Investigation of the Discharging Energy and Current Waves In Fine-Wire WEDM

• Main Authors: Hsiang-Kuo Lee, 李祥國
• Other Authors: John Chou
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/92877214479788982708

碩士 === 國立臺北科技大學 === 電機工程系碩士班 === 92 === A machining groove is less than 0.1 mm for compact products like the gears of watch and high pins of lead frame of IC. The general diameters of machining wires are 0.20 mm and 0.25 mm in WEDM. Thinner wires of WEDM are necessary for these applications. The object of this study was to investigate the proper machining conditions which were faster machining speed, lower wire electrode wear, few wire break for the cutting wires with 0.1 mm and 0.05 mm diameter. A good condition can be chosen by electrode wear and cutting speed. Electrode wear could be achieved by the cutting experiment with non-traveling wire and material remove rate could be achieved by cutting experiment. This study investigated many cutting factors including wire diameter, current slope, discharge time, discharge state, discharge electrode, ignitable current, and wire tension. Experiment results are as follows. (1) The ratio of the minimal residual area to the wire tension was approach to a constant, which can be used for estimating the number of discharge for wires with of various diameters and wire tension. (2) The optimum values of current slope were from 250 A/μS to 400 A/μS. (3) The electrode wear of fine wire was low when using small ‘on time’ and higher current slope. (4) The discharge machining of negative electrode had higher cutting speed and lowest electrode wear. Positive electrode had the opposed characteristics. AC discharge had half electrode wear and half cutting speed. (5) The discharge mode of equal energy was better in AC discharge. It could be operated into two sections for reducing electrode wear. The ignition used AC discharge power and discharge used negative electrode power. The conclusions of fine-wire machining operation were summarized as follows. (1) The area of wire that could be worn by discharging machining decreased heavily when the thinner wires were used. Low discharge energy was necessary for low electrode wear, so low cutting speed occurred. (2) One of the methods for reducing the electrode wear was to limit the positive ignitable energy in AC discharge. Increasing ignitable circuit resister and reducing the ignitable current could work on fine wire. The thick wire above 0.1 mm could neglect its effect. (3) The cutting speed was 19 mm2/min when using 0.1 mm wire diameter and 10 mm2/min when using 0.05 mm wire diameter during AC discharge. The results had fairly good level when compared the WEDMs of FANUC and AGIE.