114571019 A CN 114571019A
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electrode
correction
depth
trial
electric spark
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CN114571019B (en
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史秋明
陈晓菲
高强
王园丁
张亭
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Shanghai Institute of Space Propulsion
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Shanghai Institute of Space Propulsion
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
    • B23H5/00—Combined machining
    • B23H5/04—Electrical discharge machining combined with mechanical working
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23H—WORKING OF METAL BY THE ACTION OF A HIGH CONCENTRATION OF ELECTRIC CURRENT ON A WORKPIECE USING AN ELECTRODE WHICH TAKES THE PLACE OF A TOOL; SUCH WORKING COMBINED WITH OTHER FORMS OF WORKING OF METAL
    • B23H11/00—Auxiliary apparatus or details, not otherwise provided for

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  • Mechanical Engineering (AREA)
  • Electrical Discharge Machining, Electrochemical Machining, And Combined Machining (AREA)

Abstract

The invention provides an electric spark milling method, which relates to the technical field of electric spark milling and comprises the following steps: a trial cutting process step, an on-line measurement process step, a correction trial cutting process step and a corrected on-line measurement process step; firstly, executing a trial cutting process step, wherein a wire electrode and a guider are sent out from a starting point, and performing electric spark milling on a part along a feed direction to process a trial cutting groove; then, the on-line measurement step is executed, and the machining depth compensation value delta Z and the electrode loss compensation relative speed S are measured and calculated1(ii) a Then executing a correction trial cutting process step, calculating a correction starting point according to the delta Z, and finishing a new trial cutting along the correction feed direction by the wire electrode and the guider; then, the corrected on-line measurement steps are executed, and a new round of delta Z and S is measured and calculatedi(i ═ 2,3, …). The invention can automatically keep the electric spark milling depth as a set value, and is beneficial to ensuring the continuity of the processing process and the precision of the depth dimension of the part.

Description

Electric spark milling method
Technical Field
The invention relates to the technical field of electric spark milling, in particular to an electric spark milling method capable of automatically keeping the processing depth at a set value, and particularly relates to an electric spark milling method.
Background
The electric spark milling technology adopts a layered milling principle, utilizes a numerical control system to control the motion track of an electrode with a simple shape, and controls a discharge gap between the electrode and a part in a servo mode, meanwhile, the electrode rotates at a high speed, and the electrode end faces the part to carry out electric spark machining, so that materials on the surface of the part are corroded. Unlike conventional milling techniques, the depth of material removal by spark milling is positively correlated to the time the electrode sweeps across a location on the surface of the part, so that control of the machining depth is largely empirical. The method of the layered milling can control the processing depth of each milling layer, but the layered milling principle only provides that the layered thickness is smaller than the discharge gap, and the setting of the processing depth of the first layer depends on the experience of a processor. Once the "man, machine, material, recipe, ring" changes, the machining depth of the first layer may be inaccurate, resulting in milling depth errors. This error can lead to inaccuracies in the depth dimensions of the part and, in the worst case, to an inability to continue the machining process.
The electrode itself will be worn down while discharging to remove the material of the part, and the depth of machining will be reduced accordingly. Particularly in the field of micro electric spark milling, the range of an effective discharge gap of an electrode pair for certain high-melting-point metals is narrow, and the loss of the end face of the electrode during processing is large, so that the end face of the electrode is lost outside the effective discharge gap within a few seconds, and the electrode cannot be continuously processed.
The invention patent with the publication number of CN106180923A discloses a micro three-dimensional structure electric spark milling method, wherein the forward and reverse milling mode is a mode of one-circle forward milling and next-circle reverse milling alternately, and the loss of the previous circle is compensated by the next-circle reverse electric spark milling; the compensation method based on the contact sensing method comprises the steps of setting a tool setting point before processing, carrying out contact sensing and recording coordinates, interrupting the processing after a cycle, returning to the tool setting point, carrying out contact sensing again, carrying out coordinate compensation, and then returning to a processing position for processing, wherein the specific expression is that once the program is executed, contact sensing is carried out once; the method is characterized in that: the discharge gap is 0.01 mm. The invention presets the discharge gap as a fixed value, and shows that the discharge gap still has room for improvement in the aspects of machining depth control and electrode loss compensation. The invention adopts a contact sensing method to measure the electrode loss and carries out coordinate compensation when the processing is interrupted, which shows that the method can not ensure that each milling track has equal depth, and still has an improvement space.
If the electrode loss is converted into the electrode compensation rate after the contact sensing is carried out, the loss of the electrode wire can be compensated in real time in the milling process. However, since there is a difference between the discharge condition of the electrode and the trial discharge condition during real-time compensation, the compensation accuracy is to be improved.
The invention patent with publication number CN106077853A discloses a micro three-dimensional part electric spark milling method, a tool electrode enters the bottom of a layer to be processed from a starting point; milling a groove with the length of 0.1-20 mm, ensuring that normal discharge machining removal occurs on the corresponding length, and measuring and calculating the length loss rate of the tool electrode; milling a groove with the length of 0.1-10 mm on a spare part under the condition of the selected layering thickness by taking the determined length loss rate as a parameter, generating predeformation on the milled tool electrode, and taking the predeformed tool electrode as a tool electrode for layering milling of a processed part; the length loss rate of the tool electrode is loss length/trace length. In the invention, the electrode is cut into the layer to be processed in a side discharge state, so that the problem that the effective discharge interval of the electrode end surface of some electric processing systems is extremely small under the condition of micro electric spark discharge, so that continuous processing cannot be carried out after loss, the diameter loss of the electrode cannot be supplemented, and the width of a processing track is difficult to keep consistent; the patent calculates the continuous compensation rate of the electrode by measuring the loss length of the electrode once, but because the discharge conditions of trial cutting machining and compensation machining are different, particularly the difference is great under the condition of large layered thickness, the invention has room for improvement in the aspects of electrode discharge state setting and electrode compensation accuracy.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides an electric spark milling method.
According to the electric spark milling method provided by the invention, the scheme is as follows:
a method of electric spark milling, the method comprising: a trial cutting process step, an on-line measurement process step, a correction trial cutting process step and a corrected on-line measurement process step;
wherein, trial cutting process step: comprises a wire electrode, a guider, a cutting starting point, a feeding direction, a part and a trial cutting groove; the electrode wire and the guider are sent out from a starting point, the part is subjected to electric spark milling along the feed direction, a trial cutting groove is machined, and then the online measurement step is executed;
the on-line measurement process comprises the following steps: measuring and calculating a machining depth compensation value delta Z and an electrode loss compensation relative rate S1；
Correcting and trial cutting process steps: the method comprises the steps of correcting a starting point and correcting a feed direction; calculating a correction starting point according to the delta Z, and finishing a new trial cut by the wire electrode and the guider along the correction feed direction;
the corrected on-line measurement process comprises the following steps: measure and calculate a new round Δ Z and Si(i ═ 2,3, …); if Δ Z and SiIf the current time does not converge to the preset range, returning to execute the correction trial cutting process step; and if the current time is converged, performing subsequent electric spark milling.
Preferably, during the milling process, the electrical gauge, the milling feed rate or the track coincidence rate are changed, and the subsequent process steps are executed from the trial cutting process step again.
Preferably, in the trial cutting step, the trial cutting groove is machined on the part by the electrode wire and the guider;
the electrode wire and the guider rotate at high speed in the rotating direction, and the electric spark milling is carried out on the part from the starting point along the feeding direction until the tool retracting point, so as to process a trial cutting groove.
Preferably, the feed direction is synthesized by a horizontal feed motion and an electrode loss compensation motion, wherein the horizontal feed distance is L, and the electrode loss compensation relative speed is S0The compensation distance is S0L, the direction is-Z.
Preferably, if there is empirical data of electrode wear compensating relative velocity, S is directly used0Setting as empirical data; if there is no empirical data, set S00; if the fine electric spark technology is used for milling the high melting pointMetal, then set up S0>0。
Preferably, the online measurement step includes: the wire electrode and the guider perform depth measurement movement of a tool starting point and depth measurement movement of a tool retracting point on the part, and a compensation value is calculated;
the wire electrode and the guider execute the depth measurement movement of the tool starting point and the depth measurement movement of the tool retracting point, the depths of the trial cutting groove at the two positions are obtained through measurement, and a machining depth compensation value delta Z and an electrode loss compensation relative speed S are calculated1The following were used:
ΔZ＝h10-h0
S1＝S0+(h10-h20)/L
in the formula: h is10And h20Measured values of the machining depth, h, of the tool start point and the tool retreat point, respectively0For the set value of the working depth, S0The relative rate is compensated for electrode wear in the trial cut process step.
Preferably, the correction trial cut process step includes: processing and correcting trial cutting grooves on the parts by the electrode wires and the guider;
and the electrode wire and the guider rotate at high speed in the rotating direction, and from the correction starting point, the part is subjected to electric spark milling along the correction feed direction until reaching the correction retreating point, and a correction trial cutting groove is machined.
Preferably, in the step of correcting trial cutting, compared with the previous trial cutting, the correction starting point moves by Δ Z in the + Z direction; if Δ Z <0, the movement is in the-Z direction.
Preferably, the correction feed direction is synthesized by a horizontal feed motion and an electrode loss compensation motion, wherein the horizontal feed distance is L, and the electrode loss compensation relative speed is SiI is the number of trial cutting steps and the compensation distance is SiL, the direction is-Z.
Preferably, the corrected online measurement step includes: the wire electrode and the guider perform depth measurement movement of a correction tool starting point and depth measurement movement of a correction tool retracting point on the part, and a compensation value is calculated;
the depth of the tool starting point is corrected by the wire electrode and the guiderMeasuring the depth of the correction trial cutting groove at two positions, calculating the compensation value delta Z of the processing depth and the relative rate S of electrode loss compensationi+1The following were used:
ΔZ＝h1i-h0
Si+1＝Si+(h1i-h2i)/L
in the formula: h is1iAnd h2iRespectively obtaining machining depth measured values of an ith round, namely a correction tool starting point and a correction tool retracting point of the round; h is0Setting a machining depth value; siCorrecting the electrode loss compensation relative rate of trial cutting step in this round, Si+1The relative rate is compensated for electrode wear for the next trial cut run.
Compared with the prior art, the invention has the following beneficial effects:
1. the invention adopts a method of measuring the processing depth of electric spark milling on line and adjusting the discharge gap according to the difference value of the measured depth and the set depth to correct the processing depth, the process is closed-loop and can automatically ensure the control precision of the processing depth of the starting point of the electric spark milling;
2. the method for measuring the electrode loss on line and calculating the electrode loss compensation relative rate in an iterative manner is adopted, so that the consistency of the processing depth of the whole milling track can be automatically ensured;
3. the invention allows the electrode loss compensation to be carried out during the initial trial cutting, solves the problem that the effective discharge interval of the electrode end surface is extremely small so that the continuous processing can not be carried out after the loss under the condition of micro electric spark discharge, and simultaneously the width of the processing track can be kept consistent, thereby being particularly suitable for the micro electric spark processing of high-melting-point metal;
4. on the basis of the three points, the invention can automatically keep the electric spark milling depth as a set value, and is beneficial to ensuring the continuity of the processing process and the precision of the depth dimension of the part;
5. the invention does not depend on a process database in the aspects of discharge gap setting and electrode loss compensation setting, and the system can automatically find reasonable parameters through trial cut, online measurement and adjustment;
6. the invention does not exclude relevant process data, the reasonable set values of the discharge gap and the electrode loss compensation relative speed can accelerate the convergence process, and shorten the trial cut and on-line measurement and adjustment time.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a schematic diagram of the spark milling process of the present invention;
FIG. 2 is a schematic view of the spark milling trial cut process step of the present invention;
FIG. 3 is a sectional schematic diagram of the electric spark milling on-line measuring process step of the invention;
FIG. 4 is a schematic diagram of the spark milling correction trial cut process step of the present invention;
fig. 5 is a cutting schematic diagram of the on-line measurement process after the electric spark milling correction of the invention.
Reference numerals:
trial cutting step 1 on-line measurement step 2 correction trial cutting step 3
Corrected on-line measuring process step 4 electrode wire and guider 5 part 6
Tool lifting point 7, tool feeding direction 8 and tool retracting point 9
Depth measuring movement 14 of the starting point of the trial cutting groove 11 and depth measuring movement 15 of the retracting point
Correction start point 16, correction feed direction 17, and correction retract point 18
Correcting the horizontal feed motion 21 of the trial cut groove 20 in the direction of rotation 19
Depth measurement operation of electrode loss compensation operation 22 correction start point and depth measurement operation of correction retract point
Moving 23 and 24
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the present invention.
The embodiment of the invention provides an electric spark milling method, which specifically comprises the following steps of: a trial cutting step 1, an online measurement step 2, a correction trial cutting step 3 and a corrected online measurement step 4; the device further comprises a wire electrode and guide device 5, a part 6, a tool starting point 7, a feeding direction 8, a tool retracting point 9, a trial cutting groove 11, a depth measuring movement 14 of the tool starting point, a depth measuring movement 15 of the tool retracting point, a correction tool starting point 16, a correction feeding direction 17, a correction tool retracting point 18, a correction trial cutting groove 20, a depth measuring movement 23 of the correction tool starting point and a depth measuring movement 24 of the correction tool retracting point.
Firstly, executing a trial cutting process step 1, starting from a starting point 7, carrying out electric spark milling on a part 6 along a feed direction 8 by a wire electrode and a guider 5, and processing a trial cutting groove 11; then, the online measurement step 2 is executed, and the machining depth compensation value delta Z and the electrode loss compensation relative speed S are measured and calculated1(ii) a Then, executing a correction trial cutting process step 3, calculating a correction starting point 16 according to the delta Z, and finishing a new trial cutting by the wire electrode and the guider 5 along a correction feed direction 17; then, the corrected on-line measurement step 4 is executed, and a new round Δ Z and S are measured and calculatedi(i ═ 2,3, …); if Δ Z and SiIf the current time does not converge to the preset range, returning to execute the correction trial cutting process step 3; and if the current time is converged, performing subsequent electric spark milling. In the milling process, the electrical gauge, the milling feed rate or the track coincidence rate are changed, and the subsequent process steps are executed from the trial cutting process step 1.
In the trial cutting step 1, a trial cutting groove 11 is processed on the part 6 by the electrode wire and the guider 5; the wire electrode and the guide 5 are rotated at a high speed in a rotation direction 10, and the trial cut groove 11 is machined by performing spark milling on the part 6 from a starting point 7 in a feed direction 8 to a retracting point 9. The feed direction 8 is composed of a horizontal feed motion 12, wherein the horizontal feed distance is L,electrode loss compensation relative rate of S0The compensation distance is S0L, the direction is-Z. If empirical data of electrode loss compensation relative speed exists, S is directly used0Setting as empirical data; if there is no empirical data, set S00; if the micro electric spark technology is used to mill the high melting point metal, S is set0>0。
In the online measurement step 2, the wire electrode and guide 5 executes depth measurement movement 14 of a tool starting point and depth measurement movement 15 of a tool retracting point on the part 6, and a compensation value is calculated.
The wire electrode and guider 5 executes the depth measuring movement 14 of the tool starting point and the depth measuring movement 15 of the tool retracting point, the depth of the trial cutting groove 11 at the two positions is measured, and the processing depth compensation value delta Z and the electrode loss compensation relative speed S are calculated1The following were used:
ΔZ＝h10-h0
S1＝S0+(h10-h20)/L
in the formula: h is10And h20Measured values of the machining depth, h, of the tool run-up point 7 and the tool run-down point 9, respectively0To set the depth of machining, S0The relative rate is compensated for electrode wear for trial cut step 1.
The correction trial cutting process step 3 includes: the wire electrode and guider 5 processes and corrects the trial cut groove 20 on the part 6; the wire electrode and the guide 5 are rotated at a high speed in a rotation direction 19, and from a correction start point 16, the spark milling is performed on the part 6 in a correction feed direction 17 to a correction retreat point 18, and a correction trial cut groove 20 is machined. The correction start point 16 moves Δ Z in the + Z direction (if Δ Z <0, it moves in the-Z direction) compared to the previous trial cut.
The correction feed direction 17 is composed of a horizontal feed motion 21 and an electrode loss compensation motion 22, wherein the horizontal feed distance is L and the electrode loss compensation relative velocity is Si(i is the number of trial cutting steps 3, i is 1,2,3, …) and the offset distance is SiL, the direction is-Z.
The corrected on-line measurement process step 4 includes: the wire electrode and guider 5 executes depth measurement movement 23 of a correction start point and depth measurement movement 24 of a correction retreat point on the part 6, and a compensation value is calculated;
the wire electrode and guide 5 executes a depth measuring movement 23 for correcting the starting point and a depth measuring movement 24 for correcting the retreating point, the depths of the corrected trial cut groove 20 at the two positions are measured, and a machining depth compensation value delta Z and an electrode loss compensation relative speed S are calculatedi+1The following were used:
ΔZ＝h1i-h0
Si+1＝Si+(h1i-h2i)/L，(i＝1,2,3,…)
in the formula: h is1iAnd h2iThe measured values of the machining depth of the ith round, namely the corrected tool starting point 16 and the corrected tool retracting point 18 of the round are measured respectively; h is0Setting a machining depth value; siCorrecting the electrode loss compensation relative rate of trial cutting step in this round, Si+1The relative rate is compensated for electrode wear for the next trial cut run.
Next, the present invention will be described in more detail.
The invention provides an electric spark milling method, which comprises the following specific operation flows:
step S1: the electrode wire and the guider 5 are moved to a cutting starting point 7 above the part 6, and the distance from the bottom surface of the electrode wire to the blank surface of the part 6 is smaller than the maximum discharge gap.
Step S2: the wire electrode and the guide 5 rotate at high speed in the rotation direction 10, trial cutting of electric spark milling is started on the blank surface of the part 6, horizontal feed motion 12 is started from the starting point 7, the horizontal feed distance is L (the feed path is not limited to a straight line), and meanwhile, the servo shaft of the wire electrode and the guide 5 makes vertically downward electrode loss compensation motion 13, and the compensation speed is S0(in the field of fine electric spark milling of high melting point metals, S is recommended0>0) When the two motions are combined, the wire electrode and the guide 5 reach the tool retracting point 9 along the feeding direction 8, and the trial cutting groove 11 is machined.
Step S3: the wire electrode and the guider 5 perform the depth measuring movement 14 of the tool starting point and the depth measuring movement 15 of the tool retracting point to respectively measure the processing depth h at the tool starting point 710And at the point of withdrawal 9Depth of machining h20。
Step S4: calculating the machining depth compensation value delta Z ═ h10-h0And electrode loss compensation relative rate S1＝S0+(h10-h20) L, wherein: h is0Is a set value of the processing depth.
Step S5: the wire electrode and the guide 5 are moved to a cutting start point 16 above the part 6, and the distance from the bottom surface of the wire electrode to the blank surface of the part 6 is adjusted to + Z (if Δ Z <0, adjustment is made in the-Z direction) in comparison with the adjustment amount of the previous electric discharge machining.
Step S6: the wire electrode and guide 5 rotates at high speed in the direction of rotation 19, correction trial cut machining of spark milling is started on the blank surface of the part 6, horizontal feed motion 21 is started from the starting point 16, the horizontal feed distance is L (the feed path is not limited to a straight line), and the servo axis of the wire electrode and guide 5 makes vertical downward electrode loss compensation motion 22 at the compensation speed Si(i is the number of the correction trial cutting step 3, i is 1,2,3, …), and the two motions are combined, so that the wire electrode and the guide 5 reaches the retreating point 18 along the feeding direction 17 to process the trial cutting groove 20.
Step S7: the wire electrode and the guider 5 do the depth measuring movement 23 of the tool starting point and the depth measuring movement 24 of the tool retracting point to respectively measure the processing depth h at the corrected tool starting point 16 of the ith correction trial cut1iAnd correcting the machining depth h at the tool retracting point 182i。
Step S8: calculating the machining depth compensation value delta Z ═ h1i-h0And electrode loss compensation relative rate Si+1＝Si+(h1i-h2i) L, wherein: i is 1,2,3, …, h1iAnd h2iMeasured values of the machining depth, S, for the correction start point 16 and the correction end point 18, respectivelyiTaking the electrode loss compensation relative speed of the trial cutting process step of the round, Si+1The relative rate is compensated for electrode wear for the next trial cut step.
Step S9: convergence condition Δ Z ≦ εZAnd | Si+1-Si|≤εSIn the formula: epsilonZAnd εSRespectively, machining depth and electrodeThe loss compensates for the convergence domain of the relative rates. If the convergence condition is not satisfied, returning to execute the step S5 and the subsequent steps; if the convergence condition is satisfied, step S10 is executed.
Step S10: and executing subsequent electric spark milling.
Fig. 1 shows a process consisting of a trial cut step 1, an on-line measurement step 2, a correction trial cut step 3, and a corrected on-line measurement step 4, which is performed in the direction of the arrow between the four steps.
The trial cut process step 1 is first performed. The electrode wire and the guider 5 are moved to a cutting starting point 7 above the part 6, and the distance from the bottom surface of the electrode wire to the blank surface of the part 6 is smaller than the maximum discharge gap. The wire electrode and the guide 5 are rotated at a high speed in the rotational direction 10, moved to the retracting point 9 in the feed direction 8, and the trial cut groove 11 is machined.
And then the online measurement step 2 is executed. The wire electrode and guide 5 executes a depth measuring movement 14 of a tool starting point and a depth measuring movement 15 of a tool retracting point, measures the depths of the trial cutting groove 11 at the two positions, and calculates a machining depth compensation value delta Z and an electrode loss compensation relative speed S1Used for the next trial cut.
Then, the correction trial cut process step 3 is performed. The wire electrode and the guide 5 are moved to a cutting starting point 16 above the part 6, the distance from the bottom surface of the wire electrode to the blank surface of the part 6 is delta Z compared with the adjustment amount of the previous electric discharge machining, and the positive direction is the + Z direction. The wire electrode and guide 5 is rotated at a high speed in a rotation direction 19, moved to a retracting point 18 in a feed direction 17, and a correction trial cut groove 20 is machined.
The corrected on-line measurement process step 4 is then performed. The wire electrode and guide 5 executes a depth measuring movement 23 for correcting the starting point and a depth measuring movement 24 for correcting the retreating point, the depths of the corrected trial cut groove 20 at the two positions are measured, and a machining depth compensation value delta Z and an electrode loss compensation relative speed S are calculatedi+1For determining the convergence of the machining parameters.
Convergence condition Δ Z ≦ εZAnd | Si+1-Si|≤εSIn the formula: epsilonZAnd εSThe convergence domain of the relative rates is compensated for machining depth and electrode loss, respectively.
If the machining depth compensation value Delta Z and the electrode loss compensation relative speed Si+1If the convergence condition is not met, returning to execute the correction trial cutting process step 3, and applying the parameters to a new trial cutting; if the convergence condition is satisfied, according to the converged Δ Z and Si+1And executing subsequent electric spark milling.
Fig. 2 shows the feed state of the wire electrode and the guide 5 in the trial cutting step 1. The electrode wire and the guider 5 are moved to a cutting starting point 7 above the part 6, and the distance from the bottom surface of the electrode wire to the blank surface of the part 6 is smaller than the maximum discharge gap.
The wire electrode and the guide 5 rotate at high speed in the rotation direction 10, trial cutting of electric spark milling is started on the blank surface of the part 6, horizontal feed motion 12 is started from the starting point 7, the horizontal feed distance is L (the feed path is not limited to a straight line), and meanwhile, the servo shaft of the wire electrode and the guide 5 makes vertically downward electrode loss compensation motion 13, and the compensation speed is S0(in the field of fine electric spark milling of high melting point metals, S is recommended0>0) The compensation distance is S0And L, combining the two motions into a feeding direction 8, and enabling the wire electrode and the guide device 5 to reach a tool withdrawal point 9 along the feeding direction 8 to finish the processing of the trial cutting groove 11.
Fig. 3 shows the measurement of the machining depth of the tool advancing and retracting point in the on-line measurement step 2. The wire electrode and guide 5 performs a depth measuring movement 14 of the starting point and a depth measuring movement 15 of the retracting point, measuring the depth of the test cut groove 11 at these two positions.
Calculating a machining depth compensation value delta Z and an electrode loss compensation relative rate S1The following were used:
ΔZ＝h10-h0、S1＝S0+(h10-h20)/L
in the formula: h is10And h20Measured values of the machining depth, h, of the tool run-up point 7 and the tool run-down point 9, respectively0For the set value of the working depth, S0The relative rate is compensated for electrode wear for trial cut step 1.
Fig. 4 shows the feed state of the wire electrode and the guide 5 in the correction trial cutting process step 3. The wire electrode and guide 5 is moved to the cutting start point 16 above the part 6, which is raised by a distance Δ Z relative to the cutting start point of the previous round of machining.
The wire electrode and the guider 5 rotate at high speed in the rotating direction 19, a new trial cutting process of electric spark milling is started on the blank surface of the part 6, horizontal feed motion 21 is started from the starting point 16, the horizontal feed distance is L (the feed track is not limited to a straight line), meanwhile, a servo shaft of the wire electrode and the guider 5 makes electrode loss compensation motion 22 which is vertically downward, and the compensation speed is Si(i-1, 2,3, …) and a compensation distance SiL, the two movements are combined into a feed direction 17, and the wire electrode and the guide 5 reach a retracting point 18 along the feed direction 17, completing the process of correcting the trial cut groove 20.
Fig. 5 shows the measurement of the machining depth of the tool advancing and retracting point in the corrected on-line measurement process step 4. The wire electrode and guide 5 performs a depth measuring movement 23 for correcting the starting point and a depth measuring movement 24 for correcting the retracting point, and the depths of the corrected trial cut groove 20 at these two positions are measured.
Calculating a machining depth compensation value delta Z and an electrode loss compensation relative rate Si+1The following were used:
ΔZ＝h1i-h0、Si+1＝Si+(h1i-h2i)/L (i＝1,2,3,…)
in the formula: h is1iAnd h2iMeasured values of machining depth h for the corrected tool start point 16 and the corrected tool retract point 18 of the ith round (i.e., the current round), respectively0To set the depth of machining, SiCorrecting the electrode loss compensation relative speed of the trial cutting step in the current round, Si+1The relative rate is compensated for electrode wear for the next trial cut run.
The embodiment of the invention provides an electric spark milling method, which is characterized in that the machining depth of electric spark milling is measured on line, and then the machining depth is corrected by adjusting a discharge gap according to the difference between the measured depth and the set depth, so that the control precision of the machining depth of an electric spark milling starting point can be automatically ensured in the process; the method for measuring the electrode loss on line and calculating the electrode loss compensation relative rate in an iterative manner is adopted, so that the consistency of the processing depth of the milling track can be automatically ensured; the invention allows the electrode loss compensation to be carried out during the initial trial cutting, solves the problem that the effective discharge interval of the electrode end surface is extremely small so that the continuous processing cannot be carried out under the discharge condition of micro electric spark processing high-melting-point metal, and simultaneously the width of the processing track can be kept consistent; on the basis of the three points, the invention can automatically keep the electric spark milling depth as a set value, and is beneficial to ensuring the continuity of the processing process and the precision of the depth dimension of the part; the invention does not depend on a process database in the aspects of discharge gap setting and electrode loss compensation setting, and the system can automatically find reasonable parameters through trial cut, online measurement and adjustment; the invention does not exclude relevant process data, the reasonable set values of the discharge gap and the electrode loss compensation relative speed can accelerate the convergence process, and shorten the trial cut and on-line measurement and adjustment time.
Those skilled in the art will appreciate that, in addition to implementing the system and its various devices, modules, units provided by the present invention as pure computer readable program code, the system and its various devices, modules, units provided by the present invention can be fully implemented by logically programming method steps in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system and various devices, modules and units thereof provided by the invention can be regarded as a hardware component, and the devices, modules and units included in the system for realizing various functions can also be regarded as structures in the hardware component; means, modules, units for performing the various functions may also be regarded as structures within both software modules and hardware components for performing the method.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.

Claims (10)

1. An electric spark milling method, characterized by comprising: a trial cutting process step (1), an on-line measurement process step (2), a correction trial cutting process step (3) and a corrected on-line measurement process step (4);
wherein the trial cutting process step (1): comprises a wire electrode and a guider (5), a starting point (7), a feed direction (8), a part (6) and a trial cutting groove (11); starting from a starting point (7), the electrode wire and the guider (5) perform electric spark milling on the part (6) along a feed direction (8), process a trial cutting groove (11), and then perform an online measurement step (2);
an online measurement process step (2): measuring and calculating a machining depth compensation value delta Z and an electrode loss compensation relative rate S1；
Correcting and trial cutting process step (3): comprises a correction starting point (16) and a correction feed direction (17); calculating a correction starting point (16) according to the delta Z, and finishing a new trial cut by the wire electrode and the guider (5) along a correction feed direction (17);
and (4) corrected online measurement step: measure and calculate a new round Δ Z and Si(i-2, 3, …); if Δ Z and SiIf the current time does not converge to the preset range, returning to execute the correction trial cutting process step (3); and if the current time is converged, performing subsequent electric spark milling.
2. The electric spark milling method as claimed in claim 1, characterized in that during milling, the electrical gauge, the milling feed rate or the trajectory coincidence rate is changed, and subsequent process steps are performed starting from the trial cut process step (1) again.
3. The spark milling method according to claim 1, characterized in that the trial cutting step (1) is a step in which the wire electrode and the guide (5) machine a trial cut groove (11) in the piece (6);
the wire electrode and the guider (5) rotate at high speed in the rotating direction (10), and the part (6) is subjected to electric spark milling from the starting point (7) along the feed direction (8) to the tool withdrawal point (9) to machine a trial cut groove (11).
4. The electric spark milling method as claimed in claim 3, characterized in that the feed direction (8) is lost by the horizontal feed movement (12) and the electrodeA compensation motion (13) synthesis in which the horizontal feed distance is L and the electrode loss compensation relative rate is S0The compensation distance is S0L, the direction is-Z.
5. The electric spark milling method according to claim 4, wherein S is directly added if empirical data of electrode wear compensation relative rate exists0Setting as empirical data; if there is no empirical data, set S00; if the micro electric spark technology is used to mill the high melting point metal, S is set0>0。
6. The electric spark milling method as claimed in claim 1, characterized in that said on-line measuring step (2) comprises: the wire electrode and guider (5) executes depth measurement movement (14) of a tool starting point and depth measurement movement (15) of a tool retracting point on the part (6), and a compensation value is calculated;
the wire electrode and the guider (5) execute the depth measurement movement (14) of the tool starting point and the depth measurement movement (15) of the tool retracting point, the depth of the trial cutting groove (11) at the two positions is measured, and a processing depth compensation value delta Z and an electrode loss compensation relative speed S are calculated1The following were used:
ΔZ＝h10-h0
S1＝S0+(h10-h20)/L
in the formula: h is10And h20Respectively as measured values of the machining depth h of a tool start point (7) and a tool withdrawal point (9)0To set the depth of machining, S0The relative rate is compensated for electrode wear in the trial cut process step (1).
7. The electric spark milling method as claimed in claim 1, wherein said correction trial cut step (3) comprises: the electrode wire and the guider (5) machine and correct a trial cutting groove (20) on the part (6);
the wire electrode and the guide (5) rotate at high speed in the rotating direction (19), starting from the correction starting point (16), the part (6) is subjected to spark milling along the correction feed direction (17) until the correction retreating point (18), and a correction trial cut groove (20) is machined.
8. The electric spark milling method as claimed in claim 7, characterized in that in the correction trial cut step (3), the correction start point (16) is shifted by Δ Z in the + Z direction compared to the previous trial cut; if Δ Z <0, the movement is in the-Z direction.
9. The spark milling method according to claim 8, wherein the correction feed direction (17) is synthesized from a horizontal feed motion (21) and an electrode loss compensation motion (22), wherein the horizontal feed distance is L and the electrode loss compensation relative rate is SiI is the number of trial cutting process step (3) and the compensation distance is SiL, the direction is-Z.
10. The electric spark milling method as claimed in claim 1, characterized in that said corrected on-line measurement step (4) comprises: the wire electrode and guider (5) executes depth measurement movement (23) of a correction tool starting point and depth measurement movement (24) of a correction tool retracting point on the part (6), and calculates a compensation value;
the wire electrode and guider (5) executes a depth measuring movement (23) for correcting a tool start point and a depth measuring movement (24) for correcting a tool retreat point, the depths of the two positions of the corrected trial cutting groove (20) are measured, and a processing depth compensation value delta Z and an electrode loss compensation relative speed S are calculatedi+1The following were used:
ΔZ＝h1i-h0
Si+1＝Si+(h1i-h2i)/L
in the formula: h is1iAnd h2iThe measured values of the machining depth of the ith round, namely the corrected tool starting point (16) and the corrected tool retracting point (18) of the round are respectively measured; h is0Setting a machining depth value; siCorrecting the electrode loss compensation relative rate of trial cutting step in this round, Si+1The relative rate is compensated for electrode wear for the next trial cut run.
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