LECTURE 9.pptx
- 1. MUHAMMAD WAQAS RAFIQUE LECTURE # 9 METROLOGY & QUALITY ASSURANCE (Lab)
- 2. EXPERIMENT # 8: To determine the surface roughness of sample with the help of surface texture/ Surface Analyzer.
- 3. Surface finish is basically surface presence and the three characteristics that define the surface finish are waviness, surface roughness and lay. The factor that is responsible for transportation of developed layers and produces friction is surface texture. Surface finish is quality control important factor as surface finish produces great effect on precision location, erosion, exhaustion, wear and rubbing of manufactured parts. Surface Finish:
- 4. Surface roughness often shortened to roughness, is a component of surface texture. It is quantified by the deviations in the direction of the normal vector of a real surface from its ideal form. If these deviations are large, the surface is rough; if they are small, the surface is smooth. Surface roughness
- 5. Waviness is the measurement of the more widely spaced component of surface texture. It is a broader view of roughness because it is more strictly defined as "the irregularities whose spacing is greater than the roughness sampling length". Waviness should also be distinguished from flatness, both by its shorter spacing and its characteristic of being typically periodic in nature. Waviness
- 6. Lay is the term used to describe the dominant pattern on a surface and the orientation of that pattern. Lay is generally produced by the manufacturing process and can be parallel, perpendicular, circular, crosshatched, radial, multi-directional, or isotropic (non-directional). We will discuss the symbols and interpretation of lay in the Symbols section below. Lay
- 8. Rt, total height of the profile: height between the deepest valley and the highest peak on the evaluation length. Rp, maximum profile peak height: height of the highest peak from the mean line, defined on the sampling length. Rv, maximum profile valley depth: depth of the deepest valley from the mean line, defined on the sampling length. Rz, maximum height of the profile: this parameter is frequently used to check whether the profile has protruding peaks that might affect static or sliding contact function. Ra, arithmetic mean deviation of the assessed profile: defined on the sampling length. Ra is used as a global evaluation of the roughness amplitude on a profile. It does not say anything on the spatial frequency of the irregularities or the shape of the profile. Ra is meaningful for random surface roughness (stochastic) machined with tools that do not leave marks on the surface, such as sand blasting, milling, polishing Amplitude parameters
- 9. Since Ra represents average values, and Rz is based on maximum values, Rz is almost always greater than Ra. The difference between the two parameters will depend on the uniformity of the roughness profile. If one value is known, it is possible to estimate a maximum for the other, but this approximation should not be used for critical applications. As a rough rule, if only Rz is known, Ra can be approximated by dividing by a factor of 7.2. If Ra is known, the value of Rz for the same surface can be up to 20 times higher and a little more difficult to approximate.
- 10. There are several ways to measure the smoothness of a surface but Ra (Average Roughness) and RMS (Root Mean Square) are the most commonly used. Ra gives a very simple view by measuring the difference in peaks and troughs along the surface and creating a straight line whereas RMS looks creates a broader image by also looking at the width of the peaks and troughs.
- 12. PARTS Construction: This is a portable device that contains touchscreen and its housing that is made up of rubber possess the quality of impact resistant. The explanation of this device fundamental components are given below. Measurement Button: Alongside the touch screen, the measurement button is present there that is responsible for machine starting. Lift/Lower: The mechanism of stylus lift is present in this machine which is about 50mm and it is capable for rotation at ninety degrees and can place into 70mm deeper bores. Anti-Slip Feet: The device stabilizes by Anti-Slip Feet on curved or flat surfaces. Comfort Grip The operator grips easily when settings are going to change and readings are to be noted down. Rubberized Housing: The gripping gets support by rubberized housing.
- 14. • The assessment length is selected at first and set the precision. • Put the stylus on surface and then turn on the measurement button. • The stylus on surface begins to move automatically. • On touchscreen, there will be creation of profile within some seconds along with • surface roughness different parameters. PROCEDURE
- 15. Applications: • Heavy industries like that of sheet steel, turbine shafts as well the turbine blades use this device. • It is also used in automotive industries for testing surface smoothness of crankshafts, gears and blocks.