The Effect of Cutting Nose Radius on Surface Roughness - Coursework Example

Engineering Student’s Name Institutional Affiliation The Effect of Cutting Nose Radius on Surface Roughness Introduction The current generation of consumer has developed the need for high quality metal cutting products with desirable tolerance and surface roughness. This has driven the metal cutting industry to come up with advanced techniques of producing high quality metal products. Metal cutting is the art of removing a metal from a work piece as chips with the purpose of getting products of the desired metal size, shape and roughness. This activity involves various processes such as drilling, milling, and sawing. Manufactures around the world have evaluated different processes that can be used to improve the quality of the finished products using by application of engineering principles associated with metal cutting. This report specifically seeks to examine the relationship between three major aspects of metal cutting that have got impact on the final metal product. In that case, the relationship between the radius and the cutting speed will experiment to see their effect on the roughness of the surface of the end product. Definition of Terms The quality of a finished product is determined by how close the product meets the specifications. Surface roughness is the most commonly index used to determine the surface quality in the manufacture of the products. Surface roughness is the measure or degree of smoothness in a machined product. It can also be defined as the fine irregularities of a work piece produced by a cutting tool. Surface texture is the nature of surface as determined by surface roughness, lay and waviness. Lay is the direction of the dominant surface patterns produced and determined by the cutting method used while waviness is the measure of surface irregularities within a measure that is usually greater than that of surface roughness. The cutting speed is the rate at which the cutting tool impacts or penetrates the material (Mikell, 2011).These and other terms are going to be useful in illustrating and discussing the subject matter. The effect of cutting speed and radius size on the resultant surface roughness is going to be well demonstrated using two significant graphs. The first graph is shall be an illustration of the effect of the cutting speed on the roughness of the surface when a smaller radius of 0.2 mm is used in cutting while the second graph shall illustrate the same effect when a radius of 1.2 mm is used. Fig 1: A graph representing changes of surface roughness (Ra) obtained from the instrument against cutting speed (v) when smaller cutting nose radius used. Figure 1 Surface Roughness (Ra) Cutting Speed (v) Fig 2: A graph representing changes of surface roughness (Ra) obtained from the instrument against cutting speed (v) when larger cutting nose radius used. Figure 2 Surface Roughness (Ra) Cutting Speed (v) Discussion of Results The results show two different cutting mechanisms of 0.2 mm radius and 1.2 mm radius but with the same cutting speed. In Fig 1, the mechanism involves a smaller radius as compared to the illustration in fig 2. The resultant effect is that the surface roughness increases with a smaller radius. This produces a positive gradient graph with the values on the vertical axis (those representing the surface roughness) showing an increase. The surface roughness (Ra) has increased from 3.150 um to 3.166 um as the speed increases from 36.7v to 212v. The graph in figure 2 involves a larger radius cutting material. The resultant effect is that the surface roughness reduces with the larger radius. The graph is seen as a negative gradient graph with the values on the vertical axis (surface roughness) showing a decrease. The surface roughness reduces with 2.811 um to 1.793 um as the speed increases from 36.7v to 212v. This means that the smoothness of the material increases when a larger radius cutting tool is used. The illustration in these diagrams reveals the relationship between the radius size and the surface roughness. When the speed is constant, in the two illustrations, the changes in the radius affect the roughness of the surface. A larger radius produces a smoother surface as compared to a smaller surface. In comparison to the results published in machining handbooks, the effect of roughness of the surface is explained in reference to the cutting speed. The cutting speed is said to increase the smoothness of the final product. When the cutting speed is increased, the surface roughness of the material is reduced (Mikell, 2011). At a low cutting speed, there is a large quantity flow of fibers that are cut which cause the large surface roughness. At a high speed, matrix materials deform at a lesser extent. The size of the radius is a controllable factor that affects the surface roughness. However, other factors that affect surface roughness are difficult or cannot be controlled. These include factors as cutting speed, feed, tool vibration, tool wear and degradation. The interaction of these factors influence the quality of the finish produced. When the surface does not meet the specifications of smoothness the above parameters are adjusted by inserting a new work piece into the machine centre for machining (Schmid & Kalpakjian, 2008). It is also important to note that the effect of major variables involved in determining the surface roughness depend on the surface of the material as it changes significantly. For instance, it is said that highly ductile materials tend to induce a build-up of edge on the tool nose causing degradation of surface in terms of roughness. Brittle materials create challenging machining conditions as a result of fractures making the surface roughness to increase. The aluminum alloy, the hardness of the material improves the surface roughness. At the same time, very hard surface material cause vibrations to the tools that generate the rough surface finish. For these reasons, the major variables can be independently controlled so as to obtain the desired surface roughness. For example, the cutting speed should be set at a higher speed to prevent the build-up from occurring at the tool nose (Mikell, 2011). The feed rate is usually set at a lower level to improve the surface roughness whereas the cutting depth is usually set to be small so as to decrease the machining together with the resistant cutting force from the material. Other research have also proved the effectiveness of a short tool length in providing a good surface roughness and only slight improvements can be made by controlling the cutting parameters (Schmid & Kalpakjian, 2008). Industrial Applications Many industrial applications require surface roughness information so as ensure proper functioning of their end products. It requires that they conduct a surface metrology for them to design the most appropriate surface roughness to be used in designing various products. For instance, positively and negatively skewed surfaces symmetries have a high bearing ratio in distributing the high fuel pressure load and a uniform valley lay that distributes fuel effectively. These eliminate failures due to part to part contact via the lubricant film (Smith, 2013). Directional and random surface textures on the other hand are characterized by tool arks or grinding patterns that are arranged in line and are directional in nature. These surfaces are used in automotive camshaft rollers that connect the rotating action of the valve to the reciprocating valve. The random surface textures maintain a predictable oil film, keeping the rollers form contacting cam, hence, resisting wear (Smith, 2013). Residual tensile stress and residual compressive stress surfaces make parts susceptible to premature fractures and failure when they are stressed repeatedly. This technique is applied in making springs of various types (Smith, 2013). This is especially seen in the high performance automotive valve springs which are the most highly stressed. Mixed bags comprises of compatible surfaces but different functions. Because of surface specification, the tolerance between the punch and dies can be decreased and maintained, the wall thickness of the can be controlled and reduced. All these functions are dependent on the directionality and control of the surface finish on both components (Smith, 2013). Mixed bags can therefore be useful in facilitating these activities. Conclusion The analysis of the two graphs reveals components that are significant in coming up with the desired shape objects. Changes in one variable may lead to a change in another variable which may resultantly affect the surface roughness of the final product. The study of these changes gives an impression of how manufacturers can make use of such illustrations to make quick decisions on the product sizes and shapes that they intend to make. Generally, the increase or decrease in speed of the cutting tool changes the surface roughness to a certain level but when the radius of the cutting tool is altered, the increase or decrease in speed becomes insignificant in determining the surface roughness of the product. This is a very important conclusion from figure 1 and 2 that reveals the behavior of the cutting mechanisms in determining the surface roughness of a substance. References Mikell, P. G. (2011). Principles of Modern Manufacturing, SI version, 4th edition, Wiley & Sons Schmid, S. R & Kalpakjian, S. (2008). Manufacturing Processes for Engineering Materials, 5th edition, Prentice Hall Smith, G. T. (2013). Industrial metrology: surfaces and roundness. Springer Science & Business Media. Read More