Mechanism study on microgroove forming by ultrasonic vibration assisted hot pressing

Microgrooves with a pitch at wave length level are increasingly needed in the optical system. Conventionally, the accuracy is low in microgroove forming due to the incomplete filling in the cavity of microgroove mold, as well as the surface flaws appearing with the adhesion of the resin material to the mold surface. In this research, the response behavior of resin material subjected to alternating stress is resolved based on Generalized Maxwell model. Finite Element Method (FEM) simulation is carried out to test the interface contact between the resin and the mold. Microgrooves forming effects under the pressing condition without and with ultrasonic vibration are studied. An ultrasonic vibration assisted pressing machine is developed and used to fabricate microgrooves on resin surface by using the Nickel Phosphorous (Ni-P) mold. The results show that the ultrasonic vibration can significantly decrease the resin dynamic viscosity as well as contact time with the mold, and achieve better forming accuracy and surface quality.