On the material behaviour in a progressive microforming process

• Main Author: Phee, Jeremy Jun Kai.
• Other Authors: Tan Ming Jen
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering
• Online Access: http://hdl.handle.net/10356/54036
• Institution: Nanyang Technological University

In the 21st century, miniaturization has emerged in several fields of technology, leading to the development of mini products and devices for industries such as electronics, communication and optics. With increasing demand, many researches have been initiated worldwide in microforming processes. Microforming is the technology to manufacture very small metallic parts or structures with at least two dimensions in the sub-millimeter. Currently, microforming technology is a promising way towards industrial micro-parts manufacturing so as to reduce wastage and to increase production and efficiency. There are many factors that could affect the microforming process. At the sub-millimeter range, the deformation of the workpiece can be dominated by size effects. Decreasing the specimen size can cause drastic changes in the material mechanical properties and frictional behaviour. In this report, microforming was done on copper strips. Micropins of different diameters were fabricated using different punch diameters. This allows investigation of the material flow behaviour during the microforming process and the mechanical properties of the material. Analysis of microstructure was done to observe how the material flows during the microforming process of the micro-pin. In addition, microhardness tests are carried out to study different impact of the parameters. Furthermore, the effect of fillet radius in the entrance of the die cavity is investigated. Lastly, comparison of the micro-pin from progressive microforming process to common industrial pin made from micro-machining process is also done. When a larger punch displacement was used in the microforming process, the microstructure of the pins shows that the central grains will elongate and deform more severely. Dead zone can be found at certain area of the pin head which indicate that no work hardening was done at that area during the microforming process. At the pin head, equiaxial grains can be observed as well, corresponding to dead metal zone. For micropins with larger pin diameters, the grains at the micropins will not be as severely deformed as that of micropins with smaller pin diameters. It is because it is easier for the material to flow into the die cavity during the microforming process. Entrance radius of die cavity affects the deformation of grains as it is easier for material to flow into die cavity, causing less elongation of grains. Micro-pins made from progressive microforming process has more work hardening on grains whereas pins made from micromachining process has few yet larger grains.