A Slip-Line Field for Ploughing During Orthogonal Cutting

Under normal machining conditions, the cutting forces are primarily due to the bulk shearing of the workpiece material in a narrow zone called the shear zone. However, under finishing conditions, when the uncut chip thickness is of the order of the cutting edge radius, a ploughing component of the forces becomes significant as compared to the shear forces. Predicting forces under these conditions requires an estimate of ploughing. A slip-line field is developed to model the ploughing components of the cutting force. The field is based on other slip-line fields developed for a rigid wedge sliding on a half-space and for negative rake angle orthogonal cutting. It incorporates the observed phenomena of a small stable build-up of material adhered to the edge and a raised prow of material formed ahead of the edge. The model shows how ploughing forces are related to cutter edge radius—a larger edge causing larger ploughing forces. A series of experiments were run on 6061-T6 aluminum using tools with different edge radii—including some exaggerated in size—and different levels of uncut chip thickness. Resulting force measurements match well to predictions using the proposed slip-line field. The results show great promise for understanding and quantifying the effects of edge radius and worn tool on cutting forces

Droplet Spray Behavior of an Atomization-Based Cutting Fluid (ACF) System for Machining of Titanium Alloys

The aim of this research is to study droplet spray characteristics of an atomization-based cutting fluid (ACF) spray system including droplet entrainment angle and flow development regions with respect to three ACF spray parameters, viz., droplet and gas velocities, and spray distance. ACF spray experiments are performed by varying droplet and gas velocities. The flow development behavior is studied by modeling the droplets entrainment mechanism, and the density and distribution of the droplets across the jet flare. Machining experiments are also performed in order to understand the effect of the droplet spray behavior on the machining performances, viz., tool life/wear, and surface roughness during turning of a titanium alloy, Ti-6Al-4V. Experiments and the modeling of flow development behavior reveal that a higher droplet velocity and a smaller gas velocity result in smaller droplet entrainment angle leading to a gradual and early development of the co-flow with a smaller density and a better distribution of the droplet across the jet flare. Machining experiments also show that a higher droplet velocity, a lower gas velocity and a longer spray distance significantly improve the machining performances such as tool life and wear, and surface finish

On Cutting Temperature Measurement During Titanium Machining With an Atomization-Based Cutting Fluid Spray System

The poor thermal conductivity and low elongation-to-break ratio of titanium lead to the development of extreme temperatures (in excess of 550 C) localized in the tool-chip interface during machining of its alloys. At such temperature level, titanium becomes highly reactive with most tool materials resulting in accelerated tool wear. The atomization-based cutting fluid (ACF) spray system has recently been demonstrated to improve tool life in titanium machining due to good cutting fluid penetration causing the temperature to be reduced in the cutting zone. In this study, the cutting temperatures are measured both by inserting thermocouples at various locations of the tool-chip interface and the tool-work thermocouple technique. Cutting temperatures for dry machining and machining with flood cooling are also characterized for comparison with the ACF spray system temperature data. Findings reveal that the ACF spray system more effectively reduces cutting temperatures over flood cooling and dry conditions. The tool-chip friction coefficient indicates that the fluid film created by the ACF spray system also actively penetrates the tool-chip interface to enhance lubrication during titanium machining

Transiently Stable Emulsions for Metalworking Fluids

Modern high speed machining would not be possible without the use of metalworking fluids (MWFs). MWFs perform a number of useful functions like cooling and lubrication. They also assist with metal chip evacuation and short-term corrosion protection. It is estimated that 90 million U.S. gallons of water-soluble MWF concentrate are manufactured annually in the U.S. alone to meet the above needs. MWFs become process effluents when the accumulation of contaminants such as extraneous oil, particulate debris from machining operations, and bacteria negatively impact functionality. One to two billion U.S. gallons of oily wastewater result annually from the use of MWFs. Reducing this environmental footprint has become an important objective for both manufacturers and end-users of MWFs. Oil-containing MWFs are conventionally formulated to be highly stable emulsions. These emulsions are difficult to maintain, recycle, and treat (Byers, 1994). Preliminary work indicated that transiently stable emulsions can provide comparable lubrication, while also potentially being easier to maintain and recycle. They also offer fewer problems for waste treatment than their stable counterparts. This report focuses on a rational approach to designing such transiently stable emulsions by elucidating the important factors affecting lubrication, cooling, and phase separation.Illinois Sustainable Technology Center/Grant No. HWR05191published or submitted for publicationis peer reviewe

Database Development for Comparative Analysis of the Performance of Metalworking Fluids Based on Drilling Operations

Metalworking fluids (MWFs) play a significant role in machining operations. Despite their importance, the manufacturing industry lacks tools to make functionally sound and economical decisions about them. In this research project, a second generation drilling testbed was developed to evaluate the performance of MWFs with respect to lubricity and cooling capacity. A desktop drilling machine was used to make the testbed with a load cell sensor and a thermocouple located in the oil-hole of the drill. The testbed characterized MWFs based on torque, thrust, and temperature measurements. A standardized test procedure was developed to ensure that comparisons of fluids were accurate, repeatable, and representative of the actual differences in the fluids. System repeatability was found to be very good with a coefficient of variation well under 0.1. The system was found to determine differences within 1-2.9% for torque, 1.4-2.5% for thrust, and 2.7-8.2% for temperature based on five replicates per experimental condition and an ?? = 0.05 statistical analysis. Ten MWFs were chosen, representing a cross-section of soluble oils, semi-synthetics, and synthetic products from a variety of manufacturers. The performance of these fluids at a 10% concentration was analyzed based on a set of four separate comparative experiments designed to compare various drilling conditions and reveal how the MWFs performed based on changes of workpiece material, feedrate, and dilutent. The results were evaluated within each experiment by comparing how individual fluids performed within their type and how fluid types performed with respect to each other. Comparative analysis was also conducted among separate experiments to determine how changes in feedrate, workpiece material, and dilutent affect MWF performance. Conclusions based on the data analysis are presented. Additional MWF evaluation tests were used to further characterize the fluids. Tests for viscosity, surface tension, emulsion stability, and corrosion inhibition were conducted. These results were compared with the lubricity and cooling results to check for correlation. General trends indicated a correlation between fluid performance in lubrication and viscosity and surface tension results. Surface tension was found to be more a function of the emulsifiers and additives used in a fluid than the concentration of oil, while viscosity showed a definite correlation with oil content. It was also found that the synthetic fluids showed the most resistance to fluid breakdown due to hard water as measured by emulsion stability titration testing. There was no correlation found between type of fluid (soluble oil, semi-synthetic, and synthetic) and corrosion inhibition or surface tension.Illinois Sustainable Technology Center/Grant No. HWR07208published or submitted for publicationis peer reviewe

Applicability of Microfiltration for Recycling Semi-Synthetic Metalworking Fluids

This research seeks to investigate the applicability of microfiltration technology by investigating the membrane fouling mechanisms at work in the system. It also aims to reduce fouling through adjustment of operating parameters and the design of a new semi-synthetic MWF that significantly reduces the impact of membrane fouling.Illinois Waste Management and Reearch Center/Contract No. HWR04186published or submitted for publicationis peer reviewe