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In this study, three types of material which are aluminum, brass, and stainless steel have been chosen. Aluminum is widely used in many applications. The advantages of aluminum are corrosion resistance, ease of machinability and high strength to weight ratio and easily to be forming. Aluminum widely used in many applications and industries. For examples, aluminum is used in packaging such as drink cans. Furthermore, aluminum also can be used as material for structural parts in aerospace and engine parts in automobile industries.
Brass is an alloy with combination of copper and zinc. Addition of zinc to copper is able to enhance the strength of brass. Brass is most suitable material to manufacture products due to its good strength, ease of machinability and high corrosion resistance. Brass is been used in architecture, plumbing hardware, fasteners and marine hardware. Besides that, brass also is used in radiator and tanks due to its high thermal conductivity.
Stainless steel is a steel alloy with high corrosion resistance and the predominant element in stainless steel is chromium. Others alloying element are nickel, aluminum, nitrogen, sulfur, columbium, manganese, silicon, titanium, copper, and molybdenum. Chromium in stainless steel is able to increase or enhance corrosion resistance of it. Due to the high corrosion resistance, stainless steel is widely used as household hardware, platform accommodation in oil and gas sectors and surgical equipment in medical sectors. Besides that, stainless steel also is used in high temperature gas turbine, aircraft and nuclear power generating unit.
Milling is a cutting process of cutting away material of a workpiece by using multiple tooth cutters which is a cutting tool that produces a number of chips in one revolution. It is able to create a variety of features such as holes, pockets, slots and three dimensional contours. Milling process is able to produce different types of surface finish with different machining parameters. Machining parameters such as depth of cut, spindle speed and feed rate. Optimized machining parameters are able to save the production cost and time.
Surface finish is surface texture or as known as characteristics of surface. In industries, the quality of surface finish is very important. This is because quality of surface finish is able to affect the quality of product. Therefore optimized machining parameters are able to produce high quality of surface finish of machined workpiece. Surface finish also will affect the production cost in manufacturing industries. Manufacturing industries require high demand on the quality of surface finish but require low machining cost. Therefore, optimized machining parameter is very important in manufacturing industries.
Machinability of a material is defined as the ease of the material to be machined. Machinability is depending on surface finish, tool life, force and power required and chip formation characteristics. Therefore, material with good machinability as known as the material is machined with low cutting force and power, good surface finish and minimum tool wear.
1.2 Objective Project
The objectives in the project are:
To analysis the machinability and surface finish of different types of material with high speed cutting tools using conventional milling machine.
To study the effect of machining parameter on quality of surface finish of different material.
1.3 Scope Project
This project focuses on how to get optimized machining parameter by using conventional milling machine to evaluate the machinability and surface texture of different materials with high speed steel cutting tools. Surface finishes of different types of material are obtained by using different types of machining parameter which are spindle speed and feed rate. Materials which have been used in this study are stainless steel, aluminum and brass.
1.4 Problem Statement
In manufacturing industries, good quality of surface finish is important to products. Different types of material require different machining parameters to produce a good quality of surface roughness. By finding a set of optimized machining parameter for different types of material, this is able to save the cost and time. Manufacturing industries are able to save the cost and time by using the optimized machining parameters for different types of material.
A good quality of surface finish able to decrease friction during contact of two surfaces, increase efficiency and wear resistance of two workpieces. Hence, to produce good quality of surface finish, optimized parameters such as cutting speed and feed rate for different materials must be obtained.
1.5 Problem Analysis
From the problems of this project, the optimized machining parameters such as feed rate and spindle speed must be evaluated for getting a good surface finish. Materials in this project are aluminium, stainless steel and brass. Therefore, different optimized machining parameters for different types of material will be evaluated in this project for getting a good quality of surface finish.
Machinability can be defined as the metal or material can be machined into an acceptable range of surface finish. Machinability also can be determined in four factors which are cutting power is required, surface finish, tool life and chips are produced. Therefore, material which is ease of machinability is the material can be machined easily by low cutting force or power, good quality of surface finish is produced on the machine surface, do not wear the cutting tool which is used during the machining process and good curls or chip breakdown of chips. Method to evaluate the machinability of material is using the surface roughness method in this final year project. When lower value of surface roughness, the better of machinability of material. Material which is high strength or toughness is difficult to be machined and requires high cutting force or power to machine them. While for material which is low strength and toughness is more easily to be machined than high strength material (M.Ramesh 2011).
Surface finish is defined as surface texture of machined surface. In evaluation of the quality of machined products, surface roughness is very important (Suleiman Abdulkareem, Usman Jibrin Rumah and Apasi Adaokoma 2011). In manufacturing industry, quality of surface finish will affect the performance of product. Good quality of surface finish is able to help product to achieve high efficiency. In an engine manufacturing company, good surface finish of piston is able to keep the horse power of the engine in high efficiency while low quality of surface finish will decrease the efficiency of the engine. Good quality of surface finish is able to increases the wear resistance of the product. In evaluation of the quality of machined products, surface roughness is very important. Rougher surface or low quality of a product will wear more quickly and have high friction coefficient compare with good quality of surface finish (M. Ramesh et al 2011). Furthermore, good quality of surface finish is able to reduce the friction between two components during the assembly of products.
Machining parameters which will affect the quality of surface roughness are:
Depth of cut
Geometry of chip formation
In term of tool geometry, as the radius of tool increases and rake angle increases, the better quality of surface finish of machined surface. Besides that, surface roughness depends on the friction which is created between the chips formed and tool surface during milling process. While for cutting fluid, it is able to reduce the friction of coefficient and the size of built up edge chips during machining process. An increase in feed rate and depth of cut and a decrease in spindle speed may results high surface roughness of the machined surface. Surface roughness depends on the feed rate because at a critical value of feed rate, the size of built up edge is negligible. When the surface speed reach at the critical value of surface speed, the value of surface roughness reduces greatly because of the reduction in the size of built up edge. (Mathew A. Kuttolamadom, Sina Hamzehlouia, M. Laine Mears 2010)
Figure 2.1: standard terminology to describe surface finish.
There are some following guidelines in surface finish terminology are:
Roughness is defined as the height, width, and distance irregularities on small scale.
Lay is defined as the propagation of the direction of predominant surface pattern and normally it can be determined by naked eyes.
Flaws are random irregularities which are cracks, tears, scratchs and so on.
Roughness is charaterized by two methods. The arithmetric mean value and defined as:
The root mean square roughness is defined as:
'n' is the number of measurement points and '' is the surface deviation at measurement point 'i.'
Aluminum is non-ferrous alloy and alloying elements in the aluminum are copper, magnesium, silicon, manganese, and zinc. Principal ore of aluminum is bauxite and bauxite is a hydrous aluminum oxide with other oxides. The advantages of aluminum are low density which is 2.7g/cm3, high electrical and thermal conductivities, corrosion resistance, high ductility, nonmagnetic, good machinability and ease of formability. Due to the advantages of aluminum, aluminum is used in food packaging as aluminum cans. Besides that, aluminum also has been used in aerospace industry, automobiles industry and electrical applications (Serope Kalpakjian 2010)
Brass is an alloy which is a combination of copper and zinc. When the percentage of zinc is 35%, the brass is known as alpha phase condition. Alpha brass is soft, ductile and easily cold worked.
This chapter will start by describing the detail of methodology to make this project is in working well and complete. Aluminum, brass and stainless steel are selected as the material. Surface roughness of different types of material will be created by using high speed cutting steel end mill and conventional vertical milling machine. Besides that, different machining parameters will create different value of surface roughness on test specimen. To determine the optimized machining parameters to produce good quality of surface finish in milling process and evaluate the machinability and surface roughness, the methodology is divided into several parts.
Conventional Vertical Milling Machine
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Figure 3.2: Conventional Vertical Milling Machine
This conventional vertical milling machine is JTM 1050VSE in machine lab. There are some functions of the conventional milling machine need to be practiced and understood before conduct the experiment. Hand brake is used to stop the spindle after stop button of conventional vertical milling machine is pressed off. Digital readout is able to display the data of x, y, and z axis in the milling machine. Digital readout is able to help in accuracy of conventional vertical milling machine in milling process. Table is a platform for test specimen to be machined and lock tightly with vice. Hand wheels are used to move the table manually in the x, y and z direction. Control unit is used to alter the rotational direction of cutter. Besides that, there are power button to turn on the conventional vertical milling machine and stop button to turn off the conventional vertical milling machine. There is a emergency button to stop the conventional milling machine to stop immediately.
DATA OF SURFACE ROUGHNESS MEASURING
Three different types of material which are aluminum, brass and stainless steel are used in this project. First, three 12mm diameter long rods with different types of material are cut into 15mm rods. The cutting machine is from the fabrication lab and it is call as Bench Saw Machine. For aluminum, brass and stainless steel, there are about forty five test specimen is required in this project. While for aluminum, brass and stainless steel rods can be obtained from the welding lab. After that, conventional milling machine is used to machine these test specimens in the dimension of 15mm x 12mm x 8mm. The conventional milling machine in the testing is a conventional vertical milling machine (JTM 1050VSE).
Coordinate of the test specimen is set by using edge finder and a high speed steel end mill is installed into the spindle of the conventional vertical milling machine. Safety equipment such as safety goggles and safety boot are worn before handling the conventional milling machine. 15mm rod is put at the vice and is fixed at a position. After that, edge finder is use to set the coordinate of the test specimen for an accurate dimension. A 12mm high speed steel end mill cutting tool is installed into the spindle of conventional milling machine for machining the top and bottom surface of test specimen into flat surfaces. Apply cutting fluid during machining process to cool down the temperature and flush away the chips have been produced. These steps are repeated for all aluminum, brass and stainless steel rods.
The experiment is carried out with a conventional vertical milling machine and it model is JTM 1050VSE with a high speed steel end mill cutting tool. After the forty five test specimens are prepared, the milling process will be started. Before the milling process is started, safety equipment such as safety boots and safety goggles is worn for personal safety purpose. This is because safety goggles can protect operator eyes from dangerous while safety boots can prevent slip occurs and heavy object drops on your feet. Edge finder is used for setting the coordinate of test specimen before the milling process is started. Cutting tool which is chosen in this milling process is a 12mm diameter high speed steel end mill. Install it into the spindle of conventional vertical milling machine. There are three machining parameters which are spindle speed, feed rate and depth of cut in this experiment. Spindle speed and feed rate are set as variable machining parameter. The values of spindle speed are 1000rpm, 1200rpm, 1400rpm, 1600rpm and 1800rpm. For the values of feed rate are 37mm/min, 141mm/min and 240mm/min. Depth of cut is set as constant machining parameter which is 0.2mm for three different types of material which are aluminum, brass and stainless steel in this experiment. Cutting fluid is applied during milling process to cool down the temperature at cutting zone and improve tool life. This is because temperature will be developed during milling process. Besides that, cutting fluid is able to flush away the chips which is created during milling process and prevent chips from interfere with the milling process. Remove the test specimen carefully and place into the box. Prevent any contact on the machined surface of the test specimen.
Surface Roughness Test
The surface roughness test is conducted by using Mitutoyo surface tester. Mitutoyo surface tester instrument is used to analysis the surface roughness of test specimens. The parameters of surface roughness which are surface roughness average in micrometer, Ra and maximum surface roughness, Rmax. Do a calibration on Mitutoyo surface analyzer by using references. Fix the position of test specimen by using a jig. Press the power button of Mitutoyo surface tester. The detector stylus traces is placed on the machined surface of test specimen for measurement. The start button of Mitutoyo surface tester is pressed to start the surface roughness test. The detector stylus will begin the measurement of surface roughness of the test specimen. The Mitutoyo surface tester will start the calculation of the surface roughness value. The detector will return to its original position after measurement has done. Mitutoyo surface tester will display the measured data on the screen. Print the measured data or result by pressing the print button. Surface roughness test is done until all test specimens have been tested.
Figure 3.2: Mitutoyo Surface Tester