Materials and Manufacturing - Surface Roughness in Turning - Research Paper Example

Surface Roughness in Turning Student University Abstract Surface roughness is one of the key components considered in the manufacturing industry. In simple terms, surface roughness can be referred to as surface texture. In the determining the roughness of equipment, the deviations of the normal vector relative to its ideal direction is considered. It is therefore important to note that, the larger the deviations, the rougher the surface and vice versa. When the surface is rough, high friction is experienced which results to faster wear to the surfaces. In any operation dealing with machine, the turning process is basic. In most cases, it involves a rotating part and a cutting tool placed parallel to the rotating axis. This is vital mostly when reshaping different metals as well in reducing the overall cross-section area in the industry Table of Contents Abstract 2 Abbreviations 4 Introduction 5 Purpose of the experiment 6 Equipment required 6 Materials needed: 8 Procedure 8 Calculations 9 Table 1: collected data 10 Analysis and Discussion of collected Data 10 Discussion and analysis 12 Conclusion 12 Reference 13 Abbreviations V cutting speed Ra surface roughness N spindle speed F feed L low cutting speed H high cutting speed Work piece diameter. Surface Roughness in Turning Introduction Surface roughness is an important factor to consider in any instrument. This is because; the roughness of a surface will dictate the coefficient of friction. The rougher the surface, the higher the frictional forces hence high chances of wear. As the wear interferes with the integrity of the instrument it can be rendered useless and never be used anymore. This can impact negatively on the economy. On the other hand, when the wear is so severe, the use of the instrument can be dangerous. Therefore, it is important to determine the best surface roughness that can be economical to use and also durable enough to meet the desired requirements. In investigating the surface roughness of an instrument, a number of factors have to be considered. Some of the factors that influence the surface roughness of any instrument may include; feed per revolution, the cutting speed and the radial depth of the cut. In this experiment, the main objective is to determine the influence of the cutting speed using different sizes of nose radii on the surface roughness. The feed rate is to be kept constant so that the cutting speed remains the only parameter to be considered. The depth of cut is only specified so as not to interfere with the result to be obtained in the investigating the effect of the cutting speed to the surface roughness. Therefore, the whole experiment will be based on investigating the effect of cutting speed on the surface roughness. Also, the effect of varying the size of the nose radius to the surface roughness is closely monitored. Surface can be determined manually or mechanically. The key factors that affect the roughness of a surface are, the feed rate, the cutting speed and also in most cases the radial depth of cut. In investigating the factors that affect the surface roughness, it is important to identify the factor to be investigated so that the other factors that affect the surface roughness are kept constant so that only one of the factors is investigated to avoid obtaining confusing results. In this experiment, the cutting speed is the parameter to be considered. Therefore, the feed rate and the radial depth of cut have to be kept constant throughout the experiment. The effect of the size of the nose radius to the surface roughness is also considered in this experiment. Therefore, the two key parameters are conclusively covered in this experiment. The effect of each should also be illustrated properly using graphs for proper conclusions to be reached at comprehensively. Purpose of the experiment The purpose of the experiment was to examine the effects of parameter change in resultant surface roughness. Equipment required The following are the names and pictures of each of the equipment used in the determining of the effects of changes in parameter to the surface roughness. Lathe Surface roughness comparator and Surface-finish measuring instrument Two sharp single edge carbide-cutting tools with suitable nose radii Materials needed: One cylindrical carbon steel work piece material of approx. Ø50 mm X 200 mm From the literature, the surface roughness is the arithmetic mean of the roughness throughout the cut surface. The graph of surface roughness against the distance of the cut surface is as shown in figure below. Procedure i. A low cutting speed of 350 rev/min and a high cutting speed of 2000 rev/min was chosen. ii. The equation was applied that relates spindle speed (N) in rev/min to cutting speed (v) in m/min and work piece diameter (Do) in mm. For this task Do is 45 mm. iii. A feed, f, of 0.24 mm/rev was chosen. iv. The length of the rotational work piece material was divided into four sections, each approximately 50 mm long. v. Using a lathe the following tasks were performed keeping the depth of cut maximum 2 mm: a) The work piece was clamped on the chuck such that two sections on the other end can be machined. b) Using a cutting tool with sharp nose radius (0.2 mm) section 1 was turned with a low cutting speed. c) Section 2 was turned with a high cutting speed and the same cutting tool. d) The work piece was clamped from the other end such that two sections on the other end can be machined. e) A larger cutting tool nose radius (1.2 mm) was used and section 3 turned with the same machining parameters used for section 1. f) Section 4 was turned with the same machining parameters used for section 2 but with the larger cutting tool nose radius. vi. The roughness of each surface machined was measured using the Surface Roughness Measuring Instrument. Calculations Determining the cutting speed V Rearranging the equation; Given, For low cutting speed, Therefore, For high cutting speed, Therefore, The experimental results obtained were as follows; Table 1: collected data Nose radius Ra1 Ra2 Ra3 Ra average / 0.2 L 3.855 3.578 3.718 3.717 0.2 H 3.385 3.257 3.4 3.348 1.2 L 3.397 3.178 3.754 3.442 1.2 H 1.935 1.923 1.954 1.937 Analysis and Discussion of collected Data To effectively analyze the obtained data, a line graph of surface roughness, Ra, against cutting speed, V, was used. The size of the nose was also factored in. The graphs obtained when a smaller radius and a larger radius is used respectively are shown below. The trend of the graph should be properly determined for easy analysis. The changes of the cutting speed with their corresponding values of surface roughness should be taken into account when analyzing the results. Figure 1: Surface roughness, Ra, against cutting speed, v, when small cutting radius is used Figure 2: Surface roughness, Ra, against cutting speed, V, when larger cutting radius is used Discussion and analysis From the obtained line graphs, it can be seen that the surface roughness decreases with increase in cutting speed although the decrease is non-linear. The feed rate is kept constant throughout the experiment. At a low cutting speed the surface roughness is generally higher than at a high cutting speed. Considering figure 1; the highest value of the surface roughness is obtained when the cutting speed is the lowest, 49.5 m/min and lowest when the cutting speed is at 237.5m/min. The surface roughness decreases linearly from point A to point B, it then increases linearly to point C and consequently decreases at varying rates to the lowest point E. The graph satisfactory represents the values of the surface roughness at the low and high cutting speeds. Considering figure 2; the highest value of the surface roughness is obtained at a cutting speed of 143.5 m/min and the lowest value is obtained at a cutting speed of 237.5m/min. The surface roughness decreases linearly from point A to B, then it increases at a constant rate from point B to C, thereafter, the surface roughness decreases linearly with increase in speed from point C to point D. The surface roughness value increases at a very low rate from point D thru E to point F. Comparing the values of surface roughness from the two figures, the values are higher when a small cutting radius is used than when a larger cutting radius is used. Conclusion In conclusion, the surface roughness of an instrument is dependent on the cutting speed as well as the size of the cutting radius. The surface roughness value is generally high at a low cutting speed and low at a high cutting speed. When small nose radius is used, the surface roughness values are higher than the values obtained when a larger nose radius is used. When feed rate is kept constant, it is easier to accurately determine the effect of the cutting speed on the surface roughness of an instrument (Koepfer & Chris, 2010). It is therefore important to accurately monitor the cutting speed when trying to achieve a specific allowed surface roughness. It is also important to point out that there are other factors such as the feed rate and the cut depth that should also be considered so as to achieve a certain value of surface roughness. The roughness of an instrument affects the durability of the same instrument because the higher the roughness the higher the friction coefficient. This results to high frictional forces when the instrument is in contact with another instrument hence as a result, the instrument is bound to wear earlier than a smoother surface, therefore, a rough surface is less durable than a smoother surface which can be uneconomical in the manufacturing industry. Reference Koepfer, P. Chris, R. (2010). Hard Turning as an Alternative to Grinding, Production Machining. Read More