Real-time measuring system of contact resistance for milling operations

• Main Authors: Chien-Ju Hua, 華健儒
• Other Authors: Chuang-Wen Yao
• Format: Others
• Language: zh-TW
• Published: 2015
• Online Access: http://ndltd.ncl.edu.tw/handle/39170878572619959412

碩士 === 國立高雄應用科技大學 === 模具系碩士在職專班 === 103 === The research develops a set of instant measurement system of contact resistance value during milling process. The using method is to apply Agilent 34420A (Micro-Ohm Meter) and Labview software to measure contact resistance. During milling process, if the milling cutter doesn’t contact processed metals, the Micro-Ohm Meter would appear a high resistance status. If the milling cutter contacts processed metals, the Micro-Ohm Meter would measure contact resistance response of corresponding low resistance value. When low resistance value of metals is measured, utilize the GPIB interface of the Micro-Ohm Meter to connect USB of computers, and use computer programs to control the measurement sampling actions. The instant measurement system can respectively count and analyze the data it measures. Its automatic reports function is good for establishing database of various milling cutters and collecting milling cutter information in the future. In the past, the measurement of cutters abrasion was usually carried out in laboratories with manual devices, or judged by experienced milling machine masters on site based on their years of processing experience. The method costs a lot of time and can’t collect abundant data. Due to different workers, the reliance of cutter abrasion data is also doubted. Therefore, the research has developed a set of instant measurement system of contact resistance value. In addition to being applied to measuring contact resistance of milling cutters, the measurement system can indirectly measure impedance changes caused by milling cutters and processed items due to processing temperature rise. In all the conditions above, contact resistance can be directly measured during milling process. The previous experience method and time-consuming laboratory measurement method are abandoned. The new method can rapidly obtains authentic measurement value and save measurement time. The research utilizes ultrasonic wave detection to scan the contact area between milling cutters and processing metals. After the disposal by image analytical software, calculate the contact area between new milling cutters (no abrasion) and old milling cutters (serious abrasion). According to different contact loads and contact rate, the contact area of new milling cutters (no abrasion) is between 5 mm² and 38 mm².The contact area of old milling cutters (no abrasion) is between 5 mm² and 70 mm². According to the laboratory results, the contact area can be increased by 30 mm² after cutters are abraded. Based on the actual measurement experience value above, find out the relationship between contact area and contact resistance, the research result discovers the relevant changes of contact areas and resistance. The actual measurement result shows that when cutters are more abraded, the contact area is bigger, and the corresponding contact resistance is smaller. Therefore, it proves the inverse relationship of contact area and resistance. During the milling process, the higher the temperature rise, the bigger the resistance between contact area and resistance. Data shows that when temperature is increased by 1 degree, the contact resistance is increased by 1.5mΩ. Thus, it proves the direct proportion between temperature rise and resistance.