The Use of Virtual Circles Gauge for a Quick Verification of Portable Measuring Arms

What is it about?

Portable Measuring Arms or Articulated Arm Coordinate Measuring Machines (AACMMs) unique characteristics bring flexibility to the inspection task and allow outside laboratory measurements. However, still a few works study their metrological behavior, uncertainty or assessment. In fact, AACMM assessment involves time consuming and expensive processes mainly inherited from CMM field. A virtual circle gauge similar to ball bars and a methodology based on international standards are proposed in order to simplify the evaluation test. Additionally, two metrological laboratories have evaluated different AACMM models with this gauge. Also, two gauge lengths (distance between circles) have be included in this study. Results have proved that virtual circle gauges are suitable to evaluate AACMMs and tested the influence of distance between virtual circles.

Featured Image

Why is it important?

A new gauge with virtual circles has been manufactured and successfully used to evaluate AACMMs. Additionally, a new evaluation methodology was developed and two evaluation test were carried out with two AACMMs at different laboratories. Virtual circle centers, diameters and the distance between virtual circle centers were chosen as evaluation parameters. These parameters are similar to the ones included in standards and manufacturer specifications. The test results have proved this gauge as a suitable instrument for fast and inexpensive AACMM evaluation. Test results show that virtual circles can be used to control the measurement capability of AACMM. AACMMs present a low repeatability for each parameter, lower than manufacturer specifications. The repeatability of gauge extreme positions is significantly higher than for the rest of positions so it should be considered for AACMM evaluation and future work. A comparison of this kind of feature with virtual spheres or solid spheres should be implemented as well. Not a significant influence has been found when varying virtual circle distances apart for the volume evaluated. A combination of several gauge lengths can be implemented in a new evaluation test in order to include measurements at several ranges within AACMM work volume.