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Process on Single Channel Scanning Milling of Micro-electrical Discharge Based on Integration Mechanism
Available online at www.sciencedirect.com
ScienceDirect Procedia CIRP 68 (2018) 808 – 812
19th CIRP Conference on Electro Physical and Chemical Machining, 23-27 April 2018, Bilbao, Spain
Process on Single Channel Scanning Milling of Micro-electrical Discharge Based on Integration Mechanism Rang-jie Wu, Yong-bin Zhang*, Guang-min Liu, Yan-hua Lei, Zhi-qun Wu * Corresponding author.. E-mail address: [email protected]
Abstract During the process of three-dimensional scanning milling of micro-electrical discharge, both positive and negative poles usually present as arc shape. This phenomena is called “arc shape phenomena” in this paper. This paper is to introduce erosion mechanism of electrical pulse discharged on both. Typically, the hollow electrode is applied to modeling and simulation. And then real experiments will be conducted. There are two conditions for the electrode in the analysis and tests: rotating at 300 rpm and 0 rpm. Finally, the profiles of tool electrode and workpiece are provided. Results show that there are different erosion effects on both poles. It shows that the process parameters have a significant influence on the final machining results. © 2018 2018The The Authors. Published by Elsevier B.V. © Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 19th CIRP Conference on Electro Physical and Chemical Machining. Peer-review under responsibility of the scientific committee of the 19th CIRP Conference on Electro Physical and Chemical Machining
Keywords: Integration mechanism, Micro-electrical discharge machining, Single channel, Scanning milling.
1. Introduction Micro-Electrical discharge machining (Micro-EDM) technology plays an irreplaceable role in the national economy and defense production. Soft materials, such as copper or graphite can be used to process high hardness and high strength metal, alloy, semiconductor and other conductive materials [1-2]. The superiority has been verified in many applications, and the effect is remarkable [3-5]. A significant amount of micro cavity bottom corner radius has high accuracy requirement; its typical features are shown in Figure 1. In addition to the accuracy requirements, in terms of surface quality: a lot of mesoscale precision cavities have put forward higher index to the surface quality to obtain the more ideal physical and mechanical properties. However, arc shape phenomena are common during threedimensional milling of micro-electrical discharge. It requires a certain overlap rate with scanning trajectory to obtain highquality surface accuracy, thus prolonging the processing time. Moreover, the residual amount of trace between each layer is a major factor which affects the surface quality of high precision, as shown in Figure 2a). In this regard, if arc shape
phenomena could be controlled more precisely, the surface of each track can be made smoother, and the overlapping rate of the scanning track can be reduced, as shown in Figure 2b). Also, there are still some narrow groove mesoscopic characteristics; their width is slight, which usually can only use single channel scanning processing trajectory. It is hard to achieve multi-track overlapping, which makes the impact of arc shape phenomena on the processing precision more evident, as shown in Figure 3. Parts that contain these types of features usually have requirements for higher accuracy and higher efficiency. Therefore, the studying of the influence factors of arc shape phenomena will be helpful for improving the machining accuracy and effectiveness. narrow groove
boss
workpiece workpiece corner of the micro groove
corner of the micro platform
Fig.1. characteristics of the typical corner machining
2212-8271 © 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 19th CIRP Conference on Electro Physical and Chemical Machining doi:10.1016/j.procir.2017.12.160
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electrode
tool electrode
limiting resistor puls power
workpiece
workpiece
(a)blunt electrode increase the track overlap rate
Fig.4. Typical processing track of three dimensional milling of microelectrical discharge
electrode
2. Erosion mechanism of electrical pulse discharged
workpiece
(b) flat electrode reduce the tool path overlap rate Fig.2.Effect of arc phenomena on track overlap rate and the surface integrity electrode
electrode
narrow groove
narrow groove
workpiece
workpiece
Fig.3. Effect of arc phenomena on machined contour
Figure 4 shows the typical micro EDM 3D layered scanning process. Firstly, the trajectory of the single layer is extracted and then expanded into a straight line. The motion track in a single layer can be regarded as a single-track scanning process. Thus, the entire three-dimensional cavity can be processed by a single scanning process; single channel scanning processing is the basis of hierarchical scanning. The paper introduces erosion mechanism of electrical pulse which is discharged on both positive and negative poles. The common hollow electrode is applied to do some modeling and simulation. Then, real experiments have been done. There are two conditions for the electrode: rotating with 300 rpm and 0 rpm in the analysis and experiments. In the end of the report, their profiles of tool electrode and workpiece will be provided. Results show that the simulation results are relevant with the experimental data.
During three-dimensional scanning milling of microelectrical discharge, the typical tool-path of each layer of single channel scanning milling is shown in Figure 5a). Cylindrical shape tool electrode is rotated rapidly and move forward along a straight line at the same time. The layer thickness is less than the discharge gap, thereby controlling the release, which mainly occurs between the bottom surface of the tool electrode and micro groove on the workpiece, trying to avoid discharge between the device electrode cylindrical side wall and the side wall of the microgroove on the workpiece. In this process, since unit micro electrical field energy is slight, removal amount of both positive and negative pole, which is far less than the poles of the mesoscopic scale geometry size, is between sub-micron and nanometer level. Therefore, in the process of scanning, the removal of a single micro energy pulse field can be regarded as a subtle unit, and the discharge area between tool electrode and workpiece can be meshed, as shown in Figure 5b). And the size of the grid is related to the energy of single pulse discharge. Due to the polarity effect of the discharge process, given electrical parameters, it could assume that the single pulse discharge in the positive and negative poles respectively into a certain percentage of removal in volume. Tool electrode moves forward along the length direction during single channel scanning milling and rotation at an absolute angular velocity at the same time, as shown in Figure 6. In the figure, when the tool electrode is processed from the point S1 to the position S2, the tool electrode and the part of the discharge eclipse will have different release times. On the one hand, the point Ai1 on the electrode is the synthetic motion of circular motion and linear motion, namely the spiral movement. The discharge region for each rotation of a circle will include a circumferential region(Tai)of a radius of Rai. For points of the different space on the tool electrode, the size of the discharge area is different. The different ratio of the rotating speed of the tool electrode and the linear feed rate can also lead to the difference of the discharge area. On the other hand, the time of discharge action of a Cj1 point on the workpiece and the erosion area WCj are directly related to the LCj due to the different distances from the center line. Also, when the distance between the two ends of the positive and negative poles reaches its minimum and the minimum is less than the critical distance of the discharge, an efficient discharge will be produced. Moreover, during each
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sufficient discharge, the removal of positive pole is proportion to the elimination of negative pole. If there are more than one pair of points has a distance less than the discharge of the critical distance, the direct feed will be suspended. When a layer of scanning processing finished, tool electrode will move up and then return to the starting point, and then fell to a new layer and repeat linear scanning, and so on until processing to the setting depth. At the same time, under the condition of a constant volume of unit corrosion, a different thickness of each layer means a different number of discharge, which affects feed speed, eventually leading to various discharge times on each point. The accumulation of this difference will make the tool electrode and the workpiece of each point as the scan to appear different processing depth, resulting in a different section contour. tool electrode scanning dirction
narrow groove
(a) processing track of rotating electrode during single channel scanning milling bottom of the electrode
part surface
(b) Meshing of bottom of the electrode and part surface Fig.5. processing track of tool electrode during single channel scanning milling workpiece electrode
single channel scanning milling
electrode
discharge gap, the layer thickness, the geometry parameters of the electrode, the scanning speed and the rotation speed. For different radius points on tool electrode and workpiece, there are different erosion amount. The outline of the positive and negative poles forming process is an accumulating process of discharge pulse function. In this process, the shape of the tool electrode and the cross-section profile of the single-track scanning feature are mutually influenced. 3. Simulation and experiment of single channel scanning process of hollow electrode
3.1. Modeling and simulation Based on the analysis of erosion mechanism of electrical pulse discharged, the project team developed a micro EDM single-channel scanning process simulation software. Typical hollow electrode is applied to do some modeling and simulation, and the effectiveness of the simulation analysis was verified [6]. To verify the effectiveness of the mechanism analysis furtherly, a typical hollow electrode was simulated and compared with the experimental results. The external diameter of the hollow tool electrode is 30μm, and the inner diameter of the electrode is 18μm; the volume ratio of discharge to the electrode and the specimen is VT:VM=1:3; the discharge frequency is 100kHz; the thickness of single layer is 2μm; the horizontal feed rate is 100μm/s; the total depth is 10μm; and the total length is 100μm. There are two conditions for the electrode: rotating with 300 rpm and 0 rpm in the analysis and experiments. The test results are shown in Table 1 and Table 2 respectively, and the characteristics of the specimen and the characteristics of the tool electrode are given. The simulation results show that when the tool electrode is not rotated, arc shape phenomena could be found in both tool electrode and workpiece. And due to the lack of the central part of the hollow electrode, the shape of the cross section is different from that of the solid cylinder electrode. When the tool electrode is rotating with 300 rpm, the cross sections of the specimen and the tool electrode have no obvious arc phenomenon, which can be approximated to a straight state. Thus, it is concluded that arc shape phenomena can be controlled by adjusting the different process parameters (such as rotating speed) during the single channel scanning milling of micro-electrical discharge. Table 1. Simulation results of Single channel scanning milling(Specimen characteristics)
As is explained above, during single channel scanning milling, the effect of the discharge on the positive and negative electrodes is a comprehensive function, which is closely related with the electrical pulse parameters, the
Electrodes do not rotate(0 rpm)
Electrodes rotates(300 rpm)
Top View
Fig.6. Different integration erosion effects on both poles during single channel scanning milling
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Side view
tool electrode
grinding wire
Table 2. Simulation results of Single channel scanning milling(Electrode characteristics)
Electrodes do not rotate(0 rpm)
Electrodes rotates(300 rpm) Fig.7. Lower end face of the flat electrode is processed by the grinding wire
Top View
tool electrode
specimen
Side view
Fig.8. Adjusting the surface of the specimen to the horizontal
3.2. Experiment Based on erosion mechanism of electrical pulse discharged and its simulation analysis, the project team carried out the experimental research on the prototype of micro electro discharge machining. In the experimental process, to eliminate the error on the surface of the electrode and the surface roughness of the specimen, two preparations are made. Firstly, the lower end face of the electrode is processed by the wire electrode grinding wire in horizontal position to carry out trimming and processing to the lower end face of the electrode, as is shown in Figure 8. Then, using this electrode, with the three-dimensional micro adjustment fixture, the use of contact sensing function, after multiple adjustments, the perception of each point coordinate range within the allowable range. The typical hollow electrode is applied to do some modeling and simulation. There are two conditions for the electrode, rotating at 300 rpm and 0 rpm in the analysis and experiments. The processing result is shown in Figure 9. Figure 9a) is the small straight groove and its cross section profile when the electrode is rotating with 0 rpm, its bottom cross section is of typical M type. While Figure 9b) is the small straight groove and its cross-section profile when the electrode is rotating at 300 rpm, the bottom of the cross section is relatively flat. Therefore, it is suggested that there are different integration erosion effects on both poles. The difference can be controlled by adjusting some techniques parameters.
(a)Hollow electrode rotating with 0 rpm, bottom cross section is of typical M type
(b)Hollow electrode rotating with 300 rpm, bottom of the cross section is relatively flat Fig.9. Results of single channel scanning milling processing cavity with hollow electrode
4. Conclusions The paper introduces arc shape phenomena during threedimensional milling of micro-electrical discharge and the main factors that influence the phenomenon. Then, erosion mechanism of electrical pulse discharged on both positive and negative poles has been analyzed. The common hollow electrodes have been applied to multiple modeling and simulation. Furthermore, real experiments have been conducted. There are two conditions for the electrode in the analysis and experiments: rotating with 300 rpm and 0 rpm. Results show that there are different erosion effects on both poles. Experiments verify the actual existence of the
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phenomenon. In the single channel scanning machining of micro electrical discharge machining, the different effects of electrical pulse discharged on positive and negative poles have also been proved. It shows that the process parameters have a significant influence on the final machining results. Acknowledgments This research was financed by the National Natural Science Foundation of China (Grant No. 51475439), the Applied Basic Research Programs of Sichuan Provincial Science and Technology Department (Grant No. 2016JY0109) and Laboratory of Precision Manufacturing Technology of CAEP (Grant No.ZZ14005).
References [1] U.Maradia, M.Scuderi, R.Knaak, et al. Super-finished Surfaces using Meso-micro EDM. Procedia CIRP.2013,6:157-162. [2] Zu-yuan Yu. Dong-min Guo,Zhen-yuan Jia. Micro Electrical Discharge Machining[J]. Science paper Online. 2007.03:214-220. [3] Hong-gang Zhu, Pei Xu, Huan-qing Wang,et al. Study on electric machining technology of titanium alloy narrow deep slot[J]. 2010 Symposium on Aerospace advanced manufacturing technology. 2010.09:13-20. [4] Ji-lun Chen. Application and Prospect of numerical control electrical discharge machining technology in the aerospace field[J]. Electromachining & Mould. 2011.04:27-30. [5] Hai-nan Zhu, Xin-xia Qi. Technology and development of gas film hole machining of turbine blades[J]. Aeronautical Manufacturing Technology. 2011.07:71-74. [6] Yong-bin Zhang, Guang-min Liu, Zhi-qun Wu, Yan-hua Lei. Integration Mechanism on Single Channel Scanning Milling of Micro-electrical Discharge[J]. Electromachining & Mould. 2015.12:1-5.
ScienceDirect Procedia CIRP 68 (2018) 808 – 812
19th CIRP Conference on Electro Physical and Chemical Machining, 23-27 April 2018, Bilbao, Spain
Process on Single Channel Scanning Milling of Micro-electrical Discharge Based on Integration Mechanism Rang-jie Wu, Yong-bin Zhang*, Guang-min Liu, Yan-hua Lei, Zhi-qun Wu * Corresponding author.. E-mail address: [email protected]
Abstract During the process of three-dimensional scanning milling of micro-electrical discharge, both positive and negative poles usually present as arc shape. This phenomena is called “arc shape phenomena” in this paper. This paper is to introduce erosion mechanism of electrical pulse discharged on both. Typically, the hollow electrode is applied to modeling and simulation. And then real experiments will be conducted. There are two conditions for the electrode in the analysis and tests: rotating at 300 rpm and 0 rpm. Finally, the profiles of tool electrode and workpiece are provided. Results show that there are different erosion effects on both poles. It shows that the process parameters have a significant influence on the final machining results. © 2018 2018The The Authors. Published by Elsevier B.V. © Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 19th CIRP Conference on Electro Physical and Chemical Machining. Peer-review under responsibility of the scientific committee of the 19th CIRP Conference on Electro Physical and Chemical Machining
Keywords: Integration mechanism, Micro-electrical discharge machining, Single channel, Scanning milling.
1. Introduction Micro-Electrical discharge machining (Micro-EDM) technology plays an irreplaceable role in the national economy and defense production. Soft materials, such as copper or graphite can be used to process high hardness and high strength metal, alloy, semiconductor and other conductive materials [1-2]. The superiority has been verified in many applications, and the effect is remarkable [3-5]. A significant amount of micro cavity bottom corner radius has high accuracy requirement; its typical features are shown in Figure 1. In addition to the accuracy requirements, in terms of surface quality: a lot of mesoscale precision cavities have put forward higher index to the surface quality to obtain the more ideal physical and mechanical properties. However, arc shape phenomena are common during threedimensional milling of micro-electrical discharge. It requires a certain overlap rate with scanning trajectory to obtain highquality surface accuracy, thus prolonging the processing time. Moreover, the residual amount of trace between each layer is a major factor which affects the surface quality of high precision, as shown in Figure 2a). In this regard, if arc shape
phenomena could be controlled more precisely, the surface of each track can be made smoother, and the overlapping rate of the scanning track can be reduced, as shown in Figure 2b). Also, there are still some narrow groove mesoscopic characteristics; their width is slight, which usually can only use single channel scanning processing trajectory. It is hard to achieve multi-track overlapping, which makes the impact of arc shape phenomena on the processing precision more evident, as shown in Figure 3. Parts that contain these types of features usually have requirements for higher accuracy and higher efficiency. Therefore, the studying of the influence factors of arc shape phenomena will be helpful for improving the machining accuracy and effectiveness. narrow groove
boss
workpiece workpiece corner of the micro groove
corner of the micro platform
Fig.1. characteristics of the typical corner machining
2212-8271 © 2018 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer-review under responsibility of the scientific committee of the 19th CIRP Conference on Electro Physical and Chemical Machining doi:10.1016/j.procir.2017.12.160
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Rang-jie Wu et al. / Procedia CIRP 68 (2018) 808 – 812
electrode
tool electrode
limiting resistor puls power
workpiece
workpiece
(a)blunt electrode increase the track overlap rate
Fig.4. Typical processing track of three dimensional milling of microelectrical discharge
electrode
2. Erosion mechanism of electrical pulse discharged
workpiece
(b) flat electrode reduce the tool path overlap rate Fig.2.Effect of arc phenomena on track overlap rate and the surface integrity electrode
electrode
narrow groove
narrow groove
workpiece
workpiece
Fig.3. Effect of arc phenomena on machined contour
Figure 4 shows the typical micro EDM 3D layered scanning process. Firstly, the trajectory of the single layer is extracted and then expanded into a straight line. The motion track in a single layer can be regarded as a single-track scanning process. Thus, the entire three-dimensional cavity can be processed by a single scanning process; single channel scanning processing is the basis of hierarchical scanning. The paper introduces erosion mechanism of electrical pulse which is discharged on both positive and negative poles. The common hollow electrode is applied to do some modeling and simulation. Then, real experiments have been done. There are two conditions for the electrode: rotating with 300 rpm and 0 rpm in the analysis and experiments. In the end of the report, their profiles of tool electrode and workpiece will be provided. Results show that the simulation results are relevant with the experimental data.
During three-dimensional scanning milling of microelectrical discharge, the typical tool-path of each layer of single channel scanning milling is shown in Figure 5a). Cylindrical shape tool electrode is rotated rapidly and move forward along a straight line at the same time. The layer thickness is less than the discharge gap, thereby controlling the release, which mainly occurs between the bottom surface of the tool electrode and micro groove on the workpiece, trying to avoid discharge between the device electrode cylindrical side wall and the side wall of the microgroove on the workpiece. In this process, since unit micro electrical field energy is slight, removal amount of both positive and negative pole, which is far less than the poles of the mesoscopic scale geometry size, is between sub-micron and nanometer level. Therefore, in the process of scanning, the removal of a single micro energy pulse field can be regarded as a subtle unit, and the discharge area between tool electrode and workpiece can be meshed, as shown in Figure 5b). And the size of the grid is related to the energy of single pulse discharge. Due to the polarity effect of the discharge process, given electrical parameters, it could assume that the single pulse discharge in the positive and negative poles respectively into a certain percentage of removal in volume. Tool electrode moves forward along the length direction during single channel scanning milling and rotation at an absolute angular velocity at the same time, as shown in Figure 6. In the figure, when the tool electrode is processed from the point S1 to the position S2, the tool electrode and the part of the discharge eclipse will have different release times. On the one hand, the point Ai1 on the electrode is the synthetic motion of circular motion and linear motion, namely the spiral movement. The discharge region for each rotation of a circle will include a circumferential region(Tai)of a radius of Rai. For points of the different space on the tool electrode, the size of the discharge area is different. The different ratio of the rotating speed of the tool electrode and the linear feed rate can also lead to the difference of the discharge area. On the other hand, the time of discharge action of a Cj1 point on the workpiece and the erosion area WCj are directly related to the LCj due to the different distances from the center line. Also, when the distance between the two ends of the positive and negative poles reaches its minimum and the minimum is less than the critical distance of the discharge, an efficient discharge will be produced. Moreover, during each
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sufficient discharge, the removal of positive pole is proportion to the elimination of negative pole. If there are more than one pair of points has a distance less than the discharge of the critical distance, the direct feed will be suspended. When a layer of scanning processing finished, tool electrode will move up and then return to the starting point, and then fell to a new layer and repeat linear scanning, and so on until processing to the setting depth. At the same time, under the condition of a constant volume of unit corrosion, a different thickness of each layer means a different number of discharge, which affects feed speed, eventually leading to various discharge times on each point. The accumulation of this difference will make the tool electrode and the workpiece of each point as the scan to appear different processing depth, resulting in a different section contour. tool electrode scanning dirction
narrow groove
(a) processing track of rotating electrode during single channel scanning milling bottom of the electrode
part surface
(b) Meshing of bottom of the electrode and part surface Fig.5. processing track of tool electrode during single channel scanning milling workpiece electrode
single channel scanning milling
electrode
discharge gap, the layer thickness, the geometry parameters of the electrode, the scanning speed and the rotation speed. For different radius points on tool electrode and workpiece, there are different erosion amount. The outline of the positive and negative poles forming process is an accumulating process of discharge pulse function. In this process, the shape of the tool electrode and the cross-section profile of the single-track scanning feature are mutually influenced. 3. Simulation and experiment of single channel scanning process of hollow electrode
3.1. Modeling and simulation Based on the analysis of erosion mechanism of electrical pulse discharged, the project team developed a micro EDM single-channel scanning process simulation software. Typical hollow electrode is applied to do some modeling and simulation, and the effectiveness of the simulation analysis was verified [6]. To verify the effectiveness of the mechanism analysis furtherly, a typical hollow electrode was simulated and compared with the experimental results. The external diameter of the hollow tool electrode is 30μm, and the inner diameter of the electrode is 18μm; the volume ratio of discharge to the electrode and the specimen is VT:VM=1:3; the discharge frequency is 100kHz; the thickness of single layer is 2μm; the horizontal feed rate is 100μm/s; the total depth is 10μm; and the total length is 100μm. There are two conditions for the electrode: rotating with 300 rpm and 0 rpm in the analysis and experiments. The test results are shown in Table 1 and Table 2 respectively, and the characteristics of the specimen and the characteristics of the tool electrode are given. The simulation results show that when the tool electrode is not rotated, arc shape phenomena could be found in both tool electrode and workpiece. And due to the lack of the central part of the hollow electrode, the shape of the cross section is different from that of the solid cylinder electrode. When the tool electrode is rotating with 300 rpm, the cross sections of the specimen and the tool electrode have no obvious arc phenomenon, which can be approximated to a straight state. Thus, it is concluded that arc shape phenomena can be controlled by adjusting the different process parameters (such as rotating speed) during the single channel scanning milling of micro-electrical discharge. Table 1. Simulation results of Single channel scanning milling(Specimen characteristics)
As is explained above, during single channel scanning milling, the effect of the discharge on the positive and negative electrodes is a comprehensive function, which is closely related with the electrical pulse parameters, the
Electrodes do not rotate(0 rpm)
Electrodes rotates(300 rpm)
Top View
Fig.6. Different integration erosion effects on both poles during single channel scanning milling
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Side view
tool electrode
grinding wire
Table 2. Simulation results of Single channel scanning milling(Electrode characteristics)
Electrodes do not rotate(0 rpm)
Electrodes rotates(300 rpm) Fig.7. Lower end face of the flat electrode is processed by the grinding wire
Top View
tool electrode
specimen
Side view
Fig.8. Adjusting the surface of the specimen to the horizontal
3.2. Experiment Based on erosion mechanism of electrical pulse discharged and its simulation analysis, the project team carried out the experimental research on the prototype of micro electro discharge machining. In the experimental process, to eliminate the error on the surface of the electrode and the surface roughness of the specimen, two preparations are made. Firstly, the lower end face of the electrode is processed by the wire electrode grinding wire in horizontal position to carry out trimming and processing to the lower end face of the electrode, as is shown in Figure 8. Then, using this electrode, with the three-dimensional micro adjustment fixture, the use of contact sensing function, after multiple adjustments, the perception of each point coordinate range within the allowable range. The typical hollow electrode is applied to do some modeling and simulation. There are two conditions for the electrode, rotating at 300 rpm and 0 rpm in the analysis and experiments. The processing result is shown in Figure 9. Figure 9a) is the small straight groove and its cross section profile when the electrode is rotating with 0 rpm, its bottom cross section is of typical M type. While Figure 9b) is the small straight groove and its cross-section profile when the electrode is rotating at 300 rpm, the bottom of the cross section is relatively flat. Therefore, it is suggested that there are different integration erosion effects on both poles. The difference can be controlled by adjusting some techniques parameters.
(a)Hollow electrode rotating with 0 rpm, bottom cross section is of typical M type
(b)Hollow electrode rotating with 300 rpm, bottom of the cross section is relatively flat Fig.9. Results of single channel scanning milling processing cavity with hollow electrode
4. Conclusions The paper introduces arc shape phenomena during threedimensional milling of micro-electrical discharge and the main factors that influence the phenomenon. Then, erosion mechanism of electrical pulse discharged on both positive and negative poles has been analyzed. The common hollow electrodes have been applied to multiple modeling and simulation. Furthermore, real experiments have been conducted. There are two conditions for the electrode in the analysis and experiments: rotating with 300 rpm and 0 rpm. Results show that there are different erosion effects on both poles. Experiments verify the actual existence of the
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phenomenon. In the single channel scanning machining of micro electrical discharge machining, the different effects of electrical pulse discharged on positive and negative poles have also been proved. It shows that the process parameters have a significant influence on the final machining results. Acknowledgments This research was financed by the National Natural Science Foundation of China (Grant No. 51475439), the Applied Basic Research Programs of Sichuan Provincial Science and Technology Department (Grant No. 2016JY0109) and Laboratory of Precision Manufacturing Technology of CAEP (Grant No.ZZ14005).
References [1] U.Maradia, M.Scuderi, R.Knaak, et al. Super-finished Surfaces using Meso-micro EDM. Procedia CIRP.2013,6:157-162. [2] Zu-yuan Yu. Dong-min Guo,Zhen-yuan Jia. Micro Electrical Discharge Machining[J]. Science paper Online. 2007.03:214-220. [3] Hong-gang Zhu, Pei Xu, Huan-qing Wang,et al. Study on electric machining technology of titanium alloy narrow deep slot[J]. 2010 Symposium on Aerospace advanced manufacturing technology. 2010.09:13-20. [4] Ji-lun Chen. Application and Prospect of numerical control electrical discharge machining technology in the aerospace field[J]. Electromachining & Mould. 2011.04:27-30. [5] Hai-nan Zhu, Xin-xia Qi. Technology and development of gas film hole machining of turbine blades[J]. Aeronautical Manufacturing Technology. 2011.07:71-74. [6] Yong-bin Zhang, Guang-min Liu, Zhi-qun Wu, Yan-hua Lei. Integration Mechanism on Single Channel Scanning Milling of Micro-electrical Discharge[J]. Electromachining & Mould. 2015.12:1-5.