On-line measurement of clamping force for injection molding machine using ultrasonic technology

The on-line measurement of clamping force is essential for injection molding equipment and process. A method for on-line measurement of clamping force using ultrasonic technology is proposed in this study. Based on the sono-elasticity theory, a new mathematical model is established to describe the relationship between ultrasonic propagation time and clamping force. A series of experiments are then performed to validate the proposed method. Findings show this method corresponds well with the magnetic enclosed type clamping force tester method, with difference squares less than 0.65 (MPa)(2), and standard deviations less than 0.11 MPa. Ultrasonic parameters influence measurement results, with larger ultrasonic probe wafer diameter and higher ultrasonic probe frequency producing better measurement accuracy. Additionally, measurement accuracy is insensitive to the sampling frequency of ultrasonic signals. The proposed method has the advantages of high accuracy and high stability, being non-interfering, non-destructive, low-cost, on-line and with good adherence to health and safety, and it has significant application prospects in injection molding production.