Comparative Analysis of the Results of Measuring Roundness

Abstract

Coordinate measuring machines are devised for most complex measurements. Besides their dimension measuring abilities, the CNC operated machines can measure geometrical characteristics of form, such as straightness, roundness, cylindricity, etc. These are vital features currently, when inspection needs to submit very thorough reports not only on the form, but also on the geometrical features of the given workpiece. Yet the question arises: are these measuring data regarding roundness received from the CMM accurate and reliable enough to be exploited? In order to confirm this statement, the geometrical roundness characteristics were measured on three types of coordinate measuring machines, the results of which were analyzed from several aspects. The results showed a special importance of specific measuring parameters and proved to be independent of the type of measuring machines.

Towards Compensation for Servo-Control Defects in Coordinate Measuring Machines (CMMs)

“…Typically, form dimensions on a single surface are applied to any cross sections (ACS [ 7 ]) by default. In this case, the measurement should be taken along a perfect plane perpendicular to the part’s axis.…”

“…With a runout tolerance of 0.1 mm on any cross section (ACS), this part would be accepted through direct measurement, but rejected using the other two methods [ 7 ]. In addition, the measured characteristic does not meet the normative specifications for orientation, which is a problem.…”

“…There are as many planes as constructed lines. The direction of the measured deviation must follow the theoretical normal vector [ 7 ], which these constructions allow.…”

“…This second method allows many circles to be constructed by the intersection with different planes, answering the ACS specification [ 7 ], but it needs scanning capabilities to be performed. The point density of the scan should be matched to the curvature in order to maintain sufficient accuracy.…”

“… Representation of the direction of the measurement of a runout on a conical surface without any direction feature (black arrows) [ 7 ]. Example of tolerance zone for the runout at a given height (red arrows).…”

Towards Compensation for Servo-Control Defects in Coordinate Measuring Machines (CMMs)

“…Typically, form dimensions on a single surface are applied to any cross sections (ACS [ 7 ]) by default. In this case, the measurement should be taken along a perfect plane perpendicular to the part’s axis.…”

“…With a runout tolerance of 0.1 mm on any cross section (ACS), this part would be accepted through direct measurement, but rejected using the other two methods [ 7 ]. In addition, the measured characteristic does not meet the normative specifications for orientation, which is a problem.…”

“…There are as many planes as constructed lines. The direction of the measured deviation must follow the theoretical normal vector [ 7 ], which these constructions allow.…”

“…This second method allows many circles to be constructed by the intersection with different planes, answering the ACS specification [ 7 ], but it needs scanning capabilities to be performed. The point density of the scan should be matched to the curvature in order to maintain sufficient accuracy.…”

“… Representation of the direction of the measurement of a runout on a conical surface without any direction feature (black arrows) [ 7 ]. Example of tolerance zone for the runout at a given height (red arrows).…”

Towards Compensation for Servo-Control Defects in Coordinate Measuring Machines (CMMs)

“…Typically, form dimensions on a single surface are applied to any cross sections (ACS [ 7 ]) by default. In this case, the measurement should be taken along a perfect plane perpendicular to the part’s axis.…”

“…With a runout tolerance of 0.1 mm on any cross section (ACS), this part would be accepted through direct measurement, but rejected using the other two methods [ 7 ]. In addition, the measured characteristic does not meet the normative specifications for orientation, which is a problem.…”

“…There are as many planes as constructed lines. The direction of the measured deviation must follow the theoretical normal vector [ 7 ], which these constructions allow.…”

“…This second method allows many circles to be constructed by the intersection with different planes, answering the ACS specification [ 7 ], but it needs scanning capabilities to be performed. The point density of the scan should be matched to the curvature in order to maintain sufficient accuracy.…”

“… Representation of the direction of the measurement of a runout on a conical surface without any direction feature (black arrows) [ 7 ]. Example of tolerance zone for the runout at a given height (red arrows).…”

Towards Compensation for Servo-Control Defects in Coordinate Measuring Machines (CMMs)

“…Typically, form dimensions on a single surface are applied to any cross sections (ACS [ 7 ]) by default. In this case, the measurement should be taken along a perfect plane perpendicular to the part’s axis.…”

“…With a runout tolerance of 0.1 mm on any cross section (ACS), this part would be accepted through direct measurement, but rejected using the other two methods [ 7 ]. In addition, the measured characteristic does not meet the normative specifications for orientation, which is a problem.…”

“…There are as many planes as constructed lines. The direction of the measured deviation must follow the theoretical normal vector [ 7 ], which these constructions allow.…”

“…This second method allows many circles to be constructed by the intersection with different planes, answering the ACS specification [ 7 ], but it needs scanning capabilities to be performed. The point density of the scan should be matched to the curvature in order to maintain sufficient accuracy.…”

“… Representation of the direction of the measurement of a runout on a conical surface without any direction feature (black arrows) [ 7 ]. Example of tolerance zone for the runout at a given height (red arrows).…”