Developing New Capability Indices for the Positional Tolerance of a Multidimensional Machining Process

• Activity Number: 88
• Type: Contributed
• Date/Time: Sunday, August 1, 2010 : 4:00 PM to 5:50 PM
• Sponsor: Section on Quality and Productivity
• Author(s): Chun-Yi Lee*+ and Jeh-Nan Pan
• Companies: National Chiayi University and National Cheng Kung University
• Keywords: Process capability analysis ; Engineering tolerance ; Geometric dimensioning and tolerancing ; Positional tolerance ; Geometric dimensioning and tolerancing ; Positional tolerance ; Geometric dimensioning and tolerancing

Abstract

Positional tolerance is a special type of geometric dimensioning and tolerancing (GD&T) which describes the tolerance region between the actual location of machining results and the target location. Several capability indices have been developed for measuring the positional performance of a multidimensional machining process (MMP) under the assumption that the variances of machining results on different directions are equal. However, this assumption may not be true in most practical situations. In this paper, we propose three novel indices for measuring the precision and accuracy of the positional performance of a MMP under the assumption that the variances are equal. The statistical properties of the point estimators for the new indices are derived and their confidence intervals are established too. Finally, the usefulness of our indices is demonstrated by a numerical example.