Tool life comparison between servo and pneumatic ultrasonic welders for cutting polylactic acid film

Abstract

<p>Polylactic acid (PLA) is a biobased plastic that is the polymerization product of lactic acid which is produced by fermentation of starches derived from renewable feedstocks. PLA is used for many commercial applications such as medical implants, food packaging, and disposable tableware. In many applications, such as packaging, the PLA film needs to be cut to produce the final product.</p> <p>The purpose of this research is to determine the effect of tool wear during ultrasonic cutting of PLA films. In more, this study compares tool wear between pneumatic and servo ultrasonic cutting systems. The study also investigated the effect of different amplitudes (using boosters with gains of; 1:1, 1:1.5, and 1:2) on tool life for servo and pneumatic systems.</p> <p>There were significant differences in performance between the servo and pneumatic systems for the different amplitudes. The pneumatic system had consistently higher wear compared to the servo system for all the different amplitudes. It was believed that this was the result of cutting tool and horn contact was reduced for the servo driven system. In contrast, the pneumatic driven system, required cutting tool and horn contact to terminate the cutting cycle, that resulted in tool wear. In addition, it was found that high amplitudes, generally reduced tool wear. While this observation may initially be counter intuitive, it is believed that this was the result of faster cutting rates, that reduced the number of ultrasonic cycles (20 kHz) required to cut the films, reducing the tool wear.</p>