The Woodruff School

SUMMARY

Recent innovations in micro manufacturing processes are enabling the fabrication of micro and meso scale structures and devices utilizing a wide range of engineering materials. One technique that has been researched extensively in recent years is mechanical micro milling, which has distinct advantages over photolithography-based micromachining methods. However, certain factors limit the types of workpiece materials that can be processed using mechanical micromachining methods. For difficult-to-machine materials, such as tool and die steels and ceramics, limitations in cutting tool stiffness and strength which affect the accuracy of the machined features are major impediments for mechanical micromachining methods. Due to these limitations, there is a need to develop hybrid micro manufacturing processes capable of generating three dimensional micro scale features in hard-to-machine materials. This proposal aims to develop a novel laser assisted micro milling (LAMM) process that addresses the limitations of micro milling of hard-to-machine materials. The basic concept involves creating highly localized thermal softening of the hard material by focusing a solid-state continuous wave laser beam in front of a miniature cutting tool (end mills of diameters, 0.1 to 0.5 mm). By suitably controlling the laser power, spot size and speed, it is possible to produce a sufficiently large reduction in the flow strength of the work material and consequently the cutting forces and tool deflections. The specific objectives of the proposed research are to: (1) develop a process to machine three dimensional micro features in hard materials, (2) experimentally characterize the LAMM process (cutting forces, tool wear, burr height, surface roughness), (3) improve tool life of micro tools used in the LAMM process by the usage of wear resistant coatings, (4) develop a process for fabricating micro-features in ceramics. The proposal details specific tasks to achieve these objectives. It is expected that the proposed research will result in a laser assisted micro machine tool and process capable of creating micro and meso scale features in hard molds and dies for plastic injection molding of meso-scale biomedical parts. In addition, the characterization of the process will serve as a basis for users of the process to select optimal process parameters.

SUBJECT:	Ph.D. Proposal Presentation

BY:	Mukund Kumar

TIME:	Monday, November 15, 2010, 3:00 p.m.

PLACE:	MARC Building, 114

TITLE:	Laser Assisted Micro Milling of Hard Materials

COMMITTEE:	Dr. Shreyes N. Melkote, Chair (ME) Dr. Steven Y. Liang (ME) Dr. Rhett J. Mayor (ME) Dr. Steven W. Johnson (MSE) Dr. Roshan J. Vengazhiyil (ISyE)

SUMMARY Recent innovations in micro manufacturing processes are enabling the fabrication of micro and meso scale structures and devices utilizing a wide range of engineering materials. One technique that has been researched extensively in recent years is mechanical micro milling, which has distinct advantages over photolithography-based micromachining methods. However, certain factors limit the types of workpiece materials that can be processed using mechanical micromachining methods. For difficult-to-machine materials, such as tool and die steels and ceramics, limitations in cutting tool stiffness and strength which affect the accuracy of the machined features are major impediments for mechanical micromachining methods. Due to these limitations, there is a need to develop hybrid micro manufacturing processes capable of generating three dimensional micro scale features in hard-to-machine materials. This proposal aims to develop a novel laser assisted micro milling (LAMM) process that addresses the limitations of micro milling of hard-to-machine materials. The basic concept involves creating highly localized thermal softening of the hard material by focusing a solid-state continuous wave laser beam in front of a miniature cutting tool (end mills of diameters, 0.1 to 0.5 mm). By suitably controlling the laser power, spot size and speed, it is possible to produce a sufficiently large reduction in the flow strength of the work material and consequently the cutting forces and tool deflections. The specific objectives of the proposed research are to: (1) develop a process to machine three dimensional micro features in hard materials, (2) experimentally characterize the LAMM process (cutting forces, tool wear, burr height, surface roughness), (3) improve tool life of micro tools used in the LAMM process by the usage of wear resistant coatings, (4) develop a process for fabricating micro-features in ceramics. The proposal details specific tasks to achieve these objectives. It is expected that the proposed research will result in a laser assisted micro machine tool and process capable of creating micro and meso scale features in hard molds and dies for plastic injection molding of meso-scale biomedical parts. In addition, the characterization of the process will serve as a basis for users of the process to select optimal process parameters.