https://escholarship.org/content/qt8rf718jm/qt8rf718jm.pdf?t=krnesf

Recent Advances in Mechanical Micromachining

Rayleigh–Taylor and Richtmyer-Meshkov instability induced flow, turbulence, and mixing. II

This paper provides a comprehensive review of the literature, mostly of the last 10-15 years, that is enhancing our understanding of the mechanics of the rapidly growing field of micromachining. The paper focuses on the mechanics of the process, discussing both experimental and modeling studies, and includes some work that, while not directly focused on micromachining, provides important insights to the field. Experimental work includes the size effect and minimum chip thickness effect, elastic-plastic deformation, and microstructure effects in micromachining. Modeling studies include molecular dynamics methods, finite element methods, mechanistic modeling work, and the emerging field of multiscale modeling. Some comments on future needs and directions are also offered.

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The Mechanics of Machining at the Microscale: Assessment of the Current State of the Science

On The Measurement of Temperature in Material Removal Processes

This paper examines the surface generation process in the micro-endmilling of both single-phase and multiphase workpiece materials. We used 508 μm dia endmills with edge radii of 2 and 5 μm to machine slots in ferrite, pearlite, and two ductile iron materials at feed rates ranging from 0.25 to 3.0 mm/flute. A surface generation model to predict the surface roughness for the slot floor centerline is then developed based on the minimum chip thickness concept. The minimum chip thickness values were found through finite element simulations for the ferrite and pearlite materials. The model is shown to accurately predict the surface roughness for single-phase materials, viz., ferrite and pearlite. Two phenomena were found to combine to generate an optimal feed rate for the surface generation of single-phase materials: (i) the geometric effect of the tool and process geometry and (ii) the minimum chip thickness effect. The surface roughness measurements for the ductile iron workpieces indicate that the micromilling surface generation process for multiphase workpiece materials is also affected by the interrupted chip-formation process as the cutting edge moves between phases resulting in burrs at the phase boundaries and the associated increases in surface roughness.

On the Modeling and Analysis of Machining Performance in Micro-Endmilling, Part I: Surface Generation

Experimental analysis of chip formation in micro-milling

A model is developed to predict the effects of thermal distortion of the drill and workpiece on the diameter and cylindricity of dry drilled holes. Experiments using embedded thermocouples verify that the model predicts the flow of heat into the workpiece and into the drill reasonably well. The model predicts that thermal expansion of the drill is the dominant effect and leads to oversized holes with diameters that increase with depth.

The effects of thermal distortions on the diameter and cylindricity of dry drilled holes

This study analyzes the temperature profile along the cutting edges of a drill and describes how the temperature on the chisel edge can exceed the temperature on the primary cutting edges. A finite element model predicts the temperature distribution in the drill, where the heat flux loads applied to the finite element model are determined from analytical equations. The model for the heat flux loads considers both the heat generated on the shear plane and the heat generated on the rake face of the tool to determine the amount of heat flowing into the tool on each segment of the cutting edges. Contrary to the conventional belief that the maximum temperature occurs near the outer corner of the drill, the model predicts that the maximum temperature occurs on the chisel edge, which is consistent with experimental measurements of the temperature profile.

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The Location of the Maximum Temperature on the Cutting Edges of a Drill

A model is developed for predicting the heat that flows into the workpiece during dry drilling processes. The model can be applied to any drill of known geometry. The measured drilling thrust and torque are used as inputs in an oblique cutting analysis, and an advection heat partition model is developed to calculate heat flux loads on a finite element model of the workpiece. Experiments using embedded thermocouples have verified that the model accurately predicts the temperature field in the workpiece for a range of drilling speeds and feeds.

A Model for Predicting the Heat Flow into the Workpiece in Dry Drilling

A drill-foil thermocouple system is developed for measuring the temperature distribution along the cutting edges of a drill. The system is simple to implement, and it does not suffer the problems experienced by previously developed methods. Experiments show that the method is accurate, produces repeatable measurements, and is sensitive to the drilling conditions, including the speed, feed, and drill geometry.

Matthew Bono

Papers

Experimental analysis of chip formation in micro-milling

The effects of thermal distortions on the diameter and cylindricity of dry drilled holes

The Location of the Maximum Temperature on the Cutting Edges of a Drill

A Model for Predicting the Heat Flow into the Workpiece in Dry Drilling

A Method for Measuring the Temperature Distribution Along the Cutting Edges of a Drill