Ultrasonic Molding Technology: Recent Advances and Potential Applications in the Medical Industry

Abstract

Recently, ultrasonic molding (USM) has emerged as a promising replication technique for low and medium volume production of miniature and micro-scale parts. In a relatively short time cycle, ultrasonic molding can process a wide variety of polymeric materials without any noticeable thermal degradation into cost-effective molded parts. This research work reviews recent breakthroughs of the ultrasonic injection molding and ultrasonic compression molding process regarding the equipment and tooling development, materials processing and potential applications in the medical industry. The discussion is centered on the challenges of industrializing this technology, pointing out the need for improvement of the current process’s robustness and repeatability. Among the most important research areas that were identified are the processing of novel engineered and nanomaterials, the understanding and control of the ultrasonic plasticization process and the tooling and equipment development.

Manufacturing PLA/PCL Blends by Ultrasonic Molding Technology

“…Regarding the variable process parameters, mainly the amplitude and the ultrasonic time during the plasticizing stage (which takes place between preheating and melting) are included. These are the most influential parameters revealed in the literature to process most materials [ 29 , 33 ] and obtain complete parts, including by studies that processed PLA [ 35 , 40 ], another discussed in the introduction that processed other materials and by the company that developed the machine. In this work, the mold was kept at room temperature.…”

“…Although several machine configurations [ 33 ] exist, the machine used in this work (Sonorus 1G) ( Figure 1 a) uses a sonotrode to melt the material and a plunger to push it into the mold cavity to apply the specific force required for packing it into the mold ( Figure 1 b). As explained in detail in the literature [ 29 , 33 ], the process consists of six main stages: feeding, compaction, preheating, melting, injection/packing and cooling.…”

“…In terms of manufacturing, injection molding has been the predominant manufacturing process for processing PLA and PCL blends; however, focusing on medical applications, they often require small production batches with miniature/microscale components at an affordable cost. In that sense, ultrasonic molding (USM) technology has significant advantages, allowing the fabrication of polymeric microcomponents with: (a) good replication, repeatability and high precision of microcharacteristics [ 27 , 28 ]; (b) a low ratio of material waste and energy saving, as only the material required per a single shot is melted, leading to the efficient use of raw materials and energy, with a positive impact on cost and environmental impact [ 29 , 30 ]; (c) short temperature exposure time of polymers, lasting only a few seconds [ 31 , 32 ]; and, finally, (d) small batches of production at an affordable cost, especially when high-performance applications are required [ 29 , 33 ].…”

“…USM can process an extended range of polymers, and the literature reveals a great potential for manufacturing expensive and sensitive polymers used in biomedical applications, such as drug delivery or tailored implants [ 29 ], where polymeric blends and composites are important objectives to fulfill with essential medical requirements such as biodegradability or bioactivity. However, there is a gap in PCL processing, its combination with PLA and the simulation of the volumetric degradability under similar conditions to the human body.…”

Study on the Mechanism of Interfacial Friction Heating in Polymer Ultrasonic Plasticization Injection Molding Process

“…UPIM has developed for its unique potential in materials and energy efficiency [9,10] and is gradually becoming an effective processing technology for the preparation of polymer micro-mold samples in recent years [11]. Compared to micro injection molding, UPIM does not exhibit significant thermal degradation when molding polymers and has good energy-saving effects [12].…”