Investigation of the Mechanical Properties of Parts Fabricated with Ultrasonic Micro Injection Molding Process Using Polypropylene Recycled Material

Modeling the Ultrasonic Micro-Injection Molding Process Using the Buckingham Pi Theorem

Dimensional analysis through the Buckingham Pi theorem was confirmed as an efficient mathematical tool to model the otherwise non-linear high order ultrasonic micro-injection molding process (UMIM). Several combinations of processing conditions were evaluated to obtain experimental measurements and validate the derived equations. UMIM processing parameters, output variable energy consumption, and final specimen's Young modulus were arranged in dimensionless groups and formulated as functional relationships, which lead to dimensionless equations that predict output variables as a function of the user-specified processing parameters and known material properties.

Polypropylene-Based Polymer Locking Ligation System Manufacturing by the Ultrasonic Micromolding Process

In recent years, there has been a growing demand for biocompatible medical devices on the microscale. However, the manufacturing of certain microfeatures has posed a significant challenge. To address this limitation, a new process called ultrasonic injection molding or ultrasonic molding (USM) has emerged as a potential solution. In this study, we focused on the production of a specific microdevice known as Hem-O-Lok, which is designed for ligation and tissue repair during laparoscopic surgery. Utilizing USM technology, we successfully manufactured the microdevice using a nonabsorbable biopolymer that offers the necessary flexibility for easy handling and use. To ensure high-quality microdevices, we extensively investigated various processing parameters such as vibration amplitude, temperature, and injection velocity. Through careful experimentation, we determined that the microdevice achieved optimal quality when manufactured under conditions of maximum vibrational amplitude and temperatures of 50 and 60 °C. This conclusion was supported by measurements of critical microfeatures. Additionally, our materials characterization efforts revealed the presence of a carbonyl (C=O) group resulting from the thermo-oxidation of air in the plasticizing chamber. This finding contributes to the enhanced thermal stability of the microdevices within a temperature range of 429-437 °C.

Feasibility Study of the Flatness of a Plastic Injection Molded Pallet by a Newly Proposed Sequential Valve Gate System

The investigation of plastic pallet molding, assisted by a sequential valve gate system, has not yet been performed due to the limitations of the pallet scale. Furthermore, at present, the application of recycled plastics by chemical industries has become extremely popular around the world. This study aimed to determine pallet flatness experimentally and numerically using recycled polypropylene with a large-scale pallet. Short-shot testing on injection molding was performed to obtain short-shot samples for confirmation of the flow front during simulated filling. The real injected pallet profile, which was measured by an ATOS, was compared after confirmation to the numerical profile of the pallet. The pallet’s flatness was accurately compared to the real experimental and numerical results. By adjusting the temperature of the cooling channel within the cavity plate to 55 °C, the flatness of the pallet achieved by the newly proposed sequential valve gate-opening scheme was about 7 mm, which meets the height directional warpage standard determined by the pre-set sequential scheme. The numerical flatness is in line with existing flatness values for pallets. Furthermore, the proposed cooling temperature gives the highest yield in terms of pallet molding from the perspective of the stakeholders.