Ultrasonic Hot Embossing of polymers is one of the most attractive manufacturing methods of high-quality and complex microparts needed for biological and chemical processes. A little simulation work has been done to study the deformation mechanism and the required load in the Ultrasonic Hot Embossing of polymethyl methacrylate (PMMA). This paper developed a 2D coupled thermo-mechanical finite element model to simulate the forming behavior of the ultrasonic embossing process of PMMA, optimize the mold microfeature corner, and predict the embossing load as well. VDISP ABAQUS subroutine has been used to describe the downward motion of the mold assisted with ultrasonic vibration. The Arbitrary Eulerian-Lagrangian re-meshing technique has been implemented to refine the deformation zone during simulation to avoid divergence due to localized excessive deformation. Embossing load, temperature, stresses, strains, and energy dissipation have been recorded and analyzed. Simulation results revealed that the coupled thermo-mechanical FE Model efficiently captures the deformation behavior and Embossing load. It also proved that a Mold microfeature corner of 20 μm filet radius is recommended to adequately fill out the area around the mold and maintain uniform temperature and strain distributions.

Ultrasonic micro hot embossing (UMHE) is a prominent technique used in numerous sectors to produce micro parts since it is cheaper, faster, and more accurate. Amplitude uniformity is a crucial parameter in UMHE in order to manufacture micro parts with accurate dimensions and high-quality surfaces, even though limited research has been conducted on the uniformity of ultrasonic amplitude at the horn face during the embossing process. This paper presents an experimental and numerical study for designing an ultrasonic transducer and horn tailored to the micro hot embossing of polymer micro parts. A finite element (FE) simulation model combined with the Taguchi method has been developed to optimize the horn geometry and maximum amplitude uniformity. The Taguchi orthogonal array of 25 design runs has been generated and simulated using the developed FE modal analysis model, and then the optimized geometry was used to fabricate the horn. Applied torque and operating time calibrate and evaluate the transducer vibration characteristics. Experimental and simulation results revealed that the fabricated ultrasonic transducer and horn of a straight microfeature has a natural frequency of 28.8 kHz and has an 11 µm average peak-to-peak amplitude with 0.963 amplitude homogeneity along the microfeature face. The achieved frequency separation was greater than 0.85 kHz, whereas the gain ratio was 1.2. The design methodology developed in this paper showed great potential and has been numerically validated for various microfeature shapes across the horn face. Consequently, it can be applied to various ultrasonic applications beyond UMHE.