698 IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, VOL. 58, NO. 3, MARCH2009 Stand-Alone Surface Roughness Analyzer Saeid Moslehpour, Member, IEEE, Claudio Campana, Devdas Shetty, and Brian Deryniosky Abstract—This paper details the design and implementation of a noncontact surface roughness probe from a PC-based data- acquisition system to a stand-alone measurement instrument system. A Cadence layout for the fabrication of the printed circuit board (PCB), which interfaces and drives the surface roughness probe, was used to prototype this project. Index Terms—Cadence layout, light-scattering techniques, optical, portable roughness evaluator, surface roughness measurement. I. I NTRODUCTION T HE DEMAND for higher product quality requires contin- uous monitoring of various processes and product condi- tions. It is obvious that one of the essential aspects of quality control in many manufacturing operations is the measurement of surface finish quality of the machined parts during the man- ufacturing process. Variation in the texture of a critical surface of a part influences its ability to resist wear and fatigue. Many techniques have been developed to measure surface roughness, which vary from the conventional profilometer to the recently developed laser diffraction technique. An attempt is made in this paper to present a simple, reliable, and robust way of evaluating the roughness of an engineering surface, regardless of the workpiece orientation. The research has wide applica- tions in manufacturing industries. This paper illustrates surface roughness characteristics, measurement techniques, proce- dures, surface analyzer probe, a measurement algorithm, soft- ware, the complete system, and actual measurements. II. SURFACE ROUGHNESS CHARACTERIZATION A traditionally machined surface consists of many compo- nents from different sources that are generated during the man- ufacturing process. It is the combination of these components that compose surface texture. Fig. 1 illustrates the components of a turned surface. They are roughness, waviness, profile, errors of form, flaws, and lay. Roughness: As the material is cut, a spiral or helix pattern is formed on the part surface. This commonly known tool mark is called the roughness com- Manuscript received February 18, 2007; revised June 19, 2008. First pub- lished October 7, 2008; current version published February 9, 2009. The Associate Editor coordinating the review process for this paper was Dr. George Giakos. S. Moslehpour and C. Campana are with the University of Hartford, West Hartford, CT 06117 USA (e-mail: moslehpou@hartford.edu; campana@ hartford.edu; Shetty@ltu.edu). D. Shetty is with the College of Engineering, Lawrence Technological University, Southfield, MI 48075-1058 USA (e-mail: Shetty@ltu.edu). B. Deryniosky is with the University of Hartford, West Hartford, CT 06117 USA, and also with Sikorsky Aircraft, Stratford, CT 06614 USA. Color versions of one or more of the figures in this paper are available online at http://ieeexplore.ieee.org. Digital Object Identifier 10.1109/TIM.2008.2005820 ponent of the surface. The roughness height is called the amplitude, which is caused by the depth of the cut. The roughness spacing repre- sents the wavelength, which is caused by the rotation speed and the feed rate of the cutting tool. The most common representation of rough- ness uses the notation R a , which represents the arithmetic average roughness value. Waviness: Waviness is caused by vibration. The source of vibration could be either from the environment, indicating that the lathe is not perfectly isolated, or from the lathe itself, indicating possible bear- ing wear, bearing condition, gearbox clamping, or other problems. Profile: During the machining process, all the compo- nents are actually superimposed over each other, creating a highly complex surface. The combi- nation of these components, namely, roughness, waviness, and errors of form, is called the total profile, as schematically illustrated in Fig. 1. Lay: Lay is the direction of the predominant surface pattern, which is generally determined by the production method used. When the profilometer is used to measure surface finish, the stylus tip has to traverse at 90 ◦ to the lay. In all, surface texture can provide information about the man- ufacturing process. In metal machining, for example, surface texture is generated by the “tool noise” and is related to the feed rate. However, it is also affected by many other variables such as vibration, cutting fluid quality, and tool wear. Therefore, the measurement of surface texture components can poten- tially provide diagnostic information for process control appli- cations. Techniques for surface roughness measurements are discussed next. III. MEASUREMENT TECHNIQUES A. Stylus Technique This technique involves contact with the surface (of the sample) in question, which could potentially be harmful to the surface (the stylus is typically made from a harder material such as tungsten). The stylus is drawn over the sample to detect and record variations in surface geometry. Surface statistics can then be calculated from the profile record. To quantify the aver- age topography, many statistical parameters and functions have been developed. The most common parameter is the arithmetic average roughness R a , given by the following equation, where L is the sampling length: R a = 1 L |y(x)| dx. 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