Geometric Dimensioning and Tolerance
Solid Models, Virtual Inspection and the Position Tolerance
E. R. Evans, Jr. School of Engineering & Engineering Technology Penn State Erie, The Behrend College, Station Road, Erie, PA 16563
ABSTRACT - In industrial practice, position is the most widely used geometric tolerancing characteristic. A thorough understanding of the concepts associated with position tolerancing is, therefore, an essential skill that graduating engineering and engineering technology students should possess. In the Mechanical Engineering Technology program at Penn State Erie, The Behrend College, geometric dimensioning and tolerancing (GD&T) skills are introduced to students during an advanced solid modeling course. Position tolerance is discussed in class providing a basic understanding of the geometric control, the use of datums and the concept of applying the maximum material condition modifier to the tolerance value. An activity has been developed in which students are given a drawing of a part and are asked to inspect five solid models, which simulate real world parts made according to the specifications on the provided drawing. The solid model parts are provided in the Initial Graphics Exchange Specification (IGES) format with all dimensional information removed. Students are asked to use the measuring tools in the solid modeling software to complete an inspection report for the parts. From the measurement data, the students determine if the position of the two holes in the part meet the specified tolerance. Students are then asked to use a paper gage with their measurements to verify the results obtained in the inspection report. The last part of the activity involves having the students assemble the sample parts into a functional gage assembly that is provided by the instructor. The students then perform an interference check on the assembly to determine if the
holes are within the prescribed position tolerance. This activity reinforces the concepts discussed in class and
E. R. Evans, Jr. School of Engineering & Engineering Technology Penn State Erie, The Behrend College, Station Road, Erie, PA 16563
ABSTRACT - In industrial practice, position is the most widely used geometric tolerancing characteristic. A thorough understanding of the concepts associated with position tolerancing is, therefore, an essential skill that graduating engineering and engineering technology students should possess. In the Mechanical Engineering Technology program at Penn State Erie, The Behrend College, geometric dimensioning and tolerancing (GD&T) skills are introduced to students during an advanced solid modeling course. Position tolerance is discussed in class providing a basic understanding of the geometric control, the use of datums and the concept of applying the maximum material condition modifier to the tolerance value. An activity has been developed in which students are given a drawing of a part and are asked to inspect five solid models, which simulate real world parts made according to the specifications on the provided drawing. The solid model parts are provided in the Initial Graphics Exchange Specification (IGES) format with all dimensional information removed. Students are asked to use the measuring tools in the solid modeling software to complete an inspection report for the parts. From the measurement data, the students determine if the position of the two holes in the part meet the specified tolerance. Students are then asked to use a paper gage with their measurements to verify the results obtained in the inspection report. The last part of the activity involves having the students assemble the sample parts into a functional gage assembly that is provided by the instructor. The students then perform an interference check on the assembly to determine if the
holes are within the prescribed position tolerance. This activity reinforces the concepts discussed in class and
References: Dimensioning and Tolerancing, (ASME Y14.5-1994). New York: American Society of Mechanical Engineers McCuistion, Patrick. On-Line GD&T Training Manual Module 9 – Position Tolerancing Theory. New York: American Society of Mechanical Engineers, 2003. Wilson, Bruce A. Design Dimensioning and Tolerancing. South Holland, Illinois: The GoodheartWillcox Company, Inc., 1996. 158