GE Bolt Mike III Operating Guide

Injection molding presses rely on tiebars to apply clamping forces to molds during plastic injection and cooling cycles. 
Balancing the loads applied to individual tiebars ensures uniform clamping pressure of the mold improving overall process 
quality. Irrespective of process quality another very important reason to measure tiebar-clamping forces is to ensure that 
individual tiebars are not overloaded leading to eventual failure of the Injection molding press itself.

While numerous methods have been employed in an attempt to address this issue, the Ultrasonic Extensometer provides a 
simple, fast, and repeatable alternative.

Ultrasonic Extensometers are designed to provide precise length measurement of acoustically conductive materials. The 
instrument applies an electrical pulse to an ultrasonic transducer creating an acoustic wave.  Piezo electric material within 
the transducer converts the electrical pulse to mechanical energy and vise versa.

The mechanical energy produced by the transducer is that of a sound wave with a specific center frequency typically in the 
range of 1.0 to 25.0 MHz. The sound wave generated by the transducer travels through the material being tested to the op-
posite surface or back wall of the tiebar. The sound wave is then reflected off of the back wall and returns to the transducer 
where it is again converted to electrical energy. The ultrasonic instrument measures the time it takes the sound energy to 
travel from the transducer through the tiebar and return to the transducer – referred to as time of flight. The instrument then 
calculates the length of the tiebar based on this time of flight and the velocity of sound for the tiebar material.