Cutting fluid is a fluid used in metal machining process for a variety of reasons such as improving tool life, reducing workpiece thermal deformation, improving surface finish and flushing away chips from the cutting zone. The objectives of this dissertations are to find the suitable methodology on cutting fluid selection methods and evaluate the cutting fluid in terms of its performances cost to the production line. A broad overview of the many selection and evaluation methods applied to cutting fluids has been observed. Turning test has been selected for evaluating cutting fluid in terms of heat transfer performance. Cutting fluid database has been created with addition of heat transfer model and cost model, and integrated into the software as the optimisation for the current method.  The results obtained still need further validation and additional improvements has been discussed for future works.

Keywords:

Cutting Fluid, Fluid Selection Method, Heat Transfer, Cost

Table of Contents

Abstract…………………………………………………..

Acknowledgements…………………………………………..

Table of Contents…………………………………………….

List of Figures………………………………………………

List of Tables……………………………………………….

Nomenclature……………………………………………….

1 Introduction………………………………………………

1.1 Aim and Objectives

1.2 Problem Statement………………………………………

1.3 Scope……………………………………………….

1.4 Overview of Dissertation………………………………….

2 Literature Review

2.1 Cutting Fluids

2.1.1 Straight oils

2.1.2 Synthetic Fluids

2.1.3 Soluble Oil Fluids

2.1.4 Semi-synthetic fluids

2.2 Role of Cutting Fluids

2.2.1 Chips Transportation

2.2.2 Prevent Rewelding

2.2.3 Corrosion Protection

2.2.4 Power Reduction

2.2.5 Extend Tool Life and Increase Productivity

2.2.6 Create Certain Type of Chip

2.2.7 Cooling

2.2.8 Lubrication

2.3 Application of Cutting Fluid

2.4 Selection of suitable cutting fluids

2.4.1 Type of machining processes.

2.4.2 Type of machined workpiece material.

2.4.3 Type of cutting tool material.

2.5 Factors Associated when Using Cutting Fluid

2.5.1 Health and Safety

2.5.2 Economic Cost

2.5.3 Environmental

2.6 Cutting Fluid Selection Methods

2.6.1 Pin and V-Block Test

2.6.2 Block on Ring

2.6.3 Four-Ball Test

2.6.4 Soda Pendulum

2.6.5 Lathe Tests

2.6.6 Grinding Test

2.6.7 Drilling Test

2.6.8 Tapping Torque Test

2.7 Summary

3 Evaluation Test Program……………………………………..

3.1 Heat Transfer Model in Turning Operations…………………….

3.2 Cost Model for Cutting Fluids………………………………

3.3 Creating Database for Cutting Fluids………………………….

3.4 Integrating Database into Program……………………………

4 Results and Discussions……………………………………..

5 Validation of Cutting Fluid Test Program Data……………………..

5.1 Pendular Scratch Test…………………………………….

6 Conclusion and Recommendation……………………………….

6.1 Future Work…………………………………………..

References…………………………………………………

Appendix 1 – Machinability Groups……………………………….

Appendix 2 – Installation guide…………………………………..

List of Figures

Figure 2‑1: Manufacturing cost pie chart (Brinksmeier and Brockhoff, 1997).

Figure 2‑2 Pin and V block test (Byers, 2006)

Figure 2‑3 Block on ring test (Byers, 2006).

Figure 2‑4: Four ball test (Kirkpatrick,1980).

Figure 2‑5: Soda Pendulum (Byers, 2006) .

Figure 3‑1 Velocity vectors in flood application (M. Daniel, Olson and Sutherland, 1996).

Figure 3‑2:Integrating formula into database.

Figure 3‑3: Cutting fluid and workpiece material database in excel.

Figure 3‑4: Opening software

Figure 3‑5: Selecting database

Figure 3‑6: Selecting cutting fluid and workpiece material.

Figure 4‑1: Oil concentration effect on heat transfer coefficient

Figure 4‑2: Spindle speed effect on heat transfer coefficient.

Figure 4‑3: Fluid velocity effect on heat transfer coefficient.

Figure 5‑1 : General view of pendular instrument (Liang.1996).

Figure 5‑2: Work piece sample submerged in cutting fluid (Franco,1989).

Figure 5‑3: Specific energy consumed during scratching with mass loss (Sales et al., 2007).

List of Tables

Table 2.1: Guide to cutting fluid selection for general workshop application (Trent and Wright, 2000).

Table 2.2: Cutting fluids recommendation by machinability groups (Trent and Wright, 2000).

Table 2.3 Pin and V block results (Byers, 2006)

Table 2.4: Lathe test results (DeChiffre,1982).

Table 2.5: Surface grinding results.

Table 2.6: Tapping torque results (Byers, 2006).

Table 3.1: Cutting Fluid Properties (M. Daniel, Olson and Sutherland, 1996).

Table 4.1: Input data

Table 4.2: Heat transfer coefficients between four fluids.

Table 4.3: Cutting fluid costs.

Nomenclature

1         Introduction

In this section, the aims and objectives of this dissertation as well as the problem statement will be discussed.

1.1         Aim and Objectives

The principle aim of this dissertation is to define optimised cutting fluid selection method and the objectives are:

1. To determine the important properties of cutting fluid when making the selection.
2. To develop a standardised test program aimed at measuring the above properties.
3. Use the data from the standardised test program to select the most suitable cutting fluid

1.2         Problem Statement

Current scenario is every month, there are vendors suggesting cutting fluids to Rolls Royce and they want to find the most effective way of testing the cutting fluid for their production. At the moment, Rolls Royce did have a method testing it, it involves grinding test, milling test, turning test, tapping test, and drilling test. Rolls Royce used these to compare the cutting fluid but they never convince that it gives a right result as the result didn’t give total cost. In overall cost operations, more demanding materials put more demands on cutting fluids as well. So any changes, any modification by cutting fluids supplier becomes more sensitive to Rolls Royce product at the end.

At present, as there are no known standardize test for cutting fluid in Rolls Royce production and they want to know the available methods out there that can be utilize. Rolls Royce prefers using tools or models and simulation rather than testing methods to predict the results. They can use a real example from production that they know the answer already and put the input into the models.

1.3         Scope

The first part of this work presents general view of cutting fluid with highlighting its criteria and selection methods. Only heat transfer performance and cost performance were discussed in this dissertation. A wide overview of the various selection and evaluation methods applied to cutting fluids has been identified. Turning test has been selected for evaluating cutting fluid in terms of heat transfer performance. Cutting fluid database has been created with addition of heat transfer model and cost model, and integrated into the software as the optimisation for the current method.

It is not the intention to perform a detailed comparison between cutting fluid selection methods, nor deciding which one is the best, simply to determine which cutting fluid main characteristics have the greatest influence on the selection process and develop a range of standardised tests to allow different fluids to be compared.

1.4         Overview of Dissertation

The works carried out during the research project will be presented in this dissertation in six chapters.

Chapter 1, the Introduction provides the background to this research, giving reasons as to why the research was conducted, a list of aims and objectives, and describes the scope and structure of the dissertation.

Chapter 2, the Literature Review gives general information about cutting fluids, their roles and application to the machining operations as well as factors associated when using them. This chapter also highlights the evaluation and selection methods currently available for cutting fluids

Chapter 3, Evaluation Test Program, presents theoretical analysis for heat transfer performance for different types of cutting fluids in turning operation by using software developed from Microsoft Visual Studio.

Chapter 4, Results and Discussions, putting the input into the software and discussing the results.

Chapter 5, Validation of Cutting Fluid Test Program, details the experimental work pendular scratch test. The results from the experiment are correlated with the results from the software presented in chapter four, in order to evaluate the effectiveness of the test program.

Chapter 6, Conclusions and Recommendations, lists the conclusions that have arisen from the research, and suggestions for areas of further work that would be beneficial in extending the optimisation of cutting fluids selection method.

2         Literature Review

2.1         Cutting Fluids

Cutting fluids have been used in the machining process with the purpose improve the tribological characteristics of the work piece–tool–chip system. It is interesting to note that the use of coolants for machining was first reported by Taylor in 1907, who achieved up to 40% increase in cutting speed when machining steel with high speed steel tools using water as coolant (Taylor, 1907). Cutting fluids improve the efficiency of machining in terms of increased tool life, improved surface finish, improved dimensional accuracy, reduced cutting force and reduced vibrations. Cutting fluids provide lubrication between the work piece and tool and remove heat generated during the metal cutting process (Xavior and Adithan, 2010). But application of conventional cutting fluids creates several techno-environmental problems. Environmental pollution due to chemical dissociation/break-down of the cutting fluid at high cutting temperature, biological (dermatological) problems to operators coming in physical contact with cutting fluid, water pollution and soil contamination during disposal. The use of conventional petroleum-based cutting fluids is potentially dangerous. The effects of a cutting fluid on mankind, working environment, the work piece and machine tool as well as generally on living environment are usually expressed by their ecological parameters. Machine operators are affected by contact with various substances within the cutting fluids (Soković and Mijanović, 2001).

Practically all cutting fluids presently in use fall into one of four categories:

1. Straight oils (neat mineral oils)
2. Soluble oils (water based cutting fluids)
3. Semisynthetic fluids
4. Synthetic fluids

2.1.1          Straight oils

Straight oils are non-emulsifiable and are used in machining operations in an undiluted form. They are composed of a base mineral or petroleum oil and often contains polar lubricants such as fats, vegetable oils and esters as well as extreme pressure additives such as Chlorine, Sulphur and Phosphorus. Straight oils provide the best lubrication and the poorest cooling characteristics among cutting fluids.

2.1.2          Synthetic Fluids

Synthetic Fluids contain no petroleum or mineral oil base and instead are formulated from alkaline inorganic and organic compounds along with additives for corrosion inhibition. They are generally used in a diluted form (usual concentration = 3 to 10%). Synthetic fluids often provide the best cooling performance among all cutting fluids.

2.1.3          Soluble Oil Fluids

Soluble Oil Fluids form an emulsion when mixed with water. The concentrate consists of a base mineral oil and emulsifiers to help produce a stable emulsion. They are used in a diluted form (usual concentration = 3 to 10%) and provide good lubrication and heat transfer performance. They are widely used in industry and are the least expensive among all cutting fluids.

2.1.4          Semi-synthetic fluids

Semi-synthetic fluids are essentially combination of synthetic and soluble oil fluids and have characteristics common to both types. The cost and heat transfer performance of semi-synthetic fluids lie between those of synthetic and soluble oil fluids.

2.2         Role of Cutting Fluids

Salmon (2006) had mention that there are eight roles of cutting fluid in machining operation but its main functions is to cool and then to lubricate. This section will deal with those eight areas first and come back to the effect of cooling and lubricating later.

2.2.1          Chips Transportation

It is also necessary to take the formed chip away quickly from cutting tool and machined workpiece surface. Hence the effect of the formed chip on the machined surface would be eliminated causing poor surface finish. Moreover, part of the generated heat will be taken away by transferring formed chip (Cakir, Yardimeden and Ozben, 2007).

Aside from transporting the chips away from the cutting zone, small particles and dust from the machining process will be damped down by cutting fluid and avoiding respiratory health hazard as well as unpleasant and dirty environment (Salmon, 2006)

2.2.2            Prevent Rewelding

The cutting fluid helps to prevent rewelding. This is the reaction of material, at high temperature, to stick back onto itself at the tool edges and surfaces, as seen in the built-up-edge that occurs and is more pronounced in slower speed machining. It is also prevalent in terms of wheel loading when grinding soft materials. The chemistry of dissimilar materials works here. Copper compounds, in particular, may be added to a fluid when machining ferrous materials to prevent the rewelding.

2.2.3          Corrosion Protection

The cutting fluid should offer a level of corrosion protection to the machined workpiece. The “just machined” nascent metal surface is chemically active and will readily oxidize or react with the surroundings. Whereas most fluids will provide some corrosion protection, others may do just the opposite and cause some staining or discoloration due to their high surface active properties. The cutting fluid should not only protect the workpiece but also the machine tool, fixtures, and tooling.

2.2.4          Power Reduction

Most cutting fluids reduce friction, and in so doing reduce the power required to machine a given material. Not only is this energy saving, but also if less power is consumed then less heat is generated. It will generally follow that if less heat is generated, the tools will last longer and the surface integrity of the workpiece will be protected. Overall, the system will tend to be more stable. The closer the system can be kept to ambient temperature, the more thermally stable the process, which impacts the integrity of the workpiece — both metallurgically and dimensionally. Thus, refrigeration of the cutting fluid may play a beneficial role in certain cases.

2.2.5          Extend Tool Life and Increase Productivity

The cutting fluid should be designed to first and foremost assist in the machining operation, maximizing stock removal rate and maximizing tool life. Surface active fluids with enhanced wetting agent chemistry will penetrate the surface of the workpiece and chemically react with the surface and subsurface to reduce shear stress. In so doing, it will reduce power consumption and reduce heat generation. This not only allows faster cutting rates, but also increases tool life for a given cutting speed.

2.2.6          Create Certain Type of Chip

According to (Merchant, 2001), there are three types of chips: discontinuous or segmented chips, continuous chips with a built-up-edge, and continuous chips without a built-up-edge. Depending on the material, chips may be long and stringy, tightly curled, or virtually dust-like particles.

Tool geometry in combination with the fluid chemistry can produce either the continuous (not preferred) or the discontinuous chip (preferred). The fluid application method will also affect the chip formation. High-pressure systems tend to act as a liquid chip breaker. The high-pressure blast, onto the back of the chip, not only cools the chip along with the tool face, but also causes the chip to break into smaller particles.

2.2.7          Cooling

The cooling effect of cutting fluids is the most important parameter. It is necessary to decrease the effects of temperature on cutting tool and machined workpiece. Therefore, a longer tool life will be obtained due to less tool wear and the dimensional accuracy of machined workpiece will be improved (El Baradie, 1996).

Attempts have been made to cool the tool using cryogenics. Liquid nitrogen was used as a cutting fluid in a research application at Wright State University in 1995, particularly in the milling of titanium. The application of a cryogenic fluid resulted in a substantial increase in tool life, but of course there are other concerns with this method, such as environmental and the overall economics of the process (Ding, Y. and Hong, S. ,1995).

2.2.8          Lubrication

Cooling and lubrication are the two main reasons to use cutting fluids. There is always heated discussion among machinists as to which is the most important — the water vs. oil argument. Water is the best coolant with a heat capacity far in excess, and a latent heat of evaporation an order of magnitude greater than a typical straight oil. No matter how much heat is generated, the water will take it away from the cutting zone. Oil, on the other hand, lubricates where water does not. Lubrication reduces friction so that heat is not generated, and therefore does not need to be taken away.

The lubrication effect will cause easy chip flow on the rake face of cutting tool because of low friction coefficient. This would also result in the increased by the chips. Moreover, the influence of lubrication would cause less built-up edge when machining some materials such as aluminium and its alloys. As a result, better surface roughness would be observed by using cutting fluids in machining processes (Cakir, Yardimeden and Ozben, 2007).

2.3         Application of Cutting Fluid

The principal methods of cutting fluid application include: