47 Electrical Discharge Truing for Electroplated Diamond Tools Koji Watanabe Hisashi Minami Hatsumi Hiramatsu Kiyonori Masui (211 7 8 ) Electroplated diamond tools are widely used for grinding because of their high grinding efficiency. However, the height of the grain protrusion of the electroplated diamond tool is not uniform, which degrades the surface roughness. Therefore, it is necessary to make the height of diamond grains uniform. Herein, we propose a new electrical discharge truing (ED truing) method for electroplated diamond tools. This ED truing method is applicable to a conventional electroplated diamond tool whose grains (diamond) have no electrical conductivity. Results show the capability of truncating only the diamond grain tips directly using this new ED truing method and the ability to obtain an electroplated diamond tool with uniform grain height. Moreover, results show that the ground surface roughness is improved using the ED-trued electroplated diamond tool. Key words : electrical discharge truing, electroplated diamond tool, truncate 1. E.D.M. 1 2) 1) ( ) 2) 3)
48 4 6) Electrode Electroplated diamond tool Measuring instrument Fig. 1 Appearance of experimental equipment for electrical discharge truing. 2. Fig. 1 ( ) (2 min 1 ) ( ) Table 1 ( ) Fig. 2 1 LED ( = 1 μm) Z ( ) Table 1 Experimental conditions. EDM-machine Sodick AP1L Discharge current Open circuit voltage Discharge duration Duty factor Workpiece Electrode Rotating speed Step feed Dielectric working fluid i e = 2 A u i =12 V t e =1 s =1 % Electroplated diamond tool : ( + ) Diameter mm grain size #14 Gold deposition almost 5 nm Cu-W : ( - ) 2 min -1 1 m, 5 m EDM oil Electroplated diamond tool LENS LENS Detector LED Diameter Fig.2 Measuring system for profile of diamond tool.
49 Fig. 3 Z ( 1 μm) 1/1(1 μm) 1/2 3. 3.1 #4 ( = 42 μm) Fig. 4 (ie) 1 A (te) (N) (te) ( N te) Fig. 5 1 μs ie = 2 A ie = 5 A (1 μs) ie = 5 A te = 1 μs ie = 2 A 3.2 Fig.6 1 μm 5 μm 5 μm ( ) 1 μm 1 μm 1 μm Removal rate [mm 3 /h] 8 6 4 2 3.5 3. 2.5 1.5.5.5.52.54.56.58.6 Radius [mm] Measured area Fig. 3 Profile of electroplated diamond tool. Removal rate Number of discharge 2 4 6 8 1 12 Discharge duration [μs] 2 15 1 5 Fig. 4 Relationship between removal rate and number of discharge (ie = 1 A). Removal rate [mm 3 /h] 12 1 8 6 4 2 1 2 3 4 5 6 Discharge current [A] Fig. 5 Relationship between removal rate and discharge current (te = 1 μs). Fig. 7 Number of discharge [/Jump]
5 voltage [V] 15 1 5 Before truing After truing 8μm After truing 3μm Current [A] voltage [V] Current [A] 3. 5 1 15 2 Time [ms] (a) step feed = 1 μm 15 1 5 3. 5 1 15 2 Time [ms] (b) step feed = 5 μm Fig. 6 Wave form of gap voltage and discharge current. 1.8 1.6 1.4 1.2.8.6.4.2.5.52.54.56.58.6 Radius [mm] Fig. 8 Profile of the electroplated diamond tool. A 3 Number of discharge [/s] 25 2 15 1 5 -.5.5 1.5 2.5 3. 3.5 4. Time [min.] Fig. 7 Change in number of discharge. 2 3 Fig. 8 3 μm( 3 ) ( ) 8 μm( 8 ) Fig. 9 A Fig. 9 Surface of electrode after ED-truing. SEM (Fig. 9 A A ) (Fig. 1)
51 Radius of diamond tool [mm].45.5.55.6.65 1.8 1.6 3.5 3.Non truing area Before truing After truing 3μm After truing 6μm 1.4 1.2 Diamond tool.8.6 2.5 1.5 Truing area.4.2 Electrode -.1-5 5.1 Profile of electrode [mm] Fig. 1 Comparison of electroplated diamond tool and electrode after ED-truing..5.48.5.52.54.56.58.6 Radius [mm] Fig. 11 Profile of electroplated diamond tool before and after ED-truing. Fig. 11 15 Fig.12 SEM 3.3 Fig.13, ( ) ( = 15, min 1 ) ( ) Z ( = 1 m/s) Y (a) Before ED-truing (b) After ED-truing Fig. 12 SEM images of diamond tool. ( ( ) ) 6.6 μmrz Fig. 14 SEM 2.4 μmrz.81 μmrz
52 㼆㻌 Air turbine spindle 㼅㻌 Finished surf ssurface r ace ace Diamond tool surf r ace e EDMed surface Fig. 13 Appearance of the spindle for grinding and schematic diagram of tool paths for grinding of EDMed surface. Pre-machining 1st finishing 㸦EDMed surface㸧 Final finishing 䠄by not trued tool) 䠄by trued diamond tool) SEM 6.6μmRz 5μm 2.4μmRz 5μm.81μmRz 5μm Surface roughness.2mm.2mm.2mm Fig. 14 Improved surface by grinding with ED-trued diamond tool. ングを行った電着ダイヤモンド砥石は 硬脆材料であ るため 台金さえあれば複雑な形状の砥石でも比較的 る超硬合金の研削加工が可能であること また 放電 容易に作製できる このため 円筒形状の砥石だけで ツルーイングで砥粒の突き出し高さを均一化すること なく 円錐形状や球形状の砥石なども一般に用いられ で ツルーイングを行っていない砥石に比べて加工面 ている そこで 三次元形状加工にも適用可能な球形 の表面粗さを向上できることを確認した 状電着ダイヤモンド砥石に対して放電ツルーイングを 3.4 球形状砥石への放電ツルーイングの適用例 試みた ここでは ф25 μm の走行ワイヤ ( 黄銅 ) を 電着砥石は めっき製法で砥粒を固定したものであ 電極とし Z X 軸の円弧補間を用いて加工を行った Before ED-truing After ED-truing SEM Fig. 15 ED-truing for spherical electroplated diamond tool.
53 Fig. 15 ф1 mm SEM Fig. 16 ( = 5.9 μm) 4. (1) (2) (3) (4).5.4.3.2.1 Before truing After truing:3μm Target curve.1.2.3.4.5.6.7 Radius [mm] (5) Measured area Fig. 16 Profile of spherical electroplated diamond tool before and after ED-truing. 1), 61 (1995) 819. 2) 25 (25) 41. 3), 32 (1998) 1. 4) 22 (22) 61. 5), 39 (25) 24. 6), 44 (21) 17.