⚡ electrical engineering

Experimental Analysis of Surface Roughness by Optimizing Machining Parameters in Turning of Aluminium Alloy 075-T651 With Avocado Oil-Based Cutting Fluid Using Taguchi Based Grey Relational Analysis

This study utilizes Taguchi-based Grey Relational Analysis to determine that turning Aluminium Alloy 075-T651 with a tungsten carbide insert at 820 rpm, 132 mm/min feed rate, 1.5 mm depth of cut, and 9% avocado oil-based cutting fluid yields an optimal surface roughness of 0.12 μm.

Original authors: Abera Ayza, Devendra Kumar

Published 2026-06-24

📖 4 min read☕ Coffee break read

CC BY 4.0

Original authors: Abera Ayza, Devendra Kumar

Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). ✨ This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer

Imagine you are a chef trying to slice a block of soft aluminum cheese into perfect, smooth rounds. If your knife is dull, your speed is wrong, or you don't use enough oil, the cheese will tear, leaving a rough, jagged edge. In the world of manufacturing, this "cheese" is Aluminium Alloy 7075-T651 (a super-strong metal used in planes and cars), and the "knife" is a tungsten carbide cutting tool.

The goal of this research was to figure out exactly how to slice this metal so the surface comes out as smooth as glass, while using an eco-friendly "oil" instead of harsh chemicals.

Here is the breakdown of their experiment, explained simply:

1. The Problem: Heat and Roughness

When a machine spins a tool against metal, it creates a lot of heat—like friction when you rub your hands together too fast. This heat can damage the tool and leave the metal surface rough and bumpy. Usually, factories use synthetic chemicals to cool things down, but these can be toxic and bad for the environment.

The researchers wanted to see if Avocado Oil (yes, the kind you put on toast) could work as a cooling fluid. They mixed it with water to create a "flood" that would keep the metal cool and the cut smooth.

2. The Recipe: The "Taguchi" Method

Instead of trying every possible combination of speed, pressure, and oil (which would take forever and cost a fortune), the researchers used a smart statistical shortcut called the Taguchi Method.

Think of this like a master chef creating a "tasting menu." Instead of cooking 1,000 different meals to find the best one, they cook 16 specific, carefully chosen meals. By analyzing these 16, they can mathematically predict the perfect recipe without having to make every single variation.

They tested four main ingredients:

Spindle Speed: How fast the metal spins (like how fast you spin the cheese on the board).
Feed Rate: How fast the knife moves forward.
Depth of Cut: How deep the knife digs into the metal.
Avocado Oil Mix: How much avocado oil was in the water (0%, 3%, 6%, or 9%).

3. The Results: Finding the "Golden Ratio"

After running the 16 tests and measuring the smoothness of the metal (called Surface Roughness), they used a special math tool called Grey Relational Analysis to find the absolute best combination.

The Winning Recipe:
To get the smoothest possible surface (measured at an incredibly tiny 0.12 micrometers—that's smoother than a human hair!), they needed:

9% Avocado Oil: This was the most important "secret ingredient." It turned out that adding a specific amount of avocado oil made a huge difference in smoothing the cut.
Specific Speed and Pressure: They found a "sweet spot" for how fast the machine should spin and how hard the tool should press.

The Surprising Twist:
While the avocado oil was the star of the show for improving the cut, the machine's Cutting Speed was actually the biggest factor that caused roughness if it wasn't set correctly. It's like driving a car: even if you have the best tires (oil), if you drive at the wrong speed, the ride will be bumpy.

4. Did the Math Work?

The researchers used a computer to predict the perfect result, and then they ran one final test to see if the prediction was right.

The Prediction: 0.11 micrometers (smooth).
The Reality: 0.12 micrometers (very smooth).
The Error: Only about 9%.

In the world of science, a 9% difference is considered a "home run." It means their math model was very accurate.

5. The Bottom Line

This study proves that you don't need toxic chemicals to get a perfect finish on strong aluminum. By mixing a little bit of avocado oil with water and tuning the machine's speed and pressure just right, you can get a surface that is incredibly smooth.

Why does this matter?

It's Green: Avocado oil is biodegradable and non-toxic, unlike many industrial chemicals.
It's Safe: It reduces health risks for factory workers.
It Works: It produces a finish that is just as good, if not better, than traditional methods.

In short: The researchers found that with the right "recipe" of speed, pressure, and a splash of avocado oil, you can slice aluminum like a pro, leaving a surface so smooth it's almost invisible to the touch.

Technical Summary: Experimental Analysis of Surface Roughness in Turning Aluminium Alloy 075-T651 Using Avocado Oil-Based Cutting Fluid

Problem Statement
The machining of Aluminium Alloy 075-T651 (a material widely utilized in aerospace, automotive, and marine sectors due to its high strength-to-weight ratio) presents challenges regarding surface quality and tool life. Excessive heat generated during turning operations can degrade tool performance, alter workpiece dimensions, and compromise surface finish. Surface roughness is a critical constraint in process planning, directly influencing fatigue life, precision fits, and aesthetic requirements. Furthermore, traditional cutting fluids often pose environmental and health risks. This study addresses the need to optimize machining parameters to minimize surface roughness while utilizing an environmentally friendly, biodegradable, and non-toxic avocado oil-based cutting fluid.

Methodology
The research employed a systematic experimental design based on the Taguchi method integrated with Grey Relational Analysis (GRA) to optimize turning parameters.

Workpiece and Tooling: Experiments were conducted on a CNC lathe using Aluminium Alloy 075-T651 cylindrical bars (60 mm diameter, 500 mm length) and uncoated tungsten carbide inserts.
Cutting Fluid: An avocado oil-based emulsion was prepared using an ultrasonic vibration machine to mix avocado oil with distilled water. Four concentration levels were tested: 0%, 3%, 6%, and 9%.
Experimental Design: A Taguchi $L_{16}(4^4)$ $L_{16} (4^{4})$ orthogonal array was utilized to conduct 16 experiments. The study investigated four control factors, each at four levels:
1. Cutting Speed (900, 1000, 1100, 1200 rpm)
2. Feed Rate (85, 90, 95, 100 mm/min)
3. Depth of Cut (0.5, 1.0, 1.5, 2.0 mm)
4. Avocado Oil Concentration (0%, 3%, 6%, 9%)
Analysis Techniques: Surface roughness ( $R_a$ ) was measured using a portable surface roughness tester. Statistical analysis was performed using Minitab software (Version 19) via Analysis of Variance (ANOVA) to determine parameter significance and Signal-to-Noise (S/N) ratios. Multi-response optimization was achieved by converting the problem into a single objective using Grey Relational Grade (GRG).

Key Results

Optimal Parameters: The study identified specific parameter settings that yielded the minimum surface roughness. The optimal combination for minimizing $R_a$ $R_{a}$ was determined to be:
- Avocado Oil Concentration: 9% (Level 4)
- Cutting Speed: 900 rpm (Level 1)
- Feed Rate: 95 mm/min (Level 3)
- Depth of Cut: 1.5 mm (Level 3)
- Note: The abstract mentions a specific optimal result of 0.12 μm achieved with these settings.
Parameter Significance (ANOVA): The ANOVA results revealed that Cutting Speed was the most significant factor affecting surface roughness, contributing 76.78% to the variability. The Avocado Oil concentration was the second most significant factor at 11.45%, followed by Depth of Cut (2.67%) and Feed Rate (2.82%). All factors were found to be statistically significant with P-values less than 0.05.
Grey Relational Analysis: The GRA confirmed that the 9% avocado oil concentration had the strongest influence on the Grey Relational Grade, indicating its superior impact on the overall performance characteristics compared to other parameters. Experiment 16 (corresponding to the optimal levels) achieved the highest GRG rank.
Validation: A confirmation test was conducted using the derived regression equation ( $R_a = 7.12 - 0.005CS - 0.1FR - 0.07DoC + 0.788AO$ ). The predicted surface roughness was 0.11 μm, while the experimental value was 0.12 μm. This resulted in a percentage error of 9.09%, which the authors deem statistically acceptable (below 10%), validating the regression model.

Significance and Claims
The paper claims that the formulated avocado oil-based cutting fluid is a viable and effective substitute for conventional cutting fluids in the turning of Aluminium Alloy 075-T651. The study concludes that:

Performance: The optimized use of 9% avocado oil emulsion significantly reduces surface roughness, achieving a value as low as 0.12 μm.
Environmental and Economic Benefits: The use of avocado oil offers potential advantages in reducing occupational health risks and lowering waste treatment costs due to its high biodegradability and non-toxic nature.
Methodological Validation: The integration of the Taguchi method with Grey Relational Analysis proved effective in identifying optimal machining parameters with a reduced number of experimental runs.

The authors modestly suggest that while the current study focuses on turning, future work should extend to other machining processes (grinding, drilling, milling) and investigate additional variables such as cutting forces, friction coefficients, and temperature to further validate the fluid's effectiveness across the manufacturing industry.

1. The Problem: Heat and Roughness

2. The Recipe: The "Taguchi" Method

3. The Results: Finding the "Golden Ratio"

4. Did the Math Work?

5. The Bottom Line

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