Environmental Analysis of Sustainable and Traditional Cooling and Lubrication Strategies during Machining Processes

Connor Hopkins,Basil Darras,Mohamd Imad,Hussien Hegab,Amr Salem,Hossam A Kishawy

doi:10.3390/su12208462

Abstract

Due to rising demands of replacing traditional cooling strategies with sustainable cooling strategies, the development of sustainable strategies such as minimum quantity lubrication (MQL) of nano-cutting fluids (NCFs) is on the rise. MQL of NCFs has received a lot of attention due to its positive impact on machining process efficiency. However, environmental and human health impacts of this strategy have not been fully investigated yet. This work aims to investigate the impacts of MQL of molybdenum disulfide (MoS2), multi-walled carbon nanotubes (MWCNTs), titanium dioxide (TiO2), and aluminum oxide (Al2O3) NCFs by employing a cradle-to-gate type of life cycle assessment (LCA). Besides, this paper provides a comparison of the impacts and machining performance when utilizing MQL of NCFs with other cooling strategies such as traditional flood cooling (TFC) of conventional cutting fluids and MQL of vegetable oils. It was found that NCFs have higher impacts than conventional cutting fluids and vegetable oils. The impacts of TiO2-NCF and MoS2-NCF were lower than the impacts of MWCNTs-NCF and Al2O3-NCF. MQL of NCFs presented higher impacts by 3.7% to 35.4% in comparison with the MQL of vegetable oils. TFC of conventional CFs displayed the lowest impact. However, TFC of conventional cutting fluids is contributing to severe health problems for operators. MQL of vegetable oils displayed higher impacts than TCFs of conventional cutting fluids. However, vegetable oils are considered to be environmentally friendly. According to the findings, the MQL of vegetable oils is the most sustainable strategy for machining processes with associated low/medium cutting temperatures. While MQL of TiO2 and MoS2 NCFs are the sustainable strategy for machining processes associated with high cutting temperatures.

Highlights

Usage of cutting fluids (CFs) results in increasing the machining process efficiency in terms of power reduction, rust control, and tool life improvement
While damage impact categories are used in life cycle assessment (LCA) of the considered CFs and cooling strategies
Cooling techniques included in the second category were: flood cooling for two conventional CFs, minimum quantity lubrication (MQL) cooling technique for two vegetable oils, and MQL cooling technique for eight nano-cutting fluids (NCFs)

Summary

Introduction

Usage of cutting fluids (CFs) results in increasing the machining process efficiency in terms of power reduction, rust control, and tool life improvement. CFs improve tool life and workpiece surface quality, during any metal cutting operation by decreasing the cutting temperatures [1]. A certain CF’s lubrication property is significant, due to its influence on the friction between the cutting tool-workpiece interface. Appropriate lubrication decreases the friction and prompts smooth chip flow from the workpiece over the cutting tool [1]. CFs can remove formed chips from the cutting zone and prevent any potential surface damage on the machined workpiece due to the flying chips [1]. One of the most significant CFs’ parameters is the cooling effect which directly influences the generated high heat during cutting processes [1]

Objectives

Methods

Results

Conclusion