Experimental Study on the Bending of a Polyamide Tube Using High-Power Ultrasound

Abstract

Ultrasonic tube forming is an innovative and promising technology that could replace the conventional thermoforming process for plastic automotive tubes. This process allows for the forming of extruded tubes four times faster, with a substantial increase in energy efficiency. This research focuses on the experimental study of this innovative process and its comparison to the conventional thermoforming in a hot air table. A prototype has been designed and assembled to study the main process variables that are significant to the forming result. A complete design of experiments (DOE) has been applied to quantify the effect of each process parameter, thereby obtaining a mathematical model that allows for the prediction of the curvature angle for a specific parameter combination. It has been concluded that the application of ultrasonic cycles, with short cooling cycles in between, is the best option, in comparison to a continuous application. The amplitude of vibration, ultrasonic time for the cycle, and number of cycles have proven to be the most significant variables of the process. Furthermore, the cooling time between cycles and the position of the squares for the initial bending angle are also important parameters that can be set up to refine the result. Quality control tests related to material degradation and geometry have been passed successfully, showing a high stability of the results. Consequently, this new process has a promising place in the future of plastic tube forming.