Measuring Part Geometry On The Shop Floor: MMSOnline.com - 0 views
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RoundnessAs noted above, roundness (also called out-of-roundness or circularity) is a self-referenced parameter. After the workpiece has been centered on the turntable, the gage generates a centered polar trace, creates a reference circle that represents "ideal roundness," and then calculates roundness as deviation from that circle. There are four different methods by which reference circles can be established mathematically, and these are described in the ANSI B89.3.1 standard. (They are: Minimum Radial Separation, Least Squares Circle, Maximum Inscribed Circle, and Minimum Circumscribed Circle.)Without going into detail here, we can state that results may vary by as much as 10 to 15 percent between the four methods. Minimum Radial Separation is a default method according to standards, but many geometry gages allow the user to select any one of the four, so it is important that the QA/QC manager study the practical applications of each method and understand their strengths and weaknesses. Gage operators who do not have sufficient expertise to make these determinations should be instructed in the appropriate method for each roundness measurement task.
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"Roundness As noted above, roundness (also called out-of-roundness or circularity) is a self-referenced parameter. After the workpiece has been centered on the turntable, the gage generates a centered polar trace, creates a reference circle that represents "ideal roundness," and then calculates roundness as deviation from that circle. There are four different methods by which reference circles can be established mathematically, and these are described in the ANSI B89.3.1 standard. (They are: Minimum Radial Separation, Least Squares Circle, Maximum Inscribed Circle, and Minimum Circumscribed Circle.) Without going into detail here, we can state that results may vary by as much as 10 to 15 percent between the four methods. Minimum Radial Separation is a default method according to standards, but many geometry gages allow the user to select any one of the four, so it is important that the QA/QC manager study the practical applications of each method and understand their strengths and weaknesses. Gage operators who do not have sufficient expertise to make these determinations should be instructed in the appropriate method for each roundness measurement task."
