Metalworking Fluids Research Articles

Nanofluid Minimum Quantity Lubrication (NMQL): Overview of Nanoparticle Toxicity and Safer-Design Guidelines

Minimum Quantity Lubrication (MQL) has received much attention from the research community as a potential lubricating system to reduce environmental hazards and health issues that can be commonly found in flood cooling/lubricating systems based on metalworking fluids. The addition of nanoparticles in MQL systems (NMQL) has led to improved machining performance, increasing the cooling capability and reducing friction and tool wear, and some researchers have proved the applicability of this type of system for difficult-to-cut materials. However, the mist generated by MQL systems due to both the MQL system itself and the machining operation may pose an additional hazard to operators which is being overlooked by the research community. These hazards become more severe when using nanoparticles, but unfortunately very few works have paid attention to nanoparticle toxicity as applied in MQL systems, and this issue should be clearly understood before encouraging its implementation in industry. Furthermore, current legislation does not help since regulation of permissible exposure limits when dealing with nanoparticles is still ongoing in most cases. In this work, the toxicity of nanoparticles applied in MQL systems is analyzed, and recent research on studies of nanoparticle toxicity both in vitro and in vivo is presented. A relative comparison of toxicity is provided for those nanoparticles that have been reported in the literature as potential additives for MQL. The review is focused on analyzing the main factors of toxicity of nanoparticles which are identified as size, shape, surface properties, agglomeration and solubility. This review presents guidelines for safer nanolubricant formulations, guiding practitioners towards proper NMQL implementations in industry. Furthermore, current occupational exposure limits and recommendations are provided for all the nanoparticles potentially used in MQL systems, which is of interest in terms of work safety.

Sustainable Machining of Hard to Cut Material Using Bio-mimicked Structured Tool Combined with Nano-green Cutting Fluid

Sustainable Machining of Hard to Cut Material Using Bio-mimicked Structured Tool Combined with Nano-green Cutting Fluid

Dominant Circulating Cell-free Mycobacterial Proteins in In-use Machining Fluid and their Antigenicity Potential.

Occupational exposure to industrial Metalworking Fluid (MWF) colonized by Mycobacterium immunogenum (MI) has been associated with immune lung disease hypersensitivity pneumonitis (HP) in machinists. This warrants regular fluid monitoring for early detection of mycobacterial proteins, especially those with antigenic potential. To detect and identify dominant MI proteins and antigens directly from the field-drawn in-use MWF using an integrated immunoproteomic-immunoinformatic approach. An MI-positive MWF selected by DNA-based screening of several field-drawn MWF samples was cultured to isolate the colonizing strain and profiled for dominant circulating cell-free (ccf) MI proteins, including antigens using an integrated immunoproteomic (1D- and 2Dgel fractionation of seroreactive proteins combined with shotgun proteomic analysis using LC-MS/MS) and immunoinformatic strategy. A new MI strain (MJY-27) was identified. The gel fractionated MI protein bands (1Dgel) or spots (2D-gel) seroreactive with anti-MI sera probes (Rabbit and Patient sera) yielded 86 MI proteins, 29 of which showed peptide abundance. T-cell epitope analysis revealed high (90-100%) binding frequency for HLA-I & II alleles for 13 of the 29 proteins. Their antigenicity analysis revealed the presence of 6 to 37 antigenic determinants. Interestingly, one of the identified candidates corresponded to an experimentally validated strong B- and T-cell antigen (AgD) from our laboratory culture-based studies. This first report on dominant proteins, including putative antigens of M. immunogenum prevalent in field in-use MWF, is a significant step towards the overall goal of developing fluid monitoring for exposure and disease risk assessment for HP development in machining environments.

Towards cleaner machining: Experimental investigation of collagen-in-water as a novel type of metalworking fluids – A technical feasibility study

Driven by environmental challenges, health concerns and increasing legislative restrictions, a high demand for research regarding alternative metalworking fluids (MWFs) to substitute the conventional mineral oil-containing fluids emerges. In recent years, bio-based fluids have continuously gained attention, as their usage could mitigate the disadvantages of conventionally used fluids, which usually contain mineral oil. Against this background, this research aims to contributing towards biological MWFs by investigating the technical applicability of collagen-in-water fluids through evaluations and comparisons with MWFs. The analyzed bio-based MWF is based on collagen-hydrolysate powder dissolved in water, with collagen acting as a viscosity-increasing additive. The prepared fluids were investigated regarding their viscosity and tribological behavior in cylinder-on-ring experiments as well as tapping-torque tests. Afterwards, first machining experiments were performed for honing and grinding of hardened steel. Force-led cylinder-on-ring experiments show a significant wear reduction, e.g. a value of 13.4 mm2 at 3 wt.% collagen compared to 33.0 mm2 with pure distilled water. Wear further decreased with increasing collagen content. At 3 wt.% and again compared to pure water, tapping torque was reduced by 29 % to 181.7 N·cm, no further torque reduction was observed with increasing collagen concentration. In honing, roughness was reduced using collagen-in-water, however, an 8 wt.% collagen fluid resulted in an 18 % reduction in material removal rate compared to honing oil. In internal grinding, an 8 wt.% collagen fluid achieved an Ra of approximately 0.8 μm, compared to around 0.55 μm with emulsion. The application results demonstrate a high potential for collagen-in-water fluids, however, adjustments are necessary for obtaining competitive fluids.

Assessment of Workers’ Personal Exposure to Metalworking Fluid Aerosols in an Automotive Parts Manufacturing Facility and Their Health Outcomes

Assessment of Workers’ Personal Exposure to Metalworking Fluid Aerosols in an Automotive Parts Manufacturing Facility and Their Health Outcomes

Experimental Research on Pollution-Free Alcohol Cutting Fluid in Scratching of Single-Crystal Copper Material

Cutting fluid can improve the heat dissipation and lubrication in the cutting process and thus increase the machining quality. In this work, a pollution-free alcohol solution was proposed as the cutting fluid in an ultra-precision cutting process to explore green cutting fluids. The scratching experiments were conducted with the alcohol cutting fluid to study its effect on the cutting process. It is found that the use of an alcohol cutting fluid, on average, reduces the tangential and normal force about 27–53%, but exhibits few effects on the friction coefficient in the cutting process. Compared to dry cutting, the alcohol cutting fluid reduces the exposed shear slip steps on the outside surface of the chip, which implies the decreased chip deformation degree of workpiece material in the cutting process. The alcohol cutting fluid can reduce microburrs and decrease the machined surface roughness Ra from 21 nm to 9.9 nm in the ultra-precision turning application on single-crystal copper material.

Synthesis and characterization of carbon-based MWCNT combined with CaO to improve the surface characteristics of DED-processed Ti64 alloy machined under MQL conditions

The capacity of additive manufacturing (AM) to create intricate geometries and minimise material waste has drawn a lot of attention. Nevertheless, post-processing steps like machining are frequently needed for AM components to improve their functional surfaces. High temperatures are produced at the tool-workpiece-chip contacts during cutting operations, which lowers tool life and efficiency. Although petroleum-based cutting fluids (CFs) are commonly used to control these temperatures, they pose environmental, health, and cost concerns. Minimum quantity lubrication (MQL) with vegetable oil (VO) has emerged as a promising alternative that offers improved machining performance and environmental friendliness. However, MQL’s effectiveness of MQL may be limited under aggressive machining conditions, necessitating the use of nanoparticles (NPs) to enhance performance. In this investigation, the wettability, dynamic viscosity, density, and thermal conductivity of multi walled carbon nanotubes (MWCNT) at varying wt. concentrations (0.25% to 1.25%) are examined. Following that, the milling tests are conducted in the following conditions: dry, flood, MQL (CaO), and nanofluid-MQL (N-MQL). The outcomes show that the addition of NPs to CaO reduces the contact angle to 15.53° at 1.00 wt%, indicating better wettability. Furthermore, the incorporation of MWCNTs results in a significant improvement in the dynamic viscosity, thermal conductivity, and density of the VO. N-MQL, on the other hand, results in an enhancement in surface quality in contrast to other cutting strategies.

Development and Characterization of Novel Green Cutting Fluids with Nano-additives

In this current investigation, novel cutting fluids developed through a unique combination of food grade emulsifiers, plant based additives (EA) and nano particles (NP) as cutting fluid additives in corn oil (CO) based vegetable oil. Five dissimilar corn-based green cutting fluids (CBGC1, CBGC2, CBGC3, CBGC4, CBGC5) were prepared by varying the weight percentages (wt.%) of EAs (5, 10, 15, 20, 25) with CO, and their thermo-physical properties were meticulously analyzed. Among these formulations, CBGC2 demonstrated superior lubrication performance, making it the most promising oil for further investigation. Subsequently, the effect of different NP was investigated by adding alumina (Al2O3), graphene (Gr) and multi walled carbon nanotubes (MWCNT) NPs in the CBGC2 solution in the ratio of 0.4, 0.8 and 1.2 in weight percent (wt.%) and the experimental results reveal substantial enhancements in thermophysical properties. Among various samples, the nanofluid containing 0.8 wt.% concentration of Al2O3 nanoparticles in CBGC2 exhibited the highest viscosity. Additionally, the thermal conductivity of the nanofluid enhanced by 24.82% when 1.2 wt.% of Gr nanoparticles added oil compared to CBGC2. Furthermore, in tribological tests, CBGC2 with 0.4% Al2O3 exhibited the lowest frictional force among the prepared cutting fluids. The contact angle reduced to a maximum extent by 11.14% for cutting fluids containing 1.2% alumina nanoparticles. These findings suggest that these innovative green cutting fluid formulations with nano-additives hold great potential for improving machining processes in various industrial applications towards sustainability.

Formulation Ratio Effectiveness of Green Metal Working Fluid (GMWF) as a Bio Alternative for Green Manufacturing

Metalworking fluid (MWF) is essential for ensuring quality products and extended tool life during machining operations. While there are various sources of MWF, the need to minimize health hazards associated with mineral-based metal working fluid now calls for more environmentally friendly green metal working fluid (GMWF) from bio-degradable sources. Also, the effectiveness of vegetable-based GMWF significantly depends on the degree of functionalization. Though some studies considered the issue, the comparative analysis of the effect formulations (variation in concentration) of the constituting elements of the GMWF, especially for the base vegetable oil under consideration; has been grossly underreported. In this study, a GMWF emulsion has been developed from soybeans, palm fruits, and coconut with varying formulation ratios. Physicochemical characterization such as flash point, fire point, pour point, pH, density, and viscosity of the developed GMWF were analyzed. Also, a performance evaluation of the said GMWF was carried out and the investigation has shown that the physicochemical properties of the developed GMWF matched, as a potential substitute for conventional mineral-based MWF. Additionally, a performance evaluation conducted during a mechanical machining operation revealed that the GMWF showed an improved surface roughness of about 10.77% compared to conventional mineral MWF. Observations during the machining operation further revealed that the formulated GMWF demonstrated some level of environmental tolerance as it was not associated with misting or the discharge of fumes. The research outcome will impact green machining science and MWF technology for sustainable mechanical machining and cutting fluid development.

Occupational respiratory disease in Eastern Slovakia between 1990-2021: a shift from agriculture to industrial manufacturing.

Occupational allergic respiratory diseases frequently occur in individuals working in the agricultural and food production sectors, textile manufacturing, and industries involving exposure to isocyanates. The study aimed to describe trends surrounding the prevalence of occupational asthma (OA), occupational rhinitis (OR), and occupational hypersensitivity pneumonitis (OHP) in Eastern Slovakia between 1990-2021. All cases of OA, OR, and OHP registered in a database at the Louis Pasteur University Hospital in Košice, Slovakia, between 1990 and 2021, were divided into categories based on economic sector (agricultural, food production sectors, textile manufacturing, healthcare, industrial manufacturing, and tertiary sector) and causal agent. Changes in disease prevalence, causal agents, and economic sector association over time were analysed. There were 287 occupational respiratory cases (179 OA, 65 OR, and 43 OHP cases). The annual prevalence of OA declined significantly over the study period (p < 0.05). Overall, there was a significant decrease in cases from the agricultural (p < 0.001) and an increase in the industrial manufacturing (p < 0.01). The number of cases due to farming agents fell markedly over the study period, while metalworking fluids (MWFs) were found to be the most common causes of allergic respiratory diseases since 2018. This study found a decrease in the number of OA cases, as well as changes in economic sectors and causal agents associated with OA and OHP, specifically, in the agricultural sector, with MWFs from the industrial manufacturing sector now being the most common aetiological agent.

Evaluation of Surface Quality and Productivity in Conventional Milling of Copper Beryllium Using Minimum Quantity Lubrication

Copper Beryllium (C17200) has ideal physical and mechanical properties of high fatigue strength, thermal conductivity, and hardness, making the alloy ideal for various high-reliability applications in aerospace, producing inserts and tooling for hazardous environments. However, surface quality and productivity challenges are prominent when processing the alloy due to its properties. This study evaluates the surface quality and productivity in end-milling of Copper Beryllium by analyzing the effects of feed rate, minimum quantity lubrication (MQL) flow rate, and cutting depth on surface roughness (Ra) and material removal rate (MRR). The experiment was designed using the Box-Behnken design, and the samples were machined on a CNC milling machine. The results showed that the MQL flow rate was significant to surface roughness, while the cutting depth was significant to MRR. The optimum parameters were determined as a feed rate of – 60 mm/min, an MQL flow rate of – 80 ml/hr., and a cutting depth of – 0.511 mm, which yielded a surface roughness of 0.12 µm and MRR of 10.19 g/min. The study's novelty is that it considers MQL flow using vegetable oil-based cutting fluid (CF) as an input parameter in machining, offering insight into eco-friendly and cost-effective machining practices. Finally, the significance of the study lies in investigating the machinability of Cu-Be alloy material, addressing challenges related to surface quality and productivity during milling operation.

Validating real time compensation: A thermal test piece for 5-axis machine tools to separate thermal errors in Z-direction

The accuracy of 5-axis machine tools is a key factor to manufacture multi-axes machined workpieces. However, thermal deformations of the machine structure often cause significant deviations at the tool centre point. To evaluate the impact of thermal errors on the accuracy of 5-axis machine tools under machining conditions, suitable thermal test pieces are required. Therefore, this paper introduces a 5-axis thermal test piece which is based on the thermal test piece for rotary axes being part of the standard ISO 10791-10:2022. The new thermal test piece identifies ten instead of five thermal errors during eight time steps. The additional features enable an error separation of the table-related thermal error and the thermal error pointing consistently in Z-direction. This error separation is especially important to analyse the accuracy of five-axis milling operations. In total, the developed 5-axis thermal test piece analyses five location, two length and three orientation errors without requiring a kinematic model of the machine tool. The conducted experiments comprise thermal load cases without and with metal working fluid and show a clear agreement between the thermal location errors and the dominant thermal orientation errors of the thermal test piece and an on-machine measurement cycle. On the other hand, the analysed thermal length errors of the thermal test piece indicate a clear effect of the thermal material expansion compared to the thermal positioning errors of the analysed machine tool. Furthermore, the analysed thermal load cases of the linear and rotary axes conducted without and with metal working fluid result in a different thermal behaviour of the machine tool depending on the use of metal working fluid. Finally, the developed 5-axis thermal test piece is used to evaluate a thermally compensated 5-axis machine tool under machining conditions for thermal load cases without and with metal working fluid. The self-learning thermal error compensation reduces the mean of the thermal location errors at the thermal test piece by up to 71%.

Graphene nanoplatelets-water nanofluids: A sustainable approach to enhancing Ti-6Al-4V grinding performance through minimum quantity lubrication

This study introduces a stable, water-based graphene nanoplatelets (GNPs) nanofluid as a sustainable cutting fluid for grinding Ti-6Al-4V alloy under minimum quantity lubrication (MQL). Using ethanol and sodium deoxycholate (SDOC) surfactant, the dispersion stability of GNPs in water was remarkably extended from 1 h to 57 days. This novel nanofluid formulation enhances wettability, thermal conductivity, and tribological properties. Grinding tests showed a 0.35 mg/mL water-GNPs concentration reduced grinding forces by 74.44 % and 33.37 % compared to dry and conventional flood lubrication, respectively, while improving surface roughness. Raman spectroscopy confirmed graphene's presence on the machined surface, highlighting the potential of water-GNPs nanofluids as an eco-friendly alternative to traditional metalworking fluids, enhancing sustainability in manufacturing.

Characterization of occupational inhalation exposures to particulate and gaseous straight and water-based metalworking fluids

Exposure assessments to metalworking fluids (MWF) is difficult considering the complex nature of MWF. This study describes a comprehensive exposure assessment to straight and water-based MWFs among workers from 20 workshops. Metal and organic carbon (OC) content in new and used MWF were determined. Full-shift air samples of inhalable particulate and gaseous fraction were collected and analysed gravimetrically and for metals, OC, and aldehydes. Exposure determinants were ascertained through observations and interviews with workers. Determinants associated with personal inhalable particulate and gaseous fractions were systematically identified using mixed models. Similar inhalable particle exposure was observed for straight and water-based MWFs (64–386 µg/m3). The gaseous fraction was the most important contributor to the total mass fraction for both straight (322–2362 µg/m3) and water-based MWFs (101–699 µg/m3). The aerosolized particles exhibited low metal content irrespective of the MWF type; however, notable concentrations were observed in the sumps potentially reaching hazardous concentrations. Job activity clusters were important determinants for both exposure to particulate and gaseous fractions from straight MWF. Current machine enclosures remain an efficient determinant to reduce particulate MWF but were inefficient for the gaseous fraction. Properly managed water-based MWF meaning no recycling and no contamination from hydraulic fluids minimizes gaseous exposure. Workshop temperature also influenced the mass fractions. These findings suggest that exposures may be improved with control measures that reduce the gaseous fraction and proper management of MWF.

DNA damage in workers exposed to mineral oils

Mineral oils, untreated or mildly treated, have been classified in group 1 as a potential source of cancer by the International Agency for Research on Cancer (IARC). Although numerous studies have implicated metalworking fluids (MWFs) as human carcinogens, toxicology data regarding the mechanism of carcinogenicity are limited. This study is intended to examine the systemic effects of machining workers’ exposure to MWFs. The potential toxicity of mineral oils was investigated in 65 lathe workers compared to controls (66 men). The occupational exposure was measured by the National Institute for Occupational Safety and Health (NIOSH) 5026. The DNA damage has been examined by the comet assay method. According to the field assessments, the time-weighted average (TWA) exposure to mineral oil mist was 7.67 ± 3.21 mg/m3. A comet assay of peripheral blood cells showed that tail length (TL) and olive moment (OM) were significantly higher in the exposed group (p < 0.05). A multiple logistic regression analysis revealed that, within subjects with over 10 years of exposure, the odds ratio of worker with high TL, percent of DNA in tail, OM, and tail moment (TM) were 1.68, 1.41, 1.71, and 2.71, respectively. DNA strand break in exposed workers was associated with higher exposure time in years. Mineral oil toxicity could be altered in the presence of by-products and impurities. For a better understanding of genotoxicity, further studies are required.

In pursuit of sustainability in machining titanium alloys using phosphonium-based halogen-free ionic liquids as potential metalworking fluid additives

In recent years, researchers have investigated ionic liquids (ILs) as suitable metalworking fluids (MWFs) additive. Most commonly used ILs contain halogen anions, which creates issues related to corrosion and toxicity. However, phosphonium-based halogen-free ILs (HF-ILs) provide a safer alternate with enhanced biodegradability and minimal adverse effects on the environment. This research examines the potential of HF-ILs as an additive to canola oil. In this research two halogenated ILs [BMIM][PF6]- and [BMIM][BF4]- and one halogen-free IL ([P6,6,6,14][i(C8)2PO2]-) were added 1 % by volume in canola oil. First, the thermophysical properties of these synthesized MWFs were evaluated. Result concluded that the HF-ILs reduced contact angles on both the workpiece and the cutting tool surfaces by 12– 15 % compared to pure canola oil. Whereas, improved the thermal conductivity by 10.5 %. Furthermore, the machining operation was carried out at two cutting speeds (80 and 100 m/min) and feed (0.1 and 0.2 mm/rev) to analyse the effect of synthesized MWFs under the minimum quantity lubrication method. Findings concluded that phosphonium-based halogen-free IL showed better cutting performance, with reduction in tool wear, cutting temperature by 10–33 %, and surface roughness by 34−46 %. Additionally, this approach supports a "greener" and more sustainable work environment by lowering MWF consumption by using minimal quantity lubrication, reducing tool wear and surface roughness which helps in cost reduction and product rejection for any manufacturing industry.

Modeling and mitigation of vortex formation in ejector deep hole drilling with smoothed particle hydrodynamics

Ejector deep hole drilling achieves high-quality boreholes in production processes. High feed rates are applied to ensure a high productivity level, requiring reliable chip removal from the cutting zone for a stable process. Therefore, a constant metalworking fluid flow under high volume flow rates or high pressure is required. Experimental results show a vortex formation at the outer cutting edge. This vortex can lead to delayed chip removal from the cutting zone, and ultimately, it can lead to chip clogging and result in drill breakage due to increased torque. This paper investigates modified drill head designs using the smoothed particle hydrodynamics method. The investigated modifications include various designs of the chip mouth covering. Besides graphical analysis based on flow visualizations, flow meters are placed at the tool’s head to evaluate the impact of the modifications on the flow rate and possible increased resistance and relocation of the fluid flow from the outer cutting edge to other parts of the tool. The simulation results for the reference design show the experimentally observed vortex formation, validating the simulation model. By adding the tool’s rotation in the SPH simulation, which is not included in the experiments for observation reasons, the vortex formation is positively influenced. In addition, some designs show promising results to further mitigate the vortex formation while maintaining a sufficient fluid flow around the cutting edges.

Prostate Cancer Incidence and Mortality Linked to Metalworking Fluid Exposure: A Systematic Review and Meta-Analysis

Introduction: Prostate cancer is a significant health concern, and occupational exposures, including metalworking fluid (MWF) exposure, have been implicated as potential risk factors. This protocol outlines a systematic review and meta-analysis methodology to investigate the association between MWF exposure and prostate cancer risk among male workers. Methods: Eligible studies include cohort, case-control, and cross-sectional studies published until between 1990 and 2023 focusing on MWF exposure and prostate cancer risk in male workers. Two independent reviewers will screen studies, extract data using a standardized form, conduct a meta-analysis using random-effects models, and assess study quality using the Newcastle-Ottawa Scale. Heterogeneity will be assessed, and sensitivity analyses will be conducted to explore sources of bias. Results: Anticipated outcomes include a comprehensive list of eligible studies, a synthesized analysis using random-effects meta-analysis models to estimate the association between MWF exposure and prostate cancer risk, and a quality assessment report of included studies. Subgroup analyses based on MWF type, exposure duration, and study design will be performed to explore heterogeneity. Conclusion: This systematic review and meta-analysis protocol aim to provide robust evidence on the association between MWF exposure and prostate cancer risk among male workers. The anticipated findings will have implications for occupational health practices and may guide future research and intervention strategies.

A Novel Grinding Process on Compacted Graphite Iron Using Cutting Fluid with Nano-solid Lubricant Additives

A Novel Grinding Process on Compacted Graphite Iron Using Cutting Fluid with Nano-solid Lubricant Additives

Investigation of metal concentration distribution and corresponding health exposure assessment of fabricated metal product manufacturers

The fabricated metal product industries were identified as producers of variable and heterogeneous pollution. Workers in these manufacturing facilities are exposed to multiple pollutants present at variable concentrations. Specific known adverse health effects include bladder cancer associated with metalworking fluid exposure and lung cancer associated with electroplating processes. To reduce the incidence of these adverse effects, the main challenge is to identify the most hazardous pollutants within this complex exposure environment and evaluate the corresponding health potentials. In this study, exposure indices were formulated to assess multiple metal exposures with the ultimate goal of providing relevant information for exposure reduction and control measures. Fifteen plants, including metal mold manufacturing, metal casting, and surface treatment plants, were investigated in terms of total concentration, summation of corresponding ratio to threshold limit value (STLVr), hazard index (HI), and incremental cancer risk. The results revealed that emissions of aluminum, iron, and manganese were primarily found in the metal mold manufacturing/casting plants, while emissions of chromium, nickel, and zinc were found in surface treatment plants. STLVr and HI were more useful than the total concentration for identifying hazardous metals, which were chromium and nickel, and could specify the facilities that were in need of control measures. As for cancer risk, the metal mold manufacturing/casting plants had lower risk than the surface treatment plants, and the contributing metals for these two plant types were cobalt and chromium, respectively. This study established a useful procedure to evaluate health hazards and cancer risk. The resulting information is useful for prioritizing mitigation control of multiple metal exposures.