Measurement of Edge Creep Using Digital Calipers
The first analysis was a gauge repeatability and reproducibility(R&R) study of the effectiveness of using the digital calipers to measure the extent fo creepback at a specified location. Each operator made five measrements at each of three locations. The total variance in the measurement was 0 =3.34 mm . Of that total variance, the position-to-position variance due to repeatability was 0.008 mm and the variance due to reproducibility was 0.006 mm .The variance due to the measurement technique was only 0.42% of the total variance, giving a discrimination ratio of 22. These data indicate that the use of digital calipers is a very good method for measuring the edge creep at a disignated position on the panel because the variation in the edge creep measurements that are the result of the measurement technique are very small compared to the variation in the amount of edge creep typically measure.
If the toatl variance of the edge creep measurements on a panel is less than approximately 0.2 mm , then the variance due to the use of the calipers to measure the edge creep will be approximately 7.7% of the total variance. At the point, one should begin to use caution in interpreting the results as the contribution of the measurement technique is becoming a significant contributor to the total variance