Through-tool minimum quantity lubrication and effect on machinability

doi:10.1016/j.jmapro.2018.03.047

Journal of Manufacturing Processes

Volume 34, Part B, August 2018, Pages 750-757

https://doi.org/10.1016/j.jmapro.2018.03.047 Get rights and content

Abstract

This paper simulated through-tool minimum quantity lubrication (MQL) to characterize micromist droplet size and distribution. The effect of nozzle surface roughness and air pressure was experimentally performed to study the lubricant droplet and its effectiveness in micromilling of Inconel alloy. The external MQL simulated internal flow in commercially available drill with internal cooling channels. Droplets were collected on a glass plate from which the average airborne diameters and standard deviation were calculated. The droplet diameter and distribution were most sensitive when using nozzle with rough internal surface. MQL at different conditions was used in micromilling of Inconel 718 blocks that were additively printed by selective laser melting technique. Micromist generated from a rough nozzle at 550 kPa effectively improved tool life and produced micromilled slots with surface finish S_a of 1.5 μm.

Introduction

Flood cooling or wet machining has been traditionally used to improve machinability in metal cutting. However, applying a large amount of cutting fluid would raise the manufacturing cost while having a negative impact on the environment. With ever increasing of environmental control and manufacturing cost competitiveness, the use of minimum quantity lubrication (MQL) –or near dry lubrication– has been gaining momentum not only because of the above mention effects but also because of tool life improvement when properly applying MQL. Although many researchers have shown the effectiveness of externally applied MQL on tool life enhancement in machining, very limited study was published for results of MQL applied through built-in channels inside a cutting tool. The objectives of this paper are to:

i)
Simulate through-tool MQL and experimentally characterize the resulting liquid droplets.
ii)
Apply the results to study machinability of 3D-printed Inconel 718 (IN718).

Section snippets

Minimum quantity lubrication

A MQL system uses compressed air to aerosolize a typically oil based lubricant. The resulted pressurized air-oil mixture is then flow at high speed toward cutting tool and being-machined workpiece. The amount of lubricant used in MQL was reported to be in the range of 5–100 mL/h which was significantly lower than 20 L/min in typical flood lubrication. As MQL is applied in form of micron-size droplets, a system can be adjusted so that the droplets are completely used up and evaporated due to

Experiments

Experiments were performed in two stages. The first stage characterized the resulting droplets due to different air pressures and surface roughness of a MQL nozzle. In the second stage, MQL at different operating conditions were applied when micromilling SLM'ed IN718 with uncoated WC microtools. Tool wear and surface finish were used to assess the effectiveness of MQL. The effect of different tool coatings was investigated in a parallel study, and would not be covered in this paper.

Results and discussions

The ABS (acrylonitrile, butadiene, and styrene) polymer reacts chemically with acetone. Since both acrylonitrile and styrene are dissolved in acetone, the viscous ABS and acetone mixture allows surface wetting, thus smoothening the 3D printed ABS nozzle ([11,12]). The surface roughness S_a of the as-printed (rough) and acetone polished (smooth) nozzles were measured to be 16.8 μm and 3.2 μm respectively. Since the internal flow of micromist inside a ϕ3 mm nozzle affected by its surface finish,

Conclusions and recommendations

Simulation of through-tool minimum quantity lubrication (MQL) was performed by mimicking geometry of a twist drill with internal cooling channels. Droplet sizes and their effects on micromilling of Inconel 718 were investigated. This study showed:

1)
Both air pressure and surface roughness of MQL nozzle affected the lubricant droplet sizes. The smallest diameter airborne droplet of ∼5 μm was achieved.
2)
The 5 μm droplets under high air pressure effectively reduced tool wear while improving surface

Acknowledgement

The authors would like to thank Unist for providing the MQL system and lubricant, Knust-Godwin for Inconel specimens, and Performance Microtools for their micromilling tools.

References (17)

Y. Kamata et al.
High speed MQL finish-turning of Inconel 718 with different coated tools
J Mater Process Technol
(2007)
T. Obikawa et al.
Micro-liter lubrication machining of Inconel 718
Int J Mach Tools Manuf
(2008)
S. Zhang et al.
Tool life and cutting forces in end milling Inconel 718 under dry and minimum quantity cooling lubrication cutting conditions
J Clean Prod
(2012)
I. Ucun et al.
An experimental investigation of the effect of coating material on tool wear in micro milling of Inconel 718 super alloy
Wear
(2013)
T. Obikawa et al.
High-speed grooving with applying MQL
Int J Mach Tools Manuf
(2006)
M. Ziberov et al.
v Effect of cutting fluid on micromilling of Ti-6Al-4V titanium alloy
Proc Manuf
(2016)
Z. Wang et al.
Built-up-edge effects on surface deterioration in micromilling processes
J Manuf Processes
(2016)
J.M. Dasch et al.
A characterization of mist generated from minimum quantity lubrication (MQL) compared to wet machining
Int J Mach Mach Mater
(2010)

There are more references available in the full text version of this article.

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Proper mist flow is important to Minimum Quantity Lubrication (MQL) machining as only a small amount of lubricant-air mixture is applied to the cutting zone. This paper presents an optical-tomography-based method to visualize the lubricant distribution of MQL mist flow in through-tool channels, particularly for drilling. High-speed images of the flow are acquired from multiple view angles to capture the 2D projections of 3D flow. The Filter Back Projection (FBP) algorithm is used to perform tomography and produce tomographic reconstruction image of the lubricant distribution in the through-tool channels. The method is validated with a known annular flow created using a vertical pipe flow. The method is also applied to two 3D printed drill bits, one with two straight channels and another with two helical channels to emulate actual through-tool channel geometries of drills. The tomographic reconstructions obtained using FBP match with the literature and show a clear influence of the channel geometry on the lubricant distribution. Physical, imaging, and lighting requirements to achieve proper results using this technique are also detailed in the paper.
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Metal cutting fluids have a huge negative impact on human health and environmental ecology, thus posing a serious threat to the sustainable development of the global manufacturing industry. Meanwhile, turning processing is an important part of metal material removal processing, and achieving sustainable lubrication is a major problem that needs to be solved urgently. Using vegetable oil to atomize and spray the tool/chip and tool/workpiece interface through the minimum quantity lubrication (MQL) supply system is a feasible way to achieve environmentally friendly turning. Moreover, the preparation of nanofluid by adding nano-reinforced phases to the degradable bio-lubricant can greatly improve the lubricating performance of the micro-droplets. However, conventional research have only focused on individual factors, such as cutting parameters, types of base oil and nanoparticles, and supply parameters. Thus, these studies are unable to provide effective guidance for the turning processing applications related to nanofluid minimum quantity lubrication (NMQL). In order to fill the gaps in the relevant literature, this paper examines the current advanced research on NMQL and explains the experimental phenomenon through the concept of lubrication mechanism. First, the advanced multi-energy field atomization technology and the influence mechanism of the physical and chemical properties of vegetable oil were reviewed. Subsequently, the influence laws governing nanofluid preparation as well as nanoparticle characteristics and concentration were summarized. Furthermore, textured tool and ultrasonic vibration-assisted nanofluid turning are proposed to increase the effective flow rate. Finally, the challenges and future trends of vegetable oil-based NMQL turning processing are proposed.
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Through-tool minimum quantity lubrication and effect on machinability

Abstract

Introduction

Section snippets

Minimum quantity lubrication

Experiments

Results and discussions

Conclusions and recommendations

Acknowledgement

J Mater Process Technol

Int J Mach Tools Manuf

J Clean Prod

Wear

Int J Mach Tools Manuf

Proc Manuf

J Manuf Processes

A characterization of mist generated from minimum quantity lubrication (MQL) compared to wet machining

Int J Mach Mach Mater