Metrology_linear - Engineering Metrology Linear...

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Engineering Metrology Linear measurements Dr. Belal Gharaibeh 10/7/2011 1 Dr. B. Gharaibeh 10/7/2011
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Introduction modern manufacturing can produce features that are more accurate than we can measure by hand, therefore we need tools to assist us. • These tools allow us to quantitatively evaluate physical properties of objects. • EVERY industry uses these tools to some extent, for example, - machine shops - tailors - dentists - automotive manufacturers - etc. 2 Dr. B. Gharaibeh 10/7/2011
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Definitions Assembly - the connection of two or more separate parts to make a new single part. Basic Dimension - The target dimension for a part. This typically has an associated tolerance. Dimension - A size of a feature, either measured, or specified. Dimensional Metrology - The use of instruments to determine object sizes shapes, form, etc. Limits - These typically define a dimensional range that a measurement can be expected to fall within. Machine Tool - Generally used to refer to a machine that performs a manufacturing operation. This is sometimes confused with the actual cutting tools, such as a drill bit, that do the cutting. 3 Dr. B. Gharaibeh 10/7/2011
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Definitions Measurement - The determination of an unknown dimension. This requires that known standards be used directly, or indirectly for comparison. Metric System - A measurement system that has been standardized globally, and is commonly used in all modern engineering projects. Metrology - The science of measurement. The purpose of this discipline is to establish means of determining physical quantities, such as dimensions, temperature, force, etc. Repeatability - Imperfections in mechanical systems can mean that during a Mechanical cycle, a process does not stop at the same location, or move through the same spot each time. The variation range is referred to as repeatability. Standards - a known set of dimensions, or ideals to compare others against. Standard Sizes - a component, or a dimension that is chosen from a table of standard sizes/forms. Tolerance - The allowable variation in a basic dimension before a part is considered unacceptable 4 Dr. B. Gharaibeh 10/7/2011
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Tolerance Impossible to make perfect parts Too small tolerance, cost is high Boeing 747-400 has 6 million parts, measurement of 28 features, 150 million measurements NIST (U.S. National Institute of Standard and technology); tolerance shrink by a factor of 3 every 10 years ultra-precision ion-beam machining 0.001 m m 5 Dr. B. Gharaibeh 10/7/2011
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6 Dr. B. Gharaibeh 10/7/2011
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Importance of tolerance Parts from the same machine can be different Speed of operation Temperature Lubrication Variation of incoming material Other factors ISO system; definitions 7 Dr. B. Gharaibeh 10/7/2011
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8 Dr. B. Gharaibeh 10/7/2011
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Scales The most common tool for crude measurements is the scale (also known as rules, or rulers) These are limited by the human eye Parallax error can be a factor when making measurements with a scale-line of sight not being normal to the scale of the instrument 9 Dr. B. Gharaibeh 10/7/2011
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  • Spring '16
  • Metro, Vernier scale, Metalworking measuring instruments, Micrometer, Dimensional instruments, Dr. B. Gharaibeh, Dr. Belal Gharaibeh

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