Hong-Tsu Young

Allowing for Nose Radius Effects in Predicting the Chip Flow Direction and Cutting Forces in Bar Turning

A model is presented for predicting the chip flow direction and cutting forces for bar turning with nose radius tools. A comparison which is made of predicted and experimental results shows excellent agreement.

Predicting cutting forces in face milling

Abstract It is shown how orthogonal machining theory can be applied to predict the cutting forces in face milling from a knowledge of the work material properties and cutting conditions. Predicted and experimental results are compared.

Cutting temperature responses to flank wear

Abstract This paper discusses one feature of a continuing research program with the ultimate objective of tracking continuously the deterioration of the machining process, which must be overcome in order to achieve unmanned machining stations. Recent work using the non-contact infrared (IR) thermographic technique to investigate the cutting temperatures during chip formation has shown a clear relationship between the measured chip-back temperatures and the tool-chip interface temperatures. This result and the very fast response of the technique provide the potential means for tracking the progress of tool wear. The measured temperature increases rapidly corresponding to a sudden breakdown of the sharp cutting edge; this is followed by a slight increase in the temperature with increasing uniform wear, and then by acceleration after a critical wear value has been reached. Other early results indicate a definite correlation between the measured temperature and tool flank wear, suggesting that control over the process is feasible if the chip-back temperatures are monitored during cutting.

Allowing for End Cutting Edge Effects in Predicting Forces in Bar Turning with Oblique Machining Conditions

Oblique machining tests are described which were made to determine how the cutting which occurs at the end (secondary) cutting edge in bar turning affects the direction of chip flow and the cutting forces. Normally in developing a predictive machining theory only the cutting action at the side (main) cutting edge is considered, with no account taken of the contribution of the end cutting edge. By introducing the concept of an equivalent cutting edge which in essence combines both the side and end cutting edges it is shown how the influence of the latter can be accounted for in predicting cutting forces.

An analytical model of chatter vibration in metal cutting

Abstract A new analytical model of chatter vibration in metal cutting is presented. The basic cutting mechanics adopted in the model is derived from a predictive machining theory based on a shear zone model of chip formation. A feature of this model is that variations of the undeformed chip thickness and rake angle due to the machine tool vibration are taken into account in determining the cutting forces and the forces are then coupled with the equations of motion to solve for the vibrational amplitudes with iterative techniques. Non-linearities in dynamic cutting processes caused by the effects of tool disengagement from the cut and cutting process damping are also included in the model. It is shown that the proposed model can be applied to make predictions for the suppression of chatter vibration by a change of tool geometries.

Innovative through-silicon-via formation approach for wafer-level packaging applications

Through-silicon via (TSV) is an emerging technology for three-dimensional integrated circuit, system-in-packaging and wafer-level packaging applications. Among several available TSV formation methods, Bosch deep reactive ion etching (DRIE) is widely used because it enables the fabrication of TSVs with almost any diameter, from the submicrometer level to hundreds of micrometers. However, the high cost of Bosch DRIE makes it uneconomical for industrial production. We present a novel wafer-level TSV formation approach that is effective and cost-efficient. The proposed method integrates a diode-pumped solid-state ultraviolet nanosecond pulsed laser and rapid wet chemical etching. The former is effective in drilling through 400 ?m thick silicon wafers and the latter is used for removing the unwanted heat-affected zone, recast layer and debris left after drilling. Experimental results demonstrate that the combined approach effectively eliminates the unwanted material formed by nanosecond laser pulses. Furthermore, this approach has a significant cost advantage over Bosch DRIE. In summary, the proposed approach affords superior TSV quality, higher TSV throughput and lower cost of process ownership than Bosch DRIE. These advantages could provide the necessary impetus for rapid commercialization of the several high-density fabrication methodologies that depend on TSVs.

A strain-hardening slipline field analysis of the plastic deformation observed in a model asperity interaction experiment

Abstract S caled-up model asperity experiments are described in which a hard wedge is indented into and then slid along the surface of a relatively soft material with the resulting plastic deformation measured using printed grids. A slipline field analysis of the deformation occurring once steady-state conditions have been achieved is described. This shows that tensile stresses can exist in a small region of the field when in calculating stresses account is taken in the stress equilibrium equations of variations in flow stress resulting from the strain-hardening properties of the deforming material.This result could be important in considering the viability of processes such as low cycle fatigue and fracture as possible wear mechanisms.

High-Speed Spindle Fault Diagnosis with the Empirical Mode Decomposition and Multiscale Entropy Method

The root mean square (RMS) value of a vibration signal is an important indicator used to represent the amplitude of vibrations in evaluating the quality of high-speed spindles. However, RMS is unable to detect a number of common fault characteristics that occur prior to bearing failure. Extending the operational life and quality of spindles requires reliable fault diagnosis techniques for the analysis of vibration signals from three axes. This study used empirical mode decomposition to decompose signals into intrinsic mode functions containing a zero-crossing rate and energy to represent the characteristics of rotating elements. The MSE curve was then used to identify a number of characteristic defects. The purpose of this research was to obtain vibration signals along three axes with the aim of extending the operational life of devices included in the product line of an actual spindle manufacturing company.

Investigation of edge effect from the chip-back temperature using IR thermographic techniques

Abstract An experimental investigation of the edge effect during chip formation from measurement by non-contact infrared (IR) thermographic techniques is presented. Results are analyzed for variation of the b t ratio (b is the undeformed chip width and t is the undeformed chip thickness) for the orthogonal turning of steel. The degree of edge effect is seen to be influenced greatly by the b t ratio and the distance from the cutting edge. As expected, the edge effect is less prominent with an increase of the b t ratio, for a b t ratio of 5.2 less than 5% of the edge effect being observed on the chip back within the tool chip contact area. From the viewpoint of cutting temperature, the result indicates that two-dimensional chip formation model is a good approximation.

Predicting the chip flow for nose radius tools under oblique machining conditions

Abstract A model is presented which predicts the chip flow direction for nose radius tools with inclination angles. Experimental verification was made in turning that cut on the bars. A comparison of the predicted and experimental results shows excellent agreement, and the results are consistent with previous findings of other workers. The usefulness of the present model is its capacity to predict the chip flow for a given general tool used with any combination of cutting conditions, without any prior knowledge of the work material properties or any machining tests required to determine an empirical formula.