Sangkee Min

Optimization and control of drilling burr formation of AISI 304L and AISI 4118 based on drilling burr control charts

Control charts for drilling burr formation for stainless, AISI 304L, and low alloy steel, AISI 4118, were developed. Split point twist drills are used for the experiments of this work. A Drilling Burr Control Chart, based on experimental data, is a tool for prediction and control of drilling burrs. Burr classification was carried out based on the geometric characteristics, burr formation mechanisms and sizes of the burrs. New parameters consisting of cutting condition variables and drill diameter were developed, and used to show unique distributions of the burr types. Burr types and the resultant burr size showed great dependence on the new parameters regardless of the drill diameters. Through the chart, burr type can be predicted with given cutting conditions. Also cutting conditions that are believed to create preferred burr types can be selected.

FINITE ELEMENT MODELING OF BURR FORMATION IN METAL CUTTING

In order to advance understanding of the burr formation process, a series of finite element models are introduced. First, a finite element model of the burr formation of two-dimensional orthogonal cutting is introduced and validated with experimental observations. A detailed and thorough examination of the drilling burr forming process is undertaken. This information is then used in the construction of an analytical model and, leads to development of a three-dimensional finite element model of drilling burr formation. Using the model as a template, related burr formation problems that have not been physically examined can be simulated and the results used to control process planning resulting in the reduction of burr formation. We highlight this process by discussing current areas of research at the University of California in collaboration with the Consortium on Deburring and Edge Finishing (CODEF).

Development of a drilling burr control chart for low alloy steel, AISI 4118

Abstract A control chart for drilling burr formation for low alloy steel, AISI 4118, was developed. A drilling burr control chart, based on experimental data, is a tool for the prediction and control of drilling burrs. High-speed steel split-point twist drills with different diameters were used for the tests. Burr classification was carried out based on the geometric characteristics, burr formation mechanisms, and sizes of the burrs. Four different burr types such as uniform burr (Types I and II), transient burr, and crown burr were found. New parameters consisting of process parameters and drill diameter were developed, and used to show a unique distribution of the burr types. Burr types and the resultant burr size showed great dependence on the new parameters regardless of the drill diameter. Through the chart, burr type can be predicted as a function of given cutting conditions. Also, cutting conditions that are believed to create preferred burr types can be selected.

A Study on Tribology in Minimal Quantity Lubrication Cutting

Despite the fact that minimal quantity lubrication (MQL) machining produces almost similar cutting performance to conventional flood supply machining while using much less metal working fluid (MWF), it has not been fully utilized in industry due to lack of understanding of the fundamental process physics. To take full advantage of MQL machining and expand its applicability, an understanding of its tribological behavior is critical. Hence, in this study, the adsorption characteristics of MQL media during orthogonal cutting was investigated using two experimental setups; one in a high vacuum chamber with a mass spectrometer to observe mass changes of MQL media during cutting, and another setup in an atmospheric chamber where the supply of MQL media can be controlled. The former is mainly for analysis of the tribological behavior of MQL media, and the latter for cutting performance monitoring. It was found that the adsorption amount of MQL media was closely related to lubrication behavior. Oxygen in MQL supply plays a significant role in lubrication. Ultrasonic vibration cutting tests with MQL were conducted for further understanding of lubrication mechanism.

Variation in Machinability of Single Crystal Materials in Micromachining

For practical application of micromechanical machining, four levels of process realization are required; fundamental understanding of process physics, development of microplanning (processing parameter optimization), macroplanning (tool path planning), and design optimization. This study surveyed the influence of localized variation in the microstructure on final process outcome and machinability of brittle optical material in a ductile regime. A clear correlation between burr height, critical depth of cut and crystallographic orientation was found on single crystal materials (copper and magnesium fluoride), giving insight into optimal orientations and process parameters for acceptable micromachining process outcome.

Surface and Edge Quality Variation in Precision Machining of Single Crystal and Polycrystalline Materials

Abstract The surface and edge quality of single-crystal and polycrystalline copper workpieces has been observed to vary significantly as a function of crystallographic orientation. On the precision scale, the chip formation process is influenced by the microstructure of the material, such as grain boundaries and grain orientation in polycrystalline materials, and crystallographic orientation in single-crystal materials. Such variation in the microstructure has a significant effect on the resulting surface, edge, and burr topography.

Investigation of adsorption behaviour of lubricants in near-dry machining:

Abstract Near-dry machining (NDM) is a technology with many ecological and economic benefits that uses very small amounts of metal working fluid (MWF). In order to increase the applications of this technology, the tribological mechanism during this process needs to be better understood. To accomplish this, two experimental set-ups were configured. The first involved a vacuum chamber where changes of gas near the cutting area can be traced by a mass spectrometer. The second has an atmospheric chamber where practical cutting can be done for cutting-performance comparison. Three gases - argon, nitrogen, and oxygen - were used with and without an ester in a series of orthogonal cutting tests to understand their roles in lubrication. It was found that oxygen adsorbs best onto a newly generated work surface and plays a significant role in promoting adsorption of the ester and, in turn, creating a lubrication film. Therefore, it is important to supply an abundant amount of oxygen in NDM to provide good lubrication conditions.

Thrust Force Analysis of Drilling Burr Formation Using Finite Element Method

This study is focused on thrust force analysis of the drilling burr formation. A finite element model (FEM) for drilling burr formation was proposed with a stainless steel (AISI 304L) workpiece and a conventional twist drill. The thrust force variation during drilling process from FEM was obtained and compared with the experimental results. The estimation of burr size was briefly discussed.

CAD/CAM for scalable nanomanufacturing: A network-based system for hybrid 3D printing

Micro- and nano-structuring have been highlighted over several decades in both science and engineering fields. In addition to continuous efforts in fabrication techniques, investigations in scalable nanomanufacturing have been pursued to achieve reduced feature size, fewer constraints in terms of materials and dimensional complexity, as well as improved process throughput. In this study, based on recent micro-/nanoscale fabrication processes, characteristics and key requirements for computer-aided design and manufacturing (CAD/CAM) systems for scalable nanomanufacturing were investigated. Requirements include a process knowledge database, standardized processing, active communication, adaptive interpolation, a consistent coordinate system, and management of peripheral devices. For scalable nanomanufacturing, it is important to consider the flexibility and expandability of each process, because hybrid and bridging processes represent effective ways to expand process capabilities. As an example, we describe a novel CAD/CAM system for hybrid three-dimensional (3D) printing at the nanoscale. This novel hybrid process was developed by bridging aerodynamically focused nanoparticle printing, focused ion beam milling, micromachining, and spin-coating processes. The system developed can print a full 3D structure using various inorganic materials, with a minimum process scale of 50 nm. The most obvious difference versus CAD/CAM at ‘conventional’ scales is that our system was developed based on a network to promote communication between users and process operators. With the network-based system, it is also possible to narrow the gap among different processes/resources. We anticipate that this approach can contribute to the development of CAD/CAM for scalable nanomanufacturing and a wide range of hybrid processes.

Investigation of Tribological Mechanism of Near Dry Machining (NDM)

This paper describes tribological mechanism of Near Dry Machining (NDM). Two special setups to understand Tribological mechanism of near dry machining are designed. One is mainly to measure the behavior of some fed gases in controlled atmosphere. The other is to make sure the effectiveness of gasses like oxygen or nitrogen, and that of lubricants. As a result, oxygen has a very important roll in lubrication when steel is cut.Copyright