CN101829822A - Method for reducing electrode loss of micro electron discharge machining tool by connecting diode with interelectrode in series - Google Patents
Method for reducing electrode loss of micro electron discharge machining tool by connecting diode with interelectrode in series Download PDFInfo
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- CN101829822A CN101829822A CN201010102045A CN201010102045A CN101829822A CN 101829822 A CN101829822 A CN 101829822A CN 201010102045 A CN201010102045 A CN 201010102045A CN 201010102045 A CN201010102045 A CN 201010102045A CN 101829822 A CN101829822 A CN 101829822A
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Abstract
The invention relates to a method for reducing the electrode loss of a micro electron discharge machining tool by connecting a diode with interelectrode in series. A high-speed switch diode or a superfast recovery diode is connected with a position nearest to an electrode of the tool or a workpiece, and is forwards biased; and the diode, the interelectrode and a pulse power supply form a series loop. The method is applied to a micro electron discharge machining discharging loop; and the electrode loss of the micro electron discharge machining tool can be obviously reduced particularly when largely distributed electrical inductance exists in the discharging loop.
Description
Technical field
The present invention is used for the discharge loop of fine electric spark processing, especially a kind of by with the interpolar series diode to reduce the method for fine electric spark machining tool export license.
Technical background
Power supply commonly used has RC speed a formula pulse power and free-standing transistor pulse generator in the spark machined.No matter which kind of power supply adds man-hour carrying out fine electric spark, all there is the oscillatory occurences of discharge current during discharge, be illustrated in figure 1 as and use the RC power supply to carry out the voltage across poles current waveform that fine electric spark adds man-hour.Desirable discharge current waveform is shown in figure (a), but the discharge current waveform of actual measurement is shown in the single step of releasing electric process and exists vibration as figure (b).
From Fig. 1 (b) as can be seen, after interpolar is breakdown, voltage across poles descends, electrode current sharply rises simultaneously, produce spark discharge, after the current impulse first time finishes, produced the opposite current impulse second time of direction, then also have for the third time, the 4th primary current pulse ... i.e. current impulse has for the first time produced current oscillation after finishing, about this current oscillation phenomenon two kinds of different explanations can be arranged: a kind of explanation thinks that the forward current pulse is a discharge current for the first time, and current impulse for the second time is the electromagnetic viscosimeter during discharge finishes back dielectric insulation recovery; Another explanation thinks that the forward current pulse is a discharge current for the first time, and the current impulse after reaching for the second time is because the back discharge electric current that distributed inductance causes in the circuit.
The inventor herein has carried out experimental study to above-mentioned phenomenon, and result of study has proved that above-mentioned second kind of explanation is correct, i.e. exist positive reversed polarity multiple discharge phenomenon during the vibration of the breakdown moment generation of interpolar discharge current.Electrical spark working man-hour, people usually utilize polar effect to reduce export license when roughing (tool-electrode connects negative pole during fine finishining, otherwise), because interpolar breakdown moment exists positive and negative multiple discharge, this will inevitably weaken polar effect, thereby can aggravate export license.For this reason, this patent proposes in interpolar serial or parallel connection speed-sensitive switch diode (or Ultrafast recovery diode) method respectively in order to reduce export license.This patent proposes a kind of method at interpolar series high-speed switching diode (or Ultrafast recovery diode) for this reason, make the positive polarity discharge in breakdown moment multiple discharge be reversed to the negative polarity discharge, the equal negative polarity discharge of multiple discharge in then once discharging, thus reach the purpose that reduces tool electrode loss.
Summary of the invention
The essence of spark machined is, constantly produces the spark discharge of pulse feature between instrument and the electrode, and the high temperature of part, instantaneous generation gets off the metal ablation when discharging, and promptly electric energy is converted into the heat energy ablation metal.Again owing to have polar effect during spark discharge: during discharge, energy is at both positive and negative polarity---and be that distribution between workpiece and the electrode is different, cause workpiece and electrode to be subjected in various degree galvanic corrosion.Existing research is as follows to the mechanism explain of this phenomenon: during roughing, pulse power pulsewidth broad, discharge time is longer, discharge energy is bigger, this moment, electrode connect positive source, workpiece connects power cathode, the a large amount of plasma of the breakdown moment generation of interpolar, the cation of positively charged from electrode to workpiece motion s, electronegative electronics from workpiece to electrode movement, particle bombardment workpiece (or electrode) surface produces a large amount of heat etchings and removes metal, because the quality of cation is big more a lot of than electronics, so the energy of positive ion bombardment surface of the work is more a lot of greatly than the energy of electron bombard electrode surface, therefore, workpiece by the speed ratio electrode of ablation by big many of the speed of ablation, so export license is than little (export license than for the loss volume of electrode and workpiece by the ratio of ablation volume); During fine finishining, pulse power pulsewidth is minimum, so the breakdown back of interpolar is also extremely short discharge time, discharge energy is less, the connection of electrode and workpiece is opposite during just in time with above-mentioned roughing, electrode connects the power cathode workpiece and connects positive source at this moment, the a large amount of plasma of the breakdown moment generation of interpolar, to workpiece motion s, the electron bombard surface of the work produces a large amount of heat to electronegative electronics from electrode, thus the metal of ablation surface of the work, the cation of positively charged is because its quality is big more a lot of than electronics, inertia is also big a lot, because discharge time is extremely short, cation has just begun from workpiece to electrode movement, also have little time to bombard electrode surface, and the power supply pulsewidth has finished, and discharge process is terminated subsequently, thus from workpiece to electrode movement and to bombard the cation of electrode surface few, so the energy of positive ion bombardment electrode surface is little more a lot of than the energy of electron bombard surface of the work, therefore, the ablation speed of the ablation speed ratio electrode of workpiece is much bigger, so export license is than little.Electrical spark working man-hour, optimal situation is the metal on the ablation workpiece, not the metal on the ablation electrode.From boosting productivity and reducing the angle of tool loss, polar effect is remarkable more good more.Therefore, spark machined generally adopts the unidirectional pulse power supply, and workpiece connects anodal instrument and connects negative pole when roughing (otherwise) during fine finishining.Fine electric spark adds man-hour general workpiece and connects anodal instrument and connect negative pole and consider exactly and will improve process velocity and reduce export license.
At the current oscillation phenomenon shown in Fig. 1 (b), this patent has proposed the method for passing through to reduce at interpolar series high-speed switching diode fine electric spark machining tool export license shown in Figure 2, wherein Fig. 2 (a) is at the RC pulse power, and Fig. 2 (b) is at free-standing transistor pulse generator.Behind the interpolar series high-speed switching diode (or Ultrafast recovery diode) and since filtering the back discharge electric current, strengthened polar effect, so can reduce tool electrode loss.
The present invention is a kind of method that is used for fine electric spark processing reducing tool electrode loss, it is characterized in that, said method comprising the steps of:
(a) at first between tool-electrode and workpiece, apply pulse power voltage;
(b) disconnect above-mentioned electric power loop from tool-electrode or the nearest place of workpiece, and inserting speed-sensitive switch diode or Ultrafast recovery diode at gap, the diode forward biasing, diode, interpolar and pulse power three form a series loop;
(c) the power supply electrifying processing of discharging.
The described speed-sensitive switch diode reverse recovery time will be in 50ns, and diode can be in operate as normal under the high frequency condition; The breakdown reverse voltage of diode is than the electrical spark working operating voltage height in man-hour; The peak point current of the peak point current of diode during than spark discharge is big; Resistance is little during forward conduction.
When selecting, the diode model considers that at first its operating voltage must be greater than electrical spark working maximum voltage in man-hour, the maximum current when peak point current of diode must be greater than spark discharge, last more vital be exactly reverse recovery time of diode must be extremely short, generally can select following model: 1N6621,1N5806, UF4004, (discharge of the following 200mA electric current of 40V is processed) can select small-signal speed-sensitive switch diodes such as 1N4148 under the atomic details condition.
Description of drawings
● Fig. 1 prior art RC power supply carries out the electrical spark working voltage across poles current waveform in man-hour: figure (a) is desirable discharge waveform, and figure (b) is the discharge waveform of actual measurement.
● Fig. 2 interpolar series diode is to reduce export license: figure (a) is at the RC pulse power, and figure (b) is at free-standing transistor pulse generator.
● Fig. 3 interpolar series diode is to the influence of export license ratio: among the figure as can be seen behind the series high-speed switching diode tool electrode loss than obviously reducing.。
● the influence of Fig. 4 diode pair voltage across poles current waveform: figure (a) is the discharge waveform when not having parallel diode, there is vibration in discharge current as can be seen, the sense of current is positive and negative alternately, the discharge waveform when figure (b) is parallel diode, and the negative direction discharge current is by filtering.
● table 1 experiment condition
Specific embodiment
Of the present invention by with the interpolar series diode to reduce the method for fine electric spark machining tool export license, may further comprise the steps:
(a) at first between tool-electrode and workpiece, apply pulse power voltage;
(b) disconnect above-mentioned electric power loop from tool-electrode or the nearest place of workpiece, and inserting speed-sensitive switch diode or Ultrafast recovery diode at gap, the diode forward biasing, diode, interpolar and pulse power three form a series loop;
(c) the power supply electrifying processing of discharging.
The described speed-sensitive switch diode reverse recovery time will be in 50ns, and diode can be in operate as normal under the high frequency condition; The breakdown reverse voltage of diode is than the electrical spark working operating voltage height in man-hour; The peak point current of the peak point current of diode during than spark discharge is big; Resistance during forward conduction during than spark discharge is little.
Current oscillation phenomenon in once discharging when distributed inductance in the discharge loop is big is obvious, adopts the method shown in Figure 2 can less effectively tool electrode loss at interpolar series high-speed switching diode (or Ultrafast recovery diode) in this case.Result of the test shows that tool electrode loss can reduce more than 10% at least.Especially the influence of distributed inductance is more obvious during fine finishining, and the vibration of discharge current is more violent, so adopt the effect of the less tool electrode loss of speed-sensitive switch diode also more remarkable.Yet to Fig. 2 (b), promptly for free-standing transistor power supply, this method is only applicable to fine finishining, because (especially the fine electric spark that carries out under the ultrashort pulsewidth processing conditions when transistor pulse generator adds man-hour) current oscillation is obvious during fine finishining, and the electric current pulsewidth is very wide during roughing, and that the oscillating part of electric current seems by comparison is very little, so roughing is DeGrain.
Adopt the method shown in Fig. 2 (a), carry out the blind hole machining experiment under the experiment condition shown in the table 1, hole depth is 800 μ m, and processing and survey tool export license discharge under the situation of series connection and series diode not respectively.Adopt the carbon tungsten alloy electrode of Φ 80 μ m in the experiment, because electrode diameter is little, the aspect ratio of machining hole is big again, so export license clearly, contrast experiment's effect is also remarkable.Use interpolar state-detection and servo during experiment.The experiment equipment therefor is a spark machined three-axis numerical control experiment porch, and the minimum movement displacement is 0.078 μ m.
The interpolar discharge voltage current waveform that records as shown in Figure 3.Can find out except forward current is arranged, to also have reversing the current to exist during diode-less among the figure, behind the series diode then filtering reversing the current.Fig. 4 is the influence of interpolar series diode to the export license ratio, the export license ratio was not that 0.46 (hole depth is 800 μ m when therefrom interpolar had the series high-speed switching diode as can be seen, export license is 368 μ m), interpolar series high-speed switching diode rear electrode loss ratio is that 0.3875 (hole depth is 800 μ m, export license is 310 μ m), as seen behind the interpolar series high-speed switching diode, export license has reduced 16.3%.
Table 1 experiment condition
Claims (2)
- One kind by with the interpolar series diode to reduce the method for fine electric spark machining tool export license, it is characterized in that, said method comprising the steps of:(a) at first between tool-electrode and workpiece, apply pulse power voltage;(b) disconnect above-mentioned electric power loop from tool-electrode or the nearest place of workpiece, and inserting speed-sensitive switch diode or Ultrafast recovery diode at gap, the diode forward biasing, diode, interpolar and pulse power three form a series loop;(c) the power supply electrifying processing of discharging.
- 2. method according to claim 1 is characterized in that, the described speed-sensitive switch diode reverse recovery time will be in 50ns, and diode can be in operate as normal under the high frequency condition; The breakdown reverse voltage of diode is than the electrical spark working operating voltage height in man-hour; The peak point current of the peak point current of diode during than spark discharge is big; Resistance during forward conduction during than spark discharge is little.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201010102045A CN101829822A (en) | 2010-01-28 | 2010-01-28 | Method for reducing electrode loss of micro electron discharge machining tool by connecting diode with interelectrode in series |
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| CN201010102045A CN101829822A (en) | 2010-01-28 | 2010-01-28 | Method for reducing electrode loss of micro electron discharge machining tool by connecting diode with interelectrode in series |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102601472A (en) * | 2011-01-19 | 2012-07-25 | 通用电气公司 | Electric discharge machining system and method |
| CN104646774A (en) * | 2014-12-15 | 2015-05-27 | 哈尔滨工业大学 | Electrode loss real-time compensation method based on spark discharge rate |
| CN110608020A (en) * | 2019-10-18 | 2019-12-24 | 中国石油大学(华东) | Downhole operation pulse electrode structure |
-
2010
- 2010-01-28 CN CN201010102045A patent/CN101829822A/en active Pending
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102601472A (en) * | 2011-01-19 | 2012-07-25 | 通用电气公司 | Electric discharge machining system and method |
| CN104646774A (en) * | 2014-12-15 | 2015-05-27 | 哈尔滨工业大学 | Electrode loss real-time compensation method based on spark discharge rate |
| CN104646774B (en) * | 2014-12-15 | 2016-11-16 | 哈尔滨工业大学 | A kind of export license real-time compensation method based on spark discharge rate |
| CN110608020A (en) * | 2019-10-18 | 2019-12-24 | 中国石油大学(华东) | Downhole operation pulse electrode structure |
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Open date: 20100915 |