Non-intrusive ultrasonic measurement of tie-bar stress for molding equipment

Abstract

For molding equipment, the accurate measurement of tie-bar stress helps improve product quality and prolong the lifespan of the machine. In our previous work, the mathematical model between the ultrasonic time difference (UTD) and the tie-bar stress was established, and this model was shown to have high accuracy with the maximum of difference square being only 1.5678 (MPa)2. Nevertheless, when calculating the ultrasonic time difference using the cross-correlation function (CCF) method, it is necessary to manually divide the position of the echoes. This makes it impossible to automate the stress measurement and it is incompetent when dealing with massive data. In this paper, a non-intrusive (N-I) ultrasonic measurement method for tie-bar stress based on the minimum entropy blind deconvolution is firstly proposed. The results of simulation and verification experiments show that the proposed method has high precision, and the maximum relative error is only 2.4392%. Hence this method has been successfully applied in the tie-bar stress measurement in molding equipment. Compared with the CCF method, the accuracy is improved and the maximum relative error is reduced from 3.67% to 1.68% when the clamping force is small. In summary, the proposed method is comparable to the CCF method in accuracy, and has a higher resolution during echos disturbance. Moreover, this approach does not require human intervention and is helpful to realize the automation of the tie-bar stress measurement for the molding equipment.

Effects of Cavity Thickness and Mold Surface Roughness on the Polymer Flow during Micro Injection Molding

“…Injection molding [ 1 , 2 ] is a critical molding method of thermoplastics and their composites [ 3 ] and it has been widely used. Micro injection molding (μIM) [ 4 , 5 , 6 ] is an injection molding process that has been used in manufacturing precision microscale plastic parts, such as automotive, micro biomedical and optical elements [ 7 , 8 , 9 ].…”

Effects of Cavity Thickness on the Replication of Micro Injection Molded Parts with Microstructure Array

“…There are several methods for manufacturing polymer parts with microstructure arrays [7][8][9][10]. Micro injection molding (µIM) is the preferred manufacturing method because of its capability for mass-production and its low production cost [11][12][13]. However, the uneven pressure and temperature distribution during µIM usually introduces non-uniform microstructures in the molded parts, especially for the microstructures with different distances from the gate [14,15].…”