Sustainable Machining
IONIC LIQUIDS AS METALWORKING FLUIDS IN MQL
Sustainable manufacturing seeks to optimize material conversion into products while minimizing resource and energy use, environmental impact, and health risks. Machining, a highly energy-intensive process, traditionally relies on cutting fluids to manage the heat generated. However, conventional cutting fluids pose environmental and health risks, such as toxic waste disposal and occupational diseases caused by exposure to harmful substances. To address these challenges, researchers are exploring alternatives like Minimum Quantity Lubrication (MQL) systems, which use minimal, non-recirculated lubricants, reducing ecological and disposal concerns.
MQL systems commonly employ mineral oils, synthetic chemicals, or vegetable oils, with advancements including nano-particle additives. However, limitations persist, necessitating better, eco-friendly alternatives. Ionic liquids, known for their tribological properties under high stresses and temperatures, have emerged as potential green lubricants in MQL machining. This study investigates ionic liquids as additives to vegetable oil in interrupted orthogonal machining under MQL conditions.
The study tested different combinations of ionic liquids, such as BMIMPF6, BMIMBF4, BMIMTFSI, and tributyl(nonyl)phosphonium bis(2-ethylhexyl) phosphate, mixed with canola oil or Polyethylene Glycol (PEG). Experiments showed that ionic liquid-enhanced vegetable oils significantly reduced cutting forces and surface roughness compared to dry machining, traditional fluids, and neat vegetable oils. Fluorine-containing ionic liquids decomposed at high temperatures, forming iron fluorides that minimized tool adhesion, further lowering forces. In contrast, ionic liquids without fluorine showed limited improvement.
Thermal modeling revealed that at low cutting speeds, lubricant viscosity played a key role, while at higher speeds, decomposition mechanisms dominated. Oil-miscible ionic liquids performed better at lower speeds, while higher concentrations were advantageous for severe conditions. PEG with hydrophilic ionic liquids improved cutting forces but not surface roughness.
The findings highlight the potential of ionic liquids in sustainable MQL machining, with further research needed to optimize formulations for diverse machining conditions.
Surface Textured cutting tools
In metal cutting, material removal generates significant heat and friction at the tool-chip interface. Cutting fluids are traditionally used to mitigate these effects but pose environmental, health, and economic challenges. Surface textured cutting tools have emerged as a promising alternative, enabling dry and near-dry machining by reducing or eliminating the need for cutting fluids. These tools utilize microcapillary networks to enhance access to air or lubricants at the sliding zone of the tool-chip interface, altering tribological conditions and improving machining performance.
Research on surface textured tools has demonstrated their potential in machining operations, particularly in orthogonal machining of AISI 1045 steel with uncoated carbide tools. Textures on the rake and flank surfaces of the cutting tool influence machining outcomes, with specific patterns improving overall performance. Surface parameters such as roughness, spacing, waviness, and hybrid characteristics significantly impact friction conditions at the tool-chip and tool-workpiece interfaces.
Experiments in natural atmospheric conditions reveal that atmospheric gases influence friction through both mechanical interactions and chemical reactions at the interfaces. Textured surfaces regulate air access, affecting friction and machining performance. Additional experiments under controlled gas environments demonstrate that different gases have varying effects on friction and cutting efficiency.
Surface texture also affects workpiece quality. Textured flank surfaces improve surface roughness and influence subsurface hardness, enhancing surface integrity. Challen’s wave model supports the hypothesis that chemical reactions, alongside mechanical interactions, affect machining forces. An empirical model developed from the study predicts cutting and thrust forces based on surface texture parameters.
In summary, surface textured cutting tools enhance machining performance by altering tribological and chemical conditions at the tool-chip interface. These findings support their potential for sustainable machining, highlighting opportunities for further research into optimizing texture designs and exploring diverse machining environments.