Effect factors and evaluation method of part accuracy formed by ultrasonic micro punching with a flexible punch

Abstract

In this paper, an automatic and quick evaluating method for micro-hole size and form accuracy with computer-aided technique was proposed. Using this method, the form accuracy of the micro-hole punched by a special ultrasonic microforming method, that is Micro Ultrasonic thin Sheetmetal Forming using molten plastic as flexible punch (short as Micro-USF), was discussed. Using this microforming method, micro-holes with diameters of 500,600 and 700 mm were punched from a thin sheet of purple copper with a thickness of 30 mm. The experimental results showed that the ratios of the maximum size error and the maximum roundness error of the micro-hole to the corresponding punching die diameter were 1.40% and 1.47%, respectively, and the ratios of the maximum size error range and the maximum form error range to the corresponding punching die diameter were 0.70% and 0.72%, respectively, indicating that this Micro-USF method has high accuracy and precision for punching micro-holes. Moreover, it was found that there is no significant direct correlation between micro-holes sample errors and these forming parameters when the forming parameters such as ultrasonic power, ultrasonic time and cylinder pressure were varied, which indicated that the sample errors were random in some extent.